Gallium–platinum promoted
HZSM-5 is found to be a promising
catalyst for ethane aromatization reaction. The influence of Pt as
a promoter on the activity of Ga/HZSM-5 catalyst for ethane aromatization
has been investigated. Comparative study was performed between bimetallic
Ga–Pt based and Mo based HZSM-5, where the GaPt/HZSM-5 showed
better aromatic and hydrogen selectivity. Pt promoted Ga/HZSM-5 catalyst
exhibited higher activity compared to pure Ga/HZSM-5 catalyst. The
presence of platinum in the gallium zeolite considerably accelerated
dehydrogenation step in ethane aromatization. In addition, GaPt/HSZM-5
deactivated significantly slower than Mo/HZSM-5 and Ga/HZSM-5. TPO
study of spent catalysts revealed that carbonaceous deposit on GaPt/HZSM-5
catalyst was burnt off at lower temperature compared to pure Ga/HZSM-5
catalyst, indicating the presence of Pt facilitated hydrogen spillover
resulting in hydrogenolysis of coke precursors. The reaction mechanism
associated with aromatic formation is postulated based on the correlation
between catalytic performance and surface characterization.
Direct nonoxidative conversion of ethane to aromatics has become an effective way of upgrading shale gas. Metal-promoted shape selective zeolite catalysts are often used for aromatization. Although the coking issue of the catalysts in ethane aromatization has been reported, the deactivation mechanism and the performance of regenerated Ga−Pt promoted HZSM-5 needs to be further investigated. The objective of this study is to elucidate deactivation mechanism of Ga−Pt promoted HZSM-5 and investigate the feasibility of regenerating deactivated catalysts for commercial viability. When using lower concentration of oxygen (2 vol %) for regeneration, decreased catalyst deactivation rate was observed. The metal particle size, crystalline structures, and acidity are characterized by various analytical instrumentations (TEM, XRD, NH 3 -TPD). The change of Bronsted acidity was observed on regenerated catalysts. The results showed that metal agglomeration and leaching of Pt from homogeneous Ga−Pt particle were the main causes of deactivation other than coke deposition, indicating that stabilization of bimetallic metal particles on zeolite surface is critical.
This study presents our recent findings that under microwave irradiation and/or microwave plasma conditions, nitrogen can react with methane to form ammonia and other value-added by-products, hydrogen and carbon nanotubes, at atmospheric pressure.
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