Bio-based monomers are synthesized in a two-step process starting from common platform chemicals. The featured sequence of heterogeneously-catalyzed reduction and gas phase dehydration makes for a promising alternative to traditional Reppe chemistry.
Succinic acid is a valuable biomass-derived platform molecule, which can be further catalytically converted into many industrially-relevant molecules such as γ-butyrolactone, 1,4-butanediol or tetrahydrofuran. The influence of the support nature...
For the first time ammonium perrhenate (APR) supported on zeolites of the types H-β, H-ZSM-5 and HÀ Y were shown to be efficient catalysts for the deoxydehydration (DODH). They catalyzed the transformation of 1,2-hexanediol (1,2-HDO) to 1hexene in the presence of 3-octanol as reductant and solvent with productivities up to 0.24 mol 1-hexene • g Re À 1 • h À 1 . The productivity decreased with increasing Si : Al ratio, independent of the zeolite structure. Catalyst characterization indicates Re-species to preferably bind to the Al centers of the support, resulting in a higher amount of active metal centers.
Pt–Re
bimetallic catalysts have many applications, ranging
from catalytic reforming to the reduction of carboxylic acid derivatives.
However, the exact role of Re in these systems has remained a matter
of discussion, partly due to the plethora of suggested synthesis protocols
and analysis conditions. This study presents an extensive comparison
of such literature protocols and the resulting materials. In detail,
characterization by N2 physisorption, X-ray diffraction,
temperature-programmed reduction, CO pulse chemisorption, Fourier-transform
infrared spectroscopy of adsorbed CO, scanning transmission electron
microscopy, energy-dispersive X-ray spectroscopy, and in
situ X-ray photoelectron spectroscopy is combined with catalytic
testing to yield synthesis–structure–activity correlations.
Accordingly, the investigated catalysts share common features, such
as Pt0 nanoparticles (1–4 nm) decorated with partially
reduced Re species (ReO
x–y
). The remaining rhenium oxide is spread over the TiO2 support and enhances Pt dispersion in sequential impregnation protocols.
While differences in the number of active sites (Pt0/ReO
x–y
) mostly explain
catalytic results, small variations in the extent of Re reduction
and site composition cause additional modulations. The optimal bimetallic
catalyst outperforms Ru/C (previous benchmark) in the reduction of N-(2-hydroxyethyl)succinimide, an important step in the
production of a bio-based polyvinylpyrrolidone polymer.
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