The present review reports the current literature of the last 10 years on selective oxidation reactions of fatty acid derivatives and vegetable oils. The work is structured in divisions including epoxidation, radical oxidations, Wacker-type oxidation, dihydroxylation and C=C double bond cleavage.
Porous architectures of noble metal nanocrystals are promising for many catalytic as well as for fuel cell applications. Here we present the synthesis of porous, extremely lightweight aerogels of self-supported Pt nanocubes and nanospheres by direct destabilization from nonpolar colloidal solution using hydrazine monohydrate (N 2 H 4 •H 2 O) as gelation reagent. The template-free voluminous lyogels of the Pt nanocrystals are converted to macroscopic solid aerogel monoliths by supercritical drying. The aerogels from Pt nanocubes mostly exhibit (100) as the exposed crystal facets throughout the entire monolithic surface, while the aerogels from quasispherical Pt nanocrystals exhibit many crystal facets such as ( 111) and (100). Furthermore, the aerogels exhibit remarkably low densities of ∼0.19 g cm −3 ± 0.038 g cm −3 (∼0.9% of bulk Pt) and a specific surface area in the range of ∼6400−7000 m 2 mol −1 . The nanocube gels show better catalytic performance than the nanosphere gels when employed for asymmetric hydrogenation reaction, which is exemplarily shown for 4,4-dimethyldihydrofuran-2,3-dione to D-/L-pantolactone conversion with an excess of 9% for the D-enantiomer. Owing to their high specific surface area and certain type of exposed crystal facets, Pt aerogels developed here are highly promising for possible future applications in facet selective catalytic reactions.
A multitude of synthesis methods for azelaic acid is evaluated in terms of feasibility and sustainability. Up to now, no alternative to industrially employed ozonolysis of oleic acid was developed.
Carbon dioxide can be used in various ways as a cheap C1 source. However, the utilization of CO2 requires energy or energy-rich reagents, which leads to further emissions, and therefore, diminishes the CO2-saving potential. Therefore, life cycle assessment (LCA) is required for each process that uses CO2 to provide valid data for CO2 savings. Carbon dioxide can be incorporated into epoxidized fatty acid esters to provide the corresponding carbonates. A robust catalytic process was developed based on simple halide salts in combination with a phase-transfer catalyst. The CO2-saving potential was determined by comparing the carbonates as a plasticizer with an established phthalate-based plasticizer. Although CO2 savings of up to 80 % were achieved, most of the savings arose from indirect effects and not from CO2 utilization. Furthermore, other categories have been analyzed in the LCA. The use of biobased material has a variety of impacts on categories such as eutrophication and marine toxicity. Therefore, the benefits of biobased materials have to be evaluated carefully for each case. Finally, interesting properties as plasticizers were obtained with the carbonates. The volatility and water extraction could be improved relative to the epoxidized system.
With the increasing efforts to substitute fossil resources by renewable ones, there is a strong demand for the establishment of both new basic chemicals and innovative synthesis methods. Meeting the high degree of purity needed for monomers that are used for polymer synthesis is challenging. Intelligent processing methods are necessary because available feedstocks often are mixtures of different components. Linear molecules are favored for the synthesis of high-grade polymers such as polyamides or polyesters, but applications of monomers with chain lengths beyond 13 carbons are scarce. Monoenic fatty acid derivatives might comprise a well-suited raw material base because of their preformed linear structure. The isomerization of the internal double bond to the end of the chain, which is thermodynamically unfavorable, and further selective reaction at this position to a,w-functionalized monomers seems to be the bottle neck. Only a few successful ideas have been developed so far. Behr and co-workers obtained only 36 % of the linear product in the hydroformylation of methyl oleate.[1] A more convincing concept was presented by Cole-Hamilton and co-workers.[2] The authors reported a highly selective isomerizing methoxycarbonylation of methyl oleate to dimethyl 1,19 nonadecanedioate. In the presence of CH 3 SO 3 H and a sterically strongly hindered Pd bisphosphine catalyst the double bond was shifted initially to the terminal position in the chain. This reaction step was followed by the addition of CO and the insertion of a methoxy group, which proceeded exclusively at the C18 carbon for sterical reasons. Mecking et al. [3] used this methoxycarbonylation recently for the synthesis of new polyester types.In this contribution, a more global approach is presented, involving i) catalytic reactions of high selectivity; and ii) the use of a high-oleic sunflower oil (HOSO) as a vegetable oil (1), instead of fatty esters, in a simplified one-pot procedure (Scheme 1).[4] Such processing may be advantageous for technical applications. Thus, the 1,19-diester 2 is utilized as a platform chemical for 1,19-building blocks, leading to novel polymers.During the last years, intensive studies on the methoxycarbonylation of lower olefins and of unsaturated carboxylic acids and esters have been published in the literature.[2, 3, 5] According to our investigations, the formerly used catalytic system Pd/ bis(di-tert-butylphosphinomethyl)-benzene/CH 3 SO 3 H [2] is surprisingly capable of a three-stage reaction in one batch. Consequently, 1 was converted directly into 2 via a parallel and/or subsequent sequence of transesterification/isomerization, and methoxycarbonylation.[4] The highly selective reaction towards 2 was neither affected by the formation of glycerol nor by minor components in the technical grade oil 1, such as free fatty acids (approx. 0.1 %) or unsaponifiables (approx. 1.5 % lecithin, sterols). Moreover, an up-scaling of the reaction over several orders of magnitude was possible without any significant loss in yield and sele...
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