Supported metal particles play an important role in heterogeneous catalysis. It has been shown lately that the size of the metal crystallites in the supported metal catalysts has a profound effect on the catalytic activity, thus necessitating the need for synthesis methods aimed at a strict control of the metal crystallite size in these catalysts. The classical methods used to synthesize supported metal catalysts typically yield a wide metal crystallite size distribution, and average crystallite sizes which are difficult to control. Suitable techniques have been developed to obtain supported metal catalysts with defined crystallite size distributions, inter alia impregnation of reverse micelle microemulsions, colloid impregnation following reverse micelle precipitation or crystallization, and deposition-precipitation. Using these techniques, a series of supported Ru/γ-Al 2 O 3 , Co/SiO 2 , Fe/γ-Al 2 O 3 , Fe/C, and Au/ZnO catalysts have been prepared and characterized.
It has been a great pleasure to work with all the guys and girls in the group because of the ambience that exists in the group, allowing us to enjoy the student-life we love to live. Salutations to James and Miles, who were always willing to share their wisdom and experience, either academically or socially. Thanks to Klaus, for his invaluable suggestions when all else failed. Thanks to Connie, Leslie and Pam, without whom all the things we take for granted would never get done. Without the technical support of Tony Barker, Rob Senekal and Charlie Ledger, I would not have had the equipment which by now has become one of my closest friends and greatest enemies. A special thanks to my parents, Ton and Ank, for their unassuming belief in me, and to Marc and Marjolijn, who've had to put up with me for over two decades.
MFI type zeolites
have been known for decades for their strong
tendency toward gas formation in hydrocracking. Our strategy for selectivity
control in hydrocracking turns strong adsorption in micropores, responsible
for secondary cracking, to an advantage. Enhancing diesel yield is
a challenging goal in hydrocracking catalysis. Additionally, linear
alkanes increase the diesel fuel cetane number and, consequently,
effect a dramatic reduction in exhaust emissions. This study demonstrates
for a set of Pt on mesoporous MFI zeolite catalysts that the gains
in activity and selectivity attributed to enhanced mass transport
are but modest by comparison to the effects of the competitive adsorption
of water. Water suppresses secondary cracking, and primary cracking
is now reported over MFI zeolites. Furthermore, competitive adsorption
of water in shape-selective MFI zeolites facilitates desorption of
the primary n-C16 cracking products and
suppresses subsequent isomerization resulting in high yields of linear
alkanes. The selectivity for linear alkanes from hydrocracking of
n-hexadecane over Pt/MFI nanosheets reaches 80% at 80% conversion.
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