Catalysts, Volume 12, Issue 6 (June 2022) – 101 articles

The replacement of noble metal catalysts by abundant iron as an active compound in CO oxidation is of ecologic and economic interest. However, improvement of their catalytic performance to the same level as state-of-the-art noble metal catalysts requires an in depth understanding of their working principle on an atomic level. As a contribution to this aim, a series of iron oxide catalysts with varying Fe loadings from 1 to 20 wt% immobilized on a γ-Al₂O₃ support is presented here, and a multidimensional structure–activity correlation is established. The CO oxidation activity is correlated to structural details obtained by various spectroscopic, diffraction, and microscopic methods, such as PXRD, PDF analysis, DRUVS, Mössbauer spectroscopy, STEM-EDX, and XAS. Low Fe loadings lead to less agglomerated but high percentual amounts of isolated, tetrahedrally coordinated iron oxide species, while the absolute amount of isolated species reaches its maximum at high Fe loadings. Consequently, the highest CO oxidation activity in terms of turnover frequencies can be correlated to small, finely dispersed iron oxide species with a large amount of tetrahedrally oxygen coordinated iron sites, while the overall amount of isolated iron oxide species correlates with a lower light-off temperature. Full article

CuCe mixed oxide is one of the most studied catalytic systems for preferential CO oxidation (CO-PrOx) for the purification of hydrogen-rich gas stream. In this study, a series of ceria supports were prepared via a citrates-hydrothermal route by altering the synthesis parameters (concentration and temperature). The resulting supports were used for the preparation of CuCe mixed-oxide catalysts via wet impregnation. Various physicochemical techniques were utilized for the characterization of the resulting materials, whereas the CuCe oxide catalysts were assessed in CO-PrOx reaction. Through the proper modification of the hydrothermal parameters, CeO₂ supports with tunable properties can be formed, thus targeting the formation of highly active and selective catalysts. The nature of the reduced copper species and the optimum content in oxygen vacancies seems to be the key factors behind the remarkable catalytic performance of a CO-PrOx reaction. Full article

Activated bentonites are low-cost acid catalysts used in several reactions. However, their application at an industrial scale is affected by the formation of colloidal suspensions when these bentonites are in aqueous solutions. In order to overcome these limitations, this work proposes obtaining a catalyst based on a composite containing natural bentonite within a silica–resin structure, which allows separating and re-utilizing the catalyst more easily and without centrifugal filtration requirements. By means of characterization techniques, the present study determined that the activated bentonite composite presented a total specific surface area of ~360 m² g⁻¹, ~4 mmol of acid sites per gram of bentonite, and sites with strong acid strength, all of which bestowed activity and selectivity in the solketal synthesis reaction from glycerol and acetone, reaching equilibrium conversion within a short reaction time. Furthermore, the present work developed a Langmuir–Hinshelwood–Hougen–Watson kinetic model, achieving an activation energy of 50.3 ± 3.6 kJ mol⁻¹ and a pre-exponential factor of 6.4 × 10⁶ mol g⁻¹ L⁻¹ s⁻¹, which are necessary for reactor design. Full article

The photocatalytic transformation of CO₂ to valuable man-made feedstocks is a promising method for balancing the carbon cycle; however, it is often hampered by the consumption of extra hole scavengers. Here, a synergistic redox system using photogenerated electron-hole pairs was constructed by employing a porous carbon nitride with many cyanide groups as a metal-free photocatalyst. Selective CO₂ reduction to CO using photogenerated electrons was achieved under mild conditions; simultaneously, various alcohols were effectively oxidized to value-added aldehydes using holes. The results showed that thermal calcination process using ammonium sulfate as porogen contributes to the construction of a porous structure. As-obtained cyanide groups can facilitate charge carrier separation and promote moderate CO₂ adsorption. Electron-donating groups in alcohols could enhance the activity via a faster hydrogen-donating process. This concerted photocatalytic system that synergistically utilizes electron-hole pairs upon light excitation contributes to the construction of cost-effective and multifunctional photocatalytic systems for selective CO₂ reduction and artificial photosynthesis. Full article

Photoelectro-Fenton (PEF) process can continuously promote the occurrence of Fenton reaction and the generation of active species, which is an advanced oxidation technology for pollutant degradation. However, the lack of bifunctional catalysts restricts the development of PEF technology. In this study, the electronic rearrangement MOF-525 modified by metalloporphyrin (named MOF-525-Fe/Zr) was prepared, to load on the carbon felt as a novel cathode catalyst, which is used in PEF process. A series of characterization and photoelectric chemical properties tests combined with DFT calculation showed that the modification of MOF-525 could not only have the large specific surface area and multistage pore structure but also co-stimulate the metal-to-ligand charge transfer (MLCT) and ligand-to-cluster charge transfer (LCCT) by photoelectric synergy. These charge transitions provide periodic electron donor-acceptor conduction paths in MOF-525-Fe/Zr, which can improve the active species formation and transfer efficiency. Owing to their favorable pore and electronic structure as well as stability, MOF-525-Fe/Zr shows great promise for the application in the catalytic process of PEF. Sulfamethoxazole (SMX) degradation was enhanced by MOF-525-Fe/Zr with the TOC removal rate above 75% both in river water and tap water. Finally, the reasonable pathway of PEF catalytic degradation of SMX was proposed by HPLC-MS analysis. In conclusion, this study provides a new idea for reconstructing the electronic structure of MOFs catalyst and broadening the practical application of PEF technology. Full article

Sodium-ion batteries (SIBs) are promising candidates for the replacement of lithium-ion batteries (LIBs) because of sodium’s abundant reserves and the lower cost of sodium compared to lithium. This is a topic of interest for developing novel anodes with high storage capacity. Owing to their low cost, high stability, and conductivity, carbon-based materials have been studied extensively. However, sp²-C based carbon materials have low-rate capacities. Intensive density functional theory calculations have been implemented to explore the applicability of α, β, and γ graphyne nanotubes (αGyNTs, βGyNTs, and γGyNTs, respectively) as SIB anodes. Results suggest that (3, 0)-αGyNT, (2, 2)-βGyNT, and (4, 0)-γGyNT have, respectively, maximum Na storage capacities of 1535, 1302, and 1001 mAh/g, which exceeds the largest reported value of carbon materials (N-doped graphene foams with 852.6 mAh/g capacity). It was determined that αGyNTs have the largest storage capacity of the three types because they possess the largest specific surface area. Moreover, the larger pores of αGyNTs and βGyNTs allow easier diffusion and penetration of Na atoms compared to those of γGyNTs, which could result in better rate capacity. Full article

The water pollution caused by industry emissions makes effluent treatment a serious matter that needs to be settled. Heterogeneous Fenton oxidation has been recognized as an effective means to degrade pollutants in water. Attapulgite can be used as a catalyst carrier because of its distinctive spatial crystal structure and surface ion exchange. In this study, iron ions were transported on attapulgite particles to generate an iron-supporting attapulgite particles catalyst. BET, EDS, SEM and XRD characterized the catalysts. The particle was used as a heterogeneous catalyst to degrade rhodamine B (RhB) dye in wastewater. The effects of H₂O₂ concentration, initial pH value, catalyst dosage and temperature on the degradation of dyes were studied. The results showed that the decolorization efficiency was consistently maintained after consecutive use of a granular catalyst five times, and the removal rate was more than 98%. The degradation and mineralization effect of cationic dyes by granular catalyst was better than that of anionic dyes. Hydroxyl radicals play a dominant role in RhB catalytic degradation. The dynamic change and mechanism of granular catalysts in catalytic degradation of RhB were analyzed. In this study, the application range of attapulgite was widened. The prepared granular catalyst was cheap, stable and efficient, and could be used to treat refractory organic wastewater. Full article

A morphological strategy consisting of nanocasting synthesis of nickel aluminate spinel precursor was addressed. Two nanocasted catalysts were synthesized involving different template-removal procedures (i.e., Teflon-assisted calcination vs. NaOH washing) for spinel recovery. As a reference, spinel NiAl₂O₄ supported by SBA-15 and bare nickel aluminate spinel were selected. The obtained solids were characterized in detail, examining their textural, acid–base, structural and compositional characteristics, either in the calcined or reduced forms. The as-obtained catalysts’ performance was evaluated in the aqueous-phase reforming of glycerol at 235 °C and 35 bar. Exhausted samples were also characterized to enlighten changes in catalyst properties during the aqueous-phase reaction. NiAl/SBA-15 and NiAl-NCF catalyst showed very poor catalytic performance for the glycerol transformation. NiAl-NCN catalyst presented improved activity with respect to NiAl, with a 20% higher hydrogen production rate but, as a drawback, higher methane formation for a whole range of glycerol conversions. Exhausted catalyst indicated nickel oxidized in liquid phase reaction. Full article

The COVID-19 pandemic has been transformed into one of the main worldwide challenges, in recent years. For controlling symptoms that are caused by this disease (e.g., chills or fever, shortness of breath and/or difficulty in breathing, cough, sore throat, fatigue, headache, muscle aches, the new loss of tastes and/or smells, congestion or runny nose, nausea, vomiting and/or diarrhea), lots of medicines including analgesics, mucolytics, and anti-biotic/viral/inflammatory drugs have been frequently prescribed. As these medicines finally contaminate terrestrial and aquatic habitats by entering surface waterways through pharmaceutical production and excreting trace amounts of waste after human usage, they have negative impacts on wildlife’s health and ecosystem. Residual drugs in water have the potential to harm aquatic creatures and disrupt their food chain as well as the breeding cycle. Therefore, proper degradation of these broadly used medicines is highly crucial. In this work, the use of nanomaterials applicable in photocatalytic degradations of analgesics (e.g., acetaminophen, aspirin, ibuprofen, and naproxen), mucolytics (e.g., ambroxol), antibiotics (e.g., azithromycin and quinolones including hydroxychloroquine and chloroquine phosphate), anti-inflammatory glucocorticoids (e.g., dexamethasone and cortisone acetate), antihistamines (e.g., diphenhydramine), H2 blockers (e.g., famotidine), anthelmintics (e.g., praziquantel), and finally antivirals (e.g., ivermectin, acyclovir, lopinavir/ritonavir, favipiravir, nitazoxanide, and remdesivir) which widely used in controlling/treating the coronavirus have been reviewed and discussed. Full article

Sodium titanate nanorods were synthesized by a hydrothermal method and subsequently modified with an iron precursor. For comparison, Fe₂O₃ nanocubes were also obtained through a similar hydrothermal treatment. Pristine, Fe-modified nanorods and Fe₂O₃ nanocubes were suspended in diluted ammonia solutions (20 ppm) and exposed to ozone and simulated light irradiation. Ammonia abatement, together with the resulting nitrogen-containing products (NO₃⁻), was monitored by ion chromatography measurements. The generation of reactive oxygen species (·OH and O₂⁻) in the investigated materials and their photoelectrochemical behaviour were also investigated. Morphological and structural characterizations (SEM, XRD, XRF, UV–Vis, H₂-TPR, NH₃-TPD, PL, PZC) of the studied catalysts were correlated with their activity for ammonia degradation with ozone- and photo-assisted oxidation. An increase in ammonia conversion and a decreasing amount of NO₃⁻ were achieved by combining the above-mentioned processes. Full article

In a batch reactor, the EF advanced oxidation decolorization of aqueous solutions of methyl orange MO, a commercial azo reactive textile dye, was investigated in the presence of two different electrodes. The evaluation included various operational variables such as the I_C current intensity (60 mA, 80 mA, and 100 mA), initial concentration of pollutant MO (20 mg/L, 40 mg/L, and 60 mg/L), initial pH of solution (3, 5, and 7), temperature of solution (20 °C, 30 °C, and 50 °C), and initial concentration of catalyst [Fe²⁺] (0.1 mM, 0.2 mM, and 0.3 mM) on the discoloration rate. A Box-Behnken Design of Experiment (BBD) was used to optimize the parameters that directly affect the Electro-Fenton (EF) process. Under the optimal experimental conditions such as [Fe²⁺] = 0.232 mM, pH = 3, I_C = 80 mA, [MO] = 60 mg/L, and T = 30 ± 0.1 °C, the maximum discoloration rate achieved was 94.9%. The discoloration of the aqueous MO solution during the treatment time was confirmed by analysis of the UV-visible spectrum. After a review of the literature on organic pollutant degradation, the EF system provided here is shown to be one of the best in terms of discoloration rate when compared to other AOPs. Full article

The solvent effect in the catalytic depolymerization of the three-dimensional network of lignin is discussed based on recent reports in this field. Also, the results of an experimental study on the depolymerization of kraft lignin are presented. The cleavage of ether bonds within the lignin network was promoted using ruthenium and platinum on activated carbon (Ru/C and Pt/C), two common hydrogenolysis catalysts. Methanol was identified as a suitable solvent. Noteworthy, under the chosen reaction conditions, the catalysts showed significant resilience to the sulfur present in kraft lignin. The conversion of kraft lignin to lignin oil was strongly affected by the reaction conditions. Although the Ru/C catalyst provided the highest yield at supercritical conditions, a maximum yield was obtained for the Pt/C catalyst at near-critical conditions. The formation of guaiacol, 4-alkylguaiacols, isoeugenol, and 4-ethyl-2,6-dimethoxyphenol is attributed to the solubility of oligomeric lignin fragments in the solvent and the relative propensity of specific groups to adsorb on the catalyst surface. Full article

Densely aligned CoS₂ nanowires (NWs) on chemically durable stainless steel fibers felt (SSF) substates were synthesized by thermal sulfuring Co₃O₄ NWs, which were oxidized from hydrothermal synthesized Co(OH)_y(CO₃)_(1−0.5y)·nH₂O NWs precursors. The effect of sulfuration temperature on the composition, morphology, and HER performance of the products was studied in detail. The results show that the high purity together with the enlarged density of active sites given by the twisted morphology of the CoS₂ NWs sulfured at 500 °C guarantee its superior hydrogen evolution reaction (HER) performance compared with other samples sulfured at lower temperatures. Full article

MnO₂-CeO₂/PG-FA catalysts were prepared by supporting MnO₂-CeO₂ to PG-FA and used to remove Hg⁰ in simulated flue gas. The results show that MnO₂-CeO₂/PG-FA catalyst had excellent and stable Hg⁰ removal activity, which was mainly due to the combination effect of the catalytic oxidation activity by MnO₂-CeO₂ and the adsorption ability by PG-FA. Mn8-Ce0.5/PG-FA (with 8.0% MnO₂ and 0.5% CeO₂ loading) catalyst showed the highest Hg⁰ removal efficiency at 140 °C and Hg⁰ removal efficiency could be maintained above 95% with the space velocity of 6000 h⁻¹ and Hg⁰ concentration of 160 μg/m³. O₂ promoted Hg⁰ removal by MnO₂-CeO₂/PG-FA catalyst, while SO₂ and H₂O had inhibitory effects. In the presence of O₂, the inhibitory effect of SO₂ and H₂O can be obviously weakened. MnO₂-CeO₂/PG-FA catalysts were characterized with scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption experiments (TPD). The results of SEM and XRD showed that the active components MnO₂-CeO₂ dispersed well on the surface of PG-FA support. The results of XPS and TPD show that the Hg⁰ removal process over MnO₂-CeO₂/PG-FA catalyst included adsorption and oxidation, HgO and HgSO₄ were generated and adsorbed on the catalyst. MnO₂-CeO₂/PG-FA catalyst also showed excellent regeneration performance after Hg⁰ removal. Full article

The ISO standard 22197-1:2016 used for the evaluation of the photocatalytic nitric oxide removal has a main drawback, which allows only the decrease of nitric oxide to be determined specifically. The remaining amount, expressed as “NO₂”, is considered as a sum of HNO₃, HONO NO₂, and other nitrogen-containing species, which can be potentially formed during the photocatalytic reaction. Therefore, we developed a new methodology combining our custom-made analyzers, which can accurately determine the true NO₂ and HONO species, with the conventional NO one. Their function was validated via a photocatalytic experiment in which 100 ppbv of either NO or NO₂ dispersed in air passed over (3 L min⁻¹) an Aeroxide© TiO₂ P25 surface. The gas-phase analysis was complemented with the spectrophotometric determination of nitrates $\left({\mathrm{NO}}_3^{-}\right)$and/or nitrites (${\mathrm{NO}}_2^{-})$deposited on the P25 layer. Importantly, an almost perfect mass balance (94%) of the photocatalytic NOx abatement was achieved. The use of custom-made analyzers enables to obtain (i) no interference, (ii) high sensitivity, (iii) good linearity in the relevant concentration range, (iv) rapid response, and (v) long-term stability. Therefore, our approach enables to reveal the reaction complexity and is highly recommended for the photocatalytic NOx testing. Full article

The multicomponent reaction of aldehydes, amines, and alkynes, known as A³ coupling, yields propargylamines, a valuable organic scaffold, and has received significant interest and attention in the last years. In order to fully realise the potential of the metal-based catalytic protocols that facilitate this transformation, we summarise substrates, in situ and well-characterised synthetic methods that provide this scaffold and attempt a monumental classification considering several variables (Metal, Coordinating atom(s), Ligand type and name, in-situ or well-characterised, co-catalyst, catalyst and ligand Loading (mol%), solvent, volume, atmosphere, temperature, microwave, time, yield, selectivity (e.e. d.r.), substrate name, functionality, loading (amines, aldehydes, alkynes), and use of molecular sieves). This pioneering work creates a valuable database that contains 2376 entries and allows us to produce graphs and better visualise their impact on the reaction. Full article

The economic uncertainty associated with cellulosic bioethanol can be overcome through the inclusion of cheap substrates and methodologies that can extend the shelf life of cellulolytic enzymes. In this study, wild Trichoderma viride was used to produce cellulases, media formulation studies were conducted to enhance the cellulase production further and immobilization strategies were tested for stable cellulase–iron oxide magnetic nanoparticle coupling. Out of the seven different production media designed, media containing glucose, wheat bran, cellulose and corn steep liquor supported the highest biomass growth (60 Packed cell volume) and cellulase formation (7.4 U/mL), and thus was chosen for the fiscal analysis at a larger scale (1000 m³). The profitability of the cellulase production process was assessed to be 20.86%, considering both the capital expenditure and operating expenses. Further, the effect of cost of different carbon sources, nitrogen sources and cellulase yields on the annual operating costs was explored, which led to the choice of delignified sugarcane bagasse, corn steep liquor and productivity levels to be respective decisive factors of the overall cost of the cellulase production. Likewise, the break-even period of such a large-scale operation was gauged given the market price of cellulases at USD 17 for 10⁵ U of cellulases. Moreover, enzyme immobilization led to enhanced cellulase shelf life and ultimately contributed toward saccharification cost reduction. Full article

In this study, three solid acid catalysts, namely mesoporous aluminophosphate-supported 12-tungstophosphoric heteropoly acid (HPW/MAP), mesoporous aluminosilicate-supported 12-tungstophosphoric heteropoly acid (HPW/MAS), and gamma alumina-supported 12-tungstophosphoric heteropoly acid (HPW/γ-Al₂O₃) were prepared and characterized. Mesoporous aluminophosphate (MAP) and mesoporous aluminosilicate (MAS) were synthesized via sol-gel and hydrothermal methods, respectively, and 25 wt.% of 12-tungstophosphoric heteropoly acid (HPW) was immobilized on the support materials using the wet impregnation method. The features of the fabricated catalysts were comprehensively investigated using various techniques such as BET, XRD, NH₃-TPD, TGA, and TEM. The surface area of the supported catalysts decreased after HPW impregnation according to BET results, which indicates that HPW loaded on the supports and inside of their pores successfully. The density and strengths of the acid sites of the support materials and the catalysts before reaction and after regeneration were determined by the NH₃-TPD technique. Accordingly, an increase in acidity was observed after HPW immobilization on all the support materials. The catalytic performance of the catalysts was studied through alcoholysis reaction using unrefined green seed canola oil as the feedstock. The maximum biodiesel yield of 82.3% was obtained using 3 wt.% of HPW/MAS, with a methanol to oil molar ratio of 20:1, at 200 °C and 4 MPa over 7 h. The reusability study of HPW/MAS showed that it can maintain 80% of its initial activity after five runs. Full article

The dynamic growth in green organic synthetic methodologies for diverse heterocyclic scaffolds has substantially contributed to the field of medicinal chemistry over the last few decades. The use of hybrid metal nanocatalysts (NCs) is one such benign strategy for ensuring the advancement of modern synthetic chemistry by adhering to the principles of green chemistry, which call for a sustainable catalytic system that converts reacting species into profitable chemicals at a faster rate and tends to reduce waste generation. The metal nanoparticles (NPs) enhance the exposed surface area of the catalytic active sites, thereby making it easier for reactants and metal NCs to have an effective interaction. Several review articles have been published on the preparation of metal NCs and their uses for various catalytic heterocyclic transformations. This review will summarize different metal NCs for the efficient green synthesis of various O-heterocycles. Furthermore, the review will provide a concise overview of the role of metal NCs in the synthesis of O-heterocycles and will be extremely useful to researchers working on developing novel green and simple synthetic pathways to various O-heterocyclic-derived molecules. Full article

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence of additional hydride sources. The described reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). The bimetallic Ir(I) involving triNHC carbene ligands exhibits high TONs, and the reaction mechanism, including the bimetallic Ir(triNHC) catalyst, is proposed based on mechanistic studies. Full article

Biofuels produced via thermochemical conversions of waste biomass could be sustainable alternatives to fossil fuels but currently require costly downstream upgrading to be used in existing infrastructure. In this work, we explore how a low-cost, abundant clay mineral, bentonite, could serve as an in situ heterogeneous catalyst for two different thermochemical conversion processes: pyrolysis and hydrothermal carbonization (HTC). Avocado pits were combined with 20 wt% bentonite clay and were pyrolyzed at 600 °C and hydrothermally carbonized at 250 °C, commonly used conditions across the literature. During pyrolysis, bentonite clay promoted Diels–Alder reactions that transformed furans to aromatic compounds, which decreased the bio-oil oxygen content and produced a fuel closer to being suitable for existing infrastructure. The HTC bio-oil without the clay catalyst contained 100% furans, mainly 5-methylfurfural, but in the presence of the clay, approximately 25% of the bio-oil was transformed to 2-methyl-2-cyclopentenone, thereby adding two hydrogen atoms and removing one oxygen. The use of clay in both processes decreased the relative oxygen content of the bio-oils. Proximate analysis of the resulting chars showed an increase in fixed carbon (FC) and a decrease in volatile matter (VM) with clay inclusion. By containing more FC, the HTC-derived char may be more stable than pyrolysis-derived char for environmental applications. The addition of bentonite clay to both processes did not produce significantly different bio-oil yields, such that by adding a clay catalyst, a more valuable bio-oil was produced without reducing the amount of bio-oil recovered. Full article

The mechanism in palladium-catalyzed carboxylation of thiophene and CO₂ is investigated using the density functional theory (DFT) calculations, including three consecutive steps of the formation of carbanion through breaking the C–H bond(s) via the palladium acetate, the elimination of acetic acid and the nucleophile attacking the weak electrophile CO₂ to form C–C bond. Results show that the C–C bond is formed through taking the three-membered cyclic conformation arrangement involving the interaction of the transition metal and the CO₂, and the CO₂ insertion step is the rate-determining step for this entire reaction process. Aiming to precisely disclose what factor determine the origin of the activation energy barrier in this carboxylation reaction, the distortion/interaction analysis is performed along with the entire reaction coordinate. Full article

Chitin is one of the most abundant biopolymers on Earth but under-utilized. The effective conversion of chitin biomass to useful chemicals is a promising strategy to make full use of chitin. Among chitin-derived compounds, some furan derivatives, typically 5-hydroxymethylfurfural and 3-acetamido-5-acetylfuran, have shown great potential as platform compounds in future industries. In this review, different catalytic systems for the synthesis of nitrogen-free 5-hydroxymethylfurfural and nitrogen-containing 3-acetamido-5-acetylfuran from chitin or its derivatives are summarized comparatively. Some efficient technologies for enhancing chitin biomass conversion have been introduced. Last but not least, future challenges are discussed to enable the production of valuable compounds from chitin biomass via greener processes. Full article

Natural bearing (raw and calcined at 500 °C) and iron-enriched (impregnation and pillaring) montmorillonitic clay samples were prepared. The obtained samples were characterized (X-ray diffraction, Fourier Transformed Infrared Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy) and evaluated as catalysts in catalytic wet oxidation of Brilliant Green and Crystal Violet. Experiments were conducted in the same conditions (0.5 g catalysts, 300 mL air/min or 0.5 mL H₂O₂, 25 mL of dye solution, 25 °C, initial solution pH = 6.0, for 3 h) in thermostated batch reaction tubes. Process evolution was followed using UV-Vis spectrometry (200–1100 cm⁻¹) and total organic carbon. Dye removal efficiencies (decolorization) between 98 and 99% were determined, while total organic carbon removal efficiencies were calculated to be in the 53–98% range. Iron leakage investigation showed that iron is lost in higher amounts for the catalysts prepared using the impregnation method by comparison with the pillared sample. Full article

Compressed natural gas (CNG) and liquefied petroleum gas (LPG) are included in the group of promoted transport fuel alternatives in Europe. Most studies on emissions factors are based on old technology CNG and LPG fueled vehicles. Furthermore, there are not many data at low ambient temperatures, on-road driving, or unregulated pollutants, such as ammonia (NH₃). In this study we measured the emissions of one Euro 6b CNG light commercial vehicle, one Euro 6b and one Euro 6d-Temp bi-fuel LPG passenger car, one Euro 6d-Temp bi-fuel CNG passenger car, and four Euro 6d-Temp CNG passenger cars. Tests included on-road testing and worldwide harmonized light vehicles test cycles (WLTC) in the laboratory with cold and hot engine, at 23 °C and −7 °C. The results showed 10–23% CO₂ savings in gas modality compared to gasoline, lower CO and particle number emissions, and relatively similar total and non-methane hydrocarbons and NO_x emissions. The ammonia emissions were high for all vehicles and fuels; higher than gasoline and diesel vehicles. The results also showed that, following the introduction of the real-driving emissions regulation, even though not applicable to the examined vehicles, Euro 6d-Temp vehicles had lower emissions compared to the Euro 6b vehicles. Full article

Phospholipase B (PLB) harbors three distinct activities with broad substrate specificities and application fields. Its hydrolyzing of sn-1 and sn-2 acyl ester bonds enables it to catalyze the production of L-alpha-glycerylphosphorylcholine (L-α-GPC) from phosphatidylcholine (PC) without speed-limiting acyl migration. This work was intended to obtain high-level active PLB and apply it to establish an efficient system for L-α-GPC synthesis. PLB from Pseudomonas fluorescens was co-expressed with five different molecular chaperones, including trigger factor (Tf), GroEL-GroES (GroELS), DnaK-DnaJ-GrpE (DnaKJE), GroELS and DnaKJE, or GroELS and Tf or fused with maltose binding protein (MBP) in Escherichia coli BL21(DE3) to improve PLB expression. PLB with DnaKJE-assisted expression exhibited the highest catalytic activity. Further optimization of the expression conditions identified an optimal induction OD₆₀₀ of 0.8, IPTG concentration of 0.3 mmol/L, induction time of 9 h, and temperature of 25 °C. The PLB activity reached a maximum of 524.64 ± 3.28 U/mg under optimal conditions. Subsequently, to establish an efficient PLB-catalyzed system for L-α-GPC synthesis, a series of organic-aqueous mixed systems and surfactant-supplemented aqueous systems were designed and constructed. Furthermore, the factors of temperature, reaction pH, metal ions, and substrate concentration were further systematically identified. Finally, a high yield of 90.50 ± 2.21% was obtained in a Span 60-supplemented aqueous system at 40 °C and pH 6.0 with 0.1 mmol/L of Mg²⁺. The proposed cost-effective PLB production and an environmentally friendly PLB-catalyzed system offer a candidate strategy for the industrial production of L-α-GPC. Full article

It has been shown that structured lipids, formed in the process of enzymatic modification of natural hard fat with walnut oil, are capable of stabilizing emulsion systems without the need to add additional emulsifiers. This is especially true for emulsions containing fat formed during enzymatic modification when the amount of added water to the reaction catalyst was in the range of 12–16 wt%. Physicochemical evaluations, i.e., the average particle size, its growth, distribution, and dispersity coefficient, were comparable with the reference emulsion where the emulsifier was lecithin, well-known for its emulsifying properties. Microstructure studies also confirmed the above observations. Rheological studies performed on a set of emulsions containing structured lipids of variable composition confirmed that interesterified lipid blends can be directly utilized as a fat base in the preparation of stable emulsions. The consistency, thixotropic behavior, long-term shelf life, and thermal stability of these emulsions were found to be comparable to systems stabilized with conventional emulsifiers, i.e., sunflower lecithine. Our approach offers the opportunity for the preparation of stable emulsion systems, free from additional emulsifiers, for the food or cosmetics industry, which is extremely important from the point of view of the preparation of products free from allergens. Full article

HCN catalytic hydrolysis mechanism over Cu-ZSM-5 was investigated based on the density functional theory (DFT) with 6-31++g (d, p) basis set. Five paths (A, B, C, D, and E) were designed. For path A and path B, the first step is the nucleophilic attack of water molecule. Next, the hydrogen atom of H₂O is transferred to the nitrogen atom first for path A, while in path B, the hydrogen atom of the HCN is first transferred to the nitrogen atom. In path C, HCN isomerizes to HNC initially, and the remaining steps are similar to that of path A. The H atom of HCN shifts to Cu-ZSM-5 initially in path D, and the H atom is transferred to N atom subsequently. The last step is the attack on water molecule. The first step for path E is similar to that of path D. The next step is the attack on water molecule, in which the H atom of water molecule shifts to N atom, and the H on Cu-ZSM-5 shifts to the N atom. Meanwhile, the H atom of oxygen atom is transferred to the N atom. The results show that path C is the most favorable path, with the lowest free energy barrier (35.45 kcal/mol). The results indicate that the Cu-ZSM-5 strongly reduces the energy barrier of HCN and isomerizes to HNC, making it an effective catalyst for HCN hydrolysis. Full article

Exploring new raw starch-hydrolyzing α-amylases and understanding their biochemical characteristics are important for the utilization of starch-rich materials in bio-industry. In this work, the biochemical characteristics of a novel raw starch-degrading α-amylase (HL11 Amy) from Roseateles terrae HL11 was firstly reported. Evolutionary analysis revealed that HL11Amy was classified into glycoside hydrolase family 13 subfamily 32 (GH13_32). It contains four protein domains consisting of domain A, domain B, domain C and carbohydrate-binding module 20 (CMB20). The enzyme optimally worked at 50 °C, pH 4.0 with a specific activity of 6270 U/mg protein and 1030 raw starch-degrading (RSD) U/mg protein against soluble starch. Remarkably, HL11Amy exhibited activity toward both raw and gelatinized forms of various substrates, with the highest catalytic efficiency (k_cat/K_m) on starch from rice, followed by potato and cassava, respectively. HL11Amy effectively hydrolyzed cassava pulp (CP) hydrolysis, with a reducing sugar yield of 736 and 183 mg/g starch from gelatinized and raw CP, equivalent to 72% and 18% conversion based on starch content in the substrate, respectively. These demonstrated that HL11Amy represents a promising raw starch-degrading enzyme with potential applications in starch modification and cassava pulp saccharification. Full article

Cu and Co have shown superior catalytic performance to other transitional elements, and layered double hydroxides (LDHs) have presented advantages over other heterogeneous Fenton catalysts. However, there have been few studies about Co–Cu LDHs as catalysts for organic degradation via the Fenton reaction. Here, we prepared a series of Co–Cu LDH catalysts by a co-precipitation method under different synthesis temperatures and set Rhodamine B (RhB) as the target compound. The structure-performance relationship and the influence of reaction parameters were explored. A study of the Fenton-like reaction was conducted over Co–Cu layered hydroxide catalysts, and the variation of synthesis temperature greatly influenced their Fenton-like catalytic performance. The Co–Cu_t=65°C catalyst with the strongest LDH structure showed the highest RhB removal efficiency (99.3% within 30 min). The change of synthesis temperature induced bulk-phase transformation, structural distortion, and metal–oxygen (M–O) modification. An appropriate temperature improved LDH formation with defect sites and lengthened M–O bonds. Co–Cu LDH catalysts with a higher concentration of defect sites promoted surface hydroxide formation for H₂O₂ adsorption. These oxygen vacancies (Ovs) promoted electron transfer and H₂O₂ dissociation. Thus, the Co–Cu LDH catalyst is an attractive alternative organic pollutants treatment. Full article