Method for inhibiting gas hydrate by non-corrosive quaternary ammonium compounds

A method for inhibiting the formation of hydrocarbon hydrates comprising contacting a fluid including a mixture comprising water and hydrate-forming guest molecules at gas hydrate forming conditions with a quaternary ammonium hydroxide QOH or a quaternary ammonium compound QA, in which A is not a halogen atom, prepared by the following steps:

• i. a quaternary ammonium halide QX is reacted with a metal hydroxide M(OH)x, or with a metal salt MA, in a solvent comprising an alcohol, to form a quaternary ammonium hydroxide QOH, or a quaternary ammonium compound of formula QA, and metal halide MX;
• ii. optionally, the quaternary ammonium hydroxide QOH is reacted with an organic or inorganic acid AH which is different from a hydrogen halide to form the quaternary ammonium compound QA;
• the metal halide MX is removed from the reaction mixture deriving from i. or from ii. by phase separation after addition of water or of a water/solvent mixture, or by filtration.