Synthesis,Characterization, and Evaluation of Mesoporous MCM-41-supported Molybdenum Hydrotreating Catalysts

Abstract

Mesoporous MCM-41 material with high surface area and narrow pore size distribution was synthesized and used as a support for Mo, CoMo, and NiMo catalysts. The molybdenum loading was varied from 2–14 wt% on MCM-41. On 10 wt% Mo/MCM-41, the promoter Co or Ni concentration was varied from 1–5 wt%. All the catalyst samples were characterized by surface area, low temperature oxygen chemisorption, x-ray diffraction (XRD), and temperature programmed reduction methods. Characterization results show that Mo is well dispersed on MCM-41 up to 10 wt%. The catalytic activities were evaluated for thiophene hydrodesulphurization (HDS), cyclohexene hydrogenation (HYD), and furan hydrodeoxygenation (HDO). All three catalytic functionalities vary in a similar manner to that of oxygen chemisorption as a function of Mo loading, indicating that there is a correlation between oxygen uptake and catalytic sites. The activities of these catalysts were compared with γ-Al₂O₃- and amorphous SiO₂-supported catalysts. It was found that MCM-41-supported Mo catalysts displayed superior activities.     

Preparation and characterization of FeNi/Al2O3 catalysts for production of light olefins

The 24%Fe-36%Ni/Al₂O₃ catalyst was prepared using sol-gel method. This research investigated many variable factors for conversion synthesis gas to C₂?CC₄ light olefins by using Fisher-Tropsch synthesis. The effects of calcination atmospheres and calcination heating rates and also operation conditions such as the H₂/CO molar feed ratios, gas hourly space velocity (GHSV), temperatures and total reaction pressure on the catalytic performance of 24%Fe-36%Ni/Al₂O₃ catalyst was investigated. The stability of the catalyst for 240 h has been tested at optimal operating conditions (T = 260°C, H₂/CO = 2/1, GHSV = 3200 h^?1 and P = 3 bar). The results indicated that this catalyst was highly stable for production C₂?CC₄ light olefins. Characterization of precursors and calcined catalysts were carried out by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement, temperature program reduction (TPR) and thermal analysis methods such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

乙苯选择性氧化制苯乙酮的实验研究

以V2O5和H3PO4为原料,采用有机溶剂法制得VPO催化剂,用于乙苯选择性催化氧化。研究了反应条件对乙苯选择性氧化制苯乙酮的影响,并用XRD对VPO催化剂的物相进行了表征。结果表明,VPO催化剂是由V4+的(VO)2P2O7物相和V5+的VOPO4物相组成;冰醋酸为该催化反应体系的最佳溶剂;当反应温度为343 K、催化剂用量为30 mg、乙苯用量为10.0 mL、冰醋酸用量为10.0 mL、H2O2用量为10.0 mL时,目的产物苯乙酮收率可达17.2 %。     

W 对 W-Ni2P/SBA-15催化剂结构及二苯并噻吩氢脱硫性能的影响

 以硝酸镍为镍源,磷酸氢二铵为磷源,介孔分子筛 SBA-15为载体,采用共浸渍法制备Ni₂P/SBA-15前驱体,再将一定量的偏钨酸铵水溶液引入,采用程序升温还原制备了一系列 W-Ni₂P/SBA-15催化剂。采用 XRD、N₂吸附-脱附、NH₃-TPD 和 XPS 表征了催化剂的结构,并评价了催化剂的二苯并噻吩加氢脱硫活性。结果表明,W-Ni₂P/SBA-15催化剂中均只存在Ni₂P物相;催化剂的比表面积和孔体积随着W含量的增加先增大后减小;强酸量和总酸量都随W含量的增加有明显增加;W的加入使得催化剂表面的 Ni^δ+含量有所降低,而 P^δ-含量有所增加;在大于360℃时,催化剂对二苯并噻吩具有很好的深度加氢脱硫活性,并且以直接脱硫生成联苯的脱硫机理为主。     

Change of asphaltene and resin properties after catalytic aquathermolysis

Resin and asphaltene were separated from Liaohe heavy oil. Catalytic aquathermolysis of asphaltene and resin was investigated by using water soluble catalysts （NiSO4 and FeSO4） and oil soluble catalysts （nickel naphthenate and iron naphthenate）. Before and after aquathermolysis, the properties of the resin and asphaltene was compared by means of ultimate analysis, vapor pressure osmometer （VPO） average molecular weight, X-ray diffraction （XRD）,^13C and ^1H nuclear magnetic resonance （NMR）. The conversion sequence was as follows： No-catalyst〈NiSO4〈FeSO4〈nickel naphthenate〈iron naphthenate. In the presence of catalysts, the amount of H2 and CO increased significantly, while H2S in the gas product decreased. The molecular weight of asphaltene and resin increased after reaction without catalyst. But the catalysts restrained this trend. The H/C ratio of asphaltene and resin decreased after reaction. From the results of average structural parameters and molecular weight, it was found that asphaltene and resin were partly aggregated after aquathermolysis.     

Mechanochemical-treated Cr-promoted Vanadyl Pyrophosphate Catalyst for n-Butane Oxidation to Maleic Anhydride

Abstract

Cr-promoted vanadium phosphate (VPO) catalyst was synthesized by mechanotreating VOHPO₄·0.5H₂O in cyclohexane for 2 hr using a high energy planetary ball miller followed by calcination in a flow of n-butane/air mixture at 673 K. The physico-chemical properties of the sample were investigated by several characterization techniques such as BET, XRD, redox titration, SEM, and TPR. The data were compared to the unmilled material. BET surface area measurement of the milled catalyst showed that it possesses higher surface area (13.2 m² g^?1) compared to the unmilled catalyst (6.4 m² g^?1). Milling also caused a slight increment in the average oxidation state of vanadium as well as the percentage of V⁵⁺ oxidation state. XRD pattern of the milled material revealed that the major diffraction peaks were broadened thus indicating a reduction of particle size. SEM micrographs showed the lost in the blossom morphology and the formation of layer packages, with more circular particles in the milled catalyst. The amount of active lattice oxygen species being removed from V⁴⁺-O^? pairs increased significantly for mechanochemical treated Cr-doped VPO catalyst leads to the enhancement of the catalytic activity for n-butane oxidation to maleic anhydride.     

Co负载量对Co/γ-Al2O3催化剂F-T合成催化性能的影响

 制备了不同Co负载量的系列Co/γ-Al₂O₃催化剂,采用XRD、H₂-TPR和H₂-TPD等方法对其进行表征,并考察Co负载量对Co/γ-Al₂O₃催化剂催化F-T合成反应性能的影响。结果表明,随Co负载量的增加,Co/γ-Al₂O₃催化剂的催化活性先增加后降低,在Co负载量25％附近达到最大。Co/γ-Al₂O₃催化剂上Co₃O₄晶粒尺寸随Co负载量增加而逐渐增大,而催化剂的还原温度变化不大,催化剂的还原度和氢吸附量则随Co负载量增加先增大后降低。Co/γ-Al₂O₃催化剂的催化活性与其氢吸附量呈线性关系。     

Preparation of VPO Catalysts and Effect of Zirconium Promoter on the Selective Oxidation of Pentane

1. Introduction The C5 cut, a relatively low-cost hydrocarbon stream in oil refining, has not found adequate use in petrochemical industry (Weissermel and Arpe, 1978). If it is used as liquid-petroleum-gas (LPG) component, the C5 cut is too heavy; while if it is used as gasoline component, the C5 cut is relatively too light. On the contrary, the demand for phthalic and maleic anhydrides is expected to grow at a rate of about 5% per year (Gleaves and Centi, 1993) due to their increasing app…     

In Situ Preparation of Mesoporous Catalyst WSiOx

Abstract

A series of mesoporous catalysts WSiOx with different tungsten contents was prepared under hydrothermal conditions using cetyltrimethyl-ammonium bromide (CTAB) as a structure-directing agent, tetraethyl orthosilicate (TEOS) as a silica source, and ammonium paratungstate as a tungsten source. The catalyst samples were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) to confirm the mesoporous structure: the specific surface area of 966 m²/g, an average pore diameter of 4.68 nm, and high pore volume of 1.5 cm³/g. The catalytic performance of prepared catalysts for hydrodesulfurization (HDS) was evaluated using fluid catalytic cracked (FCC) diesel oil as feed in a high-pressure hydrogenation microreactor. The results indicated that the WxC/MCM-48 catalysts exhibited good catalytic HDS activity.     

邻甲酚加氢脱氧还原型催化剂的实验研究

以邻甲酚为生物质热解油模型化合物,研究了几种还原型加氢催化剂的催化脱氧性能的差异。采用孔饱和浸渍法制备了Mo/Al₂O₃、CoMo/Al₂O₃和CoMoEDTA/Al₂O₃加氢脱氧催化剂,采用H₂ -TPR、XRD对它们进行了表征;在H2气氛下对催化剂进行了还原,并在连续流动固定床加氢微反装置中,考察了邻甲酚在不同还原态催化剂催化下加氢脱氧反应的转化率和产物的选择性。结果表明,在相同的加氢反应条件下,CoMoEDTA/Al₂O₃的催化活性和稳定性均比Mo/Al₂O₃和CoMo/Al₂O₃催化剂高;在反应过程中,Mo/Al₂O₃催化剂表现出较高的直接脱氧选择性,而CoMo/Al₂O₃和CoMoEDTA/Al2O3催化剂表现出较高的加氢脱氧选择性。     

正丁烷氧化制顺丁烯二酸酐VPO催化剂活性相性质的研究

采用三种典型的还原方法制备VPO催化剂 ,并且进行了XRD、IR、TG和DTA的表征测试及其由正丁烷、丁烯选择性氧化制顺丁烯二酸酐的评价试验。研究了VPO催化剂活性相的生成与其性质 ,探讨了活性相结构对其催化性能的影响。结果表明 ,不同的还原方法可以制备具有不同性质的活性相 (VO) 2 P2 O7,( 0 2 0 )晶面适宜失序变形的(VO) 2 P2 O7,对于促进催化性能的提高具有重要的作用。     

The Effect of Pd Precursors on the Catalytic Activity of a Pd/Al2O3 Catalyst for Cumene Hydroperoxide Hydrogenation

Abstract

Abstract Pd/Al₂O₃ catalysts were prepared by wet impregnation using K₂PdCl₄, (NH₄)₂PdCl₄, and Pd(NO₃)₂ as precursors. All catalysts were characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and CO chemisorption. The results obtained in the hydrogenation of cumene hydroperoxide (CHP) to α-cumyl alcohol (CA) showed that Pd/Al₂O₃ catalyst prepared from Pd(NO₃)₂ exhibited the highest turnover frequency (TOF) value and the greatest deactivation extent, whereas Pd/Al₂O₃ catalyst prepared from (NH₄)₂PdCl₄ displayed the lowest TOF value but the best stability.     

Selective Hydrogenation of Maleic Anhydride to Succinic Anhydride Over Nickel-palladium Catalysts

Hydrogenation of maleic anhydride (MA) to succinic anhydride (SA) over Ni-Pd bimetallic catalysts prepared by impregnation method has been studied at different Pd contents, pressures and temperatures. Catalytic activity was greatly influenced by the Pd content, pressure and temperature. Use of 5wt%Ni-0.02wt%Pd/clay catalyst, the 100% conversion for MA and 100% selectivity for SA were obtained for MA hydrogenation at normal pressure. The catalysts were characterized by an array of techniques, including X-ray diffraction (XRD) and H₂ temperature-programmed reduction (TPR). XRD and TPR studies showed that nickel was present as Ni²⁺ species on the support, and that there was no elemental nickel (Ni⁰) and Ni₂O₃ in the unreduced samples. XRD and TPR also showed that Pd was as amorphous existence on the catalysts.     

Sulfuration Pretreatment of Ni/Al2O3 Catalyst to Remove Butadiene in FCC C4 Fraction

Abstract

The Ni-based catalysts have more advantages than the most widely used Pd-based catalysts in selective hydrogenating of the butadiene in fluid catalytic cracking (FCC) C₄ fraction. But the selectivity and stability of the Ni-based catalysts aren't good. The sulfuration pretreatment is an effective process to improve the performance of the Ni/Al₂O₃ catalysts. The sulfuration conditions of the Ni/Al₂O₃ catalyst have been studied in this article. The results showed the fittest conditions are that the catalyst was in-situ presulfurized for 60 min by the solution of S concentration 0.07 mol/L. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the presulfurization declined the Ni crystal dimension.     

Surface Properties and Reactivity of Iron-Doped Titanium Oxides Catalysts in Oxidative Dehydrogenation of Ethylbenzene with CO2

Abstract

The effect of Fe³⁺ doping level on the surface properties and catalytic performance of a series of iron-doped titanium oxide catalysts (1–7 mol% Fe³⁺) prepared using an acid-catalyzed sol-gel method was investigated in oxidative dehydrogenation of ethylbenzene with CO₂. The characterization of catalysts was carried out by means of x-ray powder diffraction (XRD), temperature programmed reduction (TPR), and the method of Brunauer, Emmett, and Teller (BET). It was found that the capacity of isolated Fe³⁺ centers in titania matrix is responsible for the catalytic performance; the catalysts exhibit the best activity at the loading level of Fe³⁺, about 3 mol%. In addition, it was shown that the appropriate pore size of the catalysts ranges from 5 nm to 25 nm; the selectivity to styrene increases with an increase in the specific surface area of the appropriate pores.     

FISCHER-TROPSCH SYNTHESIS: IMPACT OF PRETREATMENT OF ULTRAFINE IRON OXIDE UPON CATALYST STRUCTURE AND SELECTIVITY

ABSTRACT

The present study has shown that activation of a high surface area Fe₂O₃ catalyst in CO in a CSTR using tetralin as solvent results in an activity that is three times that of the material that is activated in H₂ or directly in the syngas. Independent of the catalyst activation, similar methane and CO₂ selectivities are obtained. This suggests that the active catalytic phase is the same for the three pretreatments. Since the particle size estimated by XRD shows a variation within 30%, the difference among the activities of the differently activated catalysts can be attributed to differences in the concentration of active sites on the catalyst surface rather than the extent of the surface.     

Conversions of mixtures of propane and benzene on Pt,Re/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + H-zeolite systems

The conversion of C₆H₆: C₃H₈C mixtures on mixed catalysts composed of the metal catalysts Pt,ReOx/Al₂O₃ and zeolites Y, M, and ZSM-5 in the H form was studied. The products of benzene dehydroalkylation by propane and propane dehydrogenation products are formed at 180–350°C. It has been shown that propane is activated on the metal catalysts and C₆H₆ interacts with the zeolites yielding the C₆H₇ ⁺ intermediate, which acts as an agent of proton transfer from a zeolite to a metal catalyst, and another intermediate C₉H₁₃⁺ (I). Cumene, alkylbenzenes, and propene are formed as a result of the conversion of I. A comparison of the results of the conversion of these mixtures on the composite catalysts with different zeolites shows that the formation of cumene and propene is thermally controlled and the formation of the other products is kinetically controlled. It has been concluded that the coupling of the redox properties of the metal catalysts with the acid-base properties of the zeolite catalysts facilitates the low-temperature transformations of the mixtures.     

Vanadium-catalyzed extractive oxidesulfurization of commercial diesel in ionic liquid with combined oxidizing agents

A series of vanadium catalysts were synthesized and employed in pyridinium phosphate [HPy][H₂PO₄] with various oxidants for extractive catalytic oxidesulfurization (ECODS) of diesel. The VO(acac)₂ showed high catalytic activity with HNO₃/H₂SO₄ and ionic liquid via microwave radiations in the MECODS of diesel. The sulfur removal could reach 98.9% in 210?s at 500?W, which was superior to that of the simple ECODS (89.3%) under optimal conditions (V_diesel?=?20?mL, VIL/Vdiesel volume ratio?=?0.075, m(VO(acaca)₂)/m_diesel?=?0.5?wt%, V(HNO₃)/V(H₂SO₄)?=?1 and T?=?80?°C). The catalytic system could be regenerated six times without significant loss of activity.     

Mathematical modeling of catalytic behavior of catalyst pellets in crude oils after blocking by liquid sulfur

The sulfur recovery unit converts H₂S to elemental sulfur by the Claus process. The process occurs during two combustion and catalytic reactions. Alumina (γ-Al₂O₃) and bauxite (Al₂O₃H₂O) are the main Claus catalysts in crude oils. The volume distribution of micro- and macropores and the parameter of Bethe lattice representing the complex structure of catalyst pellets pores are the most important parameters affecting catalyst performance. This research is aimed at evaluating these parameters impact on effective efficiency of catalyst bed after blocking by liquid sulfur for the second and third reactors. It can be done by considering micro- and macropores as a function of pellet diameter. The results show that pellets with a minimum coordination number or Bethe lattice parameter of 6 are more suitable to use in catalytic reactors. There is a great consistency between the modeling results and the industrial ones. In addition, a catalytic pellet with a diameter of 4.55 mm has the most optimal performance for sulfur recycling processes in industrial crude oil.     

Effects of Impregnation Solvents on Catalytic Performance of Co-Ru-ZrO2/γ-Al2O3 Catalyst for Fischer-Tropsch Synthesis

Abstract

Used ZrO₂ modified γ-Al₂O₃ as support, Co-Ru catalysts were prepared by incipient impregnation method. The effects of impregnation solvents on the performances of catalysts were examined. The catalyst was prepared with ethanol solution and high Co dispersion was obtained, exhibiting highest activity of CO hydrogenation, very low methane selectivity, and high heavy hydrocarbon C₅ ⁺ selectivity. The catalysts were prepared with aqueous solution and methanol solution, and the reaction behaviors were similar. The solvent isopropanol caused the lowest catalytic activity and highest methane selectivity. Increasing the reaction temperature enhanced the CO hydrogenation rate, and the CO conversion slightly increased the CO₂ selectivity and favored the formation methane and light hydrocarbons, while the chain growth probability decreased. For the catalyst prepared with ethanol, the CO conversion, the CH₄ selectivity, and the C₅ ⁺ selectivity were 94.16%, 5.65%, and 88.2%, respectively, and the chain growth probability was 0.87 at 493 K, 1.5 MPa, 800 h^?1, and n(H₂):n(CO) = 2.0 in feed.