焙烧温度对Ni/CaO-Al2O3结构及其催化重整性能的影响

采用共沉淀法制备了一系列具有类水滑石结构前驱体的Ni/CaO-Al₂O₃复合催化剂，考察了制备过程中焙烧温度对复合催化剂结构及性能的影响。结果表明，焙烧温度可调控活性组分Ni与载体之间的相互作用力，进而调变复合催化剂的比表面积、活性组分Ni的颗粒粒径。当焙烧温度为700 ℃时，Ni与载体之间相互作用力适宜，复合催化剂具有最大的比表面积（21.42 m²/g）和最小的Ni颗粒粒径（19.51 nm）；该复合催化剂在CO₂吸附强化CH₄/H₂O重整制氢过程中可得到98.31%的H₂浓度和94.87%的CH₄转化率，循环10次后，H₂浓度仍能保持在97.35%以上。这是因为大的比表面积为反应提供了更多的活性位点，利于CO₂吸附过程的强化，而小的Ni颗粒粒径提高了复合催化剂的抗烧结能力。     

Carbon dioxide reforming of methane over Ni/Mo/SBA-15-La2O3 catalyst: Its characterization and catalytic performance

The Ni/Mo/SBA-15 catalyst was modified by La2O3 in order to improve its thermal stability and carbon deposition resistance during the CO2 reforming of methane to syngas. The catalytic performance, thermal stability, structure, dispersion of nickel and carbon deposition of the modified and unmodified catalysts were comparatively investigated by many characterization techniques such as N2 adsorption, H2-TPR, CO2-TPD, XRD, FT-IR and SEM. It was found that the major role of La2O3 additive was to improve the pore structure and inhibit carbon deposition on the catalyst surface. The La2O3 modified Ni/Mo/SBA-15 catalyst possessed a mesoporous structure and high surface area. The high surface area of the La2O3 modified catalysts resulted in strong interaction between Ni and Mo-La, which improved the dispersion of Ni, and retarded the sintering of Ni during the CO2 reforming process. The reaction evaluation results also showed that the La2O3 modified Ni/Mo/SBA-15 catalysts exhibited high stability.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

Glucose Isomerization into Fructose Catalyzed by MgO/NaY Catalyst

The MgO/NaY catalysts prepared by impregnation method were used for the conversion of glucose to fructose in water medium.The effects of MgO loading, reaction temperature, glucose concentration and reaction time on the catalytic performance for the reaction were studied.The activity testing results indicated that fructose could be generated effectively by controlling the components of the catalyst and reaction conditions.The maximal fructose yield of 33.8% with the selectivity of 67.3% was achieved over the 10% MgO/NaY catalyst at 100 ℃ for 2 h.Moreover, the catalysts were characterized by XRD, BET, and CO₂-TPD techniques.The structural property of NaY with higher surface area facilitated glucose conversion, and the modulated basicity of the catalyst with MgO addition contributed to the formation of fructose in the tautomerization of aldose to ketose.     

Properties of anodic RuNiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(OH)<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> catalysts synthesized on carbon supports with various dispersion degree

A number of catalysts of the (Ru-Ni)/C system is synthesized and studied for application in anodes of alkaline ethanol-air fuel cells. The carbon supports used are carbon blacks with different specific surface area and graphite powders. The X-ray photoelectron spectroscopy technique allowed detecting on the catalyst surface metallic ruthenium and nickel in the form of Ni(OH)2 hydroxide and possibly oxyhydroxide NiOOH. It is shown that the catalyst activity in the reaction of ethanol electrochemical oxidation grows at an increase in the specific surface area of the carbon support. The method of carbon monoxide oxidative desorption was used to determine the values of the specific surface area of the catalyst metallic phase. It is shown that at an increase in the relative ruthenium content from (1Ru3Ni)/C to Ru/C, the specific catalytic activity in the catalysts of the (Ru-Ni)/C system reaches the maximum value near the composition of (2Ru1Ni)/C. It is shown that the found optimum catalyst composition is independent of the carbon support dispersion degree. Activity in ethanol electrooxidation of the (2Ru1Ni)/C catalyst supported on the Ketjenblack EC-600 carbon black is 18 ± 3 A/g of the catalyst (>120 A/g of Ru) at 40°C and potential E = 0.5 V in the 2MKOH + 1 M C₂H₅OH electrolyte.     

Effect of Calcined Temperature on Coke Deposition for Autothermal Reforming of Methane with Ni-Cu Catalyst

Ni/CuO-ZrO₂-CeO₂-Al₂O₃ catalysts were prepared by co-precipitation method at pH=9 and using Na₂CO₃ as the precipitant. The Ni loading (mass fraction) of the catalysts was 10%. The catalysts were characterized by X-ray diffraction, temperature-programmed oxidation (TPO), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The effects of calcined temperature of support on coke deposition were studied. TPO, SEM and XPS results indicated there was no peak of higher temperature oxygen consumption on Ni/CuO-ZrO₂-CeO₂-Al₂O₃catalyst (support was calcined at 800 ^oC), which could lead to the deactivation of the catalyst. The carbon species were carbonate and inactive carbon (filamentous carbon species) on the surface of catalyst reacting for 40 h which perhaps led to the deactivation of the catalyst.     

氮化SBA-16负载镍基催化剂的制备及其对甲烷二氧化碳重整反应的催化性能

通过软模板法合成了SBA-16分子筛,采用高温氨气氮化的方法使有序介孔硅材料中的氧原子部分被氮原子取代,得到氮化的SBA-16载体(SBA-16-N)。采用满孔浸渍法制备了镍基催化剂,并将制得的Ni/SBA-16和Ni/SBA-16-N催化剂用于甲烷二氧化碳重整反应。通过透射电镜、氮气物理吸附、X射线衍射、X射线光电子能谱和二氧化碳程序升温脱附等手段研究了载体和催化剂的结构,并利用热重分析对反应之后回收催化剂进行了表征。结果表明,高温氮化后的分子筛中掺入了氮元素,增加了载体的碱性,改善了载体对反应气体的吸附活化能力,增强了载体与金属之间的相互作用,从而提高了催化剂的活性和抗积炭性能。     

不同载体Ni基负载型催化剂对甲烷部分氧化制合成气催化行为研究

采用浸渍法制备了单一载体(Al₂O₃、ZrO₂、CeO₂)和ZrO₂、CeO₂改性的Al₂O₃复合载体的Ni催化剂,考察了在甲烷部分氧化制备合成气反应中的催化性能。通过N₂-物理吸附、H₂程序升温还原、X射线衍射、NH₃程序升温脱附和程序升温氧化等技术对催化剂进行了表征。结果表明,在单一载体催化剂中,Ni/Al₂O₃具有较大的比表面积,其初始反应活性较高,但该催化剂表面易形成大量的积炭而快速失活。Ni/ZrO₂和Ni/CeO₂催化剂比表面积较小,活性金属Ni在其表面分散性差,催化剂具有较低的CH₄转化率。而CeO₂和ZrO₂改性的Al₂O₃复合载体催化剂,具有较大的比表面积,反应活性明显高于单一载体催化剂。CeO₂-Al₂O₃复合载体催化剂具有最高的反应活性和较好的反应稳定性。同时表明,含CeO₂催化剂反应后表面积炭较少,CeO₂的储放氧功能增强了催化剂对O₂的活化,提高催化剂活性的同时,可以抑制积炭的生成。     

Development of Methane Decomposition Catalysts for CO<Subscript>x</Subscript> Free Hydrogen

Now-a-days, catalytic decomposition of methane (CDM) into hydrogen and carbon is a promising technique for production of fuel cell grade hydrogen. The Ni based catalysts seems promising particularly for the production of CO_x free H₂ by methane decomposition process. The CDM activity and longevity of the Ni based catalysts are mainly influenced by the amount of Ni and type of support material. In this paper the CDM activity results are correlated with NiO crystallite size, Ni metal surface area and acidity of the catalysts. In case of bimetallic catalysts addition of Cu to Ni catalysts lead to enhance the CDM activity at higher temperature thus resulting in the increased concentration of hydrogen in the outlet stream. Finally, some of the carbon-based catalysts are studied for methane decomposition activity at higher temperature. The surface changes over carbon catalysts with methane decomposition are studied using various characterization techniques.     

特定碱性MgO纳米晶暴露晶面上铁基催化剂及其费-托合成反应的研究

本研究采用等量浸渍法、化学沉淀法和超声浸渍法合成了一系列具有良好外露晶面的Fe/MgO催化剂。采用X射线粉末衍射、高分辨透射电子显微镜、CO₂程序升温脱附、H₂程序升温还原、X射线光谱学和N₂物理吸附等物理化学方法对催化剂进行了表征。MgO纳米晶载体的碱性会影响费-托合成产物的选择性。在超声浸渍过程中,MgO纳米晶载体的碱性得到了保持。研究结果显示,Fe/MgO催化剂的碱性会提高CO解离速率和产物中烯烃的选择性。此外,相比于MgO（100）晶面,MgO（111）晶面负载铁基催化剂具有更高的活性（TOF）和烯烃选择性。MgO（111）晶面上更有利于CO的吸附,抑制二次加氢反应,提高产物中烯烃的收率。     

Cu-Ni-Al尖晶石催化甲醇水蒸气重整制氢性能的研究

以氢氧化铜、醋酸镍和拟薄水铝石为原料,通过固相法合成了Cu-Ni-Al尖晶石催化剂。采用N2物理吸附、XRD、H2-TPR和XPS等表征方法,研究Cu/Ni/Al的物质的量比和焙烧温度对催化剂的比表面积、物相、还原性能以及表面性质的影响,并以甲醇水蒸气重整制氢为探针反应,考察催化剂的缓释催化性能。结果表明,随着焙烧温度的升高,Cu-Ni-Al催化剂的尖晶石含量增加,但尖晶石晶粒增大,且比表面积下降。不同的焙烧温度和Cu/Ni/Al物质的量比,所得催化剂的比表面积、还原性能和表面性质不同,从而表现出不同的缓释催化性能。与计量比Cu/Al=1∶2的合成比较,Cu/Al=1∶3形成了非计量比的富Al尖晶石固溶体,生成的晶体粒子小、比表面积和孔容大、难还原的尖晶石部分增多,呈现出更好的缓释催化性能。甲醇制氢反应性能评价结果显示,Cu-Ni-Al尖晶石在反应条件下逐渐释放活性铜而催化反应的进行,其中,CNA3-1000催化剂表现中最高的催化活性和稳定性。     

Ce含量对Ni-Ce/Al_2O_3催化剂结构及浆态床CO甲烷化性能的影响

以γ-Al2O3为载体,采用等体积浸渍法制备了不同Ce含量的Ni-Ce/Al2O3催化剂,并考察了其浆态床CO甲烷化反应性能。借助XRD、BET、H2-TPR及CO-TPD等对催化剂进行了表征分析,研究了催化剂的微观结构与甲烷化性能之间的关系。结果表明,助剂Ce的引入能够加强Ni物种与载体之间的相互作用、增强活性组分Ni对CO的吸附能力。随着Ce含量的升高,Ni物种在载体表面的分散度提高、Ni晶粒粒径减小,催化剂的比表面积及与载体相互作用较强的β-NiO相对含量先升后降。催化剂的浆态床甲烷化活性随Ce含量的升高呈现规律性的变化,CO转化率和CH4时空收率先增加后略有下降,当Ce含量为4%(质量分数)时,催化剂甲烷化活性最佳。     

Novel Flower‐Like Ag‐SiO2‐MgO‐Al2O3 Material: Preparation,Characterization and Catalytic Application in Methanol Dehydrogenation

Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag‐SiO₂‐MgO‐Al₂O₃ catalysts prepared by sol‐gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al₂O₃ and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X‐ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet‐visible spectroscopy (UV‐Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH₃‐TPD), desorption of CO₂ (CO₂‐TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag‐SiO₂‐ MgO‐Al₂O₃ catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side‐products is attributed to its unique flower‐like structure with a surface area less than 1 m²/g, and the strong interactions between neutralized support and the nano‐sized Ag particles as active centers.     

Promoting effect of group VI metals on Ni/MgO for catalytic growth of carbon nanotubes by ethylene chemical vapour deposition

The incorporation of 1 mass % of group VI metals (chromium, molybdenum, and tungsten) into 4 mass % of Ni/MgO catalysts was evaluated for the synthesis of carbon nanotubes (CNTs) by the catalytic chemical vapour deposition of ethylene. All materials were characterised by XRD, surface area, TEM, SEM, Raman spectroscopy, and TGA-DTA. The resulting data demonstrated that the addition of group VI metals improved the surface area and metal dispersion, thereby achieving a remarkable enhancement in catalytic growth activity. Among the metals of group VI, Mo was found to be the most effective promoter for catalysing the CNTs’ growth. From TEM observation, long CNTs with a higher degree of graphitization were obtained on the Ni-Mo/MgO catalyst. TGA and DTA analysis showed that the as-grown CNTs over both Ni-Mo and Ni-W/MgO catalysts exhibited higher thermal stability.     

双金属NiCu/MgO催化剂上葡萄糖氢解制备高附加值C2-C4化学品

采用共沉淀法制备了不同 Ni ／Cu 比的 NiCu／MgO 双金属催化剂,并通过 N2物理吸附、X 射线衍射（XRD）、X 射线光电子能谱（XPS）和程序升温还原等方法对 NiCu／MgO 催化剂结构进行表征。表征结果表明,Cu 和 Ni 之间存在协同相互作用,NiMgO2的存在抑制了镍物种的还原和 Cu-Ni 合金的形成,催化剂的 Ni ／Cu 比和焙烧温度对其表面金属组成有非常重要的影响。以葡萄糖氢解反应为探针反应,考察了 Ni ／Cu 比、焙烧温度、H2压力、反应温度、反应时间等因素对 NiCu／MgO 催化性能的影响。研究表明相对于单金属催化剂,双金属催化剂对葡萄糖氢解生成 C2-C4和1,2-PD 具有较高的催化活性,这与铜镍之间的协同作用有关。     

Production of Hydrogen from Methane by a CO2 Emission-Suppressed Process: Methane Decomposition and Gasification of Carbon Nanofibers

Catalytic methane decomposition into hydrogen and carbon nanofibers and the oxidations of carbon nanofibers with CO₂, H₂O and O₂ were overviewed. Supported Ni catalysts (Ni/SiO₂, Ni/TiO₂ and Ni/carbon nanofiber) were effective for the methane decomposition. The activity and life of the supported Ni catalysts for methane decomposition strongly depended on the particle size of Ni metal on the catalysts. The modification of the catalysts with Pd enhanced the catalytic activity and life for methane decomposition. In particular, the supported Ni catalysts modified with Pd showed high turnover number of hydrogen formation at temperatures higher than 973 K with a high one-pass methane conversion (>70%). However, sooner or later, every catalyst completely lost their catalytic activities due to the carbon layer formation on active metal surfaces. In order to utilize a large quantity of the carbon nanofibers formed during methane decomposition as a chemical feedstock or a powdered fuel for heat generation, they were oxidized with CO₂, H₂O and O₂ into CO, synthesis gas and CO₂, respectively. In every case, the conversion of carbon was greater than 95%. These oxidations of carbon nanofibers recovered or enhanced the initial activities of the supported Ni catalysts for methane decomposition.     

助剂铬对Ni/MgO催化剂CVD法制备碳纳米管的促进作用

采用溶胶-凝胶法制备了助剂Cr改性的Ni/MgO催化剂, 用化学气相沉积(CVD)法在600 ℃下裂解甲烷生长碳纳米管, 研究了助剂Cr的引入对催化剂微结构和制备碳纳米管性能的影响. 催化剂样品用XRD, TPR和CO-TPD进行了分析, 制备的碳纳米管用TEM和XRD进行了表征. 实验结果表明, NiO和MgO之间存在着强相互作用而形成固溶体, Ni/MgO催化剂经氢气处理后其中的镍氧化物只有极少部分被还原成为镍. 助剂铬的引入明显促进了镍的还原, 使得催化剂表面的Ni活性中心数增多, 从而使催化剂的活性和性能得到了明显的改进. 在加入助剂后碳纳米管的产率明显增加, 当Cr质量分数为8%时, 碳纳米管的产量为未加助剂时产量的5倍, 碳纳米管和催化剂的质量比达到1928. 当Cr含量进一步增加时, Ni在催剂表面聚集形成大颗粒, 制备出的产品中含有大量的碳纳米纤维和无定形碳. 以8%Cr-Ni/MgO催化剂合成的碳纳米管具有比较高的产率且质量较好.     

镁铝混合氧化物负载镍催化剂上液化石油气的预重整

采用共沉淀-浸渍法并在较低温度(400～700℃)下焙烧制备了镁铝混合氧化物(MgmAl)负载的Ni催化剂.X射线衍射和程序升温还原结果表明,Ni物种高度分散于催化剂表面,没有形成尖晶石NiAl2O4.在650℃可被还原成金属Ni纳米晶粒,在400℃和较低水/碳摩尔比(S/C=2)条件下表现出较好的催化液化石油气(LP...     

MgO助剂对甲烷部分氧化Ni/Al2O3催化剂结构和性能的影响

采用分步浸渍法制备了MgO改性的Ni/Al2O3催化剂，采用BET、XRD、H2 TPR、TEM和活性评价等研究方法，考察了MgO助剂对Ni/Al2O3催化剂物化性质和甲烷部分氧化制合成气反应性能的影响。实验结果表明，MgO助剂提高了催化剂镍物种的均一性，抑制了NiAl2O4尖晶石的形成，并且增强了镍物种与载体的相互作用，这与MgO、NiO形成固溶体及与Al2O3形成MgAl2O4有关。同时，适量的MgO助剂可以提高Ni物种在催化剂中分散度，并提高其有效利用率，改性后的催化剂在甲烷部分氧化反应中显示出较好的反应性能。过量的MgO助剂对催化剂的反应性能产生负面影响，MgO的碱性可以促进逆水煤气变换反应，从而导致H2选择性降低和CO选择性提高。     

镍基钙钛矿型催化剂的结构调控及其在甲烷干重整反应中的应用

钙钛矿材料在催化领域具有广泛的应用,其微观结构的调控对催化性能有显著的影响.我们采用柠檬酸配合法、溶胶凝胶法、燃烧法和浸渍法一系列不同的制备过程对镍基钙钛矿材料的结构进行调控,并将其应用于甲烷干重整反应,研究了制备方法对活性组分Ni的化学形态、Ni与基底的相互作用以及活性氧物种的调控,进而影响其催化活性和抗积碳能力.结果表明,燃烧法可以显著提高催化剂的结晶度,从而提高Ni与基底的相互作用以及表面氧物种的含量,使其具有较强的抗积碳能力.燃烧法合成的Ni基钙钛矿催化剂在CH4∶CO2=1.25∶1,800℃的条件下反应300 h后,积碳量仅为1.0%,而在同样条件下浸渍法合成的催化剂积碳量则高达14.6%.