Velichkina.qxp 1/7/09 3:18 pm Page 45
Catalysts
Catalytic Activity in the Conversion of Platinum, Nickel, Iron and
Zinc Nanoparticles in Hydrocarbon Systems
a report by
Ludmila M Velichkina and AV Vosmerikov
Institute of Petroleum Chemistry, Siberian Branch, Russian Academy of Sciences
High-silica ZSM-5-type zeolites are effective catalysts for the The zeolite structure was determined and categorised with the
manufacturing of high-octane gasoline from various hydrocarbon ZSM-5 type by means of X-ray diffraction (XRD) on a Philips X’pert
feedstocks. The incorporation of metals in the zeolite framework diffractometer equipped with a graphite monochromator using CuK
α
makes it possible to prepare bi-functional catalysts that combine radiation (λ=0.154nm).
hydrogenation–dehydrogenation and carbocation rearrangement
functions. As a rule, the metal catalyses the first step and Brönsted The electronic state of the metal nanopowders on the zeolite surface
acid sites (zeolite hydroxyl groups) mediate the second step. was studied by means of ultraviolet (UV) spectroscopy on a Cary 300
Scan (Varian) spectrometer equipped with a diffuse-reflection
Platinum (Pt), nickel (Ni), iron (Fe) and zinc (Zn) are known as active attachment, as well as by X-ray photoelectron spectroscopy (XPS)
dehydrogenation agents and are conventionally used as promoting with a Riber-Cameka Mac-3 spectrometer using AlK
α
radiation
additives for catalysts in oil-refining processes. The high surface area (hν=1486.6eV). The activity of the obtained catalysts was tested
of the metal nanopowders used to modify zeolites necessitates an using a flow unit during the process of conversion of the straight-run
increased contribution of surface states and facilitates the gasoline fraction (initial boiling point [IBP] – 180°C) of oil having the
concentration of defects and energy density. As a result, the catalysts following composition (wt%): paraffins 73.1, naphthenes 14.8 and
should exhibit a specific reactivity. The introduction of metal ions into aromatic hydrocarbons 8.5. The octane rating was 55. The
the zeolite framework is accompanied by neutralisation of some of experiments were carried out at atmospheric pressure. The feed-
the protic (Brönsted) sites and the appearance of new Lewis acid space velocity was 2h
-1
. The temperature of the process was
sites. This extends the range of surface groups responsible mainly for 300–380°C. The products were determined with the use of
the aromatisation reaction. gas–liquid chromatography. The catalysts coked during the
upgrading of the petroleum straight-run gasoline fraction were
Thus, the distribution of metal and acid sites on the surface of the calcined at 550°C in air for seven hours.
catalyst affects its activity and selectivity in the hydrocarbon
conversion process. Information about the metal’s distribution over Results and Discussion
the zeolite surface and the nature and electronic state of the metal Modified metal-containing zeolite catalysts exhibit high activity in
facilitates prediction of the catalytic effect, making it possible to the isomerisation and aromatisation reactions of hydrocarbon,
prepare catalysts with anticipated properties. thereby resulting in the formation of high-octane gasoline
components. A change in the oxidation state of the modifying
This aim of this article is to study the catalytic activity of zeolites additives on the zeolite surface has a strong effect on the catalyst’s
modified by Pt, Ni, Fe and Zn nanopowders using both freshly activity and selectivity in the conversion of a hydrocarbon feedstock.
prepared catalyst samples and catalysts coked during the treatment The yield and the octane number (ON) of the liquid products, as well
of the petroleum straight-run gasoline fraction and then calcined as the concentrations of isoalkanes and arenes in the gasoline
in air. obtained on the freshly prepared Pt-, Ni-, Fe- and Zn-containing
zeolites, are given in Figure 1.
Materials and Methods
The high-silica ZSM-5 zeolite used in the study had a silica ratio of 60 A common property of all of these catalysts is a decrease in the yield
and was prepared via hydrothermal synthesis from alkaline of the liquid product as a result of the enhancement of the cracking
aluminosilica gel with hexamethylenediamine as an organic additive. reactions with an increase in the temperature of the process (see
The zeolite was converted into the active H-form via treatment with
a 25% ammonium chloride aqueous solution followed by drying at
Ludmila M Velichkina is a Senior Research Scientist
100°C and calcination in air at 550°C for six hours.
in the Laboratory of Catalytic Conversion of Light
Hydrocarbons at the Institute of Petroleum Chemistry,
Metal nanopowders with a prevalent particle size of 70nm were
Russian Academy of Sciences. Her research fields
include the synthesis of ZSM-5 zeolites and the
obtained by means of the wire explosion technique in argon. The
catalysts on their base, the development of methods
catalyst systems were prepared via the dry mechanical mixing of the
for the modification of the catalysts’ properties, non-
conventional methods of hydrocarbon refining and the
powdered zeolite and Pt, Ni, Fe and Zn nanopowders in a vibrating
investigation of the reactivity of metal nanopowders in
ball mill for two hours in air without subsequent calcination. The the reactions of light hydrocarbons conversion and in
amount of nanosized metal powder in the catalysts was 1.5wt%. All
organic synthesis.
of the samples were compacted and ground, and the 1–2mm fraction
E:
dmps@ipc.tsc.ru
was taken for testing.
© TOUCH BRIEFINGS 2009
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