两种甲醇水蒸气重整制氢催化剂的研究

对采用共沉淀法制备的CuZnAlO类铜系催化剂和采用水滑石类层柱材料（LDHs）前驱体制备的催化剂在甲醇水蒸气重整制氢反应中的性能进行了研究。对共沉淀法制备的CuZnAlO类铜系催化剂考察了ZrO2助剂的加入对催化剂反应性能的影响，发现Zr的质量分数为10％的催化剂显著提高CuZnAlO催化剂的反应性能。该催化剂的最佳反应条件：0.1 MPa、250 ℃、H2O/MeOH摩尔比1.0～1.3、3.56 h－1。在此反应条件下进行了COPZr2催化剂150 h稳定性实验。结果表明，该催化剂具有很好的反应稳定性。甲醇转化率和氢产率分别约为88％和83％，产物湿基组成中H2和CO的质量分数分别为>63％和0.20％～0.31％。对LDHs前驱体制备的催化剂，进行了70 h反应稳定性实验，结果表明，催化剂虽具有较高的起始活性，但随反应进行，活性有所下降，30?h后基本保持稳定，甲醇转化率和产氢率分别为73％和66％，产物湿基组成中H2和CO的质量分数分别为>55％和0.07%～0.08%。该类催化剂的反应稳定性虽较差，但却可以显著降低产物湿基组成中CO的摩尔分数。对LDHs前驱体制备的催化剂进行XRD和SEM表征结果表明，ZrO2的加入使催化剂中CuO晶粒分散更为均匀，颗粒更细。     

Methanol Steam Reforming Reactions on CuZn（Zr）AlO Catalyst

The catalytic performances of methanol steam reforming reactions on CuZn(Zr)AlO catalysts were studied. When the ZrO2 promoter was added to a CuZnAlO catalyst, its methanol conversion, H2 production and H2 selectivity improved greatly. By using the (?)COPZr-2 catalyst as an example, which exhibited the best catalytic performance, the optimized reaction conditions were established to be:     

Efficiency of Zn/TiO<Subscript>2</Subscript> catalyst operation in a microchannel reactor in methanol steam reforming

The activity of a Zn/TiO₂ catalyst deposited on metal microchannel plates in methanol steam reforming was studied. The catalyst exhibited maximum activity upon deposition on microchannel plates made of copper foam. In this case, the specific hydrogen production of a microreactor at 450°C was 78.6 l (g Cat)^?1 h^?1. The catalysts deposited on a microchannel plate of nickel foam and on corrugated brass foil exhibited lower activity because of the lower efficiency of heat transfer to the reaction zone. A correlation between the thermal conductivity of the microchannel plate material and the activity of the catalyst was observed in the following order: copper, brass, and nickel. The kinetic parameters of the process of methanol steam reforming in a microreactor were calculated with the use of a plug-flow reactor model. In this case, the calculated formal activation energy of 132 kJ/mol was independent of the microchannel plate material. A comparison of the equilibrium concentrations of reaction products at the reactor outlet, which were calculated from thermodynamic data, with the experimental data demonstrated that methanol steam reforming at a temperature higher than 400°C occurred in the nonequilibrium region. The concentration of carbon monoxide at the microreactor outlet was lower than 1 mol %, which is lower than the equilibrium concentration by one order of magnitude. This effect was attributed to the suppression of the reversed water gas shift reaction on the catalyst.     

程序升温连续流动反应器技术及其应用

在运用连续流动反应(CFR)技术(尾气技术)的基础上提出了1种可筛选催化剂并能进行非均相催化动力学研究的实验原理和方法--程序升温连续流动反应器(TPCFR)技术。在用此法筛选过的Cu-Ni催化剂上对甲醇分解反应和甲醇水蒸汽重整反应进行了系统研究,证明这种方法合理、可信。利用1条TPCFR曲线可求出各个动力学参数。     

Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming

Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.     

水蒸气对Ni/Ce-Zr-Al-Ox催化剂上CO2重整CH4瓜的影响

采用水热合成-负载法制备了Ni/Ce-Zr-Al-Ox催化剂,测试了该催化剂上CO2重整CH4反应的活性和稳定性,并考察了添加少量水蒸气对CO2重整CH4反应的影响.结果表明,在不含水蒸气的反应气中反应198 h后CH4和CO2的转化率分别为89%和98%,H2/CO摩尔比约为1.00,且没有任何失活.添加3.2%的水蒸气后,CH4转化率提高到94%,CO2转化率不变,H2/CO摩尔比约提高0.06,同时稳定性也很好.计算结果表明,添加少量水蒸气后,CO2重整CH4被促进,逆水煤气反应被抑制,而水蒸气重整CH4没有明显变化.     

甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO₂-ZrO₂/SiC整体催化剂，并将其用于甲醇水蒸气重整制氢反应中。结果表明，与CuO/CeO₂-ZrO₂颗粒催化剂相比，CuO/CeO₂-ZrO₂/SiC整体催化剂催化活性较好，产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响，结果表明，当CeO₂-ZrO₂复合氧化物涂层涂覆量在15%±1%，CuO负载量为5%±1%时，催化性能较好；当反应温度为340℃，水醇物质的量比为1.2，甲醇水蒸气气体空速为4840 h^-1时，甲醇转化率为86.0%，产氢速率为1490.0 L/（m³·s），重整气中CO体积分数为1.55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明，随着气体空速变大，甲醇转化率下降，产氢速率上升，重整气中CO体积分数下降。随着水醇物质的量比增加，甲醇转化率先上升后下降，产氢速率先上升后下降，重整气中CO体积分数下降。随着反应温度的升高，甲醇转化率、产氢速率和重整气中CO体积分数均上升。     

CeO_2改性Cu/Zn-Al水滑石衍生催化剂对甲醇水蒸气重整制氢性能的影响

采用原位合成法在γ-Al2O3表面合成了锌铝水滑石,再采用顺次浸渍法制备了Ce/Cu/Zn-Al催化材料;将其应用于甲醇水蒸气重整制氢,探讨了Ce含量对Cu/Zn-Al催化剂催化性能的影响.催化剂表征结果表明,CeO_2的引入改善了活性组分铜的分散度、铜的比表面积以及催化剂的氧化还原性质,进而提高了催化剂的催化活性和产氢率.当Ce含量为4%时,催化剂活性最佳,在250℃时,甲醇转化率达到100%,CO摩尔分数为0.39%,与Cu/Zn-Al催化剂相比,甲醇转化率提高了近40%.     

载体焙烧气氛对甲醇水蒸气重整制氢CuO/CeO2催化剂的影响

采用沉淀法和浸渍法制备了具有氧空位的CeO₂纳米材料和甲醇水蒸气重整制氢CuO/CeO₂催化剂,探索不同焙烧气氛对CeO₂纳米材料结构、性质和甲醇水蒸气重整制氢性能的影响。采用SEM、XRD、BET、H₂-TPR、N₂O滴定和XPS等手段对催化剂进行了表征。结果表明,CuO/CeO₂催化剂的催化活性与催化剂的Cu比表面积大小、Cu-Ce的相互作用强弱、表面缺陷和表面氧空位的多少有关。其中,在氢气气氛下焙烧所得的CeO₂负载CuO后的CuO/CeO₂-H催化剂催化活性最佳。在反应温度为250℃,水醇物质的量比为1.2时,甲醇气体空速为800 h^-1,甲醇转化率达到了100%,重整尾气中CO含量为0.87%。     

甲醇水蒸气重整制氢Cu/ZnO/Al2O3催化剂的研究

燃料电池作为一种无污染、高效率的能源引起世界各大汽车公司的广泛关注[1,2]。用于燃料电池的燃料目前研究较多的是氢气,用氢气作燃料存在储存、安全、运输等问题,寻求合适贮氢方法或替代燃料,实现车载制氢是解决问题的办法。甲醇作为液体燃料,因具有高能量密度,低碳含量,以及运输和贮存等优势成为车载制氢的理想燃料,甲醇水蒸气重整制氢反应也成为研究的热点[3～10]。车载制氢对甲醇水蒸气重整制氢反应体系中的产氢速率,氢气和CO的含量都有一定的要求。尤其对CO含量要求更为苛刻,因CO易引起燃料电池阳极催化剂中毒[11,12]。因此,开…     

镍基整体式催化剂上生物质粗燃气重整调变的特性研究

采用浸渍法制备了Ni基整体式催化剂,考察了不同条件(温度、时间、空速、水蒸气添加等)对催化剂上生物质粗燃气重整反应性能的影响。结果表明,催化剂在较低温度下(≤500 ℃)只具有CO加氢反应活性,随着反应温度的升高粗燃气重整反应逐渐进行,在800 ℃以上,CH₄和C₂转化率均高达95 %以上,CO₂转化率达到92%,但随着反应空速和水蒸气添加量的增加,CH₄和CO₂等转化率呈现缓慢降低的趋势。此外,通过改变水蒸气添加量可对合成气中H₂/CO体积比在0.85~4.00进行较好调节。结合XRD表征发现,Ni基整体式催化剂中Ni°的生成可较好地促进重整反应的进行。     

Ni/ZrO2催化剂上甲烷水蒸气重整反应的研究

研究了Ni/ZrO2催化剂对甲烷水蒸气重整制合成气的反应性能。考察了催化剂的还原温度、载体焙烧温度以及反应温度、原料配比和空速等对催化剂性能的影响。利用XRD、TEM、XPS等手段对催化剂的织构形貌进行了表征。研究表明，Ni/ZrO2催化剂用于甲烷水蒸气重整制合成气不仅具有较高的活性，也具有较好的稳定性。水蒸气比增加，CH4转化率增大、CO选择性下降。CH4转化率及CO选择性均随空速增大而下降。使用10%Ni/ZrO2催化剂，在650 ℃、空速1.984×104 h－1、原料气配比H2O∶CH4∶N2=2∶1∶2.67的条件下，获得CH4转化率85%、CO选择性70%的结果。     

ZrO2在Cu-ZnO-ZrO2甲醇水蒸汽重整制氢催化剂中的作用

通过对一系列Cu-ZnO-ZrO2甲醇水蒸汽重整(SRM)催化剂的XRD、TEM和BET表征及催化性能测定,研究催化剂中ZrO2对催化剂粒径、比表面以及对SRM反应性能的影响.结果表明,ZrO2的加入,使催化剂的粒径从15 nm降至10 nm（其中CuO和ZnO的平均粒径分别从7.7和10.4 nm降至3.9和8.7 nm）,BET比表面从60 m2•g－1增至78 m2•g－1.随着催化剂含ZrO2量不同,甲醇的转化率和H2、CO2的选择性均产生变化,当催化剂中Zr含量为24.0％(w),反应温度为220 ℃,水、醇摩尔比为1.3时,甲醇的转化率达到51.6％, H2和CO2的选择性达到100％(CO和CH4在产物气体中的体积分数小于10－4),这一结果对甲醇燃料电池甲醇重整器的应用具有重要的意义.     

Comparative theoretical study of formaldehyde decomposition on PdZn, Cu, and Pd surfaces

Methanol steam reforming, catalyzed by Pd/ZnO (PdZn alloy), is a potential source of hydrogen for on-board fuel cells. CO has been reported to be a minor side product of methanol decomposition that occurs in parallel to methanol steam reforming on PdZn catalysts. However, fuel cells currently used in vehicles are very sensitive to CO poisoning. To contribute to the understanding of pertinent reaction mechanisms, we employed density functional slab model calculations to study the decomposition of formaldehyde, a key intermediate in methanol decomposition and steam reforming reactions, on planar surfaces of Pd, Cu, and PdZn as well as on a stepped surface of PdZn. The calculated activation energies indicate that dehydrogenation of formaldehyde is favorable on Pd(111), but unfavorable on Cu(111) and PdZn(111). On the stepped PdZn(221) surface, the dehydrogenation process was calculated to be more competitive to formaldehyde desorption than on PdZn(111). Thus, we ascribe the experimentally observed small amount of CO, formed during steam reforming of methanol on the Pd/ZnO catalyst, to occur at metallic Pd species of the catalyst or at defect sites of PdZn alloy.     

甲烷自热重整制氢的热力学和动力学分析

对甲烷自热重整进行了系统的热力学分析,并采用预混合层流模型结合甲烷氧化、蒸汽重整、干重整机理对反应过程进行了动力学分析。结果表明,甲烷自热重整的平衡产物及其浓度主要受温度、O₂/CH₄、H₂O/CH₄的影响;压力影响不是十分明显,主要影响达到平衡的速度。在715℃~730℃、压力0.7MPa~1.0MPa,控制O₂/CH₄在0.60~0.70、H₂O/CH₄在3.15~3.25,可以得到H₂>68%、CO<10%的产物气,积炭率接近于0。动力学分析表明,自热重整过程分为两个主要阶段进行,在起始阶段主要发生甲烷氧化反应,产物主要为H₂O和CO₂;第二阶段以甲烷蒸汽重整反应为主,伴随水气变换反应（WGS）和微弱的干重整,H_2、CO和CO₂为主要产物。调节初始水浓度可以控制快速氧化阶段反应速率,避免“热点”出现,抑制CO的生成。     

甲烷三重整制合成气

甲烷三重整是利用CO₂-H₂O-O₂ 同时重整甲烷的过程。该工艺既可以生产H₂/CO 为1.5 —2.0的合成气,又可以缓解甚至消除催化剂的积炭,适合于更廉价地生产用于合成甲醇、二甲醚以及清洁燃料等下游产品的合成气。本文重点评述了近年来国内外甲烷三重整制合成气在热力学、催化剂、反应器、动力学等方面的研究进展,指出甲烷三重整反应在电厂烟气、煤层气、天然气综合利用方面具备良好前景,但要通过该过程实现廉价合成气的生产,仍需研制高活性、抗积炭性能强的催化剂,并对反应器进行改进,以及进行反应机理和反应动力学的深入研究。     

湿混法制备甲醇氧化重整制氢CuZnAlZr催化剂

用简易湿混法制备了用于甲醇氧化重整制氢的CuZnAlZr催化剂，与共沉淀法制备的催化剂比较，结果表明，湿混法制备的催化剂具有相当的中高温活性和略低的低温活性，有较高的CO2选择性。XRD、TPR、TG-DSC等表征结果显示，湿混法制备的催化剂中铜组分易于向表面迁移和富集，并可能与氧化铝作用生成铜铝复合氧化物，具有了更高的Cu分散度和Cu0比表面浓度。湿混法制备的催化剂对甲醇氧化重整反应有较好的稳定性，经100 h的连续反应，在275 ℃时甲醇转化率在90％以上，重整气中氢气体积分数大于60％，CO2选择性接近99％。     

前驱体和沉淀剂浓度对CuO/ZnO/CeO2-ZrO2甲醇水蒸气重整制氢催化剂性能的影响

采用共沉淀法制备了CuO/ZnO/CeO₂-ZrO₂甲醇水蒸气重整制氢催化剂,探讨了前驱体和沉淀剂浓度对催化剂性能的影响,并采用BET、XRD、H₂-TPR和XPS等手段对催化剂进行了表征。结果表明,前驱体和沉淀剂浓度对催化剂的结构和性能影响很大,当前驱体浓度为0.1mol/L,沉淀剂浓度为0.5mol/L时,所得催化剂CO选择性最小,催化活性最佳。在360h稳定实验中,甲醇最高转化率达100%,重整尾气中H₂含量保持在74.5%以上,CO含量低于0.8%,催化剂稳定性良好。     

微型平板式反应器中甲醇水蒸气重整制氢的研究

研制了一种高效平板式微型制氢反应器,将甲醇重整和催化燃烧集于一体,吸热、放热合理耦合,实现快速启动和制氢过程自热运行;在反应器中进行甲醇水蒸气重整实验,考察了反应器腔内的温度分布,以及温度、空速和水醇比对制氢过程的影响。结果表明,当温度为270℃,空速为870h-1,水醇比为1.3时,甲醇转化率最高为94.85%,重整气组成为74.53%H2、1.76%CO、23.71%CO2;累计运行400h,重整最大产氢量接近6000mL/h,可为便携式燃料电池提供稳定氢源。     

Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450 ℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800 ℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800 ℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.