Upgrading Of Glycerol Research Articles

Trimetallic FeNiCo layered double hydroxide catalysts for industrial-level electrochemical glycerol upgrading

Trimetallic FeNiCo layered double hydroxide catalysts for industrial-level electrochemical glycerol upgrading

Electrocatalytic Glycerol Upgrading into Glyceric Acid on Ni3Sn Intermetallic Compound.

Electrochemical glycerol oxidation features an attractive approach of converting bulk chemicals into high-value products such as glyceric acid. Nonetheless, to date, the major product selectivity has mostly been limited as low-value C1 products such as formate, CO, and CO2, due to the fast cleavage of carbon-carbon (C-C) bonds during electro-oxidation. Herein, the study develops an atomically ordered Ni3Sn intermetallic compound catalyst, in which Sn atoms with low carbon-binding and high oxygen-binding capability allow to tune the adsorption of glycerol oxidation intermediates from multi-valent carbon binding to mono-valent carbon binding, as well as enhance *OH binding and subsequent nucleophilic attack. The Ni3Sn electrocatalyst exhibits one of the highest glycerol-to-glyceric acid performances, including a high glycerol conversion rate (1199µmol h-1) and glyceric acid selectivity (62 ± 3%), a long electrochemical stability of > 150 h, and the capability of direct conversion of crude glycerol (85% purity) into glyceric acid. The work features the rational design of highly ordered catalytic sites for tailoring intermediate binding and reaction pathways, thereby facilitating the efficient production of high-value chemical products.

Tunable-pH Environment Induced by Local Anchor Effect of High Lewis Basicity Conductive Polymers toward Glycerol Upgrading Assisted Hydrogen Evolution.

Hybrid organic/inorganic composites with the organic phase tailored to modulate the local chemical environment at the transition metal-based catalyst surface arise as an enchanting category of catalysts for electrocatalysis. A fundamental understanding of how the conductive polymers of different Lewis basicities affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), and poly(vinyl alcohol) (PVA) manifesting different Lewis basicities are compared for their regulatory roles on the hydrogen evolution reaction (HER) and glycerol electrooxidation (GOR) pathways regarding local proton coverage. Concerted efforts from in situ Raman and DFT theoretical calculations unveil that conductive polymer/V2O5 surface with tunable local pH regulated by Lewis acidity/basicity. As a result of the tailored chemical environment, the restructured V2O5/PANI/NF composite demonstrates a low overall potential of 1.55 V at the partial current density of 50 mA cm-2 for formate. The glycerol upgrading assisted hydrogen evolution device composed of V2O5/PANI/NF exhibits excellent electrochemical performance at a maximal Faraday efficiency of 82%, ranking among state of the art.

Bifunctional Au-Sn-SiO2 catalysts promote the direct upgrading of glycerol to methyl lactate.

Valuable alkyl lactates can be obtained from (waste) glycerol, through a two-step process that entails (i) the oxidation of glycerol to dihydroxyacetone (DHA) catalyzed by support Au nanoparticles and (ii) a rearrangement of DHA with an alcohol effectively catalyzed by Sn-based heterogeneous catalysts. To solve selectivity and processing issues we propose to run the process as a cascade reaction, in one step, and with a single bifunctional catalyst. Tackling the challenge associated with the preparation of such bifunctional catalysts, here, an aerosol-assisted sol-gel route is exploited. The catalysts feature small Au nanoparticles (3-4 nm) embedded at the surface of mesoporous Sn-doped silica microspheres. The preparation successfully leads to insert both active sites in their most active forms, and in close proximity. With the bifunctional catalysts, the yield for the final product of the cascade reaction (methyl lactate) is higher than the DHA yield when only the first reaction is carried out. This highlights a beneficial substrate channeling effect which alleviates side reactions. Interestingly, the bifunctional catalysts also markedly outcompeted mechanical mixtures of the corresponding monofunctional Au- and Sn-based catalysts. Thus, the spatial proximity between the two active sites in bifunctional catalysts is identified as a key to stir the cascade reaction towards high lactate yield.

Sustainable upgrading of glycerol into glycidol and its derivatives under continuous-flow conditions

This study develops a safe and efficient flow process to convert glycerol, a biodiesel byproduct, into glycidol and its derivatives. The method has significant environmental and economic benefits compared to conventional glycidol synthesis routes.

PtAu alloying-modulated hydroxyl and substrate adsorption for glycerol electrooxidation to C3 products

A honeycomb-like PtAu alloy catalyst has been developed to modulate the adsorption capacity of OH− species and adsorption configuration of glycerol on the catalyst surface for electrocatalytic glycerol upgrading of C3 chemicals.

Metal Organic Frameworks Derived Catalysts for the Upgrading of Platform Chemicals

AbstractBiomass plays a significant role in replacing fossil resources, and catalytic transformation of platform chemicals to high‐value chemicals is an effective approach to maximize the utilization of biomass. Among of which, efficient and durable catalysts are the heart for upgrading of these platform chemicals, and metal–organic frameworks (MOFs)‐derived catalysts have attracted much attentions due to their suitable and versatile physicochemical properties. In this work, we present a short review on the applications of MOFs‐derived catalysts in upgrading of platform chemicals. The design and synthetic strategies of MOFs‐derived catalysts were summarized in detail, and their application in the catalytic upgrading of glycerol, ethanol, furanic compounds, levulinic acid and vanillin were addressed. The final section outlines the potential industrial applications of MOFs‐derived catalysts for upgrading platform chemicals.

C-C Bond Formation Coupled with C-C Bond Cleavage during Oxidative Upgrading of Glycerol on a Nanoporous BiVO4 Photoanode.

Production of biodiesel generates glycerol as a 10 wt% byproduct. Therefore, efficient and selective glycerol upgrading is critical for the sustainable production of biodiesel as well as for the production of chemicals from renewable feedstocks. In this study, the photoelectrochemical glycerol oxidation reaction (GOR) was investigated using a nanoporous BiVO4 photoanode in pH 9.3 and pH 2 buffer solutions. In both solutions, glycolaldehyde (GCAD), a C2 species, was the major product, which has never been the major product in any previous electrochemical or photoelectrochemical GOR study. To produce GCAD from the C3 species glycerol, C-C cleavage should occur to produce C2 and C1 species with a 1:1 ratio. Intriguingly, our results show that, during photoelectrochemical GOR on BiVO4, more GCAD is produced than can be explained by simple C-C cleavage, meaning that GCAD is also produced from C-C coupling of two C1 species produced from C-C cleavage. This is equivalent to converting two glycerol molecules to three GCAD molecules, which offers an extraordinary way to maximize GCAD production. To gain further insight into the nature of this unprecedented C-C coupling during GOR, photoelectrochemical oxidation of intermediate oxidation products (glyceraldehyde and 1,3-dihydroxyacetone) and glycerol-1,3-13C2 was compared to that of standard glycerol. Photoelectrochemical GOR was also compared with electrochemical GOR on BiVO4 to interrogate whether light is critical for the observed C-C coupling. Results obtained from comprehensive control experiments revealed critical information about C-C cleavage and C-C coupling during GOR on BiVO4.

Current and Future Trends for Crude Glycerol Upgrading to High Value-Added Products

Crude glycerol is the main byproduct of biodiesel manufacturing from oleaginous crops and other biomass-derived oils. Approximately 10% crude glycerol is produced with every batch of biodiesel. Worldwide, there is a glut of glycerol and the price of it has decreased considerably. There are real opportunities for valorizing crude glycerol into higher value-added chemicals which can improve the economic viability of biodiesel production as an alternative fuel. Exploring new potential applications of glycerol in various sectors is needed such as in pharmaceuticals, food and beverages, cosmetics, and as a transportation fuel. However, crude glycerol produced directly from biodiesel often contains impurities that hinder its direct industrial usage and thus, a refining process is needed which is typically expensive. Hence, this review reports on current upgrading crude glycerol technologies—thermo-, bio-, physico-, and electrochemical approaches—that valorize it into higher value-added chemicals. Through comparison between those viable upgrading techniques, future research directions, challenges, and advantages/disadvantage of the technologies are described. Electrochemical technology, which is still underdeveloped in this field, is highlighted, due to its simplicity, low maintenance cost, and it working in ambient condition, as it shows promising potential to be applied as a major glycerol upgrading technique.

Tailoring the impact of synthetic strategies on the catalytic upgrading of crude glycerol to produce bio-based aromatics in hierarchical HZSM-5

The catalytic upgrading of renewable biomass derived crude glycerol to generate bio-based aromatics is a promising alternative to petroleum route for the synthesis of valuable and versatile aromatics. The effects of synthetic strategies on the physicochemical property of hierarchical HZSM-5 as well as their corresponding catalytic upgrading performances of crude glycerol to bio-based aromatics were systematically investigated in this work. HZSM-5/0.3M NaOH catalyst exhibited smaller improvement in aromatic yields than microporous HZSM-5, which could be ascribed to the uncontrollable large intra-mesopore diameter and less increment in the amounts of acid sites during the introduction of mesoporosity via destructive alkali treatment. The soft templated HZSM-5/TPOAC catalyst produced more BTX and C9+ monocyclic aromatics, which could be attributed to its larger crystal sizes, higher external surfaces, luxuriant L acid amounts, uniform and small mesopore sizes. However, the hard templated HZSM-5/CNT-OH catalyst exhibited higher yields of polycyclic aromatic hydrocarbons and coke during the crude glycerol upgrading process, which could be assigned to its smaller crystal sizes, abundant B acid quantities, uniform and large mesopore diameters. The reusability of desilicated HZSM-5/0.3M NaOH was also deteriorated than the templated HZSM-5/CNT-OH and HZSM-5/TPOAC due to the inferior stability of incorporated mesoporosity via desilication. Finally, plausible reaction pathway involved catalytic upgrading of crude glycerol to produce aromatics was proposed in detail.

Hafnium-doped silica nanotubes for the upgrading of glycerol into solketal: Enhanced performances and in-depth structure-activity correlation

An unprecedented type of Hf-doped silica nanotubes was synthesized using a straightforward one-pot sol–gel procedure. The well-defined nanotubes with a diameter of 14–20 nm exhibited high specific surface area and a widely open texture. The method – involving a key pH adjustment step – allowed a quantitative insertion of hafnium in the materials (Si/Hf = 74) and favored the insertion of Hf as dispersed species. Depending on the synthesis parameters, the chemical environment around Hf was modified, as evidenced by XPS, NH3-TPD and NH3-IR. Hf-doped silica nanotubes showed excellent activity in the conversion of glycerol to solketal, a reaction of high relevance in the context of biorefineries. Importantly, the turnover frequency and the acidity were unambiguously correlated with the insertion of Hf in the silica matrix. The best catalyst was proven to be stable and recyclable, and this sustainable reaction was also amenable to further catalytic enhancement upon optimized reaction conditions.

Bifunctional Mn-doped CoSe2 nanonetworks electrode for hybrid alkali/acid electrolytic H2 generation and glycerol upgrading

Electrolytic water splitting, as a promising route to hydrogen (H2) production, is still confronted with the sluggish anodic oxygen evolution reaction (OER) and its less value-added O2 production. Herein, we report a bifunctional electrode fabricated by in situ growth of Mn-doped CoSe2 nanonetworks on carbon fiber cloth (Mn-CoSe2/CFC), which shows attractive electrocatalytic properties toward glycerol oxidation reaction (GOR) in alkali and hydrogen evolution reaction (HER) in acid. A flow alkali/acid hybrid electrolytic cell (fA/A-hEC) was then developed by coupling anodic GOR with cathodic HER with the Mn-CoSe2/CFC bifunctional electrode. Such fA/A-hEC enables a rather low voltage of 0.54 V to achieve 10 mA cm−2, and maintain long-term electrolysis stability over 300-h operation at 100 mA cm−2 with Faraday efficiencies of over 99% for H2 and 90% for formate production. The designed bifunctional electrode in such innovative fA/A-hEC device provides insightful guidance for coupling energy-efficient hydrogen production with biomass upgradation.

Hafnium-Doped Silica Nanotubes for the Upgrading of Glycerol into Solketal: Enhanced Performances and In-Depth Structure-Activity Correlation

Hafnium-Doped Silica Nanotubes for the Upgrading of Glycerol into Solketal: Enhanced Performances and In-Depth Structure-Activity Correlation

Cost-effective and durable electrocatalysts for Co-electrolysis of CO2 conversion and glycerol upgrading

As the renewable energy gradually penetrates into practical production, electrolytic systhesis technique is considered as a promising avenue for producing some fuels or chemicals. Electrocatalytic conversion CO2 into value-added products is a prominent case that holds impressive potential to promote achievement of carbon-neutral target. However, its practice application is still confronted with rough challenges from lack of high-performance and cost-effective electrocatalysts and high energy consumption. We herein report a low-cost, durable, and energy-efficient electrolysis system that convert CO2 and glycerol to dual value-added products in anode and cathode, in this manner can the electron be utilized for electrolytic upgrading. To this end, the atomically Ni-N single sites on carbon nanosheets (NiSAs/FN-CNSs) is fabricated as the cathode catalysts for CO2 electrochemical reduction, and interconnected CoSe2 nanostructure is developed as anode catalysts for high-selectivity glycerol oxidation reaction (GOR) toward formate production. The assembled electrolytic cell is implemented by the prepared low-cost and scalable nano catalysts electrodes and shows high faradaic efficiencies of CO production (>90%) and formate production (~90%) at a current density more than 100 mA cm−2 over half-month continuous operation. The present work promises to provide a sustainability and economic viable electrolysis route by cost-effectively resourcing CO2 and valorizing glycerol.

The high activity of mesoporous Ga-SiO2 catalysts in the upgrading of glycerol to solketal explained by in-depth characterization

Mesoporous Ga-silicates were prepared using a sustainable and continuous aerosol synthesis procedure. The novel solids showed record activity in the synthesis of solketal from glycerol and acetone. Three different Si/Ga ratios of 34, 74 and 148 were investigated and all materials displayed favorable features for catalytic applications such as high surface area and calibrated mesoporosity. An in-depth characterization allowed to elucidate the remarkable catalytic performance. The insertion of Ga predominantly as single site in tetrahedral coordination in the silica framework was highlighted by X-ray photoelectron spectroscopy (XPS), using the Auger parameter of Ga in a Wagner plot representation. The speciation of Ga was further clarified using solid state 71Ga NMR spectroscopy, confirming the formation of mainly isolated Ga species. Consistently, the aerosol-made Ga-silicates displayed outstanding turnover frequencies (up to 677 h−1) and selectivity, markedly outcompeting other reference metallosilicate catalysts reported in literature. Moreover, the most active catalyst was successfully reused in multiple catalytic cycles thus proving its stability under the selected reaction conditions.

Visible light driven selective photocatalytic synthesis of high-value carbonyl compounds from glycerol over Ag-AgBr/TiO2 nanocomposites in acetonitrile

Ag-AgBr/TiO2 ternary nanocomposites fabricated by facile photo-deposition were applied for selective oxidation of glycerol into glyceraldehyde (GAD) and dihydroxyacetone (DHA) in non-aqueous solvent under aerobic conditions. Although a lower conversion of glycerol was observed in acetonitrile than in water after 240 min, a significantly higher yield of GAD (19%) and DHA (13%) was obtained likely due to the lower generation of non-selective •OH radicals in the non-aqueous solvent. Obtained results underscore the vital role of solvent in photocatalytic upgrading of glycerol.

New Glycerol Upgrading Processes

Energy policies in the US and in the EU during the last decades have been focused on enhanced oil and gas recovery, including the so-called tertiary extraction or enhanced oil recovery (EOR), on one hand, and the development and implementation of renewable energy vectors, on the other, including biofuels as bioethanol (mainly in US and Brazil) and biodiesel (mainly in the EU) [...]

Recent advances in (chemo)enzymatic cascades for upgrading bio-based resources.

Developing (chemo)enzymatic cascades is very attractive for green synthesis, because they streamline multistep synthetic processes. In this Feature Article, we have summarized the recent advances in in vitro or whole-cell cascade reactions with a focus on the use of renewable bio-based resources as starting materials. This includes the synthesis of rare sugars (such as ketoses, L-ribulose, D-tagatose, myo-inositol or aminosugars) from readily available carbohydrate sources (cellulose, hemi-cellulose, starch), in vitro enzyme pathways to convert glucose to various biochemicals, cascades to convert 5-hydroxymethylfurfural and furfural obtained from lignin or xylose into novel precursors for polymer synthesis, the syntheses of phenolic compounds, cascade syntheses of aliphatic and highly reduced chemicals from plant oils and fatty acids, upgrading of glycerol or ethanol as well as cascades to transform natural L-amino acids into high-value (chiral) compounds. In several examples these processes have demonstrated their efficiency with respect to high space-time yields and low E-factors enabling mature green chemistry processes. Also, the strengths and limitations are discussed and an outlook is provided for improving the existing and developing new cascades.

Surface-functionalized mesoporous gallosilicate catalysts for the efficient and sustainable upgrading of glycerol to solketal

Hybrid gallosilicate catalysts prepared in a continuous one-pot procedure are proposed as active and reusable solids in the conversion of glycerol into solketal

Utilization of biochars as sustainable catalysts for upgrading of glycerol from biodiesel production

Abundant bioglycerol generated via transesterification of triglycerides was used to synthesize valuable glycerol carbonate, GC. This was achieved by pyrolyzing cow dung (CDB) and fish scale (FSB) biowastes at various temperatures (500 °C to 750 °C) and utilizing the obtained biochar catalysts to propagate the synthesis of GC. The results indicate that pyrolysis temperature promoted the biochars basicity and the catalytic activity. Also, the FSB biochar catalytic activity was limited by the nature or amount of surface basicity and was significantly improved when 3 wt.% potassium fluoride (KF) was added. The highest catalytic activity for KF modified FSB (>96% GC yield) was achieved under 60 min reaction time at a mild reaction condition of 85 °C and DMC/glycerol molar ratio of 2. Also, the CDB catalyst presented similar GC yield under similar conditions with longer reaction time (90 min). The biochars could be reused in four consecutive reaction cycles without serious deactivation.