A method for direct hydrogenation of maleic anhydride to produce 1,4-butanediol and co-produce succinic anhydride

A method for direct hydrogenation of maleic anhydride to produce 1,4-butanediol and co-produce succinic anhydride, which is characterized by:

• maleic anhydride is hydrogenated in two steps to obtain products of 1,4-butanediol and succinic anhydride;
• the method includes the following steps:
• a. hydrogenating maleic anhydride:
• the liquid-phase maleic anhydride and the γ-butyrolactone from the subsequent separation unit are mixed and heated by a feeding heater and then enter the top of a gasification tower, fresh hydrogen and circulated hydrogen are mixed and heated and then enter the bottom of the gasification tower, the maleic anhydride is gasified in the gasification tower, a gas-phase material at the top of the tower is heated by the discharge material produced from the maleic anhydride hydrogenation reaction and then enters the maleic anhydride hydrogenation reactor, a small part of the material at the bottom of the gasification tower is separated and sent to the heavy oil tank in the intermediate tank area, and the rest is returned to the gasification tower after being heated;
• in the maleic anhydride hydrogenation reactor, maleic anhydride and hydrogen react under the action of a hydrogenation catalyst to generate γ-butyrolactone, succinic anhydride, tetrahydrofuran, and water, meanwhile the succinic anhydride is hydrogenated to generate γ-butyrolactone, and a small amount of succinic anhydride is hydrated to form succinic acid, the hydrogenation product is cooled step by step to realize gas-liquid separation, the gas-phase hydrogenation product enters the circulating hydrogen compressor after cooling and returns to hydrogen heater of the maleic anhydride gasification unit, and the liquid-phase product is separated in the subsequent succinic anhydride product refining unit;
• b. refining the succinic anhydride products:
• which involves stabilization tower, dehydration tower, light removal tower and weight removal tower;
• firstly, maleic anhydride reaction solution enters the stabilization tower, water, n-butanol, tetrahydrofuran, and the like separated from the top of the stabilization tower enter the dehydrating tower, the process wastewater containing a small amount of n-butanol and tetrahydrofuran is separated from the top of the dehydrating tower and sent to the outside for water treatment;
• γ-butyrolactone and a small amount of succinic acid at the bottom of the dehydration tower are returned to the stabilization tower, and the products at the bottom of the stabilization tower are γ-butyrolactone, succinic anhydride, and succinic acid, which are pumped to the light removal tower;
• the non-condensed gas product cooled at the top of the light removal tower is sent to the dehydration tower for separation, and the liquid-phase product at the top of the tower is divided into three parts after being cooled, one part is recycled to the maleic anhydride hydrogenation unit as solvent, one part is sent to the tank area as the product, and the rest part enters the γ-butyrolactone hydrogenation unit;
• the dehydration reaction of succinic acid in the light removal tower generates succinic anhydride;
• and the crude succinic anhydride at the bottom of the tower is pumped to the weight removal tower for further separation;
• the succinic anhydride product is obtained by separation at the top of the weight removal tower, then it is pumped to a product tank of succinic anhydride at the tank area, heavy oil is obtained at the bottom of the weight removal tower, and is pumped to the heavy oil storage tank in the tank area;
• c. hydrogenating γ-butyrolactone:
• γ-butyrolactone (GBL) generated from the succinic anhydride product refining unit is mixed with the GBL returned from the subsequent 1,4-butanediol refining unit, and then is pumped and heated into the GBL hydrogenation reactor to react with fresh hydrogen supplied from the outside and circulated hydrogen from the GBL hydrogenation reaction, to generate 1,4-butanediol, as well as a small amount of tetrahydrofuran, n-butanol, and acetal;
• after being cooled step by step, the reaction product is separated into gas and liquid, the gas-phase product returns to the reactor after being pressurized by the recycling hydrogen compressor, and the liquid-phase product enters the subsequent 1,4-butanediol product refining unit;
• d. refining 1,4-butanediol product:
• the liquid-phase product of GBL hydrogenation product is transported to GBL recovery tower through pipeline after cooling, the GBL is transported by pump to the γ-butyrolactone hydrogenation unit for following reactions after the product at the top of the tower is cooled, the non-condensed gas at the top of the tower is further cryogenically separated, and the water and light components are sent to the outside for water treatment;
• the material at the bottom of the tower is pumped to the BDO product tower, the BDO product is produced at the top of the BDO product tower, and is pumped to the product tank at the tank area;
• acetal and other heavy components are produced at the bottom of the BDO product tower, and are pumped to the tank area for storage.