Mixed base complex antifoulant compositions and use thereof

Description

Background of the Invention

[0001] The processes involved in oil, gas and petrochemical refining, for example, reforming, hydroforming, absorption, hydrocracking, isomerization, extraction, cracking, fractionation, hydrofining, desalting and the like, expose hydrocarbon streams to relatively elevated temperatures. These temperatures are most commonly attained by the use of heaters and heat exchangers in which the hydrocarbon feeds, products and intermediates are intimately contacted with heated surfaces. These conditions are known to promote the formation of fouling deposits which can drastically limit refining capacities and flow rates.

[0002] Many areas in refining operations are subject to fouling, including such areas as preheat exchangers on crude units, hydrodesulfurizers, fluid catalytic cracking units, overhead condensers, reformer reboilers, coker furnaces, vacuum towers, alkylation reboilers and the like.

[0003] Although the problems associated with fouling are most acute in the oil refining industry, they are also a persistent problem in gas plant refining operations and in petrochemical processes involving, for example, ethylene, styrene, butadiene, isoprene, acrylonitrile and other chemicals.

[0004] The formation of fouling deposits accompanying the thermally initiated physical or chemical modification of hydrocarbons and deivatives is observed any time a hydrocarbon or derivative phase is exposed to a retaining surface, metallic or otherwise, at elevated temperatures in process equipment. Deposits of this nature are known to materially decrease heat transfer characteristics of the affected systems and are generally removed only with considerable difficulty. The consequent increases in operating and maintenance expense accompanying the formation and removal of such deposits is often substantial. Consequently, considerable effort has been devoted to attempts to eliminate fouling problems, with the result that numerous methods have been proposed for either preventing foulant deposition or removing fouling deposits. These methods have met with varying degrees of success but the essential problem remains.

[0005] The fouling deposits which are encountered as a result of the physical and/or chemical modification of hydrocarbon feeds initiated by elevated process temperatures may consist of sticky, tarry, polymeric or carbonaceous material. The most common fouling deposits can be generally classified as inorganic salts, corrosion products, metal-organic compounds, organic polymers and coke. The inorganic salts such as sodium, calcium and magnesium chloride are probably carried into the process system with the crude feed stock. Metal-organic compounds may also be present in the feed stock or may be formed on heat transfer surfaces by combination with corrosion products or other metals carried into the system. The formation of organic polymers is most commonly attributed to reaction of unsaturated hydrocarbons. Coke deposition is usually associated with the occurrence of hot spots caused by the accumulation of fouling deposits. Consequently, it can be shown that, in such processes, the metal and organic elements of fouling deposits interact with each other.

[0006] Several approaches have been taken to minimize the accumulation of foulant materials in process equipment. Some approaches involve polishing or coating process equipment in an effort to reduce affinity for fouling materials. It is practically impossible, however, to prevent the formation of fouling deposits by coating metal surfaces with protective permanent coatings without a consequent loss of process efficiency due to the loss of heat transfer capacity attributable to the coating itself.

[0007] Another approach, which does not necessitate the expense involved in process equipment coating and does not result in the accompanying loss in heat transfer capacity, involves the addition of chemicals to the hydrocarbon feed which act to either prevent the formation of fouling material or to prevent adhesion thereof to process equipment. Numerous compositions have been suggested for the purpose of preventing or mitigating the effects of fouling deposit formation in process systems but none is considered completely successful.

Field of the Invention

[0008] This invention relates to novel antifoulant compositions and to the use thereof to inhibit fouling of equipment used in the refining of crude oil, gas and petrochemicals and in the thermal processing of other organic materials. In particular, the invention relates to the use of colloidally dispersed overbase complex antifoulants in oil refineries, gas plants and petrochemical refineries. More particularly, the invention relates to overbase complexes of magnesium oxides and magnesium carbonates with at least one complexing agent and to their use as antifoulants in oil, petrochemical and gas refining operations.

Prior Art

[0009] A wide variety of antifoulants has been used in attempts to inhibit fouling associated with the decomposition of crude and refined oils, gases and petrochemical feed streams. A partial, but representative, listing of patents relating to antifoulant compositions and their uses is set forth below.
2,895,913      4,410,418
3,364,130      4,425,223
3, 92,219      4,431,514
3,546,097      4,440,625
3,666,656      4,444,649
3,772,182      4,456,526
4,024,051      4,469,586
4,107,030      4,510,041
4,200,518       4,511,457
4,319,063      4,529,500
4,397,737      4,552,643 /DL>4,404,087      4,556,476

[0010] These patents describe the use of oil dispersible magnesium-containing organic compositions in lubricating oils (2,895,913), amide condensation products in petroleum processing equipment, metal deactivators for use in hot petroleum charge stock, mixtures of methacrylate polymers and a nitrogen-containing material, oil-soluble addition type copolymers, a mixture of nitrogen-containing methacrylate polymer, a Schiff's base and a diarylamine, inorganic phosphorous-containing acids and salts, sulfanilic acid amine salts, polyalkylene amines, a mixture of a sulfonate, amine and phenylhydrazine, poly(oxyalkylene)carbamates, metals such as tin, antimony and germanium, halogen-containing silicon compounds, mixtures of a phosphorus acid ester and a hydrocarbon sulfonic acid, the reaction product of a polyalkylene amine and a hydroxy fatty acid, a mixture of a hydroxylamine and an organic surfactant, phosphates, a mixture of a hydroxylamine and a catechol, saturated sulfoxides, mixtures of phenothiazines and phenols, mixtures of phenothiazines, catechols and hydroquinones, phenothiazine dimers, combinations of tin, copper and antimony and mixtures of phenothiazines and hydroxylamines. Additionally, UK Patent Appln. 2017747 A describes sodium di-2-ethylhexylsulphosuccinates as fouling inhibitors for crude petroleum oil and UK Patent 2021144 B describes polyalkylenoxy sulfoxy salts for preventing and removing fouling deposits on refining equipment for hydrocarbon feed streams.

[0011] Overbased oil-stable, fluid dispersions or "solutions" of complexes, containing, e.g., magnesium and calcium, and their preparation and use are well known to those skilled in the art. The term "overbase" historically refers to metal base/acid reaction products containing an amount of metal in stoichiometric excess of that required to form a neutral organic acid salt of such base. Synonomous terms frequently used include "basic", "highly basic" and "hyperbased".

[0012] Many processes are known for preparing overbased metal-containing dispersions. Representative U. S. Patents which disclose processes for preparing overbased metal complexes including the following:

[0013] U. S. 2,585,520 discloses the preparation of high ly basic magnesium and calcium petroleum sulfonates useful as additives for lubricating oils.

[0014] U. S. 2,895,913 discloses the preparation of stable oil-dispersible over-based organo-magnesium compounds useful as additives in lubricating oils.

[0015] U. S. 3,057,896 discloses the preparation of overbased calcium sulfonates useful as additives for lubricating oils.

[0016] U. S. 3,150,089 discloses stable dispersions of overbased organo-magnesium compounds useful as additives for lubricating oils.

[0017] U. S. 3,629,109 discloses the preparation of overbased organo-magnesium complexes which are useful as lubricant and fuel additives.

[0018] U. S. 3,764,536 discloses the preparation of an overbased calcium salt of alkenlsuccinimide which is useful as a dispersant additive for lubricating oils.

[0019] Additionally, U. S. 3,776,835 discloses detergent-dispersant compositions used as antifoulants in fouling caused by high temperature hydrocarbon streams. Such compositions include sulfonates, especially normal and basic metal salts of benzene sulfonic acids, normal and basic salts of phosphonic and thiophosphonic acids, the normal and basic salts of phenates and carboxylate and carboxylate-phenate salts, alkenyl succinimides, alkali metal naphthenates and amines and carboxylic acids. Various commercial antifoulants are also mentioned, including ethoxylated catechol,polyhydroxyl ethoxylated amines, combination of a metal deactivator, a phenolic amine and a succinimide, and a combination of morpholine and a water soluble salt of an ethoxylated imidazoline.

[0020] U. S. 3,865,737 discloses the preparation of fluid, overbased organomagnesium complex dispersion which is useful as a lubricating composition additive.

[0021] U. S. 4,129,589 discloses the preparation of overbased magnesium salts of sulfonic acids which are useful as lubricant additives.

[0022] U. S. 4,163,728 discloses the preparation of a stable, fluid organomagnesium complex dispersion useful as an acidic neutralization additive for lubricating oils. The compounds disclosed are overbased.

[0023] U. S. 4,293,429 discloses the preparation of an overbased mixture of a magnesium carboxylate and magnesium oxide in the form of a fluid dispersion of submicron-sized magnesium oxide. The compounds are useful as additives for lubricants.

[0024] U. S. 4,295,981 discloses the preparation of overbased magnesium phenates useful as lubricating oil additives.

[0025] U.S. 4,298,482 describes the preparation of an overbased mixture of magnesium salts and magnesium hydroxide in the form of a dispersion of very small particles. The overbased material is useful as an acid neutralizer for lubricating oils and fuels.

[0026] U.S. 4,347,147 discloses the preparation of magnesium sulfonates and magnesium oxide having a small particle size.

[0027] U. S. 4,474,710 discloses the preparation of overbased mixtures of magnesium hydroxide or magnesium carbonate in a liquid magnesium sulfonate dispersant. The materials are useful as lubricant additives.

[0028] None of the above-described patents suggests the use of over-base complexes of metals as described herein to reduce the fouling problems associated with refining operations.

[0029] Of the above-described patents, the disclosures of U. S. 3,865,737, 4,163,728, 4,293,429 and 4,298,482 are particularly informative with regard to the elucidation of the state of the art and the preparation of overbased metal complexes in the form of dispersions. Accordingly, the disclosures of these patents, as regards the discussion of the preparation and composition of overbased metal compounds, is incorporated herein by reference. In particular, Cols. 1-9 of U. S. 3,865,737 is incorporated herein by reference as are Cols. 1-4 of U. S. 4,163,728, Cols. 1-3 of U. S. 4,293,429 and Cols. 1-4 of U. S. 4,298,482.

Summary of the Invention

[0030] The present invention pertains to novel antifoulant compositions which are mixed overbase complexes comprising oil-stable colloidal dispersions of fine particles of magnesium oxide and magnesium carbonate and complexing agents and their use in the inhibition of fouling, particularly high temperature fouling, e.g., 500-1200°F., in refining processes.

Detailed Description of the Invention

[0031] As set forth above, prevention of fouling in oil, gas and petrochemical refining has been a particularly troublesome problem. The problem is complicated not only because of the nature of the fouling materials but because the various area of a refining operation present different environments, different feed stocks and different objectives. A fouling problem in one area of a refinery may not necessarily respond to the same antifoulant treatment as does a different area of a refinery. Accordingly, treatment of refining operations must be broken down, unit by unit, and the particular fouling characteristics of each unit must be defined and treated appropriately.

[0032] Use of antifoulant chemicals in an oil refinery are particularly important in the following areas:

1. Addition of antifoulant to the raw crude stream after the desalting operation but prior to entering the crude unit, i.e., the desalted process stream entering the preheat train.

2. Addition of antifoulant to the effluent exchanger train (atmospheric resid), i.e., the effluent from the atmospheric crude column of the crude unit.

3. Addition of antifoulant to the reactor influent and effluent streams to the hydrotreating and hydroprocessing units.

4. Addition of antifoulant to the effluent (bottoms) from the atmospheric crude column, including pumparound circuits and the influent to the gas and oil vacuum furnaces and columns.

5. Addition of antifoulant to the feed to the coker furnace (delayed or fluid) and to the coker furnace itself and the transfer lines and pumparound circuits attached to the coker furnace.

6. Addition of antifoulant to the main fractionator effluent of the alkylation unit prior to the reboiler and the reboiler pumparound circuit. Antifoulant should also be added to the reboiler itself.

7. Addition of antifoulant to the feed to the preheater to the fluid catalytic cracking unit and to the effluent from the cracking unit to the slurry exchange system, including the bottoms from the main fractionator tower and pumparound and the catalytic cracker unit pumparound circuit.

[0033] Each of the above areas of a refinery operate in individually characteristic manners in view of their special environments which do not necessarily have characteristics in common with other areas of the refinery.

[0034] The following is a summary of the important units of, for example, an oil refinery which require addition of antifoulant chemicals:
Crude unit preheat exchanger      Hydrotreater
Crude unit vacuum resid exchanger      Hydrocracker
Crude unit vacuum distillation heater and resid      Reboilers
Fluid catalytic cracker preheat      Hydrodesulfurizers
Fluid catalytic cracker slurry pumparound      Heat exchangers
Fluid catalytic cracker furnace      Hot separators
Delayed coker      Pumparound circuits
Fluid coker      Process stream tubes

[0035] In accordance with the present invention, it has been found that if an oxide and carbonate of magnesium is prepared in conjunction with organic acid complexing agents, a product results which is an overbase complex of Mg oxide and Mg carbonate, in extremely fine, preferably submicron particle size, and the magnesium metal salt of the complexing agents. It is theorized that the presence of the complexing agent, during preparation of the metal oxide and carbonate, protects the fine particles of metal oxide or carbonate from agglomerating and allows the fine particles to remain dispersed in a stable manner in the diluent used in th e reaction and, later, in a hydrocarbon stream.

[0036] The exact nature of overbase is not understood. It has been suggested that they comprise dispersions of salts formed by contacting an acidic material with a basically reacting metal compound, e.g., a metal hydroxide. Alternatively, it has been suggested that they comprise "polymeric salts". It is believed that neither theory is incorrect but that neither is completely correct. In accordance with the present invention, it is believed that the preparation of an "overbased" material results in an "overbase complex" of a metal oxide or carbonate with an organic acid dispersant or stabilizer (i.e., "complexing agent"). The nature of the complex so-formed is not completely understood.

[0037] Accordingly, as used in the present specification, an "overbase complex" is a complex of an oxide or carbonate of magnesium and a magnesium salt of an organic acid "complexing agent". The overbase complex contains a stoichiometric excess of metal, relative to the number of equivalents of acid complexing agent which is reacted with a basic metal compound to afford the complex, based on the normal stoiochiometry of the particular metal base and acid. For example, a "neutral" or "normal" metal salt of an acid is characterized by an equivalent ratio of metal to acid of 1:1, while an overbased salt is characterized by a higher ratio, e.g., 1.1:1, 2:1, 5:1, 10:1, 15:1, 20:1, 30:1 and the like. The term "metal ratio" is used to designate the ratio of (a) equivalents of metal to acid in an overbased salt to (b) the number of equivalents expected to be present in a normal salt, based on the usual stoichiometry of the metal or metals involved and the acid or acids present. Thus, an oil dispersion of an overbased magnesium salt containing two equivalents of acid and twenty equivalents of magnesium would have a metal ratio of 10 (i.e., 20÷(1+1)).

[0038] In the present specification, magnesium, for example, is regarded as having two equivalents per atomic weight; magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)₂), two equivalents per mole. Organic acids are regarded as having one equivalent of acid per acidic hydrogen or acid group. Thus, a monocarboxylic acid or monosulfonic acid or their equivalent derivatives, such as esters and ammonium and metal salts, have one equivalent per mole of acid, ester or salt; a disulfonic acid or dicarboxylic acid, or equivalent derivative, has two equivalents per mole. The basically reacting metal compounds such as the oxides and carbonates of magnesium have two equivalents per mole (i.e., two equivalents per atomic weight of metal).

[0039] The complex antifoulants of the invention are overbase complexes of magnesium oxides and magnesium carbonates and magnesium salts of organic acid complexing agents.

[0040] The mixed overbase complexes used in the present invention may be prepared in any manner known to the prior art for preparing overbased salts, provided that the overbase complex resulting therefrom is in the form of finally divided, preferably submicron, particles capable of forming a stable dispersion in oil.

[0041] Thus, a preferred method for preparing the magnesium oxide/complexing agent overbase complex of the present invention is to form a mixture of a magnesium base, e.g., Mg(OH)₂, a complexing agent, e.g., a fatty acid such as a tall oil fatty acid, which is present in a quantity much less than that required to stoichiometrically react with the hydroxide, and a non-volatile diluent. The mixture is heated to a temperature ofabout 250-350°C. whereby there is afforded the overbase complex of magnesium oxide associated with the Mg salt of the complexing agent. The magnesium carbonate/complexing agent overbase complex is prepared in the same manner as described above, except that carbon dioxide is bubbled through the initial reaction mixture.

[0042] The above-described method of preparing the overbase complexes of the present invention is particularly set forth in U. S. P. 4,163 ,728 which is incorporated herein by reference in its entirety, wherein, for example, a mixture of Mg(OH)₂ and a carboxylic acid complexing agent is heated at a temperature of about 280-330°C. in a suitable non-volatile diluent.

[0043] Complexing agents which are used in the present invention are fatty acids, e.g., tall oil fatty acids, and sulfonic acids. The sulfonic acids which are oil-soluble per se are especially useful. Oil-soluble derivatives of these acids, such as their metal salts, ammonium salts, and esters (particularly esters with lower aliphatic alcohols having up to six carbon atoms, such as the lower alkanols), can be utilized in lieu of or in combination with the free acids. When reference is made to the acid, its equivalent derivatives are implicitly included unless it is clear that only the acid is intended.

[0044] Suitable oil-soluble sulfonic acids are represented by the general formulae:
R _x - T - (So₃H) _y      I
Rʹ - (SO₃H)r      II
In formula I, T is a cyclic nucleus of the mono- or polynuclear type including benzenoid, cycloaliphatic or heterocyclic neuclei such as a benzene, naphthalene, anthracene, 1,2,3,4-tetrahydronaphthalene, thianthrene, cyclopentene, pyridine or biphenylnucleus and the like. Ordinarily, however, T will represent an aromatic hydrocarbon nucleus, especially a benzene or naphthalene nucleus. The variable R in the radical R _x can be, for example, an aliphatic group such as alkyl, alkenyl, alkoxy, alkoxyalkyl, carboalkoxyalkyl, an aralkyl group, or other hydrocarbon or essentially hydrocarbon groups, while x is at least 1 with the proviso that the variables represented by the group R _x are such that the acids are oil-soluble. This means that the groups represented by R _x should contain at least about eight aliphatic carbon atoms and preferably at least about twelve aliphatic carbon atoms. Generally x will be an integer of 1-3. The variables r and y have an average value of one to about four per molecule.

[0045] The variable Rʹ in Formula II is an aliphatic or aliphatic-substituted cycloaliphatic hydrocarbon or essentially hydrocarbon radical. Where Rʹ is an aliphatic radical, it should contain at least about 8 to about 20 carbon atoms and where Rʹ is an aliphatic substituted-cycloaliphatic group, the aliphatic substituents should contain about 4 to 16 carbon atoms. Examples of Rʹ are alkyl, alkenyl, and alioxyalkyl radicals and aliphatic-substituted cycloaliphatic radicals wherein the aliphatic substituents are alkoxy, alkoxyalkyl, carboalkoxyalkyl, etc. Generally the cycloaliphatic radical will be a cycloalkane nucleus or a cycloalkene nucleus such as cyclopentane, cyclohexane, cyclohexene, cyclopentene, and the like. Specific examples of Rʹ are cetyl-cyclohexyl, laurylcyclohexyl, cetyloxyethyl and octadecenyl radicals, and radicals derived from petroleum, saturated and unsaturated paraffin wax, and polyolefins, including polymerized mono- and diolefins containing from about 1 to 8 carbon atoms per olefin monomer unit. The groups T, R and Rʹ in Formulae I and II can also contain other substituents such as hydroxy, mercapto, halogen, nitro, amino, nitroso, carboxy, lower carbalkoxy, etc., as long as the essentially hydrocarbon character of the groups is not destroyed.

[0046] The sulfonic acids which are preferred for use herein include alkyl sulfonic acids, alkaryl sulfonic acids, dialkyl sulfonic acids, dialkylaryl sulfonic acids, aryl sulfonic acids, e.g., ethylsulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid and more complex sulfonic acid mixtures such as mahogany sulfonic acids and petroleum sulfonic acids.

[0047] Further, illustrative examples of the sulfonic acids are mahogany sulfonic acids, petrolatum sulfonic acids, mono- and poly-wax-substituted naphthalene sulfonic acids, cetylchlorobenzenesulfonic acids, cetylphenol sulfonic acids, cetylphenol disulfide sulfonic acids, cetoxycaprylbenzene sulfonic acids, dicetyl thianthrene sulfonic acids, di-lauryl beta-naphthol sulfonic acids, dicapryl nitronaphthylene sulfonic acids, paraffin wax sulfonic acids, unsaturated paraffin wax sulfonic acids, hydroxy-substituted paraffin wax sulfonic acids, tetraisobutylene sulfonic acids, tetraamylene sulfonic acids, chloro-substituted paraffin wax sulfonic acids, nitrosyl-substituted paraffin wax sulfonic acids, petroleum naphthene sulfonic acids, cetylcyclopentyl sulfonic acids, lauryl cyclohexyl sulfonic acids, mono-and polywax substituted cyclohexyl sulfonic acids, and the like.

[0048] As used herein the terminology "petroleum sulfonic acids" or "petrosulfonic acids" is intended to cover that well-known class of sulfonic acids derived from petroleum products according to conventional processes such as disclosed in U. S. Pats. 2,480,638; 2,483,800; 2,717,265; 2,726,261; 2,794,829; 2,832,801; 3,225,086; 3,337,613; 3,351,655; and the like. Sulfonic acids falling within Formulae I and II are discussed in prior U. S. patents 2,616,904; 2,616,905; 2,723,234; 2,723,235; 2,723,236; 2,777,874; and the other U. S. patents referred to in each of these patents. Thus it is seen that these oil-soluble sulfonic acids are well-known in the art and require no further discussion herein.

[0049] Of course, mixtures of the above-described organic acids and derivatives thereof may be employed in preparing the antifoulants of this invention.

[0050] The antifoulants of the present invention are a mixture of (A) an overbase complex of fine particle size magnesium oxide and the magnesium salt of a fatty acid and (B) an overbase complex of fine particle size magnesium carbonate and the magnesium salt of a sulfonic acid or mixture of sulfonic acids.

[0051] The overbase complex of magnesium oxide and the magnesium salt of a tall oil fatty acid may be prepared in accordance with the method described in U. S. 4,163,728.

[0052] The overbase complex of magnesium carbonate and the magnesium salt of a sulfonic acid may be similarly prepared by introducing CO₂ during the reaction of Mg(OH)₂ with a sulfonic acid. Also an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids is available commercially as Witco M400.

[0053] The weight ratio of one overbase complex to the other is from about 0.25/10 to about 10/0.25.

[0054] The following example illustrates the uses of a mixed overbase complex as an antifoulant.

Example

[0055] A new fractionation plant in Australia, processing a blend of crude oil and LPG, sufffered severe fouling and faltered after two months on stream. The de-ethanizer reboilers were cleaned but fouling progressively increased. After six months, production was stopped. The plant was cleaned to remove the buildup of foulant in reboilers and the de-ethanizer tower. Foulant blocking in the de-ethanizer tower was more than four feet thick. A 16" diameter pipework was reduced to a 2" diameter flow area. The foulants removed from the reboilers varied in texture from soft putty to crystalline anthracite coal.

[0056] After cleaning, an antifoulant of the invention was injected into the feed to the de-ethanizer at a rate of 100 ppm based on the weight of the hydrocarbon stream. The antifoulant was a mixture of (A) an overbase complex of magnesium oxide and the magnesium salt of a tall oil fatty acid and (B) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids (Witco M400) in a weight ratio of about 1/1.

[0057] Fouling monitoring was accomplished by measuring the overall heat transfer of the reboiler. The plant has now operated for 15 months without a fouling problem.

[0058] As described in U. S. 4,163,728 referred to earlier, the reaction of metal base and acid affords a product which undergoes decomposition to afford minute particles of metal oxide or carbonate in association with the metal salt of the acid. The minute particle s immediately become suspended and stabilized by the metal salt of the acid. The particles of metal oxide or metal carbonate are of a size no greater than about 2 microns in diameter, for example no greater than about 1 micron but, preferably, are no greater than about 0.1 micron and, especially, should be less than 0.1 micron in diameter.

[0059] The amount of antifoulant which is used to inhibit fouling in a fouling area will vary, depending on the environment of the area, the degree of fouling and the specific antifoulant used. In general, an amount of antifoulant is used which is effective to inhibit fouling in an area. Accordingly, there mya be used an amount of from about 5 ppm to about 1000 ppm or more based on the weight of the hydrocarbon stream, depending on specific circumstances. Ordinarily, from about 25 ppm to about 500 ppm are effective, especially from about 50 to about 300 ppm.

Claims

1. Method of inhibiting fouling in an oil refining process which comprises adding to fouling areas in said process other than the visbreaker unit an effective fouling inhibiting amount of an antifoulant comprising (A) an overbase complex of magnesium oxide and the magnesium salt of a fatty acid and (B) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids.

2. Method of claim 1 wherein said fatty acid is a tall oil fatty acid.

3. Method of inhibiting fouling in a gas refining process which comprises adding to fouling areas in said process an effective fouling inhibiting amount of an antifoulant comprising (A) an overbase complex of mganesium oxide and the magnesium salt of a fatty acid and (b) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids.

4. Method of claim 3 wherein said fatty acid is a tall oil fatty acid.

5. Method of inhibiting fouling in a petrochemical refining process which comprises adding to fouling areas in said process an effective fouling inhibiting amount of an antifoulant comprising (A) an overbase complex of magnesium oxide and the magnesium salt of a fatty acid and (B) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids.

6. Method of claim 5 wherein said fatty acid is a tall oil fatty acid.

7. Antifoulant composition comprising (A) an overbase complex of magnesium oxide and the magnesium salt of a fatty acid and (B) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids.