负载型高分散双组分催化剂的表面结构及催化性能研究

通过原位M ssbauer谱、PtLⅢ 边EXAFS谱、H2 吸附等对γ Al2 O3 负载高分散Pt Sn及Pt Fe双组分催化剂的表面结构进行了研究 ,并将其与异丁烷脱氢反应结果及催化剂积碳、再生性能进行了深入的关联 .结果表明 ,负载型高分散Pt Sn/Al2 O3及Pt Fe/Al2 O3 双组分催化剂中Sn或Fe均以氧化物形式存在于γ Al2 O3 载体表面 ,而Pt物种则以高分散金属态存在 .这两种催化剂表面上均存在两类表面Pt活性中心 ,即M1中心和M2中心 .M1中心为Pt直接锚定在γ Al2 O3 载体表面上的Pt活性中心 ;而M2中心则为Pt锚定在高度分散在γ Al2 O3 载体上的Sn或Fe氧化物表面上的Pt活性中心并形成Pt Sn(Fe)Ox γ Al2 O3 “夹心”结构 .M1中心对低温吸附氢有利 ,对烃类氢解有主要贡献 ,易为积炭覆盖 ;M2中心对高温吸附氢有利 ,对烷烃脱氢反应有主要贡献 ,不易为积炭覆盖 .Sn ,Fe引入Pt/γ Al2 O3 催化剂后 ,促进了M1中心向M2中心的转化 ,从而提高了异丁烷脱氢反应的选择性和稳定性 .对于Pt Sn/γ Al2 O3 催化剂 ,随着催化剂循环再生次数的增加 ,这种具有Pt SnOx γ Al2 O3 “夹心”结构的M2中心逐渐遭到破坏而使催化剂失活     

添加碱土金属对负载型铂锡催化剂长链烷烃脱氢反应性能的影响

用微型催化反应装置结合吡啶吸附 红外光谱、热重、氢化学吸附和程序升温等还原手段,研究了添加碱土金属离子助剂对负载型PtSn/γ-Al2O3催化剂长链烷烃(C10~13)脱氢反应性能的影响。结果表明,碱土金属助剂的引入可以降低催化剂积炭量、提高催化剂铂金属表面裸露度,从而提高催化剂脱氢反应稳定性。但强碱性的碱土金属助剂如Ba2+的引入增强了锡与载体之间的相互作用,减弱了锡与铂之间的相互作用, 导致反应后催化剂铂金属表面裸露度下降,故PtSnBa/γ-Al2O3催化剂脱氢活性较低。     

载体组成对负载型PtSn/ZSM-5催化剂上丙烷脱氢反应性能的影响

用微型催化反应装置结合吡啶吸附的红外光谱、NH3-程序升温脱附、热重、H2化学吸附和程序升温还原等物理化学手段研究了载体组成对负载型PtSn/ZSM-5催化剂上丙烷脱氢反应性能的影响.结果表明,负载型PtSn/ZSM-5催化剂对丙烷脱氢的催化性能与载体组成密切相关.随着ZSM-5载体中SiO2/Al2O3比的增加,催化剂表面的酸中心总量和强酸中心量逐渐减少.当SiO2/Al2O3摩尔比从45增至108时,催化剂对丙烷脱氢反应的催化活性提高,并且催化剂的积炭量下降.当SiO2/Al2O3摩尔比增至304时,Sn组分与载体ZSM-5之间的相互作用减弱,经H2还原后催化剂中Sn0物种所占的比例增加,导致催化剂H2化学吸附量和丙烷脱氢反应活性下降.     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价, 并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3, PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能. 发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性. 实验结果表明, 纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原, 导致铂金属分散度和催化剂的丙烷脱氢活性较低. 用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用, 提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性. 并且, 积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度, 故具有较高的丙烷脱氢反应稳定性. PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能可能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关, 而且与Al2O3/MCM-41载体的介孔结构有关.     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价,并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3,PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能.发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性.实验结果表明,纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原,导致铂金属分散度和催化剂的丙烷脱氢活性较低.用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用,提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性.并且,积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度,故具有较高的丙烷脱氢反应稳定性.PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能町能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关,而且与Al2O3/MCM-41载体的介孔结构有关.     

Pt-Ce掺杂对Cu/Al2O3催化剂结构及性能的影响及其用于苯催化氧化的研究

通过添加Pt-Ce作为助剂,对Al2O3担载的Cu催化剂进行修饰,制备负载型催化剂用于苯的催化氧化。利用XRD,N2吸附和H2-TPR等手段对载体和催化剂的织构-结构、活性组分的分散、还原性能及活性组分之间的相互作用进行了表征和分析。结果表明:添加Pt与Ce有利于提高CuO颗粒在Al2O3表面上的分散度,使其晶粒变小,从而改善了催化剂的性能。部分活性组分进入到Al2O3孔道中,在孔中及表面均形成了活性氧化物种。添加微量的Pt(0.1%(质量分数))及Ce可明显提高Cu/Al2O3催化剂的氧化活性,其中0.1%Pt/10%CuCe(12∶1)/Al2O3在250℃下就能完全催化氧化苯,表现出最佳的催化活性,可与贵金属催化剂(通常负载量在0.3%～2.0%)的活性相媲美。催化剂的高活性主要是在于活性组分在Al2O3表面的高分散以及PtOx,CuO和CeO2之间的相互作用。     

丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na+助剂组分的作用

用微型催化反应装置结合X射线衍射(XRD)、H₂化学吸附、NH₃吸附-程序升温脱附(NH₃-TPD)和H₂-程序升温还原等多种物理化学手段研究了丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na⁺助剂组分的作用。结果表明,Na⁺组分可中和SUZ-4载体表面的强酸中心、提高催化剂的Pt金属分散度、抑制脱氢产物的裂解和积炭的生成,从而提高催化剂的丙烷脱氢选择性和反应稳定性。但是过量Na⁺组分的存在会削弱Sn物种与载体之间的相互作用,使其易被还原,导致催化剂丙烷脱氢活性显著下降。     

PtZn-Sn/SBA-15合成、表征及对丙烷催化脱氢性能

以SBA-15为载体,利用浸渍法制备了单、双和三金属Pt催化剂,并对催化剂进行了N2物理吸附(BET)、程序升温还原(H2-TPR)、H2-化学吸附、透射电子显微镜(TEM)和O2-脉冲等技术表征,研究了它们对丙烷催化脱氢(CDH)制丙烯反应的催化性能。研究结果表明,Pt在三金属催化剂中的分散性能最好,并且部分负载组分可以进入SBA-15的孔道,Pt的分散度达到29%,Pt粒子尺寸为3 nm左右。三金属催化剂表现出优越的脱氢性能,这主要归结于载体的弱酸性、活性组分和助剂、载体之间的相互作用及Zn对Pt的电子调控作用。这些因素使催化剂的积炭量较低,因而具有较高的脱氢稳定性和极高的选择性。     

Pt-Sn/Al2O3催化剂中Sn的存在状态对丙烷脱氢反应的影响

考察了不同Sn/Pt比的Pt-Sn/Al_2O_3催化剂(络合型)的丙烷脱氢反应性能。并应用原位Mossbauer谱,TPR,O_2吸附等手段对催化剂进行了表征。结果初步表明Pt-Sn/Al_2O_3经过还原后,Sn的还原状态对该催化剂的丙烷脱氢活性及稳定性有极大的影响。在550℃以下还原,Sn以氧化态形式存在,有利于丙烷脱氢反应的活性及选择性,在600℃以上高温还原时,零价锡出现使催化剂活性组分铂的表面中毒而降低活性。当Pt含量一定时,Sn载量愈高,在高温下还原时生成的Sn~0愈多;低Sn载量的Pt-Sn/Al_2O_3无论高温还原还是低温还原都不易生成Sn~0。     

CeO2和Pd在Ni/γ-Al2O3催化剂中的助剂作用

采用脉冲微反技术研究了添加n型半导体氧化物CeO2及贵金属Pd对Ni/γ Al2O3催化剂上CH4积炭/CO2消炭反应性能的影响,并运用BET、TPR、CO2 TPSR及氢吸附等技术对催化剂进行了表征.结果表明, n型半导体氧化物CeO2的添加可以降低Ni/γ Al2O3催化剂上CH4裂解积炭活性,提高CO2消炭活性,添加少量贵金属Pd可以进一步改变载体Al2O3、助剂CeO2和活性组分Ni之间的相互作用,从而改善Ni/γ Al2O3催化剂的抗积炭性能.通过Ni Ce Pd/γ Al2O3催化剂上CH4积炭/CO2消炭模型对上述作用机制作出了新的解释.     

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。     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.     

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.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

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.