INFLUENCE OF THE SUPPORT OF COMO SULFIDE CATALYSTS AND OF THE ADDITION OF POTASSIUM AND PLATINUM ON THE CATALYTIC PERFORMANCES FOR THE HYDRODEOXYGENATION OF CARBONYL, CARBOXYL, AND GUAIACOL-TYPE MOLECULES

The present work corresponds to part of a program aimed at upgrading o il obtained by pyrolysis of biomass by hydrotreatment (hydrodeoxygenat ion HDO). CoMo sulfide catalysts, nonsupported, supported on different supports (alumina, carbon, silica), or modified by K or Pt, were used . We used a model reacting mixture containing compounds representative of the molecules that must react to permit a primary stabilisation of the pyrolytic oil: 4-methylacetophenone (4-MA), diethylsebacate (DES) , and guaiacol (GUA). In the reaction of the carbonyl group of the 4-M A it is shown that no important role is played by any acid-base mechan ism; dispersion determines the activity. Acidity of the support influe nces the formation of active sites for decarboxylation and hydrogenati on of the carboxyl group of DES. It was confirmed that guaiacol-type m olecules lead to coking reactions. The role of acidity in the mechanis m of these reactions is confirmed, but the modifications made in the c atalysts in this work are still not sufficient to control coke deposit ion. The catalysts supported on carbon lead to the direct elimination of the methoxyl group of the guaiacol. Carbon, on the whole, seems to be a promising support. This work suggests that appropriate modificati ons of the hydrotreating catalysts can lead to a more effective proces s for stabilisation of the bio-oils by reaction with hydrogen. (C) 199 5 Academic Press, Inc.