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membrane reactor units are the effective configuration for MDA process upgradation. Multiple fixed-bed reactors in parallel series can be another configuration in
which some zones can be used for catalyst regeneration under the flow of
oxygenates/H 2 .
1.5.1 Circulating Fluidized-Bed Reactor Setup
In terms of heat dissipation, catalyst regeneration, uniform temperature, etc., fluidized bed unit is advantageous in comparison to fixed-bed unit. Due to these positive
factors, MDA reaction can be studied using bubbling and circulating fluidized bed
reactors. In 2009, a comparative study of fixed and fluidized bed reactor for MDA
reaction has been performed using Mo/HZSM-5 catalyst and higher yield of benzene is claimed with fluidized bed unit having severe coke deposition [64]. Quartz
fluidized bed reactor has been reported for methane conversion into aromatic hydrocarbons under non-oxidative conditions by Wei and co-workers [65]. Similar results
as observed in fixed-bed reactor have been claimed in the experimental studies highlighting the role of temperature, space velocity and partial pressure. Concept of
circulating fluidized bed reactor for continuous periodic operation in case where
high catalyst deactivation rate occurs has been proposed in previous reports [66].
This provides effective design for continuous periodic operations with proper heat
transfer management resolving hot spot limitations as observed in fixed-bed unit.
The schematic of two-bed type of circulating fluidized bed reactor has been shown
in Fig. 10.
Figure 10 depicts the schematic design of circulating fluidized bed reactor unit in
which methane to aromatic conversion reaction occurs in reactor unit having fresh
Mo/Zeolite catalyst whereas regeneration unit is used to remove coke deposits over
spent Mo/Zeolite catalyst using oxidants such as O 2 and H 2 . Simultaneously, regenerated catalyst is circulated from regeneration unit to reactor unit for continuous
operation and high catalytic activity. This reactor configuration can be effective for
methane dehydroaromatization process at the industrial level.
In another configuration of reactor design, Menndez et al. in 2010 have proposed
a two-zone fluidized bed reactor in view of resolving the fast catalyst deactivation
issues [67]. In the reactor design, two different zones of reaction and catalyst regeneration are created making fluid bed by feeding reactant methane at an intermediate
stage and oxidant inlets from the bottom of the reactor respectively. Authors have
achieved 8% methane conversion with more than 90% aromatic selectivity at 700 °C
using 6%Mo/HZSM-5 catalyst and 1% CO 2 regenerating oxidant.
1.5.2 Membrane Reactor
As per thermodynamic studies (Sect. 1.1.2), in situ removal of hydrogen from the
MDA reaction mixture shifts the chemical equilibrium towards the desired benzene
product. This can be achieved with a suitable membrane-type reactor that has a
S. Mishra et al.
membrane reactor units are the effective configuration for MDA process upgradation. Multiple fixed-bed reactors in parallel series can be another configuration in
which some zones can be used for catalyst regeneration under the flow of
oxygenates/H 2 .
1.5.1 Circulating Fluidized-Bed Reactor Setup
In terms of heat dissipation, catalyst regeneration, uniform temperature, etc., fluidized bed unit is advantageous in comparison to fixed-bed unit. Due to these positive
factors, MDA reaction can be studied using bubbling and circulating fluidized bed
reactors. In 2009, a comparative study of fixed and fluidized bed reactor for MDA
reaction has been performed using Mo/HZSM-5 catalyst and higher yield of benzene is claimed with fluidized bed unit having severe coke deposition [64]. Quartz
fluidized bed reactor has been reported for methane conversion into aromatic hydrocarbons under non-oxidative conditions by Wei and co-workers [65]. Similar results
as observed in fixed-bed reactor have been claimed in the experimental studies highlighting the role of temperature, space velocity and partial pressure. Concept of
circulating fluidized bed reactor for continuous periodic operation in case where
high catalyst deactivation rate occurs has been proposed in previous reports [66].
This provides effective design for continuous periodic operations with proper heat
transfer management resolving hot spot limitations as observed in fixed-bed unit.
The schematic of two-bed type of circulating fluidized bed reactor has been shown
in Fig. 10.
Figure 10 depicts the schematic design of circulating fluidized bed reactor unit in
which methane to aromatic conversion reaction occurs in reactor unit having fresh
Mo/Zeolite catalyst whereas regeneration unit is used to remove coke deposits over
spent Mo/Zeolite catalyst using oxidants such as O 2 and H 2 . Simultaneously, regenerated catalyst is circulated from regeneration unit to reactor unit for continuous
operation and high catalytic activity. This reactor configuration can be effective for
methane dehydroaromatization process at the industrial level.
In another configuration of reactor design, Menndez et al. in 2010 have proposed
a two-zone fluidized bed reactor in view of resolving the fast catalyst deactivation
issues [67]. In the reactor design, two different zones of reaction and catalyst regeneration are created making fluid bed by feeding reactant methane at an intermediate
stage and oxidant inlets from the bottom of the reactor respectively. Authors have
achieved 8% methane conversion with more than 90% aromatic selectivity at 700 °C
using 6%Mo/HZSM-5 catalyst and 1% CO 2 regenerating oxidant.
1.5.2 Membrane Reactor
As per thermodynamic studies (Sect. 1.1.2), in situ removal of hydrogen from the
MDA reaction mixture shifts the chemical equilibrium towards the desired benzene
product. This can be achieved with a suitable membrane-type reactor that has a
S. Mishra et al.