Methods of removing deposits from a surface

Abstract

The invention relates to the field of removing various types of deposits from a surface, preferably the surface of industrial equipment. A removing deposits from a surface comprises the steps of applying a first precursor mix to the surface; allowing the first precursor mix to pass through the deposits; removing the first precursor mix; applying a second precursor mix to the surface; allowing the second precursor mix to pass though the deposits; removing the second precursor mix; wherein the first precursor mix reacts with the second precursor mix to produce a foam, and the foam expands inside pores and cracks of the deposits, and results in breaking the deposit from the surface.

Description

FIELD OF THE INVENTION

[0001] The invention relates to the field of removing various types of deposits from a surface, preferably the surface of industrial equipment.BACKGROUND OF THE INVENTION

[0002] One high cost of oil refineries is the maintenance money spent to clean fouled heat exchangers and the associated lost production while the exchanger is out of service. Fouled heat exchangers result in low exchange efficiency and high operation costs.

[0003] Generally, large shell-and-tube heat exchangers used in the oil refinery usually require disassembly of both ends and internals, removal of the tube bundle, transportation to a cleaning facility for cleaning, reassembly, and leak testing. This process can take days or weeks, depending on several factors like exchanger size and weight, severity of fouling, whether specialty equipment is required to extract the tube bundle etc.

[0004] A method of removing deposits from a surface according to the state of the art is disclosed in RU 2696990 C2.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The forgoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the following drawing.

[0006] FIG. 1 illustrates the structure of a shell-and-tube heat exchanger.DETAILED DESCRIPTION OF THE INVENTION Definitions

[0007] As used in the preceding sections and throughout the rest of this specification, unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one skilled in the art to which this invention belongs.

[0008] The term "a", "an", or "the" as used herein, generally is construed to cover both the singular and the plural forms.

[0009] The term "about" as used herein, generally refers to a particular numeric value that is within an acceptable error range as determined by one of ordinary skill in the art, which will depend in part on how the numeric value is measured or determined, i.e., the limitations of the measurement system. For example, "about" can mean a range of ±20%, ±10%, or ±5% of a given numeric value.

[0010] The disclosure relates to a method of removing various types of deposits from a surface. The deposits can be salt deposits, deposits of a petroleum nature including fouling of heat exchangers, asphaltene-resin-paraffin, and resin and biological (bacterial) deposits. In some embodiments, the deposit is the fouling in a heat exchanger. In an embodiment, the deposit is the fouling in a heat exchanger used in oil refinery. In an embodiment, the surface is the surface of a heat exchanger. In an embodiment, the surface is the internal surface of shell-and-tube heat exchanger (FIG. 1).Heat exchanger fouling

[0011] Heat exchanger fouling is a common problem in heat exchangers. It results in changing the surface of the heat transfer and reducing the efficiency of the heat transfer.

[0012] During fouling, the surface of a heat exchanger wall develops another layer of solid material, also called deposits. This can happen for various reasons, and causes the heat transfer coefficient at the surface to be drastically reduced, since the heat conducting wall metal is not in contact with the fluids any more. Instead, the wall is separated from fluid by a layer of 'fouling'. Therefore, fouling prevents efficient heat transfer and reduces the efficiency of heat exchanger.

[0013] There are different types of fouling.Corrosion fouling

[0014] Corrosion fouling occurs when the fluid corrodes the surface of the exchanger wall, developing a layer of corrosion. This corroded metal prevents efficient heat transfer.Particulate fouling

[0015] Particulate fouling occurs when certain suspended particulate matter in the fluid settles down on the heat exchanger wall. Over time a layer of such particulate material develops on the wall, reducing the heat transfer through it.Precipitation fouling

[0016] Precipitation fouling occurs when the circulating fluid precipitates as time goes by, then the precipitates deposit on the surface of the exchanger wall, forming precipitation fouling.Polymerization fouling

[0017] Sometimes the fluid can undergo a reaction at the heat exchanger wall surface. This reaction produces a solid that adheres to the heat exchanger wall, resulting in polymerization fouling.

[0018] This kind of fouling also happens because of temperature change in the fluid. High temperature change at the exchanger wall causes the fluids to react.Bio fouling

[0019] Organisms present in the fluid stream can get attracted to the warm surface of the heat exchanger wall. Here they can grow in size and reproduce, forming a layer of biological material, called bio fouling.Freezing fouling

[0020] Sometimes the fluid temperature near the heat exchanger walls can drop so low that some of the fluid freezes. This frozen solid remains on the heat exchanger wall. But it is not as conductive as the exchanger wall and it restricts the heat transfer across the wall, resulting in freezing fouling.

[0021] This disclosure relates to a method of for removing deposits from a surface comprising the steps of applying a first precursor mix to the surface; allowing the first precursor mix to pass through the deposits; removing the first precursor mix; applying a second precursor mix to the surface; allowing the second precursor mix to pass though the deposits; removing the second precursor mix; wherein the first precursor mix reacts with the second precursor mix to produce a foam, and the foam expands inside pores and cracks of the deposits, and results in breaking the deposit from the surface.

[0022] The deposits can be salt deposits, deposits of a petroleum nature including fouling of heat exchangers, asphaltene-resin-paraffin, and resin and biological (bacterial) deposits. In some embodiments, the deposit is the fouling in a heat exchanger. In some embodiments, the deposit is the fouling in a heat exchanger. In an embodiment, the deposit is the fouling of a heat exchanger used in oil refinery. In an embodiment, the fouling is selected from the group consisting of corrosion fouling, particulate fouling, precipitation fouling polymerization fouling, bio fouling, freezing fouling, and mixtures thereof.

[0023] In one embodiment, the method described herein is used to clean the heat exchangers used in oil refinery. In one embodiment, the heat exchanger is a shell-and-tube heat exchanger.

[0024] The advantage of the cleaning method described herein is that it does not require to disassemble the heat exchanger; it can be performed in a short period of time; it takes advantage of the high internal pressure in the process of foam formation to break the deposits from the surface (e. g. the heat exchanger wall).

[0025] Therefore, any type of forming materials can be used for the invention. In some embodiments, the foam is a polymer foam selected from the group consisting of polyethylenes, polyurethanes, polyesters, and acrylonitrile-butadiene-styrene.

[0026] In some embodiments, the foam is a polyurethane foam, also called urethane foam.Polyurethane

[0027] Polyurethane foams are widely used in a variety of applications, including the packaging industry, in which polyurethane foams are used for cushioning fragile articles for shipping and handling. Various processes for producing polyurethane foams are known in the art. In general, a polyol-containing precursor and an isocyanate-containing precursor are brought together and mixed in the presence of a catalyst to cause a reaction which leads to curing and solidification of the mixture. In some embodiments, a blowing agent is introduced into the mixture so that foaming of the mixture occurs.

[0028] In one embodiment of the method in accordance with the invention, the polyurethane foaming composition comprises a first precursor mix and a second precursor mix. It is understood in the art that polyurethane is formed by a polyol reacting with a poly isocyanate. Therefore, the polyol or the poly isocyanate can be present in either the first precursor mix or the second precursor mix, but not both. Other additives, e.g. a catalyst, a blowing agent, a surfactant, a chain extender, a crosslinker, a flame retardant, and an antioxidant, can be in either the first precursor mix or the second precursor mix or both.

[0029] In one embodiment, the first precursor mix comprises a polyol; the second precursor mix comprises a polyisocyanate. In one embodiment, the first precursor mix comprises a polyisocyanate; the second precursor mix comprises a polyol. In one embodiment, the first precursor mix comprises a polyol, a catalyst, a blowing agent, and a surfactant. The first precursor mix optionally comprises a chain extender, a crosslinker, a flame retardant, and / or an antioxidant. In one embodiment, the second precursor mix comprises a polyol, a catalyst, a blowing agent, and a surfactant. The second precursor mix optionally comprises a chain extender, a crosslinker, a flame retardant, and / or an antioxidant.The precursor mixFirst precursor mixPolyol

[0030] In one embodiment, the polyol is a polyester made from an acid selected from the group consisting of succinic acid, glutanic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, iso-phthalic acid, dodecanedicarboxylic acid, and mixtures thereof. In one embodiment, the polyol is a glycol selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, tetramethylene glycol, diethylene glycol, methylene glycol, pentamethylene glycol, hexamethylene glycol, xylylene glycol, and mixtures thereof. In one embodiment, the polyol is a polyether selected from the group consisting of poly(oxypropylene)glycols, poly(oxypropylene)-poly(oxyethylene)copolymer glycols, poly(oxybutylene)glycols, poly(oxyethylene)glycols, poly(oxytetramethylene)glycols, poly(oxypropylene)glycerols, poly(oxypropylene)trimethylolpropanes, poly(oxypropylene)-1,2,6-hexanetriols, poly(ethyleneoxide propyleneoxide ethylenediamine)polyethers, poly(oxyalkylene)sorbitols, poly(oxyalkylene) pentaerythritols, poly(oxyalkylene)sucrose, poly(oxyalkylene)glucose, and mixtures thereof.

[0031] In one embodiment, the weight average molecular weight of the polyol is between 1000 to 3000.

[0032] In one embodiment, the polydispersity index of the polyol is between 0.5 to 1.

[0033] In one embodiment, the polyol is present in the first precursor mix at a weight percentage range 70-95% of the total weight of the first precursor mix.Blowing agent

[0034] In one embodiment, the blowing agent is HFC-245fa (1,1,1,3,3-pentafluoropropane) and HFC-134a (1,1,1,2-tetrafluoroethane), or hydrocarbons such as n-pentane. In one embodiment, the blowing agent is selected from the group consisting of: hexafluoropropene, 2-fluoropropene, 1-fluoropropene, 1,1-difluoropropene, 3,3-difluoropropene, 3,3,3-trifluoropropene, 2,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene, 1,1,3,3-tetrafluoropropene, 1,2,3,3,3-pentafluoropropene, 4,4,4-trifluoro-1-butene, 3,4,4,4-tetrafluoro-1-butene, 1,1,3,3,3-pentafluoro-2-methyl-1-propene, octafluoro-1-butene, octafluoro-2-butene, 2,3,3,4,4,4-hexafluoro-1-butene, 1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,4,4,4-heptafluoro-2-butene, 3-fluoropropene, 2,3-difluoropropene, 1,1,3-trifluoropropene, 1,3,3-trifluoropropene, 1,1,2-trifluoropropene, 1-fluorobutene, 2-fluorobutene, 2-fluoro-2-butene, 1,1-difluoro-1-butene, 3,3-difluoro-1-butene, 3,4,4-trifluoro-1-butene, 2,3,3-trifluoro-1-butene, 1,1,3,3-tetrafluoro-1-butene, 1,4,4,4-tetrafluoro-1-butene, 3,3,4,4-tetrafluoro-1-butene, 4,4-difluoro-1-butene, 1,1,1-trifluoro-2-butene, 2,4,4,4-tetrafluoro-1-butene, 1,1,1,2-tetrafluoro-2 butene, 1,1,4,4,4-pentafluoro-1-butene, 2,3,3,4,4-Pentafluoro-1-butene, 1,2,3,3,4,4,4-Heptafluoro-1-butene, 1,1,2,3,4,4,4-Heptafluoro-1-butene, 1,3,3,3-tetrafluoro-2-(trifluoromethyl)-propene, and mixtures thereof.

[0035] In one embodiment, the blowing agent is present in the first precursor mix at a weight percentage range 0.5-5% of the total weight of the first precursor mix. In some embodiments, the blowing agent is present in the first precursor mix at a weight percentage of the total weight of the first precursor mix selected from the group consisting of about 0.5 wt. %, about 1 wt. %, about 2 wt. %, about 3 wt. %, about 4 wt. %, and about 5 wt. %.Catalyst

[0036] In one embodiment, the first precursor mix further comprises a catalyst. In one embodiment, the catalyst is selected from the group consisting of alkyl tin carboxylates, triethylenediamine, 1,4-diazabicyclo[2.2.2]octane, dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), bis-(2-dimethylaminoethyl)ether, dibutyltin dilaurate, and mixtures thereof. In one embodiment, the catalyst is present in the first precursor mix at a weight percentage range 0.1-0.9% of the total weight of the first precursor mix. In some embodiments, the catalyst is present in the first precursor mix at a weight percentage of the total weight of the first precursor mix selected from the group consisting of about 0.01 wt. %, about 0.05 wt. %, about 0.1 wt. %, about 0.15 wt. %, about 0.2 wt. %, about 0.25 wt. %, about 0.3 wt. %, about 0.35 wt. %, about 0.4 wt. %, about 0.45 wt. %, about 0.5 wt. %, about 0.5 wt. %, about 0.6 wt. %, about 0.7 wt. %, about 0.8 wt. %, about 0.9 wt. %, and about 1 wt. %.Surfactant

[0037] In one embodiment, the first precursor mix further comprises a surfactant. In one embodiment, the surfactant is selected from the group consisting of dialkyl sulfosuccinic acid metal salts, dialkyl sulfosuccinic acid organic salts, alkyl benzenesulfonic acid metal salts, alkyl benzenesulfonic acid organic salts, Silwet-L-5130, and mixtures thereof. In one embodiment, the surfactant is present in the first precursor mix at a weight percentage range 1-9% of the total weight of the first precursor mix. In some embodiments, the surfactant is present in the first precursor mix at a weight percentage range of the total weight of the first precursor mix selected from the group consisting of about 1 wt. %, about 2 wt. %, about 3 wt. %, about 4 wt. %, about 5 wt. %, about 6 wt. %, about 7 wt. %, about 8 wt. %, about 9 wt. %, and about 10 wt. %.Chain extender

[0038] In one embodiment, the first precursor mix optionally comprises a chain extender. In one embodiment, the chain extender is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol (BDO), 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, the corresponding diamine and dithiol analogs thereof, lysine ethyl ester, arginine ethyl ester, and p-alanine-based diamine. In one embodiment, the chain extender is present in the first precursor mix at a weight percentage range 1-9% of the total weight of the first precursor mix. In some embodiments, the chain extender is present in the first precursor mix at a weight percentage of the total weight of the first precursor mix selected from the group consisting of about 1 wt. %, about 2 wt. %, about 3 wt. %, about 4 wt. %, about 5 wt. %, about 6 wt. %, about 7 wt. %, about 8 wt. %, about 9 wt. %, and about 10 wt. %.Crosslinker

[0039] In one embodiment, the first precursor mix optionally comprises a crosslinker. In one embodiment, the crosslinker is selected from the group consisting of siloxane and alkyl polysilicate. In one embodiment, the crosslinker is present in the first precursor mix at a weight percentage range 1-9% of the total weight of the first precursor mix. In some embodiments, the crosslinker is present in the first precursor mix at a weight percentage range of the total weight of the first precursor mix selected from the group consisting of about 1 wt. %, about 2 wt. %, about 3 wt. %, about 4 wt. %, about 5 wt. %, about 6 wt. %, about 7 wt. %, about 8 wt. %, about 9 wt. %, and about 10 wt. %.Second precursor mix

[0040] In one embodiment, the polyurethane foam comprises a second precursor mix comprising a polyisocyanate. In one embodiment, the polyisocyanate is selected from the group consisting of ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecanediisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1, 3- and -1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorondiisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI or HMDI), 1,3- and 1,4-phenylenediisocyanate, 2,4- and 2,6-toluene diisocyanate (TDI), diphenylmethane-2,4'- and / or -4,4'-diisocyanate ( MDI), naphthylene-1,5-diiso ianate, triphenylmethane-4,4 ', 4"- triisocyanate, polyphenyl-polymethylene-polyisocyanates (MDI raw materials), norbornanediisocyanates, m- and p-isocyanatophenylsulfonylisocyanates, perchlorinated arylpolyisocyanates, modified polyisocyanates, carbodiimide-modified polyisocyanates, isocyanurate-modified polyisocyanates, urea-modified polyisocyanates, biuret-containing polyisocyanates, prepolymers with terminal isocyanate groups and mixtures thereof. In one embodiment, the polyisocyanate is a toluene diisocyanate (TDI).

[0041] In one embodiment, the polyisocyanate is present in the second precursor mix at a weight percentage range 70-90% of the total weight of the second precursor mix.

[0042] The method disclosed herein further comprises the step of removing the debris and the foam using a solvent. In one embodiment, the solvent is selected from the group consisting of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dichloromethane, perchloroethylene, chlorobenzene, dioxane, cyclohexanone or mixtures thereof.

[0043] After removing the debris and the foam using a solvent, the method disclosed herein may further comprise the step of the cleaning the surface using a composition comprising hydrogen peroxide, catalyst for decomposing peroxide compounds, SAA, chelating agent, water-soluble calixarene, anti-foaming agent and water. Such step is described in PCT / RU2017 / 05005 and PCT / RU2018 / 050154.Foam formation

[0044] The precursor mix described herein can be prepared in-place. Once it is prepared, several chemical and physical processes start simultaneously, such as polymerization reactions and foaming process during which gas bubbles are formed. The gas bubbles lead the expansion of the foaming inside the pores or cracks of the deposits, and eventually break the deposits away from the surface. Therefore, the components and concentrations thereof in the precursor mix must be chosen in such a way as foaming processes results in breaking the deposits away from the surface. The selection criterion for precursor mix formulation is the median size of bubbles which should be smaller than the median diameter of pores in the fouling deposits.

[0045] In one embodiment, the fouled equipment is soaked in the precursor mix or it is kept in contact with the precursor mix. In one embodiment, the precursor mix is allowed to be in contact with the fouled equipment in a period of time sufficient for the precursor mix to penetrate the cracks or pores inside the deposits. In some embodiments, the sufficient time is selected from the group consisting of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, and 100 minutes.EXAMPLES

[0046] The embodiments encompassed herein are now described with reference to the following examples. These examples are provided for the purpose of illustration only and the disclosure encompassed herein should in no way be construed as being limited to these examples, but rather should be construed to encompass any and all variations which become evident as a result of the teachings provided herein.Example 1: Removing deposits in a heat exchanger

[0047] The following prophetic example illustrates the applying of method for clean-up of a shell side of a small-size shell-and-tube heat-exchanger fouled with porous petcoke deposits. The fouling consists mostly of elemental carbon, the average thickness of fouling layer is 5 mm. The median pore diameter is 0.02 mm. The first precursor mix (hereinafter referred to as component A) comprises the following ingredients: Polyether polyol (M.W. 1000-3000) - 95 pbw Quadrol - 0,5-5 pbw Water - 3 pbw TMBDA - 0,5 pbw Dabco T-12 - 0,03 pbw Surfactant L-5310 - 2 pbw

[0048] The second precursor mix (hereinafter referred to as component B) is technical grade toluene diisocyanate. The clean-up proceeds as follows:

[0049] The shell side of the heat-exchanger (hereinafter referred to as contour) is filled with Component A and left undisturbed for 30 min. Component A is drained from the contour in recycle storage tank. The contour is filled with component B and left undisturbed for 2 min. Component B is drained from the contour in recycle storage tank. After 1 hour period the contour is connected to circulation pump and buffer vessel; inlet / outlet are connected by flexible hoses in a circulation loop. The circulation loop is filled with dimethylformamide. Dimethylformamide is circulated for 1 hour and than drained into recycle storage tank. Whole process is carried out at 25°C. The inspection of dismantled tube bundle showed complete removal of all fouling material.

Claims

1. A method for removing deposits from a surface comprising the steps of applying a first precursor mix to the surface; allowing the first precursor mix to pass through the deposits; removing the first precursor mix; applying a second precursor mix to the surface; allowing the second precursor mix to pass though the deposits; removing the second precursor mix; the method being characterized in that the first precursor mix reacts with the second precursor mix to produce a foam, and the foam expands inside pores and cracks of the deposits, and results in breaking the deposit from the surface.

2. The method of claim 1, wherein the foam is a polymer foam selected from the group consisting of polyethylenes, polyurethanes, polyesters, and acrylonitrile-butadiene-styrene.

3. The method of claim 1, wherein the first precursor mix comprises a polyol.

4. The method of claim 3, wherein the polyol is a polyester made from an acid selected from the group consisting of succinic acid, glutanic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, iso-phthalic acid, dodecanedicarboxylic acid, and mixtures thereof.

5. The method of claim 3, wherein the polyol is a glycol selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, tetramethylene glycol, diethylene glycol, methylene glycol, pentamethylene glycol, hexamethylene glycol, xylylene glycol, and mixtures thereof.

6. The method of claim 3, wherein the polyol is a polyether selected from the group consisting of poly(oxypropylene)glycols, poly(oxypropylene)-poly(oxyethylene)copolymer glycols, poly(oxybutylene)glycols, poly(oxyethylene)glycols, poly(oxytetramethylene)glycols, poly(oxypropylene)glycerols, poly(oxypropylene)trimethylolpropanes, poly(oxypropylene)-1,2,6-hexanetriols, poly(ethyleneoxide propyleneoxide ethylenediamine)polyethers, poly(oxyalkylene)sorbitols, poly(oxyalkylene) pentaerythritols, poly(oxyalkylene)sucrose, poly(oxyalkylene)glucose, and mixtures thereof.

7. The method of claim 1, wherein the second precursor mix comprises a polyisocyanate.

8. The method of claim 7, wherein the polyisocyanate is selected from the group consisting of ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecanediisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1, 3- and -1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (isophorondiisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI or HMDI), 1,3- and 1,4-phenylenediisocyanate, 2,4- and 2,6-toluene diisocyanate (TDI), diphenylmethane-2,4'- and / or -4,4'-diisocyanate ( MDI), naphthylene-1,5-diiso ianate, triphenylmethane-4,4 ', 4"- triisocyanate, polyphenyl-polymethylene-polyisocyanates (MDI raw materials), norbornanediisocyanates, m- and p-isocyanatophenylsulfonylisocyanates, perchlorinated arylpolyisocyanates, modified polyisocyanates, carbodiimide-modified polyisocyanates, isocyanurate-modified polyisocyanates, urea-modified polyisocyanates, biuret-containing polyisocyanates, prepolymers with terminal isocyanate groups and mixtures thereof.

9. The method of claim 7, wherein the polyisocyanate is a toluene diisocyanate (TDI).

10. The method of claim 1, wherein the first precursor mix further comprises a catalyst.

11. The method of claim 10, wherein the catalyst is selected from the group consisting of alkyl tin carboxylates, triethylenediamine, 1,4-diazabicyclo[2.2.2]octane, dimethylcyclohexylamine (DMCHA), dimethylethanolamine (DMEA), bis-(2-dimethylaminoethyl)ether, dibutyltin dilaurate, and mixtures thereof.

12. The method of claim 1, wherein the first precursor mix further comprises a surfactant.

13. The method of claim 12, wherein the surfactant is selected from the group consisting of dialkyl sulfosuccinic acid metal salts, dialkyl sulfosuccinic acid organic salts, alkyl benzenesulfonic acid metal salts, alkyl benzenesulfonic acid organic salts, Silwet-L-5130, and mixtures thereof.

14. The method of claim 1, further comprising allowing the first precursor mix and the second precursor mix to react for a sufficient time.

15. The method of claim 14, wherein the sufficient time is selected from the group consisting of 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, and 100 minutes.

Images