F-127作为模板剂合成微孔-介孔SAPO-11分子筛及其在长链烷烃异构化中的应用

在常规水热法合成SAPO-11的基础上,添加适量F-127作为软模板构造介孔结构,成功合成出了SAPO-11分子筛微介复合体.考察了F-127添加量对分子筛内部的孔道结构的影响,并通过XRD、N2吸附-脱附曲线、SEM和Py-FTIR等途径对催化剂进行表征.以正十二烷为原料,对负载Pt金属的SAPO-11分子筛进行临氢异构化反应性能评价.结果表明:添加F-127的分子筛内部出现了明显的介孔结构,并且随着F-127添加量的增加,分子筛的介孔孔容呈先增大后减小的趋势;异构化反应结果表明催化剂活性位的数量与分子筛介孔孔容有关;随着温度的升高,异构烷烃转化率升高,异构烃收率下降.催化剂的异构化转化率伴随着F-127的添加量的增加而降低,F-127添加量在一定范围内的增加可使异构烃收率得到提高.在F-127添加量为10;时,异构烃收率达到最高为57.62;.     

导向剂法制备纳米棒状丝光沸石分子筛及其加氢异构化性能

以偏铝酸钠为铝源,硅溶胶为硅源,并添加部分导向剂制备出丝光沸石分子筛.通过XRD、SEM、NH3-TPD等表征手段,表明这种制备方法形成的丝光沸石,能够在空间结构上形成纳米棒状的阵列排布.这种合成方式提高了分子筛的比表面积和孔径比,有明显的介孔产生.同时考察了该分子筛在负载一定量Pt的条件下,对于正十二烷在临氢条件下的异构化反应.结果表明,正十二烷的转化率为95.21;,异构烷烃收率为64.27;.     

微波辅助水热条件对二乙胺合成SAPO-11晶体结构与性质的影响

以二乙胺为模板剂,利用微波辅助水热合成法制备了SAPO-11晶体,研究了水热温度和时间对合成产物晶体结构性质的影响。采用XRD、FT-IR、SEM、BET和NH3-TPD等手段对SAPO-11晶体的物相组成、骨架结构、微观形貌、孔结构及表面酸性进行了分析表征。研究结果表明,不同水热条件对SAPO-11晶体结构性质影响较大。反应温度低于180℃时,合成样品仅存SiO2物相,无SAPO-11晶相生成;反应温度高于200℃时,部分SAPO-11晶体二次生长致使晶粒均匀度和比表面积大幅下降;反应时间大于1 h时,SAPO-11晶体生长易转晶生成少量AlPO4-5和CFSAPO-1(C)杂晶相;在反应温度200℃,反应时间1 h条件下制备得到的纯相SAPO-11球形晶粒表面具有弱酸特征,比表面积、孔容和平均孔径分别达199.4 m2·g-1,0.15 cm3·g-1和2.92 nm。     

ZSM-5预晶化时间对SAPO-34/ZSM-5复合分子筛物化性质及MTO反应的影响

采用原位两步晶化法制备了SAPO-34/ZSM-5复合分子筛,考察了SAPO-34分子筛合成体系的晶化pH,进一步研究了ZSM-5预晶化时间对SAPO-34/ZSM-5复合分子筛物化性质及MTO催化性能的影响.采用XRD、SEM、BET和NH3-TPD等手段对分子筛样品进行表征分析.结果表明,ZSM-5预晶化不同时间合成SAPO-34/ZSM-5复合分子筛的结构、形貌和催化性质有较大影响.预晶化时间为6 h制得复合分子筛SZ-ZSM-5(6 h)形成紧密的复合相结构,表现出丰富的微-介孔的多级孔分布和适宜的弱酸位和中强酸分布等特性,在MTO反应中甲醇转化率为98.4;,低碳烯烃选择性为93.4;,催化寿命达1400 min,具有较优越的催化性能.     

沉淀pH值对SAPO-34/CZA复合催化剂物化性质及CO2加氢反应影响

研究了液相沉淀包覆工艺终点pH值对SAPO-34/CZA复合催化剂物化性质和CO2氢还原制低碳烯烃催化性能的影响.借助XRD、SEM、BET、NH3-TPD和CO2-TPD等手段对不同复合催化剂的晶相组成、微观形貌、孔结构及表面酸碱性质进行了分析表征.研究结果表明,沉淀pH值对SAPO-34/CZA复合催化剂物化性质和CO2加氢制低碳烯烃催化性能影响较大.过高或过低的沉淀pH值制得复合催化剂中SAPO-34分子筛结晶度、微孔比表面积及表面碱量均有所下降,呈现以介孔为主的孔结构特征;而当pH值为7时,制得复合催化剂形成了包覆相结构和微-介复合孔结构(微孔比表面积53.1 m2·g-1,介孔比表面积59.8 m2·g-1,总比表面积为112.9 m2·g-1,总孔容0.4 cm3·g-1,平均孔径14.6 nm);在反应温度325℃,还原温度285℃,反应压力3.0 MPa,体积比H2:CO2=3.0,空速3500 mL·g-1·h-1反应条件下,CO2转化率为64.8;,低碳烯烃选择性为49.8;.与pH=9制得催化剂比较,CO2转化率和低碳烯烃选择性分别提高了26.2;和19.2;.     

ZrO2预处理方式对ZrO2/SAPO-34复合催化剂物化性质及MTO催化性能的影响

采用水热包覆法制备了ZrO2/SAPO-34复合催化剂,研究了ZrO2预处理方式对复合催化剂物化性质和MTO催化性能的影响.采用XRD、FT-IR、SEM、NH3-TPD和BET等手段对不同复合催化剂的晶相组成、骨架结构、微观形貌、表面酸性质及孔结构进行分析表征.结果表明,ZrO2预处理方式对复合催化剂物化性质和MTO催化性能影响较大.未焙烧和焙烧经聚电解质改性ZrO2制得复合催化剂未形成连续复合相,比表面积小,表现出较短的催化寿命,仅为410 min和530 min;450℃焙烧ZrO2制得复合催化剂形成了均匀连续复合相和层级结构孔特征(微孔比表面积112.91 m2· g-1,介孔比表面积176.02 m2· g-1,总比表面积为288.93 m2· g-1,总孔容0.19 cm3· g-1),总酸量较大(0.344 mmol/g);在常压、反应温度380 ℃、N2流速20 mL· min-1、进料空速2 h-1MTO反应条件下,复合催化剂表现出优越催化性能、稳定性及反应寿命,甲醇转化率和低碳烯烃选择性分别达100;和90.54;,催化寿命达1130 min,与单一SAPO-34分子筛相比,催化寿命延长了768 min.     

SAPO-34/CZA复合晶体相结构性质及催化CO2加氢反应研究

采用共沉淀包覆法制备了SAPO-34/CZA双功能复合催化剂,研究了复合相比例对催化剂晶体结构性质和CO2加氢制低碳烯烃催化性能的影响.采用XRD、FT-IR、SEM、BET、NH3-TPD和CO2-TPD等手段对不同催化剂的晶相组成、骨架结构、微观形貌、孔结构及表面酸碱性进行了分析表征.研究结果表明,复合相比例对SAPO-34/CZA双功能复合催化剂的结构性质和催化性能影响较大.质量比为1∶1时,制得复合催化剂具有明显微孔和介孔特征(微孔比表面积53.15 m2·g-1、介孔比表面积59.84 m2·g-1、总比表面积为113.00 m2·g-1、总孔容0.41 cm3·g-1、平均孔径14.57 nm),具有特殊包覆结构及存在复合相界面,构造了特殊反应路径,微介孔层级结构强化耦合反应,表现出较高催化性能.在还原温度285 ℃、反应温度325 ℃、压力3.0 MPa、V(H2)/V(CO2)=3.0、空速(SV)3500 mL·g-1·h-1的条件下,CO2转化率为64.80;,低碳烯烃选择性为49.68;.与物理共混催化剂SAPO-34/CZA-M相比,CO2转化率和低碳烯烃选择性分别提高了31.98;和2.43;.     

CuAPO-5分子筛的制备及对卷烟烟气中酚类的吸附性能研究

采用水热晶化法合成CuAPO-5磷酸铝改性分子筛,以XRD、XPS、BET为手段对分子筛样品进行表征,结果表明,分子筛具有AFI拓扑结构,骨架上加载上了铜离子,为正二价.在不同的金属比获得的分子筛材料中,当金属比为0.06时,所制备的CuAPO-5分子筛吸附性能最好,可降低卷烟烟气中62.46;的苯酚,高于现有的研究.研究了分子筛对苯酚的液相吸附动力学作为卷烟烟气中苯酚吸附的参考,该吸附符合二级动力力学(R2＞0.9).     

γ-Al2O3预处理方式对 γ-Al2O3/SAPO-34复合催化剂物化性质及催化性能的影响

采用水热包覆法制备了 γ-Al2O3/SAPO-34复合催化剂,考察了γ-Al2O3预处理方式对复合催化剂物化性质和MTO反应催化性能的影响.采用X射线衍射(XRD)、傅里叶红外(FT-IR)、扫描电子显微镜(SEM)、NH3程序升温脱附(NH3-TPD)、N2吸附脱附(BET)等手段对几种复合催化剂进行了分析表征.结果表明,γ-Al2O3预处理方式对复合催化剂物化性质和MTO催化性能影响较大.添加拟勃姆石和电位改性γ-Al2O3制得复合催化剂未形成包覆复合相结构,比表面积较小,表现出较短催化寿命,仅分别为360 min和450 min;添加γ-Al2O3制得复合催化剂形成了包覆相结构和微-介复合孔结构(微孔比表面积123.49 m2·g-1、介孔比表面积122.68 m2·g-1,总比表面积为246.17 m2·g-1,总孔容0.29 cm3·g-1),总酸量较大(0.30 mmol·g-1);在常压、反应温度380℃、进料空速2 h-1反应条件下,复合催化剂催化性能优越,稳定性良好,具有较长的催化寿命,甲醇转化率为100;,低碳烯烃选择性为88.10;,催化寿命达990 min.     

ZrO2相态对ZSM-5@ZrO2催化剂物化性质及甲硫醇合成的影响

采用水热包覆法成功制备了ZSM-5@ZrO2催化剂,研究了ZrO2不同相态对催化剂物化性质和甲硫醇合成的影响.借助XRD、SEM、FTIR、Raman、BET和NH3/CO2-TPD等手段对催化剂结构性质进行了分析表征.结果表明,ZrO2不同相态对催化剂物化性质和催化性能影响较大.以四方晶相t-ZrO2制得ZSM-5@t-ZrO2催化剂形成了均匀的包覆相结构和微-介孔结构(微孔比表面积114.12 m2/g、介孔比表面积125.08 m2/g、总比表面积239.2 m2/g、总孔容0.38 cm3/g),同时具有酸碱特性(总酸量0.071 mmol/g、总碱量0.077 mmol/g).在反应压力1.0 MPa、H2S/CH3 OH摩尔比2:1、氮气流量90 mL/min、反应温度370℃条件下,催化剂表现出良好催化性能和反应寿命,CH3 OH转化率和CH3 SH选择性分别为92.07;、90.89;,催化寿命达20 h.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.