Condensation product of 1-amino-2-propanol and formaldehyde and the use thereof for reducing the amount of hydrogen sulphide in liquids and gases

Abstract

Disclosed is a storage-stable condensation product prepared from 1-amino-2-propanol and formaldehyde in a molar ratio in the range from 1:2.0 to 1:3.1. The condensation product contains less than 10% by weight of water. Also, disclosed is the preparation of the condensation product and the use thereof for reducing the amount of hydrogen sulphide in liquids and gases.

Claims

1. Process for preparing a condensation product, containing less than 10% by weight of water, comprising the successive steps: Step a) of reaction of 1-amino-2-propanol is reacted with formaldehyde in a molar ratio in the range from 1:2.5 to 1:3.1 and at a temperature in the range from 50 C. to 80 C. to form a product; Step b) of removal of water from the product obtained at the end of step a), under reduced pressure to form the condensation product.

2. Process according to claim 1, wherein the reaction in step a) is carried out at a temperature in the range from 60 C. to 70 C.

3. Process according to claim 1, wherein in step a), formaldehyde is used in the form of paraformaldehyde.

4. Process according to claim 1, wherein, in step a), 1-amino-2-propanol is initially charged and formaldehyde is added.

5. Process according to claim 1, wherein the removal of water is carried out at a temperature of from 50 C. to 80 C.

6. Process according to claim 1, wherein the removal of water is carried out at a pressure in the range from 10.sup.2 to 10.sup.4Pa (1 to 100 mbar).

7. Process according to claim 1, wherein the condensation product contains less than 4% by weight of water.

8. Condensation product obtainable by a process for preparing a condensation product, containing less than 10% by weight of water, comprising the successive steps: Step a) of reaction of 1-amino-2-propanol is reacted with formaldehyde in a molar ratio in the range from 1:2.5 to 1:3.1 and at a temperature in the range from 50 C. to 80 C. to form a product; and Step b) of removal of water from the product obtained at the end of step a), under reduced pressure to form the condensation product.

9. A method for removing sulphur compounds from process streams, comprising providing a condensation product containing less than 10% by weight of water, according to claim 8, and applying the condensation product to the process streams to remove the sulphur compounds from process streams.

10. The method according to claim 9, wherein the process stream is selected from among liquid and gaseous process streams.

11. The method according to claim 9, wherein the process stream contains water, hydrocarbon or a mixture of water and hydrocarbon.

12. The method according to claim 9, wherein the sulphur compound is selected from among hydrogen sulphide, inorganic and organic sulphides, mercaptans and mercaptides.

13. The method according to claim 9, wherein the sulphur compound is hydrogen sulphide.

14. Method for removing one or more sulphur compounds from a process stream, wherein the process stream is brought into contact with a condensation product containing less than 10% by weight of water according to claim 8.

15. A method for removing one or more sulphur compounds from a process stream in order to avoid deposits, comprising providing a condensation containing less than 10% by weight of water according to claim 8, and applying the condensation product to the process streams to remove the, one or more sulphur compounds from the process stream, thereby avoiding deposits.

16. Process according to claim 1, wherein the reaction in step a) is carried out at a temperature in the range from 60 C. to 70 C.

17. Process according to claim 1, wherein in step a), formaldehyde is used in the form of paraformaldehyde.

18. Process according to claim 2, wherein in step a), formaldehyde is used in the form of paraformaldehyde.

19. Process according to claim 1, wherein, in step a), 1-amino-2-propanol is initially charged and formaldehyde is added.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in connection with FIG. 1, illustrating schematically an analytical system for the determination of H.sub.2S.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) The advantages of the present invention may be derived, in particular, from the following examples. All percentages are, unless indicated otherwise, by weight.

EXAMPLES

(3) Method of Determining the Sulphide Concentration (Based on IP 570: Determination of Hydrogen Sulphide in Mineral Oils)

(4) Description of the Method The various sulphur scavengers are allowed to act on the sample at various temperatures and for different times. The sample is diluted with alkyl benzene in order to get into the linear working range of the analytical system. The sample to be analysed (including sulphur scavenger) is injected into the analytical system (shown schematically in FIG. 1). Acid (2M H.sub.3PO.sub.4 in water) is added, and the analytical sample is optionally heated in the analytical system. The hydrogen sulphide formed is quantitatively driven off by means of air in the analytical system and the hydrogen sulphide is transferred to an electrochemical measuring electrode in the analytical instrument. The hydrogen sulphide produces a measurement signal which is proportional to the respective amount of hydrogen sulphide at the electrochemical measuring electrode. The resulting peak area (made up of measurement signal intensity against time) is determined by means of evaluation software and converted into a content of sulphide on the basis of a calibration curve.

Example 1Lack of Storage Stability of an Aqueous Solution of a Formaldehyde Condensation Product

(5) 1-Amino-2-propanol (187.8 g, 2.5 mol) was placed in a reaction vessel and paraformaldehyde (91% pure, 247.5 g, 7.5 mol) was added a little at a time while stirring in such a way that a temperature of 70 C. was not exceeded. After addition of of the amount of paraformaldehyde, the exothermic reaction had ended and the further addition of paraformaldehyde was carried out at from 60 to 70 C. with heating. After addition was complete, the mixture was stirred at 70 C. for about another hour, with the paraformaldehyde dissolving completely.

(6) A clear, yellowish solution was obtained (density at 20 C.: 1.1258 g/cm.sup.3; refraction index at 20 C.: 1.4503; Hazen colour number: 29).

(7) The stability was tested by storage at t=1 month and t=3 months at temperatures of 5 C., 25 C. and 40 C. in PE bottles (Table 1).

(8) TABLE-US-00001 TABLE 1 5 C. 25 C. 40 C. 1 month storage at: Appearance clear, y. clear, y. clear, (Zero value: clear y.) orange Formaldehyde which n.d. 45.7 33.5 can be eliminated (%) 3 months storage at: Appearance clear, clear, clear, light yellow dark yellow orange/red Formaldehyde which n.d. 59.3 59.7 can be eliminated (%) (Zero value: 50%) y: yellowish; n.d. = not determined;

(9) On storage at 40 C., significant degradation and a reduced content of formaldehyde which can be eliminated was found even after one month. After storage for three months, it could be seen that the product was ultimately not storage-stable.

(10) The condensation product of 1-amino-2-propanol and formaldehyde (in a molar ratio of 1:3) is thus not stable in aqueous solution.

Example 2Storage Stability of a Dewatered Formaldehyde Condensation Product

(11) 1-Amino-2-propanol (150.2 g, 2 mol) was placed in a reaction vessel and paraformaldehyde (91% pure, 198 g, 6 mol) was then added a little at a time while stirring in such a way that a temperature of 70 C. was not exceeded. After addition of of the amount of paraformaldehyde, the exothermic reaction had ended and the further addition of paraformaldehyde was carried out at from 60 to 70 C. with heating. After the addition was complete, the mixture was stirred at 70 C. for about another hour, with the paraformaldehyde dissolving completely. The water was subsequently removed under reduced pressure [max. 70 C. at 10.sup.3 Pa (10 mbar)]. A slightly yellowish clear solution was formed (density at 20 C.: 1.1259 g/ml; refraction index at 20 C.: 1.4710; Hazen colour number: 18; formaldehyde which can be eliminated: 59.6%). The stability after 1 month and 3 months of storage, was tested at 5, 25 and 40 C. in PE bottles (Table 2).

(12) TABLE-US-00002 TABLE 2 5 C. 25 C. 40 C. Storage for 1 month at Appearance clear, s.y.* clear, s.y. clear, s.y.h Formaldehyde which n.d. 59.6 59.8 can be eliminated (%) Storage for 3 months at Appearance clear, s.y. clear, s.y. clear, s.y. Formaldehyde which n.d. 59.3 59.7 can be eliminated (%) Storage for 6 months at Appearance clear, s.y.* clear, s.y.* clear, y* Density at 20 C. (g/ml) 1.1321 1.1297 1.1283 Refraction at 20 C. 1.4738 1.4726 1.472 Hazen colour number 17 20 91 Formaldehyde which n.d. 59.6 58.6 can be eliminated (%) Storage for 12 months at Appearance clear, s.y. clear, clear, light yellow yellow Density at 20 C. (g/ml) n.d. 1.1305 1.1306 Refraction at 20 C. n.d. 1.4727 1.4732 Hazen colour number n.d. 70 531 Formaldehyde which n.d. 58.2 57.6 can be eliminated (%) Degradation of n.d. 2.3% 3.4% formaldehyde which can be eliminated compared to the zero value s.y.: s.y. n.d. = not determined

(13) On storage at 40 C., only slight degradation and an only slightly reduced content of formaldehyde which can be eliminated was thus found even after 12 months. When dewatered, the condensation product of 1-amino-2-propanol and formaldehyde (in a molar ratio of 1:3) is thus exceptionally stable.

Example 3Viscosities and Comparative Determination of the Reduction of Hydrogen Sulphide

(14) The following formulations were studied:

(15) Formulation BK (Comparison):

(16) The reaction product of ethanolamine and paraformaldehyde (91% pure) in a molar ratio of 1:1 was formed. This gave 1,3,5-triazine-1,3,5-(2H,4H,6H)triethanol. The water of reaction and the water from the paraformaldehyde remained in the product.

(17) Formulation OX (Comparison):

(18) The reaction product of 1-amino-2-propanol and paraformaldehyde (91% pure) in a molar ratio of 2:3 was formed. This gave 3,3-methylenebis(5-methyloxazolidine). The water of reaction and the water from the paraformaldehyde were distilled off.

(19) Formulation OK (Comparison):

(20) The reaction product of 1-amino-2-propanol and paraformaldehyde (91% pure) in a molar ratio of 2:3 was formed. This gave 3,3-methylenebis(5-methyloxazolidine). The water of reaction and the water from the paraformaldehyde were distilled off. Urea and ethylene glycol were added (the mixture contained about 4.6% by weight of urea and about 9.5% by weight of ethylene glycol).

(21) B2 (Invention):

(22) The dewatered reaction product of 1-amino-2-propanol and paraformaldehyde (91% pure) in a molar ratio of 1:3 was prepared as described in Example 2.

(23) The viscosities of the formulations are shown in Table 3.

(24) TABLE-US-00003 TABLE 3 10 C. 0 C. 10 C. 20 C. 40 C. BK* 7437 mPas 2309 mPas 1004 mPas 447 mPas 105 mPas OX* 176 mPas 74 mPas 38 mPas 19 mPas 9 mPas OK* 48392 mPas n.d. n.d. 907 mPas 170 mPas B2 1940 mPas 540 mPas 220 mPas 97 mPas n.d. n.d. = not determined, *Comparison

(25) The data in Table 3 show that the condensation product according to the invention has an advantageously low viscosity over a wide temperature range, i.e. even at a low temperature of 10 C., which is advantageous for the processability of the condensation products of the invention.

(26) The formulations mentioned were also tested according to the method indicated above to determine how they can reduce hydrogen sulphide in various matrices (solvents or solvent mixtures). 0.10% of the respective formulation was added. The results are shown in Table 4.

(27) TABLE-US-00004 TABLE 4 BK* OX* OK* B2 Solvent Sulphide, T( C.) Reaction time Reduction in H2S (%) Water 200 ppm 50 C. 2 h 20.0 27.0 21.1 33.5 Alkylbenzene 200 ppm 20 C. 2 h 8.0 8.8 11.6 16.3 Alkylbenzene 200 ppm 50 C. 2 h 10.1 10.0 15.4 24.6 Alkylbenzene 100 ppm 50 C. 2 h 7.4 3.8 11.2 44.4 Alkylbenzene 200 ppm 50 C. 0.5 h 51.5 43.3 50.2 64.4 (+1% of water) *Comparison

(28) The data in Table 4 demonstrate that the condensation product according to the invention not only reduces the content of sulphide in water and in hydrocarbons better in comparison with 3,3-methylenebis(5-methyloxazolidine) or with 1,3,5-triazine-1,3,5-(2H,4H,6H)triethanol, but also that this improved action requires no additives and, in addition, is even more pronounced and sets in very quickly at elevated use temperature.

Example 4Testing of Other Molar Ratios

(29) The procedure of Example 2 was repeated, but the molar ratio of 1-amino-2-propanol to paraformaldehyde was varied in the range from 1:2 to 1:5; 1 mol of 1-amino-2-propanol was placed in a reaction vessel in each case and different amounts of paraformaldehyde (91% pure) were then added. Solutions which can be produced stably at room temperature were tested in respect of their stability by storage at 5 C., 25 C. and 40 C. in PE bottles. The results are shown in Tables 5 and 6.

(30) TABLE-US-00005 TABLE 5 A B C*** D*** E*** Molar ratio* 1:2 1:2.5 1:3.5 1:4 1:5 Appearance after clear, s.y. clear, s.y. clear, s.y. clear, s.y. not dewatering (70 C.) dissolved Appearence after clear, s.y. clear, s.y. turbid, inh., turbid, inh. cooling to 20 C. Density, 20 C. (g/cm.sup.3) 1.0802 1.1041 n.d. n.d. n.d. Refraction index, 20 C. 1.4714 1.4723 n.d. n.d. n.d. Formaldehyde which 50.2 54.7 n.d. n.d. n.d. can be eliminated (%) ***Comparison; n.d.: not determined; inh.: inhomogeneous

(31) These examples show that condensation products of 1-amino-2-propanol and paraformaldehyde in a molar ratio of 1:2 and 1:2.5 which have been dewatered according to the invention can be prepared, while dewatered condensation products of 1-amino-2-propanol and paraformaldehyde in a molar ratio of 1:3.5, 1:4 and 1:5 cannot be prepared.

(32) The inventive, stably preparable condensation products of 1-amino-2-propanol and paraformaldehyde in a molar ratio of 1:2 and 1:2.5 (products A and B in Table 5) were additionally examined in respect of their long-term storage stability (Table 6).

(33) TABLE-US-00006 TABLE 6 Storage stability of condensation products according to the invention Compound A 5 C. 25 C. 40 C. Storage for 5 months at Appearance clear, s.y. clear, s.y. clear, light yellow Formaldehyde which n.d. 49.2 50.2 can be eliminated (%) % Degradation to n.d. 2.0 0.0 zero value Storage for 9 months at Appearance clear, s.y. clear, y. clear, yellow Density at 20 C. (g/ml) n.d. 1.0817 1.0820 Refraction at 20 C. n.d. 1.4719 1.4712 Hazen colour number n.d. 23 167 Formaldehyde which n.d. 50.2 50.1 can be eliminated (%) % Degradation to n.d. 0.0 0.2 zero value Compound B 5 C. 25 C. 40 C. Storage for 5 months at Appearance clear, s.y. clear, s.y. clear, light yellow Formaldehyde which n.d. 54.3 54.4 can be eliminated (%) % Degradation to n.d. 0.7 0.5 zero value Storage for 9 months at Appearance clear, s.y. clear, y. clear, yellow Density at 20 C. (g/ml) n.d. 1.1053 1.1059 Refraction at 20 C. n.d. 1.4727 1.4730 Hazen colour number n.d. 29 232 Formaldehyde which n.d. 54.5 54.3 can be eliminated (%) % Degradation to n.d. 0.4 0.7 zero value n.d. = not determined

(34) The data in Table 6 demonstrate that the condensation products of 1-amino-2-propanol and paraformaldehyde in a molar ratio of 1:2 and 1:2.5 which have been dewatered according to the invention have good storage stability.

Example 5Testing of Particular Molar Ratios

(35) The procedure of Examples 2 and 3 was repeated, but the molar ratio of 1-amino-2-propanol to paraformaldehyde was varied in the narrow range from 1:3.1 to 1:3.3; 1 mol of 1-amino-2-propanol was placed in a reaction vessel in each case and different amounts of paraformaldehyde (91% pure) were then added. The results are shown in Table 7.

(36) TABLE-US-00007 TABLE 7 Preparation of condensation products A B** C** Molar ratio* 1:3.1 1:3.2 1:3.3 Appearance after clear, s.y. clear, s.y. slightly dewatering (70 C.) opaque, s.y. Appearance after clear, s.y. slightly Turbid cooling to 20 C. opaque, s.y. Appearance after clear, s.y. Turbid Turbid, inh. storage at 20 C. for 7 days **Comparison

(37) The preparation of dewatered condensation products of 1-amino-2-propanol and paraformaldehyde can thus be carried out successfully according to the invention up to a molar ratio of 1:3.1, while dewatered condensation products of 1-amino-2-propanol and paraformaldehyde in a molar ratio of 1:3.2 and 1:3.3 are not stable products.

Example 5Examination of the pH Values of Aqueous Solutions

(38) The inventive product as per Example 2 and formulation OX was prepared as described in Example 3. Formulation WS was prepared like formulation BK in Example 3, but from 1-amino-2-propanol (and not from ethanolamine as for formulation BK) and paraformaldehyde (91% pure) in a molar ratio of 1:1. The water of reaction and the water from the paraformaldehyde remained in the product. Formulation WS is a water-containing product containing about 80% by weight of the formaldehyde depot compound ,,-trimethyl-1,3,5-triazine-1,3,5-(2H,4H,6H)triethanol (N,N,N-tris(2-hydroxpropyl)hexahydrotriazine). The pH values of aqueous solutions of the formulations WS, OX and B2 (in each case in de-ionized water) are shown in Table 8.

(39) TABLE-US-00008 TABLE 8 Formulation Concentration, [%] WS* OX* B2 0.2 10.3 10.4 10.0 1.0 10.5 10.4 9.9 *Comparison

(40) The data in Table 8 show that condensation products which have been prepared according to the invention have an advantageously lower pH than other formaldehyde depot compounds prepared from 1-amino-2-propanol, even in aqueous dilution.