C20-22 alkyl phosphate is obtained from the reaction of alcohols, C20-22 with phosphoric anhydride

a complex mixture of esters of phosphoric acid and C20-22 alcohols; R, R', and
R'' of Figure 1 may be eicosyl, heneicosyl, docosyl, or hydrogen
sorce https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/FR671.pdf