| In China,at least 3-5 million tons of waste oil can be produced every year.They will not only cause serious pollutions but also wasted of resources if they were discharge directly to the environment.At present,the waste oil was transferred to higher fatty acids and glycerol by catalytic decomposition firstly,and then detergent,biodiesel and other primary products were produced after the initial processing while the added value of these products were not high.Therefore,it had important economic benefit and social significance to research the manufacture of fine chemical products with high added value by waste oil.In this paper,waste oil was used as a raw material to react with o-phenylenediamine and its derivative by ammonolysis-cyclization reaction to synthesize three kinds of mixed aliphatic benzimidazoline corrosion inhibitors including 2-mixed fatty benzimidazole inhibitor(MFBI),1-methyl-2-mixed fatty benzimidazole(MMFBI)and 5-nitro-2-mixed fatty benzimidazole(NMFBI).Three kinds of products were characterized by IR spectrum.The performance of products corrosion inhibition on Q235 and N80 steel in hydrochloric acid system was shown by the methods of static weight loss and electrochemical polarization curves,and the contrast tests were carried out by comparing with corrosion inhibitor of imidazoline sold in the market.Scanning electron micrograph(SEM)was used to observe and analyze the surface of N80 steel,and adsorption kinetics and thermodynamics of the corrosion inhibitor on the metal surface were researched.The results were shown as follows:Waste oil was used as a raw material to react directly with o-phenylene-diamine by amidation-cyclization reaction to produce MFBI,and the synthetic process of the MFBI was optimized by inhibition rate as the evaluation index during orthogonal design experiment.The optimized synthetic conditions were as follows: The mole ratio between o-phenylenediamine and waste oil was 1:3.3,the temperature and time of acylation reaction were 160? and 6h,respectively.The cyclization time is 15 h.Waste oil was reacted respectively with N-methyl-o-phenylenediamine hydrochloride and 4-nitro-o-phenylenedi-amine to procude MMFBI and NMFBI according to modified synthetic process conditions.Three compounds have been successfully synthesized by analyzing the results of IR spectrum and physical parameter.The results of static weight loss method showed that three kinds of novel corrosion inhibitors had the good effect of corrosion inhibition for Q235 and N80 steel in 5% HCl,and the inhibition rate rised as the concentration increases of inhibitor while it decreased as elevated temperature.Within the scope of 30? to 70?,the inhibition rate of NMFBI for N80 steel was about 95% and performanced excellent high-temperature resistance.Under the same conditions,the anti-corrosion resistance of corrosion inhibitors for N80 steel was shown as follow: MMFBI> MFBI> NMFBI.The corrosion performance is comparable to the imidazoline inhibitor on the market by contrast experiment.The results of electrochemical polarization curves method showed that showed that both cathode and anode reaction were restrained to varying degrees,MMFBI and MFBI were belong to mixed-type inhibitor for restraining cathodic process while NMFBI acted as mixed-type inhibitor for restraining anodic process.The results of SEM image analysis showed that the three kinds of corrosion inhibitors formed a layer of adsorption film on the surface of N80 steel,but NMFBI with poor film forming ability.The results of adsorption kinetics and thermodynamics of the corrosion inhibitor on the metal surface showed that the reactions of three kinds of corrosion inhibitors on the surface of N80 steel accorded with isotherm model of Langmuir,and the adsorption process was spontaneous,including physical and chemical adsorption.However,the formation of adsorption film was an exothermic reaction. |
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