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Digitale Medien

Acid function of Al‐MCM‐41 supported platinum catalysts in hydrogenation of benzene, toluene o‐xylene (1998)

Wang, Jun ; Huang, Limin ; Chen, Haiying ; [weitere]

Springer

Catalysis letters 55 (1998), S. 157-163

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ISSN: 1572-879X

Schlagwort(e): acidity ; mesoporous material ; platinum ; hydrogenation ; benzene ; toluene ; o‐xylene

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract A series of Al‐MCM‐41 mesoporous materials with different Si/Al ratios are synthesized. The acidities of catalysts are measured by the temperature‐programmed desorption of ammonia (NH3‐TPD) and IR spectra of pyridine. Their catalytic activities for hydrogenation of benzene, toluene and o‐xylene are investigated on a pulse reactor system. NH3‐TPD and IR results show that only weak and medium acid sites could be observed on the catalysts, and the number of total acid sites decreases obviously with the increase of the Si/Al ratio whereas the medium acid sites are somewhat constant. The introduction of platinum onto Al‐MCM‐41 material decreases the total acid number by a small amount. The hydrogenation activities of the 1% Pt/HAl‐MCM‐41 catalysts are found to correspond well with the ratio of medium acid sites to total acid sites in the employed catalysts. It is proposed that, in addition to metal sites, the acid sites in the metal–acid interfacial regions are also the active sites for hydrogenation and the medium acid sites play important roles in the reaction.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1019030811920

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Digitale Medien

Proof of a conjecture on the Sperner property of the subgroup lattice of an abelianp-group (1998)

Wang, Jun

Springer

Annals of combinatorics 2 (1998), S. 85-101

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ISSN: 0219-3094

Schlagwort(e): 05A05 ; 05D05 ; 06A07 ; Sperner property ; poset ; subgroup lattice

Quelle: Springer Online Journal Archives 1860-2000

Thema: Mathematik

Notizen: Abstract Let $$L_{\left( {k^n } \right)}$$ (p) denote the subgroup lattice of the abelianp-group $$(Z/p^k Z) \times \cdots \times (Z/p^k Z)(ntimes).$$ . It is conjectured that the lattice has the Sperner property. Whenk=1, the conjecture is true since it is isomorphic to the subspace lattice, and Stanley has confirmed it fork=2. In this paper, we prove that the conjecture is generally true.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01626030

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Digitale Medien

Influence of the Brönsted and Lewis Acid Sites in Platinum/Solid Acid Catalysts on the Hydrogenation of Benzene and Toluene (2000)

Wang, Jun ; Chen, Haiying ; Li, Quanzhi

Springer

Reaction kinetics and catalysis letters 69 (2000), S. 277-284

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ISSN: 1588-2837

Schlagwort(e): Aromatic hydrogenation ; Brönsted acid ; Lewis acid ; platinum

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract The hydrogenation of benzene and toluene was investigated over US-SSY, γ-Al2O3, and Ha1-MCM-41 supported platinum catalysts. The acidity of catalyst supports was measured by IR spectra of pyridine adsorption. On the Brönsted acid supported catalyst, both the hexacyclic saturation product and the pentacyclic one, the hydroisomerization product, were observed, and these two products were revealed to be primary reaction products. The two products were proposed to be formed competitively on Brönsted acid sites with carbonium ions as the reaction intermediate. By contrast, no hydroisomerization product was found on Lewis acid supported catalysts. It was inferred that the electron-deficient reaction intermediate formed on Lewis acids could not undertake any skeletal isomerization process to give a pentacyclic saturation product.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1005695715788

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Digitale Medien

Sequence Analysis of Candida albicans Phosphoribosyl-aminoimidazole Carboxylase (ADE2) Gene (1997)

Tsang, Wai-Kei Paul ; Cao, Bo-Yang ; Wang, Jun

New York, NY [u.a.] : Wiley-Blackwell

Yeast 13 (1997), S. 673-676

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ISSN: 0749-503X

Schlagwort(e): Candida albicans ; ADE2 ; phosphoribosylaminoimidazole carboxylase ; sequencing ; Life and Medical Sciences ; Genetics

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie

Notizen: The nucleotide sequence of the Candida albicans ADE2 gene, which encodes phosphoribosylaminoimidazole carboxylase, has been determined. The sequence possesses an uninterrupted open reading frame of 1704 nucleotides corresponding to 568 amino acid residues. The deduced amino acid sequence shares a high degree of homology with ADE2 homologues in other fungal species including Saccharomyces cerevisiae, Pichia methanolica, Schwanniomyces occidentalis and Schizosaccharomyces pombe. Three regions of amino acid sequence were highly conserved among all reported ADE2 genes. The hexanucleotide TGACTC characteristic of genes involved in purine and amino acid biosyntheses is located in front of putative TATA boxes in the promoter region. The GenBank Accession Number of this gene is U75582. © John Wiley & Sons, Ltd.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

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