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Concrete production is a large scale process that involves high energy consumption. In order to increase the sustainability of this process, the reduction of energy input is necessary. Bio-glycerol was demonstrated to be a highly efficient renewable-based additive in the grinding process for concrete production and helped reduce energy costs and improve the quality of the resulting product. In order to understand its excellent aiding properties, the interaction of glycerol with cement clinkers was investigated; both chemical and physical interactions were taken into account. The results of this investigation points to surface tension modification of the clinker particles as one of the main effects of bio-glycerol addition during the grinding process. [ABSTRACT FROM AUTHOR]

A series of task-specific ionic liquids (TSILs) based on glycerylimidazolium cations have been prepared by reaction of 1-chloropropanediol, a compound obtainable from glycerol (a widely available and in-expensive waste product), with the appropriate base (1-H-imidazole, 1,2-dimethylimidazole and 1-methyl-1-H-imidazole). The reaction of 3-(1H-imidazol-1-yl)propane-1,2-diol with chloroalkanes, bromoalkanes and alkyl mesylates gave the corresponding salts which were characterized. The possibility to use these ILs in palladium catalyzed reactions was evaluated, evidencing good catalyst stability and a high recyclability. [ABSTRACT FROM AUTHOR]

Glycerol, which bears green, low-cost, and good miscibility features, provides a variety of solvent portfolios to satisfy the complex market demands. Owing to its abundant feedstock and unique properties, glycerol is a good candidate in catalysis, high-value-added chemical conversion, and solvents. It can also be used as an energy transportation medium attributed to its high boiling temperature, promising thermal stability, and fertile hydrogen bond. Despite the great potential of glycerol in energy transportation, a review paper that summarizes and discusses its recent advances is blank to date. In this review paper, recent advances in the utilization of glycerol and glycerol-based mixture solvent systems in energy transportation were summarized. Thermophysical properties of glycerol-containing fluids, including their performance in various heat transfer occasions, and principles of related energy transportation were comprehensively introduced and discussed. Applications of these fluids in industrial processes were also discussed systematically. Furthermore, advantages and drawbacks of glycerol in energy transportation were concluded. It opens an important avenue to alleviate the backlog of glycerol production by means of valuable applications. [ABSTRACT FROM AUTHOR]

This study investigates the cradle-to-gate life cycle assessment of four acrylic acid production routes. Acrylic acid, an important industrial chemical, is currently produced using fossil fuel-based propylene but it can be sustainably produced from biodiesel derived glycerol through different pathways that involve intermediates such as acrolein, allyl alcohol, or lactic acid. Environmental impacts, including global warming potential, water footprint, acidification, eutrophication, ozone layer depletion, photochemical smog, and human toxicity, are evaluated. Glycerol-based processes exhibit significant environmental impacts mainly due to the energy-intensive production of epichlorohydrin-derived glycerol. The total potential global warming for glycerol-based processes having intermediates allyl alcohol, lactic acid and acrolein, was 1.67 × 105, 1.80 × 105 and 1.34 × 105 kg CO2 eq. FU-1 respectively, with epichlorohydrinderived glycerol, whilst this value was 0.552 × 105 kg CO2 eq. FU-1 for the propylene-based process. However, changing the source of glycerol to purified crude glycerol from the biodiesel industry results in a considerable reduction of the environmental impact. A sensitivity analysis using the two-factor interaction (2FI) model showed that the global warming potential varies from 0.676 × 105 to 1.45 × 105 kg CO2 eq. FU-1 depending on the purification method used to purify crude glycerol and the glycerol content in the crude glycerol. It showed that a vacuum distillation purification process with 50% glycerol content had the least global warming values. This assessment provides insights into environmental performance trade-offs, guiding efforts towards more sustainable acrylic acid production and emphasizing the potential of using by-products from other industries to enhance the sustainability in chemical production processes. [ABSTRACT FROM AUTHOR]

Herein we report the production of high-pressure (19.3 bar), carbon-negative hydrogen (H2) from glycerol with a purity of 98.2 mol% H2, 1.8 mol% light hydrocarbons (mainly methane), and 400 ppm of CO. Aqueous phase reforming (APR) of 10 wt% glycerol solution was studied with a series of NiPt alumina bimetallic catalysts supported on alumina. The Ni8Pt1-450 catalyst had the highest hydrogen selectivity (95.6%) and the lowest alkanes selectivity (3.7%) of the tested catalysts. The hydrogen selectivity decreased in the order of Ni8Pt1-450 > Ni8Pt1-260 > Ni1Pt1-260 > Pt-260. The CO2 was sequestered with CaO adsorbent which formed CaCO3. We measured the adsorption capacity of the CaO adsorbent at different temperatures. Life cycle analysis showed that the APR of glycerol coupled with CO2 capture has net negative CO2 equivalent greenhouse gas emissions. The CO2 emissions are −9.9 kg CO2 eq./kg H2 and −50.1 kg CO2 eq./kg H2 when grid electricity and renewable electricity are used, respectively, and the CO2 is allocated respectively to the mass of products produced. The cost of this H2 (denoted as "green-emerald") was estimated to be 2.4 USD per kg H2 when grid electricity is used and 2.7 USD per kg H2 when using renewable electricity. The cost of glycerol has the highest contribution of 1.71 USD per kg H2. Participation in the carbon credit markets can further decrease the price of the produced H2. [ABSTRACT FROM AUTHOR]

In this work, the reaction pathways of one-step glycerol hydrodeoxygenation in the gas phase are exploited under flow conditions over molybdena-based catalysts (8.7 wt% Mo/black carbon). Hydrodeoxygenation (HDO) experiments with possible reaction intermediates along with temperature-programmed surface reaction spectroscopy (TPSR) experiments demonstrated two possible reaction pathways. The major one involves propylene formation via hydrodeoxygenation of 2-propen-1-ol which is considered to be the main intermediate of the reaction. In the secondary route, propanal formed via 2-propen-1-ol isomerization is further converted to 1-propanol. XPS measurements in fresh-reduced and reduced-used catalysts revealed that molybdena exists as multivalent species mostly as Mo5+, Mo4+ and Mo3+, the presence of which seems to be crucial for the desired pathway of successive HDOs towards propylene. TPSR tests using methanol as the probe molecule showed that redox and acid sites co-exist on the surface of reduced molybdena catalysts, and this bifunctionality is mostly served by the undercoordinated molybdena species. The long-term catalyst test at 280 °C and 60 bar pressure under glycerol hydrodeoxygenation conditions demonstrated that the catalyst remains stable in terms of activity and selectivity for the first 10 h with a gradual drop afterwards. Regeneration of the catalyst for a short time under hydrogen flow proved to be sufficient to fully recover the initial activity and product selectivity. [ABSTRACT FROM AUTHOR]

A peculiar reactivity of glycerol carbonate (GlyC) as an innovative and highly reactive alkylating agent for phenolic compounds is investigated in this article. In particular, 2-hydroxymethyl-1,4-benzodioxane (HMB), a key intermediate for the pharmaceutical industry, has been selectively synthesized by the reaction of a slight excess of GlyC with catechol in the presence of a basic catalyst (NaOCH3, Na-mordenite, MgO), without requiring a reaction solvent. Both reagents have been quantitatively converted in just one hour at 170 °C with a HMB yield, up to 88%, in the presence of a homogeneous basic catalyst (NaOCH3). Notably, the main side product, the HMB isomer, may be an interesting intermediate for the synthesis of calone analogues, which are important scaffolds used in fragrances. A detailed mechanistic study, supported by kinetics, GC-MS, and HMBC NMR characterization, is also reported. Accordingly, this paper describes a completely innovative and greener synthesis pathway to benzodioxanes. [ABSTRACT FROM AUTHOR]

Glycerol, a by-product from biodiesel production, is currently considered as waste for disposal. Several attempts have been made to convert this wasted resource for high-value added products via either chemical or biological processes. However, complex steps are required to remove impurities and the selectivity of desired product(s) is low. In this paper, cold plasma catalysis was for the first time proposed to valorise untreated waste glycerol, greatly reducing the negative environmental impacts of waste glycerol. The attractiveness of this approach is that the process can be easily tuned toward specific products with high yields with a very short reaction time (around 16 seconds) at near ambient conditions. By altering the carrier gas, cold plasma power and packing material/catalyst, up to 99% of untreated waste glycerol was converted into either gas products consisting of hydrogen (55 mol% or 7.02 wt%), hydrocarbons (C1–C4: 9–10 wt%), CO (19 wt%) and CO2 (16 wt%), or high value liquid products such as acetol (up to 54 wt%). The findings of this work could open up new opportunities for intensification of green chemical processes and biorefining of waste materials by reducing pre-treatment steps, solvent requirements and amount of waste generation. [ABSTRACT FROM AUTHOR]

Urinary tract infection (UTI) is a major infectious disease commonly induced by uropathogenic Escherichia coli (UPEC), of which a prevalent serogroup is the mostly antibiotic-resistant O4. Therefore, protective vaccines against UPEC infection, especially serogroup O4, are needed. Polysaccharide-based glycoproteins are promising candidates for development of anti-bacterial vaccines; however, current chemical and chemoenzymatic syntheses are costly and environmentally unfriendly, because of the complex ligation strategies and chemical reagents required. Development of efficient microbial cell factories, using cheap, renewable feedstocks and avoiding the use of toxic reagents would reduce toxic waste generation and environmental concerns. An O-glycosylation Escherichia coli chassis was developed to install the O-antigen gene cluster to biosynthesize a polysaccharide-based glycoprotein, by co-utilization of a glucose/glycerol mixture with high synergistic metabolic efficiency. Towards this goal, 32 genes related to competing pathways were deleted from E. coli MG1655 and 28 genes relevant to the biosynthesis of the glycoprotein were introduced, resulting in the successful production of the target recombinant glycoprotein. Subsequently, the availability of the intracellular sugar derivative precursors dTDP- L -Rha and UDP- L -FucNAc was optimized by tuning the expression of the corresponding enzymes. Further optimization of fermentation conditions resulted in a glycoprotein titre of 27.71 mg L−1. MS and EMR confirmed the precise biosynthesis of the target glycoprotein and highly efficient glycosylation. Finally, vaccination with the glycoprotein stimulated a strong immune response in mice, which markedly reduced the bacterial burden in the bladder and kidneys after UPEC challenge. This study provides guidance for the development of a sustainable and environmentally friendly manufacturing platform for specific high-value therapeutic glycoproteins. [ABSTRACT FROM AUTHOR]

Biodiesel has attracted considerable attention as one of the best choices among alternative and renewable fuels. Large quantities of crude glycerol are produced as a main co-product with increasing biodiesel production. Currently, the problem of waste glycerol utilization needs to be crucially addressed, not only for environmental protection but also for the economy of the biodiesel industry. In this paper, the use of crude glycerol for the production of D-lactate by engineered Escherichia coli was investigated. Engineered E. coli B0013-070 with a homolactic pathway for D-lactate synthesis by elimination of byproduct pathways (ethanol, succinate, formate and acetate) could convert 20 g L-1 of crude glycerol to 13.6 g L-1 of D-lactate with a yield of 0.67 g g-1 glycerol. Overexpression of D-lactate dehydrogenase by a low-copy vector in E. coli B0013-070 resulted in the increased production and yield of D-lactate, in which 14.5 g L-1 of D-lactate was produced with a yield of 0.72 g g-1 glycerol from crude glycerol. The effect of temperature on D-lactate fermentation by the engineered strain E. coli B0013-070-pTHldhA was also investigated, and 34 °C and 40 °C were found to be the optimal temperatures for cell growth and lactate production, respectively. The engineered strain B0013-070-pTHldhA produced 100.3 g L-1 of D-lactate with 99.97% optical purity from 531.5 g of crude glycerol with an overall productivity of 2.78 g L-1 h-1 and a yield of 75.4 g per 100 g glycerol (0.77 mol mol-1) using two phase fermentation combined with a temperature shifting strategy in a 7 L bioreactor. In summary, this paper shows that crude glycerol could be directly converted to D-lactate without any prior purification. [ABSTRACT FROM AUTHOR]

Value-added formamides were sustainably synthesized by the N-formylation of amines with glycerol derivatives (1,3-dihydroxyacetone, glyceraldehyde and glycolic acid) as the carbonyl source via in situ C–C bond cleavage catalyzed over zeolite 5A supported Cu-based catalysts. Introducing a second metal ZrIV ions can greatly increase the activity of the Cu/5A catalyst. Catalyst characterization results revealed that the introduction of ZrIV ions decreases the amount of surface acidic sites, in particular, medium–strong acidic sites and promotes the formation of ˙OOH radicals. Isotopic tracing experiments confirmed that all the carbon atoms in the carbonyl group of formamide products are indeed from glycerol derivatives. Combined electron paramagnetic resonance (EPR) spin-trapping, operando attenuated total reflection (ATR)-FTIR spectroscopy and control experiments revealed that the reaction of aniline and DHA with formanilide involves GA and HCOOH intermediates and ˙NHPh radicals via a ˙OH–˙OOH radical-relay mechanism. [ABSTRACT FROM AUTHOR]

With the development of the biodiesel industry, the annual production of the byproduct glycerol has increased to a level of nearly millions of tons. Efficient and clean utilization of glycerol is thus urgent and profitable. Direct glycerol fuel cells (DGFCs) capable of selective oxidation of glycerol and co-generation of electricity and high-value added chemicals seem to be the most compelling technique. Unfortunately, selective and durable electrocatalysts for fabricating DGFCs are still not available so far. Herein, ternary Pt–Pd–Ag alloy nanowires (NWs) are designed and synthesized under the direction of the d-band theory. The resulting Pd–Pt–Ag NWs exhibit significant activity towards the glycerol electro-oxidation reaction (GOR) and oxygen reduction reaction (ORR) in an alkaline medium, which outperforms the bimetallic Pt–Ag alloy NWs and the commercial Pt/C benchmark. Moreover, a homemade DGFC based on bifunctional Pd–Pt–Ag NW anode and cathode can achieve a peak power density of 13.7 mW cm−2 under ambient conditions (∼50% enhancement compared to the DGFC based on the Pt/C benchmark) and deliver a record voltage of 1.13 V ever reported in alcohol-feeding fuel cells. Besides the electricity profits, the DGFC concurrently generates value-added formate as a selective product of glycerol oxidization. [ABSTRACT FROM AUTHOR]

Herein, we report a well-defined pincer manganese complex supported by PNP ligands for the conversion of glycerol to sodium lactate with dihydrogen liberation. Sodium lactate could be obtained in 96% yield with 96% selectivity under mild reaction conditions, with the Mn-3 complex as the catalyst. In this transformation, catalyst loadings even as low as 0.025 mol% could also result in high reactivity and excellent selectivity (up to 98%) at 180 °C in 36 hours. Mechanistic studies demonstrated that the manganese catalyst was mainly responsible for glycerol dehydrogenation, while the amount of sodium hydroxide had a crucial effect on the subsequent Cannizzaro reaction. In addition, the catalytically active species in the reaction were investigated by using in situ31P NMR spectroscopy. This catalytic system provides a green, efficient, and atom-economical approach for upgrading biodiesel waste into high-value chemicals. [ABSTRACT FROM AUTHOR]

Glyceric acid (GA), a glycerol derivative, can be used as a versatile platform molecule to produce value-added chemicals. Succinic acid (SA) is a very important bio-based molecule that acts as a fine chemical and is used in biodegradable polymer synthesis. It has been shown earlier that GA can be effectively converted to the platform chemical 3-iodopropionic acid (3-IPA) with a RhCl3/HI catalyst system. In this work, we first explored the production of SA from 3-IPA by carbonylation. With RhCl3 as the catalyst and acetic acid (AA) and water as the solvent, as high as 78% yield of SA can be achieved. Considering the similarity of the catalysts used in two steps, we then further probed the one-step synthesis of SA directly from GA. Under optimized reaction conditions, 71% yield of SA can be obtained directly from GA by reductive carbonylation with RhCl3 and I2 as the catalyst under H2 and CO atmospheres. This is the first report of the direct conversion of GA to SA, which provides a novel method for glycerol valorization. [ABSTRACT FROM AUTHOR]

In order to make recycling a viable strategy for post-consumer plastics, economically feasible revalorization processes must be developed. The ammonolysis of polyamides can be such a cutting-edge recycling technology; however, due to the rigid structure of these polyamide plastics, operating conditions of current ammonolysis processes are harsh, including high temperatures (>300 °C) and high NH3 pressures. Here, we report a very green and elegant ammonolysis process of the widely abundant polyamide 66 by using a hard Lewis acid catalyst and 1 bar of NH3 in a simple glycol solvent at 200 °C. Computational studies revealed that especially the vicinal diol moiety of these glycol solvents plays a key role in activation of the ammonia nucleophile, with glycerol being the most effective solvent, reaching the depolymerization equilibrium after 20 h even without a catalyst. To our delight, a biosourced glycerol (obtained from the saponification of triglycerides) could also directly serve as a suitable solvent, even outperforming the ammonolysis process in highly purified glycerol. [ABSTRACT FROM AUTHOR]

In this paper, we studied an original synthetic strategy to prepare bio-based surfactants by direct solvent-free etherification of glycerol with dodecanol using heterogeneous interfacial acidic catalysts dubbed Pickering Interfacial Catalysis. The conversion of dodecanol could be achieved to 60–71% with limited production of didodecyl ether (DE) as the main side product. The selectivity of the final product, alkylpolyglycerylether (AGEM), could be pushed to ＞80% with a water removal process at 150 °C, as a mixture of monolauryl polyglyceryl ethers, multilauryl polyglyceryl ethers and multilauryl cyclicpolyglyceryl ethers. AGEM could be isolated with a suitable work-up and was fully characterized by GC (MS), HPLC, SFC/HRMS, etc. The physicochemical properties of these new surfactants were evaluated, as well as their laundry performances. This solvent-free direct etherification process paves the way towards new value-added applications of glycerol. [ABSTRACT FROM AUTHOR]

The growing environmental impact of non-renewable solvents has generated an increasing interest in the development of more sustainable alternatives. Among these options, deep eutectic solvents (DES) are attracting great interest. The favourable physicochemical properties of these solvents make them a potential green alternative for several applications. However, its toxicological impact has not been studied enough to assume the absence of environmental risk. With the main purpose of establishing an initial overview of the aquatic toxicity, an acute ecotoxicity test of different eutectic solvents, composed of glycerol or glycerol-derived ethers and choline chloride (ChCl) or N,N,N-triethyl-N-(2,3-dihydroxypropyl) ammonium chloride (N00Cl), has been carried out in two aquatic biomodels: Aliivibrio fischeri (bacteria) and Raphidocelis subcapitata (algae). Furthermore, the content of chlorophyll was measured to observe the disruption of the photosynthetic process by the tested compounds. A dose-effect correlation has been observed, although very high concentrations of the solvents were necessary for the onset of the toxic effect. The toxicity of the DES, within the ChCl case, turned out to be greatly related to the polarizability and hydrophobicity of the solvents. Whereas N00Cl-based DES have shown an even-odd trend, compounds with even carbon numbers in the ether radical show lower toxicity than odd ones. These preliminary results point out a favourable eco-toxicological behaviour of glycerol derived DES, although studies in other bioindicators, as well as in cells and biodegradability tests are recommended in order to have a complete overview of the toxicological profiles of these promising solvents. [ABSTRACT FROM AUTHOR]

This work reports the first lipase-catalyzed reactions between substrates of different polarities using deep eutectic solvents as a medium. The model reaction consisted of a lipophilization process based on the alcoholysis of phenolic esters using immobilized Candida antarctica lipase B as a biocatalyst. Results showed that water could dramatically improve the lipase activity and change the reactivity of phenolic substrates. Indeed, very low conversions (＜2%) were observed in pure DES, whereas in DES–water binary mixtures, quantitative conversions were achieved. After investigating the role of various parameters, such as the substrate concentration and ratio, pH or thermodynamic activity of water, the effect of the presence of water in pure DES based on urea or glycerol was discussed. In this paper, we propose new perspectives for the enzymatic modification of polar substrates using this novel generation of green, inexpensive and easy-to-handle solvents. [ABSTRACT FROM AUTHOR]

Glycerol is an attractive bio-based platform chemical that can be converted to a variety of bio-based chemicals. We here report a catalytic co-conversion strategy where glycerol in combination with a second (bio-)feed (fatty acids, alcohols, alkanes) is used for the production of bio-based aromatics (BTX). Experiments were performed in a fixed bed reactor (10 g catalyst loading and WHSV of (co-)feed of 1 h−1) at 550 °C using a technical H-ZSM-5/Al2O3 catalyst. Synergistic effects of the co-feeding on the peak BTX carbon yield, product selectivity, total BTX productivity, catalyst life-time, and catalyst regenerability were observed and quantified. Best results were obtained for the co-conversion of glycerol and oleic acid (45/55 wt%), showing a peak BTX carbon yield of 26.7 C%. The distribution of C and H of the individual co-feeds in the BTX product was investigated using an integrated fast pyrolysis-GC-Orbitrap MS unit, showing that the aromatics are formed from both glycerol and the co-feed. The results of this study may be used to develop optimized co-feeding strategies for BTX formation. [ABSTRACT FROM AUTHOR]

The benefits of transitioning to chemical and material circularity are readily apparent. However, identifying and developing the necessary chemical transformations for platform chemical recycling is a significant challenge. Alcohols are an important industrial platform class owing to existing demand and the potential for their renewable supply through the utilization of biomass processing waste streams. Acceptorless Dehydrogenation (AD) is a critical process in the context of circularity, particularly in the transformation of alcohols. This mini-review offers an in-depth examination of both homogeneous and heterogeneous catalytic processes used in acceptorless dehydrogenation. We primarily concentrate on two sustainable feedstocks, glycerol and ethanol. Through the assessment and juxtaposition of homogenous and heterogeneous catalysts in the context of the alcoholysis of glycerol and ethanol, we aim to establish a comparison based on activity, longevity, and the green chemistry metrics associated with the catalytic processes (specifically the E-factor; energy economy coefficient, e; and environmental energy impact factor, ?). We established evaluation criteria using the matrics to provide a means for comparison among homogeneous and heterogeneous catalysts and help identify promising catalyst classes that can be further developed. This review seeks to shed light on the existing constraints that must be addressed to advance the development of catalysts that are more efficient, cost-effective, and resilient for AD reactions. [ABSTRACT FROM AUTHOR]

Production of glyceric acid (GLA) by the oxidation of glycerol is a promising green and efficient process, which could replace conventional biological fermentation with low efficiency. However, simultaneously achieving the efficient oxidation of glycerol to GLA and the separation of subsequent products remains a challenging task due to the easy decomposition and condensation of selective oxidation products at high temperature. Herein, we propose a novel glycerol to GLA process (termed as VDG process) by bringing insight into the essence of thermal-sensitivity. In the VDG process, glycerol is selectively oxidized to GLA and other thermal-sensitivity byproducts by our recently developed PtRu/MCM-41 nanocatalysts under base-free conditions. The high purity separation of products is realized at a temperature lower than its decomposition temperature through integrating the vacuum dividing wall columns. This intensified process reduces the energy consumption and production cost. Compared with the conventional glycerol to GLA process, this VDG process provided up to 61.3% increase in energy efficiency and 47.9% reduction of the total production costs. Moreover, the life cycle assessment from multi-scales obviously indicates that the performance of greenhouse gas emissions, non-renewable energy demand and waste water generation in the VDG process are about 5.0 times, 1.6 times and 9.5 times lower than the conventional process, respectively. The results in this study harbour tremendous guiding significance to the design of efficient biomass polyol conversion to value-added products. [ABSTRACT FROM AUTHOR]

Two series of functionalized mesoporous Ga silicates were prepared in a straightforward and sustainable one-pot procedure using different alkyl silanes. The efficacy of the adopted co-synthetic approach based on aerosol processing has been proved by 29Si solid-state NMR experiments revealing a degree of functionalization close to the theoretical value. The successful incorporation of gallium as single sites within the silica framework was confirmed via71Ga solid-state magic-angle-spinning NMR measurements. These materials were tested as catalysts for the synthesis of solketal from glycerol at low temperature and under solventless conditions. A systematic study evidenced the importance of a careful tuning of surface polarity, achievable with surface functionalization as well as with different thermal treatments. The solids functionalized with a low degree of methyl groups (5%) displayed enhanced performances compared to the non-functionalized analogues, highlighting the highly beneficial role of surface hydrophobicity as well as the importance of the careful tuning of the hydrophilic/hydrophobic balance. The best functionalized catalysts proved to be easily reusable for multiple catalytic runs. With such a high-performance catalyst in hand, we propose a process which shows a favorable E-factor, indicating that the production of solketal can be envisaged in a sustainable way. [ABSTRACT FROM AUTHOR]

Lignin nanosizing has received much interest as it offers new potential for value-added applications of the currently under-utilized lignin biopolymers. However, conventional lignin nanosizing technologies often rely on the use of large amounts of toxic organic solvents, and a time-consuming dialysis process that is required to remove the solvents. Herein, we present a novel and effective approach using a binary system consisting of green γ-valerolactone (GVL) and glycerol solvents to prepare lignin nanospheres (LNS) without lignin modification and additional dialysis processes. The rationale of LNS formation lies in the emulsification of uniform lignin-containing GVL droplets in glycerol by a process consisting of (1) heating to 80 °C, and (2) cooling to room temperature. Through this simple process, we obtained very high LNS yield (over 90%), with narrow size distribution (about 275 nm) by using maple kraft lignin as the raw material. This lignin nanosizing approach is universal when applied to different sources/types of lignins. The as-prepared LNS were further applied as a green reducing agent and carrier for the synthesis of Pd nanoparticles (NPs) in a facile in situ reduction process. Pd@LNS exhibited significantly enhanced catalytic capacity in the hydrogen evolution from formic acid and in the reduction of Cr(VI) to Cr(III) compared with bare Pd NPs. The Pd@LNS catalyst demonstrated high recyclability owing to the good chemical stability of LNS and robust loading of Pd NPs on LNS. Consequently, this work offers a green, universal and effective approach for LNS fabrication and presents a promising application of LNS as metal NP carriers for catalysis purposes. [ABSTRACT FROM AUTHOR]

Mono-, di- and triacetin are three glycerol esters which are usually synthesized via costly and environmentally unfriendly chemical synthesis methods. Here, Escherichia coli is metabolically engineered for the production of mono-, di- and triacetin using glycerol as a substrate. First, a novel biosynthetic route of mono- and diacetin is established by overexpression of a native enzyme, maltose O-acetyltransferase (MAA). Next, the biosynthetic pathway is extended to produce a mixture of mono-, di- and triacetin by overexpression of chloramphenicol-O-acetyltransferase (CAT). By successive strategies, including heterologous gene expression, metabolic engineering, and culture optimization, a recombinant E. coli is enabled to produce more than 27 g L−1 of a mixture of mono-, di- and triacetin in shake flask cultures, which is a >650-fold increase over the initial production of 0.04 g L−1. In vitro studies confirm the acetylation of glycerol to mono- and diacetin by MAA, and the additional acetylation to triacetin by CAT. When crude glycerol is used as a substrate, the engineered strain produced a total of 25.9 g L−1 of the acetin mixture, about the same as that achieved from pure glycerol. To our knowledge, this is the first successful report of microbial production of the artificial chemicals, acetins. [ABSTRACT FROM AUTHOR]

The increasing demand for bioderived plastics and rubbers and the large supply of glycerol makes it an excellent starting chemical for the production of biopolymers. Little success in commercially viable glycerol polymers has yet to be realized. In particular, high molecular weight thermoplastics have been especially elusive due to the multifunctional nature of glycerol. This work details the production of glycerol–acrylic biopolymers. By esterifying glycerol with acrylic acid, and subsequent RAFT polymerization to suppress the gelation, we were able to achieve glycerol thermoplastics with high molecular weights (1 MDa). After studying the thermal/mechanical properties of the polymer, it was found that these glycerol polymers had a high degree of tack. When added to wood as an adhesive, it was found that performance was comparable or exceeded standard wood adhesives such as Poly (Methylene diphenyl diisocyanate) (PMDI) and formaldehyde based adhesives. This yields wood adhesives that have less toxicity, lower environmental impact, and higher renewability. [ABSTRACT FROM AUTHOR]

At 30 °C, in the presence of Amberlyst-15 as a catalyst, a tandem sequence was implemented by which a pool of innocuous reactants (isopropenyl acetate, acetic acid and acetone) allowed upgrading of glycerol through selective acetylation and acetalization processes. The study provided evidence for the occurrence of multiple concomitant reactions. Isopropenyl acetate acted as a transesterification agent to provide glyceryl esters, and it was concurrently subjected to an acidolysis reaction promoted by AcOH. Both these transformations co-generated acetone which converted glycerol into the corresponding acetals, while acidolysis sourced also acetic anhydride that acted as an acetylation reactant. However, tuning of conditions, mostly by changing the reactant molar ratio and optimizing the reaction time, was successful to steer the set of all reactions towards the synthesis of either a 1 : 1 mixture of acetal acetates (97% of which was solketal acetate) and triacetin, or acetal acetates in up to 91% yield, at complete conversion of glycerol. To the best of our knowledge, a one-pot protocol with such a degree of control on the functionalization of glycerol via transesterification and acetalization reactions has not been previously reported. The procedure was also easily reproduced on a gram scale, thereby proving its efficiency for preparative purposes. Finally, the design of experiments with isotopically labelled reagents, particularly d4-acetic acid and d6-acetone, helped to estimate the contribution of different reaction partners (iPAc/AcOH/acetone) to the formation of final products. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is a nontoxic and inexpensive C1 building block, which can be used for the synthesis of valuable chemicals such as aromatic carbamates from anilines and methanol (MeOH), glycerol carbonate from glycerol, and cyclic carbonates from diols. However, these reactions generate water as the byproduct and suffer from thermodynamic limits, which lead to low yields. Calcium carbide (CaC2) is a renewable chemical, which can be recycled from calcium that is abundant in the Earth's crust. Furthermore, CaC2 rapidly reacts with water. In this work, we used CaC2 as a dehydrating agent for the direct synthesis of carbamates (including polyurethane precursors) from amines, CO2, and MeOH. All reagents were commercially available. In addition, CaC2 was employed for the synthesis of glycerol carbonate from glycerol and CO2 with a zinc catalyst and N-donor ligand. A similar protocol was applied to synthesize cyclic carbonates from diols and CO2. [ABSTRACT FROM AUTHOR]

The gas-phase conversion of glycerol into ethanol in a "green" one-step synthesis over a cesium metal-promoted zeolite catalyst has been reported for the first time. To our knowledge, the CsZSM-5 based catalyst presented in this work showed one of the best yields of ethanol in the gas-phase glycerol conversion. The catalyst sample's structure, texture, and acid–base properties were characterized using numerous materials characterization techniques. The catalytic evaluation was carried out in a packed-bed continuous flow reactor. The highest ethanol yield achieved was 99.6 mol% over a 20 wt% CsZSM-5 catalyst with SiO2/Al2O3 = 1500, 10 wt% glycerol feed concentration, 350 °C reaction temperature, and GHSVtotal = 625 h−1. It was demonstrated that the best catalytic performance was related to the ample amount of surface basic sites, synergistic interaction between Cs species and the HZSM-5 zeolite and to its smaller crystallite size obtained from XRD analysis. The achieved results exhibit great potential of utilizing the alkali-treated CsZSM-5 catalyst for the gas-phase conversion of glycerol into bio-based ethanol. The possible reaction route from glycerol to renewable ethanol was proposed based on direct glycerol conversion to ethanol via the thermal monodehydration, radical fragmentation, methylation and transfer hydrogenation reactions. Finally, for the first time, methanol was directly converted into ethanol in the gas-phase continuous flow packed-bed reactor over a 20 wt% CsZSM-5 catalyst. [ABSTRACT FROM AUTHOR]

Conjugate addition reactions are efficiently performed by a very simple electrochemical method using nickel complexes as catalysts. In this paper, we reported a new method for the valorization of glycerol 1,2-carbonate. Firstly, we prepared the activated glycerol 1,2-carbonate derivatives (halogen or pseudo-halide derivatives), and secondly applied these halogen derivatives in coupling reactions by electrochemical methods with organic compounds and environment-friendly solvent (propylene carbonate). To our knowledge, this is the first report of creation of carbon–carbon bonds on the glycerol 1,2-carbonate and of the synthesis of these compounds. [ABSTRACT FROM AUTHOR]

A robust continuous flow procedure for the transformation of bio-based glycerol into high value-added oxiranes (epichlorohydrin and glycidol) is presented. The flow procedure features a central hydrochlorination/dechlorination sequence and provides economically and environmentally favorable conditions involving an organocatalyst and aqueous solutions of hydrochloric acid and sodium hydroxide. Pimelic acid (10 mol%) shows an exceptional catalytic activity (>99% conversion of glycerol, a high selectivity toward 1,3-dichloro-2-propanol and 81% cumulated yield toward intermediate chlorohydrins) for the hydrochlorination of glycerol (140 °C) with 36 wt% aqueous HCl. These conditions are validated on a sample of crude bio-based glycerol. The dechlorination step is effective (quantitative conversion based on glycerol) with concentrated aqueous sodium hydroxide (20 °C) and can be directly concatenated to the hydrochlorination step, hence providing a ca. 2 : 3 separable mixture of glycidol and epichlorohydrin (74% cumulated yield). An in-line membrane separation unit is included downstream, providing usable streams of epichlorohydrin (in MTBE, with an optional concentrator) and glycidol (in water). The scalability of the dechlorination step is then assessed in a commercial pilot-scale continuous flow reactor. Next, bio-based epichlorohydrin is further utilized for the continuous flow preparation of β-amino alcohol active pharmaceutical ingredients including propranolol (hypertension, WHO essential), naftopidil (prostatic hyperplasia) and alprenolol (angina pectoris) within a concatenable two-step procedure using a FDA class 3 solvent (DMSO). This work provides the first example of direct upgrading of bio-based glycerol into high value-added pharmaceuticals under continuous flow conditions. [ABSTRACT FROM AUTHOR]

Glycerol, generated in abundance as the by-product in the process of biodiesel production and saponification, has seen attempts to convert it into value-added chemicals. However, due to the low selectivity of hydrogenolysis of the secondary hydroxyl group, valuable 1,3-substituted chemicals are difficult to obtain from glycerol by chemocatalysis. In this work, glyceric acid (GA), a renewable biomass from glycerol, was quantitatively converted to 3-iodopropionic acid (3-IPA) at 373 K in 3 h by hydroiodic acid mediated hydrogenation. As the reductant in this process, HI is oxidized to I2 and then regenerated in situ by metal catalysts and H2. The reaction pathway was proposed by intermediate identification and verified by a kinetics study and computational method. The catalytic system was shown to be stable and can be reused several times without loss in activity. As a 1,3-substituted chemical, 3-IPA is not only a potential monomer to form poly-3-hydroxypropionic acid, but also a good platform molecule to produce useful chemicals, e.g. 3-hydroxypropionic acid (3-HPA) and acrylic acid (AA), due to its highly reactive nature. [ABSTRACT FROM AUTHOR]

Multifunctional catalytic systems consisting of physical mixtures of (i) bimetallic Au–Pd nanoparticles (average size of 3–5 nm) supported on functionalised carbon nanotubes (CNTs) and (ii) Sn-MCM-41 nanoparticles (50–120 nm), were synthesised and investigated for the base-free, selective conversion of glycerol to methyl lactate in a batch reactor. The catalysts were characterised by means of transmission electron microscopy, N2-physisorption, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and by Boehm titration. The catalyst based on bimetallic AuPd/CNTs showed much higher activity than the monometallic Au or Pd counterparts, thus indicating synergetic effects. Functionalisation of the CNTs by oxidative treatments had a positive effect on catalyst performance, which was correlated to the observed increase in surface acidity and hydrophilicity. The highest yield of methyl lactate achieved in this work was 85% at 96% glycerol conversion (140 °C, 10 h at 30 bar air), which is the highest yield ever reported in the literature so far. Insights in the reaction pathway were obtained by monitoring the conversion-time profiles for intermediates and their possible role as inhibitors. Batch recycling experiments demonstrated the excellent reusability of the catalyst. [ABSTRACT FROM AUTHOR]

Due to their synergistic structural and compositional advantages, ultrathin multimetallic nanosheets are widely recognized as highly efficient electrocatalysts for alcohol electrooxidation. However, despite significant efforts, current synthetic strategies for the preparation of multimetallic nanosheets mainly focus on the reduction of metal precursors in organic solvents or in the presence of toxic CO. In this study, a one-pot aqueous synthesis method based on the self-assembly of the novel surfactant docosyltrimethylammonium chloride was employed to produce ultrathin free-standing trimetallic PdPtCu nanosheets under ambient and eco-friendly conditions. No toxic chemicals or organic solvents were employed in this synthesis. The obtained PdPtCu nanosheets were ultrathin with a dendrite-like nanostructure (with an average thickness of ∼3.5 nm) and alloyed crystalline features. The proposed synthetic strategy is also universally applicable for tuning the elemental ratios and compositions of ultrathin multimetallic nanosheets. Due to the multiple advantages of unique ultrathin dendrite nanostructures and multimetallic elemental compositions, the PdPtCu nanosheets exhibited remarkably enhanced performance in the electrooxidation of alcohols (methanol, ethanol, glycerol and glucose). The proposed one-pot eco-friendly synthetic concept could be used to build more multimetallic nanostructures with synergetic enhancement effects for a range of electrocatalytic applications. [ABSTRACT FROM AUTHOR]

Current solvents used in membrane preparation are often toxic, environmentally unfriendly and prepared from non-sustainable resources. It would be beneficial to replace common solvents, like N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF) and tetrahydrofuran, by “green” solvents. Among these, bio-based solvents were selected for this research, more specifically γ-valerolactone (GVL) and a set of glycerol derivatives. They were screened for their potential use as solvent for membrane preparation by determining solubility of a variety of common membrane polymers and by verifying their applicability in the process of phase inversion to create useful membranes with appropriate pore structures and separation properties. Polymer solubility was rationalized by Hansen solubility parameters. Membrane morphology was characterized by using scanning electron microscopy, while membrane performance was investigated using rose bengal (1017 Da) in water as feed to screen the potential to tune these polymer/solvent systems even toward the nanofiltration range. [ABSTRACT FROM AUTHOR]

In this paper we report on the one-pot transformation of glycerol into acrylic acid, catalyzed by W/V mixed oxides, with hexagonal tungsten bronze (HTB) structure. The reaction requires two different catalyst functions, i.e., an acid one, which is given by W oxide, and an oxidizing one, given by the V ions incorporated within the WO3 lattice. W–O bronze is very active and moderately selective in acrolein formation, but yields only traces of acrylic acid. The incorporation of increasing amounts of V inside the hexagonal tungsten bronze structure, with the development of a monophasic compound, allows the consecutive oxidation of acrolein into acrylic acid. An optimal atomic ratio between W and V equal to V/(W + V) = 0.12–0.21 made it possible to obtain an acrylic acid yield of 25% (with selectivity to residual acrolein of 11%). However, during reaction under the oxygen-containing feed, the V4+ incorporated into the hexagonal bronze structure underwent a slow oxidation into V5+, which caused a progressive decline of selectivity to acrylic acid and a concomitant increase of COx formation; the hexagonal structure however was stable during lifetime experiments. On the other hand, in the absence of oxygen a very rapid deactivation of the catalyst occurred, with a decrease in selectivity to acrolein and increase in heavy by-products. [ABSTRACT FROM AUTHOR]

The rise in demand for biomass as a renewable energy source is being seen as an alternative energy source to conventional fossil fuels. Blending of biodiesels and bioethanol in gasoline is the initial step towards complete utilization of biomass fuels. Glycerol is a byproduct generated in vast quantities during biodiesel production. Glycerol, on further oxidation, can produce several value-added products in conjunction with hydrogen (H2) through photo-/electrocatalysis (PEC/EC). Valuable products from glycerol include 1,3-dihydroxyacetone, glyceraldehyde, tartronic acid, formic acid, and glyceric acid. Glycerol can be used as a feedstock in PEC/EC cells along with water. An intriguing strategy unfolds by combining the oxidation of biomass-derived compounds at the anode with the hydrogen evolution reaction taking place at the cathode, all contained within a biomass electrolysis or photo-reforming reactor. This approach enables the simultaneous production of high-value chemicals and hydrogen, while minimizing energy consumption and reducing CO2 emissions. This review seeks to integrate essential insights into photo- and electro-assisted catalysis, with the objective of offering a holistic comprehension of the overall reaction mechanisms involved in the photo-/electrocatalytic oxidation of glycerol. At the same time, various transition metal-based photo-/electrocatalysts for glycerol valorization are reviewed and discussed in great detail. Moreover, this evaluation carefully examines the obstacles and possibilities for the advancement of photo-/electrocatalytic glycerol oxidation, aligning with future demands for sustainability in the global energy landscape. [ABSTRACT FROM AUTHOR]

As a widely used solvent, fuel and intermediate, the demand for ethanol continuously increases. Currently, ethanol is produced via sugar fermentation and hydration of ethylene. It is of great significance to convert abundant glycerol to ethanol. Herein, we report a novel Co/ZnO catalyst with nano-sized Co particles embedded in ZnO plates, which was obtained through calcination and reduction of CoZn-ZIF precursor, and its excellent performance in the synthesis of ethanol from glycerol. The transformation process from CoZn-ZIF to Co/ZnO-ZIF was characterized by TG-DSC, XRD, SEM, TEM and XPS. Characterization results indicated that rhombic dodecahedral composite consisting ZnCo2O4 spinel formed after calcination of CoZn-ZIF precursor, which also led to the formation of small Co particles that embedded in ZnO plates during reduction. Under optimal conditions, the best yield of ethanol reached 1.45 g-ethanol per g-cat per h at 210 °C over Co/ZnO-ZIF. On the basis of a series of controlled experiments, the reaction mechanism for the formation of alcohols from glycerol was proposed. [ABSTRACT FROM AUTHOR]

This work addresses an alternative and green route for glycerol upgrading recently highlighted as a potentially critical aspect of the economic and environmental viability of future biodiesel-based bio-refineries. For the first time we report the microwave-assisted hydrothermal process, examining the effects of the temperature (150–250 °C), pressure (50–120 bar), reaction time (0–2 h) and catalyst mass (5–15 wt%; Ni–Co/Al–Mg) during the upgrading of a 30 wt% glycerol solution. The global glycerol conversion and the carbon converted to gas and liquids varied by 5–54%, 0–21% and 3–42%, respectively. Increasing the temperature, reaction time and/or catalyst amount increased glycerol decomposition due to the positive kinetic effects that these variables have on the process. The pressure exerted two counteracting effects: a positive kinetic effect and a thermodynamic inhibitory influence; this latter being accounted for by the lower dielectric loss factor of water at high pressures. The liquid phase was made up of monohydric (10–62 wt%) and polyhydric (0–46 wt%) alcohols, carboxylic acids (0–9 wt%) and C3-ketones (0–80 wt%). Monohydric alcohols and C3-ketones were the most abundant compounds in the liquid when short reaction times and/or low catalyst amounts were used. An increase in these operating variables increased the concentration of polyhydric alcohols and decreased the amount of C3-ketones. The production of C3-ketones (72 wt%) could be maximised using a medium temperature (210 °C) and low pressure (50 bar) and catalyst mass (5 wt%) for a long reaction time (2 h). Around 40% of the glycerol can be purely converted to monohydric (79 wt%) and polyhydric (21 wt%) alcohols by employing a temperature of 250 °C, a pressure of 83 bar and a catalyst mass of 10 wt% for 2 h. [ABSTRACT FROM AUTHOR]

Commercial two-step processes to convert glycerol into epichlorohydrin are more benign compared to the predominant industrial route starting from propene in terms of materials requirements and CO2 emissions. Still, the use of alkali hydroxides in stoichiometric amounts in the second reaction, i.e., the dehydrochlorination of the dichloropropanol intermediate, leads to the formation of large amounts of salt wastes, thus limiting the greenness of the technology. Here, we show for the first time that the latter transformation can be selectively conducted in the gas phase in the presence of a heterogeneous hydrotalcite-derived mixed oxide of Al and Mg. Upon reaction, the lamellar solid is rehydrated to a hydrotalcite-like compound, which can effectively activate the alcoholic group of dichloropropanol owing to its strong Brønsted basic character and moderately high surface area. In-depth characterisation of the porous, compositional, structural and acid/base properties demonstrates that the HCl formed during the reaction causes the progressive exchange of interlayer OH groups by Cl atoms, thus gradually diminishing the reactivity of the material. Facile calcination restores the original mixed oxide structure and is shown to enable three equivalent consecutive reaction runs. Since the HCl evolved along with water upon regeneration can be recycled in the first step of the process, i.e., glycerol hydrochlorination, our approach paves the way for a waste-free and more atom efficient biobased epichlorohydrin production process. [ABSTRACT FROM AUTHOR]

The mechanism of bio-based betaine hydrochloride esterification with glycerol has been studied through DFT modelling and experimental approaches. Interestingly, our proposed mechanism differs from the classical Watson and Ingold ones. In particular, we found that the glycine betaine hydrochloride cluster contains a non-dissociated HCl molecule in its structure. This trapped HCl acted as a proton relay to favor the formation of unconstrained six-membered ring transition state structures both in nucleophilic addition (C–O bond coupling) and H2O elimination pathways. These findings led us to optimize this reaction. In particular, glyceryl betaine esters were produced in a yield up to 90% and with a space time yield up to 670 kg m−3 h−1 unreported to date. The absence of an external catalyst and solvent, as well as the use of a stoichiometric mixture of acidified glycine betaine and glycerol, two co-products of the sugar beet and vegetable oil industries, respectively, represent notable advantages within the framework of sustainable chemistry. This work opens a straightforward route to bio-based and valuable ionic building blocks which are of high interest for the synthesis of ionic surfactants or liquids. Furthermore, the results reported in this work also rationalize the high catalytic performances of glycine betaine hydrochloride recently reported in acid-catalyzed reactions. [ABSTRACT FROM AUTHOR]

Boron-doped graphene obtained by pyrolysis at 900 °C of the boric acid ester of alginate was found to be the most active graphene among a series of doped and co-doped graphenes to promote the aqueous phase reforming of glycerol at 250 °C. This reaction is of interest in the context of valorization of the aqueous wastes of carbohydrate syrups. Control experiments adding to undoped graphene 1 wt% of triphenylborane, tris(pentafluorophenyl)borane or bis(pinacolyl)diborane as models of possible boron atom types present in B-doped graphene, and boric acid that could be present in a residual amount after pyrolysis, show in all cases an increase in the catalytic activity of graphene. B-doped graphene has also activity for glucose aqueous phase reforming. B-doped graphene undergoes deactivation upon reuse, probably due to B leaching. The results show that graphenes are promising metal-free catalysts for aqueous phase reforming and are alternatives to those containing platinum. [ABSTRACT FROM AUTHOR]

The deoxydehydration (DODH) of glycerol towards allyl alcohol was revisited under continuous-flow conditions combining a microfluidic reactor setup and a unique reactive dynamic feed solution approach. Short reaction times, high yield and excellent selectivity were achieved at high temperature and moderate pressure in the presence of formic acid, triethyl orthoformate, or a combination of both. Triethyl orthoformate appeared as a superior reagent for the DODH of glycerol, with shorter reaction times, lower reaction temperatures and more robust conditions. In-line IR spectroscopy and computations provided different perspectives on the unique reactivity of glycerol O,O,O-orthoesters. [ABSTRACT FROM AUTHOR]

Electrocatalytic upgrading of glycerol to value-added commodity is demonstrated using an ultralow loading of a cobalt-based oxidation catalyst at 16 μg cm−2. Reactions take place under ambient conditions in an aqueous environment, while generating H2 as a byproduct. Selectivity towards two major products, lactic acid and glyceric acid, can be controlled via simple variation of reaction conditions. The system is scalable and functions well even in the presence of methanol, an impurity commonly found in the industrial bio-diesel waste stream. Industrial glycerol waste from a local bio-diesel plant was also shown to be upgradable after a simple aqueous pretreatment. [ABSTRACT FROM AUTHOR]

Using CO2 as a carbonyl building block to synthesize valuable chemicals is an important issue in the field of green and sustainable chemistry. Herein, the conversion of CO2 with glycerol to glycerol carbonate was investigated in the presence of 2-cyanopyridine. It was found that 2-cyanopyridine not only acts as the dehydrating agent to break the thermodynamic limit of the reaction, but also activates the carbonyl bond of CO2 to catalyze the present carbonylation as confirmed by FTIR experimental spectra. Moreover, the activation closely depends on the stereo-structure of cyanopyridine, in that 3-cyanopyridine and 4-cyanopyridine do not have such activating function. The theoretical calculation demonstrated that 2-cyanopyridine could bond CO2 through the conjugating nitrogen to form a five-membered ring, thus CO2 is activated and then reacts with glycerol to produce glycerol carbonate. The reaction parameters were examined and evaluated for the reaction catalyzed with 2-cyanopyridine in the absence of any metal catalysts and additives. With increasing CO2 pressure, the yield of glycerol carbonate increases, and under the optimum conditions an 18.7% yield is obtained which is one of the best results reported up to now. The present work provides a new way for activation of CO2. [ABSTRACT FROM AUTHOR]

Sustainable technologies for the valorisation of the burgeoning amounts of glycerol (GLY) obtained as waste in the production of biodiesel are increasingly sought after. Its conversion into lactic acid (LA) is appealing due to the versatility of this platform chemical and its high added value. Here, we introduce Ag-based catalysts for the oxidehydration of GLY to pyruvaldehyde (PAl) and demonstrate the superiority of this compound in comparison to dihydroxyacetone (DHA) as the intermediate of an alternative two-step GLY-to-LA process. Evaluation of various metals and carriers identified Ag/Al2O3 as the best performer for PAl production. This was rationalised based on the optimal redox potential of the metal and the high concentration of Lewis-acid sites and the limited Brønsted acidity of the support. At 623 K and O2/GLY = 0.5, a PAl yield of 80% was attained, which remained stable for 24 h. Characterisation of the used catalyst indicated that the surface of the silver nanoparticles was partially oxidised upon reaction. Density functional theory (DFT) modelling revealed that the oxidation of acetol obtained from GLY after the initial dehydration step is kinetically and thermodynamically favoured on a partially oxidised silver surface (AgOx/Ag) compared to metallic (Ag) or fully oxidic (Ag2O) ones. Finally, we show that PAl can be isomerised into LA and methyl lactate over Sn-containing zeolites with the same rates as DHA but at a 40 K lower temperature (343 vs. 383 K). This not only allows for energy savings but also for a remarkably increased catalyst stability. [ABSTRACT FROM AUTHOR]

The demand for 1,3-propanediol-based polymers is constantly increasing, necessitating an increase in 1,3-propanediol production. While the processes for the chemical and bacterial synthesis of 1,3-propanediol are well-known, we report for the first time the possibility of glycerol conversion to 1,3-propanediol by a fungal strain. The synthesis of 1,3-propanediol by biological means is extremely lucrative, and to the best of our knowledge, this is the first study focusing on the development of an optimized process for the production of the value-added chemical 1,3-propanediol from what can be considered as industrial waste, glycerol, via fermentation using instant baker's yeast (Saccharomyces cerevisiae). Various glycerol fermentation conditions (aerobic, semi-aerobic, and anaerobic) were tested at different reaction temperatures (25, 30, and 37 °C). Under optimal reaction conditions (anaerobic fermentation at 25 °C), 42.3 wt% 1,3-propanediol yield was achieved with 93.6 wt% glycerol conversion. [ABSTRACT FROM AUTHOR]

Potentially effective glycerol-based solvents for nitrocellulose have been designed using a top-down in silico procedure that combines Computer Assisted Organic Synthesis (CAOS) and Molecular Design (CAMD). Starting from a bio-based building block – glycerol – a large number of synthetically feasible chemical structures have been designed using the GRASS (GeneratoR of Agro-based Sustainable Solvents) program. GRASS applies well-selected industrial chemical transformations to glycerol together with a limited number of relevant co-reactants. Then, the most promising structures are considered as lead compounds for further modification in silico thanks to the IBSS (InBioSynSolv) program, which generates derivatives with alkyl, cycloalkyl, alkene, cycloalkene or phenyl substituents. Finally, IBSS ranks all the candidates according to the value of their overall performance function to best fit the predefined specifications, i.e. (i) high solubilisation of nitrocellulose, (ii) slow evaporation and non-flammability (iii) low toxicity and environmental impact. This general strategy enables the highlighting of the most relevant solvent candidate derived from any building block for a given application. To validate the approach, 15 commercially available solvents derived from glycerol were confronted with nitrocellulose and led to highlight diacetin as an effective and safe solvent. [ABSTRACT FROM AUTHOR]

A catalyst of 4.6% Cu supported on HZSM-5 with Si/Al of 38 [4.6% Cu/HZSM-5(38)] was prepared in this work. Pyridine bases including pyridine and 2- and 3-picoline, were obtained over this catalyst from glycerol and ammonia. The parameters influencing the catalyst performance were studied thoroughly. An optimized process for the reaction of glycerol with ammonia to form the pyridine bases was also obtained. Under the optimized conditions, which include a reaction temperature of 520 °C, atmospheric pressure with an ammonia/glycerol molar ratio of 7 : 1, and a GHSV of 300 h−1, the total carbon yield of the pyridine bases was nearly 42.8%. Characterization results from the IR of the adsorbed pyridine indicated that the doping of copper into HZSM-5(38) led to significant changes in the Lewis/Brønsted ratio. An appropriate proportion of the two types of acid sites is important to determine the total selectivity of pyridine bases. XRD analysis showed that copper was initially present in the CuO state and then converted into elemental Cu reduced by H2 generated in situ in the catalytic run. TEM and nitrogen adsorption–desorption characterization revealed that the catalyst deactivation was mainly caused by carbonaceous deposits on the catalyst. The catalyst can be regenerated online by blowing air into the reactor at 550 °C for 6 h. The slight decrease of the activity of the regenerated 4.6% Cu/HZSM-5(38) compared with that of the fresh one could be ascribed to the partial sintering of copper particles and dealumination of the catalyst in the catalytic run. [ABSTRACT FROM AUTHOR]

We demonstrate an electrocatalytic reactor system for the partial oxidation of glycerol in an acidic solution to produce value-added chemicals, such as dihydroxyacetone (DHA), glyceraldehyde (GAD), glyceric acid (GLA), and glycolic acid (GCA). Under optimized conditions, the carbon-supported bimetallic PtSb (PtSb/C) catalyst was identified as a highly active catalyst for the selective oxidation of glycerol in the electrocatalytic reactor. The product selectivity can be strongly controlled as a function of the applied electrode potential and the catalyst surface composition. The main product from the electrocatalytic oxidation of glycerol was DHA, with a yield of 61.4% of DHA at a glycerol conversion of 90.3%, which can be achieved even without using any oxidants over the PtSb/C catalyst at 0.797 V (vs. SHE, standard hydrogen electrode). The electrocatalytic oxidation of biomass-derived glycerol represents a promising method of chemical transformation to produce value-added molecules. [ABSTRACT FROM AUTHOR]