Studies of silica-supported metal chloride catalysts for the vapor-phase hydrochlorination of acetylene

Abstract The first phase of a systematic examination of heterogeneously catalyzed vaporphase reactions of acetylene with acids of the HQ type has involved infrared and reaction studies of silica-supported metal chloride catalysts. Examination of the infrared spectra of acetylene and propyne adsorbed on these catalysts has yielded information on the mode of adsorption. On all surfaces studied a species of the type is observed, where R is H and CH 3 and M(II) is Ca(II), Mn(II), Cu(II), and Zn(II). Shifts of propyne CC as well as propyne and acetylene CH vibrations to lower frequencies on adsorption in this configuration are related to the electron affinities of the metal ions. Studies of the catalytic activities of silica-supported Hg(II), Bi(III), Ni(II), Zn(II), Cd(II), Cu(II), Mn(II), and Ca(II) chlorides for the vapor-phase hydrochlorination of acetylene have supplemented literature information and provided some basis for interpretation of the infrared results. After a rapid decline from a higher initial activity, a nearly steady activity is attained yielding the order Hg(II) > Bi(III) > Ni(II) > Zn(II) > Cd(II) > Cu(II) > Mn(II) > Ca(II). It is possible to rationalize spectroscopic data obtained so far with the observed order of catalyst activity in terms of the adsorbed species .