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Water for Energy and Fuel Production
of hydrogen and methane as functions of reactor operating conditions and the possibility of autothermal operation by simultaneously carrying out partial oxidation
reaction with reforming reaction. The process handled fuel with sulfur. The results
were obtained at temperatures lower than conventional reforming temperature. The
autothermal operation was achieved by adding oxygen into the reacting mixture.
In a noncatalytic operation, hydrogen production of 14% of theoretical maximum
was obtained. Cremers et al. (2012, pers. comm.) studied SCW reforming of logistic
diesel fuel at 550°C in the absence of a catalyst and obtained significant hydrogen
production.
Veriansyah et al. (2012, pers. comm.) examined reforming of gasoline in SCW.
They used methanol and isooctane (2,2,4-trimethylpentane) as model compounds
for gasoline for experimental and simulation studies. The study presented the following conclusions:
1. SCW reforming of hydrocarbons offers a possible way to convert hydrocarbons to hydrogen at a lower temperature. It does not require a steam reforming catalyst, although nickel in reactor wall can act as a catalyst. It avoids
the poisoning and deactivation problems associated with the catalyst.
2. The reactor is much compact compared to conventional steam reforming
reactors. It is scalable and the reaction time is in seconds. SCW provides
dual functions—excellent reactant and homogeneous medium.
3. As reaction temperature, initial feed concentration, and residence time
increase, hydrogen, carbon dioxide, and methane productions increase
while carbon monoxide and ethane yields remain stable. At high temperature, methane yield is higher than hydrogen yield because at high temperature methanation reaction is favored. In order to increase the hydrogen
yield, methanation reaction needs to be suppressed. High inlet feed temperature decreases yields of hydrogen, carbon monoxide, and carbon dioxide
and increases the yields of methane and ethane. High inlet temperature also
forms coke in the feed line, which may plug the inlet pipes.
Numerous other studies have also examined catalytic reforming of various hydrocarbons in SCW [122,156,162,163,171,172] (Barendregt 2012, pers. comm.). Shekhawat
et al. [171] studied catalytic reforming of liquid hydrocarbon fuels for fuel cell applications. They concluded that supercritical reforming of hydrocarbons occurs at lower
temperatures than those required in conventional industrial reforming process. They
also showed that hydrogen yield increases by using commercial catalysts even if they
are not optimized for these conditions. Acetone and diesel fuel produced black liquor
and plugged the reactors. Pinkwart et al. [122] showed that under SCW, n-decane
can be converted to hydrogen-rich gas. They also showed that reforming of diesel oil
by four different commercial reforming catalysts can be carried out at a lower temperature than the conventional steam reforming process. The lower temperature also
caused lower production of coke during reforming reaction. Ramasamy and T-Raissi
[163] studied hydrogen production during reforming of lube oil in supercritical water.
They also examined the role of Ni, carbon, and alkali catalysts on the hydrogen production. Very little catalyst deactivation was observed under supercritical conditions.
Water for Energy and Fuel Production
of hydrogen and methane as functions of reactor operating conditions and the possibility of autothermal operation by simultaneously carrying out partial oxidation
reaction with reforming reaction. The process handled fuel with sulfur. The results
were obtained at temperatures lower than conventional reforming temperature. The
autothermal operation was achieved by adding oxygen into the reacting mixture.
In a noncatalytic operation, hydrogen production of 14% of theoretical maximum
was obtained. Cremers et al. (2012, pers. comm.) studied SCW reforming of logistic
diesel fuel at 550°C in the absence of a catalyst and obtained significant hydrogen
production.
Veriansyah et al. (2012, pers. comm.) examined reforming of gasoline in SCW.
They used methanol and isooctane (2,2,4-trimethylpentane) as model compounds
for gasoline for experimental and simulation studies. The study presented the following conclusions:
1. SCW reforming of hydrocarbons offers a possible way to convert hydrocarbons to hydrogen at a lower temperature. It does not require a steam reforming catalyst, although nickel in reactor wall can act as a catalyst. It avoids
the poisoning and deactivation problems associated with the catalyst.
2. The reactor is much compact compared to conventional steam reforming
reactors. It is scalable and the reaction time is in seconds. SCW provides
dual functions—excellent reactant and homogeneous medium.
3. As reaction temperature, initial feed concentration, and residence time
increase, hydrogen, carbon dioxide, and methane productions increase
while carbon monoxide and ethane yields remain stable. At high temperature, methane yield is higher than hydrogen yield because at high temperature methanation reaction is favored. In order to increase the hydrogen
yield, methanation reaction needs to be suppressed. High inlet feed temperature decreases yields of hydrogen, carbon monoxide, and carbon dioxide
and increases the yields of methane and ethane. High inlet temperature also
forms coke in the feed line, which may plug the inlet pipes.
Numerous other studies have also examined catalytic reforming of various hydrocarbons in SCW [122,156,162,163,171,172] (Barendregt 2012, pers. comm.). Shekhawat
et al. [171] studied catalytic reforming of liquid hydrocarbon fuels for fuel cell applications. They concluded that supercritical reforming of hydrocarbons occurs at lower
temperatures than those required in conventional industrial reforming process. They
also showed that hydrogen yield increases by using commercial catalysts even if they
are not optimized for these conditions. Acetone and diesel fuel produced black liquor
and plugged the reactors. Pinkwart et al. [122] showed that under SCW, n-decane
can be converted to hydrogen-rich gas. They also showed that reforming of diesel oil
by four different commercial reforming catalysts can be carried out at a lower temperature than the conventional steam reforming process. The lower temperature also
caused lower production of coke during reforming reaction. Ramasamy and T-Raissi
[163] studied hydrogen production during reforming of lube oil in supercritical water.
They also examined the role of Ni, carbon, and alkali catalysts on the hydrogen production. Very little catalyst deactivation was observed under supercritical conditions.