Preparing phosphorus containing alumina support by sol-gel method for fischer-tropsch synthesis and catalyst preparation thereof
The present invention relates to a process of preparing of a phosphorus-containing phosphorus-alumina support by a sol-gel method and a cobalt/phosphorus-alumina catalyst where cobalt is supported onto the phosphorus-alumina support as an active ingredient. The phosphorus-alumina support is prepared by a sol-gel method and has wide specific surface area with bimodal pore size distribution and high cobalt dispersion, thereby enabling to increase heat and mass transfer, stabilize the structure by modifying the surface property of alumina and decrease the deactivation rate due to the reduced oxidation of cobalt component during the F-T reaction. When Fischer-Tropsch reaction (F-T) is conducted on the catalyst, the catalyst maintains a superior thermal stability, inhibits the deactivation due to water generation during the F-T reaction and also causes relatively high conversion of carbon monoxide and stable selectivity of liquid hydrocarbons.
1. A cobalt-based catalyst for Fischer-Tropsch (F-T) synthesis, in which cobalt is supported on a phosphorus-alumina support, the catalyst made by:
preparing an aluminum alkoxide solution by mixing an aluminum alkoxide in an alcohol-based organic solvent;
preparing a phosphorus-containing boehmite sol by mixing 0.01-1 moles of an organic carboxylic acid with pKa of 3.5-5 and 2-12 moles of water relative to one mole of the aluminum alkoxide in the aluminum alkoxide solution relative to one mole of the aluminum and adding 0.001-0.4 moles of a phosphorus precursor, followed by heating the solution at 80-130° C.;
preparing a powdery phosphorus-containing boehmite by distilling and drying the phosphorus-containing boehmite sol to separate and recover alcohol;
preparing a phosphorus-alumina support by calcining the powdery boehmite at 300-800° C.; the phosphorus-alumina support having bimodal pore size distribution including smaller pores and larger pores; and
adding cobalt precursor solution to the phosphorus-alumina support to make the cobalt-based catalyst with 5-40 wt % of cobalt content;
wherein the phosphorus-alumina support has a specific surface area of 300-500 m 2 /g and an area ratio [SA 1 /SA 2 ] of 5-10, wherein the SA 1 is a specific surface area of the smaller pores and the SA 2 , is a specific surface area of the larger pores, the smaller pores being 1-20 nm and the larger pores being 21-200 nm.
2. The cobalt-based catalyst according to claim 1 , wherein the catalyst is made by:
selecting an organic carboxylic acid having a pKa of 3.5-5 from the group consisting of formic acid, acetic acid, propionic acid, and mixtures thereof;
preparing a phosphorus-containing boehmite sol by mixing 0.01-1 moles of the selected organic carboxylic acid and 2-12 moles of water relative to one mole of the aluminum alkoxide in the aluminum alkoxide solution relative to one mole of the aluminum in a mixture;
adding 0.001-0.4 moles of a phosphorus precursor to the mixture; and
heating the mixture at 80-130° C.