Modification the Oxalic Co-precipitation Method on a Novel Catalyst Cu/Zn/Al2O3/Cr2O3 for Autothermal Reforming Reaction of Methanol (original) (raw)
Related papers
2007
Cu/ZnO/Al2O3 catalysts with different composition, prepared from LDH precursors, are studied for OSRM. The catalysts are characterizad by XRD, N2 adsorption and TPR techniques. N2O passivation/TPR method is used for the measurement of Cu dispersion. Redox properties are greatly influenced by the chemical composition. Cu dispersion is a function of Cu content: nanosized Cu particles are present up to Cu content of 18at.%. Catalytic activity appears not simply related to Cu content or Cu surface area. A role of the dispersing oxide matrix on the catalytic activity is hypothesized.
Applied Catalysis B: Environmental, 2007
Cu/ZnO/Al 2 O 3 catalysts (5-45 Cu at.%) derived from layered double hydroxide (LDH) precursors were studied for oxidative steam reforming of methanol (OSRM). The precursors were prepared by homogeneous precipitation with urea. The catalysts were obtained by thermal decomposition of the precursors and subsequent reduction in H 2 stream. XRD, SEM, N 2 adsorption, TPR and NH 3 TPD techniques were employed for characterization. Catalytic activity tests were carried out in a fixed bed flow reactor at T = 200-400 8C, H 2 O/CH 3 OH/O 2 molar ratios = 1.1/1/0.12 (CH 3 OH concentration = 17.8%), GHSV = 6 Â 10 4 h À1 . Tests of simple steam reforming (SRM), partial oxidation (POM) and CH 3 OH decomposition (DEC) were also carried out. TPR measurements showed that redox properties depended on the composition of the samples and on the nature of the phases present in the precursors. The area of metallic Cu, measured by N 2 O passivation method, was correlated to Cu content. The size of Cu particles was smaller than 10 nm for Cu content up to 18 at.%. NH 3 TPD measurements showed acid sites with a wide strength distribution, the strongest ones being mainly related to Al 2 O 3 or Zn aluminate. Catalytic activity was influenced by the chemical composition: kinetic constants for OSRM varied unevenly with Cu surface area, while those for SRM increased with Cu surface area. A reaction mechanism agreeing with OSRM, SRM and DEC data was hypothesized. The mechanism involved an oxidation-reduction cycle of Cu and also the participation of the oxide matrix. #
Cu/ZnO and Cu/ZnO/ZrO 2 catalysts used for methanol steam reforming
Molecular Catalysis, 2018
Cu/ZnO and Cu/ZnO/ZrO 2 catalysts were prepared by co-precipitation method and used in methanol steam reforming at 250°C. The catalysts were characterized by N 2 adsorption, X-ray diffraction (XRD), temperatureprogrammed reduction (TPR), H 2 temperature-programmed desorption (H 2-TPD), transmission electron microscopy (TEM), X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). ZrO 2 affect the textural, structural and morphological properties of the CuO/ZnO catalyst. ZrO 2 nanoclusters or amorphous material was found in Zr-based catalyst which role was to prevent the CuO and ZnO crystallite growth causing a microstrain in Cu and Zn oxides lattice. This effect facilitated the formation of exposed CuO species, which were easier to reduce and favored the catalytic performance of Zr-based catalyst. Monoclinic ZrO 2 found in Zr-based catalyst decrease the CO formation deeply because of the higher capacity of monoclinical ZrO 2 to adsorbed CO. The Cu 2 O active site found in CuO/ZnO catalyst was not more efficient than active sites in Zr-based catalyst. The results confirmed that the interactions between Cu and ZnO/ZrO 2 were different from those between Cu and ZnO.
2006
The selective production of hydrogen via steam reforming of methanol (SRM) was performed using prepared catalysts at atmospheric pressure over a temperature range 200-260 • C. Reverse water gas shift reaction and methanol decomposition reactions also take place simultaneously with the steam reforming reaction producing carbon monoxide which is highly poisonous to the platinum anode of PEM fuel cell, therefore the detailed study of effect of catalyst preparation method and of different promoters on SRM has been carried out for the minimization of carbon monoxide formation and maximization of hydrogen production. Wet impregnation and co-precipitation methods have been comparatively examined for the preparation of precursors to Cu(Zn)(Al 2 O 3 ) and Cu(Zn)(Zr)(Al 2 O 3 ). The catalyst preparation method affected the methanol conversion, hydrogen yield and carbon monoxide formation significantly. Incorporation of zirconia in Cu(Zn)(Al 2 O 3 ) catalyst enhanced the catalytic activity, hydrogen selectivity and also lower the CO formation. Catalyst Cu(Zn)(Zr)(Al 2 O 3 ) with composition Cu/Zn/Zr/Al:12/4/4/80 prepared by coprecipitation method was the most active catalyst giving methanol conversion up to 97% and CO concentration up to 400 ppm. Catalysts were characterized by atomic absorption spectroscopy (AAS), Brunauer-Emett-Teller (BET) surface area, pore volume, pore size and X-ray powder diffraction (XRPD). The XRPD patterns revealed that the addition of zirconia improves the dispersion of copper which resulted in the better catalytic performance of Cu(Zn)(Zr)(Al 2 O 3 ). The time-on-stream (TOS) catalysts stability test was also conducted for which the Cu(Zn)(Zr)(Al 2 O 3 ) catalyst gave the consistent performance for a long time compared to other catalysts.
Catalysis Research
A precursor CuO/ZnO/Al2O3 catalyst for methanol synthesis has been prepared at room temperature by introducing a ternary salt solution into the excess of sodium carbonate solution following the reverse co-precipitation method. The catalyst was tested for the synthesis of methanol from synthesis gas. The composition (vol. %) has been presented: CO, 22; CO2, 5.8; N2, 5.5; H2, balance. The methanol productivity was recorded to be 2.7 kg kgcat–1 h–1 at a temperature of 260 °С, a pressure of 3 MPa, and a space velocity of 61,700 l (kgcat)–1 h–1. The possibility of regenerating the activity of a catalyst subjected to conditions of artificial aging (overheating in a syngas environment) has been tested: approximately 92% of the initial activity could be restored. Physicochemical studies were conducted using the thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), the scanning electron microscopy (SEM), and the X-ray diffraction (XRD) techniques using the Cu, Zn,...
International Journal of Hydrogen Energy, 2012
Binary Cu/ZnO catalysts were prepared using three different methods (coprecipitation, sequential precipitation and homogeneous precipitation) and tested in a methanol steam reforming reaction. Zirconium and yttrium were tested as promoters, and their effects were evaluated in the same reaction. The studied preparation methods influenced the surface area of the Cu-based catalysts and consequently their catalytic activity; however, we verified that surface area was not the only factor influencing activity. Different structural changes in the aurichalcite precursor resulted from the different preparation methods used, and these differences were also observed in the reduced catalysts. An expansion of the Cu lattice with an increase in microstrain were identified and attributed to the formation of a CueZn alloy. Based on the correlation found between these structural changes and the catalytic activity, the CueZn alloy was proposed as active site. We concluded that the preparation methods used influenced Cu dispersion and overall catalyst structure, and CueZn alloy formation resulted from the incorporation of Zn atoms into the Cu lattice. This influence was more pronounced in the catalysts prepared by homogeneous precipitation and coprecipitation. The yttrium promoter did not provide textural or structural advantages. In contrast, the incorporation of Zr promoted both greater Cu dispersion and structural changes in the Cu lattice.
EFFECTS OF PREPARATION OF Cu/Zn OVER Al2O3 CATALYSTS FOR HYDROGEN PRODUCTION FROM METHANOL REFORMING
A novel catalyst for hydrogen production from the catalytic methanol reforming process could play an important role in hydrogen production to be used as a feed for a fuel cell. This study focuses on the preparation methods of active Cu/Zn based catalysts with and without urea by incipient wetness impregnations to lower the metal loading and catalyst cost. The catalytic methanol reforming was studied in a fixed-bed reactor under mild conditions and a reaction temperature range of 453 and 523 K in order to lower energy costs. The activity in the hydrogen production of the impregnated catalysts and a commercial catalyst was analyzed by gas chromatography and compared in terms of hydrogen production yield. The catalysts were also characterized by XRD and SEM in order to identify the physical and chemical properties of the catalysts. The data show that the activity in hydrogen production from the catalysts with urea is higher than that of the catalysts without urea. The impregnated catalysts could exhibit activity at as low a temperature as 453 K which indicates the possibility of lowering the reaction temperature for the methanol reforming process. The Cu/Zn catalysts prepared by incipient wetness impregnation over Al 2 O 3 with urea could exhibit high activity about 28% H 2 yield with efficiency about 97% compared with the commercial catalyst. The impregnated catalysts could be alternative catalysts for hydrogen production from methanol reforming with a lower cost of the catalyst compared with the co-precipitation method used in a commercial one.
Chemical Engineering Science, 2007
The oxidative steam reforming of methanol (OSRM) was carried out to produce the hydrogen selectively for polymer electrolyte membrane (PEM) fuel cell applications over Cu-Zn-Ce-Al oxide and Cu-Zn-Al oxide catalysts of varying compositions prepared by co-precipitation method. Catalyst performance was evaluated in a packed bed reactor over a wide range of operating conditions, and reaction parameters were optimized in order to maximize the hydrogen production with minimum carbon monoxide formation. The incorporation of ceria in Cu-Zn-Al oxide catalysts enhanced the activity greatly compared to without it. The Cu/Zn/Ce/Al:30/20/10/40 exhibited 100% methanol conversion and 244 mmol s −1 kg −1 cat hydrogen rate at 553 K with carbon monoxide as low as 995 ppm, which reduces the load on preferential oxidation of CO to CO 2 significantly before feeding the hydrogen rich stream to the PEM fuel cell as a feed. Ceria had improved the dispersion and specific surface area of copper in multi-component Cu-Zn-Ce-Al oxide catalysts which were confirmed by the physicochemical properties, X-ray diffraction (XRD), temperature programmed reduction (TPR) and CO chemisorption studies. The chemisorption studies were performed at 193 K in order to hinder the spillover of carbon monoxide to ceria. The time-on-stream stability test had shown Cu-Zn-Ce-Al oxide catalysts as more stable compared to Cu-Zn-Al oxide catalysts. The amount of carbon deposited onto the catalysts was determined using TG/DTA thermogravimetric analyzer and the type of carbon species were identified using C1s X-ray photoelectron spectroscopy (XPS) spectra. ᭧
Methanol steam reforming; Effects of various metal oxides on the properties of a Cu-based catalyst
2016
Ternary Cu/ZnO/metal oxide catalysts are prepared through the co-precipitation method under strict control of parameters like pH, calcination conditions, and precipitation temperature in a systematic manner. The metal oxides applied in this study consist of Al2O3, ZrO2, La2O3 and Ce2O3. The distinction of this work in comparison with similar research is a comprehensive investigatation of the catalytic properties of metal oxides (including conversion, selectivity and stability) which have the potential for use in the methanol steam reforming process. The catalysts are characterized through XRD, SEM and BET. The prepared catalysts are applied in methanol steam reforming in a fixed bed reactor. A TGA analysis performed for all four catalysts determined that the Ce2O3 and ZrO2 metal oxide catalysts showed the best results in terms of stability with a coke formation of 0.7wt% and 0.8wt%, respectively; and maximum surface area is related to Cu/ZnO/Ce2O3, which can result in excellent s...
Steam reforming of methanol over Cu/ZrO/CeO catalysts: a kinetic study
Journal of Catalysis, 2005
Steam reforming of methanol (SRM) was investigated over Cu/ZrO 2 /CeO 2 (CZC) catalysts prepared via a novel synthetic method based on coprecipitation and polymer templating. Structural characterization of the samples was performed by N 2 adsorption-desorption, N 2 O decomposition, and X-ray diffraction. The variation of the Cu loading resulted in an increased Cu crystallite size and a decreased specific surface area of the active particles. Catalytic investigations were carried out in a fixed bed reactor at 10 5 Pa, by applying a CH 3 OH:H 2 O = 1:1 ratio. The samples with Cu contents higher than 5 % exhibited good long-term stabilities and low CO levels during continuous operation. The kinetic model suggested for the transformation involved the reverse water-gas shift (RWGS) and methanol decomposition (MD), in addition to the SRM reaction. Kinetic measurements were accomplished in the temperature range 503-573 K and the experimental results could be well simulated. The highest methanol conversions and the lowest CO levels were observed in the temperature range 523-543 K. The apparent activation energies for the individual reactions were found to depend on the Cu content of the catalyst. Since the influence of mass transport limitations on the kinetic data could be excluded, it was established that the variation of the Cu concentration in the precursor material altered the microstructure of the Cu particles and, accordingly, the active Cu surface, which resulted in the formation of significantly different catalysts.