Polyacrylonitrile （PAN） polymers with different compositions were prepared by an efficient aqueous free-radical polymerization technique. Thermal properties of polyacrylonitrile homopolymer （PAN）, poly（acrylonitr...Polyacrylonitrile （PAN） polymers with different compositions were prepared by an efficient aqueous free-radical polymerization technique. Thermal properties of polyacrylonitrile homopolymer （PAN）, poly（acrylonitrile/itaconic acid） [P（AN/IA）] and poly（acrylonitrile/itaconic acid/acrylamide） [P（AN/IA/AM）] were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetry in detail. It was found that AM had the ability to initiate and accelerate thermal oxidative stabilization process, which was confirmed by the lower initiation temperature and broader exothermic peak in P（AN/IA/AM） as compared with that in P（AN/IA） and PAN. The intensity of heat releasing during the thermal treatment was relaxed due to the presence of two separated exothermic peaks. Accompanied by DSC analysis and calculation of the apparent activation energy of cyclization reaction, two peaks were assigned to the ionic and free radical induction mechanisms, respectively. The higher rate constant in P（AN/IA/AM） indicated that the ionic mechanism actually had a kinetic advantage at promoting thermal stability over the free radical mechanism. This study clearly show that the synthesized P（AN/IA/AM） terpolymers possess larger room to adjust manufacture parameters to fabricate high performance of PAN-based carbon fibers.展开更多
CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for...CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.展开更多
HZSM-5, Al_2O_3, TiO_2 and SiO_2 supported CeO_2-ZrO_2-CrO_x catalysts were prepared by deposition-precipitation method and tested for deep catalytic oxidation of 1,2-dichloroethane（DCE）, as one of the common chlori...HZSM-5, Al_2O_3, TiO_2 and SiO_2 supported CeO_2-ZrO_2-CrO_x catalysts were prepared by deposition-precipitation method and tested for deep catalytic oxidation of 1,2-dichloroethane（DCE）, as one of the common chlorinated organic pollutants. All the catalysts were characterized by means of N_2 adsorption-desorption, X-ray photoelectron spectroscopy（XPS）, ammonia-temperatureprogrammed desorption（NH_3-TPD） and hydrogen temperature-programmed reduction（H2-TPR）. The characterization results revealed that there was strongly synergistic effect between the oxidizability of CZCr species and the acidity of supports, which obviously promoted the catalytic activity for DCE degradation. 20% CZCr/HZSM-5 showed the highest activity and good durability during the long-term continuous test. The catalytic activity decreased in the order： 20%CZCr/HZSM-5〉CZCr〉20%CZCr/TiO_2〉20%CZCr/Al_2O_3〉20%CZCr/SiO_2.展开更多
Antioxidants addition is believed as a facile and effective way to improve jet fuel thermal oxidation stability.However,amine antioxidants,as one of the most important antioxidants,have not received sufficient attenti...Antioxidants addition is believed as a facile and effective way to improve jet fuel thermal oxidation stability.However,amine antioxidants,as one of the most important antioxidants,have not received sufficient attention in the field of jet fuel autoxidation yet.Herein,the inhibition efficiency and mechanism of decane and exo-tetrahydrodicyclopentadiene(THDCPD)oxidation by di-4-tert-butylphenylamine(diarylamine)was experimentally and theoretically investigated.The results show that diarylamine can significantly inhibit decane oxidation but is less efficient for THDCPD oxidation,which is attributed to the higher energy barrier of retro-carbonyl-ene reaction(rate-determining step)in THDCPD than that in decane during diarylamine regeneration.However,the addition of diarylamine will cause undesirable color change after accelerated oxidation and produce slightly more deposits during high-temperature thermal oxidative stress for both decane and THDCPD.The results provide significant implications for the future design of effective antioxidant additives for high-performance jet fuel.展开更多
By evaluating the SEM images,specific surface area,and the catalytic synthesis reaction conditions of an activated carbon-supported p-toluenesulfonic acid catalyst,and comparing the physical and chemical properties,in...By evaluating the SEM images,specific surface area,and the catalytic synthesis reaction conditions of an activated carbon-supported p-toluenesulfonic acid catalyst,and comparing the physical and chemical properties,infrared spectra,nuclear magnetic resonance spectra,oxidation stability,thermal stability,hydrolytic stability,and extreme pressure anti-wear performance of the synthesized trihydroxymethylpropyl trioleate with imported reference esters,the feasibility of its application as a substitute was investigated.The results indicated that the activated carbon-supported p-toluenesulfonic acid catalyst exhibited loose porosity,high specific surface area,and high esterification efficiency.When synthesized under optimal conditions,the yield rate of trihydroxymethylpropyl trioleate reached 99.3%,with a simple separation process that did not require additional steps such as neutralization and washing and generated minimal wastewater.The physical and chemical properties of the synthesized trihydroxymethylpropyl trioleate were comparable to those of the reference ester in terms of color,viscosity,viscosity index,flash point,and pour point.Moreover,the peak position and peak height in the infrared and nuclear magnetic carbon spectra were essentially the same.Through comprehensive evaluations and comparisons of various properties,it was determined that the performance of trihydroxymethylpropyl trioleate was comparable to that of the imported reference esters.展开更多
Tocopherol is the most active vitamin and natural antioxidant existing in the nature known as vitamin E. Lacking of this vitamin makes drastic exchanges on the health of the living organisms. Their active chemical for...Tocopherol is the most active vitamin and natural antioxidant existing in the nature known as vitamin E. Lacking of this vitamin makes drastic exchanges on the health of the living organisms. Their active chemical form is l-α-tocopherol substance. In this article, α-thiotocopherol a tocopherol derivative was synthesized via a precursor like dl-α-tocopherol, which has better antioxidant than natural α-tocopherol. And the last compound after separation and purification via TLC and PC procedures was analyzed by FTIR, GC-MS and elemental analysis, oxidative stability is tested with TGA method in air showing roughly antioxidant effect. Another approach is measurment of redox potential against a reference electrode under inert nitrogen atmosphere.展开更多
Direct air capture (DAC) using amine-functionalized solid adsorbents holds promise for achieving negative carbon emissions. In this study, a series of additive-incorporated tetraethylenepentamine-functionalized SiO_(2...Direct air capture (DAC) using amine-functionalized solid adsorbents holds promise for achieving negative carbon emissions. In this study, a series of additive-incorporated tetraethylenepentamine-functionalized SiO_(2) adsorbents with varying tetraethylenepentamine and additive contents were prepared via a simple impregnation method, characterized by various techniques, and applied in the DAC process. The structure-performance relationship of these adsorbents in DAC was investigated, revealing that the quantity of active amine sites (or the tetraethylenepentamine content in the exposed layer), as determined by CO_(2)-TPD measurement, was an important factor affecting the adsorbent performance. This factor, which varied with the tetraethylenepentamine content, additive type, and additive content, showed a positive correlation with the CO_(2) adsorption capacity of the adsorbents. The optimal adsorbent, 40TEPA-10PEG/SiO_(2) containing 40 wt % tetraethylenepentamine and 10 wt % polyethylene glycol (Mn = 200), exhibited a stable CO_(2) capacity of 2.1 mmol·g^(-1) and amine efficiency of 0.22 over 20 adsorption–desorption cycles (adsorption at 400 ppm CO_(2)/N2 and 30℃ for 60 min, and desorption at pure N2 and 90℃ for 20 min). Moreover, even after deliberate accelerated oxidation treatment (pretreated in air at 100℃ for 10 h), the CO_(2) capacity of 40TEPA-10PEG/SiO_(2) remained at 2.0 mmol·g^(-1). The superior thermal and oxidative stability of 40TEPA-10PEG/SiO_(2) makes it a promising adsorbent for DAC applications.展开更多
基金financially supported by the National 973 Project(Nos.2011CB605602 and 2011CB605603)the Program of Introducing Talents of Discipline to Universities(No.111-2-04)
文摘Polyacrylonitrile （PAN） polymers with different compositions were prepared by an efficient aqueous free-radical polymerization technique. Thermal properties of polyacrylonitrile homopolymer （PAN）, poly（acrylonitrile/itaconic acid） [P（AN/IA）] and poly（acrylonitrile/itaconic acid/acrylamide） [P（AN/IA/AM）] were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetry in detail. It was found that AM had the ability to initiate and accelerate thermal oxidative stabilization process, which was confirmed by the lower initiation temperature and broader exothermic peak in P（AN/IA/AM） as compared with that in P（AN/IA） and PAN. The intensity of heat releasing during the thermal treatment was relaxed due to the presence of two separated exothermic peaks. Accompanied by DSC analysis and calculation of the apparent activation energy of cyclization reaction, two peaks were assigned to the ionic and free radical induction mechanisms, respectively. The higher rate constant in P（AN/IA/AM） indicated that the ionic mechanism actually had a kinetic advantage at promoting thermal stability over the free radical mechanism. This study clearly show that the synthesized P（AN/IA/AM） terpolymers possess larger room to adjust manufacture parameters to fabricate high performance of PAN-based carbon fibers.
基金PRIN 2006, "Caratterizzazione spettroscopica e morfologica di Me-POSS eterogeneizzati", MEL Chemicals
文摘CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermaUy treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.
基金Project supports from National Nature Science Foundation of China(21177110)
文摘HZSM-5, Al_2O_3, TiO_2 and SiO_2 supported CeO_2-ZrO_2-CrO_x catalysts were prepared by deposition-precipitation method and tested for deep catalytic oxidation of 1,2-dichloroethane（DCE）, as one of the common chlorinated organic pollutants. All the catalysts were characterized by means of N_2 adsorption-desorption, X-ray photoelectron spectroscopy（XPS）, ammonia-temperatureprogrammed desorption（NH_3-TPD） and hydrogen temperature-programmed reduction（H2-TPR）. The characterization results revealed that there was strongly synergistic effect between the oxidizability of CZCr species and the acidity of supports, which obviously promoted the catalytic activity for DCE degradation. 20% CZCr/HZSM-5 showed the highest activity and good durability during the long-term continuous test. The catalytic activity decreased in the order： 20%CZCr/HZSM-5〉CZCr〉20%CZCr/TiO_2〉20%CZCr/Al_2O_3〉20%CZCr/SiO_2.
基金the financial support from the Postdoctoral Science Foundation of China(2021M702810)the Haihe Laboratory of Sustainable Chemical Transformations(CYZC202103)the National Natural Science Foundation of China(21978200 and 22222808)。
文摘Antioxidants addition is believed as a facile and effective way to improve jet fuel thermal oxidation stability.However,amine antioxidants,as one of the most important antioxidants,have not received sufficient attention in the field of jet fuel autoxidation yet.Herein,the inhibition efficiency and mechanism of decane and exo-tetrahydrodicyclopentadiene(THDCPD)oxidation by di-4-tert-butylphenylamine(diarylamine)was experimentally and theoretically investigated.The results show that diarylamine can significantly inhibit decane oxidation but is less efficient for THDCPD oxidation,which is attributed to the higher energy barrier of retro-carbonyl-ene reaction(rate-determining step)in THDCPD than that in decane during diarylamine regeneration.However,the addition of diarylamine will cause undesirable color change after accelerated oxidation and produce slightly more deposits during high-temperature thermal oxidative stress for both decane and THDCPD.The results provide significant implications for the future design of effective antioxidant additives for high-performance jet fuel.
文摘By evaluating the SEM images,specific surface area,and the catalytic synthesis reaction conditions of an activated carbon-supported p-toluenesulfonic acid catalyst,and comparing the physical and chemical properties,infrared spectra,nuclear magnetic resonance spectra,oxidation stability,thermal stability,hydrolytic stability,and extreme pressure anti-wear performance of the synthesized trihydroxymethylpropyl trioleate with imported reference esters,the feasibility of its application as a substitute was investigated.The results indicated that the activated carbon-supported p-toluenesulfonic acid catalyst exhibited loose porosity,high specific surface area,and high esterification efficiency.When synthesized under optimal conditions,the yield rate of trihydroxymethylpropyl trioleate reached 99.3%,with a simple separation process that did not require additional steps such as neutralization and washing and generated minimal wastewater.The physical and chemical properties of the synthesized trihydroxymethylpropyl trioleate were comparable to those of the reference ester in terms of color,viscosity,viscosity index,flash point,and pour point.Moreover,the peak position and peak height in the infrared and nuclear magnetic carbon spectra were essentially the same.Through comprehensive evaluations and comparisons of various properties,it was determined that the performance of trihydroxymethylpropyl trioleate was comparable to that of the imported reference esters.
文摘Tocopherol is the most active vitamin and natural antioxidant existing in the nature known as vitamin E. Lacking of this vitamin makes drastic exchanges on the health of the living organisms. Their active chemical form is l-α-tocopherol substance. In this article, α-thiotocopherol a tocopherol derivative was synthesized via a precursor like dl-α-tocopherol, which has better antioxidant than natural α-tocopherol. And the last compound after separation and purification via TLC and PC procedures was analyzed by FTIR, GC-MS and elemental analysis, oxidative stability is tested with TGA method in air showing roughly antioxidant effect. Another approach is measurment of redox potential against a reference electrode under inert nitrogen atmosphere.
基金Financial support from the National Natural Science Foundation of China(Grant No.22278143)is gratefully acknowledged.
文摘Direct air capture (DAC) using amine-functionalized solid adsorbents holds promise for achieving negative carbon emissions. In this study, a series of additive-incorporated tetraethylenepentamine-functionalized SiO_(2) adsorbents with varying tetraethylenepentamine and additive contents were prepared via a simple impregnation method, characterized by various techniques, and applied in the DAC process. The structure-performance relationship of these adsorbents in DAC was investigated, revealing that the quantity of active amine sites (or the tetraethylenepentamine content in the exposed layer), as determined by CO_(2)-TPD measurement, was an important factor affecting the adsorbent performance. This factor, which varied with the tetraethylenepentamine content, additive type, and additive content, showed a positive correlation with the CO_(2) adsorption capacity of the adsorbents. The optimal adsorbent, 40TEPA-10PEG/SiO_(2) containing 40 wt % tetraethylenepentamine and 10 wt % polyethylene glycol (Mn = 200), exhibited a stable CO_(2) capacity of 2.1 mmol·g^(-1) and amine efficiency of 0.22 over 20 adsorption–desorption cycles (adsorption at 400 ppm CO_(2)/N2 and 30℃ for 60 min, and desorption at pure N2 and 90℃ for 20 min). Moreover, even after deliberate accelerated oxidation treatment (pretreated in air at 100℃ for 10 h), the CO_(2) capacity of 40TEPA-10PEG/SiO_(2) remained at 2.0 mmol·g^(-1). The superior thermal and oxidative stability of 40TEPA-10PEG/SiO_(2) makes it a promising adsorbent for DAC applications.
