Production of Propanediols through In Situ Glycerol Hydrogenolysis via Aqueous Phase Reforming: A Review

Abstract

Production of 1,2-propanediol and 1,3-propanediol are identified as methods to reduce glycerol oversupply. Hence, glycerol hydrogenolysis is identified as a thermochemical conversion substitute; however, it requires an expensive, high-pressure pure hydrogen supply. Studies have been performed on other potential thermochemical conversion processes whereby aqueous phase reforming has been identified as an excellent substitute for the conversion process due to its low temperature requirement and high H2 yields, factors which permit the process of in-situ glycerol hydrogenolysis which requires no external H2 supply. Hence, this manuscript emphasizes delving into the possibilities of this concept to produce 1,2-propanediol and 1,3-propanediol without “breaking the bank” with expenses. Various heterogenous catalysts of aqueous phase reforming (APR) and glycerol hydrogenolysis were identified, whereby the combination of a noble metal, support, and dopant with a good amount of Brønsted acid sites are identified as the key factors to ensure a high yield of 1,3-propanediol. However, for 1,2-propanediol, a Cu-based catalyst with decent basic support is observed to be the key for good yield and selectivity of product. The findings have shown that it is possible to produce high yields of both 1,2-propanediol and 1,3-propanediol via aqueous phase reforming, specifically 1,2-propanediol, for which some of the findings achieve better selectivity compared to direct glycerol hydrogenolysis to 1,2-propanediol. This is not the case for 1,3-propanediol, for which further studies need to be conducted to evaluate its feasibility.

Transition Metal Catalysts for the Glycerol Reduction: Recent Advances

“…[17] Diols, such as 1,2-PD and propane-1,3-diol (1,3-PD), are useful products, largely employed in polymer industries (e. g., packaging, fiber, filler) that can be obtained by hydrogenolysis of GL. [18,19] The reaction is a variegated process that can be conducted, for example, on a metal-acid bifunctional catalyst, able to promote dehydration, via intermediates as hydroxyacetone (Hac) and 3-hydroxypropanal (3-HPA), followed by a hydrogenation reaction occurring on metal sites. [19] It was observed that increased aqueous GL conversion (from 53 % to 74 %) and 1,3-PD yield (from 20 % to 25 %) were obtained if TiO 2 was used as support for Pt/WO 3 -ZrO 2 catalyst, carrying out the reaction in a vertical stainless steel fixed-bed reactor at 523 K and 50 bar H 2 pressure.…”

“…[18,19] The reaction is a variegated process that can be conducted, for example, on a metal-acid bifunctional catalyst, able to promote dehydration, via intermediates as hydroxyacetone (Hac) and 3-hydroxypropanal (3-HPA), followed by a hydrogenation reaction occurring on metal sites. [19] It was observed that increased aqueous GL conversion (from 53 % to 74 %) and 1,3-PD yield (from 20 % to 25 %) were obtained if TiO 2 was used as support for Pt/WO 3 -ZrO 2 catalyst, carrying out the reaction in a vertical stainless steel fixed-bed reactor at 523 K and 50 bar H 2 pressure. [20] An explanation of this improvement could be the introduction of TiO 2 that increased the Brønsted acidity of the catalyst: WO x species were linked, through O bridges, to Zr but also to Ti, with a larger electronegativity than Zr.…”

The Biosynthesis of Liquid Fuels and Other Value-Added Products Based on Waste Glycerol—A Comprehensive Review and Bibliometric Analysis

“…Because it is non-toxic, it can also be used in the food industry, e.g., as a solvent for colourings and flavourings and as a sweetener [27]. In addition, it is also subjected to thermochemical conversion into polypropylene glycol [28] or acetol [29]. Purified glycerol also undergoes a number of chemical modifications, which make it a viable raw material for the production of dihydroxyacetone, epichlorohydrin, acrylic acid and glycerol esters and ethers [30].…”

The Application of the Nanofiltration Membrane NF270 for Separation of Fermentation Broths

“…Nowadays, 1,3-propanediol (1,3-PD) is considered one of the most important valueadded chemicals which has been widely used in the polymer, pharmaceutical, and cosmetics industries. On an industrial scale, 1,3-PD is manufactured mainly from fossil-derived chemicals via Shell or Degussa processes [1][2][3]. However, the synthesis of 1,3-PD by bioconversion would be a step toward achieving sustainable development goals [4].…”