Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol （...Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol （230 ℃, autogenous pressure, batch reactor）. The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt （15.5 h-1 ） 〉Co（13.0 h 1 ） 〉Ni（5.2 h-1） while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt （53%）〉Co（21%）〉Ni （15%） as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co （as a result of the formed acids）, significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.展开更多
The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glyco...The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.展开更多
In order to efficiently produce H_(2),conventional methanol‐water thermocatalytic(TC)reforming requires a very high temperature due to high Gibbs free energy,while the energy conversion efficiency of methanol‐water ...In order to efficiently produce H_(2),conventional methanol‐water thermocatalytic(TC)reforming requires a very high temperature due to high Gibbs free energy,while the energy conversion efficiency of methanol‐water photocatalytic(PC)reforming is far from satisfaction because of the kinetic limitation.To address these issues,herein,we incorporate PC and TC processes together in a specially designed reactor and realize simultaneous photocatalytic/thermocatalytic(PC‐TC)reforming of methanol in an aqueous phase.Such a design facilitates the synergetic effect of the PC and TC process for H_(2) production due to a lower energy barrier and faster reaction kinetics.The methanol‐water reforming based on the optimized 0.05%Pt@TiO_(2) catalyst delivers an outstanding H_(2) production rate in the PC‐TC process(5.66μmol H_(2)·g^(‒1) catalyst·s^(‒1)),which is about 3 and 7 times than those of the TC process(1.89μmol H_(2)·g^(‒1) catalyst·s^(‒1))and the PC process(0.80μmol H_(2)·g^(‒1) catalyst·s^(‒1)),respectively.Isotope tracer experiments,active intermediate trapping experiments,and theoretical calculations demonstrate that the photo‐generated holes and hydroxyl radicals could enhance the methanol dehydrogenation,water molecule splitting,and water‐gas shift reaction,while high temperature accelerates reaction kinetics.The proposed PC‐TC reforming of methanol for hydrogen production can be a promising technology to solve the energy and environmental issue in the closed‐loop hydrogen economy in the near future.展开更多
A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples wer...A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples were studied in dry reforming ofCH4. XRD and H2-TPR characterization results showed that the reduced CoMgAl-x samples mainly consisted of solid solution and spinel phases with cobalt particles. The spinel phases contained COB04 and ConMgl-nAl204 （0 〈 n 〈 1 ） varying with the （Mg ＋ Co）/AI ratio, The effect of （Mg ＋ Co）/A1 molar ratio on the catalytic behavior was investigated in detail and CoMgAI-3 exhibited the highest catalytic activity and stability among the catalysts studied.展开更多
基金supported by the Smart Mix Program of the Netherlands Ministry of Economic Affairs and the Netherlands Ministry of Education, Culture and Science
文摘Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol （230 ℃, autogenous pressure, batch reactor）. The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt （15.5 h-1 ） 〉Co（13.0 h 1 ） 〉Ni（5.2 h-1） while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt （53%）〉Co（21%）〉Ni （15%） as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co （as a result of the formed acids）, significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.
基金the support of the Smart Mix Program of The Netherlands Ministry of Economic Affairs, Agriculture and Innovation and The Netherlands Ministry of Education, Culture and Science (Grant no. 053.70.011)
文摘The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.
文摘In order to efficiently produce H_(2),conventional methanol‐water thermocatalytic(TC)reforming requires a very high temperature due to high Gibbs free energy,while the energy conversion efficiency of methanol‐water photocatalytic(PC)reforming is far from satisfaction because of the kinetic limitation.To address these issues,herein,we incorporate PC and TC processes together in a specially designed reactor and realize simultaneous photocatalytic/thermocatalytic(PC‐TC)reforming of methanol in an aqueous phase.Such a design facilitates the synergetic effect of the PC and TC process for H_(2) production due to a lower energy barrier and faster reaction kinetics.The methanol‐water reforming based on the optimized 0.05%Pt@TiO_(2) catalyst delivers an outstanding H_(2) production rate in the PC‐TC process(5.66μmol H_(2)·g^(‒1) catalyst·s^(‒1)),which is about 3 and 7 times than those of the TC process(1.89μmol H_(2)·g^(‒1) catalyst·s^(‒1))and the PC process(0.80μmol H_(2)·g^(‒1) catalyst·s^(‒1)),respectively.Isotope tracer experiments,active intermediate trapping experiments,and theoretical calculations demonstrate that the photo‐generated holes and hydroxyl radicals could enhance the methanol dehydrogenation,water molecule splitting,and water‐gas shift reaction,while high temperature accelerates reaction kinetics.The proposed PC‐TC reforming of methanol for hydrogen production can be a promising technology to solve the energy and environmental issue in the closed‐loop hydrogen economy in the near future.
基金supported by the Ministry of Science and Technology(No.2009CB623506)the National Natural Science Foundation of China(No.21173050)Shanghai Leading Academic Discipline Project(No.B108)
文摘A series of Co/Mg-Al oxide samples, CoMgAl-x （x = （Mg ＋ Co）]AI molar ratio of 1-5）, were prepared by the self-combustion method followed by H2 reduction. The catalytic performance and stability of the samples were studied in dry reforming ofCH4. XRD and H2-TPR characterization results showed that the reduced CoMgAl-x samples mainly consisted of solid solution and spinel phases with cobalt particles. The spinel phases contained COB04 and ConMgl-nAl204 （0 〈 n 〈 1 ） varying with the （Mg ＋ Co）/AI ratio, The effect of （Mg ＋ Co）/A1 molar ratio on the catalytic behavior was investigated in detail and CoMgAI-3 exhibited the highest catalytic activity and stability among the catalysts studied.
