|These three dimensional aluminosilicate materials
have micropores with diameters usually less than 1 nm. They are
easily converted to Lewis acids by heating the proton-exchanged
zeolite. Water is lost, and a solid Lewis acid results.
ZSM-5 catalyses alkylations but zeolites have low activity. The
alkylation in producing phenylethane needs high temperatures and
pressures. But in such a high volume continuous process the benefits
outweigh the costs.
What is the atom efficiency of this
|Here the advantages lie in cutting down the
use of chlorinated compounds, and the reduction of waste.
|Rhone-Poulenc use Zeolite H-beta together
with ethanoic anhydride in an acylation. The original process generated
4.5 kg waste per kg of product. The new process generates only 0.035
kg aqueous effluent per kg of product, and the catalyst is recyclable.
The process is solvent free whereas the original needed chlorinated
hydrocarbon as solvent.
The small size of the
micropores prevents the formation of polyalkylated products normally
found with Friedel-Crafts alkylation.