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Enhanced Light Aromatic Yield from Lignite Pyrolysis by Remedying the Acid Sites of Different Hierarchical HZSM‑5
journal contribution
posted on 2019-11-15, 18:35 authored by Zhen Yang, Jing-Pei Cao, Xiao-Yan Zhao, Xue-Yu Ren, Chen Zhu, Xiao-Bo Feng, Xian-Yong WeiA series of HZSM-5 treated by NaOH followed by supporting
sulfated
zirconia (ATxSZ/H5) was prepared and used
for catalytic reforming of lignite pyrolysis volatiles. ATxSZ/H5 was found to be a potentially promising catalyst
for removing oxygen from vapors to produce aromatics and olefin. The
highest yields of benzene, toluene, ethylbenzene, xylene, and naphthalene
(BTEXN) were obtained over 3% SZ supported on HZSM-5 treated by 0.2
mol/L NaOH (AT0.2SZ/H5) as a result of the abundant hierarchical
pores and suitable acidic density. Moreover, raising the NaOH concentration
for zeolites caused the enhancement of olefin yields. The polycyclic
aromatic hydrocarbons chemisorbed over zeolite can be activated by
the hydrogen transfer reaction to increase the selectivity of C2+. Comprehensive catalyst characterization using temperature-programmed
desorption with ammonia, N2 physisorption, X-ray diffraction,
and inductively coupled plasma optical emission spectrometry enabled
establishing structure–performance relationships with a major
role of the zeolite structure, density of strong acid sites, and mesoporosity.
ATxSZ/H5 exhibited a suitable physicochemical
property, including the addition of strong acid species and acidity,
suitable pore structure, and specific surface area. Additionally,
in comparison to H5, the yields of BTEXN over AT0.2SZ/H5
increased from 12.8 to 18.9 mg/g, but excessive alkali over H5 had
a negative effect on the BTEXN yield because of the structure collapse.
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Keywords
surface areahydrocarbons chemisorbedacid sitesacidic densityNaOH concentrationEnhanced Light Aromatic YieldLignite PyrolysisAcid Sitesacid speciesHZSMX-ray diffractionsulfated zirconiazeolite structurepore structurephysicochemical propertyH 5temperature-programmed desorptionN 2 physisorptionolefin yieldsSZ0.2hydrogen transfer reactionComprehensive catalyst characterizationstructure collapseBTEXNpyrolysis volatilesemission spectrometry
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