Catalytic Performance Of Cu Research Articles

Tuning the Catalytic Activity and Selectivity of Cu for CO2 Electroreduction in the Presence of Halides

In the present study we demonstrate that the activity and selectivity of copper during CO2 electrochemical reduction can be tuned by simply adding halides to the electrolyte. Comparing the production rate and Faradaic selectivity of the major products as a function the working potential in the presence of Cl–, Br–, and I–, we show that the activity and selectivity of Cu depends on the concentration and nature of the added halide. We find that the addition Cl– and Br– results in an increased CO selectivity. On the contrary, in the presence of I– the selectivity toward CO drops down and instead methane formation is enhanced up to 6 times compared with the halide-free electrolyte. Even though Br– and I– can induce morphology changes of the surface, the modification in the catalytic performance of Cu is mainly attributed to halides adsorption on the Cu surface. We hypothesizes that the adsorption of halides alters the catalytic performance of Cu by increasing the negative charge on the surface according to th...

Effect of ZnO incorporation on Cu–Ni/Al2O3 catalyst for glycerol hydrogenolysis in the absence of added hydrogen

A series of Cu–Ni bimetallic catalysts were developed and used for glycerol hydrogenolysis to produce 1,2-propanediol in the absence of added hydrogen along with the isopropanol as hydrogen donor. The monometallic Cu catalyst can catalyze the dehydrogenation of isopropanol effectively, but the Cu species would be oxidized to Cu+ which led to the catalyst deactivation. Ni incorporation can change the reduction behavior of Cu catalyst and the formation of Cu–Ni alloy might promote the hydrogenation of acetol. Furthermore, the effect of ZnO incorporation on the catalytic performance of Cu–Ni/Al2O3 bimetallic catalyst for glycerol hydrogenolysis in the absence of added hydrogen was investigated. The addition of ZnO enhanced the acidity of catalyst surface, resulting in higher C–O bond cleavage activity. Comparing the H2-TPR profiles of Cu–Ni/Al2O3 with Cu–Ni/ZnO–Al2O3, it could be clearly observed that the reduction temperature was decreased remarkably by the addition of ZnO. XRD and SEM images revealed that the addition of ZnO inhibited the catalyst sintering and favored the formation of the strong interaction between Cu–Ni species and Al2O3 by the formation of the ZnAl2O4 phase.

Promotional effects of Ce4+, La3+ and Nd3+ incorporations on catalytic performance of Cu–Fe–Ox for decomposition of N2O

Promotional effects of Ce4+, La3+ and Nd3+ incorporations on FeCu2O3.5/ATS for decomposing N2O were investigated. Results showed that all the ions especially La3+ can dramatically improve the catalytic performance. FeCu2La1.5Ox/ATS, the optimal catalyst, can decompose 100% N2O at 550°C. The formed perovskite-type LaFeO3 and spinel-type CuLa2O4 largely improved catalytic performance. The ion modification increased N2O adsorption capacity, and La3+-doped catalyst enhanced desorption ability of surface oxygen. Both effects can accelerate the rate-determine steps of N2O decomposition reaction, promote catalytic performance. Moreover, the supported catalysts studied were economic efficiency for application.

Synthesis, characterization and catalytic performances of Cu- and Mn-containing ordered mesoporous carbons for the selective catalytic reduction of NO with NH3

The synergetic catalytic effect of Cu and Mn for CuxMny-OMCs catalysts on NO conversion with NH3.

Synthesis, characterisation and catalytic performance of Cu- and Co-modified Fe-Al co-precipitated catalysts for the steam reforming of ethanol

<p>This paper reports the synthesis and the investigation of the properties and performance of Fe-Al catalysts modified with Cu or Co for the steam reforming of ethanol. The materials were prepared by the precipitation method with different Fe/Al ratios. The samples were characterised by the S<sub>BET</sub>, TG/DTG, XRD, H<sub>2</sub>-TPR and TPO/DTA analyses. The increase in the Fe/Al ratio leads to a decrease in the specific surface area and shifts the reduction peaks towards higher temperatures. The partial substitution of Fe by Co or Cu modifies the structure of the materials because higher specific surface areas and crystallites of iron oxides with smaller sizes are formed. The promotion also improves the reducibility of the iron species. These changes provide higher activity and selectivity towards H<sub>2</sub> and CO for the modified samples and for the samples with lower Fe/Al ratio. The Co-containing catalyst showed the best performance because this sample exhibited the highest conversions and selectivity towards both H<sub>2</sub> and CO and the lowest formation of coke according to the TPO analysis.</p>

Effect of preparation conditions on the catalytic performance of Cu–Fe/ZrO2 for the synthesis of DPU from aniline and CO2

Abstract Diphenyl urea (DPU) is an important chemical intermediate. The synthesis of DPU from aniline and CO 2 is a green route and the studies on the catalyst for this route are of significance. The effect of preparation conditions on the catalytic performance of Cu–Fe/ZrO 2 was investigated by means of XRD, H 2 -TPR, and BET in combination with activity test. Cu–Fe/ZrO 2 was prepared by the following process: firstly an incipient wetness impregnation using cupric nitrate and ferric nitrate as the precursors and then calcination after being dried and finally reduction. The suitable conditions were as follows: metal loading based on metal oxide = 10% (wt.), molar ratio of Cu to Fe = 3:1, aging at ambient temperature for 24 h, drying at 110 °C for 10 h, calcinating at 450 °C for 6 h, and reducing at 300 °C for 3 h using a mixture of H 2 /N 2 with 20% (vol.) of H 2 . It is concluded that (1) copper and cupric oxide are the main active species while iron and ferric oxide are the promoters; (2) the reduction properties of cupric oxide and ferric oxide play important roles in the catalysis of Cu–Fe/ZrO 2 ; (3) both Lewis acid sites and Lewis base sites existed on the surface of ZrO 2 promote the catalytic performance of Cu–Fe/ZrO 2 . In addition, the catalytic mechanism of Cu–Fe/ZrO 2 in the reaction of aniline and CO 2 to DPU was proposed.

A synthesis of copper based metal-organic framework for O-acetylation of alcohols

A novel metal-organic framework, Cu–BDC was synthesized by static hydrothermal method using innocuous solvents and characterized by several techniques such as powder XRD, ESR, TG–DTA, elemental analysis, ICP-AES, SEM, EDXS, FT-IR, BET surface area, pore volume and pore size. The catalytic performance of Cu–BDC was explored for O-acetylation of alcohols under solvent-free conditions at room temperature. The catalyst exhibited remarkable activity and reusability affording the desired products in excellent yields.

Selectiveness of Copper and Polypyrrole Modified Copper Electrodes for Nitrate Electroreduction: A Comparative Study and Application in Ground Water

Nitrate and nitrite electroreduction was carried out for simulated and real groundwater samples by the chronoamperometric technique, using copper (Cu) and polypyrrole modified copper (Ppy/Cu) electrodes. The Ppy/Cu electrodes were prepared on copper substrate by electrochemical oxidation of pyrrole in salicylic acid and salicylate buffer solutions. The copper electrode showed the best catalytic activity for nitrate reduction, however with a large amount of unwanted nitrite by-product, compared to Ppy/Cu electrodes. The electroreduction of nitrate and nitrite compounds in the groundwater samples using Ppy/Cu electrodes was effectively with a considerable low formation of unwanted nitrite and ammonium products. The modified copper electrodes perform selective and stable catalytic effect on the nitrite reduction. The modification conditions affect the performance of the electrodes. The catalytic performance of Cu and Ppy/Cu electrodes for nitrate reduction was studied by cyclic voltammetry. Nitrate, nitrite and ammonium contamination in groundwater at six polluted areas in Ho Chi Minh City was analyzed, following the AOAC, ASTM, NIOSH standards by photometric and ion-chromatographic methods (NIOSH 6015, NIOSH 6014/ASTM 1607, ASTMD 1426, ASTM 3867).

Catalytic hydrogenation of nitrate on Cu–Pd supported on titanate nanotube and the experiment after aging, sulfide fouling and regeneration procedures

Although catalytic nitrate reduction is efficient for water treatment, catalysts are sensitive to other components in the environment. In this study, the catalytic performance of Cu–Pd/TNTs (palladium–copper/titanate nanotubes) toward nitrate reduction was investigated for their nitrate reduction ability in CO2-saturated condition. The inhibiting effects due to catalyst aging and sulfide fouling were also investigated. The results showed that TNTs-supported bimetallic catalysts were more resistant to catalyst poisoning than TiO2-supported ones. This could be due to the fact that the specific geometry of TNTs shelter bimetallic catalyst from oxidation as the valence state of the catalysts is evidenced by the XPS analysis. Regarding the regeneration methods, Cu–Pd/TNTs showed higher nitrate reduction rates than Cu–Pd/TiO2 after aging, sulfide fouling and regeneration procedures. The valence state of the catalyst analyzed by XPS revealed that metals on the TNTs were slightly more oxidized than metals on TiO2. Therefore TNTs can prevent the supported metals from being oxidized. Moreover, heated NaBH4-saturated nitrogen gas (403°K) could effectively revive the nitrate reduction rates of sulfide-fouled catalysts.

Controlled preparation and characterization of supported CuCr2O4 catalysts for hydrogenolysis of highly concentrated glycerol

Supported Cu–Cr catalysts were prepared by a non-alkoxide sol–gel route, and characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) measurement. Their structures were significantly tuned by the Cu–Cr molar ratio. CuCr2O4, CuCr2O4–CuO and CuCr2O4–Cr2O3 structures were confirmed in CuCr(0.5), CuCr(4) and CuCr(0.25) catalysts, respectively. A direct interaction between CuCr2O4 and CuO or Cr2O3 in CuCr(4) and CuCr(0.25) catalyst was observed by the H2-TPR and XPS results. The catalytic performance of Cu–Cr catalysts with various structures was examined by hydrogenolysis reaction of high concentrated glycerol. Under mild conditions (2.0 MPa and 130 °C) and high concentration (100 wt%), the maximum conversion (52%) was obtained over the CuCr(0.5) catalyst, while the CuCr(4) catalyst gave the highest selectivity of 1,2-PD (up to 100%). This finding will result in the production of less waste water and lower energy consumption in the following separation steps during glycerol hydrogenolysis.

Cu-doped CeO2 spheres: Synthesis, characterization, and catalytic activity

Abstract The Cu-doped CeO 2 spheres were synthesized by a simple hydrothermal method. It is confirmed that the spheres composed of many tiny particles are favorable for the gas diffusion in the inner pores. The doping copper is demonstrated to increase the storage and mobility of oxygen vacancy, surface area, and chemisorption sites for CO and enhance the redox capability, which can efficiently convert CO to CO 2 at low temperature. The excellent catalytic performance of Cu (10 at.%)-doped CeO 2 spheres are associated with the porous spherical structure, high redox capability and high oxygen vacancy.

Preparation, structure and catalytic properties of magnetically separable Cu–Fe catalysts for glycerol hydrogenolysis

The Cu–Fe catalysts with stoichiometric proportion (Cu/Fe molar ratio was 0.5) were prepared by an epoxide assisted route. The structural properties of Cu–Fe catalysts were determined by X-ray diffraction (XRD), and Mossbauer spectroscopy measurements. These results indicated that a crystalline phase transformation from c-CuFe2O4 to t-CuFe2O4 occurred when elevating the calcination temperature from 500 to 600 °C. The M–H plots exhibited that all Cu–Fe catalysts had ferromagnetic nature and the saturation magnetization values monotonously increased with increasing calcination temperature irrespective of the phases composition. The significant superparamagnetic behavior was observed in the results of magnetic and Mossbauer spectroscopy measurements. The H2 temperature-programmed reduction (H2-TPR) was also conducted for examining the reducibility of Cu–Fe catalysts. The catalytic performance of Cu–Fe catalysts was examined for the hydrogenolysis reaction of glycerol. It is found that the formation of spinel CuFe2O4 greatly enhances the hydrogenolysis activity. The highest glycerol conversion (47%) was obtained over CuFe-500 catalyst, while the selectivity of 1,2-propanediol was maintained at about 92% for all catalysts.

Gas-phase hydrogenation of maleic anhydride to γ-butyrolactone at atmospheric pressure over Cu–CeO 2–Al 2O 3 catalyst

Cu–CeO 2–Al 2O 3 catalyst, prepared by co-precipitation method, was investigated for the gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and the catalyst deactivation was also studied. Effects of catalyst composition, reaction temperature, and liquid hourly space velocity (LHSV) of raw material on the catalytic performance of Cu–CeO 2–Al 2O 3 catalyst were investigated. The catalyst (molar ratio of Cu:Ce:Al = 1:1:2) showed better catalytic performance, in which both the conversion of MA and the selectivity of GBL kept 100% within two hours under the reaction conditions of 6 mL catalyst, 0.1 MPa, 220–280 °C, 30 mL min −1 H 2, 0.6 h −1 LHSV of 20 wt.% MA/GBL. As for Cu–CeO 2–Al 2O 3 catalyst, smaller crystallite size of Cu and higher Cu surface area are favorable to increase its catalytic performance. The deactivation of Cu–CeO 2–Al 2O 3 catalyst is due to formation of the compact wax-like deposition on the catalyst surface, which is probably ascribed to the strong adsorption of succinic anhydride and then polymerization on the catalyst surface. The catalytic performance of the regenerated catalyst can be recovered completely by the regeneration method of N 2–air–H 2 stage treatment.

Effects of Synthetic Parameters on the Structure and Catalytic Performance of Cu−Cr Catalysts Prepared by a Non-Alkoxide Sol−Gel Route

The surface areas of Cu−Cr xerogels prepared by an epoxide assisted route are highly dependent on synthetic conditions like gelation temperature, amount of water in the solvent, and gel aging time. Gelation temperature affects the relative rates of hydrolysis and condensation, the amount of water in solution adjusts the solution pH, and the aging process influences the microstructural properties of the xerogels. These factors affect the stability of the sol particles in solution and the final structure of the gel. Thermogravimetric and differential thermogravimetric analysis, specific surface area measurement through nitrogen adsorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are employed to determine particle size distribution and morphology of the different particulate products (i.e., gels, powders) obtained via different synthesis conditions, both before and after thermal treatments. The xerogel surface area can reach up to 230 m2/g by adjusting the operating parameters. Moreover, the results show that the Cu−Cr catalysts with CuCr2O4 and Cr2O3 phases obtained by calcining the as-prepared xerogels in 20% O2 in Ar have better activity for glycerol catalytic conversion than catalysts with Cu and Cr2O3 phases that were obtained by calcination in Ar. In addition, the activity of catalysts increased with the surface areas of xerogels. It is noteworthy that the catalysts have significant selectivity to 1,2-propanediol (54%) and 1-propanol (36%) at 32% conversion of glycerol at 210 °C and 4.1 MPa H2 pressure.

Statistical optimization by response surface methodology for water-gas shift reaction in a H 2-rich stream over Cu–Zn–Fe composite-oxide catalysts

The catalytic performance of Cu–Zn–Fe composite-oxide catalysts prepared by the urea–nitrate combustion (UNC) method for the WGS reaction was investigated in this study. The catalysts were characterized by means of X-ray diffraction (XRD), X-ray fluorescence (XRF), and the Brunauer–Emmet–Teller (BET) method. In order to reduce the total number of experiments to achieve the optimal condition of CO conversion in the reaction and to reveal the interactions among the factors, two sets of statistical designs of experiments were carried-out. Initially, a full 2 5 factorial design with three central points was done. Increased CO conversion is obtained when increasing the H 2O concentration and the O 2 concentration in the influent, the W/ F ratio, and the reaction temperature. On the other hand, the CO conversion is decreased with increasing Cu/(Cu + Zn + Fe) molar ratio, increasing interaction between O 2 concentration in the influent and reaction temperature, and increasing interaction between Cu/(Cu + Zn + Fe) molar ratio and reaction temperature. In order to continue the optimization, the application of the face-centered central composite design (FCCCD) falling under response surface methods was done. Two independent factors were selected from the five main factors. Based on the important variabilities in the conversion, the O 2 concentration in the feedstream and the reaction temperature were then selected to achieve the optimal conditions for CO conversion. The maximum CO conversion of 0.87 was obtained when adding 0.10% O 2 and 30% H 2O in the feedstream at a reaction temperature of 333 °C, a W/ F ratio of 0.24 g s cm −3, and a Cu/(Cu + Zn + Fe) molar ratio of 0.30. After optimizing CO conversion by statistical design of the experiments, validation of the model was performed. The estimated values of the statistical response surface analysis were well fitted with the observed ones. This elucidated that the response surface methodology with appropriate experimental design can be effectively applied to the optimization of CO conversion in the WGS reaction.

Structural feature and catalytic performance of Cu―SiO2―TiO2 cogelled xerogel catalysts for oxidative carbonylation of methanol to dimethyl carbonate

Abstract Cu―SiO 2 ―TiO 2 cogelled xerogel catalysts were prepared, characterized and tested for oxidative carbonylation of methanol to dimethyl carbonate (DMC). The catalyst with 12.5 mol% of Cu loading shows better catalytic performance and reduced corrosion as compared with the CuCl catalytic system, which is attributed to highly dispersed Cu + active centers as well as lower chloride content. Further copper loading resulted in loss of copper during the preparation of the catalyst and decreased catalytic activity in DMC synthesis.

Steam reforming of methanol over Cu/Zn/Zr/Ga catalyst: effect of the reduction conditions on the catalytic performance

The effect of the reduction conditions on the catalytic performance of Cu based catalyst in the methanol steam reforming process was investigated. The catalyst was prepared in our laboratory using the method of thermal decomposition of citrates. The influence of catalyst reduction methods on the methanol steam reforming process was studied with hydrogen, carbon monoxide, methanol and water mixture and pure methanol used as reductants. The most selective catalysts were obtained by the reduction with methanol and water mixture and also with pure methanol.

Remediation of actual groundwater polluted with nitrate by the catalytic reduction over copper–palladium supported on active carbon

Catalytic reduction of nitrate (NO 3 −) in groundwater over a Cu–Pd catalyst supported on active carbon was investigated in a gas–liquid co-current flow system at 298 K. Although Cu–Pd/active carbon, in which the Cu/Pd molar ratio was more than 0.66, showed high activity, high selectivity for the formation of N 2 and N 2O (98%), and high durability for the reduction of 100 ppm NO 3 − in distilled water, the catalytic performance decreased during the reduction of NO 3 − in groundwater. The catalyst also irreversibly deactivated during the reaction in groundwater. The organic species in the groundwater caused the decrease in the catalytic performance and the irreversible catalyst deactivation. Ozone-treatment of the groundwater to remove the organic species substantially helped to maintain the catalytic activity and to halt the irreversible deactivation of the catalyst. Chloride ion (Cl −) in the groundwater also caused the decrease in the activity and selectivity, but the effects of Cl − were reversible. Sulfate ion (SO 4 2−) and cations, including Mg 2+, Ca 2+ and K +, had little or no effect on the catalytic performance of Cu–Pd/active carbon, though they were present in the groundwater sample. More than an allowable level of NH 3 (NH 4 +) was formed during the catalytic reduction of NO 3 − in the groundwater, but was completely removed by the cation-exchange process using Na-mordenite.

Influence of Pd ion-exchange temperature on the catalytic performance of Cu–ZnO/Pd–β zeolite hybrid catalyst for CO hydrogenation to light hydrocarbons

Abstract The influence of Pd ion-exchange temperature of Pd–β zeolite on the reaction of CO hydrogenation to light hydrocarbons was investigated in this paper by the catalytic activity test and characterization like BET, and CO chemisorption. The results exhibit that Pd ion-exchange temperature have an important influence on the catalytic performance of hybrid catalysts containing Cu–ZnO methanol synthesis catalysts and Pd–β zeolite for CO hydrogenation to light hydrocarbons. With ion-exchange temperature increasing, CO conversion slightly increases, the yield of DME decreases, aromatics in hydrocarbon evidently increase although the total hydrocarbon yield has no evident change. The characterization results indicate that ion-exchange temperature affects the crystallite size of the active metal Pd supported on β zeolite, which is related to the catalytic activity of the hybrid catalyst.

High performance Cu–ZnO/Pd-β catalysts for syngas to LPG

The catalytic performance of Cu–ZnO/Pd-β catalyst for syngas to LPG (Liquefied Petroleum Gas) has been investigated in this paper. The kind of zeolite, SiO2/Al2O3 ratio in Pd-β, Pd-β particle size, Pd content in Pd-β, and reaction conditions, have been optimized. The results showed that the suitable reaction conditions for syngas to LPG over Cu–ZnO/Pd-β are: 325–350 °C, 2.1–3.6 MPa, 4.5–9 g h/mol gas velocity (W/F), and 37–75 ratio of SiO2/Al2O3. At the optimal conditions, Cu–ZnO/Pd-β could exhibit an excellent catalytic performance for syngas to LPG: 72.2% CO conversion, 45.3% hydrocarbon yield and 78.0% LPG selectivity in hydrocarbons could be achieved.