Well-crystallized zeolite beta was synthesized by using acid-leached metakaolin as the silica-alumina source and tetraethylammonium hydroxide structure-directing agent.The influence of the composition of the reaction ...Well-crystallized zeolite beta was synthesized by using acid-leached metakaolin as the silica-alumina source and tetraethylammonium hydroxide structure-directing agent.The influence of the composition of the reaction mixture on product crystallinity was investigated,and the crystallization process was studied by examining solid samples obtained at different synthesis times.Results showed that the acid-leached metakaolin was fully converted into soluble aluminum and silicon species,which is crucial for the formation of well-crystallized zeolite beta.At the beginning of the crystallization process,these soluble aluminum and silicon species formed a aluminum-rich intermediate structure with layer morphology.With the crystallization proceeding,more silicon species were incorporated into the zeolite beta framework and the layered structure was changed into spherical particles of zeolite beta with high SiO 2 /Al 2 O 3 ratio and crystallinity.展开更多
A nanostructured NiAPSO-34 catalyst was hydrothermally synthesized and the effect of the template （diethylamine （DEA）, tetraethylammonium hydroxide （TEAOH） and DEA/TEAOH） on the physicochemical properties and ca...A nanostructured NiAPSO-34 catalyst was hydrothermally synthesized and the effect of the template （diethylamine （DEA）, tetraethylammonium hydroxide （TEAOH） and DEA/TEAOH） on the physicochemical properties and catalytic performance in the methanol to olefin （MTO） reaction was investigated. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy （FESEM）, particle size distribution analysis, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller anal- ysis and Fourier transform infrared spectroscopy. The X-ray diffraction patterns indicated a higher crystallinity and larger crystallite size for the catalyst synthesized using the DEA template. The FESEM results indicated that the nature of the template could affect the morphology of the nanostructured NiAPSO-34 catalyst because of its effect on the rate of crystal growth. The catalytic performance of the samples was studied in the MTO reaction at atmospheric pressure and a space velocity of 4200 cm^3 /（g h^-1 ） in a fixed bed reactor. The stability and activity of the NiAPSO-34 catalyst were improved using the DEA template because of its higher crystallinity, surface area and the greater extent of Ni incorporation into its framework. The possible stages of synthesis and the reaction mechanism for the MTO process over NiAPSO-34 are discussed in detail.展开更多
基金supported by Beijing Natural Science Foundation (Grant No.2093043)the National Natural Science Foundation of China (Grant No.20606038)
文摘Well-crystallized zeolite beta was synthesized by using acid-leached metakaolin as the silica-alumina source and tetraethylammonium hydroxide structure-directing agent.The influence of the composition of the reaction mixture on product crystallinity was investigated,and the crystallization process was studied by examining solid samples obtained at different synthesis times.Results showed that the acid-leached metakaolin was fully converted into soluble aluminum and silicon species,which is crucial for the formation of well-crystallized zeolite beta.At the beginning of the crystallization process,these soluble aluminum and silicon species formed a aluminum-rich intermediate structure with layer morphology.With the crystallization proceeding,more silicon species were incorporated into the zeolite beta framework and the layered structure was changed into spherical particles of zeolite beta with high SiO 2 /Al 2 O 3 ratio and crystallinity.
基金Sahand University of Technology for financial supportIran Nanotechnology Initiative Council for complementary financial support
文摘A nanostructured NiAPSO-34 catalyst was hydrothermally synthesized and the effect of the template （diethylamine （DEA）, tetraethylammonium hydroxide （TEAOH） and DEA/TEAOH） on the physicochemical properties and catalytic performance in the methanol to olefin （MTO） reaction was investigated. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy （FESEM）, particle size distribution analysis, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller anal- ysis and Fourier transform infrared spectroscopy. The X-ray diffraction patterns indicated a higher crystallinity and larger crystallite size for the catalyst synthesized using the DEA template. The FESEM results indicated that the nature of the template could affect the morphology of the nanostructured NiAPSO-34 catalyst because of its effect on the rate of crystal growth. The catalytic performance of the samples was studied in the MTO reaction at atmospheric pressure and a space velocity of 4200 cm^3 /（g h^-1 ） in a fixed bed reactor. The stability and activity of the NiAPSO-34 catalyst were improved using the DEA template because of its higher crystallinity, surface area and the greater extent of Ni incorporation into its framework. The possible stages of synthesis and the reaction mechanism for the MTO process over NiAPSO-34 are discussed in detail.
