Study On Pore Structure Control And Molding Of Dimethyl Adipate Hydrogenation Catalyst

1,6-Hexanediol is a widely used chemical raw material.The copper-based catalyst for the preparation of 1,6-hexanediol by hydrogenation of dimethyl adipate developed in the early stage of our research group.In the process of molding and application,it was found that internal diffusion has a significant effect on the performance of the pellet catalyst.In this paper,the catalyst pore size is adjusted by changing the preparation process in order to reduce the influence of internal diffusion;the activity and stability of the catalyst after molding are investigated to provide a basic basis for its industrial application.This article first investigated the effects of four single precipitants and four mixed precipitants on the pore structure and activity of the catalyst.The results show that the specific surface area,pore volume and average pore diameter of the CZA（Na HCO₃）catalyst prepared with Na HCO₃ as the precipitant are relatively large,which are 99.85 m²/g,0.60 cm³/g and 25.85 nm,respectively.The catalyst has a smaller copper particle size,a higher copper dispersion,and a higher catalytic activity.For the CZA（Na HCO₃）catalyst,the effects of the temperature at the high temperature section and the calcination time on the pore structure of the catalyst during the calcination process were further investigated.The results show that the average pore diameter of the CZA（Na HCO₃）catalyst obtained at the high temperature section of the calcination process at 510℃and kept for 20 min is increased to 27.61 nm.Based on the above research results,the CZA（Na HCO3）catalyst was pelletized and molded by the mold compression molding method and the spherical granulation method to obtain cylindrical and spherical pellet catalysts of different sizes.A high pressure fixed bed reactor HP-FBR-（1×70）（inner diameter of reaction tube×length of reaction tube,cm）was used to investigate the activity and stability of the catalyst after molding.The characterization results show that the average pore diameter of the catalyst is reduced to a certain extent after granulation and molding,and the overall decrease of the average pore diameter of the spherical catalyst is relatively small.The evaluation results show that the catalytic activity of the cylindrical pellet catalyst decreases with the extension of the reaction time,the influence of internal diffusion in the reaction is more serious,and the accumulation of high-boiling substances in the catalyst pores.The overall stability of the spherical pellet catalyst is better than that of the cylindrical catalyst.In the 200 h activity evaluation,both theΦ5-6 mm andΦ4-5 mm spherical catalysts maintain high catalytic stability,and theΦ4-5 mm spherical catalyst has the highest activity.When the water powder ratio is 1,and the drying temperature rise rate is 4℃/min,the prepared spherical catalyst has a larger crushing strength and a smaller wear rate,160 N/cm and 0.8%,respectively,which can meet the requirements of industrial production.Finally,the scale-up preparation of the catalyst was investigated.The physical structure and catalytic activity of the catalyst prepared by five times magnification（CZA-5）and the catalyst prepared in small batch（CZA-1）are basically the same,indicating that there is no obvious amplification effect of the catalyst at five times magnification.With a larger inner diameter HP-FBR-（5×110）reactor,increase catalyst loading,investigated the catalytic properties of spherical catalystΦ4-5 mm.In the 200 h activity evaluation,theΦ4-5 mm spherical catalyst showed good catalytic activity and stability.