Deactivated Titanosilicate Zeolite As An Efficient Catalyst For Liquid-phase Hydration Of Cyclohexene

Cyclohexanol is an important chemical intermediate material.At present,ZSM-5molecular sieve is mainly used as a catalyst in the industry to prepare cyclohexanol by one-step hydration of cyclohexene.Its core is the development of high-performance catalysts.Based on the analysis and understanding of the catalytic mechanism of this process,combined with the changes in the physicochemical properties of titanium-silicon molecular sieves in the green catalytic synthesis of cyclohexanone oxime industrial production process,The dissertation explored the catalytic performance of the deactivated titanium silicalite molecular sieve with MFI topology in cyclohexene hydration reaction.It is expected that a new high performance catalyst will be developed.The main research work is as follows.1.The effects of catalyst type,catalyst dosage,reaction temperature,reaction time,and ratio of water to oil on the hydration reaction of cyclohexene were systematically investigated.Studies have shown that the deactivated titanium silicalite has excellent cyclohexene hydration catalytic performance.Under the optimized conditions,the yield of cyclohexanol reached 11.0%,the selectivity of cyclohexanol reached 99.5%,and the stability of the catalyst was good.Compared with the traditional ZSM-5 catalyst,it showed comparable catalytic activity and higher product selectivity.Further studies have shown that the selectivity of the deactivated titanium silicalite with high cyclohexanol selectivity is determined by its unique weak Br?nsted acidic character,which favors the main hydration reaction of cyclohexene and suppresses the side reaction of cyclohexene isomerization.2.The structure of the active center of cyclohexene hydration reaction catalyzed by the deactivated titanium silicalite was explored.Selective removal of silicon-titanium binary mixture by acid washing,combined with characterization techniques such as UV/Vis,NH₃-TPD,Vacuum IR,and Py-IR.It was found that the main active center for the hydration of cyclohexene catalyzed by deactivated titanium silicalites is the silanol group adjacent to the titanium hydroxyl group.3.The formation process of the active center of hydration reaction of cyclohexene catalyzed by deactivated titanium silicalite zeolite was discussed.To simulate the environment of cyclohexanone liquid-phase ammoximation reaction,construct cyclohexene hydration catalytic activity center on TS-1 molecular sieve.It was found that the mixed solution of ammonia and hydrogen peroxide has synergistic and directional silicon-solubility effects on TS-1,thus forming a unique weak Br?nsted acid center.