Selective Conversion of Glycerol into 1,2-Propanediol at Ambient Hydrogen Pressure

Abstract

The vapor-phase reaction of glycerol was performed over a copper-alumina catalyst at ambient hydrogen pressure. Glycerol was converted into 1,2-propanediol (PDO) through dehydrationhydrogenation via hydroxyacetone (HA). We also found that 1,2-PDO was produced at the selectivity higher than 93 mol % in hydrogen flow at gradient temperatures: the dehydrogenation into HA was catalyzed at around C, while the following hydrogenation into 1,2-PDO was catalyzed by Cu-alumina catalyst at around 145-160 C.The catalytic conversion of carbon-neutral biomass into useful chemicals is expected to be a potential solution to the severe global environmental pollution problem.1,2 Renewable biomass fuels, such as bioethanol and biodiesel fuel (BDF), i.e., fatty acid methyl esters, are attracting much attention worldwide. Glycerol, a by-product of BDF production for ca. 10 mass % of BDF produced, is one of such promising renewable resources. Its quantity increases as the amount of BDF produced is increased.Recently, quite a number of studies on the reaction of glycerol have appeared in reviews 2-4 and research papers. [5][6][7][8][9][10][11][12][13][14][15][16] In liquid-phase hydrogenolysis under hydrogen pressure, glycerol is converted into 1,2-PDO and 1,3-PDO in the presence of supported Rh, 5 Ru, [6][7][8]9 In the vapor-phase hydrogenolysis of glycerol, Cu catalyzes 1,2-PDO formation in the presence of high hydrogen pressure. [10][11][12][13] Since the hydrogenolysis requires elevated hydrogen pressure, 5-11 side reactions occur to form several by-products, including ethylene glycol (EG), propanol, lactic acid, and propanoic acid. Hydroxyacetone (HA) is an intermediate product in the conversion of glycerol into 1,2-PDO through the dehydration-hydrogenation reactions. Over Cu catalysts, however, 1,2-PDO selectivity higher than 90 mol % is attained: 12,13 low temperatures and high hydrogen pressures favor the shift of equilibrium from HA to 1,2-PDO and reduce the formation of by-products resulting from HA side reactions. 13One effective operation is a two-step process composed of dehydration under vacuum and hydrogenation under hydrogen pressure. 13,15 It is known that copper works as a dehydrogenation catalyst for polyols, such as 1,2-17 and 1,3-diols. 18 However, glycerol can be dehydrated into HA over copper metal catalysts.14-16 It should be noted that copper metal catalyzes the dehydration of glycerol to produce HA with selectivity higher than 90 mol % at 250 C, and that no dehydrogenation proceeds to form dihydroxyacetone.14,16 1,2-PDO is dehydrogenated to form HA in the presence of inert carrier gas over copper catalysts, and the dehydrogenation is controlled by equilibrium.17 This reminds us that 1,2-PDO is favored at high hydrogen partial pressure even at ambient pressure. As copper metal works as a catalyst for the dehydrogenation of 1,2-PDO into HA at 210 C, 17 it is expected to be an efficient catalyst for the reverse hydrogenation at temperatures lower than 210 C. In this paper, we report that the transformation of ...

Co-Production of Ethanol and 1,2-Propanediol via Glycerol Hydrogenolysis Using Ni/Ce–Mg Catalysts: Effects of Catalyst Preparation and Reaction Conditions

“…The increase in glycerol conversion with temperature may have resulted from the enhanced energy intensity at higher temperatures for the reactions to occur, especially the dehydration reaction in glycerol hydrogenolysis. Better selectivity to 1,2-PDO at 200-215 °C was potentially caused by the balance between dehydration and hydrogenation reactions, since dehydration is favored at higher temperatures and hydrogenation at lower temperatures [42]. The decline in 1,2-PDO selectivity at 230 °C may have been caused by its further hydrogenolysis, which is evidenced by the higher ethanol and n-propanol contents in the system [18][19][20][21][22][23].…”

Pt/Al2O3 Catalyzed 1,3‐Propanediol Formation from Glycerol using Tungsten Additives

“…Degradation accounts for the formation of gaseous products and is calculated using Equation (3). In this case it is assumed that…”

“…13PD can be produced by hydrogenolysis. Although its regioisomer 1,2-propanediol (12PD) can be produced at both high conversion and selectivity, [2][3][4] this proves to be more challenging for 13PD (Table 1). [5][6][7][8][9][10][11][12][13][14][15][16] Hydrogenolysis is often mistakenly identified as the process in question, however, in most instances, the process in question is an elimination of water followed by hydrogenation of the formed double bond on a metallic surface.…”

Novel Esterification of Glycerol Catalysed by Tin Chloride (II): A Recyclable and Less Corrosive Process for Production of Bio-Additives

“…Thus, development of processes for converting glycerol into valuable chemicals is becoming the goal of numerous researchers [5,6]. Technologies proposed include the production of well-known industrial scale glycerol-derivates, such as 1,2-and 1,3-propanediols and acrolein [7,8], use of glycerol as a raw material for production of food additives, surfactants, as well as cosmetics ingredients [9]. Recent studies have investigated the use of ethers and acetals of glycerol as gasoline additives [10].…”