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Acetic acid is an important commodity chemical that is produced either by fermentation processes, or more commonly, through chemical routes such as methanol carbonylation with CO and H2, acetaldehyde oxidation, or hydrocarbon oxidation. More recently, methanol hydrocarboxylation with CO2 and H2 under thermal catalytic conditions has attracted interest. The synthesis of acetic acid from easily available CO2 is of great significance yet rarely reported. The present paper describes the first photocatalytic approach for the synthesis of acetic acid from methanol and CO2 under ambient reaction conditions without using molecular hydrogen. The maximum conversion of methanol achieved is 60% with a selectivity of 81% towards acetic acid using an octa-sulfur bound cobalt phthalocyanine (CoPc/S8) photocatalyst without an additional sacrificial electron donor. Product analysis, controlled experiments and DFT calculations suggest the formation of methylene carbene as a reactive intermediate. The developed methodology represents a potentially exciting approach for synthesizing acetic acid utilizing CO2 in a sustainable manner. [ABSTRACT FROM AUTHOR]

MOF-74 or M2(dhtp) (M = metal ions, dhtp = 2,5-dihydroxyterephthalic acid), as a typical class of metal–organic frameworks (MOF), have garnered considerable interest due to their abundant unsaturated metal sites. However, environmental and economic limitations caused by the extensive use of organic solvents in traditional syntheses hinder their industrial applications. Although water as a green solvent is considered to be the best candidate solvent, water-based MOFs often have poor crystallinity and long synthesis time, and controlling the particle size is difficult. Herein, a water-based strategy is proposed to synthesize high-quality MOF-74–Co with controllable particle sizes in a rotating packed bed (RPB) reactor using high-gravity technology. MOF-74–Co could be rapidly prepared in the RPB, and shows a smaller and more uniform particle size, higher crystallinity, and larger specific surface area, as compared to the counterpart prepared in a traditional stirred tank reactor. Further adopting acetic acid as a modulator, the as-prepared MOF-74–Co has the highest BET surface area (1599 m2 g−1) in the reported literature so far and simultaneously possesses a high space–time yield (293 kg m−3 day−1). High-quality MOF-74–Zn and MOF-74–Ni can also be prepared, proving the generality of this strategy. Furthermore, the small-sized MOF-74–Co-78 nm exhibits a faster adsorption rate and a larger saturation adsorption capacity (298 mg g−1) for CO2 compared with large-sized samples. This study not only advances the field of green synthesis of MOFs but also paves the way for efficient manufacturing processes in MOF-74 synthesis for CO2 adsorption. [ABSTRACT FROM AUTHOR]

Epoxidized vegetable oils (EVOs) are versatile building blocks for lubricants, plasticizers, polyvinyl chloride (PVC) stabilizers, and surface coating formulations. In this paper, a catalytic protocol for the efficient epoxidation of vegetable oils is presented that is based on a combination of a manganese catalyst, H2O2 as an oxidant, and acetic acid as an additive. This protocol relies on the use of a homogeneous catalyst based on the non-noble metal manganese in combination with a racemic mixture of the N,N′-bis(2-picolyl)-2,2′-bispyrrolidine ligand (rac-BPBP). The optimized reaction conditions entail only 0.03 mol% of the manganese catalyst with respect to the number of double bonds (ca. 0.1 wt% with respect to the oil) and ambient temperature. This epoxidation protocol is highly efficient, since it allows most of the investigated vegetable oils, including cheap waste cooking oil, to be fully epoxidized to EVOs in more than 90% yield with excellent epoxide selectivities (＞90%) within 2 h of reaction time. In addition, the protocol takes place in a biphasic reaction medium constituted by the vegetable oil itself and an aqueous acetic acid phase, from which the epoxidized product can be easily separated via simple extraction. In terms of efficiency and reaction conditions, the current epoxidation protocol outperforms previously reported catalytic protocols for plant oil epoxidation, representing a promising alternative method for EVO production. [ABSTRACT FROM AUTHOR]

The usefulness of ketonization reactions for the valorization of a wide plethora of biomass-derived carboxylic acids is widely recognized; however, the full potential of this reaction has yet to be suitably exploited for the production of high added-value aromatic and/or aliphatic asymmetric ketones. For this reason, herein we report for the first time in the literature the continuous-flow, gas-phase synthesis of 2-acetyl furan (AF) by means of the catalytic cross-ketonization of bio-based 2-methyl furoate (2-MF) and acetic acid (AA) over a simple and cheap ZrO2 catalyst. Interestingly, AF is considered a valuable food additive and a pharmaceutical intermediate for the synthesis of antibiotics. The optimization of the molar ratio between reactants at 350 °C allowed us to achieve 87% AF selectivity at 90% 2-MF conversion, with a space–time yield of 0.152 h−1, a value that is similar to the ones obtained by following the traditional Friedel–Crafts acylation and Wacker oxidation routes. On the other hand, the E-factor of the herein-proposed process is several times lower compared to the aforementioned traditional routes performed in the liquid phase and under batch conditions. Finally, the versatility of the cross-ketonization synthetic approach was successfully demonstrated and applied for the selective synthesis of other valuable acyl furans (i.e., propionyl furan and butyryl furan). [ABSTRACT FROM AUTHOR]

Selective production of glucose from cellulose in a molten salt hydrate (MSH) shows high efficiency but the separation of glucose is still challenging. To address this issue, we proposed a stepwise method, where cellulose was first hydrolyzed into glucan oligomers and separated via anti-solvent precipitation, followed by being hydrolyzed into glucose under mild conditions. For potential industrial applications, using raw biomass as a substrate is more attractive due to its commercial advantages. However, directly hydrolyzing raw corn stover in an MSH resulted in a low glucan oligomer yield and sugar concentration, together with insufficient separation efficiency. This work demonstrated that the generation of acetic acid during hemicellulose hydrolysis is the critical factor affecting glucan oligomer selectivity. To address this issue, a pre-extraction method using auto-hydrolysis was proposed to remove hemicellulose before MSH hydrolysis. After pre-extraction, the obtained glucan oligomer yield could be enhanced from 59.9% to 79.5%, with the separation efficiency increased from 53.7% to 80.6% by methanol precipitation. Besides, increasing the raw corn stover concentration led to an increase in acetic acid and resulted in glucan oligomer degradation. However, after removing hemicellulose, the concentration of glucan oligomers could be significantly enhanced from less than 72.1 to 121.5 mg mL−1. Thus, pre-extraction of hemicellulose followed by MSH hydrolysis provides a potential application for directly producing glucan oligomers from raw biomass with improved yield and separation efficiency. [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]

An ultrasound-assisted extraction (leaching) method of valuable metals from discarded lithium-ion batteries (LiBs) is reported. Mild organic citric or acetic acids were used as leaching agents for a more environmentally-friendly recovery of the lithium, nickel, cobalt, and manganese from the discharged and crushed lithium nickel-manganese-cobalt oxide (NMC) LiBs. The extraction was performed with the presence/absence of continuous ultrasound (US) energy supplied by a 110 W ultrasonic bath. The effect of temperature (30–70 °C), reducing agent concentration (H2O2: 0–2.0 vol%), as well as choice of specific acid on the metal dissolution were investigated. The US leaching decreased the leaching time by more than 50% and improved the leached percentage of Li, Mn, Co, and Ni due to the local heat and improved mass transfer between solid and liquid interfaces in the process. The X-ray diffraction results of residues from the US leaching further confirmed an improved dissolution of the crushed layered NMC structure, resulting in the significant improvement of the leached amounts of the valuable metals. Furthermore, it is demonstrated that using citric acid eliminated the need of additional reducing agents and suppressed the dissolution of copper (Cu) due to its inhibitor effect on the Cu surface, i.e. compared with using acetic acid as leaching reagent. Overall, it is shown that recovery of the battery metals can be facilitated and carried out in a more energy-efficient manner at low temperatures (50 °C) using ultrasound to improve metal ions mass transportation in the residue layers of the NMC during the organic acid leaching. [ABSTRACT FROM AUTHOR]

Recyclable biocatalysts and high-efficiency lignocellulose deconstruction are the crucial factors for cost-effective conversion of biomass into biofuels and bioproducts. Acetic acid-based catalytic hydrolysis of grassy lignocellulosic biomass presents a promising application because of its effectivity, recyclability, and other environmentally friendly features. However, this treatment is not as effective on woody biomass, such as poplar. One way to improve conversion performance of this process is to integrate it with other effective processes, such as pretreating biomass with protic ionic liquids (PILs) that have been shown to effectively solubilize lignin in reducing the recalcitrance of biomass to enzymatic deconstruction. In this work, an integrated acetic acid based one-pot ethanolamine acetate pretreatment (HAc–[EOA][OAc]) was developed for the efficient depolymerization of poplar polysaccharides. The configuration simultaneously removed ∼88% hemicellulose and selectively extracted up to ∼46% of the lignin from lignocellulosic biomass. HAc–[EOA][OAc] pretreated poplar yielded over 80% enzyme-hydrolyzed glucose that was attributed to an increase in the accessible surface area of cellulose to the hydrolytic enzymes. Analysis of the cellulose crystallinity and thermal decomposition profiles revealed that all pretreated samples have a higher cellulose crystallinity, indicating that amorphous cellulose had been removed during pretreatment. Conductor like screening model for real solvents (COSMO-RS) and Hansen solubility parameters (HSP) were used to provide insights into the mechanism of biomass pretreatment efficacy using both HAc and [EOA][OAc]. We found that a strong hydrogen-bonding and electrostatic misfit interaction between hemicellulose and HAc may explain the higher removal of hemicellulose during HAc pretreatment. Further, the close HSP values and COSMO-RS analysis indicate that [EOA][OAc] is a good lignin solvent, which leads to the higher delignification of biomass. This study demonstrates that the integration of IL with acid pretreatment is a promising strategy for conducting effective pretreatment on woody lignocellulose. [ABSTRACT FROM AUTHOR]

Cellulose acetate is one of the most important cellulose derivatives and commercially mainly produced using the Acetic Acid Process, in which overstoichiometric amounts of acetic anhydride and concentrated acetic acid are used to obtain cellulose triacetate. A subsequent partial hydrolysis is necessary to achieve evenly substituted cellulose acetates with lower degrees of substitution. Homogeneous acetylations in ionic liquids or other cellulose dissolving solvent systems often offer milder conditions and the possibility of a one-step synthesis of cellulose acetates with lower degrees of substitution by simply adjusting the equivalents of the acetylation agent. Here, we show an efficient homogeneous cellulose acetylation process without the need of any additional catalyst or activation step using the DBU/CO2 switchable solvent system. Vinyl acetate was used as a more benign acetylation agent under mild conditions and straightforward recyclability of all employed components was demonstrated with high recycling ratios (87.0–98.9%). Less cellulose backbone degradation compared to a cellulose acetate sample synthesized by the Acetic Acid Process from the same cellulose source was shown by size exclusion chromatography (Mn = 35 kDa vs. 12 kDa), which resulted in improved mechanical properties of solvent casted foils. Other homogeneous procedures reported so far (e.g. in ionic liquids) reached lower degrees of substitution, needed additional catalysts, proved to be less advantageous in terms of recycling, or required more reactive acetylation agents. Our results thus demonstrate a cellulose acetylation method with full focus on sustainability, efficiency, and applicability, resulting in an E-factor of 1.92 for the overall process. [ABSTRACT FROM AUTHOR]

A green and efficient method was developed for upgrading furfural to 1,10-decanediol diacetate and 1-decanol acetate. 92% yield of the acetates was obtained through the tandem benzoin condensation and hydrodeoxygenation reaction. During the benzoin condensation, furfural was catalyzed into furoin in a quantitative yield by the immobilized NHC catalyst under solvent-free conditions. After dissolving the furoin intermediate in acetic acid, the Sc(OTf)3 and Pd/C catalytic system was introduced for hydrodeoxygenation. The effects of reaction factors have been investigated in detail and the hydrodeoxygenation process has been explored by 1H-NMR and GC-MS. [ABSTRACT FROM AUTHOR]

A novel process based on cyclohexene esterification–hydrogenation for the production of cyclohexanol, the key intermediate in the production of ε-caprolactam, was devised and validated for the first time. In this process, cyclohexene obtained from the partial hydrogenation of benzene is esterified with acetic acid to cyclohexyl acetate, followed by hydrogenation to cyclohexanol. The experimentally determined equilibrium conversion of cyclohexene for cyclohexene esterification at the stoichiometric ratio is always ≥68% in the temperature range of 333–373 K over the commercial Amberlyst 15 catalyst, which is substantially higher than that of cyclohexene hydration. The apparent activation energy (Ea) for the esterification of cyclohexene with acetic acid is 60.0 kJ mol−1, which is lower than that of cyclohexene hydration. In the hydrogenation of cyclohexyl acetate to cyclohexanol, high conversion of 99.5% and high selectivity of 99.7% are obtained on the La-promoted Cu/ZnO/SiO2 catalyst prepared by the co-precipitation method. This process shows both a high overall atom economy of 99.4% comparable to that of the cyclohexene hydration process and a much higher catalytic efficiency than the phenol hydrogenation process. On the basis of the above fundamental works, a pilot-scale demonstration unit with a capacity of 8000 tonnes per annum was developed and operated smoothly for more than 1000 h with no indication of deactivation. [ABSTRACT FROM AUTHOR]

The low reactivity of lignin limits its performance in terms of selective oxidative cleavage of the C–C bond and most researchers employ lignin models as substrates for producing useful small molecules while the uses of real lignin are largely limited to low value material applications. Herein, a methanol/choline chloride (MeOH–ChCl)-based deep eutectic solvent (DES) was used to improve the solubility of lignin and the redox potential of the catalyst Cu(OAc)2/1,10-phenanthroline. A high total yield of acetovanillone and acetic acid (87.12%) was obtained from alkaline lignin under mild conditions of 60 °C for 3 h. Two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectra indicated that condensation and depolymerisation reactions of side chain groups of alkaline lignin occurred simultaneously, and longer side chains may inhibit acetic acid formation, while more guaiacyl units may increase the acetovanillone yield. Additionally, this catalytic oxidation system has the potential to produce acetovanillone and acetic acid from DES extracted lignin, pretreated corncob and raw materials of corncob. [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]

Recovery of critical metals from waste is becoming very important to bridge the gap between the limited natural resources available and their ever-increasing demand. One such vital metal is neodymium (Nd), which plays an essential role in advancing sustainable clean energy technologies. Therefore, in this work, the key parameters to selectively recover Nd over iron (Fe) from their oxides, as model systems were investigated. By investigating the effect of key parameters, we aim to understand the underpinning science principles necessary for the safe and efficient recovery of critical metals from secondary sources. A series of deep eutectic solvents, consisting of a hydrogen bond donor (HBD), lactic acid or acetic acid, and hydrogen bond acceptor (HBA), guanidine hydrochloride (GUC), have been investigated in HBA–HBD combinations, and individually in the presence of water to determine the role of the HBD and HBA towards Nd and Fe leaching efficiency and selectivity. The combination of GUC with HBDs was less beneficial for the leaching of Nd2O3, with a maximum value of 78% in comparison with the individual systems, in the absence of GUC, which demonstrated a maximum dissolution of 95%. Among the different combinations, the acetic acid aqueous solution led to the highest dissolution efficiency and selectivity, probably due to the high basicity and strong stability constants for Nd-acetate complexes. Other parameters, such as the impact of the molar ratio Nd2O3 : Fe2O3 were also explored, and a synergetic effect that promotes Nd2O3 solubility at 1 : 1 Nd : Fe weight ratio is observed across the samples. However, when increasing the amount of Fe2O3 in the mixture to simulate realistic ratios present in spent magnets, selectivity is strongly affected, and only the acetic acid solution is capable of selectively dissolving Nd2O3 with a separation factor of up to 5038, which is higher than the current state of the art (1608). Finally, the acetic acid concentration was also studied as a factor to assess its effect on selectivity while also reducing cost. [ABSTRACT FROM AUTHOR]

A green and efficient catalytic system for the one-pot production of 1-octyl acetate from biomass-derived furfural-acetone (FFA) under mild conditions was developed by selective hydrodeoxygenation over Pd/C and Sc(OTf)3 as a cocatalytic system in acetic acid. The effects of reaction conditions on product distribution have been systematically investigated. The highest 1-octyl acetate yield of 90% can be obtained under mild conditions (150 °C, 2 MPa H2, 2 h). Tetrahydrofuran ring opening and ester bond selective cleavage were found to be the key steps. In these steps, due to its suitable Lewis acidity, Sc(OTf)3 can not only promote ring-opening esterification but also selectively activate the secondary alcohol ester bond to achieve high selectivity for 1-octyl acetate. NMR and MS methods were utilized to investigate the reaction process. In addition, after 8 cycles of the Pd/C catalyst, the 1-octyl acetate yield gradually decreased from 90% to 80%. The decrease, according to XPS determination, in catalytic efficiency of the Pd/C catalyst was mainly due to the partial oxidation of metal Pd through air contact during post-treatment. [ABSTRACT FROM AUTHOR]

The reduction in CO2 emissions is an important issue across many industries. Inspired by extraterrestrial organic matter formation, we herein report a CO2 conversion approach based on high-dose rate electron beam (EB) irradiation of an acid-decomposed CaCO3/additive EtOH mixture. With 13C-CaCO3, 12C-EtOH and 100 kGy s−1 EB, H2, CO, CH4, C2H6 and organic acids are simultaneously produced within a few seconds, except for 2,3-butanediol formation from excess EtOH. According to the organic analysis results, CO and organic acids contain 13C carbon derived from 13C-CaCO3. The high-dose rate EB gives increased CO2 conversion products compared to the low-dose rate EB. The CO2 conversion yield/energy efficiency (product energy/input electrical energy) at 300 kGy is 1.51/0.50% in total (CO: 0.03/0.01%, formic acid: 1.31/0.29%, acetic acid: 0.05/0.04% and propionic acid: 0.12/0.16%), and the total radiation energy efficiency (REE, product energy/net radiation energy) of CO2 at 300 kGy is 51.5% (CO: 0.90%, formic acid: 30.3%, acetic acid: 3.71% and propionic acid: 16.6%). The CO2 conversion yield is ∼15 times larger than that of the only known CO2 gas radiolysis (0.1%, CO only). Furthermore, the REE at 100 kGy is also ∼15 times higher than that obtained in the absence of EtOH. The energy input for the 100% conversion yield is estimated to be 38 000 GJ per t-CO2. The combination of the high-dose rate EB with organic additives facilitated CO2 capture by radicals to afford improved CO2 conversion efficiency/yield. [ABSTRACT FROM AUTHOR]

Production of volatile fatty acids (VFAs) by fermentation is a potential sustainable alternative for conventional petrochemical routes to VFAs. Due to the low VFA content of fermentation broths, robust and economical separation technology has to be devised to recover the VFA. Liquid–liquid extraction of VFAs with the phosphonium phosphinate ionic liquid (IL) [P666,14][Phos] allows good VFA extractability. For an extraction process using [P666,14][Phos] to be green, it is essential to efficiently regenerate the solvent and recover the VFA. To obtain insight into the (strong) intermolecular interactions between [P666,14][Phos] and acetic acid, selected as a model VFA, 1H NMR, 31P NMR, FT-IR and isothermal titration calorimetry (ITC) were applied. The observations were used to interpret operations to recover acetic acid from the IL, which included evaporation at elevated temperature under vacuum, possibly assisted by nitrogen stripping, in situ esterification and back-extraction with volatile bases. Through evaporative regeneration with nitrogen stripping, HAc could be removed, but only down to an HAc/IL molar ratio of 1. The remaining molar equivalent of HAc–IL interacts tightly with the IL by partial proton transfer and strong hydrogen bonding interactions with the phosphinate anion. Back-extraction of HAc with trimethylamine (TMA) and subsequent decomposition of the HAc–TMA complexes allowed for successful IL regeneration. This process uses ten times less amine (TMA) than conventional amine-based extraction processes (e.g. tri-n-octyl amine), and provides a sustainable process route to obtain pure carboxylic acids from highly diluted aqueous solutions without generating large streams of byproducts. Further valorization via in-line vaporization/catalytic ketonization or via in-line thermal decomposition and ketonization of the TMA–HAc salt was also demonstrated, showing the potential of the VFAs as a green platform for bio-based chemicals. [ABSTRACT FROM AUTHOR]

Lignin as the only natural resource of aromatics has the potential to be the feedstock of choice for the production of value-added chemicals. However, the recalcitrance of lignin has limited its valorization into value-added products, and it is often burned for heat. The acid-catalyzed organosolv extraction of lignin results in the formation of interunit carbon–carbon bonds, which limit its upgrading. In this work, three different solvent systems (methanol, acetone, and acetic acid) were evaluated for the extraction of native lignin from wild-type and genetically modified poplar species (wild type, high-S, and low-S). Over 68% of the original lignin in the biomass was isolated and subjected to further upgrading over a heterogeneous Ni/C catalyst (10 wt% of catalyst in methanol solvent, under 35 bar H2 pressure at 225 °C). Three major monomeric phenolic products, guaiacol, isoeugenol, and 4-propenyl syringol, were obtained. Methanol-extracted lignin gave the best yield of ＞60% of the said aromatic products. Methanol as a nucleophile reacted with the Cα benzylic carbocation formed during the organosolv extraction, minimizing the carbon–carbon bond formation. This protection by methanol was demonstrated by NMR spectroscopy. Scanning electron microscopy (SEM) images showed differences in the isolated lignin on the micron scale from the three different treatments. [ABSTRACT FROM AUTHOR]

Acetic acid is an important bulk chemical and synthesis of acetic acid via methanol hydrocarboxylation with CO2 and H2 is a very promising route. In this work, we studied the reaction over a number of catalytic systems. It was found that Rh2(CO)4Cl2 with 4-methylimidazole (4-MI) as the ligand was very efficient in the presence of LiCl and LiI. Acetic acid began to form at 150 °C. The TOF was as high as 26.2 h−1 and the yield of acetic acid could reach 81.8% at 180 °C. The catalytic system had obvious advantages, such as simplicity, high activity and selectivity, milder reaction conditions, and less corrosiveness. The excellent cooperation of CO and Cl− in Rh2(CO)4Cl2, suitable basicity and aromaticity of the ligand 4-MI, and the hydrogen bonding ability of Cl− were crucial for the outstanding performance of the catalytic system. The control experiments showed that the reaction did not proceed via the CO pathway. [ABSTRACT FROM AUTHOR]

The asymmetric bioreduction of α,β-unsaturated γ-keto esters using ene-reductases from the Old Yellow Enzyme family proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and cyclic derivatives. Various strategies were employed to provide access to both enantiomers, which are versatile precursors of bioactive molecules. The regioselectivity of hydride addition on di-activated alkenes was elucidated by isotopic labeling experiments and showed strong preference for the keto moiety as activating/binding group as opposed to the ester. Finally, chemoenzymatic synthesis of (R)-2-(2-oxocyclohexyl)acetic acid was achieved in high ee on a preparative scale combining enzymatic reduction followed by ester hydrogenolysis. [ABSTRACT FROM AUTHOR]

A general and environmentally friendly organic photo-induced strategy was developed for the synthesis of diverse alkyl-substituted β-amino sulfone derivatives, including primary, secondary, and tertiary alkyl-substituted products. Various carboxylic acid derivatives from the simplest acetic acid to sterically bulky tertiary acids can participate in this transformation. [ABSTRACT FROM AUTHOR]

The impact of alkyl chain length on the esterification of C2–C16 organic acids with C1–C4 alcohols has been systematically investigated over bulk and SBA-15 supported sulfated zirconias (SZs). Rates of catalytic esterification for methanol with acetic acid are directly proportional to the sulfur content for both SZ and SZ/SBA-15, with the high dispersion of SZ achievable in conformal coatings over mesoporous SBA-15 confering significant rate-enhancements. Esterification over the most active 0.24 mmol gcat−1 bulk SZ and 0.29 mmol gcat−1 SZ/SBA-15 materials was inversely proportional to the alkyl chain length of alcohol and acid reactants; being most sensitive to changes from methanol to ethanol and acetic to hexanoic acids respectively. Kinetic analyses reveal that these alkyl chain dependencies are in excellent accord with the Taft relationship for polar and steric effects in aliphatic systems and the enthalpy of alcohol adsorption, implicating a Langmuir–Hinshelwood mechanism. The first continuous production of methyl propionate over a SZ fixed-bed is also demonstrated. [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]

Propylsulfonic acid derivatised SBA-15 catalysts have been prepared by post modification of SBA-15 with mercaptopropyltrimethoxysilane (MPTMS) for the upgrading of a model pyrolysis bio-oil via acetic acid esterification with benzyl alcohol in toluene. Acetic acid conversion and the rate of benzyl acetate production was proportional to the PrSO3H surface coverage, reaching a maximum for a saturation adlayer. Turnover frequencies for esterification increase with sulfonic acid surface density, suggesting a cooperative effect of adjacent PrSO3H groups. Maximal acetic acid conversion was attained under acid-rich conditions with aromatic alcohols, outperforming Amberlyst or USY zeolites, with additional excellent water tolerance. [ABSTRACT FROM AUTHOR]

Methacrylation phosphoramidites containing a linker cleavable with acetic acid were synthesized, and used for synthetic oligodeoxynucleotide (ODN) purification. During automated synthesis, the full-length ODN was tagged with the phosphoramidite. The failure sequences were not. In purification, the full-length ODN was co-polymerized into a polyacrylamide gel, and the failure sequences and other impurities were removed by washing. Pure ODN was cleaved from the gel with 80% acetic acid. Using this method, purification of sequences as long as a 197-mer, which are from the phi29 DNA polymerase gene, and at scales as large as 50 μmol was demonstrated. The products have high purity and the recovery yields are high. The method does not use any type of chromatography and purification is achieved through simple manipulations such as shaking and filtration. Compared with gel electrophoresis and HPLC purification methods, the new technology is less labor-demanding and more amendable for automation, consumes a smaller amount of environmentally harmful organic solvents and requires little energy for solvent evaporation. Therefore, it is ideal for high throughput purification and large scale ODN-based drug purification as well as small scale purification. [ABSTRACT FROM AUTHOR]

Chemical production needs to transform radically toward fossil-free sustainable chemical production to meet the targets for net-zero emissions by the year 2050. The feasibility of this transformation, the motivations, status and gaps, and perspectives are discussed after introducing how this change also implies a change in the model of production. Realizing the defossilization of chemical production involves electrifying the chemical processes, especially crucial elements such as chemical reactors, and the direct use of renewable energy to drive the chemical reaction. With a focus on electrocatalysis, the most relevant cases of (i) light olefin production, (ii) direct synthesis of main intermediates such as formaldehyde and acetic acid, and (iii) the production of aromatics are analyzed. The feasibility of these routes in the short–medium term is shown, while other cases such as the direct synthesis of ammonia from N2 require turning the approach to other directions. On a global scale, defossilization of chemical production is feasible in the medium–long term with a cut of over 800 Mt per year CO2 eq. emissions in line with the expectation to reach the net-zero emission target. A final section introduces a short discussion about some critical questions regarding the sustainability of fossil-free chemical production. [ABSTRACT FROM AUTHOR]

Selective transformation of lignin into value-added aromatics is highly attractive and rather challenging. Catalytic oxidative degradation provides a promising approach to obtain aromatics from lignin while preserving the benzene units. In this study, vanadium-catalyzed aerobic oxidation of 2-phenoxy-1-phenylethanol was studied as a lignin model compound. The solvent played a significant role in the distribution of oxidation products. In the presence of acetic acid, oxidative C–C bond cleavage was preferred, while oxidation products via C–H bond cleavage were rather limited. A one-electron transfer process was involved in the oxidation reaction. The occurrence of vanadium(v) was detected, and the carboxylic group could coordinate to vanadium(v) through exchange with the acetylacetonato ligand during oxidation in the presence of acetic acid. [ABSTRACT FROM AUTHOR]

The industrial process of recovering fermentation-based volatile fatty acids (VFAs) utilizes H2SO4 to acidify the fermentation broth containing VFA-salts [e.g. Ca(CH3COO)2] to enable formation of molecular VFAs. Molecular VFAs are then recovered by liquid–liquid extraction. However, acidification with H2SO4 results in production of large quantities of salts (e.g. CaSO4). Using CO2 rather than mineral acids for acidification of fermentation broth is an environmentally benign alternative which eliminates salt formation. In this study, CO2 was applied in pressures up to 40 bar to enhance the efficiency of extraction of acetic acid (HAc) from fermented wastewater. HAc extraction under atmospheric conditions was also investigated to obtain benchmarks. The ionic liquid [P666,14][Phos] and trioctylamine (TOA) dissolved in n-octanol were applied as solvents to extract HAc from fermented wastewater model solutions containing HAc (1 wt%) and various salts resulting in pH ranging from 2.8 to 6. A more pronounced increase in extractability of HAc, expressed as HAc distribution (D = [HAc]solvent/[HAc]aqueous), was observed for [P666,14][Phos] with increasing CO2 pressure. A mathematical model taking into account carbonic acid equilibria and dissociation of HAc and salts showed that the measured influence of CO2 cannot be explained by the effect of CO2 on aqueous phase pH. Thus, it may be concluded that the pressurized CO2 has altered the fluid properties of the solvents and made them more accessible for HAc. This suggests that applying pressurized CO2 may enhance extraction efficiency of processes other than those involving extraction of volatile fatty acids. [ABSTRACT FROM AUTHOR]

Renewable methanol can be used as a feedstock to generate value-added multicarbon components through fermentation technologies. Recently, researchers reported the production of isobutyric acid using methanol as an electron donor with open culture systems dominated by Eubacterium sp. and Clostridium sp. Here we report the ability of Clostridium luticellarii wild-type strain to produce isobutyric acid from methanol and CO2 & H2. When growing on methanol, the supplementation of acetic and butyric acid enhanced isobutyric acid final concentration, selectivity and production rate. A maximum of 5.04 ± 0.08 g L−1 isobutyric acid was produced at a rate of 0.420 ± 0.012 g L−1 d−1and selectivity of 0.70 electron per electron of total products in batch with acetic and butyric acid as electron acceptors. The pH was also found to be a major factor influencing isobutyric acid formation with maximal production at pH 6.50. Finally, in addition to its ability to produce isomers, C. luticellarii was able to perform C2-unit elongation from methanol. Overall, this study positions C. luticellarii as a promising platform for the production of isocarboxylic acids. [ABSTRACT FROM AUTHOR]

Achieving chemoselectivity is always crucial and challenging for bi-functional compounds, such as alkanolamines, that have both amines and alcohols as reactive functional groups. Achieving 100% selectivity for O-formyl and O-acyl protection of alkanolamines is one of the examples of such reactions. To avoid protection and deprotection steps and overcome this problem, a novel chemoselective, efficient, and simple protocol for functional group protection as O-formylation and O-acylation of alkanolamines and phenoxyethanols and competitive O-selectivity between alcohols and amines, catalyzed by Ni(II) and Cu(II) complexes with 8-hydroxyquinoline at a catalyst loading of only 5 mol% in a homogeneous medium has been presented here. Good to excellent yields are achieved in the absence of a solvent for O-formylation at room temperature with formic acid as the formyl source and O-acylation at 70 °C with acetic acid as the acyl source. In addition, minimal effluent and waste are generated during this reaction, as the corresponding sodium salts of acids could be recovered during the process and can be reused. This chemistry readily tolerates a variety of functional groups, as demonstrated by 20 examples with 100% chemoselectivity for O-formylation and O-acylation of alkanolamines and 30 examples of O-formylation and O-acylation of phenoxyethanols and alcohols in the presence of amines which have been synthesized successfully. [ABSTRACT FROM AUTHOR]

In many plant species, the acetate fraction is the fourth most prominent fraction by weight after cellulose, hemicellulose and lignin, and can be easily extracted as a single stable molecule, acetic acid, at high yields. Despite this, upgrading the acetate fraction of biomass has received very limited attention. Here, we demonstrate a valorization route for the acetate fraction as well as mixtures of acetic acid and other volatile fatty acids produced from the polysaccharide fraction. Aqueous solutions of acetic acid, including solutions produced during steam explosion pretreatment and subsequently purified can be upgraded at high selectivity to a valuable mixture of aromatics, substituted cycloalkenes and gas olefins in a single step using Cu/ZrO2. The catalyst displays remarkable stability despite the presence of acids, water and other biomass-derived impurities. We also show that acetic acid can be further valorized over the same catalyst by converting it in the presence of butanoic acid that was produced in a consolidated bioprocess from the same pretreated wood that was the source of the acetic acid. In this case, the acetic acid rapidly ketonizes with the butanoic acid and the resulting beta-ketones further condense to form aromatics and cycloalkenes with a higher average carbon number than those produced solely from acetic acid. Overall, our process yields a biomass-derived organic oil consisting of aromatics and cycloalkenes that spontaneously separates from water, can be tuned by varying the incoming mixture of carboxylic acids and has suitable properties for being used as a direct blend with aviation fuel. [ABSTRACT FROM AUTHOR]

A simple method was demonstrated to oxidize glucose into gluconic acid in a concentrated FeCl3 solution. The maximum gluconic acid yield (52.3%) was achieved in the 40% FeCl3 solution at 110 °C in 4 hours. Formic and acetic acids were the main coproducts with an yield of 10–20%. [ABSTRACT FROM AUTHOR]