Claims:1. An additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising:
(a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydride and mixtures thereof; and
(b) the remainder being a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof.
2. The additive composition as claimed in claim 1, wherein the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester, and wherein the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof.
3. The additive composition as claimed in claim 1, wherein the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature.
4. An additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising:
(a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydride and mixtures thereof;
(b) a compound selected from a quinol, a phenol, a diamine and mixtures thereof in an amount ranging from 5% to 40% by weight of the additive composition; and
(c) a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof.
5. The additive composition as claimed in claim 4, wherein the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester, and wherein the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof.
6. The additive composition as claimed in claim 4, wherein the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature210-240 °C.
7. The additive composition as claimed in claim 4, wherein the quinol is selected from the group comprising methyl catechol, ethyl catechol, butyl catechol, tert-butyl catechol, methyl hydroquinone, butyl hydroquinone, and tert-butyl hydroquinone, and wherein the phenol is selected from the group comprising methyl phenol, ethyl phenol, 2,4-dimethyl phenol, tert-butyl phenol, n-butyl phenol, and 2,4-di-tert-butyl phenol, further wherein the diamine is selected from the group comprising ethylene diamine, p-phenylene diamine, N-phenyl-N’(1,3-dimethylbutyl)-ethylenediamine and N-phenyl-N’(1,3-dimethylbutyl)-p-phenylenediamine.
8. The additive composition as claimed in claim 4, wherein the additive composition comprises carboxylic anhydride functionalized unsaturated fatty ester, quinol, phenol and diamine in a weight ratio ranging from 50:25:15:10 to 35:30:20:15.
9. The additive composition as claimed in claim 8, wherein the compound comprises tert-butyl catechol, tert-butyl phenol, and p-phenylene diamine, and wherein the solvent is xylene.
10. The additive composition as claimed in claim 4, wherein said additive composition comprises:
(a) a functionalized unsaturated fatty esters obtained by reacting 20 weight %of oleic acid ester, 25 weight % of linoleic acid ester, and 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride at an elevated temperature;
(b) a compound being a mixture of tert-butyl catechol, tert-butyl phenol and p-phenylene diamine; and
(c)xylene in an amount ranging from 40% to 60% by weight of the composition,
wherein carboxylic anhydride functionalized unsaturated fatty ester, tert-butyl catechol, tert-butyl phenol and p-phenylene diamine are present in a weight ratio ranging from 50:25:15:10 to 35:30:20:15.
11. A method for inhibiting fouling by deposits on internal metal surfaces of a heat processing equipment of a crude distillation unit, said method comprising adding the additive composition as claimed in any of claim 1 and claim 4 to a hydrocarbon stream in a concentration ranging from 5 to 100 ppm.
12. The method as claimed in claim 11, wherein the additive composition is added to the hydrocarbon stream during heat processing at a temperature of 200°C - 550°C.
13. The method as claimed in claim 11, wherein the additive composition is added in a concentration ranging from 10 to 30 ppm in the hydrocarbon stream.
14. A method for preparation of a carboxylic anhydride functionalized unsaturated fatty ester, said method comprising the steps of:
(a) reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester aFnd 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride, while bubbling the reaction mixture with an inert gas to remove dissolved oxygen; and
(b) mainFtaining the reaction mixture at a temperature of 210°C - 240°C with continuous stirring for a time period ranging from 3-8 hours to obtain the carboxylic anhydride functionalized unsaturated fatty ester.
, Description:FIELD OF THE INVENTION
[0001] The present invention pertains to inhibiting fouling of heat processing equipment of a distillation unit in petroleum refinery. In particular, the present invention pertains to an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures.

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] In refining process, petroleum hydrocarbon feedstocks such as crude oils, atmospheric gas oil (AGO), vacuum gas oil (VGO), etc. are subjected to various processes in order to isolate and separate different fractions of the feedstock. Crude oils and petroleum hydrocarbons are commonly heated to the elevated temperature up to 550°C for processing and separation of valuable products such as gas, naphtha, middle distillate and reformates. It is usually necessary to heat the hydrocarbon feedstock to an elevated temperature through the tube of direct fire heater orby contacting with a heated metal surface of a heating device such as tube and shell heat exchanger. Similarly, the heated petroleum hydrocarbons are frequently used as heating medium on the hot sides of heat exchanger systems. Series of heat exchanger systems are frequently used for efficient management of heat resource.
[0004] During heating process, crude oils tend to foul on metal surfaces with which they come in contact at an elevated temperature by depositing solid or semi-solid kind of materials commonly called foulant. The fouling deposits appears to contain mainly a combination of carbonaceous materials which are like high molecular weight asphaltenes, long chain paraffins, polymers, or condensate formed from the petroleum hydrocarbons or impurities present therein. Such fouling process reduces the efficiency of heat transfer from metal surface to oil, thereby increasing the amount of fuel required to heat the oil to the desired temperature. It also reduces the efficiency of the heat processing equipment and in aggravated cases may render it impossible to maintain the desired flow rate. In such cases, hydrocarbon oil processing units must be periodically shutdown to remove the deposits or the units need to be replaced. Such fouling of heat exchangers and other equipments such as furnaces, pipes, reboiler, condensers, compressors and auxiliary equipments lead to a significant economic loss due to the loss of production time and the man hours required for disassembling, cleaning and reassembling of process equipment components.
[0005] Despite of rigorous research, no additive composition is known which exhibits desired anti-fouling activity while being economic. The present disclosure provides an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures.

OBJECTS OF THE INVENTION
[0006] It is an object of the present disclosure to provide an unsaturated fatty ester based additive composition that reduces the fouling in hydrocarbon processing equipment.
[0007] It is another object of the present disclosure to provide a method of preparing unsaturated fatty ester based additive composition that reduces the fouling in hydrocarbon processing equipment.
[0008] It is another object of the present disclosure to provide an unsaturated fatty ester additive composition that reduces the energy requirement of hydrocarbon processing equipment.
[0009] It is further object of the present disclosure to provide a method for increasing the heat transfer efficiency in hydrocarbon processing equipment.
[0010] It is further object of the present disclosure to reduce the energy requirement for the heated surface by contacting additive composition with hydrocarbon oil.
[0011] It is further object of the present disclosure to provide a method for assessing fouling rate and optimizing dosage of anti-foulant required during operating conditions of crude oil heat exchangers.
SUMMARY OF THE INVENTION
[0012] The present invention pertains to inhibiting fouling of heat processing equipment of a distillation unit in petroleum refinery. In particular, the present invention pertains to an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures.
[0013] First aspect of the present disclosure provides an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising: (a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydride and mixtures thereof; and (b) the remainder being a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof. In an embodiment, the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester. In an embodiment, the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof. In an embodiment, the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature.
[0014] Second aspect of the present disclosure provides an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising: (a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydrideand mixtures thereof; (b) a compound selected from a quinol, a phenol, a diamine and mixtures thereof in an amount ranging from 5% to 40% by weight of the additive composition; and (c) a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof. In an embodiment, the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester. In an embodiment, the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof. In an embodiment, the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature. In an embodiment, the quinol is selected from the group comprising methyl catechol, ethyl catechol, butyl catechol, tert-butyl catechol, methyl hydroquinone, butyl hydroquinone, and tert-butyl hydroquinone. In an embodiment, the phenol is selected from the group comprising methyl phenol, ethyl phenol, 2,4-dimethyl phenol, tert-butyl phenol, n-butyl phenol, and 2,4-di-tert-butyl phenol. In an embodiment, the diamine is selected from the group comprising ethylene diamine, p-phenylene diamine, N-phenyl-N’(1,3-dimethylbutyl)-ethylenediamine and N-phenyl-N’(1,3-dimethylbutyl)-p-phenylenediamine. In an embodiment, the additive composition comprises carboxylic anhydride functionalized unsaturated fatty ester, quinol, phenol and diamine in a weight ratio ranging from 50:25:15:10 to 35:30:20:15. In an embodiment, the compound comprises tert-butyl catechol, tert-butyl phenol, and p-phenylene diamine. In an embodiment, the solvent is xylene. In an embodiment, the additive composition comprises: (a) a functionalized unsaturated fatty esters obtained by reacting 20 weight %of oleic acid ester, 25 weight % of linoleic acid ester, and 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride at an elevated temperature; (b) a compound being a mixture of tert-butyl catechol, tert-butyl phenol and p-phenylene diamine; and (c) xylene in an amount ranging from 40% to 60% by weight of the composition, wherein carboxylic anhydride functionalized unsaturated fatty ester, tert-butyl catechol, tert-butyl phenol and p-phenylene diamine are present in a weight ratio ranging from 50:25:15:10 to 35:30:20:15.
[0015] Third aspect of the present disclosure relates to a method for inhibiting fouling by deposits on internal metal surfaces of a heat processing equipment of a crude distillation unit, said method comprising adding the additive composition as described in first and second aspects to a hydrocarbon stream in a concentration ranging from 5 to 100 ppm. In an embodiment, the additive composition is added to the hydrocarbon stream during heat processing at a temperature of 200°C - 550°C. In an embodiment, the additive composition is added in a concentration ranging from 10 to 30 ppm in the hydrocarbon stream.
[0016] Fourth aspect of the present disclosure relates to a method for preparation of a carboxylic anhydride functionalized unsaturated fatty ester, said method comprising the steps of: (a) reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride, while bubbling the reaction mixture with an inert gas to remove dissolved oxygen; and (b) maintaining the reaction mixture at a temperature of 210°C - 240°C with continuous stirring for a time period ranging from 3-8 hours to obtain the carboxylic anhydride functionalized unsaturated fatty ester.
[0017] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0018] 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.
[0019] FIGs.1A through 1D provides exemplary graphs illustrating the efficiency of additive compositions with respect to different crude oils and dosage, in accordance with embodiments of the present disclosure.
[0020] FIG. 2 illustrates a schematic representation of additive dosing in preheat train heat exchanger systems of refinery, in accordance with embodiments of the present disclosure.
[0021] FIG. 3 illustrates a graph showing outlet temperature profile of preheat train head exchange of refinery systems, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0022] 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.
[0023] 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.
[0024] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0025] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0026] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0027] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range.
[0028] Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. 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.
[0029] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0030] Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
[0031] The following description provides different examples and embodiments of the inventive subject matter. Although, each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0032] All percentages, ratios, and proportions used herein are based on a weight basis unless otherwise specified.
[0033] 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.
[0034] The present invention pertains to inhibiting fouling of heat processing equipment of a distillation unit in petroleum refinery. In particular, the present invention pertains to an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures.
[0035] First aspect of the present disclosure provides an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising: (a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydride and mixtures thereof; and (b) the remainder being a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof. In an embodiment, the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester. In an embodiment, the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid (i.e. methyl ester of oleic acid, ethyl ester of oleic acid,or methyl ethyl ester of oleic acid), linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof. In an embodiment, the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature.
[0036] Second aspect of the present disclosure provides an additive composition for inhibiting fouling of internal metal surfaces by hydrocarbon streams at elevated temperatures, said additive composition comprising: (a) a carboxylic anhydride functionalized unsaturated fatty ester in an amount ranging from 5% to 60% by weight of the additive composition, said carboxylic anhydride component being maleic anhydride, citraconic anhydride, phenylmaleic anhydrideand mixtures thereof; (b) a compound selected from a quinol, a phenol, a diamine and mixtures thereof in an amount ranging from 5% to 40% by weight of the additive composition; and (c) a solvent selected from naphtha, kerosene, toluene, xylene and mixtures thereof. In an embodiment, the carboxylic anhydride functionalized unsaturated fatty ester is obtained by reacting a carboxylic anhydride with an unsaturated fatty ester. In an embodiment, the unsaturated fatty ester is selected from the group comprising methyl and/or ethyl ester of oleic acid, linoleic acid, linolenic acid, palmitoleic acid, arachitoric acid, eicosapentaenoic acid, gamma-linolenic aicd, docosapentaenoic acid, elaidic acid, erucic acid, vaccenic acid, nervonic acid, 11-eicosenoiic acid and mixtures thereof. In an embodiment, the functionalized unsaturated fatty ester is obtained by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 weight % of maleic anhydride at an elevated temperature. In an embodiment, the quinol is selected from the group comprising methyl catechol, ethyl catechol, butyl catechol, tert-butyl catechol, methyl hydroquinone, butyl hydroquinone, and tert-butyl hydroquinone. In an embodiment, the phenol is selected from the group comprising methyl phenol, ethyl phenol, 2,4-dimethyl phenol, tert-butyl phenol, n-butyl phenol, and 2,4-di-tert-butyl phenol. In an embodiment, the diamine is selected from the group comprising ethylene diamine, p-phenylene diamine, N-phenyl-N’(1,3-dimethylbutyl)-ethylenediamine and N-phenyl-N’(1,3-dimethylbutyl)-p-phenylenediamine. In an embodiment, the additive composition comprises carboxylic anhydride functionalized unsaturated fatty ester, quinol, phenol and diamine in a weight ratio ranging from 50:25:15:10 to 35:30:20:15. In an embodiment, the compound comprises tert-butyl catechol, tert-butyl phenol, and p-phenylene diamine. In an embodiment, the solvent is xylene. In an embodiment, the additive composition comprises: (a) a functionalized unsaturated fatty esters obtained by reacting 20 weight %of oleic acid ester, 25 weight % of linoleic acid ester, and 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride at an elevated temperature; (b) a compound being a mixture of tert-butyl catechol, tert-butyl phenol and p-phenylene diamine; and (c) xylene in an amount ranging from 40% to 60% by weight of the composition, wherein carboxylic anhydride functionalized unsaturated fatty ester, tert-butyl catechol, tert-butyl phenol and p-phenylene diamine are present in a weight ratio ranging from 50:25:15:10 to 35:30:20:15.
[0037] Third aspect of the present disclosure relates to a method for inhibiting fouling by deposits on internal metal surfaces of a heat processing equipment of a crude distillation unit, said method comprising adding the additive composition as described in first and second aspects to a hydrocarbon stream in a concentration ranging from 5 to 100 ppm. In an embodiment, the additive composition is added to the hydrocarbon stream during heat processing at a temperature of 200°C - 550°C. In an embodiment, the additive composition is added in a concentration ranging from 10 to 30 ppm in the hydrocarbon stream.
[0038] Fourth aspect of the present disclosure relates to a method for preparation of a carboxylic anhydride functionalized unsaturated fatty ester, said method comprising the steps of: (a) reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and 30 weight % of linolenic acid ester with 25 % by weight of maleic anhydride, while bubbling the reaction mixture with an inert gas to remove dissolved oxygen; and (b) maintaining the reaction mixture at a temperature of 210°C - 240°C with continuous stirring for a time period ranging from 3-8 hours to obtain the carboxylic anhydride functionalized unsaturated fatty ester.
[0039] As used herein, the term “fouling reduction” can refer to any cessation, prevention, abatement, reduction, suppression, lowering, controlling or decreasing of fouling, etc. Similarly, the term “inhibition” can refer to such reducing the fouling deposits in the heat processing systems using additive composition to some measurable extent. Furthermore, the nature of the metal surfaces protected in the methods of this disclosure is not limited and may include iron alloys, copper alloys, nickel alloys, titanium alloys, and these metals in unalloyed form as well, etc.
[0040] The present invention related to a preparation of additive composition based on carboxylic anhydride functionalized unsaturated fatty esters and their use for reduction of fouling in heat processing equipment. Further, the present invention related to a preparation of series of multifunctional anti-foulant additive compositions and their use in heat processing equipment. Such compositions can be prepared by blending carboxylic anhydride functionalized unsaturated fatty esters along with at least one additional compound such as phenols, quinols, diamines and mixture thereof.
[0041] The additive composition of the present invention can inhibit the fouling deposition across the entire heat exchanging zone, from the point where the initial injection of the additive. During heat processing of hydrocarbons at elevated temperature, these additives act as a dispersant and retain the fouling causing material in the hydrocarbon stream. Accordingly, the additive compositions of the present disclosure can effectively reduce the fouling of heat processing equipment, even when used in small quantities and thereby reduces the processing cost, eliminate operating problems caused by carbonaceous deposits in heat processing units and mitigate or inhibit deposition of fouling causing materials. Further, the additive compositions of the present disclosure are suitable for various heat processing equipments with different types of petroleum crude oils. The chemical components that are used as part of the additive composition of the present invention are readily available and/or can be readily prepared in accordance with embodiments of the present disclosure and do not require elaborate or expensive handling procedures or chemical treatment to meet environmental and safety concerns. The additive compositions of the present disclosure are thermally stable at temperatures required for fractionation of crude oil and are stable enough to be present in the residue phase. Particularly, the additive compositions of the present disclosure are effective indispersing carbonaceous materials that tend to get deposited on the metal surface of the heat processing equipment. It should be appreciated that the compositions of the present disclosure may be added to the hydrocarbon feed stock at any point in the process to be protected from fouling, particularly, for preventing or otherwise reducing fouling caused by paraffinic and asphaltene deposition. The compositions are especially effective when added to the liquid hydrocarbon medium during heat processing thereof.
[0042] The present disclosure is further explained in the form of following examples. However, it is to be understood that the examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope and spirit of the present invention.
[0043] Example 1:
[0044] Carboxylic anhydride functionalized unsaturated fatty ester was prepared by reacting 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester and30 weight % of linolenic acid ester with 25% by weight of maleic anhydride at temperatures in the range of 200 to 240°C. The reaction mixture was bubbled with nitrogen gas to remove the dissolved oxygen gas from the reaction mixture. The reaction mixture was then slowly heated to about 230?C and stirred at about 400rpm for about 6 hours while maintaining the temperature. Reaction progress was monitored through the GC analysis by estimating the free maleic anhydride content in the reaction mixture and the reaction was stopped when the free maleic anhydride content was less than 1%. After completion of the reaction, the reaction mixture was cooled and recovered as yellow liquid. 40 gm of carboxylic anhydride functionalized unsaturated fatty ester prepared above was blended with 40 gm of xylene at 80?C to prepare the additive composition 1.
[0045] Example 2
[0046] The additive composition for this example is prepared by a mixture of 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester, 30 weight % of linolenic acid ester and 25 weight % of maleic anhydride in the temperature range between200 to 240°C. Nitrogen gas is bubbled through the reaction mixture to remove the dissolved oxygen gas from the reaction mixture, followed by slowly heating the reaction mixture to a temperature of210-240 ?C for 6 hours with constant stirring at rpm 400-500.Completion of the reaction was confirmed by analyzing the % of free maleic anhydride content present in the reaction mixture through gas chromatography. After that, the reaction mixture was cooled down to 120 ?C and 5 weight % of tert-butyl catechol was added and the reaction mixture was stirred at 120 oC for 1 hour. The reaction mixture was cooled and recovered as yellow liquid. 42 gm of the reaction product was blended with 42 gm of xylene at 80 ?C to prepare the additive composition 2.
[0047] Example 3:
[0048] The additive composition was prepared by a mixture of 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester, 30 weight % of linolenic acid ester and 25 weight % of maleic anhydride at an elevated temperature. Nitrogen gas was bubbled through the reaction mixture to remove the dissolved oxygen gas from the reaction medium, followed by slowly heating the reaction mixture to a temperature of 210-240 ?C for 6 hours with constant stirring. After that, the reaction mixture was cooled to 120 ?C and 6 gm of tert-butyl catechol and 2 gm of tert-butyl phenol were added to about 40 gm of the reaction mixture and the reaction mixture was stirred at 120 ?C for 1 hour. The reaction mixture was further cooled down to ambient temperature and recovered as yellow liquid. The reaction product was blended with 48 gm of xylene at 80?C to prepare additive composition 3.
[0049] Example 4:
[0050] The additive composition was prepared by a mixture of 20 weight % of oleic acid ester, 25 weight % of linoleic acid ester, 30 weight % of linolenic acid ester and 25 weight % of maleic anhydride was reacted at an elevated temperature. Nitrogen gas was bubbled through the reaction mixture to remove the dissolved oxygen gas from the reaction mixture, followed by slowly heating the reaction mixture to a temperature of210-240 ?C for 6 hours with constant stirring. Completion of the reaction was confirmed by analyzing the % of free maleic anhydride content present in the reaction mixture through gas chromatography. After completion, the reaction mixture was cooled to 120 ?C and 6 gm of tert-butyl catechol, 2 gm of tert-butyl phenol and 4 gm of p-phenylene diamine were added to 40 gm of reaction mixture and the reaction mixture was stirred for 1 hour. The reaction product was blended with 52 gm of xylene at 80 ?C to prepare additive composition 4.
[0051] Additive compositions 1-4 prepared in example 1-4 were used separately as an additive composition for reducing the fouling in heat processing equipments. The efficacy of the additive compositions of examples 1-4 were analyzed using thermal fouling analyzer.
[0052] Example 5:
[0053] The fouling tests for assessing the efficiency of the additive compositions obtained from example 1-4 were conducted using a bench-scale thermal fouling analyzer unit. Hydrocarbons, such as petroleum crude, gas oil and heavy oils are used as a feed stock for testing additive performance. The analyzer consists of four sections, which are supply tank, lines, pump and heating section. Nearly 150 mL of hydrocarbon sample along with or without additive was poured into the reservoir and the system was pressurized followed by starting the pump to facilitate the flow of sample through the lines at a certain flow rate. The probe consists of a heater tube and a shell to simulate a single pass heat exchanger. Inlet temperature of the petroleum crude was ~100?C, whereas the heater tube temperature was about 400?C. Once the unit was started, inlet and outlet temperature of the fluid were recorded. The surface temperature was measured by a movable thermocouple that can be placed at varying positions along the tube. Once the experiment was started, the outlet temperature of the fluid was recorded at constant time intervals. At initial time period, there was not much decrease in the outlet temperature of the liquid. Over the time, as fouling accumulated in the heater tube, there was a decrease in the thermal transfer from heater tube to flowing liquids, which resulted in decrease in the outlet temperature of the liquids. The higher degree of fouling decreases the outlet temperature to greater extent and temperature fall observed will be higher. The temperature difference (?T0C) can be used as a parameter to describe the extent of fouling. Thus
?T0C= Outlet temperature at time, t - Outlet temperature at time, 0
[0054] Example 6:
[0055] The effectiveness of the compositions of the present disclosure were studied with four different types of petroleum crude oil. Crude oil containing varying amount of saturates, aromatics, resins and asphaltene contents were used for the experiments. The general properties of four different type of crude oils are shown in Table1. Petroleum crude oil 1and 2 were mostly paraffinic or naphthenic based crude oils, such as Mumbai high, Agbami kind of crude oils. Whereas the petroleum crude oil 3 and 4were mostly asphaltenic based, such as Kuwait, Arab medium and Arab high.
Table 1. Petroleum crude oil properties
Crude properties Crude Oil 1 Crude Oil2 Crude Oil 3 Crude Oil 4
Density, °API 41 47.2 31.4 28.5
Viscosity at 37.8° C, mm2/s 3.4 1.98 9.8 17.5
Conradson carbon, % mass 1.1 0.9 5.3 5.9
Asphaltene, % mass 0.25 0.3 2.86 2.2
Sulfur, % mass 0.09 0.05 2.52 2.85
Pour point, °C 30 1.6 -15 -23
[0056] Example 7:
[0057] Determination of effective dosage of the additive composition with respect to different crude oil was estimated using a thermal fouling analyzer using with and without addition of additive composition during experiments. In a typical experiment, different concentrations of additive were added to the crude oils and the antifouling efficiency was analyzed through thermal fouling analyzer. The efficiency of additive composition for a particular crude oil was determined through drop in outlet temperature of the crude oils. The greater fouling leads to a greater decrease in the outlet temperature, resulting in higher temperature difference in inlet and outlet temperature. The drop in outlet temperature was measured as ?T and was used as a parameter to describe the extent of fouling. A higher ?T is an indication of increased fouling and vice versa. The additive compositions from example 1-4 were used to determine the effective dosage level of additive composition for the heat processing equipment. Different concentrations of additive such as 10 ppm to 40 ppm were mixed with crude oils and analyzed their anti-fouling efficiency through thermal stimulator. Further, the temperature difference (?T)for each experiment was calculated and the results were plotted, which are shown in FIG. 1A through FIG. 1D.It could be observed that the fouling rate decreased with increase in the dosage of additive compositions. Further, as can be seen from FIGs. 1A-1D, addition of 20-30 ppm of additive composition was found to be enough to inhibit the fouling rate of heat processing equipment. FIG. 1A demonstrates efficiency of additive composition of Example 1 at varying dosage level against petroleum crude oils 1-4.FIG. 1B demonstrates efficiency of additive composition of Example 2 at varying dosage level against petroleum crude oils 1-4.FIG. 1C demonstrates efficiency of additive composition of Example 3 at varying dosage level against petroleum crude oils 1-4.FIG. 1D demonstrates efficiency of additive composition of Example 4 at varying dosage level against petroleum crude oils 1-4.
[0058] Example 8:
[0059] The efficiency of the antifouling additives were also analyzed by measuring the weight gain in the deposition rod. The efficiency of a particular additive composition for a particular crude oil was determined by measuring the weight gain in the deposition rod. After each thermal fouling experiment, thermal fouling rod was removed and dried in oven at 120 ?C for 3 hours. The weight difference of the rod after the experiment shows the effectiveness of the additive composition. The weights of deposition for different additive compositions against various crude oils were measured and the results are shown in Table 2. As expected, a greater deposition leads to increased drop in outlet temperature resulting in increased weight of recovered deposition from the rod. It could also be noted that the additive compositions realized in accordance with embodiments of the present disclosure are effective against varying crude oils.
Table 2. Weight of recovered depositions for different additive compositions against various crude oils
Additive Effective Dosage (ppm) Type of Petroleum Crude Temperature difference, ?T, 0C Weight of deposition in the rod, mg
No additive - Pet. Crude 1 15.6 14.3
Pet. Crude 2 13.4 13.1
Pet. Crude 3 26.5 20.5
Pet. Crude 4 27.5 21.3
Example -1, additive composition 20 ppm Pet. Crude 1 2.7 6.7
Pet. Crude 2 2.1 6.3
Pet. Crude 3 11.5 11.7
Pet. Crude 4 14.1 13.2
Example -2, additive composition 20 ppm Pet. Crude 1 2.3 6.4
Pet. Crude 2 2.0 6.1
Pet. Crude 3 9.4 10.4
Pet. Crude 4 10.5 11.4
Example -3, additive composition 30 ppm Pet. Crude 1 5.4 8.4
Pet. Crude 2 5.3 8.2
Pet. Crude 3 7.8 9.5
Pet. Crude 4 6.9 9.4
Example -4, additive composition 30 ppm Pet. Crude 1 4.7 7.9
Pet. Crude 2 4.2 7.3
Pet. Crude 3 6.2 8.7
Pet. Crude 4 7.0 9.4

[0060] It could be noted that the additive compositions of example 1 and 2 greatly reduces the drop in outlet temperature of type of crude 1 and 2, whereas the additive compositions of example 3 and 4 reduces the drop in outlet temperature of crude 3 and 4. Since, the crude 1 and 2 are more paraffinic in nature, the additive compositions of example 1 and 2seems to be better fouling dispersants for paraffinic based crude oils. Similarly, the crude 3 and 4were more asphaltene in nature, and accordingly, the additive compositions of example 3 and 4were found to be more efficacious for asphaltene based crude oils.
[0061] Example 9: Refinery plant trial
[0062] Refinery trials were conducted with the additive composition. In refinery, the crude oil was preheated to a temperature of 340 ?C - 350 ?C before going into the atmospheric distillation column. The crude oil heating was done using series of heat exchanger trains (called as preheat trains) and a crude oil heater. The crude oil was heated in preheat trains up to 270 ?C - 280 ?C, which is called heater inlet temperature. Rest of the energy requirement to heat up the crude oil up to 340 ?C - 350 ?C was completed by crude oil heater. In case of any fouling in preheat exchangers, the heater inlet temperature decreases, which demands more fuel burning in crude oil heater to bring the crude oil to a desired temperature of 340 ?C - 350 ?C before going into the atmospheric distillation column. The typical crude oil blend flowing through the preheat trains was similar to crude oil 1 and crude oil 2.The efficiency of additive composition of example 2 was conducted at refinery, in order to assess the efficiency of additive composition in real time. The refinery trials were carried out preheat train in crude distillation unit and a schematic of preheat trains are shown in Figure2.In the process, the desalted crude oil passes through preheat train 2 and subsequently goes to preflash drum. The flashed vapor is routed to atmospheric column. The topped crude oil from preflash drum passes through preheat train 3, which consists of two parallel trains of heat exchangers, where the crude oil is heated from 170 ?C to 270 ?C through a series of heat exchanger. The preheated crude oil (270 ?C) from preheat train 3 is routed to furnace/atmospheric heater for final heating to the required temperature.
[0063] During crude oil preheating in preheat exchangers, major fouling takes place in preheat train 3. The composition of example 2 was dosed at the rate of 5 ppm in the crude oil before entering into preheat train 3 in order to maintain the efficient heat transfer in preheat train 3. Temperature of crude oil before preheat train 3 and after preheat train 3 (heater inlet temperature) was recorded for a month. The anti-foulant dosing in crude oil side was done in preheat train 3 upstream of the parallel trains of heat exchanger as indicated in Figure 2.The efficiency of the additive was analyzed by measuring of inlet and outlet temperature of the preheat train 3.The heat difference between inlet and outlet temperature defines the extent of fouling. If the fouling occurs, there is a gradual decrease in the heat difference. The additive was injected for a monthat the rate of 5 ppm dosage and the efficiency is shown in Figure 3. As can be seen from Figure 3, the temperature difference between inlet and outlet temperature is almost constant for entire duration of the trial run, proving that the additive composition of the present disclosure provides better protection against fouling occurrence on internal metal surfaces of a heat exchanger systems of a crude distillation unit.

ADVANTAGES OF THE PRESENT INVENTION
[0064] The additive compositions of the present disclosure are capable of inhibiting deposit of fouling causing materials on hot surfaces of heat processing equipments.
[0065] The additive compositions of the present disclosure eliminates or otherwise reduces fouling of hot surfaces of heat processing equipment and thereby reduces system shutdown time and productivity loss due to cleaning and/or replacing fouled equipments.
[0066] The additive compositions of the present disclosure are highly effective and a veryless quantity thereof is required to disperse the fouling causing materials and retain them in the hydrocarbon stream as compared to known additive compositions.
[0067] The present disclosure provides a method for inhibiting fouling in heat exchangers of preheat train of distillation columns that is simple, reliable and highly economical.
[0068] The present disclosure provides a method for inhibiting fouling in heat exchanger system using a hot liquid processing simulator that facilitates optimization and mimicking of heat exchanger operating parameters such as additive dosing rate and fouling rate with high accuracy.
[0069] The present invention provides a method for inhibiting fouling in heat exchanger system of preheat train of distillation columns, which obviates the disadvantages associated with the art.