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ΔHR1;298 K ¼ — 1240 kJ=mol ð1Þ
are bulk catalysts typically made by pressing the active powder
into a pellet with the desired dimensions (Cavani et al., 2006). The
resulting catalyst pellets therefore have a bimodal pore structure,
i.e. the micro-porous structure from the chemical synthesis of the active powder and the macro-porous region between the powder formed by the pelleting process. Due to diffusion limitation, the global reaction rate of the catalyst pellet in the reactor can be different from the intrinsic reaction rate measured for the active powder (Sharma et al., 1991). Hence, the real performance of the VPP catalyst pellet in a technical fixed-bed reactor is an overall
ΔHR1;298 K ¼ — 2092 kJ=mol ð2Þ
C H O 2O ½r3 ]2CO 2CO H O
ΔHR1;298 K ¼ — 852 kJ=mol ð3Þ
The intrinsic rate expressions and kinetic parameters were taken from Guettel and Turek (2010), and the parameters are given in Table 1:
. Ea;j.
result of the chemistry nature of the active component and the pore structure of the pellet. Most of current research on n-butane oxidation focusses on improving the catalytic chemistry of the VPP
catalyst (Benziger et al., 1997; Centi, 1993; Trifirò and Grasselli,
2014). New synthesis methods are continuously proposed to
increase the intrinsic activity of the VPP precursors (Glaum et al.,
2012; Hutchings, 2004). To the best of our knowledge, the pore structure optimization of the VPP catalyst for n-butane oxidation is not explored yet.
r2 ¼
k2pC4 H10 pO
1 þK1pC4 H10 þ K2pH2 O
k3pC H O p0:25
ð6Þ
Early studies have shown that an optimal pore structure of the
catalyst pellet can be of great importance (Keil, 1999; Wei, 2011;
4 2 3 O2
3 ¼
þ 1 C4 H10 þ 2 H2 O
ð7Þ
Coppens et al., 2001). With the development of experimental techniques, rational design and synthesis of catalyst pellets with desired pore structure for better performance is nowadays possi-
Since the aim of the present paper is to investigate the effect of the pore structure of the catalyst pellet on the reactor perfor- mance, the above-mentioned reaction rates rj which are in units of
ble (Liu et al., 2013; Luss, 1990). The effect of the pore structure
parameters of the VPP catalyst pellet on the reactor performance
mol=ðkg
cat
U sÞ were converted to the surface area based reaction
rate rj;s which is in units of mol=ðm2 U sÞ with assumed active
for n-butane oxidation in a fixed-bed reactor is investigated in this work by means of detailed mathematical modelling. If the overall yield of maleic anhydride can be improved by 1% with altering the catalyst pore structure, this may open up a new direction for
surface per catalyst mass Sg