Modified clays
Clays are aluminosilicates with cations held to the negatively charged layers. They have large surface areas to which reagents can be attached.
negatively charged aluminosilicate layer

negatively charged aluminosilicate layer

negatively charged aluminosilicate layer
Cations and water molecules are held in the interlayer spaces
When zinc chloride is supported on the clay, montmorillonite, it shows good activity at catalysing Friedel-Crafts alkylation. Collaboration between a Merseyside company and the University of York led to the worldwide marketing of a range of similar catalysts known as 'Envirocats'.

This is now the basis of the synthesis of parabenzenediphenyl used for coating fax paper.

The Envirocat is stirred with the biphenyl and the chloromethylbenzene is added slowly. When the reaction is complete the solid catalyst is filtered off leaving the organic product ready for purification.
Question.
What advantages do you note over the earlier process?

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