452.    ---------------.[CHAFFEE, C. C., THOMPSON, O. F., KING, J. G., ATWELL, H. V., AND JONES, I. H.]  Metallgesellschaft-Lurgi.  Frankfurt am Main, Germany.  V. Fischer-Tropsch.  CIOS Rept. XXXI-23, 1945, pp. 6-18; TOM Reel 196; PB Rept. 12,624.

                 Research by the Lurgi organization has been concentrated on the development of a middle-pressure recycle operation, particularly with Fe catalysts.  This type of operation is claimed to have the following advantages:  use of a synthesis gas of CO:H₂ ratio 1:1; easier temperature control owing to high gas velocity through catalyst bed; increased olefin product; less C and CH₄ formed on the catalyst.  No commercial synthesis plants using an Fe catalyst have been built in Germany, but designs had been completed for erection of a plant in Italy.  Particular interest had been directed toward recycle operation of the Fischer-Tropsch process using the standard externally cooled middle-pressure reactor and a relatively low recycle ratio.  A pilot-plant unit, operating for 2 yr. with a Co catalyst and a single pass, gave a yield of 155-162 gm. of liquid plus gasol/m.³; increasing the recycle ratio to 3:1 increased the throughput by 30% without loss of yield or obtained a yield of 170 gm./m.³ at the same throughput.  With the active Fe catalyst (100 Fe, 25 Cu, 9 Al₂O₃, 2K₂O, 30 SiO₂) the yield was 170 gm./m.³ at the normal recycle ratio. The Fe catalyst was made by dissolving Cu and Al nitrates in 10% solution of ferric nitrate in amounts that would give the specified ratio of metals, heating nearly to boiling, adding enough 10% solution of Na₂CO₃ to precipitate the metals as hydroxides, adding kieselguhr, and washing the hot water to a pH of 8.0 and then with K₂CO₃ solution.  The nitrates must be removed completely in order to make reduction temperature control easy and positive.  After complete drying, the catalyst is reduced with H₂ at 250°-350° for 1-4 hr., the flow rate of H₂ being 1 m.³/kg. of catalyst/hr.  Reduction with synthesis gas is possible.  It is believed that the life of the catalyst would be about 1 yr.  The capital cost of a new plant is stated to be 800-900 RM./ton of liquid product/yr., although recently a quotation of 600 RM. was cited.  The operating cost is given as 24 pf./kg. of product, while the most favorable income is obtained by operating for the maximum yield of hard wax at 45 pf./kg.  Lurgi has built the charcoal-absorption units for nearly all of the Fischer-Tropsch plants in Germany.  Charcoal absorption is believed definitely more economical than oil absorption up to 10 atm. pressure, and the latter is preferable above 15 atm. with the choice between 10 and 15 atm., depending on local conditions.  A recent advance in charcoal absorption technique is the design of a plant to work at –50°, the objective being the separation of CH₄.  The costs are said to be slightly less than those for refrigeration.