Nickel catalyst auto-reduction during steam reforming of bio-oil model compound acetic acid

Abstract

Transition metal catalysts widely used in refineries are provided as oxides and require pre-reduction to become activated. The auto-reduction of a NiO/Al 2 O 3 catalyst with acetic acid (HAc) followed by HAc steam reforming was investigated in a packed bed reactor. Effects of temperature and molar steam to carbon ratio (S/C) on reduction kinetics and catalyst performance were analysed. Results showed that a steady steam reforming regime along with complete NiO reduction could be obtained after a coexistence stage of reduction and reforming. A 2D nucleation and nuclei growth model fitted the NiO auto-reduction. The maximum reduction rate constant was attained at S/C=2. Steam reforming activity of the auto-reduced catalyst was just below that of the H 2 -reduced catalyst, probably attributed to denser carbon filament formation and larger loss of active Ni. Despite this, a H 2 yield of 76.4% of the equilibrium value and HAc conversion of 88.97% were achieved at 750 °C and S/C=3.

Hydrogen Generation from Catalytic Steam Reforming of Acetic Acid by Ni/Attapulgite Catalysts

“…In the process of SRAA, coke mainly comes from these reactions, such as the thermal decomposition of AA (r1) and In this research, the PM-Ni/ATC catalyst reached the highest Y H 2 (~82%) and the relative high X AA (~85%, little lower than that of IM-Ni/ATC) at 650 • C and H 2 O/AA = 6. F. Cheng et al [55] investigated the effect of different temperature and steam to carbon (S/C) on the process of SRAA over NiO/Al 2 O 3 in a down-flow packed-bed reactor. The Y H 2 of 76.4% of the equilibrium value and X AA of 88.97% were achieved at 750 • C and S/C = 3.…”

Hydrogen production from chemical looping steam reforming of glycerol by Ni-based oxygen carrier in a fixed-bed reactor

“…To make the thermodynamic calculation manageable, the species coexisting in the equilibrium CLSR system were determined by considering the following rules: (I) the proportion of the atoms in the system, (II) the Gibbs free energy of formation of the compound and (III) previous experience with similar systems [18,19]. At the initial stage, the equilibrium calculations were performed with typical compositions including H 2 , CO, CO 2 , H 2 O, CH 4 , C 2 H 2 , C 2 H 5 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 3 H 6 , C 3 H 8 O 3 , C 4 H 6 , C 4 H 8 , CH 2 O, CH 3 OH, CH 3 HCO, NH 3 , NH 2 , and N 2 .…”

“…The main reason for the discrepancy between the equilibrium and experimental values is the kinetic limitation of WGS reaction. Some of feed molecules and intermediate product such as CO have not enough time to react with the water over the oxygen carrier before being flushed out of the reactor [19]. Moreover, the coke deposition ratio calculated by Eq.…”

Chemical looping for hydrogen production

“…Thermodynamic calculations showed that H 2 yield from liquid fuels can be similar to that obtained by POX with oxygen, but the use of an air separation unit was avoided in CLR ( Abrego et al, 2012). However, the use of NiO could be preferable because of its catalytic properties as NiO is being reduced to Ni (Cheng & Dupont, 2013). However, the use of NiO could be preferable because of its catalytic properties as NiO is being reduced to Ni (Cheng & Dupont, 2013).…”