Methods of removing fouling

Abstract

A method of removing fouling may comprise contacting a fouling material attached to a surface with an aqueous cleaning solution comprising a sulfonic acid based surfactant such that at least a portion of the fouling material is removed from the surface.

Description

86318-WO-PCT / DOW 86318 WO1METHODS OF REMOVING FOULINGCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application Serial No. 63 / 708,906 filed October 18, 2024, the entire disclosure of which is hereby incorporated by reference.BACKGROUND

[0002] Equipment used for producing and transporting polymer often becomes fouled. Common fouling materials include metal oxides (e.g., rust) and polymeric material, especially crosslinked polymeric material, salts, and various additives. This fouling can result in clogging and substantial downtime (on the order of weeks) to remove. Traditional removal strategies generally involve workers manually pressure washing the fouling off of the equipment. In addition to the time required for cleaning with pressure washing, pressure washing introduces logistical challenges, is labor intensive, is inconsistent in cleaning, and sometimes even damages coatings on the fouled units.

[0003] Thus, faster, safer, and more consistent methods of removing fouling are desired.BRIEF SUMMARY

[0004] Embodiments of the present disclosure meet this need by contacting an aqueous cleaning solution comprising a sulfonic acid based surfactant with the fouled surface. Contacting the aqueous cleaning solution with the fouled surface can break-down the fouling material and / or detach the fouling material from the surface. Thus, enabling the fouling material to be easily removed through scraping or water washing. Notably, this process often only requires a short contact time (on the order of minutes) and can be effective under low severity (moderate temperature, ambient pressure, and moderate pH) conditions yet still results in consistent removal of the fouling material. Further, the use of an aqueous solution can reduce environmental and worker safety concerns.

[0005] According to one or more embodiments, a method of removing fouling may comprise contacting a fouling material attached to a surface with an aqueous cleaning solution comprising a sulfonic acid based surfactant, such that at least a portion of the fouling material is removed from the surface.86318-WO-PCT / DOW 86318 WO2

[0006] 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

[0007] "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.

[0008] “Copolymer” refers to a polymer formed by the polymerization reaction of at least two structurally different monomers. For example, ethylene copolymers, such as ethylene -propylene copolymers, include at least two structurally different monomers (e.g., ethylene-propylene 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.

[0009] "Ethylene-based polymer" (also referred to herein as “polyethylene” or "polyethylenebased 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 and86318-WO-PCT / DOW 86318 WO3 substantially linear low density resins (m-LLDPE); Medium Density Polyethylene (MDPE); and Eligh Density Polyethylene (EIDPE).

[0010] 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 EEDPE can be made via gas-phase, solutionphase 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.

[0011] “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).

[0012] 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.

[0013] In some embodiments, a method may comprise depositing a fouling material onto a surface. 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 by reacting a hydrocarbon feedstock in a reactor to form the monomer and deposit the fouling material onto the surface.86318-WO-PCT / DOW 86318 WO4

[0014] 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 surface with an aqueous cleaning solution, such that at least a portion of the fouling material is removed from the surface.

[0015] In some embodiments, the fouling material may comprise a polymer, such as an ethylenebased polymer or a propylene-based polymer. Ethylene-based polymers may include HDPE, LDPE, and copolymers of ethylene. Generally, fouling material comprising polymer may be particularly difficult to remove by more traditional methods.

[0016] In some embodiments, the polymer of the fouling material may be crosslinked. The crosslinked polymers may be insoluble in water, hydrocarbon solvents, or other inorganic solvents.

[0017] 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 nonreinforcing 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 nanofillers. 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.

[0018] In embodiments, the fouling material may comprise one or more oxides, such as metal oxides. For example, the one or more 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.

[0019] 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. %,86318-WO-PCT / DOW 86318 WO5 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 comprises 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.

[0020] The fouling material may be attached to a surface. 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 surface may be a surface of 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 surface may be a surface of a reactor (e.g., a tubular reactor), heat exchanger, packing material, tower, devolatilizer, conveyor, or condenser.

[0021] Referring again to the cleaning solution, the cleaning solution may be an aqueous cleaning solution. As used herein an aqueous cleaning solution may comprise water. In embodiments, the aqueous cleaning solution may comprise less than 5 wt. %, less than 3 wt. %, less than 1 wt. %, or even less than 0.1 wt. % of hydrocarbon solvents and / or non-aqueous solvents. Generally, an aqueous cleaning solution may be preferred relative to non-aqueous or hydrocarbon solvent based cleaning solutions as aqueous solutions may have preferable occupational safety and environmental characteristics. Additionally, the use of an aqueous cleaning solution is more practical than non-aqueous cleaning solutions in systems that are already aqueous (e.g., the aqueous side of heat exchangers and other cooled systems like reactors).86318-WO-PCT / DOW 86318 WO6

[0022] The cleaning solution may comprise a sulfonic acid based surfactant. The sulfonic acid based surfactant may comprise a sulfonate group (e.g., a functional group having formula SO3H or SO3+) and a lipophilic group. The sulfonate group may be in acid form or may be neutralized, such as being neutralized with an amine. 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.

[0023] In some embodiments, the sulfonic acid based surfactant may be a linear alkyl sulfonic acid. The linear alkyl sulfonic acid based surfactant may comprise a sulfonic acid group and a linear alkyl group. The linear alkyl sulfonic acid based surfactant may have structure I.Structure I:

[0024] Ri may be a linear alkyl group comprising from 8 to 18 carbon atoms, such as from 8 to 10, 10 to 12, 12 to 14, 14 to 16, 16 to 18, or any combination of two or more of these ranges of carbon atoms.

[0025] In some embodiments, the sulfonic acid based surfactant may be a linear alkyl sulfonic acid such as a linear alkyl benzene sulfonic acid. A linear alkyl benzene sulfonic acid may comprise a sulfonic acid group, a benzene group, and a linear alkyl group. In embodiments, the linear alkyl benzene sulfonic acid may have structure II.86318-WO-PCT / DOW 86318 WO7

[0026] In Structure I, R2 may be an alkyl group, such as a linear alkyl group, comprising from 8 to 18 carbon atoms, such as from 8 to 10, 10 to 12, 12 to 14, 14 to 16, 16 to 18, or any combination of two or more of these ranges of carbon atoms..

[0027] In some embodiments, the sulfonic acid based surfactant may comprise two or more sulfonic acid groups. Each of the sulfonic acid groups may be covalently bonded to a benzene group. For example, the sulfonic acid based surfactant may have structure III:

[0028] R3 may be an alkyl group, such as a linear alkyl group, comprising from 8 to 18 carbon atoms, such as from 8 to 10, 10 to 12, 12 to 14, 14 to 16, 16 to 18, or any combination of two or more of these ranges of carbon atoms.

[0029] In embodiments, the sulfonic acid based surfactant may comprise a sulfosuccinate. For example, the sulfonic acid based surfactant may have structure IV:86318-WO-PCT / DOW 86318 WO8

[0030] R4 and R5 may each independently be hydrocarbyl groups comprising from 8 to 18 carbon atoms, such as from 8 to 10, 10 to 12, 12 to 14, 14 to 16, 16 to 18, or any combination of two or more of these ranges of carbon atoms. The hydrocarbyl groups may comprise or consist of alkanes and the hydrocarbyl groups may be branched or linear. In specific embodiments, the sulfonic acid based surfactant comprising a sulfosuccinate may have Structure V :

[0031] The aqueous cleaning solution may comprise from 10 wt. % to 99 wt. % of the sulfonic acid based surfactant, such as 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 40 wt. % to 45 wt. %, from 45 wt. % to 50 wt. %, from 50 wt. % to 55 wt. %, from55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, from 65 wt. % to 70 wt. %, from 70 wt. % to75 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 of86318-WO-PCT / DOW 86318 WO9 these ranges of the sulfonic acid based surfactant, on the basis of the total weight of the cleaning solution.

[0032] In some embodiments, the aqueous cleaning solution may comprise one or more alcohols.Suitable alcohols may include methanol, ethanol, and propanol. The aqueous cleaning solution may comprise from 0 wt. % to 30 wt. %, such as from 0 wt. % to 0.1 wt. %, from 0.1 wt. % to1 wt. %, from 1 wt. % to 5 wt. %, from 5 wt. % to 10 wt. %, from 10 wt. % to 15 wt. %, from15 wt. % to 20 wt. %, from 20 wt. % to 25 wt. %, from 25 wt. % to 30 wt. %, or any combination of two or more of these ranges of the alcohol, on the basis of the total weight of the aqueous cleaning solution.

[0033] The aqueous cleaning solution may comprise at least 80 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, at least 98 wt. %, at least 99 wt. %, at least 99.9 wt. %, or even at least 99.99 wt. % of the combined weight of the water, the sulfonic acid based surfactant, and optionally the alcohol, on the basis of the total weight of the aqueous cleaning solution.

[0034] In embodiments, the aqueous cleaning solution may have a pH of from 2 to 12, such as from 2 to 3, from 3 to 4, from 4 to 5, from 5 to 6, from 6 to 7, from 7 to 8, from 8 to 9, from 9 to 10, from 10 to 11, from 11 to 12, or any combination of two or more of these ranges.

[0035] In embodiments, the aqueous cleaning solution may comprise the sulfonic acid based surfactant of Structure I at a concentration of at least 10 wt. %, such as at least 20 wt. %, at least 30 wt. %, 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 40 wt. % to 45 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 and a pH of from 1 to 12, such as from 1 to 8, from 6 to 8, from 1 to 2, from 2 to 3, from 3 to 4, from 4 to 5, from 5 to 6, from 6 to 7, from 7 to 8, from 8 to 9, from 9 to 10, from 10 to 11, from 11 to 12, or any combination of two or more of these ranges.

[0036] In embodiments, the aqueous cleaning solution may comprise the sulfonic acid based surfactant of Structure II at a concentration of at least 10 wt. %, such as at least 20 wt. %, at least 30 wt. %, 10 wt. % to 15 wt. %, from 15 wt. % to 20 wt. %, from 20 wt. % to 25 wt. %86318-WO-PCT / DOW 86318 WO10 from 25 wt. % to 30 wt. %, from 30 wt. % to 35 wt. %, from 35 wt. % to 40 wt. %, from 40 wt. % to 45 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 and a pH of from 1 to 12, such as from 1 to 8, from 6 to 8, from 1 to 2, from 2 to 3, from 3 to 4, from 4 to 5, from 5 to 6, from 6 to 7, from 7 to 8, from 8 to 9, from 9 to 10, from 10 to 11, from 11 to 12, or any combination of two or more of these ranges.

[0037] In embodiments, the aqueous cleaning solution may comprise the sulfonic acid based surfactant of Structure III at a concentration of at least 10 wt. %, such as at least 20 wt. %, at least 30 wt. %, 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 40 wt. % to 45 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 and a pH of from 1 to 12, such as from 1 to 8, from 6 to 8, from 1 to 2, from 2 to 3, from 3 to 4, from 4 to 5, from 5 to 6, from 6 to 7, from 7 to 8, from 8 to 9, from 9 to 10, from 10 to 11, from 11 to 12, or any combination of two or more of these ranges.

[0038] In embodiments, the aqueous cleaning solution may comprise the sulfonic acid based surfactant of Structure IV at a concentration of at least 50 wt. %, such as at least 55 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 and a pH of from 1 to 12, such as from 1 to 8, from 6 to 8, from 1 to 2, from 2 to 3, from 3 to 4, from 4 to 5, from 5 to 6, from 6 to 7, from 7 to 8, from 8 to 9, from 9 to 10, from 10 to 11, from 11 to 12, or any combination of two or more of these ranges.

[0039] The aqueous cleaning solution may be made to contact the fouling material by spraying the aqueous cleaning solution onto the fouling material, by sponging the aqueous cleaning solution onto the surface with the fouling material thereon, by soaking the surface with the86318-WO-PCT / DOW 86318 WO11 fouling material thereon in the aqueous cleaning solution or by any other known means. In embodiments, the aqueous cleaning solution may contact the fouling material at a cleaning temperature of less than 200 °C, such as less than 180 °C, less than 160 °C, less than 140 °C, less than 120 °C, less than 100 °C, less than 90 °C, less than 80 °C, less than 70 °C, less than 60 °C, less than 50 °C, less than 40 °C, from 20 °C to 30 °C, from 30 °C to 40 °C, from 40 °C to 50 °C, from 50 °C to 60 °C, from 60 °C to 70 °C, from 70 °C to 80 °C, 80 °C to 90 °C, from 90 °C to 100 °C, from 100 °C to 110 °C, from 110 °C to 120 °C, from 120 °C to 130 °C, from 130 °C to 140 °C, from 140 °C to 160 °C, from 160 °C to 180 °C, from 180 °C to 200 °C, or any combination of two or more of these ranges. It is noted that the aqueous cleaning solution may contact the fouling material at ambient pressure (about 1 atmosphere) or at an elevated pressure (greater than 1 atmosphere). When the aqueous solution contacts the fouling material at ambient pressure, the temperature may be less than 90 °C, such as less than 80 °C, less than 70 °C, less than 60 °C, less than 50 °C, or less than 40 °C. When the aqueous cleaning solution contacts the fouling material at elevated pressure, the temperature may be greater than 60 °C, such as from 60 °C to 70 °C, from 70 °C to 80 °C, 80 °C to 90 °C, from 90 °C to 100 °C, from 100 °C to 110 °C, from 110 °C to 120 °C, from 120 °C to 130 °C, from 130 °C to 140 °C, from 140 °C to 160 °C, from 160 °C to 180 °C, from 180 °C to 200 °C, or any combination of two or more of these ranges. It is noted that use of the aqueous cleaning solution while the reactor is operating may be best enabled by operation at a temperature of from 140 °C to 200 °C, such as from 180 °C to 200 °C. Whereas, use of the aqueous cleaning solution while the reactor is offline may be best enable by cleaning at a temperature of less than 140 °C, or even less than 90 °C.

[0040] The aqueous cleaning solution may contact the fouling material for at least 10 seconds and less than 30 minutes, such as from 10 seconds to 20 seconds, from 20 seconds to 30 seconds, from 30 seconds to 1 minute, from 1 minute to 2 minutes, from 2 minutes to 3 minutes, from 3 minutes to 5 minutes, from 5 minutes to 10 minutes, from 10 minutes to 20 minutes, or any combination of two or more of these ranges.

[0041] Additionally, testing has shown that gamma terpinene, 1,3 cyclohexadiene, d-limonene, cyclohexene, pentane, and toluene may be effective in removing fouling materials.86318-WO-PCT / DOW 86318 WO12EXAMPLES

[0042] In the examples included herein, aqueous cleaning solutions consisting of water and the materials listed in Table 1 were used.86318-WO-PCT / DOW 86318 WO13Example 1

[0043] In Example 1, samples taken from a polymer conveyor in an EPDM production line were used as the fouling material. Each sample was placed in a vial at room temperature and the cleaning solutions were added. Pictures of the sample were taken and then the vial was sealed and shaken for a few minutes. The resulting dissolution was then compared with the starting sample. Table 2 provides a summary of the cleaning effectiveness of water and the different aqueous sulfonic acid-based surfactants at various pHs and concentrations.Table 2

[0044] Table 2 illustrates the success of both acidic and neutral aqueous forms of linear alkylbenzenesulfonate (ABS); benzene, 1, 1-oxybis-, tetrapropylene derivs., sulfonated (BOTS); and di-2-ethylhexyl sodium sulfosuccinate in breaking down the fouling material. In contrast, water was completely ineffective compared to the sulfonic acid based surfactants. For SI (ABS), a concentration > 10% was needed to be effective in breaking up the fouling sample into smaller particulates at a pH of 1. When 11% ABS was neutralized using sodium hydroxide, it was still an effective cleaning solvent. For S2 (BOTS), which includes two sulfonate groups compared to one in alkyl benzenesulfonate, demonstrated effective cleaning action in acidic form at a 14% concentration, as well as 23% when neutralized to pH 7 using sodium hydroxide. Additionally, the sulfosuccinate sample S3 was found to be effective at cleaning the fouling material.86318-WO-PCT / DOW 86318 WOExample 2

[0045] In Example 2, fouled samples taken from a LDPE production reactor were used as the fouling material. The samples were subjected to bulk analysis using X-ray fluorescence (XRF), the results of which are described in Table 3. Each sample was then placed in a vial at room temperature and a cleaning solution comprising a 28 wt. % aqueous solution of S2 was added. The vial was then sealed and heated to 80 °C for 48 hours. The samples were then analyzed using scanning electron microscopy / energy dispersive X-ray spectroscopy (SEM / EDS) to determine the dissolution of each element. Each sample was tested twice (e.g., Sample A was tested in a first position labeled Sample Al and a second position labeled Sample A2). A comparative example was prepared using the same procedure but with water as the cleaning solution. The results are reported in Table 4. Additionally, the vials showed substantial dissolution of the fouling material using the aqueous sulfonic acid solution of S2. Furthermore, the reduced iron content in the SEM / EDX results show the effectiveness of the cleaning solution in removing rust.Table 3Table 486318-WO-PCT / DOW 86318 WO15Example 3

[0046] Samples A, B, and D were each immersed in separate vials of 46 wt. %, 23 wt. %, and 9 wt. % aqueous solutions of S2 for two days at 80 °C. Testing showed effective cleaning of all sample, especially samples B and D, using the aqueous solution of S2 at all concentrations tested.Example 4

[0047] Samples B, C, and D were each immersed in separate vials of 60 wt. % and 12 wt. % aqueous solutions of S3 for two days at 70 °C. Testing showed effective cleaning of all sample, especially samples B and D, using the aqueous solution of S3 at all concentrations tested. However, the higher concentration did show substantially more cleaning than the lower concentration.

Claims

86318-WO-PCT / DOW 86318 WOCLAIMS1. A method of removing fouling, the method comprising contacting a fouling material attached to a surface with an aqueous cleaning solution comprising a sulfonic acid based surfactant such that at least a portion of the fouling material is removed from the surface.2 The method of claim 1, wherein the sulfonic acid based surfactant has structure I:, wherein Ri is a linear alkyl group comprising from 8 to 18 carbon atoms.3 The method of claim 1, wherein the sulfonic acid based surfactant has structure II:, wherein R2 is an alkyl group comprising from 8 to 18 carbon atoms.4 The method of claim 1, wherein the sulfonic acid based surfactant has structure III:wherein R3 is an alkyl group comprising from 8 to 18 carbon atoms.5 The method of claim 1, wherein the sulfonic acid based surfactant has structure IV:86318-WO-PCT / DOW 86318 WO17, wherein R4 and R5 are each independently hydrocarbyl groups comprising from 8 to 18 carbon atoms.6 The method of any one of claims 1 to 5, wherein the method further comprises depositing the fouling material onto the surface.7 The method of any one of claims 1 to 6, wherein a concentration of the sulfonic acid based surfactant in the aqueous cleaning solution is from 10 wt. % to 99 wt. %.8 The method of any one of claims 1 to 7, wherein the aqueous cleaning solution comprises at least 99 wt. % of the combined weight of water, sulfonic acid based surfactant, and optionally alcohol, on the basis of the total weight of the cleaning solution.9 The method of any one of claims 1 to 8, wherein the aqueous cleaning solution contacts the fouling material at a cleaning temperature of from 25 °C to 200 °C.10 The method of any one of claims 1 to 9, wherein the aqueous cleaning solution has a pH of from 2 to 12.11 The method of any one of claims 1 to 10, wherein the fouling material comprises one or more metal oxides.12 The method of any one of claims 1 to 11, wherein the fouling material comprises one or more additives and a polymer.13 The method of any one of claims 1 to 12, the surface is a metal surface.86318-WO-PCT / DOW 86318 WO1814. The method of any one of claims 1 to 13, wherein the aqueous cleaning solution is sprayed onto the fouling material.

15. The method of any one of claims 1 to 14, wherein the surface is a piece of equipment in a polymer production facility, a monomer production facility, or a hydrocarbon production facility.

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