Future Fuels
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synthesis gas. DME (CH3–O–CH3) is an LPG-like synthetic fuel that is produced through gasification of various renewable substances or fossil fuels.
The synthetic gas is then catalyzed to produce DME in a single step at lower
costs. The optimum H 2 /CO ratio for DME synthesis is lower than that for
methanol and ideally should be around one. The synthesis of DME from
producer gas/syngas is a highly exothermic reaction. DME can be produced
as a single product or in combination with methanol.
13.5.4.1 DME from Methanol
Single step DME process possesses both methanol synthesis and methanol
dehydration activity. There are two types of catalyst systems, namely, dual
catalyst systems and single catalyst systems. In dual catalyst systems, the
catalyst is a mixture of methanol synthesis and a dehydration catalyst. In
general, methanol catalysts are copper based and dehydration catalysts are
from solid acid materials such as zeolites and ɣ-alumina. The catalyst used
in the reactors may be arranged in mixed forms, one layer or in several layers. In single catalyst systems, the two functions can be achieved by the precipitated methanol synthesis components onto high surface area solid acid
materials. The DME production process occurs either in a gaseous phase in
a fixed bed reactor or a liquid phase in a slurry bed reactor.
DME production through methanol dehydration involves the following
main reactions:
Water–gas shift:
CO + H 2 O CO 2 + H 2
ΔH r = –40.9 kJ/mol.
Methanol synthesis (Zeolite):
CO + 2H 2 CH 3 OH
ΔH r = –90.7 kJ/mol
2CH 3 OH CH 3 OCH 3 + H 2 O
ΔH r = –23.4 kJ/mol.
Net reaction:
3H 2 + 3CO CH 3 OCH 3 + CO 2
ΔH r = –245.3 kJ/mol.
This methanol dehydration is exothermic and compares with methanol synthesis. The vaporized methanol is fed into the reactor. The synthesis pressure ranges from 10 to 20 bar and reactor inlet temperatures 220–250°C and
the outlet temperature is 300–350°C. The conversion efficiency of 70–85%
could be achieved. The unconverted methanol and produced water are
separated at the bottom and the methanol is returned back to the reactor
after purification. The DME is collected at the top of the reactor. For the
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synthesis gas. DME (CH3–O–CH3) is an LPG-like synthetic fuel that is produced through gasification of various renewable substances or fossil fuels.
The synthetic gas is then catalyzed to produce DME in a single step at lower
costs. The optimum H 2 /CO ratio for DME synthesis is lower than that for
methanol and ideally should be around one. The synthesis of DME from
producer gas/syngas is a highly exothermic reaction. DME can be produced
as a single product or in combination with methanol.
13.5.4.1 DME from Methanol
Single step DME process possesses both methanol synthesis and methanol
dehydration activity. There are two types of catalyst systems, namely, dual
catalyst systems and single catalyst systems. In dual catalyst systems, the
catalyst is a mixture of methanol synthesis and a dehydration catalyst. In
general, methanol catalysts are copper based and dehydration catalysts are
from solid acid materials such as zeolites and ɣ-alumina. The catalyst used
in the reactors may be arranged in mixed forms, one layer or in several layers. In single catalyst systems, the two functions can be achieved by the precipitated methanol synthesis components onto high surface area solid acid
materials. The DME production process occurs either in a gaseous phase in
a fixed bed reactor or a liquid phase in a slurry bed reactor.
DME production through methanol dehydration involves the following
main reactions:
Water–gas shift:
CO + H 2 O CO 2 + H 2
ΔH r = –40.9 kJ/mol.
Methanol synthesis (Zeolite):
CO + 2H 2 CH 3 OH
ΔH r = –90.7 kJ/mol
2CH 3 OH CH 3 OCH 3 + H 2 O
ΔH r = –23.4 kJ/mol.
Net reaction:
3H 2 + 3CO CH 3 OCH 3 + CO 2
ΔH r = –245.3 kJ/mol.
This methanol dehydration is exothermic and compares with methanol synthesis. The vaporized methanol is fed into the reactor. The synthesis pressure ranges from 10 to 20 bar and reactor inlet temperatures 220–250°C and
the outlet temperature is 300–350°C. The conversion efficiency of 70–85%
could be achieved. The unconverted methanol and produced water are
separated at the bottom and the methanol is returned back to the reactor
after purification. The DME is collected at the top of the reactor. For the