Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G75/00—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general
  • C10G75/02—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general by addition of corrosion inhibitors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
  • C09K8/524—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning organic depositions, e.g. paraffins or asphaltenes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/54—Compositions for in situ inhibition of corrosion in boreholes or wells
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G7/00—Distillation of hydrocarbon oils
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G7/00—Distillation of hydrocarbon oils
  • C10G7/10—Inhibiting corrosion during distillation
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/04—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly acid liquids
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/08—Corrosion inhibition
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/10—Feedstock materials
  • C10G2300/1033—Oil well production fluids
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/20—Characteristics of the feedstock or the products
  • C10G2300/201—Impurities
  • C10G2300/202—Heteroatoms content, i.e. S, N, O, P
  • C10G2300/203—Naphthenic acids, TAN
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/40—Characteristics of the process deviating from typical ways of processing
  • C10G2300/4075—Limiting deterioration of equipment
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
  • C10G2300/80—Additives

Definitions

• the present invention relates to the inhibition of metal corrosion in acidic hot hydrocarbons and particularly to the 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.
• 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 one gram sample, above 0.2.
• TAN neutralization number or total acid number
• naphthenic acid-containing hydrocarbon is at a temperature between about 200° C. and 400° C. (approximately 400° F.-750° F.), the fluid velocities are high and 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).
• 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:
• the molecular weight of naphthenic acid can extend over a large range.
• the majority of the naphthenic acid from crude oils is found in gas oil and light lubricating oil.
• hydrocarbons containing such naphthenic acids come in contact with 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.
• 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 by naphthenic acid.
• severe corrosion can occur in the carbon steel or ferritic steel furnace tubes and tower bottoms.
• Recently much 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 milligrams 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.
• TAN 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.
• Naphthenic acid corrosion is highly 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.
• 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.
• 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's contain hydrogen sulfide, and therefore readily form iron sulfide films on carbon steel.
• metal surfaces have been covered with a film of some sort.
• 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 example, 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.
• 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.
• these show little to no resistance to naphthenic acid.
• an austenitic stainless steel which contains at least 2.5% molybdenum, must be utilized.
• the corrosion 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 are corrosive between the ranges of about 175° C. to 420° C. At 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.
• the temperature range of primary interest for this type of corrosion is in the range of from about 175° C. to about 400° C., especially about 205° C. to about 400° C.
• 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.
• U.S. Pat. No. 4,024,049 to Shell et al disclosed compounds 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 pump-around piping, or further process steps.
• U.S. Pat. No. 4,443,609 disclosed 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.
• U.S. Pat. No. 4,542,253 to Kaplan et al described a method of reducing fouling and corrosion in ethylene cracking furnaces using petroleum feedstocks including at least 10 ppm of a water soluble amine 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 described a method for reducing fouling and corrosion by using 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 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. 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.
• the present invention provides an effective novel non-polymeric and non-fouling additive for inhibiting high-temperature naphthenic acid corrosion, comprising an effective corrosion-inhibiting amount of a second phosphate ester wherein said second phosphate ester is obtained by reacting a first phosphate ester with an oxirane compound selected from the group consisting of butylene oxide, ethylene oxide, propylene oxide or any other oxirane compound or a combination thereof, preferably with butylene oxide, capably yielding said second phosphate ester, having a structure A or B,
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other, X is H, CH 3 or C 2 H 5 ; and n may vary from 1 to 20, wherein said first phosphate ester is having a structure I or II,
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other, said first phosphate ester being obtained as a reaction product of reaction of an alcohol with a phosphorous pentaoxide.
• 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 selected from the group consisting of butylene oxides ethylene oxides and propylene oxides and other such compounds.
• the mole ratio of P 2 O 5 to alcohol is preferably 1 mole of P 2 O 5 to 1 to 10 mole of alcohol and preferably 1 mole of P 2 O 5 to 1 to 7 mole of alcohol.
• a phosphate ester, reacted by oxirane compounds such as butylene oxide are having lower phosphorus content, low acidity and, and non-fouling nature and 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.
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other.
• This mixture predominantly contains mono- and di-phosphates and other phosphorous compounds which are acidic in nature and expected to take part in reaction with the oxirane compounds like butylene oxide, ethylene oxide and propylene oxide capably yielding phosphate ester.
• Typical structures A or B, respectively, of mono- and di-phosphate ester reacted with oxides are shown below
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other, X is H, CH 3 or C 2 H 5 ; and n may vary from 1 to 20.
• 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, pump-around piping, heat exchangers and such other processing units.
• distillation column, trays, pump-around piping and related equipment it is advantageous to treat distillation column, trays, pump-around 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.
• 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 reaction mixture was cooled to 30° C.-35° C., filtered and analyzed for acid value and phosphorous content by method of Inductive Coupled Plasma (ICP).
• ICP Inductive Coupled Plasma
• Example 1 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 11.65%.
• 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.
• reaction mixture of Example 1 Into a clean four-necked round bottom flask, kept in an oil 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 30° C.-35° C., filtered and analyzed for acid value and phosphorous content, by method of ICP.
• Example 2 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 6.53%.
• 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.
• reaction mixture was cooled to room temperature of 30° C., filtered and analyzed for acid value and phosphorous content by method of ICP.
• 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 ICP.
• Example 4 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.
• the reaction apparatus consisted of a one-litre four-necked round bottom flask equipped with water condenser, N 2 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. N 2 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.
• 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 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.
• 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 ⁇ ⁇ Inhibition ⁇ ⁇ Efficiency ( Weight ⁇ ⁇ loss ⁇ ⁇ for ⁇ ⁇ blank ⁇ ⁇ without ⁇ ⁇ additive ) - ( weight ⁇ ⁇ loss ⁇ ⁇ with ⁇ ⁇ additive ) ( weight ⁇ ⁇ loss ⁇ ⁇ for ⁇ ⁇ blank ⁇ ⁇ without ⁇ ⁇ additive ) ⁇ 100
• the dynamic testing was carried out by using rotating means provided in the temperature-controlled autoclave and was carried out by using steel coupons.
• a weight-loss coupon immersion dynamic test was used to evaluate the invention compound for its effectiveness in inhibition of naphthenic acid corrosion at 260° C. temperature under dynamic condition.
• various amounts of an about 50% or neat additive prepared in accordance with Examples 1 to 4 were tested.
• a dynamic test on steel coupon was conducted without using any additive. This test provided a blank test reading.
• Example 2 along with providing lesser percent phosphorous content of 6.53, in each case, use of active dosage amounts of invention additive compound of 75 ppm and 50 ppm, the corresponding percentage efficiencies of common inhibition were respectively 95.8 and 85.8.
• Example 4 along with providing a little higher percent phosphorous content of 8.19, in each case, with use of even reduced active dosage amounts of invention additive compound of 50 ppm and 25 ppm, the corresponding percent efficiencies of corrosion inhibition were respectively 92.7 and 68.7 respectively.
• the invention additive compound of the present invention provides better efficiency of corrosion inhibition along with lower percent phosphorous content (and hence lower acidic value) and lower dosages of active invention additive compound (thereby making it more economical).
• the invention additive compound is also non-fouling as it leads to very slight solids-formation.
• the additive compound of present invention used for corrosion-inhibition has the following important distinguishing features, as compared to the prior art.
• the present invention comprises of the following items:
• Item 1 An effective novel non-polymeric and non-fouling additive for inhibiting high-temperature naphthenic acid corrosion, comprising an effective corrosion-inhibiting amount of a second phosphate ester wherein said second phosphate ester is obtained by reacting a first phosphate ester with an oxirane compound selected from the group consisting of butylene oxide, ethylene oxide, propylene oxide or any other oxirane compound or a combination thereof, preferably with butylene oxide, capably yielding said second phosphate ester, having a structure A or B,
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other, X is H, CH 3 or C 2 H 5 ; and n may vary from 1 to 20, wherein said first phosphate ester is having a structure I or II,
• R 1 and R 2 are each independently selected from the group consisting of moieties having 1 to 20 carbon atoms and R 1 and R 2 may be identical to or different from each other, said first phosphate ester being obtained as a reaction product of reaction of an alcohol with a phosphorous pentaoxide.
• Item 2 An effective additive, as described in item 1, wherein said effective additive has acidity varying from about 1 mg KOH/gm to about 20 mg KOH/gm as determined by titration of samples against normal alcoholic KOH.
• Item 3 An effective additive, as described in item 1, wherein said effective additive has phosphorus contents varying from about 0.5% to about 9% of said effective additive.
• Item 4 An effective additive, as described in item 1, wherein mole ratios of said phosphorus pentoxide and said alcohol are used, such that the mole ratio of said phosphorus pentoxide to said alcohol is preferably 1 mole of said phosphorus pentoxide to 1 to 10 mole of said alcohol and preferably 1 mole of said phosphorus pentoxide to 1 to 7 mole of said alcohol.
• Item 5 An effective additive as described in item 1, wherein active dosage of said additive is 1 to 2000 ppm.
• Item 6 A process of high temperature naphthenic acid corrosion inhibition of metallic surfaces of any of the hydrocarbon processing units of a petrochemical plant, used for processing a stream containing naphthenic acid, with said processing units comprising distillation columns, strippers, trays, pump around piping and related equipments, and said process using said second phosphate ester of item 1, comprising the steps of:

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• 2010
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