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PROCESS & TECHNOLOGY FOR METHANOL AND DME

low-temperature shift (LTS) reactor. Due to the different reaction conditions, different catalysts
must be employed at each stage to ensure optimal activity.

The typical composition of commercial HTS catalyst has been reported as 74.2% Fe O , 10.0%
2
3
Cr O , and 0.2% MgO. The chromium acts to stabilize the iron oxide and prevents sintering.
3
2
The operation of HTS catalysts occurs within the temperature range of 310 to 450 C. The
0
temperature increases along the length of the reactor due to the exothermic nature of the
reaction. As such, the inlet temperature is maintained at a level to prevent the exit temperature
0
from exceeding 550 C. Industrial reactors operate at a range from atmospheric pressure
to 8 MPa. While both the HTS and LTS catalysts are commercially available, their specific
composition varies based on vendor. [139] Depending upon the composition of feed syngas
and the target hydrogen to carbon monoxide ratio, the catalyst and operating conditions are
chosen.
The typical composition of commercial LTS catalyst has been reported as 32 -33% CuO, 34-
53% and ZnO, 15-33% Al O . The active catalytic species is CuO. The function of ZnO is to
3
2
provide structural support as well as to prevent the poisoning of copper by sulfur. The Al O
2
3
prevents dispersion and pellet shrinkage. The LTS shift reactor operates at a range of 200 to
250 C. Low reaction temperatures must be maintained to prevent the copper from thermal
0
sintering. The lower temperatures also reduce the occurrence of side reactions. Noble metals
such as Pt supported on Ceria have been reported for LTS.
2.2 CONVERSION OF SYNGAS TO METHANOL/DME

The syngas is the building Block for FT Diesel, methanol and other hydrocarbons such as
olefins, DME, and other alcohols and aldehydes. The different products from syngas with and
without going via methanol are shown in Fig. 5.
While FT diesel production process from syngas can handle a wide range of hydrogen to
carbon monoxide ratio, for methanol production this ratio has to be more than 2. The typical
operating conditions for FT Diesel are 150 to 300 C, in presence of Cobalt or Iron based
0
catalyst in fixed bed or slurry reactors. A wide range of products from jet fuel to waxes and
lubricants may be produced with proper catalyst design and operating conditions [18].

2.2.1

MANUFACTURE OF METHANOL

With regard to methanol there are several options. Syngas conversion to methanol as
intermediate for other chemicals is well established technology. However, with the recent
trends to use methanol as gasoline and DME, coupled with the recent interest in producing
olefins as well as synthetic gasoline, it has become important to use the syngas to directly
convert to the desired product without going via methanol.
Once the synthesis gas of the correct composition is manufactured, methanol is produced
by high pressure reaction over catalyst in fixed bed. The pressure for the older generation
catalyst and process was close to 100 bar. The conversion and selectivity are high. The natural
gas reforming process results in a considerable hydrogen surplus in syngas. If an external
source of CO is available, the excess hydrogen can be consumed and converted to additional
2
methanol.
The main reaction which governs the formation of methanol from syngas is as below:

40 Methanol and DME Production: Survey and Roadmap | 2017