CREATES: CO2 REduction for grAphiTE Synthesis
- Acadian Research & Development LLC
The purpose of the research performed in this project was to develop a catalyst capable of conversion of CO2 to carbon, as well as in situ graphite production from this conversion process. The proposed catalyst is phyllosilicate-based, composed of metal particles supported on nanofibers, which protects against particle agglomeration, and has surface chemistry that resists coking. Both of these characteristics translate to higher catalyst stability. The catalysts chosen for this project are Ni-, Cu-, and Fe-pyhllosilicates, with metals chosen based on performance with conversion of CO2 and were produced using a variety of synthesis methods. In addition, cerium was incorporated to examine the benefit of this effective promoter. Catalyst characterization was performed via a selection of techniques and was used to evaluate the success of the synthesis and to support the performance results. The planned catalyst testing via TGA was found to be unreliable, so instead catalysts were tested in a packed bed reactor. Some of the catalysts were tested using CO2 as the feed, but it was found that the conversion was very low. To improve the conversion, hydrogen was added to the feed to promote the Bosch reaction (CO2 + 2 H2 → C + 2 H2O), but this was found to be dominated by the reverse water gas shift reaction (CO2 + H2 → CO + H2O). To then validate the synthesis and activity of the catalysts, tests with methane as the feed were performed. When good performance in the CH4 tests was observed, it was then decided to push the reaction toward the Sabatier reaction (CO2 + 4 H2 → CH4 + 2 H2O) in order to produce methane as an intermediate. While this is the testing rationale, a selection of catalysts were nonetheless tested with only CO2 to check for activity under these conditions, and CH4 to validate activity. Typical tests had a space velocity of 680 h-1 for a bed with mixed catalyst and inert sand for gas flow assurance. For catalysts with no Ce promotor tested with a CO2 feed, ammonia evaporation and urea hydrolysis methods produced catalysts with the highest CO2 conversion. For a 2:1 H2:CO2 feed ratio, ammonia evaporation again produced a catalyst with the highest CO2 conversion. For a CO2 feed, the Ce promoted catalysts typically had much lower CO2 conversion compared to the Ce-free catalysts (below 1.5%). For a 2:1 H2:CO2 feed ratio, the Ce promoted catalysts typically had similar CO2 conversion compared to the catalysts with no Ce, but for a 4:1 feed ratio, a method using sodium hydroxide to produce a catalyst with Ce promoter showed the highest CO2 conversion overall. For a CH4 feed, the CO2 conversion for catalysts with no promoter shows that the urea hydrolysis method produced the most active catalyst. The long-term stability of a nickel-based catalyst produced using the ammonia evaporation method with no Ce promoter showed ~80% activity after 103 h of operation. For pellet production methods examined in this work, a simple bentonite binder method was superior to surface growth of catalyst and was a facile process. Despite the CO2 conversion achieved and the carbon produced, no graphite was detected in the harvested carbon or on the growth substrates. The carbon formed was only found in the catalyst bed.
- Research Organization:
- Acadian Research & Development LLC
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0020776
- OSTI ID:
- 1838514
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- Final report: DOE-ARD-00776-1
- Country of Publication:
- United States
- Language:
- English
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