V/SBA-15的制备及催化氧化性能研究

以柠檬酸处理过的偏钒酸铵为钒源,采用后合成法制备出了V/SBA-15负载型催化剂,研究其在氧化苯乙烯制苯甲醛反应中的催化性能.结果表明,在钒负载量低于15％时,V/SBA-15仍保持SBA-15的高度有序的二维六方孔道结构,且具有较大的比表面积和孔体积,负载的活性组分金属钒氧化物均匀分布在介孔分子筛表面;在优化条件下催化氧化苯乙烯制苯甲醛,苯乙烯转化率达65.62％,苯甲醛的选择性81.21％,且V/SBA-15具有较好的催化剂稳定性.     

HClO4/SBA-15固体酸催化剂的制备及催化性能

将高氯酸引入具有较大孔径和比表面积的介孔分子筛SBA-15中,制备了用于异相催化的固体酸催化剂HClO4/SBA-15,并通过采用X-射线衍射(XRD)、多孔性检测、透射电镜(TEM)分析等方法,对其结构进行了分析表征.HClO4被负载后,材料的比表面积、孔径及孔容等多孔性参数都有所降低,但并没有破坏介孔分子筛SBA-15的孔道结构.为了证明HClO4/SBA-15的催化性能,探究了HClO4/SBA-15催化的选择性脱异丙叉基及乙酰化的一锅法反应.在室温条件和催化量的HClO4/SBA-15作用下,反应30 min内即可完成,产率达到98％,产物的化学结构通过1H NMR、13C NMR及MS等手段得到了表征.该法后处理简单、收率较高,而且不需要任何溶剂.     

Mn/Al-SBA-15催化剂的制备及其催化氧化甲苯的性能研究

以凹凸棒土为原料，采用原位晶化法制备Al-SBA-15分子筛，负载Mn制备出一系列Mn/Al-SBA-15催化剂，利用XRD、SEM、TEM、H₂-TPR等表征催化剂物化性质，并考察了催化剂催化氧化甲苯性能。结果表明，Al的掺杂能够使Mn活性物种在Al-SBA-15分子筛表面与孔道中高度分散，进一步提升催化剂氧化还原能力。Mn元素质量分数为8%时，催化剂活性最佳，当甲苯浓度为2 000 ppm、空速为60 000 mL/（g·h）时，8%Mn/Al-SBA-15能够将甲苯的T₅₀和T₉₀分别降至201℃和278℃;8%Mn/SBA-15能够将甲苯的T₅₀和T₉₀分别降至223℃和298℃。     

Co掺杂对Ce/MCM-41和Ce/SBA-15催化剂催化氧化甲苯性能的影响

以分子筛为载体,采用等体积浸渍法制备Ce/SBA-15、Ce/MCM-41、Ce Co/SBA-15和Ce Co/MCM-41催化剂。用N2吸附-脱附、X射线衍射、扫描电子显微镜、H2程序升温还原、X射线光电子能谱和傅立叶变换红外光谱等对载体和催化剂进行表征,并考察催化剂催化氧化甲苯的活性。结果表明,与载体相比,随着Ce和Co的浸渍,催化剂的比表面积和孔容下降,但仍然保持了载体的有序介孔结构。引入的Ce和Co没有进入分子筛骨架,而是以立方相固溶体形式存在于分子筛表面和孔道中。催化剂催化氧化甲苯活性顺序依次为:Ce Co/SBA-15>Ce Co/MCM-41>Ce/MCM-41>Ce/SBA-15。共浸渍Ce和Co的催化剂活性明显优于只浸渍Ce的催化剂,活性与其还原性能直接相关,Ce Co/SBA-15催化剂具有最低的还原温度和最好的供氧能力,从而表现出最优的催化性能。     

介孔材料TiO2/SBA-15制备及光催化性能研究

以三嵌段共聚物P123为结构导向剂、甘油作为助溶剂合成了孔道长度可控的六方介孔硅基材料SBA-15,随后在绿色溶媒超临界二氧化碳中合成介孔材料TiO2/SBA-15,利用XRD、N2吸附-脱附、SEM、TEM和EDX等技术对其结构进行分析表征。结果表明甘油的加入可以有效调控SBA-15的孔道长度,TiO2纳米颗粒负载之后,SBA-15六方介孔结构可以得到保持。以染料亚甲基蓝作为模拟污染物对其进行光催化降解测试,合成的负载材料TiO2/SBA-15的降解效果要远远超过纳米TiO2颗粒,同时SBA-15孔道长度越短,其降解效果越好。     

Fe/SBA-16介孔分子筛催化苯选择氧化性能研究

本文考察了不同负载量的Fe/SBA- 16催化剂对苯选择氧化制备苯酚催化活性的影响.运用小角XRD、N2吸附及紫外漫反射光谱对催化剂的结构和催化剂表面活性物种进行研究.结果表明:Fe/SBA-16催化剂保持了SBA-16介孔分子筛的三维立方的孔道结构,高分散的铁物种是催化反应的活性物种.     

M/SBA-15(M=Cu、Fe、Cr)介孔分子筛的制备、表征及其催化NO+CO反应研究

以介孔分子筛SBA-15为载体,采用浸渍法制备M/SBA-15(M=Cu、Fe、Cr) 介孔分子筛催化剂。采用XRD、BET、FT-IR、H₂-TPR和XPS等对样品进行分析表征,在固定床微型反应器中评价M/SBA-15(M=Cu、Fe、Cr)分子筛催化剂催化NO+CO的反应性能。结果表明,负载金属的SBA-15分子筛仍保持高度有序的二维六方介孔结构,比表面积和孔径略有减少,负载的活性金属组分在SBA-15分子筛表面具有较高的分散度。Cu/SBA-15、Cr/SBA-15和Fe/SBA-15催化剂对NO+CO反应体系均有一定活性,但由于活性金属自身的特性及其在载体表面负载量的差异,3种催化剂上呈现的NO还原活性不同,顺序为：Cr/SBA-15＞Cu/SBA-15＞Fe/SBA-15。     

Cr/SBA-15的优化合成及其环己烷氧化性能研究

采用高温水热嫁接的方法,通过调节反应溶液的p H和水热处理温度,成功地将金属铬离子嫁接到SBA-15氧化硅骨架上,制备得到高度规整有序的介孔孔道结构的Cr/SBA-15催化剂,并研究了Cr/SBA-15在以乙腈为溶剂,H_2O_2为氧化剂的环己烷催化氧化反应中的性能。结果表明,当p H=3,Si/Cr摩尔比为15时,合成的Cr/SBA-15催化剂具有高度有序的二维六方介孔结构,同时表现出良好的催化活性和选择性。反应温度为80℃,反应时间为4 h条件下,环己烷催化氧化的转化率可达17%,环己酮和环己醇的选择性分别为65%、35%。Cr/SBA-15催化剂重复使用3次后活性基本不变,表明该催化剂具有良好的稳定性。     

无溶剂法镧改性SBA-15的制备、表征及催化性能

以介孔分子筛SBA-15为载体,采用固相研磨法掺杂La元素,以SO₄^2-或S₂O₈^2-为助催化剂同时掺杂在介孔分子筛中增强SBA-15表面活性中心,制备了La-SO₄^2-/SBA-15和La-S₂O₈^2-/SBA-15负载型固体酸催化剂。用X射线衍射、透射电镜、低温N2吸附－脱附、红外光谱、热重分析和NH₃-TPD等分析方法对改性材料的结构性能及表面酸性能进行了表征。表征结果显示,制得的La-SO₄^2-/SBA-15和La-S₂O₈^2-/SBA-15保持高度有序的二维六方介孔结构。用Hammett指示剂法测得La-SO₄^2-/SBA-15和La-S₂O₈^2-/SBA-15表面酸强度（H₀）分别为2.77~3.30和0.78~0.99,表明制备的改性材料为固体酸。以改性的SBA-15为催化剂,催化合成乙酸正丁酯,在酸醇物质的量比为1∶1.2、催化剂用量0.375 g（为冰醋酸质量的5%）和反应时间140 min的条件下,采用La-S₂O₈^2-/SBA-15和La-SO₄^2-/SBA-15为催化剂,其酯化率分别为97.31%和89.28%。     

VO_x/SBA-16催化CO_2氧化乙苯脱氢性能

采用等体积浸渍法制备了不同钒负载量的VOx/SBA-16催化剂,通过XRD、N_2吸附、H_2-TPR和TGA表征和催化剂性能评价,研究了VO_x/SBA-16催化剂对CO_2氧化乙苯脱氢制苯乙烯的催化性能。结果表明,VO_x/SBA-16催化剂具有良好的乙苯脱氢活性,钒负载量为1.2 mmol/g的催化剂活性最佳,乙苯转化率可达57.6%,苯乙烯选择性98.6%。VO_x/SBA-16催化剂上的乙苯脱氢活性和稳定性明显高于VO_x/MCM-41,是由于SBA-16载体畅通的三维孔道结构更有利于钒物种的高度分散和反应介质的扩散,提高了催化剂的可还原性能,减缓了积炭的生成。     

La-Ni2P/SBA-15/堇青石整体式催化剂及加氢脱硫性能

以介孔分子筛SBA-15为载体,制备一系列不同La含量的La-Ni₂P/SBA-15催化剂前驱体,将La-Ni₂P/SBA-15前驱体涂覆在预处理的整体式载体堇青石上,在H2气氛程序升温还原,制备不同La含量的La-Ni2P/SBA-15/堇青石整体式催化剂。对合成的催化剂进行X射线衍射和N2吸附-脱附结构表征,并评价对二苯并噻吩的加氢脱硫活性。结果表明,Ni₂P存在于所有的La-Ni2P/SBA-15/堇青石整体式催化剂中,且随着La含量的增加,La-Ni2P/SBA-15/堇青石整体式催化剂的比表面积和孔体积均有一定程度的提高,催化活性也提高。对于Ni2P/SBA-15/堇青石整体式催化剂,在300 ℃和380 ℃时,二苯并噻吩加氢脱硫转化率仅为27.2%和91.3%;而1.5%La-Ni₂P/SBA-15/堇青石催化剂在300 ℃和380 ℃时,二苯并噻吩转化率分别为36.8%和96.3%,显示出较好的二苯并噻吩加氢脱硫活性。La-Ni₂P/SBA-15/堇青石整体式催化剂在对二苯并噻吩的加氢脱硫过程中,以直接脱硫和加氢脱硫两种脱硫方式同时进行,并且以直接脱硫为主。     

Effect of the preparation method on the structural stability and hydrodesulfurization activity of NiMo/SBA-15 catalysts

Defined hexagonal cylindrical pore structure SBA-15 material was synthesized as support for hydrotreating catalysts. The stability of the mesoporous material under acid and basic environments commonly used to prepare hydrotreating catalysts was investigated. The effects of the acid and basic treatments on the stability of SBA-15 and NiMo/SBA-15 catalysts were evidenced by different characterization techniques such as N₂ adsorption–desorption, X-ray diffraction (XRD), Raman Spectroscopy and high resolution transmission electron microscopy (HRTEM). Supported NiMo/SBA-15 catalysts prepared by pore volume co-impregnation in acidic, neutral and basic solutions of the Ni and Mo precursor salts were characterized to evaluate the textural and structural changes caused by the method of preparation. Characterization of the support after accelerated stability tests indicates large deterioration of the SBA-15 structural order at basic pH. The characterization results of oxide and sulfided catalysts indicate, for the catalysts prepared at high pH, an increasing presence of β–NiMoO₄ phase in the oxide catalysts, and a relatively lower population of MoS₂ in the sulfided catalysts. The activity of the different catalysts evaluated in the thiophene hydrodesulfurization reaction was higher for the catalysts prepared at low pH.     

Preparation, characterization, and catalytic properties of the Mo2C/SBA-15 catalysts

A series of Mo₂C/SBA-15 catalysts with different Mo contents were prepared by temperature-programmed carburization (TPC). The materials obtained and their oxide precursors (MoO₃/SBA-15) were characterized by Nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) spectroscopy. The activities of the catalysts for deep hydrodesulfurization (HDS) of thiophene were evaluated. The results of N₂ adsorption-desorption isotherms indicated that the surface area and pore diameter of the oxide precursors increase after carburization. The XRD patterns show that Mo₂C particles are highly dispersed in the SBA-15 ordered mesoporous. The test results show that Mo₂C/SBA-15 catalysts have an excellent performance for the deep HDS under the lower temperature region.     

Catalytic combustion of benzene over metal oxides supported on SBA-15

The catalytic combustion of benzene over metal oxides supported on SBA-15 was investigated. The catalysts were prepared by the incipient wetness method and characterized by XRD, BET, TEM, ESR and TPR. The calcined siliceous SBA-15 and CuO/SBA-15 samples displayed well-resolved patterns with a sharp peak at about 1.0°. It is clear that the loading of CuO on the silica matrix drastically decreases the surface area and pore volume of the catalysts, as would be expected for the incorporation of CuO. Among the supported metal oxides, CuO supported on SBA-15 was found to have the highest activity for benzene oxidation. In addition, copper oxide supported on SBA-15 gives higher catalytic activity than copper oxide supported on MCM-41. From the ESR results, the CuO dispersed on the SBA-15 acts as the active site of the CuO/SBA-15 catalysts in the oxidative decomposition of benzene. The catalytic activity gradually increases with increasing CuO loading on SBA-15.     

Characterization and catalytic properties of mesoporous CuO/SBA-16 prepared by different impregnation methods

CuO/SBA-16 catalysts were prepared by two different routes – the conventional impregnation method and the modified impregnation method with pH adjustment. These catalysts were characterized by X-ray diffraction (XRD), atomic absorption spectrometry (AAS), N₂ physisorption and hydrogen temperature programmed reduction (H₂-TPR) measurements which reveal that the cubic cage-like (Im3m) pore structure of the parent SBA-16 molecule sieves was well maintained throughout the synthesis. After introduction of Cu, a different CuO dispersion exists on these catalysts. The CuO/SBA-16 prepared by modified impregnation method has a single highly dispersed CuO which is considered as a highly efficient species for hydroxylation of phenol with H₂O₂. CuO/SBA-16 prepared by the conventional impregnation method shows the presence of bulk CuO species which is undesirable for this reaction.     

SBA-15 as Support for MoS2 and Co-MoS2 Catalysts Derived from Thiomolybdate Complexes in the Reaction of HDS of DBT

Molybdenum sulfide and cobalt-molybdenum sulfide catalysts supported on mesoporous SBA-15 were prepared by thermal decomposition of ammonium thiomolybdate (ATM). SBA-15 was synthesized at 353 K and 413 K to obtain pore diameters of about 6 and 9 nm, respectively. The (Co)-MoS₂/SBA-15 catalysts were characterized with X-ray diffraction (XRD), N₂-physisorption and high-resolution transmission electron microscopy (HRTEM). HRTEM images give evidence for the presence of a poorly dispersed MoS₂ phase with long MoS₂ slabs and a pronounced MoS₂ stacking. The catalytic performance in the hydrodesulfurization (HDS) reaction of dibenzothiophene (DBT) was examined at T = 623 K and P = 3.4 MPa. The Co-MoS₂/SBA-15 materials show a relatively high catalytic activity with a strong preference for the direct desulfurization (DDS) pathway. This is an interesting result in view of the significant stacking of MoS₂ particles and the size of the slabs. The generation of the catalytically active CoMoS phase and a large number of coordinately unsaturated sites (CUS) may explain the high performance of Co promoted MoS₂/SBA-15 catalysts in the HDS reaction. A confinement effect of the mesoporous channels of SBA-15 is observed for the unpromoted MoS₂/SBA-15 catalysts. SBA-15 with 9 nm channel diameter with 11 wt.% Mo loading shows a higher selectivity for the hydrogenation pathway than SBA-15 with 6 nm channel and 16 wt.% Mo loading.     

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.