Formaldehyde has been a key platform reagent in the chemical industry for many decades in a large number of bulk scale industrial processes. Thus, the annual global demand reached 30 megatons per ...year, and currently it is solely produced under oxidative, energy intensive conditions, using high-temperature approaches for the methanol oxidation. In recent years, new fields of application beyond the use of formaldehyde and its derivatives as
i.e.
a synthetic reagent or disinfectant have been suggested. For example dialkoxymethane could be envisioned as a direct fuel for combustion engines or aqueous formaldehyde and paraformaldehyde may act as a liquid organic hydrogen carrier molecule (LOHC) for hydrogen generation to be used for hydrogen fuel cells. To turn these new perspectives in feasible approaches, it requires also new less energy-intensive technologies for the synthesis of formaldehyde. This perspective article spreads light on the recent directions towards the low-temperature reductive synthesis of formaldehyde and its derivatives and low-temperature formaldehyde reforming for hydrogen generation. These aspects are important for the future demands on modern societies' renewable energy management, in the form of a methanol and hydrogen economy, and the required formaldehyde-feedstock for the manufacture of many formaldehyde-based daily products.
This perspective article spreads light on the recent directions towards the low-temperature reductive synthesis of formaldehyde and its derivatives and low-temperature formaldehyde reforming for hydrogen generation.
Herein we present a systematic investigation on the promotional effect of base in metal catalysed hydrogenolysis of lignin model compounds and organosolv lignin. The research started with the ...evaluation of pH effects (pH 1–14) on the hydrogenolysis of a lignin β-O-4 model compound over a Ru catalyst (a stable catalyst over a wide pH range), from which a significantly increased selectivity towards monomeric compounds was observed in the presence of base. This promotional effect was studied in detail over bimetallic Ni7Au3 nanoparticles. Addition of a strong base such as NaOH significantly enhanced the activity and selectivity for C-O bond hydrogenolysis over undesired hydrogenation reactions, not only in lignin model compounds but also in real lignin conversion. Notably, the yield for monomeric aromatic compounds from lignin over Ni7Au3 catalyst increased ca. 100% after adding NaOH as a promoter, under the same reaction conditions. Mechanistic study suggest that addition of base significantly reduced the benzene ring hydrogenation activity of the metal catalysts. The effect of adding different bases over various metal catalysts were also investigated.
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•The first systematic study of base promotional effect in lignin hydrogenolysis..•Lignin hydrogenolysis into aromatics was carried out in pure water under mild conditions.•The yield for monomeric aromatic compounds from lignin increased ca. 100% in the presence of base.•Base promotional effect was observed over Ru (a typical noble metal) and Ni (a typical non-noble metal) catalysts.
Imitating nature′s approach in nucleophile‐activated formaldehyde dehydrogenation, air‐stable ruthenium complexes proved to be exquisite catalysts for the dehydrogenation of formaldehyde hydrate as ...well as for the transfer hydrogenation to unsaturated organic substrates at loadings as low as 0.5 mol %. Concatenation of the chemical hydrogen‐fixation route with an oxidase‐mediated activation of methanol gives an artificial methylotrophic in vitro metabolism providing methanol‐derived reduction equivalents for synthetic hydrogenation purposes. Moreover, for the first time methanol reforming at room temperature was achieved on the basis of this bioinduced dehydrogenation path delivering hydrogen gas from aqueous methanol.
Imitating nature′s approach for nucleophile‐activated formaldehyde dehydrogenation: Air‐stable ruthenium complexes are catalysts for the dehydrogenation of formaldehyde hydrate as well as for transfer hydrogenation to unsaturated organic substrates. In combination with an oxidase‐mediated activation of methanol, an artificial methylotrophic in vitro metabolism provides hydrogen gas in a room‐temperature methanol‐reforming pathway.
A selective hydrogenation method for forming (Z)-alkenes from alkynes has been developed using a catalyst system of cheap Ni-NPs in a nitrile functionalised imidazolium based ionic liquid (IL) ...operating under very mild reaction conditions of 30-50 °C and 1-4 bar H2 pressure.
N-Heterocyclic compounds have been tested in the selective hydrogenation catalysed by small 1-3 nm sized Ru nanoparticles (NPs) embedded in various imidazolium based ionic liquids (ILs). Particularly ...a diol-functionalised IL shows the best performance in the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline (1THQ) with up to 99% selectivity.
Iron(0) nanoparticles in ionic liquids (ILs) have been shown to catalyse the semi-hydrogenation of alkynes. In the presence of a nitrile-functionalised IL or acetonitrile, stereoselective formation ...of (Z)-alkenes was observed. The biphasic solvent system allowed facile separation and re-use of the catalyst.
In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation ...catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process.
A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. ...Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions which all have in common the use of ionic liquids as reaction media and the use of palladium nanoparticles as reservoir for the catalytically active palladium species.
Ionic liquid (IL) based H2 storage for H2 generation from NH3BH3 derivatives is shown. These systems promote H2 generation at low temperature, with good reaction rates and high total H2 yields. The ...effects of ILs and the H2 yield in correlation with the basicity, the cations of the ILs, and the role of carbenes are discussed. Furthermore, mechanistic findings on the dehydrogenation are described. IL material blends are competitive with conventional H2 storage materials with experimental efficiencies of at least 6.5 wt % H2.
Ionic liquid (IL) based H2 storage systems based on NH3BH3 derivatives promote H2 generation at low temperature, with good reaction rates, and high total H2 yields. IL material blends are competitive to conventional H2 storage with experimental efficiencies of at least 6.5 wt % H2.
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