DNL-6, a silicoaluminophosphate（SAPO） molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent（SDA）, N,N＇-dimethylethylenediamine. The obtained samples were characte...DNL-6, a silicoaluminophosphate（SAPO） molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent（SDA）, N,N＇-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6 s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning（MAS） nuclear magnetic resonance（13 C, 29 Si, 27 Al, 31 P, and 27 Al multiple-quantum（MQ）） was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals（about 4.4 SDAs per α-cage）, which was the reason for the formation of DNL-6 with an ultrahigh Si content（36.4% Si per mole）. Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.展开更多
基金supported by the National Natural Science Foundation of China(21476228,21676262)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-JSC040)~~
文摘DNL-6, a silicoaluminophosphate（SAPO） molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent（SDA）, N,N＇-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6 s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning（MAS） nuclear magnetic resonance（13 C, 29 Si, 27 Al, 31 P, and 27 Al multiple-quantum（MQ）） was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals（about 4.4 SDAs per α-cage）, which was the reason for the formation of DNL-6 with an ultrahigh Si content（36.4% Si per mole）. Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.
