Increasing Copper Loading Research Articles

Direct conversion of CH4 and CO2 to alcohols using plasma catalysis over Cu/Al(OH)3 catalysts

The direct conversion of CH4 and CO2 into high-value alcohols is a highly desirable route for efficiently utilizing these two C1 sources while mitigating greenhouse gas emissions. However, this reaction is considered one of the most challenging research topics since it suffers from the contradiction between thermodynamics and kinetics. In this study, plasma-catalytic conversion of CH4 and CO2 for the production of high-value alcohols, with methanol being the major liquid product, was achieved using Cu-based catalysts at ∼190 °C and atmospheric pressure. Herein, the Cu-based catalysts were tuned by controlling the support material (Al(OH)3, γ-Al2O3, TiO2 and CeO2), calcination temperature (400–600 °C) and copper loading (1–20 wt%) to promote alcohol production in this reaction. The results show that the 5 wt% Cu/Al(OH)3 calcined at 540 °C exhibited the highest selectivity of alcohols (∼38%), which is the best result achieved so far in the presence of a catalyst. Catalyst characterization results reveal that the redox capacity and valence state of the copper species play a crucial role in tuning the product distribution. The Cu/Al(OH)3 catalyst with strong redox capacity and abundant Cu2+ species significantly improves the selectivity of alcohols. Interestingly, the predominant alcohol gradually shifts from methanol to ethanol with increasing copper loading, and the optimal copper loading for producing methanol and ethanol was found to be 5 wt% and 15 wt%, respectively. This work provides valuable insights for designing efficient catalysts to tune the production of alcohols through the single-step plasma-catalytic conversion of CH4 and CO2.

A study of ethanol dehydrogenation to acetaldehyde over supported copper catalysts: Catalytic activity, deactivation and regeneration

10 % and 30 % wt.CuO/wtsupport CuO/Al2O3, CuO/ZnAl2O4 and CuO/MgAl2O4 were prepared through wet impregnation, starting from commercial supports (Sasol). The catalysts were characterized, before and after catalytic runs, by XRD, IR and UV–vis spectroscopies, SEM and energy dispersive X-ray spectroscopy, surface area and porosity measurements. The fresh CuO-containing powders are converted into supported Cu metal catalysts in an ethanol/nitrogen stream, and act as efficient dehydrogenation catalysts producing acetaldehyde yields in the range 65–90 % at 500−650 K. The best selectivity observed on Cu/ZnAl2O4 is apparently mostly associated to the low activity of the uncovered support surface in the dehydration reactions to diethyl ether and ethylene. These catalysts are progressively deactivated already at 623 K by carbon deposition on copper sites, which leaves almost intact the activity of the uncovered support surface for dehydration reactions. This effect is easily reversed by burning in oxygen at around 650 K. Increasing copper loading only produces some increase in acetaldehyde selectivity. At higher temperature, Cu particle sintering is also observed, but it not necessarily causes evident deactivation.

Production of hydrogen by oxidative steam reforming of methanol over Cu/SiO2 catalysts

Selective production of hydrogen by oxidative steam reforming of methanol (OSRM) was studied over Cu/SiO2 catalyst using fixed bed flow reactor. Textural and structural properties of the catalyst were analyzed by various instrumental methods. TPR analysis illustrates that the reduction temperature peak was observed between 510 K and 532 K at various copper loadings and calcination temperatures and the peaks shifted to higher temperature with increasing copper loading and calcination temperature. The XRD and XPS analysis demonstrates that the copper existed in different oxidation states at different conditions: Cu2O, Cu0, CuO and Cu(OH)2 in uncalcined sample; CuO in calcined sample: Cu2O and metallic Cu after reduction at 600 K and Cu0 and CuO after catalytic test. TEM analysis reveals that at various copper loadings, the copper particle size is in the range between 3.0 nm and 3.8 nm. The Cu particle size after catalytic test increased from 3.6 to 4.8 nm, which is due to the formation of oxides of copper as evidenced from XRD and XPS analysis. The catalytic performance at various Cu loadings shows that with increasing Cu loading from 4.7 to 17.3 wt%, the activity increases and thereafter it decreases. Effect of calcination shows that the sample calcined at 673 K exhibited high activity. The O2/CH3OH and H2O/CH3OH molar ratios play important role in reaction rate and product distribution. The optimum molar ratios of O2/CH3OH and H2O/CH3OH are 0.25 and 0.1, respectively. When the reaction temperature varied from 473 to 548 K, the methanol conversion and H2 production rate are in the range of 21.9–97.5% and 1.2–300.9 mmol kg−1 s−1, respectively. The CO selectivity is negligible at these temperatures. Under the optimum conditions (17.3 wt%, Cu/SiO2; calcination temperature 673 K; 0.25 O2/CH3OH molar ratio, 0.5 H2O/CH3OH molar ratio and reaction temperature 548 K), the maximum hydrogen yield obtained was 2.45 mol of hydrogen per mole of methanol. The time on stream stability test showed that the Cu/SiO2 catalyst is quite stable for 48 h.

Thermal and mechanical properties of copper/photopolymer composite

Purpose The purpose of this study is to increase the thermal and mechanical properties of the photopolymer by filling with the copper powder for the application of rapid tooling. Design/methodology/approach In this study, the photopolymer is filled with the different loading of copper powder for investigating the thermal and mechanical properties of the copper/photopolymer composite. The thermal properties of the copper/photopolymer composite are characterized with the degradation temperature and with the thermal conductivity. The mechanical properties of copper/photopolymer composite are performed with the tensile strength and hardness testing. Moreover, the copper/photopolymer composite is imaged by using a scanning electron microscopic with energy dispersive spectroscopy. Findings The tensile strength of the copper/photopolymer composite is increased over 45 per cent at 20 phr copper loading. The hardness of the photopolymer has a negative correlation with the increasing copper loading and is decreased about 28.5 per cent at 100 phr copper loading. The degradation temperature of the copper/photopolymer composite is increased about 7.2 per cent at 70 phr copper loading. The thermal conductivity of the copper/photopolymer composite is increased over 65 per cent at 100 phr copper loading. Originality/value The photopolymer used in rapid prototyping system is generally fragile and has poor thermal properties. This study improves the thermal and mechanical properties of the photopolymer with the copper filling which has been never investigated in the field of rapid prototyping applications.

Vapor-Phase Hydrogenolysis of Glycerol to 1,2-Propanediol over Cu/Al2O3 Catalyst at Ambient Hydrogen Pressure

In this paper, we report that the hydrogenolysis of glycerol can be carried out at atmospheric pressure and low temperature with high selectivity to 1,2-propanediol (1,2-PDO) over reduced copper catalyst. The vapor-phase reaction was carried out over the copper-based catalysts supported on alumina at ambient pressure, and the effects of temperature, space time, and H2 molar fraction in the feed were analyzed. The textural and structural characteristics of the catalysts with increasing copper loading were determined by N2 sorptometry (BET), inductively coupled plasma-atomic spectroscopy (ICP-AES), powder X-ray diffraction (PXRD), temperature-programmed reduction (TPR), and N2O chemisorption (metallic area). On the basis of both characterization and activity results, it was possible to conclude that the hydrogenolysis of glycerol to 1,2-propanediol in vapor phase at atmospheric pressure over copper-based catalysts is a structure sensitive reaction. Activity results suggests that the most probable pathway fo...

Conversion of 2,3-butanediol to butenes over bifunctional catalysts in a single reactor

In this study, Cu/ZSM-5 catalysts were used to catalyze the hydrodeoxygenation of 2,3-butanediol to butenes in a single reactor in the presence of hydrogen. The carbon selectivity of butenes increased with increasing SiO2/Al2O3 ratio (lowering acidity of zeolite) and H2/2,3-butanediol ratio. Cu/ZSM-5 with a SiO2/Al2O3 ratio of 280 showed the best activity toward the production of butenes; however, Cu/ZSM-5 with SiO2/Al2O3 of 23 was favorable for the dehydrogenation reaction of 2,3-butanediol even in the excess of hydrogen. On zeolite ZSM-5(280), the carbon selectivity of butenes increased with increasing copper loading and 19.2wt% of CuO showed the highest selectivity of butenes (maximum 71%). The optimal reaction temperature is around 250°C. Experiments demonstrated that methyl ethyl ketone (MEK) and 2-methylpropanal are the intermediates in the conversion of 2,3-butanediol to butenes. The optimal performance toward the production of butene is the result of a balance between copper and acid catalytic functions.

Selectivity control of Cu promoted iron-based Fischer-Tropsch catalyst by tuning the oxidation state of Cu to mimic K

The effect of activation gas on the Fischer-Tropsch synthesis (FTS) performance of copper and potassium promoted precipitated iron-based catalysts was investigated in an earlier study [Catal. Lett. 144 (2014) 1624-1635]. In that study, CO and syngas (H2/CO=0.7) activation methods were tested after varying the copper promoter loading (0, 2, and 5%, atomic ratios relative to iron). At similar CO conversion level, the selectivities for the CO-activated catalysts were identical for the various copper loaded catalysts, whereas for the syngas activated catalysts, light hydrocarbon (methane and C2–C4) selectivities decreased and higher hydrocarbon (C5+) selectivities increased with increasing copper loading. To understand the reason for that behavior, the catalyst samples were characterized by XANES/EXAFS spectroscopy following each activation procedure before and after exposure to FTS conditions. Cu K-edge normalized XANES results indicate that for the syngas activated catalyst copper is present primarily in the Cu1+ state, whereas for CO activated catalyst the copper is more reduced (greater fraction in the Cu0 state). The Cu1+ in the syngas activated catalyst behaved like K1+; therefore, the C5+ selectivity was enhanced and light hydrocarbon selectivity was suppressed.

Caso clínico 4. ¿Cuál sería su abordaje diagnóstico y terapéutico?

The effect of activation gas on the Fischer-Tropsch synthesis (FTS) performance of copper and potassium promoted precipitated iron-based catalysts was investigated in an earlier study [Catal. Lett. 144 (2014) 1624-1635]. In that study, CO and syngas (H2/CO = 0.7) activation methods were tested after varying the copper promoter loading (0, 2, and 5%, atomic ratios relative to iron). At similar CO conversion level, the selectivities for the CO-activated catalysts were identical for the various copper loaded catalysts, whereas for the syngas activated catalysts, light hydrocarbon (methane and C2–C4) selectivities decreased and higher hydrocarbon (C5+) selectivities increased with increasing copper loading. To understand the reason for that behavior, the catalyst samples were characterized by XANES/EXAFS spectroscopy following each activation procedure before and after exposure to FTS conditions. Cu K-edge normalized XANES results indicate that for the syngas activated catalyst copper is present primarily in the Cu1+ state, whereas for CO activated catalyst the copper is more reduced (greater fraction in the Cu0 state). The Cu1+ in the syngas activated catalyst behaved like K1+; therefore, the C5+ selectivity was enhanced and light hydrocarbon selectivity was suppressed.

Spectroscopic characterization of CuOx/TiO2–ZrO2 catalysts prepared by a-step sol–gel method

Copper–titania–zirconia mixed oxides with TiO2/ZrO2 1:1 atomic ratio and copper content of 1, 3 and 5wt% were prepared by one-step sol–gel method. X-ray diffraction and gas-volumetric analysis showed poor crystallinity and high specific surface area (around 250m2/g) of the catalysts calcined at 400°C. The nature of the copper species in the mixed oxides was characterized by temperature-programmed reduction in hydrogen (TPR), low-temperature electron paramagnetic resonance (EPR) and diffuse reflectance (DR) UV–Vis spectroscopies. These techniques suggested the presence of different copper species including distorted octahedral Cu2+ ions (isolated or quasi-isolated) in the solid solution bulk, characterized by a TPR peak above 400°C (labeled as T1), electronic d–d transitions around 800nm and an anisotropic EPR signal with two hyperfine interactions in the g|| region. The symmetry of this site changed from rhombic (S1) to axial (S3) while increasing copper loading. The inclusion of copper ions in the TiO2–ZrO2 matrix was also testified by changes in the mixed-oxide edge position. Two families of supported copper oxide were found. CuO “bulk-like” showed relatively high reduction temperature (T2, around 250°C), while highly dispersed CuOx nanoparticles/clusters resulted in TPR peaks around 170 and 200°C (T4 and T3). These species were responsible for the UV–Vis adsorption above 400nm and for the broad and asymmetric axial EPR signal with g|| in the range from 2.14 to 2.29 (S2 and S2′). Finally, 2-propanol decomposition was employed as a test reaction to probe the catalyst's surface properties. The results suggested a marked effect of copper loading on the reactivity pattern, confirming the presence of CuO/CuOx particles on the surface of the TiO2–ZrO2 support.

Fischer–Tropsch Synthesis: Effect of Activation Gas After Varying Cu Promoter Loading Over K-Promoted Fe-Based Catalyst

The effects of activation gas and copper promoter loading on the Fischer–Tropsch synthesis performance of potassium promoted precipitated iron-based catalysts were investigated using a continuously stirred tank reactor. In this study, CO and syngas (H2/CO = 0.7) activated catalysts were tested after varying the copper promoter loading (0, 2 and 5 %, atomic ratios relative to iron). After attaining a steady-state conversion for the CO-activated catalysts, similar or slightly higher CO conversions were exhibited with increasing copper loading, and the induction period was reduced with increasing copper loading. Partial pressure of hydrogen in the activation gas influenced the resulting activity of the catalysts. For syngas activated catalysts, CO conversion was found to increase with increasing copper loading up to 2 %, and slightly decrease with further increases in copper (5 %) loading. For similar CO conversion levels, the selectivities were similar for the CO activated catalysts, whereas for the syngas activated catalysts, the selectivity varied with copper loading. With increasing copper loading, lower hydrocarbon (methane and C2–C4) selectivities decreased and the corresponding higher hydrocarbon (C5+) selectivity increased.

The effect of Cu-loading on different reactions involved in NH3-SCR over Cu-BEA catalysts

In this study, we investigate the effect of varying copper loading in Cu-BEA on different reactions involved in the SCR mechanism. The catalysts were characterized by BET, ICP-AES, and UV–Vis. Enlarged ammonia storage was observed when increasing the copper loading mainly owing to loosely bonded NH3, but for over-exchanged samples, a new high-temperature shoulder was also observed. The N2O production significantly grew with increasing copper loading. In addition, the reaction rates of NO oxidation and NH3 oxidation per Cu site were higher on the high-loaded copper samples compared to those with lower loading. However, the opposite results were found for NH3 SCR, but differences were small for this reaction. Ammonium nitrate formation and decomposition were examined during a variety of temperature-programmed desorption (TPD) experiments, and three regions related to the presence of acid sites and low- versus high-loaded copper sites were observed. When dosing NO2 before NH3, ammonium nitrate species were formed but in lower amounts than if NH3 and NO2 were dosed simultaneously.

Characterization and deNO x activity of copper-hydroxyapatite catalysts prepared by wet impregnation

Copper loaded hydroxyapatite catalysts have been prepared by wet impregnation and have been tested in the selective catalytic reduction of NO by NH3. The catalyst characterization showed the presence of copper oxide nanoparticles entrapped in the mesoporous matrix thus obstructing the Ca-Hap channel apertures. With increasing copper loading, there is a deposition of copper oxide clusters, on the surface of the carrier, containing Cu2+ and Cu+ ions. Compared to the catalyst prepared by the ion exchange method, Cu(1.12)Hapi.e, which exhibited excellent NO conversion over a broad temperature range, the impregnated catalysts are less efficient in the selective catalytic reduction of NO by NH3.

Low-temperature loading of Cu+ species over porous metal-organic frameworks (MOFs) and adsorptive desulfurization with Cu+-loaded MOFs

Porous metal-organic frameworks (MOFs, MIL-100-Fe, iron-benzenetricarboxylate) supported with Cu+ species were obtained for the first time under mild condition without high temperature calcinations. The Cu+-loaded MOFs were evaluated as efficient adsorbents for the liquid-phase adsorption of benzothiophene (BT). The effect of Cu+ loading on the adsorption kinetics and maximum adsorption capacity (Q0) for the adsorption of BT was also studied. Q0 increased with increasing copper loading up to a Cu/Fe (wt./wt.) ratio of 0.07 in Cu+-loaded-MIL-100-Fe, resulting in an increase in the Q0 by 14% compared with the virgin MIL-100-Fe without Cu+ ions. Since the surface area and pore volume decrease with the loading of copper, the increased Q0 over the Cu+-loaded MIL-100-Fe adsorbents suggests specific favorable interactions (probably by π-complexation) between Cu+ and BT.

Supported Copper Catalysts for Direct Vapor-Phase Oxycarbonylation of Methanol

The supported copper catalysts were prepared by the incipient wetness impregnation method and used for direct vapor-phase oxycarbonylation of methanol to dimethyl carbonate (DMC). The effects of impregnation solvents, supports, promoters, and Cu loading on the catalytic activity were investigated. The results showed that the activated carbon (AC)-supported copper catalyst prepared using CuCl as the starting material and ammonia as the impregnation solvent had high catalytic activity for methanol oxycarbonylation. Under the specified conditions, methanol conversion and DMC selectivity reached 27.7% and 95%, respectively. Compared with the AC support, the zeolite-supported copper catalyst gave methanol conversion of less than 1% and DMC selectivity as high as 100%. The catalytic activity increased with increasing copper loading. However, the DMC selectivity decreased when the copper loading exceeded a certain amount. The addition of palladium compounds or potassium hydroxide enhanced the activity of the catalyst prepared using CuCl2 as the starting material; however, the side reactions were promoted simultaneously. During the reaction for 60 h, the DMC selectivity remained stable, whereas methanol conversion decreased because of the loss of active components.

Cu based zeolites: A UV–vis study of the active site in the selective methane oxidation at low temperatures

An extensive series of 30 Cu exchanged zeolites and Cu impregnated silicas and aluminas have been tested in their capacities to stabilize the bis(μ-oxo)dicopper core. This core shows a remarkably activity towards methane, as it selectively hydroxylates methane into methanol at the low temperature of 125 °C. UV–vis spectroscopy is an easy approach to detect the presence of this bis(μ-oxo)dicopper core since it is characterized by an intense charge transfer band at 22 700 cm −1. In this way it was found that after calcination, only the Cu exchanged zeolites ZSM-5 and MOR are capable of stabilizing this core. In addition, an optimum in the Si/Al ratio and in the calcination temperature were observed, indicating that this core requires a rather specific coordination environment. For ZSM-5, the optimal Si/Al ratio for bis(μ-oxo) dicopper core formation is between 12 and 30 and the amount of this core increases with increasing copper loading above Cu/Al = 0.2. Calcination in O 2 should be done at temperatures higher than 280 °C and lower than 700 °C. After reaction with methane at low temperature (150 °C), it was found that only Cu-ZSM-5 and Cu-MOR yielded methanol, whereas all the other Cu based materials yielded almost no methanol. At higher temperatures (200 °C) however, Cu-FER and Cu-BEA showed comparable methanol yields as Cu-ZSM-5 and also the methanol yield of Cu-MOR increased at this higher reaction temperature, indicating that a second not yet identified Cu-oxygen species is activated in the FER, BEA and MOR zeolites at higher temperatures.

Thermal study of copper adsorption on montmorillonites

Copper was adsorbed onto Ca-exchanged montmorillonite (Cheto clay) under basic conditions. Differential thermogravimetric analysis (DTGA) combined with mass spectroscopy (MS) was employed as the principal technology to study the distributions and structures of adsorbed copper species on Cheto clay. The results showed that the original Cheto clay was easily rehydrated. After copper adsorption, a step-by-step replacement of hydrated calcium ions by copper–ammonia complex was observed through the gradual decrease of the first DTGA dehydration peak intensity with the increasing copper loading amount. Compared with the original Cheto clay, copper-loaded samples showed new DTGA peaks assigned to NH 3 and N 2O. The presence of N 2O peak suggested that the loaded copper species were in agglomerated copper oxide form, which dispersed well over the edge and external surface of the clay layers.

Study of copper adsorption on montmorillonites using thermal analysis methods

Copper was adsorbed onto Ca-exchanged montmorillonite (Cheto clay) under basic conditions. Differential thermogravimetric analysis (DTGA) combined with evolved gas mass spectroscopy (MS) was employed as the principal technology to study the distribution and structure of adsorbed copper species on the montmorillonite clay. The results showed that the original clay was easily rehydrated. After copper adsorption, a step-by-step replacement of hydrated calcium ions by copper–ammonia complex was observed through the gradual decrease of the first DTGA dehydration peak intensity with increasing copper loading. Compared with the original clay, copper loaded samples showed new DTGA peaks assigned to NH 3 and N 2O. The presence of the N 2O peak suggested that the loaded copper species were in agglomerated copper oxide form, which dispersed well over the edges and external surfaces of the clay layers.

Indication of Interaction of Metals from TPR and XPS in Relation with Their Reactivity for 1,3-Butadiene Hydrogenation

A series of nickel base catalysts supported on silica has been used for selective hydrogenation of 1,3-butadiene. The materials were characterized by means of temperature-programmed reduction, hydrogen chemisorption, x-ray photoelectron spectroscopy, and x-ray absorption near edge structure. Cu-Ni interaction affected the reduction behavior of the catalysts. TPR results reveal the presence of more reducible nickel species formed by interaction of nickel with the surface of copper oxide. These results are in agreement with XPS results of Ni 2p spectra showing significant shifts towards lower binding energies with increasing copper loading. XPS shows that the Ni-Cu alloy is formed with enrichment of Ni on the surface. The addition of copper on Ni/SiO2 causes the conversion rate to decrease and increases selectivity to l-butene. This selectivity behavior is explained by the variation of the electronic properties of nickel induced by copper Hydrogen chemisorption results show that the dilution of the nickel surface atoms is responsible for the decrease in activity.

γ‐Alumina supported Cu‐Ni bimetallic catalysts: Characterization and selective hydrogenation of 1,3‐butadiene

AbstractAddition of a second metal often improves the selectivity of a supported catalyst for the hydrogenation of 1,3‐butadiene. Catalysts containing 15 wt% Ni and varying amounts of Cu were prepared and characterized by TPR, XRD and XPS. The Cu‐Ni interaction affects the reduction behavior of the catalysts. TPR result shows that the synergetic effect of copper and nickel modifies the capability of metal to combine with hydrogen in bulk phase. The Ni 2p spectra in XPS shows significant shifts toward lower binding energies with increasing copper loading. From XRD results it is represented that aggregation of nickel occurs more easily due to the copper addition. The adding of copper on Ni/Al2O3 makes the conversion rate decreased and increases the selectivity to 1‐butene.

Selective catalytic reduction of nitric oxide over Cu and Co ion-exchanged ZSM-5 zeolite: the effect of SiO 2/Al 2O 3 ratio and cation loading

The performance of Cu-ZSM-5 and Co-ZSM-5 zeolites for selective catalytic reduction (SCR) of nitric oxide (NO) was examined and compared in a packed-bed tubular reactor using methane and propene as reducing agents. Emphasis was given to the effects of SiO 2/Al 2O 3 ratio and Cu or Co ion loading on the catalyst performance as indicated by the levels of NO conversion into N 2. For Cu ion-exchanged zeolites, the catalysts with the same copper loading but different SiO 2/Al 2O 3 ratios showed different activities. At temperatures greater than 350°C, the NO conversion with increasing SiO 2/Al 2O 3 ratio, whereas the maximum NO conversion decreases with increasing copper loading when the catalysts have the same SiO 2/Al 2O 3 ratio. Catalysts with identical Cu ion-exchange levels, but different SiO 2/Al 2O 3 ratios and different copper loadings, do not show the same activities, indicating the important role of SiO 2/Al 2O 3 ratio. For Co ion-exchanged catalysts with the same Co loadings, however, the activity increases with decreasing SiO 2/Al 2O 3 ratio. For catalysts with the same SiO 2/Al 2O 3 ratios, the catalytic activity decreases with increasing Co loading. Performance of Co ion-exchanged catalysts also appears to be dependent on the preparation method.