Deactivation of the Pd-Ag-Al2O3 catalyst and Ag-Al2O3 chemisorbent at joint operation in the process of selective acetylene hydrogenation

The deactivation of the commercial Al-Pd catalyst promoted with silver and Ag-containing chemisorbent in selective acetylene hydrogenation in an ethane-ethylene mixture was studied. It was found that carbonaceous deposits are formed on dispersed silver particles of the Pd-Ag-Al2O3 catalyst and on large silver crystallites of the Ag-Al2O3 chemisorbent. The lightest rapidly burning hydrocarbons of composition CH2.5m with a low degree of aromaticity are sorbed on the silver particles or in the nearest neighborhood of them. Slowly burning hydrocarbons of composition CH1.5–1.8m with high a degree of aromaticity are fixed on the alumina support. It was suggested to replace the Pd-Ag-Al2O3 catalyst currently used at the Nizhnekamskneftekhim plant in the process of selective acetylene hydrogenation by a system with a lower content of silver or without it.