The low‐temperature hydrothermal stabilities of Cu‐SAPO‐34samples with various Si contents and Cu loadings were systematically investigated.The NH3oxidation activities and NH3‐selective catalytic reduction(SCR)act...The low‐temperature hydrothermal stabilities of Cu‐SAPO‐34samples with various Si contents and Cu loadings were systematically investigated.The NH3oxidation activities and NH3‐selective catalytic reduction(SCR)activities(mainly the low‐temperature activities)of all the Cu‐SAPO‐34catalysts declined after low‐temperature steam treatment(LTST).These results show that the texture and acid density of Cu‐SAPO‐34can be better preserved by increasing the Cu loading,although the hydrolysis of Si-O-Al bonds is inevitable.The stability of Cu ions and the stability of the SAPO framework were positively correlated at relatively low Cu loadings.However,a high Cu loading(e.g.,3.67wt%)resulted in a significant decrease in the number of isolated Cu ions.Aggregation of CuO particles also occurred during the LTST,which accounts for the decreasing NH3oxidation activities of the catalysts.Among the catalysts,Cu‐SAPO‐34with a high Si content and medium Cu content(1.37wt%)showed the lowest decrease in NH3‐SCR because its Cu2+content was well retained and its acid density was well preserved.展开更多
The performance of ion-exchange resin catalysts during isobutene (IB) dimerization was investigated under different IB contents,temperatures and liquid-volume hourly space velocity (LHSV) using a plug flow reactor in ...The performance of ion-exchange resin catalysts during isobutene (IB) dimerization was investigated under different IB contents,temperatures and liquid-volume hourly space velocity (LHSV) using a plug flow reactor in the absence of any selectivity enhancing component.High IB content and temperature resulted in a high conversion and C12 selectivity bu low C8 selectivity.The influence of LHSV was related with the IB content:LHSV had great effect at high IB content,while the performance of ion-exchange resin changed little with LHSV if IB content was low.The effect of water on the stability of resins was also studied.Desulfonation was observed during the C4 dimerization reaction when water was added to the feed.Chlorinated resin was more stable than conventional polystyrene-based resins during the test.展开更多
Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Neverth...Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Nevertheless,balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium.Herein,a polyarylether-based covalent organic framework functionalized with open-chain amidoxime(COF-HHTF-AO)was synthesized with remarkable chemical stability and excellent crystallinity.Impressively,the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g,which is 1.61 times higher than that for vanadium.Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime.Combining enhanced adsorption capacity,excellent selectivity and ultrahigh stability,COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.展开更多
The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides （MOP, Ni2P, Co2P, and Fe2P） wer...The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides （MOP, Ni2P, Co2P, and Fe2P） were prepared by wet impregnation and temperature-programmed reduction and characterized by X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, EDX mapping, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, brunauer-emmett- teller （BET）, temperature-programmed desorption of ammonia （NH3-TPD）, and fourier transform infrared spectroscopy of pyridine （pyridine-FTIR）. Of all the transition metal phosphides MoP was formed at a lower reduction temperature, which resuited in smaller particle size that enhanced the overall surface area of the catalyst. The existence of weak, moderate, and Lewis acidic sites over MoP were responsible for its high tetralin selectivity （90%） and stability during the 100 h reaction on-stream in a fixed-bed reactor.展开更多
基金supported by the National Natural Science Foundation of China(21676262,21506207,21606221)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-JSC040)~~
文摘The low‐temperature hydrothermal stabilities of Cu‐SAPO‐34samples with various Si contents and Cu loadings were systematically investigated.The NH3oxidation activities and NH3‐selective catalytic reduction(SCR)activities(mainly the low‐temperature activities)of all the Cu‐SAPO‐34catalysts declined after low‐temperature steam treatment(LTST).These results show that the texture and acid density of Cu‐SAPO‐34can be better preserved by increasing the Cu loading,although the hydrolysis of Si-O-Al bonds is inevitable.The stability of Cu ions and the stability of the SAPO framework were positively correlated at relatively low Cu loadings.However,a high Cu loading(e.g.,3.67wt%)resulted in a significant decrease in the number of isolated Cu ions.Aggregation of CuO particles also occurred during the LTST,which accounts for the decreasing NH3oxidation activities of the catalysts.Among the catalysts,Cu‐SAPO‐34with a high Si content and medium Cu content(1.37wt%)showed the lowest decrease in NH3‐SCR because its Cu2+content was well retained and its acid density was well preserved.
基金supported financially by the Purolite Company and the Chinese National Natural Science Foundation (20674069)
文摘The performance of ion-exchange resin catalysts during isobutene (IB) dimerization was investigated under different IB contents,temperatures and liquid-volume hourly space velocity (LHSV) using a plug flow reactor in the absence of any selectivity enhancing component.High IB content and temperature resulted in a high conversion and C12 selectivity bu low C8 selectivity.The influence of LHSV was related with the IB content:LHSV had great effect at high IB content,while the performance of ion-exchange resin changed little with LHSV if IB content was low.The effect of water on the stability of resins was also studied.Desulfonation was observed during the C4 dimerization reaction when water was added to the feed.Chlorinated resin was more stable than conventional polystyrene-based resins during the test.
基金supported by the Science Challenge Project(TZ2016004)the National Natural Key Research and Development Program of China(2018YFC1900105 and 2017YFA0207002)Beijing Outstanding Young Scientist Program。
文摘Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Nevertheless,balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium.Herein,a polyarylether-based covalent organic framework functionalized with open-chain amidoxime(COF-HHTF-AO)was synthesized with remarkable chemical stability and excellent crystallinity.Impressively,the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g,which is 1.61 times higher than that for vanadium.Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime.Combining enhanced adsorption capacity,excellent selectivity and ultrahigh stability,COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.
基金financial support from the Special Funds of the National Natural Science Foundation of China(21127011)National High Technology Research and Development Program of China(2011AA050606)National Natural Science Foundation of China(Petrochemical Joint Fund,U1162106)
文摘The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides （MOP, Ni2P, Co2P, and Fe2P） were prepared by wet impregnation and temperature-programmed reduction and characterized by X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, EDX mapping, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, brunauer-emmett- teller （BET）, temperature-programmed desorption of ammonia （NH3-TPD）, and fourier transform infrared spectroscopy of pyridine （pyridine-FTIR）. Of all the transition metal phosphides MoP was formed at a lower reduction temperature, which resuited in smaller particle size that enhanced the overall surface area of the catalyst. The existence of weak, moderate, and Lewis acidic sites over MoP were responsible for its high tetralin selectivity （90%） and stability during the 100 h reaction on-stream in a fixed-bed reactor.
