Hydrogenolysis of Glycerol to Propylene Glycol: Energy, Tech-Economic, and Environmental Studies

Abstract

Hydrogenolysis of glycerol to propylene glycol represents one of the most promising technologies for biomass conversion to chemicals. However, conventional hydrogenolysis processes are often carried out under harsh H2 pressures and temperatures, leading to intensive energy demands, fast catalyst deactivation, and potential safety risks during H2 handling. Catalytic transfer hydrogenolysis (CTH) displays high energy and atom efficiency. We have studied a series novel solid catalysts for CTH of glycerol. In this work, detailed studies have been conducted on energy optimization, tech-economic analysis, and environmental impact for both processes. The key finding is that relatively less energy demands and capital investment are required for CTH process. CO2 emission per production of propylene glycol is much lower in the case of transfer hydrogenolysis. The outcome of this study could provide useful information for process design and implementation of novel hydrogenolysis technologies for other energy and environmental applications.

A review on non-noble metal catalysts for glycerol hydrodeoxygenation to 1,2-propanediol with and without external hydrogen

“…Other key findings are: (i) relatively fewer energy demands (83% of conventional hydrogenolysis) and capital investment for CTH; (ii) CO 2 emission per production of 1,2-PDO is much lower. 224…”

“…In spite of all these facts, in CTH the 1,2-PDO productivity is lower than the hydrogenolysis process, as the economy has been balanced due to co-production of another high valuable product acetol. 224 From these reports, it could be clearly inferred that the CTH and the glycerol hydrogenolysis under ambient hydrogen pressure has the potential for the commercialization encompassing its process and environmental viability. However, there are some more aspects need to be contemplated critically viz.…”

Insights on production mechanism and industrial applications of renewable propylene glycol

“…Catalytic transfer hydrogenolysis (CTH) is perceived as one of environmentally friendly alternative to conventional hydrogenolysis that occurs without the addition of external hydrogen. CTH requires much milder reaction temperature and lower operating pressure ( Sun et al., 2022 ). The process occurs in the presence of a catalyst that facilitates the production of renewable hydrogen donors in the liquid medium.…”

“…Pd catalysts are often preferred due to their promising hydrothermal stability and high selectivity for the cleavage of C–O bonds over C–C bonds.

Figure 6 Comparison between conventional hydrogenolysis and catalytic transfer hydrogenolysis (CTH) Reproduced from Sun et al.,(2022) .

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Combined dehydrogenation of glycerol with catalytic transfer hydrogenation of H2 acceptors to chemicals: Opportunities and challenges

“…In general, as a chemical building block, the glycerol can be converted to a series of value-added chemicals, such as lactic acid (LA), propanediol (PDO), ethylene glycol (EG), glyceric acid, dihydroxyacetone, glycolic acid, and tartronic acid. ( Zhang et al, 2019 ; Meng et al, 2020 ; Liu et al, 2021 ; Sun et al, 2021 ; Yan et al, 2021 ; Zhang et al, 2021 ; Md Rahim et al, 2022 ). These products are widely used in food, medicine, organic synthesis, chemical industry, and other fields.…”