Hydrogen sulphide and mercaptans scavenging compositions

1. A composition for scavenging hydrogen sulphide and mercaptans from hydrocarbon streams, said composition comprising at least an oxazolidine compound and at least an additive comprising at least one reaction product of a poly(C2-20-carboxylic acid) having at least one tertiary amino group with secondary amines, wherein the composition comprises from 50 to 99% wt of oxazolidine compound(s) and from 1 to 50% wt of said additive(s), based on the total weight of the composition,

wherein the oxazolidine compound is a bisoxazolidine compound,

wherein the oxazolidine compound has a structure of formula (I):

wherein

n is an integer ranging from 1 to 6;

R1 and R2, identical or different, are selected from a hydrogen atom and a linear, branched or cyclic alkyl or alkenyl groups having from 1 to 6 carbon atoms, and wherein the additive is an amide, an amidoammonium salt or ammonium salt, or a mixture thereof, of aminoalkanecarboxylic acids of formulae (II) or (III):

where

X is a radical of 1 to 19 carbon atoms, and

Y is a straight-chain or branched alkylene of 2 to 6 carbon atoms.

2. The composition according to claim 1 , wherein the weight ratio of bisoxazolidine compound(s) to said additive(s) ranges from 1 to 100.

3. The composition according to claim 1 , further comprising a solvent.

4. The composition according to claim 3 , wherein the solvent is present in an amount ranging from 1 to 80% wt, based on the total weight of the composition.

5. The composition according to claim 1 , comprising:

From 19 to 80% wt of bisoxazolidine compound(s),

From 1 to 30% wt of said additive(s), and

From 1 to 80% wt of solvent(s),

based on the total weight of the composition.

6. Process for improving the efficiency of a bisoxazolidine compound for scavenging hydrogen sulphide and/or mercaptans in hydrocarbon streams, the process comprising a step of adding the additive defined in claim 1 in a bisoxazolidine compound.

7. Hydrocarbon stream comprising hydrocarbons and a composition according to claim 1 .

8. Hydrocarbon stream according to claim 7 , wherein the hydrocarbons are selected from crude oil, fuel oil, fuel, Light Petroleum Gas and natural gas.

9. A method for scavenging hydrogen sulphide and/or mercaptan in hydrocarbon streams, comprising contacting the hydrocarbon stream with the composition according to claim 1 .

10. The method according to claim 9 , wherein the weight ratio between hydrogen sulphide contained in the hydrocarbon stream before the step of contacting and the composition ranges from 1:2 to 1:0.05.

11. The composition according to claim 1 , wherein the polycarboxylic acid contains 3 to 12 carboxyl groups.

12. The composition according to claim 1 , wherein the polycarboxylic acid contains 3 to 5 carboxyl groups.

13. The composition according to claim 1 , wherein the secondary amines are of the formula HNR 2 , wherein R radicals are independently straight-chain alkyl radicals having from 10 to 30 carbon atoms.

14. The composition according to claim 1 , wherein the secondary amines are of the formula HNR 2 , wherein R radicals are independently straight-chain alkyl radicals having from 14 to 24 carbon atoms.