Synthesis And Evaluation Of Phosphonate Scale Inhibitor And Anticorrosion (DPPA)

In this paper,a new phosphonate corrosion and scale inhibitor-2, 6-diphosphonoheptane-1,7-dicarboxylic acid(DPPA)was designed and synthesized according to optimized molecule structure theory.It has the common feature and molecule structure of phosphonate and phosphonopoly carboxylic acid corrosion and scale inhibitors.Furthermore,it containes phosphate content and Carboxyl structure. Its phosphor content is 20.4%.It's lower than DETPMP whose phosphor content is 22.83%.So its biodegradability is improved.It can replace lower oxygen content of DETPMP(44.26%)and PBTCA(53.31%)which with one less phosphate.So it is accorded with the requirements of environmental protection and avoided the nitrogen cycling.It can be extensively applied in circulating cooling water.One-Pot Synthesis of 2,6-dibromo diethyl pimelate was synthesized through three reactive steps by using heptanedioic acid,bromine and phosporus trichloride as raw material.In alkaline condition,combined with Diethyl phosphite,then was purified by multi-times recrystallization,multi-times dehydrated,dried in vacuum. The character of DPPA was characterized by phosphor content test and IR spectra.The antiscaling property of synthetic product was studied by using method of bubble,the effect of scale inhibitor concentration;Ca²⁺concentration,pH,as well as reaction time on scale inhibiting performance were discussed.The results showed: increased DPPA concentration,pH and decreased Ca²⁺concentration,action time can add scale inhibiting performance.The results showed that DPPA is fit for conditions as follows:middle rigidity(calcium concentration 240 mg/L),pH value 6.5,water temperature 60℃.The synthetic product has 97.3%favorable scale inhibiting properties for CaCO₃.Under low hardness,DPPA is better than PBTCA and DETPMP.A rotary hanged weight losing method was used to measure the anticorrosion properties of the synthetic products in different dosages.The result indicates:Under pH 7,20 mg/L of DPPA shows well effect of 72.28%anticorrosion rate for A₃ carbon steel.If 120 mg/L of DPPA is used in pretreatment film,10 mg/L of DPPA is enough to reach the same effect.Furthermore,between 4 mg/L to 10 mg/L of Zn²⁺greatly enhance the anticorrosion effect of DPPA.When it is used in pretreatment film,10 mg/L of DPPA shows up to 90%anticorrosion rate.If 120 mg/L of DPPA and 6 mg/L of Zn²⁺are used in pretreatment film for 24h,10 mg/L of DPPA and 2 mg/L of Zn²⁺are enough to reach the same effect in 48h(94.06%).Furthermore,between 4 mg/L to 10 mg/L of Zn²⁺greatly enhance the anticorrosion effect of DPPA.When it is used in pretreatment film,10 mg/L of DPPA shows up to 92.92%anticorrosion rate.The studied results show:the synthetic products have excellent anticorrosion and antiscaling properties,so the product can be used in industrial cooling water treatment system.