Heterogeneous Catalysis Research Papers - Academia.edu (original) (raw)

2025, International Letters of Chemistry, Physics and Astronomy

A library of 3,4-dihydropyrimidin-2(1H)-ones/thiones derivatives were synthesized via Biginelli condensation reaction of β-keto esters, aryl aldehydes and urea/thiourea under solvent-free conditions utilizing nickel nanoparticles under microwave irradiation (CEM Discover). The structures of the all compounds were elucidated with the aid of elemental analysis, IR, 1H-NMR and Mass spectral data. Nickel nanoparticles can be recovered and reused five times without loss of their efficiency. Short reaction time, high yield of products and simple workup procedure, solvent-free conditions and reusability of the catalyst are the superior features of this protocol.

2025, Journal of Molecular Catalysis A: Chemical

2025, Reaction Kinetics, Mechanisms and Catalysis

Three samples of NiAl layered double hydroxides with takovite-like structure were prepared by a co-precipitation method at Ni 2+ /Al 3+ molar ratios of 1.5, 2.5 and 4.0. The samples were investigated as catalysts for hydrogen production by means of water-gas shift reaction (WGSR). The properties and catalytic behavior of the unmodified as-synthesized materials are compared with those of the same materials used as a support on which gold particles have been deposited. All samples were characterized by N 2 physisorption, Powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) techniques. Catalytic activity of all materials was studied towards conversion of CO at atmospheric pressure within the temperature interval 140-300 °C. The dependence of WGS activity on the Ni 2+ /Al 3+ molar ratio and the presence of gold were investigated. The promotional role of Au on the WGS performance was clearly demonstrated by Au-NiAl2.5 catalyst, which reached equilibrium conversion value of 97.6% at 240 °C. The stability test of the most active Au-NiAl2.5 catalyst resulted in the same CO conversion degree within 32 h under stream at 260 °C. A plausible scheme for the reaction mechanism, including the redox Ni 2+ ↔ Ni 3+ transition on the catalyst surface as well as adsorption and activation of the CO molecule on the Au particles, is proposed.

2025, Reaction Kinetics, Mechanisms and Catalysis

Diatomite supported NiMgAg catalysts, NiMgAg/D, were prepared by the precipitation-deposition method followed by drying, reduction and passivation. The preparation of the catalysts was performed with different loading of silver ranging from 0.16 to 5.88 wt% and constant molar ratios of SiO 2 /Ni and Mg/Ni equal to 1.07 and 0.1, respectively. The characterization of the catalysts was performed with N 2 -physisorption, mercury intrusion porosimetry, H 2 -chemisorption, X-ray diffraction, temperature programmed reduction, and scanning electron microscopy-energy dispersive X-ray analysis. The partial hydrogenation of soybean oil from initial to final iodine value of 90 was carried out at 160 °C and H 2 pressure of 0.16 MPa using stirred semi-batch reactor. Soybean oil was hydrogenated over NiMgAg/D catalysts and NiMg/D catalyst (without silver addition) that was prepared using the same procedure as used for catalysts modified with silver. The selectivity towards trans fatty acid and saturated fatty acid formation was determined for both types of catalysts. By comparing the selectivity of the NiMgAg/D catalysts with the NiMg/D catalyst the promoting effect of silver modifier on the catalyst behavior in the hydrogenation of soybean oil was observed, and correlated with changing of the catalyst surface characteristics caused by the different Ag loading. It was found that the addition of silver to NiMg/D catalyst decreased both the selectivity towards trans fatty acids formation and the selectivity towards saturated fatty acids. For the same iodine value decay, the catalyst with the highest Ag loading (5.88 wt%) had the lowest level of both trans fatty acids and saturated fatty acids in the hydrogenation of soybean oil under studied operating conditions. The

2025, Applied Catalysis B: Environmental

The catalytic activity of a wide range of transition metal oxides in oxidation of sulphide ions by air in aqueous medium was studied. Some specific features of the reaction mechanism on some of the studied oxides were considered. The transition metal oxides are promising catalysts for practical application. Some of these oxides will allow the preparation of catalysts possessing activity comparable to that of the cobalt phthalocyanine based catalysts, popular in industrial practice.

2025, Catalysis Today

The selective catalytic reduction (SCR) of NO by methane in the presence of excess oxygen has been studied on a series of Pd catalysts supported on sulfated zirconia (SZ). This support is not as sensitive to structural damage by steaming as the acidic zeolites, such as H-ZSM-5 and H-Mor. In previous studies, it was shown that this type of acidic zeolites are able to stabilize Pd 2+ ions and promote high SCR activity and selectivity, which are typically not seen in Pd catalysts. In this contribution, it has been demonstrated that SZ is able to promote the NO reduction activity in a similar way to the acidic zeolites, by stabilizing Pd 2+ ions that is selective for NO reduction. As in the case of acidic zeolites, the stabilization of Pd 2+ ions can occur through a transfer of Pd species from particle to particle. One of the attractive features of Pd/SZ catalysts is that they are less sensitive to water and SO 2 poisoning than Pd/H-ZSM-5 catalyst and exhibit higher reversibility after removal of water or SO 2 .

2025, Journal of Catalysis

Layered nanoslabs of a WS 2 phase with a well-defined hexagonal crystalline structure, average slab length of 3.6 nm, and stacking number of 3.2 were inserted into the nanotubular channels of SBA-15, an ordered pure silica material (surface area of 800 m 2 /g, uniform mesopore diameter of 6.5 nm) at loadings up to 60 wt.%. Sonication of a slurry containing SBA-15 in a W(CO) 6 -sulfur-diphenylmethane solution yielded an amorphous WS 2 phase inside the mesopores. By sulfidation with 1.5% dimethyldisulfide in toluene under a hydrogen flow at 593 K and 5.4 MPa, the amorphous phase was transformed into hexagonal crystalline WS 2 nanoslabs (as shown by XRD, HRTEM, and selected area electron diffraction (SAED)). The WS 2 nanoslabs were distributed exclusively inside the mesopores in a uniform manner (HRTEM, quantitative microanalysis), without blocking the pores (N 2 -sorption), and were oriented with their edge planes toward the support surface. This study constitutes the first report of such a combination of high loading of a well-defined crystalline catalytic phase into the nanotubular channels of mesoporous silica without blocking them. The first well-resolved HRTEM images of the well-defined crystalline catalytic phase (WS 2 ) inside the SBA-15 nanotubes are presented. A Ni component was introduced into the WS 2 /SBA-15 composite by impregnation from an aqueous solution of nickel acetate. It increased the catalytic activity up to a Ni/W ratio of 0.4. In the hydrodesulfurization (HDS) of dibenzothiophene and the hydrogenation (HYD) of toluene, the activity of the optimized Ni-W-S/SBA-15 catalyst was 1.4 and 7.3 times higher, respectively, than that of a sulfided commercial Co-Mo/Al 2 O 3 . This finding illustrates the excellent potential of high loading Ni-W-S/SBA-15 catalysts for deep hydrotreatment of petroleum feedstocks.

2025, Eurasian Chemico-Technological Journal

Evaluation of catalytic performances of selected metal chlorides such as AlCl 3 , SnCl 4 , ZnCl 2 , FeCl 3 , InCl 3 and GaCl 3 with solid acids such as sulfated zirconia, and zeolite beta was accomplished for acetylation of anisole, toluene and naphthalene. Presence of super acidity (Lewis or Bronsted acid) is found to be indispensable for activation of substrates towards acetylation reactions. In addition, presence of redox centers would further complement with the Lewis acid sites rendering catalytic stamina against deactivation. Strength of Lewis acid basically determines the activity of the metal chlorides towards acetylation. Among the Lewis acids investigated, FeCl 3 , InCl 3 and GaCl 3 exhibit their catalytic behaviour mostly through redox property as is evident from the conservation of Turn over number even after first cycle. Sulfated zirconia surpasses all the acid catalysts including metal chlorides and exhibits extended catalytic activity in acetylation of anisole. The pre-eminence of sulphated zirconia over other catalytic systems is owing to the synergistic effect of Lewis and Bronsted acidity.

2025, Microporous and Mesoporous Materials

The assembling mode of transition metal oxides and metallic guest phases (GP) embedded in nanotubular pores of ordered mesostructured silicas (OMS) hosts was evaluated based on N 2 adsorption-desorption data. The corresponding isotherms were measured for sample sets of composite materials MoO 3 /Al-MCM-41, WO 3 /SBA-15, TiO 2 /SBA-15, ZrO 2 /SBA-15, NiO/SBA-15 and Ni°/SBA-15 with GP loadings in the range of 20-80 wt%. The materials were also characterized by XRD, HRTEM and local/total EDS. It was shown that a combination of composite surface area values normalized per gram of OMS with pore size distribution (PSD) derived from the adsorption or desorption branch of the isotherm distinguishes the ensemble of small nanoparticles with a size of less than an OMS mesopore diameter and single nanoparticles of a size comparable with OMS mesopore diameter. It also discerns amorphous layer at the surface of OMS pore walls from the ensemble of amorphous nanoparticles. At high GP loadings the PSD derived from the adsorption branch of the N 2 -adsorption isotherm more reliably reflects the filling of OMS mesopores with crystalline or amorphous guest nanoparticles.

2025, Applied Catalysis A-general

Ammoxidation of p-cresol to p-hydroxybenzonitrile (pHBN) was studied over a large number of catalysts, mainly oxides of Bi-Mo and B-P. Supported boria-phosphoria on silica displayed superior performance. Feed composition and rate had a significant effect on catalyst performance. The best performance was measured at ammonia, air and nitrogen to cresol molar ratios of 10, 40, 120, respectively. The best performance of fresh catalyst was 63 wt.% yield of pHBN at P:B molar ratio ranging from 5 to 8 and total oxide content on silica between 10-18 wt.%. Polymeric deposits on the catalyst generated extensive deactivation. Regeneration of catalyst in a mixture of air-nitrogen and steam restored initial performance. Testing of various promoters indicated that 0.03 wt.% Pt improved both catalyst stability and regenerability with no effect on selectivity. Cycled operation of 12 h ammoxidation and 12 h regeneration over 200 h on-stream demonstrated that an average yield of 55 wt.% pHBN could be maintained. A tentative mechanism was derived based on reaction and adsorption measurements: p-cresol and ammonia adsorbed on medium strength acidic sites form p-hydroxybenzylamine as intermediate product. p-Hydroxybenzylamine reacts with oxygen to produce pHBN. Two different routes for formation of polymeric coke were identified: direct condensation of p-cresol on acidic sites and ammonia-induced condensation of p-hydroxybenzaldehyde formed by p-hydroxybenzylamine oxidation.

2025, Fuel Processing Technology

The conversion of ethanol on the Zn x Zr y O z catalyst was studied over a wide range of operating conditions to determine the possibility of producing organic liquid (olefins, aromatics and oxygenates). The content of water in the feed was found to be the key parameter. At ≥60 wt% water, no organic liquid is formed. As water content decreased, the yield of organic liquid increased. Furthermore, increasing pressure increased the yield of organic liquids. Experiments conducted at increasing residence time indicated that ethanol was first converted to oxygenates then to aromatics and higher olefins (C 5 -C 11 ) with propylene, ethylene, carbon dioxide and hydrogen as the main by-products. Increasing temperature at high residence time (WHSV = 0.8 h -1 ) decreased the yield of liquid oxygenates while increasing the yield of aromatics and higher olefins. A tentative scheme of reactions was proposed considering the special nature of the Zn x Zr y O z catalyst with balanced basic-acidic sites. The catalyst was stable, tested for > 300 h. Tail gas containing light olefins, mainly propylene and ethylene, was converted by oligomerization on a commercial H-ZSM-5 catalyst to higher olefins (> 90%) and aromatics at high conversion (> 90%). The organic liquid from the two reactors can be used as feedstock for chemicals or as blending stock for gasoline.

2025, Topics in Catalysis

The strong drive to commercialize fuel cells for portable as well as transportation power sources has led to the tremendous growth in fundamental research aimed at elucidating the catalytic paths and kinetics that govern the electrode performance of proton exchange membrane (PEM) fuel cells. Advances in theory over the past decade coupled with the exponential increases in computational speed and memory have enabled theory to become an invaluable partner in elucidating the surface chemistry that controls different catalytic systems. Despite the significant advances in modeling vapor-phase catalytic systems, the widespread use of first principle theoretical calculations in the analysis of electrocatalytic systems has been rather limited due to the complex electrochemical environment. Herein, we describe the development and application of a first-principles-based approach termed the double reference method that can be used to simulate chemistry at an electrified interface. The simulations mimic the half-cell analysis that is currently used to evaluate electrochemical systems experimentally where the potential is set via an external potentiostat. We use this approach to simulate the potential dependence of elementary reaction energies and activation barriers for different electrocatalytic reactions important for the anode of the direct methanol fuel cell. More specifically we examine the potential-dependence for the activation of water and the oxidation of methanol and CO over model Pt and Pt alloy surfaces. The insights from these model systems are subsequently used to test alternative compositions for the development of improved catalytic materials for the anode of the direct methanol fuel cell.

2025, Advanced Functional Materials

Vacuum level shifts Δ ( d ) at metal-organic (m-O) interfaces indicate the formation of surface dipoles for fi lm thickness d ≤ ≤ d ML up to a monolayer (ML). Shifts or profi les Δ ( θ ) of submonolayer fi lms are nonlinear in the coverage θ = d / d ML ≤ ≤ 1, which points to cooperative interactions between adsorbed molecules. Adsorption with weak nonspecifi c bonding is modeled as charge transfer (CT) between molecules M and localized surface states S of the metal. The dipole μ 0 of ions S -M + or S + M -gives upper bounds for the vacuum level shift Φ 0 and dipole-dipole repulsion V 0 at θ = 1. Partial CT ρ ( θ ) < 1 is found self consistently and accounts for published profi les Δ ( θ ) of representative planar and nonplanar molecules with d ML ∼ 4 and ∼ 10 Å. Initial adsorption at θ ∼ 0 has considerable ionic character, ρ (0) ∼ 1/2, that decreases to ρ (1) ∼ 1/10 at θ = 1. Planar molecules with small μ 0 and V 0 have slightly nonlinear profi les while molecules with large μ 0 and V 0 have highly nonlinear Δ ( θ ). Collective CT is a phenomenological model for m-O interfaces with nonspecifi c bonding. The CT model is contrasted to fi xed dipoles on the surface, to calculations of Δ (1) and to simulations of sub-ML fi lms.

2025, Journal of Synchrotron Radiation

Ni species on the spent NiMo catalyst from ultra-deep hydrodesulfurization of gas oil in a commercial plant were studied by Ni K-edge EXAFS and TEM measurement without contact of the catalysts with air. The Ni-Mo coordination shell related to the Ni-Mo-S phase was observed in the spent catalyst by quasi in situ Ni K-edge EXAFS measurement with a newly constructed high-pressure chamber. The coordination number of this shell was almost identical to that obtained by in situ Ni K-edge EXAFS measurement of the fresh catalyst sulfided at 1.1 MPa. On the other hand, large agglomerates of Ni 3 S 2 were observed only in the spent catalyst by quasi in situ TEM/EDX measurement. MoS 2 -like slabs were sintered slightly on the spent catalyst, where they were destacked to form monolayer slabs. These results suggest that the Ni-Mo-S phase is preserved on the spent catalyst and Ni 3 S 2 agglomerates are formed by sintering of Ni 3 S 2 species originally present on the fresh catalyst.

2025, KEK Prog Rep

Introduction NiMo/Al2O3 and NiW/Al2O3 catalysts are widely used for the hydradesulfurization (HDS) and hydrogenation (HYD) reactions of petroleum feedstock. It is an urgent issue to improve their catalytic activity to meet severe... more

2025, Applied Surface Science

The effect of sulfiding pressure on the surface structure of Ni-Mo (or W)/AI203 was investigated in the range of 0.1 to 5.1 MPa by in-situ FT-IR/DRA of adsorbed NO. The distribution of the Ni site and Mo (or W) site on the surface of every catalyst examined was sensitive to the sulfiding pressure. In the Ni-Mo/Al203 catalyst, the intensity of the Mo site-band was weaker when the catalyst was sulfided at a pressure above 1.1 MPa than when sulfided at 0.1 MPa, while the Ni site-band was insensitive to the sulfiding pressure. On the other hand, in the Ni-W/AI203 catalyst, the W site-band could not be discriminated distinctly in the range of 0.1 to 5.1 MPa and the Ni site-band sensitively decreased with increasing the sulfiding pressure. Comparing the results with those of the physical mixture of Mo(or W)/AI20 3 and Ni/AI203, it was suggested that sulfiding induces the interaction between Ni and Mo in Ni-Mo/AI203 (or W in Ni-W/AI203), and that the interaction between Ni and Mo was promoted by higher pressure sulfiding above 1.1 MPa.

2025, Catalysts

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO 2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO 2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (T ig ). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than T ig . The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO 2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at T ig to form CO 2 . Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO 2 support interaction, and PdO formation and decomposition.

2025, Journal of Sol-Gel Science and Technology

Amberlite XAD 16N mesoporous polystyrene spheres were used as a template to create silicon dioxide (SiO 2 ), silicon, and silicon carbide (SiC) mesoporous spheres. Polystyrene spheres, infiltrated with either hydrochloric acid catalyzed tetraethyl orthosilicate or dimethylethylamine catalyzed tetramethyl orthosilicate, were heated to 550 °C to induce oxidation and/or decomposition of the polystyrene template and yielded SiO 2 spheres. To create Si and SiC spheres, SiO 2 and SiO 2infiltrated spherical polystyrene templates, respectively, were distributed in finely grated magnesium before heating to 675 and 700 °C each in an argon atmosphere. Mg byproducts in the form of magnesium silicates and residual SiO 2 were removed by washing the spheres with hydrochloric acid and hydrofluoric acid, respectively. X-ray diffraction, Brunauer-Emmet-Teller model specific surface area analysis, Barrett-Joyner-Halenda model pore diameter analysis, transmission electron microscopy and scanning electron microscopy were employed to investigate the microstructure and porosity during and after synthesis of the spheres. All three types of spheres maintained high porosity and their spherical shape throughout the synthesis. SiO 2 spheres had a surface area of 700 m 2 g -1 , Si spheres a surface area of 160 m 2 g -1 , and SiC spheres a surface area of 215 m 2 g -1 . SiO 2 spheres with dispersed Ag nanoparticles were also successfully created by adding AgNO 3 to the precursor solution; they had a surface area of 220 m 2 g -1 . To prove the versatility of this infiltration method, Dy 2 O 3 spheres were also fabricated, though they were not porous. This infiltration method is not only versatile, as it is suitable for the preparation of numerous types of mesoporous spheres, but it is also a simple synthesis method that guarantees a well-defined spherical shape and narrow particle size distribution, primarily while maintaining a high surface area.

2025, Physical Characterization of Pharmaceutical Solids

Thermo gravimetric analysis (TGA) of the samples is carried out using Mettler Toledo analyzer Model: TGA/DSC 1, STAR e system, SW 9.20, USA, by heating the samples in the range of 50-1000 °C with a heating rate of 10°C/min under nitrogen... more

2025

Developing micro-and nanomaterials for environmental pollution remediation is hot topic presently. Among the plethora of strategies, designing supported nanocatalysts for the degradation of pollutants witnessed constant renewal. In this context, we are addressing one of the UN Sustainable Development Goals by valorizing agrowaste as a source of biochar which serves as support for bimetallic nanocatalysts. Herein, Olive pit powder particles were impregnated with copper and nickel nitrates and pyrolyzed at 400 °C. The resulting material consists of bimetallic CuNi-decorated biochar. CuNi nanocatalysts were found to be as small as 10 nm and very well dispersed over biochar with zero valent copper and nickel and formation of copper-nickel solid solutions. The biochar@CuNi exhibited typical soft ferromagnet hysteresis loops with zero remanence and zero coercivity. The biochar@CuNi was found to be efficient catalyst of the reduction of methyl orange (MO) dye, taken as model pollutant. To sum up, the one pot method devised in this work provided unique CuNi-decorated biochar and opens new horizons for the emerging topic of biochar-supported nanocatalysts.

2025, Applied Catalysis O: Open

From the recovery of Ni, Co, and Mn from Li-ion batteries using the hydrometallurgical technique, two catalysts supported on γ-Al₂O₃ with different metal load concentrations were prepared. The catalysts were characterized using XRD, SEM, TPR, XPS and BET surface area measurements. These catalysts were studied in the dry reforming of methane reaction at 600 °C. The results showed that the solids prepared from a leach solution of lithium-ion batteries exhibit good catalytic activity in the DRM reaction at low temperatures (600 °C). The prepared catalysts demonstrated good performance, with conversion rates comparable to those in other studies and an H₂/CO ratio of 0.7–0.8, making them promising for catalytic applications aimed at reducing greenhouse gases and hazardous waste, such as those found in these batteries.

2025, ChemistrySelect

For environmental concerns, there is need of cost effective method for the removal of toxic and carcinogenic dyes used in industries that pose a serious threat to humankind as well as marine life/ecosystems. FeS 2 is a promising semiconductor photocatalyst because of its high potential to degrade dyes as well as organic materials. In the present study, FeS 2 was successfully synthesized using low cost and more effective hydrothermal method. The different features of synthesized FeS 2 material was confirmed by X-ray diffraction, transmission electron microscopy, UV-visible spectrophotometry. Methyl orange dye and also a textile dye that contribute as a major organic pollutant was effectively degraded by photo catalytically active FeS 2 nanostructures. The maximum degradation efficiency (93.09%) was occurred in 120 minutes with 1 g/L FeS 2 catalyst dose. The dye removal efficiency for a textile dye Novacron yellow Huntsman (NYH) approximately 98.15 % was achieved with 1 g/L FeS 2 catalyst in just 80 min irradiation of visible light. This work further insights to develop FeS 2 nanostructures photocatalyst for the removal of toxic and hazardous water contaminants.

2025, Catalysis Today

LaNiO 3 and La 2 NiO 4 , as such and in combination with CeO 2 , were prepared by microwave assisted coprecipitation procedure and tested in the catalytic partial oxidation of methane (CPO). The materials were characterized by BET, TGA/DTG, XRD, TPR and TEM techniques. In the absence of CeO 2 , the microwave processing allowed obtaining perovskite and spinel phases in high percentage at milder conditions as compared to traditional methods. In the presence of CeO 2 , Ce 1-x La x O 2-x/2 solid solutions and NiO formed. At high temperature (∼800 °C) all the catalysts exhibited high methane conversion with near 100% CO selectivity and good stability. Activation of the catalysts occurred during temperature cycling. At the temperature corresponding to ∼60% conversion, the CeO 2 -free sample deactivated quickly, differently from the CeO 2 containing sample being very stable during the 18 h of reaction. The temperature surface reaction (TPSR) of CH 4 without O 2 confirmed the differences between the two systems, i.e. with and without CeO 2 . The LaNiO 3 -CeO 2 activated the decomposition of methane with simultaneous CO/CO 2 evolution in a large range of temperature contrary to LaNiO 3 activating methane decomposition only in a narrow range of temperature, without any CO/CO 2 evolution. As shown from TPR analyses, an intimate contact between nickel phases and ceria was required to promote CPO activity. According to TGA and as confirmed by TEM analyses, formation of carbon was inhibited over the CeO 2 containing catalysts, whereas different types of carbons were formed over the spinel and the perovskites formulation samples.

2025, Catalysis Today

The effect of different supports, silica HMS and Ti doped silica HMS, on the catalytic performance of mono (Pd) and bimetallic (Pd-Au, Pd-Re) catalysts, containing 2 wt% of each metal, for the hydrogenation of levulinic acid in water was studied. The catalytic behavior of the materials was evaluated in terms of conversion of the starting levulinic acid and selectivity to ␥-valerolactone. The surface and structural properties of the catalysts were investigated by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) performed on fresh and spent materials. A synergic effect of Au and Ti on Pd sample was observed with the consequent formation of a PdTi alloy responsible of the good performance of the catalyst.

2025, Journal of Solid State Chemistry

A series of aluminosilicates with an Al/Si ratio ranging from 0 to N (0 for pure silica and N for pure alumina) was prepared by sol-gel process and characterized by surface and structure techniques. Aluminum trisecbutoxide and tetramethylorthosilicate were used as precursors for the sol-gel synthesis. The acidic properties of the oxides were studied by determination of the zero point charges, through mass titration method, and, for selected samples, by FT-IR spectroscopy of adsorbed pyridine used as a probe for both Br^nsted and Lewis acidity. A dependence of the acidity on the Al/Si atomic ratio was found. According to the X-ray diffraction patterns, all the oxides have an amorphous structure except pure alumina exhibiting a g-alumina pattern. The surface areas of the mixed oxides increase with increasing amount of alumina and are higher as compared to the individual oxides. The surface elemental distribution and electronic properties were investigated by X-ray photoelectron spectroscopy. According to the results, good agreement between the surface Al/Si atomic ratio and the analytical ratio is obtained.

2025, Catalysis Today

Sulfonic acid-functionalized hybrid silicas with different structure (amorphous, HMS, SBA-15) were synthesized by different methodologies, with a variable amount of organic moieties (propyl SO 3 H). The obtained catalysts, characterized by X-Ray photoelectron spectroscopy, low angle X-Ray diffraction, N 2 adsorption and acid capacity measurements, were tested in the transesterification reaction of short chain esters (from hexanoic to lauric ethyl ester). The optimized reaction was carried out under mild condition in the presence of 15% mol of the corresponding organic acid in order to reproduce a typical low-grade oil. A correlation between the catalytic activity of the materials and their acid capacities was found. The propyl-sulfonic SBA-15 catalyst presented the best performance in terms of activity and structural stability with no leaching of the sulfonic groups.

2025, Applied Catalysis A: General

The structural properties and the hydrodesulfurization (HDS) activity of sodium doped and sodium free CoMo catalysts supported on amorphous aluminosilicates (ASA) were investigated as a function of different SiO 2 :Al 2 O 3 ratios. The support yielding the most active catalyst, (66% alumina) doped with different amounts of sodium, was used for a series of similar catalysts in order to study the effect of the alkali ion on the catalytic performance. The supports were prepared by sol-gel method and the catalysts were prepared by incipient wet impregnation method. The structure and the surface of the various samples were investigated by X-ray diffraction (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic behaviour was tested in the hydrodesulfurization of thiophene carried out in a continuous flow system at atmospheric pressure, in a range of temperature between 603 and 633 K. Changes of activity with the support composition were observed. The presence of sodium, modifying the Brønsted acidity of the supports, enhances such effect. Moreover, the increase of the activity with increasing amount of sodium was a clear indication of the promoting effect of the alkali ion.

2025, Chemistry of Materials

This work focuses on the synthesis and photocatalytic performance of mesoporous TiO 2 films containing embedded gold nanostructures. The TiO 2 films were prepared by the EISA (evaporation-induced selfassembly) process and loaded with Au either by impregnation followed by reduction with NaBH 4 or by pulsed cathodic electrodeposition. The latter approach represents a considerably easier and faster synthetic method and results in dendritic Au nanostructures as a replica of the pore system. The as-prepared composite films were characterized by scanning and transmission electron microscopy (SEM and TEM), UV-vis spectroscopy and Kr adsorption. Photocatalytic oxidation of NO was chosen as the test reaction for elimination of air pollutants. For mesoporous TiO 2 films deposited on an ITO layer, the photonic efficiency is higher than for films prepared on glass, because the pore structures are altered. Incorporation of Au results in a significant improvement in the photonic efficiency due to the generation of Schottky barriers, which inhibit the recombination of electron-hole pairs and thereby increase the concentration of photogenerated holes at the film surface reacting with NO. Compared to the impregnated nanocomposites, mesoporous TiO 2 films with electrochemically incorporated dendritic Au nanostructures provide comparable photocatalytic activities, but their preparation is much less time-consuming and of lower cost. An additional treatment with O 2 plasma leads to further increase in the photocatalytic activity due to the higher amount of hydroxyl groups on the surface, which play a significant role in the photocatalytic oxidation of NO. Mesoporous nanocomposite films are promising in photocatalysis and self-cleaning technologies.

2025, Materials Research

In this paper, a new way for γ-alumina synthesis was proposed, the raw material being aluminum powders obtained by high-energy milling of aluminum cans. This seems a good option for this metal recycling and energy saving, as well as hydrogen production. The materials were prepared by precipitation techniques, in which aluminum powders reacted with hydrochloric acid, giving aluminum chloride, which was subsequently transformed into aluminum hydroxide by reaction with ammonium hydroxide or sodium hydroxide as precipitant agents, and finally into γ-alumina by calcination. Results showed that the used preparation methods gave a γ-alumina structure, confirmed by XRD, with surface areas values (174 and 204 m 2 g -1 ) close to those of a commercial γ-alumina Cyanamid Ketjen (180 m 2 g -1 ) or an alumina prepared by a typical precipitation route (203 m 2 g -1 ). Using sodium hydroxide as precipitant agent turned out to be more ecologically compatible since it did not release harmful environmental compounds.

2025, Catalysis Today

In order to get high methane conversions and to avoid coke deposition, by methane cracking (Eq. ( )) or by Boudouard reaction (Eq. ( )), the process is carried out under large amounts of steam Catalysis Today 142 (2009) 52-60

2025, Journal of the Brazilian Chemical Society

The conversion of ethanol into hydrocarbons, particularly into light olefins, was studied over MCM-22 zeolite in their acid form (HMCM-22) and its derived forms obtained by dealumination with oxalic acid (HMCM-22(OA)) and delamination (HITQ-2). The treatment with oxalic acid did not affect zeolite textural properties but reduced the total density and strength of the acid sites. As to the delamination process, HITQ-2 zeolite presented the highest Brunauer, Emmett and Teller (BET) specific area, mesopore volume, and external area, but the microporosity was not affected. This sample showed a lower SiO2/Al2O3 ratio than the precursor HMCM-22, resulting in the highest acid site density but with the predominance of acid sites with weak and intermediate strength. Both dealumination and delamination led to an increase in the number of structural defects in the samples. The comparison of the catalytic performance at 500 ºC showed that despite the differences in the acidic and textural proper...

2025, RSC Advances

Ni promoted tungsten carbides have been shown to be an effective catalyst for cellulose conversion reaction.

2025, Catalysis Letters

Palladium and/or molybdenum catalysts supported on mordenite were prepared and characterized by XRD, UV-vis, DRS, textural properties analysis, TPR, TPD and chemical analysis. The Mo-catalyst rapidly deactivated after the first minutes reaction. The Pd-catalysts were active in the NO decomposition reactions. The incorporation of Mo in the Pd-catalysts improved their catalytic properties.

2025, Applied Catalysis A: General

Perovskite-type oxides La 1-x Ce x CoO 3 (x = 0, 0.05 and 0.10) were prepared, characterized and evaluated in the selective CO oxidation reaction (SELOX). The citrate synthesis methodology favored the formation of perovskites with rhombohedral structure and low specific surface area (<14 m 2 g -1 ). TPR profiles showed intermediates during the reduction process but the addition of cerium not only inhibited its formation but also promoted structural modifications in the perovskite lattice. XRD diffractograms showed the formation of perovskite without phase segregation. Temperature programmed reactions showed selective CO oxidation at low temperature besides undesired reactions at higher temperatures. Catalytic tests of the SELOX reaction showed 100% of CO conversion at 200 • C. Higher temperatures favored hydrogen oxidation and methanation. Catalysts LaCoO 3 and La 0.95 Ce 0.05 CoO 3 presented good stability during 48 h of reaction. The LaCoO 3 catalyst was sensitive to the presence of H 2 O and CO 2 in the feed stream, however its CO conversion was easily restored after removing these compounds from the feed stream.

2025, ChemistrySelect

The regioselective synthesis of functionalized pyrazole˗1,2,3-triazoles is reported via oxidative [3 + 2]-cycloaddition reactions of azides with β-nitrostyrenes and chalcone derivatives using Zn(OAc) 2 -t BuOOH or ZnO nanoparticles as catalyst system in aqueous medium. The catalyst dependent product selectivity was observed with β-nitrostyrenes to give the triazoles with and without -NO 2 group Zn(OAc) 2 and ZnO nanoparticles. The chalcones gave the triazoles selectively as sole products with good regioselectivity. The resulting products were further converted into sulfonamides and oxazoles respectively.

2025, Die Makromolekulare Chemie

Studies of the distribution of cyclic oligomers formed in the first step of the cationic polymerization of hexamethylcyclotrisiloxane disclosed a correlation between the kinetically controlled concentrations of cyclic species and the statistical conformations adopted by the corresponding acyclic chains. The correlation found experimentally is in good agreement with the theoretical one predicted by the macrocyclization theory for non‐equilibrium chemical system and can be taken as evidence for the formation of macrocycles (even those containing about 100 atoms in the skeleton) by the intramolecular reaction between chain ends, a process which competes with the linear growth of the macromolecule. This approach may be useful in solving mechanistic problems involving polyreactions.

2025, Journal of Environmental Chemical Engineering

A series of Ni-Ce/SBA-15 catalysts with 6 wt% Ce and 5 wt% Ni were synthesized using conventional impregnation (Ni-Ce/SBA-15(C-IM)), ultrasonic-assisted impregnation (Ni-Ce/SBA-15(US-IM)) and reflux-assisted impregnation (Ni-Ce/SBA-15(R-IM)) methods The samples were characterized using XRD, TEM, SEM, BET, FTIR, H 2 -TPR, XPS and TGA. The characterization results showed that Ni-Ce loading methods greatly influence the properties of Ni-Ce/SBA-15 whereby the homogeneity of metal dispersion and strength of metal-support interaction followed the order of Ni-Ce/SBA-15(C-IM) < Ni-Ce/SBA-15(R-IM) < Ni-Ce/SBA-15(US-IM). The smaller metal particle size and higher metal dispersion in Ni-Ce/SBA-15(US-IM) have led to the stronger metal-support interaction and further decreased the surface area and porosity of the catalyst. The activity and stability of catalysts followed the order of Ni-Ce/SBA-15(C-IM) < Ni-Ce/SBA-15(R-IM) < Ni-Ce/SBA-15(US-IM), with the conversion of CH 4 and CO 2 over Ni-Ce/SBA-15(US-IM) was about 96.3% and 93.5%, respectively, and H 2 /CO ratio of 1.02 at reaction temperature of 800 °C and almost remained constant during 48 h of reaction. The superior catalytic performance of Ni-Ce/SBA-15(US-IM) probably was related with the smaller metal particles, stronger metalsupport interaction and more homogenous metal dispersion, which altered the properties of catalyst towards an excellent catalytic performance. The characterization of spent catalysts showed the lowest carbon formation in Ni-Ce/SBA-15(US-IM) catalyst, demonstrating the positive role of ultrasonic effect on al-teration of catalyst properties towards carbon resistance. This study provides new perspective on the preparation of Ni-Ce/SBA-15 towards an excellent performance of CO 2 reforming of CH 4 .

2025, Journal of Materials Chemistry

2025

In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.

2025

Reactivation of spent FCC catalyst for its application in the adsorption of heavy metals from wastewater was investigated in this research. The most effective reactivation route of spent FCC catalyst was oxidation of spent FCC catalyst using H 2 O 2 at oxidant-to-catalyst ratio of 16 ml/g, contact time of 60 minutes and a temperature of 90 o C, followed by treatment with CH 3 COOH solution at acid-to-catalyst ratio of 20 ml/g, 75 minutes contact time and at a temperature of 50 o C. The reactivation process was monitored using the Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX), X-ray fluorescence (XRF) and X-ray diffraction (XRD). The result showed significant decreases in impurities of coke and metal, and the crystallinity of the treated spent FCC catalyst was much greater than that of the spent FCC catalyst.

2025, Fuel Processing Technology

Recent studies on the exploration of eco-friendly approach by utilizing large-scale waste materials as potential catalyst in biodiesel production have attracted much attention. The development of heterogeneous catalysts especially from calcium has gained much awareness due to the large availability of calcium-rich waste materials and their corresponding high catalytic activity in the transesterification of oil. Most of the waste materials employed as heterogeneous catalysts have an abundance of natural Ca content and they have high catalyst activity and selectivity despite being environment-friendly and cost-effective. Heterogeneous catalysts with high activity can be produced from Ca based waste materials when calcined at high temperatures. This review gives a brief overview of the developments of various Ca based catalysts derived from waste materials as an efficient catalyst for biodiesel production with significant yield. Industrial wastes (red mud, slag, ash) and biological catalysts (chicken eggshells, mollusk shells, animal bones) possess enormous potential towards developing an economical catalyst and subsequently, low-cost biodiesel generation. However, future challenges await a better utilization of useless wastes into a useful resource to satisfy human needs.

2025, The journal of physical chemistry. A

An efficient method was developed for the acetalization of secondary alcohols in the presence of simple protic pyridinium salts. Direct correlations between the structure and activity of the synthesized catalysts were described. Stabilization via hydrogen bonding of the hemiacetal intermediate by the pyridine derivatives, along with an appropriate increase in the reaction rate, was revealed. The nature of the observed experimental acceleration of the examined reactions catalyzed by pyridinium salts comprising electron-withdrawing groups at certain positions of the pyridinium ring was studied. In this vein, the interpretation of the hydrogen-bonded pre-transition-state complexes and transition-state complexes with strong catalysts was also discussed in terms of partial proton transfer. It was concluded that optimized pre-transition-state complexes of the catalyst and reactant are useful for the prediction of catalyst efficiency prior to the experiment.

2025, Graphene Oxide - Applications and Opportunities

Nanochemistry has evolved as an important part in catalysis for both academic as well as industrial research. Traditional homogeneous catalytic systems have gained significant importance due to the molecular level analysis of their catalytic activity and the excellent homogeneity of the catalysts and the reactants. However, removal of the catalysts from the reaction mixture without product contamination requires tedious purification steps. With increasing ecological and economical demands towards sustainable chemical synthesis, the recovery and reuse of catalysts has been an important factor. In this drive, various heterogeneous catalytic systems including mesoporous materials, solid catalysts, organometallics, noble-metal nanoparticles, etc. have been developed for photochemical and electrochemical conversion, environmental remediation as well as catalyst for important chemical transformations. Carbon nanomaterial specially graphene oxide and carbon dots have received significant research importance due to their large scale availability, easy surface modification, non-toxicity and other surface properties. Here, we review the continuous progress in the development of graphene based materials and their catalytic activity in organic synthesis.

2025, Angewandte Chemie International Edition

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2025

Phosphorus (P) modified H-ZSM-5 catalysts were prepared by wet impregnation method by varying P loadings from 0 to 7.43 wt % using phosphoric acid (H 3 PO 4 ) as the P source. The catalysts were tested for ethanol dehydration in the temperature range of 523-723 K. The P-modified catalysts were found to be highly active and selective toward ethylene at 673 K and atmospheric pressure. In addition, the P-modified catalysts were found to be extremely stable more than 200 h without any sign of deactivation. However, the selectivity was found to be strongly dependent on several factors such as P content, reaction temperature, and space velocity (WHSV). The P-modified ZSM-5 catalysts were also found to be highly active for the dehydration of aqueous ethanol solutions (10 wt %) showing very high ethylene selectivity (above 98%) at significantly lower temperature 623 K. The catalysts were thoroughly characterized using various methods, including N 2 physisorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric differential thermal analysis (TG-DTA), 1 H, 27 Al, and 31 P magic angle spinning nuclear magnetic resonance (MAS NMR), and amonia temperature programmed desorption (NH 3 -TPD). Al MAS NMR spectra suggest that P addition facilitate the breaking of Si-O-Al bond that lead to a partial dealumination. NH 3 -TPD results indicate that total acidity as well as density of high strength acid sites were decreased with P loading.

2025

Breve resumen sobre las leyes de velocidad que aplican para el diseño de reactores catalíticos heterogéneos y breve descripción de la Ley de velocidad con cinética de Langmuir-Hinshelwood