ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1572-879X
    Keywords: Faujasite X hosted rhodium ; rhodium particle size ; IR-spectroscopy ; TEM ; CO hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different metal dispersions of Na-faujasite X hosted rhodium were generated and characterized by transmission electron microscopy (TEM) and IR-spectroscopy. CO hydrogenation has been studied over these Rh/NaX-zeolite catalysts. The finer rhodium dispersion with a mean particle size of 1–2 nm shows a higher selectivity towards oxygenates (methanol, ethanol and dimethyl ether) as compared to the coarser dispersion (4–5 nm), where nearly exclusively methane and higher hydrocarbons are formed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1572-879X
    Keywords: Dimethylether amination ; methylamines ; zeolite T ; acidic properties ; TPDA ; IR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Freshly prepared and used H/Na, K-T-zeolite catalysts for the conversion of dimethyl ether and ammonia to the three methylamines have been characterized by temperature-programmed desorption of ammonia and IR spectroscopy. Activity and selectivity depend on the nature and number of the acid sites. With time on-stream, deep alterations in the catalyst behaviour have been observed. The activity of the catalyst is decreased by blocking of active sites ≈ 5–10 h: furthermore, during an initial period hydrocarbons were formed almost exclusively on strong-acid sites. A second period is characterized by an increased “shape selectivity” observed in the distribution of the methylamines. The amination will proceed probably on left weak-acid sites and on the outer surface in a third period, however, without “shape selectivity” due to the progressive blocking of the inner catalyst surface.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1572-879X
    Keywords: Alkali zeolites ; acid zeolites ; proton exchange ; phase selectivity ; methylated amines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract T-zeolites with different H+-exchange degrees (0, 44, 68 and 89%) were used for the amination of dimethyl ether in the temperature range of 603 to 703 K. On a Na, K-T-zeolite sample (synthesis form) at low dimethyl ether conversion high selectivities of lower methylated amines were observed and methanol was formed as by-product. By proton exchange the conversion could be enlarged, but the selectivity distribution was shifted to trimethylamine.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 19 (1993), S. 247-255 
    ISSN: 1572-879X
    Keywords: Iridium catalyst ; supported catalyst ; vapor-phase carbonylation ; methanol carbonylation ; active carbon support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Iridium on active carbon (Ir/A.C.) is an effective catalyst for the vapor-phase carbonylation of methanol. In contrast to rhodium-catalysts the reaction rate is nearly independent of the partial pressure of the methyl iodide promoter and the methanolysis of an iridium-acetyl species has been found to determine the rate. Undesired methane formation accompanying the carbonylation is suggested to proceed via proteolysis of iridium-methyl species by methanol or water. Methyl chloride has been found to be a less effective promoter than methyl iodide.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1572-879X
    Keywords: faujasite-hosted rhodium ; in situ FTIR spectroscopy ; CO hydrogenation ; rhodium dispersion ; methanol selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In situ FTIR spectroscopy has been applied to study the reason of the different selectivity behaviour of rhodium in the CO hydrogenation reaction in dependence on the different particle size. Several forms of molecularly adsorbed CO are observed, such as linearly- and bridgedbonded CO on metallic rhodium as well as dicarbonyl species with Rh(I) centres formed by oxidation of Rh(0) with protons in presence of CO. Furthermore, non-reactive formate, acetate, and carbonate species are produced as side products of the reaction. The higher selectivity to oxygenates, particularly to methanol, is explained by the existence of multiple-bonded CO present only on small rhodium crystallites. The multiple-bonded CO formed at low temperatures is converted at higher temperatures to the highly reactive formyl species, which is hydrogenated to methanol.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1041
    Keywords: Emiglitate (BAY o 1248) ; sucrose ; starch ; postprandial hyperglycaemia ; glucosidase inhibitor ; blood glucose ; serum insulin ; serum GIP ; breath hydrogen ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorbable deoxynojirimycin derivative emiglitate (BAY o 1248) is a potent competitive inhibitor of small intestinal α-glucosidases in man. In two similar randomized, placebo-controlled, double blind investigations, the efficacy, duration of action and tolerability of single doses of 10, 20 and 40 mg emiglitate have been assessed in healthy male volunteers after repeated sucrose or maize-starch loads at 08.00, 12.00 and 17.00 h. Even at the lowest dose used, emiglitate almost abolished the glycaemic (−88%) and hormonal responses after the first sucrose meal, simultaneously evoking significant hydrogen evolution (mean peak H2-concentration 〉100 ppm), which was not related to the dose, and which induced unacceptable symptoms of carbohydrate malabsorption, i.e. at the dosages tested, the inhibition of glycaemic and hormonal responses was at the expense of intolerable gastrointestinal adverse effects. Flattening of postprandial responses of blood glucose, serum insulin and gastric inhibitory polypeptide was still apparent after a second sucrose load 4 h later, demonstrating long-lasting inhibition of α-glucosidase activity. After starch, the dose dependency of inhibition emerged more clearly than after sucrose, i.e. the reduction was less pronounced. However, emiglitate led to significant reduction of the glycaemic and hormonal rises after both the first and second starch meals. Symptoms of carbohydrate malabsorption were absent after 10 mg and were negligible with 20 mg or 40 mg emiglitate. Breath hydrogen concentration increased gradually, indicating slight but significant carbohydrate malabsorption after the highest dose of the α-glucosidase inhibitor. The results show that a single morning dose of 20–40 mg emiglitate might be useful in the control of postprandial hyperglycaemia after breakfast and lunch. This dose of the inhibitor was effective after either both 50 g starch or 50 g sucrose as the substrate, but was only tolerable after the starch meal.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 43 (1991), S. 583-588 
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Исследовали парофазное окисление 4-пиколина до пиридин-4-карбоксиальдегида на (VO)2P2O7. Предшественником катализатора служил VOHPO4·0,5H20. Образующийся альдегид ловили в виде оксима с помощью раствора гидрохлорида гидроксиламина. В оптимальном интервале температур (683–703 К) была достигнута высокая конверсия 4-пиколина с хорошей селективностью к альдегиду.
    Notes: Abstract The vapor-phase oxidation of 4-picoline to pyridine-4-carboxaldehyde on (VO)2P2O7 has been studied. VOHPO4·0.5 H20 was used as catalyst precursor. The resulting aldehyde was trapped as oxime with hydroxylamine hydrochloride solution in a subsequent reaction. In the optimum temperature range (683–703 K), a high 4-picoline conversion with good selectivity for the aldehyde was observed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the synthesis of p-hydroxybenzonitrile as a herbicide intermediate the nitrile formation is the most important reaction step. Possible feed compounds could be pure p-cresole, cresole mixtures or OH-protected cresoles like methoxy- or acetoxytoluenes. The ammoxidation of m- and p-methoxytoluene and a m,p-methoxytoluene-mixture over vanadium-titanium oxide catalysts has been investigated using flow reactors in a temperature range of 630-703 K. On comparable reaction conditions the conversion of pure compounds leads to a higher selectivity of p-methoxybenzonitrile (approx. 70%, conversion 85 mol-%) than that of the m-compound (only 35%, conversion 45 mol-%). For synthesis of the p-nitrile the feedstock can be p-methoxytoluene obtained by methylation of p-cresole, but it is also possible to use a m,p-methoxytoluene mixture obtained by methylation of an industrial cresole mixture. The ammoxidation of such a mixture affords a higher reactivity of the p-isomer and p-methoxybenzonitrile as the main reaction product, whereas m-methoxytoluene remains unreacted for the most part. Generally, the results obtained show that an amount of approx. 79% of the converted p-methoxytoluene was transformed into p-methoxybenzonitrile, whereas the corresponding transformation into the m-isomer was lower than 36%. An important part of the m-isomer was degraded by oxidation towards CO, CO2 and HCN.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 1990-01-01
    Print ISSN: 0166-9834
    Electronic ISSN: 1873-3867
    Topics: Chemistry and Pharmacology
    Published by Elsevier
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...