Methods of removing fouling

Abstract

According to one or more embodiments, a method of removing fouling may comprise contacting a workpiece with a cleaning solution comprising a hydrocarbon or alcohol solvent and an alkyl sulfonic acid-based surfactant. The workpiece may comprise a metal surface with a fouling material attached thereto. The contacting the workpiece with the cleaning solution may cause at least a portion of the fouling material to be removed from the metal surface.

Description

86316-WO-PCT / DOW 86316 WO1METHODS OF REMOVING FOULINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 708,903 filed October 18, 2024, the contents of which are incorporated in their entirety herein.BACKGROUND

[0002] Fouling is a common problem in the production of monomers (e.g., ethylene, propylene, and acrylates) and polymers (e.g., polyethylenes and polypropylenes). The fouling material varies by application but usually involves polymeric species attached to metal surfaces, such as those in tubular reactors, heat exchangers and rotating equipment. Common fouling materials include polymers, such as crosslinked polymers which are generally insoluble and are particularly difficult to remove. The fouling materials may also include additives, salts, and metal oxides (e.g., rust). Additionally, while the fouling materials may be attached to any metal surfaces, attachment to rusted metal surfaces may be of particular concern. The rust may provide enhanced attachment points for the fouling materials, thereby making the fouling materials even more difficult to remove.

[0003] This fouling material builds up on equipment, resulting in decreased production rates, decreased heat transfer capacity, increased pressure drop, and eventually complete shutdown of plant for cleaning. Cleaning often requires passing high viscosity polymer through the equipment at high shear rates to “scrub” the foulant from the surface. Eventually, cleaning requires disassembly of the equipment and hydroblasting or replacing the equipment. Such cleaning processes involve substantial capital expenditures and require the plant to be offline for several weeks.

[0004] Accordingly, faster, cheaper, and more reliable cleaning methods are desired.BRIEF SUMMARY

[0005] Embodiments of the present disclosure meet this need by through the use of a cleaning solution comprising a hydrocarbon solvent and an alkyl sulfonic acid-based86316-WO-PCT / DOW 86316 WO2 surfactant. Contacting the cleaning solution with the fouling material can break-down the fouling material and / or detach the fouling material from the surface. In some circumstances, the cleaning solution can even help to remove oxidized metal (e.g., rust) from the metal surface, thereby detaching any fouling material attached to the oxidized metal. Generally, the use of a hydrocarbon solvent or an alcohol solvent may be preferred as it is better able to dissolve desired compounds, more convenient to use at elevated temperatures, and less likely to introduce corrosion concerns, relative to other common solvents (e.g., aqueous solvents). Generally, the use of alkyl sulfonic acid-based surfactants is believed to be more effective at detaching and / or dissolving the fouling materials than other surfactants.

[0006] According to one or more embodiments, a method of removing fouling may comprise contacting a workpiece, comprising a metal surface with a fouling material attached thereto, with a cleaning solution comprising a hydrocarbon or alcohol solvent and an alkyl sulfonic acid-based surfactant, such that at least a portion of the fouling material is removed from the metal surface.

[0007] These and other embodiments are described in more detail in the Detailed Description. It is to be understood that both the foregoing general description and the following detailed description present embodiments of the presently disclosed technology, and are intended to provide an overview or framework for understanding the nature and character of the technology as it is claimed.DETAILED DESCRIPTION

[0008] "Polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The term polymer thus embraces the term homopolymer (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term copolymer or interpolymer. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and / or within the polymer. A polymer may be a single polymer or a polymer blend.

[0009] “Copolymer” refers to a polymer formed by the polymerization reaction of at least two structurally different monomers. For example, ethylene copolymers, such as ethylene-86316-WO-PCT / DOW 86316 WO3 propylene copolymers, include at least two structurally different monomers (e.g., ethylenepropylene copolymer includes copolymerized units of at least ethylene monomer and propylene monomer) and can optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride functional groups. Put another way, the copolymers described herein comprise at least two structurally different monomers, and although the copolymers may consist of only two structurally different monomers, they do not necessarily consist of only two structurally different monomers and may include additional monomers or functional materials or modifiers. Other comonomers may include, but are not limited to, octene, hexene, and butene.

[0010] "Ethylene-based polymer" (also referred to herein as “polyethylene” or "polyethylene-based polymers”) refers to polymers comprising greater than 50% by weight of units which have been derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include Low Density Polyethylene (LDPE); Linear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m-LLDPE); Medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

[0011] The term “LLDPE” includes resins made using the traditional Ziegler-Natta catalyst systems as well as single-site catalysts such as metallocenes (sometimes referred to as “m- LLDPE”). LLDPEs contain less long chain branching than LDPEs and include the substantially linear ethylene polymers, which are further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923 and U.S. Pat. No. 5,733,155; the homogeneously branched linear ethylene polymer compositions such as those in U.S. Pat. No. 3,645,992; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Pat. No. 4,076,698; and / or blends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 or U.S. Pat. No. 5,854,045). The LLDPE can be made via gas-phase, solution-phase or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art, including, but not limited to, gas and solution phase reactors.86316-WO-PCT / DOW 86316 WO4

[0012] “HDPE” generally refers to polyethylenes having densities greater than about 0.930 g / cm3and up to about 0.970 g / cm3, which are generally prepared with Ziegler-Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).

[0013] The term “polypropylene” or “propylene-based polymer” as used herein, refers to a polymer that comprises, in polymerized form, greater than 50% by mole of units, which have been derived from propylene monomer. This includes propylene homopolymer, random copolymer polypropylene, impact copolymer polypropylene, propylene / a-olefin copolymer, and propylene / a-olefin copolymer.

[0014] The term “workpiece” refers to any object which is capable of being worked upon. The workpieces of the present disclosure may have surfaces, such as metal surfaces. The surfaces may have fouling materials attached thereto. The workpiece may be a piece of equipment in a polymer production facility, such as a piece of equipment used for transporting polymer, such as a conveyor. In embodiments, the workpiece may be a reactor, heat exchanger, packing material, tower, devolatilizer, conveyor, condenser, compressor, pump, or the like.

[0015] In some embodiments, a method may comprise depositing a fouling material onto a surface of a workpiece. For example, the method may comprise producing a polymer by polymerizing one or more C2-C14 a-olefins and optionally one or more C2-C14 a-olefin comonomers, thereby depositing the fouling material onto the surface. In some embodiments, the method may comprise producing a monomer (e.g., ethylene and / or propylene) by reacting a hydrocarbon feedstock in a reactor to form the monomer and deposit the fouling material onto the surface.

[0016] As described hereinabove, it is desirable to remove fouling materials from surfaces. In some embodiments, a method of removing fouling may comprise contacting a fouling material attached to a metal surface with a cleaning solution such that at least a portion of the fouling material is removed from the metal surface.86316-WO-PCT / DOW 86316 WO5

[0017] In some embodiments, the fouling material may comprise a polymer, such as an ethylene-based polymer or a propylene-based polymer. Ethylene-based polymers may include, without limitation, UHDPE, HDPE, MDPE, LLDPE, ethylene propylene diene terpolymers (EPDM), and high-pressure polyethylenes (such as ethylene acid copolymers / terpolymers, ethylene vinyl acetate, ethylene-acrylate copolymers). Generally, fouling material comprising polymer may be particularly difficult to remove by more traditional methods.

[0018] In some embodiments, the polymer of the fouling material may be crosslinked. The crosslinked polymers may be insoluble in water or hydrocarbon solvents. The crosslinked polymer may be formed by oxygen or other chemical crosslinking or thermal crosslinking. Such crosslinked polymer may be particularly difficult to remove by traditional methods.

[0019] In some embodiments, the fouling material may further comprise one or more salts and / or additives. The one or more salts and / or additives may include such as reinforcing and non-reinforcing fillers, scratch resistant agents, plasticizers, antioxidants, heat stabilizers, extender oils, lubricants, antiblocking agents, antistatic agents, anti-fogging agent, waxes, foaming agents, pigments, flame / fire retardants, dyes and colorants, ultraviolet absorbers, and nano-fillers. Other additives include, for example, blowing agents, processing aids, tackifying resins, and other processing aids known in the polymer compounding art. Specific nonlimiting examples of the one or more salts and / or additives may include calcium stearate (CaSt) and calcium chloride; stabilizers, such as antioxidant stabilizers, such as phenolic antioxidant stabilizers, such as primary phenolic antioxidant stabilizers, such as Irganox® 1010 or 1076 commercially available from by BASF; norbornenes such as ethylidene norbornene (ENB) and vinyl norbornene (VNB); dicyclopentadiene (DCPD); siloxanes; and naphthenic petroleum oils.

[0020] In embodiments, the fouling material may comprise one or more metal oxides. For example, the one or more metal oxides may comprise iron oxide (rust), aluminum oxide, zinc oxide, or any combination thereof. In some embodiments, the one or more metal oxides may be formed from the surface to which the fouling material is attached.

[0021] In embodiments, the fouling material may comprise from 1 wt. % to 99 wt. %, such as from 1 wt. % to 5 wt. %, from 5 wt. % to 10 wt. %, from 10 wt. % to 15 wt. %, from 1586316-WO-PCT / DOW 86316 WO6 wt. % to 20 wt. %, from 20 wt. % to 25 wt. %, from 25 wt. % to 30 wt. %, from 30 wt. % to 35 wt. %, from 35 wt. % to 40 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, from 65 wt. % to 70 wt. %, from 70 wt. % to 75 wt. %, from 75 wt. % to 80 wt. %, from 80 wt. % to 85 wt. %, from 85 wt. % to 90 wt. %, from 90 wt. % to 95 wt. %, from 95 wt. % to 99 wt. %, or any combination of two or more of these ranges of the polymer, such as crosslinked polymer, on the basis of the total weight of the fouling material. In embodiments, the fouling material may comprise from 1 wt. % to 99 wt. %, such as from 1 wt. % to 5 wt. %, from 5 wt. % to 10 wt. %, from 10 wt. % to 15 wt. %, from 15 wt. % to 20 wt. %, from 20 wt. % to 25 wt. %, from 25 wt. % to 30 wt. %, from 30 wt. % to 35 wt. %, from 35 wt. % to 40 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, from 65 wt. % to 70 wt. %, from 70 wt. % to 75 wt. %, from 75 wt. % to 80 wt. %, from 80 wt. % to 85 wt. %, from 85 wt. % to 90 wt. %, from 90 wt. % to 95 wt. %, from 95 wt. % to 99 wt. %, or any combination of two or more of these ranges of the one or more salts and / or additives, on the basis of the total weight of the fouling material. In embodiments, the fouling material may comprise at least 80 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of the combined weight of polymer the one or more salts and / or additives, and the one or more metal oxides, on the basis of the total weight of the fouling material.

[0022] The fouling material may be attached to a surface of the workpiece. For example, the fouling material may be attached to the surface by physical attachment, rust surface attachment (e.g., attachment to rust particles on the surface), hydrogen bonding, covalent bonding, adhesion, or a combination thereof. In some embodiments, the surface may be a metal surface, such as a stainless steel surface, a duplex stainless steel surface, or a carbon steel surface. The surface may have one or more coatings applied thereon, such as a non-stick coating or a membrane coating. In such embodiments, the fouling material may be attached to the exterior surface of the coating. The workpiece may be a piece of equipment in a polymer production facility, such as a piece of equipment used for transporting polymer, such as a conveyor. In embodiments, the workpiece may be a reactor (e.g., a tubular reactor), heat exchanger, packing material, tower, devolatilizer, conveyor, or condenser. In embodiments, the surface may be an interior surface of a pipe.86316-WO-PCT / DOW 86316 WO7

[0023] Referring again to the cleaning solution, the cleaning solution may comprise a mixture of a hydrocarbon or alcohol solvent and an alkyl sulfonic acid-based surfactant. In embodiments, the cleaning solution may comprise less than 5 wt. %, less than 3 wt. %, less than 1 wt. %, or even less than 0.1 wt. % of water. Generally, a hydrocarbon solvent may be be suitable, relative to aqueous or non-hydrocarbon, non-aqueous solvents, due to the boiling point and corrosion characteristics of hydrocarbon solvents and due to the ability of hydrocarbon solvents to solubilize many of the target fouling materials. Generally, an alcohol solvent may be suitable due to its excellent ability to solubilize many of the target fouling materials. Generally, an alkyl sulfonic acid-based surfactant may be particularly effective in solubilizing and / or detaching the target fouling materials, relative to other types of surfactants, both relative to sulfonic acid-based surfactants lacking a alkyl group and to surfactants lacking a sulfonic acid group.

[0024] The cleaning solution may comprise an alkyl sulfonic acid-based surfactant (e.g., a linear or branched alkyl sulfonic acid surfactant). The alkyl sulfonic acid-based surfactant may comprise a sulfonate group (e.g., a functional group having formula SOsH-1-) and a lipophilic group. The sulfonate group may be in acid form (e.g., not having been neutralized). The sulfonic acid-based surfactant may comprise one or more of the sulfonate groups, such as 2, 3, 4, or 5 sulfonate groups. In embodiments, the lipophilic group may comprise a benzene group; an alkyl group, such as a branched alkyl group or a linear alkyl group; or a combination of these. In embodiments, the sulfonic acid-based surfactant may have a hydrophilic-lipophilic balance (HTB) of from 7 to 15, such as from 7 to 9, from 9 to 11, from 11 to 13, from 13 to 15, or any combination of two or more of these ranges.

[0025] In some embodiments, the alkyl sulfonic acid-based surfactant may comprise a sulfonic acid group and a alkyl group. In embodiments, the alkyl sulfonic acid-based surfactant, such as a linear alkyl sulfonic acid-based surfactant or a branched alkyl sulfonic acid-based surfactant may have structure I.86316-WO-PCI7 DOW 86316 WOStructure I:

[0026] In Structure I, Ri may be an alkyl group, such as a linear alkyl group or a branched alkyl group, comprising from 1 to 24 carbon atoms, such as from 1 to 4, from 4 to 8, from 8 to 10, from 10 to 12, from 12 to 14, from 14 to 16, from 16 to 18, from 18 to 24, or any combination of two or more of these ranges.

[0027] In some embodiments, the alkyl sulfonic acid may comprise a sulfonic acid group, a benzene group, and an alkyl group (e.g., a linear alkyl group or a branched alkyl group). In embodiments, the alkyl sulfonic acid may be an alkyl benzene sulfonic acid, such as a linear alkyl benzene sulfonic acid or a branched alkyl benzene sulfonic acid, having structure II.

[0028] In Structure II, R2 may be an alkyl group, such as a linear alkyl group or a branched alkyl group, comprising from 1 to 24 carbon atoms, such as from 1 to 4, from 4 to 8, from 8 to 10, from 10 to 12, from 12 to 14, from 14 to 16, from 16 to 18, from 18 to 24, or any combination of two or more of these ranges.

[0029] In embodiments, the alkyl sulfonic acid-based surfactant may have Structure III86316-WO-PCT / DOW 86316 WO9

[0030] In Structure III, each of R3 and R4 may independently be an alkyl group, such as a linear alkyl group, comprising from 1 to 24 carbon atoms, such as from 1 to 4, from 4 to 8, from 8 to 10, from 10 to 12, from 12 to 14, from 14 to 16, from 16 to 18, from 18 to 24, or any combination of two or more of these ranges.

[0031] The cleaning solution may have a concentration of the alkyl sulfonic acid-based surfactant of from 5 wt. % to 90 wt. %, such as 5 wt. % to 10 wt. %, from 10 wt. % to 20 wt. %, from 20 wt. % to 30 wt. %, from 30 wt. % to 40 wt. %, from 40 wt. % to 50 wt. %, from 50 wt. % to 60 wt. %, from 60 wt. % to 70 wt. %, from 70 wt. % to 80 wt. %, from 80 wt. % to 90 wt. %, or any combination of two or more of these ranges, on the basis of the total weight of the cleaning solution.

[0032] The hydrocarbon solvent or alcohol solvent may comprise any hydrocarbons or alcohols having a boiling point of from 25 °C to 290 °C, such as from 25 °C to 60 °C, from 60 °C to 90 °C, from 90 °C to 120 °C, from 120 °C to 150 °C, from 150 °C to 180 °C, from 180 °C to 210 °C, from 210 °C to 230 °C, from 230 °C to 260 °C, from 260 °C to 290 °C, or any combination of two or more of these ranges. Generally, the hydrocarbon solvent may be selected such that it is a liquid across the entire anticipated operating range of the cleaning process and, in some cases, such that the foulant materials are at least partially soluble in the hydrocarbon solvent. Suitable alcohol solvents may include, but are not limited to, methanol, ethanol, propanol, isopropanol, and mixtures thereof.

[0033] In some embodiments, the hydrocarbon solvent may comprise isoparaffinic solvents (e.g., solvents comprising or consisting of alkanes, such as branched chain alkanes), aromatic hydrocarbons, or a mixture thereof. In embodiments, the hydrocarbon solvent may comprise86316-WO-PCT / DOW 86316 WO10 linear hydrocarbons, branched hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, or a mixture thereof. In embodiments, the hydrocarbon solvent may comprise at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, at least 96 wt. %, at least 97 wt. %, at least 98 wt. %, at least 99 wt. %, or even at least 99.9 wt. % of the isoparaffinic solvents, aromatic solvents, linear hydrocarbons, branched hydrocarbons, cyclic hydrocarbons, or mixtures thereof, on the basis of the total weight of hydrocarbon solvents in the cleaning solution.

[0034] In embodiments, the cleaning solution may have a concentration of the hydrocarbon or alcohol solvent of from 10 wt. % to 90 wt. %, such as from 10 wt. % to 20 wt. %, from 20 wt. % to 30 wt. %, from 30 wt. % to 40 wt. %, from 40 wt. % to 50 wt. %, from 50 wt. % to 60 wt. %, from 60 wt. % to 70 wt. %, from 70 wt. % to 80 wt. %, from 80 wt. % to 90 wt. %, or any combination of two or more of these ranges, on the basis of the total weight of the cleaning solution.

[0035] In embodiments, the cleaning solution may comprise at least 80 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, at least 97 wt. %, at least 99 wt. %, or even at least 99.9 wt. % of the combined weight of the cleaning solution and the hydrocarbon solvent, on the basis of the total weight of the cleaning solution.

[0036] The cleaning solution may contact the workpiece in-situ or ex-situ. In embodiments, the ex-situ cleaning method may comprise removing the workpiece from its location and contacting it with the cleaning solution by, for example, immersing the workpiece in a tank of the cleaning solution. In embodiments, the in-situ cleaning method may comprise flushing the cleaning solution through a workpiece (e.g., one or more reactors, tubes, pumps, valves, or other processing equipment) without removing the workpiece from its operation location in the plant.

[0037] Whether in-situ or ex-situ, the cleaning solution may contact the workpiece at a cleaning temperature of from 25 °C to 290 °C, such as from 25 °C to 60 °C, from 60 °C to 90 °C, from 90 °C to 120 °C, from 120 °C to 150 °C, from 150 °C to 180 °C, from 180 °C to 210 °C, from 210 °C to 230 °C, from 230 °C to 260 °C, from 260 °C to 290 °C, or any combination of two or more of these ranges. Generally, elevated temperatures may provide enhanced cleaning properties, at the cost of energy usage and increased hazard to workers.86316-WO-PCT / DOW 86316 WO11

[0038] The cleaning solution may contact the workpiece at a shear rate of at least 10 seconds'1, such as at least 50 seconds'1, at least 100 seconds'1, at least 250 seconds'1, at least 500 seconds'1, at least 750 seconds'1, or even at least 1000 seconds'1. Generally, the use of higher shear rates may cause the cleaning solution to physically dislodge fouling materials from the workpiece.

[0039] The cleaning solution may contact the workpiece for at least 10 seconds, such as at least 30 seconds, at least 1 minute, at least 5 minutes, at least 10 minutes, at least 30 minutes, at least 1 hour, at least 2 hours, at least 4 hours, at least 6 hours, at least 10 hours, at least 15 hours, from 10 seconds to 30 seconds, from 30 seconds to 1 minute, from 1 minute to 5 minutes, from 5 minutes to 10 minutes, from 10 minutes to 30 minutes, from 30 minutes to 1 hour, from 1 hour to 2 hours, from 2 hours to 4 hours, from 4 hours to 6 hours, from 6 hours to 8 hours, from 8 hours to 10 hours, from 10 hours to 20 hours, from 20 hours to 40 hours, from 40 hours to 60 hours, or any combination of two or more of these ranges.EXAMPLESMaterials

[0040] Unless otherwise specified, Isopar™ E or H or L, was used as the hydrocarbon solvent in the following examples. Isopar™ is an iso -paraffinic hydrocarbon solvent commercially available from Exxon Mobil Inc.

[0041] Surfactants S-l, S-2, CS-A, and CS-B were used in the following experiments.S-l :S-l is a mixture of solvents where R2 varied from C8-C24 (linear / branched)86316-WO-PCT / DOW 86316 WO12S-2:Ri = CiR2 in CS-B was from Cio-CieVial Methods

[0042] For experiments conducted in vials, appropriately 40 mF vials with pressure relief caps were used. Different surfactant solvent systems were added to each vial. A sample workpiece with foulant material attached was then added to the vial. The vial was then secured and placed on a shaker block at 100 °C for two days. Before and after pictures were used to evaluate the effectiveness of fouling removal.Parr Reactor Methods

[0043] For experiments conducted in a Parr reactor, around 500 g of the surfactant-solvent system and a workpiece was added to a 1 L capacity Parr reactor. The reactor was then sealed86316-WO-PCT / DOW 86316 WO13 and leak tested with 100 psig N2 for 15 minutes. The reactor was then heated to 140 °C under continued N2 purge at ambient pressure and constant mixing, typically at 500 rpm. The system was then held steady at 80 psig N2 and 140 °C for the treatment time. The system was then allowed to cool and purged with N2 again at ambient pressure before removing the workpiece to take pictures and document the effect on fouling.Example 1

[0044] Fouled post reactor heater (PRH) tubes from an EEDPE production process were used as workpieces. The fouling materials were mainly rust, polymer and CaCb. The tubes were cut in half, and several pieces were tested according to the vial method with 50 wt. % of surfactant S-l in Isopar-H. Visual inspection showed near complete removal of the fouling material from the surface.Example 2

[0045] Example 1 was repeated with Isopar-E as the solvent instead of Isopar-H. As with Example 1, visual inspection showed near complete removal of the fouling material from the surface.Example 3

[0046] To test the effect of temperature and duration, the PRH tubes were cleaned in a Parr reactor using S-l in Isopar™-E as described in the Parr reactor section above, except that a cleaning time of 21 hours at 140 °C was used. Example 4 was repeated twice, showing a weight loss (e.g., fouling material removal) of 17.3 % and 18.9 % (an average weight loss of 18.1%).Example 4

[0047] Example 3 was repeated with temperature of 50 °C for 24 h with 20 wt. % of surfactant S-2 in ethanol. Visual inspection showed near complete removal of the fouling material from the surface. Example 4 was repeated twice, showing a weight loss (e.g., fouling material removal of 8.52 % and 9.31 % (an average weight loss of 8.92%). Similar results were found when the alcohol was changed to methanol.86316-WO-PCT / DOW 86316 WO14Example 5

[0048] Carbon steel coupons with crosslinked LDPE attached to the surface were used as workpieces. The polymer-containing metal coupons were placed in vials containing 40 vol% S-l in different vials containing different solvents: Isopar H; Stoddard solvent; Cyclooctane; a mixture of xylene, cyclohexane, Isopar L; and a mixture of Dowtherm Q and Stoddard Solvent. Vials were heated to 100 °C under 150 rpm agitation in a shaker block for 3 days. Complete removal of the films from each and every sample was then achieved by using tweezers, with minimal force needed. This example demonstrates that S-l can be effective when used with a variety of solvents comprising isoparaffins, cyclic compounds, and hydrocarbon mixtures containing aromatics, isoparaffins, and naphthenic / cyclic compounds.Comparative Example 1 (CE-1)

[0049] In CE-1, an aromatic wash oil (Exxon Aromatic 200, commercially available from Exxon Mobil Inc.) was used as the cleaning solution and the samples were tested according to the same method as Example 4. Upon visual inspection, the aromatic wash oil was found to be completely ineffective in cleaning the fouling materials. A weight loss of only 0.60 % was observed after cleaning, further indicating the ineffectiveness of the cleaning process.Comparative Example 2 (CE-2)

[0050] In CE-2, Isopar-H or Ewas used as the cleaning solution and the samples were tested according to the same method as Example 4. Upon visual inspection, the Isopar-H or E was found to be completely ineffective in cleaning the fouling materials. A weight loss of only 0.54 % with Isopar-H and 0.34% with Isopar-E was observed.Comparative Example 3 (CE-3)

[0051] In CE-3, CS-A or CA-B in hydrocarbon solvent was used as the cleaning solution and the samples were tested according to the same method as Example 4. The composition of the cleaning solution was 65.5 wt. % of CS-A or 50 wt% of CS-B in a hydrocarbon solvent comprising aromatic hydrocarbons, heavy and medium naphtha, and benzene. It is noted that CS-A and CS-B are a non-acidic forms of a sulfonic acid-based surfactant. The CS-A or CS-86316-WO-PCT / DOW 86316 WO15B in hydrocarbon solvent were found to be ineffective in cleaning the fouling materials when compared with S-l .Rusting of Coupons

[0052] For the next set of experiments, carbon steel coupons were used. A portion of the coupons were rusted by placing carbon steel coupons in either pure water or a 3.5 wt. % sodium-chloride solution in a 40 ml vial. The vials were then heated to 50 °C for 2 weeks. After two weeks, the coupons were removed, dried, and weighed.Crosslinked EPDM Film Preparation

[0053] A crosslinked EPDM film was used in the following experiments. The crosslinked EPDM was prepared according to the following conditions in a microcompounder: a. EPDM: NORDEE™ 4520 b. Peroxide: DiCup 40K (40% dicumyl peroxide on clay carrier) c. PDM-75 (N,N'-m-Phenylenedimaleimide, a curing coagent) d. Compounding Temp: 100 °C e. Press temp: 180 °C f. Curing temp: 180 °C g. Curing time: 20 minutes at 180 °C h. Overall formulation: 18.3 gm NORDEE™'4520 + 1.46 gm DiCup 40KE + 0.24 gm PDM-75

[0054] The crosslinked EPDM was then pressed into films. Additionally, a non-crosslinked EPDM film was prepared according to the same method, except no peroxide was added.Comparative Example 4 (CE-4)

[0055] To develop a baseline, the crosslinked and non-crosslinked films were laminated onto the non-rusted coupons. The crosslinked polymers shouldn’t dissolve in Isopar H whereas the non-crosslinked one would dissolve. The non-crosslinked films (produced without peroxide) dissolved in Isopar™-H. The crosslinked film with peroxide stayed as a film and detached from the coupon. This indicates that the with a clean surface, the86316-WO-PCT / DOW 86316 WO16 crosslinked EPDM film would detach from the surface but not dissolve in the hydrocarbon solvent alone.Comparative Example 5 (CE-5)

[0056] The crosslinked EPDM films were then pressed onto rusted coupons (both rusted with pure water and with 3.5 % NaCl). The samples were then placed in Isopar™ H to investigate their ability to detach the films from the rusted coupons.

[0057] In the case of rusted coupons (rusted with ultra-pure water and 3.5 % NaCl), parts of the crosslinked EPDM films were broken but parts of the film still attached to coupons where rust was prominent on the coupons. This experiment was repeated many times, and the observation was the same. This result confirms that hydrocarbon solvents such as Isopar H can swell the crosslinked EPDM but cannot to remove from the surface of a rusted coupon.Example 6

[0058] The coupons were placed in a solution of 50 wt. % S-l and 50 wt. % of Isopar™-H at a temperature of 100 °C for 1 hour. The cleaning solution including 50 wt. % of S-l and Isopar™-H was able to detach the film from the surface of the coupon and it also removed the rust from the surface of the coupon. However, the film stayed as an intact film.Example 7

[0059] To verify that the mixture of 50 wt. % S-l and 50 wt. % of hydrocarbon solvent could actually remove rust, several rusted coupons (with no polymer) were placed in vials with the cleaning solution at 100 °C for 1 hour. After treatment, visual inspection clearly showed complete removal of the rust. The weight loss after cleaning is shown in Table 1.Comparative Example 6 (CE-6)

[0060] To verify that the cleaning was actually being caused by the mixture of 50 wt. % S- 1 and 50 wt. % of Isopar-H, rather than by the Isopar-H alone, the rusted coupons were placed in vials of Isopar™-H at 100 °C for 1 hour. Visual inspection showed no removal of rust. The weight loss after cleaning in shown in Table 1. As is shown in Table 1, the samples which were cleaned in the 50 % S-l - 50 % hydrocarbon solvent cleaning solution experienced86316-WO-PCT / DOW 86316 WO17 about 40 x the weight loss upon cleaning of the samples which were cleaned in the hydrocarbon solvent alone.Table 1Comparative Example 7 (CE-7)

[0061] Tubes from a pilot plant fouled with crosslinked EPDM were exposed to Isopar-H at 100 °C for 6 hours. After the exposure, the fouled material had swelled up slightly, but it was still not possible to detach it from the tube surface. No rust had been visibly removed.Example 8

[0062] The same tubes used in Comparative Example 7 were exposed to a mixture of 50 wt. % S-l and 50 wt. % hydrocarbon solvent at 100°C for 6 hours. At the end of the treatment, the fouled polymer film was easily detached from the tube surface in large sections. The surface was visibly cleaner and most of the rust had been removed from the tube surface as well.Example 9

[0063] The same tubes used in Example 8 were placed in a Parr reactor with the mixture of 50 wt. % S-l and 50 wt. % hydrocarbon solvent at 140 °C for 20+ hours with an impeller speed of 800rpm. The fouled polymer film was broken into small pieces. The tube piece was rendered completely clean after rinsing with Isopar™-H at room temperature after the high temperature treatment with the S-l- hydrocarbon solvent mixture. This result indicates that86316-WO-PCT / DOW 86316 WO18 in a continuous flow-through process with a high flow rate (i.e., high shear rate) the fouled film should break down into smaller pieces. These smaller pieces are expected to reduce the risk of plugging, relative to the larger pieces formed at lower temperatures and lesser shear rates.

Claims

86316-WO-PCT / DOW 86316 WO19CLAIMS1. A method of removing fouling, the method comprising contacting a workpiece, comprising a metal surface with a fouling material attached thereto, with a cleaning solution comprising a hydrocarbon or alcohol solvent and an alkyl sulfonic acidbased surfactant, such that at least a portion of the fouling material is removed from the metal surface.

2. The method of claim 1, the method further comprising producing a polymer by polymerizing one or more C2-C14 a-olefins and optionally one or more C2-C14 a- olefin comonomers, thereby producing the polymer and the fouling material attached to the metal surface.

3. The method of claim 1, the method further comprising producing a monomer by reacting a hydrocarbon feedstock in a reactor to form the monomer and the fouling material attached to the metal surface.

4. The method of any one of claims 1 to 3, wherein the alkyl sulfonic acid-based surfactant is in acidic form.

5. The method of any one of claims 1 to 4, wherein the alkyl sulfonic acid-based surfactant has structure I:I: wherein Ri is a alkyl group comprising from 1 to 24 carbonatoms.

6. The method of any one of claims 1 to 4, wherein the alkyl sulfonic acid-based surfactant is a alkyl benzene sulfonic acid having structure II:86316-WO-PCT / DOW 86316 WO20carbon atoms.

7. The method of any one of claims 1 to 4, wherein the alkyl sulfonic acid-based surfactant has structure III:III:, wherein R3 and R4 are each independently alkyl groups comprising from 1 to 24 carbon atoms.

8. The method of any one of claims 1 to 7, wherein the hydrocarbon or alcohol solvent has a boiling point of from 60 °C to 290 °C.

9. The method of any one of claims 1 to 8, wherein a concentration of the alkyl sulfonic acid-based surfactant is from 5 wt. % to 90 wt. %, on the basis of the total weight of the cleaning solution.

10. The method of any one of claims 1 to 9, wherein the solvent is the hydrocarbon solvent and comprises linear hydrocarbons, branched hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, or a mixture thereof.

11. The method of any one of claims 1 to 10, wherein the solvent is the hydrocarbon solvent and comprises isoparrafinic solvents, aromatic hydrocarbons, or a mixture thereof.86316-WO-PCT / DOW 86316 WO2112. The method of any one of claims 1 to 11, wherein the solvent is the alcohol solvent and comprises methanol or ethanol or a mixture thereof.

13. The method of any one of claims 1 to 12, wherein the cleaning solution contacts the workpiece at a cleaning temperature of from room temperature to 290 °C and a shear rate of at least 10 seconds'1.

14. The method of any one of claims 1 to 13, wherein the fouling material comprises one or more of solid phase polymeric material, metal oxides, or metal salts.

15. The method of any one of claims 1 to 14, wherein the cleaning solution contacts the workpiece in-situ or ex-situ, and wherein the workpiece is at least a portion of a piece of equipment in a polymer production facility, a monomer production facility, or a hydrocarbon production facility.

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