High catalytic activity of an insoluble acidic caesium salt of dodecatungstophosphoric acid for liquid-phase alkylation

Abstract

The use of solid acid catalysts is often desirable for liquid-phase reactions [1] in the place of homogeneous catalysts such as H2SO4 [2] and HA12CI: [2,3]. Among the various solid acids that were tested for liquid-phase alkylation of aromatic hydrocarbons [4-8], perfluorinated resinsulfonic acid (Nation-H) has been reported as being a good catalyst [4,5]. The authors have previously found that solid heteropoly compounds, H3PW1204o and their acidic caesium salt, where highly active catalysts for the dehydration of alcohols in the gas phase [9-12] and for the decomposition of ester in the liquid phase [ 13 ]. Here we wish to report on the high activities of Ho.sCs2.~PW12040 for the alkylation of aromatic compounds with cyclohexene. This catalyst was found to be much more active than HY, H-ZSM-5, and Nafion-H. Ho..~Cs2.sPW1204o (abbreviated as Cs2.5-salt) was obtained as a precipitate by the titration of an aqueous solution of H3PWI2QO (Nippon Inorganic Colour and Chemicals) with an aqueous solution of Cs2CO3 as described before [9-13 ]. Carbon-supported H3PW~204o [14] was prepared with an activated carbon (Wako Pure Chemicals) and an aqueous solution of H3PW~204o. The amount of H3PWI204o loaded was 18 wt.-%. This is denoted by H3PW~204o/ AC. SiO2-A12Os (SA-1, Catalysts and Chemicals Industries; A1203 : 13 wt.-% ), Nafion-H (NR-50, Mitsui Toatsu Fine Chemicals), H-ZSM-5 (25H, Mobil Catalysts Company of Japan), HY-zeolite (prepared from SK-40, Linde), aluminium exchanged montmorillonite (prepared from Kunipia-F, Kunimine Kogyo), H2SO4-treated ZrO~ (abbreviated as SO42-/ZrO2) [15,16], and HA12C17 [3] were used as reference catalysts.