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

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.     

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.     

硫化行为对Ni2P/SBA-15催化剂结构和加氢脱硫性能的影响

以介孔分子筛SBA-15为载体、硝酸镍为镍源、磷酸氢二铵为磷源,等体积浸渍法制备了Ni2P/SBA-15催化剂前驱体,然后在H2流中程序升温还原,得到Ni2P/SBA-15催化剂,再用CS2溶液对催化剂进行了硫化处理,制备出了硫化态xCS2-Ni2P/SBA-15催化剂。采用XRD、N2吸附-脱附、XPS对催化剂的结构进行了表征,对催化剂的二苯并噻吩加氢脱硫活性进行了评价,考察了硫化条件对催化剂结构和二苯并噻吩加氢脱硫催化活性的影响。结果表明,xCS2-Ni2P/SBA-15催化剂的物相有Ni2P、Ni12P5、Ni3S2,催化剂的比表面积随硫化溶液中CS2质量分数的增加有一定程度的增加,催化剂表面的Ni以Niδ+和Ni 2+形式存在,P以Pδ-和P5+形式存在。采用5%CS2硫化溶液硫化的催化剂对二苯并噻吩加氢脱硫具有最高的催化活性,380℃时二苯并噻吩的转化率可达99.3%。硫化过程形成的Ni3S2活性物相对二苯并噻吩的转化和直接脱硫都有利。     

The Effect of Cr,Ni, Fe,and Mn Dopants on the Performance of Hydrothermal Synthesized Vanadium Phosphate Catalysts for n-Butane Oxidation

Abstract

Vanadium phosphorus oxide (VPO) catalysts synthesized via hydrothermal method were introduced with some different dopants, Cr, Ni, Fe, and Mn during the preparation of the precursors, VOHPO₄ · 0.5H₂O. All modified precursors were subsequently transformed under reaction conditions to give the active phase, (VO)₂P₂O₇. Several techniques were used to characterize the physicochemical properties of the catalysts, such as X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), H₂-temperature programmed reduction (TPR), laser Raman spectroscopy (LRS), and chemical analysis. The catalytic performance of the catalysts for selective oxidation of n-butane to maleic anhydride has been carried out by using a fixed bed microreactor (673 K, gas hourly space velocity [GHSV] = 2,400 hr^?1). The results show that the addition of dopants into the VPO catalysts increased the surface area of the catalysts and induced the formation of V⁵⁺ phases as shown in XRD and LRS spectra that promoted the catalytic performance. A further water reflux treatment to all the precursors gave catalysts with only (VO)₂P₂O₇ phase. However, the activity and selectivity of these catalysts were reduced markedly.     

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.     

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。     

Fe 3+x-TiO2/Shell光催化剂的制备及其对石油的光催化降解

 以自制的贝壳基规整吸附体为载体,采用浸渍煅烧法制备了Fe ³⁺_x-TiO₂/Shell光催化剂。采用XRD、SEM-EDS和UV-Vis等技术对制备的Fe ³⁺_x-TiO₂/Shell光催化剂进行表征。以石油为降解对象,考察了Fe³⁺掺杂量、Fe ³⁺_x-TiO₂/Shell的负载次数及光照时间对Fe ³⁺_x-TiO₂/Shell光催化活性的影响。结果表明,Fe³⁺掺杂量为0.7%(m(Fe³⁺ )/m(TiO₂)×100%)、Fe ³⁺_0.7-TiO₂负载次数为4次时,制备的Fe ³⁺_0.7-TiO₂/Shell光催化剂的光催化活性最高,300 W碘钨灯照射16 h,石油的光催化降解率达76%。     

Influence of catalyst support structure on ethene/decene metathesis and coke formation over WO3/SiO2 catalyst

8wt%WO3/SiO2 metathesis (disproportionation) catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorption-desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS) and scanning transmission electron microscopy-high-angle annular dark field (STEM HAADF). The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure: The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster.     

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.     

Magnetic hybridized Fe3O4/HKUST-1 composite modified with graphite oxide to remove thiophene from model fuels

Abstract

To improve the desulfurization adsorption performance of the magnetic hybrid material Fe₃O₄/HKUST-1, an innovative adsorbent Fe₃O₄/GO/HKUST-1 was synthesized. The desulfurization performance of Fe₃O₄/GO/HKUST-1 increased 24%, and the adsorption capacity increased to 38.21?mg/g because of a higher surface area and higher porosity than the parent materials. Moreover, the desulfurization capacity of Fe₃O₄/GO/HKUST-1 decreased 10% after five adsorption desorption cycles. Therefore, excellent adsorption properties and reusability make Fe₃O₄/GO/HKUST-1 attractive in the field of fuel desulfurization.     

Characterization of Al2O3–ZrO2 Mixed Oxide Supported Mo Hydrotreating Catalyst

Abstract

A series of molybdenum catalysts supported on Al₂O₃–ZrO₂ mixed oxide containing 50% ZrO₂ and 50% Al₂O₃ were prepared by incipient wetness technique and characterized by BET surface area, X-ray diffraction, temperature programmed reduction and oxygen chemisorption. The catalytic activities for hydrodesulphurization (HDS), hydrogenation (HYD), and hydrocracking (HYC) were determined using thiophene, cyclohexene, and cumene as model compounds, respectively. Results indicate that up to 8 wt% Mo loading, the catalyst is well dispersed and crystallite growth occurred beyond this loading. Also both oxygen uptake and catalytic activities increase with Mo loading up to 8 wt% and then decreases at higher loading. A linear correlation was obtained between oxygen uptake and all catalytic activities and the correlation coefficients obtained suggest that the order of catalytic activities for HDS, HYD, and HYC is: HDS > HYD > HYC. Furthermore, the catalytic activities of the mixed oxide supported catalyst for HDS, HYD, and HYC were higher than those supported on pure alumina and pure zirconia. The incorporation of 3% Co on 8% Mo catalyst was determined to result in enhanced activity for HDS, HYD, and HYC.     

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.     

重质油催化工艺多产乙烯过程中污染铁对催化剂性能发挥的影响

采用N2吸附容量法、BET、热重原位NH₃-TPD、吡啶吸附红外光谱(Py-IR)法分析了污染铁对重油制取乙烯专用催化剂性能发挥的影响。结果表明,有机铁污染催化剂微孔部分的比表面积和孔体积都有明显损失,低于200℃的NH₃-TPD脱附峰代表的弱酸中心损失约为26%。L酸点和B酸点的混合酸对重油催化制乙烯中甲烷、氢气的产生起到关键的作用。环烷酸铁污染后的催化剂沸石晶内酸性大量损失,预示在重油催化制乙烯工艺中有机铁污染催化剂中毒部分主要位于沸石晶内,而非外表面或微晶的孔口处;且原油中Fe³⁺比Fe²⁺更具有金属活性,表现出的氧化脱氢性能更为明显。在重油催化制乙烯工艺中,铁污染催化剂会导致氢气、焦炭的急剧增加,丙烯产率也会明显减少,而干气和汽油产率基本不受影响。     

Reduction of NOx in fluid catalytic cracking flue gas over Mg-Al spinel modified with transition metal oxides

Mg-Al spinel modification with transition metal oxides of CuO, Mn₂O₃, and Fe₂O₃ was prepared to catalyze the NO+CO reaction for the DeNOx of fluid catalytic cracking flue gas. Mg-Al spinel modification with CuO showed the best catalytic performance for the easy adsorption of CO on CuO. The Cu⁺ in amorphous state of the catalyst surface was contributed for the main adsorption site of CO from the characterization results by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy technology. The additive amount of CuO was optimized to 4%, and the excess CuO sintered and converted to crystal phase.     

钒作为加氢催化剂活性组分的研究 Ⅱ 钒对NiMo/Al2O3催化剂渣油加氢活性的影响

 采用浸渍法制备了一系列含V的NiMo/Al₂O₃催化剂。对硫化态含V的NiMo/Al₂O₃催化剂进行了XPS和TEM表征;以科威特常压渣油为原料,考察了V对NiMo/Al₂O₃催化剂渣油加氢活性的影响。结果表明,由于渣油中金属和硫的存在形态不同,并且V-Mo-S相和V-S相对于加氢脱金属的催化作用大于加氢脱硫的催化作用,因此V能引起NiMo/Al₂O₃催化剂上渣油脱金属率的增加;但是V含量较高时,V会造成NiMo/Al₂O₃催化剂上渣油脱硫率的降低。     

ZrO2-SiO2 AEROGEL SUPPORTED COBALT CATALYSTS FOR THE SYNTHESIS OF LONG-CHAIN HYDROCARBON FROM SYNGAS

ABSTRACT

The effect of support and preparation method on the texture, surface area, extent of reduction, H₂ desorption and Fischer-Tropsch synthesis(FTS) reaction properties of ZrO₂-SiO₂ aerogel supported cobalt-based catalysts was investigated. The results indicate that under the conditions that favor the formation of long-chain hydrocarbons, cobalt catalyzed FTS reaction appears to be structure sensitive. Support effects significantly influence the catalytic behavior. Cobalt catalyst supported on zirconia-coated silica aerogel leads to heavy products from syngas, in which case C5⁺ yield could reach 150g/Nm³(CO+H₂) under the optimal conditions (T=293K, P=2.0MPa, GHSV=500h^?1); cobalt catalyst supported on ZrO₂-SiO₂ mixed aerogel, however, was shown to produce middle distillate and the yield of C5-C₂₀ products for this catalyst is about 120g/NM³ (CO+H₂)     

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.     

The Synthesis and Application of CuO-ZnO/HZSM-5 Catalyst With Core-shell Structure

Abstract

CuO-ZnO/HZSM-5 catalyst was prepared hydrothermally by CuO-ZnO as the core and HZSM-5 as the shell and used in hydrogenation of CO₂ to produce dimethyl ether. The morphologies, phase structure, and acid properties of this catalyst were investigated with transmission electron microscopy, X-ray diffraction, and NH₃-temperature programmed desorption in detail. The experimental results showed that the catalyst exhibited higher catalytic activity compared with the catalysts prepared by traditional mechanically mixing method and impregnation method.     

Structure and Reactivity of Vanadia/Dolomite Catalysts

Abstract

Supported vanadium oxide catalysts containing surface vanadia species on oxide supports are extensively employed as catalysts for many hydrocarbon oxidation reactions. This article studies the structure and reactivity of surface vanadia species supported on purified natural dolomite. CaO-MgO oxide support was derived from purified calcined dolomite mineral. Ammonium metavanadate was used as a source of V₂O₅, and the vanadia contents were varied from 10–18 wt%. The CaO-MgO support and the prepared vanadia catalysts (V₁, V₂, V₃) were characterized by means of X-ray, FTIR, and scanning electron microscopy. The activity of the prepared catalysts and the influence of vanadium loading on the catalytic performance for oxy-dehydrogenation of methyl cyclohexane were investigated at reaction temperatures ranging from 250°C to 450°C and under atmospheric pressure.     

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.