Phenol alkylation

In the process of preparing monoalkylphenols wherein an olefin hydrocarbon having from 8 to 18 carbon atoms is reacted with a phenol selected from the group consisting of phenol, cresol, and xylenol in the presence of a catalyst consisting essentially of an acid activated clay, the improvement comprising passing a stream of the liquid mixture of phenol and olefin through a stationary bed of activated clay catalyst in granular form in a vertically elongated reaction zone at a rate corresponding to a space velocity of 0.2 to 0.5 volumes per volume of catalyst per hour and a temperature of 250.degree. to 350.degree. F., said catalyst having an acid value of about 12-15, an acidity of about 3-3.4 pH, and a particle size of about 15 to 40 mesh, maintaining an excess of phenol in said catalyst bed corresponding to a mol ratio of about 1.5 to 3.5, distilling unreacted phenol from the stream leaving the catalyst and recyling said recovered phenol to said reaction zone, further distilling to provide a monoalkylphenol distillate and a residue consisting principally of dialkyl phenol, and recycling said dialkyl phenol to the said reaction zone to suppress formation of further amounts of dialkyl phenol therein.