Hydrogenolysis of Glycerol over γ-Al2O3-Supported Iridium Catalyst

Abstract

In recent years, much attention has been focused on the hydrogenolysis of biodiesel derived glycerol to other high IntroductionThe fluctuating increasing oil prices and the increased world-wide environmental concerns towards minimizing CO 2 emissions tend to highlight the necessity of renewable resources. Biodiesel derived from renewable resources comprising, for instance, vegetable oils and animal fats has attracted great attention recently. Glycerol is considered to be the main byproduct that results during biodiesel production. Nevertheless, increases in the production of glycerol from biodiesel refining accompanied with the tight markets of glycerol supply and demand created a glut in the glycerol market. This resulted in a significant fall in the glycerol price and limited options for glycerol byproduct management are hence available to biodiesel refiners [1]. Thus, finding solutions for the effective utilization of glycerol waste is crucial to achieve both economic and environmental benefits. Consequently, this will turn the biofuel producers to view the byproduct as a valuable resource for their own production processes instead of viewing glycerin as a waste [2,3].Over the past decades, the hydrogenolysis of higher polyols like sorbitol, xylitol, and glycerol has been investigated in literature [4,5]. Recently, the hydrogenolysis of glycerol into value-added chemicals emerged as an attractive process for glycerol valorization [6,7]

Heterogeneous Catalysts for Glycerol Biorefineries: Hydrogenolysis to 1,2-Propylene Glycol

“…This caused a drop in the selectivity values to 1,2-PG, in contrast to the results obtained by other authors [113]. Ahmed et al also detected side products due to the reaction between EG and GLA under basic conditions, employing a Ru/AlF 3 -Al 2 O 3 catalyst [75].…”

“…The most commonly employed Ru precursors have been RuCl 3 [48,53,[72][73][74][75][76][77][79][80][81][85][86][87][88][89][90][91][92], Ru(NO)(NO 3 ) 3 [48,77,84,86,91], Ru (AcAc) 3 [48,82], and Ru 3 (CO) 12 [82].…”

“…With respect to the preparation methods, the most commonly employed have been the wetness incipient impregnation [43,48,72,73,75,77,[79][80][81][82][84][85][86][87][88]90,93] and depositionprecipitation [76,90]. Balaraju et al prepared Ru/TiO 2 catalysts employing both methods.…”

“…With respect to Ru/Al 2 O 3 catalysts, the modification of the support with AlF 3 for contents between 17 and 58 wt.% allowed the maximum glycerol conversions to be reached, due to a higher dispersion of Ru particles; however, it also promoted the formation of EG and gases such as methane [75], probably due to the surface acidity generated by the presence of the modifier.…”

“…Materials 2023, 16, x FOR PEER REVIEW 2 of 75 and include all organic matter from plants, as well as organic waste from humans, animals, aquatic life, and plants. Biomass sources allow for obtaining not only energy, such as heat and electricity through thermal conversion processes, but also gaseous fuels, such as methane and hydrogen, and liquid fuels such as ethanol and biodiesel.…”