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  • 1
    ISSN: 1572-879X
    Keywords: shape-selective catalysis ; biphenyl ; isopropylation ; H-mordenite ; carbonaceous deposits ; encapsulated biphenyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To understand the relationships between shape-selectivity and coke deposition in the alkylation of biphenyl over H-mordenite (HM), thermogravimetric analyses were examined for the catalyst after the reaction. The coke deposition during the catalysis was very severe over HM with low SiO/Al2O3 ratio, however, dealumination enhanced the decrease of coke deposition. Over highly dealuminated HM, volatile organic compounds, mainly biphenyl derivatives, were observed in addition to carbonaceous deposits. The deposits are produced from biphenyl derivatives on acid sites in the HM pore, and the ease of their formation is governed by acid site density and acid strength. The decrease of carbonaceous deposits and the increase of encapsulated biphenyl derivatives are related with the increase of both selectivity and yield of 4,4′-diisopropylbiphenyl (4,4′-DIPB). The increase of reaction temperature up to 250°C enhanced the catalysis over highly dealuminated HM, however, further increase of the temperature resulted in extensive decrease of the selectivity of 4,4′-DIPB. Coke deposition also increased with the temperature although its level was low. The composition of 4,4′-DIPB in encapsulated DIPB isomers remained as high as 80% in spite of a change of the distribution of bulk products.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-879X
    Keywords: Shape-selective catalysis ; biphenyl ; isopropylation ; cerium exchanged sodium mordenite ; H-mordenite ; propylene pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Liquid phase isopropylation of biphenyl with propylene was studied over a cerium exchanged sodium mordenite (Ce/NaM25) and a H-mordenite (HM25) with the same SiO2/Al2O3 ratio of 25. Shape-selective catalysis occurred to give 4,4′-diisopropylbiphenyl (4,4′-DIPS) in high selectivity over Ce/NaM25 under any propylene pressures. HM25 gave 4,4′-DIPS shape-selectively under high propylene pressures. However, the reaction was severely deactivated at a conversion of ca. 60% under such a low pressure as 0.8 kg/cm2 because of coke formation in the pore. The yields of 4-isopropylbiphenyl (4-IPBP) and 4,4′-DIPB decreased with the increase of those of 3-IPBP and 3,4′-DIPB because of non-selective alkylation and isomerization at external acid sites that are alive in spite of severe deactivation. No significant isomerization of 4,4′-DIPB over Ce/NaM25 was observed even at low propylene pressure. In the case of HM25, the isomerization of 4,4′-DIPB to 3,4′-DIPB occurred significantly under low propylene pressures, while it decreased under high pressure. These differences are ascribed to the differences of nature of acid sites between Ce/NaM25 and HM25 zeolites.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 8 (1952), S. 657-657 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 4931-4938 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Macroporous hydrophilic poly-vinylpyridine beads were prepared by suspension copolymerization of 4- (or 2-)vinylpyridine and hydrophilic cross-linking agents, such as ethylene glycol dimethacrylate (1EG) and tetraethylene glycol dimethacrylate (4EG), and their physical properties were studied. Immobilized enzymes were obtained by adsorption of urease on vinylpyridine polymers and commercially available hydrophobic polymers. The poly-4-vinylpyridine resin crosslinked with 4EG (degree of crosslinkage, 25%) showed higher water regain, larger average pore radius, and the highest adsorption of urease. Leakage of urease from immobilized urease was scarcely observed in the buffer solution used. The hydrophilicity and hydrophobicity of support affected markedly the enzymatic reaction of the immobilized enzyme. As one of the applications of the polymer-supported urease, blood urea nitrogen in human sera was determined.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 51 (1962), S. 225-228 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde der Einfluß von aliphatischen Estern, Aldehyden und Verunreinigungen, die im Vinylacetat üblicherweise vorhanden sind  -  wie Monovinylacetylen und Divinylacetylen - auf die Polymerisation von Vinylacetat untersucht. Ester und gesättigte aliphatische Aldehyde, wie z. B. Methylacetat, Äthylacetat, Isopropylacetat, Dimethyloxalat usw., Acetaldehyd und Butyraldehyd, wirken nur als Überträger. Ihre Übertragungskonstanten wurden bestimmt. Ungesättigte Aldehyde, wie Crotonaldehyd, aber auch Benzaldehyd, ferner Mono- und Divinylacetylen wirken als Verzögerer. Die Polymerisationsgeschwindigkeit von Vinylacetat in Gegenwart solcher Verzögerer wurde nach der Gleichung von KICE analysiert, und die verschiedenen Geschwindigkeitskonstanten wurden bestimmt.
    Notes: Effects of aliphatic esters, aldehydes and some impurities, as monovinyl and divinyl acetylene which exist normally in vinyl acetate, on the polymerization of vinyl acetate were studied. Esters and saturated aldehydes such as methyl acetate, ethyl acetate, isopropyl acetate and dimethyl oxalate etc. and acetaldehyde and butyraldehyde act only as transfer agent and the values of the transfer constants on these substances were determined. Unsaturated aldehyde such as crotonaldehyde and also benzaldehyde, and monovinyl and divinyl acetylene act as retarder. The several reaction constants relating the retarding effect were obtained.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 4 (1966), S. 589-593 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 4 (1966), S. 861-867 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 1 (1963), S. 497-499 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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