Seminar Series: Development of Green Processes using Novel Solid Superacids and Bases
|Event Date:||October 16, 2007|
|Speaker:||Dr. G. D. Yadav, Darbari Seth Professor and Head|
|Speaker Affiliation:||Dept. of Chemical Engineering, University Institute of Chemical Technology, University of Mumbai, India|
There are a large number of well studied solid acids as replacement for liquid acids, amongst which zeolites have emerged as an alternative. Unfortunately the slow diffusion of reactants through the zeolitic microporous structure makes them relatively poor catalysts and their stability is susceptible in reactions where acids are generated (e.g. anhydrous HCl as a co-product), which may remove aluminum species from the framework of the zeolite. Furthermore zeolites are found to deactivate at high temperatures due to coke formation. Mesoporous materials with tailored catalytic centers will be most suitable for reactions of bulky molecules. Hexagonally ordered mesoporous silicates such as FSM-16, HMS (hexagonal mesoporous silica) and MCM-41, possessing large surface areas (>800m2/g) and highly ordered mesopores (2-10 nm) can be functionalized to extend their applications to a variety of areas.
Among many solid acid systems other than zeolites and clays, sulfated zirconia has received the most attention due to its superacidity. A number of attempts have been made to improve the acidity of zirconia based catalysts by incorporating different transition metals but it suffers from deactivation at high temperatures. Thus, a series of new catalysts were developed and named as UDCaT incorporating different combinations of shape selectivity, mesoporosity and superacidity, The abbreviation UDCaT is used to denote the series of solid acid catalysts developed in this laboratory, which was famously known as University Department of Chemical Technology (UDCT).
O-Alkylation reactions are very useful for the synthesis of alkyl aromatic compounds both in laboratory and on an industry scale. The reaction is generally carried out with alkylation agents such as alkenes, alkyl halides and alcohols by using acid/ base catalysts. The work was aimed at dimethylcarbonate use as an alkylating agent and as well as a green solvent. A series of solid bases were synthesised and used in these reactions.
Phase transfer catalysis (PTC) has been practised in industry for over 3 decades covering some 600 odd processes. We have developed some novel processes in this area.
So the seminar will broadly cover these 3 areas – solid superacids, bases and PTC.