Gas-phase hydrodeoxygenation of phenol over Zn/SiO2 catalysts:Effects of zinc load, temperature, weight hourly space velocity, and H 2 volumetric flow rate

The hydrodeoxygenation (HDO) of phenol catalyzed by Zn/SiO2 under atmospheric H2 pressure was investigated in a continuous fixed bed reactor. The effects of several process parameters (zinc load, reaction temperature, weight hourly space velocity (WHSV), and H2 volumetric flow rate) were evaluated to optimize process conditions. Phenol was selected as a stable model component for lignin degradation products in fast pyrolysis bio-oil. Silica-supported zinc catalysts were prepared with different loadings of the active metal (0.5%, 1%, 2%, 3%, and 4%) and assessed using characterization techniques such as XRD, ICP-OES, BET, H2-TPR/TPD, and FESEM–EDX. Reaction products including benzene, cyclohexene, and cyclohexane were identified through GC/FID analysis. Experimental results revealed that process yield increased with reaction temperature, metal loading, and WHSV. The selectivity percentages of the products were slightly changed by varying process parameters. Moreover, H2 volumetric flow rate exerted a negligible effect on product yield and selectivity

Kinetic parameters for glycerol electrooxidation over nitrogen- and fluorine-doped composite carbon:Dynamic electrochemical impedance spectroscopy analysis based

This study explores the mechanistic, kinetic process and parameters of nitrogen and fluorine-doped activated carbon black composite catalyst during glycerol electrooxidation in alkaline so under some precise experimental parameters. The influence of catalyst and electrochemical impedance spectroscopy (EIS) perturbation amplitude were systematically studied. The kinetic parameters from steady-state measurement and microkinetic modelling study reveal that glycerol electrooxidation undergoes complicated mechanism. From the chronoamperometry study, the nitrogen-doped sample (ACB-N2) shows a remarkable activity and stability, but the performance was improved upon the simultaneous doping of fluorine to form ACB-N2F2. The best rate constant was obtained by ACB-N2F2 (7.335 × 10−3), which is by far greater than those of ACB-N2 (2.533 × 10−3) and ACB-F2 (2.012 × 10−3) for steady-state. The slope obtained from the Tafel plot of both the voltammetry and the non-linear electrochemical impedance spectroscopy measurement also confirms the superior performance of ACB-N2F2 compared to ACB-N2 and ACB-F2. The rate constant of ACB-N2F2 is almost 6 times of that of ACB-N2, and 4 times of the of ACB-F2 for the forward sweep. The exchange current density of ACB-N2F2 is almost 7 times of that of ACB-N2, and 3 times of the of ACB-F2 for the forward sweep. The methods in this study for evaluation of glycerol electrooxidation kinetic process and kinetic parameters could be used to investigate other electrocatalysts

A review of recent progress on electrocatalysts toward efficient glycerol electrooxidation

Glycerol electrooxidation has attracted immense attention due to the economic advantage it could add to biodiesel production. One of the significant challenges for the industrial development of glycerol electrooxidation process is the search for a suitable electrocatalyst that is sustainable, cost effective, and tolerant to carbonaceous species, results in high performance, and is capable of replacing the conventional Pt/C catalyst. We review suitable, sustainable, and inexpensive alternative electrocatalysts with enhanced activity, selectivity, and durability, ensuring the economic viability of the glycerol electrooxidation process. The alternatives discussed here include Pd-based, Au-based, Ni-based, and Ag-based catalysts, as well as the combination of two or three of these metals. Also discussed here are the prospective materials that are yet to be explored for glycerol oxidation but are reported to be bifunctional (being capable of both anodic and cathodic reaction). These include heteroatom-doped metal-free electrocatalysts, which are carbon materials doped with one or two heteroatoms (N, B, S, P, F, I, Br, Cl), and heteroatom-doped nonprecious transition metals. Rational design of these materials can produce electrocatalysts with activity comparable to that of Pt/C catalysts. The takeaway from this review is that it provides an insight into further study and engineering applications on the efficient and cost-effective conversion of glycerol to value-added chemicals

Glycerol Electrocatalytic Reduction Using an Activated Carbon Composite Electrode:Understanding the Reaction Mechanisms and an Optimization Study

The conversion of biomass-derived glycerol into valuable products is an alternative strategy for alleviating energy scarcity and environmental issues. The authors recently uncovered an activated carbon composite electrode with an Amberlyst-15 mediator able to generate 1,2-propanediol, diethylene glycol, and acetol via a glycerol electrocatalytic reduction. However, less attention to mechanistic insights makes its application to industrial processes challenging. Herein, two proposed intermediates, acetol and ethylene glycol, were employed as the feedstocks to fill the gap in the mechanistic understanding of the reactions. The results discovered the importance of acetol in producing 1,2-propanediol and concluded the glycerol electrocatalytic reduction process has a two-step reduction pathway, where glycerol was initially reduced to acetol and consecutively hydrogenated to 1,2-propanediol. At 353 K and 0.28 A/cm2, 1,2-propanediol selectivity achieved 77% (with 59.8 C mol% yield) after 7 h of acetol (3.0 mol/L) electrolysis. Finally, the influences of the temperature, glycerol initial concentration, and current density on the glycerol electrocatalytic reduction were evaluated. The initial step involved the C-O and C-C bonds cleavage in glycerol plays a crucial role in producing either acetol or ethylene glycol intermediate. This was controlled by the temperature, which low to moderate value is needed to maintain a selective acetol-1,2-propanediol route. Additionally, medium glycerol initial concentration reduced the hydrogen formation and indirectly improved 1,2-propanediol yield. A mild current density raised the conversion rate and minimized the growth of intermediates. At 353 K and 0.21 A/cm2, glycerol (3.0 mol/L) electrocatalytic reduction to 1,2-propanediol reached the maximum yield of 42.3 C mol%

Electrochemical valorization of glycerol: optimization and characterization studies of glycerol dehydration

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