Search Results (550)

Broth cooking is a traditional pretreatment and ripening strategy for high-commercial-value dehydrated marine food, effectively enhancing its texture and rehydration properties. In this work, we characterized the structural information of Maillard reaction products (MRPs) derived from beef scrap stock and investigated their effects on the texture and rehydration performance of dehydrated abalone. The optical and structural properties of the MRPs were analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and fluorescence spectroscopy. These MRPs showed osmosis in abalone processing including pretreatment and drying. Low-field nuclear magnetic resonance (LF-NMR) results revealed that MRP pretreatment improved the moisture migration and physicochemical properties of dehydrated abalone. These findings suggest that MRPs, owing to their high osmotic efficiency and nanoscale size, could serve as promising food additives and potential alternatives to traditional penetrating agents in the food industry, enhancing the rehydration performance of dried seafood and reducing quality deterioration. Full article

Catalytic upgrading of pyrolysis oils is an important step for producing replacement hydrocarbon-rich liquid biofuels from biomass and can help to advance pyrolysis technology. Catalysts play a pivotal role in influencing the selectivity of chemical reactions leading to the formation of main compounds in the final upgraded liquid products. The present work involved a systematic study of solvent-free catalytic reactions of cyclohexanone in the presence of hydrogen gas at 160 °C for 3 h in a batch reactor. Cyclohexanone can be produced from biomass through the selective hydrogenation of lignin-derived phenolics. Three types of catalysts comprising undoped NbOPO₄, 10 wt% NiO/NbOPO₄, and 30 wt% NiO/NbOPO₄ were studied. Undoped NbOPO₄ promoted both aldol condensation and the dehydration of cyclohexanol, producing fused ring aromatic hydrocarbons and hard char. With 30 wt% NiO/NbOPO₄, extensive competitive hydrogenation of cyclohexanone to cyclohexanol was observed, along with the formation of C₆ cyclic hydrocarbons. When compared to NbOPO₄ and 30 wt% NiO/NbOPO₄, the use of 10 wt% NiO/NbOPO₄ produced superior selectivity towards bi-cycloalkanones (i.e., C₁₂) at cyclohexanone conversion of 66.8 ± 1.82%. Overall, the 10 wt% NiO/NbOPO₄ catalyst exhibited the best performance towards the production of precursor compounds that can be further hydrodeoxygenated into energy-dense aviation fuel hydrocarbons. Hence, the presence and loading of NiO was able to tune the activity and selectivity of NbOPO₄, thereby influencing the final products obtained from the same cyclohexanone feedstock. This study underscores the potential of lignin-derived pyrolysis oils as important renewable feedstocks for producing replacement hydrocarbon solvents or feedstocks and high-density sustainable liquid hydrocarbon fuels via sequential and selective catalytic upgrading. Full article

The physicochemical processes that occur during selective transfer in the contact area of a bronze/steel friction pair lubricated with glycerin are experimentally studied by the polarization method to observe how they influence the tribological properties (friction and wear) of the pair. The proposed method allows for the study of tribochemical transformations of glycerin and the friction pair materials during the work process with selective transfer. The analysis of the experimental results allows for the establishment of the conditions for a stable and stationary selective transfer during the operation of the bronze/steel pair, by friction, at which the friction coefficient (COF) values and wear are low. This was achieved by implementing continuous lubrication with fresh glycerin in the contact area, choosing the optimal flow rate, and maintaining an optimal ratio between glycerin and the chemical transformation products, within well-established limits, to avoid undesirable consequences. Acrolein, as a product of chemical transformation (resulting from the catalytic dehydration of glycerin), is the most important for the initiation and stability of the selective transfer, and as the main reaction product, also represents a pathway of regeneration. Thus, it was found that the friction relative moments and the acrolein concentration presented conclusive/specific results at loads of 4–15 MPa and a sliding speed of 0.3 m/s. The optimum lubricant entry speed is 15–30 mg/min, for a minimum COF and reduced wear (about 0.028–0.03 at relatively high operating temperatures (45 and 60 °C)), and at low temperatures (30 °C) the minimum COF is about 0.038, but the lubricant inlet entry speed increases considerably, by around 1000 mg/min. Therefore, this paper aims to demonstrate the possibility of moving to another stage of practical use of a friction pair (with greatly improved tribological properties) that operates with selective transfer, much different from the ones still present, using a lubricant with special properties (glycerin). The research method used (polarization) highlights the physicochemical properties, tribochemical transformations of the lubricant, and the friction pair materials present in the contact area, for the understanding, maintenance, and stability of selective transfer, based on experiments, as a novelty compared to other studies. Full article

This article presents a review of several non-exclusive pathways for the sequestration of soil organic carbon, which can be classified into two large classical groups: the modification of plant and microbial macromolecules and the abiotic and microbial neoformation of humic substances. Classical studies have established a causal relationship between aromatic structures and the stability of soil humus (traditional hypotheses regarding lignin and aromatic microbial metabolites as primary precursors for soil organic matter). However, further evidence has emerged that underscores the significance of humification mechanisms based solely on aliphatics. The precursors may be carbohydrates, which may be transformed by the effects of fire or catalytic dehydration reactions in soil. Furthermore, humic-type structures may be formed through the condensation of unsaturated fatty acids or the alteration of aliphatic biomacromolecules, such as cutins, suberins, and non-hydrolysable plant polyesters. In addition to the intrinsic value of understanding the potential for carbon sequestration in diverse soil types, biogeochemical models of the carbon cycle necessitate the assessment of the total quantity, nature, provenance, and resilience of the sequestered organic matter. This emphasises the necessity of applying specific techniques to gain insights into their molecular structures. The application of appropriate analytical techniques to soil organic matter, including sequential chemolysis or thermal degradation combined with isotopic analysis and high-resolution mass spectrometry, derivative spectroscopy (visible and infrared), or ¹³C magnetic resonance after selective degradation, enables the simultaneous assessment of the concurrent biophysicochemical stabilisation mechanisms of C in soils. Full article

Pruned branches from persimmon trees are a largely untapped agricultural waste resource. This study explores the conversion of these branches into an enhanced fuel source through hydrothermal carbonization. The branches were subjected to hydrothermal treatment under various conditions to identify the optimal parameters. Higher temperatures and longer treatment durations increased the carbon content to 69.2% and reduced the oxygen content to 20.4%. A Van Krevelen diagram showed that dehydration was the primary reaction, with decarboxylation occurring at 250 °C. The energy value increased from 18.2 MJ/kg for raw branches to 28.5 MJ/kg under the optimal conditions, indicating a 57% improvement. These findings demonstrate that hydrothermal carbonization effectively utilizes persimmon pruning waste, offering a sustainable method for converting biomass into energy and aiding agricultural waste management. Full article

Furfural is a fascinating bio-based platform molecule that can be converted into useful cyclic compounds, among others. In this work, the hydrogenative rearrangement-dehydration of furfural towards cyclopentanone using a commercially available Pt/C catalyst was investigated in terms of its reaction performance to assess its feasibility as an industrial process. However, acquiring an acceptable cyclopentanone yield proved very difficult, and the reaction was constrained by unforeseen parameters, such as the relative liquid volume in the reactor and the substrate concentration. Most strikingly, the sacrificial formation of furanoic oligomers that precipitated onto the catalyst’s surface was a troublesome key factor that mediated the product’s selectivity versus the carbon mass balance. By applying a biphasic water–toluene solvent system, the yield of cyclopentanone was somewhat improved to a middling 59%, while tentatively positive distributions of reaction components over these solvent phases were observed, which could be advantageous for anticipated down-stream processing. Overall, the sheer difficulty of controlling this one-pot cascade transformation towards a satisfactory product output under rather unfavorable reaction parameters renders it unsuitable for industrial process development, and a multi-step procedure for this chemical transformation might be considered instead. Full article

The objective of this study was to analyze the impact of solar and hybrid dryers on the physicochemical characteristics, fingerprints, and cognitive-sensory perceptions of Mexican consumers of traditional tostadas made with corn of different races. Corn tostadas from different native races were evaluated with solar and hybrid (solar-photovoltaic solar panels) dehydration methods. Proximal chemical quantification, instrumental analysis (color, texture), fingerprint by Fourier transform infrared spectroscopy (FTIR), and sensory-cognitive profile (emotions and memories) and its relationship with the level of pleasure were carried out. The data were evaluated using analysis of variance models, Cochran Q, and an external preference map (PREFMAP). The results showed that the drying method and corn race significantly (p < 0.05) affected only moisture content, lipids, carbohydrates, and water activity. Instrumental color was influenced by the corn race effect, and the dehydration type influenced the fracturability effect. FTIR fingerprinting results revealed that hybrid samples exhibited higher intensities, particularly associated with higher lime concentrations, indicating a greater exposure of glycosidic or protein structures. Race and dehydration type effects impacted the intensity of sensory attributes, emotions, and memories. PREFMAP vector model results revealed that consumers preferred tostadas from the Solar-Chiquito, Hybrid-Pepitilla, Hybrid-Cónico, and Hybrid-Chiquito races for their higher protein content, moisture, high fracturability, crunchiness, porousness, sweetness, doughy flavor, corn flavor, and burnt flavor, while images of these tostadas evoked positive emotions (tame, adventurous, free). In contrast, the Solar-Pepitilla tostada had a lower preference because it was perceived as sour and lime-flavored, and its tostada images evoked more negative emotions and memories (worried, accident, hurt, pain, wild) and fewer positive cognitive aspects (joyful, warm, rainy weather, summer, and interested). However, the tostadas of the Solar-Cónico race were the ones that were most rejected due to their high hardness and yellow to blue tones and for evoking negative emotions (nostalgic and bored). Full article

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

2,5-Furandicarboxylic acid (FDCA) is a bio-based platform chemical with high potential to replace terephthalic acid in polymer production, particularly for polyethylene furanoate (PEF), a biopolymer with superior thermal and barrier properties. This study investigates the selective oxidation of 5-hydroxymethylfurfural (HMF) into FDCA using nickel-based heterogeneous catalysts, aiming at a cost-effective and sustainable alternative to noble metal catalysts. A series of nickel oxide catalysts were synthesized and screened. The NiOx catalyst synthesized without thermal treatment via Route B showed the best performance, achieving a FDCA yield of 11.77%, selectivity of 27.41%, and concentration of 0.9 g/L under preliminary conditions. Reaction kinetics revealed that the controlled addition of NaClO enhanced FDCA yield by 2.28 times. Optimization using a 2³ factorial design identified the optimal conditions as 6% (w/v) catalyst concentration, 25 °C, and a NaClO:HMF molar ratio of 12:1, leading to 34.14% yield and 42.57% selectivity. The NiOx catalyst maintained its activity over five successive cycles, indicating good recyclability. Moreover, NiOx demonstrated catalytic activity with crude HMF derived from glucose dehydration, confirming its practical applicability. These results support the potential of nickel-based catalysts in sustainable FDCA production, contributing to the advancement of bio-based polymer synthesis. Full article

The protective materials for cultural relic buildings generally have a deficiency of relatively shallow penetration depth. Based on the principle of changing the permeability coefficient of cultural relic buildings by “water blocking water” and considering the characteristics of magnesium acrylate polymer and the requirement of extending the curing time, a method of modifying magnesium acrylate polymer with glycerol and sodium methyl silicate is proposed. Experimental studies on magnesium acrylate, glycerol–magnesium acrylate, and sodium methyl silicate—glycerol–magnesium acrylate polymers were carried out, and tests and analyses on curing time, swelling performance, water loss rate, and soil sample protection were conducted. The results show that the initiator concentration is a key factor affecting the curing rate of magnesium acrylate polymers. When the initiator content is ≥4%, the curing time is significantly shortened to 20–67 min, and the incorporation of glycerol prolongs the curing time by more than 100 min through the dilution reaction system. Glycerol modification significantly enhanced the swelling capacity of the polymer, with the swelling rate increasing by approximately 15–20% compared to the unmodified system. Sodium methyl silicate effectively improved the construction performance of magnesium acrylate and prevented the occurrence of bubbles. The optimal formula of magnesium acrylate polymer is 25% magnesium acrylate, 40% glycerol, and 2% sodium methyl silicate. While maintaining curing for 120 min, it features a high swelling rate (equilibrium swelling ratio Ew ≈ 0.32) and a low dehydration rate (dehydration rate ≤ 35% after 48 h), and has volume stability after interaction with soil samples. Full article

A green and mild chemical reaction of calcium citrate (CC) was successfully prepared from reactions between mussel shell waste and citric acid in the presence of acetone (AC), ethanol (Et), and isopropyl alcohol (IPA). All the synthesized CCs contained the same functional groups such as citrate (C₆H₅O₇³⁻), water (H₂O), and calcium–oxygen (Ca–O). However, the differences in the spectra pointed out the differences in the crystal environment and structure of CCs. CC-AC and CC-IPA mainly crystallized in the monoclinic [Ca₃(C₆H₅O₇)₂(H₂O)₂]·2H₂O crystal system, whereas CC-Et mainly crystallized in the triclinic Ca₃(C₆H₅O₇)₂∙(H₂O)₄ structure. The molecular alignments of triclinic CC-Et were different from monoclinic CC-AC and CC-IPA, resulting in differences in thermal behaviors. Two dehydration steps were observed for the monoclinic CC-AC and CC-IPA, whereas the triclinic CC-Et showed a single dehydration process. The TG mass losses further demonstrated that anhydrous Ca₃(C₆H₅O₇)₂ phase, in addition to the Ca₃(C₆H₅O₇)₂∙4H₂O, was also observed for CC-AC and CC-IPA, whereas CC-Et contained a single Ca₃(C₆H₅O₇)₂∙(H₂O)₄ phase. The morphologies of CC-AC and CC-IPA also differed from that of CC-Et. The differences in some properties of the synthesized CCs could be attributed to the change in the supersaturation state of the reaction solution. Due to the superior polarity, ethanol is more compatible with citric acid. The presence of ethanol could suppress the supersaturation rate of the reaction solution, causing the modulation of the precipitation mechanisms and reducing the particle growth rate of CC-Et, thereby explaining the difference in vibrational, structural, thermal, and morphological characteristics of CC-Et, compared to CC-AC and CC-IPA. Full article

Chicken manure (CM) is a nutrient-rich but environmentally problematic biomass that requires sustainable management. This study applied a three-step process consisting of hydrothermal activation (ZnCl₂ or H₃PO₄), catalytic hydrothermal carbonization (HCl or FeCl₃), and low-temperature pyrolysis (250 °C) to develop an energy-efficient method for producing biochar. The resulting biochars were systematically analyzed for their physicochemical properties, heavy metal content, and carbon sequestration potential, and compared with conventional pyrolysis-based biochars. Among the tested samples, the biochar produced via H₃PO₄ activation and HCl-catalyzed HTC [P-HTC(HCl)] exhibited the most favorable characteristics, including the highest carbon content (59.5 wt.%) and the lowest H/C ratio (0.65). As a result, it achieved the highest total potential carbon (TPC, 158.8 g_carbon/kg_biochar) and CO₂ reduction potential (CRP, 465.9 g_CO2-eq/kg_biochar), attributed to the strong dehydration and decarboxylation reactions and effective inorganic removal induced by Brønsted acid action. In contrast, conventional pyrolysis biochars showed significantly higher concentrations of heavy metals—up to 633 mg/kg of Cu and 2331 mg/kg of Zn—due to thermal concentration effects, whereas P-HTC(HCl) biochar presented a more balanced and environmentally acceptable heavy metal profile. In conclusion, the proposed low-temperature hydrothermal-assisted process demonstrates great potential for producing high-performance biochar from chicken manure with enhanced environmental safety and carbon storage efficiency. Full article

NASICON-type titanium and zirconium phosphates doped with rare-earth cations, A_0.33M₂(PO₄)₃ (M = Ti, Zr; A = Dy, Y, Yb), were synthesized using the sol–gel method and investigated as catalysts for ethanol dehydration at 300–400 °C. The catalysts were characterized via XRD, SEM, BET, and FTIR spectroscopy. The relationships between the catalyst composition, acidity and the dehydration activity were evaluated. Diethyl ether (DEE) formation is promoted by the presence of the zirconium phosphates (ZrP), while the presence of titanium phosphate (TiP) catalyzes the formation of both ethylene and diethyl ether (DEE). The application of Fourier-transform infrared (FTIR) spectroscopy to the analysis of adsorbed C₆H₆ has revealed the presence of hydroxyl groups exhibiting varying degrees of proton-donating mobility. This finding has enabled the correlation of the structure of the active sites with the process’s selectivity. The results underscore the key function of OH-group localization and framework geometry in the control of form-selective reactions. Full article

Enhancing the utilization rate of waste glass in concrete is crucial for achieving solid waste reduction and low carbon emissions in the construction industry. This study employs the method of simultaneously replacing fine aggregate and cementitious materials in concrete with glass sand and glass powder to prepare composite waste glass concrete (CGC). The compressive strength, alkali–silicate expansion, and thermal properties of CGC were investigated experimentally. The experimental results show that the pozzolanic activity of fine glass powder in CGC can effectively mitigate the ASR reaction, enhance glass utilization, and allow the glass content to reach up to 17.79% of the total concrete mass. The thermal conductivity of the compounded waste glass concrete decreased linearly with increasing temperature, and the specific heat capacity showed three distinct peaks in the range of 180–800 °C, which were caused by chemical dehydration, quartz phase transition, and CaCO₃ decarbonization, respectively. Furthermore, to examine the impact of replacement mode on the high-temperature resistance of waste glass concrete, the residual strength, physical properties, and microstructure of the concrete were evaluated. It was found that the residual strength ratio of CGC (0.73) exhibited a distinct advantage at 600 °C. At this time, the melting effect of glass can reduce the pore size of concrete and transform large pores into capillary pores. However, as the temperature rises to 800 °C, the melting effect of glass no longer alleviates the high-temperature damage to concrete, and the degree of decomposition of hydration products determines the concrete strength. Full article

The rational development of single-atom catalysts (SACs) for selective formic acid dehydrogenation (FAD) requires an atomic-scale understanding of metal–support interactions and electronic modulation. In this study, spin-polarized density functional theory (DFT) calculations were performed to systematically examine platinum-group SACs anchored on graphitic carbon nitride (g-C₃N₄). The findings reveal that Pd and Au SACs exhibit superior selectivity toward the dehydrogenation pathway, lowering the free energy barrier by 1.42 eV and 1.39 eV, respectively, compared to the competing dehydration route. Conversely, Rh SACs demonstrate limited selectivity due to nearly equivalent energy barriers for both reaction pathways. Stability assessments indicate robust metal–support interactions driven by d–p orbital hybridization, while a linear correlation is established between the d-band center position relative to the Fermi level and catalytic selectivity. Additionally, charge transfer (ranging from 0.029 to 0.467 e) substantially modulates the electronic structure of the active sites. These insights define a key electronic descriptor for SAC design and offer a mechanistic framework for optimizing selective hydrogen production. Full article