INFLUENCE OF ALKALI ADDITIVES ON ACTIVITY AND TOXICITY OF H2S AND THIOPHENE OVER A NI SIO2 CATALYST/

The influence of alkali-doping of a Ni/SiO2 catalysts on the d-activat ion by thiophene and H2S during benzene hydrogenation at 200 degrees C has been studied. An initial toxicity higher for thiophene than for H 2S has been found for all the catalyst tested. Furthermore, in compari son with the undoped catalyst, the thiophene/H2S toxicity ratio decrea ses on alkali-doped catalyst. On the basis of benzene hydrogenation ac tive sites, alkali-doping decreases both thiophene and H2S initial tox icity, Temperature programmed surface reaction (TPSR) results suggest that the difference in toxicity may be explained by a layer of hydroca rbon species remaining on the nickel surface after thiophene adsorptio n at 200 degrees C. (C) 1998 Elsevier Science B.V.