(1) chlorohydrin method
Chlorohydrin method has a long history and has been industrialized for more than 60 years, represented by the chlorohydrin method of Dow Chemical Company in the United States. The main technological processes of propylene chlorohydrination, lime milk saponification and product refining have the characteristics of mature production process, high flexibility of operation load, good selectivity and low requirement on the purity of raw propylene, which improves the safety of production and reduces the construction investment. Because of less investment in fixed assets and lower product cost, its products have strong cost competitiveness. At present, about 40% of the world's propylene oxide production capacity is chlorohydrin process. The disadvantage of chlorohydrination method is that it consumes a lot of water resources and produces a lot of wastewater and waste residue. Every time 1t propylene oxide is produced, 40~50t chlorine-containing saponified wastewater and more than 2t waste residue are produced. This kind of wastewater has the characteristics of high temperature, high pH value, high chloride content, high COD content and high suspended solids content, and it is difficult to treat. At the same time, chlorohydrination also consumes a lot of chlorine and lime raw materials with high energy consumption, while chlorine and calcium are discharged into wastewater and waste residue, and hypochlorous acid produced in the production process also seriously corrodes the equipment. The production of propylene oxide in China began in the 1960s, and the chlorohydrin process route was developed independently. In the late 1980s and early 1990s, China introduced chlorohydrination technology from Asahi Glass Company, Mitsui East Asia Company, Showa Electric Company and Dow Company. After the propylene oxide plants of Jinhua Chemical Company, Shandong Hua Bin Company, Sinopec Shanghai Gao Qiao Petrochemical Company and Tianjin Dagu Chemical Company were put into operation, good economic benefits were achieved and the production level was greatly improved. At present, except for CNOOC Shell's 250,000 t/a propylene oxide plant, 80% of China's existing propylene oxide production capacity adopts chlorohydrin method.
(2) Oxidation method
* * * oxidation method, also known as Haakon method, includes isobutane oxidation method and ethylbenzene oxidation method. Isobutane or ethylbenzene and propylene respectively undergo * * * oxidation reaction to generate tert-butyl alcohol or styrene and co-produce propylene oxide. * * * The oxidation method was developed by Oakland Company of the United States and is now owned by Leandre Company of the United States. * * * oxidation method overcomes the disadvantages of large corrosion and much sewage of chlorohydrin method, and has the advantages of low product cost (joint product sharing cost) and little environmental pollution. Since the industrialization of 1969, it has developed rapidly in the world. At present, the production capacity of propylene oxide by oxidation method accounts for about 55% of the world's total production capacity. The disadvantages of * * * oxidation method are long process flow, many kinds of raw materials, high requirements for propylene purity, high process operation pressure, high equipment cost and large construction investment. At the same time, in the production of propylene oxide by * * * oxidation method, there are only/kloc-0 by-products, and the output is small, with 2.2~2.5t styrene or 2.3t tert-butyl alcohol as by-products per ton of propylene oxide. The source of raw materials and the sales of products have great mutual constraints and must be properly solved. Only when the market demand of propylene oxide and by-products matches, the advantages of this process can be shown. In addition, the sewage produced by * * * oxidation method also contains high COD, and the treatment cost accounts for about 65,438+00% of the total investment. China has always used chlorohydrin method to produce propylene oxide. In March 2006, with the commissioning of China Shipping Shell's propylene oxide plant with an annual output of 250,000 tons, the production pattern of propylene oxide has changed to some extent. At present, China Shipping Shell Project is the largest 1 propylene oxide plant in China, and it is also the only propylene oxide plant that adopts propylene oxide/styrene oxidation co-production process. It is estimated that by the end of 2009, the 280,000-ton/year propylene oxide production plant jointly built by leander and Sinopec in Zhenhai will be completed and put into operation.
(3) cumene oxidation method
The cumene oxidation method was developed by Sumitomo Chemical Company of Japan. A titanium-based catalyst is used in a fixed bed reactor. Using cumene hydroperoxide (CHP) as oxidant, propylene was epoxidized by CHP to obtain propylene oxide and dimethyl benzyl alcohol. The latter was dehydrated to produce α -methylstyrene, and then hydrogenated to produce cumene, which was oxidized to produce CHP for recycling. In fact, cumene oxidation method is an improvement of * * * oxidation method 1. The main difference between cumene oxidation method and * * * oxidation method is that cumene is used instead of ethylbenzene, and cumene can be recycled without producing by-products. Because this process does not need the auxiliary equipment for co-production of styrene, the investment cost of the device is about 1/3 lower than that of the oxidation method, and it does not need the anti-corrosion equipment required by the chlorohydrination process of chlorine gas. In May 2003, Sumitomo Chemical Company invested US$ 654.38 billion to build a 200,000-ton/year propylene oxide plant in Chiba, Japan, and adopted its unique cumene oxidation process. In addition, Sumitomo's joint venture with SaudiAramco, Saudi Arabia, will also use Sumitomo's cumene oxidation technology to build a 200,000-ton/year propylene oxide plant.
(4) Direct oxidation of hydrogen peroxide (HPPO method)
The real contact oxidation of hydrogen peroxide is a new process of propylene epoxidation to propylene oxide catalyzed by hydrogen peroxide. In the production process, only propylene oxide and water are produced. Simple technological process, high product yield, no other by-products and basically no pollution. Belonging to an environment-friendly cleaner production system. At present, the real hydrogen peroxide oxidation process is jointly developed and industrialized by Evonik Industrial Group (formerly Degussa), Uhde, Dow Chemical and BASF. In 200 1 year, Evonik Industries Group and Wood Company built 1 set of hydrogen peroxide experimental device in Frankfurt, Germany, to test the best catalyst and determine the critical parameters, and started industrial design technology. In 2003, Evonik introduced the commercial process package of this technology. In May, 2006, SKC Company, a South Korean manufacturer of propylene oxide and polyester film, purchased the patents of Evonik and Wood, and began to build a global 1 hydrogen peroxide propylene oxide plant in Ulsan, South Korea. The production scale of the plant is 654.38+10,000 t/a, which was completed and put into operation in July 2008, and the production runs well. Evonik Industries Group is negotiating with Sibur, a subsidiary of Gazprom, a Russian gas oligarch, to establish a joint production plant of hydrogen peroxide and propylene oxide in Russia. 200 1 Dow Chemical purchased the laboratory technology of producing propylene oxide with hydrogen peroxide as oxidant from EniChem Company, including the Italian 1 experimental device. In 2003, Dow Chemical and BASF began to cooperate to develop and commercialize hydrogen peroxide technology. In 2006, Dow Chemical and BASF announced that they would jointly build a 300,000-ton/year propylene peroxide plant in Antwerp, Belgium, which is scheduled to be completed and put into operation in early 2009. In June 2008, SCG-DOW Group, a joint venture between Dow Chemical and Siam Cement Group (SCG) of Thailand, started the propylene oxide plant in Thailand, using the hydrogen peroxide process jointly developed by Dow and BASF, with a production capacity of 390,000 t/a, and the project is expected to be put into production at 201. Dow Chemical also plans to start construction of a 380,000 t/a hydrogen peroxide propylene oxide project in Switzerland on 20 10. China Dalian Institute of Chemical Physics is also engaged in the research of hydrogen peroxide technology. In 2002, Dalian Institute of Chemical Technology signed a pilot cooperation contract with Sinopec. In the first half of 2005, Dalian Institute of Chemical Technology passed the technical appraisal organized by Sinopec. In August 2008, the technology of producing propylene oxide by direct oxidation of propylene with hydrogen peroxide developed by Dalian Institute of Chemical Technology passed the appraisal organized by Liaoning Science and Technology Department.
(5) oxygen direct oxidation method
Lyondell is developing a direct oxidation technology to convert propylene, hydrogen and oxygen into propylene oxide. It uses 1 bifunctional catalyst composed of palladium and titanosilicate to generate hydrogen peroxide from hydrogen and oxygen, and immediately converts propylene into propylene oxide. The whole process is completed in 1 reactor. The company set up 1 set of experimental devices in the United States, further pushing this process to industrialization. At present, the process is still in the experimental stage.