Fischer-Tropsch synthesis over Ru/Al2O3 catalysts

Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al₂O₃ catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al₂O₃ was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.     

H2-induced CO adsorption and dissociation over Co/Al2O3 catalyst

The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.     

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。     

钡改性的Ni/γ- Al2O3催化剂用于甲烷部分氧化的研究

800 ℃、80 000 h－1、CH4/O2/N2=14/7/79下比较了质量分数20%的Ni/γ- Al2O3和Ba改性的Ni/γ- Al2O3催化剂，用于甲烷部分氧化反应的活性和选择性。结果表明，Ba的添加提高了镍基催化剂的活性和稳定性。BET和XRD表明，Ba的加入有利于高温焙烧下抑制大颗粒的Ni Al2O4的形成，保持了高比例的活性镍组分，提高了催化剂催化活性。常压下，xCH4接近100%，sCO、sH2达到92.2%和98.1%，催化剂15 h内活性稍微下降。Ba的加入使Al2O3的晶型转化温度由800 ℃提高到900 ℃，提高了载体的稳定性。     

Selective oxidation of methane to formaldehyde by oxygen over silica-supported iron catalysts (Special column of methane transformation, Article)

FeO_x-SiO₂ catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeO_x-SiO₂ with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeO_x-SiO₂ catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeO_x/SiO₂ prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H₂-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeO_x-SiO₂ by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeO_x-SiO₂ catalyst (P/Fe = 0.5) at 898 K. Raman spectroscopic measurements indicated the formation of FePO₄ nanoclusters in this catalyst, which were more selective toward formaldehyde formation.     

助剂对甲烷部分氧化制合成气镍基催化剂性能的影响

考察了添加助剂铈、镧和钙对镍基催化剂反应性能的影响，发现助剂对以α-Al2O3为载体的镍基催化剂的调变作用比以γ-Al2O3为载体的镍基催化剂好，且助剂铈对催化剂的性能改善最好。在此基础上，研究了不同载量的铈对催化剂性能的影响。结果表明，铈的质量分数为1%时对催化剂的性能改善最好。同时采用XRD、XPS、TG等技术，研究了助剂铈对10％Ni/γ-Al2O3催化剂的改性作用。XRD分析表明，铈负载量较低时，催化剂中的CeO2高度分散在催化剂表面，铈负载量较高时，CeO2形成微晶颗粒，降低了催化活性。     

甲烷部分氧化制合成气Pt-Ni/Al~2O~3催化剂的研究

研究了Ni/Al~2O~3,Pt/Al~2O~3和一系列Pt-Ni/Al~2O~3催化剂对甲烷部分氧化制合成气的催化作用,发现Pt-Ni/Al~2O~3催化剂显示了比Ni/Al~2O~3和Pt/Al~2O~3更高的活性和稳定性。H~2-TPR,CO-TPD,CO~2-TPD,SEM,XPS和XRD等结果证明:Pt和Ni之间存在较强的相互作用,Pt和部分Ni形成固溶体合金并且Pt在催化剂表面富集。Pt和Ni之间的相互作用提高了催化剂的活性和稳定性,甲烷在Pt-Ni/Al~2O~3上的催化部分氧化具有不同于在Pt/Al~2O~3和Ni/Al~2O~3上的反应性能。     

FT-IR photoacoustic spectra of the surface of Ru3(CO)12/Al2O3 system

The FT-IR photoacoustic spectra of Ru₃(CO)₁₂/Al₂O₃ (acidic and basic alumina) system have been measured for different ageing times. The behaviors of oxidation states of Ru on the surface of basic or acidic alumina and their difference are discussed on the ground of CO stretching bands of their spectra.     

Oxidative conversion of methane and methanol on M/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/cordierite structured metal oxide catalysts (m = Ni,Cu, Zn)

A study was carried out on the properties of Ni/Al₂O₃ and Cu-ZnO/Al₂O₃ composites supported on ceramic honeycomb monoliths made from synthetic cordierite in the carbon dioxide conversion of methane and the partial oxidation of methanol. The structured nickel-alumina catalysts are significantly more efficient than the conventional granulated catalysts. The improved working stability of these catalysts was achieved by adjusting the acid-base properties of the surface by introducing sodium and potassium oxides, which leads to inhibition of surface carbonization. The hydrogen yield was close to 90% in the partial oxidation of methanol with a stoichiometric reagent ratio in the presence of the Cu-ZnO/Al₂O₃/cordierite catalyst. A synergistic effect was found, reducing the selectivity of CO formation in the presence of the Cu-ZnO catalyst relative to samples derived from the individual components Cu and ZnO. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 299–306, September–October, 2007.     

碱土Sr对Co/Al2O3催化剂甲烷部分氧化反应的影响

以γ-Al₂O₃为载体,采用共浸渍法制备了Sr-Co/Al₂O₃系列催化剂,研究了助剂Sr对Co/Al₂O₃催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N₂物理吸附、X射线衍射、H₂-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al₂O₃和800℃焙烧的Sr-Co/Al₂O₃催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H₂还原为单质的Co₃O₄;另一类是与载体相互作用较强、难还原、无催化活性的CoAl₂O₄尖晶石。在焙烧过程中,Sr易形成Sr₄Al₁₄O₂₅,从而削弱Co与Al₂O₃之间的相互作用,能在一定程度上抑制CoAl₂O₄物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al₂O₃在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl₂O₄的产生。     

CO Hydrogenation by K-Promoted Coprecipitated Co/Al2O3

Effect of K promotion on the CO hydrogenation activity and selectivity of coprecipitated Co/Al₂O₃ has been studied. K addition is found to lower total activity while enhancing C₂-C₄ olefins selectivity; kinetic data indicate that the reaction mechanism is not affected.     

焙烧温度对甲烷催化部分氧化Ni/MgO-Al2O3催化剂结构和性能的影响

采用TPR、BET、XRD、TG及反应性能评价等研究方法,考察了焙烧温度对甲烷催化部分氧化制合成气Ni/MgO-Al2O3催化剂结构和性能的影响。研究结果表明,随焙烧温度的升高, Ni/MgO-Al2O3中的镍物种与载体作用逐渐增强,生成了NiAl2O4尖晶石和NiMgO2固熔体。虽然焙烧温度提高会使催化剂比表面降低,由于尖晶石结构的形成,其热稳定性会明显提高,将有利于抑制催化剂在反应过程中因烧结而失活的可能性。与低温焙烧的催化剂相比,高温焙烧的催化剂仍表现出良好催化反应性能,并具有相对较好的稳定性。高温焙烧的催化剂在反应过程中床层的热点温度相对较低,热点温度波动幅度也较小。低温和高温焙烧的Ni/MgO-Al2O3催化剂在常压、1 083 K、CH4与O2摩尔比为1.8、空速2.66×105 h－1的反应条件下均具有良好的抗积炭性能。     

Al2O3/MeSO3H (AMA) as a New Reagent for the Thia-Fries Rearrangement of Arylsulfonates to Hydroxyaryl Sulfones

A new facile method for thia-Fries rearrangement of arylsulfonates has been developed. A variety of arylsulfonates rearrange in excellent yields in the presence of Al₂O₃/MeSO₃H as a new reagent without the use of any solvent.     

Mn/Al2O3 Systems: Structure and Activity

-Mn₂O₃ and KMn₈O₁₆ were detected on catalysts prepared by pore volume impregnation of -alumina using manganous nitrate and ammonium permanganate, respectively. While the surface texture was not remarkably affected: decomposition activities towards H₂O₂ and 2-propanol were higher for the later.     

Influence of ZrO2 on Carbon Monoxide Oxidation Over Pd/Al2O3

The influence of ZrO₂ on the properties of Al₂O₃ and performances of Pd/Al₂O₃ catalyst in CO oxidation have been investigated. TPD results show that the activity enhanced is due to the increase of the adsorptive capacity of CO and the activation of C=O bond after the introduction of ZrO₂.     

CeO2-ZrO2-La2O3-Al2O3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

Composite supports CeO2-ZrO2-Al2O3 (CZA) and CeO2-ZrO2-Al2O3-La2O3 (CZALa) were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles (NGVs) operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction (XRD) and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperature-programmed reduction (H2-TPR) and oxygen storage capacity (OSC) measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Catalytic activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. They also have significant potential in industrial application because of their high performance and low cost.     

EXAFS characterization of Ti/Al2O3 supports and Co/Ti/Al2O3 catalysts

The structure of Ti/Al₂O₃ supports (0–14 wt% Ti) and Co/Ti/Al₂O₃ catalysts (3 wt% Co) was examined by EXAFS. The results indicated that the Ti was present primarily as a highly dispersed surface phase. The Ti EXAFS results indicated that the Ti species were octahedrally coordinated. Evidence of Ti—Ti interactions was found for all loadings (2–14 wt% Ti) suggesting that the Ti surface species are present as small clusters of TiO₂.The Co EXAFS results showed evidence for several structurally different Co surface phases as a function of Ti loading. Evidence of a Co species interacting with the Ti surface phase was observed for the 3% Co/2% Ti-3%Co/6%Ti catalysts. At the highest loadings studied, 3%Co/8%Ti and 3%Co/14%Ti, evidence was found for a CoTiO₃-like phase.     

New Gelation Process for Pt/Al2O3 Catalysts Preparation

Gel of platinum and aluminum was prepared by an anhydrous gelation process using a mixture of aluminum sec butoxid, platinum acetylacetonate and Butanol-2. The investigation of this gelation by FTIR, UV-vis and ²⁷Al NMR spectroscopies suggest that a slow polymerization of aluminum precursors occurs according to an etheration mecanism likely catalysed by metallic platinum which could be formed by the reduction of platinum in Pt(acac)₂ by sBuOH in the mixture during aging.     

Comparative study of LaNiO3 and La2NiO4 catalysts for partial oxidation of methane

The catalytic activity and stability of LaNiO₃ and La₂NiO₄, prepared using a citric acid complex method, have been investigated for partial oxidation of methane (POM) to synthesis gas. The catalysts were characterized by thermo-gravimetric analysis (TG), temperature-programmed reduction (TPR) and temperature-programmed desorption of ammonia (NH₃-TPD). The results show that the catalytic activity and stability of La₂NiO₄ are higher than those of LaNiO₃, due to the stronger interactions between Ni and La₂O₃ in La₂NiO₄ and to its lower acidity as demonstrated by TPR and NH₃-TPD. TG result indicates that carbon deposition occurs on both catalysts, and the carbon species deposited on La₂NiO₄ are mainly metal carbides, while on LaNiO₃ are mainly graphite.