Mesoporous CuO/TixZr1 − xO2 catalysts for low-temperature CO oxidation

Mesoporous CuO/Ti_xZr_1 − xO₂ catalysts were prepared by a surfactant-assisted method, and characterized by N₂ adsorption/desorption, TEM, XPS, in-situ FTIR and H₂-TPR. The catalysts exhibited high specific surface area (S_BET = 241 m²/g) and uniform pore size distribution. XPS and in-situ FTIR displayed that Cu⁺ and Cu²⁺ species coexisted in the catalysts. The CuO/Ti_xZr_1 − xO₂ catalysts presented obviously higher activity in CO oxidation reaction than the CuO/TiO₂ and CuO/ZrO₂ catalysts. Effect of molar ratios of Ti to Zr and calcination temperature on catalytic activity was investigated. The CuO/Ti_0.6Zr_0.4O₂ catalyst calcined at 400 °C exhibited excellent activity with 100% CO conversion at 140 °C.     

Hydrogen production via methanol steam reforming over Au/CuO,Au/CeO2, and Au/CuO–CeO2 catalysts prepared by deposition–precipitation

The production of hydrogen (H₂) with a low concentration of carbon monoxide (CO) via steam reforming of methanol (SRM) over Au/CuO, Au/CeO₂, (50:50)CuO–CeO₂, Au/(50:50)CuO–CeO₂, and commercial MegaMax 700 catalysts were investigated over reaction temperatures between 200 °C and 300 °C at atmospheric pressure. Au loading in the catalysts was maintained at 5 wt%. Supports were prepared by co-precipitation (CP) whilst all prepared catalysts were synthesized by deposition–precipitation (DP). The catalysts were characterized by Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy (SEM). Au/(50:50)CuO–CeO₂ catalysts expressed a higher methanol conversion with negligible amount of CO than the others due to the integration of CuO particles into the CeO₂ lattice, as evidenced by XRD, and a interaction of Au and CuO species, as evidenced by TPR. A 50:50 Cu:Ce atomic ratio was optimal for Au supported on CuO–CeO₂ catalysts which can then promote SRM. Increasing the reaction time, by reducing the liquid feed rate from 3 to 1.5 cm³ h^?1, resulted in a catalytic activity with complete (100%) methanol conversion, and a H₂ and CO selectivity of ～82% and ～1.3%, respectively. From stability testing, Au/(50:50)CuO–CeO₂ catalysts were still active for 540 min use even though the CuO was reduced to metallic Cu, as evidenced by XRD. Therefore, it can be concluded that metallic Cu is one of active components of the catalysts for SRM.     

Pd/Ce0.9Cu0.1O1.9-Y2O3 catalysts for catalytic combustion of toluene and ethyl acetate

A dual-functional Pd/CuO-CeO₂-Y₂O₃ (Pd/CCY) using CuO-CeO₂ as precursor was prepared and tested for catalytic combustion of toluene and ethyl acetate. It was found that the catalyst is much higher active and thermally stable for combustion of both toluene and ethyl acetate, compared with the catalyst prepared with the conventional method. Therefore, the formation of the CuO-CeO₂ solid solution before coating is the key to high activity and thermal stability. Moreover, Pd/PdO species are the active phase for oxidation of toluene, while CuO or CuO-CeO₂ is responsible for oxidation of ethyl acetate, and the formation of the Pd probably impels the enhancement of activity for the catalyst calcined at 1000 °C.     

Liquid phase hydrogenation of biomass-derived ethyl lactate to propane-1,2-diol over a highly active CoB amorphous catalyst

Amorphous CoB alloy catalysts were prepared using chemical reduction method by changing the concentration of cobalt acetate from 0.5 to 1.0 mol/L and examined for the liquid phase hydrogenation of ethyl lactate. The catalyst, prepared with cobalt acetate concentration being 0.75 mol/L, gave a 99.8% selectivity to propane-1,2-diol at a conversion of 98.3%. The catalysts were characterized by XRD, TEM, BET, H₂-TPD and XPS. For all the catalysts, Co was electron-rich whereas B electron-deficient, and B was rich on the surface. The change in the concentration of cobalt acetate results in different surface composition of B/Co, various types of Co active sites, and different distribution of particles, which have large influence on activity and selectivity of the catalyst.     

Effect of the hybrid catalysts preparation method upon direct synthesis of dimethyl ether from synthesis gas

Direct synthesis of DME from synthesis gas attains more attention recently due to higher conversion and lower cost in comparison to dehydration of the methanol. In this work Synthesis gas To Dimethylether (STD) conversion was examined on various hybrid catalysts prepared by seven different methods. These catalysts had the same general form as CuO/ZnO/Al₂O₃ with theoretical weight ratio 31/16/53, respectively. A novel preparation method for hybrid catalyst namely sol–gel impregnation has also been developed which showed better performance in comparison with the other methods. Also, in order to find out the effect of various alumina contents at a fixed CuO/ZnO ratio on the performance of the hybrid catalyst, a series of catalysts with different contents of alumina have been prepared by sol–gel impregnation method. The optimum weight ratio for CuO/ZnO/Al₂O₃ catalyst has been found to be about 2:1:5, respectively. These catalysts characterized by TPR, XRD, XRF, BET, TGA, N₂O absorption. The catalysts performance were tested at 240 °C, 40 bar and space velocity 1000 ml/g_cat.h, with the inlet gas composition H₂/CO/N₂ = 64/32/4 in a micro slurry reactor.     

Influence of CeO2 morphology on the catalytic oxidation of ethanol in air

Nano-CeO₂ catalysts of different shapes were synthesized at different hydrothermal crystallization temperatures from an alkaline aqueous solution. X-ray diffraction (XRD), transmission electron microscope (TEM), and H₂ temperature-programmed reduction (H₂-TPR) were used to study the synthesized nano-CeO₂ catalyst samples. The catalytic properties of the prepared nano-CeO₂ catalysts for the catalytic oxidation of ethanol in air were also investigated. TEM analysis showed that CeO₂ nanorod and nanocube catalysts have been synthesized at hydrothermal crystallization temperatures of 373 K and 453 K, respectively. XRD results showed that the synthesized nano-CeO₂ catalysts have similar cubic fluorite structures. H₂-TPR results indicated that CeO₂ nanorod and nanocube catalysts exhibit different reduction behaviors for H₂ and that the nanorod catalyst has better low-temperature reduction performance than the nanocube catalyst. Ethanol catalytic oxidation results indicated that oxidation and condensation products (including acetaldehyde, acetic acid, CO₂, and ethyl acetate) have been produced from the prepared catalysts. The ethyl acetate and acetic acid can be ignited by ethanol at low temperature on the CeO₂(R) catalyst to give low catalytic combustion temperature for ethyl acetate and acetic acid molecules. CeO₂ nanorods gave ethanol oxidation conversion rates above 99.2% at 443 K and CO₂ selectivity exceeding 99.6% at 483 K, while CeO₂ nanocubes gave ethanol oxidation conversion rates of about 95.1% until 508 K and CO₂ selectivity of only 93.86% at 543 K. CeO₂ nanorod is a potential low-cost and effective catalyst for removing trace amounts of ethanol to purify air.     

Steam reforming of methanol over copper–manganese spinel oxide catalysts

The steam reforming of methanol was studied over a series of copper–manganese spinel oxide catalysts prepared with the urea–nitrate combustion method. All catalysts showed high activity towards H₂ production with high selectivity. Synthesis parameters affected catalyst properties and, among the catalysts tested, the one prepared with 75% excess of urea and an atomic ratio Cu/(Cu + Mn) = 0.30 showed the highest activity. The results show that formation of the spinel Cu_xMn_3 − xO₄ phase in the oxidized catalysts is responsible for the high activity. Cu–Mn catalysts were found to be superior to CuO–CeO₂ catalysts prepared with the same technique.     

Hydrogen production from steam reforming of kerosene over Ni–La and Ni–La–K/cordierite catalysts

Ni–La and Ni–La–K catalysts supported on cordierite were prepared for steam reforming of kerosene to produce hydrogen. All these catalysts were tested in a fixed-bed reactor under different conditions. The catalysts obtained under different calcination temperatures and different reaction temperatures were characterized by TG–DTG and XRD techniques respectively. The influence of NiO and La₂O₃ contents on the activity of catalysts for steam reforming of kerosene to produce hydrogen was also investigated in our experiments. The experimental results indicate that the calcination temperature has much more influence on catalyst activity. The catalyst supported the promoter 5 wt% K₂O, 25 wt% NiO and 10 wt% La₂O₃, is the optimal catalyst under 773 K of reaction temperature and 2300 h⁻¹ of space velocity. Composition of Ni is highly dispersed on the catalyst surface. And through the duration test, the catalyst activity and stability are very satisfactory at 873 K of the reaction temperature.     

Promotion effect of metal oxides on inverse CeO2/CuO catalysts for preferential oxidation of CO

The MO_x–CeO₂/CuO (M = Co, Mn, Sn and Zn) catalysts were synthesized by the hydrothermal method and characterized by XRD, BET, SEM, H₂-TPR and HRTEM techniques. It is found that the MnO₂–CeO₂/CuO catalyst exhibits the best activity from 75 °C to 115 °C, suggesting that the addition of Mn is the most effective for improving low-temperature activity. The reasons are that MnO₂ improves the dispersion of CeO₂ and the textural property of CeO₂/CuO catalyst. Moreover, the presence of MnO₂ is favorable for preventing the reduction of CuO, and MnO₂ also enhances the interaction between CeO₂ and CuO.     

Preparation,characterization and testing of Cr/AlSBA-15 ethylene polymerization catalysts

Ethylene polymerization catalysts have been prepared by grafting chromium(III) acetylacetonate onto AlSBA-15 (Si/Al = ∞, 156, 86 and 30) mesoporous materials. A combination of XRD, nitrogen adsorption, TEM, ICP-atomic emission spectroscopy, H₂-TPR, TGA, UV–vis and FT-IR spectroscopy, were used to characterize the prepared Cr–AlSBA-15 catalysts. By reducing the Si/Al ratio of the AlSBA-15 supports increases the amount of chromium anchored, promotes the stabilization of chromium species as chromate and decreases the reduction temperature of Cr⁶⁺ ions determined by H₂-TPR. Attachment of Cr species onto AlSBA-15 surface results from the interaction of hydroxyl groups with the acetylacetonate ligands through H-bonds. On the contrary, a ligand exchange reaction may occur over siliceous SBA-15.The polymerization activity of Cr–AlSBA-15 catalysts is significantly improved by increasing aluminium content of the AlSBA-15 supports. Particularly, the chromium catalyst prepared with AlSBA-15 (Si/Al = 30) support is almost four times more active than a conventional Cr/SiO₂ Phillips catalyst. Polymers obtained with all the catalysts showed melting temperatures, bulk densities and high load melt indexes indicating the formation of linear high-density polyethylene.     

Selective esterification of tert-butanol by acetic acid anhydride over clay supported InCl3, GaCl3, FeCl3 and InCl2 catalysts

Clay (kaolin, mont-K10 and mont-KSF) supported InCl₃, GaCl₃, FeCl₃ and ZnCl₂ catalysts (metal chloride loading=1.1 mmol g⁻¹) show high selectivity (⩾98%) at high conversion in the esterification of tert-butanol by acetic anhydride to tert-butyl acetate (t-BA) and very low activity for the dehydration of tert-butanol at ⩽50°C. For all the catalysts, mont-K10 is the best support and the order of their esterification activity (at 26°C) is: InCl₃/mont-K10 (TOF=0.025 s⁻¹) > GaCl₃/mont-K10 (0.023 s⁻¹) > FeCl₃/mont-K10 (0.02 s⁻¹) ⩾ ZnCl₂/mont-K10 (0.019 s⁻¹). InCl₃/mont-K10 is highly active, selective and reusable catalyst for the esterification.     

Mercury oxidation by hydrochloric acid over TiO2 supported metal oxide catalysts in coal combustion flue gas

Mercury oxidation by hydrochloric acid over the metal oxides supported by anatase type TiO₂ catalysts, 1 wt.% MO_x/TiO₂ where M = V, Cr, Mn, Fe, Ni, Cu, and Mo, was investigated by the Hg⁰ oxidation and the NO reduction measurements both in the presence and absence of NH₃. The catalysts were characterized by BET surface area measurement and Raman spectroscopy. The metal oxides added to the catalyst were observed to disperse well on the TiO₂ surface. For all catalysts studied, the Hg⁰ oxidation by hydrochloric acid was confirmed to proceed. The activity of the catalysts was found to follow the trend MoO₃ ~ V₂O₅ > Cr₂O₃ > Mn₂O₃ > Fe₂O₃ > CuO > NiO. The Hg⁰ oxidation activity of all catalysts was depressed considerably by adding NH₃ to the reactant stream. This suggests that the metal oxide catalysts undergo the inhibition effect by NH₃. The activity trend of the Hg⁰ oxidation in the presence of NH₃ was different from that observed in its absence. A good correlation was found between the NO reduction and the Hg⁰ oxidation activities in the NH₃ present condition. The catalyst having high NO reduction activity such as V₂O₅/TiO₂ showed high Hg⁰ oxidation activity. The result obtained in this study suggests that the oxidation of Hg⁰ proceeds through the reaction mechanism, in which HCl competes for the active catalyst sites against NH₃. NH₃ adsorption may predominate over the adsorption of HCl in the presence of NH₃.     

A facile synthesis of CuO nanowires and nanorods,and their catalytic activity in the oxidative degradation of Rhodamine B with hydrogen peroxide

In this study, a new and facile solution-phase route to prepare CuO nanowires and nanorods with the assistance of salicylic acid was reported. Compared with the commercial CuO nanoparticles, both the CuO nanowires and nanorods exhibited significantly improved catalytic activity in the degradation of Rhodamine B with H₂O₂, which may result from their special one dimensional nanostructures. The apparent activation energy of Rhodamine B oxidation with H₂O₂ in the presence of the CuO nanowires and nanorods was 30.95 kJ·mol^− 1 and 32.07 kJ·mol^− 1, respectively, which was much lower than that in the absence of catalysts.     

Effect of Cu doping on the SCR activity of CeO2 catalyst prepared by citric acid method

CeO₂–CuO catalyst prepared by citric acid method was investigated for selective catalytic reduction of NO with NH₃. The activity of the CeO₂ catalyst was enhanced about 8–27% in the temperature range of 125–225 °C at a space velocity of 28,000 h⁻¹ by the addition of Cu. It was found that the state of Cu species had great impact on the SCR performance of CeO₂–CuO catalyst. Cu²⁺ can enhance the low temperature activity of SCR reaction, while CuO would promote NH₃ oxidation before SCR reaction at high temperature, which would cause the decrease of its high temperature SCR activity.     

Simultaneous catalytic removal of NOx and soot particulates over CuMgAl hydrotalcites derived mixed metal oxides

A series of CuMgAl hydrotalcites derived oxides were prepared by co-precipitation and calcination methods and tested for the simultaneous catalytic removal of NOx and soot. The obtained samples were characterized by XRD, N₂ adsorption-desorption, H₂-TPR and ICP-AES techniques. The crystal phases, porous structures and redox properties of the catalysts were strongly influenced by Cu substitution contents and calcination temperatures. The CuMgAl mixed oxides with mesoporous properties exhibit high activity for the simultaneous NOx-soot removal. Among the tested catalysts, 3.0Cu-800 sample shows the best performance with the ignition temperature of soot = 260 °C and the total amounts of N₂ = 6.0 × 10^− 5 mol. Based on the experimental work, a primitive kinetics analysis was carried out from the non-steady (dynamic) TPR measurements. Linear Arrhenius plots of rates of CO₂, N₂ and N₂O formation were observed around the onset of formation curves where the substantial amount of the soot still remains in the soot/catalyst mixture and the effective area of the soot/catalyst contact can be regarded as constant. Finally, a compensation effect was found for the formation of CO₂, N₂ and N₂O over CuMgAl mixed oxides with CuO as the predominant phase.     

Influences of preparation methods of ZrO2 support and treatment conditions of Cu/ZrO2 catalysts on synthesis of methanol via CO hydrogenation

ZrO₂ supports were prepared by different methods (conventional precipitation method, shortened as “CP”, and alcogel/thermal treated with nitrogen method, shortened as “AN”), and Cu/ZrO₂ catalysts were prepared by impregnation method. The supports and catalysts were characterized by BET, XRD, TEM and TPR. The effects of the preparation methods of ZrO₂ supports and the treatment conditions (calcination and reduction temperatures) of the catalyst precursors on the texture structures of the supports and catalysts as well as on the catalytic performances of Cu/ZrO₂ in CO hydrogenation were investigated. The results showed that the support ZrO₂-AN had larger BET specific surface area, cumulative pore volume and average pore size than the support ZrO₂-CP. Cu/ZrO₂-AN catalysts showed higher CO hydrogenation activity and selectivity of oxygenates (C₁–C₄ alcohols and dimethyl ether) than Cu/ZrO₂-CP catalysts. Calcination and reduction temperatures of supports and catalyst precursors affected the catalytic performance of Cu/ZrO₂. The conversion of CO and the STY of oxygenates were 12.7% and 229 g/kg h, respectively, over Cu/ZrO₂-AN-550 at the conditions of 300 °C, 6 MPa.     

Heterogeneous alkenylation of aromatics under oxygen

A novel heterogeneous Pd/polymer catalyst containing co-catalytic functional groups catalyses the direct alkenylation of anisole with ethyl trans-cinnamate under oxygen. The properties of the polymeric catalyst were compared to other immobilised catalysts. The activity of the polymeric catalyst typically increased with temperature and oxygen pressure exhibiting the optimal activity up to 100 TON at 383 K under 1.2 MPa of O₂. The most abundant product was 3-(p-methoxyphenyl)-3-phenylpropanoate (≈45%). The reaction selectivity was practically independent of the conditions. Split-tests and AAS measurements confirm heterogeneous character of the catalyst.     

Effect of K promoter on the stability of Pd/NFY catalysts for acetylene hydrochlorination

Pd and PdK bimetallic catalysts were prepared and applied in acetylene hydrochlorination reaction. Using NFY zeolites as supports, the Pd-K/NFY catalyst showed both high activity and excellent stability, with a C₂H₂ conversion of 99% more than 50 h. Characterized results indicate that the K promoter can stabilize the Pd^2 + species and weaken the occurrence of carbon deposition on the catalyst surface, thus improving the stability of the Pd-based catalysts.     

Deactivation of supported skeletal Ni catalyst and effect of regeneration temperature on its catalytic performance

Deactivation and regeneration of supported skeletal Ni catalyst applied to hydrogenation of indene and styrene in fixed-bed reactor were investigated. The significant aggregation of skeletal Ni and formation of coke precursors were the main reasons for deactivation of catalyst. Furthermore, TG-DTA, XRD, SEM, BET and H₂-TPR were utilized to characterize the regenerated catalysts and calcining the spent catalysts in air at 550 °C for 3 h and then reducing in H₂ at 450 °C for 3 h under 240 h^− 1 (GHSV) could recover its activity according to hydrogenation evaluation results.     

Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/Al–SBA-15 catalysts for the reduction of NO with ammonia

Mesoporous Al–SBA-15 has been synthesized by a hydrothermal method and used as a support for Mn/Al–SBA-15, Fe/Al–SBA-15, and Mn–Fe/Al–SBA-15 catalysts. XRD, N₂ sorption, XPS, H₂-TPR and activity tests have been used to assess the properties of catalysts. The Mn–Fe/Al–SBA-15 catalyst exhibited a higher SCR activity than Mn/Al–SBA-15 or Fe/Al–SBA-15 due to a synergistic effect between Mn and Fe. After the addition of Fe, the binding energy of Mn 2p_3/2 on Mn–Fe/Al–SBA-15(573) decreased by about 0.4 eV and the Mn^4 +/Mn^3 + ratio decreased to 1.10. The appropriate Mn^4 +/Mn^3 + ratio may have a great effect on the reduction of NO over Mn–Fe/Al–SBA-15(573) catalyst.