Promoting hydrogen production and minimizing catalyst deactivation from the pyrolysis-catalytic steam reforming of biomass on nanosized NiZnAlOx catalysts

Abstract

Hydrogen production from the thermochemical conversion of biomass was carried out with nano-sized NiZnAlOx catalysts using a two-stage fixed bed reactor system. The gases derived from the pyrolysis of wood sawdust in the first stage were catalytically steam reformed in the second stage. The NiZnAlOx catalysts were synthesized by a co-precipitation method with different Ni molar fractions (5, 10, 15, 25 and 35%) and a constant Zn:Al molar ratio of 1:4. The catalysts were characterized by a wide range of techniques, including N2 adsorption, SEM, XRD, TEM and temperature-programmed oxidation (TPO) and reduction (TPR). Fine metal particles of size around 10-11 nm were obtained and the catalysts had high stability characteristics, which improved the dispersion of active centers during the reaction and promoted the performance of the catalysts. The yield of gas was increased from 49.3 to 74.8 wt.%, and the volumetric concentration of hydrogen was increased from 34.7 to 48.1 vol.%, when the amount of Ni loading was increased from 5 to 35%. Meanwhile, the CH4 fraction decreased from 10.2 to 0.2 vol.% and the C2-C4 fraction was reduced from 2.4 vol.% to 0.0 vol.%. During the reaction, the crystal size of all catalysts was successfully maintained at around 10-11 nm with lowered catalyst coke formation, (particularly for the 35NiZn4Al catalyst where negligible coke was found) and additionally no obvious catalyst sintering was detected. The efficient production of hydrogen from the thermochemical conversion of renewable biomass indicates that it is a promising sustainable route to generate hydrogen from biomass using the NiZnAl metal oxide catalyst prepared in this work via a two-stage reaction system.

Development of Heterogeneous Catalysts for Thermo-Chemical Conversion of Lignocellulosic Biomass

“…This increase in hydrogen production and reduction of the catalyst deactivation rate were also observed in the case of the NiZnAlO x system used in the pyrolysis and subsequent steam reforming reactions [77]. The H 2 yield more than doubled, while the amount of introduced nickel on the catalyst surface rose from 5% to 35%.…”

“…The H 2 yield more than doubled, while the amount of introduced nickel on the catalyst surface rose from 5% to 35%. Dong et al [77] indicated that this was connected with the growth of the number of catalytically active sites (Ni • ) on the support. According to the obtained results, the presence of zinc oxide could protect a catalyst against an agglomeration of nickel particles and the formation of a coke deposit.…”

Coke formation and deactivation during catalytic reforming of biomass and waste pyrolysis products: A review

“…At the catalyst level, many attempts have been performed to control the deposition of coke in these reactions or minimize its impact. Changing the morphology of the metal (Ni) has recurrently been used to control catalyst deactivation, either by decreasing the particle size [254,255], changing the chemical environment of Ni [256], using a different synthetic pathway [257], using different calcination/reduction methods [144], or using other metals such as the incorporation of Co [258,259], the use of Fe-Zn [260] or other metals all together [261]. On the other side, several attempts have been made to control the catalyst deactivation trough support modification, either by changing porosity or metal placement on the support [28], or by using other conventional supports such as ZrO2, SiO2, MgO, TiO2 [262] or unconventional ones [263].…”

Preparation, modification and development of Ni-based catalysts for catalytic reforming of tar produced from biomass gasification

“…The impregnation method usually produces large metal particles, a weak interaction between metal particles and support, and a large inhomogeneity in the composition of catalysts [63,88,114]. Therefore, hydrotalcite-like compounds (HTlcs) [88,[119][120][121], palygorskite-like compounds [95], mayenite-like compounds [79] and other kinds of co-precipitated catalysts [110,122] attract increasing attention, since the preparation of uniform nanoparticles catalyst is important for the catalytic performance. Wang et al [85] reported that Ni-based catalysts prepared by co-precipitation had smaller metal nanoparticles, higher dispersion and stronger metal-support interaction than that prepared by wet impregnation, leading to a more stabilized solid structure and lower metal reduction extent.…”