Thermogravimetric analysis of the iso-butene oligomerization activity of various forms of synthetic mica-montmorillonite
| Autor: | A. P. Vogel, M. Kojima, C. T. O'Connor |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Thermogravimetric analysis
Thermal desorption spectroscopy Inorganic chemistry chemistry.chemical_element 020101 civil engineering 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences 0201 civil engineering Catalysis Propene chemistry.chemical_compound Nickel Adsorption chemistry Geochemistry and Petrology Differential thermal analysis Pyridine 0105 earth and related environmental sciences |
| Zdroj: | Clay Minerals. 25:355-362 |
| ISSN: | 1471-8030 0009-8558 |
| DOI: | 10.1180/claymin.1990.025.3.10 |
| Popis: | The iso-butene oligomerization activity of pure and metal-substituted synthetic mica-montmorillonite (SMM) was studied by simultaneous thermogravimetric-differential thermal analysis (TG-DTA). The incorporation of matrix Ni and ion-exchanged Co, Ni and Zn into SMM increased its iso-butene oligomerization activity while the presence of water in the olefinic feed reduced activity. These findings corresponded to trends found in previous work on high pressure (50 MPa) propene oligomerization over SMM and metal-substituted SMM. Synthetic mica-montmorillonite (SMM) and various metal-substituted forms thereof have been used in the oligomerization of light olefins to diesel fuels (Bercik et al., 1978; Fletcher et al., 1986; O'Connor et al., 1988). Kojima et al. (1986) investigated the nature and distribution of acid sites present in calcined SMM by means of an infrared spectroscopic and temperature programmed desorption study of adsorbed pyridine. They found that water played an important role in the type and strength of acidity. In particular, the presence of water during catalyst pretreatment increased the amount of pyridine adsorbed by an order of magnitude. In a propene oligomerization study by Fletcher et al. (1986) it was found that catalyst pretreatment at 500~ yielding predominantly Lewis acidity, gave high activity and long catalyst lifetime, while the presence of water led to temperature runaway followed by rapid deactivation. O'Connor et al. (1988) showed that incorporating nickel into the SMM framework (NiSMM) resulted in an increase in activity and proposed that the enhanced activity may be associated with an increase in BET surface area. Swift & Black (1974) suggested that the Ni caused smaller platelets to crystallize out yielding a greater number of high activity edges. The presence of water in the propene feed reduced the lifetime of NiSMM while ion-exchanging Ni, Co or Zn into the interlayer spaces of SMM increased activity for propene oligomerization. Combined thermogravimetric (TG) and differential thermal analysis (DTA) can be used to obtain additional information on the catalytic activity of the above mentioned forms of SMM. TG-DTA provides information on the exo- or endothermicity of reactions occurring under atmospheric conditions, and on the temperatures at which the various reactions take place. |
| Databáze: | OpenAIRE |
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