This invention is directed at a Fischer-Tropsch process for hydrocarbon production. More specifically, the present invention is directed at a multi-catalyst Fischer-Tropsch process in which CO and hydrogen are contacted by a first catalyst having high olefin selectivities. The resulting olefin, additional CO and hydrogen are contacted with a second catalyst which converts olefins, CO and hydrogen into higher molecular weight products.
Fischer-Tropsch type processes are well known for the production of hydrocarbons from carbon monoxide and hydrogen in the presence of certain catalysts under specific reaction conditions. The specific hydrocarbons produced are dependent on the catalyst utilized and the reaction conditions. The reaction of carbon monoxide and hydrogen to produce hydrocarbons is exothermic. Frequently, it is necessary to maintain the reaction temperature within relatively narrow limits to produce the desired products with a minimum of undesired by-products, such as methane.
In addition, the reactors used for Fischer-Tropsch synthesis typically are relatively large and have relatively low through-put per unit volume. To minimize the production of methane catalysts having relatively low reactivities usually are employed. In addition, the operating conditions in the reactor usually are closely regulated.
U.S. Pat. No. 2,450,500 discloses a multistage Fischer-Tropsch catalyst process utilizing a plurality of reaction zones and different catalysts in which the exothermic heat is utilized to increase the temperature of the flowing gases and of the catalyst in the direction of the flow. Each successive catalyst has a higher optimum reaction temperature than the preceding catalyst. However, the catalysts disclosed are not particularly well-suited for the manufacture of relatively high molecular weight compounds, such as paraffinic compounds having molecular weights in the 72 to 14,000 range.
Therefore, it would be desirable to utilize a process which was operable at relatively high space velocities.
It also would be advantageous to utilize a process which produced relatively large quantities of paraffinic hydrocarbons in the C.sub.5 to C.sub.100 range, while producing relatively low quantities of low molecular weight compounds, such as methane.
It also would be desirable to utilize a process in which accurate temperature control of the system was not critical.
The present invention is directed at a multi-catalyst system in which a first catalyst is utilized to convert hydrogen and carbon monoxide into olefinic compounds and in which a second catalyst is utilized to convert the resulting olefin, and additional quantities of carbon monoxide and hydrogen, into paraffinic compounds.