Chemical building blocks are obtained from microalgae biomass via an integrated extraction/catalytic upgrading approach.

A two-step one-pot synthesis of benzene from the five-fold unsaturated fatty acid eicosapentaenoic acid (EPA), a component of microalgae oils, is presented. By a sequence of olefin metathesis and the catalytic dehydrogenation of the resulting 1,4-cyclohexadiene, two equivalents of benzene are effectively formed per EPA substrate molecule. As the only major by-products, 5-octenoic acid and 5-decenedioic acid are formed. Performing the dehydrogenation step under hydrogen pressure results in the formation of their saturated analogues, sebacic acid and octanoic acid, both desirable products, while the simultaneous dehydrogenation step to benzene is not hampered.

Microalgae oil serves as a feedstock for a biorefinery approach to mid-chain (di-)carboxylic acid esters, currently only accessible via demanding synthetic routes. Via the butenolysis of mono- and poly-unsaturated fatty acids, short-chain unsaturated fatty acid methyl esters and mono- and di-enes were produced in a high selectivity. These olefins were further processed into value added linear mid-chain (di-)carboxylic acid esters via isomerizing alkoxycarbonylation. Model compounds such as eicosapentaenoic acid were used to study the reactions including the screening of metathesis catalysts and to identify all formed products. Notably, eicosapentaenoic acid, a five-fold unsaturated fatty acid relatively abundant in algae, is successfully converted to four equivalents of heptadiene, which was carbonylated to the linear diester (dimethyl azelate). The butenolysis and subsequent isomerizing alkoxycarbonylation were performed on the algae oil extracted from the diatom Phaeodactylum tricornutum. Despite the multicomponent mixture of numerous lipids and non-lipid compounds present in algae oil, high conversion and high selectivity for the desired products were achieved in both reactions. This approach provides access to several carboxylic mono- and di-acid esters of chain length ranging from C6 to C12 (amongst others azelaic acid ester, suberic acid ester and dodecanedioic acid ester), that are in demand but to which access is limited currently, fully based on algae oils as a renewable resource.

Current efforts to technically use microalgae focus on the generation of fuels with a molecular structure identical to crude oil based products. Here we suggest a different approach for the utilization of algae by translating the unique molecular structures of algae oil fatty acids into higher value chemical intermediates and materials. A crude extract from a microalga, the diatom Phaeodactylum tricornutum, was obtained as a multicomponent mixture containing amongst others unsaturated fatty acid (16:1, 18:1, and 20:5) phosphocholine triglycerides. Exposure of this crude algae oil to CO and methanol with the known catalyst precursor [{1,2-(tBu2 PCH2)2C6H4}Pd(OTf)](OTf) resulted in isomerization/methoxycarbonylation of the unsaturated fatty acids into a mixture of linear 1,17- and 1,19-diesters in high purity (>99 %). Polycondensation with a mixture of the corresponding diols yielded a novel mixed polyester-17/19.17/19 with an advantageously high melting and crystallization temperature.