Steam reforming of acetic acid over Ni-containing mesoporous magnesia (MgO) and alumina (γ-Al2O3) supported catalysts

In the present study, environmentally friendly, renewable, sustainable, and clean hydrogen production from bio-oil derived acetic acid was investigated over robust Ni-based, MgO and γ-Al2O3 supported catalysts with large surface area, excellent thermal stability, high catalytic activity, and high anti-coking resistance. Mesoporous MgO and γ-Al2O3 catalyst supports were synthezied through hydrothermal and EISA (Evaporation-Self-Induced-Assembly) method, respectively. Subsequently, Ni, Mg and/or La metal contents were introduced into the catalyst supports' (MgO and γ-Al2O3 ) structure following a wet-impregnation route. The synthesized Ni-containing, MgO and γ-Al2O3 supported catalysts have been characterized by XRD, N2 adsorption-desorption, SEM, EDS, FTIR, DRIFTS and TGA-DTA analysis to define their physical and chemical properties. The catalytic activity tests were conducted in a packed bed continuous reactor system at a reaction temperature of 750°C and a feed molar ratio of 1/2.5/2: AA/H2O/Ar for 3 hours. Complete acetic acid conversion (100%), high carbon formation (37.15%), and high hydrogen selectivity (81.75%) were obtained over the mesoporous 5Ni@γ〖-Al〗_2 O_3 catalyst. Moreover, the incorporation of Mg into the mono-metallic 5Ni@γ-Al2O3 catalyst structure lessens its catalytic acticity performance, enhances its thermal stability, and reduces its surface acidity. TGA results reveal that, the proportion of carbon formed over the mono-metallic catalyst surface was lowered to 12.44% after the addition of Mg metal. It was concluded that, the catalyst support has a significant effect on acetic acid conversion, hydrogen yield and coke formation. Furthermore, temperature (550°C, 650°C and 750°C) and feedstock molar composition (AA/H2O: 1/2,5; 1/5 and 1/10) effect on conversion and hydrogen selectivity were investigated over 5Ni-3Mg@γ-Al2O3 catalyst giving the highest catalytic activity performance. It was found that, increasing the amount of water in the feedstock noticeably enhances hydrogen yield. Besides, increasing temperature remarkably increases the acetic acid conversion. However, no significant effect of varying feedstock composition on conversion has been observed. Results of long-life experiment conducted at the reaction temperature shows that, the promising 5Ni-3Mg@γ-Al2O3 catalyst was highly active and thermally stable for 12 hours. Therefore, using the newly developed Ni-based catalysts, it is feasible to produce alternative, clean fuel hydrogen from biomass-derived acetic acid.