J. van Grondelle

Moessbauer spectroscopy of supported bimetallic catalysts: 1:5 FeM/SiO2 (M = Ru, Rh, Pd, Ir, Pt)

Mössbauer spectra of SiO2-supported bimetallic FeM (M=Ru, Rh, Pd, Ir, and Pt) with FeM=1∶5 arter treatments such as reduction, exposure to CO and passivation in air are described and compared with previous results obtained on 1∶1 FeM/SiO2 catalysts.

Influence of zeolite pore structure on catalytic reactivity

The influence of zeolite pore-size and shape on the hydro-isomerization of n-hexane was studied. Computer simulations and kinetic measurements, in combination with Positron Emission Profiling (PEP) experiments have been performed. Results showed that, for zeolites with a Al/Si molar ratio of less than 0.1 acidic protons had the same activity. Differences in reactivity are due to differences in the heat of adsorption. Smaller pores result in a higher steady state concentration of adsorbed substrate and adsorbed alkoxy species. Based on a kinetic model, and using experimental heats of adsorption and theoretical protonation energies, the activation energy of hydro-isomerization of n-hexane was found to be approximately 127 kJ/mol. This is consistent with results of a recent quantum chemical model of reactions catalysed by a zeolite proton.

Methanol from synthesis gas over bimetallic FePd catalysts

Bimetallic FePd/SiO2 catalysts exhibit higher activities in the formation of methanol from synthesis gas than Pd/SiO2. The catalysts are a complex mixture of bcc and fcc FePd alloy, α-Fe and some unreduced iron.

Imaging of n-hexane in zeolites by Positron Emission Profiling (PEP)

Positron Emission Profiling (PEP) has been used for in-situ measurement of the surface coverage of H-mordenite by n-hexane, as a function of hexane partial pressure, at the elevated temperatures typically used for hydroisomerization by monitoring the retention time of an injected radio-labelled pulse of n-hexane. The labelled molecules ( 11 CH 3 C 5 H 11 ) were produced via a two-step alkene homologation reaction in which 11 C, produced using a cyclotron, was added to 1-pentene. The PEP method described is similar to the “tracer pulse technique” however it has the significant advantage of in-situ imaging of the pulse.

Metal-catalysed alkylation of pentene to hexane

The use of 11C-labelled CO in the formation of 11C-labelled n-hexane from pent-1-ene over 5% Ru/SiO2 gives clear evidence for the presence of different reaction pathways for production of iso- and n-hexane; recombination of pentene fragments appears to be the dominant route in hexane formation.