Catalysts, Volume 14, Issue 3 (March 2024) – 58 articles

This study investigates the potential of bimetallic alloy catalysts, specifically Ni₉₉Pt₁, Cu₉₉Ni₁, Cu₉₉Fe₁, Fe₉₉Pt₁, and Fe₉₉Pd₁, for the synthesis of isobutanol via the Guerbet route. The catalysts were synthesized with a doping of 1 at% Ni, Fe, Pt, and Pd in the base metals Fe, Cu, and Ni. The catalytic properties of these bimetallic alloy catalysts were explored for their potential for promoting the Guerbet reaction. The study aims to test the usability of the theoretically predicted d-band values in the synthesized bimetallic catalysts, which were prepared by means of incipient wetness impregnation, and shows that doping amounts smaller than 1 at% already significantly improved the catalytic activity of the base metals. In particular, the doping of nickel with platinum yielded an effective catalyst for the synthesis of isobutanol via the Guerbet pathway. The Ni₉₉Pt₁/C catalyst from the presented experiments had the highest Space Time Yield (STY) and is, therefore, also a promising catalyst for the hydrogen-borrowing reactions class. Full article

From reactions involving sodium molybdate and dianilines [2,2′-(NH₂)C₆H₄]₂(CH₂)_n (n = 0, 1, 2) and amino-functionalized carboxylic acids 1,2-(NH₂)(CO₂H)C₆H₄ or 2-H₂NC₆H₃-1,4-(CO₂H)₂, in the presence of Et₃N and Me₃SiCl, products adopting H-bonded networks have been characterized. In particular, the reaction of 2,2′-diaminobiphenyl, [2,2′-NH₂(C₆H₄)]₂, and 2-aminoterephthalic acid, H₂NC₆H₃-1,4-(CO₂H)₂, led to the isolation of [(MoCl₃[2,2′-N(C₆H₄)]₂}{HNC₆H₃-1-(CO₂),4-(CO₂H)]·2[2,2′-NH₂(C₆H₄)]₂·3.5MeCN (1·3.5MeCN), which contains intra-molecular N–H∙∙∙Cl H-bonds and slipped π∙∙∙π interactions. Similar use of 2,2′-methylenedianiline, [2,2′-(NH₂)C₆H₄]₂CH₂, in combination with 2-aminoterephthalic acid led to the isolation of [MoCl₂(O₂CC₆H₃NHCO₂SiMe₃)(NC₆H₄CH₂C₆H₄NH₂)]·3MeCN (2·3MeCN). Complex 2 contains extensive H-bonds between pairs of centrosymmetrically-related molecules. In the case of 2,2′ethylenedianiline, [2,2′-(NH₂)C₆H₄]₂CH₂CH₂, and anthranilic acid, 1,2-(NH₂)(CO₂H)C₆H₄, reaction with Na₂MoO₄ in the presence of Et₃N and Me₃SiCl in refluxing 1,2-dimethoxyethane afforded the complex [MoCl₃{1,2-(NH)(CO₂)C₆H₄}{NC₆H₄CH₂CH₂C₆H₄NH₃}]·MeCN (3·MeCN). In 3, there are intra-molecular bifurcated H-bonds between NH₃ H atoms and chlorides, whilst pairs of molecules H-bond further via the NH₃ groups to the non-coordinated carboxylate oxygen, resulting in H-bonded chains. Complexes 1 to 3 have been screened for the ring opening polymerization (ROP) of both ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) using solvent-free conditions under N₂ and air. The products were of moderate to high molecular weight, with wide Ð values, and comprised several types of polymer families, including OH-terminated, OBn-terminated (for PCL only), and cyclic polymers. The results of metal-free ROP using the dianilines [2,2′-(NH₂)C₆H₄]₂(CH₂)_n (n = 0, 1, 2) and the amino-functionalized carboxylic acids 1,2-(NH₂)(CO₂H)C₆H₄ or 2-H₂NC₆H₃-1,4-(CO₂H)₂ under similar conditions (no BnOH) are also reported. The dianilines were found to be capable of the ROP of δ-VL (but not ε-CL), whilst anthranilic acid outperformed 2-aminoterephthalic acid for both ε-Cl and δ-VL. Full article

Through the implementation of a one-pot strategy, five examples of non-symmetrical [N,N-diaryl-11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-diimine]iron(II) chloride complexes (aryl = 2,6-Me₂Ph Fe1, 2,6-Et₂Ph Fe2, 2,6-i-Pr₂Ph Fe3, 2,4,6-Me₃Ph Fe4, and 2,6-Et₂-4-MePh Fe5), incorporating fused six- and seven-membered carbocyclic rings and appended with a remote para-phenyl group, were readily prepared. The molecular structures of Fe2 and Fe3 emphasize the variation in fused ring size and the skewed disposition of the para-phenyl group present in the N′,N,N″-ligand support. Upon activation with MAO or MMAO, Fe1–Fe5 all showed high catalytic activity for ethylene polymerization, with an exceptional level of 35.92 × 10⁶ g (PE) mol⁻¹ (Fe) h⁻¹ seen for mesityl-substituted Fe4/MMAO operating at 60 °C. All catalysts generated highly linear polyethylene with good control of the polymer molecular weight achievable via straightforward manipulation of run temperature. Typically, low molecular weight polymers with narrow dispersity (M_w/M_n = 1.5) were produced at 80 °C (MMAO: 3.7 kg mol⁻¹ and MAO: 4.9 kg mol⁻¹), while at temperatures between 40 °C and 50 °C, moderate molecular weight polymers were obtained (MMAO: 35.6–51.6 kg mol⁻¹ and MAO: 72.4–95.5 kg mol⁻¹). Moreover, analysis of these polyethylenes by ¹H and ¹³C NMR spectroscopy highlighted the role played by both β-H elimination and chain transfer to aluminum during chain termination, with the highest rate of β-H elimination seen at 60 °C for the MMAO-activated system and 70 °C for the MAO system. Full article

Improper disposal of waste plastic has caused serious ecological and environmental pollution problems. Transforming plastics into high value-added chemicals can not only achieve efficient recycling of waste plastics, but is also an effective way to control white pollution. The catalyst selectively breaks the C–C bond of polyolefin plastic under heat treatment and converts it into liquid fuel, thus realizing sustainable recycling of plastics and has a good development prospect. This review provides a detailed overview of the current development of catalytic pyrolysis, catalytic hydrolysis, solvent decomposition, and supercritical hydrothermal liquefaction for cracking plastics to make fuel oil. The reaction mechanism, influencing factors, and promoting effects of catalysts in various degradation technologies are analyzed and summarized, and the latest proposed tandem reaction for degrading plastics is briefly introduced. Finally, some optimization paths of waste plastic pyrolysis to fuel oil technology are proposed: synergies between mixed raw materials, in-depth exploration of catalysts, design and manufacture of reactors that match the pyrolysis technology. All these are important research directions for promoting the industrialization of plastic pyrolysis to fuel oil. Full article

Thermal degradation is a leading cause of automotive catalyst deactivation. Because high-entropy oxides are uniquely stabilized at high temperatures via an increase in configurational entropy, these materials may offer new mechanisms for preventing the thermal deactivation of precious metal catalysts. In this work, we evaluated platinum loaded on simple and high-entropy aluminate spinels (MAl₂O₄, where M = Co, Cu, Mg, Ni, or mixtures thereof) in carbon monoxide oxidation before and after aging at 800 °C. Pt supported on all simple spinels showed significant deactivation after thermal aging compared to the fresh samples, with T₉₀ increasing by at least 60 °C. However, Pt on high-entropy spinels had nearly the same or better activity after aging, with T₉₀ increasing by only 6 °C at most. During aging and reduction, copper exsolved from the spinel supports and alloyed with platinum. This interaction promoted low temperature oxidation activity, presumably through weakened CO binding, but did not prevent deactivation. On the other hand, Co, Mg, and Ni constituents promoted stronger CO bonding, as evidenced by apparent negative order kinetics and poor activity at low temperatures. High-entropy spinels, containing a variety of active metals, displayed synergetic reactant adsorption capacity and cooperative effects with supported platinum particles, which collectively prevented thermal deactivation. Full article

Nitriles are versatile and highly desired chemical intermediates for a range of products. Their economic large-scale production requires highly efficient and selective synthesis. The nickel-catalyzed hydrocyanation of C=C double bonds provides such selective and 100% atom-economical access to nitriles, but the catalysts hitherto lack activity and longevity. Yet, the literature focusing on increased catalytic activity or optimized operational procedures is scarce, at the least. Here, we present a thorough investigation and optimization of operational procedures using a commercially available diphosphite ligand and styrene as a model substrate. This led us to achieve a TOF₂₀ of more than 300,000 h⁻¹. Full article

Since the signing of the Minamata Convention in 2013, attempts have been primarily focused on reducing the emission of elemental mercury (Hg⁰) from coal-fired power plants (CFPPs). The most cost-effective measure for controlling the emission of mercury involves oxidizing Hg⁰ to mercury oxides, which are then removed using wet flue gas desulfurization (WFGD). Thus, novel photocatalysts with the best properties of photocatalytic ability and thermal stability need to be developed urgently. In this study, titanium dioxide (TiO₂)-based photocatalysts were synthesized through the modification of three metal oxides: CuO, CeO₂, and Bi₂O₃. All the photocatalysts were further characterized using X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and ultraviolet-visible spectrometry. The photocatalytic oxidation efficiencies of Hg⁰ were evaluated under an atmosphere of N₂ + Hg⁰ at 100–200 °C. The photocatalytic reactions were simulated by kinetic modeling using the Langmuir–Hinshelwood (L–H) mechanism. The results showed that Bi₂O₃/TiO₂ exhibited the best thermal stability, with the best oxidation efficiency at 200 °C and almost the same performance at 100 °C. L–H kinetic modeling indicated that photocatalytic oxidation reactions for the tested photocatalysts were predominantly physical adsorption. Additionally, the activation energy (E_a), taking into account Arrhenius Law, decreased dramatically after modification with metal oxides. Full article

A new membrane-less bioelectrochemical reactor configuration was developed for contaminated groundwater remediation. The new bioelectrochemical reactor configuration was inspired by the utilisation of a permeable reactive barrier (PBR) configuration with no separation membrane. The corresponding reactive zones were created by using graphite granules and mixed metal oxide (MMO) electrodes to stimulate the reductive and oxidative biological degradation of chlorinated aliphatic hydrocarbons. In the present study, the PBR-like bioelectrochemical reactor has been preliminarily operated with synthetic contaminated groundwater, testing the reductive dechlorination activity on cis-dichloroethylene (cisDCE). Moreover, to assess the effects of competing anions presence for the electron donor (i.e., the cathode), the synthetic wastewater contained sulphate and nitrate anions. In the PBR-like reactor operation, nearly all cisDCE was removed in the initial sampling port, with only VC detected as the observable RD product. During the same biotic test of the PRB reactor, the presence of both the reductive dechlorination and anions reduction was confirmed by the complete nitrate reduction in the cathodic chamber of the PRB reactor. On the contrary, sulphate reduction showed a lower activity; indeed, only 25% of the influent sulphate was removed by the PRB reactor. Full article

Traditional methods for synthesizing single-site catalysts are typically complicated and require special chemicals due to their tendency to agglomerate. In this study, we present a self-disperse copper-based catalyst synthesized via a dry mixing method for acetylene hydrochlorination. During the reaction, the copper precursor compounds, i.e., CuBr, and CuI, were converted to CuCl. Subsequently, the formed CuCl crystals underwent a significant structural transformation, leading to the formation of small clusters and Cu single sites. The catalytic activity of 5% CuCl + C prepared through the dry mixing method decreased from 93.7% to 92.9% after 100 h of reaction under the condition of GHSV (C₂H₂) = 60 mL·h⁻¹·g⁻¹. A comparison of the 5% CuCl + C with the 5% CuCl/C obtained by the impregnation method reveals that the catalytic stability of the former was higher than the one prepared by the conventional impregnation method. The exceptional catalytic performance can be attributed to the reaction-induced active sites being highly dispersed and the porous structure of activated carbon being maximally preserved, which was confirmed by HAADF-STEM, BET, TPR, and TG. The reaction-induced dispersion of CuCl on carbon provides a new strategy for preparing single-site catalysts for acetylene hydrochlorination. Full article

Ni-based catalysts play a fundamental role in catalytic CO₂ methanation. In this study, the possibility of using siderite ore as a catalyst or catalytic support material for nickel-based catalysts was investigated, aiming at the exploitation of an abundant natural resource. The catalytic performance of Ni-based catalysts with reduced siderite ore as a support was evaluated and compared to MgO as a support material. MgO is known as an effective support material, as it provides access to bifunctional catalysts because of its basicity and high CO₂ adsorption capacity. It was shown that undoped and Ni-doped reduced siderite ore have comparable catalytic activity for CO₂ hydrogenation (20−23%) at 648 K, but show limited selectivity toward methane (<20% for siderite_reduced and 60.2% for Ni/siderite_reduced). When MgO was added to the support material (Ni/siderite_reduced/MgO), both the CO₂ conversion and the selectivity toward methane increased significantly. CO₂ conversions were close to the thermodynamic equilibrium, and methane selectivities of ≥99% were achieved. Full article

A Zn–air battery serves as an energy storage solution to address fossil energy and environmental concerns. However, sluggish kinetics in oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) demand innovative, cost-effective, and stable bifunctional catalysts to replace precious metal catalysts. In this study, an FeCo-CNTs/KB catalyst was synthesized by pyrolyzing NH₂-MIL-101(Fe) coated with glu-Co and conductive carbon (KB). This hierarchical structure comprises carbon nanotubes (CNTs) grafted onto a carbon matrix, housing abundant FeCo nanoparticles within the nanotubes or matrix. KB introduction enhances FeCo nanoparticle dispersion and fosters uniform CNT formation with smaller diameters, thus exposing active sites. Consequently, the FeCo-CNTs/KB catalyst exhibits remarkable bifunctional electrocatalytic activity: an ORR half-wave potential of 0.84 V and an OER overpotential of 0.45 V (10 mA cm⁻²). Furthermore, the FeCo-CNTs/KB catalyst in a secondary Zn–air battery showcases enduring charge–discharge performance (≥300 h). Full article

The hydrogenation of carbon dioxide (CO₂) to produce light olefins is one of the most promising ways to utilize CO₂ in power plant flue gas. However, the low concentration of CO₂ (~10%) and the existence of water steam in the flue gas pose great challenges for the catalyst design. To address these problems, we introduced a Mg promoter and hydrophobic component into the Fe-based catalyst to improve the CO₂ adsorption capacity and weaken the negative effects of water. The yield of light olefins on an optimized multifunctional Fe-based catalyst increased by 37% in low-concentration CO₂ hydrogenation with water steam. A variety of characterizations proved that the Mg promoter played critical roles in regulating the adsorption capacity of CO₂, increasing the surface electron density of Fe species, and promoting the formation of iron carbide active sites. The hydrophobic component mainly contributed to constraining the oxidation of iron carbides via water steam. It benefited from the rational design of the catalyst, showing how our multifunctional Fe-based catalyst has great potential for practical application in CO₂ utilization. Full article

The effects that the catalyst-to-feed ratio have on the yields of products and composition of the naphtha and light cycle oil (LCO) fractions in the hydrocracking of a blend composed of high-density polyethylene (HDPE) and vacuum gasoil (VGO) using a PtPd/HY catalyst were assessed. The hydrocracking runs were carried out in a batch reactor fixing the following operation conditions: 420 °C, 80 bar, 120 min and an HDPE-to-VGO ratio of 0.2 g_HDPE g_VGO⁻¹, varying the catalyst-to-feed mass ratio within the 0.05–0.1 g_catalyst g_feed⁻¹ range. The obtained results exposed that a catalyst-to-feed mass ratio of 0.075 g_catalyst g_feed⁻¹ provided the best results, since the conversion of the heavy cycle oil (HCO) fraction and of the HDPE offered quite high values (73.1 and 63.9%, respectively) without causing an excessive overcracking in the form of gas products (the yield of gases was of 25%). Moreover, an interesting yield of naphtha (37.0 wt%) with an RON within the commercial standards (92.5) was obtained. With regard to coke formation, not-so-developed structures were formed for a catalyst-to-feed mass ratio of 0.075 g_catalyst g_feed⁻¹, easing their combustion and presumably extending the lifespan of the catalyst. Full article

The present study deals with the development, characterization, and performance of a Ni-based catalyst over a ceria-doped alumina support as a post-gasification step, in the conversion of biomass-derived tars. The catalysts were prepared using the incipient wetness technique and characterized chemically and physically using NH₃-TPD, CO₂-TPD, H₂-TPR, XRD, Pyridine-FTIR, N₂ physisorption, and H₂-Pulse Chemisorption. It was observed that the 5 wt% CeO₂ reduced the strong and very strong acid sites of the alumina support and helped with the dispersion of nickel. It was noticed that the nickel crystallite sizes and metal dispersion remained unchanged as the nickel loading increased. The performance of the catalysts was studied in a mini-fluidized CREC Riser Simulator at different temperatures and reaction times. The selected tar surrogate was 2-methoxy-4-methylphenol, given its functional group similarities with lignin-derived tars. A H₂/CO₂ gas blend was used to emulate the syngas at post-gasification conditions. The obtained tar surrogate conversion was higher than 75%, regardless of the reaction conditions. Furthermore, the catalysts used in this research provided an enhancement in the syngas product composition when compared to that observed in the thermal experiments. The presence of hydrocarbons greater than CH₄ (C₁₊) was reduced at 525 °C, from 96 ± 3% with no catalyst, to 85 ± 2% with catalyst and steam, to 68 ± 4% with catalyst and steam-H₂/CO₂. Thus, the catalyst that we developed promoted tar cracking, tar reforming, and water-gas shift reactions, with a H₂/CO ratio higher than 3.8, providing a syngas suitable for alcohol synthesis. Full article

Due to their unique chemical structure, MXenes have been recognized as a potential material, having a high surface area, high thermal and electrical conductivity, and a tunable band gap, showing great hydrophilicity and stability. The adsorption and reducing properties of MXene-based 2D nanomaterials make them efficient photocatalysts for degrading organic pollutants. Silver nanoparticles were synthesized over the exfoliated MXene sheets (1:50 and 1:20 by weight to silver salt) using polyvinyl pyrrolidone as a dispersant. The elemental composition and morphology of the nanocatalysts Ag20@Ti₃C₂T_x and Ag50@Ti₃C₂T_x were analyzed by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) spectroscopy, and field-emission scanning electron microscopy (FESEM). FESEM micrographs reveal porous exfoliated Ti₃C₂T_x sheets obtained by continuously stirring Ti₃AlC₂ for 44 h at 60 °C, providing a platform for the growth of Ag nanoparticles. Diffused reflectance spectroscopy (DRS) indicates that the bare silver nanoparticles show a decrease in the band gap value from 2.4 to 1.35 and 1.41 eV in Ag50@Ti₃C₂T_x and Ag20@Ti₃C₂T_x, respectively, which enables the nanocomposites to show excellent catalytic performance and degrade around 99% of safranin dye within 15 min at a concentration of 5 mg Ag50@Ti₃C₂T_x. Full article

The thermo-chemical conversion of biomass wastes is a practical approach for the value-added reclamation of bioenergy in large quantities, and pyrolysis plays a core role in this process. In this work, poplar (PR) and cedar (CR) were used as staple wood biomasses to investigate the apparent kinetics of TG/DTG at different heating rates. Secondly, miscellaneous wood chips (MWC), in which PR and CR were mixed in equal proportion, were subjected to comprehensive investigations on their pyrolysis behavior and product evolution in a fixed bed reactor with pyrolysis temperature, catalyst, and the flow rate H₂O steam as influencing factors. The results demonstrated that both PR and CR underwent three consecutive pyrolysis stages, the TG/DTG curves shifted to higher temperatures, and the peak temperature intervals also enhanced as the heating rate increased. The kinetic compensation effect expression and apparent reaction kinetic model of CR and PR pyrolysis were obtained based on the law of mass action and the Arrhenius equation; the reaction kinetic parameter averages of Ea and A of its were almost the same, which were about 72.38 kJ/mol and 72.36 kJ/mol and 1147.11 min⁻¹ and 1144.39 min⁻¹, respectively. The high temperature was beneficial for the promotion of the pyrolysis of biomass, increased pyrolysis gas yield, and reduced tar yield. This process was strengthened in the presence of the catalyst, thus significantly increasing the yield of hydrogen-rich gas to 117.9 mL/g_-biomass. It was observed that H₂O steam was the most effective activator for providing a hydrogen source for the whole reaction process, promoted the reaction to proceed in the opposite direction of H₂O steam participation, and was beneficial to the production of H₂ and other hydrocarbons. In particular, when the flow rate of H₂O steam was 1 mL/min, the gas yield and hydrogen conversion were 76.94% and 15.90%, and the H₂/CO was 2.07. The yields of H₂, CO, and CO₂ in the gas formation were significantly increased to 107.35 mL/g_-biomass, 53.70 mL/g_-biomass, and 99.31 mL/g_-biomass, respectively. Therefore, H₂ was the most dominant species among gas products, followed by C-O bond-containing species, which provides a method for the production of hydrogen-rich gas and also provides ideas for compensating or partially replacing the fossil raw material for hydrogen production. Full article

Reaction mixtures of naturally abundant aldoses and CH nucleophiles allow for the formation of functionalized furan precursors using low temperatures and metal-free catalysis in aqueous solutions of dilute base catalysts. We employ in situ NMR assays to clarify the mechanism and kinetics of the conversion. Catalysis serves a double role in ring-opening of stable aldoses such as glucose and xylose and facilitating the subsequent reactions with CH acids such as malononitrile or cyanoacetamide. Resultant acyclic products are shown to convert quickly to a monocyclic product prior to the slower formation of a more stable bicyclic intermediate and dehydration to tri-functionalized furan. Especially the reversible 5-exo-dig ring closure entailing oxygen attack onto a nitrile carbon is surprisingly fast with an equilibrium vastly towards the cyclic state, sequestering reactive groups and allowing the selective conversion to tri-functionalized furan. The reaction hinges on the fast formation of intermediates without CH acidity and competes with the oligomerization of CH nucleophiles. Insight derived from in situ NMR analysis shows the prowess of high-resolution in situ spectroscopy in clarifying the interplay between catalysts and reactants. Such insight will be vital for the optimization of reactions that upgrade biorenewables under benign conditions. Full article

Heterogeneous catalysts containing cobalt and molybdenum supported on mesoporous materials types SBA-15 and AlSBA-15 were synthesized for application in the HDS reactions of thiophene in the n-heptane stream. The materials were synthesized by the hydrothermal method using Pluronic P123 as a template. The calcined SBA-15 and AlSBA-15 supports were submitted to co-impregnation with solutions of cobalt nitrate and ammonium heptamolybdate, aiming for the production of 15% in mass of metal loading with an atomic ratio of [Co/(Co + Mo)] = 0.45. The obtained materials were dried and calcined to obtain the mesoporous catalysts in the forms of CoMo/SBA-15 and CoMo/AlSBA-15. The catalysts were characterized by XRD, TG/DTG, SEM, and nitrogen adsorption. From XRD analysis, it was verified that after the decomposition of the cobalt and molybdenum salts, MoO₃, Co₃O_4, and CoMoO₄ oxides were formed on the supports, being attributed to these chemical species, the activity for the HDS reactions. The catalytic activity of the obtained catalysts was evaluated in a continuously flowing tubular fixed-bed microreactor coupled on-line to a gas chromatograph, using an n-heptane stream containing 12,070 ppm of thiophene (ca. 5100 ppm of sulfur) as a model compound. The synthesized catalysts presented suitable activity for the HDS reaction, and the main obtained products were cis- and trans-2-butene, 1-butene, n-butane, and low amounts of isobutane. The presence of 1,3-butadiene and tetrahydrothiophene (THT) was not detected. A mechanism of the primary and secondary reactions and subsequent formation of the olefins and paraffins in the CoMo/SBA-15 and CoMo/AlSBA-15 mesoporous catalysts was proposed, considering steps of desulfurization, hydrogenation, dehydrogenation, THT decyclization, and isomerization. Full article

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH₃ being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h⁻¹. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm⁻² under H₂ fuel and 398 mW cm⁻² under cracked NH₃ fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production. Full article

This research work is focused on the transformation of light alkane (propane) into high-value aromatics using gallo-alumino-silicate catalysts. Two sets of gallo-alumino-silicates were synthesized for this study. In the first set, the ratio of Ga/(Al+Ga) was modified, while the Si/(Al+Ga) ratio was held constant. In the subsequent set, the Si/(Al+Ga) ratio was adjusted, while maintaining a consistent Ga/(Al+Ga) ratio. This approach aimed to directly assess the impact of each ratio on catalyst performance. The comprehensive characterization of all catalysts was conducted using various instrumental techniques, i.e., BET surface area, XRD, NH₃-TPD, ²⁷Al, ⁷¹Ga and ²⁹Si MAS NMR, and XPS. A gradual reduction in the percentage of crystallinity and rise in meso-surface area was noticed with a rise in Ga/(Al+Ga) ratio. The total acidity (NH₃-TPD) demonstrated a decline as the Si/(Al+Ga) ratio increased, attributed to an overall decline in Al³⁺ or Ga³⁺ species. The XPS intensity of the Ga 2p_3/2 peak rose in correlation with an elevated ratio of Ga/(Al+Ga), suggesting the formation of extra-framework Ga species. The propane conversion, aromatic yield, and aromatization/cracking ratio exhibited an increase with an increasing Ga/(Al+Ga) ratio, reaching an optimum value of 0.46 before declining. Conversely, an appreciable drop in the conversion of propane and yield of aromatics was detected with the rise in Si/(Al+Ga) ratio, attributing to the decline in acidity. The catalyst having a Ga/(Al+Ga) ration of 0.46 exhibited the highest propane conversion and aromatic yield of 83.0% and 55.0% respectively. Full article

The present study explored machine learning methods to predict the catalytic activities of a dataset of 165 α-diimino nickel complexes in ethylene polymerization. Using 25 descriptors as the inputs, the XGBoost model presented the optimal performance among six different algorithms (R² = 0.999, R_t² = 0.921, Q² = 0.561). The results of the analysis indicate that high activity is related to the presence of polarizable atoms and less bulky substituents within the N-aryl group. This approach offers valuable insights on the variation principle of catalytic activity as a function of complex structure, helping to effectively design and optimize α-diimino Ni catalysts with desirable performance. Full article

The synthesis of nylon 6 and nylon 66 can be performed, starting with the selective hydrogenation of benzene to cyclohexene, which is deemed to be environmentally friendly and cost-saving and to have higher atom efficiency. Nano-Ru catalyst was synthesized via a precipitation method. The prepared catalyst was evaluated in the selective hydrogenation of benzene toward cyclohexene generation in the presence of ZnSO₄ in a liquid batch reactor. The promotion effect of the addition of amines, i.e., ethylenediamine, ethanolamine, diethanolamine, and triethanolamine, was investigated. The fresh and spent catalysts were thoroughly characterized by XRD, TEM, AES, N₂-sorption, FT-IR, and TPR. It was found that the addition of amines could significantly improve the catalytic selectivity toward cyclohexene formation in the presence of ZnSO₄. This was attributed to the formation of (Zn(OH)₂)₅(ZnSO₄)(H₂O)_x (x = 0.5, 3 or 4) through the reaction between ZnSO₄ and the amines, which could be chemisorbed on the Ru surface. This led to retarding the formation of cyclohexane from the complete hydrogenation of benzene and, thus, increased the catalytic selectivity toward cyclohexene synthesis. Therefore, with the presence of ZnSO₄, the amount of chemisorbed (Zn(OH)₂)₅(ZnSO₄)(H₂O)_x increased with increasing amounts of added amines, leading to a decline in the catalytic activity toward benzene conversion and selectivity toward cyclohexene generation. When 7.6 mmol of diethanolamine and 10 g of ZrO₂ were applied, the highest cyclohexene yields of 61.6% and 77.0% of benzene conversion were achieved over the Ru catalyst. Promising stability was demonstrated after six runs of catalytic experiments without regeneration. These achievements are not only promising for industrial application but also beneficial for designing other catalytic systems for selective hydrogenation. Full article

This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction of mono- and disaccharides to sugar alcohols. Unlike traditional air-unstable non-precious metal catalysts, these are stable in air, eliminating the need for strict anaerobic conditions or pre-reduction. Moreover, when combined with supports, metal phosphides exhibit significantly enhanced activity, demonstrating high activity, selectivity, and durability in these hydrogenation reactions. Full article

The use of gold nanoparticles (Au NPs) as catalysts has gained widespread attention in various reactions due to their high activity and selectivity under mild reaction conditions. However, one major challenge in utilizing these catalysts is their tendency to aggregate, leading to catalyst deactivation and hindering their amplification and industrial application. To overcome this issue, herein, we used a method by coating the surface of Au NPs with a thin layer of SiO₂, which resulted in the formation of a superior catalyst denoted as Au@SiO₂/ZA. Characterization studies revealed that the SiO₂ layer is coated on the surface of Au NPs and effectively prevents the aggregation and growth of the gold particles during the reaction process, which makes the catalyst display excellent stability in furfural (FF) oxidative esterification to methyl furoate (MF). Moreover, the stabilization strategy is not limited to SiO₂ alone. It can also be extended to other oxides such as ZrO₂, CeO₂, and TiO₂. We believe this work will provide a good reference for the design and development of an efficient and stable gold catalyst for the oxidative esterification reaction. Full article

Effective electrochemical reduction of carbon dioxide to formate under mild conditions helps mitigate the energy crisis but requires the use of high-performance catalysts. The addition of a third metal to the binary metal catalyst may further promote the electrochemical reduction of carbon dioxide to formate. Herein, we provided a co-electrodeposition method to grow CuSnBi catalysts on pretreated copper foam and discussed the effects of both pH value and molar ratio of metal ions (Cu²⁺, Sn²⁺, and Bi³⁺) in the electrodeposition solution on the electrocatalytic performance of CO₂ to HCOO⁻. When the pH value of the electrodeposition solution was 8.5 and the molar ratio of Cu²⁺, Sn²⁺, and Bi³⁺ was 1:1:1, the electrode showed the highest FE_HCOO⁻ of 91.79% and the formate partial current density of 36.6 mA·cm⁻² at −1.12 V_RHE. Furthermore, the electrode kept stable for 20 h at −1.12 V_RHE, and FE_HCOO⁻ was always beyond 85% during the electrolysis process, which is excellent compared to the previously reported ternary metal catalytic electrodes. This work highlights the vital impact of changes (pH value and molar ratio of metal ions) in electrodeposition liquid on catalytic electrodes and their catalytic performance, and refreshing the electrolyte is essential to maintain the activity and selectivity during the electrochemical reduction of CO₂ to HCOO⁻. Full article

Sulfur-resistant Mo-based catalysts have become promising for the one-step synthesis of methanethiol (CH₃SH) from CO/H₂/H₂S, but the low reactant conversion and poor product selectivity have constrained its development. Herein, we synthesized K-MoS₂/Al₂O₃ and K-Mo₂C/Al₂O₃ catalysts via the sulfurization and carbonization of K-Mo-based catalysts in the oxidized state, respectively. During the synthesis of CH₃SH, both K-Mo₂C/Al₂O₃ and K-MoS₂/Al₂O₃ showed excellent catalytic performance, and the activity of the former is superior to that of the latter. The effect of different treatments on the catalytic performance of Mo-based catalysts was investigated by XRD, BET, Raman spectroscopy, H₂-TPR, and reactants-TPD characterization. The results showed that the sulfide-treated sample showed stronger metal-support interactions and contributed to the formation of K₂S, which exposed more active sites and stabilized the formation of C-S bonds. Carbonized samples enhanced the activation of H₂, which promoted the hydrogenation of the intermediate species of carbonyl sulfide (COS) and thus improved the selectivity of CH₃SH. Full article

A large variety of pharmaceutical compounds have recently been detected in wastewater and natural water systems. This review highlighted the significance of removing pharmaceutical compounds, which are considered indispensable emerging contaminants, from wastewater and natural water systems. Various advanced oxidation processes (AOPs), including UV-H₂O₂, Fenton and photo-Fenton, ozone-based processes, photocatalysis, and physical processes, such as sonolysis, microwave, and electron beam irradiation, which are regarded as the most viable methods to eliminate different categories of pharmaceutical compounds, are discussed. All these AOPs exhibit great promising techniques, and the catalytic degradation process of the emerging contaminants, advantages, and disadvantages of each technique were deliberated. Heterogeneous photocatalysis employing metal oxides, particularly anatase TiO₂ nanoparticles as catalysts activated by UV light irradiation, was reviewed in terms of the electron–hole separation, migration of the charge carriers to the catalyst surfaces, and redox potential of the charge carriers. This brief overview also emphasized that anatase TiO₂ nanoparticles and TiO₂-based nanomaterials are promising photocatalysts, and a combination of photocatalysis and other AOPs enhanced photocatalytic degradation efficiency. Finally, the challenges of applying anatase TiO₂-based photocatalysis in environmental remediation and wastewater treatments to degrade pharmaceutical compounds, including mass spectroscopic analysis and a biological activity test of by-products of the emerging contaminants resulting from photocatalysis, are summarized. Full article

The catalytic cracking of pyrolysis gasification tar into H₂ has garnered significant attention due to its exceptional conversion efficiency. In this study, the effects of pollutant concentration, residence time, weight hourly space velocity (WHSV), and reaction temperature on the hydrogen performance of LaFe_0.5Ni_0.5O₃ perovskite were comprehensively investigated. Results revealed that moderate pollutant concentration (0.3 g/L), low-medium residence time (250 SCCM), and low WHSV (0.24 g_toluene/(g_cat·h)) facilitated efficient interaction between LaFe_0.5Ni_0.5O₃ and toluene, thus achieving high hydrogen production. An increase in reaction temperature had minimal effect on the hourly hydrogen production above 700 °C but caused a significant increase in methane production. Additionally, the effects of oxygen evolution reactions, methane reactions, and methane catalytic cracking reactions of perovskite induced by different reaction conditions on tar cracking products were discussed in detail. Compared to previous reports, the biggest advantages of this system were that the hydrogen production per gram of tar was as high as 1.002 L/g, and the highest hydrogen content in gas-phase products reached 93.5%, which can maintain for approximately 6 h. Finally, LaFe_0.5Ni_0.5O₃ showed good thermal stability, long-term stability, and catalyst reactivation potential. Full article

The practical application of formic acid production through the hydrogenation of CO₂ has garnered significant attention in efforts to tackle the challenges associated with (1) achieving net-zero production of formic acid as a chemical feedstock and (2) improving hydrogen storage and transport. This study focuses on demonstrating the continuous operation of a trickle bed reactor for converting CO₂ into formate using palladium on activated carbon (Pd/AC). Optimal temperature conditions were investigated through a dynamic operation for 24 h, achieving the maximum productivity of 2140 mmol_FA·g_Pdsurf.⁻¹·h⁻¹ at 150 °C and 8 MPa, with an H₂/CO₂ ratio of 1:1; however, catalyst deactivation was observed in the process. Stability tests performed under continuous operation at 120 °C and 8 MPa with an H₂/CO₂ ratio of 1:1 indicated a gradual decline in productivity, culminating in a 20% reduction after 20 h. A comprehensive analysis comparing fresh and spent catalysts revealed that the diminished catalytic activity at elevated temperatures was attributed to the partial sintering and leaching of Pd nanoparticles during the hydrogenation process. These findings offer insights for the future development of novel Pd-based catalyst systems suitable for continuous hydrogenation processes. Full article

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO₃ perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N₂ adsorption–desorption isotherms, H₂ temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface. Full article