For selected examples of hydrogenation reaction of nitro compounds under continuous-flow conditions, see: (a) Chen, J.; Przyuski, K.; Roemmele, R.; Bakale, R. P. Org. Process. Res. Dev . ASAP; (b) Javaid, R.; Kawasaki, S-i.; Suzuki, A.; Suzuki, T. M
A convenient and simple PdCl2-based hydrogenation catalyst has been developed. The liquid, air, and moisture stable precursor is pumped into the reactor where it is temporarily immobilized and reduced on the channel surface into Pd(0), providing a constant high activity for hydrogenation reaction. The catalyst is leached with time, avoiding any kind of clogging problems during long time runs.
Hydrogen sorption properties and some corresponding changes in the crystallization of amorphous TM33Zr67 (TM=Fe, Co, Ni) alloys have been investigated. Relatively large amount of hydrogen was found to dissolve into the amorphous alloys
during electrochemical hydrogen charging. The microstructural evolution during annealing of H-charged Ni33Zr67 was studied as well. The weaker bonded hydrogen desorbs in a large temperature range (440–625 K) before the crystallization
of the amorphous alloys to start. A hydride phase (ZrH2) was found to form during annealing the H-charged amorphous Ni33Zr67 alloy. During heating at constant heating rate the hydride decomposes at about 715 K and formation of Zr2Ni immediately takes place. The final microstructure of the Zr2Ni, crystallized from the H-charged matrix, is noticeably finer compared to the material crystallized from the H-free amorphous
alloy, most probably due to the higher temperature of Zr2Ni formation in the H-charged amorphous alloy than in the H-free sample.
Authors:József Madarász, Gergely Farkas, Szabolcs Balogh, Áron Szöllősy, József Kovács, Ferenc Darvas, László Ürge, and József Bakos
Highly active immobilized hydrogenation catalytic systems were used in the H-Cube™ hydrogenation reactor. “In situ” produced [Rh(COD)((S)-MonoPhos)2]BF4 complex was immobilized on commercially available Al2O3 and mesoporous Al2O3 by means of phosphotungstic acid (PTA), respectively. The optimum reaction conditions were determined and studied at different temperature, pressure, and flow rate values. Furthermore, the effect of the substrate concentration, microstructure of the support, and the stability of the complex were investigated. A continuous-flow reaction system using a stationary-phase catalyst for the asymmetric hydrogenation of methyl acetamidoacrylate was developed and run continuously for 12 h with >99% conversion and 96–97% enantioselectivity.
Authors:Tuong Van Le Doan, Petr Stavárek, and Claude de Bellefon
A methodology that may be applied to help in the choice of a continuous reactor is proposed. In this methodology, the chemistry is first described through the use of eight simple criteria (rate, thermicity, deactivation, solubility, conversion, selectivity, viscosity, and catalyst). Then, each reactor type is also analyzed from their capability to answer each of these criteria. A final score is presented using “spider diagrams.” Lower surfaces indicate the best reactor choice. The methodology is exemplified with a model substrate nitrobenzene and a target pharmaceutical intermediate, N-methyl-4-nitrobenzenemethanesulphonamide, and for three different continuous reactors, i.e., stirred tank, fixed bed, and an advanced microstructured reactor. Comparison with the traditional batch reactor is also provided.
Authors:Tsutomu Osawa, Mari Onogi, I-Yin Sandy Lee, and Tadao Harada
enantioselectivities [ 1 – 6 ], although the C=C double bond and C=N double bond have not been hydrogenated efficiently. Generally, the hydrogenations of prochiral ketones were carried out under high hydrogen pressure (9 MPa) in an autoclave. Under these conditions
Authors:E. V. Dokuchits, A. V. Khasin, and A. A. Khassin
This work deals with two aspects of catalysis. The first one is the mechanism of hydrogen oxidation on silver. This reaction is essential for chemical kinetics and catalysis as a model catalytic redox reaction. It
Authors:Alex Szakál, Gerhard Krexner, Andreas Grill, György Káli, Márton Markó, and László Cser
., Beaudry B. J. The effect of impurities, particularly hydrogen on the lattice parameters of the “ABAB” rare earth metals, Journal of Less Common Metals , Vol. 25, No. 1, 1971, pp. 61–73.
Beaudry B. J
The surface diffusion of active species plays an important role in heterogeneous catalytic reactions [ 1 ], especially the diffusion of hydrogen species on the catalyst surface. Hydrogen molecules in the gaseous