Hydrogenolysis Of Sorbitol Research Articles

Catalytic hydrogenolysis of sorbitol to glycols over chromium oxide silica: Effect of chromium loading

Cr2O3-SiO2 (CrSi) catalysts were prepared using the sol-gel method with varying Cr2O3 loadings (5%, 10%, 15%, 20%, and 25% by weight). The physical properties of the synthesized catalysts were characterized through N2 physisorption analysis, X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Additionally, NH3-TPD analysis was employed to assess the acidity of the catalysts. The results indicated the presence of ordered mesopores with uniform pore sizes in the synthesized catalysts. The 20CrSi catalyst exhibited high total acidity, which correlated with its catalytic performance. The catalytic activities of the synthesized samples were tested in the sorbitol hydrogenolysis reaction to produce propylene glycols (PG) and ethylene glycols (EG) in a stirred high-pressure reactor under various process conditions. It was found that 20CrSi catalyst recorded maximum sorbitol conversion (70.08%) at optimum reaction condition. The catalyst was reusable up to 5 times with only a minor activity loss. This work contributes to sustainable and green chemical synthesis from renewable sources, offering insights into catalyst design for efficient glycol production.

Biobased Glycols – Towards the Use of Solid Bases in the Hydrogenolysis of Sorbitol

AbstractIn this study, mixed metal oxides of alkaline earth metals and Ti or Zr were synthesized and investigated as solid bases in the hydrogenolysis of sorbitol in combination with Ru/C. Desired products of this reaction are glycols, which are today produced from fossil feedstock and find application as monomers or anti‐freezes. The most promising mixed metal oxide CaZr−O possesses CaO, Ca(OH)2, perovskite and ZrO2 phases. CaO and Ca(OH)2 leach out over the reaction making the solid a depot for the homogeneous base. Additionally, catalytic activity also results from a synergistic effect of the solid perovskite and ZrO2 phases increasing the sum of liquid phase products. After an optimization of the process parameters, a maximum selectivity to glycols of 50 % was achieved at 74 % conversion within 4 h at 220 °C.

Liquid-phase sorbitol hydrogenolysis over Co catalysts: Effect of external vs endogenous H2 on the product distribution

Aqueous sorbitol hydrogenolysis (6.25 wt% aq. solution) in batch reactor was studied over bare and Pt-modified cobalt aluminate-based catalysts at distinct reaction atmospheres (N2 and H2 pressurized) focusing on the correlation between the physico-chemical properties of catalysts and the product distribution. It was found that over trimetallic xPt/CoAl catalysts (x = 0.3 and 1 wt%) operating at 240 °C and hydrogen pressure (60 bar) resulted in a yield of 27–35 molC % C5-6 hydrocarbons. Under inert atmosphere, the highest yield (57–70 molC %) was to monofunctional products with only one oxygen functionality, for all catalysts. A preferential retro-aldol condensation route is manifest. Post-reaction analyses showed less structural and chemical modification in the Pt-containing catalysts and a slight positive difference in those used under hydrogen pressure over those used under inert atmosphere.

Regulating isomerization of gasoline-alkanes in aqueous-phase hydrodeoxygenation of sorbitol using regenerable Ni@MoOx catalysts

Aqueous-phase hydrodeoxygenation (HDO) has been regarded as an efficient biorefinery strategy for sustainable production of gasoline-alkanes from bio-polyols. However, current research focuses mainly on exploiting noble-metal HDO catalysts to acquire straight-chain C5-C6 alkanes. Herein, the aqueous-phase HDO route was firstly proposed to regulate isomerization of gasoline-alkanes in the sorbitol hydrogenolysis utilizing non-noble Mo-based catalysts in a continuous-flow fixed-bed reactor. The selective reduction removal of hydroxyl groups and isomerization of carbon chains were strongly coupled together for boosting the octane value of gasoline-alkanes over the regenerable Ni@MoOx binary catalysts derived from NiMoO4 spinel. Further characterization studies revealed that the synergism of Ni0 and MoOx played a crucial role in regulating selective dissociation of CO bonds and rearrangement of CC bonds, and suppressing excessive cleavage of CC bonds toward C1-C4 alkanes and CO/CO2. The effects of reaction parameters including reaction temperature, H2-pressure and reduction temperature were also evaluated for manipulating the product distribution between n-alkanes and isoalkanes. After optimization, a high C5-C6 yield of 87.5% with 51.7% of C5-C6 isoalkanes mainly including cycloalkanes was achieved at 280 °C under H2-pressure of 1.0 MPa over the Ni@MoOx catalyst reduced at 500 °C. This catalytic strategy could create new opportunities for producing high-quality biofuels from biomass-derived oxygenated compounds.

Suitability of different supported Ru, Pt and Ni catalysts for the hydrogenolysis of sorbitol

In this article, the results of sorbitol hydrogenolysis (15% aq. solution), done in an autoclave reactor, over Ru, Pt and Ni loaded on SBA15, carbon coated SBA15 (SBA15C), activated carbon (AcC), Na–Y, Fly Ash (FA) and hydroxyapatite (HAP) catalysts by our group, were compared to find the best metal-support combinations. The metal loading was 1 wt% for Ru and Pt, 6 wt% for Ni and the catalysts' preparations were carried out by impregnation of respective salts. The catalysts were characterized with nitrogen and hydrogen adsorption measurements and X-ray diffraction. Addition of a base (Calcium hydroxide) to the reactants' mixture increased the overall conversion and selectivities of the glycols, ethylene glycol (EG) and 1,2-propylene glycol (PG). The catalysts’ performance at 60 bar and 220 °C with the presence of base (B), evaluated by the yield of glycols (PG + EG), showed the following order:Ni/Na–Y > Ru/AcC ∼ Ru/SBA15C > Ni/HAP ∼ Ru/SBA15 > Ni/SBA15 > Ru/Na–Y > Ni/FA ∼ Ni/AcC and the yields were 57, 40, 39, 33, 31, 29, 26, 22 and 21 wt%, respectively.Na–Y appeared to be the best support, especially for Ni metal; AcC and SBA15C were good supports for Ru and Pt respectively. Reusability studies revealed that Ni on HAP was the best catalyst and exhibited only a small deactivation during four runs of loading it.

Selective hydrogenolysis of biomass-derived sorbitol to propylene glycol and ethylene glycol on in-situ formed PdZn alloy catalysts

Sorbitol hydrogenolysis to industrially important propylene glycol and ethylene glycol receives increasing attention, recently. Here, we developed an efficient and stable PdZn alloy catalyst, in-situ formed from a physical mixture of Pd/ZrO2 and ZnO, for the sorbitol hydrogenolysis with Mg3AlOx as a solid base, and obtained a 54.6% yield of the two target glycols (493 K and 5.0 MPa H2). The amounts of ZnO and Mg3AlOx strongly influenced the activity and selectivity, due to their effects on the formation of the PdZn alloys and the competitive metal-catalyzed dehydrogenation/hydrogenation and base-catalyzed retro-aldol condensation steps. The kinetic isotope effects, combined with the inhibiting effects of H2 pressure on the activity in a broad range (3.0–8.0 MPa), confirm that the sorbitol dehydrogenation to hexose intermediates is the kinetically-relevant step in the sorbitol hydrogenolysis. This study provides insights into the catalytic functions and reaction parameters for the hydrogenolysis of polyols to the target glycols.

Lattice strained bimetallic PtPd nanocatalysts display multifunctional nature for transfer hydrogenolysis of sorbitol in base-free medium

Catalytic transfer hydrogenolysis (HDO) of polyols by in situ formed H2 under mild reaction conditions and displays both technological and environmental advantages over conventional HDO processes operating at elevated temperatures and pressures. Current studies on catalyst design are primarily focused on compositional features of solid catalysts to obtain superior activity and selectivity to value-added products. A major challenge is to understand the electronic nature of catalysts in C–H, C–C, and C–O cleavage of polyols. In this work, we report a design principle for modulating lattice and electronic configuration of bimetallic PtPd-N-doped mesoporous carbon (NMC) catalysts, immobilized on N-doped carbon, for highly efficient transfer HDO of sorbitol to renewable glycols and alcohols in base-free medium. The finding is that lattice strain and electronic coupling at metal-N interface induce confined growth of PtPd crystal facets, leading to strained structures with Pt lattice contraction and Pd phase segregation. While conventional PtPd nanoparticles exhibit monofunctional nature in facilitating C–H cleavage of sorbitol with poor activity, such unique PtPd-NMC catalysts display a synergistic fourfold activity enhancement (Turnover frequency (TOF): 58 h−1 at 200 °C) for tandem C–H, C–C, and C–O cleavage of polyols. Chemisoprtion and X-ray photoelectron spectroscopy spectroscopy studies reveal that N-doped carbon functions as a Lewis base and lattice modulator to manipulate electronic properties of bimetallic nanocatalysts for facile tandem C–H (H2 generation) and C–O/C–C cleavage (HDO) catalysis.

Hydrogenolysis of biomass-derived sorbitol over La-promoted Ni/ZrO2 catalysts

Ni/La2O3/ZrO2 catalysts were prepared by a step-by-step impregnation method through regulation of the contents of the active component and alkali. The introduction of an alkaline promoter not only enhanced the alkalinity of the catalyst but also improved the dispersion of Ni on the catalyst owing to the strong interaction between Ni2+ and alkali promoter. The synergistic effect between Ni and La2O3 was beneficial to selective hydrogenolysis of sorbitol. Under the optimal reaction conditions, sorbitol conversion reached nearly 100% and target products (ethylene glycol, 1,2-propanediol, and glycerol) selectivity reached 74.8%. Metal–alkali coordination mechanism and possible pathways for target products formation were proposed.

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Production of linear deoxygenated C4 (butanetriols, -diols, and butanols), C5 (pentanetetraols, -triols, -diols, and pentanols), and C6 products (hexanepentaols, -tetraols, -triols, -diols, and hexanols) is achievable by hydrogenolysis of erythritol, xylitol, and sorbitol over supported-bimetallic Rh-ReOx (Re/Rh molar ratio 0.5) catalyst, respectively. After validation of the analytical methodology, the effect of some reaction parameters was studied. In addition to CO bond cleavage by hydrogenolysis, these polyols can undergo parallel reactions such as epimerization, cyclic dehydration, and CC bond cleavage. The time courses of each family of linear deoxygenated C4, C5, and C6 products confirmed that the sequence of appearance of the different categories of deoxygenated products followed a multiple sequential deoxygenation pathway. The highest selectivity to a mixture of linear deoxygenated C4, C5, and C6 products at 80% conversion was favoured under high pressure in the presence of 3.7wt.%Rh-3.5wt.%ReOx/ZrO2 catalysts (54–71% under 80 bar) at 200 °C.

Effect of carbon chain length on catalytic C[sbnd]O bond cleavage of polyols over Rh-ReOx/ZrO2 in aqueous phase

Production of linear deoxygenated C4 (butanetriols, -diols, and butanols), C5 (pentanetetraols, -triols, -diols, and pentanols), and C6 products (hexanepentaols, -tetraols, -triols, -diols, and hexanols) is achievable by hydrogenolysis of erythritol, xylitol, and sorbitol over supported-bimetallic Rh-ReOx (Re/Rh molar ratio 0.5) catalyst, respectively. After validation of the analytical methodology, the effect of some reaction parameters was studied. In addition to CO bond cleavage by hydrogenolysis, these polyols can undergo parallel reactions such as epimerization, cyclic dehydration, and CC bond cleavage. The time courses of each family of linear deoxygenated C4, C5, and C6 products confirmed that the sequence of appearance of the different categories of deoxygenated products followed a multiple sequential deoxygenation pathway. The highest selectivity to a mixture of linear deoxygenated C4, C5, and C6 products at 80% conversion was favoured under high pressure in the presence of 3.7wt.%Rh-3.5wt.%ReOx/ZrO2 catalysts (54–71% under 80 bar) at 200 °C.

Cu/C‐catalyzed Hydrogenolysis of Sorbitol to Glycols–On the Influence of Particle Size and Base

AbstractHerein, a series of Cu catalysts supported on activated carbon with increasing particle size was tested for the conversion of sorbitol to glycols including 1,2‐propanediol and ethylene glycol in the presence of Ca(OH)2. Activity measurements reveal a distinct correlation between TOF and particle size, which increases until 14 nm (N2O chemisorption based) after which a plateau is reached. However, variation of the particle size has no apparent effect on the selectivity for C3/C3 and C2/C4 cleavage. In contrast, variation of the Ca(OH)2 equivalence has a profound impact on selectivity. The ratio of C3/(C2+C4) products reaches an optimum at 0.45 equiv. of Ca(OH)2. Notably, the time course of the reaction demonstrates that the by‐products lactic acid and glycerol are in‐situ converted to the desired product 1,2‐propanediol, contributing to the unprecedented combined glycol selectivity of 84.5 % at 513 K, 5 MPa H2 and 0.3 equiv. of Ca(OH)2. Furthermore, recycling tests reveal a rapid deactivation which is attributed to aggregation of Cu observed in TEM.

A simple way to nickel based mesoporous carbons: Inexpensive nanocatalysts for the hydrogenolysis of sorbitol

A simple way to nickel based mesoporous carbons: Inexpensive nanocatalysts for the hydrogenolysis of sorbitol

Sorbitol transformation into biofuels over bimetallic platinum based catalysts supported on SiO2-Al2O3 – Effect of the nature of the second metal

Sorbitol hydrogenolysis in aqueous medium was carried out over Pt based catalysts supported on SiO2-Al2O3 and modified by a second metal (Re, Ir, Rh and Pd). The catalysts were synthetized by two preparation methods, co-impregnation and successive impregnations. The metallic properties of these catalysts were characterized by transmission electron microscopy and X-ray diffraction, H2 chemisorption, temperature programmed reduction and by the model reaction in gas phase of cyclohexane dehydrogenation. The acidic properties were characterized by ammonia thermodesorption and by the model reaction in gas phase of 3,3-dimethyl-1-butene. The catalytic performances were compared to those of corresponding monometallic catalysts under hydrothermal conditions, in a batch reactor at 240 °C under 60 bar H2 pressure. The main products were poly- and mono‑oxygenated compounds in liquid phase and hydrocarbons in gaseous phase. Among the studied modifiers, Re allowed to promote the catalytic performances of Pt leading to a synergistic effect for the transformation of sorbitol into liquid fuels (hexane). The highest efficiency of the Re-Pt/SiO2-Al2O3 catalyst prepared by co-impregnation was explained by an optimal balance between the acidic and metallic functions constituted of bimetallic particles of small size dispersed on the acidic support.

Ordered Mesoporous NiCeAl Containing Catalysts for Hydrogenolysis of Sorbitol to Glycols

Cellulose-derived sorbitol is emerging as a feasible and renewable feedstock for the production of value-added chemicals. Highly active and stable catalyst is essential for sorbitol hydrogenolysis. Ordered mesoporous M–xNiyCeAl catalysts with different loadings of nickel and cerium species were successfully synthesized via one-pot evaporation-induced self-assembly strategy (EISA) and their catalytic performance were tested in the hydrogenolysis of sorbitol. The physical chemical properties for the catalysts were characterized by XRD, N2 physisorption, H2-TPR, H2 impulse chemisorption, ICP and TEM techniques. The results showed that the ordered mesopores with uniform pore sizes can be obtained and the Ni nanoparticles around 6 nm in size were homogeneously dispersed in the mesopore channels. A little amount of cerium species introduced would be beneficial to their textural properties resulting in higher Ni dispersion, metal area and smaller size of Ni nanoparticles. The M–10Ni2CeAl catalyst with Ni and Ce loading of 10.9 and 6.3 wt % shows better catalytic performance than other catalysts, and the yield of 1,2-PG and EG can reach 56.9% at 493 K and 6 MPa pressure for 8 h after repeating reactions for 12 times without obvious deterioration of physical and chemical properties. Ordered mesoporous M–NiCeAl catalysts are active and stable in sorbitol hydrogenolysis.

Hydrogenolysis of sorbitol into valuable C3-C2 alcohols at low H2 pressure promoted by the heterogeneous Pd/Fe3O4 catalyst

The hydrogenolysis of sorbitol and various C5-C3 polyols (xylitol; erythritol; 1,2- 1,4- and 2,3-butandiol; 1,2-propandiol; glycerol) have been investigated at low molecular hydrogen pressure (5 bar) by using Pd/Fe3O4, as heterogeneous catalyst and water as the reaction medium. Catalytic experiments show that the carbon chain of polyols is initially shortened through dehydrogenation/decarbonylation and dehydrogenation/retro-aldol mechanisms followed by a series of cascade reactions that include dehydrogenation/decarbonylation and dehydration/hydrogenation processes. At 240 °C, sorbitol is fully converted into lower alcohols with ethanol being the main reaction product in liquid phase.

Hydrogenolysis of sorbitol over Ni supported on Ca- and Ca(Sr)-hydroxyapatites

Ca-hydroxyapatite (HAP) was synthesized with different morphologies, in needle (N), sphere (S) and rod (R) shapes. A partially Sr-substituted sample (Ca(Sr)-hydroxyapatite) with the stoichiometric composition of Sr0.6Ca9.4(PO4)6(OH)2, and possessing a rod shaped morphology was also hydrothermally synthesized (SrHAP-R). The samples were characterized by X-ray diffraction, Fourier-Transform infra-red spectroscopy (FT-IR), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS) and surface area measurement. Nickel (6 wt%) was loaded on the samples by an impregnation method. Rod-shaped hydroxyapatite (HAP-R) was more crystalline than the others. FT-IR results showed characteristic bands for (PO4)3− and OH vibrations. XPS results indicated Ni to be in the 2+ state, and O 1s satellite features revealed a phosphoric oxide environment in all the samples. The catalytic activities of the Ni-containing samples were tested in the hydrogenolysis of sorbitol into ethylene and propylene glycols in an aqueous medium in a stirred high pressure reactor at different process conditions. The most active catalyst was Ni/SrHAP-R. The catalyst was reusable many times with only a minor activity loss.

Influence of the functional groups of multiwalled carbon nanotubes on performance of Ru catalysts in sorbitol hydrogenolysis to glycols

Different functional groups (i.e. NH2, COOH, OH and nitrogen-doping) modified CNTs (denoted as AMCN, CMCN, HMCN and NMCN, respectively) supported ruthenium catalysts (Ru/AMCN, Ru/CMCN, Ru/HMCN and Ru/NMCN) were prepared by incipient wetness impregnation method. They were fully characterized by XRD, TG, Raman, XPS, TPD and TEM to elucidate the relationship between the physical property and their catalytic performance. TEM results shown that Ru particles were well dispersed on the surface for all the samples with the size of 1.48–1.99nm. The effects of functional groups of carbon nanotubes (CNTs), nitrogen doping and base additive types on activity and selectivity of ethylene glycol (EG) and propylene glycol (1,2-PD) were investigated. In addition, the activity and final products distribution were much influenced by the properties of functional groups on CNTs and the type of metal cation of the base promoters, which probably participated in the reaction for accelerating a retro-aldol reaction for CC cleavage. Among the catalysts, Ru supported on AMCN exhibited the best catalytic activities and glycols selectivities than on MCN, CMCN, HMCN and NMCN.

Kinetic Modeling of Sorbitol Hydrogenolysis over Bimetallic RuRe/C Catalyst

Sorbitol hydrogenolysis kinetics using bimetallic RuRe catalyst is reported based on multiple experiments in parallel batch slurry reactors (H2 pressure: 1.0–6.5 MPa, temperature: 473–503 K) to obtain concentration–time profiles. It is observed that RuRe/C bimetallic catalysts with Ca(OH)2 as a base promoter show significantly higher activity and selectivity toward liquid phase products such as 1,2-propanediol, lactic acid, ethylene glycol, and linear alcohols compared with monometallic Ru/C catalysts and other base promoters. It is further found that sorbitol hydrogenolysis initiates with dehydrogenation and subsequent C–C cleavage via retro-aldolization to form smaller molecules (C2–C4). Those smaller intermediates undergo dehydration, reorganization, and C–O cleavage to form C2–C3 acids, glycols, and linear alcohols as products, which are very similar to glycerol conversion chemistry. For the kinetic modeling, experimental data on concentration–time profiles were obtained using RuRe/C catalysts with Ca...

Sorbitol transformation over bimetallic Ru-Pt/SiO2-Al2O3 catalysts: Effect of the preparation method

Sorbitol hydrogenolysis in aqueous medium was carried out over Ru-Pt based catalysts supported on SiO2-Al2O3 and synthetized by three preparation methods (co-impregnation, successive impregnations or a surface redox deposition). These catalysts were characterized by N2 isothermal adsorption desorption, transmission electron microscopy, H2 chemisorption, temperature programmed reduction and by the model reaction in gas phase of cyclohexane dehydrogenation. The catalytic performances were compared to those of monometallic catalysts (Pt/SiO2-Al2O3 and Ru/SiO2-Al2O3) under hydrothermal conditions, in a batch reactor at 240°C under 60bar H2 pressure. The main products were poly- and mono-oxygenated compounds in liquid phase and hydrocarbons in gaseous phase. The best yield of hydrocarbons was obtained in the presence of Ru-Pt bimetallic catalyst prepared by successive impregnations, for which a synergetic effect was observed. This effect can be explained by the existence of bimetallic particles of small size favoring an electronic exchange from Ru to Pt. Under the experimental conditions used in this study, it appeared that the reaction pathway of sorbitol transformation was not the same on Pt- or Ru-based catalysts.

Effects of alkaline additives on the formation of lactic acid in sorbitol hydrogenolysis over Ni/C catalyst

Lactic acid is produced as a major byproduct during sorbitol hydrogenolysis under alkaline conditions. We investigated the effects of two different alkaline additives, Ca(OH)2 and La(OH)3, on lactic acid formation during sorbitol hydrogenolysis over Ni/C catalyst. In the case of Ca(OH)2, the selectivity of lactic acid was 8.9%. In contrast, the inclusion of La(OH)3 resulted in a sorbitol conversion of 99% with only trace quantities of lactic acid being detected. In addition, the total selectivity towards the C2 and C4 products increased from 20.0% to 24.5% going from Ca(OH)2 to La(OH)3. These results therefore indicated that La(OH)3 could be used as an efficient alkaline additive to enhance the conversion of sorbitol. Pyruvic aldehyde, which is formed as an intermediate during sorbitol hydrogenolysis, can be converted to both 1,2-propylene glycol and lactic acid by hydrogenation and rearrangement reactions, respectively. Notably, these two reactions are competitive. When Ca(OH)2 was used as an additive for sorbitol hydrogenolysis, both the hydrogenation and rearrangement reactions occurred. In contrast, the use of La(OH)3 favored the hydrogenation reaction, with only trace quantities of lactic acid being formed.