CHOLINE HYDROXIDE FOR SALT DISPLACEMENT IN RENEWABLE FEEDSTOCK PROCESS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application claims priority to U.S. Provisional Patent Application Ser. No. 63/575,150 filed on Apr. 5, 2024, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002]The present invention generally relates to compositions and methods for displacing corrosive salts in processing or co-processing renewable feedstocks. More specifically, the invention relates to displacing corrosive salts through the addition of choline-based hydroxides in the affected section of process units that experience high levels of ammonia, amines, or chlorides and their use in reducing salt fouling and corrosion.

BACKGROUND OF THE INVENTION

[0003]Renewable feedstocks are the raw materials that can be used to produce biofuels, bioproducts, and biopower. Some examples of renewable feedstocks are agricultural residues, dedicated energy crops, forestry residues, or waste streams and re-usable carbon sources. There is a growing interest in processing and co-processing renewable feedstocks in refinery units due to the economic and environmental advantages over processing conventional feedstocks, such as fossil fuels. An example of an advantage is the transportation fuels produced by processing or co-processing renewable feedstocks have a lower carbon intensity than traditional fuels.

[0004]Where there is a sufficient amount of ammonia and chloride present in the refining process, ammonium chloride salts deposit on the equipment. This salt deposition causes salt fouling and corrosion. Salt fouling forms on the surface of the equipment inhibiting heat transfer in the process, which diminishes efficiency and productivity in refineries. Corrosion of the equipment leads to production loss and cost associated with increased maintenance, repairs, and replacement of the equipment.

[0005]Processing or co-processing renewable feedstocks presents a higher risk of chloride salt fouling and corrosion due to the increased amounts of chlorides found in renewable feedstocks. Solid ammonium chloride precipitates onto the equipment. Ammonium chloride is water soluble, so the best way to prevent ammonium chloride fouling and corrosion is to use a water washing system. This can be a tower washing program of feeding water into the equipment until enough water can condense the salt deposits. However, this process can take hours or even days. This water washing process can introduce water into the refinery process. Because the refinery process produces water, there is a risk of thermodynamic imbalance during the refinery process.

[0006]In addition to the water washing system, an additive of an amine blend is injected and may be used to inhibit fouling and corrosion by dispersing the corrosive salts. This method however has a risk of corrosion because the reaction causes the pH of the water to decrease.

[0007]Thus, a need for a more effective solution to salt fouling in processing renewable feedstocks exists.

SUMMARY OF THE INVENTION

[0008]One aspect of the invention is a method for inhibiting fouling or corrosion of a surface in contact with a renewable process fluid comprising contacting a salt dispersant agent with a corrosion salt, wherein a process for refining a renewable feedstock comprises the renewable process fluid and the salt dispersant agent reacts with the corrosion salt to produce an aqueous-soluble dispersant salt.

[0009]The salt dispersant agent can comprise an organic amine.

[0010]The salt dispersant agent can comprise a quaternary trialkylalkanolamine; preferably, a quaternary tri (C₁-C₆ alkyl) C₁-C₆ alkanolamine; or more preferably, a quaternary trimethyl alkanolamine.

[0011]Preferably, the salt dispersant agent can comprise trimethyl ethanolamine hydroxide (choline hydroxide) or trimethyl iso-propanolamine hydroxide (β-methyl choline hydroxide).

[0012]The quaternary trialkylalkanolamine can be stabilized. Preferably, the quaternary trialkylalkanolamine is stabilized with an alkanolamine or a diamine.

[0013]The salt dispersant agent can have a concentration from about 1 to about 5000 ppm by weight based on the total weight of the corrosion salt in the renewable process fluid.

[0014]Preferably, the salt dispersant agent contacts the corrosion salt by injecting the salt dispersant agent into the renewable process fluid.

[0015]The renewable process fluid can comprise ammonium, alkyl ammonium, aryl ammonium, alkyl-aryl ammonium, and chloride ions.

[0016]The corrosion salt can comprise chloride ions, ammonium ions, alkyl ammonium ions, aryl ammonium ions, alkyl-aryl ammonium ions, or a combination thereof.

[0017]The corrosion salt can comprise ammonium chloride, alkyl ammonium chloride, aryl ammonium chloride, alkyl-aryl ammonium chloride, or a combination thereof.

[0018]The aqueous-soluble dispersant salt can be a quaternary trialkyl alkanolamine chloride; preferably, trimethyl ethanolamine chloride (choline chloride) or trimethyl iso-propanolamine chloride (β-methyl choline chloride).

[0019]The aqueous-soluble dispersant salt can have a higher water solubility than the corrosion salt.

[0020]The aqueous-soluble dispersant salt has a water solubility of at least about 0.2 mole, 0.3 mole, or 0.4 mole aqueous-soluble dispersant salt per mole water at a temperature of 0° C.

[0021]The aqueous-soluble dispersant salt has a water solubility of up to about 1.4 mole aqueous-soluble dispersant salt per mole water at a temperature of 0° C.

[0022]The corrosion salt can be formed in the renewable process fluid during refining of the renewable feedstock.

[0023]The renewable feedstock can comprise soybean oil, palm oil, corn oil, waste oil, an animal fat, biomass waste, recycled carbon, a sugar, a starch crop, or a combination thereof.

[0024]The aqueous-soluble dispersant salt can dissolve in an aqueous phase of the renewable process fluid.

[0025]The surface can be a metal surface in a piece of equipment in the process for refining the renewable feedstock.

[0026]Another aspect of the disclosure is a method for inhibiting fouling or corrosion of a surface in a piece of equipment in a process for refining a renewable feedstock, the method comprises contacting a salt dispersant agent with a corrosion salt produced in the process for refining the renewable feedstock, wherein the salt dispersant agent comprises choline hydroxide or β-methyl choline hydroxide, and the corrosion salt comprises ammonium chloride, alkyl ammonium chloride, or aryl ammonium chloride, whereby choline chloride or β-methyl choline chloride is formed.

[0027]Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a graph comparing the solubility of salts as function of temperature. The graph includes data available in literature, indicated with “Literature.” Data not available through literature was experimentally obtained, indicated with “EXP.” The salts compared are ammonium chloride (NH₄Cl), choline chloride (ChCl), and beta-methylcholine chloride (β-MeChCl) between 0 C and 200 C.

[0029]FIG. 2 is a graph comparing the critical relative humidity (CRH) of salts as function of temperature. The graph includes data available in literature, indicated by “Literature.” Data not available through literature was calculated, indicated by “Calculated.” The salts compared are ammonium chloride (NH₄Cl), choline chloride (ChCl), and beta-methylcholine chloride (β-MeChCl) between 0 C and 200 C.

[0030]FIG. 3 is a schematic of a hydrotreated vegetable oil (HVO)/Co-processing renewable feedstock unit.

[0031]FIG. 4 is a schematics of a fluid catalytic cracking unit (FCCU) for co-processing biofeedstocks.

[0032]Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

[0033]A salt dispersant agent has been discovered to effectively prevent or reduce salt fouling on the equipment in areas of processing renewable feedstocks which experience high concentrations of ammonia/amines and chlorides. The salt dispersant agent contacts the corrosion salt within an aqueous solution to form a choline-chloride salt which has higher solubility in water than the corrosion salt. The choline-chloride salt is dissolved, transferred, and remains in the aqueous phase throughout the remainder of the processing of the renewable feedstock.

[0034]Renewable feedstocks can be co-processed in the reformer, fluid catalytic cracking unit (FCCU), alkylation unit, isomerization, hydrotreater, cracker, and coker. Corrosion salts are formed where there are ammonia/amines and chlorides in processing renewable feedstocks. This typically occurs in the overheads of the crude distillation unit or vacuum distillation unit, stripper overheads, separators, and reactor effluent coolers can be susceptible to ammonium chloride deposition of the refinery process. The ammonia or amines are generated from nitrogen-containing compounds which can be in the renewable feedstocks but are generally more prevalent in crude oil. Renewable feedstocks typically have a higher level of chlorides than non-renewable feedstocks. Therefore, the concentration of corrosion salts is higher in the processing of renewable feedstocks.

[0035]Corrosion salts are salts which precipitate as a solid on to equipment's metal surface. This precipitation causes reduction in heat transfer capabilities, lowering process efficiency and corrosion and shortening the lifespan of the equipment. Nonlimiting examples of corrosion salts found in the present invention are hydrochloride, ammonium chloride, alkyl ammonium chloride, aryl ammonium chloride, or a combination thereof.

[0036]One aspect of the invention is a method for inhibiting fouling or corrosion of a surface in contact with a renewable process fluid comprising contacting a salt dispersant agent with a corrosion salt, wherein a process for refining a renewable feedstock comprises the renewable process fluid, and the salt dispersant agent reacts with the corrosion salt to produce an aqueous-soluble dispersant salt.

[0037]The salt dispersant agent can comprise an organic amine.

[0038]The salt dispersant agent can comprise a quaternary trialkylalkanolamine; preferably, a quaternary tri(C₁-C₆ alkyl) C₁-C₆ alkanolamine; or more preferably, a quaternary trimethyl alkanolamine.

[0039]Preferably, the salt dispersant agent can comprise trimethyl ethanolamine hydroxide (choline hydroxide) or trimethyl iso-propanolamine hydroxide (β-methyl choline hydroxide).

[0040]The salt dispersant agent comprises a choline. In one embodiment, the salt dispersant agent comprises choline-based hydroxide represented by the compounds below.

[0041]The choline based hydroxide in the salt dispersant agent contacts the corrosion salt such that the chloride from the salt replaces the hydroxide ion on the choline forming a choline-chloride salt. This is represented in the chemical reaction below.

[0042]The choline based hydroxide can be 2-Hydroxy-N,N,N-trimethylethanaminium hydroxide (choline hydroxide) which reacts with the corrosion salt, ammonium chloride, alkyl ammonium chloride, or aryl ammonium chloride, to create a choline chloride (ChCl). The choline-based hydroxide is (2-Hydroxypropyl)trimethylammonium hydroxide (Beta-methyl choline hydroxide) which reacts with the corrosion salt, ammonium chloride, alkyl ammonium chloride, or aryl ammonium chloride to create beta-methyl choline chloride (β-MeChCl).

[0043]The choline hydroxide has a concentration from 44 to 47 wt. % in water.

[0044]The effectiveness of a salt to dissolve in an aqueous solution is characterized by its solubility and critical relative humidity (CRH) at various temperatures. Solubility describes how much humidity is needed for a salt to absorb moisture. The CRH is the relative humidity of the surrounding atmosphere at which the salt begins to absorb moisture from the atmosphere. Lower CRH values translate to lower levels of water needed in the atmosphere for the salt to dissolve into the aqueous solution.

[0045]Example 2 provides a detailed description of the relationship between CRH and the water solubility of ammonium chloride (NH4Cl), choline chloride (ChCl), and Beta-methyl choline chloride (β-MeChCl).

[0046]In accordance with the invention, ChCl is more soluble than NH₄Cl, and β-MeChCl is much more soluble than both at all tested temperatures.

[0047]In further accordance with the invention, the CRH at all temperatures is lower for the choline-based salts (ChCl and β-MeChCl) than NH₄Cl.

[0048]The salt displacement agent displaces the corrosion salt with a salt that is more soluble in the aqueous solution. If the moisture level stays above the CRH, the salt remains dissolved, rather than precipitates on to the process equipment, and moves in the aqueous stream throughout the remainder of the process. This displacement lowers the concentration of the corrosion salts and, accordingly, the fouling risk.

[0049]The quaternary trialkylalkanolamine can be stabilized. Preferably, the quaternary trialkylalkanolamine is stabilized with an alkanolamine or a diamine.

[0050]Examples of suitable commercially stabilized choline useful in the practice of the present invention include the stabilized choline sold under the tradename Choline Hydroxide, commercially available from Balchem, or the tradename Tamisolv, commercially available from Eastman.

[0051]The salt dispersant agent can have a concentration from about 1 to about 5000 ppm, from about 1 to about 4000 ppm, from about 1 to about 3000 ppm, from about 1 to about 2000 ppm, from about 1 to about 1000 ppm, from about 1 to about 750 ppm, from about 1 to about 500 ppm, from about 1 to about 400 ppm, from about 1 to about 300 ppm, from about 1 to about 200 ppm, or from about 1 to about 100 ppm by weight of the total salt dispersant agent composition (including its solvent) based on the amount of corrosion salts in the renewable process fluid.

[0052]The salt dispersant agent can be contacted with the renewable process fluid at a concentration of active compound from about 1 ppm to about 100 ppm.

[0053]Preferably, the salt dispersant agent contacts the corrosion salt by injecting the salt dispersant agent into the renewable process fluid. The injection point can be at a convenient point upstream from any of the areas identified as potential salting locations in the process schematics represented in FIGS. 2 and 3.

[0054]The renewable process fluid can comprise ammonium, alkyl ammonium, aryl ammonium, alkyl-aryl ammonium, and chloride ions.

[0055]The corrosion salt can comprise chloride ions, ammonium ions, alkyl ammonium ions, aryl ammonium ions, alkyl-aryl ammonium, or a combination thereof.

[0056]The corrosion salt can comprise ammonium chloride, alkyl ammonium chloride, aryl ammonium chloride, alkyl-aryl ammonium chloride, or a combination thereof.

[0057]The aqueous-soluble dispersant salt can be a quaternary trialkyl alkanolamine chloride; preferably, trimethyl ethanolamine chloride (choline chloride) or trimethyl iso-propanolamine chloride (β-methyl choline chloride).

[0058]The aqueous-soluble dispersant salt can have a higher water solubility than the corrosion salt.

[0059]The aqueous-soluble dispersant salt has a water solubility of at least about 0.2 mole, 0.3 mole, or 0.4 mole aqueous-soluble dispersant salt per mole water at a temperature of 0° C.

[0060]The aqueous-soluble dispersant salt has a water solubility of up to about 1.4 mole aqueous-soluble dispersant salt per mole water at a temperature of 0° C.

[0061]The corrosion salt can be formed in the renewable process fluid during refining of the renewable feedstock.

[0062]The renewable feedstock can comprise soybean oil, palm oil, corn oil, waste oil, animal fats, biomass waste, recycled carbon, sugar, starch crops, or a combination thereof.

[0063]The aqueous-soluble dispersant salt can dissolve in an aqueous phase of the renewable process fluid.

[0064]The surface can be a metal surface in a piece of equipment in the process for refining the renewable feedstock.

[0065]To support energy transition, oil and gas industry has been proactively exploring the use of biofeedstocks to produce renewable fuels. Processing biofeedstocks or co-processing with conventional fossil-fuel based feeds presents different challenges to refiners in terms of material susceptibility. Particularly, aggressive fouling and corrosion is encountered in equipment with high risk of ammonium or amine hydrochloride salt formation could occur.

[0066]Renewable feedstocks can be introduced into the refinery process at different locations (1) biomass into the crude unit, or (2) biomass intermediates into conversion units or finishing units, such as the reformer, FCCU, alkylation, isomerization, hydrotreater, cracker, and coker. In either case, the chlorides present in the feedstock will hydrolyze and lead to the formation of HCl in the overheads of the unit. The presence of ammonia or amines with the produced HCl results in the formation of solid ammonium chloride or amine-hydrochloride salt.

[0067]FIG. 3 demonstrates a hydrotreated vegetable oil (HVO)/Co-processing renewable feedstock Unit designating process steps where corrosion salts are likely to form and potential injection points of the salt dispersant agent into the process would be at convenient places upstream of the formation of the corrosion salts.

[0068]FIG. 4 demonstrates a fluid catalytic cracking unit (FCCU) co-processing biofeedstocks designating process steps where corrosion salts are likely to form and potential injection points of the salt dispersant agent into the process.

[0069]Another aspect of the disclosure is a method for inhibiting fouling or corrosion of a surface in a piece of equipment in a process for refining a renewable feedstock, the method comprises contacting a salt dispersant agent with a corrosion salt produced in the process for refining the renewable feedstock, wherein the salt dispersant agent comprises choline hydroxide or β-methyl choline hydroxide, and the corrosion salt comprises ammonia chloride, whereby choline chloride or β-methyl choline chloride is formed.

[0070]The alkyl ammonium ions can be primary, secondary, or tertiary alkyl ammonium ions where the alkyl groups contain from 1 to 30 carbon atoms.

[0071]The aryl ammonium ions can be primary, secondary, or tertiary aryl ammonium ions where the aryl groups contain from 5 to 12 carbon atoms.

[0072]The alkyl-aryl ammonium ions can also be substituted with one alkyl group having 1 to 30 carbon atoms and one aryl group having 5 to 12 carbon atoms, with one or two alkyl groups and one aryl group or one alkyl group and one or two aryl groups.

[0073]The alkyl groups described herein can be branched or linear and have from 1 to 30 carbon atoms, from 1 to 20 carbon atoms, 1 to 10 carbon atoms, from 1 to 6 carbon atoms, or from 1 to 3 carbon atoms.

[0074]The aryl groups described herein can have from 5 to 12 carbon atoms, or from 5 to 6 carbon atoms.

EXAMPLES

[0075]The following non-limiting examples are provided to further illustrate the present invention.

Example 1: Choline Hydroxide Salt Displacement

[0076]Choline hydroxide represented by Formula 1 or 2 was used to react with acidic components comprising chlorine to create a water soluble chloride salt according to scheme 1 in processing or co-processing renewable feedstocks. The chloride salt moves with the aqueous stream in the refinery processing renewable feed stocks.

Example 2: Determine Effectiveness of Salt Dissolution in the Aqueous Phase

[0077]The effectiveness of the salt to dissolve in the aqueous phase was determined by its critical relative humidity (CRH) at various temperatures. CRH was defined by the ratio of the partial pressure of water in the solution (Pw) to the partial pressure of pure water (P*w) shown below.

$\mathrm{CRH}=\frac{P_w}{P_w^{*}}$

[0078]The CRH of the salt at a specified temperature was calculated from thermodynamic parameters found in the equation:

[0079]In

$\frac{{\mathrm{CRH}}_2{T}_2}{{\mathrm{CRH}}_1{T}_1}=\frac{\Delta H_s}{R}\left[A\left(\frac{1}{T_2}-\frac{1}{T_1}\right)-B\ln \frac{T_2}{T_1}-C\left(T_2-T_1\right)\right]$

[0080]Where CRH was the critical relative humidity, T was the temperature, ΔHs was the heat of solution at infinite dilution, R is the gas constant, and A, B, and C are solubility parameters obtained from solubility as a function of temperature of the salt.

[0081]A lower Critical Relatively Humidity translated to lower levels of water needed in the atmosphere for the salt to dissolve in the aqueous phase. Critical Relative Humidity for ammonium chloride, choline chloride, and methyl choline chloride were calculated by determining the heat of solution at infinite dilution and solubility of the salts. Data not available in the literature was experimentally performed in triplicate by an enthalpy experiment and a solubility experiment.

[0082]The enthalpy experiment was conducted by recording changes in temperature as different amounts of the salt dissolved in a set volume of water located in a calorimeter. The enthalpy of solution was calculated for each of the different amount of salt used. The enthalpy data was then fitted and extrapolated to determine enthalpy of solution at an infinite dilution.

[0083]The solubility experiment was conducted by adding different amounts of salt to a set amount of water in glass vials. The amount of water used was such that the salt was mostly insoluble at room temperature. The vials were then heated up until all salts were dissolved. Temperature was recorded as each vial cooled. The temperature at which crystallization began was noted. This data was then used to construct the solubility curve using molar ratios (mol salt/mol water).

[0084]As demonstrated in FIG. 1, the solubility of ammonium chloride (NH₄Cl), choline chloride (ChCl), and beta-methylcholine chloride (β-MeChCl) as a function of temperature were compared. ChCl was more soluble than NH₄Cl, and β-MeChCl was much more soluble than both at all tested temperatures.

[0085]Then the CRH values at room temperature for MeChCl, ChCl, and NH₄Cl were plotted as a function of temperature and compared. These values are shown in FIG. 2. The CRH values at room temperature were found in literature or calculated from the solubility data following the below equations. Where aw is the water activity of the salt, χ_w is the mole fraction of water, γ_w is the water activity coefficient, γ_± is the mean ionic activity coefficient, z is the charge of the ion, and I_c is the ionic strength (in mol/L).

$a_w={\chi }_w{\gamma }_w=\mathrm{CRH}$$\ln {\gamma }_{\pm }=-\frac{1.173❘z_{+}{z}_{-}❘I_c^{\frac{1}{2}}}{1+I_c^{\frac{1}{2}}}+0.2I_c$

[0086]The CRH was lower at all temperatures for the choline-based salts than NH₄Cl. Therefore, the choline based salts required lower levels of water in the atmosphere for the salt to dissolve in the aqueous solution.