CoMo/Ti-SBA-15 catalysts for dibenzothiophene desulfurization

With a view to reducing the sulfur content in diesel fuels, novel desulfurization CoMo catalysts were supported on a Ti-loaded hexagonal mesoporous SBA-15 material. The Ti-SBA-15 substrates were synthesized using triblock copolymers as structure-directing agents. Catalytic activity was assessed in the model reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT), carried out in a batch reactor at T = 623 K and with a total hydrogen pressure of 3.1 MPa. The reaction proceeds via the direct desulfurization route (main route) and the hydrogenation (HYD) pathway. The incorporation of Ti into the SBA-15 afforded catalysts that were more active than the Ti-free counterpart, due to the enhancement of the DDS route in this reaction. This difference was explained in terms of a larger number of coordinately unsaturated sites (CUS) of the metal sulfide on Ti-loaded catalysts. Under steady-state conditions, the CoMoST20 catalyst with a Si/Ti ratio of 20 was the most active among the catalysts studied. Since this catalyst exhibited both Ti⁴⁺ ions incorporated into the SBA-15 framework and separate anatase TiO₂ clusters located on its surface, the activity enhancement on this sample was explained by the larger intrinsic activity of the “Co–Mo–S” phase located on these TiO₂ nanoparticles. The Ti-SBA-15 supports and the CoMo/Ti-SBA-15 catalysts were studied by N₂ adsorption–desorption isotherms, XRD, TEM, FTIR of adsorbed pyridine and NO, UV–vis DRS, TPR, micro-Raman and XPS spectroscopy.     

Iron species incorporated over different silica supports for the heterogeneous photo-Fenton oxidation of phenol

Iron-containing catalysts have been prepared following different synthesis routes and silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials were assessed on the photo-Fenton degradation of phenolic aqueous solutions using near UV irradiation (higher than 313 nm) at room temperature and initial neutral pH. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions. Aromatic compounds and carboxylic acids as by-products coming from incomplete mineralization of phenol as well as the efficiency of each catalytic system in the use of the oxidant were also studied. Stability of the materials throughout the photo-Fenton reaction was evaluated in terms of metal leachibility. Activity and stability depend on the environment of iron species and features of silica support. The evolution of pH with the reaction time and their relationship with TOC degradation and leaching degree has been discussed. A nanocomposite material of crystalline iron oxides supported over mesostructured SBA-15 material is shown the most successful catalyst for degradation of phenolic aqueous solutions by photo-Fenton processes, achieving an outstanding overall catalytic performance accompanied with a noteworthy stability.     

Hydrotreating of gas oil on SBA-15 supported NiMo catalysts

The siliceous and the metal substituted (B or Al)-SBA-15 molecular sieves were used as a support for NiMo hydrotreating catalysts (12 wt.% Mo and 2.4 wt.% Ni). The supports were characterized by X-ray diffraction (XRD), scanning electron microscopy and N₂ adsorption–desorption isotherms. The SBA-15 supported NiMo catalysts in oxide state were characterized by BET surface area analysis and XRD. The sulfided NiMo/SBA-15 catalysts were examined by DRIFT of CO adsorption and TPD of NH₃. The HDN and HDS activities with bitumen derived light gas oil at industrial conditions showed that Al substituted SBA-15 (Al-SBA-15) is the best among the supports studied for NiMo catalyst. A series of NiMo catalysts containing 7–22 wt.% Mo with Ni/Mo weight ratio of 0.2 was prepared using Al-SBA-15 support and characterized by BET surface area analysis, XRD and temperature programmed reduction and DRIFT spectroscopy of adsorbed CO. The DRIFT spectra of adsorbed CO showed the presence of both unpromoted and Ni promoted MoS₂ sites in all the catalysts, and maximum “NiMoS” sites concentration with 17 wt.% of Mo loading. The HDN and HDS activities of NiMo/Al-SBA-15 catalysts were studied using light gas oil at temperature, pressure and WHSV of 370 °C, 1300 psig and 4.5 h⁻¹, respectively. The NiMo/Al-SBA-15 catalyst with 17 wt.% Mo and 3.4 wt.% of Ni is found to be the best catalyst. The HDN and HDS activities of this catalyst are comparable with the conventional Al₂O₃ supported NiMo catalyst in real feed at industrial conditions.     

X-ray diffraction study of a CoMo sulfide obtained by the impregnated thiosalt decomposition method

X-ray powder diffractometry was used to characterize the phases produced during the preparation of MoS₂ catalysts promoted with Co, by the impregnated thiosalt method. After a crystallization process at 673 K and 1043 K the X-ray analysis seems to indicate the presence of a mixed CoMo sulfide, in addition to the MoS₂ and Co₉S₈.     

超声对Cu(I)/SBA-15脱硫吸附剂制备和性能的影响

分别采用超声浸渍法和普通浸渍法制备了Cu(I)/SBA-15吸附剂,利用静态吸附实验比较了这两种方法制备的吸附剂在模型汽油中的噻吩吸附脱硫性能,并利用BET,TEM,XPS等手段对所制备的吸附剂进行了表征.结果表明,超声浸渍法制备的Cu(I)/SBA-15吸附剂的脱硫性能明显优于普通浸渍法制备的吸附剂.BET结果显示,超声促进了活性组分铜在吸附剂表面的分散.TEM分析表明,在超声场下制备的Cu(I)/SBA-15吸附剂表面的铜粒子颗粒较小,且分布均匀.XPS分析显示,超声有效地提高了铜离子在吸附剂表面的负载量,并且促进Cu(I)在其表面含量的增加,从而有利于吸附脱硫性能的提高.     

Heterogeneous photo-Fenton degradation of phenolic aqueous solutions over iron-containing SBA-15 catalyst

A novel iron-containing mesostructured material has been successfully tested for the heterogeneous photo-Fenton degradation of phenolic aqueous solutions using near UV–vis irradiation (higher than 313 nm) at room temperature and close to neutral pH. This catalyst is a composite material that contains crystalline hematite particles embedded into the mesostructured SBA-15 matrix in a wide distribution of size (30–300 nm) and well dispersed ionic iron species within the siliceous framework. The outstanding physico-chemical properties make this material a promising photocatalyst leading to better activity than other unsupported iron oxides. An experimental design model has been applied to assign the weight of catalyst and hydrogen peroxide concentrations in the photo-Fenton processes over this particular material. The catalytic performance has been monitored in terms of aromatics and total organic carbon (TOC) conversions, whereas the catalyst stability was evaluated according to the metal leached into the aqueous solution. Hydrogen peroxide concentration plays an important role in the stability of the iron species, preventing their leaching out into the solution, in contrast to the effect shown in typical dark-Fenton reaction. The homogeneous leached iron species result in very little contribution to the overall photocatalytic process. Catalyst loadings of 0.5 g/L and concentration of hydrogen peroxide close to the stoichiometric amount have yielded a total abatement of phenol and a remarkable organic mineralization.     

Promotion effect of cerium and lanthanum oxides on Ni/SBA-15 catalyst for ammonia decomposition

CeNi/SBA-15 and LaNi/SBA-15 catalysts were prepared by deposition–precipitation (DP) method and characterized by N₂ physical adsorption, XRD, H₂-TPR, H₂-chemisorption and TEM. Their catalytic performances in the ammonia decomposition reaction were tested and compared with Ni/SBA-15 catalyst. Addition of cerium and lanthanum oxides to the Ni/SBA-15 catalyst caused some decrease of BET surface area and pore volume of the catalysts, but led to a promotion effect to their catalytic activity which was closely related to the ratio of Ce (La)/Ni. The highest conversion of ammonia could be obtained when the Ce (La)/Ni ratio was around 0.3. The promotion effect is more evident on CeNi/SBA-15(0.3) than on LaNi/SBA-15(0.3) catalyst under identical reaction conditions. The CeNi/SBA-15 and LaNi/SBA-15 catalysts show smaller nickel particle size and easier reducibility in comparison with the Ni/SBA-15 catalysts.     

P/SBA-15催化合成十六烷基苯

采用负载磷酸的SBA-15分子筛作为催化剂,以苯和十六碳烯为原料,经烷基化反应合成十六烷基苯。在微型液相固定床反应器上考察了反应温度、空速、体系压力、磷酸负载量以及苯烯摩尔比等反应条件对催化剂性能的影响。研究结果表明,磷酸的适宜负载量约为7%(质量分数),适宜反应条件为反应温度180℃、空速为2.0 h-1、体系压力为2.0 MPa和苯、烯摩尔比为10。在此条件下,十六碳烯的转化率可达到94.5%,十六烷基苯选择性可达93%。催化剂单程寿命达到120 h以上。负载磷酸的SBA-15催化剂呈现较好的催化活性和稳定性。     

SBA-15的改性及催化文冠果油制备生物柴油

以介孔分子筛SBA-15为载体,采用直接合成法和后合成法镀饰Al后再负载碱金属盐KNO₃,制得负载型固体碱催化剂KNO₃-AlSBA-15和KNO₃-Al-SBA-15。用XRD、BET、SEM以及CO₂-TPD对催化剂进行表征。结果表明：在SBA-15上镀饰Al可以保护分子筛的介孔结构;进一步负载KNO₃,能够增强催化剂的碱性。将其应用于催化文冠果油酯交换制备生物柴油,结果显示催化剂KNO₃-Al-SBA-15的催化活性最好,优于传统均相催化剂,所得生物柴油产率可达92%,重复使用多次仍具有较好的催化效果。     

Copper-based efficient catalysts for propylene epoxidation by molecular oxygen

Among a series of SBA-15-supported transition metal oxides with and without modification, the CuO_x/SBA-15 after K⁺ modification exhibited the best catalytic performance for the epoxidation of propylene by molecular oxygen. Potassium was the best modifier among various alkali and alkaline earth metal ions examined, and potassium acetate was a superior precursor of K⁺ for propylene oxide formation. The highest propylene oxide selectivity was obtained over a catalyst with copper content of 1 wt.% and K/Cu molar ratio of 0.7. Kinetic studies reveal that the allylic oxidation mainly proceeds over the CuO_x/SBA-15 providing acrolein as the main partial oxidation product, and the K⁺ modification switches the main reaction route from allylic oxidation to epoxidation. The characterizations suggest that copper species with content of ≤5 wt.% are located in the mesoporous channels of SBA-15 existing mainly as CuO_x clusters and Cu²⁺ ions, and there exists an interaction between K⁺ and the copper species. This interaction is proposed to play pivotal roles in epoxidation of propylene. As compared with other reported Cu-based catalysts for propylene epoxidation, the present catalyst possesses several distinct features.     

Overview of support effects in hydrotreating catalysts

The commercial hydrotreating catalysts are usually composed of a sulfide active phase supported on alumina. It has been known for more than 15 years that other supports might lead to enhanced catalytic properties. The present article summarizes the progress which have been made in this area, often related to new methods of preparation of supports, active phases deposition or activation procedures. The properties of active phases supported on oxides, pure or mixed, basic and acidic supports, zeolites, mesoporous materials, carbon and clays are examined.     

Direct synthesis of mesoporous M-SBA-15 (M = Al, Fe, B, Cr) and application to 1-hexene oligomerization

M-SBA-15 materials (M = Al, B, Cr, Fe) were prepared by different direct synthesis methods, characterized and tested catalytically in the 1-hexene oligomerization reaction at 125 °C. Al-SBA-15 were synthesized within the range Si/Al = 12–86 using aluminium isopropoxide as aluminium source. ²⁷Al MAS NMR spectra point out that the three Al-SBA-15 samples contain more tetrahedral aluminium than octahedral and the ratio tetrahedral/octahedral diminished with increasing aluminium contents. B-SBA-15 was prepared with a Si/B = 51–106 using two direct synthesis methods (sol–gel and hydrothermal) and three different boron sources (solid boric acid, aqueous boric acid and boron isopropoxide). The best results in terms of boron incorporation (Si/B = 51) were achieved with solid boric acid and the sol–gel method, although a lower degree of mesoscopic ordering was obtained compared to the hydrothermal procedure. ¹¹B MAS NMR showed that trigonal boron is the principal coordination state obtained after calcination. Cr-SBA-15 was also achieved by direct synthesis method at different pH (1.5, 3, 5) but the incorporation degree was low, at best Si/Cr = 240 at pH 5. UV–vis spectroscopy indicated that all Cr species were Cr⁶⁺ formed during the calcination step. Oligomerization of 1-hexene at 125 °C showed that the highest conversion (30%) was attained over Al-SBA-15 (Si/Al = 30) although Cr-SBA-15 material exhibited close conversion (21%) despite its low heteroatom content (Si/Cr = 240). Dimers were the major products over Al-SBA-15, Cr-SBA-15 and Fe-SBA-15 catalysts (selectivity ≥ 40%) while strikingly, sol–gel B-SBA-15 lead mostly to heavy oligomers (>60%), with less than 10% of dimers.     

SBA-15改性固体酸催化合成乙酸正丁酯的研究

以SBA-15为载体利用尿素水解法制备Zro2/SO2(4)-改性的固体酸SZ/SBA-15,通过XRD、N2吸附-脱附、IR、SEM 、Hammett指示剂法和N H3-TPD法对合成材料的孔结构、骨架结构及表面酸性等进行了表征.实验结果表明,所合成的固体酸催化剂具有典型的介孔结构特征,酸强度在0.80 < Ho <...     

介孔分子筛SBA-15在催化领域的应用进展

从负载固体酸催化剂、金属和金属氧化物以及手性催化剂三方面综述了介孔分子筛SBA-15在催化领域应用的研究进展;并展望了介孔分子筛SBA-15在催化领域的研究方向。     

Hydrotreating properties of mixed NbxMo1−xS2 alumina supported catalysts

Niobium-molybdenum disulfide solid solution (Nb_xMo_1−xS₂) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb_xMo_1−xS₂ solid solution (HDS of DBT, P_tot=33 bar) is not decreased in the presence of H₂S up to p(H₂S)=200 Torr, at least up to x=0.4.     

Novel utilization of mesoporous molecular sieves as supports of cobalt catalysts in Fischer–Tropsch synthesis

Mesoporous molecular sieves (MCM-41 and SBA-15) with different pore diameters have been studied as supports of high loading of Co catalysts, and the performances in FT synthesis have been examined with a fixed bed stainless steel reactor at 2.0 MPa for the purpose of efficient production of C₁₀–C₂₀ fraction as the main component of diesel fuel. The method of exchanging template ions in uncalcined MCM-41 with Co²⁺ ions is effective for holding 10–20% Co within the mesopores while keeping the structure regularity of MCM-41 to some extent, compared with the conventional impregnation method using calcined MCM-41. At 523 K, CO conversion and selectivity to C₁₀–C₂₀ hydrocarbons are both higher at larger loading of 20% Co for the exchanged catalysts with pore diameters of 2.7–2.9 nm. When four kinds of 20% Co/SBA-15 with the diameters of 3.5–13 nm, prepared by the impregnation method using an ethanol solution of Co acetate, are used in FT synthesis at 523 K, the catalyst with the diameter of 8.3 nm shows the largest CO conversion, which is higher than those over MCM-41 supported Co catalysts. At a lower temperature of 503 K, however, the acetate-derived Co is almost inactive. In contrast, the use of Co nitrate alone or an equimolar mixture of the acetate and nitrate as Co precursor drastically enhances the reaction rate and consequently provides high space–time yield (260–270 g C/kg_cat h) of C₁₀–C₂₀ hydrocarbons. The X-ray diffraction and temperature-programmed reduction measurements show that the dependency of the catalytic performance of 20% Co/SBA-15 on its precursor originates probably from the differences in not only the reducibility of the calcined catalyst but also the dispersion of metallic Co. Catalyst characterization after FT synthesis strongly suggests the high stability of the most effective Co/SBA-15 in the dispersion and reducibility of the oxide species and in the mesoporous structure.     

Ruthenium promotion of Co/SBA-15 catalysts with high cobalt loading for Fischer–Tropsch synthesis

30 wt.%Co/SBA-15 catalysts with different ruthenium contents (0.05–0.5 wt.%) were prepared by incipient wetness impregnation and characterized by diffuse reflectance infrared fourier transform spectroscopy, N₂ adsorption-desorption, X-ray diffractometry, temperature-programmed reduction and H₂ desorption, oxygen titration as well as X-ray photoelectron spectroscopy. The addition of a small amount of Ru promoter to Co/SBA-15 shifted the reduction temperature of both steps (Co₃O₄ → CoO and CoO → Co⁰) to lower temperatures and suppressed the formation of Co²⁺ species. After reduction, ruthenium atoms were encapsulated partially with cobalt cluster. There was no strong electronic interaction between metal cobalt and ruthenium, however, hydrogen spillover from ruthenium to cobalt oxide clusters occurred. With increasing ruthenium content, catalyst reducibility increased and the surface was enriched in cobalt atoms. Moreover, the peak intensities of both the linear and bridge types CO adsorption increased with the increase of ruthenium content, enhancing the catalytic activity on Fischer–Tropsch synthesis.     

固相微萃取涂层材料CH2OCHCH2O(CH2)3-SBA-15的制备与表征

以甲基三乙酰氧基硅烷（γ-glycidoxypropyltrimethoxy silane, CH2OCHCH2O（CH2）3Si（OCH3）3; GPTES）为偶联剂,将醚基官能团接枝于SBA-15介孔分子筛孔道中,制备了无机-有机复合介孔材料CH2OCHCH2O（CH2）3-SBA-15,用小角X射线衍射,N2吸附-脱咐,元素分析,红外光谱和滴定法对复合材料进行了表征.结果表明,醚基有机基团成功接枝到SBA-15孔道内壁,而且SBA-15仍保持了有序的孔道结构.并研究了CH2OCHCH2O（CH2）3-SBA-15的萃取效能,结果表明,该涂层材料对多环芳烃有较高的萃取效率.     

Co-Mo／SBA-15柴油加氢脱硫研究

以介孔分子筛SBA-15为载体,担载Co—Mo双金属活性组分制备了深度加氢脱硫催化剂。通过XRD和BET表征表明,负载金属后SBA-15分子筛仍然保持二维晶相结构,表面积略有下降。以直馏柴油为原料,在固定床反应器上评价了催化剂的脱硫反应活性的结果表明,SBA-15介孔分子筛Co—Mo的负载量为W（CoO）=5％,w（MoO3）=25％;脱硫适宜的反应条件为：反应温度360℃,压力4．0MPa,氢油体积比400．0,空速2．0h^-1。在此条件下,柴油硫含量可由1350μg／g降至39μg／g。