Field of concentrations and conditions of template structure formation of a silica mesoporous molecular sieves of MCM-48 type

The region of composition and concentration of the reaction mixtures for template structure formation of silica mesomorphous molecular sieves of the MCM-48 type have been determined, the boundary concentrations of the reagents have been determined, and also the effects of synthesis conditions (in particular the ratio of the template and the skeleton-forming elements and the temperature factor) on the structure transformation in the CTAB-TEOS-NaOH-H₂O system. Reproducible methods have been developed for the synthesis of highly ordered MCM-48 with minimization of the amount of surfactant and without the use of additional organic substances. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 186–190, May–June, 2008.     

Nonparametric Estimation for Gibbs Random Fields Specified Through One‐Point Systems

The problem of nonparametric estimation for Gibbs random fields is considered. The field is supposed to be specified through a translation invariant quasilocal one‐point system. An estimator of one‐point system is constructed by the method of sieves, and its exponential and L^p consistencies are proved in different setups. The results hold regardless of non‐uniqueness and translation invariance breaking. This revised version was published online in June 2006 with corrections to the Cover Date.     

Issues in the synthesis of crystalline molecular sieves: towards the crystallization of low framework-density structures.

Fundamental and practical interest in crystalline, microporous, molecular sieves is largely a direct consequence of the fact that their bulk properties can be manipulated through variations in atomic structure. This correspondence between the macroscale and the atomic scale is due to the uniformity of these crystalline materials. Control of the atomic structure therefore is of extreme importance, and is the thesis of this Review. Synthesis mechanisms and the parameters that can direct the crystal assembly pathway and the ultimate product formed are discussed and rationalized.     

Quantitative analysis of sesquiterpenes and comparison of three Curcuma wenyujin herbal medicines by micro matrix solid phase dispersion coupled with MEEKC

A simple, efficient and environmental friendly method was proposed for determining five sesquiterpenoids of Curcuma wenyujin by MSPD extraction coupled with MEEKC separation. Molecular sieve was applied as a solid support for extraction of sesquiterpenoids for the first time. Various parameters affecting extraction and separation efficiency were investigated. The optimized conditions involved dispersing sample (200 mg) with 200 mg of TS‐1 for 150 s and using 1000 μL of methanol to elute five target analytes. Finally, they were well separated by using a running buffer containing 1.3% SDS, 5.0% 1‐butanol, 0.5% ethyl acetate and 10% acetonitrile in 10 mM borate buffer at pH 9.0. Consequently, the developed method was fully validated and successfully applied to determine the five sesquiterpenoids including curdine, curcumenol, germacrone, furanodiene and β‐elemene in Curcuma wenyujin origin's Chinese herbal medicines. Furthermore, hierarchical cluster analysis was performed based on the contents of target compounds for distinguishing steamed and non‐steamed drugs. The present study provided a promising method for fast investigation and discrimination of chemical difference in steam & non‐steamed Chinese medicines from Curcuma wenyujin origin.     

Metrical Theorems on Prime Values of the Integer Parts of Real Sequences

Let a_n be an increasing sequence of positive reals with a_n as n . Necessary and sufficient conditions are obtained foreach of the sequences to take on infinitely many prime values for almost all > rß.For example, the sequence a_n is infinitely often prime for almostall > 0 if and only if there is a subsequence of the a_n,say b_n, with b_{n + 1} > b_n + 1 and with the series divergent. Asymptotic formulae areobtained when the sequences considered are lacunary. An earlierresult of the author reduces the problem to estimating the measureof overlaps of certain sets, and sieve methods are used to obtainthe correct order upper bounds. 1991 Mathematics Subject Classification:primary 11N05; secondary 11K99, 11N36.     

Low Temperature Synthesis of Zeolite Films on Glassy Carbon: Towards Designing Molecularly Selective Electrochemical Devices

Faujasite‐type zeolite films have been grown on glassy carbon electrode surfaces embedded in an epoxy resin matrix by a quasi ambient temperature hydrothermal synthesis. The resulting zeolite modified electrodes are mechanically stable and provide an advantageous combination of electrochemical detection with charge and size selectivities at the molecular level, as demonstrated with the aid of some model electroactive probes or analytes (Ru(NH₃)₆³⁺, Fe(CN)₆^3?, Ru(bpy)₃²⁺, dopamine, ascorbic acid). To act efficiently as a physical molecular sieve barrier between the electrode surface and the external solution, these films must have a thickness of about 0.7 μm. These results open the door for further development of molecular sieving electrochemistry.     

The transition state shape-selective aromatic alkylation over MnAPO-11 molecular sieve catalysts

MnAPO-11 molecular sieves with medium size elliptical pore are synthesized and characterized. Transition state shape-selective catalysis of these molecular sieves are studied. Methylation of alkylaromatic compounds were efficiently catalyzed by these molecular sieves while aromatic ethylation was almost negligible. The size of the alkylating agents was the key factor for the transition state dimension in the aromatic alkylation, not the size of aromatic compounds. The mole fraction of o-isomer for methylation of alkylaromatic compounds was dependent on the size of the alkyl groups.     

费托(FT)合成及相关反应的研究进展(英文)

按催化剂分类介绍了改性ＦＴ合成及与其相关反应的近期研究成果。即通过调制催化剂组成和反应条件,由合成气直接合成其他有价值的化工原料如醇、烯烃、芳香烃和石蜡等。分子筛,如ＡＩ－ＭＣＭ－４１和ＺＳＭ－５／磷铝分子筛等在ＦＴ及其相关反应中扮演着越来越重要的角色,但由于金属作为反应活性中心,所以金属催化剂如Ｆｅ,Ｃｏ、Ｐｄ、Ｒｈ和Ｎｉ,双金属如Ｆｅ－Ｉｒ和Ｐｔ－Ｍｏ仍然是人们研究的重点。另外,一些新的反应方法和新的材料也被采用,如超临界方法及超微粒催化剂等。     

以沸石纳米簇构筑介孔AlMSU-2：与其他合成方法的比较研究及水热稳定性考察

采用含有β沸石基本结构单元的纳米簇为孔壁构造物合成了蠕虫状AlMSU-2介孔材料，并与通过直接合成和后处理嫁接途径所得的AlMSU-2进行了系统的比较研究。测试结果表明在适宜的酸度条件下，采用中性TX-100为中孔结构导向剂，以β沸石纳米簇为无机前驱物可便捷地将铝原子引入AlMSU-2骨架结构中，但目标产物并未显示出较后处理途径制得的AlMSU-2更为优越的水热稳定性。