Effective dispersion of Au and Au–M (M = Co, Ni, Cu and Zn) bimetallic nanoparticles over TiO2 grafted SBA-15: Their catalytic activity on dehydroisomerization of α-pinene

Mesostructured siliceous SBA-15 was synthesized via direct hydrothermal crystallization from acidic solution of poly-(ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol)-copolymer and tetraethyl orthosilicate. The amorphous surface of the calcined Si-SBA-15 was modified with 20 wt.% of TiO2 by chemical grafting method using titanium isopropoxide as the titanium source in ethanol solution. Various metal nanoparticles Au, Au–M (M = Co, Ni, Cu and Zn) were supported on TiO2/SBA-15 by deposition–precipitation method (DP) using urea as the precipitating agent. The structural features of the synthesized materials were characterized by various physico-chemical techniques such as X-ray diffraction, nitrogen physisorption (BET), XPS and HR-TEM. BET results of Si-SBA-15 revealed the formation of mesoporous structure with an average pore size of 5.9 nm, pore volume of 1.12 cm3/g and the specific surface area of 846 m2/g. HR-TEM results demonstrated that metal nanoparticles were highly dispersed over TiO2/SBA-15 and long range ordering of hexagonal mesopores of Si-SBA-15 was well retained after loading of 20 wt.% TiO2 and 3 wt.% of bimetallic nanoparticles. The catalytic performances of the prepared catalysts were studied on dehydroisomerization of α-pinene under gas phase conditions using hydrogen atmosphere. The stability and catalytic activity of Au–M–TiO2/SBA-15 (DP) catalysts upon conversion of α-pinene into p-cymene was explored in comparison with the catalysts prepared by conventional method. AuNi–TiO2/SBA-15 catalysts prepared via DP method were found to be stable upon longer reaction time as well as superior in terms of conversion and selective towards the formation of p-cymene.

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► Synthesis of mesoporous and highly dispersed TiO2/SBA-15.
► Au containing bimetallic nano particles on TiO2/SBA-15 was obtained by DP method.
► Metal nano particles were homogeneously distributed on TiO2/SBA-15.
► Preparation conditions does not affect the characteristics of the support Si-SBA-15.
► Supported metals play important role on selectivity of the reaction products.