Unsymmetrically substituted dicarboxylic acid diamido ammonium salts and their use for gas hydrate anti-agglomeration

Abstract

The instant invention concerns a gas hydrate inhibitor comprising an N alkyl N′ (N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salt represented by the formula (I) ##STR00001##
wherein R is an alkyl or alkenyl group having from 8 to 22 carbon atoms, R.sup.1 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C.sub.22 alkenyl group, R.sup.2 and R.sup.3 are each independently an alkyl group containing 1 to 10 carbon atoms or together form an optionally substituted ring having 5 to 10 ring atoms, wherein the ring may carry up to 3 substituents, R4 is hydrogen, A is an optionally substituted hydrocarbyl group containing from 1 to 18 carbon atoms, B is an alkylene group having from 2 to 6 carbon atoms, Y is NR.sup.5, R.sup.5 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C.sub.22 alkenyl group, and M− is an anion,
a process for producing a compound according to formula (I), the use of an N alkyl N′—(N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salt of the formula (I) as an anti-agglomerant for gas hydrates, and a method for inhibiting the agglomeration of gas hydrates which comprises the addition of an N alkyl N′ (N″,N″dialkylammmoniumalkyl)dicarboxylic acid diamide salt of the formula (I) to a fluid containing gas and water.

Claims

1. A gas hydrate inhibitor comprising an N-alkyl-N′—(N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salt represented by the formula (I) ##STR00010## wherein R is an alkyl or alkenyl group having from 8 to 22 carbon atoms, R.sup.1 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C.sub.22 alkenyl group, R.sup.2 and R.sup.3 are each independently an alkyl group containing 1 to 10 carbon atoms or together form an optionally substituted ring having 5 to 10 ring atoms, wherein the ring may carry up to 3 substituents, R.sup.4 is hydrogen, A is an optionally substituted hydrocarbyl group containing from 1 to 18 carbon atoms, B is an alkylene group having from 2 to 6 carbon atoms, Y is NR.sup.5, R.sup.5 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C.sub.22 alkenyl group, and M− is an anion.

2. The gas hydrate inhibitor according to claim 1 wherein R.sup.1 is hydrogen or methyl.

3. The gas hydrate inhibitor according to claim 1, wherein R.sup.1 is hydrogen.

4. The gas hydrate inhibitor according to claim 1, wherein R.sup.2 and R.sup.3 are each independently an alkyl group having 1 or 6 carbon atoms.

5. The gas hydrate inhibitor according to claim 1, wherein R.sup.2 and R.sup.3 are each independently an alkyl group having 4 or 5 carbon atoms.

6. The gas hydrate inhibitor according to claim 1, wherein R.sup.2 and R.sup.3 are each independently a linear alkyl group.

7. The gas hydrate inhibitor according to claim 1, wherein R.sup.2 and R.sup.3 are the same.

8. The gas hydrate inhibitor according to claim 1, wherein R.sup.5 is hydrogen.

9. The gas hydrate inhibitor according to claim 1, wherein R is an alkyl or alkenyl group having from 10 to 18 carbon atoms.

10. The gas hydrate inhibitor according to claim 1, wherein A is an alkylene group having 2 to 6 carbon atoms.

11. The gas hydrate inhibitor according to claim 1, wherein A is an aromatic group having 6 to 12 carbon atoms.

12. The gas hydrate inhibitor according to claim 1, wherein B is an alkylene group having 2, 3 or 4 carbon atoms.

13. The gas hydrate inhibitor according to claim 1, wherein B is an ethylene group having the formula CH.sub.2—CH.sub.2— or a propylene group having the formula CH.sub.2—CH.sub.2—CH.sub.2—.

14. The gas hydrate inhibitor according to claim 1, wherein M− is selected from the group consisting of sulfate, sulfide, carbonate, bicarbonate, nitrate, halogenides and carboxylates.

15. The gas hydrate inhibitor according to claim 1, wherein M− is a carboxylate anion.

16. The gas hydrate inhibitor according to claim 1, wherein M− is the anion of a monocarboxylic acid having 1 to 22 carbon atoms.

17. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor corresponds to formula (Ib) ##STR00011##

18. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor corresponds to formula (Ic) ##STR00012##

19. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor corresponds to formula (Id) ##STR00013##

20. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor corresponds to formula (If) ##STR00014##

21. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor comprises both an N-alkyl-N′—(N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salt according to formula (I) ##STR00015## and its corresponding base which is an N-alkyl-N′—(N″,N″-dialkylaminoalkyl)dicarboxylic acid diamide according to formula (II) ##STR00016## wherein R is an alkyl or alkenyl group having from 8 to 22 carbon atoms, R.sup.1 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C22 alkenyl group, R.sup.2 and R.sup.3 are each independently an alkyl group containing 1 to 10 carbon atoms or together form an optionally substituted ring having 5 to 10 ring atoms, wherein the ring may carry up to 3 substituents, A is an optionally substituted hydrocarbyl group containing from 1 to 18 carbon atoms, B is an alkylene group having from 2 to 6 carbon atoms, Y is NR.sup.5, and R.sup.5 is hydrogen, a C.sub.1- to C.sub.22 alkyl group or a C.sub.3- to C.sub.22 alkenyl group.

22. The gas hydrate inhibitor according to claim 1, wherein the gas hydrate inhibitor contains an organic solvent.

23. A method for inhibiting the agglomeration of gas hydrates which comprises the addition of a gas hydrate inhibitor according claim 1, to a fluid containing gas and water.

24. The method according to claim 23 wherein the dosage rate of the gas hydrate inhibitor according claim 1, is between 0.01 and 5% by volume (based on the volume of the aqueous phase).

Description

EXAMPLES

General Method for the Preparation of N-alkyl-N′—(N″,N″-dialkylaminoalkyl)dicarboxylic acid diamides Starting from Dicarboxylic Acids

(1) The amounts of dicarboxylic acid, fatty amine and optionally solvent given in the reaction protocols below were charged into a five-neck flask equipped with distillation condenser or optionally a Dean-Stark trap connected with a reflux condenser, overhead stirrer, internal thermometer and nitrogen inlet tube. The temperature of the mixture was increased to 130° C. while gently stirring. As the temperature approached 130° C., the mixture slowly melted to a tan liquid. Heating and stirring were continued with continuous removal of water from the reaction mixture.

(2) The progress of the reaction was monitored by potentiometric amine number titration of aliquots of the reaction mixture with perchloric acid. Amine number is abbreviated as AN. It was determined by potentiometric titration of the sample with perchloric acid after dilution of the sample with acetic acid. When titration showed AN≤1 mmol/g, the formation of the cyclic imide intermediate was considered to be completed. The cyclic imide product was characterized by .sup.1H-NMR spectroscopy (CDCl.sub.3, δ=2.67 ppm, 4H singlet).

(3) The reaction mixture was cooled down to 80° C. and an equimolar amount of the diamino alkane given in the respective protocol was added to the reaction mixture.

(4) The reaction mixture was heated to 120-130° C. with stirring for up to 18 hours. The reaction progress was followed by means of .sup.1H-NMR spectroscopy. When the four symmetric ring hydrogen signals of the cyclic imide structure at δ=2.67 ppm in the .sup.1H-NMR spectrum were no longer visible the reaction was stopped. The unsymmetric diamide structure was confirmed by .sup.1H-NMR.

Example 1: N-dodecyl-N′-[3-(dimethylamino)propyl]-succinic acid diamide

(5) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 86.85 g (0.85 mol) of N,N-dimethyl-propane-1,3-diamine were used to obtain 298 g of N-dodecyl-N′-[3-(dimethylamino)propyl]-succinic acid diamide as a brownish solid.

Example 2: N-dodecyl-N′-[6-(dimethylamino)hexyl]-succinic acid diamide

(6) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 122.62 g (0.85 mol) of N,N-dimethyl-hexane-1,6-diamine were used to obtain 330 g of N-dodecyl-N′-[6-(dimethylamino)hexyl]-succinic acid diamide as a brownish solid.

Example 3: N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide

(7) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 379 g of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide as a brownish solid.

Example 4: N-cocoyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide

(8) 100 g (0.85 mol) of succinic acid, 166.14 g (0.85 mol) of cocoylamine (AN=287.15 mgKOH/g) and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 374 g of N-cocoyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide as a brownish solid.

Example 5: N-dodecyl-N′-[3-(dibutylamino)propyl]-malic acid diamide

(9) 114 g (0.85 mol) of malic acid, 156.96 g (0.85 mol) of dodecylamine and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 392 g of N-dodecyl-N′-[3-(dibutylamino)propyl]-malic acid diamide as a brownish solid.

Example 6: N-cocoyl-N′-[3-(dibutylamino)propyl]-malic acid diamide

(10) 114 g (0.85 mol) of malic acid, 166.14 g (0.85 mol) of cocoylamine (AN=287.15 mgKOH/g) and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 397 g of N-cocoyl-N′-[3-(dibutylamino)propyl]-malic acid diamide as a brownish solid.

Example 7: N-dodecyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide

(11) 127.58 g (0.85 mol) of tartaric acid, 156.96 g (0.85 mol) of dodecylamine and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 408 g of N-dodecyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide as a brownish solid.

Example 8: N-cocoyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide

(12) 127.58 g (0.85 mol) of tartaric acid, 166.14 g (0.85 mol) of cocoylamine (AN=287.15 mgKOH/g) and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 400 g of N-cocoyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide as a brownish solid.

Example 9: N-dodecyl-N′-[4-(dibutylamino)butyl]-succinic acid diamide

(13) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 170.31 g (0.85 mol) of N,N-dibutyl-butane-1,4-diamine were used to obtain 401 g of N-dodecyl-N′-[4-(dibutylamino)butyl]-succinic acid diamide as a brownish solid.

Example 10: N-dodecyl-N′-[2-(dibutylamino)ethyl]-succinic acid diamide

(14) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 146.48 g (0.85 mol) of N,N-dibutyl-ethane-1,2-diamine were used to obtain 363 g of N-dodecyl-N′-[2-(dibutylamino)ethyl]-succinic acid diamide as a brownish solid.

Example 11: N-dodecyl-N′-[3-(dibutylamino)propyl]-phthalic acid diamide

(15) 141.21 g (0.85 mol) of phthalic acid, 156.96 g (0.85 mol) of dodecylamine and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 407 g of N-dodecyl-N′-[3-(dibutylamino)propyl]-phthalic acid diamide as a brownish solid.

Example 12: N-dodecyl-N′-[3-(1-piperidyl)propyl]-succinic acid diamide

(16) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 167.34 g (0.85 mol) of 3-piperidinopropylamine were used to obtain 301 g of N-dodecyl-N′-[3-(1-piperidyl)propyl]-succinic acid diamide as a brownish solid.

Example 13: N-dodecyl-N′-[3-(4-methylpiperazin-1-yl]-succinic acid diamide

(17) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine and 185.00 g (0.85 mol) of 3-(4-methylpiperazin-1-yl)propylamine were used to obtain 301 g of N-dodecyl-N′-[3-(4-methylpiperazin-1-yl]-succinic acid diamide as a brownish solid.

Example 14: N-dodecyl-N-methyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide

(18) 100 g (0.85 mol) of succinic acid, 169.47 g (0.85 mol) of N-methyldodecylamine and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 390 g of N-dodecyl-N-methyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide as a brownish solid.

Example 15: N-dodecyl-N′-[3-(dibutylamino)propyl]-malonic acid diamide

(19) 100 g (0.96 mol) of malonic acid, 177.94 g (0.96 mol) of dodecylamine and 178.88 g (0.96 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 450 g of N-dodecyl-N′-[3-(dibutylamino)propyl]-malonic acid diamide as a brownish solid.

Example 16: N-[3-(Dibutylamino)-propyl]-N′-dodecyl-succinamide; Preparation in Xylene

(20) 100 g (0.85 mol) of succinic acid, 156.96 g (0.85 mol) of dodecylamine, xylene 415 g and 158.40 g (0.85 mol) of N,N-dibutyl-propane-1,3-diamine were used to obtain 379 g of a 50% active solution of N-[3-(dibutylamino)-propyl]-N′-dodecyl-succinamide in xylene.

General Method for the Preparation of N-alkyl-N′—(N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salts

(21) A reaction flask equipped with overhead stirrer, reflux condenser and thermometer was charged with equimolar amounts of an N-alkyl-N′—(N″,N″-dialkylaminoalkyl)dicarboxylic acid diamide synthesized in examples 1 to 16, the solvent and the acid given in examples 17 to 35. The temperature of the apparatus was increased to 50° C. and the mixture was gently stirred for 2 hours.

Example 17: N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate

(22) 100 g (0.22 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 3, 15.66 g (0.22 mol) acrylic acid and 115.66 g methanol were used to obtain 231.32 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate in methanol.

Example 18: N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acetate

(23) 100 g (0.22 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 3, 12.99 g (0.22 mol) acetic acid and 112.99 g methanol were used to obtain 126 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acetate in methanol.

Example 19: N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide dodecanoate

(24) 100 g (0.22 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 3, 44.07 g (0.22 mol) dodecanoic acid and 144.07 g methanol were used to obtain 288, 14 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide dodecanoate in methanol.

Example 20: N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide cocoate

(25) 100 g (0.22 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 3, 48.04 g (0.22 mol) coconut fatty acid and 148.04 g methanol were used to obtain 296.08 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide cocoate in methanol.

Example 21: N-cocoyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate

(26) 100 g (0.21 mol) of N-cocoyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 4, 15.13 g (0.21 mol) acrylic acid and 115.13 g methanol were used to obtain 130.26 g of a 50% active solution of N-cocoyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate in methanol.

Example 22: N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate

(27) 100 g (0.11 mol) of 50% active solution of N-dodecyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide in xylene according to example 15 and 7.83 g (0.11 mol) acrylic acid were used to obtain 107.83 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate in xylene.

Example 23: N-dodecyl-N′-[3-(dibutylammonium)propyl]-malic acid diamide acrylate

(28) 100 g (0.21 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-malic acid diamide according to example 5, 15.34 g (0.21 mol) acrylic acid and 115.34 g methanol were used to obtain 230.68 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-malic acid diamide acrylate in methanol.

Example 24: N-cocoyl-N′-[3-(dibutylammonium)propyl]-malic acid diamide acrylate

(29) 100 g (0.22 mol) of N-cocoyl-N′-[3-(dibutylamino)propyl]-malic acid diamide according to example 6, 15.85 g (0.22 mol) acrylic acid and 115.85 g methanol were used to obtain 231.7 g of a 50% active solution of N-cocoyl-N′-[3-(dibutylammonium)propyl]-malic acid diamide acrylate in methanol.

Example 25: N-dodecyl-N′-[3-(dibutylammonium)propyl]-tartaric acid diamide acrylate

(30) 100 g (0.21 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide according to example 7, 15.34 g (0.21 mol) acrylic acid and 115.34 g methanol were used to obtain 230.68 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-tartaric acid diamide acrylate in methanol.

Example 26: N-cocoyl-N′-[3-(dibutylammonium)propyl]-tartaric acid diamide acrylate

(31) 100 g (0.23 mol) of N-cocoyl-N′-[3-(dibutylamino)propyl]-tartaric acid diamide according to example 8, 16.57 g (0.23 mol) acrylic acid and 116.57 g methanol were used to obtain 233.14 g of a 50% active solution N-cocoyl-N′-[3-(dibutylammonium)propyl]-tartaric acid diamide acrylate in methanol.

Example 27: N-dodecyl-N′-[4-(dibutylammonium)butyl]-succinic acid diamide acrylate

(32) 100 g (0.26 mol) of N-dodecyl-N′-[4-(dibutylamino)butyl]-succinic acid diamide according to example 9, 18.72 g (0.26 mol) acrylic acid and 118.72 g methanol were used to obtain 237.44 g of a 50% active solution of N-dodecyl-N′-[4-(dibutylammonium)butyl]-succinic acid diamide acrylate in methanol.

Example 28: N-dodecyl-N′-[2-(dibutylammonium)ethyl]-succinic acid diamide acrylate

(33) 100 g (0.23 mol) of N-dodecyl-N′-[2-(dibutylamino)ethyl]-succinic acid diamide according to example 10, 16.38 g (0.23 mol) acrylic acid and 116.38 g methanol were used to obtain 232.77 g of a 50% active solution of N-dodecyl-N′-[2-(dibutylammonium)ethyl]-succinic acid diamide acrylate in methanol.

Example 29: N-dodecyl-N′-[3-(dimethylammonium)propyl]-succinic acid diamide acrylate

(34) 100 g (0.27 mol) of N-dodecyl-N′-[3-(dimethylamino)propyl]-succinic acid diamide according to example 1, 19.48 g (0.23 mol) acrylic acid and 119.48 g methanol were used to obtain 238.96 g of a 50% active solution of N-dodecyl-N′-[3-(dimethylammonium)propyl]-succinic acid diamide acrylate in methanol.

Example 30: N-dodecyl-N′-[6-(dimethylammonium)hexyl]-succinic acid diamide acrylate

(35) 100 g (0.25 mol) of N-dodecyl-N′-[6-(dimethylamino)hexyl]-succinic acid diamide according to example 2, 17.50 g (0.23 mol) acrylic acid and 117.50 g methanol were used to obtain 235 g of a 50% active solution of N-dodecyl-N′-[6-(dimethylammonium)hexyl]-succinic acid diamide acrylate in methanol.

Example 31: N-dodecyl-N′-[3-(1-piperidylium)propyl]-succinic acid diamide acrylate

(36) 100 g (0.24 mol) of N-dodecyl-N′-[3-(1-piperidyl)propyl]-succinic acid diamide according to example 12, 17.58 g (0.24 mol) acrylic acid and 117.58 g methanol were used to obtain 235.16 g of a 50% active solution of N-dodecyl-N′-[3-(1-piperidylium)propyl]-succinic acid diamide acrylate in methanol.

Example 32: N-dodecyl-N′-[3-(4-methylpiperazin-1-ylium]-succinic acid diamide acrylate

(37) 100 g (0.23 mol) of N-dodecyl-N′-[3-(4-methylpiperazin-1-yl]-succinic acid diamide according to example 13, 16.56 g (0.23 mol) acrylic acid and 116.56 g methanol were used to obtain 233.12 g of a 50% active solution of N-dodecyl-N′-[3-(4-methylpiperazin-1-ylium]-succinic acid diamide acrylate in methanol.

Example 33: N-dodecyl-N′-[3-(dibutylammonium)propyl]-phthalic acid diamide acrylate

(38) 100 g (0.20 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-phthalic acid diamide according to example 11, 14.40 g (0.20 mol) acrylic acid and 114.40 g methanol were used to obtain 228.8 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-phthalic acid diamide acrylate in methanol.

Example 34: N-dodecyl-N-methyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate

(39) 100 g (0.21 mol) of N-dodecyl-N-methyl-N′-[3-(dibutylamino)propyl]-succinic acid diamide according to example 14, 15.39 g (0.21 mol) acrylic acid and 115.39 g methanol were used to obtain 130.78 g of a 50% active solution of N-dodecyl-N-methyl-N′-[3-(dibutylammonium)propyl]-succinic acid diamide acrylate in methanol.

Example 35: N-dodecyl-N′-[3-(dibutylammonium)propyl]-malonic acid diamide acrylate

(40) 100 g (0.22 mol) of N-dodecyl-N′-[3-(dibutylamino)propyl]-malonic acid diamide according to example 15, 16.37 g (0.22 mol) acrylic acid and 116.37 g methanol were used to obtain 232.74 g of a 50% active solution of N-dodecyl-N′-[3-(dibutylammonium)propyl]-malonic acid diamide acrylate in methanol.

(41) TABLE-US-00001 TABLE 1 Characterization of inhibitors tested Example R A B R.sup.1 R.sup.2 R.sup.3 R.sup.4 R.sup.5 M.sup.− 17 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 18 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acetate 19 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H dodecanoate 20 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H cocoate 21 C.sub.8H.sub.17—C.sub.18H.sub.37 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 22 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 23 C.sub.12H.sub.25 CH(OH)—CH.sub.2 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 24 C.sub.8H.sub.17—C.sub.18H.sub.37 CH(OH)—CH.sub.2 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 25 C.sub.12H.sub.25 CH(OH)—CH(OH) C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 26 C.sub.8H.sub.17—C.sub.18H.sub.37 CH(OH)—CH(OH) C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 27 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.4H.sub.8 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 28 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.2H.sub.4 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 29 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H CH.sub.3 CH.sub.3 H H acrylate 30 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.6H.sub.12 H CH.sub.3 CH.sub.3 H H acrylate 31 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H 1-piperidyl H H acrylate 32 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 H 4-methyl- H H acrylate piperazin- 1-yl 33 C.sub.12H.sub.25 C.sub.6H.sub.4 C.sub.3H.sub.6 CH.sub.3 C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 34 C.sub.12H.sub.25 C.sub.2H.sub.4 C.sub.3H.sub.6 CH.sub.3 C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate 35 C.sub.12H.sub.25 CH.sub.2 C.sub.3H.sub.6 H C.sub.4H.sub.9 C.sub.4H.sub.9 H H acrylate

(42) To evaluate the performance of the presently disclosed N-alkyl-N′—(N″,N″-dialkylammoniumalkyl)dicarboxylic acid diamide salts (I) as low dose gas hydrate inhibitors, a rocking cell test was used. The rocking cell test is a commonly used test in the art for assessing the performance of anti-agglomerant chemistry. Briefly, additives are evaluated based on their ability to effectively minimize the size of hydrate particle agglomerates and then to disperse those particles into the hydrocarbon phase. The results were classified as “pass” or “fail” based on whether hydrate blockages were detected. Performance was evaluated by determining the minimum effective dose (MED) required to register as a “pass” in the rocking cell test. The effective dosages (MEDs) were screened for 5.0 wt % NaCl brine at 50 respectively 60 vol.-% watercut and 138 bar at 4° C.

(43) The rocking cell apparatus (“rack”) is comprised of a plurality of sapphire tubes, each placed within a stainless steel support cage. Each assembled sapphire tube and steel cage (hereby referred to as a rocking cell) is typically loaded with fluids containing a hydrocarbon fluid phase and a brine phase, along with a stainless steel ball for mixing. The rocking cell can withstand pressures of up to 200 bar (2900 psi). The rocking cell, once loaded with the fluids, is then mounted on the rack with gas injection and pressure monitoring. During testing, as the gases cooled and hydrates formed, the consumed gas was substituted via a high-pressure syringe pump to maintain the system at constant pressure.

(44) The rack was loaded with 10 rocking cells in a 2×5 configuration (two cells wide and 5 cells tall). The center position on the rack (between both cells) was fixed and allowed to rotate while the outer positions on the rack were moved vertically up and down. This vertical motion allowed the rocking cells to rotate into a positive or negative angle position. The steel ball placed inside the sapphire tube moved from one end of the cell to the other during a rocking motion. The rack rocked up and down at a rate of about 5 complete cycles (up and down) every minute. The rack was further contained within a temperature controlled bath attached to a chiller with temperature control from −10° C. to 60° C.

(45) The rocking cells were filled with three components: hydrocarbon, aqueous phase, and gas. First, each rocking sapphire tube was filled with 5 ml of dodecane and a 5 ml of 5% NaCl brine (watercut 50 vol.-%) respectively 4 ml of dodecane and 6 ml of 5% NaCl brine (watercut 60 vol.-%) for a total liquid loading of 50% total tube volume (20 mL total). The inhibitor was added as a 50 wt.-% active solution at dose rates in percent, by volume of water (vol.-%). Green Canyon gas was used for this testing with its composition given in Table 2.

(46) TABLE-US-00002 TABLE 2 Green Canyon gas composition Component Name Chemical Symbol Amount (mol-%) Nitrogen N.sub.2 0.14 Carbon Dioxide CO.sub.2 0 Methane C.sub.1 87.56 Ethane C.sub.2 7.6 Propane C.sub.3 3 i-Butane i-C.sub.4 0.5 n-Butane n-C.sub.4 0.8 i-Pentane i-C.sub.5 0.2 n-Pentane n-C.sub.5 0.2
Rocking Cell Test Procedure: A. Pretest Steps: Once the rack has been loaded with the rocking cells containing hydrocarbon fluid and brine, the rocking cells are evacuated with a vacuum pump for 15-20 minutes. While evacuating, the bath temperature is increased to the starting test temperature of 49° C. Once the bath has reached 49° C., the cells and the syringe pump are pressurized with Green Canyon gas to 138 bar and the syringe pump is switched on to maintain pressure during initial saturation. B. Saturation Step: The apparatus is set to rock at 5 rocks per minute for 2 hours to ensure the hydrocarbon fluids and brine loaded in the cell have been saturated with gas. This testing is performed at constant pressure and the syringe pump remains switched on and set at 138 bar for the remainder of the test. C: Cooling Step: While maintaining a rocking rate of 5 rocks per minute, the system is cooled from 49° C. to 4° C. over 6 hours. D. Steady State Mixing Step before Shut-in: At the constant temperature of 4° C., the apparatus is kept rocking at 5 rocks per minute for 12 hours to ensure complete hydrate formation. E. Shut-in Step: The apparatus is set to stop rocking and to set the cell position to horizontal and kept at a constant temperature of 4° C. for 12 hours. F. Steady State Mixing Step after Shut-in: At the conclusion of the shut in period, the apparatus is restarted at the rate of 5 rocks per minute at the constant temperature of 4° C. for 4 hours. G. Test Completion: At the conclusion of the experiment, the apparatus is set to stop rocking and the cells are set at a negative inclination to keep fluids away from the gas injection port. The chiller bath is set to 49° C. to melt any formed hydrates and allow for depressurization and cleaning.

(47) To determine the relative performance of each inhibitor or dose rate of inhibitor, visual observations were made during the shut in period and correlated with an interpretation of the time required for the ball within the cell to travel between two magnetic sensors. Each experiment was conducted in duplicate to confirm reproducibility. Table 2 below shows the results from some of the rocking cell tests.

(48) For comparison the following substances according to the state of the art were tested C1: N-[3-(Dibutylammonium)propyl]-cocoylamide acrylate according to WO 2005/042675 C2: The reaction product of N-(3-Dibutylamino-propyl)-N′-octadecyl-propanamide with acrylic acid according to WO 2016/069987. C3: N-(2-Dibutyl-2-methylammonium-ethyl)-tetrapropylenesuccinate methylsulfate according to example 5 of US 2004/163306

(49) TABLE-US-00003 TABLE 3 Test results as anti-agglomerant with a water-cut of 50 vol.-% Test Inhibitor MED (vol.-%) T1 Example 17 0.2% T2 Example 18 0.4% T3 Example 19 0.3% T4 Example 20 0.3% T5 Example 21 0.3% T6 Example 22 0.6% T7 Example 23 0.6% T8 Example 24 0.6% T9 Example 25 0.6% T10 Example 26 0.6% T11 Example 27 0.4% T12 Example 28 0.4% T13 Example 29 0.6% T14 Example 30 0.6% T15 Example 31 0.4% T16 Example 32 0.5% T17 Example 33 0.6% T18 Example 34 0.4% T19 Example 35 0.5% T20 (comp.) Example C1 0.7% T21 (comp.) Example C2 0.8% T22 (comp.) Example C3 0.9% MED = minimum effective dose; comp. = comparative, not according to the invention.

(50) TABLE-US-00004 TABLE 4 Test results as anti-agglomerant with a water-cut of 60 vol.-% Test Inhibitor MED (vol.-%) T23 Example 17 0.3% T24 Example 18 0.5% T25 Example 19 0.5% T26 Example 20 0.4% T27 Example 21 0.4% T28 Example 22 0.7% T29 Example 23 0.7% T30 Example 24 0.8% T31 Example 25 0.8% T32 Example 26 0.7% T33 Example 27 0.5% T34 Example 28 0.6% T35 Example 29 0.9% T36 Example 30 0.8% T37 Example 31 0.5% T38 Example 32 0.7% T39 Example 33 0.7% T40 Example 34 0.6% T41 Example 35 0.7% T42 (comp.) Example C1 1.1% T43 (comp.) Example C2 1.2% T44 (comp.) Example C3 1.5% MED = minimum effective dose; comp. = comparative, not according to the invention.

(51) In a further set of tests the temperature was set at 4° C. and the time in hours was measured for hydrates to form under isobaric conditions using the same dose rate of 0.6 vol.-% for all products (induction time)

(52) TABLE-US-00005 TABLE 5 Induction times at 4° C. Test Inhibitor Induction Time (Hours) T44 Example 17 20 T45 Example 18 12 T46 Example 19 12 T47 Example 20 15 T48 Example 21 16 T49 Example 22 12 T50 Example 23 10 T51 Example 24 12 T52 Example 25 12 T53 Example 26 10 T54 Example 27 12 T55 Example 28 12 T56 Example 29 9 T57 Example 30 10 T58 Example 31 13 T59 Example 32 10 T60 Example 33 12 T61 Example 34 15 T62 Example 35 18 T63 (comp.) Example C1 3 T64 (comp.) Example C2 2 T65 (comp.) Example C3 3

(53) As can be seen from the above test results, the products according to the invention show an improved performance over the gas hydrate inhibitors according to the state of the art. They require lower dosage rates even at raised water cuts and allow for longer shut-in times.