Process for preparing hexahydrophthalic anhydride (HHPA) by means of catalytic hydrogenation

Abstract

The invention discloses a process for preparing hexahydrophthalic anhydride (HHPA) by means of catalytic hydrogenation. The process includes preparing Pd-NiO / SiO2 catalysts by the aid of impregnation processes by SiO2 used as a carrier; catalytically hydrogenating tetrahydrophthalic anhydride in a trickle-bed reactor to prepare the hexahydrophthalic anhydride (HHPA). The process has the advantages that the optimal reaction conditions and process parameters are explored; the SiO2-supported Pd and Ni binary-metal catalysts are adopted, the activity of the catalysts is appropriately deteriorated, the hydrogen partial pressures are increased, and accordingly the selectivity of the hexahydrophthalic anhydride (HHPA) which is a target product can be effectively improved; hydrogen can flow into the trickle-bed reactor from an upper location, a middle location and a lower location, accordingly, reaction layout is uniform and controllable, and side reaction can be reduced; heat generating reaction is carried out during catalyst hydrogenation, the internal circulation speed of the hydrogen in the reactor can be increased, the hydrogen is used as a heat transfer medium, accordingly, reaction heat can be timely transferred, local overheating phenomena can be effectively prevented, and the side reaction can be reduced.

Description

technical field [0001] The invention relates to a process for preparing hexahydrophthalic anhydride (HHPA) by catalytic hydrogenation, specifically referring to the catalyst Pd-NiO / SiO 2 The preparation and the process of preparing hexahydrophthalic anhydride (HHPA) through catalytic hydrogenation belong to the field of chemistry. Background technique [0002] The full name of hexahydrophthalic anhydride is hexahydrophthalic anhydride, the English abbreviation is HHPA, and the molecular formula is C 8 h 10 o 3 , relative molecular weight 154.2, relative density 1.2, easily soluble in tetrahydrofuran, benzene, toluene, xylene and other solvents. [0003] Hexahydrophthalic anhydride (HHPA), as the basic raw material of high-grade polyester coatings, has excellent product performance, such as strong adaptability, low viscosity, obvious improvement in brightness and gloss, especially can greatly improve the weather resistance of coatings, and the product quality is obvious i...

AI Technical Summary

Problems solved by technology

[0004] As an epoxy resin curing agent, hexahydrophthalic anhydride (HHPA) is widely used in semiconductor molding compounds and potting compounds. With the rapid development of the information industry, the demand for epoxy resin curing agents has increased rapidly, increasing the demand for hexahydrophthalic anhydride ( HHPA) market demand, only some enterprises in my country produce in small batches, which is far from meeting the market demand at home and abroad. The establishment of large-scale industrial production of hexahydrophthalic anhydride (HHPA) has broad development prospects

During the hydrogenation process of tetrahydrophthalic anhydride, because the double bond is easily activated, the double bond is easily transferred, resulting in incomplete hydrogenation. Under the attack of hydrogen atoms, the acid anhydride is more likely to undergo side reactions such as condensation, hydrogenolysis, and crosslinking. , produce difficult-to-separate products, which affect the selectivity and yield of the reaction, and high-boiling point products are also easy to coke at high temperatures, resulting in attachment to the surface of the catalyst, causing the catalyst to be poisoned and lose its activity

[0006] Traditional tetrahydrophthalic anhydride to hexahydrophthalic anhydride (HHPA) catalysts usually use combined Pd / C, Pd / Al supported by different carriers 2 o 3 , Pd / Fe 2 o 3 , Pd / BaSO 4 , Pd / K 2 SO 4 , the catalytic hydrogenation activity of Pd series catalyst is very good, but the price is expensive, can produce by-product such as trans-hexahydrophthalide and trans-4-cyclohexene-1,2-dicarboxylic acid, directly affects hexahydrophthalic anhydride ( HHPA) purity and selectivity

In particular, the boiling points of trans-hexahydrophthalide and hexahydrophthalic anhydride (HHPA) are very close, and it is very difficult to completely separate them, which eventually leads to a relatively small purity of hexahydrophthalic anhydride (HHPA), which greatly affects the scope of use and added value.

Images