87
Methanol
This reaction combines to produce approximately 40% conversion of CO
to methanol. The gas mixture is cooled and methanol and water condense
out. The remaining gas is returned to the circulator, mixed with incoming
compressed synthesis gas and recycled through the methanol converter.
Hence, the overall reactions by which methanol are produced from synthesis
gas may be summarized into the following equation (http://nzic.org.nz 2009;
Olah, Goeppert, and Prakash 2006):
CO 2 + CO + 5H 2 → 2CH 3 OH + H 2 O + heat.
Synthesis gas is usually made from CH 4 or natural gas in a process called
CO 2 or dry reforming, because it does not involve steam. This reaction is
more endothermic (ΔH = 206 kJ/mol) than steam reforming with a reaction
enthalpy of ΔH = 246 kJ/mol (Bhattacharyya, Chang, and Schumacher 1998;
Olah, Goeppert, and Prakash 2006):
CH 4 + CO 2 ↔ 2CO + 2H 2
ΔH r = 246 kJ/mol.
Another way of making synthesis gas from natural gas is the direct oxidation of CH 4 . This reaction is exothermic and H 2 to CO ratio of the product
is more desirable (2:1) for downstream process (Bhattacharyya, Chang, and
Schumacher 1998):
CH 4 + ½ O 2 ↔ CO + 2H 2
ΔH r = –39 kJ/mol.
The production of methanol from coal is not that simple. Coal contains many
other compounds and impurities that would interfere with the methanol
synthesis process. Coal often contains such compounds as nitrogen, sulfur,
ash, oxygen, and water. Before coal can be gasified, it must first be dried.
Methanol production from coal involves several steps that are coal gasification, acid gas removal, WGS reaction, methanol synthesis, and methanol
refining.
The first step in the production of methanol is the gasification of coal to CO
and H 2 . The overall reaction for coal gasification is
C x H y + (x/2) O 2 x CO + (y/2) H 2 ,
with x and y depending on the actual coal composition. The main by-product
of coal gasification is acid gas, which is composed of hydrogen sulfide (H 2 S)
and CO 2 . The H 2 S needs to be removed from the synthesis gas.
Sulfur recovery can be applied via a method known as the Claus process;
products that result are either liquid or solid elemental sulfur, or sulfuric
acid. A modified Claus process involves a two-stage process. The first stage
involves the combustion of one-third the total H 2 S to form SO 2 and water; the
second is a low temperature catalytic stage that involves the reaction of SO 2
Methanol
This reaction combines to produce approximately 40% conversion of CO
to methanol. The gas mixture is cooled and methanol and water condense
out. The remaining gas is returned to the circulator, mixed with incoming
compressed synthesis gas and recycled through the methanol converter.
Hence, the overall reactions by which methanol are produced from synthesis
gas may be summarized into the following equation (http://nzic.org.nz 2009;
Olah, Goeppert, and Prakash 2006):
CO 2 + CO + 5H 2 → 2CH 3 OH + H 2 O + heat.
Synthesis gas is usually made from CH 4 or natural gas in a process called
CO 2 or dry reforming, because it does not involve steam. This reaction is
more endothermic (ΔH = 206 kJ/mol) than steam reforming with a reaction
enthalpy of ΔH = 246 kJ/mol (Bhattacharyya, Chang, and Schumacher 1998;
Olah, Goeppert, and Prakash 2006):
CH 4 + CO 2 ↔ 2CO + 2H 2
ΔH r = 246 kJ/mol.
Another way of making synthesis gas from natural gas is the direct oxidation of CH 4 . This reaction is exothermic and H 2 to CO ratio of the product
is more desirable (2:1) for downstream process (Bhattacharyya, Chang, and
Schumacher 1998):
CH 4 + ½ O 2 ↔ CO + 2H 2
ΔH r = –39 kJ/mol.
The production of methanol from coal is not that simple. Coal contains many
other compounds and impurities that would interfere with the methanol
synthesis process. Coal often contains such compounds as nitrogen, sulfur,
ash, oxygen, and water. Before coal can be gasified, it must first be dried.
Methanol production from coal involves several steps that are coal gasification, acid gas removal, WGS reaction, methanol synthesis, and methanol
refining.
The first step in the production of methanol is the gasification of coal to CO
and H 2 . The overall reaction for coal gasification is
C x H y + (x/2) O 2 x CO + (y/2) H 2 ,
with x and y depending on the actual coal composition. The main by-product
of coal gasification is acid gas, which is composed of hydrogen sulfide (H 2 S)
and CO 2 . The H 2 S needs to be removed from the synthesis gas.
Sulfur recovery can be applied via a method known as the Claus process;
products that result are either liquid or solid elemental sulfur, or sulfuric
acid. A modified Claus process involves a two-stage process. The first stage
involves the combustion of one-third the total H 2 S to form SO 2 and water; the
second is a low temperature catalytic stage that involves the reaction of SO 2