Recent advances on the reduction of CO2 to important C2+ oxygenated chemicals and fuels

The chemical utilization of CO_2 is a crucial step for the recycling of carbon resource. In recent years, the study on the conversion of CO_2 into a wide variety of C_(2+) important chemicals and fuels has received considerable attention as an emerging technology. Since CO_2 is thermodynamically stable and kinetically inert, the effective activation of CO_2 molecule for the selective transformation to target products still remains a challenge. The welldesigned CO_2 reduction route and efficient catalyst system has imposed the feasibility of CO_2 conversion into C_(2+) chemicals and fuels. In this paper, we have reviewed the recent advances on chemical conversion of CO_2 into C_(2+) chemicals and fuels with wide practical applications, including important alcohols, acetic acid, dimethyl ether, olefins and gasoline. In particular, the synthetic routes for C\\C coupling and carbon chain growth, multifunctional catalyst design and reaction mechanisms are exclusively emphasized.

The adsorption properties of NaY zeolite for separation of ethylene glycol and 1,2-butanediol: Experiment and molecular modelling

The separation of ethylene glycol(EG)and 1,2-butanediol(1,2-BDO)azeotrope in the synthesis process of EG via coal and biomass is becoming of increasing commercial and environmental importance.Selective adsorption is deemed as the most promising methods because of energy saving and environment favorable.In this paper,NaY zeolite was used to separate 1,2-BDO from EG,and its adsorption properties was then investigated.The isotherms of EG and 1,2-BDO in vapor and liquid phases from 298 to 328 K indicated that they fitted Langmuir model quite well,and the NaY zeolite absorbent favored EG more than 1,2-BDO.The Grand Canonical Monte Carlo(GCMC)and molecular dynamics(MD)simulation techniques were conducted to investigate the competition adsorption and diffusion characteristics in different adsorption regions.It was observed that EG and 1,2-BDO molecules all have the most probable locations of the center of the 12-membered ring near the Na cations.The diffusivities of EG are lower than those of 1,2-BDO at the same adsorption concentration.At last,the breakthrough curves of the binary mixture regressed from the empirical Dose–Response model in fixed-bed column showed that the adsorption selectivity of EG could reach to as high as 2.43,verified that the NaY zeolite could effectively separate EG from 1,2-BDO.This work is also helpful for further separation of other dihydric alcohol mixtures from coal and biomass fermentation.

Green and selective hydrogenation of aromatic diamines over the nanosheet Ru/g-C_(3)N_(4)-H_(2) catalyst prepared by ultrasonic assisted impregnation-deposition method

In this study,nanosheet g-C_(3)N_(4)-H_(2) was prepared by thermal exfoliation of bulk g-C_(3)N_(4) under hydrogen.A series of Ru/g-C_(3)N_(4)-H_(2) catalysts with Ru species supported on the nanosheet g-C_(3)N_(4)-H_(2) were synthesized via ultrasonic assisted impregnation-deposition method.Ultrafine Ru nanoparticles(<2 nm)were highly dispersed on nanosheet g-C_(3)N_(4)-H_(2).Strong interaction due to Ru-Nx coordination facilitated the uniform distribution of Ru species.Meanwhile,the involvement of surface basicity derived from abundant nitrogen sites was favourable for enhancing the selective hydrogenation performance of bi-benzene ring,i.e.,almost complete 4,40-diaminodiphenylmethane(MDA)conversion and>99%4,40-diaminodicyclohexylmethane selectivity,corresponding to a reaction activity of 35.7 mol_(MDA) mol_(Ru)^(-1) h^(-1).Moreover,the reaction activity of catalyst in the fifth run was 36.5 mol_(MDA) mol_(Ru)^(-1) h^(-1),which was comparable with that of the fresh one.The computational results showed that g-C_(3)N_(4) as support was favorable for adsorption and dissociation of H_(2) molecules.Moreover,the substrate scope can be successfully expanded to a variety of other aromatic diamines.Therefore,this work provides an efficient and green catalyst system for selective hydrogenation of aromatic diamines.

Multi-objective optimization of methane production system from biomass through anaerobic digestion

This work addressed the multi-objective optimization of a biogas production system considering both environmental and economic criteria. A mixed integer non-linear programming(MINLP) model was established and solved with non-dominated sorting genetic algorithm Ⅱ, from which the Pareto fronts, the optimal technology combinations and operation conditions were obtained and analyzed. It's found that the system is feasible in both environmental and economic considerations after optimization. The most expensive processing section is decarbonization; the most expensive equipment is anaerobic digester; the most power-consuming processing section is digestion, followed by decarbonization and waste management. The positive green degree value on the process is attributed to processing section of digestion and waste management. 3:1 chicken feces and corn straw, solar energy, pressure swing adsorption and 3:1 chicken feces and rice straw, solar energy, pressure swing adsorption are turned out to be two robust technology combinations under different prices of methane and electricity by sensitivity analysis. The optimization results provide support for optimal design and operation of biogas production system considering environmental and economic objectives.

Emerging single-atom nanozymes for catalytic biomedical uses

The past four years have witnessed booming progress in single-atom nanozymes(SANs),one of the newest generations of nanozymes with atomically dispersed metal sites for catalytic biomedical uses.They show distinct advantages over their nanoparticle-based counterparts,such as well-defined electronic/geometric structures and complete atomic utilization efficiency,thus offering opportunities to develop advanced nanozymes for practical uses.The atomically dispersed active centers in SANs could also facilitate the precise regulation of catalytic performance,while probing structure–activity relationship for in-depth understanding of mechanism.In this review,we first introduce the synthetic approaches,surface engineering,and characterization techniques of SANs.Subsequently,we discuss the enzyme-like properties of SANs,including some strategies for boosting their catalytic activities.Furthermore,we present their biomedical applications,ranging from biosensors,antibacterial uses,antioxidants,to therapeutics.Finally,the challenges and opportunities of SANs are prospected.

考虑地下水可持续开采约束条件的海河流域水资源优化配置（英文）

This study applies a hydroeconomic optimization method for water resources management in the highly water stressed Haihe River basin. A multi-objective, multi-temporal deterministic hydroeconomic optimization model has been built to quantify the economic trade-offs and reveal "minimum cost strategies" when reducing groundwater abstraction to sustainable levels. A complex basin representation, with ～140,000 decision variables is formulated where each decision variable represents a flow-path from a water source to a sink. Available water sources are runoff generated by the sub-basins upstream the nine major surface water reservoirs, the inter-basin transfers from Yellow River and South to North Water Transfer Project(SNWTP) and the natural groundwater recharge to the three main groundwater aquifers. Water demands, i.e. sinks, are aggregated for each model sub-basin in categories of the major agricultural users, domestic, industrial and ecological water demands. Each demand is associated with a curtailment cost and groundwater abstraction with a pumping cost. Groundwater overdraft is constrained in each model scenario, ranging from unlimited overdraft in the plain area groundwater aquifer to sustainable abstractions over an 8-year period. Inflow upstream Yuqiao reservoir, and the inter-basin transfers from SNWTP and Yellow River are identified as the water resources with the highest increase in average shadow prices when limiting groundwater overdraft. An increase in inflow shadow prices of 37.5% indicates that these water sources will be most valuable if sustainable groundwater abstraction should be achieved. The shadow prices of water sources reveal when and where in the Haihe River basin users are curtailed if water resources are managed in the most optimal way. Average shadow prices of 1.6 yuan/m3 for all surface water sources in the sustainable abstraction scenarios shows that overdraft can be avoided by curtailment of users with a willingness-to-pay ≤1.6 yuan/m3. The shadow prices of the existing surface water res-ervoirs represented in the model shows that no costs can be saved from expanding their capacities. Finally, the cost of achieving sustainable groundwater abstraction with present water resource availability is found to be minimum 8.2 billion yuan/year.

How Off-farm Employment Affects Technical Efficiency of China＇s Farms＂ The Case of Jiangsu

Using three-wave survey data for four villages of Jiangsu Province in China, the present paper examines whether and to what extent off-farm employment affects the technical efficiency of agricultural production. The level of technical efficiency is measured using a stochastic frontier production function approach. Based on estimation results from instrumental variable panel quantile regressions we find that there is a positive significant effect of off-farm employment on the level of farm technical efficiency. We also find that fragmentation of farmland is a barrier to the improvement of technical efficiency. In addition, we find a downward trend in the level of agricultural technical efficiency among our sample. Therefore, the Chinese Government should stimulate agricultural mechanization and the development of farming techniques to improve technical efficiency in the context of increasing off-farm employment.

Efficient hydrogenation of ethylene carbonate derived from CO_(2) to synthesize methanol and ethylene glycol over core-shell Cu@GO catalyst

The synthesis of sustainable methanol and ethylene glycol(EG)via hydrogenation of ethylene carbonate(EC)has caught researchers’growing interests on account of the indirect chemical utilization of CO_(2).Core-shell Cu@GO catalysts with random nanoporous network of graphite oxide(GO)were synthesized via a simple method of ul-trasonic precipitation.Cu@GO catalysts were analyzed systematically by N_(2) physisorption,TGA measurement,XRD,FT-IR,Raman,TEM,SEM,and XPS(XAES).In particular,the mentioned method was confirmed to be effective to fabricate the high dispersity core-shell Cu@GO catalysts through promoting the specific surface area.The as-prepared Cu@GO catalyst was then successfully applied in the hydrogenation of CO_(2)-derived EC to pro-duce methanol and EG.A high TOF of 1526 mg EC g cat^(-1) h^(-1) could be attained in EC hydrogenation at the reaction temperature of 493K.Accordingly,the correlation of catalytic structure and performance disclosed that the synergistic effect between Cu^(+) and Cu^(0) was responsible for achieving high activity of the catalyst.In addition,the reusability of Cu@GO catalyst suggested that graphite oxide shell structure could decrease the aggregation of Cu particles,thus enhance the stability of Cu-based catalysts.DFT calculation results suggested that the involvement of carbon film on Cu was favorable for the stabilization of the active sites.This study is helpful for developing new and stable catalytic system for indirect chemical utilization of CO_(2) to synthesize commodity methanol and EG.

Influence of functional groups on the self-assembly of liquid crystals

Functional groups in the molecule play an important role in the molecular o rganization process.To reveal the influence of functional groups on the self-assembly at interface,herein,the self-assembly structures of three liquid crystal molecules,which only differ in the functional groups,are explicitly characterized by using scanning tunneling microscopy(STM).The high-resolution STM images demonstrate the difference between the supramolecular assembly structures of three liquid crystal molecules,which attribute to the hydrogen bonding interaction andπ-πstacking interaction between different functional groups.The density functional theory(DFT)results also confirm the influence of these functional groups on the self-assemblies.The effort on the self-assembly of liquid crystal molecules at interface could enhance the understanding of the supramolecular assembly mechanism and benefit the further application of liquid crystals.