Polyepoxysuccinic Acid & PESA is a phosphorus-free, nitrogen-free, biodegradable green scale inhibitor with dual functions of corrosion inhibition and scale inhibition. This substance is good for water systems with high alkali, hardness, and solids. Its scale inhibition is high, and a small amount (3 mg/L) works well. When tested against common scale inhibitors like ATMP & Amino Trimethylene Phosphonic Acid and HEDP & Etidronic Acid, PESA’s scale inhibition doesn’t drop as much when calcium ion concentration and alkalinity in water go up. PESA remains good at scale inhibition even with high calcium ion concentration and alkalinity. Due to the excellent performance of PESA and its compliance with the development direction of green water treatment agents, the development of PESA has important practical significance. At present, the research on PESA in China is basically in the laboratory stage, the production process is unstable, and it is difficult to be widely used. Therefore, it is necessary to develop a stable PESA synthesis process. This work synthesized PESA through experiments, optimized the synthesis process conditions, and characterized the product by infrared spectroscopy.
Experimental part
Raw materials
Maleic anhydride & MA, Sodium hydroxide & Lye (50% by mass), Hydrogen peroxide & H2O2 ( 30% by mass), sodium tungstate, ammonium molybdate, ammonium vanadate, 5-nitrosalicylic acid, Chloroacetic Acid & CAA, sodium thiosulfate are all analytically pure and commercially available. Water is deionized water.
Synthesis principle
The synthesis principle of PESA is shown in Figure 1
Synthesis method
Synthesis of epoxysuccinic acid (ESA)
In a four-necked flask equipped with a thermometer, condenser, dropping funnel and constant speed stirring device, MA is added, water is added to dissolve, and NaOH solution is slowly added dropwise under stirring. Heat in a water bath. When the temperature rises to 55°C, an appropriate amount of catalyst is added, and then the dropping speed is controlled to drip a certain amount of H,O, within 20 minutes. At the same time, the pH value is adjusted with NaOH solution, and the reaction temperature is controlled to be a constant value within a certain period of time. The product is extracted and purified with acetone.
Synthesis of PESA
To synthesize ESA, begin by adding a Ca(OH)2 initiator. Then, maintain a specific reaction temperature and stirring speed for a set time to achieve PESA.
Analysis and testing
Determination of maleic acid monomer concentration: Because maleic acid contains double bonds, the concentration of maleic acid can be determined by measuring the bromine value of the sample. That is, in an acidic solution, bromine molecules react with unpolymerized monomers in the sample, and KI solution is added to react with excess bromine to release I2, which is titrated with sodium thiosulfate standard solution.
Determination of ESA content: The epoxy group in the ESA molecule can react with MgCl2 to generate the corresponding chlorohydrin. The reaction can be carried out in a variety of solvents such as water, ethanol, and ether. Following reaction completion, titration of the remaining hydrochloric acid with an alkali solution enables the calculation of epoxy group or compound content, thus providing insight into the yield of epoxy soybean oil.
Determination of byproduct tartaric acid: Under the condition of pH 25-3.0, 5-nitrosalicylic acid and Fe3+ ions can react to form orange-red complex 5-nitrosalicylic acid iron, and the addition of a small amount of tartaric acid can make the color of 5-nitrosalicylic acid iron solution lighter. Using this characteristic, the content of tartaric acid can be accurately determined by spectrophotometry.
Determination of relative molecular mass: The relative molecular mass of PESA is determined by viscosity method.
Conclusion
a. The study found that several factors influence the yield of ESA, with reaction temperature being the most important, followed by NaOH dosage, reaction time, and catalyst dosage. The best results for ESA synthesis were achieved with a reaction temperature of 60°C, a n(MA) / n(NaOH) ratio of 1.0:2.0, a reaction time of 1.5 hours, and a composite catalyst dosage of 1.0%. Under these specific conditions, the average ESA yield reached 95.7%.
b. the optimal conditions for PESA synthesis involved a reaction temperature of 85°C, a reaction time of approximately 1.5 hours, a n[Ca(OH)2]/n(MA) ratio of 1:3, and Ca(OH)2 added in two batches. These conditions resulted in a PESA yield of 93.7%.
