In-phase and out-of-phase spin pumping effects in Py/Ru/Pysynthetic antiferromagnetic structures

The spin pumping effect in magnetic heterostructures and multilayers is a highly effective method for the generationand transmission of spin currents. In the increasingly prominent synthetic antiferromagnetic structures, the two ferromagneticlayers demonstrate in-phase and out-of-phase states, corresponding to acoustic and optical precession modes. Withinthis context, our study explores the spin pumping effect in Py/Ru/Py synthetic antiferromagnetic structures across differentmodes. The heightened magnetic damping resulting from the spin pumping effect in the in-phase state initially decreaseswith increasing Py thickness before stabilizing. Conversely, in the out-of-phase state, the amplified damping exceeds thatof the in-phase state, suggesting a greater spin relaxation within this configuration, which demonstrates sensitivity to alterationsin static exchange interactions. These findings contribute to advancing the application of synthetic antiferromagneticstructures in magnonic devices.

Thermogravimetric characteristics of corn straw and bituminous coal copyrolysis based the ilmenite oxygen carriers

Herein,the co-pyrolysis reaction characteristics of corn straw(CS)and bituminous coal in the presence of ilmenite oxygen carriers(OCs)are investigated via thermogravimetry coupled with mass spectrometry.The results reveal that the participation of OCs weakens the devolatilization intensity of co-pyrolysis.When the CS blending ratio is<50%,the mixed fuel exhibits positive synergistic effects.The fitting results according to the Coats-Redfern integral method show that the solid-solid interaction between OCs and coke changes the reaction kinetics,enhancing the co-pyrolysis reactivity at the high-temperature zone(750-950C).The synergistic effect is most prominent at a 30%CS blending ratio,with copyrolysis activation energy in the range of 26.35-40.57 kJ·mol^(-1).

Characteristics of reactivity and structures of palm kernel shell (PKS) biochar during CO_2/H_2O mixture gasification

Palm kernel shell(PKS)biochars with different levels of carbon conversion were initially prepared using a tube furnace,after which the reactivity of each sample was assessed with a thermogravimetric analyzer under a CO_2 atmosphere.The pore structure and carbon ordering of each biochar also examined,employing a surface area analyzer and a Raman spectroscopy.Thermogravimetric results showed that the gasification index R_sof the PKS biochar decreased from 0.0305 min^(-1) at carbon conversion(x)=20% to 0.0278 min^(-1)at x=40%.The expansion of micropores was the dominant process during the pore structure evolution,ad mesopores with sizes ranging from 6 to 20,48 to 50 nm were primarily generated during gasification under a CO_2/H_2O mixture.The proportion of amorphous carbon in the PKS biochar decreased significantly as x increased,suggesting that the proportion of ordered carbon was increased during the CO_2/H_2O mixed gasification.A significantly reduced total reaction time was observed when employing a CO_2/intermittent H_2O process along with an 83.46% reduction in the steam feed,compared with the amount required using a CO_2/H_2O atmosphere.

Experimental and mechanistic study on chemical looping combustion of caking coal

Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.

Energy and economic analysis of a hydrogen and ammonia co-generation system based on double chemical looping

In this work,a model of hydrogen production by double chemical looping is introduced.The efficiency benefit obtained was investigated.The chemical looping hydrogen generation unit is connected in series to the downstream of a chemical looping gasification unit as an additional system for 100 MWh coal gasification,with the function of supplementary combustion to produce hydrogen.Using Aspen Plus software for process simulation,the production of H_(2) and N_(2) in the series system is higher than that in the independent Chemical looping gasification and Chemical looping hydrogen generation systems,and the production of hydrogen is approximately 25.63%and 12.90%higher,respectively;The study found that when the gasification temperature is 900C,steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5,the hydrogen production rate of the system was the maximum.At the same time,through heat exchange between logistics,high-pressure steam at 8.010×10^(4) kg·h^(-1) and medium-pressure steam at 1.101×10^(4) kg·h^(-1) are generated,and utility consumption is reduced by 61.58%,with utility costs decreasing by 48.69%.An economic estimation study found that the production cost of ammonia is 108.66 USD(t NH_(3))^(-1).Finally,cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.

Performance of anaerobic fluidized bed microbial fuel cell with different porous anodes

Anode materials were used to construct microbial fuel cells(MFCs),and the characteristics of the anodes were important for successful applied performance of the MFCs.Via the cyclic voltammetry(CV)method,the experiments showed that 5 wt%multiwalled carbon nanotubes(MWNTs)were optimal for the PANI/MWNT film anodes prepared using 24 polymerization cycles.The maximum output voltage of the PANI/MWNT film anodes reached 967.7 mV with a power density of 286.63 mW·m-2.Stable output voltages of 860 mV,850 mV,and870 mV were achieved when the anaerobic fluidized bed microbial fuel cell(AFBMFC)anodes consisted of carbon cloth with carbon black on one side,copper foam and carbon brushes,respectively.Pretreatment of the anodes before starting the AFBMFC by immersion in a stirred bacterial fluid significantly shortened the AFBMFC startup time.After the AFBMFC was continuously run,the anode surfaces generated active microbial catalytic material.

The effect of the Ce content on the oxidative dehydrogenation of propane over CrOy-CeO2/γ-Al2O3 catalysts

A series of CrOy(17.5 wt%)-CeO2(X wt%)/γ-Al2O3 catalysts(X=0,0.5,2,5,8)with various Ce contentswere prepared by a wetness impregnation method and were applied to the dehydrogenation of propane to propylene at 550℃ and 0.1 MPa.The prepared catalysts were characterized by BET,H2-TPR,O2-TPD,XPS,XRD,SEM-EDS and Raman spectroscopy.Among the prepared catalysts,the 17.5Cr-2Ce/Al catalyst with the largest amount of lattice oxygen exhibited the best catalytic performance for the dehydrogenation of propane to propylene with lattice oxygen.The decreased presence of oxygen defects and reducibility were the factors responsible for the improved dehydrogenation activity of the catalysts.The CeO2 layer could inhibit the evolution of lattice oxygen(O2^−)to electrophilic oxygen species(O2^−),and the oxygen defects on the catalyst surfacewere reduced.The inhibited lattice oxygen evolution prevented the deep oxidation of propane or propylene,the average COx selectivity decreased from 24.41%(17.5Cr/Al)to 5.71%(17.5Cr-2Ce/Al),and the average propylene selectivity increased from 60.15%(17.5Cr/Al)to 85.05%(17.5Cr-2Ce/Al).

Suppressing byproduct formation for high selective CO_(2) reduction over optimized Ni/TiO_(2) based catalysts

One of the challenges for catalytic CO_(2)reduction is to control product selectivity,and new findings that can modify selectivity would be transformative.Herein,two kinds of TiO_(2)(homemade and commercial)with the same crystal phase but different surface properties are chosen as supports to prepare Ni-based catalysts for CO_(2)reduction,which show distinctly different product selectivity for CO_(2)reduction to CH_(4) or CO,as well as the CO_(2)conversion.The catalysts based on the homemade TiO_(2)support are highly selective for CH_(4) formation,while the latter ones are about 100%selective for CO formation under the same reaction conditions.In addition,the former ones are much active(more than 3 times)than the latter ones.We found that the collaborative contribution of Ti^(3+)and Ni^(2+)species and the electronic metal-support interactions effect maybe the main driving force behind for determining the product selectivity.Methane is almost exclusively produced over the catalysts with abundant Ti^(3+)and Ni^(2+)species and greater electronic metal-support interaction,otherwise,it will give priority to CO generation.The addition of CeO_(2)can reduce the Ni particle size and improve the dispersion of Ni nanoparticles,as well as create more Ti^(3+)species,contributing to the enhancement of CO_(2)conversion,but shows a negligible effect on product selectivity.Furthermore,the in situ DRIFT experiments and kinetic experiments indicate that the CO route is probably involved in the CO_(2)reduction process over the homemade Ni-CeO_(2)/TiO_(2)-CO catalyst with abundant Ti^(3+)and Ni^(2+)species and a strong electronic transform effect.

Spin transport in epitaxial Fe3O4/GaAs lateral structured devices

Research in the spintronics community has been intensively stimulated by the proposal of the spin field-effect transistor(SFET),which has the potential for combining the data storage and process in a single device.Here we report the spin dependent transport on a Fe_(3)O_(4)/GaAs based lateral structured device.Parallel and antiparallel states of two Fe_(3)O_(4) electrodes are achieved.A clear MR loop shows the perfect butterfly shape at room temperature,of which the intensity decreases with the reducing current,showing the strong bias dependence.Understanding the spin-dependent transport properties in this architecture has strong implication in further development of the spintronic devices for room-temperature SFETs.

Simulation study on the gasification process of Ningdong coal with iron-based oxygen carrier

Chemical looping gasification(CLG) of Ningdong coal by using Fe_(2) O_(3) as the oxygen carriers(OCs) was studied,and the gasification characteristics were obtained.A computation fluid dynamics(CFD) model based on Eulerian--Lagrangian multiphase framework was established,and a numerical simulation the coal chemical looping gasification processes in fuel reactor(FR) was investigated.In addition,the heterogeneous reactions,homogeneous reactions and Fe_(2) O_(3) oxygen carriers' reduction reactions were considered in the gasification process.The characteristics of gas flow and gasification in the FR were analyzed and it was found that the experiment results were consistent with the simulation values.The results show that when the O/C mole rate was 0.5:1,the gasification temperature was 900℃ and the water vapor volume flow rate was 2.2 ml·min^(-1),the mole fraction of syngas reached a maximum value of the experimental result and simulation value were 71.5% and 70.2%,respectively.When the O/C mole rate was 0.5:1,the gasification temperature was 900℃,and the water vapor volume flow was 1.8 ml·min^(-1);the gasification efficiency reached the maximum value was 62.2%,and the maximum carbon conversion rate was 84.0%.

Research progress of MOF-based materials in the photocatalytic CO_(2)reduction

Photocatalytic technology could utilize solar energy to reduce CO_(2)into high-value-added fossil fuels,providing promising solutions for global energy and environmental issues.Metal-organic frameworks(MOFs)are a class of crystalline porous solids with high porosity and flexible structure.MOF-based photocatalysts have excellent CO_(2)capture ability,photochemical and structural characteristics and have shown infinite development potential in CO_(2)reduction.However,in practical large-scale applications,MOF-based photocatalysts still have some urgent problems to be solved,such as high composite rate of photogenerated carriers,limited response range to visible spectrum,poor photocatalytic activity and weak reduction ability.This paper introduces series of MOF-based photocatalysts,including pure MOF materials,compounds,and derivatives,were reviewed based on recent reports.Emphasis was placed on the modification strategy of photocatalysts,the photocatalytic reaction’s key physical and chemical parameters,and the mechanism of synergistic improvement of chemical fuel yield.Ultimately and most importantly,the future development trends and prospects of MOF-based catalysts for photocatalytic CO_(2)reduction were discussed.

Facile preparation of coal-based ultramicroporous carbon microspheres for selective CO_(2)capture

The basic structure of aromatic compounds that are abundant in coal is the carbonaceous precursor derived from carbon microspheres.However,it remains to be a huge challenge to prepare carbon microspheres using coal due to the complex construction and composition of coal.Herein,a simple and viable way to obtain coal-based microporous carbon microspheres was developed by means of ethanol pyrolysis and a sequential extraction strategy.The as-prepared carbon microsphere featured aspherical micron particles of a uniform size(0.6-1.6㎛),abundant O-functional groups,excellent thermal stability,high SBET(415.5-983.2 m^(2)/g),and plentiful ultra-micropores(63.15-72.72%).The coal-based carbon microsphere exhibited a noteworthy CO_(2)uptake(3.19-4.97 mmol/g at 273 K and 1.0 bar),acceptable CO_(2)/N_(2)selectivity(IAST:23-46)and moderate isosteric heats(20-32 kJ/mol).This synthetic strategy is important for the preparation of ultramicroporous carbon microspheres using coal,and the synthetic carbon microspheres have promising prospects for highly efficient CO_(2)capture.

Developments and challenges on enhancement of photocatalytic CO_(2)reduction through photocatalysis

The conversion of CO_(2)into high-value fuels and chemicals has garnered research interest worldwide.The conversion and utilization of CO_(2)has become one of the most urgent tasks for society.In this context,using solar energy to convert CO_(2)into high-value fuels such as CH4 and CH_(3)OH has extremely high potential application value.Herein,the research progress and results of applying various photocatalysts in photocatalytic CO_(2)reduction with various novel catalysts were reviewed.Furthermore,strategies for improving photocatalytic performance were reviewed.Finally,improving the catalytic mechanism of catalysts and designing novel highactivity,high-stability catalysts through comprehensive exploration of the reaction mechanism were suggested to meet the future requirements of industrial production.

Efficient CO_(2) adsorption and mechanism on nitrogen-doped porous carbons

In this work,nitrogen-doped porous carbons(NACs)were fabricated as an adsorbent by urea modification and KOH activation.The CO_(2) adsorption mechanism for the NACs was then explored.The NACs are found to present a large specific surface area(1920.72-3078.99 m2·g^(-1))and high micropore percentage(61.60%-76.23%).Under a pressure of 1 bar,sample NAC-650-650 shows the highest CO_(2) adsorption capacity up to 5.96 and 3.92 mmol·g^(-1) at 0 and 25℃,respectively.In addition,the CO_(2)/N_(2) selectivity of NAC-650-650 is 79.93,much higher than the value of 49.77 obtained for the nonnitrogen-doped carbon AC-650-650.The CO_(2) adsorption capacity of the NAC-650-650 sample maintains over 97% after ten cycles.Analysis of the results show that the CO_(2) capacity of the NACs has a linear correlation(R^(2)=0.9633)with the cumulative pore volume for a pore size less than 1.02 nm.The presence of nitrogen and oxygen enhances the CO_(2)/N_(2) selectivity,and pyrrole-N and hydroxy groups contribute more to the CO_(2) adsorption.In situ Fourier transform infrared spectra analysis indicates that CO_(2) is adsorbed onto the NACs as a gas.Furthermore,the physical adsorption mechanism is confirmed by adsorption kinetic models and the isosteric heat,and it is found to be controlled by CO_(2) diffusion.The CO_(2) adsorption kinetics for NACs at room temperature and in pure CO_(2) is in accordance with the pseudo-first-order model and Avramís fractional-order kinetic model.

3 MW_(th)煤化学链气化商业示范装置的自热运行和参数分析

为实现MW_(th)规模化学链气化商业示范装置的自热运行,使用Aspen Plus进行模拟研究。通过实验数据,验证了过程模型的可靠性。考察了3 MW_(th)煤化学链气化系统的质量和热量平衡。通过分析反应器温度、蒸汽流率和温度、旋风分离器效率、载氧体活性成分含量等工艺参数对系统合成气产率、合成气组分浓度、合成气H_(2)/CO、固体循环流率等工艺性能的影响,确定了合成气产量最大化的自热操作条件。结果表明,3 MW_(th)煤化学链气化系统的净热功率越接近于0,系统越趋于自热运行。系统自热运行时的最佳操作条件为燃料反应器温度850℃、空气反应器温度950℃、蒸汽流率305.25 kg/h、蒸汽温度300℃、旋风分离器效率98%,系统的固体循环流率最小,约为10 555~10 580 kg/h,合成气总浓度(CO+H_(2))最大,约为75.1%。此外,使用活性成分含量较高的钛铁矿颗粒作为载氧体,有利于减少系统的固体循环流率。

Influence of CaO and HZSM-5 on oxygen migration in Chlorella vulgaris polysaccharide pyrolysis

With polysaccharides of Chlorella pyrenoidosa as the raw material,the effects of CaO and HZSM-5 on the yield of bio-oil and the oxygen content in each phase in the pyrolysis of Chlorella vulgaris polysaccharides(CVP),which occurred in a tube furnace at 600℃,were comprehensively investigated.The reaction path of deoxidation was also analyzed by TG,GC and GC-MS.The GC-MS analysis of liquids showed that liquids from the pyrolysis of chlorella polysaccharides included a range of light oxygenated compounds(e.g.,furans,ketones and phenols),and the oxygen content of furan compounds decreased significantly with CaO and HZSM-5.Compared with the direct pyrolysis of polysaccharides(CVP),the catalytic pyrolysis contributed to the decrease in the oxygen content of organic components by 7.32%and 5.76%.The GC analysis showed that there was a remarkable downtrend in the release of oxygen-containing gas(CO and CO_(2)),and the emission of CO_(2) decreased from 53.11%to 32.92%.The results of the thermogravimetric analysis indicated that the reaction paths of deoxidation in the pyrolysis process of polysaccharides(CVP)with CaO and HZSM-5 varied from those of the direct pyrolysis process:the catalytic pyrolysis with HZSM-5 promoted the conversion of carbohydrate from furans to aromatics over strong acid sites,which was consistent with previous studies;CaO not only acted as a catalyst but also participated in the reaction to change the reaction paths.All results and findings can help to further understand the thermochemical utilization of CPP for bio-oil.

Cotton stalk activated carbon-supported Co-Ce-B nanoparticles as efficient catalysts for hydrogen generation through hydrolysis of sodium borohydride

Porous cotton stalk activated carbons(CSAC)were prepared by phosphoric acid activation of cotton stalks in a fluidized bed.The CSAC-supported Co-B and Co-Ce-B catalysts were prepared by the impregnation-chemical reduction method.The samples were characterized by the nitrogen adsorption,XRD,FTIR and TEM measurements.The effects of the sodium borohydride(NaBH_(4))and sodium hydroxide(NaOH)concentrations,reaction temperature and recyclability on the rate of NaBH_(4)hydrolysis over the CSAC-supported Co-Ce-B catalysts were systematically investigated.The results showed that the agglomeration of the Co-Ce-B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium.The CSAC-supported Co-Ce-B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min^(−1)g^(−1)Co at 25℃,which is higher than the most reported cobalt-based catalysts.The catalytic hydrolysis of NaBH_(4)was zero order with respect to the NaBH_(4)concentration,and the hydrogen generation rate decreased with the increase in the NaOH concentration.The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol^(−1).A kinetic rate equation was also proposed.

Directional preparation of naphthalene oil-rich tar from Beisu low-rank coal by low-temperature catalytic pyrolysis

Low-rank coal(LRC)can be converted to high value-added naphthalene and its alkylated derivatives through low-temperature catalytic pyrolysis.In this paper,the catalytic pyrolysis of Beisu LRC in a fixed-bed at low temperature was investigated.And the catalytic effects of HZSM-5,low-temperature carbocoal(LtC),and LtC-HZSM-5 on the content and yield of naphthalene oil were examined.The results showed that the generation of naphthalene oil in low-temperature LRC pyrolysis(LT-LP)process could be improved when LtC(prepared at 550℃)or HZSM-5 was individually used as a catalyst.Compared with sole pyrolysis of raw LRC,the addition of the LtC-HZSM-5 catalyst increased the content of naphthalene oil from 11.19 wt.%to 31.49 wt%.And the yield of naphthalene oil was increased from 1.07 wt%to 5.31 wt%.The reactions of micromolecular hydrogen-containing radicals(⋅MHCR)were optimized by LtC.⋅MHCR could be captured in relatively low-temperature region(200-400℃)and released at high temperature by LtC.The generation of phenolics was inhibited by HZSM-5.As a result,the naphthalene oil-rich tar was obtained through low-temperature LtC-HZSM-5 catalytic pyrolysis of Beisu LRC.

Retention mechanism of calcium ferrite and compositions of ash on selenium during chemical looping gasification

Selenium pollution by coal utilization is of increasing concern.Calcium-iron(Ca-Fe)oxygen carriers(OCs)and alkali metal ions have strong inhibitory effects on selenium,which can reduce the emissions of selenium vapor.The retention mechanisms of selenium by Fe_(2)O_(3),CaFe_(2)O_(4),Ca_(2)Fe_(2)O_(5) and bottom ash are investigated during chemical looping gasification(CLG).Iron-based OC can oxidize H_(2)Se(g)to SeO_(2)(g);furthermore,lattice oxygen is released by Fe_(2)O_(3),contributing to the formation of an Fe-O-Se structure to retain selenium and form selenite.Because calcium ferrite is poorly oxidizing,it cannot oxidize H_(2)Se(g),but the CaO produced when OCs are reduced can react with H_(2)Se(g)to form CaSe(s),and this process can be promoted by H_(2)S(g).The best retention rates reached 32.301%when Ca_(2)Fe_(2)O_(5) was used.In the cyclic experiment,the selenium retention of the bottom ash gradually increases.Alkali metal ions in bottom ash are the main factor in retaining selenium.Ca^(2+) and Mg^(2+) do not easily vaporize due to their high melting points;therefore,their selenium retention is significantly better than that of K^(+) and Na^(+).This research provided a new idea for the removal of selenium by using OCs and bottom ash par-ticles during CLG.