Showing papers on "Acetic acid published in 2022"

Au-ZSM-5 catalyses the selective oxidation of CH4 to CH3OH and CH3COOH using O2

Abstract: The oxidation of methane, the main component of natural gas, to selectively form oxygenated chemical feedstocks using molecular oxygen has been a long-standing grand challenge in catalysis. Here, using gold nanoparticles supported on the zeolite ZSM-5, we introduce a method to oxidize methane to methanol and acetic acid in water at temperatures between 120 and 240 °C using molecular oxygen in the absence of any added coreductant. Electron microscopy reveals that the catalyst does not contain gold atoms or clusters, but rather gold nanoparticles are the active component, while a mechanism involving surface adsorbed species is proposed in which methanol and acetic acid are formed via parallel pathways.

Using sound to synthesize covalent organic frameworks in water

Abstract: Covalent organic frameworks (COFs) are typically synthesized using solvothermal conditions (>120 °C, >72 hours) in harmful organic solvents. Here we report a strategy to rapidly (<60 minutes) synthesize imine-linked COFs in aqueous acetic acid using sonochemistry and thus avoid most of the disadvantages of solvothermal methods. Using the sonochemical method, we synthesized to our knowledge previously unreported COFs. The crystallinity and porosity of these COFs is comparable to or better than those of the same materials made by established solvothermal routes. The sonochemical method even works in sustainable solvents, such as food-grade vinegar. The generality of the method is shown in the preparation of a 2D COF with pendant functionalization and of a COF with 3D connectivity. Finally, a COF synthesized sonochemically acts as an excellent photocatalyst for the sacrificial hydrogen evolution from water, showing a more sustained catalytic performance compared with that of its solvothermal analogue. The speed, ease and generality of this sonochemical method together with improved material quality makes the use of sound an enabling methodology for the rapid discovery of functional COFs. A sonochemical route rapidly synthesizes covalent organic frameworks (COFs) in aqueous solutions of acetic acid. This method has operational advantages compared with conventional solvothermal routes and yields COFs of higher crystallinity and porosity, and hence improved materials properties.

Micro-structural characteristics deterioration of intact loess under acid and saline solutions and resultant macro-mechanical properties

Abstract: When exposed to chemicals, the micro-structural evolution of the loess and the impacts on the macro-mechanical properties are considered crucial for contaminated land reclamation. In this study, the micro-structural characteristics of the loess specimens that are exposed to acetic acid or sodium sulfate, are studied using scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy analyses. Further, their macro-mechanical properties are determined by direct shear tests. The corrosion of the cement between particles under acetic acid environments and the salt-induced swelling under saline conditions play an important role in the micro-structural deterioration. The cohesion and friction angle for the wetted loess are about 16 kPa and 19° respectively, while for the acetic acid-contamianted loess, they reduce to 10 kPa and 15° respectively. They, for the sodium sulfate-contaminated loess, reduce further to below 10 kPa and 13° respectively. The macro-mechanical properties show good correspondence with the micro-structural deterioration.

Fe binuclear sites convert methane to acetic acid with ultrahigh selectivity

Abstract: •Fe/ZSM-5 converted methane to CH3COOH with ultrahigh selectivity •[Fe(III)–(μO)2–Fe(III)–(OH)2] was suggested to be the active site •The direct-coupling pathway of ·CH3, CO∗ and OH∗ favored the formation of CH3COOH The direct conversion of methane to C2 oxygenates with high selectivity under mild conditions has attracted wide attention but still remains a great challenge. Herein, we report the conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity for oxygenated products by the direct coupling of CH4, CO, and H2O2 over ZSM-5-supported Fe binuclear sites under 30°C. The unexpected ultrahigh selectivity toward CH3COOH was attributed to the unique Fe binuclear site structure of [Fe(III)–(μO)2–Fe(III)–(OH)2], which was evidenced by advanced spectroscopic techniques and density functional theory (DFT) calculations. It was suggested that the lower energy barriers for the direct coupling of methyl radicals (·CH3) and adsorbed CO∗ and OH∗ species to form CH3COOH, compared with the oxidation of CH4 by OH∗ to form CH3OH, benefited the CH3COOH formation. The direct conversion of methane to C2 oxygenates with high selectivity under mild conditions has attracted wide attention but still remains a great challenge. Herein, we report the conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity for oxygenated products by the direct coupling of CH4, CO, and H2O2 over ZSM-5-supported Fe binuclear sites under 30°C. The unexpected ultrahigh selectivity toward CH3COOH was attributed to the unique Fe binuclear site structure of [Fe(III)–(μO)2–Fe(III)–(OH)2], which was evidenced by advanced spectroscopic techniques and density functional theory (DFT) calculations. It was suggested that the lower energy barriers for the direct coupling of methyl radicals (·CH3) and adsorbed CO∗ and OH∗ species to form CH3COOH, compared with the oxidation of CH4 by OH∗ to form CH3OH, benefited the CH3COOH formation.

Effects of different carbon sources on the efficiency of sulfur-oxidizing denitrifying microorganisms

Abstract: This study aims to compare the effects of different carbon sources on sulfur-oxidizing denitrifying microorganisms by using glucose, ethanol, and acetate as carbon sources. Under the same chemical oxygen demand Cr (CODCr), nitrate, and sulfide concentrations, the removal rate of nitrate and total organic carbon, and the yield of elemental sulfur in a static experiment and a continuous flow reactor with glucose as the carbon source were lower than those with ethanol and acetic acid as the carbon source. The core sulfur-oxidizing denitrifying bacteria that use glucose as the carbon source were Azoarcus, Geoalkalibacter, and Mangroviflexus; those that use ethanol as the carbon source were Arcobacter, Pseudomonas, and Thauera; those that use acetate as the carbon source were Pseudomonas and Azoarcus. The metabolic activity of microorganisms that use different carbon sources was explained by functional gene detection. The fluctuation of gltA, a functional gene indicating heterotrophic metabolism of microorganisms, was small in three reactors, but that of the sulfur oxidation gene, Sqr, in the reactor with acetic acid as the carbon source was larger. Our results suggest that acetate is a more suitable carbon source for denitrification-desulfurization systems.

Asymmetric Coupled Dual‐Atom Sites for Selective Photoreduction of Carbon Dioxide to Acetic Acid

Abstract: Photocatalytic reduction of CO2 to value‐added liquid fuels is a promising approach to alleviate the global energy and environmental problems. However, highly selective production of C2+ products from CO2 reduction reaction (CO2RR) is very difficult because of the sluggish CC coupling reaction. An asymmetric coupled heteronuclear photocatalyst is designed to overcome this limitation. The new catalyst contains single atoms of nickel and cobalt loaded on titanium dioxide. It exhibits an impressive 71% selectivity for acetic acid. The experimental data and theoretical calculations reveal that the Ni and Co single atom sites not only significantly lower the energy barrier of electron transfer in photocatalysis but also efficiently promote the CC coupling toward CH3COOH. The high activity of such a heteronuclear catalyst system will shed light on the future development of effective materials for CO2RR.

Production of succinic acid through the fermentation of Actinobacillus succinogenes on the hydrolysate of Napier grass

Abstract: Napier grass biomass can be hydrolyzed mainly containing glucose and xylose after alkaline pretreatment and enzymatic hydrolysis. This biomass can be fermented using Actinobacillus succinogenes to produce succinic acid. The yield of succinic acid was 0.58 g/g. Because metabolizing xylose could produce more acetic acid, this yield of succinic acid was lower than that achieved using glucose as the sole carbon source.The addition of glycerol as a fermentation substrate to Napier grass hydrolysate increased the reducing power of the hydrolysate, which not only increased the production of succinic acid but also reduced the formation of undesirable acetic acid in bacterial cells. At a hydrolysate:glycerol ratio of 10:1, the succinic acid yield reached 0.65 g/g. The succinic acid yield increased to 0.88 g/g when a 1:1 ratio of hydrolysate:glycerol was used. For the recovery of succinic acid from the fermentation broth, an outside-in module of an ultrafiltration membrane was used to remove bacterial cells. Air sparging at the feed side with a flow rate of 3 L/min increased the filtration rate. When the air flow rate was increased from 0 to 3 L/min, the average filtration rate increased from 25.0 to 45.7 mL/min, which corresponds to an increase of 82.8%. The clarified fermentation broth was then electrodialized to separate succinate from other contaminated ions. After electrodialysis, the acid products were concentrated through water removal, decolorized through treatment with activated carbon, and precipitated to obtain a purified product.The yield of succinic acid was increased by adding glycerol to the hydrolysate of Napier grass. The downstream processing consisting of ultrafiltration membrane separation and single-stage electrodialysis was effective for product separation and purification. An overall recovery yield of 74.7% ± 4.5% and a purity of 99.4% ± 0.1% were achieved for succinic acid.

Recent advances in biomass derived platform chemicals to valeric acid synthesis

Abstract: The biomass-derived carbohydrates are selectively converted into platform chemicals such as levulinic acid (LA) and 5-Hydroxymethylfurfural (HMF). Among those platform chemicals, LA is one of the most promising and sustainable...

Insight into the Synthesis of Alcohols and Acids in Plasma-driven Conversion of CO2 and CH4 over Copper-based Catalysts

Abstract: Direct conversion of CO2 and CH4 into value-added oxygenates under mild conditions is highly desirable since it has great potential to deliver a sustainable low-carbon economy and a carbon-neutral ecosystem. However, tuning the distribution of oxygenates in this process remains a major challenge. Here, the electronic structure and acidic properties of copper-based catalysts were exploited as strategies to tune the distribution of oxygenates (alcohols and acids) in the plasma-catalytic conversion of CO2 and CH4 at a reaction temperature of 60 °C and atmospheric pressure. We use support, on which copper is anchored, to regulate the distribution of Cu2+ and Cu+ in the Cu-based catalysts. Comprehensive characterization of the catalysts together with the reaction performances reveals that Cu2+ species are favorable to the formation of alcohols, whereas Cu+ species are critical to enhancing acetic acid production. Furthermore, the Brønsted acid sites of HZSM-5 significantly improved the selectivity of acetic acid, while the synergy of isolated Cu+ center and Brønsted acid sites, developed via Cu-exchange HZSM-5, exhibits potential for acetic acid formation. Finally, possible pathways for the formation of alcohols and acetic acid have been discussed. This work provides new insights into the design of highly selective catalysts for tuning the distribution of alcohols and acids in the plasma-catalytic conversion of CO2 and CH4 to oxygenates.