In the last decade, there has been a continuing increase in global production of biodiesel. In China, the utilization of biodiesel is projected to be 2 million tonnes by 2020. Glycerol from biodiesel plants was initially considered as a waste, while it has been widely recognized that the upgrading of glycerol will considerably reduce the cost of biodiesel and create new chemical routes for high-value-added products. The sorption enhanced steam reforming (SESR) technology has the potential to produce high purity hydrogen by Le Chatelier’s principle. However, its practice is limited by sorbent sintering and deactivation at high reaction/decarbonation temperatures. We have developed a bi-functional catalyst composed of calcium aluminate, calcium oxide and cobalt as active metal for the SESR of glycerol (SESRG), where the refractory aluminate was used as a spacer to prevent sintering. In this contribution, we propose a novel strategy to enhance the stability of SESRG, in which misfit layered materials, i.e. calcium cobaltates (CCO), were used as a dual-functional material combining CO2 absorption and catalytic reforming. Differing from conventional approach to enhancing the robustness of catalysts/sorbents, we exploited the reversible phase change of CCO: Ca3Co4O9 --&gt; Co + CaO, during the decarbonation and reaction steps respectively.(Fig.1) By doing so, the sintering of CaO sorbent and Co catalyst can be suppressed because they were homogenized into CCO on an atomic level in every decarbonization stage. The CCO catalyst displayed a very stable performance for producing high purity H2 through SESRG for up to 120 reaction-decarbonization cycles, without noticeable changes of H2 production and CO2 absorption capacity.(Fig. 2) In-situ XRD and microscopy studies demonstrated the reversible phase transition and the accompanied formation of hierarchical CCO micro-structures that facilitated the catalytic reforming and CO2 absorption, benefited from the complex phase equilibria among different CCO compounds. The results in this study shed light on a new paradigm for the design of materials working at high temperatures thus suffering from serious sintering.

Designing a stable and efficient dual-functional catalyst for the sorption-enhanced steam reforming of glycerol

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.