Preparation of alkylated phenols

A lubricating additive comprises a phenol which has been alkylated with an olefin polymer in the presence of a montmorillonite clay catalyst having a surface area of at least 100 square metres per gram, further treated with P2S5-treated polybutene and the resultant product reacted with Ba(OH)2 and CO2.ALSO:Phenols are alkylated by reacting the phenol with an olefin polymer in the presence of a montmorillonite clay catalyst having a surface area of at least 100 square metres/gram. The clay may be activated by treatment with acid, particularly when olefin polymers of wide boiling range are used. The preferred olefins contain 7-12 carbon atoms. Examples describe the alkylation of phenol itself. Lubricant additives may be prepared by treating the alkylated phenol with barium oxide and then with sulphur.