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Keywords:

  • carbides;
  • heterogeneous catalysis;
  • nickel;
  • renewable resources;
  • supported catalysts

Abstract

The production of syngas was investigated by steam reforming glycerol over Ni/Al2O3, Ni/CeO2, and Ni/SiC (which have acidic, basic, and neutral properties) at temperatures below 773 K. The complete and stable conversion of glycerol with a yield (higher than 90 %) of gaseous products (mainly syngas) was achieved over Ni/SiC during a 60 h reaction, whereas the conversion of glycerol continually decreases over Ni/Al2O3 (by 49.8 %) and Ni/CeO2 (by 77.1 %). The deactivation of Ni/Al2O3 and Ni/CeO2 is mainly caused by coke deposition because of the C[BOND]C cleavage of the byproducts produced by dehydration over acidic sites and condensation over basic sites. Gaseous products with a 1.0–1.9 syngas ratio (H2/CO) are produced over Ni/SiC. This ratio is required for the Fischer–Tropsch synthesis. However, a syngas ratio of more than 3.0 was observed over Ni/Al2O3 and Ni/CeO2 because of the high activity of the water–gas-shift reaction. Any dissociative or associative adsorption of water on Al2O3 and CeO2 promotes a water–gas-shift reaction and produces a higher syngas ratio. H2 and CO were mainly produced by decomposition of glycerol through dehydrogenation and decarbonylation over Ni sites. Thus, SiC promotes an intrinsic contribution of nickel (dehydrogenation, and decarbonylation) without any byproducts from the dehydration and condensation.