FER型沸石的合成、结构与吸附性质

在TMEDA(四甲基乙基二胺)-Na2O-SiO2-Al2O3-H2O体系(I),Na2O-K2O-Al2O3-SiO2-H2O-HCO3^--CO3^2^-体系(II)及Py(吡啶)-PrNH2(正丙胺)-HF-SiO2-H2O体系(III)中, 分别合成了纯相FER沸石及FER硅沸石。用粉末XRD, FT-IR, 29Si MAS NMR及TG/DTA等表征其结构性质, 并用超微量电子真空吸附天平测定这些沸石样品对正己烷, 甲醇和水的吸附等温线。结果表明: 各体系合成的样品虽然结晶度高, 呈现出FER沸石的典型结构特征, 但由于它们的组成和晶格微结构不同, 热稳定性与吸附性质有明显的差异。在(I)体系中合成的FER沸石层错缺陷少, 晶格完美, 正己烷与甲醇的吸附量可达到理论值, 结构破坏温度为1190℃。红外精细谱及29Si MAS NMR高分辨谱证明FER硅沸石具有十分完美的骨架结构。由于晶胞收缩, 它对正己烷与甲醇吸附量略低于理论值, 并呈现出高度的疏水性。它的结构破坏温度高于1300℃。在(II)体系中合成的FER型沸石结构缺陷多, 沸石孔中的钾离子不易被质子完全交换。它的正己烷与甲醇吸附量均较低, 而水的吸附量相对较高。吸附现象表明, 正己烷和甲醇都被吸附于FER沸石的十元环主孔道中, 分压较高时, 甲醇可通过八元环进入小笼, 而水的吸附性质则主要与各样品的Si-OH缺陷及骨架中的阳离子含量有关。     

CXN天然沸石的研究2: 吸附性质

采用N~2,NH~3,CO~2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m^2/g和0.20m^3/g。根据NH~3和CO~2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol。乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性。在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质。     

CXN天然沸石的研究2: 吸附性质

采用N~2,NH~3,CO~2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m^2/g和0.20m^3/g。根据NH~3和CO~2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol。乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性。在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质。     

CXN天然沸石的研究Ⅱ.吸附性质

采用N2,NH3,CO2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m2/g和0.20m3/g.根据NH3和CO2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol.乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性.在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质.     

经过吸附处理的Ti-Si沸石的IR和UV-Vis光谱研究

用IR和UV-Vis光谱对Ti-Si沸石吸附H₂O、H₂O₂、烯丙基氯后的变化情况进行了研究。观察到H₂O₂的吸附将引起Ti-Si沸石IR光谱中960cm^-1谱带的减弱,同时一个弱带在880cm^-1处形成;而在UV-Vis光谱中,吸附H₂O₂将导致一个新的电子跃迁带在425nm处形成。这时若吸附烯丙基氯,则可发现880cm^-1的弱带及UV-Vis425nm的宽带会进一步减弱,同时一个新的IR带重又出现在980cm^-1处。吸附H₂O₂后导致的IR880cm^-1弱带的出现及UV-Vis425nm宽带的出现均证实此时在沸石表面形成了过氧钛物种。推测骨架晶格钛可能在H₂O₂参加的氧化反应中起活性中心作用。     

ZSM-5 晶粒度对其负载的 TiO2 光催化剂性能的影响

 采用透射电子显微镜、扫描电子显微镜、X 射线荧光分析、X 射线光电子能谱、紫外-可见漫反射光谱和吡啶吸附傅里叶变换红外光谱等表征方法以及偶氮染料甲基橙的吸附和光降解反应, 研究了 ZSM-5 晶粒度对 TiO2/ZSM-5 光催化剂性能的影响. 结果表明, TiO2 主要负载于 ZSM-5 沸石外表面, 因而减小载体晶粒度有利于提高 TiO2 的负载量和分散性. 纳米 ZSM-5 沸石负载的 TiO2 催化剂具有较高的甲基橙吸附量, 且吸附发生在 ZSM-5 外表面的酸中心上, 催化剂良好的吸附能力促进了甲基橙的光降解.     

红外光谱法研究几种类型的沸石分子筛对于2,6-二甲基呲啶的吸附特性

本文利用红外光谱法研究了几种类型的沸石分子筛对于2,6-二甲基吡啶的吸附特性。结果发现2,6-二甲基吡啶在同一种类型的沸石分子筛表面上与B酸中心、L酸中心结合的稳定性是不同的,前者比后者稳定;它在不同类型的沸石分子筛表面上与L酸中心结合的稳定性也是不相同的:对于NaHY分子筛在300-400℃,对于HM、HZSM-5、HZSM-11在150-400℃,2,6-二甲基吡啶只能选择性地被吸附在B酸中心上。在HZSM-5上进行的置换吸附实验表明,150℃在时吡啶可以定量地置换与L酸中心结合的2,6-二甲基吡啶。     

MgO催化剂上甲醇分解反应机理的研究

自Greenler等用IR光谱研究了甲醇在氧化铝上的分解反应后,对各种氧化物表面上甲醇的吸附及反应的IR光谱、TPD及NMR研究已有较多报道.田丸等研究了酸性氧化铬表面上甲醇分解反应机理,认为甲醇首先形成甲氧基吸附态,然后变成甲酸根吸附态,再进一步分解为H_2、CO、H_2O及CO_2,并认为稳定的吸附态甲酸根离子在甲醇气氛下更易于分解为产物.本文对碱性MgO表面上甲醇分解反应机理进行了探讨.     

锌在ZnZSM-5沸石中的形态及其催化作用

采用NH_3－TPD和吡啶吸附红外光谱法，研究了不同含Zn量ZnHZSM-5沸石中Zn的存在状态．结果表明，用浸渍方式将Zn引入到HZSM-5沸石后，在NH_3－TPD谱上产生两个新的NH_3脱附峰．峰位分别在原HZSM－5沸石的低温峰与高温峰之间和比高温峰较高温区处，其相应的吸附中心分别以L_1、L_2表示．L_1可能与ZnHZSM－5沸石上ZnO物种相对应; L_2与吡啶吸附红外光谱的L_(1616)吸收带有关，可能与ZnHZSM-5上的ZnOH~＋物种相对应．丙烷芳构化反应结果表明，芳烃收率随L_2的脱附NH_3量的增加有一最宜值，而活性的稳定性则随之降低。     

层叠层技术组装纳米沸石——沸石涂饰纤维和沸石空 心纤维

以纳米沸石为基元构件,通过层(layer-by-layer)组装技术在碳纤维模板上成功制备了纳米沸石涂饰纤维(zeolitecoatedfibers),焙烧除去碳纤维模板后,制微了完整的沸石空心纤维(hollowzeolitefibers),并系统研究了它们的制备条件和材料结构。发现纳米沸石胶体溶液的pH值是制备沸石涂饰纤维和空心沸石纤维的关键因素,其它条件,诸如吸附液的离子强度,每层吸附后的干燥以及每次干燥前是否用PDDA溶液预浸泡,对纤维的完美性也有影响。通过改变吸附纳米沸石的类型和层数可能调变沸石层的组成和厚度,而交替吸附不同的纳米沸石可能制备复合沸石涂饰纤维及复合空心沸石纤维。     

Density Functional Theoretical Studies on the Methanol Adsorption and Decomposition on Ru(0001) Surfaces

Periodic density functional theory(DFT) calculations are presented to describe the adsorption and decomposition of CH₃OH on Ru(0001) surfaces with different coverages, including p(3×2), p(2×2), and p(2×1) unit cells, corresponding to monolayer(ML) coverages of 1/6, 1/4, and 1/2, respectively. The geometries and energies of all species involved in methanol dissociation were analyzed, and the initial decomposition reactions of methanol and the subsequent dehydrogenations reactions of CH₃O and CH₂OH were all computed at 1/2, 1/4, and 1/6 ML coverage on the Ru(0001) surface. The results show that coverage exerts some effects on the stable adsorption of CH₃O, CH₂OH, and CH₃, that is, the lower the coverage, the stronger the adsorption. Coverage also exerts effects on the initial decomposition of methanol. C-H bond breakage is favored at 1/2 ML, whereas C-H and O-H bond cleavages are preferred at 1/4 and 1/6 ML on the Ru(0001) surface, respectively. At 1/4 ML coverage on the Ru(0001) surface, the overall reaction mechanism can be written as 9CH₃OH→3CH₃O+6CH₂OH+9H→6CH₂O+3CHOH+18H→7CHO+COH+CH+OH+26H→8CO+C+O+36H.     

等离子体引发CH3OH/NH3偶联反应合成腈类化合物

腈类化合物广泛用于医药和精细化学品合成。然而,许多腈类的生产过程产生大量污染物。本文采用介质阻挡放电(DBD)等离子体活化甲醇和氨气分子,发现等离子体引发的CH₃OH/NH₃偶联反应可合成二甲基氰胺、二甲基氨基乙腈和氨基乙腈等高附加值含N有机化合物。系统研究了反应器结构、放电条件、反应条件和填充材料对甲醇转化率和产物选择性的影响。实验结果表明,在最优条件下,甲醇的转化率达到51.5%,腈类化合物选择性达到22.1%。CH₃OH/NH₃等离子体发射光谱结果表明,C≡N自由基物种可能是生成腈类化合物的重要中间体。该CH₃OH/NH₃等离子体偶联反应为二甲基氰胺、二甲基氨基乙腈和氨基乙腈提供了一种绿色合成方法,也为甲醇和氨气精细化利用开辟了一种新途径。     

醇-二苯甲酮光化夺氢反应活泼自由基的ESR研究

本文用自由基捕捉剂2,3,4,6-四甲基亚硝基苯(ND)及苯亚甲基叔丁基氮氧化合物(PBN)与ESR相结合的方法研究了CnH_2n+1OH(n=1,2,…8)、(CH₃)₂CH(CH₂)_nOH(n=0,1,2)、CH₂=CHCH₂OH及C₆H₅CH₂OH等十三种醇与二苯甲酮的光化夺氢反应中的活泼自由基,结果表明: 1.用ND时,二苯酮分别夺取CnH_2n+1OH、(CH₃)₂CH(CH₂)_nOH及RCH₂OH(R=CH₂=CH、C₆H₅)中α-C、叔-C及α-C上的氢,而捕捉到C_n-1H_2n-1CHOH、(CH₃)₂CH(CH₂)_nOH及RCHOH自由基。 2.用PBN时,捕捉的自由基与ND捕获的相同。     

Tricarbonylrhenium(I) complexes of phosphine-derivatized amines, amino acids and a model peptide: structures, solution behavior and cytotoxicity

Modified Mannich reactions of amines, amino acids and a model peptide with Ph₂PH and CH₂O gave bis(diphenylphosphinomethyl)amines (Ph₂PCH₂)₂NR [R=Ph (1), CH₂CH₂OH (2), CH₂COOCH₂Ph (3), CH₂CONHCH₂COOCH₂Ph (4), CH₂COOH (5)] and (Ph₂PCH₂)₂NCH₂CH₂N(CH₂PPh₂)₂ (6). Reaction with [ReBr₃(CO)₃]²⁻ under mild conditions led to [ReBr(CO)₃]{(Ph₂PCH₂)₂NR} [R=Ph (7), CH₂CH₂OH (8), CH₂COOCH₂Ph (9), CH₂CONHCH₂COOCH₂Ph (10), CH₂COOH (11)] and [ReBr(CO)₃(Ph₂PCH₂)₂NCH₂]₂ (12). All new complexes have been characterized by NMR and IR spectroscopy and for 7, 9 and 10, single-crystal X-ray diffraction analyses. Electrospray mass spectrometric studies show that the rhenium–phosphine chelates are very stable, especially in neutral methanolic solution. Hydrolysis of the ester and amide linkages slowly occur in acidic and basic solutions over several weeks; displacement of the bromide ligand also occurs in basic medium. Cytotoxicity testing of 7–10 and 12 showed that all the complexes are active against specific tumor cell lines, especially MCF-7 breast cancer and HeLa-S³ suspended uterine carcinoma.     

Primary yields of CH3O and CH2OH radicals resulting in the radiolysis of high purity methanol

The triethylsilane radical R₃^•Si, produced by radiolysis in an airfree methanol/silane-system, acts as a specific scavenger for the CH₃^•O and ^•CH₂OH transients with rate constants, k₁₄(R₃^•Si + CH₃^•O) = 1.1 x 10⁸ dm³ mol^-1s^-1 and k₁₅(R₃^•Si + ^•CH₂OH) = 0.7 x 10⁸ dm³ mol^-1s^-1, resulting in R₃Si—OCH₃ (triethylmethoxysilane) and R₃Si—CH₂OH (triethylsilylmethanol). By increasing the silane concentration (range: 10^-2-6 mol dm^-3 R₃SiH) the formation of the otherwise major products of methanol radiolysis, formaldehyde and glycol, is successively reduced to nil. The yield of R₃Si—CH₂OH, studied under the same conditions, passes a maximum at about 0.8 mol dm^-3 R₃SiH and then also diminishes. On the other hand, the yield of R₃Si—OCH₃ is increased correspondingly and reaches an interpolated value of G = 3.75 ± 0.1 at 4 mol dm^-3R₃SiH. This indicates that the radical CH₃^•O (G = 3.75 ± 0.1) is the primary radiolytic transient of methanol in addition to H, e^-_sol etc., but not ^•CH₂OH species. The latter one is obviously formed by the secondary reaction: CH₃^•O + CH₃OH→ CH₃OH + ^•CH₂OH.     

Density functional and multiphoton ionization studies of N,N-dimethylformamide–(methanol)n clusters

The multiphoton ionization of the hydrogen-bonded clusters N,N-dimethylformamide–(methanol)_n (DMF–(CH₃OH)_n) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated DMF–(CH₃OH)_nH⁺ ions was obtained. The clusters were also investigated by density functional theory B3LYP method in conjunction with basis sets 6-31+G(d,p) and 6-311+G(2d,p). Equilibrium geometries of both neutral and ionic DMF–CH₃OH clusters, and dissociation channels and dissociation energies of the ionic clusters are presented. The results show that when DMF–CH₃OH is vertically ionized and dissociated, DMFH⁺ and CH₃O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of DMFH⁺ and CH₂OH disfavored. In the DMF–(CH₃OH)H⁺ ion, the proton prefers to link with the O atom of DMF molecule. Variation of atomic charges during proton transfer in hydrogen bond of the protonated cluster DMF–(CH₃OH)H⁺ ion is also discussed.     

Adsorption and dissociation of methanol on Au(1 1 1) surface: A first-principles periodic density functional study

The adsorption and dissociation of methanol on Au(111) surface were studied using the first-principles calculations based on density functional theory (DFT) with the generalized gradient approximation (GGA). Adsorption energies, geometric structures, Mulliken charges population, and vibrational frequencies of the various intermediates were computed from full-geometry optimization with a three-layer slab model. The most stable adsorption modes of the species, i.e. CH₃OH, CH₃O, and HCHO were considered in calculation. The possible decomposition pathways were investigated with transition state search methods. The results indicate that methoxyl radical is likely the decomposition intermediate.     

碱金属阳离子对Cu+Y催化甲醇氧化羰基化性能影响的密度泛函理论研究

基于密度泛函理论方法构建并优化了CuMY(M为碱金属阳离子)分子筛的稳定构型, 采用速控步骤CO插入CH₃O形成CH₃OCO反应, 研究了碱金属阳离子对Cu⁺Y分子筛中活性中心周围电子环境及催化甲醇氧化羰基化合成碳酸二甲酯性能的影响. 计算结果表明, Li⁺, Na⁺和K⁺稳定落位于Y分子筛小笼中, 且随着金属离子半径的增大, CH₃OH, CO, CH₃O在CuMY上的吸附能和CO/CH₃O的共吸附能均逐渐增加, CO插入CH₃O反应的过渡态结构稳定性逐渐降低, 活化能逐渐上升, 相应的反应活性逐渐下降. 而落位在超笼中Ⅱ^*位的Rb⁺与Cs⁺则随着离子半径的增大, 反应过渡态的结构稳定性提高, 克服的活化能降低, 反应活性升高. 不同CuMY分子筛上催化活性顺序为CuLiY-Ⅰ'>CuCsY-Ⅱ^*>CuNaY-Ⅰ'>CuRbY-Ⅱ^*>CuKY-Ⅰ'>CuCuY-Ⅰ', 其中CuLiY-Ⅰ'分子筛克服速控反应的活化能垒(52.74 kJ/mol)最低.     

CVD modified KL zeolite supported Pt for n-hexane aromatization

Modification of non-acidic KL zeolite by chemical vapor deposition (CVD) of Si(OEt)₄ and (CH₃)₃Si–O–Si(CH₃)₃ followed by Pt loading was used to study the influence of zeolite support on the aromatization of n-hexane. Deposited on the framework oxygen ions of the non-acidic zeolite, the silica layer effectively narrowed the pores of KL zeolite. But owing to the appearance of new basic sites, such as potassium oxide (K₂O), the interaction between Pt metal and zeolite support was strengthened, causing Pt particles to be more electron-excess. n-Hexane pulse-flow microreactions were carried out to study the effects on the aromatization reactivity and sulfur poisoning properties.     

丝光型Si-Fe沸石表面酸碱性的研究

本文藉助红外光谱(IR)、程序升温脱附—质谱(TPD—MS)等手段研究了丝光型Si—Fe沸石分子筛表面的酸碱性质。结果表明:丝光沸石骨架中的铝原子被铁原子取代以后,其表面酸性大为减弱,但其碱性相对增强,Si—Fe沸石分子筛大部分表面羟基的酸性很弱,仍有一定量的L酸中心存在于沸石的表面上。