Nitrogen-containing anti-agglomerants for preserving the fluidity of fluids containing gas hydrates
The present invention relates to the use of a specific group of acylated nitrogen-containing compounds as anti-agglomerants for gas hydrates. The anti-agglomerants are surface active nitrogen-containing compounds with 1-7 nitrogen atoms, which compounds have at least two hydrophobic groups with 6-24 carbon atoms, and where the hydrophobic groups are connected to the remainder of the molecule by an amine moiety or an amide moiety, and which compounds have at least one C2-C5 acyl group; or a salt thereof. The invention also relates to a method for inhibiting the agglomeration of gas hydrates in a conduit, and compositions comprising the gas hydrate anti-agglomerant, a corrosion inhibitor and/or a paraffin deposition inhibitor.
1. A method for inhibiting agglomeration of gas hydrates formed in a mixture including hydrocarbons and water, the method comprising:
preparing a surface-active nitrogen-containing compound having the following general formula I
wherein R is H or a hydrocarbyl group having 2-24 carbon atoms, G is a hydrocarbyl group having 6-24 carbon atoms or E, whereby R and G are selected such that the compound has at least one hydrocarbyl group with 6-24 carbon atoms connected to a nitrogen atom; each E is independently H, CH3, —CH2CH3 or an acyl group —C(═O)Ri, wherein each —C(═O)R 1 is independently the acyl group having 2-24 carbon atoms; provided that at least one of the —C(═O)R 1 groups is the acyl group having 2-5 carbon atoms, and at least one —C(═O)R 1 is an acyl group having 6-24 carbon atoms; and provided that when both R is H, then there are at least two of —C(═O)R 1 that are the acyl group having 6-24 carbon atoms; m is 2 or 3; and a is a number from 1 to 3;
whereby in formula I E is selected such that the compound contains 2-7 amide groups, as an anti-agglomerant for gas hydrates; and
adding the surface-active nitrogen-containing compound to the mixture to inhibit agglomeration of the gas hydrates.
2. The method according to claim 1 wherein the anti-agglomerant has formula I, wherein a=2, m=2 and R=H; the groups, and wherein two of the groups E are the acyl groups having 6-24 carbon atoms and one E is the acyl group having 4 carbon atoms.
3. The method according to claim 1 wherein the anti-agglomerant has formula I, wherein a=3, m=2 and R=H; the group, and wherein two of the groups E are the acyl groups having 6-24 carbon atoms, one E is the acyl group having 2 carbon atoms and one E is the acyl group having 4 carbon atoms.
4. The method according to claim 1 wherein the anti-agglomerant has formula I, wherein a=1, m=3 and one R is the hydrocarbyl group having 8-24 carbon atoms; wherein G is E, and wherein one of E is the acyl group having 6-24 carbon atoms, one of E is the acyl group having 4 carbon atoms and one of E is the acyl group having 2 carbon atoms.
5. The method according to claim 1 wherein the anti-agglomerant has formula I, wherein a=1, m=3 and one R is the hydrocarbyl group having 8-24 carbon atoms; wherein G is E, and wherein one of E is the acyl group having 6-24 carbon atoms and two of E are the acyl groups having 4 carbon atoms.
6. The method according to claim 1 wherein the anti-agglomerant has formula I, wherein a=2, m=3 and one R is the hydrocarbyl group having 8-24 carbon atoms; wherein G is the hydrocarbyl group having 8-24 carbon atoms, and wherein G and R are situated on the same carbon atom; and two of E are the acyl groups having 4 carbon atoms and one of E is the acyl group having 2 carbon atoms.