PROCESS FOR REMOVAL OF ACID GASES FROM A FLUID STREAM

Abstract

A process for removing acid gases from a fluid stream, wherein the fluid stream is contacted with an absorbent to obtain a treated fluid stream and a laden absorbent, the absorbent comprising at least one diluent and a compound of the general formula (I) wherein R1 is C.sub.1-C.sub.3-alkyl; R2 is C.sub.1-C.sub.3-alkyl; R3 is selected from hydrogen and C1-C3-alkyl; R4 is selected from hydrogen and C.sub.1-C.sub.3-alkyl and n is an integer in the range of 1 to 4.

Claims

1.-13. (canceled)

14. A process for removing acid gases from a fluid stream, wherein the fluid stream is contacted with an absorbent to obtain a treated fluid stream and a laden absorbent, the absorbent comprising at least one diluent and a compound of the general formula (I) ##STR00007## wherein R1 is C.sub.1-C.sub.3-alkyl; R2 is C.sub.1-C.sub.3-alkyl; R3 is selected from hydrogen and C.sub.1-C.sub.3-alkyl; R4 is selected from hydrogen and C.sub.1-C.sub.3-alkyl and n is an integer in the range of 1 to 4.

15. The process according to claim 14, wherein each of R1, R2 and R3 are C.sub.1-alkyl.

16. The process according to claim 14, wherein the compound of general formula (I) is 2-[2-(tert-butylamino)ethylsulfanyl]ethanol

17. The process according to claim 14, wherein the diluent comprises water.

18. The process according to claim 17, wherein the absorbent additionally comprises an acid.

19. The process according to claim 14, wherein the diluent comprises a non-aqueous organic solvent.

20. The process according to claim 19, wherein the organic solvent is selected from C.sub.4-10 alcohols, ketones, esters, lactones, amides, lactams, sulfones, sulfoxides, glycols, polyalkylene glycols, di- or mono(C.sub.1-C.sub.4 alkyl ether) glycols, di- or mono(C.sub.1-4-alkyl ether) polyalkylene glycols, cyclic ureas, thioalkanols and mixtures thereof.

21. The process according to claim 14, wherein the absorbent comprises at least one activator selected from a sterically unhindered primary amine and/or a sterically unhindered secondary amine.

22. The process according to claim 21, wherein the activator is piperazine.

23. The process according to claim 14, for selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

24. The process according to claim 14, wherein the laden absorbent is regenerated by means of at least one of the measures of heating, decompressing and stripping with an inert fluid.

25. The use of an absorbent as defined in claim 14 for removal of acid gases from a fluid stream or the use of absorbent as defined in claim 14 for selective removal of hydrogen sulfide from a fluid stream comprising carbon dioxide and hydrogen sulfide.

26. Process for the manufacture of a compound of formula (I) by converting an amine of formula (II) ##STR00008## wherein R1 is C.sub.1-C.sub.3-alkyl; R2 is C.sub.1-C.sub.3-alkyl; R3 is selected from hydrogen and C.sub.1-C.sub.3-alkyl; with an alcohol of formula (III) ##STR00009## wherein R4 is selected from hydrogen and C.sub.1-C.sub.3-alkyl and n is an integer in the range of 1 to 4; in the liquid phase and in the presence of a catalyst.

Description

EXAMPLE 1: PREPARATION OF 2-[2-(TERT-BUTYLAMINO)ETHYLSULFANYL]ETHANOL

[0191] 1.7 of sodium methylate were dissolved in 15 ml dry ethanol. Mercaptoethanol was added to the solution under stirring. After completion of the mixing, the mixture was stirred for 15 more minutes, A solution of 2.5 g 2-chloro-N-tert-butylethylamine hydrochloride dissolved in 50 ml dry ethanol was added dropwise to maintain a temperature in the range of 35 to 40 C. After completion of the mixing process, the resulting suspension was heated to 75 C. and stirred for another 90 minutes, After stirring overnight at room temperature, the suspension was filtered and the filtrate was evaporated at 90 C. and 60 mbar in a rotary evaporator.

[0192] 2.5 g of 2-[2-(tert-butylamino)ethylsulfanyl]ethanol were obtained, The yield was calculated to be 97%. The structure of the compound was confirmed by .sup.1H-NMR.

EXAMPLE 2: COMPARISON OF PROPERTIES OF 2-[2-(TERT-BUTYLAMINO)ETHYLSULFANYL]ETHANOL (TBAESE) AND 2-[2-(TERT-BUTYLAMINO)ETHOXY]ETHANOL (TBAEE)

a) Thermal Stability

[0193] The thermal stability of TBAESE, was compared to TBAEE and MDEA with and without acid gas loading.

[0194] A cylinder (10 mL) was initially charged with the respective solution (8 mL) and the cylinder was closed. The cylinder was heated to 150 C. for 125 h. In the experiments conducted under acid gas loading, the acid gas loading of the solutions was 20 Nm.sup.3/t.sub.solvent of CO.sub.2 and 20 Nm.sup.3/t.sub.solvent of H.sub.2S. The decomposition level of the amines was calculated from the amine concentration measured by gas chromatography before and after the experiment. The results are shown in the Table 1.

TABLE-US-00001 TABLE 1 Ratio of Degradation Without Acid With Acid Aqueous Solution Gas Loading Gas Loading 40 wt.-% MDEA + 0.98 0.89 60 wt.-% H.sub.2O* 30 wt.-% TBAEE + 70 wt.-% 0.99 0.92 H.sub.2O* 20 wt.-% TBAESE + 75 wt.-% 0.99 0.96 H.sub.2O *comparative example

[0195] It is evident that TBAESE have a higher thermal stability than MDEA and TBAEE in aqueous solutions in the presence of acid gas loading.

b) Acid Gas Loading and Regeneration

[0196] The pK.sub.a-values for TBAESE and TBAEE were measured in the temperature range between 20 C. and 120 C. The results are shown in FIG. 1. For that an aqueous solution of the amine with a concentration of 0.01 mol/l was 50% neutralized by 0,005 mol/1 HCl solution. So, the measured pH of the 50% neutralized amine solution is equal to the pKa value of the amine. The measurement was performed in a glass vessel pressurized with nitrogen to avoid any water and solvent loss.

[0197] It can be seen that the pK.sub.a-values of TBAESE and TBAEE are comparable over the measured range and significantly higher than the pKa value of M DEA. From these measurements it can be concluded that the acid gas loading and the regeneration of TBAESE is comparable to TBAEE.

[0198] In summary, while TBAESE and TBAEE have similar absorption properties, TBAESE shows slightly improved thermal stability. This allows TBAESE to be handled under slightly higher regeneration temperatures, allowing more complete regeneration of the absorbent. Further TBAESE combines the benefits of sterically hindered amines, such a high selectivity for H.sub.2S, and thioalcohols, a high removal rate of the sulfur compounds which may be present in the feed gas, in particular mercaptans, in a single molecule.