纳米Pd/ZSM-5的原位法制备及催化肉桂醛加氢

采用共沸精镏辅助的原位法成功合成了高度分散的Pd纳米颗粒负载在ZSM-5中(Pd/ZSM-5-IS)分子筛催化剂。通过XRD、TEM、XPS等手段对Pd/ZSM-5-IS的样品进行了表征,并考察反应压力、反应温度、反应时间对肉桂醛加氢催化性能的影响。结果表明:原位法制备的Pd/ZSM-5-IS催化剂比浸渍法制备的Pd/ZSM-5-IM催化剂具有更高的催化稳定性,其主要归因于Pd纳米颗粒进入ZSM-5的晶内介孔有效防止活性位点的损失和聚集。当反应温度为80℃,反应压力为1 MPa,反应时间为3 h时为最佳反应条件,肉桂醛的转化率为87.23%,苯丙醛的选择性为76.68%。     

纳米Pd/ZSM-5的原位法制备及催化肉桂醛加氢

采用共沸精镏辅助的原位法成功合成了高度分散的Pd纳米颗粒负载在ZSM-5中（Pd/ZSM-5-IS）分子筛催化剂。通过XRD、TEM、XPS等手段对Pd/ZSM-5-IS的样品进行了表征,并考察反应压力、反应温度、反应时间对肉桂醛加氢催化性能的影响。结果表明：原位法制备的Pd/ZSM-5-IS催化剂比浸渍法制备的Pd/ZSM-5-IM催化剂具有更高的催化稳定性,其主要归因于Pd纳米颗粒进入ZSM-5的晶内介孔有效防止活性位点的损失和聚集。当反应温度为80℃,反应压力为1 MPa,反应时间为3 h时为最佳反应条件,肉桂醛的转化率为87.23%,苯丙醛的选择性为76.68%。     

多酸基深度加氢脱硫催化剂的原位表征和反应性能

采用浸渍法合成了镍盐复合的磷钨酸(HPW)/纳米晶HZSM-5固体酸催化剂,其在催化裂化(FCC)汽油加氢改质反应中显示出了良好地深度加氢脱硫活性。 原位电子自旋共振和原位吡啶吸附红外光谱表征手段的研究结果表明,纳米晶HZSM-5沸石上Ni(Ⅱ)结合3电子还原态的HPW(Ⅲ)是FCC汽油深度加氢脱硫反应的活性中心。 探讨了多酸基催化剂在FCC汽油深度加氢脱硫反应中活性改善的原因。     

离子液体功能化有序介孔SBA-15孔壁定域化磷钨酸催化活性中心构建及其催化性能

采用溶胶-凝胶法合成了一种桥键嵌入型双咪唑离子液体功能化介孔硅基材料(Bis-PImBr-PMO-SBA-15),然后离子交换将Keggin型磷钨酸负载于其上,制备了PW-Bis-PImBr-PMO-SBA-15催化剂,并运用X射线衍射、N2吸附-脱附、透射电子显微镜、傅里叶变换红外光谱和热重分析等手段对其进行表征.结果表明,该催化剂具有SBA-15分子筛的有序六方孔道结构,且负载后的磷钨酸阴离子仍保持其完整的Keggin结构.在以水为溶剂,30%H2O2为氧化剂的苯甲醇氧化反应中,该催化剂表现出比均相的或负载于SBA-15表面的Keggin型HPW更高的催化活性,苯甲醇转化率和苯甲醛选择性分别可达95%和94%.离子液体的咪唑阳离子可调节磷钨酸阴离子的氧化-还原性能,从而有利于提高催化剂的催化活性..     

纳米ZSM-5沸石对芳烃苄基化反应的催化性能

采用晶种有机硅烷化法合成了纳米团簇 ZSM-5 沸石, 考察了其在芳烃苄基化反应中的催化活性. X 射线衍射、N2 吸附和扫描电镜等结果表明, 该沸石为由约 20 nm 的小晶粒聚集成的团簇体, 并形成晶间中孔, 其具有的外表面积是普通 ZSM-5 沸石的 5 倍之多. NH3-程序升温脱附和吡啶吸附的红外光谱结果显示, 沸石的纳米化可使其表面酸中心, 尤其是强酸中心的数目增多, 大大提高了大分子的酸性位可接近性. 在芳烃苄基化反应中, 纳米 ZSM-5 沸石克服了反应分子空间位阻对催化活性的影响, 表现出优异的催化活性, 363 K 时, 甲苯苄基化反应的速率常数是普通 ZSM-5 沸石的约 13 倍.     

磷钼酸和钛硅纳米复合氧化物构筑高活性氧化脱硫催化剂

采用溶胶凝胶法合成了钛硅纳米复合氧化物(TiO₂-SiO₂),并以其为载体用原位合成技术或浸渍法负载Keggin结构磷钼酸(HPMo)制备了复合催化剂,使用扫描电子显微镜(SEM)、傅里叶红外光谱仪(FT-IR)、紫外可见光谱仪(UV-Vis)、X射线衍射光谱(XRD)和比表面分析仪(BET)等测试手段对催化剂的结构进行表征。 结果表明,采用原位法合成的催化剂为纳米粒子,纳米晶骨架内存在微孔和介孔共存的孔道结构。 原位合成技术或浸渍法制备的催化剂中HPMo保持Keggin骨架结构。以模拟油品(二苯并噻吩、苯并噻吩或噻吩的正辛烷溶液)的氧化脱硫为探针反应,在选定的条件下:硫含量为200.0 g/g的正辛烷溶液和无水乙醇各10.0 mL,反应温度60 ℃,催化剂质量0.15 g,n(H₂O₂)∶n(S)=5∶1,二苯并噻吩的脱除率高于96.0%,产物中硫含量低于10.0 μg/g。 在相同的实验条件下,受电子云密度的影响,脱硫由易到难的顺序为二苯并噻吩>苯并噻吩>噻吩。 催化剂循环使用4次后活性未见明显降低,是一类绿色的模型有机硫化物氧化脱除工艺用催化剂。     

煤质炭负载杂多酸催化剂上气-固相合成邻乙氧基苯酚

 研究了煤质炭负载杂多酸催化剂对邻苯二酚和乙醇的O－乙基化反应的催化性能．发现相同负载量的Keggin型磷钨酸催化剂的活性远高于硅钨酸和Dawson型磷钨酸；负载杂多酸催化剂上邻乙氧基苯酚的选择性明显高于磷酸催化剂．采用BET，XRD及TPD技术对催化剂进行了表征，并考察了Keggin型磷钨酸的负载量和反应温度对催化性能的影响．还发现在10h的反应时间内催化剂的活性随着反应时间的延长而降低．     

ZSM-5-TiO2协同吸附-光催化去除空气中甲苯污染物的研究

通过溶剂热制备纳米晶TiO2,再通过浸渍法将其负载于ZSM-5,获得ZSM-5-TiO2复合材料.考察了多种因素对吸附和光催化性能的影响,发现控制TiO2负载量及改变ZSM-5样品的硅铝比可显著改善HI疏水因子,提高对有机污染物的吸附能力和光催化降解效率,实现吸附和光催化协同净化空气.结合表征,对吸附及光催化的构效关系和协同效应进行了初步探索.     

多酸结构对纳米钛硅TS-1沸石催化氧化脱硫性能的影响

采用浸渍法合成了纳米钛硅TS-1沸石负载的钼系列多金属氧酸盐(POM)复合催化剂,采用扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)、固体紫外漫反射(UV-Vis)、X-ray粉末衍射(XRD)、氮气吸附脱附(BET)、³¹P和²⁹Si魔角核磁共振(MAS-NMR)等对催化剂的结构进行表征。 研究结果表明,在低温焙烧或烘干条件下,负载后催化剂多酸的结构保持,钼酸铵高温(550 ℃)焙烧后转变为三氧化钼。 以有机硫化物噻吩(TH)、苯并噻吩(BT)和二苯并噻吩(DBT)的正辛烷溶液为模拟油品评价了催化剂的氧化脱硫性能。 实验结果表明,纳米TS-1沸石载体上不同结构多酸作为脱硫催化剂对硫化物的脱除活性顺序为:Keggin型Mo-POM＞Anderson型Mo-POM＞Dawson型Mo-POM＞Mo-金属氧化物。以上述负载的多酸为催化剂,在反应条件为:V(模拟油)=V(乙醇)=10.0 mL,m(催化剂)=0.2 g,n(H₂O₂)∶n(S)=10∶1,温度60 ℃,硫化物按照由易到难的脱除顺序为TH＞DBT＞BT,与常规的TS-1沸石或者多酸催化剂的脱除顺序存在明显差异。 这是纳米TS-1沸石对于有机硫分子氧化反应的择形效应和POM催化氧化脱硫的电子云密度影响综合作用的结果。 Keggin型Mo-POM催化剂具有良好的循环使用性能,是一类制备方法简单、催化活性高且稳定性好的绿色环保型催化剂。     

甲醇脱水制二甲醚的杂多酸/纳米HZSM-5复合固体酸催化剂

开发低温、高活性和良好稳定性的催化剂成为甲醇气相脱水制二甲醚乃至合成气一步法制二甲醚反应的核心.在氧化铝挤条成型的纳米HZSM-5沸石上负载Keggin结构12-磷钨酸制备了复合固体酸催化剂, 通过FT-IR、UV-Raman、³¹P MAS-NMR和XRD对所制备的样品进行表征. 以甲醇气相脱水制二甲醚为探针反应的研究结果表明, 在选定的操作条件下连续运转超过300 h, 甲醇摩尔转化率大于87%(理论转化率90.9%), 二甲醚摩尔选择性高于99.0%, 是目前该反应非常有效的催化剂之一.     

Keggin结构多阴阳离子构筑高活性多酸基氧化脱硫催化剂

设计开发高活性超深度氧化脱硫催化剂是解决未来石化工业适应日益严格要求的清洁燃油标准的重要出路之一。本文合成了Keggin结构多聚铝阳离子烷基硫酸盐Al_13-SDS和磷钨酸(HPW)多阴离子构筑的催化剂HPW-Al_13-SDS(SDS=十二烷基硫酸钠),采用傅里叶红外光谱(FT-IR)、紫外可见光谱(UV-Vis)、热重分析(TG)、X射线衍射(XRD)和Brunauer-Emmett-Teller(BET)等测试手段对催化剂的结构进行表征。FT-IR和UV-Vis的表征结果表明,焙烧后的催化剂中多聚铝阳离子和HPW同时保持Keggin骨架结构。以有机硫二苯并噻吩(DBT)的正己烷溶液为模拟油品的氧化脱硫为探针反应,在选定的条件下,DBT有机硫的脱除率达到99.5%。反应后HPW-Al_13-SDS催化剂的FT-IR和XRD的表征证实产生过氧化多钨酸化合物。催化剂能够循环使用,易分离,循环使用后活性未见明显降低,是理想的模型有机硫化物氧化脱除用催化剂。     

磷钨酸功能化氮化碳的制备及其氧化脱硫研究

以磷钨酸和氮化碳为原料,合成磷钨酸功能化的氮化碳(g-C₃N₄/HPW),并采用XRD、SEM、FT-IR对其结构进行表征。以g-C₃N₄/HPW为催化剂,过氧化氢作为氧化剂,咪唑氟硼酸盐为萃取剂氧化萃取一体法脱除模拟油中的二苯并噻吩(DBT)。考察了反应温度、催化剂加入量、双氧水加入量、萃取剂加入量、硫化物类型等因素对脱硫效果的影响。结果表明,在模拟油为5 mL,g-C₃N₄/HPW为0.02 g,H₂O₂加入量为1.0 mL,BF₄ 为1.5 mL,反应温度70 ℃,反应120 min的条件下,DBT的转化率可达到93%。反应体系循环使用4次催化剂的活性没有明显的降低。     

Photocatalytic Degradation of Imidacloprid by Phosphotungstic Acid Supported on a Mesoporous Sieve MCM‐41

Solid catalysts consisting of polyoxometalates (POM) namely phosphotungstic acid H₃PW₁₂O₄₀ (HPW) supported on a mesoporous sieve MCM‐41 have been prepared and characterized by FT‐IR, X‐ray diffraction, nitrogen adsorption and high resolution transmission electron microscope (HRTEM). The HPW/MCM‐41 with different HPW loadings from 10 to 60 wt% possess large specific surface area and rather uniform mesopores. Keggin structure of HPW retains on the prepared composite catalysts. The photocatalytic performance of HPW/MCM‐41 was examined by degradation of a durable pesticide imidacloprid. It is found that the prepared photocatalysts exhibit high activity under irradiation of 365 nm monochromatic light. For 50 mL of imidacloprid (10 mg/L), conversion of imidacloprid using 20 mg of HPW/MCM‐41 with 50 wt% loading level and calcined at 300°C reaches 58.0% after 5 h irradiation.     

Location, acid strength, and mobility of the acidic protons in Keggin 12-H3PW12O40: a combined solid-state NMR spectroscopy and DFT quantum chemical calculation study

Solid-state 13C NMR experiments and quantum chemical Density Functional Theory (DFT) calculations of acetone adsorption were used to study the location of protons in anhydrous 12-tungstophosphoric acid (HPW), the mobility of the isolated and hydrated acidic protons, and the acid strength heterogeneity of the anhydrous hydroxyl groups. This study presents the first direct NMR experimental evidence that there are two types of isolated protons with different acid strengths in the anhydrous Keggin HPW. Rotational Echo DOuble Resonance (REDOR) NMR experiments combined with quantum chemical DFT calculations demonstrated that acidic protons in anhydrous HPW are localized on both bridging (Oc) and terminal (Od) atoms of the Keggin unit. The CP/MAS NMR experiments revealed that the isolated acidic protons are immobile, but hydrated acidic protons are highly mobile at room temperature. The isotropic chemical shift of the adsorbed acetone suggested that the acid strength of the H(H2O)n+ species in partially hydrated HPW is comparable to that of a zeolite, while the acidity of an isolated proton is much stronger than that of a zeolite. Isolated protons on the bridging oxygen atoms of anhydrous HPW are nearly superacidic.     

合成条件对磷钨酸负载的金属有机框架催化剂氧化脱硫性能的影响

通过一步水热合成法制备了大比表面积、高脱硫活性的磷钨酸(HPW)负载的金属有机框架HPW@MIL-101(Cr)催化剂,对其进行了FT-IR、XRD和氮吸附等表征,并研究了合成时间、合成温度、酸碱度及HPW负载量等参数对催化剂脱硫性能的影响。结果表明,随着合成时间的延长、合成温度的提高,HPW@MIL-101(Cr)孔道有序度提高;合成温度低于等于140℃时,不能形成M IL-101(Cr)晶体结构;酸性合成条件合成的HPW@M IL-101(Cr)的孔道有序度降低;随着HPW负载量的增加,HPW@MIL-101(Cr)的催化性能呈现先升高后降低的趋势。在12 h、220℃和中性条件下制备得到的负载量为3.5 g的HPW@MIL-101(Cr)催化剂具有最佳脱硫活性;在模拟油20 mL、催化剂用量0.24 g、氧硫比为8和50℃条件下反应120 min,对苯并噻吩、二苯并噻吩和4,6-二甲基二苯并噻吩脱硫率分别为99%、100%和99%;与HPW相比,苯并噻吩脱硫率提高了2.4倍。     

New Insights into Keggin‐Type 12‐Tungstophosphoric Acid from 31P MAS NMR Analysis of Absorbed Trimethylphosphine Oxide and DFT Calculations

The acid and transport properties of the anhydrous Keggin‐type 12‐tungstophosphoric acid (H₃PW₁₂O₄₀; HPW) have been studied by solid‐state ³¹P magic‐angle spinning NMR of absorbed trimethylphosphine oxide (TMPO) in conjunction with DFT calculations. Accordingly, ³¹P NMR resonances arising from various protonated complexes, such as TMPOH⁺ and (TMPO)₂H⁺ adducts, could be unambiguously identified. It was found that thermal pretreatment of the sample at elevated temperatures (≥423 K) is a prerequisite for ensuring complete penetration of the TMPO guest probe molecule into HPW particles. Transport of the TMPO absorbate into the matrix of the HPW adsorbent was found to invoke a desorption/absorption process associated with the (TMPO)₂H⁺ adducts. Consequently, three types of protonic acid sites with distinct superacid strengths, which correspond to ³¹P chemical shifts of 92.1, 89.4, and 87.7 ppm, were observed for HPW samples loaded with less than three molecules of TMPO per Keggin unit. Together with detailed DFT calculations, these results support the scenario that the TMPOH⁺ complexes are associated with protons located at three different terminal oxygen (O_d) sites of the PW₁₂O₄₀³⁻ polyanions. Upon increasing the TMPO loading to >3.0 molecules per Keggin unit, abrupt decreases in acid strength and the corresponding structural variations were attributed to the change in secondary structure of the pseudoliquid phase of HPW in the presence of excessive guest absorbate.     

In situ synthesis, characterization, and catalytic performance of tungstophosphoric acid encapsulated into the framework of mesoporous silica pillared clay

Mesoporous silica pillared clay (SPC) incorporated with tungstophosphoric acid (HPW) has been synthesized via in situ introducing P and W source in the acidic suspension of the clay interlayer template during the formation of the silica pillared clay. The samples were characterized by XRD, XRF, FT-IR, TG-DTA, N(2) adsorption-desorption, and SEM techniques. The results showed that the HPW formed by in situ method has been effectively introduced into the framework of mesoporous silica pillared clay and its Keggin structure remained perfectly after formation of the materials. In addition, samples with similar HPW loadings were also prepared by impregnation method using SPC as the support. HPW in the incorporated samples was better dispersed into the silica pillared clay than in the impregnated samples. The results of catalytic tests indicated that the encapsulated materials demonstrated better catalytic performance than the impregnated samples in oxidative desulfurization (ODS) of dibenzothiophene (DBT).     

Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

Ordered mesoporous phosphotungstic acid/SiO₂ (HPW/SiO₂) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO₂ framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H₂O₂ as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.     

Hydrothermal Synthesis and Structure of a Mixed-valence Polyoxotungstate Decorated by Copper(I) Coordination Group, [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]·2H2O

A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]·2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction.It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) (A), V = 11711(4) (A)3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm-1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I).The crystal structure is composed of [{Cu(en)2}HPW12O40]2- anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions.The anionic [{Cu(en)2}HPW12O40]2- is formed by the mixed valance {HPWVI11WVO40}3- Keggin unit covalently linked by a {Cu(en)2}+ group.     

Hydrothermal Synthesis and Structure of a Mixed-valence Polyoxotungstate Decorated by Copper(I) Coordination Group, [Cu(en)_2H_2O]_2[{Cu(en)_2}HPW_(12)O_(40)]·2H_2O

1 INTRODUCTION Polyoxometalates (POMs) are early transition metal oxygen clusters and have aroused much inte- rest because of their discrete structures of definite sizes, shapes[1] and potential applications in cata- lysis, medicine, materials science, g…