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1.
This work studied the effect of the nature of the support on the performance of Pt/Al2O3, Pt/ZrO2, Pt/CeO2 and Pt/Ce0.50Zr0.50O2 catalysts on partial oxidation of ethanol. The reducibility and oxygen transfer capacity were evaluated by temperature-programmed reduction (TPR) and oxygen storage capacity (OSC) experiments. The results showed that the support plays an important role on the products distribution of the partial oxidation of ethanol. Acetic acid was the main product on Pt/Al2O3 catalyst whereas methane and acetaldehyde were the only products detected on Pt/ZrO2, Pt/CeO2 and Pt/Ce0.50Zr0.50O2 catalysts.The products distribution obtained on Pt/ZrO2, Pt/CeO2 and Pt/Ce0.50Zr0.50O2 catalysts was related to their redox properties. The OSC experiments showed that the oxygen exchange capacity was higher on Pt/CeO2 and Pt/Ce0.50Zr0.50O2 catalysts. A high oxygen storage capacity favored the formation of acetate species, which could be decomposed to CH4 and/or oxidized to CO2 via carbonate species. On the other hand, the lower oxygen exchange capacity of Pt/ZrO2 catalyst led to a higher ethoxy species formation. These species can be dehydrogenated and desorb as acetaldehyde. Then, the higher selectivity to acetaldehyde observed on Pt/ZrO2 catalyst could be assigned to its low oxygen storage/release capacity.In the case of Pt/Al2O3 catalyst, the production of acetic acid could be related to its acidic properties, since this material did not show redox properties, as revealed by OSC analysis.  相似文献   

2.
Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al2O3 supports that were either unpromoted or promoted with CeO2, ZrO2 and CeO2–ZrO2. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO2 and/or ZrO2 showed that the variations induced in the Al2O3 by the addition of CeO2 and/or ZrO2 alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO2–ZrO2, improved catalytic activity by increasing the H2 yield and the CO2/CO and the H2/CO values while decreasing coke formation. This results from the addition of ZrO2 into CeO2. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products.  相似文献   

3.
The reactivity of the PtNi supported on CeO2-nanorods was performance on methanol steam reforming (MSR). COads revealed that outer of the PtNi-catalyst could be mainly Pt-terminated and, COads was slightly attenuated on the surface of the CeO2-R. The catalytic performance of the bimetallic PtNi/CeO2-NR catalyst exhibited better methanol conversion and H2 selectivity than the monometallic samples. The surface species associated with the reaction mechanism from TPD-MSR-DRIFTS identified on the CeO2-NR sample showed stronger bands associated at the methoxy species complemented with stretching C–H bands, while on the Pt/CeO2-NR catalyst, the methoxy groups diminish indicating that it decomposes to CO and hydrogen and, new peaks of formate (HCOO?) groups emerge. This finding suggests that the methoxy groups interacted with the surface oxygen of the support during the reaction to yield formate species and the Pt had important role to promote it as intermediary of the reaction.  相似文献   

4.
The effect of metal oxide (CeO2, Al2O3 and ZrO2) support and In2O3 co-supported Pt catalysts has been investigated on steam reforming of methanol in microreactors. CeO2, Al2O3 and ZrO2 were prepared by the sol-gel method and they were used as a support, which was impregnated with In2O3 as co-support followed by the introduction of Pt species via the wet impregnation method. The size and dispersion of the Pt nanoparticles on In2O3/support have been examined by transmission electron microscopy. From these TEM and XPS results, it was found that the addition of In2O3 supports the formation of a high concentration of metallic Pt nanoparticles with enhanced dispersion and controlled particle size on the surface. The activity and stability of all the developed catalysts were tested for the steam reforming of methanol in microreactors at different temperatures. Under reforming conditions without prior reduction, a Pt/CeO2 catalyst containing 15 wt % of Pt exhibited complete methanol conversion and high selectivity towards hydrogen at 350 °C. However, the CO formation was found to be very high (7.0 vol %) for this catalyst. Upon addition of In2O3 as a co-support to this formulation the formation of CO decreased considerably. Pt/In2O3/CeO2 catalyst containing 15 wt % of Pt and 15 wt % of In2O3 showed excellent catalytic performance at much lower concentration of CO. This change could be closely associated with the formation of metallic Pt nanoparticles with smaller size, higher dispersion with strong interaction between Pt, In2O3 and support, which creates more oxygen vacancies to activate the water molecule which then react with methanol to produce H2 and CO2 suppressing the CO formation. Moreover, CeO2 supported Pt/In2O3 catalyst displayed higher stability with lowest CO formation under continuous steam reforming operation of 100 h. The superior performance of this catalyst is thought to be due to the relative abundance of redox sites on the CeO2 surface, which is able to create an oxygen vacancy as it possesses higher oxygen storage capacity and oxygen exchange capacity. This work demonstrates that the nature of support plays a crucial role for the continuous activation of reactants and determines the catalytic stability during methanol steam reforming.  相似文献   

5.
Present study evaluated the catalytic steam gasification of furniture waste to enhance the biohydrogen production. To do this, 10 wt% nickel loaded catalysts on the variety of supports (Al2O3, CeO2, CeO2-La2O3, and CeO2–ZrO2) were prepared by the novel solvent deficient method. The hydrogen selectivity (vol%) order of the catalysts was achieved as Ni/CeO2–ZrO2>Ni/CeO2>Ni/Al2O3?Ni/CeO2-La2O3. The best catalytic activity of Ni/CeO2–ZrO2 catalyst (~82 vol % H2 at 800 °C) was ascribed to the smaller size of nickel crystals, finely dispersed Ni on the catalyst surface, and Ce1-xZrxO2-δ solid solution. The role of Ce1-xZrxO2-δ solid solution in Ni/CeO2–ZrO2 catalyst was observed as bi-functional; acceleration of water-gas-shift and oxidation of carbon reaction. The high resistance of Ni/CeO2–ZrO2 towards the coke formation showed its potential to establish a cost-effective commercial-scale biomass steam gasification process. This study is expected to provide a promising solution for the disposal of furniture wastes for production of clean energy (biohydrogen).  相似文献   

6.
In this paper the steam reforming of bioalcohols over Ni and Pt catalysts supported on bare Al2O3 and La2O3 and CeO2-modified Al2O3 to produce H2 was studied. Catalytic activity results showed that the glycerine and the intermediate liquid products may hinder the ethanol adsorption on metal active sites of the catalysts, especially at temperatures below 773 K. In fact, ethanol conversion was lower than glycerine conversion in the steam reforming reaction at low temperatures. H2 chemisorption revealed that La2O3 doping of the Ni/Al2O3 catalyst improved the metal dispersion providing a better behaviour to the Ni/Al2O3-O2 catalyst towards H2 production. In the case of Pt catalysts, the good reducibility and the H2 spillover effect provided to the Pt/Al2O3-O1 catalyst the capacity to produce higher H2 yields.  相似文献   

7.
The water–gas shift reaction (WGSR) performance was experimentally studied using Pt-based catalysts for temperature, time factor and steam to carbon (S/C) molar ratio at ranges of 750–850 °C, 10–20 gcat h/molCO, and 1–5, respectively. Al2O3 spheres were used as the catalyst support. For the high S/C cases, it was found that CO conversion can be enhanced when Pt/CeO2/Al2O3 catalyst was used as compared with Pt/Al2O3. For the low S/C ratio cases, CO conversion enhancement was not significant with the addition of CeO2. It was also found that CO conversion was not influenced by the CeO2 amount to a large extent. Using bimetallic Pt–Ni/CeO2/Al2O3 catalyst, it was found that higher CO conversion can be obtained as compared with CO conversions obtained from monometallic catalysts (Pt/Al2O3 or Pt/CeO2/Al2O3). The experimental data also indicated that good thermal stability can be obtained for the Pt-based catalysts studied.  相似文献   

8.
The composition (CuO/ZnO/Al2O3 = 30/60/10) of a commercial catalyst G66B was used as a reference for designing CuO/ZnO/CeO2/ZrO2/Al2O3 catalysts for the oxidative (or combined) steam reforming of methanol (OSRM). The effects of Al2O3, CeO2 and ZrO2 on the OSRM reaction were clearly identified. CeO2, ZrO2 and Al2O3 all promoted the dispersions of CuO and ZnO in CuO/ZnO/CeO2/ZrO2/Al2O3 catalysts. Aluminum oxide lowered the reducibility of the catalyst, and weakened the OSRM reaction. Cerium oxide increased the reducibility of the catalyst, but weakened the reaction. Zirconium oxide improved the reducibility of the catalyst, and promoted the reaction. A lower CuO/ZnO ratio of the catalyst was associated with greater promotion of ZrO2. The critical CuO/ZnO ratio for the promotion of ZrO2 was approximately 0.75–0.8. Introducing of ZrO2 into CuO/ZnO/Al2O3 also improved the stability of the catalyst. Although Al2O3 inhibited the OSRM reaction, a certain amount of it was required to ensure the stability and the mechanical strength of the catalysts.  相似文献   

9.
Nano CeO2–ZrO2 composites with different shapes are synthesized by using hydrothermal and deposition-precipitation methods, and used to obtain Pt/CeO2–ZrO2/RGO catalysts, where reduced graphene oxide(RGO) acts as a carrier. X-ray Diffrattometry (XRD), Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) detection methods are used to characterize morphology, phase composition, exposed planes and oxygen defects of the catalyst. The obtained CeO2–ZrO2 supports are in the form of nanorods, nanospheres, and nanocubes, which mainly expose (110), (111), and (100) planes, respectively. Electrocatalytic methanol oxidation tests onto the Pt/CeO2–ZrO2/RGO catalysts show that the electrochemically active surface area and the peak current density of nanorods are the largest ones among the three catalysts, reaching 61.4 m2/g and 230 A/g. In addition, the long-term discharge stability and CO poisoning resistance of the nanorod-shaped Pt/CeO2–ZrO2/RGO catalyst are the highest ones among the examined catalysts.  相似文献   

10.
In this research, the activity and selectivity of a platinum-based catalyst for H2 production through aqueous phase reforming (APR) in a fixed-bed reactor (FBR) as well as, a structured catalyst microreactor (MR) were investigated. In this venue, first, an in-house designed MR was fabricated and the catalytic material was deposited on the channel walls of this steel made reactor. After verification of the stability of the coated layer, the prepared reactor was employed to investigate the APR reaction. In this regard, APR of the ethylene glycol and glycerol over Pt/Al2O3 and Pt/CeO2Al2O3 catalyst were conducted in an MR and FBR. Obtained results demonstrated that employing Pt/CeO2Al2O3 as a highly active catalyst in an FBR, slightly reduced the H2 selectivity for the APR reaction of the ethylene glycol. Moreover, this effect appeared even more pronounced in reforming of glycerol. On the other hand, utilization of an MR for the APR of glycerol improved the H2 selectivity due to the more active Pt/CeO2Al2O3 catalyst, for this process. Comparison of the results revealed that the highly active catalyst alongside a reactor alleviating mass transfer limitations were two complementary factors leading to better performance of such chemical systems. Moreover, this research emphasized that obtained values of the APR conversion and H2 selectivity in an MR coated with the Pt/CeO2Al2O3 catalyst was superior to those obtained from an FBR. Ultimately, the best results obtained for the aforementioned catalytic species indicated that the APR of glycerol in a structured catalyst MR led to 75.3% conversion of glycerol and 92.4% selectivity to hydrogen production both of which were considerably better than results determined in an FBR.  相似文献   

11.
A novel nanostructured support of ZrO2/nitrogen-doped graphene nanosheets (ZrO2/NGNs) hybrid was synthesized successfully by atomic layer deposition (ALD) technology to significantly improve the activity and stability of Pt electrocatalyst. Electrochemical test shows that Pt–ZrO2/NGNs catalyst has 2.1 times higher activity towards methanol oxidation reaction (MOR) than Pt/NGNs catalyst, due to the promotion by ZrO2 to the MOR on Pt surface. Pt–ZrO2/NGNs catalyst has higher electrochemical surface area (ECSA) and better oxygen reduction reaction (ORR) activity than Pt/NGNs catalyst. Pt–ZrO2/NGNs catalyst has also demonstrated 2.2 times higher durability than that of Pt/NGNs. The enhanced activity and durability were attributed to the unique triple-interaction of ZrO2–Pt–NGNs. These findings indicate that metal oxide-metal-support is a promising catalyst structure for low temperature fuel cells.  相似文献   

12.
《Journal of power sources》2006,159(2):1296-1299
Hydrogen production by steam reforming of methanol is studied over Cu/Zn-based catalysts (Cu/ZnO, Cu/ZnO/Al2O3, Cu/ZnO/ZrO2/Al2O3). Cu/Zn-based catalysts are derived from hydrotalcite-like precursors prepared by a co-precipitation method. The catalysts are characterized by N2O chemisorption, XRD, and BET surface area measurements. ZrO2 added to the Cu/Zn-based catalyst enhances copper dispersion on the catalyst surface. Among the catalysts tested, Cu/ZnO/ZrO2/Al2O3 exhibits the highest methanol conversion and the lowest CO concentration in the outlet gas. A micro-channel reactor coated with a Cu/ZnO/ZrO2/Al2O3 catalyst in the presence of an undercoated Al2O3 buffer layer exhibits higher methanol conversion and lower CO concentration in the outlet gas than in the absence of an undercoated Al2O3 buffer layer. The micro-channel reactor with a undercoated Al2O3 buffer layer produces large amounts of hydrogen compared with one without a buffer layer. The undercoated Al2O3 buffer layer enhances the adhesion between catalysts and micro-channel walls, which leads to improvement in reactor performance.  相似文献   

13.
The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al2O3 and CeO2 catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al2O3 catalyst showed significant deactivation compared to the Ni/CeO2 catalyst, both in terms of production rates and the selectivity to H2 and CO2. The Ni/CeO2 catalyst demonstrated higher selectivity for H2 and CO2, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al2O3 sample. For the Ni/Al2O3 catalyst, the selectivity to CO increased with temperature, while the Ni/CeO2 catalyst produced no CO. For the Ni/CeO2 catalyst, the activation energies for H2 and CO2 production were 146 and 169 kJ mol−1, while for the Ni/Al2O3 catalyst these activation energies were 158 and 175 kJ mol−1, respectively. The difference of the active metal dispersion on Al2O3 and CeO2 supports, as measured from H2-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al2O3 catalyst. It is unlikely that carbon would build up on the Ni/CeO2 catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO2 lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO2 mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO2 with H2.  相似文献   

14.
Ti modified Pt/ZrO2 catalysts were prepared to improve the catalytic activity of Pt/ZrO2 catalyst for a single-stage WGS reaction and the Ti addition effect on ZrO2 was discussed based on its characterization and WGS reaction test. Ti impregnation into ZrO2 increased the surface area of the support and the Pt dispersion. The reducibility of the catalyst was enhanced in the controlled Ti impregnation (∼20 wt.%) over Pt/ZrO2 by the Pt-catalysed reduction of supports, particularly, at the interface between ZrO2 and TiO2. The significant CO2 gas band in the DRIFTS results of Pt/Ti[20]/ZrO2 indicated that the Ti addition made the formate decomposition rate faster than the Pt/ZrO2 catalyst, linked with the enhanced Pt dispersion and reducibility of the catalyst. Consequently, Ti impregnation over the ZrO2 support led to a remarkably enhanced CO conversion and the reaction rate of Pt/Ti[20]/ZrO2 increased by a factor of about 3 from the bare Pt/ZrO2 catalyst.  相似文献   

15.
To develop a single stage water–gas shift reaction (WGS) catalyst for compact reformers, Pt/CeO2, Pt/ZrO2, and Pt/Ce(1−x)Zr(x)O2 catalysts have been applied for the target reaction. The CeO2/ZrO2 ratio was systematically varied to optimize Pt/Ce(1−x)Zr(x)O2 catalysts. Pt/CeO2 showed the highest turnover frequency (TOF) and the lowest activation energy (Ea) among the catalysts tested in this study. It has been found that the reduction property of the catalyst is more important than the dispersion for a single stage WGS. Pt/CeO2 catalyst also showed stable catalytic performance. Thus, Pt/CeO2 can be a promising catalyst for a single stage WGS for compact reformers.  相似文献   

16.
Liquid organic hydrogen carrier (LOHC) is a chemical hydrogen storage method that stores hydrogen in the form of liquid organics. Dibenzyltoluene (DBT) is a promising LOHC material due to its high storage density, low ignitability, and low cost. In this study, Pt/Al2O3 and Pt/CeO2 catalysts are synthesized using a combustion nanocatalyst synthesis method called the glycine nitrate process (GNP) to obtain high catalytic activity for the dehydrogenation of perhydro-dibenzyltoluene (H18-DBT). Pt/CeO2 exhibits much faster dehydrogenation than Pt/Al2O3, 80.5%/2.5 h versus 3.5%/2.5 h. To investigate the causes of the difference in the dehydrogenation rates, microstructural characterization by N2 physisorption, CO chemisorption and transmission electron microscopy analysis are conducted, and the catalytic activities are evaluated at various liquid hourly space velocities (LHSVs). The differences in dehydrogenation can be attributed to the mass transport of liquid H18-DBT into the catalyst pores being slow due to the small pores in Pt/Al2O3, which is a rarely addressed issue for other LOHC materials. This is because many LOHC materials are dehydrogenated at the gas phase, which has higher diffusivity than that of the liquid phase. Pt/CeO2 synthesized by the GNP is also compared with a commercial Pt/Al2O3 catalyst. The commercial Pt/Al2O3 catalyst shows a dehydrogenation of 17.8%/2.5 h, which is much slower than that of Pt/CeO2 synthesized by the GNP, at 80.5%/2.5 h.  相似文献   

17.
Wash-coated Pt/CeO2, Pt/CeO2/ZrO2 and Pt/Cu/CeO2 and Pt/CeO2/Al2O3 based formulations were tested in sandwich type microreactors for water–gas shift (WGS) activity. At low reaction temperature of 260 °C, low conversion of carbon monoxide was initially observed which increased considerably upon the addition of air, a behaviour which was observed even after multiple cycles of start-up, operation with and without air and shut-down. At a higher reaction temperature of 400 °C air addition did not further improve the performance of the catalysts, which converted the carbon monoxide already close to equilibrium. One of the catalysts was incorporated into a larger reactor of kW scale and tested for its performance under conditions of WGS and oxygen enhanced WGS. The carbon monoxide conversion was increased by the air addition also on the larger reactor.  相似文献   

18.
The water–gas shift (WGS) reaction on co-precipitated NiO–ZnO catalysts at different reduction temperatures has been studied by a temperature-programmed reaction using in situ diffuse reflectance infrared Fourier Transform Spectroscopy, coupled with mass spectroscopic (in situ DRIFTS/MS) techniques. The results reveal that a catalyst reduced at 493 K (labeled H220) showed higher activity than one reduced at 673 K (labeled H400) due to the ability of NiO on the H220 catalyst to promote CO conversion of the WGS reaction. In situ DRIFTS/MS studies show that there are three adsorbed species over the H220 catalyst at room temperature: adsorbed CO bands, molecularly adsorbed H2O and carboxyl species. Increasing the temperature to 423 K led to the emergence of CO2 and H2 and the disappearance of carboxyl species. However, the low catalytic activity of the H400 catalyst could be attributed to the conversion of the NiO sites to reduced Ni metal sites, which (i) adsorbed CO as the strong linearly bonded CO on the catalyst surface, slowing down the CO reaction, and (ii) showed a lower H2O uptake.  相似文献   

19.
CuO/ZnO/CeO2/ZrO2 nanoflowers catalyst was grown on an Al2O3 foam ceramic by a one-step hydrothermal process, while a naked Al2O3 foam ceramic and an Al2O3 foam ceramic grown with ZnO nanorods that directly impregnated into the catalyst precursor solution were also fabricated simultaneously. The morphology, composition, redox property and specific surface area of catalysts on the three ceramics were investigated in detail. The catalyst-loaded ceramics were used as catalyst supports in a microreactor to study the catalytic performance for methanol steam reforming. Results showed that the microreactor with Al2O3 support grown with nanoflowers catalyst achieved 99.8% methanol conversion rate, 0.16 mol/h H2 flow rate at 310 °C, and an inlet methanol flow rate of 0.048 mol/h. Moreover, the microreactor exhibited 92% methanol conversion rate after 30 h continuous reaction.  相似文献   

20.
Decline in catalyst performance due to coke deposition is the main problem in diesel steam (SR) and autothermal reforming (ATR) reactions. Good redox potential and strong interaction of CeO2 with nickel increase activity and coke resistivity of Ni/Al2O3 catalysts. In this study, mesoporous Al2O3, CeO2/Al2O3, and CeO2/ZrO2/Al2O3 supported nickel catalysts were successfully synthesized. The highest hydrogen yield, 97.7%, and almost no coke deposition were observed with CeO2/ZrO2/Al2O3 catalyst (Ni@8CeO2-2ZrO2-Al2O3-EISA) in SR reaction. The second highest hydrogen yield, 91.4%, was obtained with CeO2/Al2O3 catalyst (Ni@10CeO2-Al2O3-EISA) with 0.3 wt% coke deposition. Presence of ZrO2 prevented the transformation of cubic CeO2 into CeAlO3, which enhanced water gas shift reaction (WGSR) activity. Ni@10CeO2-Al2O3-EISA did not show any decline in activity in a long-term performance test. Higher CeO2 incorporation (20 wt%) caused lower steam reforming activity. Change of synthesis route from one-pot to impregnation for the CeO2 incorporation decreased the number of acid sites, limiting cracking reactions and causing a significant drop in hydrogen production.  相似文献   

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