Liquid-phase Glycerol Hydrogenolysis Research Articles

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO x with metal Ru particles can form “MoO x -Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.

Copper-Containing Catalysts in the Liquid-Phase Hydrogenolysis of Glycerol

The features of the liquid-phase hydrogenolysis of glycerol to 1,2-propylene glycol over Cu/Al2O3 catalysts (Cu = 2–80 wt %) and individual copper particles have been studied. It has been shown that the main factor determining the activity of the catalysts is the specific surface area of copper. It has been found that the Cu/Al2O3 catalyst containing 60 wt % Cu is the most efficient. A new reaction mechanism is proposed based on the obtained data.

Effect of support acidity during selective hydrogenolysis of glycerol over supported palladium-ruthenium catalysts.

We report the role of the acidity of support during the selectivity hydrogenolysis of glycerol over supported bimetallic palladium-ruthenium (PdRu) catalysts. The PdRu nanoparticles were supported on a series of metal oxides and zeolitic supports via the modified impregnation method and tested for the liquid-phase hydrogenolysis of glycerol using gaseous hydrogen. The relative acid site densities of selected catalysts were determined by ammonia temperature-programmed desorption and pyridine desorption experiments. Based on these studies, we report a direct correlation between the catalytic activity (conversion and 1,2 propane diol yield) and two different acid sites (strong acid sites and very strong acid sites). Besides zeolite-supported catalysts, TiO2 supported PdRu nanoparticles exhibit moderate catalytic activity; however, this catalyst shows high selectivity for the desired C-O bond cleavage to produce C3 products over the undesired C-C bond cleavage to produce < C3 products. This article is part of a discussion meeting issue 'Science to enable the circular economy'.

Identification of the dehydration active sites in glycerol hydrogenolysis to 1,2-propanediol over Cu/SiO2 catalysts

Metal–support interaction is a hot topic in catalysis, but attention has seldom been drawn to the promotional effect of metal–irreducible SiO2 interfaces. Here, Cu/SBA-15 catalysts with CuOSiO interface structures were prepared by simple grinding, and showed high activity and selectivity to 1,2-propanediol above 97% in liquid-phase glycerol hydrogenolysis. Glycerol conversion of ground Cu/SBA-15 with 10% Cu loading was about seven times that of its impregnation counterpart. The linear relationship between turnover frequency and (CuOSiO induced Lewis acid sites)/Cu0 ratio indicated that CuOSiO structures were crucial for achieving excellent hydrogenolysis performance. More importantly, in situ Fourier transform infrared spectroscopy of glycerol adsorption and density functional theory calculation results confirmed that CuOSiO species were the dominant active dehydration sites of glycerol hydrogenolysis, while the adjacent Cu sites were involved in subsequent hydrogenation of the generated hydroxyacetone.

Influence of Boron, Tungsten and Molybdenum Modifiers on Zirconia Based Pt Catalyst for Glycerol Valorization.

The influence of boron, tungsten and molybdenum modifiers on zirconia-based Pt catalyst was studied for glycerol valorization. Zirconia modified supports were prepared by impregnation of ZrO2 with either boric, silicontungstic or phosphomolybdic acids to obtain supports with enhanced Brönsted acidic properties. The modified supports were subsequently impregnated with chloroplatinic acid to obtain Pt-based catalysts. Pt incorporation resulted in the increase in Lewis acidity of the solids, being more significant for the Pt//W/ZrO2 catalyst. Reduced Pt catalysts were tested for the liquid-phase glycerol hydrogenolysis, observing a synergistic effect between catalyst acid sites and metal function that proved to be crucial in glycerol hydrogenolysis. The Pt//W/ZrO2 catalyst was the most active catalyst in this reaction, being the only leading to 1,3-PDO (45% sel., 160 °C) while Pt//Mo/ZrO2 is the best option for 1,2-PDO (49% sel., 180 °C). Reusability studies carried out for Pt//W/ZrO2 showed that catalytic activity dropped after the first use, remaining constant for the second and subsequent ones. Selectivity to reaction products also changes during reuses. Therefore, the selectivity to 1,2 PDO increases in the first reuse in detriment to the selectivity to n-propanol whereas the selectivity to 1,3-PDO remains constant along the uses. This behavior could be associated to the lixiviation of W species and/or catalyst fouling during reaction runs.

Kinetic modelling for the hydrogenolysis of bio-glycerol in the presence of a highly selective Cu–Ni–Al2O3 catalyst in a slurry reactor

A kinetic study on the liquid phase hydrogenolysis of glycerol was carried out in a slurry reactor in the presence of a highly selective Cu–Ni–Al2O3 catalyst at different reaction temperatures (180–220 °C) and pressures (3–6 MPa), and very high selectivity was achieved (∼95%) towards 1,2-propanediol (1,2-PDO).

HYDROGENOLYSIS OF GLYCEROL: COMPARISON OF CONTINUOUS AND BATCH MODE REACTIONS OVER Ni-ZnO CATALYSTS

Ni-Zn mixed oxide catalysts with varying mole ratios were prepared by the coprecipitation method. These catalysts were characterized by Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction, temperature programmed reduction, H2 chemisorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. Selective hydrogenolysis of glycerol to 1,2-propanediol was carried out with these catalysts both in continuous (fixed bed) and batch (liquid phase) conditions. Higher glycerol conversion was achieved in a fixed bed than in liquid phase glycerol hydrogenolysis. The selectivity to 1,2-propanediol was more in batch mode hydrogenolysis, whereas acetol is the main product in the continuous mode. The activity of catalysts depended on the Ni to Zn mole ratio, which in turn influenced the metal surface area of Ni on ZnO. The catalyst with a Ni to Zn mole ratio of 2 exhibited the highest activity. The observed activity was corroborated with the derived physicochemical properties of the catalysts. Different reaction parameters were studied and optimum reaction conditions were established.

Development of Kinetic Model for Hydrogenolysis of Glycerol over Cu/MgO Catalyst in a Slurry Reactor

Kinetics of the liquid phase hydrogenolysis of glycerol was investigated over 35 wt % Cu/MgO catalyst in a slurry batch reactor. The power law and Langmuir–Hinshelwood–Hougen–Watson (LHHW) models were tried to fit the experimental data. To develop the kinetic model, a new reaction mechanism is proposed. To simulate the experimental concentration–time data, the set of differential equations were developed and solved numerically by using ode23 stiff system coupled with the genetic algorithm optimization technique. Kinetic parameters were estimated by minimizing the residual sum of squares between the predicted and experimental concentrations of glycerol, 1,2-propanediol (1,2-PDO), and ethylene glycol (EG). Power law showed that hydrogenolysis of glycerol over 35 wt % Cu/MgO catalyst followed the overall reaction order of 1.2 with respect to glycerol with an activation energy of 84.9 kJ/mol. The LHHW model satisfactorily correlated the rate data, and this model showed good fit between the experimental and calculated concentration of glycerol as well as products.

Diols Production From Glycerol Over Pt-Based Catalysts: On the Role Played by the Acid Sites of the Support

A series of 1 wt% AuPt (6:4) catalysts were prepared by sol immobilization using acidic [TiO2, H-Mordenite, SiO2, MCM-41, sulphated ZrO2 (S-ZrO2)] and one basic (MgO) oxide supports. A careful characterization of the catalyst was performed by HRTEM and FTIR spectroscopy. EDX analysis showed that on all catalysts only alloyed AuPt nanoparticles are present, but the final size of AuPt particles is significantly affected by the support. Indeed, on TiO2 the mean AuPt nanoparticles diameter is 3.7 nm, whereas for all the remaining supports, larger AuPt nanoparticles with diameter of 6–7.5 nm were obtained. AuPt catalysts result very active in catalyzing the liquid phase hydrogenolysis of glycerol to 1,2-propandiol (68% conversion after 16 h) and 90% selectivity with ethylene glycol, 1-propanol and 2-propanol as main by-products. The role of the support has been highlighted in terms of acidic properties. The medium strength of Lewis acid sites of TiO2 leads to the best performance in terms of activity, selectivity and stability of the catalytic system.

Liquid Phase Hydrogenolysis of Glycerol over Highly Active 50%Cu–Zn(8:2)/MgO Catalyst: Reaction Parameter Optimization by Using Response Surface Methodology

In this study, a highly promising bimetallic 50%Cu–Zn(8:2)/MgO catalyst was developed for selective hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). The catalytic activity was evaluated in a high pressure autoclave reactor. Results demonstrated that the incorporation of Zn into Cu/MgO catalysts enhanced the glycerol conversion and selectivity to 1,2-PDO due to the hydrogen spillover effect. Experimentally maximum glycerol conversion of 98.7% with 94.6% selectivity to 1,2-PDO was achieved at mild reaction conditions. Response surface methodology (RSM) was employed to study the interaction of the various reaction parameters and develop an empirical process model followed by the optimization of the reaction parameters. The high values for determination coefficients (>0.95) obtained by analysis of variance indicated that the quadratic regression models developed were highly satisfactory. The results of numerical optimization demonstrated that 97.8% glycerol conversion with 93.5% selectivity to 1,2-PDO...

Bio-propylene glycol by liquid phase hydrogenolysis of glycerol with Ni/SiO2-C catalysts

The development of catalytic materials, hydrothermally stable and selective to the desired products, is still a challenge. The aim of the present work is to prepare a nickel catalyst with a metal loading of 5wt% Ni supported on a SiO2-C composite, to be used in the liquid-phase glycerol hydrogenolysis reaction. The most active and selective catalyst to 1,2-propylene glycol (1,2-PG) was Ni/SC-095, which presented surface acidity fundamentally represented by the presence of carboxylic groups which promoted the CO cleavage reactions of the glycerol primary carbon to produce acetol, and subsequently by hydrogenation to produce 1,2-PG.Concerning the selection of operating conditions, the influence of the most relevant variables of the process were analyzed, i.e., temperature (220–260°C), glycerol concentration (30–65%), and hydrogen partial pressure (0–4MPa). The best result was obtained at 260°C with 30wt% glycerol, 6h on reaction and a hydrogen partial pressure of 2MPa. Under these conditions, selectivities of 77% towards 1,2-PG and 3% to acetol were obtained, with 56% of conversion.It was demonstrated that there are no important structural changes through the characterization of the used samples. Both the SC-095 support and the Ni/SC-095 catalyst maintained their BET surface area. By XRD and TEM, there could be a slight increase in particle size, which would indicate good resistance to sintering against the severe hydrothermal conditions of this reaction.

Kinetic study of liquid-phase glycerol hydrogenolysis over Cu/SiO2 catalyst

The kinetics of glycerol hydrogenolysis reaction to 1,2-propanediol was studied over a stable 18wt%Cu supported on commercial silica gel catalyst in a batch reactor. This catalyst is extremely selective to 1,2-propanediol (up to 95%). The second largest product formed is 1,3-propanediol. The reaction kinetics was investigated over a temperature range of 453–513K, hydrogen concentration in liquid phase of 4.52–93.8mmol/L (by varying H2 pressure between 2 and 8MPa), initial glycerol concentration 20–40v/v/% and catalyst weight 0.05–0.35g. Glycerol hydrogenolysis reaction proceeds via a two-step dehydration–hydrogenation mechanism with different intermediates (acetol and 3-hydroxypropionaldehyde) formed which sequentially lead to 1,2- and 1,3-propanediol production. In the kinetic regime studied, the overall reaction rate showed an almost zero order dependence on glycerol initial concentration and nearly first order on hydrogen concentration in liquid phase. The formation rate of 1,2-propanediol also seems to not to be affected of the initial glycerol concentration, depending (almost first order) on H2 concentration. Furthermore, the formation rate of the 1,3-propanediol, is strongly dependent on glycerol concentration and presents variable order to H2 from 0.94 (nearly first order) at lower pressures to zero at higher pressures. The activation energies calculated for the overall (96.8kJ/mol) and the two parallel reaction routes (1,2-propanediol=94.3 and 1,3-propanediol=135.3kJ/mol) demonstrate the selective formation of the 1,2-propanediol at lower temperatures.

Liquid-phase glycerol hydrogenolysis by formic acid over Ni–Cu/Al2O3 catalysts

Two series of Ni–Cu/Al2O3 catalysts with different Cu/Ni ratio and different total metal contents were prepared and tested in the glycerol hydrogenolysis to 1,2-propanediol under N2 pressure and using formic acid as hydrogen donor molecule. The results from the deep characterization of the catalysts by N2-physisorption, transmission electron microscopy (TEM), temperature-programed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programed desorption of ammonia (TPD-NH3), together with the results from the activity tests allowed deeper understanding of the role played by Ni, Cu, and acid catalytic sites. The kinetic study performed with the optimized catalyst revealed that the OH groups of glycerol and of the target product, 1,2-propanediol, compete for adsorption on the acid sites of the Al2O3 support. 90% glycerol conversion and 82% 1,2-propanediol selectivity after 24h reaction time were achieved when operating at 493K.

Liquid-phase glycerol hydrogenolysis to 1,2-propanediol under nitrogen pressure using 2-propanol as hydrogen source

2-Propanol was studied as a hydrogen donor molecule in the transfer hydrogenation process to selectively convert glycerol into 1,2-propanediol under N 2 pressure and using Ni or/and Cu supported on Al 2O 3 catalysts. The results were compared to those obtained under the same operating conditions but under H 2 pressure. The results of the activity tests and catalyst characterization techniques (N 2-physisorption, H 2-chemisorption, TPD of NH 3, TPR, TPO and XPS) suggest that glycerol hydrogenolysis to yield 1,2-propanediol occurred through a different mechanism regarding the origin of the hydrogen species. When atomic hydrogen came from dissolved molecular hydrogen dissociation, glycerol was first dehydrated to acetol and then hydrogenated to 1,2-propanediol. On the other hand, when the hydrogen atoms were produced from 2-propanol dehydrogenation, glycerol was directly converted to 1,2-propanediol through intermediate alkoxide formation.

Hydrogenolysis of glycerol to 1,2‐propanediol catalyzed by Cu‐H4SiW12O40/Al2O3 in liquid phase

AbstractBACKGROUND: Crude glycerol will increase to over 400 million L year−1, and the market is likely to become saturated due to the limited demand for glycerol. The main aim of this work is to develop a novel process for the sustainable conversion of glycerol to 1,2‐propanediol (l,2‐PD).RESULTS: Cu‐H4SiW12O40/Al2O3 catalysts with different H4SiW12O40 (STA) loadings were prepared for the hydrogenolysis of glycerol to produce l,2‐PD in liquid phase. At 513 K, 6 MPa and LHSV of 0.9 h−1 in 10% (w/w) glycerol aqueous solutions, the catalyst with 5% (w/w) STA showed the best performance with 90.1% of glycerol conversion and 89.7% selectivity to l,2‐PD. More important, both the initial glycerol conversion and l,2‐PD selectivity were maintained over 250 h.CONCLUSION: l,2‐PD can be continuously produced with high yields via the liquid phase hydrogenolysis of glycerol over Cu‐H4SiW12O40/Al2O3. Furthermore, the characterization indicated that catalyst acidity could be greatly modified by STA, which promoted Cu reducibility. It was also found that hydrogenolysis could be favored by a bi‐functional catalyst with the appropriate amount of both acid and metal sites. Copyright © 2010 Society of Chemical Industry