JPS6125408B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to gas cleaning compositions. Natural and man-made gases containing acidic components such as CO ₂ , H ₂ S and COS are treated with aqueous alkanolamine solutions on an industrial scale to remove the acidic components. Severe corrosion resulting from the presence of these components, especially in the strong absorbent regeneration sector, makes it necessary to maintain a low concentration of amine, i.e. generally 10-30%, and a low loading in the absorbent, i.e. low H ₂ S/CO ₂ content. In need of. Due to the need to save energy, it may be advantageous to load the gas treatment liquid more heavily with acidic components. It would be further advantageous if a more concentrated absorption liquid could be used. However, to achieve this desired result it would be necessary to prevent increased corrosion, and it would be desirable to have less corrosion than is currently experienced at lower loads and fluid concentrations. In reviewing the prior art, numerous patents cite the use of various polyamines as corrosion inhibitors in various liquids. For example, Dickson et al., US Pat. No. 3,262,791, describes polyalkyleneimines having a molecular weight of 800 or greater as being useful in preventing corrosion of iron, steel, and iron alloys when used with rust inhibiting oils. U.S. Pat. No. 2,143,393 describes acid-absorbing gases in aqueous solutions of polymerized alkyleneimines. Although there are many publications on nitrogen-containing compounds useful as corrosion inhibitors, only a few can be used industrially. Although these available inhibitors have provided some improvement, the old limits on absorbent concentration and absorbent loading have been met by the energy deficit driven demands for more efficient operation at higher absorbent concentrations and higher loads. It is obvious to anyone with experience in operating factory equipment that this is not sufficient. The above-mentioned drawbacks of the conventional methods have been substantially overcome by the composition of the present invention. Its composition is formula (1): [In the formula, n is an integer from 1 to 3, m is 2, and the molecular weight is 800.
R ₁ , R ₂ , R ₃ and
R ₄ is each −H, −Cn′H _2o ′OH, −Cn′H _2o ′, or −
Cn′H _2o ′N(R ₃ )R ₄ (However, n′ can be 1 or 2 or
When R ₁ and R ₄ are bonded, and when R ₂ and R ₃ are bonded, n' is 2. ) represents an item selected from the group consisting of ) The amine compound or mixture of compounds represented by
(2) 0 to 1000 ppm of copper or a copper ion-forming compound; and (3) 0 to 1000 ppm of sulfur or a sulfur atom-forming compound. Amine compounds falling within the above formula are polyethyleneimine (polyethylene polyamines) with a molecular weight of about 60 to 800, which may also be a mixture of various amines, such as 30-35% by weight of pentaethylenehexamine, tetra Ethylenepentamine 8-9% by weight, hexaethyleneheptamine
EA-10 (or E-100) PEI3 (molecular weight 300
±50) and PEI6 (molecular weight approximately 600); EA-17 tris(aminoethyl)-amine (approximately 90% branched); EA-19 pentaethylenehexamine (molecular weight approximately 232); EA−
15 (diethylenetriamine 35-45%, triethylenediamine 10-15%, piperazine 5-15%);
EA-25 (reaction product of triethylenetetramine and divinylbenzene); EA-26 (divinylbenzene-ethylvinylbenzene-diethylenetriamine mixture); EA-11 (aminoethylpiperazine-diethylenetriamine mixture); commercially available polyalkylene polyamines, 1・2-polypropyleneimine, tetraethylenepentamine, triethylenetetramine, diethylenetriamine,
There are ethylenediamine and dihydroxyethylethylenediamine. Copper metal or a copper ion generating compound such as CuCO ₃ is used. The sulfur or sulfur ion-generating compound is H ₂ S,
in compositions containing COS or other sulfur-containing ingredients. This inhibitor has a H ₂ S to CO ₂ ratio of 10/1 to 1/10.
It is most effective in diethanolamine solutions within the range of . The performance of this inhibitor depends on the gas being treated.
Compatible with inhibitor performance when containing H ₂ S and CO ₂ at a ratio of up to 40 parts CO ₂ per 1 part H ₂ S. If only H ₂ S is present, it is better to use an absorbent than to use the inhibitor of the present invention.
DEA and MDEA prevent corrosion more effectively, but the results are less dramatic when CO ₂ is also present. The alkanolamines used as absorbents for acidic gases are monoethanolamine (MEA),
Things like monoisopropanolamide (MIPA)
_C23 alkanolamines; dialkanol _C2 - _C3 amines such as diethanolamine (DEA) and their N-alkyl substituted derivatives, ie methyldiethanolamine (MDEA). Dialkanolamines show significant improvement in corrosion protection when using the inhibitors of this invention. Method Modified sparkler 40psig (28Kg/cm ² )
Laboratory data was obtained from a test of approximately 17 hours at 125°C. A 4 oz (114 g) bottle was also filled with the inhibitor to be tested and a 50% diethanolamine (DEA) - 50% water solution and 1020 mild steel specimens (etched with 5N hydrochloric acid and soap) were saturated with various _H2S / _CO2 gas ratios. ) was rinsed with water and acetone and weighed. Initially, the total volume of each bottle was 120 ml. At the end of the test, the mild steel pieces were again etched with acid (containing HCl inhibitor), washed with soap and water, rinsed with acetone, and weighed.
The corrosion rate and prevention rate were calculated from the weights of the mild steel piece before and after using the following formula. Where, W = weight loss (mg) D = specific gravity of test piece (g/cc) A = area (in square inches) T = exposure time (hours) Protection rate % = average corrosion rate of white test piece - test piece corrosion rate/white Test average corrosion rate x 100 The following tables show the tests conducted and the results of the test series. White test corrosion rates without inhibitors were tested for each series so that they could be directly compared with other tests in that series. In each table, the corrosion rate is expressed in mils per year (MPY).
It is expressed as mm/year (MPY×0.0254). The following symbols are used for the following substances in the table: E-100 Polyethylene polyamine, molecular weight 250-
300 PEI6 Polyethyleneimine, average molecular weight 600, TRT-3 Marketing inhibitor, EA-75 Polyethyleneimine (E-75), E-
100% solids. PEI3 Polyethyleneimine, average molecular weight 300, RCC-9 Tetradecylalkylpyridinium bromide, FO-6 Commercially available quaternary amine.

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Claims (1)

[Claims] 1. Formula of treatment liquid (1) 10 to 2000 ppm: [In the formula, n is an integer from 1 to 3, m is from 2 to molecular weight 800
R ₁ , R ₂ , R ₃ and R ₄ are each -H, -Cn′H _2o ′OH, -Cn′H _2o ′, or -Cn′H _2o ′N ( R ₃ ) R ₄ (However, n' is an integer of 1 or 2, and if R ₁ and R ₄ are combined and R ₂ and R ₃
n' is 2 if they are combined). ] An amine compound or a mixture of compounds represented by (2)0 to
1000ppm of copper or copper ion-generating compounds and
(3) Corrosion inhibiting compositions in the form of aqueous alkanolamine solutions for gas treatment, characterized in that they contain 0 to 1000 ppm of sulfur or sulfur atom-forming compounds. 2. Claim 1, wherein the amine compound is a polyethylene polyamine having an average molecular weight of 250 to 300.
The composition described in Section. 3. The composition according to claim 1, wherein the amine compound is polyethyleneimine having a molecular weight of 300. 4. The composition according to claim 1, wherein the amine compound is polyethyleneimine having an average molecular weight of 600. 5. The composition according to claim 1, wherein the amine compound is a polyethylene polyamine mixture having an average molecular weight of 250 to 300. 6. The composition according to claim 1, wherein the alkanolamine is diethanolamine.