载体对镍基催化剂CH4/CO2重整反应性能的影响

采用等体积浸渍法制备了Ni/BaTiO3、Ni/Al2O3和Ni/BaTiO3-Al2O3催化剂,对催化剂进行表征,并与催化剂活性相关联.发现与单一载体催化剂相比,具有适当比例组成的Ni/BaTiO3-Al2O3催化剂有更为优越的催化性能.结果表明Ni/BaTiO3-Al2O3催化剂有较大的比表面积;复合载体在制备过程中发生了反应,所生成的BaAl2O4可以阻止γ-Al2O3的相变并极大的提高了载体的热稳定性.     

钙钛矿型复合氧化物LaNiO_3的制备及其在CH_4/CO_2重整反应中的应用

采用溶胶-凝胶法制备钙钛矿型复合氧化物LaN iO3,采用XRD、TG-DTA作为表征手段,并且研究其在CH4/CO2重整反应中的应用。结果表明:经800℃焙烧,钙钛矿型复合氧化物的结构已经完全形成。在CH4/CO2重整反应中,H2/CO的比值总是小于1,这是因为存在逆水煤气反应。     

Ni/ZrO2/Al2O3催化剂在CO2重整CH4反应中催化性能研究

Ni/ZrO2/Al2O3催化剂在二氧化碳重整甲烷反应中,其催化活性和稳定性均优于Ni/ZrO2和Ni/Al2O3催化剂.XRD、TPD、TPR结果表明,在Ni/ZrO2/Al2O3催化剂上能形成较稳定的活性中心,负载型纳米ZrO2/Al2O3复合载体中,ZrO2以四方相形式出现,粒径为5 nm,微波和超声波的作用能诱导ZrO2和Al2O3产生新的碱性中心,有利于二氧化碳的吸附和提高活性组分的分散度.TG-DSC结果表明Ni/ZrO2/Al2O3催化剂上表面炭主要是活性较高的α炭,而Ni/ZrO2和Ni/Al2O3催化剂表面炭主要是活性较低的β炭和γ炭.     

MgO助剂对CH4/CO2重整反应Ni/BaTiO3催化剂性能的影响

采用分步浸渍法制备了MgO改性的Mg-Ni/BaTiO3催化剂,考察了MgO助剂对催化剂性能的影响,运用H2-TPR、XRD、BET等测试技术对催化剂进行表征,并与催化剂Ni/BaTiO3、Ni/γ-Al2O3比较。发现MgO的添加有利于提高催化剂的催化活性和抗积炭性能;适量的MgO助剂可以改善催化剂的性能,但过量的MgO却会对催化剂的性能产生不良影响,随着MgO含量的增加,反应活性基本呈下降趋势。同时研究了不同的制备方法对催化剂催化活性的影响,用溶胶-凝胶法制备的催化剂具有更高的催化活性。     

有机溶胶凝胶法制备Al2O3纳米粉及其机理研究

将异丙醇铝分散在有机溶剂中，水解合成超细Al2O3纳米粉。针对纳米粉形成团聚的直接原因，改善了传统工艺，用IR，SEM验证了其合理性，并用TEM对煅烧后的产品进行了表征。     

金刚石表面涂覆TiO2/Al2O3薄膜及性能

采用溶胶-凝胶法在金刚石磨料表面涂覆TiO2/Al2O3薄膜.通过环境扫描电子显微镜、能谱仪、Fourier变换红外光谱仪、X射线衍射、热重-差示扫描量热、金刚石抗压强度检测等方法,对涂膜后金刚石表面形貌、结构、抗氧化性能和抗压强度进行分析,同时研究了TiO2/Al2O3薄膜对陶瓷结合剂金刚石砂轮磨削性能的影响.结果表...     

CuO/Al2O3-ZrO2催化剂的制备与表征

以溶胶-凝胶加浸渍法制备了CuO/Al2O3-ZrO2催化剂,对催化剂结构与催化性能进行了表征。结果表明以Al2O3稳定的ZrO2做载体制得的CuO/Al2O3-ZrO2催化剂具有较好的NO转化性能和较低的反应温度。     

Ni/Al2O3催化剂对高纯HCl中微量CO2甲烷化反应的催化性能

用浸渍法制备了以Al₂O₃为载体、Ni为活性组分的Ni/Al₂O₃二氧化碳甲烷化催化剂,在等温固定床反应器中研究了在Ni/Al₂O₃催化剂作用下,高纯氯化氢中微量CO₂甲烷化反应效果,并考察了温度、压力、氯化氢体积空速以及H₂/CO₂摩尔比对CO₂转化率的影响,同时研究了催化剂活性、稳定性及其再生性能。结果表明,在温度为250℃、压力为4.0 MPa、氯化氢空速为100 h^-1、H₂/CO₂摩尔比为500:1条件下,CO₂甲烷化反应效果最好,其转化率可达到90%左右,对于高纯氯化氢中微量CO₂的脱除起到很好的效果;催化剂在温度高于300℃时,反应不久后会迅速失活;催化剂再生性能只能部分恢复到新鲜水平。     

溶胶-凝胶法制备Al2O3纳米粉

以Al(NO3) 3和NH3·H2 O为原料制备AlOOH勃姆石溶胶 ,加入PVA作为分散剂 ,干燥后制成干凝胶。干凝胶经不同温度下煅烧得到不同晶型的Al2 O3纳米粉。X—射线衍射分析结果表明 ,勃姆石干凝胶在煅烧过程中的物相变化为AlOOH→ε-Al2 O3→ -Al2 O3→δ -Al2 O3→θ -Al2 O3→α-Al2 O3,采用电子显微镜和BET比表面积法测量出Al2 O3纳米粉的颗粒大小     

Au/Fe2O3催化剂上CO选择氧化反应性能的研究

采用共沉淀法、沉积-沉淀法和浸渍法制备了1.5%Au/Fe2O3催化剂,考察了不同方法制备的Au/Fe2O3催化剂对富氢气体中CO选择氧化反应性能的影响。结果表明,浸渍法制得的催化剂在40℃~60℃时CO的转化率为100%;共沉淀法与沉积-沉淀法制得的催化剂在80℃以下CO的转化率均为100%;沉积-沉淀法制得的催化剂在100℃时CO的转化率依然高于95%。上述三种催化剂CO氧化反应的选择性均高于40%,且在CO完全转化时选择性在50%以上。     

Investigation of CH4 Reforming with CO2 on Meso-Porous Al2O3-Supported Ni Catalyst

Meso-porous Al₂O₃-supported Ni catalysts exhibited the highest activity, stability and excellent coke-resistance ability for CH₄ reforming with CO₂ among several oxide-supported Ni catalysts (meso-porous Al₂O₃ (Yas1-2, Yas3-8), -Al₂O₃, -Al₂O₃, SiO₂, MgO, La₂O₃, CeO₂ and ZrO₂). The properties of deposited carbons depended on the properties of the supports, and on the meso-porous Al₂O₃-supported Ni catalyst, only the intermediate carbon of the reforming reaction formed. XRD and H₂-TPR analysis found that mainly spinel NiAl₂O₄ formed in meso-porous Al₂O₃ and -Al₂O₃-supported catalysts, while only NiO was detected in -Al₂O₃, SiO₂, CeO₂, La₂O₃ and ZrO₂ supports. The strong interaction between Ni and meso-porous Al₂O₃ improved the dispersion of Ni, retarded its sintering and improved the activated adsorption of CO₂. The coking reaction via CH₄ temperature-programed decomposition indicated that meso-porous Al₂O₃-supported Ni catalysts were less active for carbon formation by CH₄ decomposition than Ni/-Al₂O₃ and Ni/-Al₂O₃.     

Ni-Cu-Mo/Al_2O_3催化剂用于CH_4/CO_2重整的研究

甲烷和二氧化碳重整制合成气是有效利用二氧化碳资源的重要途径,对于环境保护和综合利用资源具有重大意义。文章采用浸渍法制备一系列不同镍钼质量比的Ni-Cu-Mo/Al_2O_3催化剂,通过固定床反应器考察不同Ni/Mo质量比和反应温度对催化剂性能的影响,并采用XRD,BET,SEM,CO_2-TPD技术对催化剂进行了表征。结果表明:催化剂的最佳反应温度是800℃,Ni/Mo质量比为0.75的催化剂表现出最好的催化活性。在800℃,空速182 m L/(g·min)的反应条件下,CH_4、CO_2的转化率分别为97.7%,99.1%,CO,H2的选择性分别达到94.4%,92.1%。     

CO Adsorbed Infrared Spectroscopy Study of Ni/Al2O3 Catalyst for CO2 Reforming of Methane

CO adsorbed infrared spectroscopy study was conducted in this work in order to better understand the significantly improved anti-coke performance of Ni/Al₂O₃ catalyst obtained via argon glow discharge plasma treatment. The present study revealed a significant decrease of linear to bridge (L/B) adsorbed CO for glow discharge plasma treated Ni/Al₂O₃, compared to that for untreated Ni/Al₂O₃, indicating an enhancement of close packed plane concentration. This structure change leads to lower methane turnover frequency (TOF) and better balance of carbon formation-gasification, resulting in better anti-coke property of Ni/Al₂O₃ for CO₂ reforming of methane.     

A Novel Catalyst Pt/CoAl2O4/Al2O3 for Combination CO2 Reforming and Partial Oxidation of CH4

Pt/CoAl₂O₄/Al₂O₃, Pt/CoO_x/Al₂O₃, CoAl₂O₄/Al₂O₃ and CoO_x/Al₂O₃ catalysts were studied for combination CO₂ reforming and partial oxidation of CH₄. The results indicate that Pt/CoAl₂O₄/Al₂O₃ is the most effective, and XRD results indicate that Pt species are well dispersed over the Pt/CoAl₂O₄/Al₂O₃. High dispersion is related to the presence of CoAl₂O₄, formed during calcining at high temperature before Pt addition. In the presence of Pt, CoAl₂O₄ in the catalyst could be reduced partially at 973 K. Based on these results, it appears that zerovalent platinum with high dispersion and zerovalent cobalt resulting from CoAl₂O₄ reduction are responsible for high activity in the Pt/CoAl₂O₄/Al₂O₃ catalyst.     

Catalyst Design of Pt-Modified Ni/Al2O3 Catalyst with Flat Temperature Profile in Methane Reforming with CO2 and O2

Pt(0.3)/Ni(10)/Al₂O₃, prepared by a sequential impregnation method, exhibited a more excellent performance in methane reforming with CO₂ and O₂ in terms of the catalytic activity and the temperature profile of the catalyst bed than Pt(0.3) + Ni(10)/Al₂O₃ prepared by a coimpregnation method, Ni(10)/Al₂O₃, Pt(0.3)/Al₂O₃, and Pt(10)/Al₂O₃. It is thought that this is because the surface Pt atoms on Ni catalyst can contribute to the enhancement of the catalyst reducibility.     

Kinetic Study of CO2 Reforming of Propane over Ru/Al2O3

The rate of reaction of propane over a Ru/Al₂O₃ catalyst was determined as a function of the partial pressures of the reactants, C₃H₈ and CO₂ at 600 and 650°C. The order of the reaction was found to be fractional with respect to carbon dioxide, indicating its involvement in the rate-determining step of the reaction. The order of the reaction was zero in propane indicating the fast reaction of propane over the catalyst. The apparent activation energies for propane and the formation of hydrogen and carbon monoxide were investigated. Values for the formation of hydrogen and carbon monoxide indicated a decrease in the CO:H₂ ratio with an increase in temperature. Modelling of the kinetic data was inconclusive in the selection of a possible mechanism as good fits were observed for a Langmuir–Hinshelwood and a Mars–van Krevelen mechanism.     

Isotopic Studies on the Mechanism of Partial Oxidation of CH4 to Syngas over a Ni/Al2O3 Catalyst

Silica-supported PdZn catalysts have been studied in CO and CO₂ hydrogenation and in ethylene hydroformylation. The dilution of surface Pd by Zn lowers the hydrogenating capability of the catalysts and favours the production of higher hydrocarbons in CO hydrogenation. The catalyst with a molar ratio Pd:Zn = 3 showed an enhanced ability to insert CO into an M–alkyl bond; this catalyst produced higher oxygenates in the CO hydrogenation and was the most active in all reactions studied.     

Methane Steam Reforming Kinetics on a Ni/Mg/K/Al2O3 Catalyst

The kinetics of methane steam reforming were studied on a Ni/Mg/K/Al₂O₃ catalyst that was developed for conditioning of biomass-derived syngas. Reactions were conducted in a packed-bed reactor while the concentrations of reactants (methane and steam) and products (hydrogen, carbon monoxide, and carbon dioxide) were varied at atmospheric pressure, with the effects of temperature (525–700 °C) and residence time also being investigated. A power law rate model was developed using nonlinear regression to provide a predictive capability for the rate of methane conversion over this catalyst, to be used for reactor design and technoeconomic analysis of process designs. In order to provide some mechanistic insight, and to compare this catalyst to other non-promoted Ni/Al₂O₃ catalysts reported in the literature, a reaction mechanism consisting of five elementary steps, using a Langmuir–Hinshelwood type approach, was also considered. These five steps included: (i) CH₄ adsorption, (ii) H₂O adsorption, (iii) surface reaction of adsorbed CH₄ and H₂O to form CO and H₂, (iv) CO desorption, and (v) H₂ desorption. Nonlinear regression was then used to fit each of the rate laws to the experimental data. From these results, the model that assumed CH₄ adsorption to be the rate determining step provided the best fit of the experimental data. This finding is consistent with literature studies on non-promoted Ni/Al₂O₃ catalysts, in which methane adsorption has been proposed to be the rate determining step during catalytic methane steam reforming. Both the power rate laws and the rate law assuming CH₄ adsorption to be the rate determining step can be used as predictive tools for determining methane conversion for a given set of process conditions. Additionally, a rate expression that assumed the rate was only a function of methane partial pressure was considered, namely, $rate = k*P_{{CH_{4} }}$ rate = k ? P CH 4 , where $k = k_{0} *e^{{^{{ - {\text{Ea}}/{\text{RT}}}} }}$ k = k 0 ? e ? Ea / RT , with P_CH4 in units of Torr. This first-order-methane rate expression fit the data well, yielding an apparent activation energy over this catalyst of E_a = 93 kJ/mol and the pre-exponential rate constant of k₀ = 7.67 × 10⁵ mol/(g-cat s Torr CH₄).     

CH4/CD4 isotope effect on the reaction of adsorbed hydrocarbon species in CO2-reforming over Ni/Al2O3 catalyst

By replacing CH₄ with CD₄, the isotope effect on the reaction of adsorbed hydrocarbon species with CO₂ over Ni/Al₂O₃ catalyst was studied using pulse surface reaction rate analysis (PSRA). The first-order rate constant for this step was 1.45 times larger for CH₄ than for CD₄. The observed isotope effect suggests that the reaction of adsorbed hydrocarbon species with CO₂ (or adsorbed oxygen) is rate-controlling for the reforming of CH₄.