Patent Application
20230136801
The United States is the world's largest producer of waste cooking oils (WCOs). Annually, the U.S. produced 20 billion pounds of in 2007, representing 55% of global WCO production. It is expected that annual vegetable oil production by 2023 will be more than 115 billion pounds in the U.S., approximately 20 billion pounds of which will be consumed in edible products. As a result, significant amounts of WCO are available for the production of fuels and chemicals.
To date, most studies have focused on fuel (bio-diesel) production through traditional transesterification processes rather than synthesis of value added bio-products. However, the cost of biodiesel is a major drawback against its commercial availability. WCOs typically contain high amounts of C8 to C24 fatty acids with average molecular weights of about 850 g/mol and kinematic viscosity at 40° C. of about 35 cSt. In particular, C16 and C18 fatty acids with zero, one, or two double bonds account for more than 60% of WCOs. Although vegetable oils have relatively good lubricity qualities, they cannot serve as robust base oils for industrial machinery lubricants because of their low oxidative tolerance, poor solubility of additives in the oil, and poor low-temperature performance.
Bio-lubricants (BL) can refer to lubricants produced from natural raw materials such as vegetable and animal oils that are renewable, biodegradable, and non-toxic to humans, as well as being environmentally friendly. Raw vegetable oils have good lubricity, low viscosity, and relatively low pour point. Although virgin cooking oils may possess desirable lubricant properties such as low pour point and high viscosity index, their direct application as lubricant is quite unfavorable because of competition with food chain. Thus, waste cooking oils (WCOs) are considered a better alternative for biofuel and bio-lubricant (BL) feedstocks.
Additionally, thermal instability can render products to not be useful as lubricants. At high temperatures, triglycerides decompose to free fatty acids (FFAs), thus increasing the total acid number. Thereafter, FFAs undergo self-polymerization and form macromolecules with much higher viscosity and pour point. In addition, vegetable oils present extremely poor response to pour point depressants and additives because of lack of suitable chemical functionalities. WCOs require chemical modifications to restore their positive lubricant properties. Current developments for producing lubricants from vegetable oils rely on traditional (trans)esterification, etherification, and chemical modifications of triglycerides and free fatty acids (FFAs). However, the final products are undesirable as they suffer from poor low-temperature characteristics, low oxidation stability, low viscosity index, and/or poor solubility of additives. Therefore, there exists a need for an improved production process to provide lubricants with desirable characteristics.
Accordingly, the present disclosure provides improved biolubricant compositions and methods of making the same. For instance, the present disclosure provides an exemplary approach to produce bio-lubricants (BL) from the reaction of waste cooking oils (WCOs) and cyclic oxygenated hydrocarbons (COHCs) via a four-step pathway: hydrolysis, dehydration/ketonization, Friedel-Crafts (FC) acylation/alkylation, and hydrotreatment. This process is capable of producing biolubricants comprising molecules with several desirable properties, including but not limited to 1) long and linear hydrocarbon chains, 2) low to zero unsaturation, 3) minimal branching, 4) inclusion of naphthenic rings and cyclic structures, and 5) inclusion of polar molecules. The biolubricant compositions and methods of the present disclosure have numerous benefits compared to those known in the art. First, the biolubricant compositions may comprise favorable characteristics, including low-temperature characteristics, oxidation stability, viscosity index, or solubility of additives. Various characteristics may be characterized by pour point, kinematic viscosity (at 40° C.), viscosity index, and Noack volatility.
Other objects, features and advantages of the present disclosure will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Various embodiments of the invention are described herein as follows. In an illustrative aspect, a method of producing a lubricant composition is provided. The method comprises the steps of hydrolyzing a starting material to provide a hydrolyzed product mixture, reacting the hydrolyzed product mixture under conditions capable of producing a condensation product mixture, contacting the condensation product mixture with a cyclic compound to provide a coupled product mixture, and hydrogenating the coupled product mixture to provide the lubricant composition.
In an embodiment, the lubricant composition is a biolubricant. The term biolubricant is referred to herein according to common knowledge in the art, for instance a lubricant that is capable of being produced or obtained from natural raw materials. Such biolubricants can be renewable, biodegradable, nontoxic, and/or environmentally friendly. In an embodiment, the biolubricant is obtained from a non-synthetic starting material. In an embodiment, the non-synthetic starting material is selected from the group consisting of a vegetable oil, an animal oil, and a combination thereof. In an embodiment, the non-synthetic material is a vegetable oil. In an embodiment, the non-synthetic material is an animal oil. As described herein, an animal oil or animal fat can interchangeably refer to oils or fats obtained from an animal. For instance, the animal oil may be provided from the cooking of an animal or an animal part. For instance, an animal oil can include one or more animal fats.
In an embodiment, the lubricant composition comprises a mixture of one or more lubricants. For instance, the lubricant composition can be a mixture of various components that can be characterized as lubricants and/or biolubricants. In an embodiment, a lubricant can comprise a mixture of hydrocarbons with any suitable functionalization. For instance, the hydrocarbons may vary in length, saturation, branching, substituents, and heteroatom content. In an embodiment, the lubricant comprises a mixture of one or more cyclic oxygenated hydrocarbons (COHCs). In an embodiment, a lubricant can include a base oil and an additive. In an embodiment, a lubricant can be a base oil.
In an embodiment, the hydrolyzing of step i) is performed in the presence of a catalyst. In an embodiment, the catalyst is selected from the group consisting of an acid, a base, a metal oxide, and any combination thereof.
In an embodiment, the catalyst is an acid. In an embodiment, the acid is an inorganic acid or organic acid. In an embodiment, the acid is a solid acid. In an embodiment, the acid is a homogenous or heterogeneous acid. In an embodiment, the acid is a sulfuric acid or a sulfonic acid. In an embodiment, the acid is a sulfuric acid. In an embodiment, the acid is a sulfonic acid.
In an embodiment, the catalyst is a base. In an embodiment, the catalyst is a metal oxide. In an embodiment, the metal oxide is TiO2.
In an embodiment, the starting material is a non-synthetic starting material. In an embodiment, the starting material is an oil. In an embodiment, the oil is a cooking oil. In an embodiment, the cooking oil is selected from the group consisting of a vegetable oil, an animal oil, and any combination thereof. In an embodiment, the cooking oil is a vegetable oil. In an embodiment, the cooking oil is an animal oil.
In an embodiment, the oil is a waste cooking oil. In an embodiment, the waste cooking oil is selected from the group consisting of a vegetable oil, animal oil, and combination thereof. In an embodiment, the waste cooking oil is obtained from cooking processes. For instance, the waste cooking oil can be obtained from the preparation of food. In an embodiment, the waste cooking oil is a vegetable oil. In an embodiment, the waste cooking oil is an animal oil.
In an embodiment, the oil is a crude oil. In an embodiment, the oil is a purified oil. In an embodiment, the purified oil is provided by a filtration step, a water removal step, or any combination thereof. In an embodiment, the purified oil is provided by a filtration step. In an embodiment, the purified oil is provided by a water removal step.
In an embodiment, the starting material comprises one or more triglycerides, one or more fatty acids, and a combination thereof. In an embodiment, the starting material comprises one or more triglycerides.
In an embodiment, the starting material comprises one or more fatty acids. In an embodiment, the fatty acid comprises a C5 to C40 fatty acid.
In an embodiment, the hydrolyzed product mixture comprises one or more carboxylic acids. In an embodiment, the carboxylic acid comprises one or more fatty acids. In an embodiment, the fatty acid comprises a C5 to C40 fatty acid.
In an embodiment, the reacting of step ii) comprises a dehydration reaction. In an embodiment, the reacting of step ii) comprises a ketonization reaction.
In an embodiment, the reacting of step ii) is performed in the presence of a catalyst. In an embodiment, the catalyst is selected from the group consisting of an acid, a metal, a metal oxide, a zeolite, and any combination thereof. In an embodiment, the catalyst is an acid. In an embodiment, the acid is selected from the group comprising a formic acid, a sulfuric acid, a Lewis acid, an acid halide, and any combination thereof.
In an embodiment, the catalyst comprises a metal. In an embodiment, the metal comprises cobalt. In an embodiment, the metal comprises nickel. In an embodiment, the catalyst is a metal oxide. In an embodiment, the metal oxide is selected from the group consisting of ZrO2, ZrO2/H2SO4, Fe3O4, TiO2, B2O3, WO3, PbO, MgO, CoO, Al2O3, SiO2, SiO2/Al2O3, and any combination thereof. In an embodiment, the catalyst is a zeolite. In an embodiment, the zeolite is erionite, gmelinite, mordenite, or ZSM-5. In an embodiment, the catalyst is montmorillonite.
In an embodiment, the condensation product mixture of step ii) comprises an anhydride, a ketone, an ether, an acyl halide, an arene, and any combination thereof. In an embodiment, the condensation product mixture of step ii) comprises an anhydride. In an embodiment, the condensation product mixture of step ii) comprises a ketone. In an embodiment, the condensation product mixture of step ii) comprises an ether. In an embodiment, the condensation product mixture of step ii) comprises an acyl halide. In an embodiment, the condensation product mixture of step ii) comprises an arene.
In an embodiment, the contacting of step iii) comprises an alkylation reaction, an acylation reaction, an esterification reaction, or an etherification reaction. For instance, the reaction performed according to step iii) can utilize a Friedel-Crafts reaction as it is commonly understood in the art. For instance, a Friedel-Crafts reaction can be an alkylation or an acylation. A Friedel-Crafts reaction can also be utilized to functionalize a cyclic aromatic compound. For instance, the reaction performed according to step iii) can utilize a Fischer reaction as it is commonly understood in the art including, for example, an esterification.
In an embodiment, the contacting of step iii) is performed in the presence of a catalyst. In an embodiment, the catalyst is selected from the group consisting of an acid, a metal, a metal oxide, a zeolite, and any combination thereof. In an embodiment, the catalyst is an acid. In an embodiment, the acid is a Lewis acid. In an embodiment, the Lewis acid is AlCl3 or FeCl3.
In an embodiment, the catalyst comprises a metal. In an embodiment, the catalyst is a metal oxide. In an embodiment, the metal oxide is selected from the group consisting of ZrO2, Fe3O4, TiO2, B2O3, WO3, PbO, MgO, CoO, Al2O3, SiO2, SiO2—Al2O3, and any combination thereof. In an embodiment, the catalyst is a zeolite. In an embodiment, the zeolite is metal-loaded or beta zeolite-based. In an embodiment, the zeolite is selected from the group consisting of erionite, gmelinite, mordenite, ZSM-5, Cu/ZSM-5-MgO, and any combination thereof. In an embodiment, the catalyst is montmorillonite.
In an embodiment, the cyclic compound of step iii) is a compound is selected from the group consisting of an aliphatic compound, an aromatic compound, a heterocyclic compound, a heteroaromatic compound, and any combination thereof.
In an embodiment, the cyclic compound of step iii) is an aliphatic compound. In an embodiment, the aliphatic compound is selected from the group consisting of a cyclic C4-C10 alcohol, a cyclic C4-C10 ketone, or a cyclic C4-C10 acyl halide. In an embodiment, the aliphatic compound is a cyclic C4-C10 alcohol. In an embodiment, the cyclic C4-C10 alcohol is, cyclohexanol or cyclopentanol. In an embodiment, the aliphatic compound is a cyclic C4-C10 ketone. In an embodiment, the cyclic C4-C10 ketone is cyclohexanone or cyclopentanone.
In an embodiment, the cyclic compound of step iii) is an aromatic compound. In an embodiment, the aromatic compound is a C5-C12 monocyclic or bicyclic compound. In an embodiment, the aromatic compound is an aromatic amine, phenol, aldehyde, ketone, amide, diol, dione, acyl halide, or halide. In an embodiment, the aromatic compound is a phenyl, biphenyl, phenol, anisole, guaiacol, aniline, catechol, naphthalene.
In an embodiment, the cyclic compound of step iii) is a heterocyclic compound. In an embodiment, the heterocyclic compound is a cyclic C4-C10 with independently one or more heteroatoms of 0, N, or S. In an embodiment, the cyclic C4-C10 is a tetrahydrofuran, pyrrolidine, piperidine, tetrahydrothiophene, or morpholine.
In an embodiment, the cyclic compound of step iii) is a heteroaromatic compound. In an embodiment, the heteroaromatic compound is a monocyclic or bicyclic C4-C12 with independently one or more heteroatoms of O, N, or S. In an embodiment, the monocyclic or bicyclic C4-C12 is a furan, furfural, pyridine, thiophene, morpholine, quinoline.
In an embodiment, the coupled product mixture of step iii) comprises an ester. In an embodiment, the coupled product mixture of step iii) comprises a ketone.
In an embodiment, the step of contacting the condensation product mixture with a cyclic compound is optionally performed multiple times. In an embodiment, the step of contacting the condensation product mixture with a cyclic compound is optionally performed 2 times, 3 times, 4 times, 5 times, or 6 times. In an embodiment, for each step of contacting, the cyclic compound is independently selected. For instance, if multiple steps of contacting are performed, a single cyclic compound can be utilized in each of the independent steps. In addition, if multiple steps of contacting are performed, more than one cyclic compound can be utilized for the each of the independent steps.
In an embodiment, the hydrogenating of step iv) comprises a hydrotreatment. In an embodiment, the hydrotreatment comprises a hydro(deoxy)genation.
In an embodiment, the hydrogenating of step iv) is performed in the presence of a catalyst. In an embodiment, the catalyst comprises one or more transition metal, one or more noble metal, or any combination thereof. In an embodiment, the catalyst comprises a transition metal. In an embodiment, the catalyst comprises a noble metal. In an embodiment, the catalyst comprises a support. In an embodiment, the support comprises a metal oxide or carbon. In an embodiment, the catalyst is Ni/Al2O3, CoMo/Al2O3, NiMo/Al2O3, Ru/C, Pt/C, Pd/C, NiMo/C, or CoMo/C. In an embodiment, the method further comprises a step of neutralizing the lubricant composition. In an embodiment, the neutralizing step comprises adding an acid or a base. In an embodiment, the acid is selected from the group consisting of hydrochloric acid, sulfuric acid, acetic acid, nitric acid, formic acid, and any combination thereof. In an embodiment, the base is sodium hydroxide, potassium hydroxide, or a combination thereof.
In an embodiment, any one of the steps of the method may be performed at a suitable temperature. In an embodiment, step i), step ii), step iii), or step iv) may be optionally independently performed at an elevated temperature. For instance, an elevated temperature may fall in any of the following ranges: above about 25° C., above about 40° C., above about 60° C., above about 100° C., above about 150° C., above about 200° C., above about 250° C., above about 300° C., between about 25° C. and about 400° C., between about 40° C. and about 100° C., and between about 200° C. and about 400° C.
In an illustrative aspect, a second method of producing a lubricant composition is provided. The method comprises the steps of reacting a starting material to provide a condensation product mixture, contacting the condensation product mixture with a cyclic compound to provide a coupled product mixture, and hydrogenating the coupled product mixture to provide the lubricant composition. The previously described embodiments of the first method of producing a lubricant composition are applicable to the second method of producing a lubricant composition animal described herein.
In an illustrative aspect, a lubricant composition is provided. The lubricant composition is produced according to one of the methods of producing a lubricant composition described herein.
In an embodiment, the lubricant composition comprises an additive. In an embodiment, the additive is selected from the group consisting of a surface protective additive, a performance additive, a lubricant protective additive, and any combination thereof.
In an embodiment, the additive comprises a surface protective additive. In an embodiment, the surface protective additive is selected from the group consisting of an anti-wear agent, a corrosion and rust inhibitor, a detergent, a dispersant, a friction modifier, and any combination thereof. In an embodiment, the surface protective additive is an anti-wear agent. In an embodiment, the anti-wear agent comprises one or more of a zinc dithiophosphate, an organic phosphate, an acid phosphate, an organic sulfur, a chlorine compound, a sulfurized fat, a sulfide, and a disulfide. In an embodiment, the surface protective additive is a corrosion and rust inhibitor. In an embodiment, the corrosion and rust inhibitor comprises one or more of a zinc dithiophosphate, a metal phenolate, a basic metal sulfonate, a fatty acid, and an amine
In an embodiment, the surface protective additive is a detergent. In an embodiment, the detergent comprises one or more metallo-organic compounds. In an embodiment, the metallo-organic compound is selected from the group consisting of barium, calcium phenolate, magnesium phenolate, phosphate, and sulfonate.
In an embodiment, the surface protective additive is a dispersant. In an embodiment, the dispersant comprises one or more of a polymeric alkylthiophosphonate, an alkylsuccinimide, and an organic complex containing nitrogen. In an embodiment, the surface protective additive is a friction modifier. In an embodiment, the friction modifier comprises one or more of an organic fatty acid, an amine, a lard oil, a high molecular weight organic phosphorus, and phosphoric acid ester.
In an embodiment, the additive comprises a performance additive. In an embodiment, the performance additive is selected from the group consisting of a pour point depressant, a seal swell agent, a viscosity improver, and any combination thereof. In an embodiment, the performance additive is a pour point depressant. In an embodiment, the pour point depressant comprises one or more of an alkylated naphthalene, a phenolic polymer, and a polymethacrylate.
In an embodiment, the performance additive is a seal swell agent. In an embodiment, the seal swell agent comprises one or more of an organic phosphate, an aromatic, and a halogenated hydrocarbon. In an embodiment, the performance additive is a viscosity additive. In an embodiment, the viscosity additive comprises one or more of a polymer of methacrylate, a copolymer of methacrylate, a butadiene olefin, and an alkylated styrene.
In an embodiment, the additive comprises a lubricant protective additive. In an embodiment, the lubricant protective additive is selected from the group consisting of an anti-foaming agent, an antioxidant, a metal deactivator, and any combination thereof. In an embodiment, the lubricant protective additive is an anti-foaming agent. In an embodiment, the anti-foaming agent comprises a silicone polymer, an organic copolymer, or a combination thereof.
In an embodiment, the lubricant protective additive is an antioxidant. In an embodiment, the antioxidant comprises one or more of a zinc dithiophosphate, a hindered phenol, an aromatic amine, and a sulfurized phenol. In an embodiment, the lubricant protective additive is a metal deactivator. In an embodiment, the metal deactivator comprises one or more of an organic complex containing nitrogen or a sulfur, an amine, a sulfide, and a phosphite.
The following numbered embodiments are contemplated and are non-limiting:
i. hydrolyzing a starting material to provide a hydrolyzed product mixture,
ii. reacting the hydrolyzed product mixture under conditions capable of producing a condensation product mixture,
iii. contacting the condensation product mixture with a cyclic compound to provide a coupled product mixture, and
iv. hydrogenating the coupled product mixture to provide the lubricant composition.
26. The method of clause 23, any other suitable clause, or any combination of suitable clauses, wherein the cooking oil is an animal oil.
i. reacting a starting material to provide a condensation product mixture,
ii. contacting the condensation product mixture with a cyclic compound to provide a coupled product mixture, and
iii. hydrogenating the coupled product mixture to provide the lubricant composition.
The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
The instant example provides exemplary materials and methods utilized in Examples 2-4 as described herein. In addition, the examples and description of Jahromi et al.,
“Synthesis of Novel Biolubricants from Waste Cooking Oil and Cyclic Oxygenates through an Integrated Catalytic Process,” ACS Sustainable Chem. Eng., 2021; 9:13424-13437 is incorporated by reference herein in its entirety.
In the present disclosure, a four-step catalytic pathway to produce BLs from waste cooking oil and cyclic oxygenated hydrocarbons (COHCs) using integrated catalytic processes was established. These steps include 1) hydrolysis, 2) dehydration/ketonization, 3) Friedel-Crafts (FC) acylation/alkylation, and 4) mild hydro(deoxy)genation (
Materials. Oleic acid (90+%), stearic acid (90+%), mineral oil (white paraffin oil), cyclopentanone (CPN) (99%), cyclopentanol (CPL) (99%), anisole (ASL) (99%), anhydrous sodium sulfate, and ZSM-5, were purchased from Alfa Aesar (Haverhill, MA, USA) and used as received throughout the experiments. 2-methylfuran (2-MF), magnesium nitrate hexahydrate (Mg(NO3)2.6H2O), and Ni/SiO2—Al2O3 catalyst were obtained from Sigma-Aldrich (St. Louis, Mo., USA). Iron (II, III) oxide (97%) (magnetite) and copper nitrate trihydrate (Cu(NO3).3H2O) were purchased from BeanTown Chemical (Hudson, N.H., USA) and (Ward's Scince, ON, Canada), respectively. Waste cooking oil (WCO) from canola oil was procured from household cooking. Noack reference oil SNC-150 was bought from Tannas Co. (Midland, Mich., USA). In addition, three different commercial engine oils with different brands, including OW-20 (Mobil), 10W-40 (Valvoline), 15W-40 (Shell), were purchased for comparative characterization studies. Methanol, and potassium hydroxide (KOH) pellets were obtained from VWR chemicals (USA), while hydrochloric acid (HCl) was purchased from Macron Fine chemicals (USA).
Catalysis. Hydrolysis of waste cooking oil (WCO) was performed using 0.1 M sulfuric acid in deionized water at subcritical condition (250° C., 400 psi N2 cold pressure, 25% water loading). Magnetite (iron (II,III) oxide), which is known to catalyze dehydration/ketonization reaction effectively, was used as received for pre-processing of fatty acids and hydrolyzed WCO under inert atmosphere (350 psi N2). For the FC acylation/alkylation step, a Cu/ZSM5-MgO catalyst was prepared using wet impregnation method. Briefly, calculated amount of Mg(NO3)2.6H2O solution was added dropwise to a slurry solution of ZSM-5 (in DI water). The mixture was stirred continuously while heated to about 90° C. until a thick paste was formed. This paste was dried at 105° C. for six hours and then calcined at 575° C. for another six hours. The calcined ZSM5-MgO that contained approximately 10% MgO was used as catalyst support by doping with Cu(NO3).3H2O solution (in DI water) via wet impregnation similar to support preparation. The catalyst precursor that contained approximately 5% Cu (dry-basis) was calcined at 575° C., and reduced in-situ (using 10% H2 in N2 at 400° C.) prior to FC acylation/alkylation reaction. Ni/SiO2—Al2O3 was used as hydro(deoxy)genation catalyst without any pre-processing and activation.
Brunauer-Emmett-Teller (BET) specific surface area of the catalyst samples were evaluated from N2-adsorption-desorption isotherm, which was carried out at 77 K by liquid N2 using the surface area analyzer (Autosorb-iQ, Quantchrome Instruments, USA). Initially, the samples were outgassed at 80° C. for 1 h, followed by 150° C. for 6 hours under vacuum (10-6 bar). The multipoint BET equation was used to calculate the specific surface area of the samples. The average pore size of catalysts was also measured during the BET analysis. The catalyst samples were characterized by CuKα radiation (λ=1.5418 Å) using a bench-top powder X-ray diffraction (XRD) system (AXRD, Proto manufacturing, MI, USA) from 20° to 100° (2θ) with 2 seconds of dwell time and 0.014° of Δ2θ at 30 mA and 40 kV.
Synthesis of bio-lubricants. All pressure experiments were performed using a 100 mL Parr 4598 bench-top reactor outfitted with a pressure gauge, thermocouple, adjustable stirrer, heating mantle, and Parr 4848 reactor controller. Two series of FFA model compound experiments as well as two series of WCO experiments were carried out for BL synthesis in this work. Oleic acid (after dehydration/ketonization) was selected to react with CPN while stearic acid (after dehydration/ketonization) was reacted with an equimolar mixture of ASL and 2-MF. WCO, once underwent hydrolysis and dehydration/ketonization, was reacted with ASL in one set of experiments, and with equimolar ASL/CPL/2-MF mixture in another set of experiments. The selected cyclic oxygenates (2-MF, ASL, CPN, and CPL) can be sourced from lignocellulosic biomass, alternatively. Hydrolysis of WCO was performed under 400 psi N2 at 250° C. with oil-to-water mass ratio of 3:1, typically 30 g WCO and 10 g DI water. Dehydration/ketonization reactions were carried out using magnetite as a catalyst under 350 psi cold N2 pressure and feed-to-catalyst ratio of 35 to 1. After each experiment, the liquid products were collected in centrifuge test tubes and centrifuged (using a DYNAC centrifuge, Clay Adams, Parsippany, N.J., USA) for 10 minutes at g-force of 2147 to separate the resulting oil and residual solids and catalyst. Dehydration/ketonization product mixture was then transferred to the Parr reactor. Selected COHC compound (or equimolar mixture of COHCs) was added to the reactor to as limiting reactant(s) to minimize self-condensation to achieve 15 wt. % of the total liquid fed. To this mixture, Cu/ZSM5-MgO catalyst (feed-to-catalyst mass ratio of 30 to 1) was added and then the reactor was closed and pressurized to 350 psi with nitrogen to ensure liquid-phase reaction. In addition, the pH of feed mixture was adjusted to 4.5-5.5 using a 510 Series Oakton pH meter (Thermo Fisher Scientific, Waltham, Mass., USA) by adding 0.1M sulfuric acid. FC acylation/alkylation reaction was allowed to take place at 80° C. (slow heating rate, approximately 5° C./min) for 3 hours. The reactor was then cooled to room temperature, and liquid products were separated by centrifugation. Mild hydrotreatment was then performed at 200 psi using 10% H2 (balance nitrogen) in the presence of Ni/SiO2—Al2O3 catalyst. The reactor pressure change was monitored as an indication of reaction completion until no hydrogen consumption (pressure drop) was observed. Then the reactor was cooled, and liquid products were separated using centrifugation. To neutralize unreacted compounds (such as FFAs) that contribute to total acid number (TAN), the BL was neutralized using 0.1M KOH, and then subjected to rotary evaporation (under approximately 650 mmHg vacuum) at 95° C. to remove water and low-molecular-weight volatiles. A summary of the step-wise experimental matrix used in this work is presented in Table 1.
Physicochemical characterization. Fatty acid profile of waste cooking oil (WCO) was determined via traditional saponification and transesterification reaction with methanol. A solution of 0.5 M methanolic KOH was prepared by dissolving 2.8 g KOH pellets into 100 ml methanol. Methanolic HCl solution was then prepared at 4:1 HCl-to-methanol volumetric ratio (i.e. 5 ml methanol was added to 20 ml concentrated HCl). 400 μl WCO was then introduced into a round-bottom flask that was submerged in water bath at 85° C. To the WCO, 8 ml of 0.5 M methanolic KOH was added, and a reflux condenser was installed to circulate the vapors back to the flask. After 15 minutes, the flask was cooled to room temperature and 3.2 ml methanolic HCl was added to the flask and heated at 85° C. for another 30 minutes. Fatty acid methyl esters (FAME) were then extracted by adding 16 ml DI water and 12 ml n-hexane to the flask. Then the liquids were transferred to a separatory funnel to remove the top layer that contained n-hexane and FAMEs. Hexane extraction was repeated three times, and then the extracts were passed through anhydrous sodium sulfate bed and filtered (0.2 μm Teflon filter). Finally, the extracts were analyzed using GC-MS as described below (also refer to supporting information).
Thermal decomposition and stability of produced BLs and commercial engine oils were evaluated using a Shimadzu TGA-50 (Shimadzu, Japan) under nitrogen atmosphere with heating rate of 10° C./min from room temperature up to 700° C. Noack volatility studies of synthesized bio-lubricants was carried out according to ASTM D6375 using thermogravimetric method on the same Shimadzu TGA-50 (Shimadzu, Japan) that was calibrated using SNC-150 Noack reference oil. The total acid number (TAN) of BL samples was determined through a titration according to ASTM D664-07 using a Mettler Toledo T50 Titrator (Columbus, Ohio, USA). The kinematic viscosities at 40 and 100° C. (KV40 and KV100), and viscosity index (VI) of the samples were measured using a viscometer (SVM 3001, Anton Paar, Austria). The VI was determined according to ASTM D2270, while KV40 and KV100 were determined according to ASTM D445. Pour point measurement was conducted following ASTM D97 method. The chemical composition of bio-lubricants was analyzed using an Agilent Technologies 7890A Gas Chromatograph (GC) System outfitted with a 7683B Series Injector and 5975C Inert Mass Selective Detector (MSD) with Triple-Axis Detector. The GC-MS was equipped with 30 m×250 μm×0.25 μm DB-1701 Column. An estimated 20 mg of each sample into a clean vial and diluting each sample with dichloromethane (DCM) until each diluted sample contained nearly 2 wt. % BL. The filled vial was then loaded into an auto sampler and injected using a 10 μL syringe into the GC System. The GC oven was programmed to heat to an initial temperature of 50° C. and hold for 2 minutes before being heated at a heating rate of 5° C./min to a final temperature of 280° C. and holding time of 15 minutes, unless specified otherwise. All chemical structures presented in this work are obtained from NIST (National Institute of Standards and Technology) MS Library paired with the GC-MS operating software. All suggested chemical structures from the MS software were carefully evaluated and the most possible products that could form from each reaction were presented.
In the instant example,
In the instant example, the GC-MS chromatogram and fatty acid profile of WCO are presented in
In addition to ketonization, decarboxylation of fatty acids was another source of carbon loss in the form of CO2. Considering the relatively high reaction temperature (350° C.) in dehydration/ketonization step and multifunctionality of the magnetite catalyst, some in-situ hydrogen could have reacted with anhydrides, thus, deoxygenated the C═O bonds, producing compounds such as C15 ether in P1 and P6 (
Chemical characterization of the FC acylation/alkylation reaction products; P2, P7, P13, and P17; are presented in
However, in the case of anisole, the alkylation reaction could take place via both reactions (4) and (5) using anhydrides and carboxylic acids as reactants, respectively45, 46:
Both reactions may result in aromatic ketonic products with similar chemical structure. Hence, more detailed reaction studies would be needed to quantify the extent of each reaction. Chemical characterization of P2 (
Phenolic alkylation of fatty acid methyl esters on C═C bond has been studied in a two-step process, including a first HDO step to eliminate the hydroxyl group of phenol and a second alkylation of benzene or toluene. However, the presence of aromatic-alkylated (such as peak 7 in
In P17, some unreacted oleic acid and anhydride were identified (peaks 5 and 8, respectively, in
Chemical analysis of hydrotreatment products; P3, P8, P14, and P18; are provided in
Solid acid catalysts offer a reusable and safer alternative, and they have been successfully employed in aromatic alkylation of alkenes. The two acid types in solid acid catalysts work together during aromatic alkylation. Brønsted acid sites catalyze the formation of carbocations from alkenes and Lewis acid sites improve the interaction between carbocations and aromatics. GC-MS semi-quantification of the final BLs (P5, P10, P16, and P20) is provided in Table 24. Unsaturated FFAs and FAMEs can react with aromatic hydrocarbons via alkylation reaction because of the presence of C═C bond in the fatty chain. It has been shown that hydrodeoxygenation-alkylation using solid acid catalysts is a promising pathway to synthesize phenyl-branched FAME that can serve as a potential lubricant improver. In Aldol condensation, an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxy aldehyde or β-hydroxy ketone, followed by dehydration to produce a conjugated enone. In its usual form, aldol condensation involves the nucleophilic addition of a ketone enolate to an aldehyde to form a β-hydroxy ketone, or “aldol” (aldehyde+alcohol), a structural unit found in many naturally occurring molecules. Without being bound by any theory, the structure of C28 in P5 could suggest that oleic acid underwent chain prolongation during ketonization (P1) and then the C═O bond was deoxygenated. However, a C28 ketone was not detected in P1 which could be due to GC-MS limitations. In P10 BL, more diverse molecules were detected with cyclic or aromatic structures attached to long a long chain. Oelic acid and stearic acid reactions demonstrated that CPN, ASL, and 2-MF were suitable chemicals to react with long chain anhydrides derived from fatty acids and WCO-derived molecules. Chemical analysis of P16 BL suggested the presence of 49.5% (area percent) desired molecules that were consisted of molecules with cyclic structure attached to linear chains. The P20 BL also showed the presence of molecules with cyclic structures incorporated into linear structures with total area percent of 48.4%.
These pathways resulted in synthesis of novel bio-lubricants molecules that include cyclic compounds attached to long chain compounds of vegetable oil. These structures share several properties (simultaneously) to provide optimum lubricant characteristics: 1) long and linear hydrocarbon chains would provide good lubricity (by reducing the boundary friction coefficient) and viscosity index (VI) (viscosity temperature stability), 2) low-to-zero unsaturation could give excellent stability to the mixture, 3) minimal branching may result in very low wearing rate, 4) presence of one or two naphthenic rings (cyclic structures) can increase oxidation resistance, decrease viscosity variations with temperature (resulting greater VI), and may significantly lower the pour point (PP), and 5) polarity of some of these molecules may provide a great boundary layer with a metal surface because of the interaction of the polar groups with the metal surface (the non-polar ends form a molecular layer or barrier that separates the subbing surfaces and thus prevents direct contact). Therefore, without being bound by any theory, this process could successfully address several issues of the current bio-lubricants at the same time, without negatively influencing their suitable properties.
In the instant example, the experimental matrix used in this work was shown in Table 1. Two sets of experiments were performed using oleic acid (exp. 1-5 in Table 1) and stearic acid (exp. 6-10 in Table 1) as WCO model compounds. In addition, two series of experiments were carried out using real WCO feedstock presented by exp. 11-16 and exp. 18-21 in Table 1. Several parameters, namely pour point (PP), KV40, VI, Noack volatility, and TAN of the liquid products were measured after each step to track down the influence of each process on such properties as presented in
A very high viscosity will increase the oil temperature and drag whereas a very low viscosity will increase the metal-to-metal contact friction between the moving parts. The carbon chain length is one of the factors which affects the viscosity of the lubricant. Low-viscosity lubricants are less resistant to flow, hence their fuel economy benefits. Without being bound by any theory, hydrolysis, had a positive effect on reducing KV40 of the WCO (
The viscosity index (VI) is an arbitrary, unit-less measure of a fluid's change in viscosity relative to temperature change. A high VI is an essential characteristic of good lubricant since it is an indication that the lubricant can be used over a wide range of temperatures by maintaining the thickness of the oil film. Lower viscosity in conjunction with maximizing the VI ensures that the oil viscosity varies as little as possible with temperature. This means that the lubricant should have a low viscosity upon cold-start, so that the oil reaches engine parts rapidly, and should not drop in viscosity at higher temperatures, thereby maintaining wear protection once the engine has warmed up. VI of oleic acid decreased from 200 to 157 after dehydration/ketonization and from 157 to 140 after FC acylation/alkylation with CPN. Even though different oxygenates were reacted with oleic acid and stearic acid (CPN and ASL respectively), the VI increased consistently after the FC acylation/alkylation step (
The Noack volatility test determines the evaporation loss of lubricants in high-temperature service. For example, the minimum acceptable volatility specifications for SAE 5W-30, low-30, and 15W-30 engine oils allow maximum evaporative weight losses of 25, 20 and 15% respectively by the Noack method. As expected, hydrolysis of WCO increased its Noak volatility from 14.8% to 16.4% (
Hydrolytic stability (normally determined by ASTM D2619-09) implies the tendency of lubricant molecules to hydrolyze. Hydrolysis is the degradation of BL molecules in the presence of water and high temperature to cleave back into acid and alcohol. Hydrolysis is an undesirable phenomenon in the utilization of organic esters. Bio-lubricants having a lower total acid number (TAN) show higher hydrolytic stability. Therefore, the TAN of BLs was monitored between steps as presented in
The economic performance of many modern production processes is substantially influenced by process yields. Their first effect is on product cost—in some cases, low-yields can cause costs to double or worse. Yet measuring only costs can substantially underestimate the importance of yield improvement.
Lubricant properties of feedstocks (fatty acids and WCO) and synthetic BLs, including PP, KV40, KV100, VI, TGA Noack, and TAN are presented in Table 25. For comparison, such analyses were performed on three selected commercial engine oils; OW-20 (full synthetic), 10W-40 (conventional engine oil), and 15W-40 (heavy duty diesel engine oil) as well as mineral oil. It is important to note that the commercial engine oils contain 10-25 wt. % additives including pour point depressants, anti-wear agents, VI improvers, and antioxidants. Thus, in order to provide fair comparison, our BL samples are also compared with vegetable oil-based BLs and synthetic BLs produced from pure chemicals as reported in the literature (Table 25). In general, pure synthetic BLs are reported to have much lower PP compared to those derived from vegetable oil feedstocks, however, such products require more expensive reactants compared to WCO. PP results of P16 and P20 showed clear improvement compared with those adopted from the literature. Quite interestingly, all BLs produced in the present study had significantly higher VIs than pure BLs and even commercial engine oils. Except P10, other BLs showed evaporative loss less than 20% with TAN values comparable to commercial lubricants. Nevertheless, the need for product purification, fractionation, and the study of synthesized molecules in pure form is not questionable. As seen in Table 25, P5, P10, P16 and P20 have slightly lower kinematic viscosities (KV40 and KV100) and relatively higher VIs than engine oils, indicating that they may be able to offer fuel economy benefits over current synthetic lubricants. These results clearly suggested that our proposed method could be a superior approach for the production of novel bio-lubricants from WCO with good flow properties.
1Fatty acid
2Trimethylolpropane
Additionally, thermal stability of WCO feedstock, P16 and P20 bio-lubricants, and the three commercial engine oils were studied using TGA (under 40 ml/min air and heating rate of 10° C./min from room temperature to 600° C.) as shown in
This application claims the benefit under 35 USC § 119(e) of U.S. Provisional Application Ser. No. 63/241,830, filed on Sep. 8, 2021, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63241830 | Sep 2021 | US |
