No abstract

Currently most technologies available to produce esters require acid or base catalysts for esterification or transesterification reactions. Production of dimerate esters (DE) exhibiting potential as a biolubricant for low temperature applications using catalyst‐ and solvent‐free approaches is presented in this article. Hydrogenated C36 dimer acid and alcohol are reacted under the following conditions: dimer acid/alcohol (1:4.5 molar ratio), 150–200 °C, 24 h, 3Å molecular sieve (15% w/w). The performances of four DE species—dibutyl, dihexyl, di‐(2‐ethylhexyl), and dioctyl dimerate—as lubricant base stocks are evaluated by kinematic viscosity, viscosity index, cloud and pour point (cold flow properties) as well as oxidative stability, and compared with commercial synthetic lubricant base stock and DE, Radialube 7121. High viscosity indexes ranging between 129 and 138 are observed for the synthesized DEs, which are comparable with two commercial base stock, polyalpha olefin (PAO), and polyolester (POE). Significantly low pour point, less than −42 °C, is observed for di‐(2‐ethylhexyl) dimerate attributed to the branching of the side chain. The DEs are categorized as ISO VG 68 based on their viscosity according to ISO 3448 classification and show potential as biolubricant with high viscosity index and excellent cold flow properties. Practical Applications: DFAE obtained have high potential to be used as lubricant base stock for equipment and machinery operating at extremely low temperature.

Acetalization of glycerol with acetone (1 : 5) at 60 °C catalyzed by A‐46 (10 wt %) under nitrogen (N2) afforded 63 % solketal 1 a in just 15 min. Subsequently, acetalization of glycerol and bio‐based aldehydes i. e. acetaldehyde, isobutyraldehyde, n‐heptaldehyde, p‐anisaldehyde and benzaldehyde were investigated under optimized reaction conditions. The conversion and selectivity of this reaction was found to be affected by structure of aldehydes employed. Excellent conversion of 97 and 99 % were obtained using acetaldehyde and isobutyraldehyde, respectively while longer chain or aromatic aldehyde gave poor conversion between 17 and 36 %. Aldehyde with branching or aromatic ring gave better selectivity towards 6‐membered ring acetal b at the expense of conversion: p‐anisaldehyde > benzaldehyde>isobutyraldehyde>acetaldehyde>n‐heptaldehyde. Conversely, organic solvent gave adverse effects to both conversion and selectivity towards b. Optimized acetalization of glycerol/benzaldehyde was also studied. A‐46 has shown excellent stability and reactivity with no significant loss of catalytic activity in 10 subsequent runs.

Plant oil-based lubricants are used as alternative for mainstream petroleum-based lubricants mainly because they are known to be environmentally friendly. However, their market acceptance is limited by their high pour point and poor oxidation stability. This study presents an approach to make biodegradable lubricant from oleic acid that shows low pour point and satisfactory oxidation stability. A mixture of estolides with acetyl and hydroxy functionalities is prepared from reaction between oleic acid, acetic acid, and hydrogen peroxide. Subsequently, the hydroxy groups of estolide are end-capped with lauric acid to improve oxidation stability. Further reaction with alcohol and amine yielded estolide ester and amide, respectively. Physicochemical properties evaluation of prepared estolide ester and amide reveal that they have properties comparable to commercial samples in terms of pour point, oxidation stability, viscosity index, and antiwear. Furthermore, both estolide ester and amide are found to be readily biodegradable, which support their use as environmental friendly lubricant. Therefore, the inferior properties of plant oil-based lubricants can be resolved by chemical modifications that yield specific estolide ester and amide with excellent properties suitable for lubricants. Practical Applications: The prepared estolide ester and amide have good potential to be used as lubricant base oil for environmentally acceptable lubricants due to their inherent readily biodegradability nature and excellent lubricant properties.

The physico-chemical and electrical insulating properties of certain palm oil products, including triglyceride oils, fatty acids, fatty esters, and glycerol were evaluated for use in oil-immersed transformers. The studied triglyceride oils have excellent kinematic viscosity values: 30.25-40.49 mm 2 s À1 at 40 C, 6.46-8.34 mm 2 s À1 at 100 C; flash point: 278-320 C; moisture content: 16-175 mg kg À1 and dielectrical breakdown voltage: 29.1-40.9 kV. Fatty acids and fatty esters have relatively lower kinematic viscosity and flash point values than triglyceride oils. The type of hydrocarbon chain, hydrocarbon chain length and molecular size were shown to have substantial effects on the physico-chemical and electrical properties of the studied oils. The drying process imposed on refined-bleached-deodorized palm olein (RBD POo) has reduced the moisture from 400 mg kg À1 to 100 mg kg À1 and improved the dielectrical strength from 31.1 kV to 76.8 kV. Blending of RBD POo with fatty acids or fatty esters has improved the kinematic viscosity of RBD POo and offers even higher flash and fire points than mineral oil. This study showed that palm oil and palm oil products have strong potential to serve as coolants and may be safer for use in oil-filled transformers as compared to mineral oil.