Sonochemical preparation of supported hydrodesulfurization catalysts

Sonochemical preparation of Co and Ni promoted MoS(2) supported on alumina was achieved by high-intensity ultrasonic irradiation of isodurene solutions containing molybdenum carbonyl, dicobalt octacarbonyl, elemental sulfur, and Al(2)O(3) or Ni-Al(2)O(3) under Ar flow. The sonochemically prepared catalysts were characterized by elemental analysis, XPS, SEM, TEM, and XEDS, and hydrodesulfurization (HDS) activity evaluated for thiophene and dibenzothiophene substrates. The TEM studies on the sonochemically prepared catalysts indicate the formation of layered hexagonal MoS(2) (lattice fringes approximately 6.2 A) on the alumina support. The sonochemically prepared Co-Mo-S/Al(2)O(3), Ni-Mo-S/Al(2)O(3), and Co-Ni-Mo-S/Al(2)O(3) are extremely active catalysts for the HDS of thiophene and dibenzothiophene, with activities severalfold those of comparable commercial catalysts under identical conditions. The layered structure of MoS(2) remained intact after 120 h of HDS, and the catalyst is reusable.     

新型介孔分子筛KIT-1加氢脱硫催化剂的研究

制备了新型的结构排列无序的介孔分子筛KIT-1和负载Ni, Mo的KIT-1加氢脱硫催化剂。实验结果表明MoO3较易分散在KIT-1的表面,而NiO则容易在其表面形成小晶粒。与以MCM-41和NaY分子筛为载体的Ni, Mo催化剂相比, KIT-1负载催化剂具有较高的加氢脱硫催化活性,因为KIT-1载体具有相互交错的三维孔道结构, 有利于反应物和产物的扩散, 而不容易受孔道堵塞的影响。     

Activity of Ni?Mo hydrodesulfurization catalysts supported on mixed alumina-zirconia

The hydrodesulfurization (HDS) of thiophene by nickel-molybdenum catalysts supported on alumina-zirconia has been investigated. The effect of varying the ratios of oxides in the support is to produce a minimum in the activity for HDS, and the coimpregnated catalysts are shown to be more active than the analogous co-precipitated catalysts.

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(HDS) -, . HDS. , .

     

载体性质对Pd催化剂加氢脱硫性能的影响

以Si O2、全硅MCM-41(Si-MCM-41)、通过机械混合Si-MCM-41与ZSM-5得到的Z-MCM-41-M以及通过在ZSM-5外部包覆MCM-41制备得到的Z-MCM-41四种材料为载体,制备了四种负载型Pd催化剂。采用XRD、HRTEM、N2吸附-脱附、NH3-TPD手段对Pd催化剂进行了表征;以二苯并噻吩(DBT)为模型化合物,在固定床反应器上对四种催化剂的加氢脱硫(HDS)活性、加氢路径选择性和加氢裂化活性进行了考察,研究了不同类型载体对Pd催化剂加氢脱硫性能的影响。结果表明,载体的性质会显著影响负载型Pd催化剂的加氢脱硫性能。载体的比表面积对负载型Pd催化剂加氢脱硫活性影响不大,但是HYD路径的选择性与载体的孔道结构有关;具有介孔孔道结构有利于加氢路径选择性的提高。酸性载体负载的Pd催化剂表现出较好加氢脱硫活性和加氢选择性,这与氢溢流有关。介孔材料的孔道结构与微孔沸石的酸性有机结合,所得到的Z-M CM-41复合材料是是潜在的贵金属Pd加氢脱硫催化剂优良载体,可有效提升其加氢脱硫活性。     

Fraction of the CoMoS phases accessible to NO in Co-Mo hydrodesulfurization catalysts

It is established by using Co-Mo model sulfide catalysts, XAFS and FTIR that Co atoms constituting CoMoS phases are not oxidized by NO adsorption and that only 55% of the CoMoS phases is susceptible to NO adsorption even at the maximum coordinative unsaturation attainable under usual HDS reaction conditions (623-673 K).     

Selectivity of Fischer-Tropsch synthesis on supported nickel catalysts

Alumina supported Ni as well as Ni²⁺ exchanged CaNaX zeolites were used to study Fischer-Tropsch synthesis. Two significant selectivity effects can be distinguished, which are related to the different structures and acidities of the catalysts.

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CaNaX, Ni, Ni⁺² , -. , .

     

The studies of hydrodesulfurization activity over molybdenum catalysts supported on Al-MCM-41 modified by lanthanum

A series of lanthanum modified Al-MCM-41 substrates served as supports to prepare the Mo/La-Al-MCM-41 catalysts. The catalysts were characterized by XRD, BET, FT-IR, XPS, TPR and TPD, and their catalytic activities were determined for thiophene hydrodesulfurization (HDS).     

Nitrogen forms on supported catalysts for ammonia synthesis

Nitrogen chemisorption on supported Fe–Co, Fe–Mo and Co–Mo catalysts for ammonia synthesis has been studied. No considerable effect of carrier (carbon fibers) on nitrogen chemisorption has been found. It is shown that for these samples chemisorbed nitrogen has various dissociative forms.

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Fe–Co, Fe–Mo Co–Mo . ( ) . , .

     

Effect of the support calcination temperature on selective hydrodesulfurization of TiO2 nanotubes supported CoMo catalysts

TiO₂ nanotubes (TiO₂-NTs) were synthesized by the hydrothermal method. Co and Mo active components were supported on a series of the as-prepared TiO₂-NTs samples which were calcined at different temperatures. The effects of support calcination temperature of CoMo/TiO₂-NTs catalysts on their catalytic performance were investigated for selective hydrodesulfurization (HDS). The samples were characterized by means of the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), N₂ adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy and H₂ temperature-programmed reduction (H₂-TPR). The experimental results revealed that TiO₂-NTs support calcined under 500 °C can maintain the nanotubular structure with higher surface area and pore volume. Meanwhile, the obtained supported CoMo/TiO₂-NTs catalysts exhibited weak metal-support interaction, more octahedral Mo⁶⁺ species and high catalytic performance in selective HDS.     

A new method of direct synthesis of bimetallic phases: Silica supported Pd---Cu catalysts from mixed acetylacetonates

The direct synthesis on a silica support of well defined, crystalline, mixed Pd---Cu bis-acetylacetonates has been achieved and the structure of these new compounds was determined by powder X-ray diffraction. These clusters have been deposited on a silica support and their thermal decomposition under helium was followed by in situ X-ray diffraction, thermo-gravimetry and mass spectroscopy. Microcrystalline metallic alloys with a narrow distribution of composition and particle size in the 2–4 nm range are obtained. Infrared experiments of CO chemisorption confirm the homogeneity of composition of the particles but conclude to a partial coverage of palladium by copper.     

负载Ni催化剂上低温甘油蒸汽重整制氢

采用等体积浸渍法制备了Al₂O₃、CeO₂、TiO₂及MgO负载Ni催化剂,考察了它们对甘油蒸汽重整制氢反应的催化性能。采用X射线衍射、N₂吸附、透射电镜及H₂程序升温还原等方法对催化剂进行了表征。结果表明,载体对Ni催化剂的活性有显著影响。在400 ℃下Ni/CeO₂的催化活性明显好于其他催化剂,活性次序为Ni/CeO₂> Ni/Al₂O₃ > Ni/TiO₂ ~ Ni/MgO。Ni/CeO₂也具有好的稳定性,反应20 h未见活性下降,甘油转化率70%,氢气收率69.2%。这与CeO₂的本性及其与活性组分的相互作用有关。Al₂O₃具有较大的比表面积与孔体积,有利于CO吸附及甲烷化反应的进行,使得Ni/Al₂O₃催化剂在较高温度下具有很高的甘油转化率85.7%,但H₂选择性较差。由于MgO载体与活性组分强的相互作用而生成NiMgO₂固溶体,导致Ni/MgO低温活性差。     

Cobalt catalysts supported on silica nanotubes for Fischer-Tropsch synthesis

Silica nanotubes(SNT) have been synthesized using carbon nanotubes(CNT) as a template.Silica-coated carbon nanotubes(SNT-CNT) and SNT were loaded with a cobalt catalyst for use in Fischer-Tropsch synthesis(FTS).The catalysts were prepared by incipient wetness impregnation and characterized by N2 physisorption,X-ray diffraction(XRD),hydrogen temperature programmed reduction(H2-TPR) and transmission electron microscopy(TEM).FTS performance was evaluated in a fixed-bed reactor at 493 K and 1.0 MPa.Co/CNT and Co/SNT catalysts showed higher activity than Co/SNT-CNT in FTS because of the smaller cobalt particle size,higher dispersion and stronger reducibility.The results also showed that structure of the support affects the product selectivity in FTS.The synergistic effects of cobalt particle size,catalytic activity and diffusion limitations as a consequence of its small average pore size lead to medium selectivity to C5+ hydrocarbons and CH4 over Co/SNT-CNT.On the other hand,the Co/CNT showed higher CH4 selectivity and lower C5+ selectivity than Co/SNT,due to its smaller average pore size and cobalt particle size.     

Synthesis and properties of hydrodesulfurization catalysts. IV. Thiophene hydrodesulfurization on molybdenum catalysts containing heteropoly compounds

Water soluble analogues of aluminium and cobalt heteropolymolybdates have been shown as possible precursors of active sites for thiophene hydrodesulfurization along with other molybdenum compounds. For the characterization of the catalysts Raman spectroscopy has been applied, and the catalytic activity of the samples is discussed.

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Effect of the support calcination temperature on selective hydrodesulfurization of TiO2 nanotubes supported CoMo catalysts

TiO₂ nanotubes（TiO₂-NTs） were synthesized by the hydrothermal method.Co and Mo active components were supported on a series of the as-prepared TiO₂-NTs samples which were calcined at different temperatures.The effects of support calcination temperature of CoMo/TiO₂- NTs catalysts on their catalytic performance were investigated for selective hydrodesulfurization（HDS）.The samples were characterized by means of the scanning electron microscopy（SEM）,the transmission electron microscopy（TEM）,N₂ adsorption-desorption,X-ray diffraction （XRD）,Raman spectroscopy and H₂ temperature-programmed reduction（H₂-TPR）.The experimental results revealed that TiO₂-NTs support calcined under 500℃can maintain the nanotubular structure with higher surface area and pore volume.Meanwhile,the obtained supported CoMo/TiO₂-NTs catalysts exhibited weak metal-support interaction,more octahedral Mo⁶⁺ species and high catalytic performance in selective HDS.     

In situ FT-IR spectroscopy investigations of carbon nanotubes supported Co-Mo catalysts for selective hydrodesulfurization of FCC gasoline

To better understand the nature of carbon nanotubes supported Co-Mo catalysts （Co-Mo/CNTs） for selective hydrodesulfurization （HDS） of fluid catalytic cracking （FCC） gasoline, studies are carried out using in situ Fourier transform infrared spectroscopy （FT-IR）. The catalytic performances of Co-Mo/CNTs catalysts were evaluated with a mixture of cyclohexane, diisobutylene, cyclohexene, 1-octene （60 ： 30 ： 5 ： 5, volume ratio） and thiophene （0.5%, ratio of total weight） as model compounds to simulate FCC gasoline. The HDS experimental results suggested that the HDS activity and selectivity of Co-Mo/CNTs catalysts were affected by Co/Mo ratio; the optimal Co/Mo atomic ratio is about 0.4, and the optimum reaction temperature is 260 ℃. The in situ FT-IR studies revealed that 1-octene can be completely saturated at 200 ℃. In the FT-IR spectra of diisobutylene, the characteristic absorption peak around 3081 cm^-1 for the stretching vibration peak of =C-H bond was still clear at 320 ℃ indicating that diisobutylene is difficult to be hydrogenated. As for the thiophene, no characteristic absorption peak could be found around 3092 cm^-1 and 835 cm^-1 when the reaction temperature was raised to 280 ℃, indicating that thiophene had been completely hydrodesulfurized. On the basis of FT-IR results, it can be deduced that thiophene HDS reaction occurred mainly through direct hydrogenolysis route, whereas thiophene HDS and diisobutylene hydrogenation reaction over Co-Mo/CNTs catalysts might occur on two different kinds of active sites.     

Effect of preparation method on halloysite supported cobalt catalysts for Fischer-Tropsch synthesis

Novel cobalt Fischer-Tropsch synthesis(FTS) catalysts were prepared from natural halloysite nanotubes(HNT) by double-solvent and wetimpregnation methods,and characterized by TEM,XRD,TPR and N2 adsorption-desorption.Comparing with the catalyst prepared by wetimpregnation method,the catalyst prepared by double-solvent method reduces Co3O4 particle migration and agglomeration due to size-induced effect,thus showing higher catalytic activity for Fischer-Tropsch synthesis.     

Interfacial impregnation chemistry in the synthesis of nickel catalysts supported on titania

The interfacial chemistry of the impregnation step involved in the preparation of nickel catalysts supported on titania is presented. Several methodologies based on deposition data, pH measurements, potentiometric mass titrations, and microelectrophoresis have been used in conjunction with diffuse reflectance UV/Vis/NIR spectroscopy, simulations, and semiempirical quantum chemical calculations. Three mononuclear inner-sphere complexes were formed at the compact layer of the "titania/electrolyte solution" interface: A monosubstituted, dihydrolyzed complex above a terminal oxo group, a disubstituted, dihydrolyzed complex above two terminal adjacent oxo groups, and a disubstituted, nonhydrolyzed complex above one terminal and one bridging adjacent oxo groups. The monosubstituted, dihydrolyzed complex predominates. The contribution of the disubstituted configurations is also important at very low Ni(II) surface concentration, but it decreases as the Ni(II) surface concentration increases. In addition, bi- and trinuclear inner-sphere complexes were formed. The receptor site involves one bridging and two terminal oxo groups in the first case and two bridging and three terminal oxo groups in the second case. The relative surface concentrations of these configurations increase initially with Ni(II) surface concentration and then remain practically constant. The understanding of these interfacial processes at a molecular level is very important to shift the catalytic synthesis from an art to a science as well as to obtain strict control of the impregnation step and, to some extent, of the whole preparative sequence. This study is very relevant to the synthesis of submonolayer/monolayer nickel catalysts supported on TiO(2) following equilibrium deposition filtration (otherwise called equilibrium adsorption).     

水对SBA-15负载的钴基费-托合成催化剂催化性能的影响

以SBA-15分子筛为载体,采用等体积浸渍法制备了负载量为20%的钴基催化剂,采用TEM、XRD、H2-TPR和N2物理吸附-脱附等方法对催化剂进行了表征,并在浆态床反应器中考察了水的加入对费-托合成反应性能的影响.结果表明,金属钴物种进入到SBA-15载体的孔道中;产物在孔道中的滞留以及水促进的金属钴物种的团聚,引起了催化剂活性的降低;水的加入有利于反应物和产物在孔道中的传输,增加CO的转化率;在SBA-15负载的钴基催化剂中,产物在孔道中的滞留对催化剂活性影响较大,引起的扩散限制是催化剂活性降低的重要原因.     

硅纳米管负载的钌基催化剂费-托合成催化性能研究

以模板法合成的硅纳米管（SNT）为载体,用浆态浸渍法制备了钌基催化剂,采用氮气物理吸附、透射电子显微镜（TEM）、X射线粉末衍射（XRD）和氢气程序升温还原（H₂-TPR）等手段对其进行了表征。在固定床反应器上（503K,1.0MPa）考察了该催化剂的费-托合成反应活性及产物选择性,并与用商业二氧化硅为载体制备的催化剂上的反应结果进行了比较。结果表明,SNT和SiO₂负载的氧化钌在623K可被H₂完全还原;SNT负载的钌基催化剂上,钌氧化物颗粒较小、分散性好,还原后钌颗粒被较好地分散在硅纳米管上,且几乎所有的钌颗粒都分布在管内。与以SiO₂为载体的催化剂相比,以硅纳米管为载体的钌基催化剂具有较高的费-托合成活性。