Coking characteristics and deactivation mechanism of the HZSM-5 zeolite employed in the upgrading of biomass-derived vapors

Coking characteristics and deactivation mechanism of the HZSM-5 zeolite employed in the upgrading of biomass-derived vapors

HZSM-5 zeolite was employed in the upgrading of biomass pyrolysis vapors in this study. The cokingcharacteristics were investigated by means of TG, FT-IR, XRD, N2 adsorption–desorption, NH3-TPD, Py-IR,SEM and TEM methods. When the zeolite was used for three times about 120 min, its activity had beenlost and the amount of coke was 12.15% composed of 9.90% of I typefilamentous coke and 2.25% of II typegraphite-like coke. The skeleton structure of zeolite was basically intact, which had not been seriouslydestroyed by coke. The surface area, pore volume and acidity of zeolite were all deteriorated vary degreeswith the usage time. The zeolite granules became larger after deactivated, and thefilamentous coke canbe observed both on the surface and in the pore. The compositions of the coke precursors were analyzedby FT-IR and GC/MS. The precursors of coke deposited in the pore were mainly aromatic hydrocarbons,while the species of the precursors deposited on the outer surface was more including many long-chainsaturated hydrocarbons. The deactivation of HZSM-5 zeolite began from inner, large molecularsubstances blocked the pores which resulted in the zeolite deactivation eventually

HZSM-5 zeolite was employed in the upgrading of biomass pyrolysis vapors in this study. The cokingcharacteristics were investigated by means of TG, FT-IR, XRD, N2 adsorption–desorption, NH3-TPD, Py-IR,SEM and TEM methods. When the zeolite was used for three times about 120 min, its activity had beenlost and the amount of coke was 12.15% composed of 9.90% of I typefilamentous coke and 2.25% of II typegraphite-like coke. The skeleton structure of zeolite was basically intact, which had not been seriouslydestroyed by coke. The surface area, pore volume and acidity of zeolite were all deteriorated vary degreeswith the usage time. The zeolite granules became larger after deactivated, and thefilamentous coke canbe observed both on the surface and in the pore. The compositions of the coke precursors were analyzedby FT-IR and GC/MS. The precursors of coke deposited in the pore were mainly aromatic hydrocarbons,while the species of the precursors deposited on the outer surface was more including many long-chainsaturated hydrocarbons. The deactivation of HZSM-5 zeolite began from inner, large molecularsubstances blocked the pores which resulted in the zeolite deactivation eventually