Patent Application
20150275377
This invention relates to novel nanoparticles of diquaternary Schiff dibases as corrosion inhibitors for protecting petro chemical equipment, pipelines, and steel plates against exposure to acidic fluids and to methods for making such inhibitors.
Acid solutions are extensively used in a variety of industrial processes such as oil well acidification, acid pickling and acidic cleaning [1]. This use leads to serious metallic corrosion. However, the addition of inhibitors is one of the more practical methods of corrosion protection. Among such inhibitors, heterocyclic organic compounds containing sulfur, phosphorus, oxygen, nitrogen and aromatic rings are somewhat effective and efficient inhibitors for the metals in acidic medium due to their molecular structure [2-4]. In many factors for the inhibiting effects, the planarity of heterocycles and the presence of lone pairs of electrons on heterocyclic atoms are particularly important structural characteristics because they mainly determine the adsorption of inhibitor molecules on metal surfaces [5-7]. On the other hand, the surface state and excess charge of the metal surface also affect the adsorption behavior of inhibitor molecules on metal surface [8].
Generally, the tendency to form a stronger coordination bond and consequently resulting in the high inhibition efficiency, increases in the following order O<N<S<P [9]. Nitrogen-containing organic compounds have been found to act as good corrosion inhibitors and their inhibition mechanism has been illustrated in terms of the number of lone electron pairs, the p orbital character of free electrons and the electron density around the nitrogen atom [4, 10-14]. Recently, benzimidazole and its derivatives have received considerable attention on the inhibition properties for metallic corrosion and have been demonstrated that they are excellent inhibitors for metals and alloys in acidic solution. Since the nitrogen atom and the aromatic ring in molecular structure facilitate the adsorption of compounds on the metallic surface [15-24]. However, the above compounds studied are of simple molecules and have only one hydrophilic and one hydrophobic group in their structure.
Several studies described synthesize and evaluation of different corrosion inhibitors, including aliphatic, aromatic and heterocyclic compounds and their tests in oilfields. The main target of these studies was the low concentration of these inhibitors and also the high efficiency. However, the target was not obtained by the needed efficiencies and concentrations. The recent trends are directed to the nanoparticles and their role in the increase of the efficiency of the chemical compounds in different applications. Silver, gold, zinc, cobalt and nickel nanoparticles were incorporated in the application of different compounds and also in the petroleum field protection processes.
A corrosion inhibitor for steel against exposure to acidic fluids comprises or consists of a mass of metallic nanoparticles and a diquaternary Schiff dibase loaded on the metallic nanoparticles. In a preferred embodiment of the invention, the metal nanoparticles are selected from the group consisting of silver, zinc, cobalt, manganese and mixtures thereof.
A further embodiment of the invention contemplates a method for synthesizing an efficient corrosion inhibitor for petroleum equipment, pipelines, joints and steel plates from a corrosion reaction with an acidic medium. The method comprises or consists of the following steps.
In a first step, 1 mole of acetyl acetone was reacted with 2 moles of 2-aminobenzoimidazole (1) and/or 2-aminobenzothiazole (2) in acetone as a solvent and in the presence of p-toluene sulphonic acid as a dehydrating agent.
A second step calls for removing water of reaction followed by a third step of changing a pH of the medium to alkaline at a pH of about 9 using a 1N—KOH alcoholic solution to produce a precipitate.
The fourth step calls for adding 2.1 moles of methyl iodide and reflexing for 6 hours. Two inhibitors, namely C21H22I2N6 and C21H23I2N4S2 having the following formulas.
Loading of the inhibitors on the silver, zinc, cobalt, nickel, gold and/or manganese nanoparticles was performed by the following: silver nitrate, zinc acetate, cobalt acetate, nickel acetate, potassium gold cyanide and/or manganese acetate were reduced using reducing agents (mainly citric acid and preferably trisodium citrate, TSC). The desired amount of the different salts is dissolved in bidistilled water and trisodium citrate (TSC) was mixed in molar ratio of 1 metal to 3 TSC. The mixture is heated at 75-85° C. for 2-4 h. Then, the corrosion inhibitor dissolved in bidistilled water and added portion wise to the reduced form of the metal solution. The ratio of inhibitor to metal particles is maintained at 1 metal to 2 inhibitors by molar amount and preferably 1 metal to 3 inhibitors by molar amount. The mixture is then mixed for 6 hours at 40° C. After that, the mixture is allowed to cool and the water is allowed to evaporate in open air. The precipitates are represented the different metal nanoparticles loaded by the inhibitors.
The two inventive compounds are produced by the same synthetic procedure as follows.
1 mole of acetyl acetone was reacted by two moles of 2-aminobenzoimidazole (1) and/or 2-aminobenzothiazole (2) in acetone as a solvent and in presence of p-toluene sulphonic acid as a dehydrating agent. The reaction was equipped by a suitable water trapping system to remove the produced water of reaction. After the water of the reaction was obtained, the pH of the medium was changed to alkaline at pH=9, using KOH alcoholic solution (1N—KOH). After the precipitation of the product, 2.1 mole of methyl iodide was added and the system was refluxed for 6 hours. The products of the two inhibitors were obtained as represented in Scheme 1 as provided.
The inhibitors can be loaded on silver, zinc, cobalt, nickel, gold or manganese nanoparticles to obtain nano-structured corrosion inhibitors which are more highly efficient than the parent inhibitors (efficiency=100%) in the acidic medium. Loading of the inhibitors on the silver, zinc, cobalt, nickel, gold and/or manganese nanoparticles was performed by the following: silver nitrate, zinc acetate, cobalt acetate, nickel acetate, potassium gold cyanide and/or manganese acetate were reduced using reducing agents (mainly citric acid and preferably trisodium citrate, TSC). The desired amount of the different salts is dissolved in bidistilled water and trisodium citrate (TSC) was mixed in molar ratio of 1 metal to 3 TSC. The mixture is heated at 75-85° C. for 2-4 h. Then, the corrosion inhibitor dissolved in bidistilled water and added portion wise to the reduced form of the metal solution. The ratio of inhibitor to metal nanoparticles is maintained at 1 metal to 2 inhibitors by molar amounts and preferably 1 metal to 3 inhibitors by molar amounts. The mixture is then mixed for 6 hours at 40° C. After that, the mixture is allowed to cool and the water is allowed to evaporate in open air. The precipitates are represented the different metal nanoparticles loaded by the inhibitors. The loading of the inhibitors on the metal nanoparticles increases the efficiency of the inhibitors.
In addition to the above, tests were also conducted on the inhibitory action of novel quaternary Schiff dibases on the acid dissolution of carbon steel in 1M hydrochloric acid solutions. An article by N. A. Negm, E. A. Badr, I. A. Aiad, M. F. Zaki and M. M. Said discloses corrosion inhibition of four diquarternary N,N-pentane-2,4-diylidenedipyridin-4-amine (NDSI), N,N-(3-benzylidenepentane-2,4-diylidene)dopyridin-4-amine (NBDSI), N,N-[3-(4-methoxybenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NMDSI) and N,N[3-(4-chlorobenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NCDSI) on carbon steel. Investigations were made by gravimetric measurements, polarization and electrochemical impedance spectroscopy (EIS). The effect of concentration and immersion time was studied. The results showed that the inhibitors are good inhibitors for corrosion reaction of carbon steel with exposure to acidic fluids showed that they obey Langmuir adsorption isotherm. Polarization curves showed their behavior as mixed-type inhibitors. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The disclosure of the aforementioned article are incorporated herein in their entirety by reference. As disclosed the experimental process includes the synthesis of the Schiff dibase (NDS).
Acetyl acetone and 3-aminopyridine in one to two molar ratio were condensed under reflux condition in dioxan (50 mL) as a solvent and in the presence of a dehydrating agent (how much) for 3 hours to produce a crystalline product of N,N-pentane-2,4-diylidenedipyridin-4-amine (NDS). The product was filtered off, recrystallized from methanol and dried in vacuum oven at 40° C.
The synthesized Schiff dibase was condensed with benzaldehyde, 4-methoxybenzaldehyde and/or 4-chlorobenzaldehyde under reflux conditions in ethanol for 3 hours. The produced Schiff dibases were N,N-(3-benzylidenepentane-2,4-diylidene)dopyridin-4-amine (NBDS), N,N-[3-(4-methoxybenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NMDS) and N,N[3-(4-chlorobenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NCDS).
The different inhibitors under investigation were synthesized by quaternization reaction between the synthesized Schiff dibases (NDS, NBDS, NMDS, NCDS) and excess amount of ethyl iodide under reflux condition in presence of acetone as a solvent for 6 hours. The reaction flask was then kept overnight to complete precipitation and then filtered off. The products were then recrystallized from acetone and dried under vacuum at 60° C. to obtain the desired diquaternary Schiff dibase inhibitors which are symbolized as (NDSI, NBDSI, NMDSI, NCDSI).
Tests were performed on carbon steel of the following composition (wt. %): 0.11% C, 0.45% Mn, 0.04% P, 0.05% S, 0.25% Si and the remainder is Fe.
The compounds listed above were loaded onto metallic nanoparticles as described above and tested. The test showed significant improvement of the compounds loaded on nanoparticles over the compounds themselves.
The inhibition efficiency tests were performed by a weight loss method showed inhibition efficiency at 85% in the presence of 50 ppm by weight of inhibitor CI-1 in 1 molar sulphuric acid and 80% in 1 molar hydrochloric acid. While, in the presence of 10 ppm by weight of CI-1 loaded on cobalt nanoparticles increased the efficiency to 99.7% in 1 molar sulphuric acid and similar result were obtained in the presence of 1 molar hydrochloric acid. Decreasing the amount of the CI-1 loaded on metal nanoparticles to 5 ppm by weight did not change the protection efficiency of the metal in the acidic medium of 1 molar sulphuric acid or 1 molar hydrochloric acid.
While the invention has been described in connection with its accompanying figures it should be recognized that changes and modifications may be made therein without departing from the scope of the claims.
