The application of MCM-41 type mesoporous molecular sieves as heterogeneous acid catalysts and catalyst supports.
Two types of mesoporous molecular sieves, MCM-41 and MMS, were
prepared, fully characterised and tested as solid acid catalysts and catalyst
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