Catalysts for the isomerization of C7 paraffins

Catalysts having similar chemical compositions were tested for the isomeriz ation of C7 paraffins, mainly branching of n-heptane. The principal objecti ve was to maximize isomerization at minimal hydrocracking levels. Catalysts were prepared using commercially available zeolites with some modification s. Metals (mainly platinum) were incorporated in the conventional way (disp ersed metal) but also as organometallic complexes. Initial activity tests u sed a stirred batch autoclave while time on stream tests used an automated continuous flow tubular microreactor. Products were analyzed by gas chromat ography. Model compounds included other C7 hydrocarbons such as 2,4-dimethy lpentane, methylcyclohexane, and toluene. A prototype catalyst provided 66% n-heptane isomerization with only 4% cracking per pass at high space veloc ities (LHSV = 5). Its selectivity was similar to that of a highly active co mmercial alumina-based catalyst while showing an improved tolerance for aro matic hydrocarbons and a longer catalyst life. Simple kinetic models were e xamined and used to simulate the sequence of events on the catalyst surface .