Propylene oxide technology progress and capacity distribution

Propylene oxide (PO) producers and capacity distribution

Propylene oxide (PO) is the third largest propylene derivative besides polypropylene and acrylonitrile, and it is also an important basic chemical raw material. The downstream is mainly used to produce polyether polyols, etc. The end point is polyurethane soft foam and hard foam. It is widely used in automotive, building energy conservation, refrigerator freezers, food tobacco, medicine and cosmetics.

I. Propylene oxide production enterprises and capacity distribution

By the end of 2015, there were 22 domestic PO production enterprises with a total capacity of 3.19 million tons/year. The production enterprises and capacity distribution are shown in the table below.

POS production enterprises and capacity distribution in our country (10,000 tons/year)

II. Current status of propylene oxide (PO) production technology

At present, the methods for industrialized production of PO abroad are: chlorine alcoholization, co-oxidation and direct oxidation of hydrogen peroxide. The co-oxidation method is divided into ethylbenzene co-oxidation and isobutane co-oxidation. Direct oxidation with oxygen as an oxidant is also being developed.

1. Chlorohydrin method

Process principle of chlorohydrin method: Propylene and chlorine are used as raw materials. First, chlorohydrin is produced after chlorohydrin reaction, and then chlorohydrin is saponified to produce propylene oxide. Finally, the product of propylene oxide is obtained after being stationary. The technical core of chlorohydrin production of PO is chlorohydrin reactor technology. At present, the representative reactor technology in the world is the tubular reactor technology of Dow Chemical (Dow) in the United States, the tubular tower reactor technology of Asahi Nitrate Company in Japan, and the tower reactor technology of Mitsui Dongping Company and Showa Denko Company. In the late 1980s, our country's Jinhua, Binhua, Dagu and other manufacturers successively introduced the chlorohydrin production process and achieved good economic benefits.

In 2000, the United States eliminated the chlorohydrin process due to the serious environmental pollution caused by the traditional chlorohydrin production of propylene oxide. In our country, the chlorohydrin process was also included in the restricted items of the "Industrial Structure Adjustment Guidance Catalog 2011". The new projects mainly consider co-oxidation and direct oxidation.

2. Co-oxidation

The patent holders of PO/SM technology include Lyondell, Shell and Repsol, Lyondellhe and Shell, and their main differences are in the epoxidation reaction catalyst. Lyondell uses molybdenum complex solution as the catalyst, which needs to be processed and recycled after the reaction; Shell uses TiO2/SiO2 as the catalyst, which avoids the disadvantage of the catalyst entering the reaction product and simplifies the separation process. However, due to the difficulty of heat transfer in the heterogeneous reaction system, the reactor structure is complicated and the investment is increased. And the selective Shell method is 98.18%, and the Lyondellhe method is 87.14%. Foreign countries prefer Shell technology. The only patent holders of PO/TBA technology are Texaco and Huntsman. The difference is mainly in the use of catalysts, the separation of products and the purification unit of PO.

In 2006, CNOOC and Shell built a 250,000-ton/year propylene oxide plant in Guangdong using Shell technology, breaking the pattern of our country's propylene oxide production relying solely on the chlorine alcohol process. In 2010, Sinopec Zhenhai Refining and Lyondell Basell jointly built a 285,000-ton/year PO/SM plant, which is currently the largest PO/SM production plant in the world. Huntsman has successively established a joint venture with Yantai Wanhua Chemical and Sinopec Group Jinling Branch. Using the self-developed isobutane co-oxidation technology, they built a 240,000-ton/year PO/TBA plant in Jiangsu and Shandong respectively, which is expected to be put into operation in 2015. The commissioning of the co-oxidation PO plant has greatly reduced the production capacity ratio of the chlorine alcohol process.

3. Direct oxidation

The basic production principle of hydrogen peroxide direct oxidation is a process in which propylene and hydrogen peroxide (H2O2) are directly oxidized in a fixed bed reactor under relatively mild conditions in a methanol/water mixture using a special titanium-silicon catalyst (TS-1).

1) HPPO technology from Degussa-Uhde and Dow-BASF

At present, the foreign HPPO process is jointly developed and industrialized by Evonik Industrial Group (Degussa) and Wood (Uhde), Dow Chemical (Dow) and BASF (BASF). In July 2008, South Korea's SKC company adopted the HPPO technology developed by Degussa and Uhde, and applied the HPPO production process to commercial production for the first time in the world. The production scale of the device is 100,000 tons/year. In 2011, Shenhua Group introduced the HPPO technology of Degussa and Uhde, invested 2.50 billion yuan, and built the first and largest HPPO device in Jilin, with an annual design capacity of 300,000 tons. It was put into operation in July 2014. BASF and Dow have built the first commercial-scale HPPO plant in Belgium using self-developed hydrogen peroxide to propylene oxide technology. The annual design and production of 300,000 tons was put into operation at the end of 2008, which significantly reduced wastewater discharge and energy consumption. In September 2011, Dow and SC Group jointly built a 390,000-ton/year HPPO plant in Thailand.

2) Sinopec HPPO Technology

Sinopec Petrochemical Institute, Sinopec Changling Branch and Hunan Changling Petrochemical Technology Development Co., Ltd. have jointly developed the technology of propylene and hydrogen peroxide epoxidation to synthesize propylene oxide catalyzed by titanium silicon molecular sieve. On the basis of laboratory research, small-scale test and side-line test, a pilot plant for the preparation of propylene oxide by epoxidation of propylene and hydrogen peroxide was established at 1.0 kt/a, and the conditions were investigated and tested. After two years of operation, all technical indicators met the requirements of pollution-free green production, and some indicators were better than similar foreign processes. In 2012, the technology was reviewed and approved by Sinopec Corporation. In January 2013, Sinopec invested about 1.28 billion yuan to build a 100 kt/a industrial plant in Changling Refining Chemical Co., Ltd. using the domestic self-developed and fully intellectual property rights technology of hydrogen peroxide to propylene oxide.

On July 25, 2014, the plant was completed in CCCC, and the commissioning was successful on December 6 of the same year. The successful development of this environmentally friendly clean production process will enable the hydrogen peroxide process (HPPO process) to replace the chlorohydrin-based propylene oxide process that is still widely used in China, with serious environmental pollution and outdated technology. It will have a positive impact on the market, economy, ecological environment and society. It was listed as one of the top ten scientific and technological achievements in global energy conservation and emission reduction in 2014. At the same time, it also marks that Sinopec has become the third patent holder in the world to own the technology of hydrogen peroxide to propylene oxide, breaking the monopoly of foreign countries on this technology.

3) HPPO Technology of East China University of Science and Technology

East China University of Science and Technology in the laboratory test and single tube test on the basis of 2007 and Tianjin Dagu Chemical joint stock company cooperation built the first set of non-pollutant emission of propylene deteriorated hydrogen peroxide direct epoxidation of propylene oxide to propylene oxide industrial test device, the design scale of 1.50 kt/a, using TS-1 molecular sieve catalyst, to investigate the operation of the device and product properties. The results show that the conversion rate of hydrogen peroxide in the epoxidation reaction reaches 90% to 96%, the selectivity of propylene oxide reaches 90% to 92%, and the production capacity reaches the design requirements of 1.50 kt/a. After distillation and purification, the properties of the product meet the requirements of high-quality products, and the clean production of propylene oxide is realized. Provide design basis and reference for the 10,000-ton propylene direct epoxidation plant to produce propylene oxide.

4) HPPO Technology of Dalian Institute of Chemicals, Chinese Academy of Sciences

The "Experimental Study on Reaction-Controlled Phase Transfer Catalytic Oxidation of Propylene to PO" undertaken by Chinese Academy of Sciences Dalian Chemicals passed the technical appraisal organized by Sinopec Group in 2005. The third-generation reaction-controlled phase transfer quaternary ammonium phosphotungstate salt catalyst was used in the small test. The H2O2 produced in situ by the anthraquinone method was used as an oxidizing agent. Under the reaction conditions of 70 ℃, pressure less than 0.3 MPa, and the molar ratio of propylene to H2O2 was 3:1, the catalytic epoxidation of propylene to PO was carried out. The PO yield was not less than 86% (calculated as H2O2), the selectivity of PO was greater than 94% (calculated as propylene), and the mass collection rate of the catalyst was greater than 93%. The third-generation reaction-controlled phase transfer phosphotungstic acid quaternary ammonium salt catalyst can be recycled many times. In August 2008, it passed the appraisal organized by the Liaoning Provincial Department of Science and Technology, achieving the goal of environmentally friendly propylene oxide process route, and is expected to be industrialized in China in the next few years.

Conclusion

Compared with the chlorohydrin process and the co-oxidation process, the HPPO process is short, less investment, low energy consumption, no by-products, no pollutant emissions, clean and environmentally friendly, good product distribution selectivity, and high conversion rate. It is the future development direction of the industry. Due to the serious environmental pollution caused by the chlorohydrin process, the new chlorohydrin production capacity is restricted by policies and environmental regulations. The "Industrial Structure Adjustment Guidance Catalogue 2011" points out that "new chlorohydrin-based propylene oxide and saponified propylene oxide production plants are restricted below 1 million tons/year. In principle, new chlorohydrin-based projects will not be approved in the future, and direct oxidation of propylene oxide above 150,000 tons and co-oxidation of propylene oxide above 200,000 tons will be encouraged."