Zalomaeva, Olga, VPodyacheva, Olga YuSuboch, Arina N.Kibis, Lidiya S....
9页
查看更多>>摘要：Carbon nanotubes (CNTs) doped with nitrogen were prepared using two methodologies, chemical vapor deposition (N-CNTs) and post-modification (N-CNTs-P), and characterized by N2 adsorption, TEM, XPS, Raman spectroscopy, and water capacity measurements. Their catalytic performance was assessed for aerobic oxidation of syringyl alcohol, a model of syringyl unit of lignin. With N-CNTs, the reaction readily proceeds under mild conditions (40-80 degrees C, 1 atm of air, isopropanol, ethanol, or water as solvents), leading to syringaldehyde with 95-97% yield. A correlation between N content in N-CNTs and oxidation rate has been established. Spectroscopic studies coupled with water capacity measurements implicated that a blend of graphitic and pyridinic nitrogen species is crucial for catalytic activity. The catalysts can be easily recovered, regenerated, and reused without significant loss of the catalytic performance. N-CNTs-P catalysts, which endow high content of quinone-type oxygen groups, provide significantly lower syringaldehyde yield due to fast deactivation.
查看更多>>摘要：The activity of Pt/Al2O3 in the hydrogenation of toluene (TOL) was found to monotonically increase in line with an increase in the Pt particle size from 1.0 to 2.5 nm, but was constant for a size above 2.5 nm. Comparing different crystalline phases of Al2O3, the activity of Pt/gamma-Al2O3 was found to be around 1.5 times higher than that of Pt/gamma-Al2O3 for the same Pt particle size. Scanning transmission electron microscopy showed the presence of amorphous Pt nanoparticles (NPs) with a size of < 2.0 nm and Pt nanocrystals (NCs) with a size of >= 2.0 nm on Al2O3. Furthermore, the fraction of amorphous Pt NPs in Pt/gamma-Al2O3 was higher than that in Pt/gamma-Al2O3. Pt NCs were shown to be more active than the amorphous Pt NPs in the hydrogenation of TOL owing to them having an abundance of Pt plane.
查看更多>>摘要：Four clay materials, namely, bentonite, bleaching earth, attapulgite and sepiolite, were shaped into the cylindrical body by extrusion. Clays were characterized in depth by TEM, SEM-EDX, N2 physisorption, pyridine FTIR, pH measurements, contact angle measurements, 27Al MAS NMR, and the crush test. Catalytic properties were investigated in the citronellal cyclization as a model reaction. The reaction was performed in the trickle-bed reactor at 70 degrees C, 10 bar of Ar with 0.086 M initial citronellal concentration in cyclohexane. The best results were obtained over attapulgite with isopulegols yield of 24% and stereoselectivity to the desired isopulegol isomer of 61%. Attapulgite had the highest meso-to-micropore volume ratio, the highest basicity, a low Bronstedto-Lewis acid sites ratio, and the lowest amount of Bronsted acid sites compared to other extrudates. In addition, same clay exhibited the highest mechanical strength of extrudates.
NSTL
Elsevier