Wangsa Sailendra

Śailendravamśa atau wangsa sailendra adalah nama wangsa atau dinasti raja-raja yang berkuasa di Sriwijaya, pulau Sumatera; dan di Mdaŋ (Kerajaan Medang), Jawa Tengah sejak tahun 752. Sebagian besar raja-rajanya adalah penganut dan pelindung agama Buddha Mahayana. Meskipun peninggalan dan manifestasi wangsa ini kebanyakan terdapat di dataran Kedu, Jawa Tengah, asal-usul wangsa ini masih diperdebatkan. Disamping berasal dari Jawa, daerah lain seperti Sumatera atau bahkan India dan Kamboja, sempat diajukan sebagai asal mula wangsa ini.

Asal-usul

Di Indonesia nama Śailendravamsa dijumpai pertama kali di dalam prasasti Kalasan dari tahun 778 Masehi (Śailendragurubhis; Śailendrawańśatilakasya; Śailendrarajagurubhis). Kemudian nama itu ditemukan di dalam prasasti Kelurak dari tahun 782 Masehi (Śailendrawańśatilakena), dalam prasasti Abhayagiriwihara dari tahun 792 Masehi (dharmmatuńgadewasyaśailendra), prasasti Sojomerto dari sekitar tahun 700 Masehi (selendranamah) dan prasasti Kayumwuńan dari tahun 824 Masehi (śailendrawańśatilaka). Di luar Indonesia nama ini ditemukan dalam prasasti Ligor dari tahun 775 Masehi dan prasasti Nalanda.
Mengenai asal usul keluarga Śailendra banyak dipersoalkan oleh beberapa sarjana. Berbagai pendapat telah dikemukakan oleh sejarawan dan arkeologis dari berbagai negara. Ada yang mengatakan bahawa keluarga Śailendra berasal dari Sumatra, dari India, dan dari Funan.

 Teori India

Majumdar beranggapan bahwa keluarga Śailendra di Nusantara, baik di Śrīwijaya (Sumatera) maupun di Mdaŋ (Jawa) berasal dari Kalingga (India Selatan). Pendapat yang sama dikemukakan juga oleh Nilakanta Sastri dan Moens. Moens menganggap bahwa keluarga Śailendra berasal dari India yang menetap di Palembang sebelum kedatangan Dapunta Hyang. Pada tahun 683 Masehi, keluarga ini melarikan diri ke Jawa karena terdesak oleh Dapunta Hyang dengan bala tentaranya.

Teori Funan

George Cœdès lebih condong kepada anggapan bahwa Śailendra yang ada di Nusantara itu berasal dari Funan (Kamboja). Karena terjadi kerusuhan yang mengakibatkan runtuhnya kerajaan Funan, kemudian keluarga kerajaan ini menyingkir ke Jawa, dan muncul sebagai penguasa di Medang pada pertengahan abad ke-8 Masehi dengan menggunakan nama keluarga Śailendra. Namun teori ini tidak terbukti kuat karena beberapa prasasti dan catatan sejarah menyatakan bahwa sebelum bermukim di Jawa, keluarga Sailendra telah bermukim turun-temurun di Sumatera.

 Teori Nusantara

Teori Nusantara mengajukan kepulauan Nusantara; terutama pulau Sumatera atau Jawa; sebagai tanah air wangsa ini. Teori ini mengajukan bahwa wangsa Śailendra mungkin berasal dari Sumatera yang kemudian berpindah dan berkuasa di Jawa, atau mungkin wangsa asli dari pulau Jawa tetapi mendapatkan pengaruh kuat dari Sriwijaya.
Menurut beberapa sejarawan, keluarga Śailendra berasal dari Sumatera yang bermigrasi ke Jawa Tengah setelah Sriwijaya melakukan ekspansi ke tanah Jawa pada abad ke-7 Masehi dengan menyerang kerajaan Tarumanagara dan Ho-ling di Jawa.. Serangan Sriwijaya atas Jawa berdasarkan atas Prasasti Kota Kapur yang mencanangkan ekspansi atas Bhumi Jawa yang tidak mau berbhakti kepada Sriwijaya. Ia mengemukakan gagasannya itu didasarkan atas sebutan gelar Dapunta Selendra pada prasasti Sojomerto. Gelar ini ditemukan juga pada prasasti Kedukan Bukit pada nama Dapunta Hiyaŋ. Prasasti Sojomerto dan prasasti Kedukan Bukit merupakan prasasti yang berbahasa Melayu Kuna.
Teori Nusantara juga dikemukakan oleh Poerbatjaraka. Pendapat dari Poerbatjaraka yang didasarkan atas Carita Parahiyangan kemudian diperkuat dengan sebuah temuan prasasti di wilayah Kabupaten Batang. Di dalam prasasti yang dikenal dengan nama prasasti Sojomerto itu disebutkan nama Dapunta Selendra, nama ayahnya (Santanū), nama ibunya (Bhadrawati), dan nama istrinya (Sampūla) (da pū nta selendra namah santanū nāma nda bapa nda bhadrawati nāma nda aya nda sampūla nāma nda ..). Menurut Boechari, tokoh yang bernama Dapunta Selendra adalah bakal raja-raja keturunan Śailendra yang berkuasa di Mdaŋ.
Nama Dapunta Selendra jelas merupakan ejaan Melayu dari kata dalam bahasa Sanskerta Śailendra karena di dalam prasasti digunakan bahasa Melayu Kuna. Jika demikian, kalau keluarga Śailendra berasal dari India Selatan tentunya mereka memakai bahasa Sansekerta di dalam prasasti-prasastinya. Dengan ditemukannya prasasti Sojomerto telah diketahui asal keluarga Śailendra dengan pendirinya Dapunta Selendra. Berdasarkan paleografinya, prasasti Sojomerto berasal dari sekitar pertengahan abad ke-7 Masehi.
Menurut Poerbatjaraka, Sanjaya dan keturunan-keturunannya itu ialah raja-raja dari keluarga Śailendra, asli Nusantara yang menganut agama Śiwa. Tetapi sejak Paņamkaran berpindah agama menjadi penganut Buddha Mahāyāna, raja-raja di Matarām menjadi penganut agama Buddha Mahāyāna juga. Pendapatnya itu didasarkan atas Carita Parahiyangan yang menyebutkan bahwa Rakai Sañjaya menyuruh anaknya Rakai Panaraban atau Rakai Tamperan untuk berpindah agama karena agama yang dianutnya (aliran Saiwa) ditakuti oleh semua orang. Kabar mengenai Rakai Panangkaran yang berpindah agama dari aliran Saiwa menjadi Buddha Mahayana juga sesuai dengan isi Prasasti Raja Sankhara (koleksi Museum Adam Malik yang kini hilang).
Kemudian Prasasti Canggal menyebutkan bahwa Sañjaya mendirikan sebuah lingga di bukit Sthīrańga untuk tujuan dan keselamatan rakyatnya. Disebutkan pula bahwa Sañjaya memerintah Jawa menggantikan Sanna; Raja Sanna mempunyai saudara perempuan bernama Sanaha yang kemudian dikawininya dan melahirkan Sañjaya.
Dari prasasti Sojomerto dan prasasti Canggal telah diketahui nama tiga orang penguasa di Mdaŋ (Matarām), yaitu Dapunta Selendra, Sanna, dan Sañjaya. Raja Sañjaya mulai berkuasa di Mdaŋ pada tahun 717 Masehi. Dari Carita Parahiyangan dapat diketahui bahwa Sena (Raja Sanna) berkuasa selama 7 tahun. Kalau Sañjaya naik takhta pada tahun 717 Masehi, maka Sanna naik takhta sekitar tahun 710 Masehi. Hal ini berarti untuk sampai kepada Dapunta Selendra (pertengahan abad ke-7 Masehi) masih ada sisa sekitar 60 tahun. Kalau seorang penguasa memerintah lamanya kira-kira 25 tahun, maka setidak-tidaknya masih ada 2 penguasa lagi untuk sampai kepada Dapunta Selendra.
Dalam Carita Parahiyangan disebutkan bahawa Raja Mandimiñak mendapat putra Sang Sena (Sanna). Ia memegang pemerintahan selama 7 tahun, dan Mandimiñak diganti oleh Sang Sena yang memerintah 7 tahun. Dari urutan raja-raja yang memerintah itu, dapat diduga bahwa Mandimiñak mulai berkuasa sejak tahun 703 Masehi. Ini berarti masih ada 1 orang lagi yang berkuasa sebelum Mandimiñak.
Karena teori Poerbatjaraka berdasarkan Carita Parahiyangan, maka keluarga Śailendra diduga berasal dari pulau Jawa yang berada dibawah pengaruh Sriwijaya. Tokoh Sanna dan Sanjaya berkaitan erat dengan sejarah Kerajaan Sunda dan Kerajaan Galuh. Mereka pada awalnya beragama Siwa seperti kebanyakan keluarga kerajaan permulaan di pulau Jawa seperti Tarumanagara dan Holing (Kalingga). Penggunaan bahasa Bahasa Melayu Kuna pada prasasti Sojomerto di Jawa Tengah serta penggunaan gelaran Dapunta menunjukkan bahwa keluarga Sailendra telah dipengaruhi bahasa, budaya, dan sistem politik Sriwijaya, hal ini menimbulkan dugaan bahwa mereka adalah vasal atau raja bawahan anggota kedatuan Sriwijaya. Hal ini seiring dengan kabar penaklukan Bhumi Jawa oleh Sriwijaya sebagaimana disebutkan dalam Prasasti Kota Kapur.
Berita Tiongkok yang berasal dari masa Dinasti Tang memberitakan tentang Kerajaan Ho-ling yang disebut She-po (Jawa). Pada tahun 674 Masehi rakyat kerajaan itu menobatkan seorang wanita sebagai ratu, yaitu Hsi-mo (Ratu Sima). Ratu ini memerintah dengan baik. Mungkinkah ratu ini merupakan pewaris takhta dari Dapunta Selendra? Apabila ya, maka diperoleh urutan raja-raja yang memerintah di Mdaŋ, yaitu Dapunta Selendra (?- 674 Masehi), Ratu Sima (674-703 Masehi), Mandimiñak (703-710 Masehi), R. Sanna (710-717 Masehi), R. Sañjaya (717-746 Masehi), dan Rakai Paņamkaran (746-784 Masehi), dan seterusnya.

 Era Kerajaan Medang

Candi Kalasan sebagai tempat pemujaan Dewi Tara.

Selama ini kerajaan Medang dianggap diperintah oleh dua wangsa yaitu Wangsa Sailendra yang beragama Buddha dan Wangsa Sanjaya yang beragama Hindu Siwa, pendapat ini pertama kali diperkenalkan oleh Bosch. Pada awal era Medang atau Mataram Kuno, wangsa Sailendra cukup dominan di Jawa Tengah. Menurut para ahli sejarah, wangsa Sanjaya awalnya berada di bawah pengaruh kekuasaan wangsa Sailendra. Mengenai persaingan kekuasaan tersebut tidak diketahui secara pasti, akan tetapi kedua-duanya sama-sama berkuasa di Jawa Tengah. Sementara Poerbatjaraka menolak anggapan Bosch mengenai adanya dua wangsa kembar berbeda agama yang saling bersaing ini. Menurutnya hanya ada satu wangsa dan satu kerajaan, yaitu wangsa Sailendra dan Kerajaan Medang. Sanjaya dan keturunannya adalah anggota Sailendra juga. Ditambah menurut Boechari, melalui penafsirannya atas Prasasti Sojomerto bahwa wangsa Sailendra pada mulanya memuja Siwa, sebelum Panangkaran beralih keyakinan menjadi penganut Buddha Mahayana.
Raja-raja yang berkuasa dari keluarga Sailendra tertera dalam prasasti Ligor, prasasti Nalanda maupun prasasti Klurak, sedangkan raja-raja dari keluarga Sanjaya tertera dalam prasasti Canggal dan prasasti Mantyasih. Berdasarkan candi-candi, peninggalan kerajaan Mataram Kuno dari abad ke-8 dan ke-9 yang bercorak Budha (Sailendra) umumnya terletak di Jawa Tengah bagian selatan, sedangkan yang bercorak Hindu (Sanjaya) umumnya terletak di Jawa Tengah bagian utara.
Berdasarkan penafsiran atas prasasti Canggal (732 M) Sanjaya memang mendirikan Shivalingga baru (Candi Gunung Wukir), artinya ia membangun dasar pusat pemerintahan baru. Hal ini karena raja Jawa pendahulunya, Raja Sanna wafat dan kerajaannya tercerai-berai diserang musuh. Saudari Sanna adalah Sannaha, ibunda Sanjaya, artinya Sanjaya masih kemenakan Sanna. Sanjaya mempersatukan bekas kerajaan Sanna, memindahkan ibu kota dan naik takhta membangun kraton baru di Mdang i Bhumi Mataram. Hal ini sesuai dengan adat dan kepercayaan Jawa bahwa kraton yang sudah pernah pralaya, diserang, kalah dan diduduki musuh, sudah buruk peruntungannya sehingga harus pindah mencari tempat lain untuk membangun kraton baru. Hal ini serupa dengan zaman kemudian pada masa Mataram Islam yang meninggalkan Kartasura yang sudah pernah diduduki musuh dan berpindah ke Surakarta. Perpindahan pusat pemerintahan ini bukan berarti berakhirnya wangsa yang berkuasa. Hal ini sama dengan Airlangga pada zaman kemudian yang membangun kerajaan baru, tetapi ia masih merupakan keturunan wangsa penguasa terdahulu, kelanjutan Dharmawangsa yang juga anggota wangsa Isyana. Maka disimpulkan meski Sanjaya memindahkan ibu kota ke Mataram, ia tetap merupakan kelanjutan dari wangsa Sailendra yang menurut prasasti Sojomerto didirikan oleh Dapunta Selendra.
Pada masa pemerintahan raja Indra (782-812), puteranya, Samaratungga, dinikahkan dengan Dewi Tara, puteri Dharmasetu, Maharaja Sriwijaya. Prasasti yang ditemukan tidak jauh dari Candi Kalasan memberikan penjelasan bahwa candi tersebut dibangun untuk menghormati Tara sebagai Bodhisattva wanita. Pada tahun 790, Sailendra menyerang dan mengalahkan Chenla (Kamboja Selatan), kemudian sempat berkuasa di sana selama beberapa tahun.
Candi Borobudur selesai dibangun pada masa pemerintahan raja Samaratungga (812-833). Borobudur merupakan monumen Buddha terbesar di dunia, dan kini menjadi salah satu kebanggaan bangsa Indonesia. Dari hasil pernikahannya dengan Dewi Tara, Samaratungga memiliki putri bernama Pramodhawardhani dan putra bernama Balaputradewa. Balaputra kemudian memerintah di Sriwijaya, maka selain pernah berkuasa di Medang, wangsa Sailendra juga berkuasa di Sriwijaya.

 Runtuhnya Wangsa Sailendra

Berapa sejarahwan berusaha menjelaskan berakhirnya kekuasaan Sailendra di Jawa Tengah mengaitkannya dengan kepindahan Balaputradewa ke Sriwijaya (Sumatera). Selama ini sejarahwan seperti Dr. Bosch dan Munoz menganut paham adanya dua wangsa kembar berbeda keyakinan yang saling bersaing; Sanjaya-Sailendra. Mereka beranggapan Sailendra yang penganut Buddha kalah bersaing dan terusir oleh wangsa Sanjaya yang Hindu aliran Siwa. Dimulai dengan adanya ketimpangan perekonomian serta perbedaan keyakinan antara Sailendra sang penguasa yang beragama Buddha dengan rakyat Jawa yang kebanyakan beragama Hindu Siwa, menjadi faktor terjadinya ketidakstabilan di Jawa Tengah. Untuk memantapkan posisinya di Jawa Tengah, raja Samaratungga menikahkan putrinya Pramodhawardhani, dengan anak Garung, Rakai Pikatan yang waktu itu menjadi pangeran wangsa Sanjaya. Sejak itu pengaruh Sanjaya yang bercorak Hindu mulai dominan di Mataram, menggantikan agama Buddha. Rakai Pikatan bahkan menyerang Balaputradewa, yang merupakan paman atau saudara Pramodhawardhani. Sejarah wangsa Sailendra berakhir pada tahun 850, yaitu ketika Balaputradewa melarikan diri ke Suwarnadwipa yang merupakan negeri asal ibunya. Setelah terusirnya wangsa Sailendra dari Jawa Tengah, Munoz beranggapan berakhir pula kekuasaan Sriwijaya atas Jawa selama satu abad. Munoz beranggapan bahwa orang-orang Jawa pengikut Balaputradewa merasa terancam dan akhirnya menyingkir, mengungsi ke Jawa Barat untuk mendirikan kerajaan Banten Girang. Hal ini berdasarkan temuan arca-arca bergaya Jawa Tengahan abad ke-10 di situs Gunung Pulasari, Banten Girang.
Sementara itu, sejarahwan seperti Poerbatjaraka dan Boechari percaya bahwa hanya ada satu wangsa yaitu Sailendra, dan tidak pernah disebutkan Sanjayavamça dalam prasasti apapun. Sanjaya dan keturunannya dianggap masih masuk dalam wangsa Sailendra. Secara tradisional, selama ini kurun kekuasaan Sailendra dianggap berlangsung antara abad ke-8 hingga ke-9 Masehi, dan hanya terbatas di Jawa Tengah, tepatnya di Dataran Kedu, dari masa kekuasaan Panangkaran hingga Samaratungga. Hal ini sesuai dengan penafsiran Slamet Muljana yang menganggap Panangkaran sebagai Raja Sailendra pertama yang naik takhta. Akan tetapi penafsiran paling mutakhir berdasarkan temuan Prasasti Sojomerto serta kelanjutan Sailendra di Sriwijaya mengusulkan; bahwa masa kekuasaan wangsa Sailendra berlangsung jauh lebih lama. Dari pertengahan abad ke-7 (perkiraan dituliskannya Prasasti Sojomerto), hingga awal abad ke-11 masehi (jatuhnya wangsa Sailendra di Sriwijaya akibat serangan Cholamandala dari India). Dalam kurun waktu tertentu, wangsa Sailendra berkuasa baik di Jawa Tengah maupun di Sumatra. Persekutuan dan hubungan pernikahan keluarga kerajaan antara Sriwijaya dan Sailendra memungkinkan bergabungnya dua keluarga kerajaan, dengan wangsa Sailendra akhirnya berkuasa baik di Kerajaan Medang Mataram di Jawa Tengah sekaligus di Sriwijaya, Sumatera.

 Daftar raja-raja

Beberapa sejarahwan mencoba merekonstruksi kembali urutan daftar silsilah raja-raja Sailendra; meskipun satu sama lain mungkin tidak sepakat. Misalnya, Slamet Muljana, meneruskan teori dinasti kembar Bosch, berpendapat bahwa anggota wangsa Sailendra pertama yang berhasil menjadi raja adalah Rakai Panangkaran. Sementara itu, Poerbatjaraka berpendapat bahwa wangsa Sanjaya itu tidak pernah ada. Dengan kata lain, Wangsa Sanjaya juga merupakan anggota Wangsa Sailendra. Boechari mencoba menyusun tahap awal perkembangan wangsa Sailendra berdasarkan penafsiran atas Prasasti Sojomerto. Sementara Poerbatjaraka mencoba menyusun daftar raja penguasa Sailendra pada periode menengah dan lanjut berdasarkan hubungannya dengan tokoh Sanjaya, beberapa prasasti Sailendra, serta penafsiran atas naskah Carita Parahyangan. Akan tetapi banyak kebingungan yang muncul, karena nampaknya Sailendra berkuasa atas banyak kerajaan; Kalingga, Medang, dan Sriwijaya. Akibatnya nama beberapa raja nampak tumpang tindih dan berkuasa di kerajaan-kerajaan ini secara bersamaan. Tanda tanya (?) menunjukkan keraguan atau dugaan, karena data atau bukti sejarah sahih masih sedikit ditemukan dan belum jelas terungkap.

Kurun Waktu	Nama Raja atau Penguasa	Ibu Kota	Prasasti atau Catatan Bersejarah	Peristiwa
sekitar 650	Santanu	?	Prasasti Sojomerto (sekitar 670—700)	Sebuah keluarga beragama Siwa berbahasa Melayu kuno mulai bermukim di pesisir utara Jawa Tengah, diduga berasal dari Sumatera (?) atau asli dari Jawa tapi di bawah pengaruh Sriwijaya (raja bawahan)
sekitar 674	Dapunta Selendra	Batang (pantai utara Jawa Tengah)	Prasasti Sojomerto (sekitar 670—700)	Dimulainya wangsa keluarga penguasa, pertama kalinya nama 'Selendra' (Sailendra) disebutkan
674—703	Shima (?)	Kalingga, diantara Pekalongan dan Jepara	Carita Parahyangan, Catatan Tiongkok mengenai kunjungan biksu Hwi-ning di Ho-ling (664) dan pemerintahan Ratu Hsi-mo (674)	Menguasai kerajaan Kalingga
703—710	Mandimiñak (?)	?	Carita Parahyangan
710—717	Sanna	?	Prasasti Canggal (732), Carita Parahyangan	Sanna berkuasa di Jawa, tetapi setelah kematiannya kerajaan runtuh dan terpecah-belah akibat pemberontakan atau serangan dari luar
717—760	Sanjaya	Mataram, Jawa Tengah	Prasasti Canggal (732), Carita Parahyangan	Sanjaya, putra Sannaha, keponakan Sanna memulihkan keamanan, mempersatukan kerajaan dan naik takhta, sejarahwan lama menafsirkannya sebagai berdirinya Wangsa Sanjaya, sementara pihak lain menganggap ia sebagai kelanjutan Sailendra
760—775	Rakai Panangkaran	Mataram, Jawa Tengah	Prasasti Raja Sankhara, Prasasti Kalasan (778), Carita Parahyangan	Rakai Panangkaran beralih keyakinan dari memuja Siwa menjadi penganut Buddha Mahayana, pembangunan Candi Kalasan
775—800	Dharanindra	Mataram, Jawa Tengah	Prasasti Kelurak (782), Prasasti Ligor B (sekitar 787)	Juga berkuasa di Sriwijaya (Sumatera), membangun Manjusrigrha, memulai membangun Borobudur (sekitar 770), Jawa menyerang dan menaklukan Ligor dan Kamboja Selatan (Chenla) (790)
800—812	Samaragrawira	Mataram, Jawa Tengah	Prasasti Ligor B (sekitar 787)	Juga berkuasa di Sriwijaya, Kamboja memerdekakan diri (802)
812—833	Samaratungga	Mataram, Jawa Tengah	Prasasti Karangtengah (824)	Juga berkuasa di Sriwijaya, merampungkan Borobudur (825)
833—856	Pramodhawardhani berkuasa mendampingi suaminya Rakai Pikatan	Mamrati, Jawa Tengah	Prasasti Siwagrha (856)	Mengalahkan dan mengusir Balaputradewa yang menyingkir ke Sumatera (Sriwijaya). Membangun Candi Prambanan dan Candi Plaosan. Para raja Medang penerus Pikatan, mulai dari Dyah Lokapala (850—890) hingga Wawa (924—929) dapat dianggap sebagai penerus trah Sailendra, meskipun Dyah Balitung (898—910) dalam Prasasti Mantyasih (907) hanya merunut leluhurnya hingga Sanjaya, akibatnya menumbuhkan teori Wangsa Sanjaya.
833—850	Balaputradewa	Sriwijaya, Sumatera Selatan	Prasasti Siwagrha (856), Prasasti Nalanda (860)	Dikalahkan Pikatan-Pramodhawardhani, terusir dari Jawa Tengah, menyingkir ke Sumatra dan berkuasa di Sriwijaya, mengaku dirinya sebagai pewaris sah wangsa Sailendra dari Jawa, membangun Candi di Nalanda (India)
sekitar 960	Çri Udayadityavarman	Sriwijaya, Sumatera Selatan	Utusan ke Tiongkok (960 dan 962)	Mengirim utusan dan persembahan untuk mendapat misi dagang dengan Tiongkok
sekitar 980	Haji (Hia-Tche)	Sriwijaya, Sumatera Selatan	Utusan ke Tiongkok (980–983)	Mengirim utusan dan persembahan untuk mendapat misi dagang dengan Tiongkok
sekitar 988	Sri Culamanivarmadeva	Sriwijaya, Sumatera Selatan	Utusan ke Tiongkok (988-992-1003), Prasasti Tanjore atau prasasti Leiden (1044)	Mengirim utusan dan persembahan untuk mendapat misi dagang dengan Tiongkok, Raja Jawa Dharmawangsa menyerang Sriwijaya, membangun Candi untuk Kaisar Tiongkok, pemberian desa perdikan oleh Raja-raja I
sekitar 1008	Sri Maravijayottungga	Sriwijaya, Sumatera Selatan	Utusan ke Tiongkok (1008)	Mengirim utusan dan persembahan untuk mendapat misi dagang dengan Tiongkok (1008)
sekitar 1017	Sumatrabhumi	Sriwijaya, Sumatera Selatan	Utusan ke Tiongkok(1017)	Mengirim utusan dan persembahan untuk mendapat misi dagang dengan Tiongkok (1017)
sekitar 1025	Sangramavijayottungga	Sriwijaya, Sumatera Selatan	Prasasti Chola di Candi Rajaraja, Tanjore	Serbuan kerajaan Cholamandala atas Sriwijaya, ibu kota ditaklukan oleh Rajendra Chola

Ecosystem

An ecosystem is a biological environment consisting of all the living organisms or biotic component, in a particular area, and the nonliving, or abiotic component, with which the organisms interact, such as air, soil, water and sunlight.

Overview

Rainforests often have a great deal of biodiversity with many plant and animal species. This is the Gambia River in Senegal's Niokolo-Koba National Park.

The entire array of organisms inhabiting a particular ecosystem is called a community. The number of species making up such a community may vary from a myriad to a single species such as Desulforudis. In a typical ecosystem, plants and other photosynthetic organisms are the producers that provide the food. Ecosystems can be permanent or temporary. Ecosystems usually form a number of food webs.

Ecosystems are functional units consisting of living things in a given area, non-living chemical and physical factors of their environment, linked together through nutrient cycle and energy flow."

• Natural
  • Terrestrial ecosystem
  • Aquatic ecosystem
  • Lentic, the ecosystem of a lake, pond or swamp.
  • Lotic, the ecosystem of a river, stream or spring.
• Artificial, ecosystems created by humans.

Central to the ecosystem concept is the idea that living organisms interact with every other element in their local environment. Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (ie: the "community") in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem.

 Etymology

The term ecosystem was coined in 1930 by Roy Clapham to mean the combined physical and biological components of an environment. British ecologist Arthur Tansley later refined the term, describing it as "The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment". Tansley regarded ecosystems not simply as natural units, but as mental isolates. Tansley later defined the spatial extent of ecosystems using the term ecotope.

Examples of ecosystems

• Agroecosystem
• Aquatic ecosystem
• Chaparral
• Coral reef
• Desert
• Forest
• Farm
• Greater Yellowstone Ecosystem
• Human ecosystem
• Large marine ecosystem
• Littoral zone
• Lotic
• Marine ecosystem
• Pond ecosystem
• Prairie
• Rainforest
• Riparian zone
• Savanna
• Steppe
• Subsurface Lithoautotrophic Microbial Ecosystem
• Taiga
• Tundra
• Urban ecosystem

A freshwater ecosystem in Gran Canaria, an island of the Canary Islands.

 Biomes

Map of Terrestrial biomes classified by vegetation.

Main article: Biome

Biomes are a classification of globally similar areas, including ecosystems, such as ecological communities of plants and animals, soil organisms and climatic conditions.^{[citation needed]} Biomes are in part defined based on factors such as plant structures (such as trees, shrubs and grasses), leaf types (such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna) and climate.^{[citation needed]} Unlike ecozones, biomes are not defined by genetic, taxonomic or historical similarities. Biomes are often identified with particular patterns of ecological succession and climax vegetation.

A fundamental classification of biomes is:

1. Terrestrial (land) biomes.
2. Freshwater biomes.
3. Marine biomes.

 Classification

Summer field in Belgium (Hamois). The blue flower is Centaurea cyanus and the red one a Papaver rhoeas.

The High Peaks Wilderness Area in the 6,000,000-acre (2,400,000 ha) Adirondack Park is an example of a diverse ecosystem.

Flora of Baja California Desert, Cataviña region, Mexico.

Ecosystems have become particularly important politically, since the Convention on Biological Diversity (CBD) - ratified by 192 countries - defines "the protection of ecosystems, natural habitats and the maintenance of viable populations of species in natural surroundings" as a commitment of ratifying countries. This has created the political necessity to spatially identify ecosystems and somehow distinguish among them. The CBD defines an "ecosystem" as a "dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit".

With the need of protecting ecosystems, the political need arose to describe and identify them efficiently. Vreugdenhil et al. argued that this could be achieved most effectively by using a physiognomic-ecological classification system, as ecosystems are easily recognizable in the field as well as on satellite images. They argued that the structure and seasonality of the associated vegetation, or flora, complemented with ecological data (such as elevation, humidity, and drainage), are each determining modifiers that separate partially distinct sets of species. This is true not only for plant species, but also for species of animals, fungi and bacteria. The degree of ecosystem distinction is subject to the physiognomic modifiers that can be identified on an image and/or in the field. Where necessary, specific fauna elements can be added, such as seasonal concentrations of animals and the distribution of coral reefs.

Several physiognomic-ecological classification systems are available:

• Physiognomic-Ecological Classification of Plant Formations of the Earth: a system based on the 1974 work of Mueller-Dombois and Heinz Ellenberg, and developed by UNESCO. This classification "describes the above-ground or underwater vegetation structures and cover as observed in the field, described as plant life forms. This classification is fundamentally a species-independent physiognomic, hierarchical vegetation classification system which also takes into account ecological factors such as climate, elevation, human influences such as grazing, hydric regimes and survival strategies such as seasonality. The system was expanded with a basic classification for open water formations".^[8]
• Land Cover Classification System (LCCS), developed by the Food and Agriculture Organization (FAO).
• Forest-Range Environmental Study Ecosystems (FRES) developed by the United States Forest Service for use in the United States.

Several aquatic classification systems are available, and an effort is being made by the United States Geological Survey (USGS) and the Inter-American Biodiversity Information Network (IABIN) to design a complete ecosystem classification system that will cover both terrestrial and aquatic ecosystems.

From a philosophy of science perspective, ecosystems are not discrete units of nature that simply can be identified using the most "correct" type of classification approach.^{[citation needed]} In agreement with the definition by Tansley ("mental isolates"), any attempt to delineate or classify ecosystems should be explicit about the observer/analyst input in the classification including its normative rationale.

Two Giant Sequoias, Sequoia National Park. Note the large fire scar at the base of the right-hand tree; fires do not kill the trees but do remove competing thin-barked species, and aid Giant Sequoia regeneration.

Ecosystem services

Main article: Ecosystem services

Ecosystem services are “fundamental life-support services upon which human civilization depends,”ⁱ and can be direct or indirect. Examples of direct ecosystem services are: pollination, wood and erosion prevention. Indirect services could be considered climate moderation, nutrient cycles and detoxifying natural substances. The services and goods an ecosystem provides are often undervalued as many of them are without market value. Broad examples include:

• Regulating (climate, floods, nutrient balance, water filtration)
• Provisioning (food, medicine, fur, minerals)
• Cultural (science, spiritual, ceremonial, recreation, aesthetic)
• Health (Physical, Psychological)
• Supporting (nutrient cycling, photosynthesis, soil formation).

Ecosystem legal rights

Ecuador's new constitution of 2008 is the first in the world to recognize legally enforceable Rights of Nature, or ecosystem rights.

The borough of Tamaqua, Pennsylvania passed a law giving ecosystems legal rights. The ordinance establishes that the municipal government or any Tamaqua resident can file a lawsuit on behalf of the local ecosystem.Other townships, such as Rush, followed suit and passed their own laws.

This is part of a growing body of legal opinion proposing 'wild law'. Wild law, a term coined by Cormac Cullinan (a lawyer based in South Africa), would cover birds and animals, rivers and deserts.

 Function and biodiversity

Savanna at Ngorongoro Conservation Area, Tanzania.

See also: Biodiversity

From an anthropocentric point of view, some people perceive ecosystems as production units that produce goods and services, such as wood by forest ecosystems and grass for cattle by natural grasslands. Meat from wild animals, often referred to as bush meat in Africa, has proven to be extremely successful under well-controlled management schemes in South Africa and Kenya. Much less successful has been the discovery and commercialization of substances of wild organism for pharmaceutical purposes. Services derived from ecosystems are referred to as ecosystem services. They may include

1. Facilitating the enjoyment of nature, which may generate many forms of income and employment in the tourism sector, often referred to as eco-tourisms,
2. Water retention, thus facilitating a more evenly distributed release of water,
3. Soil protection, open-air laboratory for scientific research, etc.

The side of a tide pool showing sea stars (Dermasterias), sea anemones (Anthopleura) and sea sponges in Santa Cruz, California.

A greater degree of species or biological diversity - commonly referred to as Biodiversity - of an ecosystem may contribute to greater resilience of an ecosystem, because there are more species present at a location to respond to change and thus "absorb" or reduce its effects. “Some theories predict that biodiversity will promote ecosystem integrity in changing climates, because high diversity ensures that functional groups will retain at least one species able to tolerate altered condition." This reduces the effect before the ecosystem's structure is fundamentally changed to a different state. One hypothesis about this is the Rivet Poper Hypothesis. According to Paul and Anne Ehrlich “the diversity of life is something like the rivets on an airplane. Each species plays a small but significant role in the working of the whole, and the loss of any rivet weakens the plane by a small but measurable amount. Pop too many rivets and the plane will crash that is, some vital function will collapse." They are saying if too many species die out then some sort of vital function of the ecosystem such as a food web would collapse causing the ecosystem to fail. However rivets come in different sizes and have different critical functions in construction, when thinking about species as rivets the variety and distribution in the overall structure is important.

This is not universally the case and there is no proven relationship between the species diversity of an ecosystem and its ability to provide goods and services on a sustainable level: Humid tropical forests produce very few goods and direct services and are extremely vulnerable to change, while many temperate forests readily grow back to their previous state of development within a lifetime after felling or a forest fire. Some grasslands have been sustainably exploited for thousands of years (Mongolia, Africa, European peat and mooreland communities).

 The study of ecosystems

Forest on San Juan Island

Loch Lomond in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained unchanged over a very long period of time.

 Ecosystem dynamics

Introduction of new elements, whether biotic or abiotic, into an ecosystem tend to have a disruptive effect. In some cases, this can lead to ecological collapse or "trophic cascading" and the death of many species within the ecosystem. Under this deterministic vision, the abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem; i.e. how far the ecosystem is away from its steady state.

Often, however, ecosystems have the ability to rebound from a disruptive agent. The difference between collapse or a gentle rebound is determined by two factors—the toxicity of the introduced element and the resiliency of the original ecosystem.

Ecosystems are primarily governed by stochastic (chance) events, the reactions these events provoke on non-living materials and the responses by organisms to the conditions surrounding them. Thus, an ecosystem results from the sum of individual responses of organisms to stimuli from elements in the environment.The presence or absence of populations merely depends on reproductive and dispersal success, and population levels fluctuate in response to stochastic events. As the number of species in an ecosystem is higher, the number of stimuli is also higher. Since the beginning of life organisms have survived continuous change through natural selection of successful feeding, reproductive and dispersal behavior. Through natural selection the planet's species have continuously adapted to change through variation in their biological composition and distribution. Mathematically it can be demonstrated that greater numbers of different interacting factors tend to dampen fluctuations in each of the individual factors.

Spiny forest at Ifaty, Madagascar, featuring various Adansonia (baobab) species, Alluaudia procera (Madagascar ocotillo) and other vegetation.

Given the great diversity among organisms on earth, most ecosystems only changed very gradually, as some species would disappear while others would move in. Locally, sub-populations continuously go extinct, to be replaced later through dispersal of other sub-populations. Stochastists do recognize that certain intrinsic regulating mechanisms occur in nature. Feedback and response mechanisms at the species level regulate population levels, most notably through territorial behaviour. Andrewatha and Birch suggest that territorial behaviour tends to keep populations at levels where food supply is not a limiting factor. Hence, stochastists see territorial behaviour as a regulatory mechanism at the species level but not at the ecosystem level. Thus, in their vision, ecosystems are not regulated by feedback and response mechanisms from the ecosystem itself and there is no such thing as a balance of nature.

If ecosystems are governed primarily by stochastic processes, through which its subsequent state would be determined by both predictable and random actions, they may be more resilient to sudden change than each species individually. In the absence of a balance of nature, the species composition of ecosystems would undergo shifts that would depend on the nature of the change, but entire ecological collapse would probably be infrequent events.

The theoretical ecologist Robert Ulanowicz has used information theory tools to describe the structure of ecosystems, emphasizing mutual information (correlations) in studied systems. Drawing on this methodology and prior observations of complex ecosystems, Ulanowicz depicts approaches to determining the stress levels on ecosystems and predicting system reactions to defined types of alteration in their settings (such as increased or reduced energy flow, and eutrophication.

Arctic tundra on Wrangel Island, Russia.

In addition, Eric Sanderson has developed the Muir web, based on experience on the Mannahatta project. This graphical schematic shows how different species are connected to each other, not only regarding their position in the food chain, but also regarding other services, i.e. provisioning of shelter, ...

 Ecosystem ecology

Ecosystem ecology is the integrated study of biotic and abiotic components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components such as chemicals, bedrock, soil, plants, and animals. Ecosystem ecology examines physical and biological structure and examines how these ecosystem characteristics interact.

Distillation

Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction.

Commercially, distillation has a number of applications. It is used to separate crude oil into more fractions for specific uses such as transport, power generation and heating. Water is distilled to remove impurities, such as salt from seawater. Air is distilled to separate its components—notably oxygen, nitrogen, and argon— for industrial use. Distillation of fermented solutions has been used since ancient times to produce distilled beverages with a higher alcohol content. The premises where distillation is carried out, especially distillation of alcohol, are known as a distillery.

History

Distillation apparatus of Zosimus, from Marcelin Berthelot, Collection des anciens alchimistes grecs (3 vol., Paris, 1887-1888).

The first clear evidence of distillation comes from Greek alchemists working in Alexandria in the first century AD. Distilled water has been known since at least ca. 200 AD, when Alexander of Aphrodisias described the process. Arabs learned the process from the Egyptians and used it extensively in their chemical experiments.

Clear evidence of the distillation of alcohol comes from the School of Salerno in the 12th century. Fractional distillation was developed by Tadeo Alderotti in the 13th century.

In 1500, German alchemist Hieronymus Braunschweig published Liber de arte destillandi (The Book of the Art of Distillation) the first book solely dedicated to the subject of distillation, followed in 1512 by a much expanded version. In 1651, John French published The Art of Distillation the first major English compendium of practice, though it has been claimed that much of it derives from Braunschweig's work. This includes diagrams with people in them showing the industrial rather than bench scale of the operation.

A retort.

Distillation

Old Ukrainian vodka still

As alchemy evolved into the science of chemistry, vessels called retorts became used for distillations. Both alembics and retorts are forms of glassware with long necks pointing to the side at a downward angle which acted as air-cooled condensers to condense the distillate and let it drip downward for collection. Later, copper alembics were invented. Riveted joints were often kept tight by using various mixtures, for instance a dough made of rye flour. These alembics often featured a cooling system around the beak, using cold water for instance, which made the condensation of alcohol more efficient. These were called pot stills. Today, the retorts and pot stills have been largely supplanted by more efficient distillation methods in most industrial processes. However, the pot still is still widely used for the elaboration of some fine alcohols such as cognac, Scotch whisky, tequila and some vodkas. Pot stills made of various materials (wood, clay, stainless steel) are also used by bootleggers in various countries. Small pot stills are also sold for the domestic production of flower water or essential oils.

Early forms of distillation were batch processes using one vaporization and one condensation. Purity was improved by further distillation of the condensate. Greater volumes were processed by simply repeating the distillation. Chemists were reported to carry out as many as 500 to 600 distillations in order to obtain a pure compound.

In the early 19th century the basics of modern techniques including pre-heating and reflux were developed, particularly by the French, then in 1830 a British Patent was issued to Aeneas Coffey for a whiskey distillation column, which worked continuously and may be regarded as the archetype of modern petrochemical units. In 1877, Ernest Solvay was granted a U.S. Patent for a tray column for ammonia distillation and the same and subsequent years saw developments of this theme for oil and spirits.

With the emergence of chemical engineering as a discipline at the end of the 19th century, scientific rather than empirical methods could be applied. The developing petroleum industry in the early 20th century provided the impetus for the development of accurate design methods such as the McCabe-Thiele method and the Fenske equation. The availability of powerful computers has also allowed direct computer simulation of distillation columns.

Applications of distillation

The application of distillation can roughly be divided in four groups: laboratory scale, industrial distillation, distillation of herbs for perfumery and medicinals (herbal distillate), and food processing. The latter two are distinctively different from the former two in that in the processing of beverages, the distillation is not used as a true purification method but more to transfer all volatiles from the source materials to the distillate.

The main difference between laboratory scale distillation and industrial distillation is that laboratory scale distillation is often performed batch-wise, whereas industrial distillation often occurs continuously. In batch distillation, the composition of the source material, the vapors of the distilling compounds and the distillate change during the distillation. In batch distillation, a still is charged (supplied) with a batch of feed mixture, which is then separated into its component fractions which are collected sequentially from most volatile to less volatile, with the bottoms (remaining least or non-volatile fraction) removed at the end. The still can then be recharged and the process repeated.

In continuous distillation, the source materials, vapors, and distillate are kept at a constant composition by carefully replenishing the source material and removing fractions from both vapor and liquid in the system. This results in a better control of the separation process.

Idealized distillation model

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the pressure in the liquid, enabling bubbles to form without being crushed. A special case is the normal boiling point, where the vapor pressure of the liquid equals the ambient atmospheric pressure.

It is a common misconception that in a liquid mixture at a given pressure, each component boils at the boiling point corresponding to the given pressure and the vapors of each component will collect separately and purely. This, however, does not occur even in an idealized system. Idealized models of distillation are essentially governed by Raoult's law and Dalton's law, and assume that vapor-liquid equilibria are attained.

Raoult's law assumes that a component contributes to the total vapor pressure of the mixture in proportion to its percentage of the mixture and its vapor pressure when pure, or succinctly: partial pressure equals mole fraction multiplied by vapor pressure when pure. If one component changes another component's vapor pressure, or if the volatility of a component is dependent on its percentage in the mixture, the law will fail.

Dalton's law states that the total vapor pressure is the sum of the vapor pressures of each individual component in the mixture. When a multi-component liquid is heated, the vapor pressure of each component will rise, thus causing the total vapor pressure to rise. When the total vapor pressure reaches the pressure surrounding the liquid, boiling occurs and liquid turns to gas throughout the bulk of the liquid. Note that a mixture with a given composition has one boiling point at a given pressure, when the components are mutually soluble.

An implication of one boiling point is that lighter components never cleanly "boil first". At boiling point, all volatile components boil, but for a component, its percentage in the vapor is the same as its percentage of the total vapor pressure. Lighter components have a higher partial pressure and thus are concentrated in the vapor, but heavier volatile components also have a (smaller) partial pressure and necessarily evaporate also, albeit being less concentrated in the vapor. Indeed, batch distillation and fractionation succeed by varying the composition of the mixture. In batch distillation, the batch evaporates, which changes its composition; in fractionation, liquid higher in the fractionation column contains more lights and boils at lower temperatures.

The idealized model is accurate in the case of chemically similar liquids, such as benzene and toluene. In other cases, severe deviations from Raoult's law and Dalton's law are observed, most famously in the mixture of ethanol and water. These compounds, when heated together, form an azeotrope, which is a composition with a boiling point higher or lower than the boiling point of each separate liquid. Virtually all liquids, when mixed and heated, will display azeotropic behaviour. Although there are computational methods that can be used to estimate the behavior of a mixture of arbitrary components, the only way to obtain accurate vapor-liquid equilibrium data is by measurement.

It is not possible to completely purify a mixture of components by distillation, as this would require each component in the mixture to have a zero partial pressure. If ultra-pure products are the goal, then further chemical separation must be applied. When a binary mixture is evaporated and the other component, e.g. a salt, has zero partial pressure for practical purposes, the process is simpler and is called evaporation in engineering.

Batch distillation

A batch still showing the separation of A and B.

Heating an ideal mixture of two volatile substances A and B (with A having the higher volatility, or lower boiling point) in a batch distillation setup (such as in an apparatus depicted in the opening figure) until the mixture is boiling results in a vapor above the liquid which contains a mixture of A and B. The ratio between A and B in the vapor will be different from the ratio in the liquid: the ratio in the liquid will be determined by how the original mixture was prepared, while the ratio in the vapor will be enriched in the more volatile compound, A (due to Raoult's Law, see above). The vapor goes through the condenser and is removed from the system. This in turn means that the ratio of compounds in the remaining liquid is now different from the initial ratio (i.e. more enriched in B than the starting liquid).

The result is that the ratio in the liquid mixture is changing, becoming richer in component B. This causes the boiling point of the mixture to rise, which in turn results in a rise in the temperature in the vapor, which results in a changing ratio of A : B in the gas phase (as distillation continues, there is an increasing proportion of B in the gas phase). This results in a slowly changing ratio A : B in the distillate.

If the difference in vapor pressure between the two components A and B is large (generally expressed as the difference in boiling points), the mixture in the beginning of the distillation is highly enriched in component A, and when component A has distilled off, the boiling liquid is enriched in component B.

Continuous distillation

Continuous distillation is an ongoing distillation in which a liquid mixture is continuously (without interruption) fed into the process and separated fractions are removed continuously as output streams as time passes during the operation. Continuous distillation produces at least two output fractions, including at least one volatile distillate fraction, which has boiled and been separately captured as a vapor condensed to a liquid. There is always a bottoms (or residue) fraction, which is the least volatile residue that has not been separately captured as a condensed vapor.

Continuous distillation differs from batch distillation in the respect that concentrations should not change over time. Continuous distillation can be run at a steady state for an arbitrary amount of time. For any source material of specific composition, the main variables that affect the purity of products in continuous distillation are the reflux ratio and the number of theoretical equilibrium stages (practically, the number of trays or the height of packing). Reflux is a flow from the condenser back to the column, which generates a recycle that allows a better separation with a given number of trays. Equilibrium stages are ideal steps where compositions achieve vapor-liquid equilibrium, repeating the separation process and allowing better separation given a reflux ratio. A column with a high reflux ratio may have fewer stages, but it refluxes a large amount of liquid, giving a wide column with a large holdup. Conversely, a column with a low reflux ratio must have a large number of stages, thus requiring a taller column.

General improvements

Both batch and continuous distillations can be improved by making use of a fractionating column on top of the distillation flask. The column improves separation by providing a larger surface area for the vapor and condensate to come into contact. This helps it remain at equilibrium for as long as possible. The column can even consist of small subsystems ('trays' or 'dishes') which all contain an enriched, boiling liquid mixture, all with their own vapor-liquid equilibrium.

There are differences between laboratory-scale and industrial-scale fractionating columns, but the principles are the same. Examples of laboratory-scale fractionating columns (in increasing efficiency) include:

• Air condenser
• Vigreux column (usually laboratory scale only)
• Packed column (packed with glass beads, metal pieces, or other chemically inert material)
• Spinning band distillation system.

Laboratory scale distillation

Laboratory scale distillations are almost exclusively run as batch distillations. The device used in distillation, sometimes referred to as a still, consists at a minimum of a reboiler or pot in which the source material is heated, a condenser in which the heated vapour is cooled back to the liquid state, and a receiver in which the concentrated or purified liquid, called the distillate, is collected. Several laboratory scale techniques for distillation exist (see also distillation types).

Simple distillation

In simple distillation, all the hot vapors produced are immediately channeled into a condenser that cools and condenses the vapors. Therefore, the distillate will not be pure - its composition will be identical to the composition of the vapors at the given temperature and pressure, and can be computed from Raoult's law.

As a result, simple distillation is usually used only to separate liquids whose boiling points differ greatly (rule of thumb is 25 °C), or to separate liquids from involatile solids or oils. For these cases, the vapor pressures of the components are usually sufficiently different that Raoult's law may be neglected due to the insignificant contribution of the less volatile component. In this case, the distillate may be sufficiently pure for its intended purpose.

 Fractional distillation

For many cases, the boiling points of the components in the mixture will be sufficiently close that Raoult's law must be taken into consideration. Therefore, fractional distillation must be used in order to separate the components well by repeated vaporization-condensation cycles within a packed fractionating column. This separation, by successive distillations, is also referred to as rectification.

As the solution to be purified is heated, its vapors rise to the fractionating column. As it rises, it cools, condensing on the condenser walls and the surfaces of the packing material. Here, the condensate continues to be heated by the rising hot vapors; it vaporizes once more. However, the composition of the fresh vapors are determined once again by Raoult's law. Each vaporization-condensation cycle (called a theoretical plate) will yield a purer solution of the more volatile component. In reality, each cycle at a given temperature does not occur at exactly the same position in the fractionating column; theoretical plate is thus a concept rather than an accurate description.

More theoretical plates lead to better separations. A spinning band distillation system uses a spinning band of Teflon or metal to force the rising vapors into close contact with the descending condensate, increasing the number of theoretical plates.

Steam distillation

Main article: Steam distillation

Like vacuum distillation, steam distillation is a method for distilling compounds which are heat-sensitive. The temperature of the steam is easier to control than the surface of a heating element, and allows a high rate of heat transfer without heating at a very high temperature. This process involves bubbling steam through a heated mixture of the raw material. By Raoult's law, some of the target compound will vaporize (in accordance with its partial pressure). The vapor mixture is cooled and condensed, usually yielding a layer of oil and a layer of water.

Steam distillation of various aromatic herbs and flowers can result in two products; an essential oil as well as a watery herbal distillate. The essential oils are often used in perfumery and aromatherapy while the watery distillates have many applications in aromatherapy, food processing and skin care.

Dimethyl sulfoxide usually boils at 189 °C. Under a vacuum, it distills off into the receiver at only 70 °C.

Perkin triangle distillation setup
1: Stirrer bar/anti-bumping granules 2: Still pot 3: Fractionating column 4: Thermometer/Boiling point temperature 5: Teflon tap 1 6: Cold finger 7: Cooling water out 8: Cooling water in 9: Teflon tap 2 10: Vacuum/gas inlet 11: Teflon tap 3 12: Still receiver

Vacuum distillation

Some compounds have very high boiling points. To boil such compounds, it is often better to lower the pressure at which such compounds are boiled instead of increasing the temperature. Once the pressure is lowered to the vapor pressure of the compound (at the given temperature), boiling and the rest of the distillation process can commence. This technique is referred to as vacuum distillation and it is commonly found in the laboratory in the form of the rotary evaporator.

This technique is also very useful for compounds which boil beyond their decomposition temperature at atmospheric pressure and which would therefore be decomposed by any attempt to boil them under atmospheric pressure.

Molecular distillation is vacuum distillation below the pressure of 0.01 torr. 0.01 torr is one order of magnitude above high vacuum, where fluids are in the free molecular flow regime, i.e. the mean free path of molecules is comparable to the size of the equipment. The gaseous phase no longer exerts significant pressure on the substance to be evaporated, and consequently, rate of evaporation no longer depends on pressure. That is, because the continuum assumptions of fluid dynamics no longer apply, mass transport is governed by molecular dynamics rather than fluid dynamics. Thus, a short path between the hot surface and the cold surface is necessary, typically by suspending a hot plate covered with a film of feed next to a cold plate with a line of sight in between. Molecular distillation is used industrially for purification of oils.

Air-sensitive vacuum distillation

Some compounds have high boiling points as well as being air sensitive. A simple vacuum distillation system as exemplified above can be used, whereby the vacuum is replaced with an inert gas after the distillation is complete. However, this is a less satisfactory system if one desires to collect fractions under a reduced pressure. To do this a "cow" or "pig" adaptor can be added to the end of the condenser, or for better results or for very air sensitive compounds a Perkin triangle apparatus can be used.

The Perkin triangle, has means via a series of glass or Teflon taps to allows fractions to be isolated from the rest of the still, without the main body of the distillation being removed from either the vacuum or heat source, and thus can remain in a state of reflux. To do this, the sample is first isolated from the vacuum by means of the taps, the vacuum over the sample is then replaced with an inert gas (such as nitrogen or argon) and can then be stoppered and removed. A fresh collection vessel can then be added to the system, evacuated and linked back into the distillation system via the taps to collect a second fraction, and so on, until all fractions have been collected.

 Short path distillation

Short path vacuum distillation apparatus with vertical condenser (cold finger), to minimize the distillation path; 1: Still pot with stirrer bar/anti-bumping granules 2: Cold finger - bent to direct condensate 3: Cooling water out 4: cooling water in 5: Vacuum/gas inlet 6: Distillate flask/distillate.

Short path distillation is a distillation technique that involves the distillate travelling a short distance, often only a few centimeters, and is normally done at reduced pressure. A classic example would be a distillation involving the distillate travelling from one glass bulb to another, without the need for a condenser separating the two chambers. This technique is often used for compounds which are unstable at high temperatures or to purify small amounts of compound. The advantage is that the heating temperature can be considerably lower (at reduced pressure) than the boiling point of the liquid at standard pressure, and the distillate only has to travel a short distance before condensing. A short path ensures that little compound is lost on the sides of the apparatus. The Kugelrohr is a kind of a short path distillation apparatus which often contain multiple chambers to collect distillate fractions.

Other types

• The process of reactive distillation involves using the reaction vessel as the still. In this process, the product is usually significantly lower-boiling than its reactants. As the product is formed from the reactants, it is vaporized and removed from the reaction mixture. This technique is an example of a continuous vs. a batch process; advantages include less downtime to charge the reaction vessel with starting material, and less workup.
• Pervaporation is a method for the separation of mixtures of liquids by partial vaporization through a non-porous membrane.
• Extractive distillation is defined as distillation in the presence of a miscible, high boiling, relatively non-volatile component, the solvent, that forms no azeotrope with the other components in the mixture.
• Flash evaporation (or partial evaporation) is the partial vaporization that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. This process is one of the simplest unit operations, being equivalent to a distillation with only one equilibrium stage.
• Codistillation is distillation which is performed on mixtures in which the two compounds are not miscible.

The unit process of evaporation may also be called "distillation":

• In rotary evaporation a vacuum distillation apparatus is used to remove bulk solvents from a sample. Typically the vacuum is generated by a water aspirator or a membrane pump.
• In a kugelrohr a short path distillation apparatus is typically used (generally in combination with a (high) vacuum) to distill high boiling (> 300 °C) compounds. The apparatus consists of an oven in which the compound to be distilled is placed, a receiving portion which is outside of the oven, and a means of rotating the sample. The vacuum is normally generated by using a high vacuum pump.

Other uses:

• Dry distillation or destructive distillation, despite the name, is not truly distillation, but rather a chemical reaction known as pyrolysis in which solid substances are heated in an inert or reducing atmosphere and any volatile fractions, containing high-boiling liquids and products of pyrolysis, are collected. The destructive distillation of wood to give methanol is the root of its common name - wood alcohol.
• Freeze distillation is an analogous method of purification using freezing instead of evaporation. It is not truly distillation, but a recrystallization where the product is the mother liquor, and does not produce products equivalent to distillation. This process is used in the production of ice beer and ice wine to increase ethanol and sugar content, respectively. It is also used to produce applejack. Unlike distillation, freeze distillation concentrates poisonous congeners rather than removing them.

Azeotropic distillation

Main article: Azeotropic distillation

Interactions between the components of the solution create properties unique to the solution, as most processes entail nonideal mixtures, where Raoult's law does not hold. Such interactions can result in a constant-boiling azeotrope which behaves as if it were a pure compound (i.e., boils at a single temperature instead of a range). At an azeotrope, the solution contains the given component in the same proportion as the vapor, so that evaporation does not change the purity, and distillation does not effect separation. For example, ethyl alcohol and water form an azeotrope of 95.6% at 78.1 °C.

If the azeotrope is not considered sufficiently pure for use, there exist some techniques to break the azeotrope to give a pure distillate. This set of techniques are known as azeotropic distillation. Some techniques achieve this by "jumping" over the azeotropic composition (by adding an additional component to create a new azeotrope, or by varying the pressure). Others work by chemically or physically removing or sequestering the impurity. For example, to purify ethanol beyond 95%, a drying agent or a (desiccant such as potassium carbonate) can be added to convert the soluble water into insoluble water of crystallization. Molecular sieves are often used for this purpose as well.

Immiscible liquids, such as water and toluene, easily form azeotropes. Commonly, these azeotropes are referred to as a low boiling azeotrope because the boiling point of the azeotrope is lower than the boiling point of either pure component. The temperature and composition of the azeotrope is easily predicted from the vapor pressure of the pure components, without use of Raoult's law. The azeotrope is easily broken in a distillation set-up by using a liquid-liquid separator (a decanter) to separate the two liquid layers that are condensed overhead. Only one of the two liquid layers is refluxed to the distillation set-up.

High boiling azeotropes, such as a 20 weight percent mixture of hydrochloric acid in water, also exist. As implied by the name, the boiling point of the azeotrope is greater than the boiling point of either pure component.

To break azeotropic distillations and cross distillation boundaries, such as in the DeRosier Problem, it is necessary to increase the composition of the light key in the distillate.

Breaking an azeotrope with unidirectional pressure manipulation

The boiling points of components in an azeotrope overlap to form a band. By exposing an azeotrope to a vacuum or positive pressure, it's possible to bias the boiling point of one component away from the other by exploiting the differing vapour pressure curves of each; the curves may overlap at the azeotropic point, but are unlikely to be remain identical further along the pressure axis either side of the azeotropic point. When the bias is great enough, the two boiling points no longer overlap and so the azeotropic band disappears.

This method can remove the need to add other chemicals to a distillation, but it has two potential drawbacks.

Under negative pressure, power for a vacuum source is needed and the reduced boiling points of the distillates requires that the condenser be run cooler to prevent distillate vapours being lost to the vacuum source. Increased cooling demands will often require additional energy and possibly new equipment or a change of coolant.

Alternatively, if positive pressures are required, standard glassware can not be used, energy must be used for pressurization and there is a higher chance of side reactions occurring in the distillation, such as decomposition, due to the higher temperatures required to effect boiling.

A unidirectional distillation will rely on a pressure change in one direction, either positive or negative.

Pressure-swing distillation

 

Pressure-swing distillation is essentially the same as the unidirectional distillation used to break azeotropic mixtures, but here both positive and negative pressures may be employed.
This has an important impact on the selectivity of the distillation and allows a chemist to optimize a process such that fewer extremes of pressure and temperature are required and less energy is consumed. This is particularly important in commercial applications.
Pressure-swing distillation is employed during the industrial purification of ethyl acetate after its catalytic synthesis from ethanol.

Industrial distillation

Typical industrial distillation towers

Main article: Continuous distillation

Large scale industrial distillation applications include both batch and continuous fractional, vacuum, azeotropic, extractive, and steam distillation. The most widely used industrial applications of continuous, steady-state fractional distillation are in petroleum refineries, petrochemical and chemical plants and natural gas processing plants.
Industrial distillation is typically performed in large, vertical cylindrical columns known as distillation towers or distillation columns with diameters ranging from about 65 centimeters to 16 meters and heights ranging from about 6 meters to 90 meters or more. When the process feed has a diverse composition, as in distilling crude oil, liquid outlets at intervals up the column allow for the withdrawal of different fractions or products having different boiling points or boiling ranges. The "lightest" products (those with the lowest boiling point) exit from the top of the columns and the "heaviest" products (those with the highest boiling point) exit from the bottom of the column and are often called the bottoms.

Diagram of a typical industrial distillation tower

Industrial towers use reflux to achieve a more complete separation of products. Reflux refers to the portion of the condensed overhead liquid product from a distillation or fractionation tower that is returned to the upper part of the tower as shown in the schematic diagram of a typical, large-scale industrial distillation tower. Inside the tower, the downflowing reflux liquid provides cooling and condensation of the upflowing vapors thereby increasing the efficiency of the distillation tower. The more reflux that is provided for a given number of theoretical plates, the better the tower's separation of lower boiling materials from higher boiling materials. Alternatively, the more reflux that is provided for a given desired separation, the fewer the number of theoretical plates required.
Such industrial fractionating towers are also used in air separation, producing liquid oxygen, liquid nitrogen, and high purity argon. Distillation of chlorosilanes also enables the production of high-purity silicon for use as a semiconductor.

Section of an industrial distillation tower showing detail of trays with bubble caps

Design and operation of a distillation tower depends on the feed and desired products. Given a simple, binary component feed, analytical methods such as the McCabe-Thiele method or the Fenske equation can be used. For a multi-component feed, simulation models are used both for design and operation. Moreover, the efficiencies of the vapor-liquid contact devices (referred to as "plates" or "trays") used in distillation towers are typically lower than that of a theoretical 100% efficient equilibrium stage. Hence, a distillation tower needs more trays than the number of theoretical vapor-liquid equilibrium stages.
In modern industrial uses, generally a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum.

Large-scale, industrial vacuum distillation column

This packing material can either be random dumped packing (1-3" wide) such as Raschig rings or structured sheet metal. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Unlike conventional tray distillation in which every tray represents a separate point of vapor-liquid equilibrium, the vapor-liquid equilibrium curve in a packed column is continuous. However, when modeling packed columns, it is useful to compute a number of "theoretical stages" to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance.
Another factor in addition to the packing shape and surface area that affects the performance of random or structured packing is the liquid and vapor distribution entering the packed bed. The number of theoretical stages required to make a given separation is calculated using a specific vapor to liquid ratio. If the liquid and vapor are not evenly distributed across the superficial tower area as it enters the packed bed, the liquid to vapor ratio will not be correct in the packed bed and the required separation will not be achieved. The packing will appear to not be working properly. The height equivalent of a theoretical plate (HETP) will be greater than expected. The problem is not the packing itself but the mal-distribution of the fluids entering the packed bed. Liquid mal-distribution is more frequently the problem than vapor. The design of the liquid distributors used to introduce the feed and reflux to a packed bed is critical to making the packing perform to it maximum efficiency. Methods of evaluating the effectiveness of a liquid distributor to evenly distribute the liquid entering a packed bed can be found in references. Considerable work as been done on this topic by Fractionation Research, Inc. (commonly known as FRI).

Multi-effect distillation

The goal of multi-effect distillation is to increase the energy efficiency of the process, for use in desalination, or in some cases one stage in the production of ultrapure water. The number of effects is proportional to the kW·h/m³ of water recovered figure, and refers to the volume of water recovered per unit of energy compared with single-effect distillation. One effect is roughly 636 kW·h/m³.

• Multi-stage flash distillation Can achieve more than 20 effects with thermal energy input, as mentioned in the article.

• Vapor compression evaporation Commercial large-scale units can achieve around 72 effects with electrical energy input, according to manufacturers.

There are many other types of multi-effect distillation processes, including one referred to as simply multi-effect distillation (MED), in which multiple chambers, with intervening heat exchangers, are employed.

Distillation in food processing

Distilled beverages

Main article: Distilled beverage

Carbohydrate-containing plant materials are allowed to ferment, producing a dilute solution of ethanol in the process. Spirits such as whiskey and rum are prepared by distilling these dilute solutions of ethanol. Components other than ethanol, including water, esters, and other alcohols, are collected in the condensate, which account for the flavor of the beverage.