Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent material...Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.展开更多
In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous...In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous MgCl_(2) prepared by the dehydration of bischofite is a high-quality raw material for the production of Mg.However,direct calcination of MgCl_(2)·6H_(2)O in industrial dehydration processes leads to a large amount of hydrolysis.The by-products are harmful to the electrolysis process of Mg,causing problems such as sludge formation,low current efficiency,and corrosion in the electrodes.To obtain high-purity anhydrous MgCl_(2),different advanced dehydration processes have been proposed.In this review,we focus on the recent progress of the dehydration process.Firstly,we discuss the molecular structure of MgCl_(2)·6H_(2)O and explain the reason why much hydrolysis occurs in dehydration.Secondly,we introduce the specific dehydration processes,mainly divided into direct dehydration processes and indirect dehydration processes.The direct dehydration processes are classified into gas protection heating and molecular sieve dehydration process.Indirect dehydration processes are classified into thermal dehydration of ammonium carnallite(NH_(4)Cl·MgCl_(2)·6H_(2)O),thermal dehydration of potassium carnallite(KCl·MgCl_(2)·6H_(2)O),thermal decomposition of the[HAE]Cl·MgCl_(2)·6H_(2)O,organic solvent distillation,ionic liquid dehydration process and ammonia complexation process.In the meanwhile,purity of anhydrous MgCl_(2) of each dehydration process,as well as the advantages and disadvantages,is discussed.The characteristics of different processes with a simple economic budget are also given in this paper.Finally,the main challenges are evaluated with suggested directions in the future,aiming to guide the synthesis of high-purity anhydrous MgCl_(2).展开更多
Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output ...Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output of primary magnesium accounting for>80%of the world’s total annual output.The smelting process represented by the Pidgeon process plays the leading role in China because of its simple process flow and equipment and the flexibility of the production scale.However,the Pidgeon process always has the problems of low utilization of reduction heat,a short lifetime of the reduction tank,a high cost of the reduction furnace,and a discontinuous production process.Therefore,how to produce magnesium in a clean,efficient and continuous manner has been the focus of industry development research.In this work,from the perspective of the preparation of magnesium by thermal reduction,the production of high-purity magnesium,and the recycling of waste magnesium alloys,the research status of magnesium preparation by direct vacuum and relative vacuum processes was reviewed,including the reduction mechanism,migration and condensation patterns and production efficiency of magnesium.The effects of the reducing agent,reduction temperature,holding time and other factors on the preparation of magnesium were emphasized.Finally,by comparing the production processes of magnesium by direct vacuum and relative vacuum methods,the advantages and disadvantages of the two methods for the preparation of magnesium were mainly discussed,and the future development of magnesium was proposed.展开更多
Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage ...Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage and transportation,however,the kinetic behavior and operating temperature remain undesirable.In this work,a dual-phase multi-site alloy(Ms A)anchored on carbon substrates was designed,and its superior catalytic effects on the hydrogen storage properties of MgH_(2) were reported.Mechanism analysis identified that multi-site Fe Ni_(3)/Ni Cu nanoalloys synergistically served as intrinsic drivers for the striking de/hydrogenation performance of the MgH_(2)-Ms A systems.Concretely,the unique multi-metallic site structure attached to the surface of MgH_(2)provided substantial reversible channels and accessible active sites conducive to the adsorption,activation,and nucleation of H atoms.In addition,the coupling system formed by FeNi_(3) and NiCu dual-phase alloys further enhanced the reactivity between Mg/MgH_(2) and H atoms.Hence,the onset dehydrogenation temperature of Mg H_(2)+5 wt%Ms A was reduced to 195℃ and the hydrogen desorption apparent activation energy was reduced to 83.6 k J/mol.5.08 wt%H_(2) could be released at 250℃ in 20 min,reaching a high dehydrogenation rate of 0.254 wt%H_(2)/min,yet that for MgH_(2) at a higher temperature of 335℃ was only 0.145 wt%H_(2)/min.Then,the dehydrogenated Mg H_(2)-Ms A sample could absorb hydrogen from room temperature(30℃)and charge 3.93 wt%H_(2) at 100℃ within20 min under 3.0 MPa H_(2) pressure.Benefiting from carbon substrates,the 5 wt%Ms A doped-MgH_(2) could still maintain 6.36 wt%hydrogen capacity after 20 cycles.In conclusion,this work provides experimental rationale and new insights for the design of efficient catalysts for magnesium-based solid-state hydrogen storage materials.展开更多
The robust Mg-H bonds present in magnesium hydride(MgH_(2))hinder the dissociation of hydrogen molecules on MgH_(2),leading to suboptimal thermo dynamic and kinetic properties.Transition metals such as nickel(Ni)and N...The robust Mg-H bonds present in magnesium hydride(MgH_(2))hinder the dissociation of hydrogen molecules on MgH_(2),leading to suboptimal thermo dynamic and kinetic properties.Transition metals such as nickel(Ni)and Nb exhibit superior hydrogen absorption energies as compared to Mg.By integrating two-dimensional Nb_(n)C_(n-1)T_(x)-MXene(with a large specific surface area and strong hydrogen absorption capacity provided by Nb)with Ni clusters,we developed an effective catalyst for hydrogen adsorption in MgH_(2).This study focused on the synthesis of an efficient MXene-Nb_(2)CT_(x)composite containing nano Ni cluster to enhance the hydrogenation and dehydrogenation processes of the Mg/MgH_(2)system.The Txend groups(-F,-O)were found to interact with Ni to create Ni-F or Ni-O bonds,which subsequently engage with adjacent Ni atoms to form Ni-Ni bonds.This interaction facilitates the loading of Ni clusters onto Nb_(2)CT_(x)and mitigates the inhibitory effects of-F or-O on hydrogen adsorption and desorption in the Mg-based system.Consequently,Nb_(2)C and Ni operate synergistic ally to enhance hydrogen dissociation and weaken Mg-H bonds.Theoretical simulations revealed that the inclusion of the Nb_(2)C/Ni catalyst in an elongation of Mg-H bonds enhancehydrogen dissociation and weaken Mg-H bonds.Theoretical simulations revealed that the inclusion of the Nb_(2)C/Ni catalyst in an elongation of Mg-H bonds facilitate hydrogen molecule dissociation on the Nb_(2)C/Ni composite.Hydrogen storage performance assesments demonstrated that the Nb_(2)C/Ni catalyst efficiently catalyzed hydrogen absorption and desorption;specifically,the hydrogenation/dehydrogenation capacity of Nb_(2)C/Ni@MgH_(2)reachedca.5.0 wt%at 100℃,while at 200℃,the capacities for hydrogenation and dehydrogenation reached 7.0 wt%and6.0 wt%,respectively,within 6 min.展开更多
基金supported by Shanxi Provincial Key Research and Development Project(202102090301026)Graduate Education Innovation Project of Taiyuan University of Science and Technology(SY2023024)。
文摘Currently,the solid adsorbents with porous structure have been widely applied in CO_(2)capture.However,the unmodified MgO-ZrO_(2)adsorbents appeared to be low adsorption capacity of CO_(2).The solid adsorbent materials were successfully synthesized by loading TEPA onto the pore MgO/ZrO_(2)carriers in the paper.The pore structure and surface characteristic of the samples were analyzed by using XRD,BET,FT-IR and SEM.The adsorbent materials exhibited microcrystalline state,and the crystallinity of all samples gradually decreased as the increase of TEPA content.The pore structure analysis indicated that the modification of MgO-ZrO_(2)adsorbents with TEPA led to the decrease of the specific surface areas,but the narrow micro-mesopore size distributions ranging from 1.8-12 nm in the adsorbents still were maintained.FT-IR spectrum results further verified the successful loading of TEPA.The adsorption capacity of the adsorbents for CO_(2)were tested by using an adsorption apparatus equipped with gas chromatography.The results indicated that when the TEPA loading reached 50%,the sample exhibited the maximum adsorption value for CO_(2),reaching 4.07 mmol/g under the operation condition of 75℃and atmospheric pressure.This result could be assigned to not only the base active sites but also the coexistence of both micropore and mesopore in the adsorbent.After three cycles tests for CO_(2)capture,the adsorption value of the sample for CO_(2)can also reached 95%of its original adsorption capacity,which verified the excellent cyclic operation stability.
基金funded by Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01F60)Tianshan Talents Plan of Xinjiang Uygur Autonomous Region(2022TSYCJC0001)+2 种基金National Natural Science Foundation of China(22368051)Science and Technology Plan Project of Karamay(20232023hjcxrc0038 and 2024hjcxrc0118)Projects of Talents Recruitment of GDUPT(2023rcyj2005)。
文摘In the extraction of potassium from salt lakes,Mg is abundant in the form of bischofite(MgCl_(2)·6H_(2)O),which is not utilized effectively,resulting in the waste of resources and environmental pressure.Anhydrous MgCl_(2) prepared by the dehydration of bischofite is a high-quality raw material for the production of Mg.However,direct calcination of MgCl_(2)·6H_(2)O in industrial dehydration processes leads to a large amount of hydrolysis.The by-products are harmful to the electrolysis process of Mg,causing problems such as sludge formation,low current efficiency,and corrosion in the electrodes.To obtain high-purity anhydrous MgCl_(2),different advanced dehydration processes have been proposed.In this review,we focus on the recent progress of the dehydration process.Firstly,we discuss the molecular structure of MgCl_(2)·6H_(2)O and explain the reason why much hydrolysis occurs in dehydration.Secondly,we introduce the specific dehydration processes,mainly divided into direct dehydration processes and indirect dehydration processes.The direct dehydration processes are classified into gas protection heating and molecular sieve dehydration process.Indirect dehydration processes are classified into thermal dehydration of ammonium carnallite(NH_(4)Cl·MgCl_(2)·6H_(2)O),thermal dehydration of potassium carnallite(KCl·MgCl_(2)·6H_(2)O),thermal decomposition of the[HAE]Cl·MgCl_(2)·6H_(2)O,organic solvent distillation,ionic liquid dehydration process and ammonia complexation process.In the meanwhile,purity of anhydrous MgCl_(2) of each dehydration process,as well as the advantages and disadvantages,is discussed.The characteristics of different processes with a simple economic budget are also given in this paper.Finally,the main challenges are evaluated with suggested directions in the future,aiming to guide the synthesis of high-purity anhydrous MgCl_(2).
基金the combined funding from the National Natural Science Foundation of China(U1908225,U1702253,U1508217)。
文摘Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output of primary magnesium accounting for>80%of the world’s total annual output.The smelting process represented by the Pidgeon process plays the leading role in China because of its simple process flow and equipment and the flexibility of the production scale.However,the Pidgeon process always has the problems of low utilization of reduction heat,a short lifetime of the reduction tank,a high cost of the reduction furnace,and a discontinuous production process.Therefore,how to produce magnesium in a clean,efficient and continuous manner has been the focus of industry development research.In this work,from the perspective of the preparation of magnesium by thermal reduction,the production of high-purity magnesium,and the recycling of waste magnesium alloys,the research status of magnesium preparation by direct vacuum and relative vacuum processes was reviewed,including the reduction mechanism,migration and condensation patterns and production efficiency of magnesium.The effects of the reducing agent,reduction temperature,holding time and other factors on the preparation of magnesium were emphasized.Finally,by comparing the production processes of magnesium by direct vacuum and relative vacuum methods,the advantages and disadvantages of the two methods for the preparation of magnesium were mainly discussed,and the future development of magnesium was proposed.
基金financial supports from the National Key R&D Program of China(No.2020YFA0406204)the National Natural Science Foundation of China(No.51801078)。
文摘Hydrogen,as a cheap,clean,and cost-effective secondary energy source,performs an essential role in optimizing today’s energy structure.Magnesium hydride(Mg H_(2))represents an attractive hydrogen carrier for storage and transportation,however,the kinetic behavior and operating temperature remain undesirable.In this work,a dual-phase multi-site alloy(Ms A)anchored on carbon substrates was designed,and its superior catalytic effects on the hydrogen storage properties of MgH_(2) were reported.Mechanism analysis identified that multi-site Fe Ni_(3)/Ni Cu nanoalloys synergistically served as intrinsic drivers for the striking de/hydrogenation performance of the MgH_(2)-Ms A systems.Concretely,the unique multi-metallic site structure attached to the surface of MgH_(2)provided substantial reversible channels and accessible active sites conducive to the adsorption,activation,and nucleation of H atoms.In addition,the coupling system formed by FeNi_(3) and NiCu dual-phase alloys further enhanced the reactivity between Mg/MgH_(2) and H atoms.Hence,the onset dehydrogenation temperature of Mg H_(2)+5 wt%Ms A was reduced to 195℃ and the hydrogen desorption apparent activation energy was reduced to 83.6 k J/mol.5.08 wt%H_(2) could be released at 250℃ in 20 min,reaching a high dehydrogenation rate of 0.254 wt%H_(2)/min,yet that for MgH_(2) at a higher temperature of 335℃ was only 0.145 wt%H_(2)/min.Then,the dehydrogenated Mg H_(2)-Ms A sample could absorb hydrogen from room temperature(30℃)and charge 3.93 wt%H_(2) at 100℃ within20 min under 3.0 MPa H_(2) pressure.Benefiting from carbon substrates,the 5 wt%Ms A doped-MgH_(2) could still maintain 6.36 wt%hydrogen capacity after 20 cycles.In conclusion,this work provides experimental rationale and new insights for the design of efficient catalysts for magnesium-based solid-state hydrogen storage materials.
基金financially supported by the Natural Science Foundation of Jiangsu Province of China(No.BK20210079)Xuzhou Science and Technology Project(No.KC23011)
文摘The robust Mg-H bonds present in magnesium hydride(MgH_(2))hinder the dissociation of hydrogen molecules on MgH_(2),leading to suboptimal thermo dynamic and kinetic properties.Transition metals such as nickel(Ni)and Nb exhibit superior hydrogen absorption energies as compared to Mg.By integrating two-dimensional Nb_(n)C_(n-1)T_(x)-MXene(with a large specific surface area and strong hydrogen absorption capacity provided by Nb)with Ni clusters,we developed an effective catalyst for hydrogen adsorption in MgH_(2).This study focused on the synthesis of an efficient MXene-Nb_(2)CT_(x)composite containing nano Ni cluster to enhance the hydrogenation and dehydrogenation processes of the Mg/MgH_(2)system.The Txend groups(-F,-O)were found to interact with Ni to create Ni-F or Ni-O bonds,which subsequently engage with adjacent Ni atoms to form Ni-Ni bonds.This interaction facilitates the loading of Ni clusters onto Nb_(2)CT_(x)and mitigates the inhibitory effects of-F or-O on hydrogen adsorption and desorption in the Mg-based system.Consequently,Nb_(2)C and Ni operate synergistic ally to enhance hydrogen dissociation and weaken Mg-H bonds.Theoretical simulations revealed that the inclusion of the Nb_(2)C/Ni catalyst in an elongation of Mg-H bonds enhancehydrogen dissociation and weaken Mg-H bonds.Theoretical simulations revealed that the inclusion of the Nb_(2)C/Ni catalyst in an elongation of Mg-H bonds facilitate hydrogen molecule dissociation on the Nb_(2)C/Ni composite.Hydrogen storage performance assesments demonstrated that the Nb_(2)C/Ni catalyst efficiently catalyzed hydrogen absorption and desorption;specifically,the hydrogenation/dehydrogenation capacity of Nb_(2)C/Ni@MgH_(2)reachedca.5.0 wt%at 100℃,while at 200℃,the capacities for hydrogenation and dehydrogenation reached 7.0 wt%and6.0 wt%,respectively,within 6 min.
