负载型钯催化剂硫中毒机理—模型催化剂的评价及表征

以H_2S为毒物,H_2-O_2反应为模型反应,用浸渍法制备了一系列Pd/Al_2O_3催化剂,用交替-脉冲微反应色谱技术对催化剂活性、耐硫性进行评价,用XPS、红外分析技术对不同反应阶段的催化剂进行了表征。结果表明:在一定条件下,虽然催化剂上有S_2~(2-)、S~(2-)和SO_4~(2-)物种存在,其活性也基本相同,但耐硫性差别较大。当催化剂上有S_2~(2-)存在时,其耐硫性较差,含有S~(2-)的催化剂次之,含有SO_4~(2-)的催化剂的耐毒性较好。SO_4~(2-)对催化剂的主要影响是降低了催化剂的活性,而对抗硫性影响不大。由此可以认为,H_2-O_2反应中负载型钯催化剂硫中毒时,以S_2~(2-)毒性最大,其次是S~(2-),在一定范围内SO_4~(2-)的毒性较小。     

硫物种对负载型钯催化剂上氢吸附性质的影响

用X光光电子能谱(XPS)分析了负载型Pd/Al_2O_3催化剂上硫和钯的状态。以程序升温脱附-质谱(TPD-MS)方法研究了不同硫物种及不同气氛对催化剂氢吸附性质的影响。结果表明: 硫物种对氢吸附的影响按S_2~(2-)、S~(2-)、SO_4~(2-)的顺序减小, 且前两者的影响远比SO_4~(2-)的大。这与催化剂在H_2-O_2反应中的抗硫性评价结果一致。并用原子分子轨道理论对上述结果进行了讨论。     

不同前驱体制备的SO_4~(2-)/AC催化剂在二甲醚直接氧化合成聚甲氧基二甲醚中的反应性能

分别用硫酸、硫酸铵作为前驱体,活性炭(AC)作为载体,采用浸渍法制备了SO_4~(2-)/AC双功能催化剂(SO_4~(2-)离子和AC载体分别提供催化剂的酸性和氧化还原性),考察了其在二甲醚(DME)直接氧化合成聚甲氧基二甲醚(DMMx)反应中的催化性能。结果表明,不同前驱体制备的SO_4~(2-)/AC催化剂表现出显著的催化活性差异。40%H_2SO_4/AC催化剂具有较好的反应活性,DME转化率为8.4%,DMM1-2的选择性达到59.7%,并且没有COx的生成;而在40%(NH_4)_2SO_4/AC催化剂上,反应主要生成了COx,DMM选择性仅2.7%,且无DMM2生成。XRD、BET、NH_3-TPD及O_2-TPD-MS等表征结果显示,H_2SO_4/AC催化剂中适量的弱酸性位和氧化还原性位有利于DME直接氧化合成DMMx。经过SO_4~(2-)修饰的催化剂促进了O2在活性炭表面的活化;前驱体H_2SO_4的加入提高了催化剂表面的弱酸性位数量,而(NH_4)_2SO_4的引入却促使催化剂表面产生中强酸性位。     

S_2O_8~(2-)/ZnFe_xAl_(2-x)O_4的制备及催化合成乙酸正丁酯

通过(NH4)2S2O8溶液浸渍法制备了S_2O_8~(2-)/ZnFe_xAl_(2-x)O_4固体催化剂。通过XRD、TG-DSC、IR和N_2吸附-脱附的分析方法对催化剂进行了表征,并考察了催化剂的制备条件。实验结果表明,S_2O_8~(2-)/ZnFe_xAl_(2-x)O_4-仍具有载体的尖晶石结构特征,BET表面积为37.65m~2/g,颗粒堆积后的平均孔径约为12.47nm。将S_2O_8~(2-)/ZnFe_xAl_(2-x)O_4应用于制备乙酸正丁酯的反应,研究表明,催化剂的催化活性与制备条件有关,当采用0.15mol/L(NH4)_2S_2O_8溶液浸渍ZnFe_(0.15)Al_(1.85)O_4,温度为550℃焙烧5h条件下制备的催化剂,可使乙酸的酯化率达到93.47%。     

铜锌铝催化剂上变换动力学的研究 Ⅰ.本征动力学与宏观动力学

以我们研制的内循环无梯度反应器对国产铜锌铝变换催化剂进行了一氧化碳与水蒸汽变换反应动力学的研究。实验是先以细粒度催化剂在不同浓度、温度下测定反应速率,以k 值平方差最小为目标函数,电子计算机估定参数,求得本征动力学方程为r=7.7×10~4exp(-5.7×10~4/RT)y_(CO)y_(H_2O)~(0.4)y_(CO_2)~(-0.3)y_(H_2)~(-0.3)(1-β)参数估值经过F-检验证明是可靠的。实验再在同样装置和条件下对工业原颗粒催化剂进行测定,沿用本征动力学指数方程,获得宏观动力学方程如下:r'=684exp(-4.03×10~4/RT)y_(CO)y_(H_2O)~(0.4)y_(CO_2)~(-0.3)y_(H_2)~(-0.3)(1-β)并用这些结果对年产三十万吨氨厂低温变换过程进行模拟计算,结果与实际甚为接近。     

RCOO-取代的镍(Ⅱ)配合物单组分高效催化乙烯均聚和共聚反应（英文）

合成并表征了含RCOO-基团的单核(Ni~1~Ni~2)及双核(Ni~3)镍配合物[(2,6-R_2-C_6H_3)-N=C(H)-(3-Ph-5-Ph COO-2-O-C_6H_2)-κ~2-N,O]Ni(CH_3)(pyridine)](R=i Pr;3,5-t Bu_2C_6H_3)并用于催化乙烯均聚和共聚反应。作为单组分催化剂,这些配合物可以有效地催化乙烯聚合得到中等相对分子质量的支化聚乙烯(PE)。供电性的Ph COO—基团促进了催化剂Ni~1的引发,从而在低温下比Ni~0活性更高。引入大位阻的2,6-(3,5-二叔丁基苯基)苯胺基团,催化剂Ni~2在5×10~5Pa下的活性高达1.8×10~6g PE mol~(-1)·Ni~(-1)·h~(-1),是活性最高的水杨醛亚胺中性镍催化剂之一。与相应的单核催化剂相比,双核催化剂Ni~3对三苯基膦具有更好的耐受性。这些催化剂可催化乙烯与1,5-己二烯、1,7-辛二烯、6-溴-1-己烯或10-十一烯酸甲酯的共聚合,制备功能化聚乙烯。     

α-Ti(HPO_4)_2微球负载型催化剂的合成及其烯烃聚合催化性能（英文）

2种茂金属催化剂及1种后过渡金属催化剂分别被固载于经过甲基铝氧烷处理后的α-Ti(HPO_4)_2微球表面,制备得到3种微球负载型催化剂。在烯烃聚合反应过程中,3种负载型催化剂均表现出比硅胶负载型催化剂更高的催化活性。2种茂金属负载型催化剂在乙烯、丙烯聚合反应中的活性分别高达6.8×10~7 gPE·(molZr·h)~(-1)和5.0×10~7 gPP·(molZr·h)~(-1),所产生的烯烃聚合产物分子量分布较窄(Mw/Mn2.3),表现出良好的单中心催化特性,而且丙烯聚合产物的等规度高达96.5%。负载型后过渡金属催化剂在乙烯聚合反应中的活性稍低,但也能够达到8.3×10~6 gPE·(molFe·h)~(-1)。3种负载型催化剂催化烯烃聚合产物均成微球型,能够很好地复制载体的形貌。     

SO_4~(2-)功能化处理对Fe_2O_3催化剂上氨选择性催化还原NO_x性能的促进机理研究

采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。     

镍系胶体催化丁二烯聚合反应的研究Ⅱ: 催化剂组分的 电导率和紫外光谱

在加氢汽油介质中Ni(naph)~2-Al(i-Bu)~3-(BF~3·OEt~2+n-C~8H~1~7OH)体系为胶体催化剂的基础上,本文从电导率、UV-Vis光谱对催化剂各组分之间的相互作用作进一步的分析。得出催化剂组分以离子对的形式参与反应;Ni^0在Ni(naph)~2-Al(i-Bu)~3陈化液中以团簇粒子形式存在,因吸附Ni^+naph^-而稳定,因加入BF~3·OEt~2而失去稳定性、聚结为胶粒,活性中心位于胶粒表面的观点。     

新型Sn改性固体酸催化剂SO_4~(2-)/TiO_2催化1,6-己二醇二丙烯酸酯合成（英文）

丙烯酸酯单体包括通用丙烯酸酯和特种丙烯酸酯,不仅是高分子化合物的基本单体,也是化工有机反应的原料.特种丙烯酸酯在工业合成中虽然规模小,产量低,但已经应用到皮革、造纸、纺织、涂料、粘合剂和辐射固化技术等许多领域.辐射固化材料主要包括活性稀释剂、光引发剂、齐聚物和添加剂等.其中,齐聚物的主要成分就是丙烯酸酯单体的聚合物.然而,丙烯酸酯的合成工业难度不在合成路线,而是反应所使用的催化剂.浓硫酸和对甲苯磺酸等液体酸催化剂由于后续反应难分离、腐蚀设备、污染环境和催化剂不易回收等缺点,逐渐被固体酸催化剂所替代.而SO_4~(2-)/MOx固体酸催化剂虽然没有这些缺点,但是催化剂比表面积较小,热稳定性较差,酸性难以调节.为了合成1,6-己二醇二丙烯酸酯,本文首先对多种催化剂进行了筛选,获得了活性高且稳定好的SO_4~(2-)/TiO_2-SnO_2改性催化剂.采用N2吸附-脱附、X射线衍射(XRD)、扫描电镜(SEM)、红外光谱(IR)、吡啶红外、氨程序升温脱附和热重等技术考察了催化剂的结构特征、表面酸强度和热稳定性.通过N2吸附-脱附可知,Sn改性后催化剂的比表面积增加到126m~2/,较改性前有明显提高.XRD结果表明,Sn能较好地分散在催化剂载体表面,且随着Sn的加入,催化剂晶粒尺寸逐渐减小.SEM照片进一步证实了N2吸附-脱附和XRD结果.催化剂表面酸性通过吡啶红外和氨程序升温脱附测定.由IR图谱可知,固体酸催化剂SO_4~(2-)/TiO_2-SnO_2中SO_4~(2-)和金属原子的连接方式发生变化,更趋于螯合双齿配位结合.通过吡啶红外可以看出,当Sn添加量为6%时,改性催化剂的酸性位由未改性催化剂的59μmol/g增加到167μmol/g.氨程序升温脱附.结果表明,多次使用后催化剂的酸分布几乎不变,但酸量有所下降,这可能与催化剂表面硫源的损失有关.另外,通过热重对催化剂的热稳定性进行了分析,由于高温条件下孔结构容易坍塌导致硫源损失,因此第二个失重峰归属为SO_4~(2-)的脱除峰.Sn改性后的催化剂中SO_4~(2-)的脱除峰后移100 oC左右,且失重量为SO_4~(2-)/TiO_2的2倍多,说明SO_4~(2-)/TiO_2-SnO_2催化剂有更好的热稳定性和更多的酸性位.以1,6-己二醇和丙烯酸酯化反应中1,6-己二醇转化率和1,6-己二醇二丙烯酸酯收率为指标评价了催化剂的催化活性.主要研究了催化剂中Sn含量的影响,并对酯化反应条件进行了优化.结果表明,最适宜的Sn含量为6%,最优的反应条件为:酸/醇比3.5,催化剂添加量7%,酯化温度130oC,酯化时间3 h.最后考察了改性催化剂的稳定性.结果表明,催化剂使用10次后,1,6-己二醇转化率仍可达81%以上,固体酸催化剂SO_4~(2-)/TiO_2-SnO_2有良好的稳定性.     

Adsorption of carbon dioxide on montmorillonites of different ion exchange forms

The adsorption isotherms of carbon dioxide are measured at 303, 343, 373, and 400 K and pressure P ranged from 0.1 to 6 MPa for three montmorillonites, i.e., the initial sample in the sodium form and two ion exchanged samples in pyridinium and polyhydroxyaluminum forms. It is shown that the linear character of the isosteres of CO₂ adsorption is retained for polyhydroxyaluminum and sodium montmorillonites, a deviation of the adsorption isosteres from linearity is observed for pyridinium montmorillonite at high temperatures (373–400 K) and high surface fillings. The differential excess entropies of CO₂ adsorbate are calculated for different fillings of montmorillonites. Using various approaches, the adsorption volumes for the systems studied are calculated.     

Preparation and Characterization of the Antibacterial Zn2+ or/and Ce3+ Loaded Montmorillonites

A series of modified montmorillonites including Zn²⁺ loaded montmorillonite (Zn/MMT), Ce³⁺ loaded montmorillonite (Ce/MMT) and Zn²⁺‐Ce³⁺ loaded montmorillonites (Zn‐Ce/MMT) were prepared by an ion‐exchange reaction, and characterized using X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and scanning electron microscopy (SEM). The specific surface areas, zeta potentials and antibacterial activity of the modified montmorillonites were also investigated. Zinc and cerium were proved to be present as bivalent zinc state and trivalent cerium state in the modified montmorillonites. For the modified montmorillonites, the d₀₀₁ basal spacings increased and the particles were formed of irregular shapes. The antibacterial activity of the modified montmorillonites was enhanced with the increase of specific surface areas and zeta potentials, and Zn²⁺‐Ce³⁺ loaded montmorillonites displayed obvious synergistic antibacterial effect. When Zn/Ce atomic ratio was 1.24, the Zn‐Ce/MMT showed high antibacterial efficiency and broad‐spectrum antibacterial activity, possessing the MIC against Escherichia coli, Staphylococcus aureus, Candida albicans and Mucor of 1500, 1000, 2000 and 3000 mg·L^?1, respectively.     

氯硅烷改性蒙脱土的制备与性能

基于氯硅烷与羟基的反应性,用氯硅烷对蒙脱土进行化学改性,FTIR证实硅烷已接枝到了蒙脱土上,WAXD表明,在极性分散剂中,硅烷成功地插层到了蒙脱土的片层间;而在非极性分散剂中,硅烷插层到蒙脱土片层间的量少,测定了蒙脱土阳离子交换容量(CEC),改性后其CEC值大幅度降低,分散性实验表明,由于改性后的蒙脱土颗粒以及片层间的相互作用力得到极大降低,其在水中和甲苯中的分散性更好.     

Thermal degradation of alkyl triphenyl phosphonium intercalated montmorillonites

The decomposition mechanism of intercalated montmorillonites at a particular temperature region and the activation energy involved in it are the two important aspects which determines the thermal stability of intercalated montmorillonites. In this study, montmorillonite was intercalated with alkyl (methyl, ethyl, propyl, and dodecyl) triphenyl phosphonium intercalates. Differential thermogravimetric analysis of each intercalated montmorillonites showed different peaks with associated organic loss at different temperature zone. Intercalated montmorillonites were subjected to isothermal kinetic analysis corresponding to selected temperature zone obtained from DTG peaks. Activation energies of organic decomposition process at selected temperature zones were determined. Mass spectral analysis and FTIR were done to understand the decomposition mechanisms and to relate them with the estimated activation energies.     

Surface Modification of Montmorillonites by Chlorosilanes

Montmorillonite was modified by chlorosilane derivatives (trimethylchlorosilane and tert-butyldimethylchlorosilane)based on the reaction between OH group and chlorosilane,Fourier-transformed infrared spectra(FTIR)confirmed that chlorosilanes did react with the OH groups of montmorillonite.The effect of reaction time and dispersing agents on the intercalation was studied by wide angle X-ray diffraction(WAXD) method.Further experiments proved that there is no reactive OH group on the surface of layers in the interlayer galleries of montmorillonite.The cation exchange capacity(CEC) of montmorillonites was measured.showing that after modification by chlorosilane derivatives,CEC values drastically decreased.The dispersibility measurements of montmorillonites were conducted.which showed that the dispersibility of modified montmorillonites both in H2O and toluene wer improved due to the decrease of attractions of particles and layers.     

天然蒙脱石的结构与带电性

选择了我国不同产地、有相当储量的12种蒙脱石，用化学组成结构分析法、阳离子交换容量法和直链烷基铵法对其电荷密度的来源、大小、分布进行了研究，发现所有双八面体蒙脱石的总电荷密度值在0.40～0.45 eq/[(Al, Si)4O10]之间，其中永久负电荷和端面可变负电荷由于受八面体位Al与Mg占位数间差异的影响而差别悬殊，八面体位Al占位数1.5以上，Mg占位数0.3～0.4的是低层电荷（0.28～0.33 eq/[(Al, Si)4O10]）、高端面可变负电荷（>0.16 mmol•g-1）的蒙脱石;八面体位Al占位数1.3～1.4， Mg占位数0.30左右的是高层电荷（0.40～0.45 eq/[(Al, Si)4O10]）、低端面可变负电荷（< 0.07 mmol•g-1）的蒙脱石.多数天然蒙脱石八面体片中Mg与Al的占位数介于这二者之间，层电荷密度和可变端面负电荷也介于二者之间，大部分蒙脱石的负电荷主要来自八面体位，但也有个别主要来自于四面体位中Al对Si的同晶取代.文中还讨论了影响可变端面电荷的因素和八面体片中铁对电性的影响.     

Role of montmorillonite in flame retardancy of ethylene-vinyl acetate copolymer

The effects of non-treated (MMT), organophilic (OMM), and olefin/silicone polymer intercalated (IMM) montmorillonites on the thermal stability of ethylene-vinyl acetate copolymer (EVA) and on the flammability of magnesium hydroxide filled EVA were studied. The influence of various treatments on the delamination of montmorillonites in EVA was detected by rheological measurements and by Raman microscopy. The latter was a unique method for rapid detection of the dispersion also in highly filled EVA. Enhancement of thermo-oxidative stability of EVA and flame-retarded EVA could be observed by thermal analysis in the presence of variously treated montmorillonites. The flame-retardant efficiency of magnesium hydroxide was improved by simultaneous application of MMT and IMM. The increased performance of magnesium hydroxide was explained by the rheological effect of the IMM, catalytic effect of MMT and chemical interactions of montmorillonites with the metal hydroxide.     

双单体原位接枝插层法制备聚丙烯纳米复合材料的研究Ⅰ.制备、表征及力学性能的研究

用有机插层剂处理蒙脱土原土 ,制得有机蒙脱土 (O MMT) .采用双单体 (马来酸酐和苯乙烯 )原位接枝插层法 ,制备了聚丙烯 蒙脱土纳米复合材料母料 .将母料与聚丙烯基体在双螺杆上共混挤出 ,制得聚丙烯 蒙脱土纳米复合材料 (PP Montmorillonetenanocomposites,PMNC) .这是制备聚合物纳米复合材料的一种新方法 .通过X 射线衍射测试 (XRD)表明 ,有机蒙脱土片层 0 0 1面间距从原土的 1 4 9nm扩大到 2 96nm ,复合材料中蒙脱土片层 0 0 1面间距由有机蒙脱土的 2 96nm扩大到 4 0nm .力学性能测试表明 ,复合材料的力学性能明显优于PP基体 ,在提高材料拉伸强度的同时 ,缺口冲击强度也得到很大的提高 .用扫描电镜 (SEM)对材料的冲击断面形貌进行了研究 ,并从理论上分析了断裂机理 .随着蒙脱土含量的增加 ,冲击断裂形式逐渐从脆性断裂变成韧性断裂     

Thermal transformations up to 1200 °C of Al-pillared montmorillonite precursors prepared by different OH–Al polymers

Aluminum-pillared montmorillonites are useful materials for their application as catalysts, adsorbents and ceramic composites. The precursor is a pillared montmorillonite that is not thermally stabilized. The precursor preparation methods, textural properties and catalytic activity have been extensively investigated, but comparatively, studies concerning their thermal transformations at high temperature are limited. In this work, precursors were prepared using two types of montmorillonites, Cheto (Ch) and Wyoming (W), and using two different OH–Al polymer sources: hydrolyzed (H) and commercial (C) solutions. Structural and thermal transformations of the precursors with heating up to 1200 °C were determined by X-ray diffraction and thermogravimetric analysis. Thermal analysis of these precursors below 600 °C revealed the influence of OH–Al polymers from the two solutions. The major phases developed at 1200 °C from the original montmorillonites were mullite for W and cordierite for Ch. The content of these phases depended on the aluminum in the octahedral sheet of the pristine montmorillonites. Amorphous phase, cristobalite, spinel, sapphirine and others phases were also found. The intercalation of OH–Al polymers in montmorillonites caused an increase in amorphous content after treatment at 1030 °C; however, it favored mullite development above 1100 °C. Although total aluminum content of both W and Ch precursors was similar, the transformation to mullite was directly related to the octahedral aluminum/magnesium ratio. The phase composition of the products at 1200 °C was not dependent on the type of intercalated OH–Al polymers. The increase in mullite content of the thermally treated precursors contributes to its possible application as advanced ceramic products.     

Desorption of benzoic and stearic acid adsorbed upon montmorillonites: a thermogravimetric study

The desorption of benzoic acid and stearic acid from sodium and calcium montmorillonites has been studied using thermogravimetric and differential thermogravimetric analysis. Desorption of benzoic acid from sodium montmorillonites occurs at 140 °C and from calcium montmorillonites at 179 °C. This increase in temperature is attributed to the benzoic acid bonding to the calcium in the interlayer. A lowering of the dehydroxylation temperature of montmorillonites is observed with acid adsorption. Stearic acid desorbs at 218 °C as observed by the DTG curves. The desorption pattern differs between the sodium montmorillonites and the calcium montmorillonites.