Supported Copper Catalysts Research Articles

Influence of Brønsted acid sites on chemoselective synthesis of pyrrolidones over H-ZSM-5 supported copper catalyst

Cu(0)/H-ZSM-5 was identified as a chemoselective catalyst in the reductive amination of levulinic acid for the synthesis of pyrrolidones at ambient pressure and in aqueous media. The chemoselective nature of Cu was explained by carbonyl interaction with surface Brønsted acid sites deduced by pyridine and acetone adsorbed in situ infrared (IR) spectroscopic studies in conjunction with N2O titration. A strong polarization of band at 1685 cm−1 and an increase in its intensity with a decrease in Si/Al ratio of the H-ZSM-5 was found to be a key factor in the reductive amination activity. Structure activity relationship was established using the physicochemical characteristics of the catalysts analyzed by XRD, BET-SA, H2-TPR, NH3-TPD and XPS analyses.

Novel and efficient heterogeneous polymer supported copper catalyst for synthesis of 2-substituted Benzoxazoles from 2-Haloanilides

A novel polymer supported copper complex is prepared by the immobilization of copper iodide on chemically modified polyacrylonitrile and its application in heterogeneous catalysis is described. The catalyst was prepared by easy method via synthetic modification of Polyacrylonitrile (PAN) using ethylene diamine followed by the complexation with CuI. After characterization, this complex was explored as a green and efficient heterogeneous catalyst for the synthesis of 2-benzoxazoles from 2-haloanilides. The reaction was performed without adding additional ligand and the catalyst shows activity over a broad range of substrates with quantitative product yields. The catalyst was easily recovered by simple filtration and reused successfully for further cycle.

Selective hydroxylation of aryl iodides to produce phenols under mild conditions using a supported copper catalyst.

Owing to the high activity and low-cost, copper-based catalysts are promising candidates for transforming aromatic halides to yield phenols. In this work, we report the selective hydroxylation of aromatic iodides to produce phenols using an atomically dispersed copper catalyst (Cu–ZnO–ZrO2) under mild reaction conditions. The reactions were conducted without the use of additional organic ligands, and the protection of an inert atmosphere environment is not required. The catalyst can be easily prepared, scalable, and is very efficient for a wide range of substrates. The catalytic reactions can be carried out with only 1.24 mol% Cu loading, which shows great potential in mass production.

Selective hydrodeoxygenation of 5-hydroxymethylfurfural to 2, 5-dimethylfuran over mesoporous silica supported copper catalysts

Selective catalytic hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF) to prepare 2, 5-dimethylfuran (DMF) was studied as this product is a good biofuel. A sequence of copper dispersed on SBA-15 catalysts are designed and tested their activity for HMF hydrodeoxygenation reaction. The physico-chemical characteristics of the catalysts are gained from powder XRD, TEM, N2-adsorption desorption, NH3-TPD, H2-TPR and N2O-chemisorptions studies. Characterization results indicate the fine dispersion of Cu metal on SBA-15 with high surface area and appropriate acidic sites. The catalyst with 15%Cu on SBA-15 showed high activity towards DMF with 90% yield. The optimized reaction conditions were 180 °C of reaction temperature, 20 bar H2 pressure, and a reaction time of 8 h to achieve maximum yield. The catalyst is recyclable and exhibits consistent activity.

Research Progress of Cellulose and Its Derivatives Supported Copper Catalyst Catalyzed Organic Reactions

Research Progress of Cellulose and Its Derivatives Supported Copper Catalyst Catalyzed Organic Reactions

Tuning surface-interface structures of ZrO2 supported copper catalysts by in situ introduction of indium to promote CO2 hydrogenation to methanol

Currently, highly efficient catalytic CO2 hydrogenation to produce methanol is attracting intensive attention. However, constructing high-performance catalysts for methanol synthesis that can be operated under mild reaction conditions is a challenging task. In this work, a series of indium-doped ZrO2 supported copper-based catalysts for CO2 hydrogenation were constructed via one-pot hydrogen bubble-assisted approach. It was manifested that the in situ introduction of indium facilitated the generation of interfacial defects in the form of Zr-Vo-In3+ structure (Vo: oxygen vacancy) and interfacial Cu+ sites, as well as surface basic sites originating from In-O pairs, and the catalytic performance of as-constructed In-doped Cu/ZrO2 catalysts could be efficiently promoted by tuning the indium content. Specifically, the Cu-based catalyst bearing the indium content of 4.0 wt% afforded the quite high space-time yield of methanol (0.398 gMeOH h−1·gcat−1) at 270 °C, while the one with the indium content of 8.0 wt% yielded an increased methanol selectivity by 1.8 times at 250 °C, compared with undoped one. Combining the structural characterizations with catalytic results, it was found that surface medium-strength and strong basic sites together with the contribution from interfacial defective oxygen vacancies and Cu+ sites played key promotional roles on the synthesis of methanol. This finding enables us to design new high-performance Cu-based catalysts for CO2 hydrogenation by finely turning their surface-interface structures.

Dehydrogenative Coupling of Methanol for the Gas-Phase, One-Step Synthesis of Dimethoxymethane over Supported Copper Catalysts.

Oxymethylene dimethyl ethers (OMEs), CH3-(OCH2)n-OCH3, n = 1-5, possess attractive low-soot diesel fuel properties. Methanol is a key precursor in the production of OMEs, providing an opportunity to incorporate renewable carbon sources via gasification and methanol synthesis. The costly production of anhydrous formaldehyde in the typical process limits this option. In contrast, the direct production of OMEs via a dehydrogenative coupling (DHC) reaction, where formaldehyde is produced and consumed in a single reactor, may address this limitation. We report the gas-phase DHC reaction of methanol to dimethoxymethane (DMM), the simplest OME, with n = 1, over bifunctional metal-acid catalysts based on Cu. A Cu-zirconia-alumina (Cu/ZrAlO) catalyst achieved 40% of the DMM equilibrium-limited yield under remarkably mild conditions (200 °C, 1.7 atm). The performance of the Cu/ZrAlO catalyst was attributed to metallic Cu nanoparticles that enable dehydrogenation and a distribution of acid strengths on the ZrAlO support, which reduced the selectivity to dimethyl ether compared to a that obtained with a Cu/Al2O3 catalyst. The DMM formation rate of 6.1 h-1 compares favorably against well-studied oxidative DHC approaches over non-noble, mixed-metal oxide catalysts. The results reported here set the foundation for further development of the DHC route to OME production, rather than oxidative approaches.

Surface structure-based CO2 reduction reaction modelling over supported copper catalysts

Reverse water gas shift (RWGS) is a promising green approach for CO2 capture and utilisation, which is able to valorise CO2 by reducing it to CO using hydrogen obtained via renewable electricity. Five different copper-based catalysts were synthesized – 10 wt. % Cu/M (M = Al2O3/CeO2/TiO2/SiO2/ZrO2). The catalysts were tested for activity under different conditions (pressure of 3–7 bars, temperature of 280–360 °C, 0.67–1.5 H2/CO2 reagent ratio and the gas flow rates in the range of 0.005–0.04 g/min). Cu/Al2O3 and Cu/CeO2 were the most active and reached near-equilibrium conversions at 360 °C. SEM, EDX, BET, XRD, XPS, HgP, H2 TPR, H2 TPD and N2O PSO techniques were used to characterise the catalysts. The present study is the first to demonstrate an unprecedented degree of linking the activity measurements, material surface-structure and mathematical modelling of mass transport phenomena coupled with copper microkinetics for the case of CO2 reduction.

Prepared self-growth supported copper catalyst by recovering Cu (II) from wastewater using geopolymer microspheres

Recycling metals from adsorbents is a promising strategy for utilizing metal resources with better efficiency, and improving environmental protection. In this work, NaOH-activated slag-based geopolymer microspheres (NaOH-SGS) were synthesized by the one-pot suspension solidification method. As regards Cu(II) adsorbents, their maximum adsorption capacity of 335.43 mg/g was much higher than other geopolymer materials. There are obvious changes after Cu2+ adsorption as follows. The average pore diameter of microspheres decreased from 19.91 to 10.80 nm; the pore volume increased from 0.05 to 0.27 cm3/g; the Brunauer−Emmett−Teller (BET) surface area increased from 8.23 to 91.72 m2/g; and the apparent morphology changed from gel-like layer to copper-containing nano-rods. As a result, the number of active sites for the adsorption of Cu2+ ions considerably increased. So self-growth adsorption process was named. Meanwhile the adsorbed Cu2+ species were evenly distributed on the NaOH-SGS surface. The spontaneous endothermic adsorption process which was mainly controlled by the diffusion through the external boundary layer was adequately described by the pseudo-second-order kinetic and Langmuir isotherm models. As to catalyst, the NaOH-SGS after Cu2+ adsorption (NaOH-SGS-Cu) was recycled and calcined (NaOH-SGS-Cu-calcined) to produce a supported copper catalyst that was successfully utilized to remove NO by CO. Although the optimum catalytic temperature for N2 selectivity (SN2 = 78.15%) and NO conversion (XNO = 91.96%) was a little high (350 °C), NaOH-SGS-Cu-calcined exhibits good sulfur resistance as slag contained a certain amount of sulfur. The obtained results indicated that the described method can be effectively used for copper recycling and the copper content of NaOH-SGS-Cu catalyst can be easily adjusted by varying the pH of solution, dosage, contact time, initial microsphere concentration and temperature. NaOH-SGS could be a bifunctional material (Cu2+ adsorbent and catalyst support).

Performance of Supported Copper Catalysts for Oxidative Degradation of Phenolics in Aqueous Medium: Optimization of Reaction Conditions, Kinetics, Catalyst Stability, Characterization, and Reusability

Catalytic wet oxidation (CWO) of phenolic wastewater containing phenol, o-cresol, and 2,5-dimethylphenol was carried out in a batch reactor (phenolics = 10 g/L, chemical oxygen demand (COD) = 26 000 mg/L, and total organic carbon (TOC) = 7900 mg/L). Using the Box–Behnken experimental design (BBD) approach, the following optimum CWO conditions (catalyst: 5% Cu/AC) for phenolics degradation were found: Ccat = 3.4 g/L, T = 148 °C, PO2 = 0.61 MPa, and pH = 7.4. Under these conditions, TOC and COD removals of 88 and 90%, respectively, were obtained after 4 h of reaction. p-Benzoquinone and hydroquinone were identified as major intermediates, whereas a mixture of carboxylic acids was detected in treated wastewater. At higher oxygen pressures (stoichiometric and above), mineralization of phenolics was improved although the overall degradation was lower probably due to overoxidation. Reaction kinetics, reusability of the catalysts, and detailed characterization of spent catalysts are also discussed in this paper.

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.

Competition between acidic sites and hydrogenation sites in Cu/ZrO2 catalysts with different crystal phases for conversion of biomass-derived organics

Oxides with different crystal phases can have important effects on the configuration of surface atoms, which can further affect the distribution of hydrogenation sites and acidic sites as well as the competitions of these varied types of catalytic sites. This could be potentially used to tailor the distribution of the products. In this study, zirconium oxides with different crystal phases supported copper catalysts were prepared for the hydrogenation of the biomass-derived furfural, vanillin, etc. The results showed that both calcination temperature and Cu species affected the shift of zirconia from tetragonal phase to the monoclinic phase. Monoclinic zirconia supported copper catalyst can effectively catalyze the hydrogenation of furfural to furfuryl alcohol via hydrogenation route due to its low amount of Brønsted acidic sites, although the surface area and the exposed metallic Cu surface area were much lower than the tetragonal zirconia supported copper catalyst. Zirconia with tetragonal or tetragonal/monoclinic phases supported copper catalysts contain abundant acidic sites and especially the Brønsted acidic sites, which catalyzed mainly the conversion of furfural via the acid-catalyzed routes such as the acetalization, rather than the hydrogenation. The acidic sites over the Cu/ZrO2 catalyst played more predominant roles than the hydrogenation sites in determining the conversion of the organics like furfural and vanillin.

Novel and efficient polymer supported copper catalyst for heck reaction

A novel polymer supported copper complex (m-PAN-Cu) is prepared by immobilizing Cuprous Iodide (CuI) on amidoxime modified Polyacrylonitrile (mPAN) and characterised by FTIR, XRD, EDX, ICP-MS and XPS analyses. This complex was further explored as a general and efficient heterogeneous catalyst for Heck coupling reaction of a series of aryl halides with olefins and afforded the corresponding coupling products in moderate to good yields. This catalyst offers easy preparation, good stability, excellent catalytic activity and reusability. This is the first study involving an amidoxime modified PAN supported copper catalyst towards greener and efficient Heck reaction.

Synthesis of C4 Olefins from Acetylene over Supported Copper Catalysts

AbstractConversion of acetylene to C4 olefins enables on‐purpose synthesis of C4 olefins using abundant natural gas resource due to acetylene can be synthesized from methane or ethane. In this study, Cu‐based catalysts supported on SiO2, ZSM‐5 and mordenite (MOR) were tested for acetylene hydrodimerization. Effect of promoters including Ru, Ga, Ag and Pd on the acetylene conversion and C4 olefins selectivity are investigated. The structures of these catalysts were characterized by TEM, XRD, BET, H2‐TPR, NH3‐TPD and XPS measurements. Results showed that temperature, pressure and hydrogen partial pressure had positive effect on acetylene conversion. In the presence of Ru promotor, 100 % acetylene conversion and 87 % selectivity to C4 olefins were achieved over Cu/MOR catalyst under conditions of 0.1 MPa and 200 °C. The mechanistic aspect of acetylene hydrodimerization was elucidated where the C4 intermediate was formed by the reaction between [Cu]−C2H2 π‐complex and [Cu]−C2H2 σ‐complex which were transformed to 1,3‐butadiene and butene.

Highly efficient Cu/SiO2 catalyst derived from ethanolamine modification for furfural hydrogenation

The production of furfuryl alcohol from furfural hydrogenation in gas phase is of great significance for the valorization of biomass. The existing catalyst for this transformation suffers from high cost and complex preparation process. Thus, a highly efficient copper catalyst was developed by a simple impregnation method using ethanolamine modified granular silica as carrier. The catalytic performance was related to the amount of ethanolamine used in modification. Highly dispersed copper with uniform particle size distribution was obtained from appropriate amount of ethanolamine modified granular silica. The ethanolamine modified granular silica (mass ratio between ethanolamine and silica was 3 in the initial modification mixture) supported copper catalyst exhibited the best performance in terms of catalyst lifetime thanks to its maximum amount of Cu0 sites and largest amount of Cu+ sites. A slow deactivation of the catalyst after extended time on stream evaluation is attributed to carbon deposition and slow copper sintering.

Valorization of Eggshell Waste into Supported Copper Catalysts for Partial Oxidation of Methane

Agricultural wastes are equipped with unique physicochemical traits that may be harnessed to obtain valuable end products. Therefore, the present research focused on using waste eggshells as precursors for the synthesis of catalysts for partial oxidation of methane. Catalysts were synthesized via impregnation of copper on calcined eggshell surfaces. The catalysts were tested for selective oxidation of methane at 650° C and atmospheric pressure. Eggshells loaded with 2% copper activated partial oxidation pathway to enhance yield for syngas, while 5% and 10% loading led to C2–C6 hydrocarbons as a result of oxidative coupling of methane. Oxygen concentration in the feed along with feed flow rate and temperature influenced both fractional conversion and product selectivities. Limited-oxygen supply and adequate flow rate of 0.8 L min−1 at 650° C provided better conversion with 10% Cu-loaded catalyst. While the fresh catalyst exhibited a uniform distribution of copper and a smooth catalyst surface, little surface deformation was observed in the spent catalyst. Prolonged catalytic activity was also investigated via catalyst reactivation. Our results suggest that waste eggshells may be used as catalyst supports for metals to be used in oxidation reactions.

Fabrication of copper supported on hollow silica–alumina composite spheres for catalytic decomposition of nitrous oxide

In this work, we fabricated copper supported on hollow silica–alumina composite spheres for catalytic decomposition of nitrous oxide. The copper supported on the hollow spheres was obtained by impregnation of the active copper species on the hollow silica–alumina composite sphere support prepared by the template method using spherical polystyrene particles. The supported copper catalysts on the hollow spheres showed higher conversion of nitrous oxide than supported copper catalyst on fine silica–alumina composite particles. The catalyst activity was significantly improved by adjusting impregnation temperature, and the supported copper catalyst impregnated at 353 K exhibits around 75% of nitrous oxide conversion at 573 K. The results of the DR UV–Vis spectra, the EDX analysis, and nitrogen adsorption measurement indicate that the highly active catalyst consisted of high ratio of isolated copper ions inside the shell of the hollow spheres.

A Highly Active, Recyclable and Cost-Effective Magnetic Nanoparticles Supported Copper Catalyst for N-arylation Reaction

The immobilization of a copper complex by covalent anchoring of 2-hydroxybenzophenone on the surface of amine-functionalized magnetic nanoparticles was reported. The structure and morphology of the catalyst was characterized by different techniques such as Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron micrograph (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), vibrating sample magnetometer (VSM) and inductively coupled plasma (ICP) spectroscopy. This efficient and cost effective catalyst was applied in the N-arylation reaction and the products were obtained in good to excellent yields in short reaction times. The cost-effective catalyst demonstrated high stability, which could be facilely separated from the reaction mixture by applying an external magnet and recycled at least four times with only a slight decrease in its activity.

Active catalyst construction for CO2 recycling via catalytic synthesis of N-doped carbon on supported Cu

Bridging homogeneous and heterogeneous catalysis is a long-term pursuit in the field of catalysis. Herein, we report our results in integration of nano- and molecular catalysis via catalytic synthesis of nitrogen doped carbon layers on AlOx supported nano-Cu which can finely tune the catalytic performance of the supported copper catalyst. This synthetic catalytic material, which can be generated in situ by the reaction of CuAlOx and 1,10-Phen in the presence of hydrogen, could be used for controllable synthesis of N,N-dimethylformamide (DMF) from dimethylamine and CO2/H2 via blocking reaction pathways of further catalytic hydrogenation of DMF to N(CH3)3. Detailed characterizations and DFT calculations reveal that the presence of N-doped layered carbon on the surface of the nano-Cu particles results in higher activation energy barriers during the conversion of DMF to N(CH3)3. Our primary results could promote merging of homogeneous catalysis and heterogeneous catalysis and CO2 recycling.

Catalytic furfural hydrogenation to furfuryl alcohol over Cu/SiO2 catalysts: A comparative study of the preparation methods

Furfuryl alcohol, a vital intermediate for the production of foundry resins, fragrances, pharmaceuticals and pesticide, is produced by hydrogenation of furfural in gas phase or liquid phase. The furfuryl alcohol production in gas phase over silica supported copper catalyst is favored thanks to the environmental and technical advantages. The effect of preparation methods of silica supported copper catalysts on the structure and performance was investigated by means of ICP, N2 physisorption, ex-situ/in-situ XRD, in-situ XPS, FT-IR, H2-TPR, TEM, N2O titration, TG as well as furfural hydrogenation. The results indicated that the different catalyst synthesis strategies led to the diverse copper species in the calcined samples and disparate Cu0 surface area as well as different molar ratio of Cu+/(Cu+ + Cu0) in the fresh samples. The performance of impregnation derived sample was poorer than that of commercial CuCr-Strem catalyst. The catalysts prepared by deposition precipitation and ion exchange exhibited similar performance to the CuCr-Strem. The ammonia evaporation derived catalyst (Cu/SiO2-EA) showed superior performance in the activity, selectivity and stability among all the studied catalysts. The excellent performance was related to the highest surface area of Cu0, smallest copper particle size, large surface area and pore volume as well as appropriate higher Cu+/(Cu+ + Cu0) ratio. Furthermore, all the copper catalysts went through deactivation, which was caused by carbon deposition, during the reaction. Owing to the largest amount of Cu0 sites and large SBET, the Cu/SiO2-EA exhibited the slowest deactivation rate.