Synthesis of acid-base bifunctional mesoporous materials by oxidation and thermolysis

A novel and efficient method has been developed for the synthesis of acid-base bifunctional catalyst SO₃H-MCM-41-NH₂. This method was achieved by co-condensation of tetraethylorthosilicate (TEOS), 3-mercaptopropyltrimethoxysilane (MPTMS) and (3-triethoxysilylpropyl) carbamicacid-1-methylcyclohexylester (3TAME) in the presence of cetyltrimethylammonium bromide (CTAB), followed by oxidation and then thermolysis to generate acidic site and basic site. X-ray diffraction (XRD) and transmission electron micrographs (TEM) show that the resultant materials keep mesoporous structure. Thermogravimetric analysis (TGA), X-ray photoelectron spectra (XPS), back titration, solid-state ¹³C CP/MAS NMR and solid-state ²⁹Si MAS NMR confirm that the organosiloxanes were condensed as a part of the silica framework. The bifunctional sample (SO₃H-MCM-41-NH₂) containing amine and sulfonic acids exhibits excellent acid-basic properties, which make it possess high activity in aldol condensation reaction between acetone and various aldehydes.     

Selective Oxidation of Isobutane to Methacrolein over Mo–V–Te–Sb Mixed Oxide Catalysts with Different Antimony Contents

A series of MoV_0.3Te_0.23Sb_x (x=0–0.6) mixed oxides were prepared and investigated for the selective oxidation of isobutane. Among them, MoV_0.3Te_0.23Sb_0.5 showed the best methacrolein selectivity (as high as 39%), and the yield to methacrolein reached 7.8% at 20.0% isobutane conversion at 470 °C.     

以石英砂为硅源合成4A沸石的研究

以石英砂为硅源,通过水热法合成4A沸石.详细考察了合成温度、时间、碱度以及硅铝比等因素对合成结果的影响.通过X射线粉末衍射、扫描电子显微镜和激光衍射粒径分析等方法对合成的4A沸石进行测试.结果表明石英砂在6mol/L的氢氧化钠溶液中,于密封反应釜中,200℃条件下反应4h可以完全被活化得到含活性氧化硅的碱液,以此为硅源...     

长春辉达大厦筏形基础设计的若干问题

本文简要介绍了长春辉达大厦工程及地质概况，基础选型及内力计算、主楼与裙房连接处埋置深度不满足嵌固要求时作的特殊处理，以及地下水位以下筏形基础底板沉降缝处防水，防渗的处理方法．     

还原扩散法直接制造ZrNi合金粉末的研究

对以Ｃａ作还原剂ＺｒＯ粉末和Ｎｉ粉末作原料，用还原扩散法直接制造ＺｒＮｉ合金粉末的过程进行了研究分析，发现Ｃａ不令是ＺｒＯ２的还原剂，而且Ｎｉ的溶剂和载体，在合金形成过程中，Ｎｉ通过在液体Ｃａ中溶解和扩散，到达被还原出出来的金属Ｚｒ表面，并与Ｚｒ合金化形成ＺｒＮｉ合金因此Ｃａ的添加量是过程的关键因素。     

北京市区流通领域生鲜牛肉及制品市场调查报告

为摸清我国牛肉生产流通领域分割现状,促进牛肉产业的进一步发展,我们对北京市进行了为期近1个月的市场调查。结果发现,我国存在牛肉分割方法不统一,命名混乱,地区间价格差异大,食用方法不清等问题并给出了几种牛肉增值途径。     

Effect of pH on the Catalytic Properties of Mo–V–Te–P–O Catalysts for Selective Oxidation of Isobutane

Mo–V–Te–P mixed oxide catalysts, prepared by a dry-up method at various pHs (in the range of about 1.0–9.0), have been tested in the partial oxidation of isobutane. The best catalytic performance was achieved over a catalyst prepared at a pH about 7.0. In this case, high selectivity to methacrolein (37.0%) at an isobutane conversion of 12.7% has been obtained at 380 °C. The surface V⁴⁺/V⁵⁺ ratios of the calcined samples were strongly influenced by the pH in the synthesized solution, which is one of the key factors in the catalytic performance for selective oxidation of isobutane.     

由MCM-22沸石结构前驱体合成介孔材料及其催化性能的研究

实验以两步晶化法,利用MCM-22沸石结构前驱体合成一种含介孔的催化材料,用XRD、N_2吸附-脱附、~(27)Al MAS NMR、NH_3-TPD对试样进行了表征。实验结果表明其孔径约为3.3 nm,比表面积为740～870m~2/g,其氢型试样除含有弱酸中心外,还含有强酸中心,总酸量为0.71～0.76 mmol/g。在115℃条件下,试样用于催化2,4-二叔丁基苯酚与叔丁基醇烷基化反应时,2,4-二叔丁基苯酚的转化率约为22%,2,4,6-三叔丁基苯酚的选择性约为49%,其催化活性高于微孔沸石Hβ和常规介孔分子筛HMCM-41。     

基于射频隐身的采样周期和辐射功率控制方法研究

为进一步提高雷达的射频隐身能力,合理分配相控阵雷达的工作参数,在目标跟踪时,对雷达的采样周期和辐射功率控制方法进行研究。首先,根据目标运动状态的不同,对雷达采样周期与辐射功率自适应设计方法进行分析,在满足系统跟踪性能要求的前提下,建立了控制参数的优化模型;然后,利用粒子群算法优化自适应采样周期和自适应辐射功率等参数,有效地降低了跟踪性能误差,提高了雷达系统的射频隐身性能。与传统的雷达采样周期和辐射功率算法进行了仿真比较,结果表明所提的算法取得了较好射频隐身效果。     

Alkylation of Phenol with tert-Butanol Catalyzed by Mesoporous Material with Enhanced Acidity Synthesized from Zeolite MCM-22

Using zeolite MCM-22 as source and cetyltrimethylammonium bromide (CTAB) as template, mesoporous material denoted as M-MCM-22 with enhanced acidity has been synthesized and characterized by XPD, FT-IR, N₂ adsorption–desorption, ²⁷Al-MAS NMR, IR spectra of pyridine adsorption, and NH₃-TPD techniques, etc. The catalytic performance of M-MCM-22 was tested in alkylation of phenol with tert-butanol, indicating that M-MCM-22 showed highly and steadily catalytic properties. The highest conversion of phenol could be achieved at 418 K, while the highest selectivity to 2, 4-di-TBP was obtained at 398 K. It is found that high temperature is advantageous to form 4-TBP, whereas low weight hourly space velocity (WHSV/h^?1) is helpful for both conversion of phenol and selectivity to 2,4-DTBP. It is also shown that high ratio of tert-butanol/phenol is beneficial for obtaining high conversion of phenol and selectivity to 2,4-di-TBP.