Catalysts, Volume 9, Issue 6 (June 2019) – 77 articles

High-performance oxygen evolution reaction (OER) electrocatalysts are needed to produce hydrogen for energy generation through a carbon-free route. In this work, the solution combustion synthesis (SCS) method was employed to synthesize mixed phases of Co- and Mn-based oxides, and the relationships between the crystalline structure and the catalytic properties in the mixed phases were established. The mixed phases of Co- and Mn-based oxides shows promising OER properties, such as acceptable overpotential (450 mV for 10 mA∙cm⁻²) and Tafel slope (35.8 mV∙dec⁻¹), highlighting the use of the mixed phases of Co- and Mn-based oxides as a new efficient catalysts for water splitting. Electronic structure of the mixed phases of Co- and Mn based oxides is studied in detail to give insight for the origin of high catalytic activities. In addition, excellent long-term stability for OER in alkaline media is achieved for the mixed phase of Co- and Mn based oxides. Full article

This article attempts to study changes in the microstructure of solid solutions with the perovskite structure La_0.5Ca_0.5Mn_0.5Fe_0.5O₃ under the action of the methane oxidation reaction medium. By the methods of XRD, XPS and HRTEM the initial condition of the structure and the surface of the perovskite were both investigated. A feature of the structure of this solid solution is the presence of planar defects in the direction of the planes (101). After the methane oxidation reaction, a similar study of perovskite structure was conducted to obtain the changes. It was shown that under the action of the reaction medium, Ca_1−xMn_xO particles form on the surface of the perovskite phase, while planar defects in La_0.5Ca_0.5Mn_0.5Fe_0.5O₃ structure remain. In situ XRD experiments on perovskite calcination in helium current up to 750 °C showed the formation of a similar Ca_1−xMn_xO phase on the perovskite surface. Full article

Photocatalytic degradation of pollutants is one of the cleanest technologies for environmental remediation. Herein, we prepared NiO/NiTiO₃ heterostructure nanofiber (200 nm) films by electrospinning and high temperature heat treatment, using nickel acetate and tetrabutyltitanate as nickel and titanium sources, respectively. The NiO/NiTiO₃ heterostructure has advantages of good photodegradation rate constant and stability. By controlling the temperature, we can optimize the phase composition of these nanofibers for better photocatalytic performance. Based on our findings of the Rhodamine B degradation results, the best performance was obtained with 10% NiO and 90% NiTiO₃; 92.9% of the Rhodamine B (5 mg/L) was degraded after reaction under full spectrum irradiation for 60 min. More importantly, the repeating test showed that these nanofiber films can remain active and stable after multiple cycles. The mechanisms of the photocatalysis reactions were also discussed. This demonstration provides a guideline in designing a new photocatalyst that we hope will serve the environmental needs for this and the coming century. Full article

Titanium modified FeMgO_x catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO₄ and Mg(NO₃)₂ as precursors exhibited enhanced catalytic activity from 225 to 400 °C, with a maximum NO_x conversion of 100%. Iron oxides existed as γ-Fe₂O₃ in this catalyst. They exhibited highly enriched surface active oxygen and surface acidity, which were favorable for low-temperature selective catalytic reduction (SCR) reaction. Besides, it showed advantage in surface area, spherical particle distribution and pores connectivity. Amorphous iron-magnesium-titanium mixed oxides were the main phase of the catalysts using Fe(NO₃)₃ as a precursor. This catalyst exhibited a narrow T₉₀ of 200/250–350 °C. Side reactions occurred after 300 °C producing NO_x, which reduced the NO_x conversion. The strong acid sites inhibited the side reactions, and thus improved the catalytic performance above 300 °C. The weak acid sites appeared below 200 °C, and had a great impact on the low-temperature catalytic performance. Nevertheless, amorphous iron-magnesium-titanium mixed oxides blocked the absorption and activation between NH₃ and the surface strong acid sites, which was strengthened on the γ-Fe₂O₃ surface. Full article

Nano-sized palladium nanoparticles showed high catalytic activity with severe limitations in catalytic field due to the tendency to aggregate. A solid substrate with large specific surface area is an ideal carrier for palladium nanoparticles. In present work, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/[email protected]) composite catalysts were successfully designed and prepared by electrospinning and reduction methods using PEI/PCL elexctrospun fiber as carrier. The added PEI component effectively regulated the microscopic morphology of the PEI/PCL fibers, following a large number of pit structures which increased the specific surface area of the electrospun fibers and provided active sites for loading of the palladium particles. The obtained PEI/[email protected] catalysts for reductions of 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) exhibited extremely efficient, stable, and reusable catalytic performance. It was worth mentioning that the reaction rate constant of catalytic reduction of 4-NP was as high as 0.16597 s⁻¹. Therefore, we have developed a highly efficient catalyst with potential applications in the field of catalysis and water treatment. Full article

2D nanomaterials, with unique structural and electronic features, had been demonstrated as excellent photocatalysts, whose catalytic properties could be tunable with surface defect engineering. In this work, few-layer BiOBr nanosheets with oxygen vacancies (BiOBr-Ov) have been fabricated by a simple solvothermal reaction with the help of ethylene glycol. The obtained BiOBr-Ov exhibited the superior photocatalytic performance with a complete reduction of Cr(VI) (20 mg/L) within 12 min by visible light irradiation. Moreover, Cr(VI) with a high concentration (such as 30 mg/L) only requires 2 min to be photoreduced completely under solar light irradiation. The enhanced photocatalytic performance is contributed to the existence of oxygen vacancies. It has been proved by the results of electrochemical impedance and photocurrent that oxygen vacancies can effectively suppress recombination of photogenerated carriers. Full article

This study reports on the activity and stability of PdO/γ-AlOOH/γ-Al₂O₃ monolith catalysts, promoted with varying amounts of CeO₂, for CH₄ oxidation. Although the beneficial effects of CeO₂ have been reported for powdered catalysts, this study used a cordierite (2MgO.2Al₂O₃.5SiO₂) mini-monolith (400 cells per square inch, 1 cm diameter × 2.5 cm length; ~52 cells), washcoated with a suspension of γ-Al₂O₃ combined with boehmite (γ-AlOOH), followed by sequential deposition of Ce and Pd (0.5 wt.%) by wetness impregnation. The monolith catalysts’ CH₄ oxidation activity and stability were assessed in the presence of CO, CO₂, H₂O and SO₂ at low temperature (≤550 °C), relevant to emission control from lean-burn natural gas vehicles (NGVs). The CeO₂ loading (0 to 4 wt.%) did not significantly impact the adhesion and thermal stability of the washcoat, but CeO₂ reduced the inhibition of CH₄ oxidation by H₂O and SO₂. The catalyst activity, measured by temperature-programmed methane oxidation (TPO) in a dry feed gas with 0.07 vol.% CH₄, showed that adding CeO₂ to the γ-AlOOH/γ-Al₂O₃ washcoat suppressed the activity of the catalysts; whereas, CeO₂ improved the catalyst activity when H₂O (2 and 5 vol.%) was present in the feed gas. Moreover, adding CeO₂ decreased catalyst deactivation that occurred in the presence of 10 vol.% H₂O and 5 ppmv SO₂ at 500 °C, measured over a 25 h time-on-stream (TOS) period. The highest catalyst activity and stability for CH₄ oxidation in the presence of H₂O was obtained by adding 2 wt.% CeO₂ to the washcoat. Full article

The mainstream strategy for designing hydrogen electrocatalysts is to adjust their surface electronic structure; however, the conductivity of the electrocatalyst and the synergy with its substrate are still challenges to overcome. In this work, we report a carbon-doped Co-FeS₂/CoS₂ (C/Co-FeS₂/CoS₂) electrode, prepared via a hydrothermal process with carbon cloth (CC) as the substrate and carbon doping. The C/Co-FeS₂/CoS₂ electrode shows excellent catalytic activity in the hydrogen evolution reaction (HER) with an overpotential of 88 mV at a current density of −10 mA∙cm⁻² in 0.5 M H₂SO₄ solution. The Tafel slope is 66 mV∙dec⁻¹. Such superior performance is attributed to the high electrical conductivity of the electrocatalyst and its synergy with the substrate. Our study provides an efficient alternative in the field of electrocatalysis. Full article

Nanoporous gold (npAu) supports were prepared as disks and powders by corrosion of Au-Ag alloys. The npAu materials have pore sizes in the range of 40 nm as shown by scanning electron microscopy (SEM). The surface was modified by a self-assembled monolayer (SAM) with an azidohexylthioate and then functionalized by a zinc (II) phthalocyanine (ZnPc) derivative using “click chemistry”. By atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) the content of zinc was determined and the amount of immobilized ZnPc on npAu was calculated. Energy-dispersive X-ray (EDX) spectroscopy gave information about the spatial distribution of the ZnPc throughout the whole porous structure. NpAu and ZnPc are both absorbing light in the visible region, therefore, the heterogeneous hybrid systems were studied as photocatalysts for photooxidations using molecular oxygen. By irradiation of the hybrid system, singlet oxygen is formed, which was quantified using the photooxidation of 1,3-diphenylisobenzofuran (DPBF) as a selective singlet oxygen quencher. The illuminated surface area of the npAu-ZnPc hybrid system and the coverage of the ZnPc were optimized. The synergistic effect between the plasmon resonance of npAu and the photosensitizer ZnPc was shown by selective irradiation and excitation of only the phthalocyanine, the plasmon resonance of the npAu support and both absorption bands simultaneously, resulting in an enhanced photooxidation activity by nearly an order of magnitude. Full article

The aroylhydrazone Schiff bases 2-hydroxy-(2-hydroxybenzylidene)benzohydrazide and (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide have been used to synthesize the bi- and tri-nuclear Ni(II) complexes [Ni₂(L¹)₂(MeOH)₄] (1) and [Ni₃(HL²)₂(CH₃OH)₈]· (NO₃)₂ (2). Both complexes have been characterized by elemental analysis, spectroscopic techniques [IR spectroscopy and electrospray ionization-mass spectrometry (ESI-MS)], and single-crystal X-ray crystallography. The coordination behavior of the two ligands is different in the complexes: The ligand exhibits the keto form in 2, while coordination through enol form was found in 1. Herein, the catalytic activity of 1 and 2 has been compared with the nitroaldol condensation reaction under various conditions. Complex 2 exhibits the highest activity towards solvent-free conditions. Full article

In this work, the abatement of several chlorobenzenes commonly found as pollutants in the aqueous phase has been carried out by catalytic wet peroxide oxidation using goethite as the catalyst and hydroxylamine as the promotor. Spiked water with monochlorobenzene and different positional isomers of dichlorobenzene, trichlorobenzene, and tetrachlorobenzene, at concentrations ranging from 0.4 to 16.9 mg L⁻¹ was treated. Runs were carried out batch-way, at room conditions, without headspace. The heterogeneous catalyst was commercial goethite, with a specific surface area (S_BET) of 10.24 m² g⁻¹ and a total iron content of 57.3 wt%. Iron acts as a catalyst of hydrogen peroxide decomposition to hydroxyl radicals. Hydroxylamine (in a range from 0 to 4.9 mM) was added to enhance the iron redox cycle from Fe (III) to Fe (II), remarkably increasing the radical production rate and therefore, the conversion of chlorobenzenes. Iron was stable (not leached to the aqueous phase) even at the lowest pH tested (pH = 1). The effect of pH (from 2 to 7), hydrogen peroxide (from 1 to 10 times the stoichiometric dosage), hydroxylamine, and catalyst concentration (from 0.25 to 1 g/L) was studied. Pollutant removal increased with hydroxylamine and hydrogen peroxide concentration. An operating conditions study demonstrated that the higher the hydroxylamine and hydrogen peroxide concentrations, the higher the removal of pollutants. The optimal pH value and catalyst concentration was 3 and 0.5 g L⁻¹, respectively. Operating with 2.4 mM of hydroxylamine and 10 times the stoichiometric H₂O₂ amount, a chlorobenzenes conversion of 90% was achieved in 2.5 h. Additionally, no toxic byproducts were obtained. Full article

Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C₁ + C₁ coupling reactions by theoretical calculations and kinetic isotope experiments. CH_x(x=0−3), CO, HCO, COH, and HCOH are considered as the chain growth monomer respectively, and 24 possible coupling reactions are first investigated by theoretical calculations. Eight possible C₁ + C₁ coupling reactions are suggested to be energetically favorable because of the relative low reaction barriers. Moreover, five pathways are excluded where the C₁ monomers show low thermodynamic stability. Effective chain propagation rates are calculated by deconvoluting from reaction rates of products, and an inverse kinetic isotope effect of the C₁ + C₁ coupling reaction is observed. The theoretical kinetic isotope effect of CO + CH₂ is inverse, which is consistent with the experimental observation. Thus, the CO + CH₂ pathway, owing to the relatively lower barrier, the high thermodynamic stability, and the inverse kinetic isotope effect, is suggested to be a favorable pathway. Full article

This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al₂O₃–TiO₂ (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (Mo^Oh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of Co^Oh and the catalytic performance. At low Co^Oh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS₂ slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available Co^Oh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio. Full article

RuO₂ has been used for various applications because of its good catalytic properties. To further improve its electrocatalytic properties, we used a nanocasting technique. By using this technique, we obtained structure-controlled (SC) RuO₂ with a high surface area and an ordered porous structure, which created enhanced electrocatalytic properties over commercial RuO₂ nanoparticles for both oxygen and chlorine evolution reactions. Full article

Density functional theory (DFT) methods including LC-ωPBE, CAM-B3LYP, B3LYP, and B3LYP-D3, combined with double Zeta all-electron DZVP basis set, have been employed to conduct computational investigations on nickel-mediated reaction of o-carboranylzirconacycle, n-hexene, and 2-bromophenyltrimethylsilylacetylene in toluene solution. A multistep mechanism leading to the C,C,B-substituted carborane-fused tricyclics, including (1) sequential insertion of alkene and alkyne into Ni–C bonds; (2) double 1,2-migration of the TMS group; (3) B–H activation assisted by Cs₂CO₃ additive; and (4) reduction cage B–C (sp²) coupling, was proposed. Among these steps, the B–H activation of o-carborane was located as rate-determining step (RDS). With assistance of Cs₂CO₃ additive (replaced by K₂CO₃ in simulation), the RDS free-energy barrier at PCM-LC-ωPBE/DZVP level was calculated to be 23.1–23.9 kcal·mol⁻¹, transferring to a half-life of 3.9–15.1 h at 298 K. The predicted half-life coincides well with 80% experimental yields of C,C,B-substituted carborane-fused tricyclics after 12 h. Kinetic data obtained by employing LC-ωPBE method also reproduced the experimental diastereoselective ratio well. Various B–H activation pathways with and without Cs₂CO₃ additive were taken into consideration, which illustrates Cs₂CO₃ as an essential guarantee for smooth occurrence of this reaction at room temperature. Full article

Chemoenzymatic processes have been gaining interest to implement sustainable reaction steps or even create new synthetic routes. In this study, we combined Grubbs’ second-generation catalyst with pig liver esterase and conducted a chemoenzymatic one-pot process in a tandem mode. To address sustainability, we encapsulated the catalysts in biopolymer hydrogel beads and conducted the reaction cascade in an aqueous medium. Unfortunately, conducting the process in tandem led to increased side product formation. We then created core-shell beads with catalysts located in different compartments, which notably enhanced the selectivity towards the desired product compared to homogeneously distributing both catalysts within the matrix. Finally, we designed a specific large-sized bead with a diameter of 13.5 mm to increase the diffusion route of the Grubbs’ catalyst-containing shell. This design forced the ring-closing metathesis to occur first before the substrate could diffuse into the pig liver esterase-containing core, thus enhancing the selectivity to 75%. This study contributes to addressing reaction-related issues by designing specific immobilisates for chemoenzymatic processes. Full article

Most Combi-lipases (CL) are based on mixtures of different lipases immobilized on different supports. The increased CL efficiency has been attributed solely to the complementary selectivity of lipases. However, the role of the immobilization support in CL or in co-immobilized systems (coCL) and the application of kinetic models to account CL composition effects, have not been assessed. In this work, commercial lipases from Thermomyces lunuginosus (TLL), Candida antarctica (CALB) and Rhizomocur miehei (RML) and supports as Lewatit^®VPOC1600 (LW) and Purolite^®ECR1604 (PU), were combined to produce new CL systems for the production of fatty acid ethyl esters (EE) which are the main component of ethylic biodiesel: Co-immobilization slightly altered palm olein EE yields with regard to that of equivalent CL systems, e.g., the best coCL of TLL and CALB in LW (89.5%) and the respective CL (81.8%). The support did affect CL behavior: (i) The best coCL of TLL and RML on LW produced 80.0% EE while on PU 76.4%; (ii) CL based on mixtures of the same enzyme, but immobilized on different supports (semiCL) show complementarity: The best TLL semiCL produced 86.1% EE while its constituents (LW) and (PU) produced individually 78.2 and 70.3%, respectively. The proposed model accounts adequately the EE production properties for CL systems based on TLL, CALB and LW. This work expands the tools to obtain new CL systems for EE production. Full article

Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of pyridine followed by infrared spectroscopy. The results revealed no significant change in the acidity but an increase of the pore volume. According to significant improvement in the effective diffusivity, the samples were tested in the methanol-to-hydrocarbons reaction. The catalytic stability was greatly enhanced with an increase in the pore volume, demonstrating a relation between effective diffusivity and resistance to deactivation by coke formation. Further experiments also revealed a higher toluene adsorption capacity and a raise in the breakthrough time over the most porous samples due to better accessibility of toluene molecules into the active sites of the zeolite. Full article

The oxygen reduction reaction (ORR) properties of a proprietary PtCu₃/C alloy electrocatalyst produced on a multi-gram scale are characterized by the conventional rotating disc electrode (RDE) method and by constructing a membrane electrode assembly (MEA) proton exchange membrane (PEM) single cell. The PtCu₃ nanoparticles become porous, enriched in Pt on the surface, and exhibit a high RDE activity. The single cell electrochemical study reveals that, contrary to most advanced catalysts, the high ORR activity can be transferred from the RDE to the MEA. In the latter case, at 0.9V_IRfree, a mass activity of 0.53 A/mg_Pt, at a Pt electrode loading of 0.2 mg/cm², is achieved. However, at high current density, oxygen transport becomes limited. This is proven by the analysis of polarization curves and electrochemical impedance spectroscopy (EIS) data with a Kulikovsky (physical) model. These indicate that this limitation is caused by the non-optimal microporosity of our catalyst, which hinders the mass transport of oxygen during ORR. Based on our prospective results, one can realistically plan for further efforts to bridge the gap between the RDE and MEA measurements completely and achieve high power densities for Pt-alloy electrocatalysts. Full article

The present study is a follow-up to a recent authors contribution which describes the effect of the C/O (catalyst/oil) ratio on catalytic cracking activity and catalyst deactivation. This study, while valuable, was limited to one fluidized catalytic cracking (FCC) catalyst. The aim of the present study is to consider the C/O effect using three FCC catalysts with different activities and acidities. Catalysts were characterized in terms of crystallinity, total acidity, specific surface Area (SSA), temperature programmed ammonia desorption (NH₃-TPD), and pyridine chemisorption. 1,3,5-TIPB (1,3,5-tri-isopropyl benzene) catalytic cracking runs were carried out in a bench-scale mini-fluidized batch unit CREC (chemical reactor engineering centre) riser simulator. All data were taken at 550 °C with a contact time of 7 s. Every experiment involved 0.2 g of 1,3,5-TIPB with the amount of catalyst changing in the 0.12–1 g range. The resulting 0.6–5 g _oil/g _cat ratios showed a consistent 1,3,5-TIPB conversion increasing first, then stabilizing, and finally decreasing modestly. On the other hand, coke formation and undesirable benzene selectivity always rose. Thus, the reported results show that catalyst density affects both catalyst coking and deactivation, displaying an optimum C/O ratio, achieving maximum hydrocarbon conversions in FCC units. Full article

The thermal sintering under oxidative conditions of Rh nanoparticles supported on oxides characterized by very different oxygen storage capacities (OSC) and labilities was studied at 750 and 850 °C. Under sintering conditions, significant particle growth occurred for Rh/γ-Al₂O₃ (up to 120% at 850 °C). In striking contrast, Rh/ACZ (alumina–ceria–zirconia) and Rh/CZ (ceria–zirconia) exhibited marked resistance to sintering, and even moderate (ca. −10% at 850 °C) to pronounced (ca. −60% at 850 °C) redispersion of the Rh. A model is proposed based on a double-layer description of metal–support interactions assigned to back-spillover of labile oxygen ions onto the Rh particles, accompanied by trapping of atomic Rh by the resulting surface oxygen vacancies. This model accounts for the observed resistance to sintering and actual redispersion of Rh, consistent with both alternative sintering mechanisms, namely Ostwald ripening (OR) or particle migration and coalescence (PMC). Full article

Dry reforming of methane (DRM) is an eco-friendly method of syngas production due to the utilization of two main greenhouse gases—methane and carbon dioxide. An industrial application of methane dry reforming requires the use of a catalyst with high activity, stability over a long time, and the ability to catalyze a reaction, leading to the needed a hydrogen/carbon monoxide ratio. Thus, the aim of the study was to investigate the effect of support and noble metal particles on catalytic activity, stability, and selectivity in the dry reforming process. Ni and Ni–Ru based catalysts were prepared via impregnation and precipitation methods on SiO₂, ZrO₂, Al₂O₃, and MgAl₂O₄ supports. The obtained catalysts were characterized using X-ray diffractometry (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), Brunauer–Emmett–Teller (BET) specific surface area, and elemental carbon-hydrogen-nitrogen-sulphur analysis (CHNS) techniques. The catalytic activity was investigated in the carbon dioxide reforming of a methane process at 800 °C. Catalysts supported on commercial Al₂O₃ and spinel MgAl₂O₄ exhibited the highest activity and stability under DRM conditions. The obtained results clearly indicate that differences in catalytic activity result from the dispersion, size of an active metal (AM), and interactions of the AM with the support. It was also found that the addition of ruthenium particles enhanced the methane conversion and shifted the H₂/CO ratio to lower values. Full article

Wood waste generated during the tree felling and processing is a rich, green, and renewable lignocellulosic biomass. However, an effective method to apply wood waste in anaerobic digestion is lacking. The high carbon to nitrogen (C/N) ratio and rich lignin content of wood waste are the major limiting factors for high biogas production. NaOH pre-treatment for lignocellulosic biomass is a promising approach to weaken the adverse effect of complex crystalline cellulosic structure on biogas production in anaerobic digestion, and the synergistic integration of lignocellulosic biomass with low C/N ratio biomass in anaerobic digestion is a logical option to balance the excessive C/N ratio. Here, we assessed the improvement of methane production of wood waste in anaerobic digestion by NaOH pretreatment, co-digestion technique, and their combination. The results showed that the methane yield of the single digestion of wood waste was increased by 38.5% after NaOH pretreatment compared with the untreated wood waste. The methane production of the co-digestion of wood waste and pig manure was higher than that of the single digestion of wood waste and had nonsignificant difference with the single-digestion of pig manure. The methane yield of the co-digestion of wood waste pretreated with NaOH and pig manure was increased by 75.8% than that of the untreated wood waste. The findings indicated that wood waste as a sustainable biomass source has considerable potential to achieve high biogas production in anaerobic digestion. Full article

Three bimetallic Cu–Ni nanoparticle-supported catalysts were synthesized by co-immobilization followed by H₂ reduction. A chromium(III) terephthalate metal organic framework (MIL-101), titanium dioxide (TiO₂), and carbon (C) with different properties (acidity and Brunauer–Emmett–Teller surface area) were selected as supports for studying the effect of the support nature on the catalytic activity and selectivity in the oxidation of benzyl alcohol. The physicochemical properties of the Cu–Ni-supported catalysts were characterized by XRD, NH₃-TPD, nitrogen adsorption/desorption, TEM, EDS, XPS, and ICP-OES. Bimetallic Cu–Ni nanoparticles were highly dispersed on the support. The catalytic activities of CuNi/MIL-101, CuNi/TiO₂, and CuNi/C were tested in the selective oxidation of benzyl alcohol to benzaldehyde in the presence of molecular oxygen under mild reaction conditions. The highest benzaldehyde yields were achieved with CuNi/TiO₂, CuNi/MIL-101, and CuNi/C catalysts at 100 °C within 4 h under 5, 3, and 3 bar of O₂, respectively. The bimetallic Cu–Ni-supported catalysts possessed two types of catalytic active sites: acid sites and bimetallic Cu–Ni nanoparticles. The CuNi/MIL-101 catalyst possessed a high number of acid sites and exhibited high yield during selective benzyl alcohol oxidation to benzaldehyde. Importantly, the catalysts exhibited a high functional group (electron-donating and electron-withdrawing groups) tolerance. Cu–Ni-supported catalysts with an Cu:Ni mole ratio of 1:1 exhibited the highest yield of 47% for the selective oxidation of benzyl alcohol to benzaldehyde. Reusability and leaching experiment results exhibited that CuNi/MIL-101 showed better stability than CuNi/TiO₂ and CuNi/C catalysts due to the large porous cavities of MIL-101 support; these cavities can be used to trap bimetallic Cu–Ni nanoparticles and inhibit nanoparticle leaching. Full article

The successful management of olive by-products constitutes a major challenge due to their huge volume, high organic content, and toxicity. Olive-mill wastes (TPOMW) and olive pruning residues (OLPR) were evaluated as substrates for the cultivation of Ganoderma lucidum and Pleurotus ostreatus. Chemical composition, glucans, total phenolic content, and antioxidant activity were measured in mushrooms, and their prebiotic potential was assessed by examining their effect on the growth of four intestinal bacteria. Several substrates based on olive by-products had a positive impact on P. ostreatus mushroom production, whereas only one performed adequately for G. lucidum. Increased ratios of OLPR to wheat-straw resulted in an increase of crude protein content in P. ostreatus fruit-bodies by up to 42%, while G. lucidum mushrooms from OLPR-based substrates exhibited an up to three-fold increase in α-glucan, or a significant enhancement of β-glucan content, when compared to beech sawdust (control). The mushrooms’ FTIR spectra confirmed the qualitative/quantitative differentiation detected by standard assays. In regard to prebiotic properties, mushrooms powder supported or even enhanced growth of both Lactobacillus acidophilus and L. gasseri after 24/48 h of incubation. In contrast, a strain-specific pattern was observed in bifidobacteria; mushrooms hindered Bifidobacterium bifidum growth, whereas they supported a similar-to-glucose growth for B. longum. Full article

Improving surface selectivity and maximizing electrode surface area are critical needs for the electroreduction of nitrate. Herein, preferential (100) oriented Pt nanoflowers with an extended surface area were prepared by potentiostatic deposition on carbon cloth (Pt NFs/CC), and then Cu atoms were adsorbed on the Pt NFs (Cu/Pt NFs/CC) for application of nitrate electroreduction. The results reveal that Cu/Pt NFs/CC with 8.7% Cu coverage exhibits a high selectivity for nitrate electroreduction to N₂ following two steps: Nitrate firstly converts into nitrite on Cu sites adsorbed on Pt NFs, then nitrite subsequently selective reduction and ammonia oxidation to N₂ occur on the large exposed (100) terraces in Pt NFs. In addition, electrocatalytic activity and selectivity of nitrate reduction strongly rely on the Cu surface coverage on Pt NFs, the lower activity of nitrate reduction is displayed with increase of Cu coverage. Accordingly, the selective reduction of nitrate to N₂ is feasible at such nanostructured Pt nanoflowers modified with Cu. Full article

Enzymatic hydroesterification is a heterogeneous catalyzed process suitable for the conversion of low-cost feedstocks in biodiesel production, namely, because of its tolerance to high free fatty acid contents. The current study describes the use of Fourier transform infrared spectroscopy (FTIR) to monitor biodiesel production using enzymatic hydroesterification and, as raw materials, acid oil from soapstock and olive pomace oil. Acid oil (~34 wt.% FFA) and olive pomace oil (~50 wt.% FFA) were first hydrolyzed (35 °C, 24 h, 200 rpm, 3 wt.% of lipase from Thermomyces lanuginosus, and 1:0.5 water:oil ratio, w:w), and then enzymatic esterification was performed (35 °C, 7 h, 200 rpm, 2 wt.% of lipase from Thermomyces lanuginosus, and 2:1 molar ratio of methanol to acid). FTIR analyses were conducted on the products using a Jasco FT/IR-4100 with a scanning range of 4000–650 cm⁻¹ at 4 cm⁻¹ spectral resolution and 54 scans. For free fatty acid (FFA) quantification, the C=O band at 1708 cm^–1 was used, corresponding to the carboxylic acid, whereas for fatty acid methyl ester (FAME) quantification, the peak corresponding to C=O at 1746 cm⁻¹ was considered, which corresponded to the ester. The results were calibrated using volumetric titration and gas chromatography analyses, concerning FFA and FAME quantification, respectively. The best conditions for analysis were determined, and a calibration method was established. FTIR has shown to be a simple, fast, and clean technique suitable to monitor hydroesterification of low-cost feedstocks. Full article