Two types of mesoporous molecular sieves, MCM-41 and MMS, were prepared, fully characterised and tested as solid acid catalysts and catalyst support materials. Three different methods for characterising the surface acidity of these solid acids were examined and compared. These methods were 1. Fourier Transform infrared (FTIR) spectroscopy of adsorbed pyridine, 2. Pulsed ammonia adsorption using a combination of thermogravimetry and differential scanning calorimetry (TG/DSC), and 3. Temperature-programmed desorption of amines. The acidity results of these molecular sieves were compared with zeolites and acid-treated clays. The Lewis and Br0nsted acid catalytic activities of the ion-exchanged aluminosilicate mesoporous molecular sieves were investigated in liquid phase Friedel-Crafts alkylations. Three model reactions were used to examine the Lewis and Br0nsted acid catalytic activities of the catalysts and the results were compared with acid-treated clays. Generally, the two aluminosilicate molecular sieves showed similar Br0nsted and Lewis acid catalytic activities. The Fe3+ exchanged catalysts showed high Lewis acid catalytic activities while H+ and AI3+ exchanged catalysts showed high Br0nsted acid catalytic activities. In addition to liquid phase Friedel-Crafts reactions, a new technique was developed to monitor the acid catalytic activity of catalysts. The use of temperature programmed-solid insertion probe-mass spectrometry (TP-SIPMS) for this application was investigated. The results were compared with zeolites. The catalytic results from this technique were found to have good correlation with the liquid phase Br0nsted acid catalytic test. Finally, the mesoporous molecular sieves were used as support materials for Lewis acid catalysts. Again, the catalytic activities of these catalysts were studied using a Friedel-Crafts alkylation reaction. The results were compared with some commercially available supported catalysts. Among these catalysts, FeCl) supported on MCM-41 was found to be very active while ZnCb supported on MCM-41 exhibited milder Lewis acid catalyitc activity. However, ZnCb was found to be more dependent on the nature of support.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:285629 |
| Date | January 1998 |
| Creators | Yiu, Humphrey Hak Ping |
| Publisher | University of Huddersfield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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