TY - JOUR
T1 - Methane Upgrading of Acetic Acid as a Model Compound for a Biomass-Derived Liquid over a Modified Zeolite Catalyst
AU - Yung, Matthew
AU - Wang, Aiguo
AU - Austin, Danielle
AU - Karmakar, Abhoy
AU - Bernard, Guy
AU - Michaelis, Vladimir
AU - Zeng, Hongbo
AU - Song, Hua
N1 - Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/5/5
Y1 - 2017/5/5
N2 - The technical feasibility of coaromatization of acetic acid derived from biomass and methane was investigated under mild reaction conditions (400°C and 30 bar) over silver-, zinc-, and/or gallium-modified zeolite catalysts. On the basis of GC-MS, Micro-GC, and TGA analysis, more light aromatic hydrocarbons, less phenol formation, lower coke production, and higher methane conversion are observed over 5%Zn-1%Ga/ZSM-5 catalyst in comparison with catalytic performance over the other catalysts. Direct evidence of methane incorporation into aromatics over 5%Zn-1%Ga/ZSM-5 catalyst is witnessed in 1H, 2H, and 13C NMR spectra, revealing that the carbon from methane prefers to occupy the phenyl carbon sites and the benzylic carbon sites, and the hydrogen of methane favors the aromatic and benzylic substitutions of product molecules. In combination with the 13C NMR results for isotopically labeled acetic acid (13CH3COOH and CH313COOH), it can be seen that the methyl and carbonyl carbons of acetic acid are equally involved in the formation of ortho, meta and para carbons of the aromatics, whereas the phenyl carbons directly bonded with alkyl substituent groups and benzylic carbons are derived mainly from the carboxyl carbon of acetic acid. After various catalyst characterizations by using TEM, XRD, DRIFT, NH3-TPD, and XPS, the excellent catalytic performance might be closely related to the highly dispersed zinc and gallium species on the zeolite support, moderate surface acidity, and an appropriate ratio of weak acidic sites to strong acidic sites as well as the fairly stable oxidation state during acetic acid conversion under a methane environment. Two mechanisms of the coaromatization of acetic acid and methane have also been proposed after consulting all the collected data in this study. The results reported in this paper could potentially lead to more cost-effective utilization of abundant natural gas and biomass. (Figure Presented).
AB - The technical feasibility of coaromatization of acetic acid derived from biomass and methane was investigated under mild reaction conditions (400°C and 30 bar) over silver-, zinc-, and/or gallium-modified zeolite catalysts. On the basis of GC-MS, Micro-GC, and TGA analysis, more light aromatic hydrocarbons, less phenol formation, lower coke production, and higher methane conversion are observed over 5%Zn-1%Ga/ZSM-5 catalyst in comparison with catalytic performance over the other catalysts. Direct evidence of methane incorporation into aromatics over 5%Zn-1%Ga/ZSM-5 catalyst is witnessed in 1H, 2H, and 13C NMR spectra, revealing that the carbon from methane prefers to occupy the phenyl carbon sites and the benzylic carbon sites, and the hydrogen of methane favors the aromatic and benzylic substitutions of product molecules. In combination with the 13C NMR results for isotopically labeled acetic acid (13CH3COOH and CH313COOH), it can be seen that the methyl and carbonyl carbons of acetic acid are equally involved in the formation of ortho, meta and para carbons of the aromatics, whereas the phenyl carbons directly bonded with alkyl substituent groups and benzylic carbons are derived mainly from the carboxyl carbon of acetic acid. After various catalyst characterizations by using TEM, XRD, DRIFT, NH3-TPD, and XPS, the excellent catalytic performance might be closely related to the highly dispersed zinc and gallium species on the zeolite support, moderate surface acidity, and an appropriate ratio of weak acidic sites to strong acidic sites as well as the fairly stable oxidation state during acetic acid conversion under a methane environment. Two mechanisms of the coaromatization of acetic acid and methane have also been proposed after consulting all the collected data in this study. The results reported in this paper could potentially lead to more cost-effective utilization of abundant natural gas and biomass. (Figure Presented).
KW - acetic acid
KW - aromatization
KW - catalyst
KW - methane
KW - ZSM-5
UR - http://www.scopus.com/inward/record.url?scp=85021164356&partnerID=8YFLogxK
U2 - 10.1021/acscatal.7b00296
DO - 10.1021/acscatal.7b00296
M3 - Article
AN - SCOPUS:85021164356
SN - 2155-5435
VL - 7
SP - 3681
EP - 3692
JO - ACS Catalysis
JF - ACS Catalysis
IS - 5
ER -