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8/2/2019 HK111 Nhom 9 Xuc Tac Oxy Hoa Alkane
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CONTENTINTRODUCTION
COMPOSITIONS ANDPREPARATIONS OF CATALYST
CONCLUTION
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INTRODUCTION The development around the
sixties of various processes
of selective oxidation of
alkanes has constituted a
significant breakthrough for
the large scale production of
chemicals and
intermediates.
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Today most of the monomers for the manufacture
of plastics and synthetic fibers are produced by selectivecatalytic oxidation of hydrocarbons and include large
volume products such as ethylene oxide, acrylonitrile,
vinyl chloride, maleic and phthalic anhydrides.
In addition, the world market for oxidation catalysts maybe estimated as around 200-250 million US dollars, about
half of which is in Europe.
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On the average, the costs for a chemical product producedby oxidation processes can be allocated as follows: 60% to
raw materials, 20% to capital costs, and 20% to othercosts such as labor, utilities, catalysts, etc. Therefore, alarger economic impact for chemical oxidation processesmay be realized by technologies using alternate, less-
expensive raw materials. The substitution of expensive alkenes or other
hydrocarbons (for example, aromatics) with a lessexpensive alkane feedstock can thus represent abreakthrough for the realization of shut-down economics
technologies able to reduce the transfer price of a productin a fully amortized plant as compared to the existingcompetitive technologies
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In most cases, in fact, the price of light (C2-C6) alkanes
is the same as that of fuel, due to the reduced numberof non-energy applications for these hydrocarbons.Furthermore, the functionalization of alkanes in thepresence of oxygen (oxyfunctionalization whichincludes oxidation, ammoxidation, oxidativedehydrogenation, oxychlorination and oxidativedimerization processes) in comparison to otherpossible competitive petrochemical processes ofalkane conversion is the more interesting process
option to obtain selectively high value chemicals.
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most cases, in fact, the price of light (C2-C6) alkanes isthe same as that of fuel, due to the reduced number ofnon-energy applications for these hydrocarbons.Furthermore, the functionalization of alkanes in thepresence of oxygen (oxyfunctionalization whichincludes oxidation, ammoxidation, oxidativedehydrogenation, oxychlorination and oxidativedimerization processes) in comparison to otherpossible competitive petrochemical processes of
alkane conversion is the more interesting processoption to obtain selectively high value chemicals.
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However, the possible utilization of alkane feedstocks for
selective oxidation reactions requires the discovery of a
selective catalyst for the reaction, a difficult task due to
the relative inertness of the alkane and the two-three order
of magnitude higher reactivity of possible products or
intermediates.
The control of the consecutive reactions up to carbon
oxides is thus very critical. The selective oxidation of
alkanes thus requires the development of novel concepts
and catalytic systems to fulfil the strict requirements of
controlled surface reactivity necessary for selective
behavior
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Introduction to propane oxidation catalyst
Compositions of catalysts
Catalyst preparation
Catalyst testing
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Compositions of catalysts particularly for a formulation containing the oxides of
Mo, V, Nb and W.
supported on a low-area alumina calcined at 1150C (-alumina)
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Catalyst preparationwet impregnation method
incipient wetness (or dry) impregnation method
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wet impregnation method the alumina support precursor (Alcan AA400) was firstcalcined at 1150C
a sample of 2g of this was then treated sequentially by
aqueous solutions of the salts of each metal After leaving the system to equilibrate in an excess of
solution overnight (about 15h), the samples were then driedusing a rotary evaporator at 80C and were then finallycalcined for 6h at 650C.
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calcining
mixture
drying
calcined
1150C
Al2O3
solutions of the saltsof each metal
15h
80C
6h
650C
Al2O3
catalyst
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wet impregnation method
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Catalyst testing The materials prepared were tested in a quartz microreactorusing 300mg of each sample (particle size 212-425m) diluted
with 100mg of quartz grains of the same size.
The WHSV (weight hourly space velocity) based on the weightof catalyst alone was 8000 ml g-1h-1
The catalytic experiments were carried out in the temperature
range from 400 to 650C.
The effluent from the reactor was analysed by a Varian 3400Gas Chromatograph.
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Figure 4 Results obtained with the catalysts of the F series