Selective hydrogenation of cyclopentadiene using a presulfided molybdenum catalyst

#This invention is directed to the selective hydrogenation of cyclopentadiene to cyclopentene. More specifically, this invention is directed to a process whereby cyclopentadiene is selectively hydrogenated to cyclopentene by contacting a mixture of cyclopentadiene and hydrogen with a catalyst consisting essentially of presulfided molybdenum on alumina.

#Dicyclopentadiene, as well as its monomer, cyclopentadiene, is a by-product of the thermal cracking of ethane and propane for olefin production and the pyrolysis of naphtha for ethylene production. The use of these by-products for preparing high-grade chemicals, and in particular cyclopentene, is of commercial significance since cyclopentene is an important monomer in the rubber industry. Normally, however, the catalysts of the prior art do not possess sufficient activity and/or selectivity so that the product from the hydrogenation of cyclopentadiene contains not only the desirable cyclopentene but also some desirable amounts of cyclopentane. Rather expensive distillation equipment is then required to separate the cyclopentene from the cyclopentane in the product stream. It is therefore highly desirable to develop a catalyst with reasonable activity which has a 100 percent selectivity in the conversion of cyclopentadiene to cyclopentene.

#In accordance with the invention an improved process for the selective conversion of cyclopentadiene to cyclopentene has now been discovered which comprises contacting the cyclopentadiene plus hydrogen with a catalyst consisting essentially of presulfided molybdenum on alumina and wherein the amount of molybdenum on the catalyst is from 0.52 to 1.18 .times. 10.sup.-3 gram atoms of molybdenum per 100 m.sup.2 of said alumina surface.

#55.95 grams of a 20/30 mesh alumina, whose properties are shown in Table 1 below, were contacted with about 59 ml of an aqueous solution containing (i) 21.27 grams of ammonium paramolybdate ((NH.sub.4).sub.6 (Mo.sub.7 O.sub.24.4H.sub.2 O)) and (ii) 9.30 ml of concentrated ammonium hydroxide. The amount of the solution was just sufficient to bring the alumina support to the point of incipient wetness.

#The material was oven dried for 24 hours at 120.degree. C. and then calcined for 10 hours at 538.degree. C.

#The amount of molybdenum on the catalyst was calculated to be 16.0 weight percent. By calculation the amount of molybdenum on the support was 1.01 .times. 10.sup.-3 gram atoms Mo per 100 m.sup.2 of Al.sub.2 O.sub.3 surface.