The loading-dispersion-reducibility dependence has always been one of the most critical issues in the development of high-performance supported metal catalysts.Herein,up to 40 wt%NiO over ordered mesoporous alumina(OM...The loading-dispersion-reducibility dependence has always been one of the most critical issues in the development of high-performance supported metal catalysts.Herein,up to 40 wt%NiO over ordered mesoporous alumina(OMA)was prepared by co-grinding the hybrid of template-containing OMA and Ni(NO_(3))2:6H_(2)O.Characterization results confirmed that the OMA mesostructure was still preserved even after loading NiO at a content as high as 40 wt%.More importantly,the reduction extent,dispersion,and average particle size of the Ni/OMA catalysts were maintained at≥91.0%,~13.5%,and~4.0-5.0 nm,respectively,when the Ni0 loading was increased from 20 to 40 wt%.The catalysts were evaluated for the CO methanation as a model reaction,and the similarly high turnover frequency of 24.0 h^(-1) was achieved at 300℃ for all of the Ni/OMA catalysts.For the catalyst with the highest NiO loading of 40 wt%(40Ni/OMA),the low-temperature activity at 300℃ indexed by the space-time yield of methane(over 325.8 molCH_(4)·kg_(cat)^(-1)·h^(-1))was achieved,while the catalyst was operated without an observable deactivation for a time on stream of 120 h under severe reaction conditions of 600℃ and a very high gas hourly space velocity of 240000 mL·g^(-1).h^(-1).With these significant results,this work paves the way for a rational and controllable design of supported Ni catalysts by breaking the loadingdispersion-reducibility dependence and stabilizing Ni nanoparticles under harsh reaction conditions.展开更多
MgH_(2) is considered one of the most promising hydrogen storage materials because of its safety,high efficiency,high hydrogen storage quantity and low cost characteristics.But some shortcomings are still existed:high...MgH_(2) is considered one of the most promising hydrogen storage materials because of its safety,high efficiency,high hydrogen storage quantity and low cost characteristics.But some shortcomings are still existed:high operating temperature and poor hydrogen absorption dynamics,which limit its application.Porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres(NZC/Ni@CNT)is prepared by facile filtration and calcination method.Then the different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%)is added to the MgH_(2) by ball milling.Among the three samples with different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%),the MgH_(2)-5 wt%NZC/Ni@CNT composite exhibits the best hydrogen storage performances.After testing,the MgH_(2)-5 wt%NZC/Ni@CNT begins to release hydrogen at around 110℃ and hydrogen absorption capacity reaches 2.34 wt%H_(2) at 80℃ within 60 min.Moreover,the composite can release about 5.36 wt%H_(2) at 300℃.In addition,hydrogen absorption and desorption activation energies of the MgH_(2)-5 wt%NZC/Ni@CNT composite are reduced to 37.28 and 84.22 KJ/mol H_(2),respectively.The in situ generated Mg_(2)NiH_(4)/Mg_(2)Ni can serve as a"hydrogen pump"that plays the main role in providing more activation sites and hydrogen diffusion channels which promotes H_(2) dissociation during hydrogen absorption process.In addition,the evenly dispersed Zn and MgZn2 in Mg and MgH_(2) could provide sites for Mg/MgH_(2) nucleation and hydrogen diffusion channel.This attempt clearly proved that the bimetallic carbide Ni_(3)ZnC_(0.7) is a effective additive for the hydrogen storage performances modification of MgH_(2),and the facile synthesis of the Ni_(3)ZnC_(0.7)/Ni@CNT can provide directions of better designing high performance carbide catalysts for improving MgH_(2).展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.22208205)the Fundamental Research Funds for the Central Universities(Grant No.GK202304042)the Key Research and Development Program of Shaanxi Province(Grant No.2024SF-YBXM-613).
文摘The loading-dispersion-reducibility dependence has always been one of the most critical issues in the development of high-performance supported metal catalysts.Herein,up to 40 wt%NiO over ordered mesoporous alumina(OMA)was prepared by co-grinding the hybrid of template-containing OMA and Ni(NO_(3))2:6H_(2)O.Characterization results confirmed that the OMA mesostructure was still preserved even after loading NiO at a content as high as 40 wt%.More importantly,the reduction extent,dispersion,and average particle size of the Ni/OMA catalysts were maintained at≥91.0%,~13.5%,and~4.0-5.0 nm,respectively,when the Ni0 loading was increased from 20 to 40 wt%.The catalysts were evaluated for the CO methanation as a model reaction,and the similarly high turnover frequency of 24.0 h^(-1) was achieved at 300℃ for all of the Ni/OMA catalysts.For the catalyst with the highest NiO loading of 40 wt%(40Ni/OMA),the low-temperature activity at 300℃ indexed by the space-time yield of methane(over 325.8 molCH_(4)·kg_(cat)^(-1)·h^(-1))was achieved,while the catalyst was operated without an observable deactivation for a time on stream of 120 h under severe reaction conditions of 600℃ and a very high gas hourly space velocity of 240000 mL·g^(-1).h^(-1).With these significant results,this work paves the way for a rational and controllable design of supported Ni catalysts by breaking the loadingdispersion-reducibility dependence and stabilizing Ni nanoparticles under harsh reaction conditions.
基金supported by research programs of National Natural Science Foundation of China(52101274,51731002)Natural Science Foundation of Shandong Province(No.ZR2020QE011)Youth Top Talent Foundation of Yantai University(2219008).
文摘MgH_(2) is considered one of the most promising hydrogen storage materials because of its safety,high efficiency,high hydrogen storage quantity and low cost characteristics.But some shortcomings are still existed:high operating temperature and poor hydrogen absorption dynamics,which limit its application.Porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres(NZC/Ni@CNT)is prepared by facile filtration and calcination method.Then the different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%)is added to the MgH_(2) by ball milling.Among the three samples with different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%),the MgH_(2)-5 wt%NZC/Ni@CNT composite exhibits the best hydrogen storage performances.After testing,the MgH_(2)-5 wt%NZC/Ni@CNT begins to release hydrogen at around 110℃ and hydrogen absorption capacity reaches 2.34 wt%H_(2) at 80℃ within 60 min.Moreover,the composite can release about 5.36 wt%H_(2) at 300℃.In addition,hydrogen absorption and desorption activation energies of the MgH_(2)-5 wt%NZC/Ni@CNT composite are reduced to 37.28 and 84.22 KJ/mol H_(2),respectively.The in situ generated Mg_(2)NiH_(4)/Mg_(2)Ni can serve as a"hydrogen pump"that plays the main role in providing more activation sites and hydrogen diffusion channels which promotes H_(2) dissociation during hydrogen absorption process.In addition,the evenly dispersed Zn and MgZn2 in Mg and MgH_(2) could provide sites for Mg/MgH_(2) nucleation and hydrogen diffusion channel.This attempt clearly proved that the bimetallic carbide Ni_(3)ZnC_(0.7) is a effective additive for the hydrogen storage performances modification of MgH_(2),and the facile synthesis of the Ni_(3)ZnC_(0.7)/Ni@CNT can provide directions of better designing high performance carbide catalysts for improving MgH_(2).
