Hexane cracking in ZSM-5: In situ [sup 13]C cross-polarization magic-angle-spinning NMR and flow reactor/GC experiments

The conversion of n-hexane by ZSM-5 has been studied in closed samples by [sup 13]C cross-polarization (CP) magic-angle-spinning (MAS) NMR and by flow reactor/GC analysis. The NMR experiments, carried out after various heat treatments and subsequent quenching of the sealed samples to room temperatur...

Full description

Saved in:
Bibliographic Details
Published in:Journal of catalysis 1993-12, Vol.144:2
Main Authors: Nowak, A.K., Wilson, A.E., Roberts, K., Datema, K.P.
Format: Article
Language:English
Subjects:
02 PETROLEUM
020400 - Petroleum- Processing
400201 - Chemical & Physicochemical Properties
ALKANES
CARBON 13
CARBON ISOTOPES
CATALYSIS
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CRACKING
DECOMPOSITION
EVEN-ODD NUCLEI
HETEROGENEOUS CATALYSIS
HEXANE
HYDROCARBONS
INORGANIC ION EXCHANGERS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
ION EXCHANGE MATERIALS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MATERIALS
MINERALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
PYROLYSIS
RESONANCE
SILICATE MINERALS
STABLE ISOTOPES
THERMOCHEMICAL PROCESSES
ZEOLITES
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The conversion of n-hexane by ZSM-5 has been studied in closed samples by [sup 13]C cross-polarization (CP) magic-angle-spinning (MAS) NMR and by flow reactor/GC analysis. The NMR experiments, carried out after various heat treatments and subsequent quenching of the sealed samples to room temperature, result in product distributions which are comparable to those from flow reactor/GC experiments at full conversion, with propane (47 mol%) and butanes (25 mol%) as the main products. The differences in product distributions observed by NMR and the flow reactor/GC experiments, especially the absence of olefins in all NMR experiments, are ascribed to the difference in contact time in the two experimental setups. Based on the complementary data obtained from the two techniques, it is proposed that, at temperatures below 300[degrees]C, isomerization to the methylpentanes is dominant, while at higher temperatures cracking of the reactant ant the methylpentanes takes over. Dimethylbutanes could not be detected by NMR, and it is concluded that the formation of these isomers in inhibited in the medium-pore zeolite. 23 refs., 4 figs., 4 tabs.
ISSN:0021-9517
1090-2694
DOI:10.1006/jcat.1993.1349