Tuning selectivity in the gas phase hydrogenation of phenylacetylene over the platinum-mesoporous carbon nitride composites using organic modifiers

The platinum nanocomposites with mesoporous carbon nitride (Pt/mpg-C3N4) were synthesized by in situ reduction of H2PtCl6 center dot 6H(2)O with aqueous methanol and studied as catalysts in phenylacetylene hydrogenation in the gas phase at 150 degrees C and atmospheric pressure in the flow process. The efficiency of hydrogenation can be enhanced by using available organic modifiers. The addition of pyridine, piperidine, or morpholine to the starting solution of phenylacetylene in hexane provides 95-100% conversion and 90-92% selectivity to styrene on the Pt/mpg-C3N4 catalyst. A sharp increase in the selectivity to styrene without substantial changes in conversion is observed when THF, ethanol, triethylamine, dioxane, or chloroform are used as diluents. No loss of activity or selectivity was observed during 10-h tests of the catalyst in the flow process.