The TPD equation with surface migration of adsorbed species on two kinds of adsorbingsites being put into consideration was derived.According to the equation,a series of theoretical TPD curveswere simulated by compute...The TPD equation with surface migration of adsorbed species on two kinds of adsorbingsites being put into consideration was derived.According to the equation,a series of theoretical TPD curveswere simulated by computer.From the results,one can see that surface migration of adsorbed species af-fects greatly the shape and position of the TPD peaks as well as the resolution power of TPD spectra.展开更多
Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by ...Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by the lack of facile preparation method. Here, high-performance CHA-type Pd-SAPO-34 zeolite was synthesized by a modified solid-state ion exchange(SSIE) method using PdO as Pd precursor,and demonstrated superior PNA performance as compared to Pd-SAPO-34 prepared by conventional wetchemistry strategies. Structural characterization using Raman spectroscopy and X-ray diffraction revealed that the SSIE method avoided water-induced damage to the zeolite framework during Pd loading. Mechanistic investigations on the SSIE process by in situ infrared spectroscopy and X-ray photoelectron spectroscopy disclosed that, while PdO precursor was mainly converted to Pd^(2+) cations coordinated to the zeolite framework by consuming the-OH groups of the zeolite, a portion of PdO could also undergo thermal decomposition to form highly dispersed Pd~0 clusters in the pore channels. This simplified and scalable SSIE method paves a new way for the cost-effective synthesis of defect-free high-performance Pd-SAPO-34 zeolites as PNA catalysts.展开更多
A superior Ce-Ta-Sb composite oxide catalyst prepared using homogeneous precipitation method exhibited excellent deNOx efficiency and nearly 100% Nselectivity with broad operation temperature window and better resista...A superior Ce-Ta-Sb composite oxide catalyst prepared using homogeneous precipitation method exhibited excellent deNOx efficiency and nearly 100% Nselectivity with broad operation temperature window and better resistance to higher space velocity, meanwhile strong resistance to HO and SO. This catalyst was systematically characterized using XRD, Nadsorption, SEM, TEM, XPS, ESR, Raman, H-TPR,NH3-TPD and in situ DRIFTS. There exists a synergistic effect between Ce, Ta and Sb species. It is further indicated that the prominent deNOx performance of the Ce3 Ta3 SbOx catalyst is attributed to the elevated Ce3+ concentrations, abundant active surface oxygen species, as well as surface acidity and reducibility,which is closely linked with the synergistic effect between Ce, Sb and Ta species. Results from DRIFTS reveal that the reaction mechanism of surface-adsorbed NH3 and NOspecies is linked to temperature,the L-H mechanism mainly occurs at low temperature(<300 ℃),while the E-R mechanism occurs at high temperature(>300 ℃). Overall,these findings indicate that Ce3 Ta3 SbOx is promising for NOpractical abatement.展开更多
We used an impregnation method to prepare CuO/AC(activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope(SEM), Brunauer–Emmett–Teller(BET), and Fourier ...We used an impregnation method to prepare CuO/AC(activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope(SEM), Brunauer–Emmett–Teller(BET), and Fourier transform infrared spectroscopy(FT-IR).The effect of CuO content on toluene adsorption/desorption was evaluated.We explored the reusability of AC and AC03(CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing.We used quasi-firstand quasi-second-order models, the Bangham model, and the Weber–Morris model to fit the toluene adsorption data.The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene.The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents.Low CuO content was not favorable for the formation of active adsorption sites,while high content greatly reduced the specific surface area, and even covered active adsorption sites.The toluene adsorption performance varied in the order AC03 > AC02 >AC05 > AC08 > AC01(AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively).The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g,respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C.The adsorption process was best described by the Bangham model and adsorption could be divided into three stages.展开更多
基金the National Natural Science Foundation of China.
文摘The TPD equation with surface migration of adsorbed species on two kinds of adsorbingsites being put into consideration was derived.According to the equation,a series of theoretical TPD curveswere simulated by computer.From the results,one can see that surface migration of adsorbed species af-fects greatly the shape and position of the TPD peaks as well as the resolution power of TPD spectra.
基金supported by the National Natural Science Foundation of China (No.21976058)the Natural Science Foundation of Guangdong Province (No.2023A1515011682)+3 种基金the Fundamental Research Funds for the Central Universities (No.2022ZYGXZR018)the National Engineering Laboratory for Mobile Source Emission Control Technology (No.NELMS2020A10)the funding from the Pearl River Talent Recruitment Program of Guangdong Province (No.2019QN01L170)the Innovation & Entrepreneurship Talent Program of Shaoguan City。
文摘Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by the lack of facile preparation method. Here, high-performance CHA-type Pd-SAPO-34 zeolite was synthesized by a modified solid-state ion exchange(SSIE) method using PdO as Pd precursor,and demonstrated superior PNA performance as compared to Pd-SAPO-34 prepared by conventional wetchemistry strategies. Structural characterization using Raman spectroscopy and X-ray diffraction revealed that the SSIE method avoided water-induced damage to the zeolite framework during Pd loading. Mechanistic investigations on the SSIE process by in situ infrared spectroscopy and X-ray photoelectron spectroscopy disclosed that, while PdO precursor was mainly converted to Pd^(2+) cations coordinated to the zeolite framework by consuming the-OH groups of the zeolite, a portion of PdO could also undergo thermal decomposition to form highly dispersed Pd~0 clusters in the pore channels. This simplified and scalable SSIE method paves a new way for the cost-effective synthesis of defect-free high-performance Pd-SAPO-34 zeolites as PNA catalysts.
基金supported by the National Natural Science Foundation of China(11572292)
文摘A superior Ce-Ta-Sb composite oxide catalyst prepared using homogeneous precipitation method exhibited excellent deNOx efficiency and nearly 100% Nselectivity with broad operation temperature window and better resistance to higher space velocity, meanwhile strong resistance to HO and SO. This catalyst was systematically characterized using XRD, Nadsorption, SEM, TEM, XPS, ESR, Raman, H-TPR,NH3-TPD and in situ DRIFTS. There exists a synergistic effect between Ce, Ta and Sb species. It is further indicated that the prominent deNOx performance of the Ce3 Ta3 SbOx catalyst is attributed to the elevated Ce3+ concentrations, abundant active surface oxygen species, as well as surface acidity and reducibility,which is closely linked with the synergistic effect between Ce, Sb and Ta species. Results from DRIFTS reveal that the reaction mechanism of surface-adsorbed NH3 and NOspecies is linked to temperature,the L-H mechanism mainly occurs at low temperature(<300 ℃),while the E-R mechanism occurs at high temperature(>300 ℃). Overall,these findings indicate that Ce3 Ta3 SbOx is promising for NOpractical abatement.
基金supported by Scientific Platform Project,Ministry of Education(No.fykf201907)Chongqing Feearth Environmental Technology Co.,Ltd.(No.1875029)Student Innovation Fund of Chongqing Technology and Business University(No.193019).
文摘We used an impregnation method to prepare CuO/AC(activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope(SEM), Brunauer–Emmett–Teller(BET), and Fourier transform infrared spectroscopy(FT-IR).The effect of CuO content on toluene adsorption/desorption was evaluated.We explored the reusability of AC and AC03(CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing.We used quasi-firstand quasi-second-order models, the Bangham model, and the Weber–Morris model to fit the toluene adsorption data.The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene.The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents.Low CuO content was not favorable for the formation of active adsorption sites,while high content greatly reduced the specific surface area, and even covered active adsorption sites.The toluene adsorption performance varied in the order AC03 > AC02 >AC05 > AC08 > AC01(AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively).The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g,respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C.The adsorption process was best described by the Bangham model and adsorption could be divided into three stages.
