A series of phosphorus-modified PITQ-13 catalysts was prepared by wet impregnation of NH4H2PO4 solution into an HITQ-13 parent. The catalysts were characterized using XRD, N2 adsorption, MAS NMR and NH3-TPD. Their cat...A series of phosphorus-modified PITQ-13 catalysts was prepared by wet impregnation of NH4H2PO4 solution into an HITQ-13 parent. The catalysts were characterized using XRD, N2 adsorption, MAS NMR and NH3-TPD. Their catalytic performance in 1-butene catalytic cracking was evaluated in a fixed fluidized bed reactor. The results showed that the crystallinity, surface area and pore volume of P-modified PITQ-13 catalysts decreased with the increasing amounts of P. The number of weak acid sites increased, whereas that of strong acidity decreased. The selectivity to propylene in 1-butene cracking reactions increased because of the decrease in strong acidity. The yield of propylene achieved 41.6% over PITQ-13-2 catalyst with a P content of 1.0 wt%, which was 5.1% greater than that achieved over HITQ-13 catalyst.展开更多
Adsorption desulfurization performance of Na Y,HY and Ce HY zeolites is evaluated in a miniature fixedbed flow by model gasoline containing with thiophene,tetrahydrothiophene,2-methylthiophene,benzothiophene or mixed ...Adsorption desulfurization performance of Na Y,HY and Ce HY zeolites is evaluated in a miniature fixedbed flow by model gasoline containing with thiophene,tetrahydrothiophene,2-methylthiophene,benzothiophene or mixed sulfur compounds.The structural properties of adsorbents are characterized by XRD,N2-adsorption and XPS techniques.Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work,have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules.Desulfurization experimental results show that the Ce HY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound,especially in the capture of aromatic 2-methylthiophene(about ca.28.6 mgS/gadsorbent).The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity,mainly resulting from the synergy between Br?nsted acid sites and Ce(III)hydroxylated species active sites located in the supercages of Ce HY.Meanwhile,the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites.By contrast,the oligomerization reaction of benzothiophene molecules on the active sites of Ce HY cannot occur due to the restriction of cavity size of supercages,but they can be adsorbed on the Br?nsted acid sites via protonation,and on Ce(III)hydroxylated species and extra-framework aluminum hydroxyls species via direct"S-M"bonding interaction.As to the tetrahydrothiophene,adsorption mechanism is similar to that of benzothiophene,except in the absence of protonation.The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.展开更多
Dear editor,Due to visual impairment and lack of social attention,the reading problem of the blind has not been well resolved.Many existing Braille reading devices still have many problems and are not accepted by the ...Dear editor,Due to visual impairment and lack of social attention,the reading problem of the blind has not been well resolved.Many existing Braille reading devices still have many problems and are not accepted by the public.This paper developed a portable Braille reading system based on electrotactile display technology.The proposed system is composed of a six-channel electrotactile stimulator,a flexible electrode array for Braille display and a graphical user interface(GUI)for monitoring and control.Based on the flexibility of the system,two Braille reading strategies have been designed:spatial mode and sequential mode.The system was preliminary tested by six sighted subjects.The results showed that subjects were able to recognize Braille characters with more than 80%accuracy within less than 10 seconds for the initial use.Compared to existing Braille reading systems,this system is portable,wearable and flexible in control.展开更多
Engineering of crystal morphology affects the catalytic and adsorption properties of zeolitic materials.Considering the anisotropic diffusion of molecules derived from its topological features,MFI zeolite nanosheets w...Engineering of crystal morphology affects the catalytic and adsorption properties of zeolitic materials.Considering the anisotropic diffusion of molecules derived from its topological features,MFI zeolite nanosheets with short b-axis thickness are highly desired materials to reduce diffusion resistance.However,the design and development of eco-friendly synthesis protocols with reasonable cost and high efficiency remain elusive.Herein,we reported a systematic study on the synthesis of MFI nanosheets using urea as an additive.Both silicalite-1 and ZSM-5 zeolites(MFI type framework structure)with controllable b-thicknesses ranging from 50–200 nm were achieved by optimizing the synthetic parameters including water content,urea and SDA concentrations.The concentration of hydroxide anions was found to dominate the crystallization kinetics compared with the counterpart tetrapropylammonium cations(TPA^(+)).To facilitate the crystal growth of MFI zeolites in the presence of urea,the ratio OH−/SiO_(2)has to be higher than 0.2,independent of the TPA+concentration.The role of urea in the assistance of plate-like crystal formation through the inhibition of(010)facet growth was revealed by electron microscopy and infrared(IR)spectroscopy analyses.The developed strategy for morphological engineering is not limited to the MFI-type zeolite and can be applied to other frameworks depending on the intrinsic properties of additive molecules and the interactions between them.展开更多
Starting with the relatively simple observation that the variational estimates of the commutators of the standard Calderón-Zygmund operators with the bounded mean oscillation(BMO)functions can be obtained from th...Starting with the relatively simple observation that the variational estimates of the commutators of the standard Calderón-Zygmund operators with the bounded mean oscillation(BMO)functions can be obtained from their weighted variational estimates,we establish the similar variational estimates for the commutators of the BMO functions with rough singular integrals,which do not admit any weighted variational estimates.The proof involves several Littlewood-Paley-type inequalities with the commutators as well as Bony decomposition and related para-product estimates.展开更多
The author considers the L^p boundedness for two kinds of Carleson-type maximal operators with variable kernels(Ω(x,y'))/(|y|~n),whereΩ(x,y')∈L~∞(R^n)×W_2~s(S^(n-1))for some s>0.
基金supported by PetroChina Company Limited(12-09-01-01)the National Basic Research Program of China(973 Program,2012CB215001)
文摘A series of phosphorus-modified PITQ-13 catalysts was prepared by wet impregnation of NH4H2PO4 solution into an HITQ-13 parent. The catalysts were characterized using XRD, N2 adsorption, MAS NMR and NH3-TPD. Their catalytic performance in 1-butene catalytic cracking was evaluated in a fixed fluidized bed reactor. The results showed that the crystallinity, surface area and pore volume of P-modified PITQ-13 catalysts decreased with the increasing amounts of P. The number of weak acid sites increased, whereas that of strong acidity decreased. The selectivity to propylene in 1-butene cracking reactions increased because of the decrease in strong acidity. The yield of propylene achieved 41.6% over PITQ-13-2 catalyst with a P content of 1.0 wt%, which was 5.1% greater than that achieved over HITQ-13 catalyst.
基金financially supported by the National Natural Science Foundation of China (Nos. U1662135 and 21376114, 21076100)by the China National Petroleum Corporation (Grant No. 1001A-01-01-01)
文摘Adsorption desulfurization performance of Na Y,HY and Ce HY zeolites is evaluated in a miniature fixedbed flow by model gasoline containing with thiophene,tetrahydrothiophene,2-methylthiophene,benzothiophene or mixed sulfur compounds.The structural properties of adsorbents are characterized by XRD,N2-adsorption and XPS techniques.Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work,have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules.Desulfurization experimental results show that the Ce HY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound,especially in the capture of aromatic 2-methylthiophene(about ca.28.6 mgS/gadsorbent).The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity,mainly resulting from the synergy between Br?nsted acid sites and Ce(III)hydroxylated species active sites located in the supercages of Ce HY.Meanwhile,the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites.By contrast,the oligomerization reaction of benzothiophene molecules on the active sites of Ce HY cannot occur due to the restriction of cavity size of supercages,but they can be adsorbed on the Br?nsted acid sites via protonation,and on Ce(III)hydroxylated species and extra-framework aluminum hydroxyls species via direct"S-M"bonding interaction.As to the tetrahydrothiophene,adsorption mechanism is similar to that of benzothiophene,except in the absence of protonation.The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.
基金supported by the Shenzhen Science and Technology Program(JCYJ20210324120214040)the Guangdong Science and Technology Research Council(2020B1515120064)the National Natural Science Foundation of China(61733011,62003222)。
文摘Dear editor,Due to visual impairment and lack of social attention,the reading problem of the blind has not been well resolved.Many existing Braille reading devices still have many problems and are not accepted by the public.This paper developed a portable Braille reading system based on electrotactile display technology.The proposed system is composed of a six-channel electrotactile stimulator,a flexible electrode array for Braille display and a graphical user interface(GUI)for monitoring and control.Based on the flexibility of the system,two Braille reading strategies have been designed:spatial mode and sequential mode.The system was preliminary tested by six sighted subjects.The results showed that subjects were able to recognize Braille characters with more than 80%accuracy within less than 10 seconds for the initial use.Compared to existing Braille reading systems,this system is portable,wearable and flexible in control.
基金the National Natural Science Foundation of China(NSFC)(No.22178389)S.M.acknowledges the support from NSFC(No.21975285)Z.X.Q.and S.M.acknowledge the support from PetroChina(Nos.PRIKY21084 and KYWX-21-021).
文摘Engineering of crystal morphology affects the catalytic and adsorption properties of zeolitic materials.Considering the anisotropic diffusion of molecules derived from its topological features,MFI zeolite nanosheets with short b-axis thickness are highly desired materials to reduce diffusion resistance.However,the design and development of eco-friendly synthesis protocols with reasonable cost and high efficiency remain elusive.Herein,we reported a systematic study on the synthesis of MFI nanosheets using urea as an additive.Both silicalite-1 and ZSM-5 zeolites(MFI type framework structure)with controllable b-thicknesses ranging from 50–200 nm were achieved by optimizing the synthetic parameters including water content,urea and SDA concentrations.The concentration of hydroxide anions was found to dominate the crystallization kinetics compared with the counterpart tetrapropylammonium cations(TPA^(+)).To facilitate the crystal growth of MFI zeolites in the presence of urea,the ratio OH−/SiO_(2)has to be higher than 0.2,independent of the TPA+concentration.The role of urea in the assistance of plate-like crystal formation through the inhibition of(010)facet growth was revealed by electron microscopy and infrared(IR)spectroscopy analyses.The developed strategy for morphological engineering is not limited to the MFI-type zeolite and can be applied to other frameworks depending on the intrinsic properties of additive molecules and the interactions between them.
基金supported by National Natural Science Foundation of China(Grant Nos.11871096,11471033,11571160 and 11601396)Thousand Youth Talents Plan of China(Grant No.429900018101150(2016))+1 种基金Funds for Talents of China(Grant No.413100002)the Fundamental Research Funds for the Central Universities and Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130003110003)。
文摘Starting with the relatively simple observation that the variational estimates of the commutators of the standard Calderón-Zygmund operators with the bounded mean oscillation(BMO)functions can be obtained from their weighted variational estimates,we establish the similar variational estimates for the commutators of the BMO functions with rough singular integrals,which do not admit any weighted variational estimates.The proof involves several Littlewood-Paley-type inequalities with the commutators as well as Bony decomposition and related para-product estimates.
基金supported by the National Natural Science Foundation of China(Nos.11226103,11226102)the Doctor Foundation of Henan Polytechnic University(No.B2011-034)
文摘The author considers the L^p boundedness for two kinds of Carleson-type maximal operators with variable kernels(Ω(x,y'))/(|y|~n),whereΩ(x,y')∈L~∞(R^n)×W_2~s(S^(n-1))for some s>0.