Single-atom zinc catalyst for co-production of hydrogen and fine chemicals in soluble biomass solution

Single-atom photocatalysts(SAPCs)have attracted great interests due to their remarkable atom utilization efficiency,excellent activity,and selectivity,yet no application in synchronous biorefinery and water splitting.Here,efficient SAPCs based on atomically dispersed Zn atoms on carbon nitride(named Zn-mCN)were produced.Experiments verified that Zn-mCN has widened adsorption range of visible-light and lowered ability of electron-hole recombination,leading to excellent photocatalytic redox activity for synchronous biorefinery and water splitting to co-produce lactic acid(selectivity up to 91.0%)and hydrogen(-15898.8μmolg^(-1)h^(-1)).This system has excellent universality for small-molecule monosaccharides and macromolecular xylan.Poisoning experiments showed that h^(+),1O2,·O_(2)-and·OH can promote the simultaneous production of lactic acid and hydrogen.This work realized full utilization of whole redox reaction and provided a novel strategy for efficient and concomitant production of hydrogen and value-added chemicals from biomass-derived feedstocks aqueous solutions.

The Impact of Climate Change on Maize Yield and Farmers' Adaptation Options:Evidence from Three Provinces of China

This paper tries to answer the question that whether farmers can adjust better to climate change in the short-term than in long-term by using panel data models and long difference models respectively.We find that short term weather shocks are less detrimental to maize yield than the long-term climate changes,which can be seen as the evidences of adaptations.For adaptation options,we find farmers choose to decrease maize planting area or enlarge the irrigation inputs to cope with the increase of extreme heat days;when there are more precipitations,farmers will increase the input of fertilizer or labor.

Particle residence time distribution and axial dispersion coefficient in a pressurized circulating fluidized bed by using multiphase particle-in-cell simulation

The particle residence time distribution(RTD)and axial dispersion coefficient are key parameters for the design and operation of a pressurized circulating fluidized bed(PCFB).In this study,the effects of pressure(0.1-0.6 MPa),fluidizing gas velocity(2-7 m·s^(-1)),and solid circulation rate(10-90 kg·m^(-2)·s^(-1))on particle RTD and axial dispersion coefficient in a PCFB are numerically investigated based on the multiphase particle-in-cell(MP-PIC)method.The details of the gas-solid flow behaviors of PCFB are revealed.Based on the gas-solid flow pattern,the particles tend to move more orderly under elevated pressures.With an increase in either fluidizing gas velocity or solid circulation rate,the mean residence time of particles decreases while the axial dispersion coefficient increases.With an increase in pressure,the core-annulus flow is strengthened,which leads to a wider shape of the particle RTD curve and a larger mean particle residence time.The back-mixing of particles increases with increasing pressure,resulting in an increase in the axial dispersion coefficient.

含高钙和维生素D的强化奶能有效提高健康的绝经后的中国女性体内的维生素D水平并减少骨吸收

目的钙摄入水平低以及体内维生素D不足是导致亚洲女性罹患骨质疏松的危险因素。此项研究的目的是评估高钙维生素D强化牛奶(HCM)对健康的中国绝经后妇女的体内维生素D状态和骨吸收标志物进行干预的影响。方法本试验对象为55岁以上,绝经至少5年的女性。共有124名女性进行了总体健康状况和骨密度检查筛选。63名女性被随机分为对照组和试验组,试验组在12w内每日饮用两次高钙/维生素D强化奶(含900 mg钙、96 mg镁、2.4 mg锌和6.4μg维生素D)。2组分别在试验开始、试验2 w、8 w和12 w时测量血矿物质、25(OH)维生素D3和Ⅰ型胶原C端肽(CTX)水平。结果对照组女性平均年龄为63±4.6岁,高钙强化奶(HCM)组女性平均年龄为62±3.8岁。所测得的每日钙摄入量的基线值为HCM组260～482 mg,对照组为252～692 mg。12 w后HCM组的平均身体质量指数(BMI)显著降低(P<0.05)。HCM组的血25(OH)维生素D3水平显著提高(33.13～39.49 nmol/L),而对照组则维持不变(29.27～28.21 nmol/L)。HCM组的血CTX水平在0 w和2 w之间下降了25%,并保持不变直至第12w。从第2w开始HCM组和对照组相比血CTX水平就出现了显著差异(P<0.001)。结论通过饮用含高钙和维生素D的强化奶(HCM),在2至4w内能显著提高中国绝经妇女体内维生素D水平,并减少骨吸收破坏。如果长期持续地饮用含高钙和维生素D的强化奶(HCM),能减少骨吸收和骨量丢失的风险,从而减少患骨质疏松和由此引起骨折的风险。

Current Situations and Problems of Investment in Agricultural Capital Construction from the Perspective of Investment of Different Ministries and Commissions and Recommendations

Investment in agricultural capital construction is an important factor in improving China's agricultural productivity and international competitiveness. In recent years,the attention to the investment in agricultural capital construction has been lifted to a strategic height. However,there is still little research on the investment in agricultural capital construction. From the perspective of investment of different ministries and commissions,this paper systematically analyzed current situations,problems,and came up with recommendations for the investment in the agricultural capital construction. According to the results,( i) from 1983 to the present,China's investment in agricultural capital construction experienced three stages. Especially after 2010,the scale of investment in agricultural capital construction was huge,and it showed a rapid increasing trend;( ii) the investment in agricultural capital construction is characterized by " multi-sector investment,different departments having different investment priorities and investment scale in different periods";( iii) some investment projects are overlapping between departments,local areas are weak in providing support funds,project construction standard is single,and there are problems of attaching importance to the application,belittling the management,stressing the construction,belittling the maintenance,and serious brain drain;( iv) different departments have accumulated certain experience in long-term exploration. For example,they pay more attention to the refinement and differentiation of projects,focus on the development of targeted poverty alleviation,pay more attention to the " quality" of investment,and pay more attention to the transformation of agricultural production methods. Based on current situations and problems,it came up with recommendations including promoting the integration of funds for investment and project integration,strengthening the personnel cultivation,ensuring simultaneous construction and management of projects,stressing the maintenance after project construction,exploring new modes for project design,management,investment,and financing,and enhancing the support for special investment projects.

Oxygen-doped Carbon Nitride Nanocages with Efficient Photon-to-Electron Conversion for Selective Oxidation of Xylose/Xylan to Yield Xylonic Acid

Highly efficient photon-to-electron conversion is crucial for achieving photocatalytic conversion.In this study,oxygen-doped carbon nitride nanocages(O@CNNCs)were engineered via dual strategies of morphology-controlled heteroatom doping,which was successfully used in the photocatalytic selective oxidation of xylose/xylan to xylonic acid.The nanocage-shaped O@CNNCs had a larger surface area,which was 4.02 times of carbon nitride(CN).Furthermore,with the assistance of morphology regulation and O-doping,O@CNNCs exhibit highly efficient photon-to-electron conversion,enhanced visible-light utilization,high photocurrent,low resistance,and fast separation/migration of electron-hole pairs.Correspondingly,the photocatalytic oxidation of xylose to xylonic acid using O@CNNCs was successfully achieved under mild reaction conditions with a yield of 83.4%.O@CNNCs have excellent recyclability,in which the yield of xylonic acid in the 5th cycle was 98.2%of its initial use.The O@CNNC photocatalytic system was also suitable for macromolecular xylan,and a xylonic acid yield of 77.34 mg was obtained when 100 mg xylan was used.The oxidation-active species captured experiments indicated that holes were crucial for the selective oxidation of xylose to xylonic acid.Overall,this study provides a new strategy for the preparation of photocatalysts with excellent photon-to-electron conversion and selective oxidation of biomass-derived feedstocks to xylonic acid.

Clean production of lactic acid by selective carbon-carbon bond cleavage of biomass feedstock over a novel carbon-bismuth oxychloride photocatalyst

The use of functional materials such as carbon-bismuth oxyhalides in integrated photorefineries for the clean production of fine chemicals requires restructuring.A facile biomass-assisted solvothermal fabrication of carbon/bismuth oxychloride nanocomposites(C/BiOCl)was achieved at various temperatures.Compared with BiOCl and C/BiOCl-120,C/BiOCl-180 exhibited higher crystallinity,wider visible light absorption,and a faster migration/separation rate of photoinduced carriers.For the selective C–C bond cleavage of biomass-based feedstocks photocatalyzed by C/BiOCl-180,the xylose conversion and lactic acid yield were 100%and 92.5%,respectively.C/BiOCl-180 efficiently converted different biomass-based monosaccharides to lactic acid,and the efficiency of pentoses was higher than that of hexoses.Moreover,lactic acid synthesis was favored by all active radicals including superoxide ion(·O_(2)^(−)),holes(h^(+)),hydroxyl radical(·OH),and singlet oxygen(^(1)O_(2)),with·O_(2)^(−)playing a key role.The fabricated photocatalyst was stable,economical,and recyclable.The use of biomass-derived monosaccharides for the clean production of lactic acid via the C/BiOCl-180 photocatalyst has opened new research horizons for the investigation and application of C–C bond cleavage in biomass-based feedstocks.

Influence of multi-factor interactions on particle growth during top-spray fluidized bed agglomeration

Considering the strong dependence of agglomerate characteristics on various operating parameters,this study employs the control variable methodology(CVM)and response surface methodology(RSM)to investigate the influence of multi-factor interactions on particle growth during top-spray fluidized bed agglomeration.First,CVM is conducted to assess the effects of individual operating parameters on the agglomerate properties,such as mean particle size,relative width,and sphericity.Then,the interactive relationship between these input variables and the quality attributes of the process is investigated using RSM.The results show that the mean particle size increases with the increase of binder viscosity and spray rate,while it decreases with the increase of fluidization gas velocity and inlet gas temperature.The relative width of the particle size distribution increases with the spray rate,binder viscosity,and fluidization gas velocity,and hardly changes with the inlet gas temperature.The mean particle size is more sensitive to the binder spray rate at a lower level of fluidization gas velocity or a higher level of inlet gas temperature.The fluidization gas velocity corresponding to the maximum D_(50) changes when the binder viscosity and binder spray rate are at different levels.

Comparative study of two fluid model and dense discrete phase model for simulations of gas-solid hydrodynamics in circulating fluidized beds

Computational fluid dynamics(CFD)has become a valuable tool to study the complex gas-solid hydrodynamics in the circulating fluidized bed(CFB).Based on the two fluid model(TFM)under the Eulerian-Eulerian framework and the dense discrete phase model(DDPM)under the Eulerian-Lagrangian framework,this work conducts the comparative study of the gas-solid hydrodynamics in a CFB riser by these two different models.Results show that DDPM could be used to predict gas-solid hydrodynamics in the circulating fluidized bed,and there are differences between TFM and DDPM,especially in the radial distribution profiles of solid phase.Sensitivity analysis results show that the gas-solid drag model exhibits significant effects on the results for both the two models.The specularity coefficient and the restitution coefficient in the TFM,as well as the reflection coefficient and the parcel number in the DDPM,exhibit less impact on the simulated results.

Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations

Cycle Time Distribution(CTD)plays a critical role for determining uniformity of particle coating in spray fluidized beds.However,the CTD is influenced by both geometrical structure and operating conditions of fluidized bed.In this study,a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model(CFD-DEM).To achieve different behaviors of CTD,some modifications are designed on a pseudo-2D internally circulating fluidized bed,which traditionally composes of a high-velocity upward bed and low-velocity downward bed.These modifi-cations include making the air distributor slope and/or laying a baffle in the downward bed.First,the CTD and evolution of particle size distribution under different bed structures are compared.The CTD directly influences the coating uniformity.By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications,the CTD becomes narrower and the coating uniformity is significantly improved.Second,under the optimized bed structure,the influence of oper-ating conditions on the coating uniformity is studied.Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.

Cuprous oxide/copper oxide interpenetrated into ordered mesoporous cellulose-based carbon aerogels for efficient photocatalytic degradation of methylene blue

The casual discharge of dyes from industrial settings has seriously polluted global water systems.Owing to the abundance of biomass resources,preparing photocatalysts for photocatalytic degradation of dyes is significant;however,it still remains challenging.In this work,a cuprous oxide/copper oxide composite was interpenetrated onto carbon nanosheets of cellulose-based flexible carbon aerogels(Cu_(2)O/CuO@CAx)via a simple freeze-drying-calcination method.The introduction of the carbon aerogel effectively prevents the aggregation of the cuprous oxide/copper oxide composite.In addition,Cu_(2)O/CuO@CA0.2 has a larger specific surface area,stronger charge transfer capacity,and lower recombination rate of photogenerated carriers than copper oxide.Moreover,Cu_(2)O/CuO@CA0.2 exhibited high photocatalytic activity in decomposing methylene blue,with a degradation rate reaching up to 99.09% in 60 min.The active oxidation species in the photocatalytic degradation process were systematically investigated by electron spin resonance characterization and poisoning experiments,among which singlet oxygen played a major role.In conclusion,this work provides an effective method for preparing photocatalysts using biomass resources in combination with different metal oxides.It also promotes the development of photocatalytic degradation of dyes.

Bubbling behavior of cohesive particles in a two-dimensional fluidized bed with immersed tubes

Fluidization hydrodynamics are greatly influenced by inter-particle cohesive forces. This paper studies the fluidization of large cohesive particles in a two-dimensional fluidized bed with immersed tubes using “polymer coating” to introduce cohesive force, to gain better understanding of bubbling behavior when particles become cohesive and its effect on chemical processes. The results show that the cohesive force promotes bubble splitting in the tube bank region, thereby causing an increase in the number and a decline in the aspect ratio of the bubbles. As the cohesive force increases within a low level, the bubble number increases and the bubble diameter decreases, while the aspect ratio exhibits different trends at different fluidization gas velocities. The difference in the evolution of bubble size under various cohesive forces mainly takes place in the region without tubes. When the cohesive force is large enough to generate stable agglomerates on the side walls of the bed, the bubble number and the bed expansion sharply decrease. The tubes serve as a framework that promotes the agglomeration, thus accelerating defluidization. Finally, the bubble profile around tubes was studied and found to greatly depend both on the cohesive forces and the location of tubes.

Equilibrium charge and triboelectric coefficient of spheres in a rotating container

Contact electrification occurs in many granular material systems due to particle-particle and particle-wall contacts.In this paper,we used a simple device to characterize the electrification of different spheres in a rotating spherical container.The charge of the spheres was quantified by a Faraday cup after rotating for various time and the disperse behaviors of charged spheres were recorded by a camera.The effects of the rotational time,sphere size,rotational speed,sphere material,and relative humidity on the equilibrium charge and triboelectric coefficient were analyzed.The results show that the equilibrium surface charge density is independent of the sphere size and the rotating speed,whereas the larger rotating speed enhances the triboelectric coefficient.It is also shown that charge relaxation constants are two orders of magnitude lower than the charge generation constants for all spheres at a low relative humidity.The increase of water molecules in the air was found to result in the decline of charge generation constant and the rise of charge relaxation constant,which together cause the decrease of the equilibrium surface charge density.

Solids flow characteristics and circulation rate in an internally circulating fluidized bed

Internally circulating fluidized beds(ICFBs)enable effective control of the reactions and heat distribution in reactors.The ICFB contains two or more connected fluidized regions with different gas velocities to promote controlled solid circulation.The control of solid circulation rate(G_(0))is a critical factor.We recorded single particle trajectories by tracing a fluorescent particle,based on which particle flow behaviors were analyzed in different regions.G_(0)was obtained for a wide range of operating parameters.An increase in gas velocity in the down-and upflow beds shortened the particle circulation time in both beds and G_(0)increased significantly.As the static bed height increased,the differential pressure on both sides of the circulation port increased,which resulted in an increase in the solid circulation rate.As the orifice area increased,the flow resistance through the orifice decreased and thus the solid circulation rate increased.G_(0)increased with the decrease in particle size.The gas velocity in the upflowing bed and orifice area was the most important parameter to control the solid circulation rate.G_(0)was compared with the experimental measurements in literature and predictions using the correlation based on Bernoulli’s equation,and they agreed well.

Operando modeling and measurements:Powerful tools for revealing the mechanism of alkali carbonate-based sorbents for CO_(2)capture in real conditions

Alkalicarbonate-based sorbents(ACSs),including Na_(2)CO_(3)-and K2CO_(3)-based sorbents,are promising for CO_(2)capture.However,the complex sorbent components and operation conditions lead to the versatile kinetics of CO_(2)sorption on these sorbents.This paper proposed that operando modeling and measurements are powerful tools to understand the mechanism of sorbents in real operating conditions,facilitating the sorbent development,reactor design,and operation parameter optimization.It reviewed the theoretical simulation achievements during the development of ACSs.It elucidated the findings obtained by utilizing density functional theory(DFT)calculations,ab initio molecular dynamics(AIMD)simulations,and classical molecular dynamics(CMD)simulations as well.The hygroscopicity of sorbent and the humidity of gas flow are crucial to shifting the carbonation reaction from the gas-solid mode to the gas-liquid mode,boosting the kinetics.Moreover,it briefly introduced a machine learning(ML)approach as a promising method to aid sorbent design.Furthermore,it demonstrated a conceptual compact operando measurement system in order to understand the behavior of ACSs in the real operation process.The proposed measurement system includes a micro fluidizedbed(MFB)reactor for kinetic analysis,a multi-camera sub-system for 3D particle movement tracking,and a combined Raman and IR sub-system for solid/gas components and temperature monitoring.It is believed that this system is useful to evaluate the real-time sorbent performance,validating the theoretical prediction and promoting the industrial scale-up of ACSs for CO_(2)capture.