A phosphonate-type scale inhibitor (SI) named diethylene triamine pentamethylene phosphonic acid (DETPMP) was synthesized in laboratory from two raw chemical materials – phosphorous acid (H3PO3) and phosphorous tri-chloride (PCl3). PCl3 was used to mimic the industrial
synthesis of DETPMP, while H3PO3 was used to avoid the yield of by-product hydrochloride (HCl) acidic fog. The efficiency of scale inhibition against CaCO3 and CaSO4 by the synthesized samples and a commercial sample (CP-DETPMP) were evaluated in two types of brines, respectively, and the performance of three samples were compared. For PCl3-invovled
synthesis, excess formaldehyde in aqueous solution should be introduced to compensate the volatilization of formaldehyde via exothermic hydrolysis of PCl3. 1H NMR spectra of the synthesized samples exhibited similar chemical shifts of the protons, while 31P NMR spectra indicated that the product synthesized from H3PO3 (PA-DETPMP) contains less phosphorous
impurities than that prepared from PCl3 (PC-DETPMP), probably due to the incomplete hydrolysis of PCl3. A better performance of scale inhibition against CaCO3 and CaSO4 was observed with an increase in SI concentration for PC-DETPMP and CP-DETPMP, while the performance of PA-DETPMP against both type of scales was not good at tested concentrations, At high SI concentration, massive Ca3(PO4)2 precipitates were observed and they gradually became soluble at low temperature. The overall sequence for the performance of scale inhibition is PC-DETPMP > CP-DETPMP > PA-DETPMP.