The catalytic oxidation of n-butane to maleic anhydride using a membrane reactor

Andaka, G

Abstract

Catalytic oxidation of n-butane is important in an attempt towards developing
economical and environmentally friendly processes for production of maleic
anhydride.
Methods of preparation of both the vanadium-phosphorus-oxides (VPO) catalyst and
an inorganic composite membrane as well as the performance of the membrane
obtained have been investigated in this work. The procedure used in the preparation of
vanadium-phosphorus-oxides (VPO) catalyst was similar to that described by
Katsumoto and Marquis (1979), while a dip coating method was used for preparation
of a silica coated y-A^Os membrane from the outside, and the membrane prepared
then was tested for permeance using nitrogen and air.
The kinetics of the selective oxidation of n-butane to maleic anhydride has been
studied over vanadium-phosphorus-oxides (VPO) catalyst in a differential glass reactor
in the temperature range of 380 - 480°C and at atmospheric pressure. Apart from
maleic anhydride (MA), the other detectable products were carbon monoxide (CO),
carbon dioxide (CO2), and air (HhO). Kinetic measurements demonstrated the
production of maleic anhydride, carbon monoxide, and carbon dioxide as initial
products of the reaction at low n-butane conversion. Under conditions of a large excess
of oxygen, the reaction model was represented according to a scheme of three parallel
formation reactions. The activation energies for maleic anhydride (MA), carbon
monoxide (CO), and carbon dioxide (CO2) production are 61.1 kJ/gmol, 56.1 kJ/gmol, and 70.9 kJ/gmol, respectively. These values of the activation energies are in the same
range as those obtained from previous differential reactor studies.
The oxidation of n-butane to maleic anhydride also has been compared by using fixedbed
and membrane reactors with the same VPO catalyst. The effects of operating
conditions on the conversion of n-butane, the selectivity to maleic anhydride, and the
yield of maleic anhydride have been studied in detail. A simulation study on the use of
fixed-bed and membrane reactors for oxidation of n-butane to maleic anhydride has
also been undertaken. The results of a mathematical simulation study were compared
with the experimental results.
The membrane reactor offers several advantages over the fixed-bed reactor for
selective oxidation of n-butane to maleic anhydride. The membrane reactor provides a
wider operating range particularly with respect to inlet gas composition. Furthermore,
they are inherently safer since n-butane and oxygen feeds can be separated by the
membrane. The higher butane concentrations and controlled addition of oxygen along
the reactor length by means of a membrane lead to higher product rates. A comparative
study of butane oxidation to maleic anhydride in conventional fixed-bed and a
membrane reactor show that using a membrane reactor gives a better selectivity and
yield of maleic anhydride than the conventional fixed-bed reactor.
From the simulation study, the mathematical models for both the fixed-bed and
membrane reactors are in good agreement with the experimental results, except for the
mathematical model for the fixed-bed reactor when considering the variation of the
oxygen/n-butane ratio.
For the membrane reactor, both feed n-butane concentration and oxygen/butane ratio
are shown to be not sensitive parameters for the mathematical model, while
temperature is a key parameter.

Citation

Andaka, G. The catalytic oxidation of n-butane to maleic anhydride using a membrane reactor. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Additional Information: Access Information : At the author’s request this item is not available. You may be able to access the hard copy by visiting the University of Salford Library.
• Award Date: Jan 1, 2004