稀土改性Pd/Al2O3催化剂的性能:甲醇分解的活性和选择性

用稀土金属氧化物CeO2和La2O3改性γ-Al2O3担载Pd制备了一系列甲醇分解催化剂，并考察了Pd盐前驱体（氯盐或硝酸盐），稀土种类（镧或／和铈），经的含量（0％－30％），浸渍方法（顺序浸渍或共浸渍）地催化剂性能的影响。结果表明：CeO2能提高Pd/Al2O3催化剂的甲醇分解活性，La2O3能提高催化剂的CO和H2选择性，而CeO2和La2O3在γ-Al2O3上对Pd的催化性能表现出一种协同作用。在10％的La2O3和22％的CeO2共同改性的催化剂上，250℃，甲醇液体空速1.8h^-1条件下反应甲醇转化率达到91．4％，CO（H2）的选择性几乎为100％。     

胶溶法制备铈锆镧共改性氧化铝及催化性能

γ-Al2O3是机动车尾气净化催化剂的常用载体,其高温热稳定性、比表面积、孔容、孔径及表面酸性等对催化活性有很大影响.近年来,大量研究结果表明,铈、锆、镧和钡等元素的添加可以提高氧化铝的高温热稳定性和催化活性[1～3],然而这些研究大多致力于单组分或者双组分改性氧化铝,制备方法以浸渍法和溶胶-凝胶法为主.胶溶法制备三组分共同改性氧化铝的研究很少.本文利用胶溶法制备了系列铈、锆、镧改性氧化铝,讨论了三组分共同添加对氧化铝载体的性质以及催化剂活性的影响.     

稀土Ce对制合成气用Ce-Ni/Al2O3催化剂活性和稳定性的影响

 用浸渍法制备了Ni／Al2O3和Ce－Ni／Al2O3催化剂,并用BET,TGA－DTA和XPS技术对催化剂进行了表征,考察了稀土Ce对催化剂性能的影响,探讨了催化剂失活的原因．结果表明,在甲烷部分氧化和二氧化碳重整反应中,稀土Ce存在有部分还原变价过程（Ce4＋→Ce3＋）,不仅抑制了催化剂的积碳,而且改善了催化剂的水热稳定性和催化性能．经过较长时间反应的Ce－Ni／Al2O3催化剂,其比表面积下降,活性物种Ni和助剂Ce向体相迁移或部分流失,以及Ni晶粒的烧结聚集长大可能是造成催化剂逐渐失活的主要原因．     

铈和镧改性γ-Al2O3担载Pd催化剂的结构效应

分别以镧-铈、铈-镧顺序浸渍和镧铈共浸渍的方式在γ-Al2O3载体上引入助剂La2O3和CeO2，然后担载Pd制备了一系列催化剂.以甲醇分解为探针反应，采用XRD、EXAFS和XPS对催化剂的体相和表面结构进行表征，用BET法测定比表面积，并进行了吸附态CO的FTIR研究.结果表明,La2O3容易进入CeO2的晶格中，促进了CeO2在γ-Al2O3上的分散.但不同的La2O3、CeO2加入方式对活性组分Pd在改性载体上的分散度、优势暴露面及其与CeO2之间的相互作用产生不同的影响.关联甲醇分解性能测试结果说明,Pd在载体上的高度分散以及Pd和CeO2之间通过界面产生的强相互作用是催化剂具有高活性的关键.     

胶溶法制备镧-钡共稳定氧化铝的性能

以硝酸为胶溶剂, 两种拟薄水铝石为前驱体, 用胶溶法制备了镧-钡共稳定的氧化铝. 采用X 射线衍射(XRD)、表面分析仪(BET)、氨气程序升温脱附(NH3-TPD)和NO2程序升温脱附(NO2-TPD)技术对所制备的镧改性和镧钡共改性氧化铝的结构特性和表面性能进行了表征. XRD结果表明, 改性氧化铝在1273 K焙烧后均以γ-Al2O3相存在. 当BaO添加量达到14%(w)时, 有少量BaCO3生成. BET结果表明, 在1273 K下焙烧5 h后, 5%(w)La2O3稳定的氧化铝(Ba-0)和5%La2O3与8%BaO共同稳定的氧化铝(Ba-8)均具有较大的比表面积, 各种氧化铝的吸附等温线表明它们的孔形状均为狭缝型孔和瓶型孔, 孔径分布曲线表明, 仅有样品Ba-8的孔径分布较宽, 孔径为6-10 nm, 其它三种样品的孔径均集中在10 nm; NH3-TPD结果表明, 随着氧化钡添加量的逐渐增多, 氧化铝表面的酸量、酸强度逐步减少. NO2-TPD结果表明, 添加BaO后载体对NO2的吸附量增多, 随着BaO含量的增多, 体相Ba(NO3)2增多. 由于样品Ba-8同时具有很好的织构性质、适中的表面酸量和酸强度分布及NO2吸附脱附能力, 使得以它为载体的催化剂具有最好的催化性能,丙烷的起燃温度和完全转化温度分别为526 K和593 K.     

助剂对甲烷部分氧化制合成气镍基催化剂性能的影响

考察了添加助剂铈、镧和钙对镍基催化剂反应性能的影响，发现助剂对以α-Al2O3为载体的镍基催化剂的调变作用比以γ-Al2O3为载体的镍基催化剂好，且助剂铈对催化剂的性能改善最好。在此基础上，研究了不同载量的铈对催化剂性能的影响。结果表明，铈的质量分数为1%时对催化剂的性能改善最好。同时采用XRD、XPS、TG等技术，研究了助剂铈对10％Ni/γ-Al2O3催化剂的改性作用。XRD分析表明，铈负载量较低时，催化剂中的CeO2高度分散在催化剂表面，铈负载量较高时，CeO2形成微晶颗粒，降低了催化活性。     

碱土金属修饰Al2O3的表面热稳定性

采用浸渍法,添加不同碱土金属元素对γ-Al2O3进行改性.通过BET、XRD等手段,研究考察了在1 373 K空气中,经不同时间处理γ-Al2O3的相变和烧结情况,比较了各样品烧结后比表面积的差异.结果表明,碱土金属的引入（尤其是Sr、Ca）有效地抑制了氧化铝比表面积的损失和α相变.并对Al2O3的烧结动力学进行了研究探讨,研究表明,铝酸盐的生成并不是稳定氧化铝的根本原因,碱土金属的高温稳定作用主要是分散态的碱土金属氧化物抑制氧化铝焙烧过程中最初1 h内的烧结和α相变引起的比表面积损失.     

铈和镧改性γ-Al2O3担载Pd催化剂的结构效应

分别以镧-铈、铈-镧顺序浸渍和镧铈共浸渍的方式在γ-Al2O3载体上引入助剂La2O3和CeO2,然后担载Pd制备了一系列催化剂.以甲醇分解为探针反应,采用XRD、EXAFS和XPS对催化剂的体相和表面结构进行表征,用BET法测定比表面积,并进行了吸附态CO的FTIR研究.结果表明,La2O3容易进入CeO2的晶格中,促进了CeO2在γ-Al2O3上的分散.但不同的La2O3、CeO2加入方式对活性组分Pd在改性载体上的分散度、优势暴露面及其与CeO2之间的相互作用产生不同的影响.关联甲醇分解性能测试结果说明,Pd在载体上的高度分散以及Pd和CeO2之间通过界面产生的强相互作用是催化剂具有高活性的关键.     

堇青石蜂窝陶瓷载体涂层与热稳定性研究--(Ⅰ)涂层的制备研究

比较了几种商用堇青石蜂窝陶瓷载体的性能, 研究了汽车尾气净化催化剂用载体二载涂层的制备工艺. 利用XRD, BET 等分析手段研究了添加La2O3对γ-Al2O3 性能的影响. 研究结果表明, 在γ-Al2O3 中添加La2O3有效地抑制了烧结的发生, 提高了γ-Al2O3 的相变温度, 改善了氧化铝的高温热稳定性; 添加量的最佳值范围为3%～4% La3+/Al3+.涂层所选用的成膜剂、破膜剂、添加剂和制浆工艺是可行的.     

碱土金属修饰Al_2O_3的表面热稳定性

采用浸渍法添加不同碱土金属元素对γAl2O3进行改性.通过BET、XRD等手段研究考察了在1373K空气中经不同时间处理γAl2O3的相变和烧结情况比较了各样品烧结后比表面积的差异.结果表明碱土金属的引入(尤其是Sr、Ca)有效地抑制了氧化铝比表面积的损失和α相变.并对Al2O3的烧结动力学进行了研究探讨研究表明铝酸盐的生成并不是稳定氧化铝的根本原因碱土金属的高温稳定作用主要是分散态的碱土金属氧化物抑制氧化铝焙烧过程中最初1h内的烧结和α相变引起的比表面积损失.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。     

微量钙的测定方法研究进展

介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.