Location: Bio-oils Research
2018 Annual Report
Objectives
Objective 1: Enable, from a technological standpoint, new commercial separation processes for the production of marketable low-cost high-purity fatty acids.
Objective 2: Enable new commercial products derived from fatty acid esters.
Objective 3: Enable new commercial biobased additives for applications in lubricants.
• Sub-objective 3.A. Develop novel and cost-competitive structures of biobased additives and base oils.
• Sub-objective 3.B. Investigate tribological property of novel biobased additives and base oils and use results to optimize the respective chemical structures.
This project is aimed at developing enabling new commercial technologies, processes, and biobased products for various markets including for: remediation (specifically heavy metal remediation to include water treatment/purification); lubricant additives; lubricant base oils; and chemical additives. The technologies and products from this research will be competitive in cost and performance to those currently in the respective markets. The biobased products targeted in this project will result in significant improvements to the U.S. economy and the environment as well as to the safety and health of the American people.
Approach
(1) This approach outlines work to be performed related to a) screening of feedstock oil properties and quality; b) design of the membrane-based process Step 1 to remove polyunsaturated fatty acids and enrich saturated fatty acids/ monounsaturated fatty acid (MUFA) concentrations in fatty acid or fatty acid methyl ester (FAME) mixtures; c) evaluate two techniques for the design of process Step 2 to efficiently separate and enrich individual MUFA (oleic and erucic acids) with high yield and purity; and d) integrate designs for Steps 1 and 2 into a single process to fractionate fatty acid mixtures to produce valuable MUFA with high yield and purity. These items present a series of decision points that will be addressed during the course of the research project.
(2)Recent research within the unit has shown thioalkyl derivatives of vegetable oils can be used in heavy metal remediation applications with the thioalkyl derivatives acting as metal-coordinating agents for silver ions. Building on these successful findings, new compounds featuring sulfur as the source of binding or chelation will be the primary objective. The initial feedstocks to be examined will be monounsaturated fatty compounds. This will be followed by the more chemically challenging di- and tri-unsaturated fatty compounds and, finally, vegetable oils. Emphasis will be placed on industrial oil feedstocks with enhanced sustainability. Additionally, materials from Objective 1, as they become available, will serve as unique, valuable starting materials.
(3a) New biobased additives and base oils will be synthesized from commodity oils and their derivatives. Commodity vegetable oils comprise fatty acids with unsaturation that can be used as reactive sites for chemical modification. In addition to commodity vegetable oils, polymercaptanized soybean oil, which is produced in large quantities from abundant soybean oil and cheap hydrogen sulfide will be used. Other biobased feedstocks to be used in the synthesis include: FAME, obtained from the biodiesel process, especially those with unsaturation on their hydrocarbon chains; esters of fatty acid with various alcohol structures; etc. (3b) The new biobased additives will be first investigated for their compatibility with standard base oils. Additives found to be incompatible will be investigated using various approaches to make them more compatible. Only compatible additives will be allowed into the next phase which involves the investigation of their effectiveness at performing the specific tasks relevant to its application. Additives will be investigated relative to commercial reference additives using established tests for each application. Various concentrations of the additives in each base oil will be prepared and subjected to the respective tests. Based on these results, optimum concentrations of the additives will be determined.
Progress Report
Substantial progress has been made on all the milestones of each objective.
Membranes were tested for separation of fatty acids and esters from mixtures in organic solvents. Separation tests were conducted in a pressurized stirred-cell apparatus that can be loaded with different membranes. Results will be used for the design of a scaled-up separation apparatus.
Fatty acid methyl esters (biodiesels) were mixed with branched-chain alkyl esters to test for effects on viscosity (resistance to flow) and cold flow properties. Branched-chain alkyl ester samples were synthesized by ARS scientists in Wyndmoor, Pennsylvania.
Cold temperatures can affect the ability of liquid fatty acid methyl ester mixtures to flow easily in process streams. The gelation point is defined as the temperature range where the fatty acid methyl esters phase-transform into thick gels that are very difficult to pump through process equipment. Such transitions occur undetected and can restrict or prevent flow through pipelines and filters. ARS scientists in Peoria, Illinois, discovered that the gelation points for soybean oil fatty acid methyl esters (biodiesel) were caused by trace concentrations of contaminants such as monoacylglycerols, which are side-products from conversion of the oil to biodiesel. This research increased the fundamental understanding of the liquid-phase behavior in fatty acid methyl ester mixtures. Results will be employed in the design of processes for enriching the contents of valuable fatty acid methyl esters to benefit the growing biodiesel industry in the U.S.
Fatty compounds with two or more double bonds were used in the synthesis of new compounds with several thioalkyl groups in a single molecule. The synthesis was conducted following a prior procedure used on compounds with only one double bond. It was previously shown that compounds with one added thioalkyl unit have promising properties for remediation of heavy metals from aqueous waste streams and industrial effluents. This had been demonstrated on samples containing mercury and silver metals. The new compounds with more than one thioalkyl unit per molecule are expected to show the same, if not better, remediation properties, making them competitive with or better than existing products on the market. In addition to heavy metal remediation, the new materials may have other applications such as in lubricant formulation. The new materials have the potential to generate new markets for agriculturally-derived, domestic and renewable products.
In the search for optimal disulfide soybean oil derivative, the oxidative coupling synthesis previously performed on the fatty acid methyl esters (FAMEs) of polymercaptanized soybean oil (PMSoy) was repeated on PMSoy itself. The synthesis gave product with higher molecular weight and higher viscosity than the previously synthesized FAME product. In order to better understand the chemistry of the oxidative coupling reaction, pure fatty acid esters are being mercaptanized as model compounds for further investigations.
Accomplishments
1. Biobased polyalphaolefin (BPAO) base oil with improved tribological properties over commercial polyalphaolefins (PAOs). PAOs are synthetic base oils that are used in lubricant formulations that operate under extreme conditions, where petroleum distillates are inadequate. PAOs currently in the market are exclusively petroleum-based and hence lack the environmental, health and safety benefits of a biobased base oil. In contrast, BPAO, which is produced commercially from soybean and other vegetable oils via a biorefinery process, provides all the benefits of a biobased base oil. ARS scientists in Peoria, Illinois, recently conducted comparative investigation of the two base oils. They found out that BPAO-40 has many superior tribological properties relative to PAO, including: higher viscosity index; lower coefficient of friction; lower wear; higher elastohydrodynamic (EHD) lubricant film thickness under boundary, i.e., extreme lubrication conditions (low speeds and high temperatures); and lower EHD traction coefficient, which translates into better fuel economy. Successful commercialization of BPAO will open up new markets for farmers while at the same time providing big environmental, health and safety benefits to society.
2. Stability of polymercaptanized soybean oil lubricant candidate to prolonged heat and light exposure. Polymercaptanized soybean oil (PMSoy) is a potential lubricant additive and precursor to many polymers. One of the properties of PMSoy that has not been investigated before is its stability to thermal and light exposure. ARS scientists in Peoria, Illinois, investigated the changes that occur when PMSoy was subjected to long periods of exposure to heat or light irradiation. In both cases, results showed formation of sulfide-bridged oligomers and an increase in viscosity. The structures responsible for the formation of the bridges were also identified. A correlation between the degree of formation of oligomers and increase in viscosity were developed. The finding increased our knowledge about PMSoy that will help in the development of proper storage procedures and use of this material.
Review Publications
Knothe, G., Steidley, K.R., Moser, B.R., Doll, K.M. 2017. Decarboxylation of fatty acids with triruthenium dodecacarbonyl: Influence of the compound structure and analysis of the product mixtures. ACS Omega. 2:6473-6480.
Bantchev, G.B., Vermillion, K., Lansing, J.C., Biresaw, G. 2018. Heat- and light-induced thiol-ene oligomerization of soybean oil-based polymercaptan. Journal of Applied Polymer Science. 135(17). https://doi.org/10.1002/app.46150.
Knothe, G., Steidley, K.R. 2018. The effect of metals and metal oxides on biodiesel oxidative stability from promotion to inhibition. Fuel Processing Technology. 177:75-80.
Biresaw, G. 2018. Biobased polyalphaolefin base oil – chemical, physical and tribological properties. Tribology Letter. 66:76. doi: 10.1007/s11249-018-1027-9.
Biresaw, G., Bantchev, G.B., Murray, R.E. 2017. Investigation of biobased and petroleum base oils in the entire spectrum of lubrication regimes. Journal of the American Oil Chemists' Society. 94(9):1197-1208.
Harry-O'kuru, R.E., Biresaw, G., Gordon, S.H., Xu, J. 2018. Physical characteristics of tetrahydroxy and acylated derivatives of Jojoba liquid wax in lubricant applications. Journal of Analytical Methods in Chemistry. https://doi.org/10.1155/2018/7548327.
Jordaan, E., Roux-van der Merwe, M.P., Badenhorst, J., Knothe, G., Botha, B.M. 2018. Evaluating the usability of 19 effluents for heterotrophic cultivation of microalgal consortia as biodiesel feedstock. Journal of Applied Phycology. 30(3):1533-1547. doi: 10.1007/s10811-017-1341-x.
Liu, Z., Biresaw, G., Biswas, A., Cheng, H.N. 2018. Effect of polysoap on the physical and tribological properties of soybean oil-based grease. Journal of the American Oil Chemists' Society. 95(5):629-634. https://doi.org/10.1002/aocs.12069.
Chen, J., Liu, Z., Nie, X., Zhou, Y., Jiang, J., Murray, R.E. 2018. Plasticizers derived from cardanol: Synthesis and plasticization properties for poly(vinyl chloride). Journal of Polymer Research. 25:128. https://doi.org/10.1007/s10965-018-1524-4.
Biresaw, G., Bantchev, G.B., Liu, Z., Compton, D.L., Evans, K.O., Murray, R.E. 2017. Biobased lubricant additives. In: Biresaw, G., Mittal, K.L., editors. Surfactants in Tribology. Volume 5. Boca Raton, FL: CRC Press. p. 401-463.
Knothe, G., Razon, L.F., de Castro, M.E.G. 2017. Methyl esters (biodiesel) from Melanolepis multiglandulosa (alim) seed oil and their properties. Biofuels. 10(2):239-243. https://doi.org/10.1080/17597269.2017.1309856.
Solaiman, D., Ashby, R.D., Biresaw, G. 2017. Biosynthesis and derivatization of microbial glycolipids and their potential application in tribology. In: Biresaw, G., Mittal, K.L., editors. Surfactants in Tribology, Volume 5. Boca Raton, FL: CRC Press. p. 263-288.
Dunn, R.O., Bantchev, G.B., Doll, K.M., Ascherl, K.L., Lansing, J.C., Murray, R.E. 2018. Thioether-functionalized corn oil biosorbents for the removal of mercury and silver ions from aqueous solutions. Journal of the American Oil Chemists' Society. 95:1189-1200. https://onlinelibrary.wiley.com/doi/abs/10.1002/aocs.12089.
Dunn, R.O. 2018. Correlating the cloud point of biodiesel to the concentration and melting properties of the component fatty acid methyl esters. Energy and Fuels. 32(1):455-464. https://doi.10.1021/acs.energyfuels.7b02935.
