Study On The Selective Hydrogenation Of Cyclopentadiene To Cyclopentene

Cyclopentene is an important chemical intermediate products. Cyclopentene and itsdownstream products, such as glutaraldehyde, pentanedioic acid, halogenated cyclopentane andso on， have been widely used in the organic synthesis, pharmaceutical industry and syntheticrubber, and other fields. Producing the series of products not only consume cyclopentadiene, butalso increase its additional value. This paper investigated selectivity hydrogenation of cyclepen-tadiene to cyclopentene. We got cyclopentadiene from depolymerizing dicyclopentadiene underhigh temperature, which was used as the starting material. The hydrogenation reaction wascarried on in a fixed-bed reactor where equipped with the catalyst Pd-Pb/γ-Al2O3. The suitableconditions of preparation and reaction were also determined.At first, the starting material was depolymerized in the manner of liquid-phase in the home-made rectifying column. Studies have shown that the content of cyclopentadiene is more than98%through verifying by using the gas chromatography, and the quantity of dimer is littlewhen collected fractions of the tower-top between38℃and43℃. It was suitable for selectivehydrogenation reaction.Then, Pd-Pb/γ-Al2O3was prepared by equivalent-volume impregnation method. First, Pdand Pb was supported on carrier Al2O3in sequence. Second, the content of Pd and Pb, the diptime, calcination temperature and time of the catalyst were investigated.Third, using thecharacterization methods such as XRD, BET, ICP to characterize the catalysts, and studying therelationship between the catalyst structure and reaction activity.The suitable preparation conditions of catalyst were confirmed: the content of Pd was0.1%(wt), the ratio of Pd-content and Pb-content was1.0(molar ratio), the dip time of Pd and Pbwere respectively12h and10h, calcination temperature was500℃, calcinations time was3h.Under these conditions, the activity of catalyst was good, and the yield of cyclopentene was relatively high.At last, the paper investigated the effects of reaction conditions. The Studies shown that theconversion of cyclopentadiene could reach93.1%and the selectivity of cyclopentene was86.9%in a fixed-bed reactor at atmospheric pressure when the reduction temperature was180℃,reaction temperature was120℃, the ratio of hydrogen and hydrocarbon was1.0, liquid spacevelocity was6.0h-1.