Pd/ZnO催化剂上甲醇水蒸气重整制氢

研究了并流共沉淀法制备的Pd/ZnO催化剂上的甲醇水蒸气重整制氢反应.考察了钯含量、还原温度、反应温度、重时空速（WHSV）和水-甲醇摩尔比（水醇比）对反应的影响.研究结果表明,当钯质量分数为15.9%,反应温度为523～573 K,还原温度为523～573 K,水醇比为1.0～1.2,WHSV=17.2 h^-1时,反应具有较好的CH3OH转化率、CO₂选择性、H₂产率及较低的出口CO摩尔分数.与铜基催化剂相比,Pd/ZnO催化剂表现出较好的稳定性.     

氧化铈形貌对甲醇水蒸气重整制氢CuO/CeO2催化剂性能的影响

采用简单的改变焙烧气氛的方法改变水热法合成的CeO2纳米材料的形貌,得到的CeO2纳米材料再通过浸渍法制备CuO/CeO2催化剂,并将其应用于甲醇水蒸汽重整制氢反应。采用SEM、XRD、BET、H2-TPR、N2O滴定和XPS等对催化材料进行了表征,着重探讨了氧化铈形貌对催化剂结构、性质和性能的影响。结果表明,纳米棒状结构的CeO2负载CuO后得到的CuO/CeO2催化剂性能最佳,这主要是因为纳米棒状结构的CeO2与CuO的相互作用较强,表面存在较多的晶格缺陷和氧空穴,进而使得CuO/CeO2催化剂表相Cu含量增加,Cu物种的还原温度较低,催化活性较好。当反应温度为260 °C、水醇物质的量比为1.2、甲醇气体空速为800 h-1时,甲醇转化率可达100%,重整气中CO摩尔含量为0.16%。     

甲醇水蒸气重整制氢研究进展

氢气需求的持续增长,带动制氢技术的不断进步。煤制氢技术投资较高,天然气制氢原料来源受到限制,电解水制氢成本较高。甲醇制氢投资适中,适合各种规模的制氢装置,铜基催化剂反应温度低,低温活性和氢气选择性好,价格低廉,因而甲醇制氢技术得到广泛应用。催化剂载体和助剂的改进研究,对工业催化剂的改进具有重要的指导意义。综述甲醇水蒸气重整制氢工艺、反应机理和催化剂,介绍了催化剂载体和助剂等方面的研究进展情况。     

甲醇水蒸气重整制氢研究进展

介绍了国内外甲醇-水蒸气重整制氧的研究进展,包括反应机理,热力学、动力学模型,以及催化剂的制备情况,并对其未来发展作了展望.     

CeO_2形貌对甲醇水蒸汽重整CuO/CeO_2催化剂的影响

通过改变焙烧气氛,通过水热法合成不同形貌的CeO_2纳米材料,再通过浸渍法将其制备成CuO/CeO_2催化剂,并应用于甲醇水蒸汽重整制氢反应。采用SEM、XRD、BET、H2-TPR、N2O滴定和XPS对催化材料进行了表征,着重探讨了氧化铈形貌对催化剂结构、性质和性能的影响。结果表明:空气气氛下焙烧得到的纳米棒状结构的CeO_2负载CuO制备的CuO/CeO_2催化剂性能最佳,这主要是因为纳米棒状结构的CeO_2与CuO的相互作用较强,表面存在较多的晶格缺陷和氧空穴,进而使得CuO/CeO_2催化剂表相Cu含量增加,Cu物种的还原温度较低,催化活性较好。当反应温度为260℃、n(水)/n(甲醇)=1.2、甲醇气体空速为800h–1时,甲醇转化率可达100%。     

CuO/ZnO/Al2O3不锈钢纤维毡结构整体催化剂的甲醇水蒸气重整制氢性能

以切削法制备的商用多孔不锈钢纤维毡为催化剂载体,采用浸渍法制备CuO/ZnO/Al₂O₃结构整体催化剂,研究其对甲醇水蒸气重整制氢性能的影响。采用扫描电镜(SEM)对多孔不锈钢纤维毡结构整体催化剂进行微观形貌分析。通过改变反应空速和反应温度,考察结构整体反应器与固定床反应器的制氢性能。结果表明：相比于固定床反应器,填充不锈钢纤维毡结构整体催化剂的反应器可强化反应过程的传质和传热,在反应温度为280℃时,氢气流量为0.55 mol/h,甲醇转化率为95.07%;不锈钢纤维毡结构整体催化剂可降低甲醇水蒸气重整制氢的反应温度,减少反应系统的能量消耗。     

甲醇水蒸气重整制氢催化剂性能的研究

研究共沉淀法制备Cu/Al2O3甲醇水蒸气重整制氢催化剂，考察催化剂组成和焙烧温度对催化剂性能的影响。结果表明当Cu质量分数为30．9％，焙烧温度为500℃时，催化剂性能最佳。并采用X射线衍射（XRD），程序升温还原（TPR）和热重分析等方法对催化剂表面性质进行探讨。     

Cu-ZrO_2-CeO_2/γ-Al_2O_3催化甲醇水蒸气重整制氢反应的性能

以γ-Al_2O_3为载体,采用浸渍法制备Cu-ZrO_2-CeO_2/γ-Al_2O_3催化剂,用XRD、N_2吸附-脱附、H_2-TPR、NH_3-TPD、CO_2-TPD等方法对其进行表征。在连续流动常压固定床微型反应器上评价Cu-ZrO_2-CeO_2/γ-Al_2O_3催化剂对甲醇水蒸气重整制氢反应的催化性能,考察了反应温度、水醇比和质量空速对催化性能的影响,反应结果表明Cu-ZrO_2-CeO_2/γ-Al_2O_3催化剂具有较高的催化活性和稳定性,在温度为260℃、水醇摩尔比为1.2∶1、质量空速为3.6h–1的条件下,甲醇的转化率可达99%以上,氢气的选择性为98%以上,一氧化碳的选择性低于2.5%。表征结果显示助剂CeO_2和ZrO_2的加入促进活性组分在载体表面的分散性,影响催化剂的孔结构和酸碱性,增强了催化剂的活性。     

Ni/CeO_2复合催化剂的乙醇水蒸气重整制氢研究

分别采用共沉淀法、浸渍法和水热法合成了Ni/CeO_2复合催化剂,对这三种催化剂进行乙醇水蒸气重整制氢性能测试。采用X射线衍射(XRD)、程序升温还原(H_2-TPR)、热稳定性等表征技术对催化剂的结构和催化性能之间的关系进行了关联。结果表明,制备方法对催化活性有着重要的影响,水热法合成的Ni/CeO_2复合催化剂在反应温度为325℃时可将乙醇完全转化,在热稳定性能测试过程中表现出良好的活性、选择性和热稳定性。     

Ni/ZnO-ZrO2催化低温乙醇水蒸气重整制氢

以草酸钠为共沉淀剂,采用共沉淀法制备了以ZnO-ZrO2为载体的镍基乙醇水蒸气重整制氢催化剂(Ni/ZnO-ZrO2)。考察了不同锌锆摩尔比的ZnO-ZrO2负载的镍基催化剂在300～450℃催化乙醇水蒸气重整制氢的反应性能。用TPR、TPO、XRD对催化剂试样进行了表征。结果表明,当n(Zn)∶n(Zr)=1∶1,Ni负载质量分数10%时,催化剂中有镍锌复合氧化物生成,350℃时乙醇转化率达100%,450℃氢气选择性接近90%;TPO结果表明,ZnO-ZrO2复合载体可以降低催化剂上的积炭量。     

Activity and Selectivity of a Nanostructured CuO/ZrO2 Catalyst in the Steam Reforming of Methanol

Steam reforming of methanol for production of hydrogen can be carried out over copper based catalyst. In the work presented here, the catalytic properties of a CuO/ZrO₂ catalyst (8.5wt%) synthesised by a templating technique were investigated with respect to activity, long term stability, CO formation, and response to oxygen addition to the feed. The results were obtained using a fixed bed reactor and compared to a commercial methanol synthesis catalyst CuO/ZnO/Al₂O₃. It is shown that, depending on the time on stream, the temporary addition of oxygen to the feed has a beneficial effect on the activity of the CuO/ZrO₂ catalyst. After activation, the CuO/ZrO₂ catalyst is found to be more active (per copper mass) than the CuO/ZnO/Al₂O₃ system, more stable during time on stream (measured up to 250h), and to produce less CO. Structural characterisation by means of X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) reveals that the catalyst (as prepared) consists of crystalline, tetragonal zirconia with small domain sizes (about 60Å) and small/disordered crystallites of CuO.     

甲醇水蒸汽重整制氢Au/TiO2催化剂

采用沉积-沉淀法制备了一系列Au/TiO2催化剂,考察了Au负载量、焙烧温度以及助剂等因素对甲醇水蒸汽重整制氢反应催化性能的影响;并利用XRD, TEM对催化剂进行了表征. 结果表明,制备条件对催化性能有明显影响;Au负载量为5%(w)时所得催化剂活性较好;助剂NiO可使催化剂催化甲醇水重整的催化活性明显提高;100℃烘干未焙烧制得的催化剂活性最好;TEM结果显示,NiO的加入使载体TiO2颗粒分散度提高,Au粒粒度变小.     

Ethanol Steam Reforming on Co/CeO2: The Effect of ZnO Promoter

A series of ZnO promoted Co/CeO₂ catalysts were synthesized and characterized using XRD, TEM, H₂-TPR, CO chemisorption, O₂-TPO, IR-Py, and CO₂-TPD. The effects of ZnO on the catalytic performances of Co/CeO₂ were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co⁰ via enhanced oxygen mobility of the CeO₂ support which decreased the activity of Co/CeO₂ in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO₂ exhibited minimum CO and CH₄ selectivity and maximum CO₂ selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO₂ facilitated the oxidation of CH _x and CO to form CO₂; (2) increased ZnO coverage on CeO₂ surface reduced the interaction between CH _x /CO and Co/CeO₂; and (3) suppressed CO adsorption on Co⁰ reduced CO oxidation rate to form CO₂. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO₂, which consequently affected the C₂–C₄ product distributions.     

CO/FTIR Spectroscopic Characterization of Pd/ZnO/Al2O3 Catalysts for Methanol Steam Reforming

An as-synthesized 8.8wt% Pd/ZnO/Al₂O₃ catalyst was either pretreated under O₂ at 773 K followed by H₂ at 293 K or under H₂ at 773 K to obtain, respectively, a supported metallic Pd° catalyst (Pd°/ZnO/Al₂O₃) or a supported PdZn alloy catalyst (PdZn/ZnO/Al₂O₃). Both catalysts were studied by CO adsorption using FTIR spectroscopy. For the supported PdZn alloy catalyst (PdZn/ZnO/Al₂O₃), exposure to a mixture of methanol and steam, simulating methanol steam reforming reaction conditions, does not change the catalyst surface composition. This implies that the active sites are PdZn alloy like structures. The exposure of the catalyst to an oxidizing environment (O₂ at 623 K) results in the break up of PdZn alloy, forming a readily reducible PdO with its metallic form being known as much less active and selective for methanol steam reforming. However, for the metallic Pd°/ZnO/Al₂O₃ catalyst, FTIR results indicate that metallic Pd° can transform to PdZn alloy under methanol steam reforming conditions. These results suggest that PdZn alloy, even after an accidental exposure to oxygen, can self repair to form the active PdZn alloy phase under methanol steam reforming conditions. Catalytic behavior of the PdZn/ZnO/Al₂O₃ catalyst also correlates well with the surface composition characterizations by FTIR/CO spectroscopy.     

Au/La2O3/TiO2催化甲醇水蒸汽重整制氢

用沉积-沉淀法制备了Au/La2O3/TiO2催化剂,考察了制备条件和反应条件对催化剂活性的影响,并利用X射线衍射(XRD)、透射电子显微镜(TEM)等测试手段对催化剂进行了表征. 结果表明La2O3的加入可使催化剂催化甲醇水重整的催化活性明显提高,且明显降低产物气体中CO和CH4的含量,使氢气选择性明显增加. 当nH2O/nCH3OH=1.0、液体进料空速WHSV=3.42 h-1、反应温度为275℃时,Au/La2O3/TiO2催化剂催化甲醇水蒸汽重整制氢反应的效果最佳.     

Steam Reforming of Methanol Over Cu/CeO2 Catalysts Studied in Comparison with Cu/ZnO and Cu/Zn(Al)O Catalysts

A series of Ce_1-xCu_xO_2- mixed oxides were synthesized using a co-precipitation method and tested as catalysts for the steam reforming of methanol. XRD patterns of the Ce_1-xCu_xO_2- mixed oxides indicated that Cu²⁺ ions were dissolved in CeO₂ lattices to form a solid solution by calcination at 773K when x < 0.2. A TPR (temperature-programmed reduction) investigation showed that the CeO₂ promotes the reduction of the Cu²⁺ species. Two reduction peaks were observed in the TPR profiles, which suggested that there were two different Cu²⁺ species in the Ce_1-xCu_xO_2- mixed oxides. The TPR peak at low temperature is attributed to the bulk Cu²⁺ species which dissolved into the CeO₂ lattices, and the peak at high temperature is due to the CuO species dispersed on the surface of CeO₂. The Ce_1-xCu_xO_2- mixed oxides were reduced to form Cu/CeO₂ catalysts for steam reforming of methanol, and were compared with Cu/ZnO, Cu/Zn(Al)O and Cu/AL₂O₃ catalysts. All the Cu-containing catalysts tested in this study showed high selectivities to CO₂ (over 97%) and H₂. A 3.8wt% Cu/CeO₂ catalyst showed a conversion of 53.9% for the steam reforming of methanol at 513K (W/F = 4.9 g h mol^-1), which was higher than that over Cu/ZnO (37.9%), Cu/Zn(Al)O (32.3%) and Cu/AL₂O₃ (11.2%) with the same Cu loading under the same reaction conditions. It is likely that the high activity of the Cu/CeO₂ catalysts may be due to the highly dispersed Cu metal particles and the strong metalsupport interaction between the Cu metal and CeO₂ support. Slow deactivations were observed over the 3.8wt% Cu/CeO₂ catalyst at 493 and 513K. The activity of the deactivated catalysts can be regenerated by calcination in air at 773K followed by reduction in H₂ at 673K, which indicated that a carbonaceous deposit on the catalyst surface caused the catalyst deactivation. Using the TPO (temperature-programmed oxidation) method, the amounts of coke on the 3.8wt% Cu/CeO₂ catalyst were 0.8wt% at 493K and 1.7wt% at 513K after 24h on stream.     

甲醇水蒸气重整制氢CuZnAl催化剂的制备和研究

采用机械化学法制备了用于SRM反应的CuZnAl催化剂,并通过N2吸-脱附、N2O滴定、SEM、XRD、H2-TPR及原位FT-IR等手段对催化剂进行表征,对不同方法所制备催化剂的结构和性能进行了研究.结果表明:球磨法制备的CuZnAl催化剂形成较为规整的表面介孔结构,与浸渍法相比,具有较高的Cu比表面积和分散度,在SRM反应中CuZnAl催化剂较浸渍法制备的JZ-CuZnAl催化剂展现出更为优异的催化性能,当空速为58464 mL·(g·h)-1、进料水醇摩尔比为3:2、反应温度为300℃条件下,甲醇转化率达到81.2％,重整气中CO的体积分数为1.2％.     

二甲醚水蒸气重整制氢CuO-ZnO-Al2O3-ZrO2/固体酸复合催化剂

Steam reforming(SR) of dimethyl ether(DME) was investigated for the production of hydrogen for fuel cells.The activity of a series of solid acids for DME hydrolysis was investigated.The solid acid catalysts were ZSM-5 [Si/Al=25,38 and 50:denoted Z(Si/Al)] and acidic alumina(γ-Al₂O₃) with an acid strength order that was Z(25)>Z(38)>Z(50)>γ-Al₂O₃.Stronger acidity gave higher DME hydrolysis conversion.Physical mixtures containing a CuO-ZnO-Al₂O₃-ZrO₂ catalyst and solid acid catalyst to couple DME hydrolysis and methanol SR were used to examine the acidity effects on DME SR.DME SR activity strongly depended on the activity for DME hydrolysis.Z(25) was the best solid acid catalyst for DME SR and gave a DME conversion>90% [T=24℃,n(H₂O)/n(DME)=3.5,space velocity=1179 ml·(g cat)^-1·h^-1,and P=0.1MPa].The influences of the reaction temperature,space velocity and feed molar ratio were studied.Hydrogen production significantly depended on temperature and space velocity.A bifunctional catalyst of CuO-ZnO-Al₂O₃-ZrO₂ catalyst and ZSM-5 gave a high H₂ production rate and CO₂ selectivity.     

Investigation of Promoted Cu/ZnO/Al2O3 Methanol Steam Reforming Nanocatalysts by Full Factorial Design

A Cu/ZnO/Al₂O₃ nanocatalyst was applied for hydrogen production via steam reforming of methanol in a fixed‐bed reactor. Modified forms of the catalyst were prepared by adding small amounts of Ba, Zr, and Ce oxides. The catalysts were characterized by means of N₂ adsorption‐desorption, X‐ray diffraction, and scanning electron microscope techniques. Full factorial design was used to optimize the required number of experiments and evaluate the catalytic activity in a fixed‐bed reactor. The oxide additives reduced the production of carbon monoxide and increased the selectivity of carbon dioxide as well as the yield of hydrogen production. Among the studied catalysts, the Cu/ZnO/Al₂O₃/CeO₂/ZrO₂ catalyst presented the best performance.