Claims:1. A corrosion inhibitor composition, said composition comprising:
(a) a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a Formula (I):
R4R3N-(R1-N)-(C=O)-CH2 -R2 ……Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
(b) a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
(c) an organic solvent in an amount ranging from 10% to 40% by weight of the composition.
2. The corrosion inhibitor composition as claimed in claim 1, wherein the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide.
3. The corrosion inhibitor composition as claimed in claim 1, wherein the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester.
4. The corrosion inhibitor composition as claimed in claim 1, wherein the organic solvent is selected from toluene, xylene and benzene.
5. A method of preparation of a corrosion inhibitor composition, said method comprising the steps of:
(a) contacting a fatty acid ester having Formula (II)
R5O-(C=O)-CH2 -R2 ……Formula (II)
wherein R2 represents a saturated or unsaturated hydrocarbon having C10-C20, and R5 represents a saturated or unsaturated hydrocarbon having C1-C10
with an azine compound having Formula (III)
R4R3N- NR1R6 ……Formula (III)
wherein R1, R3, R4 and R6 independently represents H or a saturated or unsaturated hydrocarbon
to obtain a fatty acid hydrazide having a Formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 ……Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20; and
(b) mixing the fatty acid hydrazide in an amount ranging from 1% to 10% with a vegetable oil being a fatty acid oil or a fatty acid in an amount ranging from 40% to 60% and an organic solvent in an amount ranging from 10% to 40% to produce the corrosion inhibitor composition.
6. The method as claimed in claim 5, wherein the fatty acid ester is selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate.
7. The method as claimed in claim 5, wherein the azine compound is selected from aceto-azine, hydrazine and alkyl substituted azine.
8. The method as claimed in claim 5, wherein the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester with the azine compound in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 30°C to 95°C for a time period ranging from 30 minutes to 12 hours.
9. The method as claimed in claim 5, wherein the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate with hydrazine hydrate in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 50°C to 85°C for a time period ranging from 3 hours to 9 hours.
10. A method of inhibiting corrosion on internal metal surface of a distillation unit, said method comprising the steps of:
(a) taking a corrosion inhibitor composition comprising:
(i) a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a Formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 …..Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
(ii) a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
(iii) an organic solvent in an amount ranging from 10% to 40% by weight of the composition; and
(b) exposing the internal metal surface of the distillation unit to about 1 ppm to about 1000 ppm of the corrosion inhibitor composition to effect inhibition of corrosion on the internal metal surface of the crude distillation unit.
11. The method as claimed in claim 10, wherein the internal metal surface of the distillation unit comprises internal metal surface of column overhead of any of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation unit.
12. The method as claimed in claim 10, wherein the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide.
13. The method as claimed in claim 10, wherein the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester.
14. The method as claimed in claim 10, wherein the organic solvent is selected from toluene, xylene and benzene.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates generally to the field of refinery processing of crude oil. Particularly, the present disclosure provides a corrosion inhibitor composition and method of inhibiting corrosion on internal metal surface of distillation units. Aspect of the present disclosure also provides a method of preparation of corrosion inhibitor composition. The corrosion inhibitor composition of the present disclosure affords superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Hydrocarbon feed stocks such as petroleum crudes, gas oil, etc. are subjected to various processes in order to isolate and separate different fractions of the feedstock. The lower boiling fractions, including naphtha, from which gasoline is derived, are recovered as an overhead fraction from the distillation column. The fractions with intermediate volatility are withdrawn from the distillation column as side-streams. Side-stream products include kerosene, jet fuel, diesel fuel, and gas oil. The overhead and side-stream products are typically cooled, condensed and sent to other units to be processed into final products.
[0004] The distillation equipments are liable to corrosive activity of acids such as HCl, H2S and organic acids. HCl, the most troublesome corrosive material, is formed by hydrolysis of calcium and magnesium chlorides originally present in crude oils. The problem of corrosion is caused by these acidic components as the water condenses in the overhead condensing system of distillation columns. The corrosive species viz. HCl, H2S, H3CO3 and organic acids, which are formed by hydrolysis of various metal salts in crude, accelerate the corrosion problem in overhead exchanger. The water condensate in the overhead condenser, highly contaminated with these corrosive species, reacts with the internal metal surface (e.g. steel) and accelerates the corrosion rate thereof. Hence, it is necessary to retard the corrosion with the use of corrosion inhibitors.
[0005] One of the conventional approach is to use different types of amines, including highly basic amines, to control or inhibit corrosion that ordinarily occurs at the point of initial condensation within or after the distillation unit. However, such methods utilizing the known amines have not been successful and specific problems have been reported in connection with the use of these amines for treating the initial condensate. For example, US patent No. 7,381,319 states that use of highly basic amines such as, morpholine, methoxypropylamine, ethylenediamine, monoethanolamine, hexamethylenediamine, etc. for treating the initial condensate has a problem that the resultant hydrochloride salts of these amines tend to form deposits in various parts of the distillation unit and thereby causes fouling and under-deposit corrosion problems.
[0006] Another approach to retard corrosion of internal surface of distillation units includes usage of film forming corrosion inhibitors, which can form protective film on metal surface. This film should preclude interaction of the corrosive ions with metal surface and retard the corrosion. Conventionally known film forming corrosion inhibitors are composed of amines, and condensation products of fatty acids with polyamines like imidazolines. US patents US8618027B2 and US9382467B2 disclose mixtures of substituted amines and fatty acids for use in a corrosion inhibitor formulation in oil and gas applications, the mixture being derived from a reaction between a complex mixture of alkanolamines with various fatty acids. However, such formulations suffer from several fold shortcomings and hence, have not been commercially successful.
[0007] In view of above, there exists a need for the corrosion inhibitor compositions that exhibits superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.

OBJECTS OF THE INVENTION
[0008] An object of the present invention is to provide a corrosion inhibitor composition.
[0009] Another object of the present invention is to provide a corrosion inhibitor composition that exhibits superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.
[0010] Another object of the present invention is to provide a corrosion inhibitor composition that is economical.
[0011] Another object of the present invention is to provide a corrosion inhibitor composition that exhibits better solubility in crude and light naphtha.
[0012] Another object of the present invention is to provide a corrosion inhibitor composition that is effective in inhibiting corrosion on carbon steel, stainless steel and copper at operating temperatures ranging from 0°C - 150°C.
[0013] Another object of the present invention is to provide a corrosion inhibitor composition that is effective in inhibiting corrosion in a wide chloride range of 0-20 ppm in crude and naphtha environments.
[0014] Further object of the present invention is to provide a method for preparation of a corrosion inhibitor composition.
[0015] Still further object of the present invention is to provide a method of inhibiting corrosion on internal metal surface of a distillation unit.

SUMMARY
[0016] The present disclosure relates generally to the field of refinery processing of crude oil. Particularly, the present disclosure provides a corrosion inhibitor composition and method of inhibiting corrosion on internal metal surface of distillation units. Aspect of the present disclosure also provides a method of preparation of corrosion inhibitor composition. The corrosion inhibitor composition of the present disclosure affords superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.
[0017] An aspect of the present disclosure provides a corrosion inhibitor composition, said composition comprising:
(a) a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a Formula (I):
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
(b) a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
(c) an organic solvent in an amount ranging from 10% to 40% by weight of the composition.
[0018] In an embodiment, the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide. In an embodiment, the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester. In an embodiment, the organic solvent is selected from toluene, xylene and benzene.
[0019] Another aspect of the present disclosure relates to a method of preparation of a corrosion inhibitor composition, said method comprising the steps of:
(a) contacting a fatty acid ester having formula (II)
R5O-(C=O)-CH2 -R2 Formula (II)
wherein R2 represents a saturated or unsaturated hydrocarbon having C10-C20, and R5 represents a saturated or unsaturated hydrocarbon having C1-C10
with an azine compound having formula (III)
R4R3N- NR1R6 Formula (III)
wherein R1, R3, R4 and R6 independently represents H or a saturated or unsaturated hydrocarbon
to obtain a fatty acid hydrazide having a formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20; and
(b) mixing the fatty acid hydrazide in an amount ranging from 1% to 10% with a vegetable oil being a fatty acid oil or a fatty acid in an amount ranging from 40% to 60% and an organic solvent in an amount ranging from 10% to 40% to produce the corrosion inhibitor composition.
[0020] In an embodiment, the fatty acid ester is selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate. In an embodiment, the azine compound is selected from aceto-azine, hydrazine and alkyl substituted azine. In an embodiment, the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester with the azine compound in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 30°C to 95°C for a time period ranging from 30 minutes to 12 hours. In an embodiment, the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate with hydrazine hydrate in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 50°C to 85°C for a time period ranging from 3 hours to 9 hours.
[0021] Another aspect of the present disclosure relates to a method of inhibiting corrosion on internal metal surface of a distillation unit, said method comprising the steps of:
(a) taking a corrosion inhibitor composition comprising:
a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
an organic solvent in an amount ranging from 10% to 40% by weight of the composition; and
(b) exposing the internal metal surface of the distillation unit to about 1 ppm to about 1000 ppm of the corrosion inhibitor composition to effect inhibition of corrosion on the internal metal surface of the crude distillation unit.
[0022] In an embodiment, the internal metal surface of the distillation unit comprises internal metal surface of column overhead of any of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation unit. In an embodiment, the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide. In an embodiment, the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester. In an embodiment, the organic solvent is selected from toluene, xylene and benzene.

BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0024] Figure 1 illustrates a Nyquist plot of Carbon Steel specimen in 20 ppm Chloride solution in the absence (shown in inset) and presence of the corrosion inhibitor composition of the present disclosure after 48 hours.
[0025] Figure 2A illustrates the impedance Bode plot and Figure 2B illustrates the phase angle Bode plot of Carbon Steel specimen in 20 ppm Chloride solution in the absence and presence of the corrosion inhibitor composition of the present disclosure after 48 hours.
[0026] Figure 3 illustrates an exemplary circuit diagram.
[0027] Figure 4 illustrates potentiodynamic polarization curves of carbon steel coupon in 20 ppm chloride environment in the absence and presence of filming corrosion inhibitor after 48 h in the potential ranging from -1.8 to +0.4 V vs. Ag/AgCl.
[0028] Figure 5 illustrates an exemplary graph of concentration/dosage of the corrosion inhibitor composition vs. corrosion rate.
[0029] Figure 6 illustrates an exemplary schematic showing dosing of corrosion inhibitor composition in atmospheric column (ADU).
[0030] Figure 7A and 7B illustrate graphs showing iron data in atmospheric column reflux drum and atmospheric column naphtha drum after injecting the corrosion inhibitor composition.
[0031] Figure 8 illustrates an exemplary schematic showing dosing of corrosion inhibitor composition in naphtha stabilizer unit (NSU).
[0032] Figure 9 illustrates a graph showing iron data in naphtha stabilizer unit reflux drum after injecting the corrosion inhibitor composition.
[0033] Figure 10 illustrates an exemplary schematic showing dosing of corrosion inhibitor composition in vacuum distillation unit (VDU).
[0034] Figure 11 illustrates a graph showing iron data in vacuum distillation unit reflux drum after injecting the corrosion inhibitor composition.

DETAILED DESCRIPTION
[0035] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0036] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0037] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0038] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0039] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0040] The present disclosure relates generally to the field of refinery processing of crude oil. Particularly, the present disclosure provides a corrosion inhibitor composition and method of inhibiting corrosion on internal metal surface of distillation units. Aspect of the present disclosure also provides a method of preparation of corrosion inhibitor composition. The corrosion inhibitor composition of the present disclosure affords superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.
[0041] An aspect of the present disclosure provides a corrosion inhibitor composition, said composition comprising:
(a) a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a Formula (I):
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
(b) a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
(c) an organic solvent in an amount ranging from 10% to 40% by weight of the composition.
[0042] In an embodiment, the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide.
[0043] In an embodiment, the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester.
[0044] In an embodiment, the organic solvent is selected from toluene, xylene and benzene.
[0045] The fatty acid hydrazide can be synthesized by reacting a fatty acid ester with an azine compound in presence of a solvent at a desired temperature (such as 30°C to 95°C) for a desired time period (such as 30 minutes to 12 hours). Alternatively, any other method, as would be known to or appreciated by a person skilled in the art, may be employed for synthesis of the fatty acid hydrazide. General reaction schematics showing synthesis of different fatty acid hydrazides are presented below:

[0046] Another aspect of the present disclosure relates to a method of preparation of a corrosion inhibitor composition, said method comprising the steps of:
(a) contacting a fatty acid ester having formula (II)
R5O-(C=O)-CH2 -R2 Formula (II)
wherein R2 represents a saturated or unsaturated hydrocarbon having C10-C20, and R5 represents a saturated or unsaturated hydrocarbon having C1-C10
with an azine compound having formula (III)
R4R3N- NR1R6 Formula (III)
wherein R1, R3, R4 and R6 independently represents H or a saturated or unsaturated hydrocarbon
to obtain a fatty acid hydrazide having a formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20; and
(b) mixing the fatty acid hydrazide in an amount ranging from 1% to 10% with a vegetable oil being a fatty acid oil or a fatty acid in an amount ranging from 40% to 60% and an organic solvent in an amount ranging from 10% to 40% to produce the corrosion inhibitor composition.
[0047] In an embodiment, the fatty acid ester is selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate.
[0048] In an embodiment, the azine compound is selected from aceto-azine, hydrazine and alkyl substituted azine.
[0049] In an embodiment, the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester with the azine compound in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 30°C to 95°C for a time period ranging from 30 minutes to 12 hours.
[0050] In an embodiment, the step of contacting the fatty acid ester with the azine compound comprises reacting the fatty acid ester selected from methyl oleate, methyl stearate, methyl palmate, methyl linoleate, methyl myristate and methyl ricinoleate with hydrazine hydrate in a molar ratio ranging from 1:1 to 2:1 in presence of a solvent at a temperature ranging from 50°C to 85°C for a time period ranging from 3 hours to 9 hours.
[0051] Another aspect of the present disclosure relates to a method of inhibiting corrosion on internal metal surface of a distillation unit, said method comprising the steps of:
(a) taking a corrosion inhibitor composition comprising:
a fatty acid hydrazide in an amount ranging from 1% to 10% by weight of the composition, said fatty acid hydrazide having a formula (I)
R4R3N-(R1-N)-(C=O)-CH2 -R2 Formula (I)
wherein R1, R3 and R4 independently represents H or a saturated or unsaturated hydrocarbon, and R2 represents a saturated or unsaturated hydrocarbon having C10-C20;
a vegetable oil being a fatty acid oil or a fatty acid ester in an amount ranging from 40% to 60% by weight of the composition; and
an organic solvent in an amount ranging from 10% to 40% by weight of the composition; and
(b) exposing the internal metal surface of the distillation unit to about 1 ppm to about 1000 ppm of the corrosion inhibitor composition to effect inhibition of corrosion on the internal metal surface of the crude distillation unit.
[0052] In an embodiment, the internal metal surface of the distillation unit comprises internal metal surface of column overhead of any of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation unit.
[0053] In an embodiment, the fatty acid hydrazide is selected from oleic acid hydrazide, linoleic acid hydrazide, myristic acid hydrazide, stearic acid hydrazide, palmitic acid hydrazide, and ricinoleic acid hydrazide.
[0054] In an embodiment, the vegetable oil is selected from castor oil, palm oil, soyabean oil, and methyl soya ester.
[0055] In an embodiment, the organic solvent is selected from toluene, xylene and benzene.
[0056] The composition and method of the present disclosure are effective in preventing corrosion of the metallurgies involved in crude, vacuum and naphtha overhead exchangers in petroleum refining processes, and are found to be suitable for corrosion prevention of metallurgies such as carbon steel, stainless steel and copper at wide operating temperatures ranging from about 0 oC to about 150 oC and at wide chloride range (e.g. 0-20 ppm) in crude and naphtha environments. The composition of the present disclosure functions effectively at a dosage as low as 1 to 10 ppm in crude, vacuum and naphtha overhead exchanger by mitigating the corrosion of these units.
[0057] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
[0058] Synthesis of Oleic Acid Hydrazide
[0059] One mole of methyl oleate was reacted with one mole of hydrazine hydrate at the temperature of about 70oC with constant stirring in the presence of methanol for about 6 hours. The product was then crystallized by alcohol and acetone. The compound yield was found to be about 80%.

[0060] Synthesis of Stearic Acid Hydrazide
[0061] One mole of methyl stearate was reacted with one mole of hydrazine hydrate at the temperature of about 70oC with constant stirring in the presence of methanol for about 6 hours. The product was then crystallized by alcohol and acetone. The compound yield was found to be about 80%.

[0062] Preparation of Corrosion inhibitor Compositions
[0063] Corrosion inhibitor composition 1 was prepared by mixing 1000 ppm oleic acid hydrazide with soyabean oil (vegetable oil) and xylene (ratio of soyabean oil : xylene was 3:2). The solubility of the oleic acid hydrazide in the above mixture (fatty acid + xylene) was found to be about 10%.
[0064] Corrosion inhibitor composition 2 was prepared by mixing 1000 ppm stearic acid hydrazide with soyabean oil (vegetable oil) and xylene (ratio of soyabean oil : xylene was 3:2). The solubility of the oleic acid hydrazide in the above mixture (fatty acid + xylene) was found to be about 8%.
[0065] Electrochemical Impedance Studies
[0066] Electrochemical impedance studies were carried out to optimize the concentration of corrosion inhibitor. The corrosion inhibitor composition 2 prepared above (containing stearic acid hydrazide, soyabean oil and xylene) with the concentration range 6 ppm was tested in 20 ppm HCl environment.
[0067] Figure 1 illustrates the Nyquist plot of Carbon Steel specimen in 20 ppm Chloride solution in the absence (shown in inset, denoted as Blank) and presence (denoted as Filming CI) of the corrosion inhibitor composition after 48 hours.
[0068] In Nyquist plots, in the absence of any corrosion inhibitor composition (denoted as Blank), has shown Warburg impedance, which is due to the presence of oxide film on the metal surface, whereas, in the presence of filming corrosion inhibitor (denoted as Filming CI), the Warburg impedance was completely absent. It infers the protective nature of corrosion inhibitor composition on metal surface.
[0069] Figure 2A illustrates the impedance Bode plot of Carbon Steel specimen in 20 ppm Chloride solution in the absence (denoted as Blank) and presence (denoted as Filming CI) of the corrosion inhibitor composition after 48 hours. Figure 2B illustrates the phase angle Bode plot of Carbon Steel specimen in 20 ppm Chloride solution in the absence (denoted as Blank) and presence (denoted as Filming CI) of the corrosion inhibitor composition after 48 hours. The corresponding impedance parameters are given in Table 1 below.

Inhibitor Conc.
(ppm) Rct
(k? cm2) Cdl
(µF cm-2) n1 RFilm
(k? cm2) CFilm
(µF cm-2) n2 Error
(%) IE
(%)
0 0.818 2.694 0.6134 0.020 2.9834 0.6165 0.1 --
20 26.61 0.404 0.8894 1.867 0.667 0.8676 0.1 96.92

[0070] In the impedance Bode plot (FIG. 2A), the impedance values were increased in the presence of corrosion inhibitor composition. In the phase angle Bode plot (FIG. 2B), the phase angle maximum was found to be 52O and it was present in lower frequency region when the corrosion inhibitor composition was absent. This infers the corrosive nature of the metal in 20 ppm chloride environment. In the presence of corrosion inhibitor composition, the phase angle maximum was increased to 72O and it was shifted to high frequency region. These results reveal the protective nature of the corrosion inhibitor composition on the metal surface. The electrochemical system may be modeled as consisting of metal/protective surface film/electrical double layer/electrolyte solution. Therefore, in the absence and presence of inhibitor, the equivalent circuit shown in Figure 3 was used. In Figure 3, Rs denotes Solution Resistance, Rct denotes Charge transfer resistance, CPEdl denotes Double layer Constant Phase element, RFilm denotes Film resistance, CPEFilm denotes Film Constant Phase Element, and W denotes Warburg impedance. The experimental data fitted with this equivalent circuit. It is interesting to note that both ??ct and ??Film are increased in the presence of the inhibitor composition. An increase in ??ct from 0.818 to 26.61 kO cm2 and an increase in ??Film from 0.02 to 1.867 kO cm2 was observed upon addition of corrosion inhibitor composition. Inhibition efficiencies were calculated from the ??ct values in the absence and presence of corrosion inhibitor composition using following equation:

[0071] In above equation, ??1ct and ??ct are the charge transfer resistances in the presence and absence of filming corrosion inhibitor, respectively. An IE% of 96.92% was observed in the presence of corrosion inhibitor. Both the (CPE)dl and (CPE)Film values reduced to extremely small values of 0.613 and 0.889 ??F cm-2, respectively in the presence of inhibitor composition, and the corresponding “??” values increased to 0.94 and 0.78, respectively. These results reveal that the concentration of corrosion inhibitor molecules in the protective film is increased and the Cu2O formation is much less. Corrosion inhibitor molecules replaced almost all the water molecules and the ions in the electrical double layer.
[0072] Figure 4 illustrates potentiodynamic polarization curves of carbon steel coupon in 20 ppm chloride environment in the absence and presence of filming corrosion inhibitor after 48 h in the potential ranging from -1.8 to +0.4 V vs. Ag/AgCl. The corresponding corrosion parameters are tabulated in Table 2 below:

Table 2. Corrosion parameters of carbon steel coupon immersed in 20 ppm chloride environment in the absence and presence of filming corrosion inhibitor after 48 h
Inhibitor Conc.
(ppm) Ecorr
(mV) icorr
(µF cm-2) ßa
(mV dec-1) ßc
(mV dec-1) IE
(%)
0 -1033 4.05 28.6 -32.5 --
20 -614.9 0.199 61.2 -34.8 95.09

[0073] The anodic polarization curve in the absence of inhibitor shows three distinct regions in between -1.0 V to -0.8V, namely, Tafel region at lower over potentials extending to the peak current density due to the dissolution of copper to Fe2+ ions, a region of decreasing current density until a minimum (??min) is reached due to the formation of FeCl2, and a region of the sudden increase in current density leading to a limiting value (??lim), due to the formation of FeCl3. In presence of corrosion inhibitor composition, these regions were completely absent and the anodic polarization curve was stable up to +0.4 V. It infers the absence of active dissolution of iron into the environment, which indicates protective nature of corrosion inhibitor composition. The corrosion potential (Ecorr) was found to be at -1.03 V, whereas in the presence of corrosion inhibitor, it was shifted to -0.615 V. The corrosion current density (icorr) in the absence of corrosion inhibitor was found to be 4.05 µF cm-2 and in the presence of corrosion inhibitor, it was reduced to 0.199 µF cm-2. The corrosion inhibition efficiencies calculated using equation below was found to be 95.09%.

wherein ??corr and ??1corr are the corrosion current densities in the absence and presence of corrosion inhibitor composition, respectively.
[0074] Weight-loss Studies
[0075] Different concentrations of corrosion inhibitor compositions were tested in 20:80 ratio of chloride and naphtha mixture at 120°C for 4 hours and weight-loss data were recorded for them. The results of the experiments are illustrated in Figure 5 and the results are tabulated in Table 3 below. From the results, it can be inferred that the corrosion inhibitor composition of the present disclosure are more effective than other commercially available inhibitors.
Table 3. Corrosion rates of carbon steel in 80:20 naphtha and chloride environment in the absence and presence of corrosion inhibitor composition
S. No. Inhibitor of present disclosure
Dosage (ppm) Corrosion Rate (MPY)
1 0 96.5
2 2 57.1
3 5 47
4 7 20.1
5 10 6

[0076] Refinery Trials in Atmospheric Distillation Unit (ADU)
[0077] The dosing of corrosion inhibitor composition in atmospheric column (ADU) was done before overhead condensers as shown in Figure 6. The iron data is presented in Figure 7A and 7B. For estimation of corrosion inhibitor performance, the iron content in boot waters of atmospheric column reflux drum and atmospheric column naphtha drum was calculated through lab experiments. During the trial, the iron content observed was well aligned with KPI (< 0.5 ppm) in ADU.
[0078] Refinery Trials in Naphtha Stabilizer Unit (NSU)
[0079] The dosing of corrosion inhibitor composition in naphtha stabilizer unit (NSU) was carried out as shown in Figure 8. The iron data is presented in Figure 9. For estimation of corrosion inhibitor performance, the iron content in boot waters of NSU was calculated through lab experiments. During the trial, the iron content observed was well aligned with KPI (< 0.5 ppm) in NSU.
[0080] Refinery Trials in Vacuum Distillation Unit (VDU)
[0081] The dosing of filming corrosion inhibitor in vacuum distillation unit (VDU) was carried out as shown in Figure 10. The iron data is presented in Figure 11. For estimation of corrosion inhibitor performance, the iron content in boot waters of VDU was calculated through lab experiments. During the trial, the iron content observed was well aligned with KPI (< 0.5 ppm) in VDU.
[0082] The corrosion inhibitor composition of the present disclosure exhibits good synergy between the components thereof, wherein the ingredients viz. fatty acid hydrazide, vegetable oil and organic solvent exhibit functional reciprocity there between affording the composition to exhibit the desired corrosion inhibitory activity. Particularly, it could be noted, during the experiments, that these constituents, when used alone, could not achieve the desired corrosion inhibitory activity and/or the concentration of fatty acid hydrazide, if used alone, needs to be significantly high (as compared to the concentration of fatty acid hydrazide present in the composition of the instant disclosure) to afford effective inhibition of corrosion of the internal metal surfaces, which is cost-prohibitive at the industrial level.
[0083] Although the subject matter has been described herein with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein. Furthermore, precise and systematic details on all above aspects are currently being made. Work is still underway on this invention. It will be obvious to those skilled in the art to make various changes, modifications and alterations to the invention described herein. To the extent that these various changes, modifications and alterations do not depart from the scope of the present invention, they are intended to be encompassed therein.

ADVANTAGES OF THE INVENTION
[0084] The present disclosure provides a corrosion inhibitor composition that exhibits superior efficacy in terms of inhibiting corrosion on internal metal surface of distillation units such as internal metal surface of column overhead of Crude Distillation Unit (CDU), Vacuum Distillation Unit (VDU), Naphtha Splitter Unit (NSU), and Hydrodesulfurization (HDS) unit of the distillation units.
[0085] The present disclosure provides a corrosion inhibitor composition that is economical.
[0086] The present disclosure provides a corrosion inhibitor composition that exhibits better solubility in crude and light naphtha.
[0087] The present disclosure provides a corrosion inhibitor composition that is effective in inhibiting corrosion on carbon steel, stainless steel and copper at operating temperatures ranging from 0°C - 150°C.
[0088] The present disclosure provides a corrosion inhibitor composition that is effective in inhibiting corrosion in a wide chloride range of 0-20 ppm in crude and naphtha environments.
[0089] The present disclosure provides a method for preparation of a corrosion inhibitor composition.
[0090] The present disclosure provides a method of inhibiting corrosion on internal metal surface of a distillation unit.