SECTION I. (b)
(2) Lurgi Gesellschaft fuer Waermetechnik. Lurgi had developed an iron catalyst which was supposed to yield a better (more olefinic) gasoline and would be more rugged than the cobalt type. They also ha developed a catalyst, which would be used in a once-through operation, for use in city gas plants to convert the CO in the coke oven gas to CH4 and hydrocarbons. This would detoxify the gas and at the same time enhance its heating value.
There actually was a unit of this type in construction (city gas plant at Leipzig), It was however of the cobalt type since the gas net of that city was operated at LP. The CO+H2 content of the feed gas was low and thus a very active catalyst was required but as complete conversion is not of great importance, a space velocity of approximately 200 at 250°-270° C was used.
For operation with their HP gas producer, Lurgi had used an iron detoxification (CO conversion) catalyst of the following compositions:
| Fe 100 pts. | Al2O3 9 pts. |
| Cu 10 pts. | Kieselguhr 120 pts. |
Lurgi proposed to use 2 types of iron catalysts. One was precipitated on silica and operated at low temperatures (230° C). This catalyst was designed to give a maximum of high boiling product through polymerization. Its composition was as follows:
|
Fe |
100 pts. |
|
Cu |
25 pts. |
|
Al |
9 pts. |
|
SiO2 |
20-30 pts. |
This catalyst is quite active as a cracking catalyst and hence must be run at low temperature
A condensed flow chart giving process data is attached to this report Lurgi drug: Ds am 103.
The second Fe catalyst was proposed for the production of the maximum amount of gasoline and olefins. The operation required for this catalyst is practically the same, except for the substantially higher temperature. The catalyst is very cheap, being made from Lauta-Masse is soaked with CuNo3, the copper is then precipitated with K2CO3 on the carrier and reduced in the conventional manner.
The operations proposed for wax production and for olefine production are compared in the table below: (See also reference I(c)5 at end of this section).
|
Basis: 1000 m3/hr. fresh feed gas/ 10 m3 catalyst volume: |
||
|
Wax Plant |
Gasoline Plant |
|
|
Catalyst |
Precipitated (Fe, Cu, Al) |
Lauta-masse (Cu impregnated) |
|
Pressure |
20 atm. |
20 atm. |
|
Temperature |
230° C |
275° C |
|
Processing |
2-stage “Kreislauf”in 1st stage only |
1-stage with “Kreislauf” |
|
“Kreislauf” gas volume |
2500 m3/hr. |
3000 m3/hr. |
|
Tailgas |
480 m3/hr. |
505 m3/hr. |
|
Fresh Feed |
Total Feed |
Tailgas |
Fresh Feed |
Total Feed |
Tailgas |
|
|
CO2 |
5.8 |
22.9 |
28.2 |
2.8 |
31.5 |
48.0 |
|
Cn Hm |
- |
1.4 |
1.9 |
- |
1.3 |
2.2 |
|
CO |
37.6 |
26.9 |
22.6 |
53.2 |
29.8 |
16.7 |
|
H2 |
48.1 |
31.8 |
17.0 |
35.6 |
19.8 |
11.3 |
|
CH4 |
0.1 |
2.0 |
2.7 |
0.1 |
3.5 |
5.3 |
|
N2 |
8.4 |
15.0 |
17.6 |
8.3 |
14.0 |
16.5 |
|
Yield/m3 ideal gas: |
||
|
FT liquid |
146 gm |
98 gm |
|
Gasol |
15 gm |
32 gm |
|
Alcohols |
9 gm |
5 gm |
|
Total |
170 gm |
135 gm |
|
Product distribution: |
|||
|
Gasoline 200° EP |
20% |
71% |
|
|
Kogasin 200-320° C |
20% |
20% |
|
|
Soft wax -320° C |
15% |
9% |
|
|
Hard wax 460° C |
45% |
||
|
Total Liquid |
100% |
100% |
|
|
Olefine Content: |
|||
| Gasoline |
60% |
71% |
|
| Kogasin |
45% |
60% |
|
These data are based on pilot plant runs and may be considered somewhat optimistic. Note that “Kreislauf” is employed in similar manner as for the MP cobalt operation. Since the catalyst consumes CO-H2 in the overall ratio of watergas, no intermediate H2 addition is required.
Note: That while over cobalt the recycle actually increases CO: H2 ratio it does not increases the CO2 content, since little CO2 is formed over cobalt. In the case of iron however, the use of recycle implies a very high concentration of CO2 in the feed of the first stage. Hence the shift reaction is impeded and the CO2 formation is accordingly suppressed.
It is not proposed to regenerate the Fe catalysts. Their life is expected to equal or exceed that of cobalt. The Fe catalysts, according to Lurgi, are just as sensitive to sulphur poisoning as cobalt. Once 3% S (wt. On Cat.) is absorbed, the catalyst has lost its activity. For a four month life the feed gas should not exceed 0.3gms/100 m3. Gum forming constituents in the synthesis gas, a frequent cause of trouble in FT units, are of course the same danger on Fe as on Co.
Oxygen up to 0.2% vol. In feed can be tolerated (possibly more; Lurgi have no data on this).
Nitrogen is considered a poison, as well as NH3, which should be removed.