Methanol Synthesis Catalyst
1. Product features and scope of application
Methanol Synthesis Catalyst is widely applicable to methanol plants employing various technologies, including medium- or low-pressure processes such as Lurgi and ICI. Properties of the Methanol Synthesis catalyst were greatly enhanced after a remarkable improvement was made on its preparation technology. As the result, the catalyst is featured by higher activity, higher space-time yield and CO conversion, better thermal stability and tolerance to heat, longer service life, better selectivity, higher methanol concentration and less organic by-products in raw product, wide range of operation condition, ease in reduction and operation, higher strength and little pressure drop across the bed.
2. Composition and scope of application
Composition:
The catalyst is based on copper and zinc.
Physical properties
|
Appearance
|
black cylinders
|
Particle size
|
Φ5×4-5mm
|
|
Bulk density
|
1.1-1.4 kg/L
|
Chemical compostion
|
CuO-ZnO-Al2O3
|
3. Operation condition
|
Pressure
|
5-15MPa
|
|
GHSV
|
5000-20000 h-1
|
|
Temperature
|
210-280℃
|
|
CO at the inlet
|
3-15 % (vol)
|
|
CO2 at the inlet
|
3-5 % (vol)
|
|
Overall sulfides in feed gas
|
max0.1ppm
|
|
Overall chloride in feed gas
|
max0.1 ppm
|
|
Oxygen in feed gas
|
0.3％
|
4. Quality standard
Test condition: 5.0MPa, 230-250℃, GHSV 10000h-1, CO at the inlet 6-10%(vol), catalyst amount 3ml, catalyst size 20-40 mesh. Catalyst is reduced via TPR.
standard: space-time yield of raw methanol min1.0ml/ml·h, and min0.8ml/ml·h after being kept at 400℃ for 3～5h.
Side crushing strength(average) min200 N/cm
loss on attrition max7％
5. Loading
(1) Screen out any dust in the catalyst before loading.
(2) Drop and disperse the catalyst from lowest possible height into the reactor.
(3) Care must be taken not to drop the catalyst into clearance of the reactor, thermometer holder or the central tube.
(4) Close the reactor. Perform warming-up and reduction, otherwise seal the reactor tightly.
(5) Never do the loading in rainy day to avoid moisture invasion, which affects performance of the catalyst.
6. Reduction
The catalyst must be activated by reduction before use.
Main reduction reaction:
CuO+H2＝Cu+H2O △H°298=－86.6kJ/mol
The reaction is highly exothermal and the bed temperature rise is directly proportional to hydrogen concentration when hydrogen concentration is low, i.e., 1％H2 is equivalent to 28℃. To avoid bed temperature surge caused by violent reaction, which may result in sintering of catalyst and hence loss of activity, low-hydrogen is usually employed. The hydrogen is diluted by inert gases ( e. g., nitrogen, natural gas) to 1-2%. This method is featured by mild reduction condition, reliable operation, ease in control of bed temperature and being favorable to attaining high activity, maintaining the strength and prolonging the service life.
Water formed during reduction accounts for about 20% of the weight of the catalyst, of which 9-12％ is chemically resultant and 8～10% physically resultant.
The reduction procedure is shown in the following table.
Reduction procedure
|
phase
|
Time
(h)
|
total time (h)
|
temp range (℃)
|
Rate (℃/h)
|
Pressure (MPa)
|
GHSV (h－1)
|
Hydrogen (％)
|
|
warming-upⅠ
warming-upⅡ
|
3
|
3
|
-70
|
15
|
2.0
|
3000
|
－
|
|
10
|
13
|
70-130
|
6
|
2.0
|
3000
|
－
|
|
Reduction early stage
|
10
|
23
|
130-160
|
3
|
2.0
|
3000
|
<0.5
|
|
Reduction Ⅰ
main stage Ⅱ
|
15
|
38
|
160-180
|
<2
|
2.0
|
3000
|
≤1.0
|
|
25
|
63
|
180-210
|
<2
|
2.0
|
3000
|
≤1.0
|
|
Reduction Ⅰ
later stage Ⅱ
|
10
|
73
|
210-230
|
2
|
2.0
|
3000
|
≤1.5
|
|
2
|
75
|
230
|
－
|
2.0
|
3000
|
≤5
|
|
low load operation
|
|
48
|
230
|
|
5.0
|
syngas
|
|
Tips:
3L: Low-temperature expel of water, low-temperature reduction and low-load operation after reduction
3S: Stable warming-up, stable hydrogen supplement, stable water emission
3N: No simultaneous increase in temperature and hydrogen, no carryover of water into the reactor, no long-term water emission at high temperature
3C: Controlled hydrogen supplement, controlled bed temperature, controlled water emission amount
7. Start-up, shutdown and operation control
Start-up:
The catalyst that has been reduced for the first time must undergo 48h of half-load operation before shifting to full-load normal operation.
Tips：
(1) Total sulfur and total chlorine in the feed gas must be up to the process requirement before passing the feed gas.
(2) Oxygen in the feed gas should be less than 0.3％.
(3) The catalyst bed temperature must be over 210℃ before passing the feed gas.
Temporary shutdown:
(1) Stop the feed gas compressor while the recycle gas compressor keeps working. Thus carbon oxides in the recycle gas continue with their reaction until their concentration keeps going down that finally there is only hydrogen and inert gases in the system.
(2)Start the electric heater and decrease recycle amount when the bed temperature begins to drop, thus maintaining the temperature at over 210℃.
(3)Decrease the pressure to 0.7-0.8MPa and maintain the bed temperature at 150℃ after carbon oxides in the system have been basically consumed.
(4) If high-purity hydrogen, nitrogen or hydrogen-nitrogen( or other inert gases) are available, purge the system with one of these gases until CO+CO2 in the system is below 0.5％. Maintain the system at positive pressure with the gas.
Long-term shutdown
(1) Stop the feed gas compressor while the recycle gas compressor keeps working. Thus carbon oxides in the recycle gas continue with their reaction until their concentration keeps going down that finally there is only hydrogen and inert gases in the system.
(2) Decrease recycle gas and pressure. Cool down the bed at no greater than 50℃/h.
(3) Purge the system with nitrogen until hydrogen concentration is below 1％.
(4) Stop recycle compressor and maintain the system at positive pressure with nitrogen.
Restart after shutdown:
Warm up with hydrogen or hydrogen-nitrogen ( or inert gas) and pass feed gas when temperature is higher than 210℃. Passing the feed gas below 210℃may cause paraffin formation, which lowers activity of the catalyst.
Unloading:
The catalyst must be passivated before unloading and kept away from combustible substance to avoid fire disaster.
8. Package and storage
The catalyst is packed in iron barrels lined inside with plastic bags. It should be stored in dry and well-ventilated place. The catalyst can usually be stored for several years without remarkable deterioration in its properties.
Leave a message for product