Hydrogenolysis of Glycidol as an Alternative Route to Obtain 1,3-Propanediol Selectively Using MO x -Modified Nickel-Copper Catalysts Supported on Acid Mesoporous Saponite

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.

Selective Production of 1,2-Propanediol or 1,3-Propanediol from Glycerol Hydrogenolysis over Transition Metal Doped Pt/TiO2

Selective hydrogenolysis of biomass-derived glycerol to propanediol is important for producing high value-added chemicals from renewable resources but faces a huge challenge. Here we report a transition metal doped Pt/TiO₂ catalyst with incorporated Cr, Mo, or W oxides, which exhibits the selective formation of 1,2-propanediol or 1,3-propanediol with a yield from 51.2% to 82.5% toward glycerol hydrogenolysis. In situ experimental studies verify that the surrounding CrO_x decreases the hydrogenating ability of Pt, leading to the formation of 1,2-propanediol, while the MoO_x or WO_x brings the Brønsted acid, giving 1,3-propanediol. This modification based on the catalyst compositions alters the reaction pathway with a different adsorption and bond scission mechanism, which can be extended to other sustainable catalytic systems.

Advances for Biorefineries: Glycerol Hydrogenolysis to 1,3-Propylene Glycol

Humanity’s growing dependence on non-renewable resources and the ensuing environmental impact thus generated have spurred the search for alternatives to replace chemicals and energy obtained from petroleum derivatives. Within the group of biofuels, biodiesel has managed to expand worldwide at considerable levels, going from 20 million tn/year in 2010 to 47 million tn/year in 2022, boosting the supply of glycerol, a by-product of its synthesis that can be easily used as a renewable, clean, low-cost raw material for the manufacture of products for the chemical industry. The hydrogenolysis of glycerol leads to the production of glycols, 1,2-propylene glycol (1,2-PG) and 1,3-propylene glycol (1,3-PG). In particular, 1,3-PG has the highest added value and has multiple uses including its application as an additive in the polymer industry, the manufacture of cosmetics, cleaning products, cooling liquids, etc. This review focuses on the study of the hydrogenolysis of glycerol for the production of 1,3-PG, presenting the main reaction mechanisms and the catalysts employed, both in liquid and vapor phase. Engineering aspects and the effect of the operating variables to achieve maximum yields are discussed. Finally, studies related to the stability and the main deactivation mechanisms of catalytic systems are presented.

Cu boosting the collaborative effect of Ni and H+ in alloyed NiCu/saponite catalysts for hydrogenolysis of glycidol

The effect of copper on various acid saponite supported Ni-Cu bimetallic catalysts, prepared with different Ni : Cu ratios, was studied for the liquid phase hydrogenolysis of glycidol on a batch reactor at 393 and 453 K. Characterization of the catalysts showed that Ni and Cu are in close contact as the XRD measurements evidenced the formation of an alloy. H2 chemisorption results revealed that the measured metallic area progressively decreased with an increase in the wt% of copper. In the presence of high metal activity (higher Ni wt%), the formation of 1,2-propanediol (1,2-PD) outweighed, while acid activity led to the formation of dimerization and oligomerization products. The addition of Cu and the increase of the reaction temperature decreased the diol formation but boosted the 1,3-PD/1,2-PD ratio. This could be explained by an improvement of the collaborative effect between the metal Ni and the H+ of the saponite. Therefore, the presence of an appropriate amount of Cu allowed the control of the hydrogenation capacity of Ni and enhanced the collaborative effect of Ni and H+ favouring the formation of 1,3-propanediol with respect to 1,2-propanediol.

Recent Advances in Glycerol Catalytic Valorization: A Review

Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.

Regioselective Ring-Opening of Glycidol to Monoalkyl Glyceryl Ethers Promoted by an [OSSO]-FeIII Triflate Complex

A Fe^III -triflate complex, bearing a bis-thioether-di-phenolate [OSSO]-type ligand, was discovered to promote the ring-opening of glycidol with alcohols under mild reaction conditions (0.05 mol % catalyst and 80 °C). The reaction proceeded with high activity (initial turnover frequency of 1680 h^-1 for EtOH) and selectivity (>95 %) toward the formation of twelve monoalkyl glyceryl ethers (MAGEs) in a regioselective fashion (84-96 % yield of the non-symmetric regioisomer). This synthetic approach allows the conversion of a glycerol-derived platform molecule (i.e., glycidol) to high-value-added products by using an Earth-crust abundant metal-based catalyst.

Selective synthesis of 1,3-propanediol from glycidol over a carbon film encapsulated Co catalyst

A carbon film encapsulated Co NP catalyst (Co@NC) was highly active, selective and stable for the hydrogenation of glycidol to 1,3-PDO.

Effect of Re promoter on the structure and catalytic performance of Ni–Re/Al2O3 catalysts for the reductive amination of monoethanolamine

In this paper, Ni/Al₂O₃ catalysts (15 wt% Ni) with different Re loadings were prepared to investigate the effect of Re on the structure and catalytic performance of Ni–Re/Al₂O₃ catalysts for the reductive amination of monoethanolamine. Reaction results reveal that the conversion and ethylenediamine selectivity increase significantly with increasing Re loading up to 2 wt%. Ni–Re/Al₂O₃ catalysts show excellent stability during the reductive amination reaction. The characterization of XRD, DR UV-Vis spectroscopy, H₂-TPR, and acidity–basicity measurements indicates that addition of Re improves the Ni dispersion, proportion of octahedral Ni²⁺ species, reducibility, and acid strength for Ni–Re/Al₂O₃ catalysts. The Ni15 and Ni15–Re2 catalysts were chosen for in-depth study. The results from SEM-BSE, TEM, and CO-TPD indicate that smaller Ni⁰ particle size and higher Ni⁰ surface area are obtained in the reduced Ni–Re/Al₂O₃ catalysts. Results from in situ XPS and STEM-EDX line scan suggest that Re species show a mixture of various valances and have a tendency to aggregate on the surface of Ni⁰ particles. During reaction, the Ni⁰ particles on the Al₂O₃ support are stabilized and the sintering process is effectively suppressed by the incorporation of Re. It could be concluded that sufficient Ni⁰ sites, the collaborative effect of Ni–Re, and brilliant stability contribute to the excellent catalytic performance of Ni–Re/Al₂O₃ catalysts for the reductive amination of monoethanolamine.

Re promoters improve the catalyst performance and stability of Ni–Re/Al₂O₃ catalysts for the reductive amination of monoethanolamine.