The effect of metal properties on the reaction routes of glycerol hydrogenolysis over platinum and ruthenium catalysts

Production of 1,3-propanediol via in situ glycerol hydrogenolysis in aqueous phase reforming using bimetallic W-Ni/CeO2

The production of 1,3-propanediol via in situ glycerol hydrogenolysis and aqueous phase reforming is a promising technique to ensure high product yield with shorter reaction times and lower costs, as demonstrated in this study by investigating the effect of tungsten (W) doping on Ni/CeO2 catalysts. Physicochemical properties of catalyst were determined using XRD, H2-TPR, NH3-TPD, BET, and FESEM-EDX techniques, and the catalytic performance was investigated at 230 °C, 20 bar, and 5 wt.% glycerol in an autoclave batch reactor. W doping ranging from 1-7% improved the catalyst's performance, with 3% W in 10% Ni/CeO₂ (3W10NC) achieving the highest yield (2.4%), selectivity (33.3%), and a good conversion rate (72.18%). The effect of reaction parameter on the 3W10NC catalyst showed that increasing pressure and temperature from the initial parameters had a detrimental effect on 1,3-propanediol attributed to the phenomenon called over-hydrogenolysis. Increasing the glycerol concentration to 20 wt.% also had a positive effect, resulting in the highest 1,3-propanediol yield of 22.27%. The effect of reaction time study revealed that the yield of 1,3-propanediol continued to increase steadily, reaching 38.29% after 4 h of reaction under the optimal conditions of 230 °C, 20 bar, and 20 wt.% glycerol. The kinetic study confirmed that the reaction follows first-order reaction with activation energy of 20.104 kJ mol-1. The catalyst reusability test revealed a decrease in the yield of 1,3-propanediol to 32.55%, likely due to deactivation caused by sintering and leaching, as indicated by the FESEM micrograph, EDX spectra, and NH3-TPD.

Catalytic Upgrading of a Mixed Hydroxy Acid Feedstock Derived from Kraft Black Liquor

Lignocellulosic feedstocks are widely studied for sustainable liquid fuel and chemical production. The pulp and paper industry generates large amounts of kraft black liquor (BL) from which a high volume of hydroxy acids (HAs) can be separated for further catalytic processing. Here, we explore the catalytic upgrading of HAs, including the conversion of (1) a model HA, gluconic acid; (2) a model mixture of HAs, and (3) a real mixture of HAs derived from kraft BL on M/Nb2O5 (M = Pd, Pt, Rh, and Ru). The hydrodeoxygenation of model gluconic acid reveals that "volatile" carboxylic acids (mainly C2 and C3), levulinic acid, and cyclic esters are significant products over all the catalysts, with Pd/Nb2O5 showing superior activity and selectivity toward valuable intermediates. The model mixture of HAs shows a wide range of reactivity over the supported metal catalyst, with the product selectivity strongly correlating to reaction temperature. Utilizing a 0.25% Pd/Nb2O5 catalyst, a real mixture of HAs derived from kraft BL is successfully dehydroxylated to produce a mixture rich in C3-C8 carboxylic acids that may be amenable for further upgrading, e.g., catalytically to ketones with high carbon chain lengths. Despite the feedstock complexity, we selectively cleaved the C-OH bonds of HAs, while successfully preserving most of the -COOH groups and minimizing C-C and C=O bond scission reactions under the operating conditions tested. The BL-derived HA stream is thus proposed to be a suitable platform for producing mixed carboxylic acid products from an overoxygenated byproduct feed.

Sr Promoted Ni/W-Zr Catalysts for Highly Efficient CO2 Methanation: Unveiling the Role of Surface Basicity

This study explores the employment of CO2 methanation for carbon dioxide utilization and global warming mitigation. For the first time, in this work, we combine the interesting properties of the WO3-ZrO2 support and the benefits of Sr to improve the performance of Ni-based catalysts in this reaction. Sr loading on 5Ni/W-Zr samples is increased to 3 wt %, resulting in improved surface basicity through strong basic site formation. After 300 min, the 5Ni + 3Sr/W-Zr catalyst exhibits high activity and stability, achieving 90% CO2 conversion and 82% CH4 yield compared to 62 and 57% on 5Ni/W-Zr. Limited sintering and absence of carbon deposits are confirmed by temperature-programmed oxidation, XRD, Raman, and TEM analyses at 350 °C for 300 min. Sr promotion creates additional CO2 adsorption and conversion sites, enhancing the catalytic performance.

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

Research on the use of biomass resources for the generation of energy and chemical compounds is of great interest worldwide. The development and growth of the biodiesel industry has led to a parallel market for the supply of glycerol, its main by-product. Its wide availability and relatively low cost as a raw material make glycerol a basic component for obtaining various chemical products and allows for the development of a biorefinery around biodiesel plants, through the technological integration of different production processes. This work proposes a review of one of the reactions of interest in the biorefinery environment: the hydrogenolysis of glycerol to 1,2-propylene glycol. The article reviews more than 300 references, covering literature from about 20 years, focusing on the heterogeneous catalysts used for the production of glycol. In this sense, from about 175 catalysts, between bulk and supported ones, were revised and discussed critically, based on noble metals, such as Ru, Pt, Pd, and non-noble metals as Cu, Ni, Co, both in liquid (2-10 MPa, 120-260 °C) and vapor phase (0.1 MPa, 200-300 °C). Then, the effect of the main operational and decision variables, such as temperature, pressure, catalyst/glycerol mass ratio, space velocity, and H₂ flow, are discussed, depending on the reactors employed. Finally, the formulation of several kinetic models and stability studies are presented, discussing the main deactivation mechanisms of the catalytic systems such as coking, leaching, and sintering, and the presence of impurities in the glycerol feed. It is expected that this work will serve as a tool for the development of more efficient catalytic materials and processes towards the future projection of glycerol biorefineries.

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

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.

Easily Recycled CuMgFe Catalysts Derived from Layered Double Hydroxides for Hydrogenolysis of Glycerol

A series of CuMgFe catalysts with different (Cu + Mg)/Fe molar ratios derived from hydrotalcites were prepared by coprecipitation for the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), vibrating sample magnetometer (VSM), hydrogen temperature-programmed reduction (H2-TPR), CO2-TPD, and H2-TPD (temperature-programmed desorption of CO2 and H2) were used to investigate the physicochemical properties of the catalysts. The CuMgFe-layered double oxides (CuMgFe-4LDO) catalyst with (Cu + Mg)/Fe molar ratio of 4 exhibited superior activity and stability. The high glycerol conversion and 1,2-propanediol selectivity over CuMgFe-4LDO catalyst were attributed to its strong basicity, excellent H2 activation ability, and an increase in the surface Cu content. The CuMgFe catalysts could be easily recycled with the assistance of an external magnetic field due to their magnetism.

Study of Ni/Al-Fe Catalyst Stability in the Aqueous Phase Hydrogenolysis of Glycerol

The present work studied the stability and reusability of Ni/Al-Fe catalyst in the aqueous phase hydrogenolysis of glycerol without external hydrogen addition. The catalyst based on 28 molar % of Ni with 3/1 molar ratio of Al/Fe was prepared through co-precipitation. This catalyst presented the best performance in our last study which compares several Ni/Al-Fe catalysts with different molar ratios of Al/Fe. To see the influence of the pressurized water on the physicochemical characteristics of Ni/Al-Fe catalyst, a test of up to 9 h has been carried out. Fresh and used catalysts were characterized by various techniques: X-ray Diffraction (XRD), N2-physisorption, field emission scanning electron microscopy (FESEM) and STEM. Glycerol conversion and carbon yield to gases and liquids did not vary significantly when compared at 3 h and 9 h. Furthermore, the morphology of the catalyst remains stable after continuous recycling under severe hydrothermal conditions. The nickel rich phase of the catalyst, which was determined by XRD and scanning transmission electron microscopy (STEM) techniques, showed a stable size after 9 h under reaction.

Selective, bifunctional Cu–WOx/Al2O3 catalyst for hydrodeoxygenation of fatty acids

Cu–WO_x/Al₂O₃ is highly selective for hydrodeoxygenation of oleic acid. Texture and acidity influenced the catalyst activity.

The route towards sustainable production of ethylene glycol from a renewable resource, biodiesel waste: a review

Ethylene glycol (EG) is a commodity chemical commercially produced via oxidation of the petrochemical-based resource, ethylene.

An Overview of Recent Research in the Conversion of Glycerol into Biofuels, Fuel Additives and other Bio-Based Chemicals

The depletion of fossil fuels has heightened research and utilization of renewable energy such as biodiesel. However, this has thrown up another challenge of significant increase in its byproduct, glycerol. In view of the characteristics and potentials of glycerol, efforts are on the increase to convert it to higher-value products, which will in turn improve the overall economics of biodiesel production. These high-value products include biofuels, oxygenated fuel additives, polymer precursors and other industrial bio-based chemicals. This review gives up-to-date research findings in the conversion of glycerol to the above high-value products, with a special focus on the performance of the catalysts used and their challenges. The specific products reviewed in this paper include hydrogen, ethanol, methanol, acetin, glycerol ethers, solketal, acetal, acrolein, glycerol carbonate, 1,3-propanediol, polyglycerol and olefins.