Chapter 16: Glycerol, the co-product of biodiesel: One key for the future bio-refinery

RAÚL A. COMELLI

Biodiesel – Quality, Emissions and By-Products

Intech Open Access Publisher

Lugar: Rijeka; Año: 2011; p. 257 - 282

The production of biodiesel generates glycerol as by-product. The conversion of glycerol in added-value compounds has benefits because it comes from renewable raw materials, enabling a sustainable environmental development, and also allows improve the economics of biodiesel process. Glycerol is intermediate in the synthesis of some compounds used in industry, such as propyleneglycol, 1,3-propanediol, and ethyleneglycol by hydrogenolysis; acetol and acrolein by dehydration; dihydroxyacetone, glyceric acid, and hydropiruvic acid by oxidation; glycidol by epoxidation; glycerol carbonate by transesterification; mono- and diglycerides by selective etherification; polyglycerol by polymerization; and bio-hydrogen by steam reforming, partial oxidation, autothermal reforming, aqueous-phase reforming, and supercritical water reforming. All these uses allow considering glycerol as an important key-compound in the environment of future biorefinery. By considering the hydrogenolysis of glycerol, the production of propyleneglycol was reported on several supported catalysts, resulting attractive the improvement in selectivity by using zeolites as base materials, while the production of 1,3-propanediol took place on Pt/WO3/ZrO2, being important a complete study of the effect of preparation technique of this material over its catalytic performance; moreover, a comparison between both liquid and gaseous phase hydrogenolysis is needed. The selective oxidation of glycerol to dihydroxyacetone has been reached on a monometallic catalyst, Pt impregnated on potassium ferrierite, reaching both conversion and selectivity similar to the ones obtained with active bimetallic materials; the pH of reaction medium played an important role over the selectivity, while the structure of zeolite favored the DHA formation. Finally, the steam reforming of glycerol to produce hydrogen was conduced on Ni impregnated on alumina catalysts, which presented Ni species on the surface difficult to reduce and mainly as NiO, reaching high conversions and selectivity for conditions studied and being carbon monoxide the main by-product followed by methane; catalyst deactivation took place during reaction but regenerating is possible restoring the catalytic performance.added-value compounds has benefits because it comes from renewable raw materials, enabling a sustainable environmental development, and also allows improve the economics of biodiesel process. Glycerol is intermediate in the synthesis of some compounds used in industry, such as propyleneglycol, 1,3-propanediol, and ethyleneglycol by hydrogenolysis; acetol and acrolein by dehydration; dihydroxyacetone, glyceric acid, and hydropiruvic acid by oxidation; glycidol by epoxidation; glycerol carbonate by transesterification; mono- and diglycerides by selective etherification; polyglycerol by polymerization; and bio-hydrogen by steam reforming, partial oxidation, autothermal reforming, aqueous-phase reforming, and supercritical water reforming. All these uses allow considering glycerol as an important key-compound in the environment of future biorefinery. By considering the hydrogenolysis of glycerol, the production of propyleneglycol was reported on several supported catalysts, resulting attractive the improvement in selectivity by using zeolites as base materials, while the production of 1,3-propanediol took place on Pt/WO3/ZrO2, being important a complete study of the effect of preparation technique of this material over its catalytic performance; moreover, a comparison between both liquid and gaseous phase hydrogenolysis is needed. The selective oxidation of glycerol to dihydroxyacetone has been reached on a monometallic catalyst, Pt impregnated on potassium ferrierite, reaching both conversion and selectivity similar to the ones obtained with active bimetallic materials; the pH of reaction medium played an important role over the selectivity, while the structure of zeolite favored the DHA formation. Finally, the steam reforming of glycerol to produce hydrogen was conduced on Ni impregnated on alumina catalysts, which presented Ni species on the surface difficult to reduce and mainly as NiO, reaching high conversions and selectivity for conditions studied and being carbon monoxide the main by-product followed by methane; catalyst deactivation took place during reaction but regenerating is possible restoring the catalytic performance.