US3668111A - Fouling rate reduction in heated hydrocarbon streams with degraded polyisobutylene - Google Patents

Abstract

The deposition of fouling deposits within process equipment operated at elevated temperatures in the presence of hydrocarbons is reduced by combining with the liquid hydrocarbon a foulant inhibiting amount of mechanically degraded polyisobutylene.

Description

United States Patent Dvoracek et a1.

[15] 3,668,l l l 51 June 6, 1972 [54] FOULING RATE REDUCTION IN HEATED HYDROCARBON STREAMS WITH DEGRADED POLYISOBUTYLENE [72] Inventors: Louis M. Dvoracek, Brea; Amir M. Sarem,

Yorba Linda, both of Calif.

[73] Assignee: Union Oil Company of California [22] Filed: July 16, 1970 {21] Appl.No.: 55,594

[52] US. Cl ..208/48 AA, 44/80, 252/59,

252/68 [51] lnt.C1 ..Cl0g 9/16,C10g 9/36,C23f14/00 [58] Field of Search ..208/48; 252/59; 44/80; 203/7 [56] References Cited UNITED STATES PATENTS 3,172,892 3/1965 Le Suer et a1 ..260/376.5

Primary Examiner-Delbert E. Gantz Assistant Examiner-G. E. Schmitkons Anomey-Milton W. Lee, Richard C. Hartman, Lannas S. Henderson, Dean Sandford, Robert E. Strauss and Michael H. Laird 57 ABSTRACT The deposition of fouling deposits within process equipment operated at elevated temperatures in the presence of hydrocarbons is reduced by combining with the liquid hydrocarbon a foulant inhibiting amount of mechanically degraded polyisobutylene.

8 Claims, No Drawings FOULING RATE REDUCTION IN HEATED HYDROCARBON STREAMS WITH DEGRADED POLYISOBUTYLENE BACKGROUND OF THE INVENTION The numerous processes involved in modifying the physical and chemical properties of hydrocarbon oils such as reforming, hydroforming, hydrocracking, isomerization, cracking fractionation, hydrofining and the like, almost without exception, necessitate exposure of the hydrocarbon feed to relatively elevated temperatures. These temperatures are most commonly attained by the use of heat exchangers in which the hydrocarbon feeds, products or intermediates are intimately contacted with heat exchange surfaces. Several of the areas in which this problem was first observed to be a limiting factor include preheat exchangers of crude units, hydrodesulfurizers and fluid catalytic cracking systems. Other problem areas include overhead condeners, reformer reboilers, coker furnaces, vacuum tower and alkylation reboilers, and deethanizers. Although the problems associated with fouling deposit fonnation are probably most acute in the hydrocarbon processing industry, they are by no means limited to those systems. For example, difficulties associated with fouling deposition have also been recognized in petrochemical processing units producing ethylene, styrene, butadiene, isoprene, acrylonitrile and other chemicals.

The problems associated with equipment fouling are well recognized in the art as discussed in Petroleum Products", Guthrie, (McGraw Hill, l960), pp. l-l3. It is also generally recognized that these problems are not necessarily limited to heat exchange apparatus as such. On the contrary, the formation of fouling deposits accompanying the thermally initiated physical or chemical modification of the hydrocarbon stream or selected constituents thereof is observed almost any time the hydrocarbon phase is exposed to a retaining surface, metallic or otherwise, at elevated temperatures in process equipment such as fractionating columns, reactors, intermediate piping, heat exchange equipment and the like.

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 of such deposits are often substantial. Consequently, considerable effort has already been devoted to the solution of these problems with the result that numerous alternative procedures have been proposed for either preventing foulant deposition or removing fouling deposits. These alternatives have met with varying degrees of success.

The fouling deposits which are encountered as a result of the physical and/or chemical modification in the hydrocarbon feed initiated by the 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 (metallic oxides and sulfides), 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 feedstock. The metal organic compounds may also be present in the original feed or may be formed on heat transfer surfaces by combination with corrosion products or other metals carried into the system with the process stream. The formation of organic polymers is most commonly attributed to reaction of unsaturated hydrocarbons. However, polymers can also be formed by the reaction of nitrogen and sulfur containing organic compounds which are believed to polymerize via a mechanism involving oxygen usually in the presence of a metal catalyst. It has been suggested that these metal catalysts may be either corrosion products, i.e., sulfurization or oxidation products, metal-organic compounds or free metal either carried into the system with the process stream or available on the interior surfaces of processing equipment. Coke deposition is usually correlated with the occurrence of hot spots caused by the accumulation of other fouling deposits. Consequently, it can be seen that the metal and organic portions of these fouling deposits interact and influence each other. Thus, any effort to completely control or eliminate fouling deposit formation should include the elimination of both the metal contaminants related to corrosion and the organic polymers referred to.

Fouling deposits may have organic contents as high as percent. However, such deposits typically contain much higher proportions of inorganic substances usually bound together with an inorganic, polymeric or tarry matrix. For example, a typical deposit isolated during the course of these investigations contained 2 weight-percent silica, 38 weight-percent Fqo 1 percent alumina, 18 percent sulfur determined as S0 and 41 percent organic material determined by loss on ignition. The nature of such deposits leads one to the conclusion that fouling results from a rather complex process involving the occurrence of many reactions.

The inorganic constituents of these fouling deposits may be present due to lack of adequate filtering of the hydrocarbon, e.g., crude or topped crude feed, while the scale deposits generally result from deterioration, i.e., corrosion, of the process equipment. The inorganic salts are most commonly derived from crude oils which have not been sufi'rciently desalted prior to processing. However, in some instances it has been found most expeditious to bypass desalination if the salt content of the crude stock, for example to a pipe still, does not exceed 20 pounds per 1,000 barrels. The presence of these inorganic salt and scale components, although undesirable, does not of itself impose a substantial burden on any given process. However, when combined with the tarry or carbonaceous organic fouling deposits these materials contribute to the formation of tenaceous deposits which can be removed only with considerable difficulty.

Several of the approaches taken to minimize these effects involve polishing or coating of the interior process equipment in an effort to reduce their affinity for the organic foulants. However, it is practically impossible to prevent the formation of these deposits by coating the metal surfaces with protective permanent coating without a consequent loss of process efficiency due to the inescapable loss of heat transfer capacity attributable to the coating itself. Nevertheless, such procedures are definitely beneficial in many instances.

Yet another alternative 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 chemical constituents to the hydrocarbon feed which act to either prevent the formation of foulant material or to prevent its adhesion to process equipment. Numerous compositions each of which serve to perform one or more desirable functions have been devised for the purpose of preventing or mitigating the efiects of fouling deposit formation in process systems. Usually these compositions are designed to operate as either metal deactivators, corrosion inhibitors, detergents, dispersants or anti-oxidants. In addition, it is also advantageous to formulate compositions that perform more than one of these functions at the same time in order to combat a plurality of undesirable effects.

Corrosion inhibitors suitable for these purposes have been discussed in detail by previous investigators such as, Bregman in his book Corrosion Inhibitors, MacMillan Company, New York, Collier-MacMillan Ltd., London, 1963. Exemplary of conventional corrosion inhibitors are monoand polyamines, monoand polyamides and polyethoxlated amines having about 5 to about 200 carbon atoms per molecule, and the salts of organic and inorganic acids such as acidic, oleic, dimeric, naphthenic, and phosphoric acids. This class of compounds is intended to include polyfunctional amphoteric compounds such as aminocarboxylic acids containing dissimilar functional groups, e.g., amino and carboxylate groups or linkages. The most common corrosion inhibiting compositions employed in such applications are the relatively high molecular weight amines preferably the cyclic or endocyclic secondary amines having about 18 to about 50 carbon atoms and one to about 3 amino groups per molecule similar to those described in connection with the detergent-dispersant compositions, infra. The

substituted and unsubstituted imadazolines, amines and aliphatic acid salts are illustrative of compounds within this class having effectiveness as corrosion inhibitors. These compositions are usually employed in concentrations within a range of l to about 1,000 ppm.

Several metal deactivators have found considerable commercial success exemplary of which are N,N-disalicylidene-1, Z-diaminopropane marketed by Ethyl Corporation as Ethyl metal deactivator and N,N -disalicylidenel 2- propanediamine in an organic solvent marketed as DMD by DuPont. The metal deactivators are usually employed to complex or otherwise inhibit the chemical activity of metals originally present in hydrocarbon stream or picked up by contact with processing equipment. As a general rule very minor concentrations of these deactivators are effective for accomplishing the prescribed purpose. These concentrations are usually within the range of about 0.1 to about 1,000 ppm based on total hydrocarbon.

A number of detergent compositions have found varying degrees of commercial acceptance. These compositions also often serve as dispersants when such functionability is desired.

Exemplary of effective detergents, which also generally exhibit dispersant properties are the sulfonates, usually including the normal and basic metal salts of petroleum sulfonic (mahogany) and long chain alkyl substituted benzene sulfonic acids usually having about eight to about 100 carbon atoms and up to about 5 sulfonic acid or sulfonate groups per molecule; phosphonates and/or thiophosphonates, including the normal and basic salts of the phosphonic and/or thiophosphonic acids obtained from the reaction of polyolefms such as polyisobutenes with inorganic phosphorus agents, principally phosphorus pentasulfide; phenates including the normal and basic metal salts of alkylphenols, alkylphenol sulfides, and alkylphenol-aldehyde condensation products usually having up to about 20 carbon atoms per molecule; alkyl substituted salicylates including the normal andb asic metal salts, especially the carboxylate and carboxylate-phenate salts, of long chain alkyl substituted salicylic acids; alkenyl succinimides having about 20 to about 200 carbon atoms per molecule, alkali metal naphthenates having about to about 30 carbon atoms; and primary and secondary amines and carboxylic acids generally having about 10 to about 50 carbon atoms and up to about four amino groups. The most effective high molecular Weight amines presently employed to any substantial degree are the endocyclic five and six membered substituted cyclic amines such as imidazoline. One or more of these detergent-dispersant com.- positions can be employed in combination in any given application. Although very minor concentrations of these constituents are effective in somewhat reducing the degree of foulant deposit accumulation they are generally employed in concentrations within a range of about 1 to about 1,000 ppm.

Currently, the most popular oxidation inhibitors are those formulated with the view of producing a composition having the ability to reduce organic peroxide concentration in a hydrocarbon process stream thereby interrupting chain oxidation reactions. Exemplary of effective anti-oxidants are the hydrocarbyl sulfides, disulfides, sulfoxides, phosphites, monoand poly-acyclic and cyclic amines such as the condensation products of cyclohexylamine or aromatic diamines with catechol, its alkaline derivatives and/or alkyl phenols, substituted and unsubstituted phenols, selenides and zinc dithiophosphates. Similar compositions are described in more detail in U.S. Pat. No. 3,342,723. Anti-oxidant compositions also often contain compounds possessing one or more of these functional groups such as N,N'-di-sec-butyl-p-phenylenediamine, N,N'-butyl-p-aminophenol, 2,6-di-t-butyl-pcresol and the like.

As mentioned above, fouling inhibitor compositions are often formulated with the view of preventing or inhibiting one or more undesirable fouling reactions. Hence, these additives often contain poly-functional compounds or one or more compounds having dissimilar functional groups. Exemplary of commercially available poly-functional additives are Polyflo and marketed by Universal Oil Products. Polyflo 135 is believed to comprise alkyl substituted ethoxylated catechol and a corrosion inhibitor comprising a long chain dimeric aliphatic acid and a primary amine. Polyflo 140 is believed to comprise a polyhydroxy ethoxylated amine. These compositions are described in more detail in U.S. Pat. No. 3,062,744 incorporated herein by reference. Another composition marketed as a fouling inhibitor is Betz AF-l04 marketed by Betz Laboratories of Philadelphia, Pa. This composition is believed to comprise a metal deactivator similar to those above described, a bi-functional phenolic amine and an alkyl substituted succinimide. Succinimides of this nature are described in U.S. Pat. No. 3,380,909. Similar compositions are discussed in more detail in U.S. Pat. Nos. 3,271,295, 3,271,296 and 3,437,583 incorporated herein by reference.

Nalco 261, available from Nalco Chemical Company, is also a commercially available fouling inhibitor and is believed to contain morpholine and a water soluble salt of ethoxylated imidazoline. Similar compositions are discussed more comprehensively in U.S. Pat. Nos. 3,105,810, 3,261,774 and 3,224,957 incorporated herein by reference. Tretolite Aftol-2l, designed primarily for the prevention of fouling in process heat exchange equipment, is marketed by the Petrolite Corporation and is believed to consist primarily of Succinimides.

It should be observed that the exact composition of these fonnulations is not generally made public by the manufacturers of the respective compositions and can be at best only approximated analytically by considerable effort. Nevertheless, the presence of certain functional groups can be established with relatively certainty and to a degree sufficient to illustrate the effectiveness of the compositions of this invention relative to previously described compositions. In addition, these compositions and information regarding their use are of course available from the respective manufacturers noted above.

Unfortunately none of the expedients intended to reduce deposit formation thus far developed are successful in completely eliminating this source of difiiculty in hydrocarbon processing. Consequently, efiorts are continuing to effect even greater improvement in both the physical and chemical systems involved in these operations to minimize if not completely eliminate fouling deposit formation. In this regard, we have discovered that a considerable reduction in deposit formation rate can be effected by adding a fouling inhibiting amount of mechanically degraded polyisobutylene to the hydrocarbon stream in contact with process equipment at elevated temperatures. f

It is therefore one object of this invention to provide a method for reducing the formation of fouling deposits in hydrocarbon process systems. Yet another object of this invention is to prevent or at least minimize the formation of fouling deposits in the interior of hydrocarbon processing equipment. Yet another object of this invention is the reduction of fouling deposit formation on heat exchange surfaces in contact with hydrocarbon media. 7

In accordance with one embodiment of this invention the fouling deposit formation rate in hydrocarbon processing equipment in contact with foulant producing hydrocarbon oils at elevated temperatures, e.g., above about 250 F is reduced by the addition of a foulant inhibiting amount of mechanically degraded polyisobutylene.

The foulant inhibiting compositions of this invention can be employed in combination with essentially any hydrocarbon process stream including light distillates, e.g., naphthas, kerosenes and the like, middle distillate stocks from cracking operations, virgin crude oils, topped crude oils, etc. The great majority of hydrocarbon streams usually employed in such processes boiled above about 200 F. However, the greater fouling problems are usually associated with high boiling stocks, particularly in those containing a substantial portion of unsaturated hydrocarbon constituents boiling between about 400 and 1,200 F. Hydrocarbons boiling substantially above 1,200 F. generally decompose on heating to temperatures above that point. Therefore, most feeds are generally characterized as having top and boiling points of 1,200 F. or less. Hydrocarbon mixtures which generally exhibit the greatest propensity for producing foulant deposits are those containing unsaturated hydrocarbons, e.g., olefins and aromatics usually in amounts of at least about 5 volume-percent and generally in excess of volume-percent. Olefin concentrations are usually in excess of about 5 volume-percent.

The fouling problem associated with these hydrocarbon mixtures is generally promoted at elevated temperatures. The mechanisms are believed to involve polymerization or a combination of polymerization and oxidation which in some respects are similar to the mechanisms leading to gum formation in gasolines. The high temperatures attained in heat transfer or other process steps are believed to promote the combination of hydrocarbons with oxygen to form a polymeric material that may deposit on the surfaces of process equipment, particularly in heat transfer areas.

Although fouling promoted by this mechanism, i.e., oxidative polymerization and the like, might be controlled by excluding oxygen from the process, that objective cannot always be economically achieved. For example, the ordinary floating roof tanks in which feedstocks are frequently stored are not completely effective in preventing contact of the hydrocarbon with atmospheric oxygen. Furthermore, many feedstocks con tain oxygen as they are received at a refinery or at a process site. Consequently the utilization of other alternatives for the prevention of foulant formation such as the antifoulant compositions of this invention are often necessary.

It is presently believed that these antifoulant compositions operate in one of two ways or a combination of both to effect reduction of foulant deposits. They may either prevent the formation of high molecular weight polymeric material or highly condensed polynuclear aromatic carbonaceous deposits in hydrocarbon process streams by interferring with the chemical mechanisms necessary to the formation of such agents. On the other hand, a mechanically degraded polyisobutylene herein described may reduce the affinity of the process equipment surfaces for the polymeric or carbonaceous substances once formed, thereby maintaining those materials in solution in the form of small dispersed particles or globules exhibiting relatively low fouling tendencies. This finding is rather surprising particularly in view of the marked superiority exhibited by mechanically degraded polyisobutylenes as compared to nondegraded isobutylene polymers lending a unique utility to these materials that provide a number of substantial economic advantages. The conclusions are believed reasonable in view of the substantial savings to be realized by either preventing or reducing the frequency of unit shutdown and turnaround necessitated by excessive heat transfer or fluid flow loss due to fouling. The expense involved in such unit shutdowns due to both maintenance expenditures and loss in operating time is generally well known and need not be elaborated upon herein.

Due to the nature of the mechanism believed to account for the observed deposit formation, the problem is usually noticed at temperatures above about 250 F. and generally within the range of about 350 to about 800 F. Temperatures substantially above this upper limit of 800 F. usually result in some thermal cracking which is generally undesirable.

Numerous procedures available for producing isobutylene polymers suitable for application within the concept of this invention are generally well known and need not be described in detail herein. The mechanically degraded polyisobutylenes presently preferred in this invention are prepared from polymers having a viscosity-average molecular weight within the range of about 100,000 to about 400,000. The desired degree of mechanical degradation is conveniently effected by subjecting the polymer either in the molten state or in the form of a relatively concentrated solution, i.e., between about 5 and weight-percent polymer in a compatible solvent such as aliphatic and/or aromatic hydrocarbons having up to 30 carbon atoms per molecule, to mechanical shear of severity sufficient to break down the polymer linkages. Shear rates on the order of at least about 1,000 reciprocal seconds and preferably 5,000 to about 50,000 reciprocal seconds are presently preferred. Contact times at the shear rates necessary to effect the desired degree of mechanical degradation are usually at least about 5 minutes, preferably 5 to about 30 minutes.

A particularly effective indicator of the degree of degradation achieved is the Brookfield viscosity of a relatively dilute solution of degraded polymer as compared to a similar solution of nondegraded polyisobutylene. As a general rule, it is preferable to reduce the Brookfield viscosity of a 5 weightpercent solution of the original polyisobutylene in a standard solvent, e.g., kerosene, by a factor of at least about 10, preferably 20 to about 500. The resulting degraded polymers generally have Brookfield viscosities within the range of about to about 10,000 centipoise.

The exact nature of the modification affected by mechanical degradation which accounts for the marked improvement in fouling inhibition exhibited by the degraded polymers is not known with certainty. As previously mentioned, the observed results may be attributable either to chemical or physical modifications of the polymer or a combination of both.

Even minute amounts of the degraded polyisobutylenes are effective for reducing fouling rates. However, any substantial degree of improvement generally necessitates the use of at least about 0.5 ppm of the degraded polymer. Concentration levels within a range of 1 to about 100 ppm are most common although it is presently preferred to employ about 1 to about 50 ppm of the polymer in most systems. The lower concentrations, i.e., up to about 50 ppm are presently preferred in view of observations based on experimentation to date indicating that concentrations of 50 ppm and above do not appear to provide the same degree of advantage realized with somewhat lower amounts of polymer. This observation itself is rather anomalous and is as yet unexplained. Nevertheless, in view of these observations there is little to be gained by employing polymer concentrations substantially in excess of 100 ppm in view of the added expense associated with high polymer concentrations, which are not presently justifiable on the basis of improved performance.

The following examples are presented to illustrate the effectiveness of the described procedures and should not be con strued as limiting thereof.

EXAMPLES l-l2 These examples were run-sequentially with different fouling inhibitors and inhibitor concentrations in a two-stage preheater employing a feed boiling between 307 and 701 F. containing 30 volume-percent aromatics, 1 percent olefins and 69 percent saturates, and having an API Gravity of 33.5 at 60 F.

The two preheaters were operated in series with the first heater operating across a temperature range of 75 F. to 425 F. and an outlet temperature of 600 F. Each heater constituted an elongate tubular shell and an axially disposed resistive heater defining an annular cross section for the passage of the process stream. This apparatus was a modification of the Erdco coker originally developed to test the thermal stability of turbine fuels in accordance with ASTM Dl 660. The ASTM apparatus usually employs aluminum tubes and filters upstream and downstream of the apparatus. In order to obtain more adequate discrimination between these several fouling inhibitors in this invention, the ASTM Erdco Coker apparatus was modified by removal of the filtering systems and substitution of a carbon steel tube for the original interior aluminum tube surrounding the resistive heater. The substitute carbon steel tube was of the same dimensions as the original aluminum apparatus and could be removed for weighing to determine the amount of weight gained during a specified period of operation. As already mentioned, further modification included the use of two of these Erdco Coker tubes in series to more closely simulate the operation of series stage heat exchange at different temperature levels.

During each run the antifoulants were injected into the hydrocarbon stream upstream of the first heating stage and the hydrocarbon-additive admixture was continuously passed through the series heaters at a rate of 4.5 pounds/per hour corresponding to -a linear flow rate of 0.07 feet per second through each heater. Each run was continued for 90 minutes at the .conditions and with the compositions illustrated in the table. The heat exchange tubes were weighed before and after each period of operation to determine the weight gain attributable to fouling deposit formation.

The mechanically degraded polyisobutylene in Examples 8 and 9 was prepared by shearing a kerosene solution of weight-percent Oppanol B-200 having a weight-average molecular weight of 200,000 in a Waring Blender at a shear rate of approximately 20,000 reciprocal seconds for a period of to about minutes sufficient to reduce the Brookfield viscosity of the solution from its original value of 37,800 centipose at 6 rpm to a final value of 365 centipose at 6 rpm. The resultant kerosene solution of the degraded material was then added as such to Examples 8 and 9 in the proportions indicated. I

TABLE Amount Wt. Gain of Tubes, gms Exp. Additive ppm 1st Tube, 2nd Tube,

1 None .0059 .0616 2 None a .0083 .0622 3 UOP Polyflo 135 10 .0063 .0358 4 Oppanol 13-200 50 .0178 .0370 5 Betz Al -104 10 .0120 .0719 6 Oppanol B200 10 .0080 .0147 7 None .0098 .0362 8 Oppanol B200 10 .0059 .0010 Degraded 9 Oppanol 5-200 50 .0051 .0394

Degraded l0 Nalco 261 10 .0042 .0117 1 1 UOP Polyflo 140 10 .0077 .0185 12 Tretollte Aftol The results of these examples illustrate that the mechanically degraded polyisobutylene (degraded Oppanol B-200) evidenced antifouling characteristics markedly superior to those of the other available fouling inhibitors, particularly at lower concentrations, i.e., 10 ppm. The undegraded polyisobutylene actually increased the fouling rate in the first tube having an outlet temperature of 425 F. as illustrated by the weight gain in Example 4 of 0.0178 grams at a level of 50 ppm of additive. However, the undegraded polyisobutylene of that example was effective in reducing the weight gain in the second tube from about 0.06 to about 0.037. This performance was markedly improved at the lower concentrations of undegraded polyisobutylene as illustrated in Example 6. In that example employing 10 ppm of the undegraded polyisobutylene the fouling rate in the first tube was only 0.008 grams for a 90 minute operation while the weight gain for the same period in the second tube was reduced to 0.0147 grams. The improvements attributable to mechanical degradation of polyisobutylene are apparent from comparison of these examples, i.e., Examples 4 and 6 to Examples 8 and 9. In Example 9 the 50 ppm of mechanically degraded polyisobutylene was sufficient to'reduce fouling in the first tube to 0.0051 gms accounting for a substantial reduction as compared to the weight gain of 0.0178 gms observed with 50 ppm undegraded polyisobutylene in Example 4. The weight gain in the second tube of both of these examples was approximately the same. However, at 10 ppm the mechanically degraded polyisobutylene employed in Example 8 was effective not only in reducing the weight gain in the first tube to 0.0059 gms but dramatically reduced fouling in the second tube to a level of only 0.001 gms, 11 times less than the next lowest value observed in Example 10 with Nalco 261. The advantages of this procedure are readily apparent from these observations.

WE CLAIM:

l. A method for reducing the fouling rate in process equipment containing foulant producing hydrocarbons boiling above about 200 F. at temperatures above about 250 F. which comprises admixing with said hydrocarbon oil at least about 0.5 ppm of mechanically degraded polyisobutylene having a Brookfield viscosity within the range of about to about 10,000 cp.

2. The method of claim 1 wherein said hydrocarbon contains at least about 5 volume percent of unsaturated constituents including olefins and aromatics and is admixed with an amount of said mechanically degraded polyisobutylene within a range of about 1 to about 100 ppm.

3. The method'of claim 1 wherein said hydrocarbon contains at least about 15 volume percent of unsaturated hydrocarbon constituents selected from olefinic and aromatic hydrocarbons, said hydrocarbon boils within a range of about 400 to about 1,200 F. and is contacted in said process equipment at a temperature within the range of about 350 to about 800 F., and said mechanically degraded polyisobutylene is produced by subjecting a polyisobutylene polymer having a viscosity-averagemolecular weight within a range of about 100,000 to about 400,000 to a shear rate of at least about 1 ,000 reciprocal seconds for at least about 5 minutes.

4. The method of claim 1 wherein said hydrocarbon boils within the range of about 400 to about 1,200 F. and contains at least about 15 volume percent of unsaturated hydrocarbon constituents selected from olefinic and aromatic hydrocarbons, and said hydrocarbon is contacted in said process equipment at a temperature within a range of about 350 to about 800 F. in the presence of about 1 to about 50 ppm of said mechanically degraded polyisobutylene produced by subjecting an isobutylene polymer having a weight-average molecular weight within a range of about 100,000 to about 400,000 to mechanical shear sufficient to reduce the Brookfield viscosity of a 5 weight-percent solution of said polymer in kerosene by a factor of at least about 10.

5. The method of reducing fouling rate in hydrocarbon heat exchange equipment operating on hydrocarbons boiling within a range of about 400 to about l,200 F. and containing at least about 15 volume-percent of unsaturated hydrocarbons selected from olefinic and aromatic hydrocarbons at a temperature within a range of about 350 to about 800 F. which comprises contacting said hydrocarbons in said heat exchange equipment in the presence of at least about 0.5 ppm of mechanically degraded polyisobutylene having a Brookfield viscosity within the range of about 100 to about 10,000 cp.

6. The method of claim 5 wherein said mechanically degraded polyisobutylene is prepared by subjecting polyisobutylene having a viscosity-average molecular weight within a range of about 100,000 to about 400,000 to a shear rate of at least about 1,000 reciprocal seconds for at least about 5 minutes.

7. The method of claim 5 wherein said mechanically degraded polyisobutylene comprises about 1 to about 50 ppm of said hydrocarbon phase and is prepared by subjecting said polyisobutylene having a weight-average molecular weight within the range of about 100,000 to about 400,000 to a shear rate and for aperiod of time sufficient to reduce the Brookfield viscosity of a 5 weight-percent solution of said polymer in kerosene by a factor of at least about 10.

8. The method of claim 5 wherein said foulant producing hydrocarbon feed is selected from normally liquid light distillate, middle distillate and residual hydrocarbon fractions and combinations thereof, and said mechanically degraded 400,000 to mechanical shear at a rate and for a period of time sufficient to reduce the Brookfield viscosity of a 5 weight-per- 7 cent solution of said polymer in kerosene by a factor of at least about 10.

k i l

Claims (7)

1. 2. The method of claim 1 wherein said hydrocarbon contains at least about 5 volume percent of unsaturated constituents including olefins and aromatics and is admixed with an amount of said mechanically degraded polyisobutylene within a range of about 1 to about 100 ppm.
2. 3. The method of claim 1 wherein said hydrocarbon contains at least about 15 volume percent of unsaturated hydrocarbon constituents selected from olefinic and aromatic hydrocarbons, said hydrocarbon boils within a range of about 400* to about 1, 200* F. and is contacted in said process equipment at a temperature within the range of about 350* to about 800* F., and said mechanically degraded polyisobutylene is produced by subjecting a polyisobutylene polymer having a viscosity-average molecular weight within a range of about 100,000 to about 400,000 to a shear rate of at least about 1,000 reciprocal seconds for at least about 5 minutes.
3. 4. The method of claim 1 wherein said hydrocarbon boils within the range of about 400* to about 1,200* F. and contains at least about 15 volume percent of unsaturated hydrocarbon constituents selected from olefinic and aromatic hydrocarbons, and said hydrocarbon is contacted in said process equipment at a temperature within a range of about 350* to about 800* F. in the presence of about 1 to about 50 ppm of said mechanically degraded polyisobutylene produced by subjecting an isobutylene polymer having a weight-average molecular weight within a range of about 100,000 to about 400,000 to mechanical shear sufficient to reduce the Brookfield viscosity of a 5 weight-percent solution of said polymer in kerosene by a factor of at least about 10.
4. 5. The method of reducing fouling rate in hydrocarbon heat exchange equipment operating on hydrocarbons boiling within a range of about 400* to about 1,200* F. and containing at least about 15 volume-percent of unsaturated hydrocarbons selected from olefinic and aromatic hydrocarbons at a temperature within a range of about 350* to about 800* F. which comprises contacting said hydrocarbons in said heat exchange equipment in the presence of at least about 0.5 ppm of mechanically degraded polyisobutylene having a Brookfield viscosity within the range of about 100 to about 10,000 cp.
5. 6. The method of claim 5 wherein said mechanically degraded polyisobutylene is prepared by subjecting polyisobutylene having a viscosity-average molecular weight within a range of about 100, 000 to about 400,000 to a shear rate of at least about 1,000 reciprocal seconds for at least about 5 minutes.
6. 7. The method of claim 5 wherein said mechanically degraded polyisobutylene comprises about 1 to about 50 ppm of said hydrocarbon phase and is prepared by subjecting said polyisobutylene having a weight-average molecular weight within the range of about 100,000 to about 400,000 to a shear rate and for a period of time sufficient to reduce the Brookfield viscosity of a 5 weight-percent solution of said polymer in kerosene by a factor of at least about 10.
7. 8. The method of claim 5 wherein said foulant producing hydrocarbon feed is selected from normally liquid light distillate, middle distillate and residual hydrocarbon fractions and combinaTions thereof, and said mechanically degraded polyisobutylene polymer is present in an amount within the range of 1 to about 100 ppm and has a Brookfield viscosity within the range of about 100 to about 10,000 and is prepared by subjecting polyisobutylene having a viscosity-average molecular weight within a range of about 100,000 to about 400,000 to mechanical shear at a rate and for a period of time sufficient to reduce the Brookfield viscosity of a 5 weight-percent solution of said polymer in kerosene by a factor of at least about 10.