Analysis and Properties of the Decarboxylation Products of Oleic Acid by Catalytic Triruthenium Dodecacarbonyl

Abstract

Recently, ruthenium-catalyzed isomerization–decarboxylation of fatty acids to give alkene mixtures was reported. When the substrate was oleic acid, the reaction yielded a mixture consisting of heptadecene isomers. In this work, we report the compositional analysis of the mixture obtained by triruthenium dodecacarbonyl catalyzed decarboxylation of oleic acid. Surprisingly, the most prominent single compound identified was heptadecane at approximately 18 wt %. A mixture of heptadecene isomers constituted the greatest percentage of the product (>75%), where all positional isomers were confirmed by GC–MS analysis of dimethyl disulfide derivatives of the product. Besides these components, minor amounts of alkyl aromatics, each with a total of 17 carbons atoms, among them undecyl benzene, were observed. Minor amounts of other compounds, such as shorter-chain hydrocarbons and polyunsaturated C17 compounds, were also observed. A reaction pathway to explain the existence of these products is proposed. Heptadecenes first cyclize to the observed alkyl aromatics under liberation of hydrogen with the formed hydrogen, then in turn hydrogenating some heptadecenes to heptadecane. Thus, triruthenium dodecacarbonyl is suggested to also promote dehydrogenation, aromatization, and hydrogenation under the present conditions. Since the product mixture consisted mainly of long-chain hydrocarbons, its properties regarding diesel fuel application were studied and compared to biodiesel and petroleum diesel. The cetane number (86.9) was high, but oxidative stability (3.4 h; EN 15751) and cold flow (cloud point −1 °C) would require improvement to meet fuel specifications. All other fuel properties were within the limits prescribed in the petrodiesel standards.

Decarboxylation of Fatty Acids with Triruthenium Dodecacarbonyl: Influence of the Compound Structure and Analysis of the Product Mixtures

“…The GC–MS analyses (see Figure 1 for a typical chromatogram with the products formed from palmitic acid as example) revealed that the same classes of compounds, an alkane, all possible alkene isomers, alkadienes, and alkylaromatics, observed previously in work on decarboxylation of oleic acid in the presence of Ru 3 (CO) 12 40 are formed in all reactions. The pattern of the reaction products appears to depend on neither the chain length, similar to the results regarding hydrothermal deoxygenation with Pt/C, 37 nor the number of double bonds and their position and configuration.…”

“…Essential fuel properties of the product mixture obtained from oleic acid were determined previously. 40 The cetane number was 86.9, the kinematic viscosity at 40 °C was 3.14 mm 2 /s, the cloud point (CP) was −1 °C, the pour point (PP) was −4 °C, the oxidative stability by the so-called Rancimat test was 3.4 h, the density at 15 °C is 791 kg/m 3 , and the wear scar in the high-frequency reciprocating rig lubricity test is 299 μm. Although no properties were determined here for the products derived from the other fatty acids and alkenes, it can be observed that the products with high amounts of alkane and lower amounts of alkenes would likely have more problematic cold flow properties (higher CP and PP) but improved oxidative stability, whereas the converse would hold for the products with reduced amounts of alkane but therefore greater amounts of alkenes.…”

A review of thermal homogeneous catalytic deoxygenation reactions for valuable products

“…A 60% yield of 10-undecenoic acid was achieved under the conditions of 0.89 wt % Ru 3 (CO) 12 at 250 C and 4 h duration (Muench et al, 2016). Moser et al (2016) further reported that 77.6% heptadecene and 18.0% heptadecane was obtained by Ru-catalyzed DCX/DCN of fatty acids. There were also other reactions such as the decarboxylation, dehydrogenation, isomerization, hydrogenation, and cyclization/aromatization took place, which made a mixture of predominantly alkenes (Knothe et al, 2017).…”

Biobased Methacrylic Acid via Selective Catalytic Decarboxylation of Itaconic Acid

“…Due to the relatively low yield of MAA given by manganese­(II) oxalate along with evolution of carbon monoxide, ruthenium catalysis was explored. Ruthenium carbonyl carboxylates were of interest because of our previous work on tandem isomerization–decarboxylation of oleic acid. − When using catalytic ruthenium­(I) dicarbonyl propionate in the present system, IA was first isomerized to mesaconic acid, which was in turn decarboxylated to MAA (Figure ). Isomerization was confirmed by a control experiment subjecting dibutyl itaconate to the reaction conditions, thereby inhibiting decarboxylation via protection of the carboxylic acid moieties as butyl esters.…”