Analysis of long term catalytic performance for isobutane alkylation catalyzed by NMA–AlCl3 based ionic liquid analog

Isobutane alkylation with 2-butene to produce high-quality gasoline was catalyzed by Nmethylacetamide(NMA)-AlCl3 based ionic liquid(IL) analog with a NMA/AlCl3 molar ratio of 0.75 and CuCl modification,which was marked as CuCl-modified 0.75 NMA-1.0 AlCl3.The long-term experiment was carried out in the autoclave operated in continuous mode to investigate the distribution of alkylate under different experimental nodes.The result indicated that the long-term alkylation was divided into three stages:rising,stable,and descending regions.C8 selectivity and molar ratio of trimethylpentanes(TMPs) to dimethylhexanes(DMHs) reached the highest level in the stable region,and research octane number(RON) of alkylate was as high as 97.Anionic Al species([AlbCl7]^-,[A1 CuC15]^-) and cationic Al species([AlCl2 L]^+) from IL analog as two active Lewis acidic species played a catalytic role in the long-term alkylation,whereas the neutral Al species did not participate into the alkylation.Moreover,the structure of CuCl-modified 0.75 NMA-1.0 AlCl3 was destroyed after the deactivation,and CuCl was enriched in the CD2 Cl2-insoluble substance,resulting in a decreasing TMP/DMH ratio.The catalytic lifetime of IL analog was similar with CuCl-modified 0.55 Et3 NHCl-1.0 AlCl3 IL,but IL analog had a lower cost.

Corrosion inhibiting performance and mechanism of protic ionic liquids as green brass inhibitors in nitric acid

Four protic ionic liquids(ILs)were synthesized via a one-step method by using benzotriazole(BTA)and benzimidazole as cations,and benzenesulfonic acid and 2-naphthalenesulfonic acid(NSA)as anions.These ILs were used as green corrosion inhibitors for brass specimens in a nitric acid solution.The structure of the protic ILs was characterized by 1H-NMR,13C-NMR,and FT-IR spectroscopy.The effects of the IL structure,IL concentration,acid concentration,and corrosion time on the surface morphology of brass specimens and the inhibition efficiency(η%)of ILs were investigated by the weight loss method combined with SEM and EDS spectroscopy.Polarization curves and impedance spectroscopy were used to analyze the electrochemical corrosion inhibition mechanism of ILs.Results showed that IL synthesis was a proton transfer process,and the proton of the–SO3H group on NSA was deprived by BTA.IL[BTA][NSA],which had a high charge density and large conjugateπband,was the most effective inhibitor for brass corrosion.Theη%of[BTA][NSA]decreased with the increase in acid concentration and corrosion time,which showed an increment with the increase in[BTA][NSA]concentration.The higher theη%of[BTA][NSA]is,the smoother the surface of the brass specimens is,and the smaller the undistributed area of Cu element will be.Corrosion inhibiting mechanism from electrochemical analysis indicated that the addition of[BTA][NSA]increased the polarization resistance of the brass electrode significantly and suppressed both anodic and cathodic reactions.

Review of drought impacts on carbon cycling in grassland ecosystems

Grasslands play a key role in both carbon and water cycles.In semi-arid and arid grassland areas,the frequency and intensity of droughts are increasing.However,the influence of a drought on grassland carbon cycling is still unclear.In this paper,the relationship between drought and grassland carbon cycling is described from the perspective of drought intensity,frequency,duration,and timing.Based on a large amount of literature,we determined that drought is one of the most prominent threats to grassland carbon cycling,although the impacts of different drought conditions are uncertain.The effects of a drought on grassland carbon cycling are more or less altered by drought-induced disturbances,whether individually or in combination.Additionally,a new conceptual model is proposed to better explain the mechanism of droughts on grassland carbon cycling.At present,evaluations of the effects of droughts on grassland carbon cycling are mainly qualitative.A data fusion model is indispensable for evaluating the fate of carbon cycling in a sustainable grassland system facing global change.In the future,multi-source data and models,based on the development of single and multiple disturbance experiments at the ecosystem level,can be utilized to systematically evaluate drought impacts on grassland carbon cycling at different timescales.Furthermore,more advanced models should be developed to address extreme drought events and their consequences on energy,water,and carbon cycling.

Vegetation and soil wind erosion dynamics of sandstorm control programs in the agro-pastoral transitional zone of northern China

To combat soil erosion and desertification,large-scale sandstorm control programs have been put in place since 2000 in the agro-pastoral transitional zone of northern China.Vegetation dynamics as well as soil wind erosion control effects are very important for assessing the ecological success of sandstorm control programs in China.However,no comprehensive evaluation of vegetation dynamics and soil wind erosion control effects in this region has been achieved.In this study,we illustrate the vegetation and soil wind erosion dynamics of sandstorm control programs in the northern Shanxi Province using remote sensing data and soil wind erosion models.There was a significant increase in vegetation cover for 63.59% of the study area from 2001 to 2014 and a significant decrease for 2.00% of the study area.The normalized difference vegetation index (NDVI) showed that the largest increase occurred in autumn.Soil wind erosion mass decreased from 20.90 million tons in 2001 to 7.65 million tons in 2014.Compared with 2001,the soil wind erosion moduli were reduced by 43.05%,36.16%,and 62.66% in 2005,2010,and 2014,respectively.Spatially,soil wind erosion in most of the study area was alleviated between 2001 and 2014.The relationship between NDVI and soil wind erosion mass showed that the increased vegetation coverage reduced the soil wind erosion mass.In addition,wind was the main driving force behind the soil wind erosion dynamics.The results indicate that the vegetation coverage has increased and soil wind erosion mass has been reduced following the implementation of the sandstorm control programs.However,the ecological effects of the sandstorm control programs may vary over different periods.While the programs appear to be beneficial in the short term,there may be unintended consequences in the long term.Research on the sustainability of the ecological benefits of sandstorm control programs needs to be conducted in the future.

Examining the efficacy of revegetation practices in ecosystem restoration programs:insights from a hotspot of sandstorm in northern China

Retrospectively evaluating the efficacy of revegetation practices is helpful in planning and imple-menting future ecosystem restoration programs(ERP).Having a good understanding of how human activities can affect vegetation cover,both before and after ERP,is particularly important in sandstorm hotspot areas.The Beijing-Tianjin Sandstorm Source Region(BTSSR)is one such area.We conducted an investigation into vegetation dynamics within the BTSSR.This was done using remote sensing data in conjunction with climate data sets and land use data spanning the 1982-2014 period.The relationships between climatic factors(such as precipitation and temperature),and vegetative change were modeled using a neural network method.By a process of residual analysis,the proportions of human-induced vegetative change both before and after the ERP were established.Our results show that:1)before the ERP(1982-2000),40.96%of the study area exhibited significantly progressive vegetation changes(p<0.05).This proportion decreased to encom-pass only 20.23%of the study area in the period following the ERP(2001-2014).2)89.55%of the study area showed signs of human-induced vegetation degradation before the ERP.Between 2001 and 2014 however,following ERP,this figure fell to only 27.78%.3)ERP implementation led to visible improvements in vegetative conditions within the BTSSR,especially in areas where ecological restoration measures were directly and anthropogenically applied.These results highlight the benefits that positive human action(i.e.,revegetation initiatives implemented under the framework of an ERP)have brought to the BTSSR.

THE DYNAMICS AND THERAPEUTIC STRATEGIES OF A SEIS EPIDEMIC MODEL

Based on an epidemic model which Manvendra and Vinay [Mathematical model to simulate infections disease, VSRD-TNTJ 3（2） （2012） 60 68] have proposed, we consider the dynamics and therapeutic strategy of a SEIS epidemic model with latent patients and active patients. First, the basic reproduction number is established by applying the method of the next generation matrix. By means of appropriate Lyapunov functions, it is proven that while the basic reproduction number 0 〈 R0 〈 1, the disease-free equilibrium is globally asymptotically stable and the disease eliminates; and if the basic reproduction number R0 〉 1, the endemic equilibrium is globally asymptotically stable and therefore the disease becomes endemic. Numerical investigations of their basin of attraction indicate that the locally stable equilibria are global attractors. Second, we consider the impact of treatment on epidemic disease and analytically determine the most effective therapeutic strategy. We conclude that the most effective therapeutic strategy consists of treating both the exposed and the infectious, while treating only the exposed is the least effective therapeutic strategy. Finally, numerical simulations are given to illustrate the effectiveness of the proposed results.