The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivative...The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivatives used in synthetic materials.Herein,K-Cr@Y with zeolite-encaged isolated O=Cr(VI)=O species modified by extraframework potassium ions is constructed,showing remarkable performance in CO_(2)-promoted ethylbenzene dehydrogenation with initial ethylbenzene conversion of 66%and styrene selectivity of 96%,outperforming other M-Cr@Y catalysts(M=Li,Na,Rb,Cs).Extraframework potassium ions can modulate the electron density of zeolite-encaged Cr(VI)species and therefore facilitate C–H bond activation in ethylbenzene molecules.The gradual reduction of zeolite-encaged O=Cr(VI)=O to less active Cr(IV)=O species by dihydrogen during ethylbenzene dehydrogenation is evidenced by comprehensive characterization results,and Cr(IV)=O can be re-oxidized to O=Cr(VI)=O species upon simple calcination regeneration.The results from in situ DRIFT spectroscopy elucidate the critical promotion role of CO_(2)in ethylbenzene dehydrogenation over K-Cr@Y by retarding the over-reduction of zeolite-encaged Cr species to inactive Cr(III)species and suppressing coke deposition.This study advances the rational design of non-noble metal catalysts for CO_(2)-promoted ethylbenzene dehydrogenation with zeolite-encaged high valence transition metal ions modulated by extraframework cations.展开更多
The complex (Bu4N) 2 [Mo2O5 (mp)2] was synthesized by the reactionof (Bu4N)2[Mo8O26] with H2mp (H2mp=o-mercaptophenol) in methanol. The molecular formula is C44H80Mo2N2O7S2, M.=1005.10. The complex is crystallized in ...The complex (Bu4N) 2 [Mo2O5 (mp)2] was synthesized by the reactionof (Bu4N)2[Mo8O26] with H2mp (H2mp=o-mercaptophenol) in methanol. The molecular formula is C44H80Mo2N2O7S2, M.=1005.10. The complex is crystallized in monoclinic, space group P21/n with unit cell parameters, a = 17. 829 (2) A, b= 13. 759 (2 )A,c= 21. 974(2) A, g=105. 386(8)°, V= 5197. 4(1) , Dc= 1. 285 g/cm3, Z=4,λ(MoKa) =0. 71073 , μ=0. 607 mm-1,F(000) = 2120, final R=0.0348 and wR=0. 0741 for 4912 independent observed reflections (FM>4σ(Fo) ). Two MoO5S units inthe complex molecule exhibits the con facial distorted bioctahedral geometry and possesses an approximate C2 symmetry.展开更多
文摘The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivatives used in synthetic materials.Herein,K-Cr@Y with zeolite-encaged isolated O=Cr(VI)=O species modified by extraframework potassium ions is constructed,showing remarkable performance in CO_(2)-promoted ethylbenzene dehydrogenation with initial ethylbenzene conversion of 66%and styrene selectivity of 96%,outperforming other M-Cr@Y catalysts(M=Li,Na,Rb,Cs).Extraframework potassium ions can modulate the electron density of zeolite-encaged Cr(VI)species and therefore facilitate C–H bond activation in ethylbenzene molecules.The gradual reduction of zeolite-encaged O=Cr(VI)=O to less active Cr(IV)=O species by dihydrogen during ethylbenzene dehydrogenation is evidenced by comprehensive characterization results,and Cr(IV)=O can be re-oxidized to O=Cr(VI)=O species upon simple calcination regeneration.The results from in situ DRIFT spectroscopy elucidate the critical promotion role of CO_(2)in ethylbenzene dehydrogenation over K-Cr@Y by retarding the over-reduction of zeolite-encaged Cr species to inactive Cr(III)species and suppressing coke deposition.This study advances the rational design of non-noble metal catalysts for CO_(2)-promoted ethylbenzene dehydrogenation with zeolite-encaged high valence transition metal ions modulated by extraframework cations.
文摘The complex (Bu4N) 2 [Mo2O5 (mp)2] was synthesized by the reactionof (Bu4N)2[Mo8O26] with H2mp (H2mp=o-mercaptophenol) in methanol. The molecular formula is C44H80Mo2N2O7S2, M.=1005.10. The complex is crystallized in monoclinic, space group P21/n with unit cell parameters, a = 17. 829 (2) A, b= 13. 759 (2 )A,c= 21. 974(2) A, g=105. 386(8)°, V= 5197. 4(1) , Dc= 1. 285 g/cm3, Z=4,λ(MoKa) =0. 71073 , μ=0. 607 mm-1,F(000) = 2120, final R=0.0348 and wR=0. 0741 for 4912 independent observed reflections (FM>4σ(Fo) ). Two MoO5S units inthe complex molecule exhibits the con facial distorted bioctahedral geometry and possesses an approximate C2 symmetry.
