Heteropolyanions based catalysts for paraffins isomerization

n-Hexane isomerization was carried over CsxH3-xPW12O40 catalysts promoted w ith Pt by mechanical mixing with a Pt on alumina catalyst. Different parame ters as caesium and platinum content in the catalyst, temperature and atmos phere of heteropolyacids pre-treatment were optimized. The catalytic perfor mances of the best catalyst were compared with those of industrial Pt promo ted mordenite. 0.3 wt.% Pt-promoted Cs2H1PW12O40 pre-treated under hydrogen flow at 473 K showed the highest conversion and selectivity. Its performan ces are very close to those of the industrial zeolitic catalyst in the same reaction conditions. The gain in dibranched isomers selectivity is really promising for the future. With this catalyst, the reaction proceeds by a no n-ideal bifunctional mechanism resulting from the superposition of a monofu nctional acid and a bifunctional metal-acid mechanism. (C) 2001 Elsevier Sc ience B.V. All rights reserved.