Catalysts
The invention relates to improvements in the design of Fischer-Tropsch catalysts comprising a support and cobalt on the support. A first aspect is the modification of the silica support with at least 11 wt % titania to prevent the formation of cobalt silicates, thereby limiting the deactivation resulting from the silicate formation. A second aspect is the provision of C0 3 O 4 particles highly dispersed on the catalyst support with an average particle diameter of the cobalt oxide particle of less than 12 nm in order to improve catalytic activity and selectivity. A third aspect is the deposition of the catalyst precursor on the support by contact with a solution or suspension comprising the catalyst metal precursors and a carboxylic acid, preferably an alpha-hydroxy carboxylic acid in order to minimize the fracturing and fragmentation of the catalyst precursor during the following steps of drying and calcining, thereby preventing the formation of smaller catalyst particles, which should be removed by screening in order to limit pressure drop in the reactor.
1. A catalyst precursor comprising:
(i) a catalyst support comprising silica and at least 11 wt % TiO 2 ; and
(ii) cobalt on the catalyst support.
2. The catalyst precursor of claim 1 , wherein the catalyst support comprises 12-18 wt % TiO 2 .
3. The catalyst precursor of claim 2 , wherein the catalyst support comprises about 16 wt % TiO 2 .
4. The catalyst precursor of claim 1 , wherein the TiO 2 is amorphous.
5. The catalyst precursor of claim 1 , which is a Fischer-Tropsch catalyst precursor.
6. The catalyst precursor of claim 1 , comprising cobalt oxide on the catalyst support.
7. The catalyst precursor of claim 1 , wherein the surface acidity of the catalyst support is such that neutralization requires 0.2 μmol NH 3 /m 2 or more.
8. The catalyst precursor of claim 1 , having a catalyst support with a ratio of FT-IR band intensities at approx. 950:980 cm −1 of 1.2 or more.
9. The catalyst precursor of claim 1 , wherein the catalyst precursor comprises:
40-44 wt % Co, 0.1 to 0.3 wt % Re, and 0.01 to 0.05 wt % Pt (each expressed as a percentage of the total weight of the catalyst precursor); and
a TiO 2 -modified silica catalyst support, comprising 12-18 wt % TiO 2 (expressed as a percentage of the total weight of the catalyst support).
10. A catalyst which is an activated catalyst precursor of claim 1 .
11. A catalyst precursor comprising:
(i) a catalyst support; and
(ii) Co 3 O 4 on the catalyst support,
wherein the numerical average particle diameter of the Co 3 O 4 is less than 12 nm as determined by XRD.
12. The catalyst precursor of claim 11 , wherein the numerical average particle diameter of the Co 3 O 4 is less than 12 nm as determined by XRD and the c value of the lognormal particle size distribution is less than or equal to 0.31.
13. The catalyst precursor of claim 11 , wherein the average particle diameter of the Co 3 O 4 is between 8 and 10 nm.
14. The catalyst precursor of claim 13 , comprising:
a TiO 2 -modified silica catalyst support;
at least 40 wt % Co at least partially in the form of Co 3 O 4 , wherein the numerical average particle diameter of the Co 3 O 4 is 8 to 10 nm as determined by XRD; and
Pt and optionally Re as promoters;
wherein:
the mean particle size distribution of the support is between 180 and 300 μm;
the mean pore volume is less than 1 ml/g;
the mean pore diameter is less than 100 Å;
the FTIR spectra band at 950 cm −1 is 50%-200% of the intensity of the band at 970 cm −1 ; and
the catalyst precursor comprises a titania-cobalt spinel as indicated by Raman spectra.
15. The catalyst precursor of claim 13 , comprising:
a TiO 2 -modified silica catalyst support;
at least 40 wt % Co at least partially in the form of Co 3 O 4 , wherein the numerical average particle diameter of the Co 3 O 4 is 8 to 10 nm as determined by XRD; and
Pt and optionally Re as promoters;
wherein:
the mean particle size distribution of the support is between 180 and 300 μm;
the mean pore volume is less than 1 ml/g;
the mean pore diameter is less than 100 Å;
the FTIR spectra band at 950 cm-1 is 50%-200% of the intensity of the band at 980 cm-1; and
the catalyst precursor comprises Co 3 O 4 as indicated by Raman spectra.
16. The catalyst precursor of claim 13 , wherein the average particle diameter of the Co 3 O 4 is about 9 nm.
17. The catalyst precursor of claim 11 , wherein the c value of the lognormal particle size distribution is less than or equal to 0.31.
18. The catalyst precursor of claim 11 , wherein the c value of the lognormal particle size distribution is less than or equal to 0.25.
19. The catalyst precursor of claim 11 , wherein the c value of the lognormal particle size distribution is at least 0.19.
20. The catalyst precursor of claim 11 , wherein the catalyst support is a TiO 2 -modified silica support.
21. The catalyst precursor of claim 20 , wherein the TiO 2 is amorphous.
22. The catalyst precursor of claim 11 , wherein the catalyst support comprises silica and at least 11 wt % TiO 2 .
23. The catalyst precursor of claim 22 , wherein the catalyst support comprises 12-18 wt % TiO 2 .
24. The catalyst precursor of claim 23 , wherein the catalyst support comprises about 16 wt % TiO 2 .
25. A catalyst precursor comprising:
(i) a catalyst support; and
(ii) Co 3 O 4 on the catalyst support,
wherein:
(a) the numerical average particle diameter of the Co 3 O 4 is less than 12 nm as determined by XRD and the c value of a lognormal particle size distribution of Co 3 O 4 is less than or equal to 0.31; or
(b) the D-value of the lognormal particle size distribution is greater than or equal to 19.
26. The catalyst precursor of claim 25 , wherein the D-value of the lognormal particle size distribution is greater than or equal to 19.
27. The catalyst precursor of claim 26 , wherein the D-value of the lognormal particle size distribution is 21≦D≦23.