Pt/Al2O3 as efficient catalyst for the dehydrogenation of Dodecahydro-N-ethylcarbazole

Abstract

The use of dodecahydro-N-ethylcarbazole in hydrogen storage for liquid organic hydrogen carrier systems holds potential for achieving large-scale application. In order to investigate the relationship between dodecahydro-N-ethylcarbazole dehydrogenation performance and Pt particles size, a series of monometallic Pt/Al2O3 catalysts with different Pt particles size from 0.70 nm to 5.12 nm were controlled synthesized by a simple impregnation method. The obtained catalysts are systematically characterized via XRD, 27Al MAS NMR, SEM-EDS, TEM, N2-adsorption, CO-IR, H2-TPR and NH3-TPD analyses, which provide essential micro-structure of these catalysts. The dehydrogenation of dodecahydro-N-ethylcarbazole over Pt/Al2O3 is a typical consecutive reaction, which follows a reaction sequence of dodecahydro-N-ethylcarbazole → octahydro-N-ethylcarbazole → tetrahydro-N-ethylcarbazole → N-ethylcarbazole. These dehydrogenation steps are quite sensitive to the Pt particle size. Large Pt particle can greatly enhance the reaction rates in octahydro-N-ethylcarbazole → tetrahydro-N-ethylcarbazole and tetrahydro-N-ethylcarbazole → N-ethylcarbazole steps. However, these two steps are difficult to take place in small Pt particles. The high performance of large Pt particle in dehydrogenation can be ascribed to its highly exposed (111) crystal face. The optimized catalyst Pt5.0/γ-Al2O3 with Pt average size of 4.63 nm demonstrated exceptional performance in dodecahydro-N-ethylcarbazole dehydrogenation at 180 °C and 101 kPa, and the dodecahydro-N-ethylcarbazole conversion of 100 %, N-ethylcarbazole selectivity of 96.44 % and dehydrogenation efficiency of 98.73 % can be achieved. These results provide valuable insights for the development of efficient metal-based catalysts for liquid organic hydrogen carriers hydrogen storage system.