Phosphate esters useful for gelling hydrocarbons in combination with a metal source are disclosed along with methods of preparation of the phosphate esters. Fouling in oil refinery towers has been attributed due to distillation of impurities present in phosphate esters used to gel hydrocarbons for oil well fracturing. The improved method of preparation of the phosphate ester results in a product that substantially reduces or eliminates volatile phosphorus, which is phosphorus impurities that distill up to 250° C., and increases the high temperature viscosity of the hydrocarbon gels formed using the phosphate esters.