Corrosion inhibitor for soft water circulation heating and cooling system and preparation method of corrosion inhibitor

Abstract

A corrosion inhibitor for a soft water circulation heating and cooling system, wherein the corrosion inhibitor is pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl, which has a chemical formula of C.sub.5H.sub.7O.sub.5{COC(CH.sub.3)[CH.sub.2OCOCH.sub.2CH(COOH)SC(NH)NH.sub.2].sub.2}.sub.5. The corrosion inhibitor provided by the present invention is non-phosphorus, biodegradable, non-toxic, low in cost and has good corrosion inhibition effect. Moreover, it has excellent corrosion inhibition performance for circulating heating and cooling systems using soft water as the water source, and can significantly improve the reuse rate of circulating water. The present invention also provides a preparation method of the corrosion inhibitor, which is simple, easy to obtain raw materials and easy to industrialize.

Claims

1. A corrosion inhibitor for a soft water circulation heating and cooling system, wherein the corrosion inhibitor is pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl, which has a chemical formula of C.sub.5H.sub.7O.sub.5{COC(CH.sub.3)[CH.sub.2OCOCH.sub.2CH(COOH)SC(NH)NH.sub.2].sub.2}.sub.5, and a structural formula of: ##STR00005##

2. A preparation method of the corrosion inhibitor for the soft water circulation heating and cooling system as recited in claim 1, the preparation method comprising steps of: (S1) under nitrogen protection and room temperature, evenly mixing 1,2,3,4,5-pentapentanol, 2,2-dimethylolpropionic acid, and p-toluene sulfonic acid, heating to 140-150° C., performing reaction for 3-5 h under atmospheric pressure, perform reaction for 3-5 h under vacuum conditions, and obtaining 1,2,3,4,5-penta(2,2-dimethylolpropionic acid) amyl alcohol ester; (S2) cooling the 1,2,3,4,5-penta(2,2-dimethylolpropionic acid) amyl alcohol ester obtained by the step of (S1) to 70-80° C., adding a first amount of acetic acid for dissolving, and then adding a mixture of maleic anhydride and a second amount of acetic acid, performing reaction for 3-5 h, and obtaining an acetic acid solution containing hyperbranched macromolecules with carboxyl-terminated pentapentanol core, wherein a chemical formula of the hyperbranched macromolecules with carboxyl-terminated pentapentanol core is C.sub.5H.sub.7O.sub.5[COC(CH.sub.3)(CH.sub.2OCOCH═CHCOOH).sub.2].sub.5; and (S3) cooling the acetic acid solution containing hyperbranched macromolecules with carboxyl-terminated pentapentanol core obtained by the step of (S2) to 40-60° C., and then adding a mixed solution of thiourea and a third amount of acetic acid, performing reaction for 3-5 h, cooling to room temperature, precipitating a solid substance, and then filtering, washing with water and drying the solid substance under vacuum in sequence, and obtaining the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl.

3. The preparation method, as recited in claim 2, wherein the 1,2,3,4,5-pentapentanol is xylitol (D-pentapentanol), DL-arabinol, D(+)-arabinol or L(−)-arabinol.

4. The preparation method, as recited in claim 2, wherein a molar ratio of 1,2,3,4,5-pentapentanol, 2,2-dimethylolpropionic acid, maleic anhydride, and thiourea is in a range of 1:(5.0-5.1):(10.0-10.2):(10.0-10.5).

5. The preparation method, as recited in claim 3, wherein a molar ratio of 1,2,3,4,5-pentapentanol, 2,2-dimethylolpropionic acid, maleic anhydride, and thiourea is in a range of 1:(5.0-5.1):(10.0-10.2):(10.0-10.5).

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(1) A corrosion inhibitor for a soft water circulation heating and cooling system and a preparation method thereof provided by the present invention are described detailedly in combination with embodiments as follows, but these embodiments are unable to be understood as limiting the protective scope of the present invention.

(2) The corrosion inhibition performance evaluation methods of the corrosion inhibitors in the following embodiments are carried out in accordance with the National Standard of the People's Republic of China “GB/T18175-2014, Determination of Corrosion Inhibition Performance of Water Treatment Agents by Rotating Hanging Piece Method”. Experimental instrument: RCC-II Rotating hanging piece corrosion tester; experimental conditions: temperature is in a range of 45 to 80° C., a rotational speed is 75 r/min, no pre-film hanging piece is provided, time is 72 hours, carbon steel test piece: 20# carbon steel with a size of 50 mm×25 mm×2 mm. Do blank experiments at the same time.

First Control Example

(3) Commercially available hydroxyethylene diphosphonic acid which is abbreviated as HEDP and has a solid content of 50%.

Second Control Example

(4) Commercially available 2-phosphate-1,2,4-tricarboxylic acid butane which is abbreviated as PBTCA and has a solid content of 50%.

Third Control Example

(5) Pentaerythritol pentaisothioureidosuccinate is prepared through a method disclosed by CN 106277376 B

First Embodiment

(6) Preparation of Pentapentanol Core Hyperbranched Macromolecule Functionalized by Isothiourea and Carboxyl

(7) At room temperature, add 15.20 g (0.10 mol) of xylitol (1,2,3,4,5-pentapentanol), 67.00 g (0.50 mol) of 2,2-dimethylolpropionic acid, and 1.00 g of p-toluene sulfonic acid to a four-necked round bottom flask with a condenser for stirring and refluxing and a thermometer and evenly stir. And then, introduce nitrogen into the four-necked round bottom flask, heat to 145° C., perform reaction for 3 h under atmospheric pressure, perform reaction for 4 h under vacuum conditions, and obtain a sticky substance. And then cool to 80° C., add 100 g of acetic acid for dissolving, and then add 196.00 g of acetic acid containing maleic anhydride (in which the maleic anhydride is 1.00 mol and has a mass concentration of 50%), and perform reaction for 4 h. And then cool to 55° C., add 152.00 g of acetic acid containing thiourea (in which the thiourea is 1.00 mol and has a mass concentration of 50%), and perform reaction for 5 h. And then cool to room temperature, precipitate a white substance, filter under vacuum, wash with deionized water until free of acetic acid, dry, and obtain a product, namely, the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl.

(8) The .sup.13CNMR (D.sub.2O) spectra of the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl are 18.35, 36.54, 37.98, 42.56, 61.98, 66.03, 68.93, 69.82, 136.23, 171.49, 174.39 and 180.93 ppm.

(9) The results of corrosion inhibition performance of the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl for carbon steel with soft circulating water are shown in Table 1. Experimental conditions are as follows: the soft circulating water has a pH value of 5.6 and an electrical conductivity of 0.96 μs/cm, temperature is 45° C.

(10) TABLE-US-00001 TABLE 1 The results of corrosion inhibition performance of the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl for carbon steel with soft circulating water Concentration Annual Corrosion of reagent corrosion inhibition (dried) rate rate Serial No. Reagent (mg .Math. L.sup.−1) (mm .Math. a.sup.−1) (%) Blank case — 0 1.8632 — First Pentapentanol core 10 0.1992 89.30 Embodiment hyperbranched 20 0.0418 97.75 macromolecule 30 0.0292 98.43 functionalized by isothiourea and carboxyl First Control HEDP 30 1.8021 3.28 Example 40 1.6935 9.11 Second PBTCA 30 1.4927 3.78 Control 40 1.5716 19.89 Example Third Control Pentaerythritol 20 0.5109 72.58 Example pentaisothioureido- 30 0.0957 94.86 succinate 40 0.0602 96.77

Second Embodiment

(11) Preparation of Pentapentanol Core Hyperbranched Macromolecule Functionalized by Isothiourea and Carboxyl

(12) At room temperature, add 15.20 g (0.10 mol) of DL-Arabitol (1,2,3,4,5-pentapentanol), 67.00 g (0.50 mol) of 2,2-dimethylolpropionic acid, and 1.00 g of p-toluene sulfonic acid to a four-necked round bottom flask with a condenser for stirring and refluxing and a thermometer and evenly stir. And then, introduce nitrogen into the four-necked round bottom flask, heat to 140° C., perform reaction for 5 h under atmospheric pressure, perform reaction for 5 h under vacuum conditions, and obtain a sticky substance. And then cool to 80° C., add 100 g of glacial acetic acid for dissolving, and then add 197.96 g of acetic acid containing maleic anhydride (in which the maleic anhydride is 1.01 mol and has a mass concentration of 50%), and perform reaction for 4 h. And then cool to 55° C., add 155.04 g of acetic acid containing maleic anhydride (in which the thiourea is 1.02 mol and has a mass concentration of 50%), and perform reaction for 5 h. And then cool to room temperature, precipitate a white substance, filter under vacuum, wash with deionized water until free of acetic acid, dry, and obtain a product, namely, the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl.

(13) The .sup.13CNMR (D.sub.2O) spectra of the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl are 18.29, 36.11, 38.36, 42.52, 61.76, 66.11, 68.94, 69.93, 136.21, 171.45, 175.12 and 179.68 ppm.

(14) The results of corrosion inhibition performance of the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl for carbon steel with soft circulating water are shown in Table 2. Experimental conditions are as follows: the soft circulating water has a pH value of 5.6 and an electrical conductivity of 0.96 μs/cm, temperature is 80° C.

(15) TABLE-US-00002 TABLE 2 The results of corrosion inhibition performance of the pentapentanol core hyperbranched macromolecule functionalized by isourea and carboxyl for carbon steel with soft circulating water Con- centration Annual Corrosion of reagent corrosion inhibition (dried) rate rate Serial No. Reagent (mg .Math. L.sup.−1) (mm .Math. a.sup.−1) (%) Blank case — 0 1.9002 — Second Pentapentanol core 20 0.0519 97.27 Embodiment hyperbranched 30 0.0306 98.39 macromolecule functionalized by isothiourea and carboxyl First Control HEDP 30 1.9013 −0.11% Example 40 1.7619 7.27 Second PBTCA 30 1.7901 5.79 Control 40 1.7226 9.34 Example Third Control Pentaerythritol 30 0.2125 88.82 Example pentaisothioureido- 40 0.1602 91.57 succinate 50 0.0712 96.25 Corrosion rate of carbon steel specified in ≤0.075 — design specification of industrial circulating cooling water treatment GB50050-2007

(16) The experimental results in Table 1 and Table 2 show that for soft water treatment systems, the traditional water treatment corrosion inhibitor hydroxyethylene diphosphonic acid (HEDP), 2-phosphate-1,2,4-tricarboxylic acid butane (PBTCA) basically has no corrosion inhibition effect on the corrosion of carbon steel. The pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl provided by the present invention has better corrosion inhibition performance for carbon steel when the dosage (20 mg.Math.L.sup.−1) is less; the corrosion rate of carbon steel is lower than the national standard of 0.075 mm.Math.a.sup.−1, and the corrosion inhibition performance is also better than that of the small molecule corrosion inhibitor pentaerythritol pentaisothioureidosuccinate disclosed in the patent CN 106277376 B.

(17) It can be seen from the above embodiments that the pentapentanol core hyperbranched macromolecule functionalized by isothiourea and carboxyl provided by the present invention has a good corrosion inhibition effect on the circulating heating and cooling water treatment system using soft water as the water source, and is a kind of phosphorus-free, biodegradable, and environmentally friendly corrosion inhibitor.

(18) The above are only preferred embodiments of the present invention, it should be noted that for those skilled in the art, without departing from the principles of the present invention, many improvements and modifications can be made, and these improvements and modifications should also be considered as the protective scope of the present invention.