Adsorption of Chlorobenzene on V2O5/γ-Al2O3 Catalyst

Isotherms of chlorobenzene adsorption on V₂O₅/-Al₂O₃ catalyst within the 0.07-18 Pa range of adsorbate partial pressure were measured, and certain thermodynamic characteristics of adsorption were found.     

A study of Pt–Pd/γ-Al2O3 catalysts for methane oxidation resistant to deactivation by sulfur poisoning

The catalytic oxidation of methane was studied over calcined and reduced Pt–Pd/γ-Al₂O₃ catalysts, in the presence and the absence of SO₂ in the CH₄–O₂ reaction feed. The effect of sulfation (SO₂ + O₂ for 4 h at 500 °C) was also studied on the catalyst resistance to deactivation by sulfur poisoning. Sulfating the calcined Pt–Pd/γ-Al₂O₃ catalysts resulted in a strong deactivation for the CH₄–O₂ reaction. However, the catalytic activity of the reduced-sulfated Pt–Pd/γ-Al₂O₃ catalyst for CH₄–O₂ reaction remained rather unaffected in the presence and in the absence of SO₂ in the reaction feed. XPS analysis revealed, over reduced-sulfated Pt–Pd/γ-Al₂O₃ catalysts, the presence of Pt(0) metallic surface species on which SO₂ interactions may be faster related to Pd surface species. The presence of Pt(0) may be necessary to prevent the interactions between SO₂ and Pd surface species. Long time catalytic tests showed that the activity of a reduced Pt–Pd/γ-Al₂O₃ catalysts for CH₄–O₂ reactions remained rather unaffected despite the presence of SO₂ in the reaction feed.     

Adsorption of benzene on the V2O5/γ-Al2O3 catalyst

Adsorption of benzene on the V₂O₅/-Al₂O₃ catalysts was studied in the temperature interval from 443 to 493 K and at partial pressures of the adsorbate ranging from 1 to 400 Pa. The adsorption isotherms were plotted. The isosteric heats and various entropy characteristics of adsorption were determined. Mobility of benzene in the adsorption layer is restricted compared to the model of ideal dimeric gas. The adsorbed amounts of benzene and chlorobenzene are compared.     

Stereoselective hydrogenation of 2-hexyne on Cu/γ-Al2O3 catalysts

The stereoselective hydrogenation of 2-hexyne in ethanol on Cu/-Al₂O₃ catalysts (1–40 % Cu) at 4–10 atm and 80–120 °C has been studied. The reaction affordscis-2-hexene as the only reaction product in 100 % yield at [Cu] 30 %. For samples with 20 % Cu, hydrogenation proceeds in parallel with absorption of H₂ by the catalyst.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1314–1315, July, 1993.     

Monolayer V2O5/TiO2–ZrO2 catalysts for selective oxidation of o-xylene: preparation and characterization

A series of TiO₂?CZrO₂ supported V₂O₅ catalysts with vanadia loadings ranging from 4 to 12 wt% were synthesized by a wet impregnation technique and subjected to various thermal treatments at temperatures ranging from 773 to 1,073?K to understand the dispersion and thermal stability of the catalysts. The prepared catalysts were characterized by X-ray powder diffraction (XRD), BET surface area, oxygen uptake, and X-ray photoelectron spectroscopy (XPS) techniques. XRD results of 773?K calcined samples conferred an amorphous nature of the mixed oxide support and a highly dispersed form of vanadium oxide. Oxygen uptake measurements supported the formation of a monolayer of vanadium oxide over the thermally stable TiO₂?CZrO₂ support. The O 1s, Ti 2p, Zr 3d, and V 2p core level photoelectron peaks of TiO₂?CZrO₂ and V₂O₅/TiO₂?CZrO₂ catalysts are sensitive to the calcination temperature. No significant changes in the oxidation states of Ti⁴⁺ and Zr⁴⁺ were noted with increasing thermal treatments. Vanadium oxide stabilized as V⁴⁺ at lower temperatures, and the presence of V⁵⁺ is observed at 1,073?K. The synthesized catalysts were evaluated for selective oxidation of o-xylene under normal atmospheric pressure in the temperature range of 600?C708?K. The TiO₂?CZrO₂ support exhibits very less conversion of o-xylene, while 12 wt% V₂O₅ loaded sample exhibited a good conversion and a high product selectivity towards the desired product, phthalic anhydride.     

异丁烷脱氢V2O5/γ-Al2O3催化剂的研究

五氧化二钒;异丁烷脱氢V2O5/γ-Al2O3催化剂的研究     

MoO3/γ-Al2O3和MoO3/SiO2体系的表面酸性研究

通过样品在溶液中对正丁胺的吸附等温线和吸附指示剂法,测定了一系列MoO_3/γ-Al_2O_3和MoO_3/SiO_2样品的表面酸性。两种方法所得结果相符。表明MoO_3/γ-Al_2O_3和MoO_3/SiO_2都具有数量可观的、较强的表面酸位;酸量取决于MoO_3的表面浓度,酸量的极大值与由XPS和XRD所测得的MoO_3在载体上单层分散的阈值相对应;酸位数与表面 MoO_3分子数之比高达0.5—1。与纯MoO_3的表面酸性相比较,可以说明作品的表面酸性正是酸性氧化物在载体表面单层分散的结果。     

Application of in-plasma catalysis and post-plasma catalysis for methane partial oxidation to methanol over a Fe2O3-CuO/γ-Al2O3 catalyst

Methane partial oxidation to methanol (MPOM) using dielectric barrier discharge over a Fe2O3-CuO/γ-Al2O3 catalyst was performed. The multicomponent catalyst was combined with plasma in two different configurations, i.e., in-plasma catalysis (IPC) and post-plasma catalysis (PPC). It was found that the catalytic performance of the catalysts for MPOM was strongly dependent on the hybrid configuration. A better synergistic performance of plasma and catalysis was achieved in the IPC configuration, but the catalysts packed in the discharge zone showed lower stability than those connected to the discharge zone in sequence. Active species, such as ozone, atomic oxygen and methyl radicals, were produced from the plasma-catalysis process, and made a major contribution to methanol synthesis. These active species were identified by the means of in situ optical emission spectra, ozone measurement and FT-IR spectra. It was confirmed that the amount of active species in the IPC system was greater than that in the PPC system. The results of TG, XRD, and N2 adsorption-desorption revealed that carbon deposition on the spent catalyst surface was responsible for the catalyst deactivation in the IPC configuration.     

Preparation and characterization of W/γ-Al2O3 and Pd–W/γ-Al2O3 catalysts from organometallic precursors. The catalytic activity for NO decomposition

The photochemical reaction of W(CO)₆ with triphenylphosphine (PPh₃) in the presence of γ-Al₂O₃ and Pd/γ-Al₂O₃ has been used to prepare W/γ-Al₂O₃ and Pd–W/γ-Al₂O₃ catalysts. Adsorbed mono- and disubstituted W species have been identified by FTIR spectroscopy. There is evidence of the adsorption of W(CO)_6−x L_x species on both the alumina and the Pd surface. After thermal decomposition and reduction at 573 K the catalysts have been characterized by FTIR spectroscopy of adsorbed NH₃, CO and NO. The retention of W and P suppresses the Lewis acidity of the alumina support. On Pd–W/γ-Al₂O₃, the W is present in a partially reduced state in close association with Pd. This interaction modifies the chemisorptive properties of NO relative to those of the monometallic Pd and W catalysts. In line with these observations the Pd–W/γ-Al₂O₃ catalyst presents an enhanced activity for NO decomposition at 473 K.     

Syngas production by combined carbon dioxide reforming and partial oxidation of methane over Ni/α-Al2O3 catalysts

Ni/α-Al2O3 catalysts were found to be active in the temperature range 600~900 ℃ for both CO2 reforming and partial oxidation of methane. The effects of Ni loading, reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated. Catalysts of xwt%Ni/α-Al2O3 (x = 2.5, 5, 8 and 12) were prepared by wet impregnating the calcined support with a solution of nickel nitrate. XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst, as compared with the other prepared catalyst samples. An increase of the Ni loading to more than 5 wt% led to a reduction in the Ni dispersion. In addition, by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction, the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.     

Synthesis of Ni2P promoted trimetallic NiMoW/γ-Al2O3 catalysts for diesel oil hydrotreatment

The Ni2P promoted and γ-Al2O3 supported NiMoW sulfide catalyst consisting of 4 wt% Mo, 22 wt% W, 2 wt% Ni and 2.5 wt% Ni2P was synthesized by a co-impregnation method. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, NH3 temperature-programmed desorption (NH3-TPD) and transmission electron microscopy (TEM). The results showed that Ni2P, Ni, Mo and W species were highly dispersed over γ-Al2O3. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) showed that the presence of Ni2P brought a strong promotional effect on the HDS activity, which was further confirmed by the HDS and hydrodenitrogenation (HDN) of diesel oil under industrial conditions. The enhancement in HDN activity and stability by Ni2P addition could be attributed more to the effect of new active sites of Ni2P than that of acidity modification. The as-prepared Ni2P-NiMoW/γ-Al2O3 catalyst showed better hydrotreating performance than NiMoW/γ-Al2O3 and commercial catalysts.     

MoO3/γ-Al2O3, MoO3/TiO2和MoO3/SiO2的还原性质及表面状态研究

本文以XPS为检测手段研究了浸渍法制备的MoO_3/γ-Al_2O_3、MoO_3/TiO_2和MoO_3/SiO_2三个系列样品的还原性质。用XPS测定还原后与还原前强度比的比值, 实验结果表明阈值后的样品还原后强度比急剧增大, 说明晶相MoO_3从内孔向颗粒外表面大幅度迁移。而单层MoO_3的性质却各不相同, TiO_2上的单层MoO_3还原后部分凝聚, SiO_2上单层则部分迁移, 而γ-Al_2O_3上的单层MoO_3既不迁移也不凝聚, 亦即单层MoO_3的稳定性是Mo(Al)>Mo(Ti)>Mo(Si)。这也是MoO_3与这三个载体表面作用力强弱的顺序。用计算机对Mo3d谱峰解叠, 结果表明, 几乎所有样品还原后都只含有四价和五价钼。Mo(Al)和Mo(Si)体系还原后Mo~Ⅳ的百分数随负载量的增大而增大。我们认为反映了两种载体表面区域的不均匀性。Mo(Ti)体系还原后Mo~Ⅳ百分数在阈值附近出现转折点, 阈值前各点还原性质相同, 说明在应用还原为探测手段时, TiO_2表面表现为均匀的。以Mo~(Ⅳ)百分数衡量时, 三个体系的还原性为Mo(Al)相似文献   

Catalytic amination of 2,6-dimethylphenol to 2,6-dimethylaniline over Ni–Cu–Cr/γ-Al2O3

A series of transition metal-based catalysts, other than Pd or Pt-based catalysts, were investigated for catalytic amination of 2,6-dimethylphenol to 2,6-dimethylaniline in a fixed-bed reactor. Ni–Cu–Cr/γ-Al₂O₃ yielded satisfactory results with 82.08 % conversion and 47.24 % selectivity. The catalysts were characterized by H₂-TPR and TEM, and the results obtained showed that the doped Cu and Cr could promote reduction of Ni/γ–Al₂O₃ and dispersion of the Ni. Reaction conditions, including reaction temperature, flow rate of hydrogen, and ammonia, were studied.     

Deep oxidation in propane oxidative dehydrogenation to propene over V2O5/γ-Al2O3 studied by in-situ DRIFTS

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150250 °C with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.     

Physical–chemical and catalytic properties of deposited MoO3 and V2O5

The deposition of molybdenum and vanadium oxides onto fumed silica, titania, and alumina as supports through dry milling has been carried out. The structure of prepared compositions has been investigated by means of XRD, DTA?CTG, FTIR, and UV?CVis spectroscopy, nitrogen adsorption. The deposited crystal phases are sufficiently uniformly distributed on support surface. The supported oxides are subjected to dispersion in process of milling to the state of oligomeric or isolated species. Milled bulk and deposited MoO₃ (first of all, on alumina) possesses improved catalytic performance in process of epoxidation of 1-octene. Vanadium pentoxide also has higher activity in this process.     

Hydrodesulfurization catalysts P-Mo-W/γ-Al2O3: Characterization and catalytic activity

P-Mo-W/γ-Al₂O₃ catalysts with various Mo and W contents have been synthesized. The parameters of the porous structure of their sulfide and oxide forms have been determined. The geometric parameters of the active phase of the sulfide catalysts have been calculated using high-resolution transmission electron microscopy data. The catalytic activity has been estimated in dibenzothiophene (DBT) hydrodesulfurization (HDS). The reaction under the conditions examined proceeds mainly as direct hydrodesulfurization. The catalytic activity has been correlated with the Mo/W molar ratio and with the proportions of edge and corner sites.     

V2O5/γ-Al2O3和V2O5/SiO2负载型催化剂对异丁烷的催化脱氢性能

V2O5/γ-Al2O3和V2O5/SiO2负载型催化剂对异丁烷的催化脱氢性能;V2O5/γ-Al2O3; V2O5/SiO2; 异丁烷; 脱氢     

Effect of the CuAl2O4 and CuAlO2 Phases in Catalytic Wet Air Oxidation of ETBE and TAME using CuO/γ-Al2O3 catalysts

This paper studies Cu/Al₂O₃ catalysts, synthesized in two ways: copper deposit in the synthesis of alumina (sol gel) and incipient impregnation stabilized at 400 °C. The materials were characterized by X-ray diffraction studies, nitrogen physisorption, temperature programmed reduction of H₂, dehydration of isopropanol, scanning electronic microscopy, transmission electronic microscopy, which were evaluated in the liquid phase oxidation reaction of ethyl tert-butyl ether and tert-amyl methyl ether. The formation of CuAl₂O₄ and CuAlO₂ in the samples synthesized by sol gel, led to a modification of the texture, thus resulting in an expansion of the specific area of the materials. CuAl₂O₄ and CuAlO₂ have been identified by DRX from a content of 10 % Copper, the first showed the highest intensity with this technique. In the same way, these species favor the presence of Lewis acid sites; this is reflected in the materials with (Di-isopropyl Ether) DIPE of 96.7 % and 91.1 % for the samples SAlCu5 and SAlCu15 respectively. The catalytic activity of the materials prepared by sol gel is in the function of the number of surface acid sites, the smaller particle size of the Cu and the surface of the contact, in the case of the ETBE meanwhile for TAME the activity was based mainly on the strength of the present acid sites. With impregnated materials, the activity is attributed to the smaller particle size of the Cu and the greater strength of the surface acid sites in the solid. The formation of spinel species inhibits the leaching phenomenon in the reaction milieu.     

γ-Al2O3改性对AlCl3/γ-Al2O3催化剂性能的影响

采用HCl和NaOH改性γ-Al2O3载体制备AlCl3/γ-Al2O3固载催化剂,用吡啶-FTIR和吡啶-TPD技术分析了催化剂的表面酸性(酸中心类型、酸强度和酸量),并以1-癸烯齐聚作为探针反应,研究了催化剂的稳定性以及催化剂对聚合反应的影响.结果表明,催化剂含有两种酸类型,即Lewis酸和Br(o)nsted酸,与未改性的催化剂相比,氢氧化钠改性载体制备的催化剂,酸量增大了47％,催化剂催化1-癸烯的齐聚反应活性增加了11.4％;而经盐酸改性制备的催化剂酸量增大112％,催化剂的活性增加了33.6％.酸强度依AlCl3/γ-Al2O3,AlCl3/γ-Al2O3(NaOH),AlCl3/γ-Al2O3 (HCl)的顺序增强.     

Selective hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol over Ni/γ-Al2O3 catalysts

Research on Chemical Intermediates - A series of nickel-based catalysts (with <5 nm Ni particle size) with γ-alumina as a support (x wt% Ni/γ-Al2O3, x represents the Ni...