A temperature-programmed desorption study of olefin oligomerization in H-ZSM-5

Journal Article · Sun Jan 01 00:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90021-3· OSTI ID:6958425

Kofke, T J.G.; Gorte, R J ^[1]

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1. Univ. of Pennsylvania, Philadelphia (USA)

The authors have used temperature-programmed desorption and thermogravimetric analysis (TPD-TGA), with gas chromatographic analysis of products, to examine the low-temperature reaction of ethene, propene, and 2-methyl-2-propanol in H-ZSM-5. Propene reacts rapidly inside the zeolite at 295 K to form large oligomer chains, while the zeolite must be heated to above 370 K for ethene oligomerization to occur. In both cases, reaction does not stop until a coverage of 7.8g/100 g is reached on a zeolite with a SiO{sub 2}/Al{sub 2}O{sub 3} ratio of 70. This is a substantial fraction of the zeolite pore volume, >50% assuming that the density of the oligomers is similar to that of polypropylene, suggesting that reaction stops only when blocking prevents reactants from approaching the acid sites. In TPD carried out under vacuum, the oligomer chains from both ethene and propene are completely removed in two desorption features centered at 420 and 550 K. Analyses of the products from both ethene and propene show a similar mixture of olefin product ranging from C{sub 2} to C{sub 7}, with no noticeable preference for monomer, dimer, or trimer products. Analysis of the butene isomers in the products indicates that the concentrations are close to that obtained for equilibrium mixtures. With 2-methyl-2-propanol, adsorption and dehydration occur at 295 K. On a zeolite sample with a SiO{sub 2}/Al{sub 2}O{sub 3} ratio of 70, concentrations of the olefin desorption products formed in TPD are essentially identical to those observed for propene and ethene, suggesting that they are due to the formation and cracking of oligomeric species very similar to that observed following olefin adsorption. On a zeolite with a SiO{sub 2}/Al{sub 2}O{sub 3} ratio of 520, this oligomerization with 2-methyl-2-propanol can be minimized and methylpropene is a major product.

• OSTI ID: 6958425
• Journal Information: Journal of Catalysis; (USA), Vol. 115:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
ETHYLENE
POLYMERIZATION
PROPANOLS
PROPYLENE
ZEOLITES
CATALYTIC EFFECTS
ADSORPTION
ALKENES
ALUMINIUM OXIDES
BUTENES
CHEMICAL ANALYSIS
CHEMICAL REACTION YIELD
DEHYDRATION
DESORPTION
GAS CHROMATOGRAPHY
POLYMERS
POROSITY
QUANTITY RATIO
SILICON OXIDES
TEMPERATURE CONTROL
TEMPERATURE DEPENDENCE
THERMAL GRAVIMETRIC ANALYSIS
ALCOHOLS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMATOGRAPHY
CONTROL
GRAVIMETRIC ANALYSIS
HYDROCARBONS
HYDROXY COMPOUNDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MINERALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
SEPARATION PROCESSES
SILICON COMPOUNDS
SORPTION
THERMAL ANALYSIS
YIELDS
020400* - Petroleum- Processing