Topsoe’s proprietary SNG technology is called TREMP™, which is an acronym for Topsoe Recycle Energy-efficient Methanation Process. The TREMP™ technology utilizes the full potential of Topsoe’s state-of-the-art methanation catalysts, such as the MCR-2 and PK-7R catalysts.
The development of Topsoe’s Recycle Methanation Process (TREMP™) is based on extensive research reflected in six scientific papers since 2000.
High-temperature methanation involves catalyst sintering at high temperatures and exposure to high partial pressures of carbon monoxides at low temperatures. High partial pressure of carbon monoxide leads to low temperature phenomena that must be eliminated in industrial operation.
Low temperature phenomena
The formation of nickel carbonyl leads to excessive growth of the nickel crystals. In practice carbonyl formation is not a problem above 300ºC, which has been proven by our experimental work.
The hydrogenation of the absorbed carbon species into methane may be accompanied by a slow formation of less reactive hydrocarbon chains, leading to a blockage of the active nickel surface, which results in a change of the temperature profile in the reactor.
This phenomenon was studied in pilot plants and by thermal desorption studies. The problem is solved by the selection of the right operating parameters.
Calculations show an upper carbon limit temperature, above which there is a thermodynamic potential for carbon depending on the size of the nickel crystals (ie the diameter of the carbon fibre). With this knowledge carbon formation can be eliminated by selection of the right operating parameters. These studies confirmed that step sites are important for the methanation reaction and our advanced electron microscope (HREM) showed that step-sites are favored for the nucleation of carbon.
Control of the sintering is critical for the high temperature methanation. It requires stable support and means to interfere with the growth of the nickel crystals. Recent studies using in-situ high-resolution microscopy (HREM) has given new insight to the understanding of sintering of nickel catalysts. Analysis of spent catalyst from pilot plants indicate that sintering proceeds via the atom migration sintering mechanism. Our sintering studies indicated that the methanation reaction is structure sensitive and that step sites may play an important role in contrast to earlier conclusions in the literature.
Reaction kinetics mechanisms
Early studies proved the methanation reaction in zero order with respect to carbon monoxide. Recent work has shown that the dissociation of carbon monoxide is the rate determining step and that the association of carbon monoxides proceeds most likely over uncoordinated sites through a COH species. The study of this mechanism was supported by DFT calculations in collaboration with the Technical University of Denmark.