38734-69-9Relevant articles and documents
Pd Nanoparticles Encapsulated in FER Zeolite through a Layer Reassembling Strategy as Shape-selective Hydrogenation Catalyst
Zhao, Zhenchao,Li, Yanlu,Feyen, Mathias,McGuire, Robert,Müller, Ulrich,Zhang, Weiping
, p. 2254 - 2259 (2018/03/21)
Noble metal nanoparticles (NPs) encapsulated in zeolites bearing distinct shape-selective properties at molecular level expand their new applications in catalysis. Here we report a synthesis strategy for the encapsulation of Pd NPs inside FER zeolite via a layer reassembling process. Pd precursors were introduced by swelling FER layers in RUB-36 through the surfactant cetyltrimethylammonium cations (CTA+) and then an ion-exchange process at ambient temperature. Pd@FER was formed with a uniform diameter distribution of Pd NPs at about 1.4 nm during the topotactic transformation from layered zeolite precursors to 3-dimensional zeolites followed by calcination. The as-prepared Pd@FER catalyst exhibits distinct shape-selective properties in hydrogenation reactions. It has relatively lower activity for 1-hexene and almost no activity for 1-phenyl-1-cyclohexene compared with Pd/RUB-37 catalyst prepared via wet impregnation due to the restrictions of channels in the FER zeolite. On the contrary, Pd@FER shows very high hydrogenation activity for benzaldehyde and very low activity for diphenylmethanone hydrogenation, while Pd/RUB-37 exhibits high hydrogenation activity for both benzaldehyde and diphenylmethanone. This synthesis strategy may be extended to other noble metals or two-dimensional layered zeolite systems for size-selective hydrogenation reactions.
Characterization of unstable products of flavin- and pterin-dependent enzymes by continuous-flow mass spectrometry
Roberts, Kenneth M.,Tormos, José R.,Fitzpatrick, Paul F.
, p. 2672 - 2679 (2014/05/20)
Continuous-flow mass spectrometry (CFMS) was used to monitor the products formed during the initial 0.25-20 s of the reactions catalyzed by the flavoprotein N-acetylpolyamine oxidase (PAO) and the pterin-dependent enzymes phenylalanine hydroxylase (PheH) and tyrosine hydroxylase (TyrH). N,N′-Dibenzyl-1,4-diaminobutane (DBDB) is a substrate for PAO for which amine oxidation is rate-limiting. CFMS of the reaction showed formation of an initial imine due to oxidation of an exo-carbon-nitrogen bond. Nonenzymatic hydrolysis of the imine formed benzaldehyde and N-benzyl-1,4-diaminobutane; the subsequent oxidation by PAO of the latter to an additional imine could also be followed. Measurement of the deuterium kinetic isotope effect on DBDB oxidation by CFMS yielded a value of 7.6 ± 0.3, in good agreement with a value of 6.7 ± 0.6 from steady-state kinetic analyses. In the PheH reaction, the transient formation of the 4a-hydroxypterin product was readily detected; tandem mass spectrometry confirmed attachment of the oxygen to C(4a). With wild-type TyrH, the 4a-hydroxypterin was also the product. In contrast, no product other than a dihydropterin could be detected in the reaction of the mutant protein E332A TyrH.
Preparation of 2-imidazolines
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, (2008/06/13)
A novel process for the preparation of 2-imidazolines by reacting 1,2-diamines with nitriles or carbonyl compounds in the gas phase at from 200° to 450° C. in the presence of an oxide or phosphate of a metal of group 3 or 4 of the periodic table and/or in the presence of silicon dioxide. The 2-imidazolines obtainable by the process of the invention are valuable starting materials for the preparation of dyes, crop protection agents and drugs.
