High Temperature Shift Catalyst Reduction Procedure The catalyst, as supplied, is Fe2O3. This reduces to the active form, Fe3O4, in the presence of hydrogen when process gas is admitted to the reactor. 1. The mildly exothermic reactions are: 3 Fe2O3 + H2 ========= 2 Fe3O4 + H2O 3 Fe2O3 + CO ========= 2 Fe3O4 + CO2

1. GBH Enterprises, Ltd.
VULCAN VSG-F101
High Temperature Shift Catalyst
Reduction Procedure
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2. REDUCTION AND OPERATION OF VULCAN VSG-F101
The catalyst, as supplied, is Fe2O3. This reduces to the active form, Fe3O4, in the
presence of hydrogen when process gas is admitted to the reactor.
1.
The mildly exothermic reactions are:
3 Fe2O3 + H2 ========= 2 Fe3O4 + H2O
3 Fe2O3 + CO ========= 2 Fe3O4 + CO2
2.
If steam is not present, reduction of Fe3O4 to metallic iron takes place:
Fe3O4 + 4 H2 ========= 3 Fe + 4 H2O (endothermic)
Fe3O4 + 4 CO ========= 3 Fe + 4 CO2 (slightly endothermic)
3.
Metallic iron must be avoided because it catalyses the following
very exothermic reactions:
CO + 3 H2 ========= CH4 + H2O
2 CO ========= CO2 + C
The reduction process is a fairly simple one:
1. Purge the reactor free of air with inert gas.
2.
If possible, heat the catalyst bed with dry gas until the process gas
condensation temperature is exceeded. Alternatively, heat the
catalyst with process gas and allow the effluent gas to go to the
vent. Pressurization to system pressure can be carried out at any
time during the reduction.
3.
Raise the catalyst temperature to 575oF at up to 100oF per hour.
Reduction begins around 300oF and is nearly complete at 575oF.
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3. 4.
The CO shift reaction will begin around 575oF and the observed
temperature rise will depend upon the inlet CO content and steamto-gas ratio. The inlet gas must contain less than 15% CO (wet
basis) because the maximum allowable temperature at this stage is
930oF.
The subsequent steps are only applicable for VULCAN Series VSG-F101
catalysts, which are low sulfur materials.
Raise the inlet temperature to ideally 750oF and hold for 1-2 hours. Reduce the
inlet temperature to the normal operating inlet, typically 680-700oF. The catalyst
is now fully activated and the process gas can now be passed forward to the next
process step.
OPERATION
In early life, the catalyst is usually operated in the inlet temperature range of 680700oF. The optimum should be determined on-line by increasing the inlet
temperature in steps of 10oF and measuring the exit CO content - after steady
conditions have been stabilized.
For extended catalyst lives, the HTS should be operated at the minimum
practical inlet temperature compatible with good CO conversion.
As the catalyst ages and performance deteriorates it may be advantageous to
elevate the operating temperature to minimize CO leakage.
Although HTS catalysts are quite strong, even in the reduced state, condensation
of steam-to-water on the catalyst should be prevented by keeping inlet process
gas temperature well above the dew point.
During short shutdowns, the catalyst may be left under process gas or steam at
either operating or lower pressures. It may even be steamed, if necessary, to
maintain operating temperatures.
It is important to ensure air does not enter the vessel when the plant is shut
down. Air re-oxidizes reduced catalyst causing an excessive temperature rise
and catalyst damage.
Typically H.T. Shift catalysts give lives of 4-5 years.
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4. POISONS
High temperature shift catalysts are not appreciably affected by those things that
act as poisons to the other catalysts in the system. Instead, loss of activity is
usually the result of deposition of boiler feed water solids and/or silica carry-over.
These block the catalyst pores and prevent the reactant gas from reaching the
catalytic sites. In extreme cases, the spaces between tablets in the upper part of
the bed become clogged causing pressure drop problems.
DISCHARGE
If the catalyst is to be discarded, it does not require a special oxidation procedure
before discharge. Once the vessel is depressured and purged free of process
gas with steam, it is cooled to about 400oF. From there, inert gas replaces steam
to cool the catalyst to the ambient temperature. A positive pressure of inert gas
is held on the reactor to prevent air from entering. The catalyst is either dumped
or vacuumed from the reactor. Water hoses should be available in case the
catalyst heats up when exposed to the air.
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Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance
Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts /
Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
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5. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown
Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass
Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance
Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts /
Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries
Web Site: www.GBHEnterprises.com