Study On Preparation And Properties Of Metal Catalysts For Synthesis Of O-phenylphenol

O-Phenylphenol?OPP?is an important chemical product with a wide range of applications in the fields of sterilization,anticorrosion,new flame retardants and printing and dyeing auxiliaries.At present,cyclohexanone is used as raw material to synthesize OPP by condensation-dehydrogenation reaction.This process has a wide range of raw materials,simple production process and low cost,so it has been studied by many scholars.However,there are many problems in the study:in the condensation reaction,the yield of OPP is low,especially the dehydrogenation catalyst can not take into account the good activity,high selectivity,long life and so on.The dehydrogenation catalyst currently used in the industrial production of OPP is mainly a precious metal catalyst,but the high cost also hinders the development of OPP.Therefore,it is important to develop low-cost,high-performance non-precious metal catalysts.Layered nitric acid ZnAl-LDHs,was successfully synthesized on the surface of?-Al₂O₃ by in-situ synthesis.The calcined hydrotalcites?CHT?supporter was obtained by calcination.The effect of the Zn content in the supporter and the pH of the solution on the reaction performance was investigated.The dehydrogenation properties of?-Al₂O₃ and CHT carriers were compared.The results showed that the conversion and selectivity of?-Al₂O₃ were close to 64%and 13.34%respectively.After adding Zn,the catalytic performance of the supporter was greatly improved.When the amount of Zn added was 0.1M,the pH of the synthesis reaction solution was 7.5,and the reaction time was 1 h,the reaction performance was the best.The conversion of 1-?2-cyclohexenyl?cyclohexanone?CHCH?was 79.64%and the selectivity of CHT was 17.66%,which indicated that the support itself had a certain catalytic effect on the reaction,but its catalytic activity is not very good.The CHT supporter?Zn=0.1M,pH=7.5?with the best catalytic effect was selected as the research object,and the Cu-CHT dehydrogenation catalyst was prepared by impregnating Cu elements.The effect of Cu loading on the catalytic performance of the catalyst for the synthesis of OPP was studied.The experimental results show that the conversion of CHCH reaches 89.6%after loading Cu.When the loading of Cu was 10%and the reaction time was 1 h,the selectivity of OPP reached99.6%.The calcined catalyst was characterized by XRD,FT-IR,BET,XPS and H₂-TPR.It was found that the crystal particle diameter increased with the increase of Cu loading,and the main active components of the catalyst was Cu in the reaction process.The characterization of the catalyst after reaction showed that after 3 h of reaction,the Cu particles became obviously larger and partially sintered,which resulted in the decrease of the surface active center of the catalyst and the decrease of the selectivity of OPP,so it was necessary to modify the catalyst with other metals to improve the stability of the catalyst.The Ce-modified Cu-CHT catalyst was doped by an impregnation method.The experimental results show that the proper amount of Ce doping improves the dispersion of Cu species,which makes the active center of Cu stable for a long time and improves the stability of the catalyst.The change of Ce content has little effect on the CHCH conversion rate.When the reaction is carried out for 6 hours,it is basically stable at 98.5%or more.When the Ce doping amount was 4%,the catalyst performance was the best.After 6 hours of reaction,the OPP selectivity is increased from 40%to 75%compared with the undoped Ce catalyst.By analyzing the catalytic mechanism,it can be seen that the calcined CeO₂ formed a certain arrangement on the surface of the carrier after the introduction of Ce,and the active center Cu existed in the region separated by CeO₂,which avoided the sintering of Cu in the reaction process and the stability of the catalyst was improved.