Filters

2016 - 20192

More filters

2021 - 20222
Reset filters

Settings

Author: Brückner, Angelika × Subject: heterogeneous catalysis ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Conversion of γ-Valerolactone to Ethyl Valerate over Metal Promoted Ni/ZSM-5 Catalysts : Influence of Ni0/Ni2+ Heterojunctions on Activity and Product Selectivity
    (Weinheim : Wiley-VCH Verlag, 2019) Velisoju, Vijay Kumar; Jampaiah, Deshetti; Gutta, Naresh; Bentrup, Ursula; Brückner, Angelika; Bhargava, Suresh K.; Akula, Venugopal
    Promoter (Cr, Mo and W) modified Ni/ZSM-5 catalysts were explored in the vapor phase conversion of γ-valerolactone (GVL) to ethyl valerate (EV; gasoline blender) at atmospheric pressure. Among the three different promoters (Cr, Mo and W) tested the Mo-modified catalyst was found to be the best candidate. In addition, this catalyst was found to be stable up to 50 h reaction time with an insignificant decrease in activity. The good catalytic performance is related to an optimal ratio of acid and hydrogenation functions provided by Ni2+ and Ni0, respectively. In situ FTIR spectroscopic studies revealed a strong adsorption of GVL on all catalysts which quickly reacts with dosed ethanol by formation of EV, most pronounced on the Mo-modified catalyst, while VA was identified as side product. These findings suggest the preferred GVL ring opening by cracking the C−O bond on the methyl side of the GVL molecule on this type of catalysts leading to pentenoic acid as intermediate, which is quickly hydrogenated and esterified. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
  • Thumbnail Image
    Item
    Tracing Active Sites in Supported Ni Catalysts during Butene Oligomerization by Operando Spectroscopy under Pressure
    (Washington, DC : ACS, 2016) Rabeah, Jabor; Radnik, Jörg; Briois, Valérie; Maschmeyer, Dietrich; Stochniol, Guido; Peitz, Stephan; Reeker, Helene; La Fontaine, Camille; Brückner, Angelika
    Supported Ni catalysts have been studied during the dimerization of butenes by operando electron paramagnetic resonance (EPR) and in situ X-ray absorption spectroscopy (XAS) at 353 K and up to 16 bar. Single NiI/NiII shuttles were identified as active sites, whereby the conversion of initial NiI to NiII by oxidative addition of butene is obviously faster than the re-reduction of NiII to NiI by reductive elimination of the C8 product, rendering the equilibrium percentage of NiI small. At p ≤ 2 bar, NiI single sites form inactive Ni0 aggregates, while this is suppressed at higher pressure (∼12 bar). A reaction mechanism is proposed.