Volatile Products Research Articles

Microkinetic Modelling of the Heterogeneously Catalyzed Hydrogenation of Glycolic Acid over Ru/C

The heterogeneously catalyzed hydrogenation of biomass‐or CO2‐derived glycolic acid (GA) is a renewable pathway for obtaining the bulk chemical ethylene glycol (EG). In this study, the reaction network of the aqueous‐phase hydrogenation of GA is investigated over a Ru/C catalyst. As previous studies indicated, several parallel and consecutive reactions can occur in addition to the desired reaction to EG. These reactions are experimentally assessed by employing different (possible) reaction intermediates and products as reactants. The data for all individual reactions and GA hydrogenation at different reaction temperatures (120‐180°C) is combined to propose a catalytic reaction pathway network and to develop a corresponding microkinetic model. The model describes the catalytic data in the range up to 150°C, where EG is the main reaction product, with high accuracy. It is shown that selectivity for EG is highest at 120°C and decreases strongly with increasing temperatures both due to the parallel reaction of GA into AcA, which has a significantly higher activation energy than the overall hydrogenation of GA into EG, and due to degradation of EG into ethanol and volatile products. Temperatures exceeding 150°C predominantly yield volatile products, suggesting low yields of EG or AcA at higher temperatures despite enhanced GA conversion.

Profiles of ambient semi- and intermediate- volatility organic compounds (S/IVOCs) in winter of urban Chengdu

Semi-volatile/intermediate-volatility organic compounds (S/IVOCs) are considered to be missing precursors of secondary organic aerosol (SOA). In this study, ambient S/IVOCs were collected in the winter of Chengdu and were analyzed by a thermal desorption-comprehensive two-dimensional gas chromatography-mass spectrometer (TD-GC×GC–MS). Molecular characteristics and volatility-polarity distributions of the S/IVOCs were specified. A total of 351 compounds were quantified with S/IVOCs concentration of 2.63 ± 1.25 μg m−3 in gas phase and 1.83 ± 1.15 μg m−3 in particle phase. The volatility-polarity distributions are generally similar during polluted days and non-polluted days. Most of the gas-phase compounds fell in the high volatility and intermediate polarity bins, with IVOCs and SVOCs accounting for 16.9 % and 0.3 %, respectively, while IVOCs and SVOCs took up 73.0 % and 9.6 % of the total particle-phase concentration. Among gaseous S/IVOCs, acids and ketones were the main compounds, and benzoic acid was the most abundant species (0.86 ± 0.47 μg m−3), followed by 1,2-diphenyl-ethanone (0.20 ± 0.17 μg m−3), 2-hydroxy-1-phenyl-ethanone (0.20 ± 0.17 μg m−3) and C12-C15 alkenes. Alcohols and esters were the most abundant compounds in particle phase (62.8 %, including volatile chemical product compounds, VCPs), with tracers like Texanol detected (0.11 ± 0.07 μg m−3). Partial least squares-discriminant analysis (PLS-DA) indicated that combustion sources, VCPs and other industrial productions were closely related to pollution levels. The SOA yield method was used to estimate contributions of gas-phase S/IVOCs oxidation to SOA. Despite of their lower concentrations (2.63 ± 1.25 μg m−3 in gas phase, 17.2 %), S/IVOCs could contributed 27.4 % of the total estimated gas-phase SOA production. Emissions with more reactive S/IVOCs during non-polluted days may result in relatively higher SOA contribution fraction of S/IVOCs. Our result provided a deep insight into the molecular composition of ambient organics and elucidated the importance of S/IVOCs to SOA formation in the ambient air of Chengdu.

Volatile fatty acid production from different spent mushroom substrates via anaerobic fermentation: Hydrolysis and acidogenesis efficiency and bacterial community structure

Converting renewable biomass resources into biofuels or chemical raw materials is expected to help alleviate energy shortage. Selecting suitable anaerobic fermentation substrates is a key factor in determining high yields of volatile fatty acids (VFAs). Spent mushroom substrates (SMSs) rich in polysaccharides, proteins, lignocellulose and micronutrients may be a high-quality feedstock for producing VFAs. However, the hydrolysis and acidogenesis efficacies of different types of SMSs remain unclear. In this study, we investigated the hydrolysis and acidogenesis performances of four SMSs, namely, Hericium erinaceus (HES), Pleurotus ostreatus (POS), Flammulina velutipes (FVS) and Pleurotus eryngii (PES), and analysed the microbial community composition in the anaerobic fermentation system via 16S rRNA sequencing. Results revealed that the PES reactor afforded the maximum VFA yield of 248.48mg/g, followed by HES, FVS and POS. This might be related to the higher content of polysaccharides and proteins in PES compared to the other three types of SMSs. The higher abundance of Bacillus, Sporolactobacillus, Clostridium_Sensu_Stricto_1 and Clostridium_Sensu_Stricto_19 associated with hydrolysis and acidogenesis in the PES anaerobic fermentation system was responsible for its higher VFA production than the other three SMSs. The carbohydrate metabolism and amino acid metabolism driven by microbes were involved in the hydrolysis and acidogenesis process of SMSs. Notably, the expression levels of key functional genes involved in the VFA production pathway with PES as the fermentation substrate were the highest. These findings provide theoretical support for the large-scale industrial application of SMSs in anaerobic digestion.

Revisiting alkali pretreatment to transform lignocellulose fermentation with integration of bioprocessible lignin

This study emphasized the synergistic production of bioprocessible lignin and carbohydrates during a sequential liquid hot water and alkali pretreatment of lignocellulose, facilitating their subsequent individual fermentation. Increasing the dose of alkaline lignin from 0 to 8 g/L inhibited cell growth in anaerobic digestion, with varying levels of inhibition observed in the following order: hydrolytic bacteria < acidogens < acetogens. Alkali pretreatment was adapted to maximize yields of bioprocessible lignin liquor without compromising utilization of the carbohydrates. Increasing the NaOH dose from 50 to 200 mg/g-feedstock monotonically improved lignin yields, but further increases in alkali loading led to a decline in lignin recovery. Volatile fatty acids production from anaerobic digestion of the carbohydrate moiety consistently increased with higher NaOH doses. The optimal conditions for maximizing lignin yields were determined to be 105 °C for 30 min, with NaOH loading in the range of 150–200 mg/g-feedstock, resulting in approximately 80 % lignin recovery, of which 35 % was biologically utilizable. Liquid hot water treatment prior to alkali pretreatment was confirmed as necessary to preserve carbohydrates of 0.1 g/g-feedstock at a low temperature of 70 °C. These findings are crucial for economically producing bioprocessible lignin without carbohydrate loss, a key step towards achieving full lignocellulose valorization.

Batrachopolyenes: Volatile Norsteroids from Femoral Scent Glands of Frogs

Steroid hormones are C18‐C21‐sterane derivatives, featuring the typical 6‐6‐6‐5 ring system. Here we report on a novel C18‐steroid ring system named batrachane with a contracted A‐ring resulting in a 5‐6‐6‐5 ring arrangement. The isolation, structural elucidation, and total synthesis of three members of the novel batrachopolyene family occurring in the tropical frog genus Odontobatrachus is reported. The batrachopolyenes represent an entirely new collection of volatile steroidal natural products produced by anuran amphibians. Alongside the contracted A‐ring, each member contains a Δ16‐17 double bond but differs in the central belt of the steroidal structure. To create these atypical structural features, syntheses featuring a combination of Breslow radical chain relay chlorination, Favorskii ring contraction, and Clemmensen reduction proved successful. The occurrence of such compounds in another distal anuran group, the Mantellinae, suggests a more widespread distribution of the batrachane‐type compounds among frogs. The new structural steroid type raises questions concerning steroid biosynthesis and reception, as well as distribution in frogs in general and the structures of their hormones.

Exploring the Linkage Between Ruminal Microbial Communities on Postweaning and Finishing Diets and Their Relation to Residual Feed Intake in Beef Cattle

Feed efficiency significantly impacts the economics of beef production and is influenced by biological and environmental factors. The rumen microbiota plays a crucial role in efficiency, with studies increasingly focused on its relationship with different rearing systems. This study analyzed 324 rumen samples from bulls and steers categorized as high and low efficiency based on residual feed intake. The animals were fed two diets (postweaning and finishing) and rumen samples were sequenced using a reduced representation sequencing (RRS) based approach. The results indicated that diet significantly affected microbial diversity and abundance. In postweaning diets, Actinomycetota, particularly Bifidobacterium, were prevalent, aiding carbohydrate fermentation. In contrast, Acetoanaerobium was identified in finishing diets, likely contributing to acetate production. Additionally, Bacteroides and Butyrivibrio were abundant during postweaning, known for fiber degradation and volatile fatty acid production. Notably, Prevotella and Fibrobacter succinogenes were associated with high feed intake and nutrient utilization, indicating their potential as microbial biomarkers. However, alpha diversity indices showed no significant relationship with feed efficiency, suggesting that diversity alone may not adequately reflect the complexity of feed efficiency phenotypes. These findings highlight the importance of diet and microbial interactions on feed efficiency and suggest further research to explore these microbial contributions to precision feeding strategies.

Batrachopolyenes: Volatile Norsteroids from Femoral Scent Glands of Frogs.

Steroid hormones are C18-C21-sterane derivatives, featuring the typical 6-6-6-5 ring system. Here we report on a novel C18-steroid ring system named batrachane with a contracted A-ring resulting in a 5-6-6-5 ring arrangement. The isolation, structural elucidation, and total synthesis of three members of the novel batrachopolyene family occurring in the tropical frog genus Odontobatrachus is reported. The batrachopolyenes represent an entirely new collection of volatile steroidal natural products produced by anuran amphibians. Alongside the contracted A-ring, each member contains a Δ16-17 double bond but differs in the central belt of the steroidal structure. To create these atypical structural features, syntheses featuring a combination of Breslow radical chain relay chlorination, Favorskii ring contraction, and Clemmensen reduction proved successful. The occurrence of such compounds in another distal anuran group, the Mantellinae, suggests a more widespread distribution of the batrachane-type compounds among frogs. The new structural steroid type raises questions concerning steroid biosynthesis and reception, as well as distribution in frogs in general and the structures of their hormones.

Potential of Trichoderma species to control Rosellinia necatrix, the etiological agent of white root rot

White root rot, caused by the fungal pathogen Dematophora necatrix (syn. Rosellinia necatrix), poses a threat to crops worldwide, leading to substantial economic losses. Biological control using antagonistic fungi, such as Trichoderma spp., has emerged as a promising alternative to chemical fungicides in fungal disease management. In this study, we investigated the potential of three Trichoderma species, Trichoderma harzianum strain 40788 from the Korean Agriculture Culture Collection (KACC), T. atroviride (KACC 43393), and T. asperellum (KACC 43821), as biocontrol agents against four R. necatrix strains (KACC 40446, 40445, 40447, and 40168). Dual-culture assays revealed that T. harzianum (KACC 40788) and T. atroviride (KACC 43393) rapidly inhibited mycelial growth, achieving up to 80% suppression of strains KACC 40445 and KACC 40446, whereas T. asperellum (KACC 43821) exhibited lower inhibition. In volatile antibiotic production assays, volatile metabolites produced by T. harzianum (KACC 40788) and T. atroviride (KACC 43393) inhibited mycelial growth of R. necatrix strains KACC 40445 and KACC 40446 by 76.52 and 74.70%, respectively. Microscopic analysis of mycoparasitism revealed that Trichoderma strains adhered to, coiled around, and lysed R. necatrix mycelia. Finally, greenhouse trials demonstrated that T. harzianum and T. atroviride treatment significantly reduced white root rot incidence, with disease symptoms in only 15% of treated pear saplings, compared with 82% in untreated controls. Collectively, our findings highlight the potential of T. harzianum and T. atroviride as effective biocontrol agents against white root rot caused by R. necatrix, thereby providing sustainable and environmental-friendly disease management strategies in agricultural systems.

Catalyst screening for conversion of Chlorella sp. to aromatic fuel additives: A sustainable strategy for CO2 capture

Developing biofuels with characteristics similar to current fossil fuels and compatibility with existing petroleum infrastructure (drop-in biofuels) is gaining prominence, aligning with global efforts towards carbon-neutral economies and decarbonization of the transportation sector. The originality of the current study involves two directions: first, the use of Chlorella sp. microalgae, cultivated under simulated post-combustion gas, as a raw material for producing drop-in biofuel precursors; and second, an investigation of the catalytic activity of hierarchical zeolites in the deoxygenation and denitrogenation of volatile pyrolysis products, enhancing hydrocarbon content. To accomplish this, a micro-furnace-type temperature-programmable pyrolyzer coupled with chromatographic separation and mass spectrometry detection (Py-GC/MS) was utilized to assess the upgrading effectiveness of distinct zeolites (faujasite-type, MFI-type, and mordenite-type) on volatile pyrolysis products. All tested zeolites effectively reduced oxygenated and nitrogenated compounds in the volatile pyrolysis products, enhancing their suitability for producing renewable fuel. This supports sustainable development goals by promoting affordable, clean energy and climate action. HMor yielded the highest hydrocarbon content (98.5 %), followed by HZSM-5 (97.6 %) and HY (85.5 %). Catalytic upgrading significantly increased the concentration of aromatic hydrocarbons (at least 66.3 %), with MFI-type zeolites showing the highest selectivity for valuable BETX compounds (benzene, ethylbenzene, toluene, xylene). Hydrocarbons in the gasoline range, with up to 91.7 %, predominantly align with the needs of the transportation fuel market. The principal component analysis illustrates that using MFI-type zeolites promoted the lowest selectivity for PAHs, constituting precursors for coke formation, which is advantageous for ensuring a longer catalyst lifespan. Our results are promising and encourage the conversion of microalgal biomass into renewable fuel additives for formulating drop-in biofuels, as hydrocarbon-rich volatile pyrolysis products could be directly integrated into existing biorefineries. Thus, microalgal biomass cultivated using flue gas as the carbon source can be viewed as a versatile and promising resource for producing renewable fuel additives, contributing to developing a sustainable, low-carbon future.

Improving hydrogen and volatile fatty acids production through pretreatment of spent coffee grounds

Consumption of coffee produces large amounts of waste in the form of spent coffee grounds (SCG), a lignocellulosic material rich in carbohydrates, proteins, and polyphenols. This abundant feedstock is promising in terms of biofuels and value-added product generation. This study investigated the impact of pretreatments, such as alkaline (NaOH), ultrasound, and static magnetic field, on SCG bioconversion in terms of biomolecule release, H2 potential and volatile fatty acids production. Following treatment, the slurry (solid and liquid fraction mixture) was utilised in anaerobic fermentation tests at varying volatile solid (VS) concentrations (23.3 and 46.7 g VS/L). The highest H2 production range, 25 – 30 mL H2/g VS, was obtained using the alkaline-pretreated SCG slurry at 23.3 g VS/L. Nevertheless, inhibition of H2 production was observed when utilising the alkaline-pretreated slurry at 46.7 g VS/L owing to the excessive use of NaOH for pretreatment and chemicals to adjust the initial pH. In contrast, increasing the VS concentration had a positive impact on volatile fatty acids accumulation, with acetic (HAc) and caproic acid being dominant. Ultrasound-pretreated SCG achieved 3260.0 mg HAceq/L at a concentration of 46.7 g VS/L.

Investigation of the atomic layer etching mechanism for Al2O3 using hexafluoroacetylacetone and H2 plasma.

Atomic layer etching (ALE) is required to fabricate the complex 3D structures for future integrated circuit scaling. To enable ALE for a wide range of materials, it is important to discover new processes and subsequently understand the underlying mechanisms. This work focuses on an isotropic plasma ALE process based on hexafluoroacetylacetone (Hhfac) doses followed by H2 plasma exposure. The ALE process enables accurate control of Al2O3 film thickness with an etch rate of 0.16 ± 0.02 nm per cycle, and an ALE synergy of 98%. The ALE mechanism is investigated using Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) simulations. Different diketone surface bonding configurations are identified on the Al2O3 surface, suggesting that there is competition between etching and surface inhibition reactions. During the Hhfac dosing, the surface is etched before becoming saturated with monodentate and other hfac species, which forms an etch inhibition layer. H2 plasma is subsequently employed to remove the hfac species, cleaning the surface for the next half-cycle. On planar samples no residue of the Hhfac etchant is observed by FTIR after H2 plasma exposure. DFT analysis indicates that the chelate configuration of the diketone molecule is the most favorable surface species, which is expected to leave the surface as volatile etch product. However, formation of the other configurations is also energetically favorable, which explains the buildup on an etch inhibiting layer. The ALE process is thus hypothesized to work via an etch inhibition and surface cleaning mechanism. It is discussed that such a mechanism enables thickness control on the sub-nm scale, with minimal contamination and low damage.

Enhancing the quality of semi-dried tilapia fillets using ultraviolet radiation to simulate the natural solar drying process: Integration of flavoromics, lipidomics, and targeted metabolomics

Ultraviolet light from the sun plays an important role in the formation of the quality of natural air-dried meat products. This study investigated the effect of UV-simulated sunlight-assisted drying on the quality of tilapia fillets by lipidomics, targeted metabolomics, and flavoromics. The results showed that UV radiation increased the gap between myofibrils. UV radiation moderately improved lipid oxidation levels and changed the flavor profile. The volatiles of the UVA or UVB groups were more abundantly and diverse than those of the other groups. The contents of taste amino acids and nucleotides were increased after UV radiation. 422 lipid molecules were identified, of which 66 differential lipids were screened. UV radiation promoted the volatiles production by accelerating the degradation of differential lipids. Best organoleptic quality of products were obtained after UVA or UVB radiation. This study provides new horizons for improving the flavor of dried meat products.

The Effects of Varied Neutral Detergent Fiber Levels on Blood Parameters, Nutrient Digestibility, Rumen Fermentation Characteristics and Rumen Tissue Morphology in Lambs

Background: Neutral detergent fiber is a common analytical measure of feed fiber content, which could play an important role as an energy source, improve the rumen ecosystem and thus improve growth performance of lambs. The aim of this study was to investigate the effects of different levels of neutral detergent fibers on growth performance, blood parameters, nutrient digestibility, volatile fatty acid concentration, ammonia nitrogen, bacterial quantification, gas production and tissue morphology of growing lambs. Methods: Seventy-two Awassi lambs of weaning age were randomly assigned to three experimental feeds with different levels of neutral detergent fiber: low (210 g/kg), medium (280 g/kg) and high (350 g/kg), each with eight replicates in a completely randomized design. The growth performance parameters were evaluated over a trial period of 84 days. At the end of the trial, hematological and serum biochemical parameters and nutrient digestibility were evaluated. In addition, rumen fermentation characteristics, including pH, ammonia-nitrogen, gas production, volatile fatty acids, bacterial quantification and indices of rumen morphology indices were measured. Result: The results showed that lambs fed a medium-neutral detergent fiber feed had better growth performance (p less than 0.05). In addition, this experimental feed showed improvements in some blood parameters (WBC, RBC, HGB, TP, GLOB and GLU) and nutrient digestibility with the exception of crude protein and ash (p less than 0.05). Rumen fermentation characteristics and rumen morphology were also positively influenced by the medium- neutral detergent fiber level (p less than 0.05). These results indicate that a medium level of neutral detergent fiber (280 g/kg) is essential for optimal growth, health and rumen development in growing lambs.

NO₂-mediated voloxidation for iodine separation from cesium iodide surrogates

ABSTRACT Heterogeneous NO2-mediated oxidation of uranium, also known as advanced voloxidation, is a proposed head-end reprocessing method for used nuclear fuel. An advantage of advanced voloxidation is the removal of volatile fission products, which complicate downstream separation and containment challenges leading to increased processing economics. Iodine, one of the volatile species of interest, has exhibited varied results in this process. Using CsI as a surrogate material, this work mimics the effect of NO2-based voloxidation on iodine and sheds light on the factors that influence the solid–gas phase reaction. Solid-state analysis using Fourier transform infrared attenuated total reflectance spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed the conversion of CsI to CsNO3. Iodine separation ranged from 46% to 100% across multiple tests. Iodine separation was most effective when multiple recharges of NO2 were administered. At the bench scale, liberating iodine from CsI appears to occur within 1 h, but the presence of surface H2O and the composition of the NO x reagent mixtures greatly influence its success.

Acidogenic Fermentation of Cassava Wastewater: Effect of the Substrate-to-Microorganism Ratio and Temperature on Volatile Fatty Acids Production

Acidogenic Fermentation of Cassava Wastewater: Effect of the Substrate-to-Microorganism Ratio and Temperature on Volatile Fatty Acids Production

Thermophilic dark fermentation for hydrogen and volatile fatty acids production from breadcrumbs

Food waste poses significant environmental challenges, with Japan generating 100 million kg of bread waste annually. This study explores the potential of thermophilic dark fermentation to convert bread waste into hydrogen (H2) and volatile fatty acids (VFA). A 3-L continuous stirred-tank reactor (CSTR) was operated for 269 days using breadcrumb as feedstock. The highest H2 production rate of 7.0 L-H2 L−1 d−1 was achieved on day 52 with the production of acetate and butyrate. However, H2 production fluctuated significantly, correlated with the shifts of microbial community structure. Initially, Thermoanaerobacterium saccharolyticum, Thermocoprobibacter melissae, and Anaerocolumna jejuensis coexisted, but An. jejuensis outcompeted others during the deterioration phase, resulting in acetate accumulation without H2 production. Metabolic potential analysis using the phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) revealed that carbohydrate degradation was primarily carried out by An. jejuensis, while protein and lipid degradation involved diverse microbial members. The low functional diversity in carbohydrate degradation was a potential cause of instability. This study demonstrates the feasibility of using bread waste for H2 and VFA production, and provided insights into microbial dynamics essential for stable reactor performance.

Characterization of Novel Multifunctional Xylanase from Rumen Metagenome and Its Effects on In Vitro Microbial Fermentation of Wheat Straw

This study investigated the characterization of a novel multifunctional enzyme, RuXyn394, derived from the metagenome of beef cattle rumen, and its impact on the in vitro microbial fermentation of wheat straw. RuXyn394, a member of the glycosyl hydrolase 11 family, displayed optimal activity under diverse pH and temperature conditions: xylanase at pH 5.5 and 50 °C, acetyl esterase at pH 6.5 and 60 °C, exoglucanase at pH 7.0 and 50 °C, and endoglucanase at pH 6.0 and 50 °C. The enzyme’s xylanase, endoglucanase, and exoglucanase activities exhibited remarkable pH stability across the range of pH 3–8 and maintained a relatively stable performance at temperatures from 20 to 50 °C, 20 to 60 °C, and 20 to 70 °C, respectively. The xylanase function, with the highest kcat/Km ratio, was identified as the predominant activity of RuXyn394. The enzyme’s various functions responded uniquely to metal ions; notably, the addition of 5 mM K+ significantly boosted the activities of xylanase, exoglucanase, and endoglucanase by 55.5%, 53.5%, and 16.4%, respectively, without affecting its acetyl esterase activity. Over the course of three time points (30 min, 60 min, 120 min), the degradation products of wheat straw xylan, including xylopentaose, xylotetraose, xylotriose, xylobiose, xylose, and total xylooligosaccharides, constituted an average of 18.4%, 33.7%, 20.6%, 22.9%, 4.3%, and 95.7% of the total products, respectively. RuXyn394 effectively hydrolyzed wheat straw, resulting in augmented volatile fatty acid production and ammonia-N levels during in vitro microbial fermentation. These findings indicate the potential of RuXyn394 as a novel and highly efficient enzyme preparation, offering promising prospects for the valorization of wheat straw, an agricultural by-product, in ruminant diets.

The Pyrolysis Characteristics of Bagasse Were Studied by TG-MS-FTIR

Sugarcane bagasse is rich in cellulose and lignin, and the recycling of bagasse has become an important research field with the increasing global concern for sustainable development and environmental protection. In this paper, TG-MS-FTIR equipment was used to analyze the pyrolysis characteristics of bagasse from Guangxi under different heating rates and different atmospheres, which is conducive to the reuse of bagasse from the waste gas produced in the sugar plant. The results showed that the pyrolysis rate of sugarcane bagasse in the air atmosphere was faster than that in the nitrogen atmosphere and showed a double-peak trend, and the Coats–Redfern computational model could more accurately simulate the process of pyrolysis. The lower heating rate could overcome the heat transfer hysteresis phenomenon in the process of pyrolysis. In the air atmosphere, the contact time between oxygen and volatile products was shorter due to the high heating rate, and more and more complex species were precipitated at 10 °C/min than at 20 °C/min. In the nitrogen atmosphere, it was favorable to produce more kinds and quantities of gas products, because it did not react with oxygen. FTIR detected CH4, CO, H2O, CO2, C-O-C, and C=O during pyrolysis in nitrogen, and some of C-O-C and C=O were cracked into small molecule compounds at high temperature.

Effect of modifiers on the stability of 1‑butyl‑3-methylimidazolium-based ionic liquids

The distinctive capabilities of 1‑butyl‑3-methylimidazolium (bmim) cation-based ionic liquids (ILs) to dissolve lignocellulosic biomass offer the potential for the development of novel green bioprocessing technologies based on their utilization as green solvents. The limited range of thermal stability of ILs necessitates the use of various co-solvents to maintain solubility. In the present study, an original approach to determine the degree of degradation of alkylimidazolium ILs was proposed, based on the application of gravimetric analysis method to determine the content of volatile degradation products and high-performance liquid chromatography-high-resolution mass spectrometry (HPLCHRMS) to determine the total degree of degradation. The proposed approach, as well as the combination of HPLCHRMS with gas chromatography-mass spectrometry (GC–MS), was employed to comprehensively characterize the impact of additives and impurities (water, dimethyl sulfoxide, hydrochloric and acetic acids, diethylamine) on the degradation of bmim acetate, chloride, and methyl sulfate during thermal treatment under typical biomass dissolution conditions (150 °C, 24 h). The presence of additives or impurities in the composition of ILs has been found to predominantly contribute to a decrease in the number of volatile compounds formed, while increasing the variety and relative content of non-volatile degradation products. The use of protic solvents and acids results in a decrease in the overall degree of degradation of ionic liquids and in the fraction of volatile compounds formed. This allows for the classification of binary mixtures based on these additives as "green" solvents at temperatures below 150 °C.

Improved volatile fatty acid production in anaerobic digestion via simultaneous temperature regulation and persulfate activation by biochar: Chemical and biological response mechanisms

Increasing volatile fatty acid (VFA) production via persulfate activation (i.e., chemical effect) in anaerobic digestion (AD) is an emerging resource utilization method. However, the reaction mechanisms responsible for improving VFA production in AD via simultaneous temperature regulation and persulfate activation by biochar remain unclear. In this study, three PB15 treatment systems of low temperature (15 °C), medium temperature (35 °C) and high temperature (55 °C) were set to explore the relationship between VFAs production and treatment temperature and the influence of temperature on the reaction mechanism. The results show that the improvement of hydrolysis and acidification efficiency of the system in the medium temperature system is the highest. The VFA yield and acid production rate in the treatment group at 35 °C were 2.49 and 5.22 times higher than those in the control group, respectively. The chemical effect effectively initiated the anaerobic acid production process and maintained the dominant role of the biological effect. The activity of persulfate is too low at low temperature, and its decomposition is too fast at high temperature. Plenty of free radicals lead to enhanced oxidation of the system, which may kill the fermentation bacteria. The NCM model indicates that microbial stability is reduced in high temperature systems. The SEM model showed that temperature change mainly affected substrate degradation by hydrolytic bacteria and indirectly affected acid production by acid-producing bacteria. This study provides a new strategy for realizing pollutant recycling and increasing VFAs production in cold area.