铂基催化剂快速部分催化氧化甲烷的研究

以Al2O3为载体,采用浸渍法制备Pt/Al2O3催化剂,通过测量重整反应过程中催化剂的温度分布情况,研究了改变甲烷快速部分氧化重整反应中反应条件(反应气体预混合温度、N2体积比例、CH4/O2比)对反应物的转化率及产物选择性的影响。研究发现,催化剂床层温度的上升可以促进CH4的转化,使H2和CO的选择性升高且H2与CO的物质的量的比(简称H2/CO比,依此类推)升高。N2体积比例及CH4/O2比的升高,会降低催化剂床层温度,进一步造成CH4的转化率和H2/CO比降低,但与仅降低混合气预热温度不同的是,提高N2体积比例及CH4/O2比会造成H2和CO的选择性升高,这可能是催化剂表面的活性氧导致的。通过对甲烷在Pt催化剂上的反应机理进行了初步讨论,认为甲烷的快速部分催化氧化反应为多种反应路径共存,不同的反应条件下各种反应路径所占比例会发生变化。     

La2O3改进Ni/γ-Al2O3催化剂上沼气重整制氢

为了寻求制备氢气的可再生资源及减少沼气的排放量,用浸渍法制备了不同La2O3含量的Ni/La2O3/γ Al2O3催化剂,用CH4/CO2体积比为1的混合气体模拟沼气,考察了还原温度、反应温度、空速等操作条件对该催化剂上沼气重整制氢性能的影响.并运用H2-TPR、TEM、TG-DSC等对催化剂进行了表征.结果表明:La2O3含量为6%的催化剂具有较好的综合性能;载体中掺杂适量La2O3能增加金属Ni的分散性,提高催化剂的可还原性及载体对CO2的吸附能力,从而改善了催化剂的活性及抗积炭性,使催化剂具有较好的稳定性.在100h的稳定性实验中,CH4及CO2转化率、H2及CO的选择性、H2/CO比平均值分别约为87.4%、88.8%、87.3%、93.8%及0.92.催化剂表面积炭速率非常低,仅为0.7279mg/(gcat·h).     

Fe-Ag/La_2O_3-ZrO_2催化乙醇水蒸气重整制氢

用草酸盐沉淀法制备La2O3-ZrO2复合氧化物载体,用浸渍法制备Fe-Ag/La2O3-ZrO2催化剂;用X射线衍射技术表征催化剂;考察了催化剂在乙醇水蒸气重整反应中的催化活性。结果表明,La含量较低的La2O3-ZrO2复合载体具有明显的四方晶相结构;Fe-Ag/La2O3-ZrO2催化剂在乙醇水蒸气重整反应中表现出良好的催化性能,气相产物中H2物质的量分数很高,CO和CH4物质的量分数很低;La,Ag,Fe含量影响催化剂的活性及选择性。在以(1Ag20Fe)20(2La8Zr)为催化剂,反应温度为823 K、乙醇与水物质的量比为1∶6,乙醇水溶液流速为0.1 mL/min的反应条件下,乙醇转化率达到95.7%,气相产物中H2物质的量分数为78.7%、CO的物质的量分数小于1.2%。     

甲烷快速部分氧化重整试验研究

采用常规浸渍法制备了Rh/α-Al2O3催化剂,建立了甲烷快速部分氧化重整试验体系。通过控制变量法,考察了甲烷快速部分氧化重整反应中反应条件参数(CH4/O2、反应气体预混合温度、空速)变化对反应物的转化率、反应产物及分布的影响。试验结果表明,在试验条件下,CH4的转化率始终大于85%,O2转化率接近100%,CO的选择性为85%左右,H2的选择性为40%～60%。反应过程大致为催化剂入口处的部分氧化反应和下游的水蒸气重整,大部分的CO由部分氧化产生,而H2的产生受水蒸气重整反应的影响较大;随着反应温度的上升,CH4的转化率上升,CO,H2的选择性也上升;随着空速的增大,H2的选择性减小,表明甲烷催化部分氧化反应是一个受传质控制的反应。     

生物柴油催化剂—CaO/ZnO固体碱的制备和表征

用浸渍法制备(CH3COO)2Ca/Zn O,再高温焙烧制得Ca O/Zn O催化剂。利用正交试验得到的制备Ca O/Zn O的优化条件为:浸渍液质量分数0.25、焙烧温度1023 K、焙烧时间2 h。在醇/油物质的量之比9∶1、催化剂用量4%(催化剂/油质量比)、反应温度338 K、反应时间5 h的条件下,蓖麻油转化率平均可达98.5%。采用Hammett指示剂法、TG-DTG、XRD及SEM对(CH3COO)2Ca/Zn O及Ca O/Zn O进行表征。结果表明:Ca O/Zn O碱强度(H-)在7.2~11.2之间,(CH3COO)2Ca/Zn O有两个明显的失重峰;Ca O/Zn O的骨架结构为Zn O晶体,Ca O在Zn O表面呈无定形高度分散状态;Ca O/Zn O催化剂呈不规则微米级孔状结构。     

Ni、Fe负载CaO催化剂作用下生物油模化物水蒸气催化重整制氢研究

采用浸渍法制备Ni/CaO、Fe/CaO、Ni-Fe/CaO催化剂,用于生物油模化物乙酸水蒸气催化重整反应.对反应前后催化剂进行BET、H2-TPR、CO2-TPD、XRD等表征.通过比较3种催化剂重整反应性能得出Ni/CaO催化剂具有最佳性能.进一步研究在Ni/CaO催化剂参与下反应温度、水碳比(S/C)、液时空速(...     

甲烷化学链重整制备合成气技术中的钙钛矿型载氧体制备及动力学特性

采用燃烧法、微乳液法、共沉淀法和溶胶-凝胶法4种方法制备钙钛矿型氧化物La Fe O3作为载氧体用于甲烷化学链重整制备合成气过程,利用X射线衍射(XRD)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、比表面积分析(BET)等技术对载氧体进行表征,在固定床反应装置上考察4种方法制备的La Fe O3与甲烷的反应性能,寻求适用于甲烷化学链重整过程载氧体的最佳制备方法,然后通过H2-TPR的多速率升温过程探讨La Fe O3的还原动力学。结果表明,4种方法制备得到的载氧体均形成钙钛矿结构,溶胶-凝胶法和燃烧法制备的La Fe O3纯度和结晶度均更好,无杂相生成;从CH4转化率、n(H2)/n(CO)、CO和H2选择性等方面综合考虑,燃烧法制备得到的载氧体反应性能最好,用于甲烷化学链重整制备合成气的生成效果最好。H2-TPR的动力学计算表明,La Fe O3载氧体的低温吸附氧还原活化能为97.001 k J/mol,高温晶格氧还原活化能为30.388 k J/mol。     

高活性Ni-Mo2C/ZrO2催化剂干重整甲烷制合成气

用浸渍法结合程序升温碳化法制备1Ni-5Mo_2C/ZrO_2与Mo_2C/ZrO_2,作为CH4和CO_2干重整制合成气反应催化剂。采用X射线衍射(XRD)、BET比表面积(BET)、X显微镜(TEM)对催化剂的结构进行表征,在常压固定床反应器上测试1Ni-5Mo_2C/ZrO_2与Mo_2C/ZrO_2催化剂在900℃时(空速为8000 cm~3·g~(-1)cat·h~(-1))重整CH4/CO_2(CH4∶CO_2=1∶1)的催化活性。研究表明,在甲烷干重整(DRM)反应中,催化剂的催化活性在7 h内保持稳定。由于1Ni-5Mo_2C/ZrO_2催化剂具有合适的孔径,丰富的表面孔以及Ni基载体之间的相互作用,CH_4和CO_2的转化率均达96%以上,H_2和CO现出高催化活性、产率,兼具优良的稳定性能。     

Ni-Co双金属催化剂上沼气重整制氢宏观动力学

用传统湿式浸渍法制备La2O3掺杂的商业γ-Al2O3负载的沼气重整催化剂Ni-Co/La2O3-γ-Al2O3,通过对NiCo双金属催化剂上沼气重整制氢在常压下的宏观动力学分析,得出该催化剂上CH4与CO2消耗、H2与CO生成时的表观反应速率方程.通过改变进料中CH4与CO2的分压,求出各物质的反应分级数,确定总反应...     

乙酸水蒸气重整制氢中载体组成对催化剂性能的影响

采用溶胶–凝胶法结合湿浸渍法制备了Ni/ZrO2、Ni/La2O3-ZrO2和Ni/La2O3催化剂,采用XRD、BET、TG及 H2-TPR等方法对催化剂的结构和性质进行了表征。通过生物油模型物乙酸水蒸气重整反应,探讨了载体组成对催化剂性能和积炭形成的影响。载体组分不同的Ni催化剂具有不同的Ni颗粒尺寸、孔结构和Ni–载体相互作用,这对乙酸水蒸气重整反应路径有重要影响。催化剂Ni/70wt%La2O3-ZrO2在乙酸水蒸重整反应中表现出较好的催化性能和稳定性,在反应时间10 h内,氢气产率保持在76.05%以上;同时,TG和XRD分析结果表明,Ni/70wt%La2O3-ZrO2具有较好的抗烧结能力和较低的积炭率。     

木屑炭水蒸气催化气化制取合成气研究

以木屑炭为原料,K2CO3作为催化剂,以固定床气化炉为实验设备,进行水蒸气催化气化木屑炭的探究。考察木屑炭水蒸气气化的炭转化率、产氢率、气体组成体积分数和H2/CO比值随K2CO3催化剂质量分数(0~8%)、水蒸气流量(0.15~0.35 g/(min·g))、气化温度(800~950℃)变化的规律。实验结果表明:K2CO3催化剂可显著提升碳转化率及产氢率,K2CO3质量分数为8%时,碳转化率和产氢率分别达到86.3%和125.6 g/kg,同时合成气中CO体积分数显著增加,H2/CO比值降至2.43。增加水蒸气流量,合成气中H2含量显著增大,H2/CO比值随之增大。温度可有效促进炭气化过程,950℃时碳转化率和产氢率分别达到84.3%和127.1 g/kg,但合成气中CO体积分数增大,H2/CO比值降至2.48。实验得到H2/CO比值在2.43~5.16范围的合成气。气化反应温度在900℃、水蒸气0.2 g/(min·g)、K2CO3质量分数3%时,碳转化率可达80.4%,产氢率109.6 g/kg,合成气中(H2+CO)体积分数82.4%,同时H2/CO比值高达3.05。     

基于活性炭的微波辐射CO_2重整CH_4的研究

以木质活性炭为催化剂,在微波加热实验台上进行了CO2重整CH4的实验研究,考察了活性炭的升温特性,比较了CH4裂解、CH4/CO2重整和CO2气化反应中反应气转化率,分析了反应温度、CH4与CO2物质的量比值和空气流速对重整反应的影响,测试了活性炭的催化活性.结果表明,微波辐射下活性炭床层温度迅速升高;重整反应中CH4转化率高于裂解反应,而CO2转化率低于气化反应;提高反应温度、减小CH4与CO2物质的量比值和降低空气流速均利于提高CH4和CO2转化率,同时降低合成气中H2与CO物质的量比值;初始阶段活性炭表现出较好的催化活性,40 min后活性炭迅速失活.     

The influence of CO,CO2 and H2O on selective CO methanation over Ni(Cl)/CeO2 catalyst: On the way to formic acid derived CO-free hydrogen

For the first time the influence of CO, CO₂ and H₂O content on the performance of chlorinated NiCeO₂ catalyst in selective or preferential CO methanation was studied systematically. It was shown that the rate of CO methanation over Ni(Cl)/CeO₂ increases with the increasing H₂ concentration, is independent of CO₂ concentration and decreases with increasing CO and H₂O concentrations; the rate of CO₂ methanation is weakly sensitive to H₂ and CO₂ concentrations and decreases with increasing CO and H₂O concentrations. High catalyst selectivity was attributed to Ni surface blockage by strongly adsorbed CO molecules and ceria surface blockage by Cl, which both inhibit CO₂ hydrogenation.For the first time, selective CO methanation over Ni(Cl)/CeO₂ was studied for deep CO removal from formic acid derived hydrogen-rich gases characterized by high CO₂ (40–50 vol%), low CO (30–1000 ppm) content and trace amounts of water. Composite Ni(Cl)/CeO₂-η-Al₂O₃/FeCrAl wire mesh catalyst was demonstrated to be effective for this process at temperatures of 180–220°С, selectivity 30–70%, WHSV up to 200 L (STP)/(g∙h). The catalyst provides high process productivity, low pressure drop, uniform temperature distribution, and appears highly promising for the development of a compact CO cleanup reactor. Selective CO methanation was concluded to be a convenient way to CO-free hydrogen produced by formic acid decomposition.     

W-doped ordered mesoporous Ni–Al2O3 catalyst for methanation of carbon monoxide

In order to simultaneously inhibit the Ni sintering and coke formation as well as investigate the effects of WO₃ promoter on catalytic performance, the ordered mesoporous Ni–WO₃/Al₂O₃ catalysts were synthesized by a facile one-pot evaporation-induced self-assembly method for CO methanation reaction to produce synthetic natural gas. Addition of WO₃ species could significantly promote the catalytic activity due to the enhancement of the Ni reducibility and the increase of active centers, and the optimal N10W5/OMA catalyst with NiO of 10 wt% and WO₃ of 5 wt% achieved the maximum CH₄ yield 80% at 425 °C, 0.1 MPa and a weight hourly space velocity of 60000 mL g⁻¹ h⁻¹. Besides, the reference catalyst N10W5/OMA-Im prepared by the conventional co-impregnation method was also evaluated. Compared with N10W5/OMA, N10W5/OMA-Im showed lower catalytic activity due to the partial block of channels by Ni and WO₃ nanoparticles, which reduced active centers and restrict the mass transfer during the reaction. In addition, the N10W5/OMA catalyst showed superior anti-sintering and anti-coking properties in a 425^oC-100 h-lifetime test, mainly because of confinement effect of ordered mesoporous structure to anchor the Ni particle in the alumina matrix.     

Synthesis of nanocrystalline mesoporous Ni/Al2O3SiO2 catalysts for CO2 methanation reaction

A series of nanocrystalline mesoporous Ni/Al₂O₃SiO₂ catalysts with various SiO₂/Al₂O₃ molar ratios were prepared by the sol-gel method for the carbon dioxide methanation reaction. The synthesized catalysts were evaluated in terms of catalytic performance and stability. The catalysts were studied using XRD, BET, TPR and SEM. The BET results indicated that the specific surface area of the samples with composite oxide support changed from 254 to 163.3 m²/g, and an increase in the nickel crystallite size from 3.53 to 5.14 nm with an increment of Si/Al molar ratio was visible. The TPR results showed a shift towards lower temperatures, indicating a better reducibility and easier reduction of the nickel oxide phase into the nickel metallic phase. Furthermore, the catalyst with SiO₂/Al₂O₃ molar ratio of 0.5 was selected as the optimal catalyst, which showed 82.38% CO₂ conversion and 98.19% CH₄ selectivity at 350 °C, high stability, and resistivity toward sintering. Eventually, the optimal operation conditions were specified by investigating the effect of H₂/CO₂ molar ratio and gas hourly space velocity (GHSV) on the catalytic behavior of the denoted catalyst.     

The Ni/ZrO2 catalyst and the methanation of CO and CO2

The Ni/ZrO₂ catalyst is one of the most active systems for the methanation of CO to be employed in the hydrogen purification for PEMFC. This contribution aims to study the effect of ZrO₂ on the methanation of CO and CO₂. The catalytic behavior of Ni/ZrO₂, Ni/SiO₂, a physical mixture comprising Ni and ZrO_2, and a double-bed reactor were evaluated. The TPD of CO and CO₂, TPSR and the cyclohexane dehydrogenation reaction were carried out to describe the catalysts and the reactions. The high activity of Ni/ZrO₂ catalyst toward the methanation of CO is related to the presence of active sites on the ZrO₂ surface. The methanation of CO occurs on ZrO₂ due to its ability to adsorb CO and also because of the hydrogen spillover phenomenon. Apparently, the effect of ZrO₂ is less relevant for the methanation of CO₂. Ni/ZrO₂ is a very promising system for the purification of hydrogen.     

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al₂O₃ preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al₂O₃ also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiCl_x/CeO₂ methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiCl_x/CeO₂ methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al₂O₃ methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.     

Nickel‒cobalt bimetallic catalysts prepared from hydrotalcite-like compounds for dry reforming of methane

Ni–Co/Mg(Al)O alloy catalysts with different Co/Ni molar ratios have been prepared from Ni- and Co-substituted Mg–Al hydrotalcite-like compounds (HTlcs) as precursors and tested for dry reforming of methane. The XRD characterization shows that Ni–Co–Mg–Al HTlcs are decomposed by calcination into Mg(Ni,Co,Al)O solid solution, and by reduction finely dispersed alloy particles are formed. H₂-TPR indicates a strong interaction between nickel/cobalt oxides and magnesia, and the presence of cobalt in Mg(Ni,Co,Al)O enhances the metal-support interaction. STEM-EDX analysis reveals that nickel and cobalt cations are homogeneously distributed in the HTlcs precursor and in the derived solid solution, and by reduction the resulting Ni–Co alloy particles are composition-uniform. The Ni–Co/Mg(Al)O alloy catalysts exhibit relatively high activity and stability at severe conditions, i.e., a medium temperature of 600 °C and a high space velocity of 120000 mL g^?1 h^?1. In comparison to monometallic Ni catalyst, Ni–Co alloying effectively inhibits methane decomposition and coke deposition, leading to a marked enhancement of catalytic stability. From CO₂-TPD and TPSR, it is suggested that alloying Ni with Co favors the CO₂ adsorption/activation and promotes the elimination of carbon species, thus improving the coke resistance. Furthermore, a high and stable activity with low coking is demonstrated at 750 °C. The hydrotalcite-derived Ni–Co/Mg(Al)O catalysts show better catalytic performance than many of the reported Ni–Co catalysts, which can be attributed to the formation of Ni–Co alloy with uniform composition, proper size, and strong metal-support interaction as well as the presence of basic Mg(Al)O as support.