Research On Catalytic Activity Of Modified HZSM-5on Hydration Of Cyclohexene

With the advocacy of the green chemical concept, there is an increasingconcerned about the study of cyclohexene hydration to cyclohexanol. Cyclohexenehydration is a typical acid catalytic reaction, which require strong acid catalyst,besides the adsorption of cyclohexene on the catalyst is also a key factor. High-silicaHZSM-5zeolite is the most used catalyst in industrial production, but theconversion rate is not high and the reaction rate is slow. To overcome this problem,the development of appropriate hydration catalyst, zeolite modification, whichmaking it more suitable in the hydration reaction is an important research direction.In this paper, a method of modify HZSM-5by using niobium oxalate ammonium isintroduced. We studied the surface acidity of Nb/HZSM-5with different Nb contentand the catalytic activity of cyclohexene hydration reaction. XRD and BETcharacterization results showed that: niobic acid has a larger surface area and behighly dispersed, when Nb2O5added to HZSM-5with suitable amount, modifiedNb/HZSM-5showed a preservation of the zeolite structure; Py-TPD showed that theintroduce of the niobium avoiding the dehydroxylation of zeolite which lead acidreduction, and also increased the framework stability of zeolite catalyst. Loading with6%(wt%)Nb2O5, calcined at450℃for4h, the optimal conditions of cyclohexenehydration were: reaction temperature120℃, pressure0.5MPa, stirring speed800r/min, catalyst content30%(w/w), oil/water ratio1.4:1(v/v), reaction time3h, theyield of cyclohexanol was14.7%.The modified zeolite samples using different silylation reagents showed apreservation of the zeolitic structure and the acidity of HZSM-5zeolite ispreserved. Modified HZSM-5use cyclohexyl trichlorosilane gave the highest catalyticactivity,120℃after3h, the yield of cyclohexanol was6.3%.This amphiphilicHZSM-5zeolite exhibited much higher catalytic activity than the parent HZSM-5zeolite in the hydration of cyclohexene phase-boundary reaction even without addingco-solvents or stirring.Amphiphilic o/w-Nb/HZSM-5zeolite loaded with niobic acid-coveredcyclohexenyl trichlorosilane is potentially capable of catalyzing the hydration ofcyclohexene at the interphase reaction. The number of active centers on the surface of HZSM-5zeolite were effectively increased with niobic acid impregnation. Understatic conditions, the reaction of cyclohexene hydration phase interface showed betterreactivity than o/w-HZSM-5.