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Fe-SiO 2 interaction is a critical issue in the study of Fischer-Tropsch Fe/SiO 2 catalyst. It has been advanced that the formation of Fe-O-Si bond is related to Fe-SiO 2 interaction and responsible for dispersing iron particles and stabilizing active phases. This work formulates studying the relationship and interconversion between Fe-O-Si bond and Fe 2 SiO 4 phase, and further concludes that Fe 2 SiO 4 is another form of Fe-SiO 2 interaction. A well mixing of Fe-O and Si-O domains in the catalyst precursor benefits the distribution of extensive Fe-O-Si bond, which in turn facilitates the formation of Fe 2 SiO 4 during the catalyst reduction process. High ramp rate and diluted H 2 favor the transition of discrete Fe-O-Si to Fe 2 SiO 4 kinetically and thermodynamically, respectively. During the transition, amorphous Fe 2 SiO 4 initially forms before undergoing a rapid crystallization process, at ca. 560 ± 10 °C, to transform to large crystals detectable by XRD. In addition, the amorphous nature of Fe 2 SiO 4 requires the combination of characterization techniques capable of detecting short-range ordered structures, e.g., XAFS, MES, and magnetometer. [Display omitted] • Fe 2 SiO 4 is another form of Fe-SiO 2 interaction for Fischer-Tropsch Fe/SiO 2 catalyst. • Well distributed Fe-O-Si bond can transform to amorphous Fe 2 SiO 4. • High ramp rate and diluted H 2 kinetically favor the transition of Fe-O-Si to Fe 2 SiO 4. • Amorphous Fe 2 SiO 4 undergoes rapid crystallization process to form large particles at 560 ± 10 °C. • The dehydration of Si-OH facilitates the crystallization of Fe 2 SiO 4. [ABSTRACT FROM AUTHOR]

Abstract: In this research, the catalytic activity of a rhodium-based (Rh) catalyst with imidazolium-based ionic liquids (IBILs) as solvents for ethylene hydroformylation was studied. The structures of IBILs had an important influence on the activity and stability of the Rh catalyst. The IBILs with longer cation side chains, which were the strong steric hindrances around the Rh catalyst, were more unfavorable for the catalytic activity. The turnover frequency (TOF) of the Rh catalyst was 10627h−1 when [Bmim][BF4] was used as solvent. The activity of the Rh complexes in the ionic liquid is better than they do in toluene. We used electrospray ionization mass spectrometry to characterize the catalyst after the reaction and found that [Bmim]+ acts as a ligand of the Rh catalyst to form a new active catalytic site [Rh(CO)(PPh3)2(Bmim)(BF4)]+ through the coordination of the Rh atom with the imidazole-2-C group of [Bmim][BF4], and it was essential for the stabilization of the Rh catalyst and prevented the formation of low-active Rh clusters. In addition, the catalyst recycling test showed that the Rh catalyst could be reused with [Bmim][BF4] as solvent without obvious loss of catalytic activity. [Copyright &y& Elsevier]

• The active oxygen on Pd/Sn 1−x Ce x O 2 (Ce-rich) is mainly lattice oxygen. • The active oxygen on Pd/Sn 1−x Ce x O 2 (Sn-rich) is mainly chemisorbed oxygen. • The active oxygen on Sn-rich oxide has better mobility than that on Ce-rich oxide. The properties of Sn-Ce solid solution have a significant effect on the CO oxidation performance of the Pd/Sn 1-x Ce x O 2 catalyst. Herein, we compared the effects of Sn-rich and Ce-rich supports on the catalytic performance of the Pd/Sn 1-x Ce x O 2 catalysts. Our results show that the active oxygen species on the Ce-rich and Sn-rich supports are mainly the lattice oxygen species and the chemisorbed oxygen species, respectively. Although the active oxygen species on the Ce-rich supports have higher intrinsic activity, the active oxygen species on the Sn-rich supports have better mobility. It leads to an interesting phenomenon that the change trend of the activity of the Pd/Sn 1-x Ce x O 2 catalysts with temperature is consistent with that of their supports. Compared with the Ce-rich supports and the corresponding supported Pd catalysts, the catalytic activity of the Sn-rich supports and the corresponding supported Pd catalysts increased faster with the increase of temperature. [ABSTRACT FROM AUTHOR]

Alkynone and enolized angelica lactone (or its anion) coordinated to Sc(III) center, forming a hexaccoordinate-Sc(III) active species. Chiral N , N '-dioxide-Sc(III) catalyst exerted asymmetric induction by bulky ortho - i Pr group and chiral backbone. • Counterion CF 3 SO 3 -accelerated the isomerization of α-angelica lactone and the construction of C H bond as proton-shuttle. • Alkynone and enolized angelica lactone (or its anion) coordinated to Sc(III) center, forming an active species. • Catalyst exerted asymmetric induction by bulky ortho - i Pr group and chiral backbone. The reaction mechanism and enantioselectivity of asymmetric Michael addition reaction between alkynone (R1) with α-angelica lactone (R2) catalyzed by chiral N , N '-dioxide-Sc(III) complex were investigated at the M06/6-31G(d,p) (acetonitrile, SMD) level. The α-angelica lactone substrate could isomerize to the active enolized form in the presence of Sc(OTf) 3 reagent, assisted by the counter trifluoromethanesulfonate anion OTf-. The alkynone substrate and enolized angelica lactone (or its anion) coordinated to Sc(III) center of N , N '-dioxide-Sc(III) complex catalyst simultaneously, forming a high active hexacoordinate-Sc(III) complex. The catalytic reaction occurred via a two-step mechanism, in which C 2 C γ bond formation was predicted to be the chirality-controlling step as well as the rate-determining step (RDS), affording predominant S -enantiomer. The counterion OTf- facilitated C H construction as a proton-shuttle, producing mainly E -configuration product observed in experiment. The steric repulsion from the ortho -substituent of amide moiety as well as the chiral backbone of N , N '-dioxide-Sc(III) catalyst played the key role for chiral induction in the asymmetric reaction. The less destabilizing Pauli repulsion and more stabilizing attractive interaction, especially the orbital interaction, along the si -face attack pathway enhanced the enantiodifference of the two competing pathways for high enantioselectivity. The energy barriers for E / Z isomerization of S or R -enantiomer assisted by HOTf was as high as 34.6–35.0 kcal mol−1, indicating that the product with Z -conformation was difficult to be obtained. These results were in good agreement with experimental observations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two-bubble class model was employed for the gas–liquid mass transfer. [•] Axial dispersions of liquid and solid phases are incorporated in above model. [•] Bench-scale experiment was carried out in a 2L stainless steel tube of 2m long. [•] Scale-up simulations at a capacity of 1.0Mt/a for VR processing were conducted. [•] Due to the non-uniform distribution of catalyst, axial dispersion model is required. [ABSTRACT FROM AUTHOR]