Study of pyridine-modified platinum- and palladium-containing selective-hydrogenation catalysts on fiber-glass woven support

Experimental results on the influence exerted by pyridine additives on the selectivity of the process in which the styrene fraction is purified to remove the microscopic admixture of phenylacetylene at low (up to 30°C) temperatures by selective hydrogenation with catalysts on an aluminoborosilicate or silica matrix with filler-metals in the form of platinum or palladium are presented. It was shown that pyridine-modified catalysts in these systems are effective in the selective hydrogenation of phenylacetylene for purification of raw styrene. The modification of a platinum catalyst on the aluminoborosilicate support results in that a deep degree of purification (>95%) is achieved even at low (up to 50°C) temperatures. Use of catalysts composed of 0.160 wt % Pt and silica woven-glass fabric, modified with pyridine additives, leads to a substantially lower loss of styrene (from 0.48 to 0.31% in some cases) in the temperature range of 30–50°C. It was demonstrated that addition of substances containing a unshared electron pair can noticeably affect the selectivity of the process in which the styrene fraction is purified from its impurity content even in the order of 0.01%. Depending from the substrate composition and active filler-metal, the temperature, together with changing the support properties, exerts varied influence on modified metallic catalysts, which is manifested in change in the activation energy and, as a consequence, in that of the hydrogenation mechanism.