Plasma-catalytic steam reforming of benzene as a tar model compound over Ni-HAP and Ni-γAl2O3 catalysts: Insights into the importance of steam and catalyst support.

[Display omitted] • High initial benzene concentration (70–190 g/Nm3) experiments are performed in NTP-catalytic system. • Performance of NTP alone and NTP-catalytic system are compared. • The catalysts facilitate the intermediates convert to gaseous products. • The Ni3-HAP catalyst exhibits the maximum benzene conversion (92.13 %) and energy efficiency (8.49 g/kWh). • Catalyst deactivation in NTP-catalytic systems is due to carbon deposition rather than metal sintering. Non-thermal plasma (NTP) coupled Ni-based catalysts are a promising method for tar steam reforming to syngas. In this work, Ni-based catalysts supported on hydroxyapatite (Ni-HAP) and γAl 2 O 3 (Ni-γAl 2 O 3) coupled with a coaxial dielectric barrier discharge (DBD) plasma were used to degrade biomass tar, and benzene was selected as a typical unbranched benzene ring structured tar model compound. In the NTP alone system, an increase in discharge power leads to benzene deep cracking to carbon deposition. In the NTP-catalytic system, the reaction temperature is a critical factor for catalysis, and the catalyst leads to a significant increase in benzene conversion and total gas yield, prompting the conversion of more cracking intermediates to gaseous products. Steam in the system has both positive and negative effects: a certain amount of steam can increase the amount of H· and ·OH, promoting benzene decomposition and carbon deposit elimination; excessive steam will compete for energetic electrons or oxidize the active metal in the catalyst, inhibiting benzene conversion. The Ni3-HAP catalyst exhibits the maximum benzene conversion (92.13 %) and energy efficiency (8.49 g/kWh), thanks to the formed Ni2+[I] and Ni2+[II] in the lattice due to the flexible ion exchange properties of the HAP support. The main reason for the catalyst activity degradation is carbon deposition rather than catalyst sintering. A good match among tar conversion rate, degree of decomposition, steam content and steam decomposition rate is critical for efficient and stable operation of the NTP-catalytic system. [ABSTRACT FROM AUTHOR]