Epichlorohydrin production adds a new green path
Latest News: On July 29, the 80,000-ton/year propylene-propylene-method epichlorohydrin (ECH) process package jointly developed by Shandong Kaitai Technology Co., Ltd. and Dalian Institute of Chemical Physics, Chinese Academy of Sciences Passed the expert review organized by China Petroleum and Chemical Industry Federation. The process package combines the advantages of the two ECH processes of hydrogen peroxide oxidation and glycerol, and realizes the resource utilization of waste hydrochloric acid through technical coupling, thereby solving the problem of severely restricting the production balance due to a large number of by-product acids, and improving the economic and environmental protection of the device. benefit. The expert group believes that this process provides a new technical path for the green development of epichlorohydrin products.
According to Meng Fanxin, deputy general manager of Kaitai Technology, the hydrogen peroxide oxidation process is an ECH green synthesis process developed by Dalian Chemical. The production process of raw material chloropropene produces hydrogen chloride by-product; while the glycerol method is another green process for the current production of ECH. The production process Just need hydrogen chloride. The propylene-propylene-method ECH process cleverly uses the hydrogen chloride by-product of synthesizing propylene chloride in the hydrogen peroxide oxidation process as the combination point of the two processes. The whole process uses propylene and glycerol (glycerol) as the main raw materials, and hydrogen peroxide oxidation as the main raw material. The core process uses the hydrogen chloride by-product of propylene chloride as the raw material of the glycerol process to couple it technically, and realize the resource utilization of high-salt wastewater and waste hydrochloric acid while producing ECH. “Based on this, we have innovatively developed an 80,000-ton/year propylene-propylene process epichlorohydrin process package, including two sets of 50,000-ton/year hydrogen peroxide oxidation method and 30,000-ton/year glycerin method.” Meng Fanxin said.
The C-C process package has carried out a number of improvements and innovations in related process technologies and key equipment.
“On the basis of the pilot test results of the 5,000-ton/year hydrogen peroxide oxidation process, we have further optimized, improved and engineered it together with engineers and technicians, and completed the development of a 50,000-ton/year DECH process package.” Dalian Chemical Researcher Gao Shuang said.
The new plant of allyl chloride adopts each 25,000 tons/year high-temperature chlorination reactor, which improves the production capacity of a single chlorination reactor and reduces the investment cost. The hydrogen peroxide oxidation process adopts a two-stage tubular reactor and a one-stage tank reactor, which increases the safety of the reaction process and is beneficial to the crystallization and separation of the catalyst; the glycerol method reactor adopts a mixing reactor without mechanical stirring to avoid leakage , reducing power consumption. At the same time, the high-salt wastewater in the C-C process can be used as the raw material for the production of ion-exchange membrane caustic soda after treatment.
“The C-C method solves the problem of by-producing a large amount of hydrochloric acid from allyl chloride, realizes the recycling of chlorine, sodium and hydrogen, and also combines the ECH refining process of the oxidation method and the glycerol method. The crude ECH produced by the two methods can be combined. Refining, which reduces the footprint of the device, and further reduces investment and energy consumption. In addition, the project construction and operation mode of this process is also more flexible, and it can be expanded to the upstream hydrogen peroxide device, caustic soda device and downstream of the industrial chain according to demand. Oxygen resin plant can also flexibly adjust the production scale of the two processes according to the supply of raw materials and market prices to maximize profits.” said Gao Zhengning, deputy chief engineer of Kaitai Technology.
According to the reporter’s understanding, the chlorohydrin process commonly used in domestic ECH production has been listed as restricted in the “Industrial Structure Adjustment Guidance Catalogue (2019)” due to the problems of high energy consumption, many by-products, and difficulty in the treatment of salt-containing organic wastewater. The technology of synthesizing ECH by direct oxidation of chloropropene is listed as a major key core technology in the industry’s “13th Five-Year Plan” to speed up the research and development of the organization. The research and development of the C-C process conforms to the policy requirements and conforms to the industry’s development trend of energy saving, pollution reduction and carbon reduction. .
Link: Main production process of epichlorohydrin
Epichlorohydrin (ECH) is an important raw material for the production of various downstream products such as epoxy resin and chlorohydrin rubber. At present, there are four main processes for producing ECH, namely chlorohydrin method, propylene acetate method, glycerol method, direct oxidation Law.
Chlorohydrin method: Using propylene and chlorine as raw materials, it has the characteristics of flexible production process, mature technology and stable operation. The disadvantages are many by-products, high energy consumption, low yield, large amount of sewage containing calcium chloride and organic matter (40-50 tons/ton of product), high treatment costs, and serious equipment corrosion. This process has been included in the list of restricted categories in the Industrial Structure Adjustment Catalogue.
Propylene acetate method: using propylene, chlorine and calcium hydroxide as raw materials, the advantages are mild reaction conditions, less by-products, and less waste water than the chlorohydrin method (about 11 tons/ton of product). The disadvantage is that there are many varieties of raw materials, long process flow, short catalyst life, high requirements for equipment corrosion resistance, and large project investment. This process is currently obsolete.
Glycerol method: Using glycerol, hydrogen hydride and sodium hydroxide as raw materials, mild operating conditions, low investment, low cost, relatively less “three wastes” discharge, and wastewater volume of 3-4 tons per ton of product. The disadvantage is that the market price of raw glycerin fluctuates greatly and cannot be supplied stably. This process is a green process.
Direct oxidation method: using propylene, chlorine and hydrogen peroxide as raw materials, the amount of waste water is small (about 0.64 tons/ton of product), and the process has not yet been industrialized. This process is a green process.