掺杂SrTiO3体系上甲烷氧化偶联催化性能的研究

用X-射线粉末衍射(XRD)、氧吸附—程序升温脱附(O2-TPD)研究了柠檬酸热分解法制备的钙钛矿型催化剂的组成、结构与甲烷氧化偶联反应(OCM)催化性能，结果表明钙钛矿型SrTi0.9M0．1O3-δ(M=Mg，Al，Zr)的B位掺杂离子的价态越低，脱附温度越高，这与催化剂对生成C2产物的选择性相关联；钙钛矿型SrTi1-x，MgαO3-δ的B位Mg^2 掺杂量越多，催化剂中的氧空位越多，脱附温度升高。当B位Mg^2 掺杂量x≤0．1时，催化剂的甲烷转化率和C2选择性明显增加，当x≥0．1时又明显下降。认为低价离子掺杂所产生氧空位为氧分子的活化提供了活性位，表面吸附态氧物种为OCM反应主要活性氧物种，较高温度脱附的吸附氧有利于甲烷氧化偶联C2选择性的提高。     

纳米金催化剂的制备及其对肉桂醛选择性加氢的催化性能

以多壁碳纳米管和椰壳活性炭为载体,分别采用溶胶固载法和等体积浸渍法制备负载型纳米金催化剂。采用N_2吸附-脱附、XRD、TEM和XPS等对碳载体和纳米金催化剂样品进行表征,并研究纳米金催化剂在肉桂醛选择性加氢反应中的催化性能。结果表明,HNO_3-H_2SO_4预处理可以增加碳载体表面的含氧基团和含氮基团,在肉桂醛加氢反应中,溶胶固载法得到的更小尺寸的纳米金催化剂对C=C双键加氢选择性高,等体积浸渍法制备的纳米金催化剂对C=O双键加氢选择性高,椰壳活性炭为载体催化剂的C=C加氢催化活性优于多壁碳纳米管。     

多孔石墨烯用作丁烷氧化脱氢催化剂

碳材料作为丁烷氧化脱氢催化剂具有活性高、氧化深度可控的优点,具有高比表面积、丰富缺陷结构的多孔石墨烯是碳材料催化剂的理想选择。本文首次将化学气相沉积(CVD)法制备的多孔石墨烯作为催化剂应用于正丁烷氧化脱氢反应过程中。结果表明,多孔石墨烯对正丁烷氧化脱氢反应表现出显著催化活性,相对于碳纳米管,采用多孔石墨烯作为催化剂得到了更高的正丁烷转化率与C4烯烃选择性。当反应温度小于550℃时,C_4烯烃的选择性较高(40%);在550℃时,C4烯烃的收率达到最大值21.1%。在7.5 h的稳定性考察中,多孔石墨烯保持了良好的催化稳定性。反应后多孔石墨烯的表面缺陷度及C=O含量下降,这说明多孔石墨烯表面的C=O键是催化正丁烷氧化脱氢反应的活性中心。     

HMS介孔分子筛合成及其在丙烷脱氢制丙烯反应中的应用

分别以正硅酸乙酯和伯胺表面活性剂为原料和模板剂成功制备HMS介孔分子筛，经负载活性组分后得到Pt-Sn/HMS催化剂并将其应用于丙烷脱氢制丙烯反应。探究合成过程中伯胺表面活性剂碳链长度及水和乙醇的比例对HMS介孔分子筛孔结构的影响。XRD和N₂吸附-脱附等分析结果表明，模板剂链长增长时，介孔分子筛孔径、孔壁厚、比表面积及孔容均增大。适当的水/乙醇比例有利于获得更大比表面积和孔体积的介孔分子筛，并表现出更有序的介孔结构。丙烷脱氢制丙烯反应评价和热分析等表征结果表明，HMS介孔分子筛孔道特征直接影响Pt-Sn/HMS催化剂的催化性能。使用孔体积且比表面积较大的HMS样品作为载体制备的脱氢催化剂在丙烷脱氢反应中表现出优异的催化活性。性能最优的Pt-Sn/HMS-0.60-16催化剂上，平均丙烷转化率达到46.5%,平均丙烯选择性为94.1%,反应24 h后积炭量仅为质量分数3.4%。     

混合碳四选择加氢制1-丁烯工艺设计

根据裂解混合碳四选择加氢制丁烯工艺和催化剂评价研究结果,提出一种提高1-丁烯收率的加氢工艺流程设计方案。该工艺流程采用烃类蒸汽裂解装置所产混合碳四做原料,经过两段加氢反应器进行选择加氢,将混合碳四中的炔烃和1,3-丁二烯加氢生成富含1-丁烯的碳四物流。流程模拟计算结果表明,加氢后,1,3-丁二烯含量小于10×10^-6,1-丁烯选择性大于55%。     

Pt/TiO_2/ZSM-5催化剂的制备及其催化转化正丁烷

采用溶胶-凝胶法和等体积浸渍法,分别对ZSM-5分子筛进行Ti O2改性和Pt负载,获得了具有脱氢-裂解双功能的Pt/Ti O2/ZSM-5催化剂,采用XRD、N2吸附-脱附、TEM、XPS和NH3-TPD对样品的晶体结构,孔结构、形貌、活性金属价态和酸性质等进行了表征,并研究了正丁烷在此催化剂上催化转化制备低碳烯烃的反应规律。研究结果表明,Ti O2的引入,一方面使得改性后的ZSM-5分子筛获得了额外的酸性中心,特别是强酸性位含量的增加,有助于促进正丁烷的活化;另一方面Pt与Ti O2之间存在"金属-载体"强相互作用(SMSI),在H2还原气氛下,Pt能够促进Ti O2的还原,生成Ti3+物种,而Ti3+的存在增加了Pt周围的电荷密度,降低了Pt对低碳烯烃(2C=~3C=)的吸附能力,抑制了深度脱氢和生焦反应,从而提高双功能催化剂对烯烃的选择性。当H2还原温度为450℃时,Pt/10Ti O2/ZSM-5催化剂在625℃下的正丁烷转化率为76.1%,低碳烯烃(2C=~3C=)收率为50.9%,分别比Pt/ZSM-5催化剂提高了16.7%和12.6%。     

二价金属改性铁酸锌用于丁烯氧化脱氢的催化性能研究

采用共沉淀法向铁酸锌催化剂中添加不同二价金属(Mg、Ni、Co、Cu和Ca),并以1-丁烯为原料,对上述改性催化剂的丁烯氧化脱氢性能进行了考察。加入Mg以后,铁酸锌催化剂催化效果显著提高,在最佳锌镁比3:1的条件下,获得了1-丁烯转化率90.3%,丁二烯选择性92.7%和丁二烯收率83.8%。比表面积和孔分布测试、X射线衍射分析和氨气程序升温脱附测试表明,铁酸锌镁催化剂具有较高催化效果的原因可归结为:铁酸锌镁催化剂较铁酸锌催化剂具有更高的比表面积、较小的平均孔径、较低的结晶度以及较强的表面酸量。     

Pd-Ag/Al2O3催化剂上丁二烯的加氢反应性能

对Pd-Ag/Al2O3催化剂在裂解混合碳四选择加氢制丁烯反应中的性能进行了研究。实验结果表明,1,3-丁二烯加氢生成1-丁烯的选择性与反应器入口1,3-丁二烯浓度和氢/丁二烯比密切相关,在反应器入口温度40℃、反应压力1.0 MPa、液空速40 h 1的条件下,当入口丁二烯摩尔分数大于2.6%,1-丁烯选择性维持在66%以上;当入口丁二烯摩尔分数降至2.6%以下时,1-丁烯选择性开始下降;当反应器入口1,3-丁二烯摩尔分数小于1.0%时,出口1,3-丁二烯摩尔分数可降至小于1.0×10-5。当反应器入口1,3-丁二烯摩尔分数为0.50%～0.85%时,1-丁烯选择性随着氢/丁二烯摩尔比的增加呈现线性下降趋势,表明过量的氢气是发生丁烯的异构化和加氢反应的重要原因。H2-TPR和XPS表征结果显示,Pd-Ag/Al2O3中的Pd和Ag还原过程中形成了Pd-Ag合金。     

ZrO2/SiO2催化乙醇乙醛制备1,3-丁二烯

采用干混法、浸渍法、溶胶凝胶法3种制备方法制备ZrO₂/SiO₂,在固定床微型反应器中进行催化剂的活性评价。通过溶胶凝胶法制备的ZrO₂/SiO₂对丁二烯选择性最高,达到64.77%。采用氨气程序升温脱附(NH₃-TPD)、X射线衍射(XRD)、透射电镜(TEM)等手段对催化剂表面酸性以及表面结构进行了表征,结果表明锆在二氧化硅表面均匀分布有利于乙醇乙醛转化率以及对1,3-丁二烯选择性的提高,同时1,3-丁二烯的生成需要合适的酸性位。以溶胶凝胶法制备的ZrO₂/SiO₂为催化剂,对其制备条件进行了优化,得出最佳制备条件为焙烧温度650℃、硝酸浓度2mol/L、混合温度30℃。     

纳米介孔分子筛球作为难溶性药物长效缓释的研究

以难溶性的药物布洛芬为模型药物,以150nm的介孔分子筛球为载体,通过三甲基氯硅烷对介孔分子筛球不同程度的修饰,精细调节有机基团(CH3)3Si-在介孔表面的嫁接量实现药物的长效释放。总结了药物释放规律,同时用粉末X射线衍射(XRD)、红外光谱(FT-IR)、高分辨率透射电镜(TEM)和N2吸附-脱附对样品进行了表征。     

Vanadium supported on hexagonal mesoporous silica: active and stable catalysts in the oxidative dehydrogenation of alkanes

Hexagonal mesoporous silica (HMS) catalysts post-synthetically doped with vanadia oxo-species were characterized by means of XRD, UV-Vis spectroscopy, H₂-TPR and studied in oxidative dehydrogenation of propane (ODH). The relationship between catalytic activity in ODH and the presence of different vanadia-oxo species (monomeric, oligomeric and oxide-like species) was suggested. Monomeric VOx species are responsible for high catalytic activity and selectivity, oligomeric species containing V-O-V bond are active but non-selective to propene and oxide-like VOx particles are significantly less active and selective.     

Chromium Supported on Mesocellular Silica Foam (MCF) for Oxidative Dehydrogenation of Propane

A series of chromium-containing mesocellular silica foam (MCF) catalysts have been prepared and characterized in the oxidative dehydrogenation (ODH) of propane between 350 and 600 °C. It is demonstrated that the chromium catalysts supported on MCF exhibit much higher catalytic activity in terms of propane conversion and propylene yield than literature results obtained over chromium-supported mesoporous SBA-15 or MCM-41 catalysts during the ODH of propane. Enhanced catalytic performance of the chromium-containing mesoporous MCF catalysts has been attributed to the unique three-dimensional (3D), continuous, ultralarge mesopore structure of the MCF materials, which allow a much faster internal molecular transport during the ODH of propane.     

丙烷氧化脱氢制丙烯的钒基介孔催化材料研究进展

介绍了近年来丙烷氧化脱氢催化技术的最新研究进展,针对其中应用最广泛的钒基介孔催化剂,对其反应机理、载体性能和制备方法进行了综述,并比较了不同催化体系的丙烷氧化脱氢性能,提出了改善钒基介孔催化剂催化活性与选择性的途径。通过比较已经报道的同类研究结果,着重阐述了载体的孔结构对于氧化脱氢过程的影响,比表面积和孔径的优化对于提高催化剂的活性组分分散度以及活性位的数量效果明显。今后研究应着重提高催化剂孔道结构在高温下的稳定性以及使用寿命。     

Selective oxidation of methanol to formaldehyde over V–Mg–O catalysts

The results of a complex investigation of V–Mg–O catalysts for oxidative dehydrogenation (ODH) of methanol are presented. The efficiency of vanadium–magnesium oxide catalysts in production of formaldehyde has been evaluated. Strong dependence of the formaldehyde yield and selectivity upon vanadium oxide loading and the conditions of heat treatment of the catalyst were observed. The parameters of the preparation mode for the efficient catalyst were identified. In optimised reaction conditions the V–Mg–O catalysts at the temperature approximate 450 °C ensured the formation of formaldehyde with the yield of 94% at the selectivity of 97%.

No visible changes in the performance of the catalyst (methanol conversion, formaldehyde yield and selectivity) were detected during the 60 h of operation in prolonged runs. Characterization of the catalyst by XRD, IR, and UV methods suggests the formation of species of the pyrovanadate type (Mg₂V₂O₇) with irregular structure on the surface of a V–Mg–O catalyst. These species make the catalyst efficient for methanol ODH.     

Remarkable effect of ordered mesoporous carbon support in tantalum oxide-catalyzed selective epoxidation of cyclooctene

The olefin epoxidation is one of the most important reactions in chemical industry. Metal oxide supports often cause drawbacks in catalytic activity and selectivity, which has been overcome by introducing hydrophobic organic groups onto the oxide supports. The present study utilizes ordered mesoporous carbon (CMK-3 and CMK-1) as structurally defined hydrophobic catalyst support. Well-dispersed tantalum oxides supported on the ordered mesoporous carbon were prepared. Their application in catalytic epoxidation of cyclooctene demonstrates that the tantalum oxide catalysts on the ordered mesoporous carbon supports show higher performances than those of the catalysts supported on activated carbon and ordered mesoporous silica SBA-15.     

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO_x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO_x with metal Ru particles can form “MoO_x-Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.     

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.     

Utilizing the Oxygen Carrier Property of Cerium Iron Oxide for the Low-Temperature Synthesis of 1,3-butadiene from 1-butene

Catalysis Letters - Low-temperature oxidative dehydrogenation (ODH) of 1-butene to 1,3-butadiene is one of the challenging reactions in the polymer industry. Towards this a highly dispersed cerium...     

Oxidative dehydrogenation of isobutane on phosphorous-modified graphitic mesoporous carbon

Graphitic mesoporous carbon was modified with phosphorous heteroatoms in order to tune the catalytic selectivity and to investigate the roles of different oxygen species for the oxidative dehydrogenation reaction of isobutane to isobutene. Small changes in the isobutane apparent activation energy are consistent with the notion that the phosphorous groups do not change the nature of the active sites but they interfere with the availability of the sites. Our results show that the improvement on selectivity is not proportional to the amount of phosphorous added. Small phosphorous content improved the selectivity by suppressing the combustion of isobutane. However, a higher amount of phosphorous groups lead to coverage of selective quinone sites and/or creation of active sites favorable to total oxidation.     

Highly Effective Oxidative Dehydrogenation of Propane Over Vanadia Supported on Mesoporous SBA-15 Silica

Vanadia-containing mesoporous SBA-15 catalysts were prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadia-supported SBA-15 catalysts exhibit a much higher catalytic activity than those reported in the literature obtained over vanadium-supported mesoporous MCM-41 catalysts in the ODH of propane. The high catalytic performance of the mesoporous SBA-15 catalysts is attributed to the particularly large pore diameters and low surface acidity.