Thermal stability of HgCl2 has a pivotal importance for the hydrochlorination reaction as the loss of mercuric compounds is toxic and detrimental to environment.Here we report a low-mercury catalyst which has durabili...Thermal stability of HgCl2 has a pivotal importance for the hydrochlorination reaction as the loss of mercuric compounds is toxic and detrimental to environment.Here we report a low-mercury catalyst which has durability over 10000 h for acetylene hydrochlorination under the industrial condition.The stability of the catalyst is carefully analyzed from a combined experimental and density functional theory study.The analysis shows that the extraordinary stability of mercury catalyst is resulted from the synergy effects between surface oxygen groups and defective edge sites.The binding energy of HgCl2 is increased to be higher than 130 kJ/mol when adsorption is at the edge site with a nearby oxygen group.Therefore,the present study revealed that the thermal stability problem of mercury-based catalyst can be solved by simply adjusting the surface chemistry of activated carbon.Furthermore,the reported catalyst has already been successfully applied in the commercialized production of vinyl chloride.展开更多
Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline...Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes(mMWCNT)were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm^(-2) for the MEA with mMWCNT was obtained at an ultra-low loading of 120μg·cm^(-2) Pt/PtRu(both cathode and anode),which was 44.7%higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.展开更多
Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure ...Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.展开更多
The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the...The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the 1.0 Mt/a CCR unit at the Guangzhou Company.The appropriate catalyst was selected to meet the demand of the unit capacity,the feedstock,and the product slate.The design parameters,including the reaction pressure,the octane number of C5+liquid product,the reaction temperature,the space velocity,the hydrogen/oil molar ratio,and the catalyst circulating rate,were chosen based on the study of process conditions and parameters.The commercial test results showed that the research octane number of C5+product reached 104 when the capacity of the CCR unit was 100%and 115%of the design value.The other technical targets attained or exceeded the expected value.展开更多
The effect of polycyclic aromatic hydrocarbons(PAHs)on the stability of the hydrogenation catalyst for production of ultra-low sulfur diesel was studied in a pilot plant using Ni-Mo-W/γ-Al_(2)O_(3)catalyst.The mechan...The effect of polycyclic aromatic hydrocarbons(PAHs)on the stability of the hydrogenation catalyst for production of ultra-low sulfur diesel was studied in a pilot plant using Ni-Mo-W/γ-Al_(2)O_(3)catalyst.The mechanisms of catalyst deactivation were analyzed by the methods of elemental analysis,nitrogen adsorption-desorption,thermogravimetry-mass spectrometry(TG-MS)technology,X-ray photoelectron spectroscopy(XPS)and high resolution transmission electron microscopy(HRTEM).The results demonstrated that PAHs had little effect on the activity of catalyst at the beginning of operation,during which the reaction temperature was increased by only 1-4℃.However,the existence of PAHs significantly accelerated the deactivation of catalyst and weakened the stability of catalyst.This phenomenon could be explained by the reason that the catalyst deactivation is not only related to the formation of carbon deposit,but is also closely related to the loss of pore volume and the decrease of Ni-W-S phase ratio after adding PAHs.展开更多
Mercuric chloride supported on activated carbon(HgCl_2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl_2 by sublimating from the surface of activated carbon causes the irreve...Mercuric chloride supported on activated carbon(HgCl_2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl_2 by sublimating from the surface of activated carbon causes the irreversible deactivation of mercury catalyst and environmental pollution. In this work, a ligand coordination approach based on the Principle of Hard and Soft Acids and Bases(HSAB) was employed to design more stable lowmercury catalyst. The low-mercury catalysts(4% HgCl_2 loading) were prepared by using HgCl_2 and potassium halides(KX, X = Cl, I) as precursors. The HgCl_2-4KI/AC catalyst showed best catalytic stability than HgCl_2/AC and HgCl_2-4KCl/AC in the hydrochloriantion of acetylene. HgCl_2 could form more stable complex with KI,K_2HgI_4 as the main active component of the HgCl_2-4KI/AC catalyst. The characterizations of XRD and EDX analysis illustrated that the active component of HgCl_2-4KI/AC was highly dispersed on the surface of activated carbon.The sublimation rates of HgCl_2 from the catalysts verified that the active component with larger stability constant had better thermal stability. Using Hg(Ⅱ) complexes with high stability constant as the active component may be the research direction of developing highly stable low-mercury catalyst for the hydrochlorination of acetylene.展开更多
In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared ...In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared via two-step ultrasonic impregnation method.The performance of Ce/SCR catalysts on Hg^(0)oxidation and NO reduction as well as the catalytic mechanism on Hg^(0)oxidation was also studied.The XRD,BET measurements and XPS were used to characterize the catalysts.The results showed that the pore volume and pore size of catalyst was reduced by Ce doping,and the specific surface area decreased with the increase of Ce content in catalyst.The performance on Hg^(0)oxidation was promoted by the introduction of CeO_(2).Ce_(1)/SCR(1%Ce,wt.%)catalyst exhibited the best Hg^(0)oxidation activity of 21.2%higher than that of SCR catalyst at 350℃,of which the NO conversion efficiency was also higher at 200-400℃.Furthermore,Ce_(1)/SCR showed a better H_(2)O resistance but a slightly weaker SO_(2)resistance than SCR catalyst.The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The Ce_(1)/SCR possed better redox ability compared with SCR catalyst.HCl was the most effective gas responsible for the Hg^(0)oxidation,and the redox cycle(V^(4+)+Ce^(4+)←→V^(5+)+Ce^(3+))played an important role in promoting Hg^(0)oxidation.展开更多
Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stac...Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.展开更多
Ultra-low emission(ULE)technology retrofits significantly impact the particulate-bound mercury(Hg)emissions from coal-fired power plants(CFPPs);however,the distribution and bioavailability of Hg in size-fractioned par...Ultra-low emission(ULE)technology retrofits significantly impact the particulate-bound mercury(Hg)emissions from coal-fired power plants(CFPPs);however,the distribution and bioavailability of Hg in size-fractioned particulate matter(PM)around the ULE-retrofitted CF-PPs are less understood.Here,total Hg and its chemical speciation in TSP(total suspended particles),PM_(10)(aerodynamic particle diameter≤10μm)and PM_(2.5)(aerodynamic particle diameter≤2.5μm)around a ULE-retrofitted CFPP in Guizhou Province were quantified.Atmospheric PM_(2.5)concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities,and it had higher mass Hg concentration than other sizefractioned PM.Total Hg concentrations in PM had multifarious sources including CFPP,vehicle exhaust and biomass combustion,while they were significantly higher in autumn and winter than those in other seasons(P<0.05).Regardless of particulate size,atmospheric PM-bound Hg had lower residual fractions(<21%)while higher HCl-soluble fractions(>40%).Mass concentrations of exchangeable,HCl-soluble,elemental,and residual Hg in PM_(2.5)were higher than those in other size-fractioned PM,and were markedly elevated in autumn and winter(P<0.05).In PM_(2.5),HCl-soluble Hg presented a significantly positive relationship with elemental Hg(P<0.05),while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg(P<0.01).Overall,these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM,and has higher bioavailable fractions,while has potential transformation between chemical speciation.展开更多
文摘Thermal stability of HgCl2 has a pivotal importance for the hydrochlorination reaction as the loss of mercuric compounds is toxic and detrimental to environment.Here we report a low-mercury catalyst which has durability over 10000 h for acetylene hydrochlorination under the industrial condition.The stability of the catalyst is carefully analyzed from a combined experimental and density functional theory study.The analysis shows that the extraordinary stability of mercury catalyst is resulted from the synergy effects between surface oxygen groups and defective edge sites.The binding energy of HgCl2 is increased to be higher than 130 kJ/mol when adsorption is at the edge site with a nearby oxygen group.Therefore,the present study revealed that the thermal stability problem of mercury-based catalyst can be solved by simply adjusting the surface chemistry of activated carbon.Furthermore,the reported catalyst has already been successfully applied in the commercialized production of vinyl chloride.
基金financial supports by the National Key Research and Development Program of China(2019YFB1504500)the National Natural Science Foundation of China(22078031,91834301,21761162015)+1 种基金the Fundamental Research Funds for the Central Universities,CQU(2020CDJQY-A032,2020CDJLHZZ064)the Natural Science Foundation of Chongqing(cstc2020jcyjmsxmX0637)。
文摘Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell(PEMFC),However,severe mass transfer polarization loss resulting in fuel cell performance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes(mMWCNT)were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm^(-2) for the MEA with mMWCNT was obtained at an ultra-low loading of 120μg·cm^(-2) Pt/PtRu(both cathode and anode),which was 44.7%higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.
基金finically supported by the National Natural Science Foundation of China(22075055)the Guangxi Science and Technology Project(AB16380030)the Innovation Project of Guangxi Graduate Education(YCSW2020052)。
文摘Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.
基金Financial support form the SINOPEC Research Program(No.107025)
文摘The development history and major technological innovations of the ultra-low pressure naphtha reforming technology with continuous catalyst regeneration in China were introduced.This technology had been adopted by the 1.0 Mt/a CCR unit at the Guangzhou Company.The appropriate catalyst was selected to meet the demand of the unit capacity,the feedstock,and the product slate.The design parameters,including the reaction pressure,the octane number of C5+liquid product,the reaction temperature,the space velocity,the hydrogen/oil molar ratio,and the catalyst circulating rate,were chosen based on the study of process conditions and parameters.The commercial test results showed that the research octane number of C5+product reached 104 when the capacity of the CCR unit was 100%and 115%of the design value.The other technical targets attained or exceeded the expected value.
基金financially supported by the Hydrogenation Process and Hydrogenation Catalyst Laboratory (RIPP,SINOPEC)
文摘The effect of polycyclic aromatic hydrocarbons(PAHs)on the stability of the hydrogenation catalyst for production of ultra-low sulfur diesel was studied in a pilot plant using Ni-Mo-W/γ-Al_(2)O_(3)catalyst.The mechanisms of catalyst deactivation were analyzed by the methods of elemental analysis,nitrogen adsorption-desorption,thermogravimetry-mass spectrometry(TG-MS)technology,X-ray photoelectron spectroscopy(XPS)and high resolution transmission electron microscopy(HRTEM).The results demonstrated that PAHs had little effect on the activity of catalyst at the beginning of operation,during which the reaction temperature was increased by only 1-4℃.However,the existence of PAHs significantly accelerated the deactivation of catalyst and weakened the stability of catalyst.This phenomenon could be explained by the reason that the catalyst deactivation is not only related to the formation of carbon deposit,but is also closely related to the loss of pore volume and the decrease of Ni-W-S phase ratio after adding PAHs.
基金Supported by the National Natural Science Foundation of China(21476207)the China Postdoctoral Science Foundation(2016M592015)
文摘Mercuric chloride supported on activated carbon(HgCl_2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl_2 by sublimating from the surface of activated carbon causes the irreversible deactivation of mercury catalyst and environmental pollution. In this work, a ligand coordination approach based on the Principle of Hard and Soft Acids and Bases(HSAB) was employed to design more stable lowmercury catalyst. The low-mercury catalysts(4% HgCl_2 loading) were prepared by using HgCl_2 and potassium halides(KX, X = Cl, I) as precursors. The HgCl_2-4KI/AC catalyst showed best catalytic stability than HgCl_2/AC and HgCl_2-4KCl/AC in the hydrochloriantion of acetylene. HgCl_2 could form more stable complex with KI,K_2HgI_4 as the main active component of the HgCl_2-4KI/AC catalyst. The characterizations of XRD and EDX analysis illustrated that the active component of HgCl_2-4KI/AC was highly dispersed on the surface of activated carbon.The sublimation rates of HgCl_2 from the catalysts verified that the active component with larger stability constant had better thermal stability. Using Hg(Ⅱ) complexes with high stability constant as the active component may be the research direction of developing highly stable low-mercury catalyst for the hydrochlorination of acetylene.
基金This work was supported by the National Key Research and Development Program of China(No.2016YFB0600603).
文摘In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared via two-step ultrasonic impregnation method.The performance of Ce/SCR catalysts on Hg^(0)oxidation and NO reduction as well as the catalytic mechanism on Hg^(0)oxidation was also studied.The XRD,BET measurements and XPS were used to characterize the catalysts.The results showed that the pore volume and pore size of catalyst was reduced by Ce doping,and the specific surface area decreased with the increase of Ce content in catalyst.The performance on Hg^(0)oxidation was promoted by the introduction of CeO_(2).Ce_(1)/SCR(1%Ce,wt.%)catalyst exhibited the best Hg^(0)oxidation activity of 21.2%higher than that of SCR catalyst at 350℃,of which the NO conversion efficiency was also higher at 200-400℃.Furthermore,Ce_(1)/SCR showed a better H_(2)O resistance but a slightly weaker SO_(2)resistance than SCR catalyst.The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The Ce_(1)/SCR possed better redox ability compared with SCR catalyst.HCl was the most effective gas responsible for the Hg^(0)oxidation,and the redox cycle(V^(4+)+Ce^(4+)←→V^(5+)+Ce^(3+))played an important role in promoting Hg^(0)oxidation.
基金supported by the National Natural Science Foundations of China(21965024,22269016,51721002)the Inner Mongolia funding(2020JQ01,21300-5223601)the funding of Inner Mongolia University(10000-21311201/137,213005223601/003,21300-5223707)。
文摘Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.
基金supported by the Science and Technology Project of Guizhou Province(No.QKHJC[2020]1Y187)the National Natural Science Foundation of China(Nos.41265008,42007305,and 22166009)。
文摘Ultra-low emission(ULE)technology retrofits significantly impact the particulate-bound mercury(Hg)emissions from coal-fired power plants(CFPPs);however,the distribution and bioavailability of Hg in size-fractioned particulate matter(PM)around the ULE-retrofitted CF-PPs are less understood.Here,total Hg and its chemical speciation in TSP(total suspended particles),PM_(10)(aerodynamic particle diameter≤10μm)and PM_(2.5)(aerodynamic particle diameter≤2.5μm)around a ULE-retrofitted CFPP in Guizhou Province were quantified.Atmospheric PM_(2.5)concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities,and it had higher mass Hg concentration than other sizefractioned PM.Total Hg concentrations in PM had multifarious sources including CFPP,vehicle exhaust and biomass combustion,while they were significantly higher in autumn and winter than those in other seasons(P<0.05).Regardless of particulate size,atmospheric PM-bound Hg had lower residual fractions(<21%)while higher HCl-soluble fractions(>40%).Mass concentrations of exchangeable,HCl-soluble,elemental,and residual Hg in PM_(2.5)were higher than those in other size-fractioned PM,and were markedly elevated in autumn and winter(P<0.05).In PM_(2.5),HCl-soluble Hg presented a significantly positive relationship with elemental Hg(P<0.05),while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg(P<0.01).Overall,these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM,and has higher bioavailable fractions,while has potential transformation between chemical speciation.
