Synthesis And Corrosion Inhibition Properties Of Novel Imidazolinyl And Benzimidazolyl Borate Derivatives

So far,the resource utilization and recycling methods for the waste oil are mainly the hydrolysis of the waste oil to produce higher fatty acids,which are then processed into chemical raw materials,soaps,and biological raw materials.However,the utilization rate of glycerol is generally low.In this paper,high-efficiency is obtained by using glycerin,a by-product of hydrolysis of waste oil,as a kind of imidazoline and benzimidazole-based corrosion inhibitor.In this paper,glycerol,a by-product of hydrolysis of waste oil,was used as raw material to synthesize diglyceride borate with boric acid,and then 2,2,6,6-tetramethylpiperidine-nitrogen-oxide(TEMPO)and sodium bromide were used as catalysts.The sodium diborate is catalytically oxidized to a boronic acid diglyceride intermediate using sodium hypochlorite as an oxidizing agent.The intermediate is then reacted with ethylenediamine,diethylenetriamine,?-hydroxyethylethylenediamine,o-phenylenediamine,N-methyl-o-phenylenediamine hydrochloride,and stepwise heating method(one-pot method)Xylene is a water-carrying agent,and five novel imidazoline corrosion inhibitors are synthesized by amidation-cyclization dehydration condensation.They are:bis(2-imidazolinyl)ethylene glycol borate(jia-1),bis(1-N-aminoethyl-2-imidazolinyl)ethylene glycol borate(jia-2),bis(1-N-?-hydroxyethyl-2-imidazolinyl)ethylene glycol borate(jia-3),bis(2-benzimidazolyl)ethylene glycol borate(jia-4)),bis(1-N-methyl-2-benzimidazolyl)ethylene glycol borate(jia-5).The optimal synthesis conditions of the five corrosion inhibitors were optimized by orthogonal experiments.The structure of the new compounds was characterized by infrared spectroscopy,ultraviolet spectroscopy,nuclear magnetic resonance spectroscopy,mass spectrometry and elemental analysis.The corrosion inhibition performance of five corrosion inhibitors on Q235 carbon steel in hydrochloric acid medium was studied by static weight loss method.The effects of corrosion inhibitor concentration,corrosion time and temperature on the corrosion inhibition effect were discussed.The results showed that in the 5%HCl pickling solution,when the concentration of the five compounds was 100 mg/L,the maximum corrosion inhibition rate was over 97%at 60? and 6 h corrosion time;The order of corrosion inhibition ability of the chemical on Q235 acid corrosion is:jia-2>jia-1>jia-3>jia-4>jia-5,indicating thatWhen the corrosion inhibitor molecule contains an amine ethyl group,the better the corrosion inhibition ability.Comparative tests show that the new corrosion inhibitor has better corrosion inhibition effect than the commercially available water-soluble imidazoline,and the corrosion inhibition rate is increased by 1%to 4%.The polarization curves and alternating current impedance spectroscopy(EIS)of five new corrosion inhibitors were determined using an electrochemical workstation.It can be seen from the polarization curve that the corrosion current density of Q235 steel decreases with the increase of the concentration of corrosion inhibitor,and the five corrosion inhibitors are corrosion inhibitors mainly for suppressing the cathode.It can be seen from the AC impedance spectrum that the Nyquist plot exhibits a single time constant of the diffuse capacitance arc resistance,and the solution resistance and charge transfer resistor increase significantly after the addition of five corrosion inhibitors.As the concentration of the corrosion inhibitor increases,the radius of the capacitive anti-arc is larger,and the corrosion inhibition effect is better.The corrosion inhibition results obtained by electrochemistry are consistent with the static weight loss method.The results of adsorption behavior study show that the adsorption behavior of corrosion inhibitor molecules on the surface of Q235 steel conforms to the Langmuir adsorption isotherm.The calculated ?G~0 ads are negative values,and the absolute value is greater than40kJ/mol,indicating that the adsorption process is spontaneous,which is mainly chemical adsorption.The adsorption of the five corrosion inhibitors on the surface of Q235 is mainly chemical adsorption by covalent bond formation by charge sharing or transfer.Scanning electron microscopy(SEM)was used to observe the surface morphology after metal corrosion.Morphological observations show that the five corrosion inhibitors are all adsorption film type corrosion inhibitors.