Acid Yield Research Articles

Tunable Hydro/Dicarboxylation of Ethylene with CO2 via a Barrierless Radiolytic Free-Radicals Pathway.

The hydro/dicarboxylation of ethylene (C2H4) feedstock with CO2 to produce high-value carboxylic acids is an industrially relevant yet challenging reaction due to their extremely low reactivities. Herein, we present an effective strategy to synthesize propionic acid and succinic acid from a mixture of CO2 and C2H4 catalyzed by high-energy water radiolysis. The process involves the generation of CO2 radical anions via the barrierless attachment of hydrated electrons to CO2, facilitating an ambient, continuous carboxylation of C2H4 with an efficiency of 81.4%. Utilizing easily available electron beam irradiation, we achieved a combined production rate of 0.34 mmol L-1 min-1 for carboxylic acids, which is unattainable by the existing methods. Notably, product selectivity between hydro- and dicarboxylation was dose-rate/beam intensity-dependent: high-dose-rate irradiation favored succinic acid formation with a proportional yield of up to 65.4%, while milder conditions resulted in an 85.1% yield of propionic acid. We suggested that the simplicity and efficiency of the present carboxylation approach promote circular carbon in the sustainable chemical industry.

Engineering Asymmetric Electronic Structure of Co─N─C Single‐Atomic Sites Toward Excellent Electrochemical H2O2 Production and Biomass Upgrading

AbstractTo advance electrochemical H2O2 production and unravel catalytic mechanisms, the precise structural coordination of single‐atomic M‐N‐C electrocatalysts is urgently required. Herein, the Co─N5 site with an asymmetric electronic configuration is constructed to boost the two‐electron oxygen reduction reaction (2e− ORR) compared to symmetric Co─N4, effectively overcoming the trade‐off between activity and selectivity in H2O2 production. Both experimental and theoretical analyses demonstrate that breaking the symmetry of Co─N sites promotes the activation of O2 molecules and moderates the adsorption of the key *OOH intermediate by disrupting the linear scaling relationship for intermediates adsorption. This modulation enables efficient H₂O₂ production and its effective retention for subsequent applications. As a proof of concept, Co─N5 achieves a H2O2 production rate as high as 16.1 mol gcat−1 h−1 in a flow cell, outperforming most recently reported counterparts. Furthermore, the coupling of 2e− ORR with the oxidation of cellulose‐derived carbohydrates accomplishes high formic acid yields (84.1% from glucose and 62.0%–92.1% from other substrates), underpinning the sustainable electro‐refinery for biomass valorization at ambient conditions. By elucidating the intrinsic relationship between 2e⁻ ORR and the asymmetry of single‐atomic sites, this work paves the way for high‐performance electrosynthesis.

Highly Active Heterogeneous Au/K2Ti6O13 Catalysts for Selective Oxidation of Furfural to Furoic Acid

A series of potassium titanate nanowires (KTO) with different K content were prepared by hydrothermal treatment, followed by anchoring Au nanoparticles (NPs) using the deposition‐precipitation method. The obtained Au/KTO‐24 showed a furfural (FF) conversion of 100% and a furoic acid (FA) yield of 96% at 80 °C and 1 MPa O2 for 2 h in FF oxidation system. K improves metallic Au NPs dispersion and induces a negative shift of Au0 4f binding energy. Kinetic studies show that Au/KTO‐24 displays low apparent activation energy (51.23 kJ/mol). The catalytic mechanism of FF oxidation to FA was investigated with in‐situ FT‐IR spectroscopy and DFT calculations, which indicates that the high performance of Au/KTO‐24 is attributed to not only its abundant numbers of surface Au active sites but also its interfacial Au−O−K structure that facilitates the activations of FF and O2.

Photocatalytic CO2 Reduction to Formate on Lead‐Free Cs3Sb2Cl9

AbstractPhotocatalytic CO2 reduction to value‐added chemicals using perovskites is being explored to mitigate CO2 emissions. This study examines lead‐free antimony‐based Cs3Sb2Cl9 halide perovskites for its photocatalytic CO2 reduction activity in solid‐liquid mode. The primary product was found to be formic acid (HCOOH) in the liquid phase, along with carbon monoxide (CO) and methane(CH4) in the gaseous phase. Cs3Sb2Cl9 displayed a selectivity of 73% toward formic acid with a yield of 54 µmol g−1 h−1. Further, the selectivity toward formic acid was enhanced to 90% by loading Ir/IrOX as a water oxidation catalyst onto Cs3Sb2Cl9. The Ir/IrOX was loaded by the thermal decomposition of iridium (III) acetylacetonate. The yield of formic acid (HCOOH) on the composite catalyst Cs3Sb2Cl9‐Ir/IrOX improved to 75 µmol g−1 h−1, suppressing the formation of gaseous products. This is the highest yield of formic acid reported for this class of materials. The catalyst stability was evaluated using different material characterization techniques. Further, the stability of the catalyst toward formic acid yield was studied throughout a 25‐h reaction.

Valorizing corn stover waste into valuable bioproducts using subcritical water hydrolysis

This study examined the behavior of the semi-continuous hydrolysis process of corn stover (CS) in subcritical water, focusing on the effects of varying pH levels (1, 2, 4.5, 7, and 8) and temperatures (113, 130, 170, 210, and 226°C). The results showed that the process at 170°C and pH 1 was able to recover the highest amount of phenolic compounds (76.82 mg Gallic Acid Equivalents g⁻¹), consequently demonstrating the highest antioxidant activities by the Ferric Reducing Antioxidant Power (FRAP) (423.85 μMol TEAC g⁻¹) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (293.12 μMol TEAC g⁻¹) methods. Additionally, it was possible to obtain the highest concentration of sugars (cellobiose, glucose, and xylose) (460.92 mg g⁻¹). High temperatures (226°C and pH 4.5) produced the highest amount of organic acids (1,157.19 mg g⁻¹). The formation of inhibitors was observed only at temperatures of 170 and 210 °C at a pH of 1.0. The highest yields of sugars, organic acids, and inhibitors were 0.565, 1.123, and 0.665 mg g⁻¹ of carbohydrates, respectively. The statistical analysis identified the optimal conditions for the recovery of various compounds: phenolic compounds at 190.7 °C and pH 1, soluble proteins at 187.4 °C and pH 1, sugars at 134.9 °C and pH 1, organic acids at 223.59 °C and pH 4.1, and for minimizing inhibitors at 114.95 °C and pH 7.3. EcoScale analysis identified subcritical water as the most sustainable and efficient method for CS hydrolysis. Subcritical water treatment effectively recovers valuable compounds from CS, promoting a circular economy by valorizing waste and reducing resource dependence.

Interfacial engineering of Co(OH)2@CN composites: A study of p-n heterojunctions with enhanced xylose/xylan photoreforming and CO2 reduction performance

Interfacial engineering of Co(OH)2@CN composites: A study of p-n heterojunctions with enhanced xylose/xylan photoreforming and CO2 reduction performance

Exploring combi-lipase catalysis of Eversa® Transform and Candida rugosa lipases for enzymatic hydrolysis of crude palm oil: Effects on fatty acid yield and retention of carotene and tocols.

Exploring combi-lipase catalysis of Eversa® Transform and Candida rugosa lipases for enzymatic hydrolysis of crude palm oil: Effects on fatty acid yield and retention of carotene and tocols.

Acidogenic fermentation of Ulva in a fed-batch reactor system: tubular versus foliose biomass.

Acidogenic fermentation of Ulva in a fed-batch reactor system: tubular versus foliose biomass.

Improving eicosapentaenoic acid yield by constructing an enzyme-constrained model of Schizochytrium

Improving eicosapentaenoic acid yield by constructing an enzyme-constrained model of Schizochytrium

Optimising medium chain carboxylate production in xylan mixed-culture monofermentation.

Optimising medium chain carboxylate production in xylan mixed-culture monofermentation.

Effective Chemical Fixation of CO2 into Phenol Using Conventional Gas-Solid and Novel Suspension-based Kolbe-Schmitt Reactions.

TThe Kolbe-Schmitt reaction is a classic route for CO2 utilisation through organic synthesis of industrially relevant chemicals. Despite the reaction's long-standing history, detailed product separation and analysis remain underexplored, which inherently limits an accurate mechanism elucidation. This study introduces a new comprehensive approach for isolating and characterising reaction products using high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (¹H-NMR). Comparative experiments at 225 °C and 30 bar CO₂ were carried out using the conventional gas-solid and novel suspension-based methods with varying reaction times. A new two-step reaction mechanism is proposed. In the first step, 2-disodium salicylate and phenol are formed. In the second step, 2-monosodium salicylate is formed, with subsequent regeneration of sodium phenoxide. This mechanism was validated by adding pure (free) phenol to the reaction media in both conventional and suspension-based methods. The presence of added phenol was found to increase the yield of salicylic acid by 25.0% and 8.5% after 2 hours of reaction, for each method, respectively, compared to experiments without added phenol. Successful application of these enhanced carboxylation methods to other biomass-derived single-ring phenolic compounds will offer new routes for potential large-scale CO₂ utilisation.

Engineering Asymmetric Electronic Structure of Co-N-C Single-Atomic Sites toward Excellent Electrochemical H2O2 Production and Biomass Upgrading.

To advance electrochemical H2O2 production and unravel catalytic mechanisms, the precise structural coordination of single-atomic M-N-C electrocatalysts is urgently required. Herein, the Co-N5 site with an asymmetric electronic configuration is constructed to boost the two-electron oxygen reduction reaction (2e- ORR) compared to symmetric Co-N4, effectively overcoming the trade-off between activity and selectivity in H2O2 production. Both experimental and theoretical analyses demonstrate that breaking the symmetry of Co-N sites promotes the activation of O2 molecules and moderates the adsorption of the key *OOH intermediates by disrupting the linear scaling relationship for intermediate adsorption. This modulation enables efficient H2O2 production and its effective retention for subsequent applications. As a proof of concept, Co-N5 achieves a H2O2 production rate as high as 16.1 mol gcat-1 h-1 in a flow cell, outperforming most recently reported counterparts. Furthermore, the coupling of 2e- ORR with the oxidation of cellulose-derived carbohydrates accomplishes high formic acid yields (84.1% from glucose and 62.0-92.1% from other substrates), underpinning the sustainable electro-refinery for biomass valorization at ambient conditions. By elucidating the intrinsic relationship between 2e- ORR and the asymmetry of single-atomic sites, this work paves the way for high-performance electrosynthesis.

Integrated Electrochemical Biomass Oxidation and CO2 Reduction over Ultra-wide Potential Window.

Electrochemical reduction of carbon dioxide (CO2) coupled with biomass oxidation using renewable electricity is considered as a promising strategy for carbon management. However, achieving both high selectivity and large current density over wide potential window remains a significant challenge, hindering practical applications. In this study, a Ni/Fe dual metal-atom catalyst is developed for CO2 reduction, achieving nearly 100% CO selectivity across an ultra-wide potential window of 1.6 V, surpassing state-of-the-art catalysts. Remarkably, this high CO selectivity is maintained above 98% even after 100 hours of continuous operation at an industrial current density of 200 mA cm-2, demonstrating excellent long-term stability. When integrated into a solar electricity-driven CO2 reduction coupled 5-hydroxymethylfurfural oxidation system, nearly 100% CO Faradaic efficiency and 90% 2,5-furandicarboxylic acid yield are simultaneously obtained. Theoretical calculations reveal that the rate-limiting step for the CO2 reduction reaction varies with the applied potential, and the synergistic interaction between Ni and Fe atoms effectively lowers the limiting energy barrier. This work offers valuable insights for the strategic design and synthesis of catalysts with high activity and selectivity across wide potential window, providing a versatile platform for coupling CO2 reduction with diverse anodic biomass oxidation reactions and renewable energy sources.

High-yield extraction of long-chain fatty acids from Chlorella vulgaris: Comparative analysis of ozone extraction methods.

High-yield extraction of long-chain fatty acids from Chlorella vulgaris: Comparative analysis of ozone extraction methods.

Copper-based catalysts for improved humic acid yield and hard-water resistance in lignite hydrothermal process

ABSTRACT KOH has traditionally been used to extract lignite or weathered coal to produce water-soluble potassium humate (KHA) fertilizer, which is essential in agriculture. However, the KHA yield from this method is constrained by the free humic acid (HA) content in the raw material, and the resulting product shows limited resistance to hard water. In this study, lignite, KOH, and copper-based catalysts, including commercial copper nitrate (CCN), hydrothermal copper oxide (HCO), and commercial copper oxide (CCO) were used in hydrothermal treatment at 150°C for 2 h. The findings indicate that CCN, HCO, and CCO increased KHA yields by 9.94%, 4.37%, and 3.76%, respectively, with a maximum yield of 66.94% achieved using CCN. Copper-based catalysts reduced the oxygen-containing functional groups in HA and promoted the release of calcium and magnesium ions from HA, thereby improving KHA’s resistance to hard water. Among the catalysts, KHA prepared with CCO exhibited the highest resistance to hard water. The time of flocculation in hard water at 20 °dH and 21 °dH was delayed by 10 h and 2.4 h respectively. Additionally, the hydrothermal residue demonstrated effective methylene blue (MB) removal, highlighting the potential for lignite’s non-fuel applications and the resource-efficient utilization of lignite waste.

Bioassay-Guide Preparative Separation of Hypoglycemic Components from Gynura divaricata (L.) DC by Conventional and pH-Zone Refining Countercurrent Chromatography.

Gynura divaricata (L.) DC is a long-used medicinal and edible plant in China folk. Its hyperglycemic effects have garnered increasing public attention in recent years. This study revealed that the ethyl acetate (EtOAc) and butanol (BuOH) partition fractions of G. divaricata crude extract exhibited significantly higher α-glucosidase inhibition activity and enhanced glucose uptake ability compared to other fractions. Guided by the hypoglycemic bioassay, these two fractions were subjected to isolation of active compounds using high-speed countercurrent chromatography (HSCCC). A two-phase solvent system composed of hexane-methyl tert-butyl ether (MtBE)-methanol-0.1% TFA water was employed for the separation of the EtOAc fraction by conventional HSCCC through a gradient elution strategy. Five major compounds were obtained and identified as chlorogenic acid (1), 3,4-dicaffeoylquinic acid (2), 3,5-dicaffeoylquinic acid (3), 4,5-dicaffeoylquinic acid (4), and kaempferol-3-O-β-D-glucopyranoside (5) by ESI-MS, 1HNMR, and 13CNMR. The chlorogenic acid and the three dicaffeoylquinic acids were found to display higher inhibitory activities against α-glucosidase compared to the flavonoid. Considering their acidic nature, pH-zone-refining CCC (PHZCCC) was then applied for further scale-up separation using a solvent system MtBE: n-butanol: acetonitrile: water with trifluoroacetic acid (TFA) as a retainer and ammonium hydroxide (NH4OH) as an eluter. A significantly higher yield of chlorogenic acid was obtained from the BuOH fraction by PZRCCC. Molecular docking between the caffeoylquinic acids and α-glucosidase confirmed their hypoglycemic activities. This study demonstrates that CCC is a powerful tool for preparative separation of active constituents in natural products. This research presents a novel and effective method for the preparative isolation of hypoglycemic compounds from Gynura divaricata.

Experimental and Kinetic Studies on the Conversion of Glucose to Levulinic Acid Catalyzed by Synergistic Cr/HZSM −5 in GVL/H2O Biphasic System

In this paper, modified HZSM-5 catalysts with different ratios of chromium (Cr/HZSM−5) were synthesized and the solvent effect of gamma valerolactone (GVL) on the enhancement of levulinic acid (LA) yield was investigated. Characterization of the Cr/HZSM−5 catalyst revealed that the introduction of Cr did not change the structure of HZSM−5. The LA yield was increased from 42.5% (H2O solvent system) to 51.4% (GVL/H2O solvent system) under optimal conditions. The influence of GVL on the reaction mechanism was investigated through kinetic analysis, revealing that the incorporation of GVL reduces the activation energy barrier for the conversion of glucose to LA, thereby enhancing the glucose dehydration process. The effect of GVL on the product (LA) was studied, based on molecular dynamics. It was found that the addition of GVL squeezes the water in the solvent system into the second solvation shell layer, which causes GVL to distribute around the carbonyl, hydroxyl, and carboxyl groups of LA, and reduces the likelihood of LA side reactions, thus increasing the yield of LA.

The Study on Growth and Yield Attributing Characteristics of Chilli (Capsicum annum L.) Using Foliar Spray of Naphthalene Acetic Acid (NAA)

Chilli (Capsicum annum L.), is one of the most important spice crops in India. It is widely used in many cuisines as a spice to add hot flavour to dishes and sauces. The production of chilli is affected by several factors governed not only by the inherent genetic factors but also by several environmental factors and management practices. Therefore, Krishi Vigyan Kendra, Maulasar, Nagaur-II, Rajasthan (Agriculture University, Jodhpur, Rajasthan, India) initiated to conduct On Farm Testing (OFT) forassess the effect of Naphthalene Acetic Acid (NAA) ongrowth and yield Attributing characteristics of chilli. The present OFT was carried out at 20 farmers fields of Nagaur district of Rajasthan under supervision of KVK, Nagaur-II, Rajasthan during Zaid season of two consecutive years i.e., 2020-21 and 2021-22. The pooled data of both the years indicated that the foliar spray of naphthalene acetic acid @ 20 PPM increased plant height (70.45 cm), number of branches/plant (14.15), fruit set (49.42%), fruit length (8.40 cm), fruit weight (3.65 g), number of fruits/plant (133.55), fruit yield (292.50 q/ha), net return (₹ 345100) and benefit cost ratio (4.68) as compared to farmers practices (no use of PGR).It isalso observed that days taken to first harvest was almost two weeks earlier with the spray ofNAA. It was 84.50 days after transplanting in treatment (NAA @ 20 PPM) whereas; it was maximum (97.35 days) in control.

Enhancing CO2 Capture and Conversion to Formic Acid via a Membrane-Photocatalytic Hybrid System with ZnO-ZnS Heterojunction Catalyst.

A combined approach for CO2 capture and photoreduction provides a comprehensive solution to address exhaust emissions. This study aims to develop a hybrid system integrating membrane contactor and photocatalytic technology for CO2 conversion to formic acid by optimizing the synthesis of ZnO-ZnS heterojunction photocatalysts through controlled variations in precursor concentrations and calcination temperatures. The catalysts are characterized to assess their structural and optical properties, photocatalytic activity, stability and reaction kinetics. Additionally, the photocatalytic performance is also tested using a model gas composition that simulates power plant emission with UV or visible light serving as the energy source. The synthesized ZnO-ZnS catalysts exhibit diffraction patterns consistent with standard references, with a measured band gap interval of 3.06-3.13 eV. Among the three most effective catalysts, labeled as Z1 (ZnO:ZnS ratio of 1:2 at 400 °C), Z2 (ZnO:ZnS ratio of 1:1 at 400 °C), and Z4 (ZnO:ZnS ratio of 1:2 at 500 °C), the formic acid yields were 0.643, 0.554, and 0.626 mmol/(L gcat h), respectively. The highest yield, 0.936 mmol/(L gcat), was achieved under a low CO2 feed gas concentration (15 vol%). Furthermore, under LED irradiation, the Z1 catalyst produced a formic acid yield of 0.394 mmol/(L gcat) after 4 h, demonstrating higher selectivity for formic acid production. Electrochemical impedance spectroscopy (EIS) analysis shows that Z1 exhibits lower resistance, enhancing charge transfer efficiency. Scanning electron microscopy (SEM) analysis reveals nanorod-like ZnO and globular ZnS structures ranging from 50 to 100 nm, while high-resolution transmission electron microscopy (HRTEM) confirms the presence of ZnO-ZnS diffraction patterns. After 4 h of photocatalytic test, the XRD analysis confirmed that most of the ZnO-ZnS catalyst peaks remained intact, indicating structural stability. Ultimately, the optimized ZnO-ZnS catalysts demonstrate promising efficiency for selective CO2 conversion to formic acid under visible light, offering a viable approach for emission reduction through advanced hybrid membrane-photocatalytic technology.

Effect of biostimulants on root yield and quality of carrots across different growing seasons

ABSTRACT Abiotic stresses are causes of losses in crop yield and quality. New technologies, including growth-enhancing products, have been tested to mitigate this impact. The application of biostimulants has shown promise in managing biotic and abiotic stress-related damage. This study evaluates the effect of a phytohormone-based biostimulant on root yield and quality of two carrot cultivars across two contrasting growing seasons. Randomised block trials were arranged in a split-plot scheme with four replicates. The carrot cultivars Nantes and Brasília were assigned to plots, and five Stimulate® doses (0, 5, 10, 15 and 20 mL L−1) to subplots. Traits assessed included root length and diameter, fresh and dry mass, root volume, β-carotene, soluble sugar, pH, titratable acidity and total root yield. A combined analysis of both trials was conducted to investigate the effect of planting time on yield and quality. Biostimulant dosage influenced root length, with 12.91 mL L−1, obtained by the regression curve, resulting in the longest roots during summer. Biostimulants had no impact on other traits, except for soluble solids, which decreased with increasing dosage. Brasília outperformed Nantes in all traits except titratable acidity. Midseason planting was advantageous for traits such as root fresh mass, total yield, root volume and diameter, especially for Brasília.