A Pt/TiH2 catalyst having
hydrogen storage and release
capability was investigated for selective hydrogenation of trans-cinnamaldehyde (CAL) to cinnamyl alcohol (COL) with
gaseous dihydrogen. The catalytic behavior of this catalyst was significantly
different from that of a reference Pt/TiO2 catalyst with
respect to the product selectivity and the hydrogenation mechanism.
The Pt/TiH2 catalyst showed a COL selectivity of 97% at
a CAL conversion of 98%, which was ascribed to the function of a Pt
crystallite–support boundary layer that caused the preferential
adsorption of CAL with its carbonyl group. Furthermore, the carbonyl
group was hydrogenated by hydride species (H+, H–) supplied from the support and the hydride species consumed were
compensated from gaseous dihydrogen; hydrogen atoms were formed by
ordinary homolytic cleavage on Pt and then these hydrogen atoms moved
onto the surface of TiH2 and diffused into the bulk of
the support, during which those simultaneously changed to hydride
species (H+, H–) via electron transfer
with titanium species and hydride vacancies therein. The surface and
bulk diffusion of the hydrogen atoms from Pt to TiH2 support
should be the dominant step rather than their addition to the carbonyl
group of CAL (ordinary hydrogenation). That is, ionic hydrogenation
occurs with Pt/TiH2 in the presence of gaseous dihydrogen.
The selective hydrodeoxygenation of lignin-derived guaiacol to value-added products, especially phenol, under relatively mild reaction conditions remains an important challenge. A Cl-modified Ru/TiO 2 catalyst exhibited higher phenol selectivity compared with an unmodified one in the conversion of guaiacol in 1,4-dioxane at 240 °C and 1 MPa H 2 . Unlike Ru/TiO 2 , the modified catalyst exhibited a modest activity of demethoxylation producing phenol but an inferior ability of hydrogenation of its aromatic ring, resulting in much slower consumption of phenol. The Cl species were likely localized at the metal−support interface and on the surface of metal particles, and these modified both Ru and Ti species electronically. It is presumed that electron-enriched Ru inhibits the ring hydrogenation reaction, and the defects on the TiO 2 surface promote the deoxygenation reaction.
The presence of Zn can promote the activity and stability as well as adjust the product selectivity due to the formation of ZnCu alloy and the reduction of acidic sites, which prevents the deactivation of the catalyst and dehydration of 1,4-PDO.
Seed- and solvent-free synthesis of MFI zeolites with tuneable Si/Al ratios (18-∞) was achieved. The key role of F− was evidenced that forming 6-coordinated “F–Al–O–Si” species drove the formation of the zeolitic framework during crystallization.
Under relatively mild conditions (240 °C and 0.4 MPa H2), Ru/Ti–SiO2 exhibited higher activity for C–O bond cleavage compared with both Ru/SiO2 and Ru/TiO2 catalysts, and achieved high guaiacol conversion (83.6%) and phenol selectivity (70.4%).
An inorganic-organic porous silica network catalyst was prepared by linking silica nanoparticles using ionic liquid and followed by anion-exchange with phosphotungstate. Characterization methods of FT-IR, TG, SEM, TEM, BET, etc., were carried out to have a comprehensive insight into the catalyst. The catalyst was used for catalyzing cyclooctene epoxidation with high surface area, high catalytic activity, and convenient recovery. The conversion and selectivity of epoxy-cyclooctene could both reach over 99% at 70˝C for 8 h using hydrogen peroxide (H 2 O 2 ) as an oxidant, and acetonitrile as a solvent when the catalyst was 10 wt. % of cyclooctene.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.