γ-Al2O3 Catalyst Research Articles

Selective CO oxidation in the hydrogen stream over Ru/Al@Al2O3 catalysts

Abstract The Al@γ-Al2O3 core-shell microstructures prepared from aluminum particles by hydrothermal surface oxidation were superior to the conventional alumina support owing to the facile heat flux through the metal-ceramic composite structures. The Ru catalysts supported on Al@γ-Al2O3 were used for the preferential CO oxidation (PROX) reaction, which is a highly exothermic reaction requiring high heat flux. For comparison, commercially available α-Al2O3 and γ-Al2O3 were also used as catalyst supports. The catalysts were characterized by N2-physisorption, X-ray diffraction, CO chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ethanol (ethanol-TPD) and ammonia (NH3-TPD), and temperature-programmed oxidation (TPO). The Ru/α-Al2O3 catalyst with the lowest Ru dispersion showed the best PROX performance among the tested catalysts in the absence of CO2 and H2O. Even though Ru/Al@γ-Al2O3 and Ru/γ-Al2O3 had similar Ru dispersions, the former catalyst exhibited a much better PROX performance than the latter. This could be explained by the fact that the Ru metal deposited on Al@γ-Al2O3 was more resistant to surface oxidation as compared to that on γ-Al2O3, based on the TPO results. A lower desorption temperature of ethanol was observed over Al@γ-Al2O3 than over γ-Al2O3 during ethanol-TPD experiments, even though both supports had similar amounts of acid sites, as determined by NH3-TPD. Among the tested catalysts, Ru/Al@γ-Al2O3 also showed the best PROX performance in the presence of CO2 and H2O. A further enhancement in the PROX performance was achieved by increasing the Ru metal particle size from 1.4 to 2.6 nm by pretreating the Ru/Al@γ-Al2O3 catalyst with 1 mol% O2 in He at 150 ℃.

Performance of Catalytic Fast Pyrolysis Using a γ-Al2O3 Catalyst with Compound Modification of ZrO2 and CeO2

To investigate the catalytic pyrolysis performance of complex metal oxide catalysts for biomass, γ-Al2O3 was prepared through the precipitation method, and then ZrO2 and γ-Al2O3 were blended in the proportion of 2:8 using the co-precipitation method. Next, CeO2 was loaded on the surface of the catalyst for further modification. The three catalysts, A, ZA and CZA, were obtained. The specific surface and acidity of the catalysts were characterized by nitrogen adsorption–desorption and NH3-Temperature Programmed Desorption (NH3-TPD) respectively. The catalytic pyrolysis performance of catalysts for bamboo residues was investigated by Pyrolysis gas chromatography mass spectrometry (Py-GC/MS). Chromatograms were analyzed for identification of the pyrolysis products and the relative amounts of each component were calculated. Experimental results indicated that catalyst A had a good catalytic activity for the fast pyrolysis of bamboo residues. The addition of ZrO2 and CeO2 could continuously enhance the acidity of the catalyst and further promote the pyrolysis of macromolecular compounds and deoxidation of oxygen-containing compounds. Finally, catalyst CZA, obtained by compound modification, could not only dramatically reduce the relative content of phenol, acid and aldehyde and other oxygen-containing compounds, but also achieved the maximum hydrocarbon yield of 23.38%. The catalytic performance of catalyst CZA improved significantly compared with catalyst A.

Alumina supported nano-platinum on copper nanoparticles prepared via galvanic displacement reaction for preferential carbon monoxide oxidation in presence of hydrogen

Improved catalytic centres with a minimum mass-loading of expensive platinum (Pt) have been anticipated for various catalytic applications, for instance preferential oxidation (PROX) of carbon monoxide (CO) in the presence of Hydrogen. Here, we report the synthesis of nano-Pt on the surface of copper (Cu) nanoparticles (NPs) supported on γ-Al2O3 (Ptn(Cu)/γ-Al2O3) via galvanic displacement reaction (GDR) for the catalytic CO-PROX reaction. Ptn(Cu)/γ-Al2O3 showed much improved CO-PROX performance compared to that of the as-synthesized Ptl(Cu)/γ-Al2O3 catalyst. Importantly, no significant conversion of hydrogen at a lower temperature range (<200 °C) is observed during the CO-PROX reaction which is one of the essential prerequisites for the CO-PROX reaction. Moreover, Ptn(Cu)/γ-Al2O3 showed the durable, long-term catalytic CO-PROX performance for 120 h. These results infer that realization of nano-Pt on the surface of the Cu NPs holds the promise as the catalytic centres with the minimum mass-loading of Pt for the CO-PROX reaction.

Production of Hydrogen-Rich Gas by Formic Acid Decomposition over CuO-CeO2/γ-Al2O3 Catalyst

Formic acid decomposition to H2-rich gas was investigated over a CuO-CeO2/γ-Al2O3 catalyst. The catalyst was characterized by XRD, HR TEM and EDX methods. A 100% conversion of formic acid was observed over the copper-ceria catalyst under ambient pressure, at 200–300 °C, N2:HCOOH = 75:25 vol.% and flow rate 3500–35,000 h−1 with H2 yield of 98%, wherein outlet CO concentration is below the equilibrium data (&lt;0.5 vol.%). The copper-ceria catalyst proved to be promising for multifuel processor application, and the H2 generation from dimethoxymethane, methanol, dimethyl ether and formic acid on the same catalyst for fuel cell supply.

Hydrogen Cyanide Removal over Ti-Al2O3 Catalyst: Activity at Low Temperature

Abstract Catalytic activity of γ-Al2O3 catalyst modified with Ti (Ti-Al2O3) for hydrogen cyanide (HCN) removal was studied, and the TiO2 and γ-Al2O3 were tested as comparisons. It was found that Ti...

CO and CO2 methanation over M (M Mn, Ce, Zr, Mg, K, Zn, or V)-promoted Ni/Al@Al2O3 catalysts

Abstract Effects of metal promoter on CO and CO2 methanation were examined over Ni-M (M = Mn, Ce, Zr, Mg, K, Zn, or V)/Al@Al2O3 catalysts prepared by the co-impregnation method. Ni-M (M = Mn, Ce, or Zr)/γ-Al2O3 catalysts were also investigated for comparison. The prepared catalysts were characterized with a variety of techniques such as N2 physisorption, CO2 chemisorption, H2 chemisorption, temperature-programmed reduction with H2 (H2-TPR), temperature-programmed desorption of CO2 (CO2-TPD), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Among different promoters, Mn, Ce, Mg, V, and Zr are beneficial to enhance both CO and CO2 methanation activity due to the improvement of the Ni dispersion. The Ni-V/Al@Al2O3 catalyst performs the highest CO methanation activity due to the largest Ni sites. However, it is not the best one for CO2 methanation among tested catalysts because of the much decrease in CO2 adsorption capacity. The promotional effect of Mn is the most remarkable for both CO and CO2 methanation. On the other hand, the negative effect of K and Zn was observed on both CO and CO2 methanation by the small number of active Ni sites and the decrease in the amount of basic sites. The CO2 methanation mechanism over Ni-Mn/Al@Al2O3 catalyst is elucidated by the transform route: adsorbed carbonate species – formate species – methane under hydrogenation process.

Maximizing Active Site Concentrations at Ni-Substituted WS2 Edges for Hydrogenation of Aromatic Molecules.

High concentrations of Ni in bimetallic sulfide catalysts lead to the formation of segregated Ni sulfides (NiSx), which are rather inactive alone as large crystallites and even impede the accessibility of active sites at the sulfide slab edges that catalyze a multitude of hydrogenation reactions and H2 and CO2 activation processes. Treatment of Ni-WS2/γ-Al2O3 catalysts in aqueous acids, particularly concentrated HCl, results in a significant reduction of NiSx and ≤5-fold enhancement of the phenanthrene hydrogenation rate. Using infrared (IR) spectroscopy of probe molecules, we show that the acid-treated catalysts have a high concentration of accessible metal edge sites, a high degree of Ni substitution, and consequently a high sulfhydryl (SH) concentration at the slab edges in the presence of H2. The site-specific "turnover frequency" (based on SH concentrations determined by IR measurements) is identical for all parent and acid-treated sulfide catalysts studied, showing that excess NiSx does not influence electronic properties.

Low temperature partial oxidation of dimethyl ether to hydrogen-rich gas over CuO-CeO2/γ-Al2O3 catalysts for fuel cell feeding

The promise of СuO-CeO2/γ-Al2O3 catalysts for partial oxidation of dimethyl ether (DME) to hydrogen-rich gas for fuel cell feeding was demonstrated. The catalysts provided complete conversion of DME to hydrogen-rich gas with low (≤ 0,8 vol.%) CH4 content and Н2 productivity ~3,1 l/(gcat · h) at 350 °C under ambient pressure using a reaction mixture (molar ratio): DME : O2 : N2 = 1 : 1 : 4 (DME : air = 1 : 5) at a flow rate 7 l/(gcat · h).

Correction to: Advantage of Co Embedded γ-Al2O3 Catalysts Over MgO and SiO2 Solid Oxides in the Selective Production of Styrene Monomer

The article Advantage of Co Embedded γ-Al2O3 Catalysts Over MgO and SiO2 Solid Oxides in the Selective Production of Styrene Monomer, written by Venkata Rao Madduluri, Kamaraju Seetha Rama Rao, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 19 July 2019 with open access

Advantage of Co Embedded γ-Al2O3 Catalysts Over MgO and SiO2 Solid Oxides in the Selective Production of Styrene Monomer

A series of cobalt oxide (Co3O4) loaded (5–20wt%) γ-Al2O3, MgO and SiO2 supported catalysts were prepared by wetness-impregnation method and tested for oxidative dehydrogenation (ODH) of ethylbenzene (EB) in vapor phase atmospheric pressure conditions. Among Co oxide doped catalysts, Co3O4/γ-Al2O3 (CA) has afforded a superior catalytic activity in view of desirable EB conversion and styrene (ST) yields. Thus unusual catalytic properties of 15CA catalyst were supposed to be due to adequate acidic-basic nature, thermal stability and synergistic effect of Co-Al species along with uniform distribution of active Co oxide ions. Moreover, dramatic catalytic activity of Co3O4 incorporated γ-Al2O3 catalyst can be explained on the basis of beneficial CO2 conversion subsequently production of better CO yields during the online gas analysis. All calcined catalysts have been characterized by different sophisticated techniques to elucidate the surface metal composition and influence of Co3O4 oxide species on catalytic activity presentation during the oxidative dehydrogenation of EB reaction.

The Synthesis of Magnesium-aluminium Spinel for Catalytic Hydrolysis of Carbonyl Sulphur at the Middle Temperature

The influences of the physical and chemical properties for the catalyst materials on the hydrolysis catalytic activity of carbonyl sulphur (COS) and the anti-oxygen property will be crucial to removing COS from gas at moderate temperature. The magnesium-aluminium spinel for catalytic hydrolysis of COS was synthesized by the dry mixing of pseudo boehmite with MgO. The performances of the prepared catalyst were characterized by XRD, nitrogen isothermal adsorption (BET), CO2-TPD, and the COS hydrolysis activities were measured in fix-bed reactor with the change of space velocity, temperature, COS concentration and O2. The results showed that the MgAl2O4 synthesized by mixing of pseudo boehmite with MgO and then calcining at 873K is feasible. By comparison with γ-Al2O3 catalyst, the synthesized MgAl2O4 catalyst possesses more pore volume and diameter so as to improve the diffusion rate of reactant and product of COS hydrolysis. MgAl2O4 spinel catalyst showed the better catalytic activity of COS hydrolysis, combining the advantages of γ-Al2O3 and MgO. As a result, MgAl2O4 catalyst in itself not only helps to improve the catalytic activity of COS, but also helps to enhance the anti-oxygen poisoning property.

Preparation of mesoporous γ-Al2O3 catalysts by dual template method

The mesoporous γ-Al2O3 was prepared by precipitation and hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) as the dual template and aluminum nitrate as the raw. The effects of template selection, reaction crystallization time and calcination temperature of γ-Al2O3 were investigated. The catalysts were characterized by TG-DTG, XRD, SEM, TEM, BET, FT-IR and CO2-TPD. The results show that the synthesized γ-Al2O3 has high crystallinity, large pore size, high thermal stability and basic surface, and it is shown that the carrier-supported hydrotalcite has effective activity for transesterification. When the reaction time was 3 h, the yield of biodiesel oil reached 95%.

Optimization study by Box-Behnken design (BBD) and mechanistic insight of CO2 methanation over Ru-Fe-Ce/γ-Al2O3 catalyst by in-situ FTIR technique

The utilization of carbon dioxide for methanization reactions in the production of synthetic natural gas (SNG) is of increasing interest in energy-related issues. The use of CO2 as a raw material in methanization reactions in the formation of SNG is of increasing concern associated with energy problems. The effect of three independent process parameters (calcination temperature, ceria loading and catalyst dosage) and their interactions in terms of conversion of CO2 was considered by response surface methodology (RSM). Box-Behnken design (BBD) revealed that the optimized parameters were 1000 °C calcination temperature, 85%wt ceria loading and 10 g catalyst dosage, which resulted in 100% conversion of CO2 and 93.5% of CH4 formation. Reaction intermediate study by in situ FTIR showed that carboxylate species was the most active species on the catalyst surface. In-situ FTIR experiments revealed a weak CO2 adsorption, that exist namely as carboxylate species over the trimetallic catalyst. As a result, dissociated hydrogen over ruthenium reacts with surface carbon, leading to *CH, which subsequently hydrogenated to produce *CH2, *CH3 and finally to the desired product methane. The use of in situ-FTIR study indicated that the CO2 methanation mechanism does not involve CO as a reaction intermediate. The more detailed mechanism of CO2 methanation pathways involved over Ru-Fe-Ce/γ-Al2O3 catalyst is discussed in accordance with IR-spectroscopic data. The better catalytic activity and stability over Ru-Fe-Ce (5:10:85)/γ-Al2O3 catalyst calcined at 1000 °C showed the presence of moderate basic sites for CO2 adsorption.

Production of propylene glycol (propane-1,2-diol) in vapor phase over Cu–Ni/γ-Al2O3 catalyst in a down flow tubular reactor: effect of catalyst calcination temperature and kinetic study

The modification of physicochemical characteristics of 20 wt% Cu–Ni (1:1)/γ-Al2O3 catalyst by varying the calcination temperature and its effect in vapor phase hydrogenolysis of glycerol to propane-1,2-diol was examined in packed bed down flow tubular reactor. The catalyst calcined at 400 °C rendered the highest glycerol conversion (~ 100%) and propane-1,2-diol selectivity (~ 89.5%) at 220 °C, 0.75 MPa and at the weight hourly velocity of (WHSV) of 1.3 h−1. The bifunctional nature of the new Cu–Ni bimetallic phase along with very high metal dispersion (~ 20%), lower crystallite size (≤ 20 nm) and high metal surface area ~ 30 m2 g−1 were the primary reason for the higher activity and selectivity to propane-1,2-diol. Furthermore, using a two-step reaction mechanism (glycerol dehydration to acetol and subsequent hydrogenation of acetol to propane-1,2-diol), a kinetic model was developed based on Eley–Rideal approach. The activation energies for the formation of acetol and propane-1,2-diol were calculated as 55.14 and 50.87 kJ mol−1, respectively.

Kinetics of long chain n-paraffin dehydrogenation over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst: Model studies using n-dodecane

A kinetic modeling study on long chain n-paraffin dehydrogenation using a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst was carried out in a continuous flow set-up using n-dodecane as a model component at various temperatures (450-470 °C), pressures (0.17-0.30 MPa), H2/paraffin mole ratios (3:1-6:1) and space times (0.22-1.57 g h mol−1). The commercial catalyst was characterized by XRD, BET, MIP, SEM and CO chemisorption. An empirical exponential equation was found to predict the mono- and di-olefin yields very well. In addition, 6 mechanistic models based on the LHMW mechanism were derived and tested by non-linear least squares fitting of the experimental data. The model which assumes that surface reactions and particularly the dehydrogenation of the metal-alkyl chain to the adsorbed mono-olefin and di-olefin as the rate determining steps was found to give the best fit with the experimental data. In addition, activation energies and adsorption enthalpies for each elementary reaction were obtained. The kinetic testing and modeling have shown that the high mono-olefins selectivity for long chain paraffin dehydrogenation can be obtained by operating at low space time (when P, T and m are same), high pressure (when τ, T and m are same) and high H2/paraffin ratio (when τ, P and T are same), as well as low reaction temperature (when τ, P and m are same) but with little effect.

Enhanced ethanol dehydration on γ-Al2O3 supported cobalt catalyst

Ethanol catalytic dehydration was studied on a γ-Al2O3 and Co-Al2O3 catalyst prepared by the strong electrostatic adsorption (SEA) method. Specific surface area characterization indicated that the Co-Al2O3 catalyst possessed higher surface area because of opening of γ-Al2O3 occluded pores. Acidity and basicity measurements of the catalysts by temperature programmed desorption (TPD) as followed by infrared and mass spectrometry (TPD-FTIR-MS) of adsorbed pyridine and CO2, respectively, indicated that the Co-Al2O3 catalyst possessed about half the Lewis acidity (accessible to pyridine) and moderately higher basicity than the parent γ-Al2O3. However, similar acidity measurements by NH3-TPD suggested the presence of occluded micropore acidity inaccessible to pyridine. XRD and IR measurements indicated that the support in the Co-Al2O3 catalyst underwent partial nitridation forming aluminum nitride and nitrogen containing Co species due to the SEA synthesis conditions. It was found that the Co-Al2O3 catalyst, under identical reaction conditions, could achieve similar ethanol conversion and ethylene selectivity to ethylene at lower temperatures than the original γ-Al2O3 support. Analysis of apparent activation energies contributions and water co-feeding tests indicated that the Co-Al2O3 was less inhibited by water and that water dimers and trimers were required to explain the experimental data. Furthermore, in situ modulation excitation-phase sensitive detection-diffuse reflectance infrared Fourier transform spectroscopy (ME-PSD-DRIFTS) during ethanol dehydration at reaction conditions confirmed the enhanced hydrophobic properties of the Co-Al2O3, making this catalyst less propense to water inhibition at low to moderate temperatures. The enhanced surface hydrophobicity in combination with new micropore acidity allowed more active sites for reaction not accessible in the parent γ-Al2O3. Additionally, evidence is also presented from in situ ME-PSD-DRIFTS for the participation of adsorbed ethanol and ethoxide species as well as terminal and bridging hydroxyls bonded to octahedral and tetrahedral Al on Al2O3 (1 0 0) and (1 1 0) facets as likely reaction intermediates in the conversion of ethanol to diethyl ether and ethylene.

Oxidative degradation of m-cresol using ozone in the presence of pure γ-Al2O3, SiO2 and V2O5 catalysts

The oxidative degradation of a potential pollutant, m-cresol with ozone was investigated both in the absence and presence of a catalyst. The oxidation reaction was studied as a function of time, where aliquots were drawn in every reaction from 3 to 24 h and dissolved in an absolute ethanol. The resultant product mixtures were analyzed using FT-IR and GC–MS spectroscopy for the identification of oxidation products. A hypothesis had been made that ethanol may affect the oxidation products as they are commonly carboxylic acids, ketones, and aldehydes, which was proved to be correct. The ethanol-mediated esterification of maleic and oxalic acid is thus reported. The oxidation products that were identified included 2,3-dihydroxy toluene and m-tolyl acetate. The catalyst materials were characterized using XRD, FT-IR, SEM and TEM techniques. Activated charcoal served as a reference catalyst to study and compare the activity to that of the metal oxides, where the order of catalytic activity was found to be SiO2 > γ-Al2O3 > activated charcoal >V2O5. However, activated charcoal resulted in higher selectivities towards products and lower substrate conversion.

Chromium-Ruthenium Oxides Supported on Gamma-Alumina as an Alternative Catalyst for Partial Combustion of Methane

Catalyst screening of γ-Al2O3-supported, single-metal and bimetallic catalysts revealed several bimetallic catalysts with activities for partial combustion of methane greater than a benchmark Pt/γ-Al2O3 catalyst. A cost analysis of those catalysts identified that the (2 wt%Cr + 3 wt% Ru)/γ-Al2O3 catalyst, denoted as 2Cr3Ru/Al2O3, was about 17.6 times cheaper than the benchmark catalyst and achieved a methane conversion of 10.50% or 1.6 times higher than the benchmark catalyst based on identical catalyst weights. In addition, various catalyst characterization techniques were performed to determine the physicochemical properties of the catalysts, revealing that the particle size of RuO2 became smaller and the binding energy of Ru 3d also shifted toward a lower energy. Moreover, the operating conditions (reactor temperature and O2/CH4 ratio), stability, and reusability of the 2Cr3Ru/Al2O3 catalyst were investigated. The stability test of the catalyst over 24 h was very good, without any signs of coke deposition. The reusability of the catalyst for five cycles (6 h for each cycle) was noticeably excellent.

Preparation and Characterization of Cu-Mn-Ce@γ-Al2O3 to Catalyze Ozonation in Coal Chemical Wastewater-Biotreated Effluent.

Cu-Mn-Ce@γ-Al2O3 was prepared by incipient wetness impregnation and used to catalyze ozonation in a coal chemical wastewater-biotreated effluent. The preparation factors that considerably affected the catalytic performance of Cu-Mn-Ce@γ-Al2O3, specifically metal oxide loading percentage, calcination temperature, and calcination time, were examined. The catalyst was characterized by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and Brunauer-Emmett-Teller analysis. The optimal catalytic ozonation operating parameters, such as ozone dosage, catalyst dosage, pH, and reaction time, were also investigated. Results showed that an optimized catalyst consisted of 17.0% CuO, 3.0% MnO2, and 2.0% CeO2 (wt.%). The optimal calcination temperature and calcination time were 600 °C and 5 h. The optimal catalytic ozonation operating parameters, including ozone dosage, catalyst dosage, pH, and reaction time, were 7, 80.0 mg/L, 20.0 mg/L, 7 and 50 min, respectively. The COD removal of biotreated effluent increased to 61% under these optimal operating conditions. Meanwhile, ozonation alone resulted in only 20% removal. This work proposes the use of easily available Cu-Mn-Ce@γ-Al2O3 catalyst and might drive the advancement of catalytic ozonation for chemical wastewater purification.

The combined process of pyrolysis and catalytic cracking of rice straw using ZSM-5 and γ-Al2O3 catalyst prepared by physically mixing

Rice straw contains high lignocellulose so it can be used as a raw material for producing bio-oil through pyrolysis process. The combined with catalytic cracking, the product of bio-oil could be shifted to the certain compound toward cyclohexene selectively using catalyst. Cyclohexene is important compound as the precursor of bio-polymer adipic acid that the route lead to the manufacture of nylon 6,6. This study is to give insight the possibility to produce cyclohexene from rice straw as renewable source material with variation of catalyst composition and the temperature. The ZSM-5/γ-Al2O3 catalyst composition is varied to observe the effect on its product distribution mainly on the influence in producing the target products. By this way, the optimum catalyst composition to maximize the target products could be confirmed. The bio-oil product and the product of catalytic cracking were characterized by Gas Chromatography Mass Spectroscopy (GC-MS). The result showed that the using of catalyst composition with 60% ZSM-5 and 40% Al2O3, the yield of cyclohexene up to 61.12% has been achieved as the main product under pyrolysis condition of 425°C in the atmospheric condition with 80 ml/min nitrogen flowrate.