New additive for inhibiting acid corrosion and method of using the new additive

A method of making a new additive for inhibiting high temperature naphthenic acid corrosion, wherein said additive comprises polymeric ethylene oxide treated derivative of polyisobutylene thiophosphate ester having low phosphorous content, high thermal stability and low acidity, and is produced by a process comprising the steps of:

• (a) reacting high reactive polyisobutylene with maleic anhydride to form polyisobutylene succinic anhydride;
• (b) reacting said polyisobutylene succinic anhydride of step (a) with a compound selected from glycols or polyols or polymeric alcohols to form hydroxyl-terminated polyisobutenyl succinate ester;
• (c) reacting resultant reaction compound of step (b) with phosphorous pentasulphide, with various mole ratios of said hydroxyl-terminated polyisobutenyl succinic ester and phosphorous pentasulphide to form thiophosphate ester of polyisobutylene succinate ester;
• (d) reacting resultant reaction compound of step (c) with ethylene oxide to form ethylene oxide treated derivative of polyisobutylene thiophosphate ester, which is high temperature naphthenic acid corrosion inhibiting additive.