Zeolites
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.
The Framework of
zeolite ZSM 5
Zeolite 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.
Question

What is the atom efficiency of this reaction?

button: providing answer to question
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.