Rational Design of Novel Ru/C Catalysts for Supercritical Water Gasification (SCWG)

This project is related to the development of novel Ru/C catalysts for SCWG within the SunCHem project. The latter aims to demonstrate the technical-economical feasibility of Bio-SNG production from microalgae using catalytic SCWG by building a small process demonstration unit operating in continuous (1 kg/h of microalgae) (Fig.1).

The necessity for having a highly efficient catalyst in terms of activity, selectivity and stability is crucial for the process feasibility and viability. So far, there is still a lack of knowledge in the understanding of the relation between the catalyst formulation and structure related to its catalytic performance for SCWG. Therefore, this project attempts to assess thoroughly the Ru/C catalyst in terms of physico-chemical and mechanical properties related to the catalytic performance for its efficient catalytic optimization for SCWG. The most relevant properties of carbon on the catalytic performance are investigated for SCWG like the effect of: the meso/microporous structure; impurities (S, Cl, P,...); the surface acidity; the graphitization degree.

The new Ru/C catalysts are characterized by conventional catalyst characterization methods: TPR/D/O coupled with MS and FTIR; H₂/CO pulse chemisorption; N₂-physisorption; TEM; CNS elemental analysis; TG-FTIR, ICP-OES; surface titration, while their catalytic performance are assessed in a plug flow reactor. As an example, Fig. 2 illustrates a typical SCWG of 10 wt. % isopropanol over a commercial 2 %Ru/C_14.3 (BASF) catalyst by working at relatively high WHSV (240 g_org/g_cat*h). As could be seen the total carbon conversion first decreased from 70 % to 35 % during the first hours of SCWG and remained stable. SCWG over only the carbon support (C_14.3) showed the same initial activity drop but stabilized around 16 %. One can appreciated the similarity in the lost of initial activity for both SCWG indicating probably that some impurities participating in the gasification were flushed out over the first hours of SCWG.