A method of modifying a phosphorus-treated zeolite catalyst is carried out by contacting an unbound and calcined phosphorus-treated pentasil zeolite with water in a water treatment wherein at least a portion of the water is in a liquid phase. The water treatment is sufficient to remove at least 80% by weight or more of phosphorus from the phosphorus-treated zeolite and provide an increase in the pore volume of the zeolite by at least 50% prior to the water treatment to form a modified phosphorus-treated zeolite catalyst. A zeolite catalyst is also provided in the form of a phosphorus-containing pentasil zeolite having a phosphorus content of 7.5% or less by weight of zeolite and a 27Al MAS NMR peak at 50 ppm that is greater than any other 27Al MAS NMR and a pore volume of 0.2 ml/g or more.