Low temperature activation of Pt/Ni supported MCM-41 catalysts for hydrogenation of benzene

A series of Pt/Ni supported MCM-41 catalysts prepared via classical methods have been investigated. The promotional effect of low activation temperature is shown in comparison to higher temperatures. Surface properties of the catalysts activated at low temperatures were studied using H2-temperature programmed reduction (H2-TPR), H2-chemisorption and H2-temperature programmed desorption (H2-TPD) methods while the morphology and size distribution of the particles were obtained using transmission electron microscopy (TEM) analysis. Surface studies showed the promoting effect of Pt on the reduction of Ni species on the support. Total reduction only occurred for the Pt100 and Pt90Ni10 catalysts. Interestingly, it was found that the active phase of the monometallic catalysts were composed of spherical metal particles in the nanosize range, while the bimetallic catalysts showed a combination of spherical and large cubic particles. Tests on the gas phase hydrogenation of benzene show that Pt50Ni50 and Pt90Ni10 exhibit high activity when compared to Pt100, though both these catalysts contain lower atomic percentages of Pt. This can be attributed to the anchoring effect of non-reduced Ni2+ ions that result in well dispersed Pt particles. Kinetic studies were conducted to understand the surface chemical process of the bimetallic catalysts.