共查询到19条相似文献,搜索用时 250 毫秒
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在酸性溶液中利用溶胶凝胶-pH值控制两步法直接合成FexOy/SBA-15介孔分子筛,同时利用场发射扫描电子显微镜(FESEM)、小角度X射线衍射(Low-angle XRD)、透射电子显微镜(TEM)以及振动样品磁强计(VSM)对制备的各种SBA-15介孔分子筛进行结构以及性能的测试、表征。结果显示FexOy均匀地分散在SBA-15的骨架中,而且会对SBA-15介孔分子筛起钉轧作用。而后着重研究了FexOy的加入对SBA-15介孔分子筛的热稳定性、催化特性以及磁学性能的影响。FexOy的引入可以增加制备的SBA-15介孔分子筛的热稳定性;FexOy的引入可以改善SBA-15介孔分子筛的催化活性,得到了开口的、石墨化程度较好的纳米碳管。FexOy的引入使SBA-15介孔分子筛具有明显的铁磁性。 相似文献
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利用沸石前驱体溶液和介孔硅球(MSS)为原料, 通过水热法成功制备了具有中强酸性介孔壳的中空介孔硅铝球形分子筛(HMAS)。利用透射电镜(TEM)、扫描电镜(SEM)、X射线衍射(XRD)、N2-吸脱附、27Al核磁共振(27Al NMR)及NH3程序升温脱附(NH3-TPD)对材料的结构和性能进行了表征。研究结果表明, 在MSS的中空过程中伴随有物质再分配和介孔结构的逐渐演变。MSS介孔孔道中的十六烷基三甲基溴化铵(CTAB)分子, 一方面保护MSS免遭强碱性沸石前驱体溶液的溶蚀, 另一方面作为形成HMAS介孔壳层的模板剂。在此CTAB分子的作用下, 沸石前驱体结构单元被引入到HMAS的介孔球壳上。所得材料具有介孔结构和中强酸性, 在催化裂解1, 3, 5-三异丙苯反应中表现出优异的催化性能。 相似文献
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钛硅(TS-1)分子筛的微孔孔道严重限制了其在复杂分子催化转化中的应用,为了克服这一问题,通过酸洗脱、碱刻蚀及二者相结合的方法制备了多级孔 TS-1 分子筛,并采用等体积共浸渍法制备了相应的 NiMo 负载型催化剂;使用 X 射线衍射(XRD)、N2吸附-脱附、吡啶吸附红外光谱(Py-FTIR)、氢气程序升温还原(H2-TPR)、X射线光电子能谱(XPS)和高分辨透射电子显微镜(HR-TEM)等方法对多级孔TS-1分子筛的理化性质进行了表征;以二苯并噻吩(DBT)为探针对催化剂的加氢脱硫(HDS)性能进行了评价。结果表明,和常规TS-1分子筛相比,多级孔TS-1分子筛保持了MFI拓扑结构,比表面积增大且具有介孔结构,分子筛表面形成了适量的Brønsted酸中心;相应催化剂上活性金属与载体间相互作用得以改善,MoS2片晶长度和堆垛层数适宜,形成了更多的 NiMoS活性相;催化剂活性和选择性均有所提升,尤其是酸洗脱获得的 NiMo/AT-TS-1催化剂的活性相较未经处理的NiMo/TS-1催化剂提升了1.2倍,直接脱硫(DDS)路径选择性提升了22%。 相似文献
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采用共沉淀法成功地合成了不同Mg掺杂量的Ce1-xMgxO2(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO2程序升温脱附(CO2-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO2晶格中Mg的含量,可以调控所制备的Ce1-xMgxO2催化材料的粒径、比表面积、表面缺陷等。其中Ce0.90Mg0.10O2展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g-1)以及最高的表面氧含量(31.98%)。将Ce1-xMgxO2催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO2和CH3OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce0.90Mg0.10O2整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO2和其余的Ce1-xMgxO2(x=0.05、0.15、0.20)催化材料。 相似文献
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钛硅(TS-1)分子筛的微孔孔道严重限制了其在复杂分子催化转化中的应用,为了克服这一问题,通过酸洗脱、碱刻蚀及二者相结合的方法制备了多级孔TS-1分子筛,并采用等体积共浸渍法制备了相应的NiMo负载型催化剂;使用X射线衍射(XRD)、N2吸附-脱附、吡啶吸附红外光谱(Py-FTIR)、氢气程序升温还原(H2-TPR)、X射线光电子能谱(XPS)和高分辨透射电子显微镜(HR-TEM)等方法对多级孔TS-1分子筛的理化性质进行了表征;以二苯并噻吩(DBT)为探针对催化剂的加氢脱硫(HDS)性能进行了评价。结果表明,和常规TS-1分子筛相比,多级孔TS-1分子筛保持了MFI拓扑结构,比表面积增大且具有介孔结构,分子筛表面形成了适量的Brønsted酸中心;相应催化剂上活性金属与载体间相互作用得以改善,MoS2片晶长度和堆垛层数适宜,形成了更多的NiMoS活性相;催化剂活性和选择性均有所提升,尤其是酸洗脱获得的NiMo/AT-TS-1催化剂的活性相较未经处理的NiMo/TS-1催化剂提升了1.2倍,直接脱硫(DDS)路径选择性提升了22%。 相似文献
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钙钛矿型LaxSr1-xNi1-yCoyO3光电催化活性研究 总被引:1,自引:0,他引:1
用甘氨酸-硝酸盐燃烧合成法, 制备LaxSr1-xNi1-yCoyO3复合氧化物的陶瓷粉末, 对钙钛矿氧化物进行了XRD结构分析. 在通氧或不通氧下测试氧还原和氧析出的循环伏安曲线. 结果表明: 该氧电极具有双功能催化特性, 但不完全可逆. 利用汞灯作为激发光源, 进行几种水溶性染料和五种混合染料光解实验, 利用紫外-可见、红外以及人工神经网络光度法研究LaxSr1-xNi1-yCoyO3的催化性能. 结果表明: LaxSr1-xNi1-yCoyO3 (x=0.7, 0.9, 1; y=0.3, 0.75)复合氧化物都具有较强光催化特性; LaxSr1-xNi1-yCoyO3的光催化活性高于LaxSr1-xNiO3, 这与B位离子(Ni2—, Co2-)的电子构型有关; Co2+的加入可使LaxSr1-xNiO3的光催化活性有所提高. 相似文献
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固定床反应器上挤条小晶粒TS-1催化丙烯环氧化反应 总被引:1,自引:0,他引:1
采用纳米TS-1母液作为晶种, 在四丙基溴化铵(TPABr)-乙胺廉价水热体系中, 合成出晶粒尺寸为600 nm×400 nm×250 nm的小晶粒钛硅分子筛(TS-1), 用挤条法将其成型, 得到的挤条小晶粒TS-1被用于催化固定床反应器中的丙烯环氧化反应. 采用X射线衍射(XRD)光谱, 傅里叶变换红外(FT-IR)光谱, 紫外-可见(UV-Vis)漫反射光谱及氮气物理吸附对挤条成型的小晶粒TS-1进行表征, 并对丙烯环氧化的最优反应条件进行考察. 其中所考察的条件包括: 反应温度, 压力, 丙烯/H2O2摩尔比(n(C3H6)/n(H2O2)), 丙烯、甲醇及H2O2的质量空速(WHSV), 以及NH3·H2O浓度. 在所考察的范围内, 温度对环氧丙烷(PO)收率的影响较小, 当反应压力为2.0 MPa, n(C3H6)/n(H2O2)为4时, 可以得到最高的PO收率. 当丙烯、甲醇及H2O2的空速分别为0.93、2.5及0.25 h-1时, PO在产物中的含量最高. 较低的NH3·H2O浓度对高PO收率更有利. 在优化的反应条件下, 对比不同晶粒大小TS-1的催化性能, 并考察了挤条小晶粒TS-1的长期运转性能, 连续反应1000 h, H2O2转化率及PO选择性仍能维持在95%以上. 相似文献
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Trimodal hierarchical yolk-shell materials consisting of TS-1 core and mesoporous carbon shell(YS-TS-1@MC) was successfully synthesized by using TS-1@mesosilica as hard template,sucrose as carbon source and organic base tetrapropylammonium hydroxide(TPAOH) as silica etching agent.The resultant YS-TS-1@MC contains the micropores(0.51 nm) in TS-1 core,the mesopores(2.9 nm) in carbon shell as well as a void or a stack pore between TS-1 fragcments(TS-1 intercrystal mesopores,~18.4 nm).Under the rigorous etching conditions,the crystalline structure of TS-1 core was well retained.The YS-TS-1@MC served as a good support for palladium nano-particles(Pd NPs) or Rh(OH)x species,giving rise to efficient bifunctional catalysts for the tandem reactions including one-pot synthesis of propylene oxide or amides. 相似文献
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C.N. Soekiman K. Miyake Y. Hayashi Y. Zhu M. Ota H. Al-Jabri R. Inoue Y. Hirota Y. Uchida S. Tanaka C.Y. Kong N. Nishiyama 《Materials Today Chemistry》2020
In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO2–SiO2 composite with highly dispersed Ti species and (2) a dry gel conversion method for the crystallization to TS-1. This investigation revealed that the dispersion of Ti in the starting materials was quite important to synthesize mesoporous TS-1 with high content of Ti besides dry conversion method. The obtained mesoporous TS-1 with a high content of titanium showed higher catalytic activity in 1-hexene epoxidation than conventional TS-1. This high activity is likely to originate from the high content of titanium in the framework. 相似文献
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Titanium silicalite-1 (TS-1) was prepared by microwave heating of a SiO2–TiO2 xerogel, which was dry-impregnated with tetrapropylammonium hydroxide (TPAOH). Highly crystalline product was obtained, with the yields higher than 90%, within 30 min after microwave irradiation. These are significant advantages over the conventional oven heating using alkoxide precursors in liquid phase, which requires 1-2 day crystallization time with low product yields. Sub-micron sized SiO2–TiO2 prepared by thermal plasma process and Ti-containing mesoporous silica, Ti-HMS, were also tested as the solid phase precursor for TS-1. These were found inferior as precursor due to difficulties in uniformly wetting the surface with TPAOH. It was possible to prepare TS-1 using diethoxysiloxane-ethyltitanate (DESET, 93.75 mol Si:6.25 mol Ti) as a single mixed alkoxide precursor, but titanium species in the sample were highly unstable and large fraction of them came out from the framework to form TiO2 clusters upon calcination. In addition, TS-1 monolith was prepared utilizing polyurethane foam as an infiltration medium of the synthesis gel. The prepared TS-1 monolith exhibited properties similar to those of TS-1 powders, but the elementary unit of the former was made of 1–2 micron-sized hexagonal shaped crystals, causing diffusion problems. Catalytic activities of all the prepared catalysts were evaluated using 1-hexene epoxidation as a probe reaction, and 2,5-dihydrofuran epoxidation was also examined using TS-1 as an alternative process to make 3,4-epoxytetrahydrofuran. 相似文献
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利用等体积浸渍法制备了M-Pd/TS-1(M=Ce,La,Pt,Fe,Co,Ni,Cr,Mn,Zn,Cd,Cu)系列催化剂,并将制得的催化剂用于常压下氢、氧直接合成过氧化氢的反应。考察了M的类型及负载量对M-Pd/TS-1催化剂催化性能的影响。结果表明,M选Ce时,催化剂的性能最好。Ce的最佳掺入量,n_(Ce)/(n_(Ce)+n_(Pd))=0.5%。对Ce改性与未改性的催化剂进行了TEM及静态化学吸附分析,结果表明,掺入Ce可使Pd在TS-1分子筛表面的粒度及分散度得到改善。考察了n_(O_2)/n_(H_2)比,气体流量,反应时间等反应条件对H_2转化率、H_2O_2选择性及收率的影响。在相对优化的工艺条件下,即n_(O_2)/n_(H_2)=3,气体流量为25 mL·min~(-1),反应时间为3 h时,H_2O_2,的收率可达到25.7%,TOF值为18.7 mol·mol~(-1)·h~(-1),此时溶液中H_2O_2的质量百分数为0.8%。 相似文献
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《Journal of Saudi Chemical Society》2022,26(6):101538
Photocatalytic degradation method is an emerging technique for complete removal of pollutants. Several semiconductor photocatalysts are reported as photocatalysts for industrial wastewater treatment in environmental applications. In this study Magnetite/TS-1 composite materials was used for photocatalytic degradation of phenol. Magnetite nanoparticles (MNP) (10 wt%) were dispersed with nanocrystalline Titanium Silicate-1 zeolite (TS-1). The Magnetite/TS-1 composite materials were characterized with various techniques. The structural analysis reveals the presence of MNP and zeolite-MFI phases in Magnetite/TS-1 composite materials. The average particles size of the magnetite nanoparticles is less than 5 nm and that of the composite nanoparticles are in the range of about 90 nm with micropore volume 0.110 cm3/g and the external surface area 120 m2/g. The photocatalytic experiments were carried out in a thin film flow photoreactor under UV radiation. The results showed that Magnetite/TS-1 composite materials exhibited improved activity for the degradation of phenol compared to TS-1. Preliminary studies proves that aeration is necessary for the photocatalytic reaction. The reaction parameters such as flow rate, pH and phenol concentration are optimized as 8 ml/min, pH 7.0 and 75 mg/L respectively. To understand the active species involved in the degradation of phenol radical scavengers such as NaI, benzoquinone and isopropyl alcohol are used to trap hole (h+), superoxide anion radical and hydroxyl radical (OH), respectively. From the obtained results it is envisaged that hydroxyl radicals are predominantly involved in complete oxidation of phenol. The extent of degradation of phenol was determined by measuring the amount of CO2 formed in the reaction. The results confirms that 99.6 % carbon in phenol is converted to CO2. 相似文献
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A new magnetic nanocatalyst (Fe3O4@KCC-1-npr-NH2) was synthesized directly through the reaction of Fe3O4@KCC-1 with (3-aminopropyl) triethoxysilane (APTES) using a hydrothermal protocol. Prepared nanocomposite was used as a magnetically reusable nanocatalyst for an efficient synthesis of a broad range of sulfonamide derivatives in water as a green solvent at room temperature and the products are collected by filtration with excellent yields (85–97%). The nanocatalyst could be remarkably recovered and reused after ten times without any significant decrease in activity. This mild and simple synthesis method offers some advantages including short reaction time, high yield and simple work-up procedure. 相似文献
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Structures and IR absorption spectra of the conformational isomers of perfluorinated aldehyde hydrates, n-CxF2x+1CH(OH)2, (x = 1-4) have been calculated using density functional theory (DFT) and compared to experimental FT-IR measurements. Two absorption peaks around 3600-3700 cm−1 were observed and are assigned to OH stretching modes of OH groups with, and without, intramolecular hydrogen bonding. For n-C3F7CH(OH)2, two absorption bands around 900-1000 cm−1 were observed in the experimental spectra, whereas only a single in-phase stretching mode of the (CF3)(C2F4CH(OH)2) and (C3F7)(CH(OH)2) bonds was calculated for each conformer. The experimental spectra were well described by composite spectra of the thermal equilibrium mixture of different conformational isomers of n-CxF2x+1CH(OH)2 calculated by DFT. 相似文献
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Pramathesh Maji Nathan J. Takas Heike Gabrisch Kevin Stokes Pierre F.P. Poudeu 《Journal of solid state chemistry》2010,183(5):1120-18852
We show that Rh substitution at the Co site in Zr0.5Hf0.5Co1−xRhxSb0.99Sn0.01 (0≤x≤1) half-Heusler alloys strongly reduces the thermal conductivity with a simultaneous, significant improvement of the power factor of the materials. Thermoelectric properties of hot-pressed pellets of several compositions with various Rh concentrations were investigated in the temperature range from 300 to 775 K. The Rh “free” composition shows n-type conduction, while Rh substitution at the Co site drives the system to p-type semiconducting behavior. The lattice thermal conductivity of Zr0.5Hf0.5Co1−xRhxSb0.99Sn0.01 alloys rapidly decreased with increasing Rh concentration and lattice thermal conductivity as low as 3.7 W/m*K was obtained at 300 K for Zr0.5Hf0.5RhSb0.99Sn0.01. The drastic reduction of the lattice thermal conductivity is attributed to mass fluctuation induced by the Rh substitution at the Co site, as well as enhanced phonon scattering at grain boundaries due to the small grain size of the synthesized materials. 相似文献
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Pei Chen Xinbing Chen Xiangshu Chen Hidetoshi Kita 《Journal of membrane science》2009,330(1-2):369-378
The preparation of the supported titanium silicalite-1 (TS-1) zeolite membrane with inexpensive tetrapropylammonium bromide (TPABr)/weak base synthesis system was studied by three methods, and the catalytic activity of the obtained TS-1 zeolite membrane was evaluated with the oxidation of 2-propanol (IPA) under pervaporation condition. It was found that TS-1 zeolite membrane could be successfully prepared with “seeding” or “seeding in situ” method, but could not be achieved with “in situ” method. Adding a little amount of promoter ions of PO43− into the synthesis gel was of benefit to the catalytic activity of the prepared TS-1 zeolite membrane, but had no obvious effect on the membrane layer formation on the mullite porous support. For “seeding” method, the membrane prepared with the synthesis gel having molar composition of SiO2:0.1TPABr:0.9Et2NH:0.03TiO2:80H2O:0.06H3PO4 at 150 °C for 48 h showed the highest oxidation conversion of IPA of 72% accompanied by a flux of 0.35 kg/m2 h. Further more, much higher IPA oxidation conversion of 76% accompanied by a flux of 0.65 kg/m2 h was obtained for the TS-1 zeolite membrane prepared with the same synthesis gel by “seeding in situ” method at 150 °C for 72 h. 相似文献