HZSM-5沸石催化剂酸性质和催化性能的研究 Ⅱ.高温水蒸汽处理的影响

用程序升温脱附(TPD)和红外光谱(IR)表征了经高温水蒸汽处理的HZSM-5沸石催化剂的酸性,并且考察了用于正己烷等烃类裂化反应的活性和选择性。实验结果表明,高温水蒸汽处理对催化剂的活性是不利的,如用700℃水蒸汽处理后,转化率降至10%左右。随着处理温度的升高酸性下降,处理温度在500—600℃、处理时间4—6h 时对程脱量和吸附氨中心数影响较为明显,而且对强酸部位的影响比弱酸部位更显著。文中讨论了发生裂化反应的可能的表面酸性部位。     

多级孔HZSM-5分子筛催化剂的制备及低碳烃芳构化应用

采用0.2 mol/L的NaOH溶液对HZSM-5分子筛进行了不同时间的碱改性处理, 并对分子筛的结构和酸性进行表征, 考察了碱改性对HZSM-5催化剂的低碳烃芳构化活性的影响. 结果表明, HZSM-5分子筛经碱改性后会产生少量介孔, 且随改性时间延长, 介孔数量增加, 平均孔径增大, 总酸量降低, B酸/L酸比值降低. 120 min碱改性HZSM-5催化剂的活性、 稳定性以及目标产物苯、 甲苯、 乙苯和二甲苯(统称BTEX)的选择性最高.     

Si(CH3)3Cl修饰的HZSM-5酸性及正己烷芳构化的催化性能研究

随着芳烃需求量的增加,低分子烃的芳构化受到广泛重视.由于HZSM-5的独特骨架结构及酸性,使其对低分子烃有良好芳构化性能~[1～3],但研究工作大多放在HZSM-5本身的硅铝比调变及加入某些金属(如Ga,Zn)来提高其芳构化性能~[4～7],而以非金属对其进行改性处理则很少见.本文以Si(CH_3)_3CI对HZSM-5进行CVD处理,并对其酸性及对正已烷芳构化能力进行了考察,研究了催化剂的结焦情况.     

合成气在 Fe/HZSM-5复合催化剂上转化制烃—沸石的特性和催化作用

对各种HZSM-5沸石的形选性和酸性作了表征,并在熔铁和HZSM-5沸石复合催化剂上考察了沸石对合成气制烃反应的催化作用。结果表明,沸石的形选性、酸性和催化作用因沸石的来源、质子化方法和水蒸汽处理条件的不同而异。沸石的存在提高了合成气转化率,产物碳数不大于11。沸石的特性差异对上述两者无显著影响,对产物选择性影响很大。讨论了不同强度的酸中心对裂化和芳构化的作用,并指出调变沸石酸性对提高目的产物选择性的重要性。对汽油馏份和沸石含碳沉积物的性质作了初步表征,并讨论了焦的成因。     

硅烷化处理对Mo/HZSM-5催化剂上甲烷脱氢芳构化活性的影响

 结合催化剂的活性评价及固体高分辨核磁共振谱、X射线光电子能谱和X射线荧光光谱和热重等技术,考察了硅烷化处理对Mo/HZSM-5催化剂上甲烷脱氢芳构化活性的影响. 结果表明,采用大分子有机硅烷对HZSM-5分子筛进行硅烷化处理,除去了分子筛外表面的酸性位,并使分子筛本身发生了脱铝. 硅烷化处理使Mo/HZSM-5催化剂在进行甲烷脱氢芳构化反应时催化剂上总的积碳量明显减少,从而提高了催化剂的活性.     

重氮甲烷对HZSM-5分子筛表面酸性的影响

本文利用重氮甲烷对HZSM-5分子筛表面酸进行改性,并对改性后的样品考察其表面性质和反应活性的变化。实验结果表明,改性后HZSM-5的比表面积明显降低,表面总酸量大大减少;改性前后的样品经水蒸汽处理后,其总酸量均比未经水蒸汽处理样品的高;在改性后的HZSM-5样品上,乙炔聚合反应的结焦量大大降低,甲醇脱水反应产物分布发生明显变化。     

硅烷化处理对Moo/HZSM-5催化剂上甲烷脱氢芳构化活性的影响

结合催化剂的活性评价及固体高分辨核磁共振谱、X射线光电子能谱和X射线荧光光谱和热重等技术,考察了硅烷化处理对Mo/HZSM-5催化剂上甲烷脱氢芳构化活性的影响.结果表明,采用大分子有机硅烷对HZSM-5分子筛进行硅烷化处理,除去了分子筛外表面的酸性位,并使分子筛本身发生了脱铝.硅烷化处理使Mo/HZSM-5催化剂在进行甲烷脱氢芳构化反应时催化剂上总的积碳量明显减少,从而提高了催化剂的活性.     

高温水蒸汽处理对HZSM-5分子筛上乙烯、苯烷基化反应性能的影响

本文用色谱法考察了直接法合成并经不同条件高温水蒸汽处理过的HZSM-5分子筛催化剂对乙烯的作用;用微反研究了这些样品用于苯和乙烯烷基化反应的催化性能;考察了这些性能与表面酸性质的关系并对水蒸汽处理条件和烷基化反应条件的选择进行了讨论.     

不同碱处理制备多级孔HZSM-5催化剂及噻吩烷基化性能研究

用Na₂CO₃、TPAOH和TPA⁺/CO₃^2-混合碱分别处理HZSM-5分子筛,采用FT-IR、XRD、XRF、N₂吸附脱附、SEM、NH₃-TPD及Py-FTIR表征手段对各类碱处理前后的HZSM-5分子筛进行表征。结果表明,3种类型的碱处理HZSM-5分子筛后,均能形成微孔-介孔多级孔道的HZSM-5(A)催化剂,并能调变催化剂的酸性,其中,TPA⁺/CO₃^2-混合碱处理得到的HZSM-5(TPA⁺/CO₃^2-)催化剂,比表面积最大,介孔数量最多。在小型固定床反应器上,考察了HZSM-5和HZSM-5(A)催化剂的噻吩烷基化性能,结果表明,HZSM-5(TPA⁺/CO₃^2-)催化剂因为具有适当的多级孔孔道和较多的B酸中心而表现出较高的噻吩转化率和1-己烯对噻吩的选择性。     

晶粒大小对ZSM-5分子筛甲醇制低碳烯烃催化性能的影响

对三种HZSM-5分子筛进行Ca改性,获得两组酸性接近的催化剂,考察了晶粒大小对甲醇制低碳烯烃(MTO)反应的影响。通过进一步与Na改性的比较,探讨了Ca在催化反应中的作用。采用扫描电镜(SEM)测定晶粒大小及形貌,氨气程序升温脱附(NH3-TPD)及吡啶红外吸附(Py-IR)表征催化剂的酸性。MTO催化性能测定结果表明,HZSM-5的低碳烯烃选择性较低且下降较快,催化活性降低也快;Ca改性降低酸性,提高了低碳烯烃选择性和催化稳定性;晶粒大小主要影响催化稳定性,小晶粒分子筛催化剂稳定性更好。高Ca含量改性效果更好;钠改性也提高了低碳烯烃选择性,但其稳定性较差。对于HZSM-5和Ca/HZSM-5,小晶粒的催化剂具有较好的催化稳定性。提出Ca参与了催化反应,MTO是一个酸碱协同作用的催化过程。     

Determination of the additive physical properties of the components of complex mixtures

Summary The density, refractive index and absorptivities at chosen wave numbers were determined for all the components of three-component mixtures. The mixtures were treated of three-component mixtures. The mixtures were treated as being of unknown qualitative and quantitative composition. The quantitative gas chromatographic analysis by means of the method of linear relationship was carried out and the values of the physical properties of complex mixtures were measured. The corresponding properties of acetone, benzene and toluene were evaluated from the set of appropriate equations.     

Study of the influence of the graphite powder particle size on the structure of the Sonogel-Carbon materials

In this paper, the influence of carbon particles size on structure and on electrochemical and physical properties of the Sonogel-Carbon electrodes, with respect to Sonogel materials without graphite, have been studied. The materials have been characterized electrochemical and structurally; several Sonogel-Carbon materials were synthesized using different types of graphite powder as massive modifiers, adding in some cases other modifiers, such as octadecyl (C18) and polyethyleneglycol (PEG). Differential pulse voltammetry and cyclic voltammetry were the voltammetric techniques employed to evaluate the electrochemical behaviour; Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Infrared Spectroscopy were the techniques employed to realize the superficial/structural characterization of the materials. The results obtained in both studies were very useful to explain the structure of the Sonogel-Carbon materials. Furthermore, they allowed to conclude that electrodes based on RW-B and UF graphites show very similar electrochemical behaviours and internal structures.     

Forecasting the characteristics of the explosives

The key techniques for forecasting of the properties of the explosives were presented. We acquired an array of the properties approximately for 200 explosives on the basis of literature information and own experimental data. Techniques of an evaluation of the main characteristics of the explosive transformation were developed. We forecasted properties of a series of compounds not synthesized earlier by computation methods. The experimental and computed data were combined into vast array of information approximately for 1000 explosives. The systematization of experimental data allows conclusions about the attained levels of efficiency and of safety, and also forecasting the properties of the promising explosives.     

Effects of the nature and composition of the solvent on the thermodynamic characteristics of the individual forms of hydrogen adsorbed on the surface of porous nickel

The effects of the nature and composition of solvents on the thermodynamic characteristics of the adsorption states of hydrogen on nickel were studied. The adsorption can be described in terms of the thermodynamic model of a surface with a discrete nonhomogeneity for three individual forms of adsorbed hydrogen. The thermodynamic characteristics of the individual forms of hydrogen adsorbed on porous nickel from aqueous solutions of sodium hydroxide, dimethylformamide, methanol, and ethanol were determined.     

Measurement of the transition dipole moment of the first hot band of the nu2 mode of the methyl radical by diode laser spectroscopy

The line strengths of five Q-branch lines of the first hot band of the out-of-plane bending vibration (2(1)(2)) of the methyl radical, CH 3, have been measured using infrared laser absorption spectroscopy. The spectra of the radical were measured in situ in a microwave discharge using ditertiary butyl peroxide, diluted in argon as the precursor. The line strengths were used to determine the transition dipole moment of the hot band. Absolute concentrations of the radical were required for this purpose, and these were determined kinetically from the measured decays of the spectral lines after the discharge was extinguished. The translational, rotational, and vibrational temperatures were also determined spectroscopically from measured integrated line intensities and line widths. The transition dipole moment of the first hot band was determined to be 0.31(6) D. This value is in satisfactory agreement with the value of 0.27(3) D from a high-precision ab initio calculation using the self-consistent electron pairs (SCEP) method reported by Botschwina, Flesch, and Meyer [Botschwina, P.; Flesch, J.; Meyer, W. Chem. Phys. 1983, 74, 321].     

Determination of hydroxyproline in tissues and the evaluation of the collagen content of the tissues

The concentrations of hydroxyproline (an amino acid specific of collagen) in a number of connective tissues were determined. Two procedures were compared. In one of them, amino acids were preseparated by chromatography and then determined on a standard amino acid analyzer. In the other procedure, hydroxyproline was selectively oxidized without amino acid separation and determined by a spectrophotometric reaction with Ehrlich’s reagent. Data obtained for purified collagen preparations in accordance with the two procedures were consistent with each other. The results can be somewhat different in unpurified preparations and tissues because of the presence of polysaccharide components in the tissues.     

镧系元素f-f跃迁光谱计算

运用不可约张量算符方法,建立了f-f超灵敏跃迁光谱的计算模型,编制了计算f离子^2s+1L~J能级、约化矩阵元、晶体场Stark能级、晶体场态-态跃迁振子强度及模拟吸收光谱的计算机程序.其中,自由f离子能级计算采用包括双电子与叁电子组态相互作用的二三参数模型,晶体场Stark分裂计算采用单电子轨道近似,用Newman角叠加模型计算晶体场参数.f-f跃迁振子强度计算包括静电诱导偶极跃、配体极化偶极跃、振动诱导电偶极跃迁及磁偶极跃迁的贡献.     

Determination of the thermodynamic functions of lead carbonate on the basis of the calculation of vibrational states

The force constants of bond angles and bonds and parameters of the interatomic potential for the natural carbonate cerussite were determined from the valence force field calculation of the vibrational states of its crystal structure. The initial force constants were calculated by the semiempirical PM5 method using the MOPAC quantum-chemical program package. As the criterion of adequacy of calculations, the consistency between the simulated IR and Raman spectra and the experimental spectra of the compound was used. The heat capacity of lead carbonate as a function of temperature was calculated based on the theory of crystal lattice dynamics and by quantum-chemical methods. The best fit to the experimental data was provided by the semiempirical PM5 method. From the calculated heat capacities, the entropy values of the compound were found.     

Interpretation of the Parameters of the EPR Spectra of Transition Metal Complexes

The calculated parameters of the EPR spectra of complexes of d¹ and d⁹ ions were presented. The covalent bond parameters used in the calculations were determined from EPR and experimental optical data (inverse problem of EPR spectroscopy). Various contributions to the expressions for the EPR parameters were compared. The observed abnormal values of the EPR parameters were discussed. The effects of charge-transfer states and the vibronic coupling on the components of g, A, and A^L tensors were considered. Mechanisms of spin density transfer to ligands in paramagnetic complexes were proposed.     

On the time behaviour of the concentration of pyrazinium radical cations in the early stage of the Maillard reaction

During the early stage of the Maillard reaction pyrazinium radical cations were detected by ESR within the reaction system d-glucose/glycine. The spectra were characterized by completely resolved hyperfine structure. The partial pressure of oxygen and the radical concentrations were measured directly in the reaction mixture by ESR using solutions of the spin probe TEMPOL and of DPPH, respectively. There are quantitative and qualitative relations of the actual concentration of the radical ions to the partial pressure of oxygen, the temperature-time regime and the mechanical mixing of the reaction system. These macroscopic parameters significantly affect both the induction period and the velocity of the time-dependent formation of free radicals. From in situ variations of p(O2) and p(Ar) including the connected mixing effects caused by the passing the gases through the reaction mixture, steric and chemical effects of the stabilization of the radical ions were established. The determination of suitable and relevant conditions for stabilization and subsequent radical reactions contributes to the elucidation of the macroscopically known antioxidant activity of Maillard products.