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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Redox mechanism,Structural Properties,Oxidative Coupling of Methane (OCM),Transition metal oxide
- چکیده:
- چکیده انگلیسی: The Oxidative Coupling of Methane (OCM) over M-Na-Mn/SiO2 catalysts (M=W, Cr, Nb and V) was investigated using a continuous-flow quartz reactor at 775°C, 1 atm and 100 cm3min-1 gas flow rates, and correlated with the observed structure and redox properties.The interaction effects of the metal-metal and metal-support on the methane conversion and C2+ yield were investigated using X-Ray Diffraction (XRD), laser Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), and Temperature Programmed Reduction with H2 (TPR). The results revealed that the improvement of C2+ selectivity (or C2+ yield) follows the order W>Cr>Nb>V, while the catalytic conversion did not change significantly. XRD data indicated that Mn is well dispersed on the SiO2 support and also show that Mn2O3 and α-cristobalite were the predominant species in the surface catalysts. TPR data show that most of the Mn is present as Mn3+ and Mn2+. FT-IR analyses combined with the Raman results show that terminal M=O and bridging M–O–M species and the metal–metal and metal–support interactions, which take place due to the presence of sodium ion, depend on the transition metal that affect the catalyst performance. Results reveal that the interaction between metal oxide and sodium is required for high selectivity and control redox mechanism in transition metal oxide in OCM reaction.
- انتشار مقاله: 13-02-1388
- نویسندگان: Somayeh Mahmoodi,Mohammad Reza Ehsani,Marzieh Hamidzadeh
- مشاهده
- جایگاه : پژوهشی
- مجله: Advances in Environmental Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Solid-State method,Ball mill,Methanol,Green catalyst,environmental-friendly
- چکیده:
- چکیده انگلیسی: In this research study, methanol synthesis catalysts were manufactured with various mole ratios of metal carbonates (zinc, copper and aluminum carbonate) and ammonium hydrogen carbonate via a green solid-state method that employed a ball mill apparatus. Some parameters for the catalyst preparation, such as Al mole percent, Cu/Zn mole ratio, rotations milling speeds and aging time, were optimized to obtain the maximum catalyst activity. The prepared catalysts were compared with the best quality industrial catalyst under the same temperature and pressure condition in a titanium tabular fixed bed reactor. This novel method has many advantages in comparison to the conventional method. The main advantage of the solid-state method is that the methanol synthesis catalyst can be produced without using solvent. Furthermore, this new method reduces operating costs due to the elimination of the filtration and washing steps. Methanol synthesis catalytic activity was maximized at an optimized mole ratio of Cu/Zn of 1.9234 and an Al mole percent of 8 at the maximum grinding speed (450 rpm) during an aging time of 30 min, which showed higher activity (240 gCH3OH/kg cat.h) in comparison with an industrial catalyst sample (218 gCH3OH/kg cat.h). The production of a green catalyst, which requires less water and results in higher catalyst activity, can be widely used for methanol synthesis catalytic applications.
- انتشار مقاله: 07-12-1395
- نویسندگان: Neda Mirhosseini,Mohammad Reza Mirani,Reza Davarnejad,Marzie Hamidzade,Abbas Taeb
- مشاهده