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 process for preparing a phosphorus-alumina support for Fischer-Tropsch (F-T) synthesis, the process comprising:
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; and
preparing a phosphorus-alumina support by calcining the powdery boehmite at 300-800° C.
2. The process according to claim 1 , wherein in the step of preparing an aluminum alkoxide solution the alcohol-based organic solvent is used in an amount of 5-200 moles relative to one mole of the aluminum alkoxide.
3. The process according to claim 1 , wherein in the step of preparing a phosphorus-containing boehmite sol the organic carboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, and mixtures thereof.
4. The process according to claim 1 , wherein in the step of preparing a phosphorus-containing boehmite sol the phosphorus precursor is selected from the group consisting of phosphoric acid (H 3 PO 4 ), phosphorus oxychloride (POCl 3 ), phosphorus pentoxide (P 2 O 5 ), phosphorus trichloride (PCl 3 ), and mixtures thereof.
5. The process according to claim 1 , further comprising adding a cobalt precursor to the phosphorus-alumina support in an amount sufficient to result in a cobalt-based catalyst having 5-40 wt % of cobalt.
6. The process according to claim 5 , wherein in the step of adding the cobalt precursor the cobalt precursor is selected from the group consisting of cobalt nitrate, cobalt acetate, cobalt chloride, and mixtures thereof.
7. A phosphorus-alumina support for Fischer-Tropsch (F-T) synthesis prepared according to the process of claim 1 ,
wherein the phosphorus-alumina support prepared has a biomodal pore size distribution including smaller pores of 1-20 nm and larger pores of 21-200 nm; and
wherein the phosphorus-alumina support prepared 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.
8. The phosphorus-alumina support according to claim 7 , further comprising 5-40 wt % of cobalt relative to the phosphorus-alumina support.