Green synthesis of alklyphosphate over Ca/HMCM-22 zeolite

The HMCM-22 catalysts were modified by impregnation with CaSO₄ which was used as the calcium source of the modification, and then the composite catalysts prepared were characterized by XRD, TPD, FT-IR and so on. The results show that the samples remain the structure and characteristic of the molecular sieve MCM-22. A little variation in the strength and content of the week acid sites, a little decrease on the content of strong acid sites and a little enhancement on the strength of the strong and week basic sites occur after the modification of the HMCM-22 by CaSO₄. The Ca/HMCM-22 catalysts exhibit a fine catalytic performance for the synthesis of MPA (monododecylphosphate) by esterification of phosphoric acid with equimolar lauryl alcohol. The conversion of phosphoric acid over the Ca/HMCM-22 catalysts enhances significantly, which indicates that the CaSO₄ and the acid site of the HMCM-22 catalyst cooperatively promote the esterification. Under the reaction temperature of 80°C, the catalyst with 3.0% CaSO₄ loading and the amount of the used catalyst equals 2.0% of the total mass, the conversion of phosphoric acid and the selectivity of MAP could reach 80.0% and 99.8%, respectively after esterification of 9 hours. It shows that the Ca/HMCM-22 molecular sieve is a kind of good novel catalytic material.