GLYCEROL TRANSFORMATIONS RACHA ARUNDHATHI [email protected] [email protected] Experts realistically predict the end of cheap oil in 2040 at the latest, a development that we can already witness as chemical manufacturers confront the rising cost of oil and natural gas. The transition to a more biobased production system is currently underway, and much attention has been given to the catalytic conversion of renewable feedstocks and chemicals. Glycerol is a potentially important biorefinery feedstock, available as a byproduct in the production of biodiesel by transesterification of vegetable oils or animal fats. For every 9 kg of biodiesel produced, about 1 kg of a crude glycerol byproduct is formed. Due to its highly functionalized nature, glycerol can be readily oxidized, reduced, halogenated, etherified, and esterified to obtain alternative commodity chemicals (Figure 1), such as dihydroxyacetone, mesoxalic acid,1,3-propanediol, 1,3-dichloropropanol, glyceryl ethers, glycerol carbonate, and glyceryl esters. PROCESSS PATHWAY FOR PRODUCTION OF LIQUID FUELS FROM BIOMASS BY INTEGRATED GLYCEROL CONVERSION Vegetable oils and animal fats Carbohydrates Transesterification Fermentation/Hydrolysis Aqueous Glycerol (25-85 wt%) Biodiesel Light alcohols and polyols Chemicals and Solvents Distillation H2/CO Reforming Integrated glycerol conversion with Fischer-Tropsch synthesis Gaseous alkanes Aqueous solution of oxygenated hydrocarbons (acetone, methanol, ethanol) Aqueous Phase Reforming Selective dehydration/ hydrogenation Fuels H2 Combustion Liquid Hydrocarbons Upgrading Naptha, Diesel Fuel, Kerosene Electricity and heat This highly anticipated depicts how practical limitations posed by glycerol chemistry are solved based on the understanding of the fundamental chemistry of glycerol and by application of catalysis science and technology. An employable, practical avenues applicable to convert glycerol into value added products of mass consumption in understanding whether biodiesel and glycerol refineries are convenient and economically sound. GENERAL GLYCEROL REACTIONS •Properties of Glycerol 1.Properties of Glycerol 2.Traditional Commercial Applications 3.Production of Bioglycerol and Commercial Trends 4.Glycerol as Solvent in Organic Reactions 5.Bioglycerol Purification •Reforming 1.Glycerol as a Platform for Green Fuels 2.Production of Hydrogen via Aqueous Phase Reforming 3.Production of Hydrocarbon Fuels via Aqueous Phase Reforming 4.Industrial Applications •Selective Reduction 1.Reduction of Glycerol 2.Hydrogenolysis to Propylene Glycol 3.Dehydroxylation to 1,3 Propanediol(PD) 4.Biological Reduction to 1,3 Propanediol (PD) 5.Commercial Applications •Halogenation 1.Chlorination of Glycerol 2.Production of Epichlorohydrin 3.Industrial Applications •Dehydration 1.Dehydration of Glycerol 2.Dehydration to Acrolein 3.Propane from Acrolein 4.Oxydehydration to Acrylic Acid 5.Dehydration to 3-Hydroxypropionaldehyde 6.Industrial Applications 7.Esterification of Glycerol •Etherification and Telomerization 1.Etherification of Glycerol 2.Butylation of glycerol to tert-butyl ethers (GTBE) 3.Direct Telomerization and Etherification over CaO 4.Polymerization to Polyglycerol 5.Glycosylation to Glucosyl Glycerol 6.Industrial Applications •Esterification 1.Esterification with Carboxylic Acids and Glycerolysis 2.Carboxylation to Glycerol Carbonate 3.Nitration 4.Industrial Applications •Selective Oxidation 1.Selective Oxidation of Glycerol 2.Thermodynamic and Kinetic Aspects of the Aerobic C-OH Oxidation 3.Platinum Group Metals Catalysis 4.Gold and Organocatalysis 5.Oxidation Using an Iron Catalyst 6.Electrochemical Oxidation 7.Biological Oxidation •Bioglycerol in the Construction Industry 1.Polyols as Additives for Cement 2.Glycerol as Anticracking and Waterproofing Agent 3.Raw Glycerol as Quality Enhancer and Grinding Aid 4.Bioglycerol as Anticorrosive Lubricant •Sustainability of Bioglycerol 1.Biofuels: A Triple Bottom Line Analysis 2.Bioglycerol Economics 3.Glycerol: A Platform Chemical for the Biorefinery applications Glycerol organic transformations PROCESS CATALYSTS MAIN PRODUCT MAIN APPLICATIONS REFERENCE Reforming Pt-Re/C Syn Gas Pt or Ni based-catalysts H2 FT synthesis energy  [2,3] Dehydration Acid catalysts acrolein [4-8] Sb-V-O acrylic acid acrylonitrile Oxidation Au based-catalysts dihydroxyacetone Chemical intermediate Polymers, resins, paints, acrylic fibers, etc. Active ingredient of sunless tanning skin care preparations Hydrogeneolysis Ru/C or Cu-based 1,2-propanediol Fermentation Enzymes Carboxylation Zeolites, Zn-based, or under supercritical conditions Mesoporous materials Esterification [11,12]  [14-20] Mesoporus materials Chemical intermediate, antifreeze 1,3-propanediol Manufacture of polyesters Glycerol carbonate Production of polycarbonates and polyurethanes Glycerides, polyglycerol Emulsifiers esters DAG, TAG Fuel additives monoalurin, dilaurin Pharmaceutical industry tBu ethers Fuel additives Sulphates MAGEs  CaO-based di- and tri-glycerol Chlorides, sulfates Etherification [9,10] Pharmaceutical industry [21-24] [25-29] [30-33] [34,35]  [37-39]  Telomerization Homogeneous catalysts C8 chain ethers Surfactant chemistry [42,43] Epicerol Carboxylic acids Production of epoxy resins [44,45] Epichlorohydrin OXIDATION OF GLYCEROL HO OH OH Glycerol (GLY) OH OH HO O OH Glyceric acid (GLYA) HO OH O dihydroxyacetone (DHA) HO O O Hydroxypyruvic acid (HPYA) Designing chemoselective catalysts to orientate the glycerol oxidation reaction towards either primary or secondary alcohol function. DHA used as a tanning agent in cosmetic industry, synthon in organic synthesis. DHA and HPYA are the possible starting materials for DL-serine synthesis. Traditionally the reaction has been carried out with supported Pt and Pd catalysts, but they suffer oxygen poisoning. Gold catalyst appeared to be more resistant to oxygen poisoning, allowing the use of higher oxygen partial pressures. HYDROGENOLYSIS OF GLYCEROL Two types of catalysts have been reported in the literature for the hydrogenolysis of glycerol: one is supported noble metal catalysts, the other is catalysts consisting of transition metal oxides, such as Raney Ni, copper chromite or Cu-ZnO catalysts. Noble metal based catalysts are usually more active than Cu based catalysts for the hydrogenolysis reaction, but the selectivity to propanediols is lower. Furicado et al. compared the catalytic performances of several supported metal catalysts (metal: Rh, Ru, Pt, Pd; support: active carbon, SiO2, Al2O3). 1,2-PDO is an important commodity chemical, which finds use as antifreeze, aircraft deicer and lubricant. 1,3-PDO is copolymerised with terephthalic acid to produce polyesters, which are used for manufacturing carpet and textile fibres exhibiting strong chemical and light resistance. Reaction mechanism for conversion of glycerol to propylene glycol proposed by Montassier et. al., Proposed reaction mechanism for conversion of glycerol to propylene glycol CURRENT AND FUTURE DEVELOPMENTS The technology to make biodiesel is simple and it is evolving to reach a high degree of efficiency with new heterogeneous processes that only afford pure glycerol as byproduct and use oil from high-yield seeds from non-edible crops such as the Jatropha trees that are being planted in Africa and Latin America by BP. The raw materials are not localized in a few countries, but instead their production is increasingly determined by land availability. The overall consequence is that glycerol will become a central raw material for the chemical industry, along with interesting novelties. Indeed, the scope and pace of the innovation in the last two years is impressive. Progress is not limited to the reactions mentioned in this account. For example, new catalytic aerobic oxidations over gold catalysts afford either 32% dihydroxyacetone or valued ketomalonic acid derivatives. It follows that a progressive move by the chemical industry towards renewable feedstocks will become a necessity; and the transition to a more bio-based production system in which biomass is catalytically converted to chemicals and transportation fuels is now underway. In 3–5 years, glycerol will be seen as an environmentally friendly way of replacing other competing petroleum products. 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