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Catalytic Membrane Reactors
Published in E. Robert Becker, Carmo J. Pereira, Computer-Aided Design of Catalysts, 2020
Theodore T. Tsotsis, Ronald G. Minet, Althea M. Champagnie, Paul K. T. Liu
The first high-temperature catalytic membrane reactors in operation used metallic (Pd, Pd alloy, and Pd/Ag) membranes. These reactors were pioneered by Gryaznov and co-workers, who studied many hydrogenation/ dehydrogenation reactions while testing various reactors containing flat foil, thin-walled straight-tube, and spiral-type membranes [5,6]. Hydrogenation reactions studied involved the production of linalool from de-hydrolinalool, the hydrogenation of cyclopentadiene to cyclopentene, naphthalene to tetralin, furan to tetrahydrofuran, nitrobenzene to aniline, and furfural to furfuryl alcohol [5–8]. The reactor used with all these reactions consisted of two chambers, separated by the flat metallic membrane, with H2 typically being fed in one of the chambers and the other reactant in the other. For all hydrogenation reactions studied in a membrane reactor, Gryaznov and co-workers reported improvements in the yield. It is not entirely obvious why membrane reactors improve the yield of hydrogenation reactions. It is probably due to the fact that atomic hydrogen is an important intermediate for such reactions and the membrane helps to optimize its surface concentrations. Gryaznov and Slink’o [9] and Nagamoto and Inoue [10–12] have addressed this exact issue. For butadiene hydrogenation, for example, the significant improvements in yield observed in a membrane reactor were attributed to butadiene inhibiting the dissociative chemisorption of H2 in the absence of the membrane.
Inorganic Nanoparticles for Catalysis
Published in Claudia Altavilla, Enrico Ciliberto, Inorganic Nanoparticles: Synthesis, Applications, and Perspectives, 2017
Selectivity of the reaction is also influenced by the particle size. For example, the selectivity of partial hydrogenation of cyclopentadiene to produce cyclopentene catalyzed by PVP-protected Pd nanoparticles increases with decrease in Pd particle size (Hirai et al. 1985). The shape or crystal structure of particles also influences the catalytic activity and selectivity. For example, rods or wires, obtained by growth of (111) face of a particle, usually have a large area of (100) face and small (111) face. Thus, they could have a high catalytic activity if (100) face can provide an active site. Thus, the studies on the effect of particle shape or crystal structure on the catalytic activity and selectivity are still in progress. This kind of researches may increase in future.
Current-Driven Desorption at the Organic Molecule–Semiconductor Interface: Cyclopentene on Si(100)
Published in Tamar Seideman, Current-Driven Phenomena in Nanoelectronics, 2016
N. L. Yoder, R. Jorn, C.-C. Kaun, T. Seideman, M. C. Hersam
The STM experiments were performed using a cryogenic variable temperature ultrahigh vacuum (UHV) STM.52 The samples were cut from n-type (arsenic-doped) and p-type (boron-doped) Si(100) wafers purchased from Virginia Semiconductor (Fredericksburg, Virginia). All wafers had a resistivity of 0.005 Q-cm. Samples were cut into rectangular sections (6 mm x 10 mm) and sonicated for 5 min in 2-propanol and then brought into the UHV chamber. Inside the chamber, the samples were degassed for 12 h at 600°C and subsequently flashed to 1250°C several times for 1-2 min to clean the sample before the experiment. Experiments were performed at temperatures between 8 and 300 K. In order to introduce adsorbate molecules into the STM chamber, cyclopentene in the liquid phase was placed in a vial that was connected to the chamber via a precision leak valve. Prior to the experiment, the cyclopentene was subjected to 10-20 freeze-pump-thaw cycles to remove dissolved gases from the liquid.
Valorisation of biomass pellets to renewable fuel and chemicals using pyrolysis: characterisation of pyrolysis products and its application
Published in Indian Chemical Engineer, 2020
Zakir Husain, Khursheed B. Ansari, Vikram S. Chatake, Yogesh Urunkar, Aniruddha B. Pandit, Jyeshtharaj B. Joshi
Hemicellulose content of biomass pellets also depolymerizes to its monomer unit (i.e. a five-membered compound) which experiences dehydration and ring opening reactions to form furfural and 1-hydropentan-2-one as shown by reactions R12, R13, R16, and R17 in Figure 6. The ring opening C5 compound undergoes dehydrogenation/hydrogenation reactions to result in cyclopentanedione/2-cyclopentene-1-one (cf. reactions R14, R15, and R27 in Figure 6) and also thermally fragments to form water, light oxygenates (viz. acetic acid, formic acid, 1-hydroxy-2-butaone and 2-propanone) and non-condensable gases (carbon monoxide, hydrogen, methane, and ethane) as demonstrated by reactions R18, R19, R21 – R26 in Figure 6.
The pressure dependence of laminar flame speed of 2-methyl-2-butene/air flames in the 0.1–1.0 MPa range
Published in Combustion Science and Technology, 2018
Bei-Jing Zhong, Zhao-Mei Zeng, Hui-Sheng Peng
Gasoline is a complex hydrocarbon mixture which mainly consists of alkanes, cycloalkanes, alkenes, and aromatics. Alkenes are significant components of gasoline accounting about 20% in the 93# gasoline in China, and they are also important intermediate products during the combustion of alkanes. Previous studies (Colket et al., 2007; Pera and Knop, 2012) found that the primary alkene components of gasoline are numerous isomers in the C5–C6 range, and among them, 2-methyl-2-butene accounts for the largest proportion (1.7 mol% of gasoline and 30 mol% for alkenes of gasoline), followed by cyclopentene (0.9 mol% of gasoline and 16 mol% for alkenes of gasoline). Moreover, alkenes contribute to determining the ignition characteristics of gasoline, including high-octane number which is related to good anti-knock performance. In particular, 2-methyl-2-butene shows strong octane sensitivity which is close to that of octane.