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Modified Vegetable Oils for Environmentally Friendly Lubricant Applications
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Brajendra K. Sharma, Gobinda Karmakar, Sevim Z. Erhan
The double bond at unsaturation sites of VOs provides a point of attack for oxidative scission. Ozonides are formed initially in the ozonolysis reaction which is a highly selective reaction [99] as shown in Scheme 24.2. These can undergo scission either reductively to mono-and dialdehydes, or oxidatively to mono- and dicarboxylic acids. By the oxidative route, ester of oleic acid gives nonanoic acid (pelargonic acid) and ester of nonane-1,9-dioic acid (azelaic acid) (Scheme 24.2) [100]. The later can be converted to diester after esterification. This kind of oxidative scission in triacylglycerol molecule can improve their thermo-oxidative stability by removing the sites of unsaturation. Lubricants with optimal performance can be obtained by an alteration of the hydrocarbon chain (of transesterified product of more resistant polyols such as PE, TMP, or NPG) using ozonolysis reaction leading to short esters after combination with an alcohol [101]. The linear diacid portion of the diester contributes to good viscosity index (VI), while the branched ends give the lubricant a good pour point. The only disadvantage of diesters is their low molecular weight, which makes them an attractive solvent because of their high polarity. It can be blended with VOs/CMVOs to make different viscosity blends. Another solution is esterification of these dicarboxylic acids with polyols, which can increase the viscosity of these products and also have high shear stability [69]. Ozonolysis of unsaturated fatty acid (oleic) ester.
Recovery utilization of triolein for producing short chain alkane by combining biocatalysis and inorganic catalysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Jie Zhang, Ling Gao, Yao Lu, Lixiu Yan, Xuemei Tan, Zhehan Yang, Huijun Zhang
The double bond of unsaturated fatty acid can be broken by hydrogen peroxide (Li, Syong, and Zhang 2018), sodium hypochlorite (Zaldman et al. 1988), ozone (Lisitsyn et al. 2004). This paper was focused on the oxidative scission of oleic acid, which yields pelargonic acid and azelaic acid through an emulsifying system (Godard et al. 2012). Oleic acid was oxidized in a batch reactor with a biphasic organic-aqueous system consisting of hydrogen peroxide (30%, v/v) as an oxidant and a peroxo-tungsten complex Q3{PO4[WO(O2)2]4} as a phase-transfer catalyst/co-oxidant, the yield of pelargonic acid was above 57.1%. Zaldman, Kisilev (Zaldman et al. 1988) broke the double bond of oleic acid by sodium hypochlorite, and the yield of pelargonic acid could reach 70.0%. However, above methods have these disadvantages including strong pollution, high energy consumption, and long reaction time. In order to improve the green and economy of the reaction under the premise of ensuring the yield, ozone, and hydrogen peroxide (30%, v/v) are combined on oxidation. The yields of pelargonic acid under different catalysts and oil-water ratios were evaluated by GC. From the results of different catalysts in Figure 3a, it is found that phosphotungstic acid (H3O40PW12) has superior catalytic performance compared with tungstic acid (H2WO4) and tungsten oxide (WO3), which probably related to the fact that oxidation of olefins by hydrogen peroxide was carried out in an acidic environment (Noyori, Aoki, and Sato 2003). The acidity of phosphotungstic acid is stronger than tungstic acid because it is a heteropoly acid. The yield of pelargonic acid reached 52.1%, under the catalysis of phosphotungstic acid. In Figure 3b, we can clearly observed that the change trend of the yield of pelargonic acid with increasing oil-water ratio. However, excessive hydrogen peroxide reduces the concentration of catalyst and is not conducive to the oxidation reaction. Therefore, the oil-water ratio of 1:4 was detected as the highest yield of nonanoic acid, which was 52.1%. Although this yield is lower than in the related reports, the immiscibility of the two phases is more advantageous for separating objective product.