Glycerol Conversion Research Articles

Ni-based catalysts supported on La/AlZn/AlLa oxides for hydrogen production via glycerol steam reforming

The effect of La/AlZn/AlLa oxide supports on Ni-based catalysts performance was assessed for glycerol steam reforming for renewable H2 production. NiAlLaOx showed the best performance providing a glycerol conversion into gaseous products of 91 % and H2 yield of 5.40 molH2·molG,in‐1 at 700 °C. Additionally, stability experiments lasting up to 24 h were performed at 625 °C, having been observed a stable behavior for NiAlLaOx with low coke formation. The materials' physicochemical properties, determined from different techniques (ICP-OES, N2-adsorption at -196 °C, XRD, TEM/EDX, TPR and TPO), allowed to comprehend how these influence their performance and stability. The NiAlLaOx good performance was assigned to the presence of LaAlO3 perovskite, which was more efficient in preventing coke formation and selective towards H2 production. Moreover, the harder reducibility of Ni species present in NiAlLaOx suggested the existence of strong interactions between them and the support, which were also responsible for this sample outstanding performance.

Oxidation of glycerol to dihydroxyacetone over highly stable Au catalysts supported on mineral-derived CuO-ZnO mixed oxide

Selective oxidation of glycerol to dihydroxyacetone (DHA) is a promising pathway for glycerol utilization. In order to fabricate a highly stable supported Au catalyst for the reaction, a series of CuO-ZnO mixed oxides derived from different minerals were synthesized. Then, the Au/CuO-ZnO catalysts were prepared by the deposition-precipitation. High yield of DHA (70%) and conversion of glycerol (76%) were obtained over the rosasite-derived Au/CuO-ZnO catalyst. While over the aurichalcite-derived Au/CuO-ZnO catalyst, the yield of DHA was only 20%. By means of XRD, H2-TPR, TEM, XPS, CO2-TPD characterization, it was found that the higher yield of DHA was attributed to the stronger interaction between CuO and ZnO, higher dispersion of Au species, higher content of Au0 and proper amount of surface basic sites. The rosasite-derived Au/CuO-ZnO catalyst also showed good stability and no obvious decrease in reactivity and DHA selectivity could be seen after five recycles. The stable structure of the support not only enhanced the interaction between CuO-ZnO that stabilized the support itself, but also improved the interaction between Au and the support, further stabilizing the particle size and chemical valence of Au.

Front Cover: Nickel‐Tin Nanoalloy Supported ZnO Catalysts from Mixed‐Metal Zeolitic Imidazolate Frameworks for Selective Conversion of Glycerol to 1,2‐Propanediol (ChemSusChem 3/2024)

Front Cover: Nickel‐Tin Nanoalloy Supported ZnO Catalysts from Mixed‐Metal Zeolitic Imidazolate Frameworks for Selective Conversion of Glycerol to 1,2‐Propanediol (ChemSusChem 3/2024)

Vapor-phase dehydration of glycerol to acetol over Cu/SiO2 prepared with organic additives

Silica-supported Cu (Cu/SiO2) catalysts prepared with organic additives showed excellent activity for the dehydration of glycerol to acetol. Among eight organic additives tested, 12-crown-4-ether (12C4) contributed the highest improvement in the activity of Cu/SiO2 catalyst. The catalytic dehydration of glycerol to acetol was accompanied by the formation of glyceraldehyde via dehydrogenation. The enlargement of Cu surface area was limited by the pore volume of SiO2 support. Acetol was the dominant product over Cu catalysts at high glycerol conversions, and the highest acetol yield of 94.3% was achieved over 12C4-Cu/SiO2 at 270 °C. The Cu surface area was proportional to the formation rate of acetol in the dehydration of glycerol at 200 °C. Consequently, we concluded that the glycerol dehydration was not catalyzed by the Lewis acid sites but catalyzed by Cu0 nanoparticles dispersed on SiO2 support.

Reaction Kinetics and Mechanism for the Synthesis of Glycerol Carbonate from Glycerol and Urea Using ZnSO4 as a Catalyst

A series of Zn salts were used as catalysts for the reaction of glycerol and urea to produce glycerol carbonate and it was found that ZnSO4 showed the highest catalytic activity. Furthermore, the effects of reaction parameters on the glycerol conversion and glycerol carbonate yield were studied in detail. The results indicated that the glycerol conversion and glycerol carbonate yield were increased with the reaction temperature, reaction time, and catalyst amount while the optimal reaction conditions were 140 °C, 240 min, catalyst amount of 5 wt% (based on the glycerol weight), and urea-to-glycerol molar ratio of 1.1:1. During the reaction, the ZnSO4 catalyst is transformed into Zn(NH3)2SO4 at the initial stage of the reaction and then further transformed into Zn(C3H6O3). Zn(C3H6O3) and (NH4)2SO4 may be the true active species for the activation of urea and glycerol, respectively. The reaction mechanism is proposed in this article. Based on the experimental results, a reaction kinetics model considering the change in volume of the reaction system was also established, and the model parameters were obtained by fitting the experimental data. The statistical results showed that the established kinetics model is accurate.

Enhancing the catalytic properties of silicalite-1 through ammonium fluoride modification for waste glycerol acetalization.

Silicalite-1 is a silica with a zeolitic MFI (Mobil Five) structure devoid of noticeable catalytically active (e.g., acid) sites. In this study, we present its modification with NH4F solutions of varying concentrations (0.5-3 M), which generates efficient and selective acid sites for the acetalization of glycerol with acetone towards solketal (2,2-dimethyl-1,3-dioxolane-4-methanol). The creation of acid sites is attributed to the partial elimination of external silanol groups in silicalite-1 and the generation of some framework defects, resulting also in increased porosity. The characterization of the modified materials was performed using various techniques, i.e. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (TPD-NH3), and Fourier-transform infrared spectroscopy (FTIR). The results demonstrate that the newly created acidic sites of Brønsted and Lewis nature exhibit significantly higher acidic strength and enhanced accessibility for reagents compared to the pristine one, resulting in exceptional glycerol conversion in the acetalization of glycerol with acetone and notable selectivity towards solketal. Glycerol conversion over modified silicalite-1 reached nearly 70%, with the selectivity to solketal exceeding 98% at 70° C after 1 hour of reaction time, using a mixture of glycerol and acetone in a 1 : 1 ratio. The proposed reaction mechanism takes into account a combination of Brønsted and Lewis acid sites. The obtained results indicated that Brønsted acid sites, especially those of higher strength, are the most beneficial in this process. The remarkable catalytic performance and stability of modified silicalite-1 make it a promising candidate for potential industrial applications in the utilization of waste glycerol formed in the biofuel industry.

Redox regulation of Ni hydroxides with controllable phase composition towards biomass-derived polyol electro-refinery.

Electrocatalytic refinery from biomass-derived glycerol (GLY) to formic acid (FA), one of the most promising candidates for green H2 carriers, has driven widespread attention for its sustainability. Herein, we fabricated a series of monolithic Ni hydroxide-based electrocatalysts by a facile and in situ electrochemical method through the manipulation of local pH near the electrode. The as-synthesized Ni(OH)2@NF-1.0 affords a low working potential of 1.36 VRHE to achieve 100% GLY conversion, 98.5% FA yield, 96.1% faradaic efficiency and ∼0.13 A cm-2 of current density. Its high efficiency on a wide range of polyol substrates further underscores the promise of sustainable electro-refinery. Through a combinatory analysis via H2 temperature-programmed reduction, cyclic voltammetry and in situ Raman spectroscopy, the precise regulation of synthetic potential was discovered to be highly essential to controlling the content, phase composition and redox properties of Ni hydroxides, which significantly determine the catalytic performance. Additionally, the 'adsorption-activation' mode of ortho-di-hydroxyl groups during the C-C bond cleavage of polyols was proposed based on a series of probe reactions. This work illuminates an advanced path for designing non-noble-metal-based catalysts to facilitate electrochemical biomass valorization.

PdAg/CoFe2O4 Bimetallic Catalyst with High Selectivity for Glyceraldehyde in Glycerol Selective Oxidation Reaction

The catalytic oxidation of glycerol was investigated in assays with palladium-silver bimetallic nanoparticles (Pd-Ag) immobilized on cobalt ferrite (CoFe2O4). Bimetallic nanoparticles were prepared by the galvanic replacement method, immobilized on CoFe2O4 by wet impregnation. Bimetallic Pd-Ag nanoparticles with 35 wt.% Pd content effectively catalyzed the selective oxidation reaction of glycerol to glyceraldehyde. Catalytic oxidation was carried out at 60-80 °C for 2-4 h in an aqueous NaOH solution (NaOH:glycerol ratio = 4 mol:mol) under O2 pressure of 4 bar; the selectivity of glyceraldehyde reached 99.35% and the conversion of glycerol of 49.07% at a temperature of 60 °C and a reaction time of 2 h. Glyceric acid and traces of tartronic acid and mesoxalic acid were also detected. The catalyst was also very stable, showing activity up to 4 runs without significant loss of activity and selectivity.

Catalytic conversion of glycerol to formic acid under mild condition over an iron-based catalytic system

Glycerol, produced in large amounts as the main by-product of biodiesel production from biomass, has great potential to be converted into formic acid which is a potential hydrogen carrier. This research aims to evaluate the performance of an iron-based catalytic system in the oxidation process of glycerol to formic acid. The methods used include preparing an iron (II) oxalate catalyst, determining the reaction medium and reaction time for glycerol oxidation, optimizing the conditions of the glycerol oxidation process, and analysing the glycerol oxidation products. Optimization of process conditions includes the influence of temperature, substrate/catalyst molar ratio, and oxidant/substrate molar ratio. The research showed that water was a better reaction medium for glycerol oxidation, with a reaction time of 240 minutes. Oxidation of glycerol with an iron (II) oxalate catalyst can produce formic acid products with the best results obtained at pH 5, temperature 50°C, substrate/catalyst molar ratio of 100, and oxidant/substrate molar ratio of four with 83.18% converted glycerol. The yield and selectivity of formic acid were 47.77% and 57.43% respectively. These results indicate that the iron-based catalytic system has the potential to be an effective catalytic system for glycerol oxidation under mild conditions.

Robust Dihydroxyacetone Production via Photoelectrochemical Glycerol Oxidation using Oxygen Vacant BiVO4 Photoanode

Photoelectrochemical conversion of glycerol into high-value dihydroxyacetone offers a sustainable approach via BiVO4 semiconductor materials, which manifest highly photoactive properties. However, dihydroxyacetone production poses a limitation due to poor charge...

Selective catalytic conversion of glycerol to lactic acid over CuO-NiO complex oxides

One of the most essential techniques to achieve effective usage of the principal by-product (glycerol) in the manufacturing of biodiesel is catalytic conversion of glycerol to lactic acid. In this paper, CuO-NiO composite metal oxides with different Cu/Ni molar ratios were prepared by co-precipitation method to catalyze the conversion of glycerol to lactic acid in alkaline medium. By using XRD, SEM, TEM, BET, XPS, and H2-TPR characterisation, the catalysts' crystalline phase, shape, and performance were assessed. The results show that the electronic synergy of CuO-NiO composite metal oxides plays a positive role in catalyzing the conversion of glycerol to lactic acid. The production of lactic acid might reach 90.08 % when Cu/Ni molar ratio (CuO1NiO2) and reaction conditions are optimum. In conjunction with the analysis using Density Functional Theory: due to the formation of heterojunctions in CuO1NiO2 the formation of good contacts between the atoms at the CuO and NiO interfaces is conducive to promoting charge transfer and electron mobility, thus enhancing the synergistic effect of electron transfer. Meanwhile, DFT calculations revealed that the Cu-Ni composite metal oxides had stronger adsorption energy for glycerol, which favored the bonding of glycerol on their surfaces.

Experimental and computational study of a packed-bed bioreactor for the continuous production of succinic acid

In this work we present a packed-bed bioreactor system packed, with immobilised cells in sodium alginate beads, for the biological conversion of glycerol to succinic acid.

Metal-doped niobate pyrochlores and double-perovskites for glycerol valorization: structural and electronic properties and DFT calculations.

In this study, metal-doped niobates and perovskites were obtained by a solid-state reaction. The solids were evaluated in the esterification of glycerol in the presence of acetic acid to produce valuable esters of glycerol. The structural features of the solids indicated the ZnNb2O6, Pb2.8Nb2O7.8 and CuNb2O6 columbite main phases and La2MnFeO6 double-perovskite. Density functional theory (DFT) studies of Pb2.8Nb2O7.8 clearly confirmed the existence of a robust orthorhombic structure and its electronic properties were correlated with the Nb and Pb interactions. The morphological and elemental analyses also indicated that not all surface elements, as well as morphology, were crucial for catalytic properties. All solids were active and selective toward triacetin formation upon glycerol esterification with acetic acid. The catalytic performance depends mainly on the availability of the surface and its structural stability, as well as defects formation. Recyclability studies indicated that the La2MnFeO6 double-perovskite was an efficient catalyst, achieving glycerol conversion of 68% and triacetin selectivity of 25% up to 4 cycles of use in the reaction. The structural defects near the Mn4+/Mn3+ surface sites resulted in the diffusion of anions and an increased concentration of oxygen vacancies contributed to the stable performance of the solid in glycerol ester production.

Plant-mediated biosynthesized Au/CuO catalysts for efficient glycerol oxidation to 1,3-dihydroxyacetone: effect of biomass component on catalytic activity

This study prepared a series of SoL-Au/CuO catalysts by isolating plant active ingredients. S3-Au/CuO enriched with polyphenols demonstrated the highest activity with a glycerol conversion of 86.6% and DHA selectivity of 82.0%.

LTA zeolites as catalysts for transesterification of glycerol with dimethyl carbonate

The objective of this study was to investigate the use of LTA-structured zeolites as catalysts for synthesizing glycerol carbonate through the transesterification of glycerol with dimethyl carbonate, under mild reaction conditions. To evaluate the catalysts, a range of characterization techniques, including XRD, AES, SEM, TPD-NH3, TPD-CO2, and FT-IR with probe molecules like pyridine and pyrrole, along with elemental analysis, were employed. The investigation focused on various forms of LTA-structured zeolites (with K, Na, and Ca cations) to assess their impact on transesterification activity, with particular attention to the type of ion utilized and their basicity. Among these zeolites, K-Na-LTA (3A) zeolites demonstrated the most promising performance, achieving glycerol conversion rates ranging from 55 % to 77 %. Moreover, increasing basicity in the 3A zeolites led to higher glycerol conversion and glycerol carbonate yield. Encouragingly, all tested samples exhibited 100 % selectivity, exclusively producing the desired glycerol carbonate. However, during catalyst recycling, the decrease in glycerol conversion was observed, likely due to the leaching of active sites from the catalyst into the reaction medium. Methanol, being a one of the products, was identified as a potential agent responsible for the removal of potassium ions, during this process.

Combining structure design and surface modification of BPO4 solid acid catalyst to boost the anti-coking performance in dehydration reaction of glycerol

Catalytic vapor-phase dehydration of glycerol is an energy-efficient and environmentally friendly route for producing acrolein, a valuable organic chemical intermediate. However, anti-coking is one of the key problems due to the excessively acid catalytic sites and sluggish mass transfer, restricting the industrial application of this reaction. Herein, potassium element modified BPO4 monolithic foams with the hierarchically porous structure were synthesized by adding potassium element in the gel precursor of BPO4. The catalyst introducing 3% K exhibited the best acrolein selectivity of 81.0% with nearly complete glycerol conversion. In a 10-hour run of the reaction at 320 °C, the selectivity of acrolein could remain at 75.9% with 94.5% glycerol conversion, indicating the superior stability. The excellent activity and stability for 3% K-BPO4 is mainly attributed to the synergetic effect between hierarchical structure providing favorable mass transfer and appropriate acid catalytic sites inhibiting over dehydration reaction. They not only boost activity but also reduce coking, providing a unique approach for the design of solid acid catalyst.

Transfer hydrogenation of quinolines with glycerol over N-doped carbon encapsulated non-noble metal catalysts: Mott-Schottky effect on the catalytic activity

Catalytic transfer hydrogenation using glycerol (GLY) as a hydrogen donor presents a sustainable and secure approach for hydrogenation of quinoline and its derivatives. Conventional non-noble metal catalysts can effectively catalyze the transfer hydrogenation reaction with GLY. However, it is inevitable that metal leaching occurs under alkaline hydrothermal conditions. In this work, N-doped carbon encapsulated non-noble metal catalysts, such as Co@NC, Ni@NC, and CoNi@NC, were prepared by one-pot method combined with an acid leaching for this reaction. According to Mott-Schottky effect, encapsulating of Co, Ni, and CoNi nanoparticles with relatively smaller work function in NC shells constructed a rectifying contact and increased the electron density on NC shells. Density Functional Theory (DFT) calculations confirm that electrons transfer from metal cores to NC shell, with CoNi transferring the most, followed by Co and Ni. As a result, the catalytic activity followed the order of CoNi@NC＞Co@NC＞Ni@NC, where CoNi@NC exhibited highest catalytic activity, 92.2% GLY conversion and full quinoline conversion can be obtained over CoNi@NC at 180 °C with 89.7% and 99.3% of the selectivity to lactic acid and 1, 2, 3, 4-tetrahydroquinoline, respectively. In addition, CoNi@NC possessed excellent stability because NC shells physically isolate metal cores from the reactive environment. Such Mott-Schottky catalyst tuning could be an efficient way to design new non-noble catalysts.

Production of glycerol carbonate from glycerol and carbon dioxide using metal oxide catalysts

This work is focused on a green production of glycerol carbonate through converting glycerol, as a by-product of biodiesel production, and a greenhouse gas, carbon dioxide, using metal oxide catalysts of MgO, CaO, and Al2O3. The catalysts were prepared by precipitation method and characterized by surface area and pore size, TGA, XRD, CO2-TPD, and SEM analyses. The catalysts’ performance was mostly influenced by the number of basic sites and the BET surface area of the catalysts. The catalysts’ activity results displayed that MgO showed the highest glycerol conversion of 22.7% and the highest yield of 10.6% among the investigated catalysts. The turnover number of the optimum catalyst was 14.9 μmol glycerol carbonate/μmol CO2. The effect of reaction parameters on the performance of the reaction was also investigated and the highest glycerol carbonate yield of 12.76 % was achieved at a catalyst loading of 5.5 wt% of glycerol amount, the temperature of 150 ⁰C, and pressure of 8 MPa. The physicochemical properties of catalysts were correlated with their activities and abilities for CO2 activation.

Kinetic & thermodynamic studies of green fuel additive solketal from crude glycerol over metakaolin clay catalyst

Biodiesel synthesis produces about 10 % glycerol as a byproduct, prompting environmental concerns. The utilization of crude glycerol into valuable products requires an Eco-friendly technique. This study depicts glycerol acetalization using acetone and novel catalyst acid-treated metakaolin clay. Raw kaolin clay was calcined at 600 °C and treated with acid at 102 °C for 3 h. Afterward, acid activated clay was filtrate and dried in oven to remove moisture content. The catalyst prepared with a 5 M solution of sulfuric acid exhibited the highest surface area of 82.33 m2. g−1 and gave the highest yield (80 %) of Solketal with 73 % of glycerol conversion under optimum conditions. The ketalization reaction of Solketal synthesis was studied in terms of thermodynamics and kinetics. A Langmuir-Hinshelwood rate expression based on two-parameter kinetic law was used in this study. From the kinetic studies, activation energies (EA) of forward and backward reactions were found to be K1 = 39.23 kJ. mol−1 and K2 = 35.70 kJ. mol−1 respectively. Furthermore, reaction was exothermic having an enthalpy of ΔHo = −18.86 kJ. mol−1 and the entropy ΔSo = −0.1 kJ. mol−1 calculated from this process. Solketal derived from sustainable sources such as bio-glycerol and biomass-based acetone, has a wide range of uses as fuel additives and medicines industry. This research marks a significant advancement in the development of a continuous synthesis technique for Solketal and its recovery from glycerol-acetone mixtures.

Valorizing biomass waste glycerol to fuel additive at room temperature using a nanostructured WO3/Nb2O5 catalyst

We developed a nanostructured catalyst consisting of WO3 nanoparticles and Nb2O5 nanorods for efficient glycerol acetalization to produce a fuel additive (solketal) at room temperature. Particularly, the WO3/Nb2O5 nanocatalyst calcined at 400 °C (WO3/Nb2O5–4) contains W5+ species and optimum acid sites, which enhanced glycerol conversion (92.3%) with 95.6% of solketal selectivity at room temperature. The structure stability of the WO3/Nb2O5–4 catalyst during the reaction is showcased by hot-filtration study and XRD/XPS characterization. However, the inadequate regeneration of the Brønsted acid sites led to a gradual decrease in the recyclable activity of the WO3/Nb2O5–4 catalyst.