Synthesis Of Dissymmetric Bis-quaternary Ammonium With Imidazoline Ring And Study On Inhibitory Performance

Imidazoline and its derivatives is a kind of inhibitor with excellent inhibition performance due to their unique molecular structure in recent thirty years. In acid pickling industry imidazoline and its derivatives show good inhibition performance on carbon steel,brass and brass alloy,aluminum and aluminum alloy ; in oil gas exploring industry imidazoline and its derivatives can inhibit from gas corrosion of H2S,CO2 in oil and gas well; in refining industry imidazoline and its derivatives can inhibit from acid medium corrosion of HCl-H2S-H2O.Moreover, as a kind of compound which has not only broad application prospect but also good surface properties, excellent corrosion inhibition performance and good bactericidal properties, bis-quaternary ammonium is considered to be the most possible newly surfactants in 21st century. At present, explore and application of bis-quaternary ammonium have become a research hot spot at home and abroad .Therefore,in consideration of designing inhibitor molecule,by combine bis-quaternary ammonium structure with imidazoline, developing a kind of newly imidazoline bis-quaternary ammonium which have multi-adsorption centers,good water solubility, good surface properties, excellent corrosion inhibition performance has important significance.Based on above consideration,a newly inhibitor molecule--dissymmetric bis-quaternary ammonium was designed in this paper.with alkylimidazoline and N-(3-chloro-2-hydroxypropyl)-N,N-dimethyl alkylammonium chloride as materials dissymmetric bis-quaternary ammonium were successfully synthsied,the structures of intermediates and final product were characterized and the synthesis optimum conditions of three compounds were discussed;inhibitory performance of dissymmetric bis-quaternary ammonium for Q235 carbon steel in 1mol/L hydrochloric acid solution was invested by electrochemical test ,surface analysis and quantum chemical method . The main results are as follow:1. Adopting infrared spectrums,nuclear magnetism resonances and mass spectrum meaned to characterize structures of target compound and intermediate,the results indicate that target compound and intermediate are in conformity with their theory structures. Adopting single factor experiments to explore the optimized synthesis conditions of intermediates and final product respectively, the optimized synthesis conditions of alkylimidazoline: the molar ratio of long chain alkyl fatty acid and diethylene triamine was 1:1.1,cyclization reaction time was 8h, cyclization reaction temperature was 240℃, the content of water carrier was 30% of reaction compound mass,the yield of product was 86.30%;the optimized synthesis conditions of N-(3-chloro-2-hydroxypropyl) -N,N-dimethyl alkylammonium chloride: the molar ratio of N,N-dimethyl alkylamine and epichlorohydrin is 2:1, reaction time was 14h, reaction temperature was 45℃, the yield of product was 84.30%; the optimized synthesis conditions of dissymmetric bis-quaternary ammonium:reaction solvent was isopropanol, the content of reaction solvent was 40% of reaction compound mass, the molar ratio of alkylimidazoline and N-(3-chloro-2-hydroxypropyl)- N,N-dimethyl alkylammonium chloride was 1.1:1, reaction temperature was 80℃, the yield of product was 86.52%.2. Weight loss measurement, polarization tests, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy(SEM) were used to investigate the corrosion inhibition performance and the growth and decay situation of film formed on Q235 steel of dissymmetric bis-quaternary ammonium in 1mol/L hydrochloric acid solution.The results show that: dissymmetric bis-quaternary ammonium attain good inhibition on the corrosion of Q235 carbon steel in 1mol/L hydrochloric acid solution when adding different concentrations. The inhibitory efficiency increases with increasing of the inhibitor concentration and is up to 98.89% with addition of 50mg/L. With increasing of the inhibitor concentration self-corrosion potential has shifted to more positive potential compared to the uninhibited solution gradually, finally tended to be stable.with the passage time the corrosion velocity decreased rapidly, but the inhibition efficiency increased continually, compact inhibitor film formed on Q235 steel; adding 50mg/L and 200mg/L two concentrations, the inhibitor film can form in1h, has ability of auto-repaired and film forming rapidly. The film of 50mg/L inhibitor achieve the best effect in 144h,then stared to decay ,but the inhibition efficiency still to be 95.41% in 192h ,the result show inhibitor film can keep a good protect performance for a long time. Addition of 200mg/L inhibitor ,the quality and velocity of film forming were better than the film of 50mg/L .3. Quantum chemistry PM6 semi-empirical method was used to calculate dissymmetric bis-quaternary ammonium. The results show that: the optimized geometry of this compound that obtained by PM6 semi-empirical method showed that several heteroatoms adsorption centers perform a approximate plan surface which make for the adsorption of inhibitor molecule on the surface of Q235 carbon steel; this compound also has low energy of ELUMO, which is a good electron acceptor and agree with the structure of inhibitor molecule. Considering protonation effect and chloride ion characteristic adsorption of this compound applying in hydrochloric acid environment, inhibitor should have good inhibitory performance which is compatible with experiment results.