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1.
A series of CuO/ZnO/Al_2O_3, CuO/ZnO/ZrO_2/Al_2O_3 and CuO/ZnO/CeO_2/Al_2O_3 catalysts were prepared by coprecipitation and characterized by N_2 adsorption, XRD, TPR, N_2O titration and HRTEM. The catalytic performances of these catalysts for the steam reforming of methanol were evaluated in a laboratory-scale fixed-bed reactor at 0.1 MPa and temperatures between 473 and 543 K. The results showed that the catalytic activity depended greatly on the catalyst reducibility and the specific surface area of Cu. An approximate linear correlation between the catalytic activity and the Cu surface area was found for all catalysts investigated in this study.Compared to CuO/ZnO/Al_2O_3, the ZrO_2-doped CuO/ZnO/Al_2O_3 exhibited higher activity and selectivity to CO,while the CeO_2-doped catalyst displayed lower activity and selectivity. Finally, an intrinsic kinetic study was carried out over a screened CuO/ZnO/CeO_2/Al_2O_3 catalyst in the absence of internal and external mass transfer effects. A good agreement was observed between the model-derived effluent concentrations of CO(CO_2) and the experimental data. The activation energies for the reactions of methanol-steam reforming, water-gas shift and methanol decomposition over CuO/ZnO/CeO_2/Al_2O_3 were 93.1, 85.1 and 116.5 k J·mol~(-1), respectively. 相似文献
2.
The effect of Pd on a Cu/ZnO/A1 2O 3 catalyst for methanol synthesis from CO 2/H 2 has been investigated. Activities of impregnated catalysts and physical mixtures were studied in an internal recycle reactor under 5 MPa, 250°C and a range of conversions. In all cases, the promotion of methanol production was greater at higher flow rates (lower conversions). The promotion achieved by use of Pd/A1 2O 3+ Cu/ZnO/Al 2O 3 physical mixtures was found to increase with Pd content. Greater promotion was observed over the Pd impregnated Cu/ZnO/Al 2O 3 catalysts, although this was insensitive to the particular Pd loadings used. The results are consistent with the proposal that hydrogen spillover is responsible for the observed promotion. The effectiveness of Pd as a promoter for the reduction of CuO in the catalysts was studied by TPR and was found to be related to the level of promotion in methanol production. 相似文献
3.
The selective catalytic reduction (SCR) of NO by C 3H 6 in excess oxygen was evaluated and compared over Ag/Al 2O 3 and Cu/Al 2O 3 catalysts. Ag/Al 2O 3 showed a high activity for NO reduction. However, Cu/Al 2O 3 showed a high activity for C 3H 6 oxidation. The partial oxidation of C 3H 6 gave surface enolic species and acetate species on the Ag/Al 2O 3, but only an acetate species was clearly observed on the Cu/Al 2O 3. The enolic species is a more active intermediate towards NO + O 2 to yield—NCO species than the acetate species on the Ag/Al 2O 3 catalyst. The Ag and Cu metal loadings and phase changes on Al 2O 3 support can affect the activity and selectivity of Ag/Al 2O 3 and Cu/Al 2O 3 catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al 2O 3 catalyst for NO reduction is higher than that of the Cu/Al 2O 3 catalyst. 相似文献
4.
The influences of calcination temperatures and additives for 10 wt.% Cu/γ-Al 2O 3 catalysts on the surface properties and reactivity for NO reduction by C 3H 6 in the presence of excess oxygen were investigated. The results of XRD and XPS show that the 10 wt.% Cu/γ-Al 2O 3 catalysts calcined below 973 K possess highly dispersed surface and bulk CuO phases. The 10 wt.% Cu/γ-Al 2O 3 and 10 wt.% Mn–10 wt.% Cu/γ-Al 2O 3 catalysts calcined at 1073 K possess a CuAl 2O 4 phase with a spinel-type structure. In addition, the 10 wt.% La–10 wt.% Cu/γ-Al 2O 3 catalyst calcined at 1073 K possesses a bulk CuO phase. The result of NO reduction by C 3H 6 shows that the CuAl 2O 4 is a more active phase than the highly dispersed and bulk CuO phase. However, the 10 wt.% Mn–10 wt.% Cu/γ-Al 2O 3 catalyst calcined at 1073 K possesses significantly lower reactivity for NO reduction than the 10 wt.% Cu/γ-Al 2O 3 catalyst calcined at 1073 K, although these catalysts possess the same CuAl 2O 4 phase. The low reactivity for NO reduction for 10 wt.% Mn–10 wt.% Cu/γ-Al 2O 3 catalyst calcined at 1073 K is attributed to the formation of less active CuAl 2O 4 phase with high aggregation and preferential promotion of C 3H 6 combustion to CO x by MnO 2. The engine dynamometer test for NO reduction shows that the C 3H 6 is a more effective reducing agent for NO reduction than the C 2H 5OH. The maximum reactivity for NO reduction by C 3H 6 is reached when the NO/C 3H 6 ratio is one. 相似文献
5.
Pd and Pd–Zn alloy were supported on various supporting materials using impregnation, co-precipitation and microemulsion methods, and their catalytic performances in oxidative methanol reforming (OMR) were investigated. Pd/ZnO exhibited much higher selectivity than either Pd/Al 2O 3 or Pd/ZrO 2 in the OMR for hydrogen production. This was attributed to the presence of Pd–Zn alloy on the ZnO support. Elemental Pd on Al 2O 3 or ZrO 2 promotes methanol decomposition reaction and increases CO formation. Using a microemulsion method, a highly selective Pd/ZnO can be obtained with much lower Pd loading than that in samples prepared by co-precipitation. Modification of Al 2O 3 with ZnO produced a ZnAl 2O 4 phase, which was found to be a good support for the Pd/ZnO catalyst. Highly active and selective Pd/ZnO/ZnAl 2O 4 catalysts for the OMR reaction, containing much lower Pd loadings have been developed by impregnation of the supports with an aqueous solution of Pd(NO 3) 2 + Zn(NO 3) 2. 相似文献
6.
The objective of this work is to investigate catalyst systems for the oxidation of phenol in water in a batch autoclave. The main experimental variables are the type and the composition of the catalyst, the catalyst loading, temperature, oxygen partial pressure, initial phenol concentration and the stirrer speed. Commercial catalysts were used. Experimental work was conducted in two different laboratories. In one laboratory, the catalysts tested were 35% CuO+65% ZnO; 5–15% CuO+85–95% Al 2O 3; 26% CuO+74% Cu Chromite. In the other laboratory, the catalysts tested included 35% CuO+65% ZnO; 5–10% Ba 2CO 3+<5% C+30–40% CuO+60–70% ZnO; and 8–15% Al 2O 3+1–5% C+35–45% CuO+40–50% ZnO. With some of these catalysts depending on the operating conditions, complete phenol conversion could be obtained within 90 min. Under certain experimental conditions, the reaction underwent an induction period after which there was a transition to a much higher activity regime. The induction period may be due to an autocatalytic reaction system or to a very slow rate of formation of hydroquinone and catechol which then readily oxidize to o- and p-benzoquinone. An increase in the temperature and the oxygen partial pressure decreased the induction period, which increased as the catalyst to phenol ratio increased. 26% CuO+74% Cu Chromite and 8–15% Al 2O 3+1–5% C+35–45% CuO+40–50% ZnO were found to be the most active catalysts. 相似文献
7.
以γ-Al 2O 3为载体采用分步浸渍法制备了不同金属氧化物进行载体改性的Cu/B/M/Al 2O 3(M=Mg,Ca,Ni)催化剂,并测试了其催化醋酸仲丁酯加氢反应的性能。结果表明,以NiO进行载体改性的催化剂导致酯加氢反应中大量酸催化产物及烃类出现;以MgO进行载体改性不利于金属Cu的分散且催化剂的结构稳定性较差;以CaO对γ-Al 2O 3载体进行改性不仅能够促进金属Cu的分散,提高催化剂的酯加氢活性和产物选择性,而且可以有效减少反应中非活性碳物种在催化剂表面的沉积。 相似文献
8.
The preparation of alumina-supported β-Mo 2C, MoC 1−x ( x≈0.5), γ-Mo 2N, Co–Mo 2C, Ni 2Mo 3N, Co 3Mo 3N and Co 3Mo 3C catalysts is described and their hydrodesulfurization (HDS) catalytic properties are compared to conventional sulfide catalysts having similar metal loadings. Alumina-supported β-Mo 2C and γ-Mo 2N catalysts (Mo 2C/Al 2O 3 and Mo 2N/Al 2O 3, respectively) are significantly more active than sulfided MoO 3/Al 2O 3 catalysts, and X-ray diffraction, pulsed chemisorption and flow reactor studies of the Mo 2C/Al 2O 3 catalysts indicate that they exhibit strong resistance to deep sulfidation. A model is presented for the active surface of Mo 2C/Al 2O 3 and Mo 2N/Al 2O 3 catalysts in which a thin layer of sulfided Mo exposing a high density of sites forms at the surface of the alumina-supported β-Mo 2C and γ-Mo 2N particles under HDS conditions. Cobalt promoted catalysts, Co–Mo 2C/Al 2O 3, have been found to be substantially more active than conventional sulfided Co–MoO 3/Al 2O 3 catalysts, while requiring less Co to achieve optimal HDS activity than is observed for the sulfide catalysts. Alumina-supported bimetallic nitride and carbide catalysts (Ni 2Mo 3N/Al 2O 3, Co 3Mo 3N/Al 2O 3, Co 3Mo 3C/Al 2O 3), while significantly more active for thiophene HDS than unpromoted Mo nitride and carbide catalysts, are less active than conventional sulfided Ni–Mo and Co–Mo catalysts prepared from the same oxidic precursors. 相似文献
9.
The NO x storage-reduction catalysis under oxidizing conditions in the presence of SO 2 has been investigated on Pt/Ba/Fe/Al 2O 3, Pt/Ba/Co/Al 2O 3, Pt/Ba/Ni/Al 2O 3, and Pt/Ba/Cu/Al 2O 3 catalysts compared with Pt/Ba/Al 2O 3, Pt/Fe/Al 2O 3, Pt/Co/Al 2O 3, Pt/Ni/Al 2O 3, Pt/Cu/Al 2O 3 and Pt/Al 2O 3 catalysts. The NO x purification activity of Pt/Ba/Fe/Al 2O 3 catalyst was the highest of all the catalysts investigated in this paper after an aging treatment. That of the aged Pt/Ba/Co/Al 2O 3 and Pt/Ba/Ni/Al 2O 3 catalysts was essentially the same as that of the aged Pt/Ba/Al 2O 3 catalyst, while that of the aged Pt/Ba/Cu/Al 2O 3 and Pt/Cu/Al 2O 3 catalysts was substantially lower than the others. The Fe-compound on the aged Pt/Ba/Fe/Al2O3 catalyst has played a role in decreasing the sulfur content on the catalyst after exposure to simulated reducing gas compared with the Pt/Ba/Al2O3 catalyst without the Fe-compound. XRD and EDX show that the Fe-compound inhibits the growth in the size of BaSO4 particles formed on the Pt/Ba/Fe/Al2O3 catalyst under oxidizing conditions in the presence of SO2 and promotes the decomposition of BaSO4 and desorption of the sulfur compound under reducing conditions. 相似文献
10.
Cu 0.5Zn 0.5Mn 2O 4 spinel-lattice catalyst has been studied for methanol decomposition by in situ infrared (IR) spectroscopy analysis and micro reactor study. Methoxy species is formed by dissociative adsorption of methanol which subsequently converts into formate species via step-wise dehydrogenation process. The activities of surface intermediates on reduced CuO, ZnO and Mn 2O 3 catalysts are strongly affected by the ease of hydrogen desorption from the site, the strength of C–H bonding and the availability of oxygen. A synergism between Cu and MnO whereby the Cu serves as a sink for reverse hydrogen atoms spillover from MnO has been proposed. The micro reactor analysis correlates well with the IR results. 相似文献
11.
Catalysts prepared as bulk VSb 0.1O x and supported V 2O 5/Al 2O 3, V 2O 5-Sb 2O 3/Al 2O 3 and Sb 2O 3/Al 2O 3 (containing 0.5, 1 or 2 theoretical monolayers of V 2O 5 or Sb 2O 3) were tested in the oxidative dehydrogenation of iso-butane at 550°C in i-C 4H 10:O 2:He=20:10:70 gas mixture. Fresh and used catalysts were characterised by BET, XRD and XPS. Reactivity and thermochemistry of active oxygen taking part in the redox cycle with ethane and hydrogene were studied using in situ differential scanning calorimetry. Temperature-programmed desorption of O 2 in He flow was also investigated and in situ DRIFT was applied to investigate surface species of the catalysts in flows of i-C 4H 10, O 2 and i-C 4H 10/O 2 mixture. Supported VSb yO x catalysts are more active and selective than bulk one. V-only supported catalysts display a high efficiency due to the high reactivity of VOX-species. In bulk catalyst, the surface is enriched with antimony. In supported samples, the surfaces V/Sb are close to the calculated ones. In the presence of antimony, the amount of active oxygen species and their reactivity in redox transformation is improved. The rates of vanadium reduction and reoxidation are also higher. Compared to V-only catalysts, supported V-Sb-catalysts display a lower coking activity and higher on-stream stability. 相似文献
12.
The role of vanadium oxide and palladium on the benzene oxidation reaction over Pd/V 2O 5/Al 2O 3 catalysts was investigated. The Pd/V 2O 5/Al 2O 3 catalysts were more active than V 2O 5/Al 2O 3 and Pd/Al 2O 3 catalysts. The increase of vanadium oxide content decreased the Pd dispersion and increased the benzene conversion. A strong Pd particle size effect on benzene oxidation reaction was observed. Although the catalysts containing high amount of V 4+ species were more active, the Pd particle size effect was responsible for the higher activity. 相似文献
13.
Among various Cu/ZnO/ZrO 2 catalysts with the Cu/Zn ratio of 3/7, the one with 15 wt.% of ZrO 2 obtains the best activity for methanol synthesis by hydrogenation of CO. The TPR, TPO and XPS analyses reveal that a new copper oxide phase is formed in the calcined Cu/ZnO/ZrO 2 catalysts by the dissolution of zirconium ions in copper oxide. In addition, the Cu/ZnO/ZrO 2 catalyst with 15 wt.% of ZrO 2 turns out to contain the largest amount of the new copper oxide phase. When the Cu/ZnO/ZrO 2 catalysts is reduced, the Cu 2+ species present in the ZrO 2 lattice is transformed to Cu + species. This leads to the speculation that the addition of ZrO 2 to Cu/ZnO catalysts gives rise to the formation of Cu + species, which is related to the methanol synthesis activity of Cu/ZnO/ZrO 2 catalyst in addition to Cu metal particles. Consequently, the ratio of Cu +/Cu 0 is an important factor for the specific activity of Cu/ZnO/ZrO 2 catalyst for methanol synthesis. 相似文献
14.
Combustion of CO, ethyl acetate and ethanol was studied over CuO x/Al 2O 3, CuO x–CeO 2/Al 2O 3, CuMn 2O 4/Al 2O 3 and Mn 2O 3/Al 2O 3 catalysts. It was found that modification of the alumina with ceria before subsequent copper oxide deposition increases the activity for combustion of CO substantially, but the effect of ceria was small on the combustion of ethyl acetate and ethanol. The activity increases with the CuO x loading until crystalline CuO particles are formed, which contribute little to the total active surface. The CuO x–CeO 2/Al 2O 3 catalyst is more active than the CuMn 2O 4/Al 2O 3 catalyst for the oxidation of CO but the CuMn 2O 4/Al 2O 3 catalyst is more active for the combustion of ethyl acetate and ethanol. Thermal ageing and water vapour in the feed caused a modest decrease in activity and did not affect the CuOx–CeO2/Al2O3 and CuMn2O4/Al2O3 catalysts differently. In addition, no difference in intermediates formed over the two catalysts was observed. Characterisation with XRD, FT-Raman and TPR indicates that the copper oxide is present as a copper aluminate surface phase on alumina at low loading. At high loading, bulk CuO crystallites are present as well. Modification of the alumina with ceria before the copper oxide deposition gives well dispersed copper oxide species and bulk CuO crystallites associated to the ceria, in addition to the two copper oxide species on the bare alumina. The distribution of copper species depends on the ceria and copper oxide loading. The alumina supported copper manganese oxide and manganese oxide catalysts consist mainly of crystalline CuMn2O4 and Mn2O3, respectively, on Al2O3. 相似文献
15.
采用浸渍法和共沉淀法制备了一系列不同Cu含量的超顺磁CuO-Bi 2O 3/Fe 3O 4-SiO 2-MgO催化剂。使用电感耦合等离子体发射光谱仪(ICP-AES)、低温N 2物理吸-脱附、X射线衍射(XRD)、H 2程序升温还原(H 2-TPR)、振动样品磁强计(VSM)对催化剂的组成、结构、织构及磁性能进行表征, 评价了该催化剂催化甲醛乙炔化合成1, 4-丁炔二醇的催化活性。结果表明, 制备方法对催化剂中活性组分CuO的存在状态及炔化性能有较大影响, 采用共沉淀法较浸渍法制备的催化剂具有更高的比表面积、CuO分散度与较好的还原能力, 表现出较高的炔化性能;Cu含量是影响催化剂炔化性能的另一重要因素, 随Cu含量的增加, 催化剂活性逐渐增加, 在本研究考察范围内, 以共沉淀法制备的Cu质量分数为30%的催化剂表现出最佳的甲醛乙炔化性能。同时, 该催化剂具有良好的超顺磁性, 可以在外加磁场的作用下迅速分离回收, 循环使用6次后, 其催化活性明显高于非磁性催化剂。 相似文献
16.
The activity of the various CuO species found in supported copper catalysts and the effect of the presence of reaction products, CO 2 and H 2O, was studied during the complete oxidation of methane. Series of copper catalysts supported on ZrO 2, Al 2O 3 and SiO 2 with different metal concentrations were analyzed under identical experimental conditions of reactant concentration and temperature. The catalysts were characterized by TPR, UV–vis spectroscopy and XRD. The results show that the activity of supported CuO is closely related to the kind of Cu species formed on the different supports. It was found that the Cu species formed on ZrO 2 and Al 2O 3 are dependent on the metal loading/support's surface area ratio, and that the activity of highly dispersed Cu is substantially higher than that of bulk CuO. In the case of silica, only the formation of bulk CuO was detected, accounting for the low activity of CuO/SiO 2 catalysts. The activity of highly dispersed Cu species formed on ZrO 2 is higher than those formed over Al 2O 3, and it is not significantly affected by the formation of bulk CuO on the surface. On the contrary, the activity of copper species formed on alumina decreases continuously as the Cu loading is increased. Thus, for the range of copper loading studied in this work, the activity of the catalysts, per gram of loaded Cu, follows the sequence: CuO/ZrO 2 > CuO/Al 2O 3 CuO/SiO 2. It was also found that CO 2 does not inhibits the activity of the CuO/ZrO 2 catalysts, while water inhibits the combustion reaction of methane, with an estimated reaction order of about −0.2 for temperatures between 360 °C and 420 °C. 相似文献
17.
A series of the Ce 1−xCu xO 2−x/Al 2O 3/FeCrAl catalysts ( x = 0–1) were prepared. The structure of the catalysts was characterized using XRD, SEM and H 2-TPR. The catalytic activity of the catalysts for the combustion of methane was evaluated. The results indicated that in the Ce 1−xCu xO 2−x/Al 2O 3/FeCrAl catalysts the surface phase structure were the Ce 1−xCu xO 2−x solid solution, -Al 2O 3 and γ-Al 2O 3. The surface particle shape and size were different with the variety of the molar ratio of Ce to Cu in the Ce 1−xCu xO 2−x solid solution. The Cu component of the Ce 1−xCu xO 2−x/Al 2O 3/FeCrAl catalysts played an important role to the catalytic activity for the methane combustion. There were the stronger interaction among the Ce 1−xCu xO 2−x solid solution and the Al 2O 3 washcoats and the FeCrAl support. 相似文献
18.
Novel NO x storage-reduction (NO xSR) catalysts prepared by Pt and/or Cu impregnation of Mg–Al (60:40) hydrotalcite (HT)-type compounds show better performances in NO x storage than Pt–Ba/Al 2O 3 Toyota-type NO xSR catalysts at reaction temperatures lower than 250 °C. The presence of Pt or Cu considerably enhances the activity, with the former more active. The nature of the HT source, however, also influences performance. The co-presence of Pt and Cu slightly worsens the low temperature activity, but considerably promotes the resistance to deactivation after severe hydrothermal treatment and in the presence of SO 2. This effect is attributed to both the possibility of formation of a Pt–Cu alloy after reduction, and the modification of the HT induced during the deposition of Cu. The overall Pt–Cu/HT performances are thus superior to those of the Pt–Ba/Al 2O 3 Toyota-type NO xSR catalysts. 相似文献
19.
采用柠檬酸络合法制备一系列不同铜铈比的Cu-Ce-O/γ-Al_2O_3催化剂,用XRD、H2-TPR对其进行表征,采用连续固定床微反装置对Cu-Ce-O/γ-Al_2O_3催化剂CO催化氧化活性进行评价。结果表明,Cu-Ce-O/γ-Al_2O_3催化剂的XRD图谱中除归属于γ-Al_2O_3的晶相峰外,还出现CuO和CeO_2的晶相峰。高温水热引起活性组分CeO_2的晶粒聚集、长大和尖晶石结构CuAl2O4物质的生成;CuO-CeO_2之间的共生共存与相互作用,使得Cu-Ce-O/γ-Al_2O_3催化剂中具有非完整结构的[Cu2+1-xCu+x][O1-12x12x]增多,Cu+离子和氧空位增多,有利于其H2-TPR还原峰温度向低温区偏移,有利于提高其CO的催化氧化活性,使得Cu-Ce-O/γ-Al_2O_3催化剂的TCO50和TCO90降低。Cu与Ce物质的量比为5∶5制备的Cu-Ce-O/γ-Al_2O_3-55催化剂的TCO50和TCO90分别降至最低的162℃和199℃,表明此时的Cu-Ce-O协同效应最佳;CuO-CeO_2二相的共生共存与相互作用有利于减少高温水热环境下活性组分的聚集和晶粒长大,有利于Cu-Ce-O/γ-Al_2O_3催化剂能够保持较高的CO催化氧化活性。 相似文献
20.
NO reduction to N 2 by C 3H 6 was investigated and compared over Cu-Al 2O 3 catalysts prepared by four different methods, namely, the conventional impregnation, co-precipitation, evaporation of a mixed aqueous solution, and xerogel methods. It was found that the catalyst preparation method as well as the Cu content exerts a significant influence on catalyst activity. For the catalysts prepared by the first three preparation methods, with the increase of Cu content from 5 to 15 wt%, the maximum NO reduction conversion decreased slightly, but the temperature for the maximum NO reduction also decreased. For the xerogel Cu-Al 2O 3, there was a significant decrease in NO reduction conversion with the increase of Cu content from 5 to 10 wt%. In the absence of water vapour, the Cu-Al 2O 3 catalyst prepared by the impregnation method exhibited the highest activity toward NO reduction. The purity of alumina support was found to be a crucial factor to the activity of the Cu-Al 2O 3 catalyst prepared by impregnation. In the presence of water vapour, a substantial decrease in NO conversion was observed for the Cu-Al 2O 3 catalysts prepared by the first three methods, especially for the impregnated Cu-Al 2O 3 catalyst. In contrast, the presence of water vapour showed only a minor influence on the xerogel 5 wt% Cu-Al 2O 3 and it showed the highest activity for NO reduction in the presence of 20% water vapour. The xerogel 5 wt% Cu-Al 2O 3 catalyst was also found to be less affected by a 5 wt% sulfate deposition than the Cu-Al 2O 3 catalysts prepared by other methods. 相似文献
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