Study on the effect of metal types in (Me)-Al-MCM-41 on the mesoporous structure and catalytic behavior during the vapor-catalyzed co-pyrolysis of pubescens and LDPE

Abstract

The catalysts (Me)-Al-MCM-41 (Me=Ni, Pd and their combination) were synthesized hydrothermally, characterized with XRD, BET, NH3-TPD, SEM, TEM, XPS, H2-TPR, chemisorption of hydrogen, and tested by experiments of co-pyrolysis of pubescens and LDPE under vapor-catalyzed condition. Characterization results suggested that the synthesis of Al-MCM-41 was successful, but the introduction of Me into Al-MCM-41 caused some changes in structure of catalyst to a certain degree, resulting in significant changes in their properties and catalytic behavior. The results obtained from vapor-catalyzed co-pyrolysis over these catalysts showed that there were some interactions between the intermediate species from the co-pyrolysis, as the relative content of aromatics in oil was high, whereas that of phenol in corresponding aqua was low, and vice versa. The type of metal in catalysts was of more importance than the metal siting. Moreover, all catalysts except Ni-Pd-Al-MCM-41 exerted strong effect of alkanisation on the primary intermediate species from the pyrolysis of LDPE, which demonstrated that the pore architecture of parent Al-MCM-41 and (Me)-Al-MCM-41 containing single Me strongly favored the reactions in relation to alkanisation; on the contrary, Ni-Pd-Al-MCM-41 exerted a strong effect of dehydrogenation on those primary intermediate species. More importantly, the synergistic effect on producing hydrogen, based on the 61.8vol.% of H2 in gaseous mixture, indicated that the combination of Ni and Pd in (Me)-Al-MCM-41 might bring about a novel performance during the vapor-catalyzed co-pyrolysis of biomass and plastics. It was predicted that Ni-Pd-Al-MCM-41 might play its special application in development of hydrogen energy, exploitation and utilization of biomass as well as municipal solid waste (MSW) such as waste plastics, etc. The major schemes of reactions involved in the vapor-catalyzed co-pyrolysis had been proposed.