Cobalt-based single-atom dehydrogenation catalysts having improved thermal stability and method for producing olefins from corresponding paraffins by using the same

Patent metadata

Field	Value
Publication number	US-11766664-B2
Application number	US-202117358230-A
Country	US
Kind code	B2
Filing date	Jun 25, 2021
Priority date	Jun 25, 2020
Publication date	Sep 26, 2023
Grant date	Sep 26, 2023

Abstract

Disclosed herein are a dehydrogenation catalyst having single-atom cobalt loaded onto a silica support that has undergone pretreatment including a thermal treatment and a high-temperature aqueous treatment (reaction), a preparation method therefor, and a method for producing olefins by dehydrogenating corresponding paraffins, particularly light paraffins in the presence of the dehydrogenation catalyst.

First claim

What is claimed is:

1. A method for preparation of a single-atom cobalt-based catalyst, which comprises the steps of:
a) thermally treating silica as a support at a temperature ranging from 600 to 870° C. to induce shrinkage of the support, and simultaneously to remove its surface hydroxyl groups, followed by subjecting the shrunken support to a high-temperature aqueous treatment in a temperature range of 70 to 150° C. to afford a pretreated silica having hydroxyl groups selectively activated thereon;
b) preparing an aqueous dispersion of the pretreated silica;
c) preparing a pH-adjusted aqueous dispersion of the pretreated silica by adding a base to the aqueous dispersion of the pretreated silica to adjust the pH of the dispersion to at least 10;
d) separately preparing a pH-adjusted cobalt precursor aqueous solution by preparing an aqueous solution of a cobalt precursor having an oxidation number of 3+ and adding a base to the aqueous solution;
e) combining the pH-adjusted aqueous dispersion of the pretreated silica with the pH-adjusted aqueous solution of the cobalt precursor to afford an aqueous dispersion in which at least a part of the cobalt ions having an oxidation number of 3+ is adsorbed onto the surface of the pretreated silica;
f) removing cobalt ions which remain not adsorbed onto the pretreated silica; and
g) thermally treating the cobalt ion-adsorbed silica obtained in step f);
wherein cobalt having an oxidation number of 2+ exists in an isolated form of single-atom on the pretreated silica while being tetrahedrally coordinated at trihydroxyl groups present on the surface of the pretreated silica.

2. The method of claim 1 , wherein the thermally treated silica in step a) reduces in volume by 75% compared to the silica before the pretreatment, and the silica after the high-temperature aqueous treatment increases in volume by 5 to 50%, compared to the thermally treated silica.

3. The method of claim 1 , wherein the silica before the pretreatment of step a) is amorphous silica.

4. The method of claim 3 , wherein the silica before the pretreatment in step a) is in a particle form with a particle size of 0.5 to 5000 μm.

5. The method of claim 1 , wherein the silica in step a) contains hydroxyl groups at a concentration of 3 to 5 mmol/cc on the surface thereof before the thermal treatment and at a concentration of less than 0.2 mmol/cc on the surface thereof after the thermal treatment, and at a concentration of 3 to 5 mmol/cc on the surface thereof after the high-temperature aqueous treatment.

6. The method of claim 1 , wherein the pretreated silica has a cobalt ion immobilization capability of at least about 0.8% by weight.

7. The method of claim 1 , wherein the high-temperature aqueous treatment in step a) is conducted by the steps of:
dispersing the thermally treated silica in an aqueous medium to give a thermally treated silica-aqueous dispersion; and
boiling the thermally treated silica-aqueous dispersion at 70 to 150° C.

8. The method of claim 7 , wherein the thermally treated silica-aqueous dispersion contains silica at a content of 1 to 30% by weight.

9. The method of claim 1 , wherein the pretreated silica obtained in step a) ranges in particle size from 0.3 to 4000 μm.

10. The method of claim 1 , wherein the pretreated silica-containing aqueous dispersion prepared in step b) ranges in concentration from 1 to 30% by weight.

11. The method of claim 1 , wherein the base used in steps c) and d) are same or different and are each at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

12. The method of claim 1 , wherein the cobalt precursor in step d) contains a cobalt complex ion having an oxidation number of 3+(Co(III)), and the aqueous solution of a cobalt precursor contains the cobalt precursor at a concentration of 0.1 to 20% by weight.

13. The method of claim 12 , wherein the cobalt precursor is Co(NH 3 ) 6 Cl 3 , or contains a cobalt complex ion obtained by treating at least one cobalt compound selected from the group consisting of Co(NO 3 ) 2 , CoCl 2 , and Co(acac) 3 with ammonia water, followed by filtration.

14. The method of claim 1 , wherein the pH-adjusted aqueous solution of the cobalt precursor and the pH-adjusted aqueous dispersion of the pretreated silica in step e) are mixed at a ratio such that the amount of the cobalt precursor is at least 1% by weight, based on the pretreated silica.

15. The method of claim 1 , wherein the thermal treatment in step g) is conducted in an oxygen-containing atmosphere at 250 to 1000° C.

16. The method of claim 1 , wherein the catalyst has cobalt at a content of at least 1% by weight.

17. The method of claim 1 , wherein the catalyst is substantially free of alkali metals.

Assignees

• Sk Innovation Co Ltd

Inventors

• Cheon Young Eun
• Kim Hee Soo
• Yun Dong Min
• Lee Ho Won
• Im Ju Hwan

Classifications

• B01J2235/00

  Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties · CPC title

• B01J2235/30

  Scanning electron microscopy; Transmission electron microscopy · CPC title

• B01J35/40

  characterised by dimensions, e.g. grain size (in a colloidal state B01J35/23; crystallite size B01J35/77) · CPC title

• B01J2235/15

  X-ray diffraction · CPC title

• B01J23/75 Primary

  Cobalt · CPC title