FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Provisional Specification
(See section 10 and rule 13)
An Effective Novel Non - Polymeric And Non - Fouling Additive For Inhibiting High - Temperature Naphthenic Acid Corrosion And Method Of Using The Same
Dorf Ketal Chemicals (I) Pvt. Ltd
Dorf Ketal Tower, D'monte Street, Orlem, Malad (W), Mumbai, 400064 Maharashtra
State, India
An Indian company registered under the Companies Act, 1956

The following specification describes the invention:
1 5 APR 2009

AN EFFECTIVE NOVEL NON - POLYMERIC AND NON - FOULING ADDITIVE FOR INHIBITING HIGH - TEMPERATURE NAPHTHENIC ACID CORROSION AND METHOD OF USING THE SAME
FIELD OF THE INVENTION
The present invention relates to the inhibition of metal corrosion in acidic hot hydrocarbons and particularly to he inhibition of corrosion of iron - containing metals in hot acidic hydrocarbons, especially when the acidity is derived from the presence of naphthenic acid and more particularly to an effective non- polymeric and non- fouling additive to effect corrosion inhibition and a method of using the same.
DISCUSSION OF PRIOR ART
It is widely known in the art that the processing of crude oil and its various fractions has led to damage to piping and other associated equipment due to naphthenic acid corrosion. These are corrosive to the equipment used to distill, extract, transport and process the crudes. Generally speaking, naphthenic acid corrosion occurs when the crude being processed has a neutralization number or total acid number (TAN), expressed as the milligrams of potassium hydroxide required to neutralize the acids in a one gram sample, above 0.2. It is also known that naphthenic acid-containing hydrocarbon is at a temperature between about 200°C and 400°C (approximately 400°F -750°F), and also when fluid velocities are high or liquid impinges on process surfaces e.g. in transfer lines, return bends and restricted flow areas.
Corrosion problems in petroleum refining operations associated with naphthenic acid constituents and sulfur compounds in crude oils have been recognized for many years. Such' corrosion is particularly severe in atmospheric and vacuum

distillation units at temperatures between 400°F and 790°F. Other factors that contribute to the corrosivity of crudes containing naphthenic acids include the amount of naphthenic acid present, the concentration of sulfur compounds, the velocity and turbulence of the flow stream in the units, and the location in the unit (e.g., liquid/vapor interface).
As commonly used, naphthenic acid is a collective term for certain organic acids present in various crude oils. Although there may be present minor amounts of other organic acids, it is understood that the majority of the acids in naphthenic based crude are naphthenic in character, i.e., with a saturated ring structure as follows:


COOH
The molecular weight of naphthenic acid can extend over a large range. However, the majority of the naphthenic acid from crude oils is found in gas oil and light lubricating oil. When hydrocarbons containing such naphthenic acid contact iron-containing metals, especially at elevated temperatures, severe corrosion problems arise.
Naphthenic acid corrosion has plagued the refining industry for many years. This corroding material consists of predominantly monocyclic or bicyclic carboxylic acids with a boiling range between 350° and 650°F. These acids tend to concentrate in the heavier fractions during crude distillation. Thus, locations such as the furnace tubing, transfer lines, fractionating tower internals, feed and reflux sections of columns, heat exchangers, tray bottoms and condensers are primary sites of attack for naphthenic acid. Additionally, when crude stocks high in naphthenic acids are processed, severe corrosion can occur in the carbon steel or ferritic steel furnace tubes and tower bottoms. Recently interest has grown in the

control of this type of corrosion in hydrocarbon processing units due to the presence of naphthenic acid in crudes from locations such as China, India, Africa and Europe.
Crude oils are hydrocarbon mixtures which have a range of molecular structures and consequent range of physical properties. The physical properties of naphthenic acids which may be contained in the hydrocarbon mixtures also vary with the changes in molecular weight, as well as the source of oil containing the acid. Therefore, characterization and behavior of these acids are not well understood. A well known method used to "quantify" the acid concentration in crude oil has been a KOH titration of the oil. The oil is titrated with KOH, a strong base, to an end point which assures that all acids in the sample have been neutralized. The unit of this titration is mg. of KOH/gram of sample and is referred to as the "Total Acid Number" (TAN) or Neutralization Number. Both terms are used interchangeably in the application.
The unit of TAN is commonly used since it is not possible to calculate the acidity of the oil in terms of moles of acid, or any other of the usual analytical terms for acid content. Refiners have used TAN as a general guideline for predicting naphthenic acid corrosion. For example, many refineries blend their crude to a TAN=0.5 assuming that at these concentrations naphthenic acid corrosion will not occur. However, this measure has been unsuccessful in preventing corrosion by naphthenic acid.
Naphthenic acid corrosion is very temperature dependent. The generally accepted temperature range for this corrosion is between 205°C and 400°C (400°F and 750°F). Corrosion attack by these acids below 205°C has not yet been reported in the published literature. As to the upper boundary, data suggests that corrosion rates reach a maximum at about 600°-700°F and then begin to diminish.

The concentration and velocity of the acid/oil mixture are also important factors which influence naphthenic acid corrosion. This is evidenced by the appearance of the surfaces affected by naphthenic acid corrosion. The manner of corrosion can be deduced from the patterns and color variations in the corroded surfaces. Under some conditions, the metal surface is uniformly thinned. Thinned areas also occur when condensed acid runs down the wall of a vessel. Alternatively, in the presence of naphthenic acid pitting occurs, often in piping or at welds. Usually the metal outside the pit is covered with a heavy, black sulfide film, while the surface of the pit is bright metal or has only a thin, grey to black film covering it. Moreover, another pattern of corrosion is erosion-corrosion, which has a characteristic pattern of gouges with sharp edges. The surface appears clean, with no visible by-products. The pattern of metal corrosion is indicative of the fluid flow within the system, since increased contact with surfaces allows for a greater amount of corrosion to take place. Therefore, corrosion patterns provide information as to the method of corrosion which has taken place. Also, the more complex the corrosion, i.e., in increasing complexity from uniform to pitting to erosion-corrosion, the lower is the TAN value which triggers the behavior.
The information provided by corrosion patterns indicates whether naphthenic acid is the corroding agent, or rather if the process of corrosion occurs as a result of attack by sulfur. Most crude contain hydrogen sulfide, and therefore readily form iron sulfide films on carbon steel. In all cases that have been observed in the laboratory or in the field, metal surfaces have been covered with a film of some sort. In the presence of hydrogen sulfide the film formed is invariably iron sulfide, while in the few cases where tests have been run in sulfur free conditions, the metal is covered with iron oxide, as there is always enough water or oxygen present to produce a thin film on the metal coupons.
Tests utilized to determine the extent of corrosion may also serve as indicators of

the type of corrosion occurring within a particular hydrocarbon treating unit. Metal coupons can be inserted into the system. As they are corroded, they lose material. This weight loss is recorded in units of mg/cm.sup.2. Thereafter, the corrosion rate can be determined from weight loss measurements. Then the ratio of corrosion rate to corrosion product (mpy/mg/cm.sup.2) is calculated. This is a further indicator of the type of corrosion process which has taken place, for if this ratio is less than 10, it has been found that there is little or no contribution of naphthenic acid to the corrosion process. However, if the ratio exceeds 10, then naphthenic acid is a significant contributor to the corrosion process.
Distinguishing between sulfidation attack and corrosion caused by naphthenic acid is important, since different remedies are required depending upon the corroding agent. Usually, retardation of corrosion caused by sulfur compounds at elevated temperatures is effected by increasing the amount of chromium in the alloy which is used in the hydrocarbon treating unit. A range of alloys may be employed, from 1.25% Cr to 12% Cr, or perhaps even higher. Unfortunately, these show little to no resistance to naphthenic acid. To compensate for the corroding effects of sulfur and naphthenic acid, an austenitic stainless steel which contains at least 2.5% molybdenum, must be utilized. The corrosive problem is known to be aggravated by the elevated temperatures necessary to refine and crack the oil and by the oil's acidity which is caused primarily by high levels of naphthenic acid indigenous to the crudes.Naphthenic acids is corrosive between the ranges of about I75°C to 420°C. At the higher temperatures the naphthenic acids are in the vapor phase and at the lower temperatures the corrosion rate is not serious. The corrosivity of naphthenic acids appears to be exceptionally serious in the presence of sulfide compounds, such as hydrogen sulfide, mercaptans, elemental sulfur, sulfides, disulfides, polysulfides and thiophenols. Corrosion due to sulfur compounds becomes significant at temperatures as low as 450°F. The catalytic generation of hydrogen sulfide by thermal decomposition of mercaptans has been identified as a cause of sulfidic corrosion.

Sulfur in the crudes, which produces hydrogen sulfide at higher temperatures, also aggravates the problem. The temperature range of primary interest for this type of corrosion is in the range of about 175°C to about 400°C, especially about 205°C to about 400°C.
Various approaches to controlling naphthenic acid corrosion have included neutralization and/or removal of naphthenic acids from the crude being processed; blending low acid number oils with corrosive high acid number oils to reduce the overall neutralization number; and the use of relatively expensive corrosion-resistant alloys in the construction of the piping and associated equipment. These attempts are generally disadvantageous in that they require additional processing and/or add substantial costs to treatment of the crude oil. Alternatively, various amine and amide based corrosion inhibitors are commercially available, but these are generally ineffective in the high temperature environment of naphthenic acid corrosion. Naphthenic acid corrosion is readily distinguished from conventional fouling problems such as coking and polymer deposition which can occur in ethylene cracking and other hydrocarbon processing reactions using petroleum based feedstocks. Naphthenic acid corrosion produces a characteristic grooving of the metal in contact with the corrosive stream. In contrast, coke deposits generally have corrosive effects due to carburization, erosion and metal dusting.
Because these approaches have not been entirely satisfactory, the accepted approach in the industry is to construct the distillation unit, or the portions exposed to naphthenic acid/sulfur corrosion, with the resistant metals such as high quality stainless steel or alloys containing higher amounts of chromium and molybdenum. The installation of corrosion - resistant alloys is capital intensive, as alloys such as 304 and 316 stainless steels are several times the cost of carbon steel. However, in units not so constructed there is a need to provide inhibition treatment against this type of corrosion. The prior art corrosion inhibitors for

naphthenic acid environments include nitrogen-based filming corrosion inhibitors. However, these corrosion inhibitors are relatively ineffective in the high temperature environment of naphthenic acid oils.
While various corrosion inhibitors are known in various arts, the efficacy and usefulness of any particular corrosion inhibitor is dependent on the particular circumstances in which it is applied. Thus, efficacy or usefulness under one set of circumstances often does not imply the same for another set of circumstances. As a result, a large number of corrosion inhibitors have been developed and are in use for application to various systems depending on the medium treated, the type of surface that is susceptible to the corrosion, the type of corrosion encountered, and the conditions to which the medium is exposed. For example, U.S. Pat. No. 3,909,447 describes certain corrosion inhibitors as useful against corrosion in relatively low temperature oxygenated aqueous systems such as water floods, cooling towers, drilling muds, air drilling and auto radiator systems. That patent also notes that many corrosion inhibitors capable of performing in non-aqueous systems and/or non-oxygenated systems perform poorly in aqueous and/or oxygenated systems. The reverse is true as well. The mere fact that an inhibitor that has shown efficacy in oxygenated aqueous systems does not suggest that it would show efficacy in a hydrocarbon. Moreover, the mere fact that an inhibitor has been efficacious at relatively low temperatures does not indicate that it would be efficacious at elevated temperatures. In fact, it is common for inhibitors that are very effective at relatively low temperatures to become ineffective at temperatures such as the 175°C to 400°C encountered in oil refining. At such temperatures, corrosion is notoriously troublesome and difficult to alleviate. Thus, U.S. Pat. No. 3,909,447 contains no teaching or suggestion that it would be effective in non¬aqueous systems such as hydrocarbon fluids, especially hot hydrocarbon fluids. Nor is there any indication in U.S. Pat. No. 3,909,447 that the compounds disclosed therein would be effective against naphthenic acid corrosion under such conditions.

Atmospheric and vacuum distillation systems are subject to naphthenic acid corrosion when processing certain crude oils. Currently used treatments are thermally reactive at use temperatures. In the case of phosphorus-based inhibitors, this is thought to lead to a metal phosphate surface film. The film is more resistant to naphthenic acid corrosion than the base steel. These inhibitors are relatively volatile and exhibit fairly narrow distillation ranges. They are fed into a column above or below the point of corrosion depending on the temperature range. Polysulfide inhibitors decompose into complex mixtures of higher and lower polysulfides and, perhaps, elemental sulfur and mercaptans. Thus, the volatility and protection offered is not predictable.
The problems caused by naphthenic acid corrosion in refineries and the prior art solutions to that problem have been described at length in the literature, the following of which are representative:
U.S. Pat. No. 3,531,394 to Koszman described the use of phosphorus and/or bismuth compounds in the cracking zone of petroleum steam furnaces to inhibit coke formation on the furnace tube walls.
U.S. Pat. No. 3,531,394 to Koszman described the use of phosphorus and/or bismuth compounds in the cracking zone of petroleum steam furnaces to inhibit coke formation on the furnace tube walls.
U.S. Pat. No. 4,024,049 to Shell et al discloses compounds substantially as described and claimed herein for use as refinery antifoulants. While effective as antifoulant materials, materials of this type have not heretofore been used as corrosion inhibitors in the manner set forth herein. While this reference teaches the addition of thiophosphate esters such as those used in the subject invention to the incoming feed, due to the non-volatile nature of the ester materials they do not

distill into the column to protect the column, the pumparound piping, or further process steps. The inventor has found that by injecting the thiophosphate esters as taught herein, surprising activity is obtained in preventing the occurrence of naphthenic acid corrosion in distillation columns, pumparound piping, and associated equipment.
U.S. Pat. No. 4,105,540 to Weinland describes phosphorus containing compounds as antifoulant additives in ethylene cracking furnaces. The phosphorus compounds employed are mono- and di-ester phosphate and phosphite compounds having at least one hydrogen moiety complexed with an amine.
U.S. Pat. No. 4,443,609 discloses certain tetrahydrothiazole phosphonic acids and esters as being useful as acid corrosion inhibitors. Such inhibitors can be prepared by reacting certain 2,5-dihydrothiazoles with a dialkyl phosphite. While these tetrahydrothiazole phosphonic acids or esters have good corrosion and inhibition properties, they tend to break down during high temperature applications thereof with possible emission of obnoxious and toxic substances.
It is also known that phosphorus-containing compounds impair the function of various catalysts used to treat crude oil, e.g., in fixed-bed hydrotreaters and hydrocracking units. Crude oil processors are often in a quandary since if the phosphite stabilizer is not used, then iron can accumulate in the hydrocarbon up to 10 to 20 ppm and impair the catalyst. Although nonphosphorus-containing inhibitors are commercially available, they are generally less effective than the phosphorus-containing compounds.
U.S. Pat. No. 4,542,253 to Kaplan et al, described an improved method of reducing fouling and corrosion in ethylene cracking furnaces using petroleum feedstocks including at least 10 ppm of a water soluble mine complexed phosphate, phosphite, thiophosphate or thiophosphite ester compound, wherein

the amine has a partition coefficient greater than 1.0 (equal solubility in both aqueous and hydrocarbon solvents).
U.S. Pat. No. 4,842,716 to Kaplan et al describes an improved method for reducing fouling and corrosion at least 10 ppm of a combination of a phosphorus antifoulant compound and a filming inhibitor. The phosphorus compound is a phosphate, phosphite, thiophosphate or thiophosphite ester compound. The filming inhibitor is an imidazoline compound.
U.S. Pat. No. 4,941,994 Zetmeisl et al discloses a naphthenic acid corrosion inhibitor comprising a dialkyl or trialky 1 phosphite in combination with an optional thiazoline.
A significant advancement in phosphorus-containing naphthenic acid corrosion inhibitors was reported in U.S. Pat. No. 4,941,994. Therein it is disclosed that metal corrosion in hot acidic liquid hydrocarbons is inhibited by the presence of a corrosion inhibiting amount of a dialkyl and/or trialkyl phosphite with an optional thiazoline.
While the method described in U.S. Pat. No. 4,941,994 provides significant improvements over the prior art techniques, nevertheless, there is always a desire to enhance the ability of corrosion inhibitors while reducing the amount of phosphorus-containing compounds which may impair the function of various catalysts used to treat crude oil, as well as a desire for such inhibitors that may be produced from lower cost or more available starting materials.
Another approach to the prevention of naphthenic acid corrosion is the use of a chemical agent to form a barrier between the crude and the equipment of the hydrocarbon processing unit. This barrier or film prevents corrosive agents from reaching the metal surface, and is generally a hydrophobic material. Gustavsen et

al. NACE Corrosion 89 meeting, paper no. 449, Apr. 17-21, 1989 details the requirements for a good filming agent. U.S. Pat. No. 5,252,254 discloses one such film forming agent, sulfonated alkyl-substituted phenol, and effective against naphthenic acid corrosion.
U.S. Pat. No. 5,182,013 issued to Petersen et al. on Jan. 26, 1993 describes another method of inhibiting naphthenic acid corrosion of crude oil, comprising introducing into the oil an effective amount of an organic polysulfide. The disclosure of U.S. Pat. No. 5,182,013 is incorporated herein by reference. This is another example of a corrosion-inhibiting sulfur species. Suifidation as a source of corrosion was detailed above. Though the process is not well understood, it has been determined that while sulfur can be an effective anti-corrosive agent in small quantities, at sufficiently high concentrations, it becomes a corrosion agent.
Phosphorus can form an effective barrier against corrosion without sulfur, but the addition of sulfiding agents to the process stream containing phosphorus yields a film composed of both sulfides and phosphates. This results in improved performance as well as a decreased phosphorus requirement. This invention pertains to the deliberate addition of sulfiding agents to the process stream when phosphorus-based materials are used for corrosion control to accentuate this interaction.
Organic polysulfides (Babaian-Kibala, U.S. Pat. No. 5,552,085), organic phosphites (Zetlmeisl, U.S. Pat. No. 4,941,994), and phosphate/phosphite esters (Babaian-Kibala, U.S. Pat. No. 5,630,964), have been claimed to be effective in hydrocarbon-rich phase against naphthenic acid corrosion. However, their high oil solubility incurs the risk of distillate side stream contamination by phosphorus.
Phosphoric acid has been used primarily in aqueous phase for the formation of a phosphate/iron complex film on steel surfaces for corrosion inhibition or other

applications (Coslett, British patent 8,667, U.S. Pat. Nos. 3,132,975, 3,460,989 and 1,872,091). Phosphoric acid use in high temperature non-aqueous environments (petroleum) has also been reported for purposes of fouling mitigation (U.S. Pat. No. 3,145,886).
Naphthenic Acid Corrosion in a Refinery Setting by Babaian-Kibala, Craig, Jr., Rusk, Blanchard, Rose, Uehlein, Quinter and Summers, Paper 631 of the 1993 NACE Annual Conference and Corrosion Show discloses the addition of certain phosphate esters to control corrosion in the high temperature areas of a distillation column by injection of the phosphate ester material into a draw tray and the packing above the heavy vacuum gas oil draw tray in a vacuum distillation tower. The injection of the phosphate ester in this manner reportedly lowered the corrosion rate in the tower.
There remains a continuing need to develop additional options for mitigating the corrosivity of acidic crudes at lower cost. This is especially true at times of low refining margins and a high availability of corrosive crudes from sources such as Europe, China, or Africa, and India. The present invention addresses this need.
In view of above, there is a need to provide alternative additive composition which is non-fouling and less acidic to provide effective high temperature naphthenic acid corrosion inhibition, which will overcome the disadvantages of the prior - art compositions.
DESCRIPTION OF THE INVENTION
The present invention uses the following reacted compound to be used as corrosion inhibitor for inhibiting high temperature naphthenic acid corrosion. This reacted compound is obtained by reaction of alcohol with phosphorous pentoxide followed by reaction with oxirane compounds such as butylene oxides.

The mole ratio of P20sto alcohol is preferably 1 mole of P205to 1 to 7 mole of alcohol and preferably I mole of P2O5 to 2 to 4 mole of alcohol.
It has been surprisingly discovered by the inventor of the present invention, that a phosphate ester, reacted by oxirane compounds such as butylene oxide having lower phosphorus content, low acidity and, and non - fouling nature gives very effective and improved control of naphthenic acid corrosion, as compared with use of only non-treated phosphate ester.
The novel additive is made in two basic steps.
1. Alcohol is reacted with phosphorus pentoxide. (The resulting reaction compound is also effective in inhibition of naphthenic acid corrosion). The reaction can be carried out by using various mole ratios of alcohol and phosphorus pentoxide. The resultant reaction compound is phosphate ester. This reaction compound is highly acidic in nature.
2. The resultant reaction - compound, of step 1 is further reacted with oxirane compounds like butylene oxide. Alternatively, the other common oxides like ethylene oxide or propylene oxide or any other oxirane compound also can be used. The resultant reaction compound obtained after this step no. 2 is butylene - oxide - treated phosphate ester.
It should be noted that the above mentioned steps can be understood better by referring to the corresponding examples.
The present invention is directed to a method for inhibiting corrosion on the metal surfaces of the processing units which process hydrocarbons such as crude oil and its fractions containing naphthenic acid. The invention is explained in details in its simplest form wherein the following method steps are carried out, when it is used to process crude oil in process units such as distillation unit. Similar steps can be

used in different processing units such as, pumparoimd piping, heat exchangers and such other processing units.
These method steps are explained below:
a) heating the hydrocarbon containing naphthenic acid to vaporize a portion of the hydrocarbon:
b) allowing the hydrocarbon vapors to rise in a distillation column;
c) condensing a portion of the hydrocarbon vapours passing through the distillation column to produce a distillate;
d) adding to the distillate, from 1 to 2000 ppm of butylene-oxide-treated phosphate ester, which is the required additive of present invention;
e) allowing the distillate containing additive compound of step (d) to contact substantially the entire metal surfaces of the distillation unit to form protective film on such surface, whereby such surface is inhibited against corrosion.
It is advantageous to treat distillation column, trays, pumparound piping and related equipment to prevent naphthenic acid corrosion, when condensed vapours from distilled hydrocarbon fluids contact metallic equipment at temperatures greater than 200 °C, and preferably 400 °C. The additive is generally added to the condensed distillate and the condensed distillate is allowed to contact the metallic surfaces of the distillation column, packing, trays, pump around piping and related equipment as the condensed distillate passes down the column and into the distillation vessel. The distillate may also be collected as product. The corrosion inhibitors of the instant invention remain in the resultant collected product.
In commercial practice, the additives of this invention may be added to a distillate return to control corrosion in a draw tray and in the column packing while a second injection may be added to a spray oil return immediately below the draw trays to protect the tower packing and trays below the distillate draw tray. It is not

so critical where the additive of the invention is added as long as it is added to distillate that is later returned to the distillation vessel, or which contact the metal interior surfaces of the distillation column, trays, pump around piping and related equipments.
The method of using the of the present invention for achieving inhibition of high temperature naphthenic acid corrosion is explained below with the help of examples and tables.
Thus it is seen that the additive compound of present invention used for corrosion - inhibition has the following important distinguishing features, as compared to the prior art.
1) The inventor of the present invention, after extensive experimentation, has surprisingly found that the additive compound used by the inventor, is highly effective in high temperature corrosion inhibition, as shown by the experimental results given in Table I.
2) Another distinguishing feature of the additive compound of present invention is that, it has very low acidity as compared to the additive compounds of prior art, for example, the phosphate esters of prior art has very high acidity. The phosphate esters of prior art are known to have a tendency to decompose, even at lower temperatures, to form phosphoric acids, which travel further along the hydrocarbon stream and react with metal surfaces of equipments such as packing of distillation column, to form solid iron phosphate. These solids plug the holes of equipments and thereby lead to fouling of distillation column.

The additive compound of the present invention does not have this deficiency.
EXAMPLE 1
Into a clean four - necked round bottom flask, kept in a water bath at 30°C, 733.4 gm of 2-ethyl-hexanol was charged, and nitrogen gas purging was started. Total amount of 266.5 gm of phosphorous pentoxide was added to the flask in six installments. Exotherm was observed after addition of phosphorous pentoxide to the flask. After addition of phosphorous pentoxide was completed , the temperature of reaction mixture was raised to 99°C and this temperature was maintained for four hours.
The reaction mixture was cooled to room temperature at 30°C, filtered and analyzed for acid value and phosphorous content by method of Inductive Coupled Plasma.
The acid value was found to be in the range of 280 to 330 mg KOH/gm. Typical acid value was 308 mg KOH/gm. The phosphorous content was in the range of 10 to 12 %. Typical value of phosphorous content was 11.6 %. The resulting reaction mixture of example 1 is prior - art's additive for Naphthenic Acid Corrosion Inhibition. The results of experiments of example 1 are given in Table 1.
EXAMPLE 2
Into a clean four - necked round bottom flask, kept in a water bath at 30°C, 200 gm of reaction mixture of example 1 was charged. Into this reaction mixture 150 gm of butylene oxide was slowly added. The exotherm was observed and the temperature was maintained below 40°C till the addition of entire quantity of 150 gm of butylene oxide was completed. The samples of resulting chemical mixture were taken intermittently and were analyzed for acid value. The reaction was continued till the acid value was 10 mg KOH/gm.

The resulting reaction mixture was then heated to 60°C temperature, and was maintained at this temperature for two hours.
The resulting reaction mixture was cooled to room temperature of 30°C, filtered and analyzed for acid value and phosphorous content, by method of Inductive Coupled Plasma.
The acid value was found to be less than 10 mg KOH/gm. Typical acid value was
1 mg KOH / gm. The phosphorous content was in the range of 5 to 7 %. Typical phosphorous content value was 6.6 %. The resulting reaction mixture of example
2 is used as Invention - Additive for Naphthenic Acid Corrosion Inhibition. The results of experiments of example 2 are given in Table 1.
EXAMPLE 3
Into a clean four - necked round bottom flask, kept in a water bath at 30°C, 486 gm of 2-ethyl-hexanol was charged, and nitrogen gas purging was started. Total amount of 265 gm of phosphorous pentoxide was added to the flask in six installments. Exotherm was observed after addition of phosphorous pentoxide to the flask. After addition of phosphorous pentoxide was completed , the temperature of reaction mixture was raised to 99°C and this temperature was maintained for four hours.
The reaction mixture was cooled to room temperature of 30°C, filtered and analyzed for acid value and phosphorous content by method of Inductive Coupled Plasma.
The acid value was found to be in the range of 320 to 350 mg KOH/gm. Typical acid value was 331 mg KOH/gm. The phosphorous content was in the range of 14 to 16 %. Typical value of phosphorous content was 14.6 %. The resulting reaction

mixture of example 3 is prior - art's additive for Naphthenic Acid Corrosion Inhibition. The results of experiments of example 3 are given in Table 1.
EXAMPLE 4
Into a clean four - necked round bottom flask, kept in a water bath at 30°C, 100 gm of reaction mixture of example 3 was charged. Into this reaction mixture 88 gm of butylene oxide was slowly added. The exotherm was observed and the temperature was maintained below 40°C till the addition of entire quantity of 88 gm of butylene oxide is completed. The samples of resulting chemical mixture were taken intermittently and were analyzed for acid value. The reaction was continued till the acid value was 10 mg KOH/gm.
The resulting reaction mixture was then heated to 60°C temperature, and was maintained at this temperature for two hours.
The resulting reaction mixture was cooled to room temperature of 30°C, filtered and analyzed for acid value and phosphorous content, by method of Inductive Coupled Plasma.
The acid value was found to be less than 10 mg KOH/gm. Typical acid value was 6.8 mg KOH / gm. The phosphorous content was in the range of 7 to 9 %. Typical phosphorous content value was 8.19 %. The resulting reaction mixture of example 4 is used as Invention - Additive for Naphthenic Acid Corrosion Inhibition. The results of experiments of example 4 are given in Table 1.
EXAMPLE 5
High Temperature Naphthenic Acid Corrosion Test
In this example, various amounts of additives prepared in accordance, with Examples 1 to 4, were tested for corrosion inhibition efficiency on steel coupons in a hot oil containing naphthenic acid. A weight loss coupon, immersion test was

used to evaluate the invention compound for its effectiveness in inhibition of naphthenic acid corrosion at 290°C temperature. Different dosages of invention additive compounds are used as shown in Table 1.
A static test on steel coupon was conducted without using any additive. This test provided a blank test reading.
The reaction apparatus consisted of a one - litre four necked round bottom flask equipped with water condenser, N2 purger tube, thermometer pocket with thermometer and stirrer rod. 600 gm (about 750 ml) paraffin hydrocarbon oil (D -130) with fractions boiling above 290°C, was taken in the flask. N2 gas purging was started with flow rate of 100 cc / minute and the temperature was raised to 100°C, which temperature was maintained for 30 minutes.
In different experiments, additive compounds of examples 1 to 4 were used for testing their effectiveness in Naphthenic Acid Corrosion Inhibition. The reaction mixture after addition of additive compound was stirred for 15 minutes at 100°C temperature. After removing the stirrer, the temperature of the reaction mixture was raised to 290°C. A pre - weighed weight - loss carbon steel coupon CS 1010 with dimensions 76mm... times 13mm... times 1.6 mm was immersed. After maintaining this condition for Ihour to 1.5 hours, 31 gm of naphthenic acid (commercial grade with acid value of 230 mg KOH/gm) was added to the reaction mixture. A sample of one gm weight of reaction mixture was collected for determination of acid value, which was found to be approximately 11.7. This condition was maintained for four hours. After this procedure, the metal coupon was removed, excess oil was rinsed away, and the excess corrosion product was removed from the metal surface. Then the metal coupon was weighed and the corrosion rate was calculated in mils per year.

Calculation of Corrosion Inhibition Efficiency.
The method used in calculating Corrosion Inhibition Efficiency is given below. In this calculation, corrosion inhibition efficiency provided by additive compound is calculated by comparing weight loss due to additive with weight loss of blank coupon (without any additive).
Corrosion (Weight loss for blank (weight loss with
Inhibition = without additive) : additive) X 100
Efficiency (weight loss for blank without additive)
The calculated magnitudes are entered in the Table -1 in appropriate columns.
Table I:

Resulting Reaction
Product from Example Typical
Phosphorous
Content % Additive
Total
Dosage Additive Active Dosage Weight
Loss in
mg MPY % Efficiency
Example 1 (Prior art) 11.65 100 100 10.9 55 86.4

50 50 42.3 212 47.4
Example 2 (Invention Additive) 6.53 75 75 3.4 17 95.8

50 50 13.8 69 82.8
Example 3 (Prior Art) 15.408 100 100 7.1 36 91.2

50 50 39.9 200 50.4
Example 4 (Invention Additive) 8.19 50 50 5.9 30 92.7

25 25 25.2 126 68.7
Blank 0 0 0 80.4 402 NA
FOULING TENDENCY OF CORROSION INHIBITING ADDITIVES
The fouling tendency of each of invention additives and prior - art additives was determined by heating 1 % solution of each additive in the oil at 290°C for two hours. The observations with respect to precipitate - formation are given in Table 2.

Table 2

Additive Observation with respect to precipitate - formation
Example 1 Heavy precipitation
Example 2 Slight solids - formation
Example 3 Heavy precipitation
Example 4 Slight solids - formation
Tributyl Phosphate Completely hazy solution