HK111 Nhom 9 Xuc Tac Oxy Hoa Alkane

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

HK111 Nhom 9 Xuc Tac Oxy Hoa Alkane

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