The effect of mg and zn dopants on pt/al2 o3 for the dehydrogenation of perhydrodibenzyltoluene

Abstract

The effects of Mg and Zn dopants on the catalytic performance of Pt/Al2 O3 catalyst were investigated for dehydrogenation of perhydrodibenzyltoluene (H18-DBT) as a liquid organic hydrogen carrier. Al2 O3 supports were modified with Mg and Zn to produce Mg-Al2 O3 and Zn-Al2 O3 with a target loading of 3.8 wt.% for dopants. The modified supports were impregnated with chloroplatinic acid solution to produce the catalysts Pt/Al2 O3, Pt/Mg-Al2 O3 and Pt/Zn-Al2 O3 of 0.5 wt.% Pt loading. Thereafter, the catalysts were characterised using inductively coupled plasma-optical emission spectrometry, scanning electron microscopy-energy dispersive X-ray spectroscopy, hydrogen temperature-programmed reduction, carbon-monoxide pulse chemisorption, ammonia temperature-programmed desorption, X-ray diffraction and transmission electron microscopy. The dehydrogenation experiments were performed using a horizontal plug flow reactor system and the catalyst time-on-stream was 22 h. Pt/Mg-Al2 O3 showed the highest average hydrogen flowrate of 29 nL/h, while an average of 27 nL/h was obtained for both Pt/Al2 O3 and Pt/Zn-Al2 O3 . This has resulted in a hydrogen yield of 80% for Pt/Mg-Al2 O3, 71% for Pt/Zn-Al2 O3 and 73% for Pt/Al2 O3 . In addition, the conversion of H18-DBT ranges from 99% to 92%, Pt 97–90% and 96–90% for Pt/Mg-Al2 O3, Pt/Zn-Al2 O3 and Pt/Al2 O3, respectively. Following the latter catalyst order, the selectivity to dibenzyltoluene (H0-DBT) ranges from 78% to 57%, 75–51% and 71–45%. Therefore, Pt/Mg-Al2 O3 showed improved catalytic performance towards dehydrogenation of H18-DBT.