Library

X
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
    Electronic Resource
    Electronic Resource
    An effective heterogeneous WO3/TiO2–SiO2 catalyst for selective oxidation of cyclopentene to glutaraldehyde by H2O2 (1999)
    Springer
    Catalysis letters 62 (1999), S. 201-207 
    Details
    ISSN: 1572-879X
    Keywords: catalytic oxidation ; cyclopentene ; H2O2 ; glutaraldehyde (GA) ; TiO2–SiO2 xerogel ; WO3/TiO2–SiO2 catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract TiO2–SiO2 mixed oxide with large pore size was synthesized by the xerogel method and it was then used to prepare the WO3/TiO2–SiO2 catalyst by an incipient wetness method. The as‐prepared WO3/TiO2–SiO2 sample was employed as the first heterogeneous catalyst in the liquid‐phase cyclopentene oxidation by aqueous H2O2, which exhibited higher selectivity (about 75%) to glutaraldehyde (GA) and, in turn, higher GA yield than the WO3/SiO2 heterogeneous catalyst and even the tungstic acid homogeneous catalyst under the same reaction conditions. The amorphous WO3 phase was identified as the active sites and the loss of the active sites was proved to be not important. The lifetime of the catalyst was determined and its regeneration method was proposed. The effects of various factors on the catalytic behaviors, such as the WO3 loading, the calcination temperature, the surface acidity and the reaction media, were investigated and discussed based on various characterizations including BET, XRD, XPS, FTIR, EXAFS and Raman spectra etc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019094905328
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Deactivation of NaCl/B2O3/Fe2O3 catalysts and their improvement for the oxidative coupling of methane (1995)
    Springer
    Catalysis letters 31 (1995), S. 183-195 
    Details
    ISSN: 1572-879X
    Keywords: alkali chloride doped ferrous oxides ; characterization ; deactivation ; oxidative activity ; oxidative coupling of methane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the present work, the deactivation of the NaCl/B2O3/Fe2O3 catalysts was studied for the oxidative coupling of methane. Several techniques, such as XPS, XRD, SEM, H2-TPR, and flow-reaction, were employed to examine the function of each catalyst component, and its change during the catalytic reaction. NaCl and B2O3 show a synergistic effect on the Fe2O3 surface. B2O3 modifies the oxidative activity of Fe2O3 and makes the first reduction peak of Fe2O3 shift from 490 to 750°C. The NaCl modified B2O3/Fe2O3 catalyst has high reduction rate, high activity and selectivity at about 750°C. It is demonstrated that the deactivation of the NaCl/B2O3/Fe2O3 catalysts is a complicated process, consisting of chloride loss, sodium change, B2O3 loss, silica deposition and catalyst sintering. The chloride loss enhances the surface basicity, which causes the silica deposition and sodium change, and aggravates the catalyst sintering. The silica deposition and catalyst sintering cause permanent deactivation. The B2O3 loss is not a direct reason for catalyst deactivation. NaCl crystal diluted NaCl/B2O3/Fe2O3 catalysts have a better stability. The deactivated catalyst has a more stable structure. When it is regenerated by impregnating with NaCl again, a more stable catalyst can be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808832
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    An infrared spectroscopic study of the mechanism of chloromethane conversion to higher hydrocarbons on HZSM5 catalyst (1995)
    Springer
    Catalysis letters 33 (1995), S. 75-90 
    Details
    ISSN: 1572-879X
    Keywords: infrared spectroscopy ; chloromethane ; HZSM5 catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Investigation of the reaction mechanism of chloromethane on ZSM5 is a new topic. In this work an in situ FTIR technique was employed to study the conversion processes of chloromethane, the active sites on HZSM5, and the desorption state of surface species. The catalytic conversion of chloromethane to higher hydrocarbons was also studied. It is demonstrated that chloromethane can be reversibly adsorbed on acidic sites of HZSM5 at room temperature. At 100°C chloromethane is irreversibly and dissociatively adsorbed on the strong acidic sites of HZSM5, on which surface methoxyl is formed as proved by infrared characteristic C-H stretchings of-CH3 at 2960 and 2870 cm−1. Alkoxyls are produced and adsorbed on the catalyst surface as characterized by the infrared absorption bands of -CH2-groups at 1460 and 2930 cm−1. At 100°C the adsorbed methoxyl and alkoxyls are the main surface species, and a small amount of aromatics might exist as detected by a characteristic absorption band at 1510 cm−1. Between 100 and 200°C the adsorbed surface methoxyl and alkoxyls are converted to aromatics, and the occupied OH groups partially appear. At temperature higher than 300°C the adsorbed aromatics are thermally desorbed into the gas phase. Aromatics and alkanes are the main products in catalytic conversion. These results reveal that the formation of aromatics from methoxyl and alkoxyls is easier than the desorption of aromatics from HZSM5 catalyst. An alkoxyl mechanism is proposed for the conversion of chloromethane on HZSM5 based upon the experimental results and the three assumptions: (a) The primary C-C bond is formed from surface methoxyl groups via the methoxyl group polarization and C-H bond weakening, (b) The adsorbed alkoxyls are converted to aromatics via hydrogen transfer and bond rearrangement similar to the conventional carbenium ion mechanism for the aromatization of olefins and alkanes on HZSM5. The hydrogen atoms from the aromatization stimulate the desorption of alkoxyls to alkanes. (c) At temperature higher than 300°C surface reactions and desorption of adsorbed species take place simultaneously, determining the product distribution in the catalytic conversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00817048
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...