Control of the directions of oxidative transformation of methane over nickel-based catalysts by acid-base properties

Two completely different directions of the oxidative transformation of methane (OTM) were performed on nickel-based catalysts due to the different acid-base properties of those catalysts. The relatively acidic LaNiO_x and LiNiLaO_x/Al₂O₃ catalysts exhibit excellent Partial Oxidation of Methane to Syngas (POM) performance. However, the relatively basic LiNiLaO_x catalyst has a good Oxidative Coupling of Methane to C₂ Hydrocarbons (OCM) activity. The basic properties of the catalyst makes it difficult to reduce nickel and keeps it in the oxidized state. Reduced nickel is necessary for POM and oxidized nickel for the OCM reaction.     

Control of the catalytic effect of cetyltrimethylammonium bromide micelles by the addition of background electrolyte and nonionic surfactant

The variation of the microscopic properties (surface potential, micropolarity, etc.) of the interface of cetyltrimethylammonium bromide micelles upon the addition of a background electrolyte or the nonionic surfactant Triton X-100 decreases the rates of ion-molecular reactions, namely, alkaline hydrolysis of carboxylic acid esters and tetracoordinate phosphorus acid esters, and results in the shift of acid-base equilibria. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1933–1940, October, 2007.     

IR study of ion-molecular interactions in the system methanesulfonic acid-ethyl acetate

The complex formation in the methanesulfonic acid (MSA)—ethyl acetate (EA) system was studied by Multiple Attenuated Total Reflection (MATR) IR spectroscopy at 30°C. In solutions with excess EA, neither protonation of a base nor formation of complexes with a strong symmetrical H bond was observed. Molecular complexes EA·MSA are found in these solutions. Complexes formed by the strong symmetric H bond are observed in the system when the MSA content exceeds 50 mol.% Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2. pp. 292–294, February, 2000.     

Solvation of complexes with strong symmetric H bonds in the methanesulfonic acid—2-pyrrolidone system

Multiple Attenuated Total Reflectance (MATR) IR spectra of solutions of methanesulfonic acid (MSA) in 2-pyrrolidone (Pyr) (0—100 % MSA) were examined at 30 °C. Depending on the ratio of components, two types of species with strong symmetric H bonds are formed: uncharged quasi-ion pairs of 1 : 1 composition and anions (AHA)^–. The solvation of quasi-ion pairs by base molecules and of the (AHA)^– anions by acid molecules was detected. The data on the influence of the hydrogen bond donor and acceptor on the IR spectra of the quasi-ion pairs and (AHA)^– anions are presented.     

Aspects of polymer surface characterization by inverse gas chromatography

The inverse gas chromatographic method has been used to evaluate dispersive surface energies and acid/base interaction values for a styrene/maleic anhydride copolymer over a substantial temperature range. Surface energy calculations require knowledge of the dimensions of adsorbed molecules; conventional values of these for linear alkanes result in reliable surface energy data at near-ambient temperatures. Above about 60°C, however, more reliable surface energy data are obtained when the dimensions of the adsorbed species are corrected by density/temperature variations of the vapors. The copolymer studied was shown to be amphoteric, but with an appreciable prevalence of basic surface sites. © 1994 John Wiley & Sons, Inc.     

Gas-solid structure differences in the donor-acceptor complex (CH3)2HN−SO2

The crystal structure of the donor — acceptor adduct (CH₃)₂HN–SO₂ is reported. Crystals of the compound are clear prisms, space group Pna2₁; at –96°C,a=9.894(1),b=6.051(2),c=16.478(3) Å,D=1.469 g/cm³,V=786.6(5) Å,Z=8. The unit cell contains two crystallographically independent adducts, with N–S bond lengths of 2.015(3) Å and 1.991(3) Å. The average value, 2.00(1) Å is 0.33(4) Å shorter than the 2.34(3) Å value previously determined from microwave spectroscopy of the gas phase species, revealing a large medium effect on the length of the donor — acceptor bond. The structural results are compared with published data for the trimethylamine — SO₂ adduct, and discussed in terms of existing experimental and theoretical results for other donor — acceptor systems.     

不同分子筛上1-己烯骨架异构化反应性能的研究

以HZSM-35、HZSM-5、HM和Hβ四种分子筛为1-己烯骨架异构化催化剂,比较研究了四种催化剂的异构化性能,对其构效关系进行了关联。结果表明,相比于HZSM-5和Hβ分子筛,HZSM-35和HM具有适宜的酸量,有效孔径为0.4-0.6 nm,而且无晶穴、无交叉孔道,具有良好的择形催化效应,在转化率高达95%的同时,C_5-和C₇₊等副产物的收率在20%左右,异己烯收率可达40%-50%。进一步对四种分子筛进行酸碱改性处理,结果显示,虽然酸性质略有改变,但是一维孔结构的HZSM-35和HM分子筛的异构化性能仍明显优于多维孔结构的HZSM-5和Hβ分子筛,说明在酸性质一定的前提下,孔结构对异构化反应起关键作用。     

基于生态教育理念的高职分析化学教学设计与实践

针对当前高职分析化学“保姆式”教学模式、学生学习无积极性等问题,依据生态教育理念,以酸碱滴定实验内容为例,从课前准备,课中渗透生态思想,课后学生反思、自查和总结等3个方面进行教学设计,并运用于实践教学中,提升了学生的实验兴趣和应用创新能力,培养了学生的工作责任心,实现了真正的和谐生态课堂。     

标准加入法在酸碱分析中的应用

本文推导了单元酸标准加入法的线性公式。在被测酸溶液中,等量加入同种酸的标准溶液多次,并记录pH值,代入线性公式计算后即可得一直线,该直线在纵轴上的截距为被测酸浓度,斜率为该酸的条件稳定常数。本文还对单元酸及其共轭碱的标准加入法同时测定进行了研究。