Metathesis as a versatile tool in oleochemistry

Olefin metathesis, awarded with the Nobel Prize in Chemistry 2005 for Chauvin, Grubbs and Schrock, has emerged as a powerful tool for organic as well as polymer chemistry. In oleochemistry, this reaction is well known and has been applied for many decades. Examples include the functionalization of the double bonds of different oleochemicals or the (direct) polymerization of plant oils via metathesis. More recent developments, particularly the development of better and more robust catalysts, allow for highly efficient cross‐metathesis reactions opening new possibilities for the direct introduction of chemical functionalities. Within this contribution, the development of metathesis in oleochemistry will be discussed, covering self‐metathesis as well as more recent developments in the field of cross‐metathesis that lead to desired platform chemicals.     

2-Fatty Acrylic Acids: New Highly Derivatizable Lipophilic Platform Molecules

This paper reports the incorporation of an alpha-methylene unit into fatty acid skeletons. Since the new olefin is conjugated with the carboxylate, it is susceptible to 1,4-(Michael) additions. We have used multifunctional thiols and amines for additions at the methylene. The resulting products possess clusters of functionality grouped at one end of a hydrophobic tail. These structural patterns will be of use in the design of new types of bio-based surfactants and polymers. One particularly promising pattern of functionality that can be obtained through oxidation and reduction chemistry is a 2-fatty 1,2,3-propanetriol, or a lipophilized glycerol moiety.     

Catalysts for Fatty Alcohol Production from Renewable Resources

Fatty alcohols may be produced through the processing of fatty acids or their esters derived from palm or coconut oils. Fatty alcohol technology can be classified into two categories (a) a slurry‐phase process in which the fatty acid or its ester is converted into alcohol using a powdered catalyst and (b) fixed bed technology in which the fatty acid or its ester is processed over a formed catalyst, e.g. tablets or extrudates. Historically copper‐based catalysts are employed for achieving ester hydrogenolysis. In recent years, studies were also focused on precious metal catalysts for this process. This paper will critically review existing literature pertaining to the catalysts that operate at diverse conditions, handle different feedstocks, and are compatible with a variety of unit operations used by the fatty alcohol manufacturers. There is an effort to develop environmentally friendly non‐chrome copper catalyst in this process. Some recent progress on bimetallic Cu‐Fe catalyst and understanding Cu‐Fe interaction has been reported. Current development on homogenous catalysts in this process was carefully reviewed. The catalyst deactivation mechanism has been investigated and effect of different impurities, mainly phosphorous, sulfur, chloride, water, glycerine and free fatty acid was thoroughly reviewed.     

Extraction of Surface Wax from Whole Grain Sorghum

Sorghum has potential as a domestic source of wax for applications in the food and nonfood industries. The waxes extracted from sorghum have similar physical properties to those of Carnauba wax, a common imported commercial wax. This work focused on the extraction, fractionation, and characterization of waxes from sorghum kernels. Extraction was performed by varying the extraction conditions including temperature and solvents (hexane, ethanol, and methanol). A fractionation technique was developed to separate and quantify waxes from nonwaxes. The fractions were then characterized using a reverse‐phase high‐performance liquid chromatography method developed in our laboratory that utilizes an evaporative light‐scattering detector for quantification. The results showed that the average amount of wax extracted from the surface of intact sorghum kernels was about 0.3 wt% using hexane at temperatures between 25 and 120°C and 1000 psi. The yield of wax via hexane extraction increased with temperature and ranged from about 0.06 to 0.39 wt%. Extraction with alcohols resulted in higher yields of extracts, but after fractionation to remove nonwax components, the yield of waxes was reduced by 31% for ethanol and 47% for methanol compared to hexane.     

Viscometric Properties of Polyethylene Glycol di-Esters of Estolides

Polyethylene glycol (PEG) diesters from estolides of oleic acid, ricinoleic acid, and 12-hydroxy stearic acid were used up to 5 wt% additive in petroleum-derived base oils: 100 N, 220 N, 600 N, PAO 2cSt, PAO 4cst, and PAO 8cSt. The viscosity indices of the petroleum base oils were the lowest (VI = 104–108); the polyalpholefin (PAO) synthetic petroleum-derived base oils were better (VI = 124–136) and the vegetable-derived oils were the best (VI = 111–205). 12-Hydroxystearic estolide PEG 400 diester gave the largest increase in viscosity index in 5% w/w admixtures with PAO 2cSt, 4cSt, 220 N, and 600 N base oils with a 12.3–16.3% increase in viscosity index. Single fatty chain esters had the least impact on viscosity index. As the molecule bulk increased, the viscosity index also increased. This viscosity index effect was demonstrated for the series of monomer to oleic estolide to oleic estolide PEG-200 diester, which gave viscosity indices of 110, 111–122, respectively, in 5% admixtures with 100 N base oil. The larger the size of the molecule coupled with the polar PEG moiety gave the largest impact on viscosity index improvement where a 5 wt% admixture of 12-hydroxystearate estolide PEG-200 diester gave a 25.8% increase in 100 °C viscosity in PAO 2cSt. Incorporation of a dihydroxyl moiety into the molecule at a central side chain location in laurate-capped ricinoleate estolide PEG-200 diester did not increase viscosity index of the base oil but greatly reduced its solubility to less than 0.5 wt%.     

Cleavage of Carboxylic Acid Moieties in Triacylglycerides During Non‐Catalytic Pyrolysis

Noncatalytic pyrolysis of triacylglyceride (TG) oils is an attractive option for production of renewable fuels and chemicals. This process produces 20–30 wt% of C₂–C₁₀ fatty acids due to the presence of carboxyl moieties in TG. To decipher this process’ mechanism, several compositionally distinct crop oil feedstocks with varied abundances of C₁₈ saturated and unsaturated TG carboxylic acid chains were pyrolyzed for short residence times in a laboratory‐scale continuous turbulent flow reactor. A comprehensive gas chromatographic analysis of the oxygenated products revealed the selective formation of linear saturated monocarboxylic acids (LSMCA) of less than C₁₁ in size, with a specific homological pattern featuring peaks for C₂–C₃, C₇ and C₉–C₁₀ LSMCA. The relative abundance of these size groups varied amongst the feedstocks cracked due to variations in the abundance of triunsaturated (linolenic), diunsaturated (linoleic) and monounsaturated (oleic) acids, respectively, in the original TG. We proposed a mechanism explaining the observed product speciation and homology profiles by the formation of acyloxyl biradicals as essential intermediates. High‐temperature C=C π‐bond hydrogenation with a concomitant σ‐bond cleavage yields C₉–C₁₀ LSMCA. This new path was confirmed by pyrolysis experiments with triolein in a GC pyroprobe.     

Low trans-Fat Spreads and Shortenings from a Catalyst-Switching Strategy

Low trans fatty acid basestocks suitable for blending with liquid oils to make spreads and shortenings are prepared by using a two-step hydrogenation process. The first step uses a nickel catalyst to hydrogenate soybean, canola, high-oleic sunflower, and high-oleic safflower oils to a predetermined iodine value. At this point in the reaction, the second step commenced. Addition of a platinum catalyst at 80 °C and 73 psi hydrogen pressure allowed for hydrogenation to proceed to iodine values of 40–50. These products had 11–18% trans fatty acid content. These were then blended with soybean oil (5–50% basestock) to give products with bulk properties similar to commercial spreads and shortenings but with about one third the levels of trans fat. Names are necessary to report factually an available data: the USDA neither guarantees nor warrants the standard of the product, and the use of the name USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Comparison of Reactivity in the Cross Metathesis of Allyl Acetate‐Derivatives with Oleochemical Compounds

The metathesis of unsaturated oleochemicals is an excellent tool for generating α,ω‐difunctional substrates, which are useful intermediates for polymer synthesis. This article describes the cross metathesis of allyl acetate and cis‐1,4‐diacetoxy‐2‐butene with methyl 10‐undecenoate and methyl oleate, which are oleochemical key substrates. Detailed optimizations led to high conversion rates and yields of the desired products under mild reaction conditions by using a low concentration of commercially available homogeneous ruthenium catalysts.     

Synthesis and Characterization of Potential Bio-Based Lubricant Basestocks via Epoxidation Process

Chemical modifications of vegetable oils may be applied for the purpose of improving their physicochemical properties in their usage for the bio-based lubricants. The vegetable oils with a high percentage of oleic acid, such as soybeans and rapeseed oils, are important raw materials to obtain the biolubricants. In this particular study, the oleic acid was esterified with 1-octanol, followed by epoxidation. The oxirane ring opening reaction was performed using different alcohol structures (linear, branched, and cyclic), in order to evaluate their influence on the final physicochemical properties with the synthesized samples. These aforesaid reaction steps were followed by ¹H nuclear magnetic resonance and the main physicochemical properties in the intermediate and final samples were assessed. The highest oxidative stability was observed for the samples obtained, using a cyclic alcohol at the oxirane ring opening reaction (230 min), followed by the linear alcohols with the branched alcohol presenting the lowest oxidative stability (124 min). The pour point values for the samples synthesized with the branched alcohol were slightly better than those with the linear and cyclic alcohols. All the synthesized samples showed high viscosity indexes (>130) and kinematic viscosities at 40 °C, ranging from 30 to 33 cSt (application degree ISO VG-32), which are adequate for their use in the formulation of bio-based lubricants.