High yield of pentane production by aqueous-phase reforming of xylitol over Ni/HZSM-5 and Ni/MCM22 catalysts

Ni/HZSM-5 and Ni/MCM22 catalysts with different Ni loadings were prepared by impregnation method and evaluated for aqueous-phase reforming (APR) reaction of xylitol at 240 degrees C and 4 MPa. Effects of Ni loadings on the xylitol conversion and pentane selectivity of the catalyst was investigated. The results showed that the catalytic activities of the two Ni/HZSM-5 and Ni/MCM22 catalysts both increased with increasing Ni loading in the range of 0-2%. and then decreased as Ni loading further increased to 4%. Maximum pentane yields of 91% and 95% could be obtained over 2%Ni/HZSM-5 and 2%Ni/MCM22, respectively. 2%Ni/HZSM-5 deactivated obviously after five recycle runs, while 2%Ni/MCM22 still kept excellent activity with the pentane yield of 90-95%. The catalysts with different Ni loading were characterized by BET, H-2-TPR and NH3-TPD techniques and the used selected 2%Ni/MCM22 and 2%Ni/HZSM-5 catalyst were also characterized by XRD, FTIR and TG. The characterization results revealed that 2%Ni/MCM22 and 2%Ni/HZSM-5 have similar amounts of Ni active sites, while the 2%Ni/MCM22 has larger surface area, more mesopore and less strong acid sites than the 2%Ni/HZSM-5. Moreover, partial dealumination and coke formation of the used 2%Ni/HZSM-5 catalyst were found. All these factors resulted in the deactivation of 2%Ni/HZSM-5 after five recycle runs. (C) 2012 Elsevier Ltd. All rights reserved.