Influence of clay binders on the performance of Pd/HZSM-5 catalysts for the hydroisomerization of n-butane

The influence of the amount of two clay binders (montmorillonite and benton ite) on the acid properties and performance of Pd/HZSM-5 zeolite with diffe rent Si/Al ratios for the hydroisomerization of n-butane has been studied. Temperature-programmed desorption of ammonia, atomic absorption spectroscop y, chemisorption, and surface area measurements were used to characterize t he catalysts. After agglomeration, some zeolite protons are neutralized by clay sodium and, consequently, a lower n-butane conversion is obtained. The product selectivity is also strongly influenced by the binder due to the f act that zeolite hydrogen transfer activity, metal/acid site balance, and d iffusion of products are modified. If the appropriate binder is selected, t he decrease in conversion will be compensated by a much higher isobutane se lectivity. Thus, a catalyst based on Pd/HZSM-5, with a zeolite Si/Al ratio of 25, and agglomerated with bentonite in a zeolite/clay ratio of 35/65 wt/ wt, showed not only an adequate mechanical resistance but also high isobuta ne selectivity and isobutane yield (87.1 and 23.9 mol %, respectively). It should be remarked that, under the same reaction conditions, the parent cat alyst without binder showed worse isomerization activity (18.5 mol % isobut ane yield with 47.3% isobutane selectivity).