Single-Atom Ruthenium Catalytic Sites for Acetylene Hydrochlorination.

The influence of Ni load and support material on catalysts for the selective catalytic oxidation of ammonia in gasified biomass

Vanadium magnesium oxide (VMgO) catalysts with different vanadium loadings were synthesized and tested for catalytic activity in the oxidative dehydrogenation of n-hexane. High surface area catalysts were obtained by the wet impregnation technique. Magnesium oxide (MgO) and magnesium orthovanadate [Mg3(VO4)2] were the only phases observed in each catalyst. All the catalysts were tested at 0.6–7.8 % of n-hexane in air within a temperature range of 350–550 °C, varying the gas hourly space velocities. Catalytic testing conducted below the lower flammability limit (0.6 % n-hexane in air) showed only benzene and carbon oxides in the product stream, whereas for experiments done above the upper flammability limit (7.8 % n-hexane in air), hexenes, in addition to benzene and carbon oxides were observed. Decreasing the feed composition from 7.8 to 5.5 % resulted in higher yields towards benzene and total dehydrogenated products. The effect of variations in the gas hourly space velocity investigated using the 19 wt% vanadium catalyst and a feed concentration of 7.8 % showed that the selectivity to benzene increased slightly with an increase in the gas hourly space velocity.

Ce0.70La0.20Ni0.10O2-δ catalyst for methane dry reforming: Influence of reduction temperature on the catalytic activity and stability

A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO3) by using an equimolar quantity of cerium nitrate (Ce(NO3)3·6H2O) and mixed precipitants (KOH + K2CO3) at room temperature. Nano-sized CeO2 supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO2 catalyst showed almost equilibrium CO conversion with 100% CO2 selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h−1. A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO3) by using an equimolar quantity of cerium nitrate (Ce(NO3)3·6H2O) and mixed precipitants (KOH + K2CO3) at room temperature. Nano-sized CeO2 supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO2 catalyst showed almost equilibrium CO conversion with 100% CO2 selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h−1.

Utilization of CO2 for syngas production by CH4 partial oxidation using a catalytic membrane reactor

Recently, CO2 methanation has become a technique that aims to reduce anthropogenic CO2 emissions by converting CO2 captured from stationary and mobile sources and H2 produced from renewable sources into CH4. Due to their excellent performance‐to‐cost ratio, Ni‐based catalysts were frequently used in such conversions. The main drawbacks, however, are that Ni has the propensity to aggregate and deposit carbon during the high‐temperature reaction. These issues can be partially resolved by including a support (e.g., MOF, zeolite, activated carbon, etc.) and a second transition metal (e.g., Mo, Co, or Fe) in Ni‐based catalysts. Therefore, the activity of Ni‐based catalysts at low temperatures needs to be improved. In this study, a series of mesoporous activated carbon (AC) supported bimetallic Ni–Mo catalysts (Ni–xMo/AC, Ni = 13 wt.%, x = 5, 7, 9, 11 wt.%) were synthesized using the incipient wetness impregnation method. The effect of Mo content on the catalyst's activity was examined in a fixed‐bed reactor. At 250–650°C, 1‐atmosphere pressure, gas hourly space velocity (GHSV): 1200 mL h−1 g−1, and H2/CO2 ratio: 4:1, the catalytic efficiency of these catalysts was examined. The catalysts were analyzed using transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), X‐ray powder diffraction (XRD), N2‐physisorption, and scanning electron microscopy/energy dispersive X‐ray spectroscopy (SEM‐EDX). Ni–7%Mo/AC catalyst showed the lowest carbon deposition rate, superior stability, and the best activity. The addition of Mo can improve the heat resistance of the Ni/AC catalyst and the interaction between the metal nickel and the support, which prevents the sintering of the catalyst. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

An investigation was carried out to study the feasibility of using 5% nickel/alumina catalysts synthesized with different methods and metal precursors for the hydrogenation of tetralin. The catalysts were characterized using atomic absorption spectroscopy, thermogravimetric analysis, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), hydrogen chemisorption, and surface area and pore volume analyses. The catalysts were tested in a continuous-flow, fixed-bed, reactor using solvent-free tetralin feed under the conditions of 5 barg hydrogen, 210 °C, a weight hourly space velocity of 5 h–1, and a H2/HC ratio of 7.5 (gas hourly space velocity, 4220 h–1). These reaction conditions were much milder than the ones reported in literature but showed considerably higher catalytic activity even with low metal loadings. The study indicated that the product’s isomer ratio was governed by kinetics. Indeed, a remarkable difference was observed in the selectivity for the catalysts synthesized with different metal precursors in relation to cis/trans decalin ratios, where catalysts derived from nickel carbonate showed higher selectivity to cis-decalin compared to catalysts prepared from nickel nitrate. It was speculated that the dispersion and particle size played an important role in this variance, as suggested by XPS and hydrogen chemisorption. It was also found that this change in selectivity was not related to conversion. Similarly, different deactivation patterns were observed over these catalysts.

Low-temperature catalytic methane deep oxidation over sol-gel derived mesoporous hausmannite (Mn3O4) spherical particles

Organotin-based catalysts prepared by a facile and green synthesis route were used in the acetylene hydrochlorination reaction. In detail, organotin-based catalysts were directly synthesized by supporting both organotin and nitrogen compounds on a coal-based columnar activated carbon (AC) using both incipient wetness impregnation and calcination methods. Interestingly, upon addition of nitrogen compounds, the resultant (SnCl4 + C16H34Cl2Sn)/AC catalysts showed higher activity and stability when compared the its (SnCl4 + C16H34Cl2Sn + C2N4H4)/AC counterpart at 200 °C and a gas hourly space velocity (GHSV, C2H2 based) of 30 h−1. According to the results, organotin was demonstrated to be the active site, whereas the incorporation of nitrogen allowed partial mitigation of the loss of active components.

Influence of nickel contents on synthesis gas production over nickel-based catalysts supported by treated activated carbon in dry reforming of methane

Monolith Ce0.65Zr0.35O2-based catalysts for selective catalytic reduction of NOx with NH3

Influence of pretreatment on the catalytic performance of Ag/CeO2 for formaldehyde removal at low temperature

The synthesis of benzaldehyde, a compound widely utilized in food, medicine, and cosmetics, was achieved through a one-step catalytic hydrogenation using the cost-effective raw material, methyl benzoate. This process aligns with the principles of atom economy and green production. Despite the development of numerous high-performance catalysts by scholars, the challenge remains in achieving lower reaction temperatures, ideally below 400 °C. In this study, a series of MnOx/γ-Al2O3 catalysts were meticulously prepared using the precipitation-impregnation method. These catalysts featured supports calcined at various temperatures and distinct manganese active components. Characterization techniques such as X-ray diffraction (XRD), N2 physical adsorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), and NH3 temperature-programmed desorption (NH3-TPD) were employed to analyze the structure and surface properties of the catalysts. Notably, the optimized reaction temperature was found to be 360 °C. The catalyst exhibited the most favorable performance when the calcination temperature of the support was 500 °C and the Mn/Al molar ratio reached 0.18. Under these conditions, the catalyst demonstrated the most suitable oxygen vacancy concentration, yielding impressive results: a conversion rate of 87.90% and a benzaldehyde selectivity of 86.1%. These achievements were attained at 360 °C, atmospheric pressure, a hydrogen to methyl benzoate molar ratio of 40:1, and a Gas Hourly Space Velocity (GHSV) of 800 h−1. This research underscores the potential for optimizing catalysts to enhance the efficiency and sustainability of benzaldehyde synthesis.

Catalytic oxidation is a feasible and affordable technology for solvent emission abatement. However, finding optimal operation conditions is important, since they are strongly dependent on the application area of VOC incineration. This paper presents the results of the laboratory experiments concerning four most central parameters, that is, effects of concentration, gas hourly space velocity (GHSV), temperature, and moisture on the oxidation of n-butyl acetate. Both fresh and industrially aged commercial Pt/Al2O3 catalysts were tested to determine optimal process conditions and the significance order and level of selected parameters. The effects of these parameters were evaluated by computer-aided statistical experimental design. According to the results, GHSV was the most dominant parameter in the oxidation of n-butyl acetate. Decreasing GHSV and increasing temperature increased the conversion of n-butyl acetate. The interaction effect of GHSV and temperature was more significant than the effect of concentration. Both of these affected the reaction by increasing the conversion of n-butyl acetate. Moisture had only a minor decreasing effect on the conversion, but it also decreased slightly the formation of by products. Ageing did not change the significance order of the above-mentioned parameters, however, the effects of individual parameters increased slightly as a function of ageing.

Experimental and modeling investigation on CO2 sorption kinetics over K2CO3-modified silica aerogels