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%。     

不同氧化锰载体对费托钴基催化剂合成低碳烯烃的影响

制备不同的Co/MnO_x (Co/MnO、Co/MnO₂、Co/Mn₂O₃、Co/Mn₃O₄) 催化剂,并利用XRD、SEM、TEM、BET、TPR、DRIFTS、XPS表征手段分析催化剂的理化性质,比较不同氧化锰载体对催化性能的影响,考察催化剂对低碳烯烃(C₂⁼～C₄⁼)的选择性影响。结果表明催化剂Co/MnO和Co/Mn₃O₄更容易还原,并且CO的吸附量较大,有利于实现较高的CO转化率;Co/Mn₂O₃和Co/Mn₃O₄中CO桥式吸附更高,有利于生成更多的-CH₂-物种。综合考虑催化剂的活性和C₂⁼～C₄⁼选择性,Co/Mn₃O₄的费托合成(FTS)性能最好,其中C₂⁼～C₄⁼选择性为50.91%,烯烷比(O/P)为3.40。     

三甲基膦和金属氧化物复合改性ZSM-5分子筛及其裂解性能研究

以三甲基膦（TMP）为前体对ZSM-5分子筛进行磷改性,以提升其水热稳定性,然后再分别通过等体积浸渍法引入Ga₂O₃或ZnO,制备得到磷和金属氧化物复合改性的ZSM-5分子筛。利用X射线衍射（XRD）、固体核磁（MAS NMR）、氨程序升温脱附（NH₃-TPD）以及吡啶吸附傅里叶变换红外光谱（Py-FTIR）等表征手段系统地研究了磷和金属氧化物复合改性对ZSM-5分子筛的物化性质、P和Al相互作用以及酸性的影响。并以正十四烷裂解为探针反应,研究磷和金属氧化物复合改性对ZSM-5分子筛催化裂解性能的影响。研究结果表明以三甲基膦为前体对ZSM-5分子筛改性,再引入金属氧化物的复合改性方式制备的催化裂解催化剂不仅具有较高的酸性保留度,具有较高的催化裂解活性,也同时保留了金属氧化物中心的脱氢作用,从而提升了C₂⁼~C₄⁼收率及选择性,同时降低了积炭的生成。     

用于丙烷催化燃烧的PdxPty-ZSM-5/Cordierite整体式催化剂

以ZSM-5分子筛、铝溶胶、硝酸钯、硝酸铂和水为原料制备分子筛浆料，采用真空抽提-一次涂覆法在堇青石蜂窝陶瓷载体表面制备出Pd_xPt_y-ZSM-5/Cordierite整体式催化剂，考察了Pd负载量、ZSM-5分子筛的硅铝比和Pd/Pt质量比对整体式催化剂的丙烷催化燃烧性能的影响，并用超声波振荡、SEM、XRD、H₂-TPR和C₃H₈-TPD等手段对整体式催化剂进行了表征。当球磨时间为60 min，分子筛浆料固含量为38%时，整体式催化剂的涂层上载量可达到178 g?L^-1，涂层脱落率低于0.5%。Pd₂Pt₃-ZSM-5/Cordierite整体式催化剂（贵金属总负载量为1.2 g?L^-1）对于丙烷的催化燃烧具有较好的催化活性（T₅₀=259℃，T₉₀=323℃）和稳定性，具有良好的工业应用前景，其中较低的ZSM-5分子筛硅铝比以及Pd和Pt之间的相互作用增加了对丙烷的吸附能力和表面活性氧物种的数量，从而提高了整体式催化剂的催化活性。     

SO42-/TiO2-HZSM-5固体超强酸催化剂的制备及酯化性能

采用溶胶-凝胶法制备了HZSM-5分子筛负载SO₄^2-/TiO₂固体超强酸催化剂, 利用直接酯化法催化合成三羟甲基丙烷油酸酯。通过IR、XRD、BET、SEM对催化剂进行了表征, 结果表明TiO₂以纳米颗粒的形式附着于HZSM-5分子筛表面, 且负载后催化剂的比表面积高达309.2m²/g, 比HZSM-5分子筛提高了45.6m²/g, 且催化剂具有强酸性(-13.8< H₀ < -12.14)。探讨了沉淀pH值、焙烧温度、焙烧时间等催化剂制备条件对SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂催化三羟甲基丙烷油酸酯酯化反应活性的影响。结果表明在沉淀pH=8、硫酸的浸渍浓度为0.5mol/L、浸渍时间为30min、焙烧温度为550℃、焙烧时间4h的条件下, SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂催化活性最高, 三羟甲基丙烷油酸酯的酯化率高达97.6%;抗乳化性能良好, 油水分离时间为5min。SO₄^2-/TiO₂-HZSM-5固体超强酸催化剂在重复使用6次的情况下, 酯化率下降8.8%, 催化剂的重复使用性能良好。     

FN-3Y型NH3-SCR脱硝催化剂开发及工业应用

以高比表面TiO₂为载体、V₂O₅为活性组分,通过掺杂分子筛和CeO₂调变酸性和氧化还原性能,采用直接挤出成型方法制备了FN-3Y型脱硝催化剂。通过BET、XRD、NH₃-TPD和H₂-TPR分析了催化剂的物理化学性质,通过NH₃-SCR小型实验装置考察了催化剂的脱硝性能。实验结果表明：通过负载分子筛和CeO₂掺杂,提高了催化剂的表面酸性和氧化还原性能,提高了催化剂的脱硝活性。工业应用表明：采用FN-3Y脱硝催化剂,乙烯裂解炉烟气脱硝反应器出口NO_x低于25 mg·m^-3,优于超低排放要求。     

CO/CO2加氢高选择性合成化学品和液体燃料

一氧化碳/二氧化碳（CO/CO₂）转化利用是碳一化学与CO₂捕集利用中的重要环节,也是当今碳资源的非石油路线利用最具挑战性的方向之一。CO₂的高效活化与定向转化是CO₂利用过程中的关键问题,而CO加氢转化最大的瓶颈问题为如何有效控制C-O键的活化、C—C键的形成、碳链增长及终止。本文主要综述 CO/CO₂加氢高选择性合成重要化工原料低碳烯烃（C₂ ⁼～C₄ ⁼）以及一步高效合成汽油馏分（C₅～C₁₁）等方面取得的突破性进展。目前,CO/CO₂加氢主要经过费托合成与氧化物/分子筛双功能两条路线合成低碳烯烃与汽油燃料。针对费托合成C₂ ⁼～C₄ ⁼,分析表明棱柱状碳化钴得到的烃类产物分布可以显著突破Anderson-Schulz-Flory（ASF）分布的限制,而分子筛已被广泛用于构建双功能费托催化剂,由于酸性分子筛具有加氢裂化、低聚与异构化等功能,使得CO/CO₂还可以直接高选择性地转化为C₅～C₁₁烃类。另一方面,将可以活化CO或CO₂到甲醇的可还原型氧化物与具有C—C偶联功能的SAPO-34或HZSM-5分子筛进行耦合,也可以实现CO/CO₂加氢一步合成低碳烯烃或汽油且具有非常优异的选择性和高转化率。今后,借鉴纳米合成领域新方法,使产物分布打破经典ASF限制,最大限度地提高目标烃类化合物的选择性并显著减少甲烷的生成是研究关键。     

甲醇制对二甲苯联产低碳烯烃改性ZSM-5催化剂在流化床中的反应性能

在流化床反应器中,对Zn、Si和P改性的ZSM-5催化剂的甲醇制对二甲苯联产低碳烯烃的反应性能进行了研究。采用X射线衍射（XRD）、BET比表面积、扫描电镜（SEM）、NH₃-程序升温脱附（NH₃-TPD）等手段进行表征分析。结果表明,Zn改性使得催化剂酸强度降低,中强酸酸量增加,对二甲苯和低碳烯烃选择性都随之提高;一定量的硅沉积改性在降低催化剂外表面酸量的同时缩小孔口,浸渍适量P能够调变分子筛的酸中心强度和酸量,这都能够提高对二甲苯选择性。在流化床反应器中甲醇制对二甲苯联产低碳烯烃反应结果表明,3Zn-3Si-3P/ZSM-5催化剂在温度425℃、常压、反应时间40min、空速1h^-1的条件下,对二甲苯在二甲苯中的选择性为76.0%,C₂~C₄低碳烯烃选择性为24.4%,特别是芳烃和C₂~C₄低碳烯烃的总选择性高达92.2%。     

丁烷脱氢工艺及催化剂研究进展

C₄烯烃作为石油化工和聚合物行业的基础原料被广泛用于合成橡胶、塑料和特种燃料等的生产。由低碳烷烃向C₄烯烃的转化,不仅可以有效缓解我国低碳烯烃紧缺的难题,而且可以大大提升低碳烷烃的附加值。综述近年来国内外丁烷催化脱氢的技术现状与研究进展,重点论述正丁烷脱氢反应的机理、催化剂活性组分、载体及助剂对催化脱氢性能的影响,概述脱氢催化剂的失活原因,并对丁烷脱氢催化剂的研究前景进行展望。     

Cu/TiO2光催化正丁烷脱氢制丁烯

采用硼氢化钠还原法制备了Cu/TiO₂催化剂,考察Cu负载量、反应温度和反应时间对Cu/TiO₂光催化正丁烷脱氢制丁烯的影响。结果表明,室温下氙灯照射60 min, 0.5-Cu/TiO₂光催化正丁烷脱氢制丁烯产量为600.2μmol/(g-cat·h),选择性为95.3%,H₂产量为858.7μmol/(g-cat·h),丁烯产量和选择性随Cu负载量的变化不大。低温有利于光催化正丁烷脱氢,反应温度过高时,丁烯和H₂产量降低,丁烯选择性降低,裂解选择性增大。1-丁烯和2-丁烯相对选择性不随反应时间变化,未发现丁烯间的异构化反应。     

Photocatalytic activity of TiO2/ZSM-5 composites in the presence of SO4 ion

TiO₂/ZSM-5 composites were prepared from SiO₂ of rice husk ash and TiO₂ sol from hydrolyzed TiOSO₄ salt. The combined effect of these two materials greatly enhanced the photocatalytic decolorization of methylene blue dye solution. The instant decolorization of the dye solution in the dark by the composite, TiO₂/ZSM-5 (wt ratio 1:1), resulted from the combination of the adsorption by ZSM-5 zeolite and TiO₂ nano-particles, and of Na₂SO₄ salt adhering to the composite surface. As a strong flocculating agent, the SO₄²⁻ ion caused the precipitation of the dye onto the composite surface which consequently enhanced the photocatalytic decolorization of the dye under UV irradiation. The composite, TiO₂/ZSM-5 (wt ratio 1:5), completely decolorized the methylene blue dye in 2.5 h, giving an equivalent performance to that of TiO₂, P-25 powder.     

The CO–H2 and CO–H2O reactions over TiO2 nanotubes filled with Pt metal nanoparticles

We have investigated the catalytic behavior of Pt encapsulated TiO₂ nanotubes for the water gas shift reaction as well as the hydrogenation of CO. Pt–TiO₂ nanotube catalysts were prepared by employing fine fiber shaped crystals of [Pt(NH₃)₄](HCO₃)₂ complex as a structure determining template material. The turnover frequencies (TOF) of these nanotube catalysts were more than one order of magnitude larger than conventional impregnation Pt/TiO₂ catalysts, and the selectivity for methanol in CO–H₂ reaction was extraordinary high compared to the impregnation catalysts. The XPS and XRD analyses of the nanotubes revealed characteristic electronic state of reduced TiO₂ (Ti³⁺ in rutile structure) with zerovalent Pt even after the calcination at 773 K. In WGS reaction, electron rich Ti³⁺ on the nanotube wall may play an important role to activate water molecules for the oxidation of CO. In CO–H₂ reaction, similar promotion effect of Ti³⁺ species may be operating for selective methanol formation by supplying active OH(a).     

Pt/TiO_2催化二甲醚部分氧化重整制氢

二甲醚是一种理想的氢载体,可用于解决氢的储存和运输。以Pt/TiO_2为部分氧化催化剂,结合Ni/Al_2O_3重整催化剂,考察钛前驱体和焙烧温度对二甲醚部分氧化重整制氢反应的影响。结果表明,以Ti(C4H9O)4为原料制备的TiO_2为金红石相,Ti(SO4)2或Ti O(OH)2为原料制备的TiO_2为锐钛矿相;以Ti(C4H9O)4为原料制备的Pt/TiO_2-E催化剂催化性能略好,转化率接近100%,H2收率约90%,表明金红石相TiO_2负载的Pt催化剂略佳;以Ti(SO4)2为原料制备的Pt/TiO_2-S催化剂500℃焙烧可获得金红石相TiO_2。与Pt/Al_2O_3催化剂相比,Pt/TiO_2催化剂具有更好的催化性能,H2收率超过90%,而Pt/Al_2O_3催化剂H2收率约80%。     

新型纳米SO42-/TiO2催化剂制备及催化合成醋酸丁酯

采用高压水热法合成纳米锐钛矿相TiO₂前驱体,通过H₂SO₄溶液浸渍制备系列新型SO₄^2-/TiO₂催化剂,采用XRD、TG-DTG和TEM对其结构和形貌进行表征,并用于催化醋酸与正丁醇的酯化反应,考察H₂SO₄溶液浓度、浸渍时间和反应时间对酯化率的影响。结果表明,在H₂SO₄浓度1 mol·L^-1、浸渍时间12 h和反应时间180 min条件下,酯化率高达99.2%,催化剂具有优异的催化性能和较佳的重复使用性。     

全结晶ZSM-5分子筛催化剂研究及工业应用

制备了全结晶ZSM-5分子筛催化剂,采用XRD、SEM、N2物理吸附-脱附及NH3-TPD等对催化剂进行表征,并考察其用于碳四烯烃催化裂解制丙烯(OCC)反应的催化性能。结果表明,制备的全结晶ZSM-5分子筛催化剂比常规成型的催化剂具有更高的结晶度、更大的比表面积、更丰富的孔结构以及更多的活性中心。高空速有利于反应的进行,提高压力对反应不利,升高温度有利于提高产物丙烯收率。在实验室研究的基础上,将全结晶ZSM-5分子筛催化剂用于OCC工业装置,取得良好的应用效果。     

Effect of Si/Al ratio on performance of Pt–Sn-based catalyst supported on ZSM-5 zeolite for n-butane conversion to light olefins

The performance of Pt–Sn-based catalyst, supported on ZSM-5 of different Si/Al ratios were investigated for simultaneous dehydrogenation and cracking of n-butane to produce light olefins. The catalysts were characterized by number of physio-chemical techniques including XRF, TEM, IR spectra, NH₃-TPD and O₂-pulse analysis. Increase in Si/Al ratio of zeolite support ZSM-5 significantly increased light olefin's selectivity, while feed conversion decreases due to lower acidity of support. The results indicated that both the n-butane cracking and dehydrogenation activity to light olefin's over Pt–Sn/ZSM-5 samples with increasing Si/Al ratios greatly enhanced catalytic performance. The catalysts were deactivated with time-on-stream due to the formation of carbon-containing deposits. A coke deposition was significantly related to catalyst activity, while at higher Si/Al ratio catalyst the coke precursors were depressed. These results suggested that the Pt–Sn/ZSM-5 catalyst of Si/Al ratio 300 is superior in achieving high total olefins selectivity (above 90 wt.%). The Pt–Sn/ZSM-5 also demonstrates resistance towards hydrothermal treatment, as analyzed through the three successive reaction-regeneration cycles.     

Preparation and characterization of sulfated TiO2 with rhodium modification used in esterification reaction and decomposition of methyl orange☆

A unique Rh/TiO_2 solid acid catalyst modified with H_2SO_4 was synthesized and evaluated in the esterification reaction of propylene glycol methyl ether and decomposition of methyl orange(MO) in aqueous phase under halogen lamp irradiation. For this purpose, rhodium(Rh) nanoparticles were loaded on SO_4~(2-)/TiO_2 via the photo-deposition method. It was found that SO_4~(2-)/Rh–TiO_2 exhibited stronger catalytic activity than SO_4~(2-)/TiO_2. The new catalysts were characterized by X-ray powder diffraction(XRD), Brunauer–Emmett–Teller(BET), Transmission electron microscopy(TEM) and high-resolution(HRTEM), X-ray photoelectron spectroscopy(XPS) and Fourier Transform infrared spectroscopy(FTIR). Results from XRD and BET show that SO_4~(2-)/Rh–TiO_2 has higher specific surface area and smaller pore size than SO42-/TiO_2. The distribution of loaded Rh was found to be uniform with a particle size of 2–4 nm. Data from XPS reveal that Rh primarily exists as Rh~0 and Rh~(3+)in Rh–TiO_2 and SO_4~(2)-/Rh–TiO_2. These valence forms of Rh likely contribute to the enhanced catalytic activity. Furthermore, FT-IR spectra of the catalysts show an abundance of surface hydroxyl groups, which help the formation of hydroxyl radicals and the enhancement of surface acid density. The results show that more acid sites are formed on the sulfated Rh–TiO_2, and these acidic sites are largely responsible for improving the catalytic performance. This superior SO_4~(2-)/Rh–TiO_2 catalyst has potential applications in reactions requiring efficient acid catalysts, including esterification reactions and waste water treatment.     

Mixed oxidation states of titanium at the metal-oxide interface.

A theoretical model has been developed to explain the XPS data for the mixed oxidation states of Ti (Ti²⁺, Ti³⁺, Ti⁴⁺) observed in the Ti-O², Ti-CO and Ti-NO interactions. The Ti/TiO hetero-junction, as well as the mixed overlayers TiO/Ti₂O₃/TiO₂ have been found to be thermodynamically stable, in comparison to TiO₂, accounting for the absence of the Ti⁴⁺ species at the metal interface. For the Ti-NO and Ti-CO systems, kinetic arguments have been shown to account for the titanium oxidation states across the oxide layer.