Deposition Precipitation Method Research Articles

High Catalytic Activity of Yttria‐Stabilized Zirconia‐Supported Gold Nanoparticles for Hydrogen Peroxide Production from Oxygen and Formic Acid under Ambient Conditions

Hydrogen peroxide (H2O2) is an important chemical widely used in industry. Recently, insulating zirconia‐supported Au nanoparticles (NPs) prepared by a modified deposition precipitation method (Au/ZrO2‐MDP) have been reported to show catalytic activity for H2O2 production from aerated HCOOH aqueous solution much higher than Au/n‐type semiconducting metal oxides (Au/n‐MOs) prepared by the normal deposition precipitation method. Here we report that Au/yttria‐stabilized zirconia (Au/YSZ‐MDP) exhibits catalytic activity for the reaction far exceeding those of Au/n‐MOs and even Au/ZrO2‐MDP. Au/YSZ‐MDP yields H2O2 from aerated 1.06 M HCOOH aqueous solution with an initial rate of 2.2 mmol h−1 gcat−1 and a turnover frequency (TOF) of 4.3 × 102 h−1 at 25oC. X‐ray photoelectron and photoluminescence spectral data, in addition to the effect of YSZ surface modification with aluminium oxide, indicate that the remarkable catalytic activity of Au/YSZ‐MDP is induced by oxygen vacancies (Ov) and Ov‐derived Zr‐OH groups on the YSZ surface in the vicinity of Au NPs.

Solar Assisted Mitigation of Chloramphenicol and H2 Evolution Using CuNi Alloy Nanoparticles on h-BN Doped g-C3N4: A Comprehensive Approach Combining Synchrotron and DFT Analysis.

A simple one-step deposition-precipitation method was used to synthesize highly active and well-defined CuNi alloy bimetallic nanoparticles supported on h-BN/g-C3N4. The nanocomposite was applied for hydrogen gas evolution via seawater splitting and photocatalytic chloramphenicol (CHP) removal. Through TEM and synchrotron studies, the formation of CuNi alloy and uniform distribution of CuNi bimetallic nanoparticles on the h-BN/g-C3N4 surface was observed. The EXAFS analysis verified the successful formation of the alloy, while the XPS and XANES spectra showed that the bimetallic nanoparticles are in a metallic state. Additionally, XANES revealed nanoparticle distortion upon interaction with the support, confirming the effective formation of the nanocomposite. The nanocomposite achieved a maximum hydrogen evolution rate of 3658.9 μmol g-1 h-1 for 5 wt % CuNi(3:1)/h-BN/g-C3N4, outperforming CuNi(3:1) nanoparticles and pristine g-C3N4 by 1.82 and 4.31 times, respectively. Additionally, it degraded chloramphenicol with a rate constant (kapp) of 0.018 min-1. Optical and electrochemical analysis revealed enhanced charge mobility, extended lifetime, improved photostability, and superior photoresponse. X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations attributed the performance to the synergy between the bimetallic nanoparticles and the h-BN/g-C3N4 sheet. DFT calculations demonstrated the effective breakdown of chloramphenicol and the promotion of hydrogen gas evolution, aligning with experimental observations. Cytotoxicity of CHP post-treatment was analyzed using Drosophila melanogaster (fruit fly) and the Oregon-R strain of D. melanogaster.

Interplay Between Metal and Acid Sites Tunes the Catalytic Selectivity Over Pd/Nanodiamond Catalysts.

Metal and acid sites are two of the most crucial catalytically active components in heterogeneous catalysis. While variations in the size, morphology, and heterogeneity of metal species, or the manipulation of the strength, location, and density of acid sites, could significantly impact the catalytic performance, the combination and interplay between these sites are even more critical and have been a recent research focus. To achieve highly efficient and selective synergistic catalysis, it is desired to design a catalyst capable of orchestrating the sequential transformation of all reactants and intermediates at different active sites. In this study, we demonstrate that both acid and metal (Pd) sites can be introduced onto a nanodiamond@graphene (NDG) support particle through simple air oxidation and metal salt deposition-precipitation methods, respectively. The presence and assembly of these two catalytically active sites significantly alter the reaction network for the cyclohexanol conversion reaction. Under this strategy, the selectivity toward designated products─cyclohexene, phenol, and benzene─can be precisely tuned by the presence and patterning of these two sites on the nanodiamond particles. Specifically, we show that the catalyst with both acid sites and Pd ensemble sites, i.e., Pd/NDG, can efficiently convert cyclohexanol through consecutive dehydration and dehydrogenation reactions to form benzene with high selectivity (>80%). These findings underscore the potential of integrating metal and acid sites to design advanced catalysts with tailored reactivity and selectivity, paving the way for more efficient and versatile catalytic processes in industrial applications.

Polyol-Intermediated Facile Synthesis of B5-Site-Rich Ru-Based Nanocatalysts for COx-Free Hydrogen Production via Ammonia Decomposition.

Herein, a B5-site-rich Ru/MgAl2O4 nanocatalyst for the production of COx-free hydrogen from ammonia (NH3) is synthesized using the polyol method. The polyol method enables size-sensitive Ru-nanoparticle growth and controlled B5-site formation on the catalyst by tuning the carbon-chain length of the polyol solvent used, obviating the use of a separate stabilizer and enhancing electron donation from Ru (with a high surface electron density) and π-back bonding. The Ru/MgAl2O4 (BG) catalyst synthesized using butylene glycol (a long-carbon-chain solvent) contains 2.5nm Ru particles uniformly dispersed on its surface and abundant B5 sites at (0 0 2)/(0 1 1). Moreover, the Ru/MgAl2O4 (BG) catalyst exhibits lower activation energy (48.9kJmol-1) and higher H2 formation rate (565-1,236mmol gcat -1 h-1 at 350-450°C and a weight hourly space velocity of 30,000mL gcat -1 h-1) during the NH3 decomposition reaction than catalysts with a similar Ru particle size and high metal dispersion synthesized by the impregnation and deposition-precipitation methods. This high performance is possibly because the abundant electron-donating B5 sites on the catalyst surface accelerate the recombination-desorption of N2, which is the rate-determining step of the NH3 decomposition reaction at low temperatures. Thus, this study facilitates clean hydrogen production.

Oxy-CO2 reforming of methane on Al2O3, MgAl2O4, CeO2 and ZrO2 supported Ni catalysts prepared by deposition-precipitation method

15 (wt%) Ni loaded on Al2O3, MgAl2O4, CeO2 and ZrO2 were synthesized by the deposition-precipitation method and tested in the oxy-CO2 reforming of methane. It was found that the specific surface area, the type of support and its surface properties are important parameters for the deposition-precipitation method. The results showed that higher metallic Ni concentration and higher surface area increased the catalytic activity and selectivity. The effect of Ni loading amount on Al2O3 was investigated and the catalytic activities were found to be close for 10 (wt%) and 15 (wt%). Among the catalysts tested, 15 (wt%) Ni/Al2O3 catalyst prepared by urea deposition-precipitation method was found to be a good alternative for oxy-CO2 reforming of methane.

Oxygen vacancies-promoted oxidative esterification of ethylene glycol to methyl glycolate over Au/ZnO catalyst

Au/ZnO-x with different morphologies were prepared by controlling the amount of (NH4)2CO3 (x) using deposition precipitation method and applied for the one-step oxidative esterification of methanol and ethylene glycol (EG) to methyl glycolate (MG). The catalytic performance of Au/ZnO-x firstly increases and then decreases with the increase of the amount of (NH4)2CO3, and the maximum is achieved in Au/ZnO-4, with EG conversion of 89.6 % and 96.4 % selectivity to MG, significantly higher than the reported Au-based catalysts. The superior catalytic behavior is mainly derived from the most oxygen vacancy concentration (Vo+) accompanied with the highest I100/I101 ratio at moderate (NH4)2CO3 dosage, promoting the adsorption and dissociation of O2 molecular. Specifically, different preferential growth ratio between the (100) and (101) crystal plane accounts for Au/ZnO-2, Au/ZnO-4, and Au/ZnO-6 with lamellar stacking morphology, orderly layer structure, and randomly stacked layers, respectively. Significantly, it was found that there was a linear positive correlation between the Vo+ and the EG conversion. Innovatively, the oxygen vacancy played the predominant role in Au/ZnO-x for the catalyzed oxidative esterification of EG, which provided a new idea for the design of efficient catalysts for the reaction.

Gold nanocatalysts supported on Mono-/Mixed oxides for efficient synthesis of methyl methacrylate

Developing sustainable methods for producing methyl methacrylate (MMA) has gained strategic importance for industrial applications and as a promising oxygenated fuel additive to enhance combustion efficiency and reduce emissions. This dual-purpose approach addresses both industrial needs and the growing demand for cleaner fuel solutions. Our study focuses on synthesizing gold nanoparticles (AuNPs) supported by alumina (Al2O3), cerium oxide (CeO2), and Al2O3/CeO2 combination by deposition–-precipitation method, aiming to advance far-reaching MMA synthesis through direct oxidative esterification (DOE) of methacrolein (MAL) with methanol. The research explores the relationship between catalyst structure and activity, particularly investigating the impact of AuNPs doping on Al2O3, CeO2, and Al2O3/CeO2 and the mechanism that promotes selective oxidation. The intimate interaction between CeO2 and Al2O3 and adequate doping of AuNPs with Al2O3/CeO2 is beneficial in enhancing catalytic activity and facilitating selective oxidation. Notably, Au/Al2O3/CeO2 demonstrated significantly higher catalytic activity compared to Au/Al2O3 and Au/CeO2 catalysts, achieving 98% MAL conversion and 95% MMA selectivity. The reaction yield, in particular, strongly correlated with surface and active oxygen species around AuNPs. This highly efficient catalytic process provides a green route for MMA production and enables its application as a sustainable fuel additive, contributing to improved engine performance and reduced environmental impact. The optimized catalyst system presents a viable pathway for both industrial chemical production and sustainable energy applications, addressing crucial environmental and energy challenges simultaneously.

Highly efficient CoAl-LDH/(110) facet-exposed BiOBr catalysts: Promotional effect of Z-type heterojunction and oxygen vacancies in photocatalytic ciprofloxacin degradation

Photocatalysis has received extensive attention as a sustainable technology. Herein, a 2D/2D CoAl-LDH/(110) facet-exposed BiOBr Z-type heterojunction photocatalyst enriched with oxygen vacancies (OVs) and Lewis acid sites was prepared by deposition-precipitation method. Results show that the removal of ciprofloxacin by the optimal heterojunction achieves 88 % within 10 min and 98.6 % within 95 min under visible light. Characterization and DFT calculation reveal that CoAl-LDH induces high-energy (110) crystal plane exposure of BiOBr, resulting in the generation of surface OVs and Lewis acid sites. OVs contribute to the adsorption of dissolved oxygen in water, thereby facilitating the generation of •O2−. And Bi(3−x)+ Lewis acid sites promote the adsorption and degradation of reactant molecules. The charge transfer recombination mechanism of the heterojunction enhances the utilization of photogenerated electrons and holes, improving the catalyst photostability. This work provides a simple method for constructing efficient and stable Z-type heterojunctions with defects for photocatalytic water treatment.

Optimizing mass-transfer and oxygen components to enhance toluene oxidation for MnOx/SAPO-34 and revealing mechanism by in-situ DRITFS

A series of MnOx/SAPO-34 was synthesized using deposition-precipitation method with acid, alkali, saline to modify their physicochemical property enhancing the performance for toluene oxidation. The structure-activity relationship was explored in depth using variant instruments. It was found that the SAPO-34 was etched by desiliconization with oxalic acid as precipitant and converting its micropores into mesopores as well as macropores, which is not only conducive to anchoring and dispersion of more active MnOx, but also promote the mass transfer of reactants. Meanwhile, the catalyst derived from oxalic acid possesses abundant redox sites with the strongest low temperature reducibility. As the results, the Mn/S34-OA exhibits the best performance of toluene oxidation with T90=237 °C and ∼100 % CO2 selectivity. Besides, the catalyst maintained long-term stability even in presence of H2O at 260 °C. Furthermore, the reaction mechanism is revealed by in-situ DRIFTS experiments. It is demonstrated that lattice oxygen directly participates in oxidation of toluene as the crucial active component in path of toluene to benzyl alcohol to benzaldehyde to benzoic acid to CO2 finally. In addition, the consumed lattice oxygen is replenished by adsorbed gaseous O2, which is the key to maintain continuous reaction cycle.

Unlocking the potential of biogenic Ag@g-C3N4 in sustainable water purification: A kinetic and photocatalytic study

This research introduces a pioneering biogenic deposition-precipitation method for synthesis of Ag@g-C3N4 nanocomposites (NCs) employing fennel seed extract (FSE). This technique involves the reduction and capping of silver nanoparticles (AgNPs) onto g-C3N4, employing polyphenolic content of FSE, consequently establishing a strong Schottky junction. The, NCs were characterized through various spectroscopic and microscopic techniques, confirming successful biogenic deposition of AgNPs and purity of prepared nanomaterials. Further, the synthesized NCs were utilized for photocatalytic degradation of various hazardous pollutants viz. Rhodamine-B (Rh-B) dye, Tetracycline (TCy) antibiotic, Imidacloprid (IMD) insecticide and deactivation of E. coli microbes. Amongst the synthesized NCs, 3 wt% Ag@g-C3N4 NCs exhibited superior photocatalytic mitigation of Rh-B (99.26%, k = 90.4 × 10−3 min−1), TCy (96.86%, k = 40.2 × 10−3 min−1), IMD (95.7%, k = 34.96 × 10−3 min−1) and E. coli deactivation (99.5%, k = 49.19 × 10−3 min−1). Moreover, the rate constants revealed many-fold increase in photocatalytic degradation of pollutants, contrary to pristine g-C3N4 (k = 11.8 × 10−3 min−1). This investigation also unveils an intricate photocatalytic mitigation pathway for the aforementioned-contaminants, elucidating key role of superoxide radical anions in photocatalytic mitigation. One of the significant highlights of this research is the sustainable and cost-effective synthesis methodology involving fennel seeds, which not only ensures the wide availability of resources but also guarantees environmental safety, in alignment with green principles.

Selective hydrogenation of acetylene over Pd/β-Mo2C catalyst: Experimental and theoretical studies

Molybdenum carbide is a promising support to tune the metal reactivity, which originates from the interaction between metal and support. In this work, Pd/β-Mo2C was prepared using a deposition-precipitation method for selective hydrogenation of acetylene. The high temperature calcination is employed to modulate the interaction between Pd and β-Mo2C. The Pd/β-Mo2C catalyst calcined at 600 °C exhibits significant promotion in selective hydrogenation, which shows 100 % acetylene conversion and 81.4 % ethylene selectivity at 160 °C. The activity promotion originates from the enhanced electronic metal-support interaction, which induces a shift of Pd 3d to higher binding energy. Besides, the Pd species become atomically dispersed after calcination. The changes in geometric and electronic structure suppress the formation of Pd hydrides, which consequently inhibits the excessive hydrogenation capacity of Pd. The structure variation also affects the adsorption of ethylene. No strong adsorbed ethylene (di-σ bonded ethylene) can be identified, which is conducive to the improvement of ethylene selectivity. Density functional theoretical (DFT) calculations confirm that Pd on β-Mo2C is positively charged. The desorption energy of C2H4* (0.78 eV) is significantly lower than that of further hydrogenation (1.45 eV), which explains the improved ethylene selectivity of the calcinated catalyst. The present study indicates calcination is an effective method to tune the activity of Pd/β-Mo2C for reactions beyond selective hydrogenation of acetylene.

2-Methylfuran hydrogenation to 2-methyltetrahydrofuran utilizing Ni/SiO2 catalysts in vapor-phase: Excellent stability via enhanced metal-support interaction

Biomass-derived 2-methyltetrahydrofuran (2-MTHF) is a significant green solvent and a promising biomass fuel, and it is usually produced from 2-methylfuran (2-MF) hydrogenation in liquid phase. It is highly desirable and challenging to develop vapor-phase hydrogenation with such a catalyst that combines high efficiency, excellent stability, easy scale up and low cost. In the present work, we prepared three Ni/SiO2 catalysts using impregnation, urea-assisted impregnation, and deposition–precipitation methods (labeled as NS-IM, NS-UIM, and NS-DP), respectively, for the synthesis of 2-MTHF from 2-MF hydrogenation in vapor-phase. The NS-DP catalyst demonstrated the highest activity and the best stability among all catalysts. Under moderate reaction conditions, a 2-MF conversion of 99.9% with a 2-MTHF selectivity of 99% were achieved on the NS-DP catalyst over 140 h, and it showed a potential significant application prospect. N2 physisorption, ICP, XRD, H2-TPR, TG, HRTEM, and in situ XPS characterization revealed that the catalyst prepared by the deposition–precipitation method possessed the smallest Ni grain size and the strongest metal-support interaction, leading to the highest performance. It was demonstrated that reaction pressure affected the conversion of 2-MF while the reaction temperature affected the selectivity of 2-MTHF. In addition, the structures of the spent catalysts were characterized, and mechanism of deactivation have been discussed in this work.

Catalytic Activity of Incorporated Palladium Nanoparticles on Recycled Carbon Black from Scrap Tires.

A stable support substrate for catalytically active metal nanoparticles (NPs) plays an important role in various chemical transformation reactions. This study describes the effective integration of catalytically active palladium nanoparticles (PdNPs) into recycled carbon black (rCB) obtained from scrap tires. The loading efficiency and dispersion degree of PdNPs prepared via a deposition-precipitation method are thoroughly compared to those prepared with conventional Vulcan CB. As the rCB powder exhibits relatively larger surface areas and wider pore size distributions, slightly polydisperse and more PdNPs are integrated across rCB than those on CB. These composite materials are subsequently tested as catalysts in the Suzuki coupling and styrene hydrogenation reactions. For the Suzuki reaction using phenylboronic acid and bromobenzene, the PdNPs on rCB exhibit slightly higher reactivity than those on CB (TOF of ∼9/h vs ∼8/h), presumably due to the structural features of the integrated PdNPs and the relatively hydrophobic characteristics of the rCB substrate. For the hydrogenation reaction, both composite materials easily result in over 99% yield under ambient conditions with similar activation energies of ∼32 kcal/mol. These composite materials are also recyclable in both reactions without a detectable loss of the PdNP catalyst and its activity. Understanding the physicochemical properties of rCB and demonstrating their potential use as a catalyst support substrate evidently suggest the possibility of replacing conventional CB, which also provides an idea of upcycling waste tires in the development of practical and green reaction systems.

Enhanced catalytic performance for gas phase epoxidation of propylene with H2 and O2 by multiple pretreated Au/TS-1 catalysts

Direct epoxidation of propylene (C3H6) with hydrogen (H2) and oxygen (O2) over Au/TS-1 catalyst was promising way for the synthesis of propylene oxide (PO). However, high selectivity of PO (>95 %) and conversion of C3H6 (>5 %) cannot be achieved at the same time. The industrialization process was severely restricted. In this paper, Au/TS-1 catalysts were synthesized by deposition precipitation method with alkali metal promoter. And alkaline gases and silane coupling post-treatment were performed to promote the catalytic activity. The prepared samples exhibited a much better C3H6 conversion (6.5 %) and PO selectivity (95.1 %) compared with general catalyst using normal synthetic technology. Cs2CO3 was beneficial to increasing Au nanoparticles uptake efficiency. Both NH3 and triethoxyvinylsilane post-treatment were good for smaller and more uniform loading of Au nanoparticles. The decreasing in surface hydroxyl density effectively alleviated the occurrence of PO ring opening isomerization. The increased hydrophobicity of TS-1 surface was conducive to the rapid desorption of generated PO and significantly increased PO selectivity. Multiple pretreatment was also favorable for extending the lifetime of Au/TS-1 catalyst.

Influence of 0.25% Indium Addition to Ni/CeO2 Catalysts for Dry Reforming of Methane

In this study, the surface and textural properties as well as the catalytic performance of Ni/CeO2 and NiIn/CeO2 catalysts prepared by wet impregnation (WI) and deposition–precipitation (DP) are investigated. The addition of Ni (3.0 wt.%) resulted in a decrease in the specific surface area and pore volume in the case of the WI method, possibly due to a blockage of mesopores. A minimal addition of In (0.25 wt.%) caused a further decrease in the surface area in both cases. XRD analysis showed that Ni deposited on CeO2 by DP resulted in some lattice incorporation, affecting the crystallinity of the support. The H2-TPR profiles altered depending on the different ways of Ni and In introduction. STEM-EDS-derived elemental maps indicated that the Ni and NiIn particles deposited on CeO2 using the DP method were somewhat smaller than in the WI synthesis. A comprehensive CO-DRIFTS analysis proved a direct Ni-In interaction in bimetallic samples, leading to the formation of a surface NiIn alloy. Ni/CeO2 catalysts showed a higher activity in the process of dry reforming of methane (DRM) than the bimetallic counterparts at 650 °C, with the Ni_DP sample performing slightly better. However, the Ni_DP catalyst showed significant coking, which was drastically reduced by the addition of In. The agglomeration of Ni and/or NiIn particles during the 6 h DRM reaction somewhat impaired the catalyst performance. Overall, this study highlights the intricate relationship between the catalyst preparation, surface properties and catalytic performance in the DRM reaction and emphasizes the beneficial role of In addition in reducing the coking of the monometallic catalyst and the critical location and surface morphology of nickel nanoparticles decorated with indium and in contact with ceria.

Unravelling the morphology effect of Pt/In2O3 catalysts for highly efficient hydrogen production by methanol steam reforming

Methanol steam reforming (MSR) constitutes an attractive reaction for high-yield on-board hydrogen production for H2-fueled fuel cell applications. Engineering the morphology of Pt/In2O3 heterogeneous catalyst is a feasible strategy for efficient MSR catalyst design, which can construct the Pt2+-In2O3 interfacial sites by utilizing the interaction between Pt and In2O3, thereby facilitating oxygen vacancy creation and activating methanol and water molecules. In this work, three kinds of In2O3 supports with different morphologies of nanorods, nanocubes and nanoplates were synthesized, and Pt/In2O3 catalysts were prepared by deposition–precipitation method. The performance of the catalysts for MSR hydrogen production was evaluated at 250 ∼ 375 ℃. The rod-shaped Pt/In2O3 catalyst with extremely low loading of Pt (0.21 wt%) exhibited the superior catalytic activity compared to the other two counterpart catalysts, achieving the complete CH3OH conversion and the CO selectivity as low as 3.8 % at 325 ℃. Moreover, the performance of Pt/r-In2O3 catalyst remained stable during the stability test for up to 40 h. Based on XRD, BET, HRTEM, XPS, Raman, UV–vis and H2-TPR characterization methods, the observed morphology-dependent reactivity of Pt/In2O3 catalysts can be correlated to the good low-temperature reducibility, abundant surface Pt2+ and adsorbed reactive oxygen species, which was originated from the exposed (211) crystal planes. The preferential exposed (211) crystal plane enables a stronger interaction of In2O3 support with Pt species resulting in the synergistic effect of high oxygen vacancy content, high proportion of Pt2+, and the formation of Pt2+-In2O3 interface active sites, which facilitates the activation and conversion of methanol and water molecules. The developed strategy may provide insight into the development of the design principles for high-performance methanol reforming catalysts for hydrogen production.

Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction.

Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.

Au Nanoparticles Supported on Hydrotalcite-Based MMgAlOx (M=Cu, Ni, and Co) Composite: Influence of Dopants on the Catalytic Activity for Semi-Hydrogenation of C2H2

Semi-hydrogenation of acetylene to ethylene over metal oxide-supported Au nanoparticles is an interesting topic. Here, a hydrotalcite-based MMgAlOx (M=Cu, Ni, and Co) composite oxide was exploited by introducing different Cu, Ni, and Co dopants with unique properties, and then used as support to obtain Au/MMgAlOx catalysts via a modified deposition–precipitation method. XRD, BET, ICP-OES, TEM, Raman, XPS, and TPD were employed to investigate their physic-chemical properties and catalytic performances for the semi-hydrogenation of acetylene to ethylene. Generally, the catalytic activity of the Cu-modified Au/CuMgAlOx catalyst was higher than that of the other modified catalysts. The TOR for Au/CuMgAlOx was 0.0598 h−1, which was 30 times higher than that of Au/MgAl2O4. The SEM and XRD results showed no significant difference in structure or morphology after introducing the dopants. These dopants had an unfavorable effect on the Au particle size, as confirmed by the TEM studies. Accordingly, the effects on catalytic performance of the M dopant of the obtained Au/MMgAlOx catalyst were improved. Results of Raman, NH3-TPD, and CO2-TPD confirmed that the Au/CuMgAlOx catalyst had more basic sites, which is beneficial for less coking on the catalyst surface after the reaction. XPS analysis showed that gold nanoparticles exhibited a partially oxidized state at the edges and surfaces of CuMgAlOx. Besides an increased proportion of basic sites on Au/CuMgAlOx catalysts, the charge transfer from nanogold to the Cu-doped matrix support probably played a positive role in the selective hydrogenation of acetylene. The stability and deactivation of Au/CuMgAlOx catalysts were also discussed and a possible reaction mechanism was proposed.

Bimetallic Ni-Co catalyst for improving selectivity in transfer hydrogenation of phenolic compounds

The study investigated the transfer hydrogenation of guaiacol, anisole, phenol, and positional isomers of dimethoxybenezene using 2-PrOH as the H-donor over Ni, Co, and Ni-Co catalysts. The catalysts, which contained 5 wt% metal, were prepared by the deposition-precipitation method. The results showed that the catalysts had developed a pore structure and fine metal particles. The Ni and Ni-Co catalysts demonstrated exceptional activity in the transfer hydrogenation of phenolic compounds with a substrate to metal molar ratio of 100 to 1. Furthermore, the addition of Co to Ni significantly impacted the selectivity of transfer hydrogenation promoting hydrodeoxygenation of anisole and guaiacol.

Preparation of Hydrophobic Au Catalyst and Application in One-Step Oxidative Esterification of Methacrolein to Methyl Methacrylate.

The water produced during the oxidative esterification reaction occupies the active sites and reduces the activity of the catalyst. In order to reduce the influence of water on the reaction system, a hydrophobic catalyst was prepared for the one-step oxidative esterification of methylacrolein (MAL) and methanol. The catalyst was synthesized by loading the active component Au onto ZnO using the deposition-precipitation method, followed by constructing the silicon shell on Au/ZnO using tetraethoxysilane (TEOS) to introduce hydrophobic groups. Trimethylchlorosilane (TMCS) was used as a hydrophobic modification reagent to prepare hydrophobic catalysts, which exhibited a water droplet contact angle of 111.2°. At a temperature of 80 °C, the hydrophobic catalyst achieved a high MMA selectivity of over 95%. The samples were characterized using XRD, N2 adsorption, ICP, SEM, TEM, UV-vis, FT-IR, XPS, and water droplet contact angle measurements. Kinetic analysis revealed an activation energy of 22.44 kJ/mol for the hydrophobic catalyst.