Study On Catalyst And Overall Process Design For Hydroalkylation Of Benzene To Cyclohexylbenzene

Cyclohexylbenzene?CHB?is an important chemical intermediate.It can be used to prepare phenol and cyclohexanone by catalytic oxidation.Compared with the process of phenol production by cumene peroxide,this process provides a new phenol production process without acetone.CHB can be used as a protective agent of lithium battery.A small amount of CHB can significantly improve the safety performance of lithium battery.With the large-scale application of catalytic oxidation of cyclohexylbenzene to phenol and the rise of electric revolution,the demand for CHB in the domestic market is increasing in recent years.At present,the main methods of CHB synthesis are alkylation of benzene with cyclohexene,hydrogenation of biphenyl,and benzene hydroalkylation.The first two routes are not suitable for large-scale production due to the limitation of raw material cost,efficiency and process conditions.Benzene hydroalkylation is one of the ideal methods to prepare CHB.Therefore,the design and development of bifunctional catalyst with high activity,especially high CHB selectivity,and the matching production process is significance.The main conclusions are as follows:?1?The effects of different loaded bifunctional catalysts?Metal/Zeolite?on the conversion of benzene and CHB selectivity in benzene hydroalkylation were studied.Pd was determined to be the effective metal,and the optimal loading was 0.2%.On the other hand,the influence of various acid supports on the benzene hydroalkylation was also studied.HBeta zeolite was selected as the suitable support for this reaction.As a result,Pd/HBeta catalyst achieve the best reaction performance among other loaded catalysts,with the conversion of benzene was 85.0%,the selectivity and yields of CHB were 25.1%and 21.3%,respectively.?2?Pd@HBeta catalyst was obtained by engineering an extra Si-Al framework outside Pd/HBeta catalyst.Compared with Pd/HBeta catalyst,it has higher benzene reaction rate and CHB selectivity,with benzene reaction rate raise to 80.1mmol?g^-1?h^-1.The yields and selectivity of CHB were increased to 44.0%and 37.7%,which was 1.75and 1.77 times higher than that of Pd/HBeta catalyst,respectively.The improvement of reaction performance is attribute to the extra Si/Al framework regulating the metal acid site matching relationship.Moreover,due to the confinement effect in the zeolite channel,Pd NPs reconstructed to small nanoparticles with higher dispersion in Pd@HBeta catalyst.This can improve the benzene reaction rate.DFT calculation shows that cyclohexene(C₆H₁₀)could easily desorbed from Pd NPs to acid site in Pd@HBeta catalyst,which further prevents the hydrogenation of C₆H₁₀ and enhances the CHB selectivity.?3?According to the reaction conditions and results of Pd@HBeta catalyst,the process of CHB production with Pd@HBeta catalyst was developed.Based on Aspen Plus,the whole process is simulated,and the process is optimized by pinch analysis.In the separation system,the extractive dividing wall column?EDWC?was designed to separate benzene-cyclohexane-DMAC mixtures.The EDWC can realize that one-time extraction operation to separate benzene,cyclohexane and DMAC effectively,which makes the process further energy saving and utilization.