English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Evolution of mesoporous materials during the calcination process: structural and chemical behavior

Kleitz, F., Schmidt, W., & Schüth, F. (2001). Evolution of mesoporous materials during the calcination process: structural and chemical behavior. Microporous and Mesoporous Materials, 44-45, 95-109. doi:10.1016/S1387-1811(01)00173-1.

Item is

Files

show Files

Locators

show

Creators

show
hide
 Creators:
Kleitz, F.1, Author              
Schmidt, W.2, Author              
Schüth, F.1, Author              
Affiliations:
1Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              
2Research Group Schmidt, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445618              

Content

show
hide
Free keywords: MCM-41; Porous titanium oxide; Porous zirconium oxide; Calcination process; High temperature XRD; Template removal
 Abstract: We describe herein the study of the temporal evolution of hexagonal mesophases of silica, titania and zirconia as a function of temperature. Detailed in situ X-ray diffraction (XRD) studies with a high temperature XRD chamber system have been conducted in conjunction with thermogravimetric–differential thermal analysis coupled with mass spectrometry (TG–DTA/MS) to better understand the processes related with template removal from MCM-41 type mesophases. The thermal behavior of the cationic surfactants in the mesostructured systems has been analyzed, and the processes involved have been elucidated. In the case of Si-MCM-41, an initial change occurs up to 250°C with an increase in intensity of all reflections, with the (1 1 0) and (2 0 0) reflections increasing later and at a higher rate than the (1 0 0) reflection. After 300°C, changes are less pronounced and the intensities remain unchanged while the sample is kept at 550°C. The TG–DTA/MS data show that the decomposition mechanism in air involves three steps. An initial endothermic step is assigned to Hofmann elimination of trimethylamine, leading to a hydrocarbon chain. The second step is exothermic and results from a carbon chain fragmentation. Finally, oxidation occurring at 320°C converts the remaining organic components to carbon dioxide. Template removal appears to be completely different for the transition metal based materials: a single step complete oxidation of the surfactant is observed around 300°C in TG–DTA/MS. This is accompanied with the drastic decrease in d-spacing and initial sharp increase in reflection intensity in the XRD pattern, which generally leads to the loss of the well ordered hexagonal structure.

Details

show
hide
Language(s): eng - English
 Dates: 2001-06-132001-04-21
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/S1387-1811(01)00173-1
 Degree: -

Event

show

Legal Case

show

Project information

show

Source 1

show
hide
Title: Microporous and Mesoporous Materials
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 44-45 Sequence Number: - Start / End Page: 95 - 109 Identifier: ISSN: 1387-1811
CoNE: https://pure.mpg.de/cone/journals/resource/954926228401