Combination Of Catalyst Research Articles

Preparation of furans from catalytic conversion of corn stover in H2O–THF co-solvent system – The effects of acids combined with alkali metal cations

Abstract The preparation of furans from catalytic conversion of corn stover is investigated in H2O–THF (tetrahydrofuran) co-solvent system, and the effects of Bronsted acids (H2SO4, HCl, HNO3) combined with alkali metal cations (Li+, Na+, K+) are studied systematically. It is found that the effect of individual acid in promoting the summary yield of 5-hydroxymethylfurfural (HMF) and furfural (FF) can be ordered as Cl− > SO42− > NO3−. When combined with a salt, the anion effect can be ranked in SO42− > Cl− > NO3−, both for the HMF yield and the summary yield of furans. Based on the best anion of SO42−, the impacts of the combined cations can be finely ranked as Na+ > K+ > Li+. For the system with Cl−, it ranks in K+ > Li+ > Na+ for the HMF yield or the summary yield of furans. The performance of NO3− is so poor that no liquid product can be detected when any alkali metal cations is combined with HNO3. The performance of H2SO4/Na2SO4 is the best among 9 tested combined catalysts, and the yield of HMF and FF from corn stover conversion under optimized conditions are 76% and 81% respectively.

Combined Magnesia, Ceria and Nickel catalyst supported over γ-Alumina Doped with Titania for Dry Reforming of Methane

This study investigated dry reforming of methane (DRM) over combined catalysts supported on γ-Al2O3 support doped with 3.0 wt. % TiO2. Physicochemical properties of all catalysts were determined by inductively coupled plasma/mass spectrometry (ICP-MS), nitrogen physisorption, X-ray diffraction, temperature programmed reduction/oxidation/desorption/pulse hydrogen chemisorption, thermogravimetric analysis, and scanning electron microscopy. Addition of CeO2 and MgO to Ni strengthened the interaction between the Ni and the support. The catalytic activity results indicate that the addition of CeO2 and MgO to Ni did not reduce carbon deposition, but improved the activity of the catalysts. Temperature programmed oxidation (TPO) revealed the formation of carbon that is mainly amorphous and small amount of graphite. The highest CH4 and CO2 conversion was found for the catalyst composed of 5.0 wt. % NiO-10.0 wt. % CeO2/3.0 wt. %TiO2-γ-Al2O3 (Ti-CAT-II), resulting in H2/CO mole ratio close to unity. The optimum reaction conditions in terms of reactant conversion and H2/CO mole ratio were achieved by varying space velocity and CO2/CH4 mole ratio.

Immobilization of Ir(I) complex on covalent triazine frameworks for C[sbnd]H borylation reactions: A combined experimental and computational study

Metal-modified covalent triazine frameworks (CTFs) have attracted considerable attention in heterogeneous catalysis due to their strong nitrogen-metal interactions exhibiting superior activity, stability and hence recyclability. Herein, we report on a post-metalation of a bipyridine-based CTFs with an Ir(I) complex for CH borylation of aromatic compounds. Physical characterization of the Ir(I)-based bipyCTF catalyst in combination with density functional theory (DFT) calculations exhibit a high stabilization energy of the Ir-bipy moiety in the frameworks in the presence of B2Pin2. By using B2Pin2 as a boron source, Ir(I)@bipyCTF efficiently catalyzed the CH borylation of various aromatic compounds with excellent activity and good recyclability. In addition, XAS analysis of the Ir(I)@bipyCTF gave clear evidence for the coordination environment of the Ir.

Efficient Synthesis of Furfural from Biomass Using SnCl₄ as Catalyst in Ionic Liquid.

Furfural is a versatile platform molecule for the synthesis of various chemicals and fuels, and it can be produced by acid-catalyzed dehydration of xylose derived from renewable biomass resources. A series of metal salts and ionic liquids were investigated to obtain the best combination of catalyst and solvent for the conversion of xylose into furfural. A furfural yield of 71.1% was obtained at high xylose loading (20 wt%) from the single-phasic reaction system whereby SnCl4 was used as catalyst and ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIMBr) was used as reaction medium. Moreover, the combined catalyst consisting of 5 mol% SnCl4 and 5 mol% MgCl2 also produced a high furfural yield (68.8%), which was comparable to the furfural yield obtained with 10 mol% SnCl4. The water–organic solvent biphasic systems could improve the furfural yield compared with the single aqueous phase. Although these organic solvents could form biphasic systems with ionic liquid EMIMBr, the furfural yield decreased remarkably compared with the single EMIMBr phase. Besides, the EMIMBr/SnCl4 system with appropriate water was also efficient to convert xylan and lignocellulosic biomass corn stalk into furfural, obtaining furfural yields as high as 57.3% and 54.5%, respectively.

Enhanced Levulinic Acid Production from Cellulose by Combined Brønsted Hydrothermal Carbon and Lewis Acid Catalysts

This study presents a synergistic catalytic system using the combination of Bronsted hydrothermal carbon-based acid (HTCG-SO3H) and Lewis acid catalysts for one-pot conversion of cellulose to levulinic acid (LA). Chromium chloride (CrCl3), among a number of other Lewis acidic metal chlorides, was found to give the highest LA yields, and was therefore used in combination with the HTCG-SO3H, for cellulose conversion to LA. With the appropriate amount of HTCG-SO3H, the formation of side products could be reduced, resulting in improved selectivity of LA. Compared with that obtained by CrCl3 alone, at 5 wt % HTCG-SO3H, 0.015 M CrCl3, 200 °C and 5 min reaction time, the LA yield was considerably enhanced from 30 wt % to 40 wt %. Since HTCG-SO3H is a heterogeneous catalyst that can be easily prepared from biomass at moderate temperature, its use in such combined catalyst system offers economic and environmental benefits, thus making large-scale implementation of such process potentially feasible.

Nitrogen-Doped Biomass Carbons Meet with Polyoxometalates: Synergistic Catalytic Reductant-Free Aerobic Hydroxylation of Benzene to Phenol

A nitrogen-doped biomass carbon catalyst SFNC(800) was prepared by carbonizing the cheap and readily available soybean flour as the starting material at 800 °C. By combining the SFNC(800) with the Keggin-type V-containing polyoxometalate Ch5PMoV2, a facilely recyclable catalytic system toward liquid-phase reductant-free aerobic oxidation of benzene to phenol was built. The combined catalyst SFNC(800)-Ch5PMoV2 exhibited a high activity with 11.2% phenol yield, 14.04 h–1 turnover frequency (TOF), and high potential for reusability under the optimized reaction conditions. The present TOF value surpassed almost all the ones of other similar previously reported reductant-free LBTP-O2 systems and was even higher than the previous noble metal involved system. On the basis of the characterization results and density functional theory calculations, the structure–activity analysis revealed that the graphitic N-containing moiety in the SFNC(800) is critical to absorb and activate the substrate benzene.

Bio-oil upgrading with catalytic pyrolysis of biomass using Copper/zeolite-Nickel/zeolite and Copper-Nickel/zeolite catalysts

The bio-oil obtained from a general pyrolysis process contains a higher concentration of oxygenated compounds and the resultant physical and chemical properties make it an unsuitable drop-in fuel. The oxygenated compounds in the bio-oil can be converted into hydrocarbons or less oxygenated compounds with the application of catalysts. This study demonstrated the bio-oil upgrading with the application of catalysts, comparing the catalytic effect of combined mono-metallic catalysts (Cu/zeolite and Ni/zeolite) and sole bi-metallic catalyst (CuNi/zeolite) on the composition of bio-oil and pyrolytic gases. The results demonstrated that in comparison to the combined mono-metallic catalysts, the sole bi-metallic catalyst showed better deoxygenation for all the oxygenated compounds and favoured the production of aliphatic hydrocarbons, whereas the combination of mono-metallic catalysts generated higher proportion of aromatic hydrocarbons in the bio-oil. In both cases, the catalysts equally favoured decarboxylation and decarbonylation reactions, as CO2/CO of approximately 1 was obtained during the pyrolysis process.

The Use of Zeolites for VOCs Abatement by Combining Non-Thermal Plasma, Adsorption, and/or Catalysis: A Review

Non-thermal plasma technique can be easily integrated with catalysis and adsorption for environmental applications such as volatile organic compound (VOC) abatement to overcome the shortcomings of individual techniques. This review attempts to give an overview of the literature about the application of zeolite as adsorbent and catalyst in combination with non-thermal plasma for VOC abatement in flue gas. The superior surface properties of zeolites in combination with its excellent catalytic properties obtained by metal loading make it an ideal packing material for adsorption plasma catalytic removal of VOCs. This work highlights the use of zeolites for cyclic adsorption plasma catalysis in order to reduce the energy cost to decompose per VOC molecule and to regenerate zeolites via plasma.

Novel synthesis of combined CaO-Ca12Al14O33-Ni sorbent-catalyst material for sorption enhanced steam reforming processes

A properly CaO-Ca12Al14O33-Ni material with combined sorbent properties and catalyst activity was developed for H2 production from hydrocarbons via sorption enhanced steam reforming (SE-SR) with simultaneous CO2 capture. The combined sorbent-catalyst material (CSCM) was successfully prepared by multi-step approach method. At first a mixed calcium-aluminium oxide (CAO) ceramic was prepared by wet mixing/sintering method and used both as spacer for CaO-based sorbent and support for nickel catalyst. Subsequently, the sorbent and catalyst were prepared by wet mixing/sintering (900 °C) and wet impregnation/calcination (500 °C) methods, respectively. Then, an intimately powdery 1:1 mixture of two functional materials were cold-pressed and air-sintered at 900 °C obtaining the desired one-body sorbent-catalyst. The CSCM characteristics were investigated in detail by XRD, SEM-EDS, TG-DTG, BET physisorption, and TPR techniques. The CO2 sorbent properties were assessed over 200th multiple sorption/desorption cycles and the stabilizing role of spacer Ca12Al14O33 ceramic against sorbent decay was confirmed, whereas the presence of foreign Ni ions did not affect the sorbent CO2 carrying capacity. A H2-rich gas (> 90%) with low concentrations of CO2 and CO was produced over ten consecutive steam methane reforming (600 °C)/regeneration (750 °C) cycles at steam/carbon=3 molar ratio using CSCM. This good performance of SE-SR of methane process was attributed to the synergistic effect of high CO2 capture capacity and catalytic activity, the latter thanks also to the facile surface NiAl2O4 spinel to Ni° reduction in the low temperature range of 400–600 °C.

Synthesis and characterization of di-nuclear bis(benzotriazole iminophenolate) cobalt complexes: catalysis for the copolymerization of carbon dioxide with epoxides.

A family of di-nuclear bis(benzotriazole iminophenolate) (BiIBTP) cobalt complexes containing diverse ancillary carboxylate derivatives have been synthesized and structurally characterized. The one-pot synthesis of the BiIBTP ligand precursor with cobalt perchlorate salt (2.0 equiv.) and carboxylic acid derivatives (2.0 or 5.0 equiv.) in the presence of triethylamine (5.0 equiv.) under refluxing methanolic solution generated bimetallic di-carboxylate Co(ii)/Co(ii) complexes [(C83CBiIBTP)Co2(O2CR)2] (R = C6H5 (1), C6F5 (2), 4-CF3-C6H4 (3), 4-OMe-C6H4 (4), CF3 (5)) in ≧65% yields. Interestingly, the Co(ii)/Co(iii) mixed-valence complex 6 resulted from the treatment of 1 with silver perchlorate (1.0 equiv.) as the oxidizing agent under an O2-atmosphere in 50% yield. The crystal structure of 6 reveals an ionic and di-nuclear benzoate species composed of a cationic moiety formulated as [(C83CBiIBTP)Co2(O2CC6H5)2]+ and a counterbalanced perchlorate anion, and both metal atoms are attributed to hexa-coordinated cobalt ions with varied coordination environments. Catalysis results of CO2/epoxide copolymerization indicated that complex 1 was more efficient than 2-6 where compound 6 was shown to be the least active. Co complex 1 incorporating benzoate coligands was demonstrated to effectively catalyze the CO2-copolymerization of cyclohexene oxide (CHO), 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide, producing the associated CO2-based polycarbonates with >99% carbonate repeated units under optimal conditions. Not only the controllable character of complex 1 for CO2/CHO copolymerization is enabled, but also 1 has been shown to catalyze such a copolymerization in the "immortal" manner. Using the same di-cobalt catalyst in combination with excess ratios of neopentyl glycol (up to 150 equiv.) as the chain transfer agent could give low molecular weight poly(cyclohexene carbonate) polyols with monomodal molecular weight distributions. This work offers the facilely prepared di-nuclear cobalt complexes as catalysts for the efficient catalysis of CO2-copolymerization.

Cylindrical shaped ZnO combined Cu catalysts for the hydrogenation of CO2 to methanol.

Hydrogenation of CO2 to chemicals is of great importance in the reduction of greenhouse gas emission. And the interaction and/or the boundary between Cu and ZnO played a crucial role in the performance of the Cu–ZnO catalyst for CO2 hydrogenation to methanol. In this work, cylindrical shaped ZnO was first synthesized via controlled hydrothermal precipitation of Zn(CO2CH3)2·2H2O, and Cu was further deposited on ZnO via in situ reduction in aqueous solution. Characterizations indicated that the crystallization degree of ZnO decreased with the increasing content of Cu, while the exposed surface area of Cu exhibited a volcano shaped curve. It was found that the cylindrical shaped ZnO combined Cu catalysts were active for the hydrogenation of CO2, and the space time yield of methanol reached 0.50 g-MeOH (g-cat h)−1 at H2/CO2 = 3, 240 °C, 3.0 MPa, and 0.54 mol (g-cat h)−1, but the methanol selectivity decreases with the reduction of the (002) polar plane of ZnO. The conversion of CO2 and methanol selectivity were discussed with the detected exposed Cu surface area and the number of oxygen vacancies.

Combined halide-free Cu-based catalysts with triple functions for heterogeneous conversion of methanol into methyl acetate

The combined catalyst exhibits extraordinary MA selectivity, which can be ascribed to the nearly anhydrous conditions achieved by WGSR catalyst CuCeO.

Understanding the Enhanced Lifetime of SAPO-34 in a Direct Syngas-to-Hydrocarbons Process

In a hybrid catalyst process, syngas is converted, via a methanol intermediate, into a mixture of short-chain hydrocarbons over a combined methanol synthesis catalyst and molecular sieve. It operates under process conditions where the hydrogen partial pressure is relatively high vs the (intermediate) methanol partial pressure. We show that, under these conditions, the lifetime of the molecular sieve (SAPO-34) is greatly enhanced and the amount and type of carbon on the spent catalyst are vastly different as compared to those in a methanol to olefins (MTO) process. The impact of the hydrogen partial pressure, temperature, and methanol partial pressure is studied, leading to a conceptual model of coke deposition and removal. This allows the identification of process conditions that lead to a stable and long lifetime of SAPO-34 in a direct syngas-to-hydrocarbons process.

Golden Face of Phosphine: Cascade Reaction to Bridgehead Methanophosphocines by Intramolecular Double Hydroarylation.

Reported herein is the first example of a gold-catalyzed cyclization of bis(arylmethyl)ethynylphosphine oxides. This represents an original approach to bridgehead methanophosphocines 1, eight-membered heterocycles. Gold catalyst in combination with triflic acid activates alkyne and induces a double hydroarylation. Mechanistic studies suggest that the reaction proceeds stepwise, forming first the 1 H-isophosphinoline 2-oxide 5. Reduction and protection of the corresponding phosphine oxides 1 described herein also highlight the effectiveness of our approach to this new class of electron-rich ligands.

Nano composite composed of MoOx-La2O3[sbnd]Ni on SiO2 for storing hydrogen into CH4 via CO2 methanation

The crucial problems for the catalysts of CO2 methanation are the low activity at low temperature and deactivation caused by metal sintering. In order to overcome the problems or to improve the shortages, a new scheme has been put forward by loading LaNi1-xMoxO3 with perovskite-type structure on SiO2. After reduction, Ni nanoparticles, MoOx and La2O3 would be all stay together and highly dispersed on SiO2 (Ni/MoOx-La2O3/SiO2). The techniques of BET, XRD, H2-TPR, HRTEM, ICP, H2 chemisorption and XPS were used to characterize the prepared samples. Through effectively combining MoOx which is active for the reaction of reverse water gas shift and Ni which can catalyze CO methanation, the resultant Ni/MoOx-La2O3/SiO2 catalyst exhibited pretty good performance for CO2 methanation, especially showing very good resistance to metal sintering. NiLa2O3/SiO2 catalyst without adding Mo was investigated for comparison. Since many metallic ions can enter into the lattice of a perovskite-type oxide, therefore, many combined catalysts for sequential reactions may be designed via this scheme.

Combined sorbent and catalyst material for sorption enhanced reforming of methane under cyclic regeneration in presence of H2O and CO2

An investigation on an innovative calcium‑nickel Combined Sorbent and Catalyst Material (CSCM) for Sorption Enhanced Reforming (SER) of methane is presented in this paper. After hydrothermal synthesis, a nominal 30 wt% CaO-based sorbent supported on mayenite was physically mixed with a commercial reforming catalyst and granulated to obtain bifunctional particles of 200–300 μm. Materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface analysis (BET) and Mercury- intrusion prosimetry (Hg-porosimetry). A novel thermo-gravimetric analysis (TGA) approach was employed for investigating SER activity, particularly the materials performance during multicycling methane reforming and sorbent carbonation followed by regeneration in oxidative atmosphere – either in the presence of steam or CO2 at high temperature. When regeneration is carried out in 100 vol% CO2 at 925 °C, an intermediate reduction step between cycles was crucial to maintain the catalytic activity of the CSCM for 100 consecutive sorption-regeneration cycles. In spite of a stable catalytic activity, the initial sorption capacity of the CSCM sorbent function (~16gCO2/100gCSCM) declined progressively with cyclic runs and stabilized at ~10gCO2/100gCSCM from cycle 90 onwards. This decline in capacity has been related to CaO depletion by solid phase reaction with the catalyst support.

Optimization and kinetics of the desulfurization of diesel fuel via high shear mixing oxidation assisted by adsorption of sulfones onto chitosan-coated bentonite

ABSTRACTRapid increase in the worldwide consumption of fuel has resulted in environmental and health hazards arising from elevated concentrations of sulfur dioxide and sulfate particulate matter in the atmosphere. In this study, the reduction of the sulfur content in commercial diesel with an initial concentration of 1428 ppm was carried out via oxidative desulfurization (ODS) assisted by high shear mixing using hydrogen peroxide as oxidant and phosphotungstic acid as catalyst in combination with the fixed-bed adsorption of sulfur compounds onto chitosan-coated bentonite (CCB) and activated carbon (AC). The effects of mixing speed (8,000–12,000 rpm), oxidation temperature (60–80ºC), and oxidation time (20–40 min) on sulfur removal were analyzed using the response surface methodology based on the Box–Behnken Design. Results show that the maximum sulfur removal of 81.97% could be attained at the following optimum conditions: 12,000 rpm, 80°C, and 34 min. Fixed-bed studies illustrated that CCB (0.2 mm) has higher adsorption efficiency of 82.66% than AC of 63.24% in the removal of sulfones from diesel.

Organocatalytic Asymmetric Cascade Reaction between o‐Hydroxycinnamaldehydes and γ/δ‐Hydroxyenones: A Route to Tetrahydrofuran/Tetrahydropyran‐Fused 3,4‐Dihydrocoumarins

AbstractThe first organocatalytic asymmetric synthesis of tetrahydrofuran/tetrahydropyran‐fused 3,4‐dihydrocoumarin has been developed via a cascade reaction between 2‐hydroxy cinnamaldehydes and γ/δ‐hydroxy enones followed by pyridinium chlorochromate oxidation. Diphenylprolinol silyl ether catalyst in combination with acetic acid was found to be the most effective for the cascade reaction. With 10 mol% of the catalyst and the additive, the desired products were obtained in high enantio‐ and diastereoselectivities.magnified image

Obtaining formaldehyde on a new catalytic system

Formaldehyde is widely used in many fields of industry. The increase in the need for formaldehyde led to an increase in scientific research, the purpose of which is to obtain the greatest yield of the product (formaldehyde) with minimal costs for raw materials, catalyst and its regeneration, energy carriers, etc. At industrial plants for the production of formaldehyde by oxidative dehydrogenation of methanol on the silver on pumice catalyst, the process temperature is maintained at 600 ° C. The process of obtaining formaldehyde by oxidation of methanol with air oxygen at the combination of catalysts "silver" and "silver on pumice" in the temperature range of 250–450 °C is investigated. The results showed the possibility of practical application of the combined catalyst. Chemical and technological parameters of the process with the use of a new catalyst are slightly lower than production indicators, however, the temperature of the pilot process is 2 times lower - this will reduce not only the energy costs, but also increase the life of the catalyst and the cost of its regeneration.

Catalytic Effect of a Combined Silver and Surfactant Catalyst on Cobalt Ore Bioleaching

The effects of Ag+, surfactants, and their combination on cobalt ore bioleaching were investigated in this article. Ag+ ions and surfactants, either individually or in combination, can significantly accelerate mineral dissolution and increase metal leaching efficiencies. When 20 mg L−1 Ag+ was added, the cobalt and copper leaching efficiencies increased from 67.8% and 58.5% to 94.3% and 80.7%, respectively. In addition, in the presence of 150 mg L−1 Tween-20, the cobalt and copper leaching efficiencies increased by more than 25% and 11%, respectively. A similar trend was observed with Tween-60 and Tween-80. When a combined catalyst of Ag+ ions and surfactant was employed, the cobalt and copper leaching efficiencies increased by more than 23% and 10%, respectively. Moreover, the leaching time decreased by one quarter. The catalytic effect of the combined catalyst was more significant than that of a single catalyst.