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Protonic ceramic fuel cells (PCFCs), as an efficient energy storage and conversion device, have great potential to solve the serious problems of energy shortage and environmental pollution. Improving the proton conductivity of the promising cathode materials is an effective solution to promote the widespread application of PCFCs at low temperatures (450-650 °C). Herein, considering the high oxygen reduction reaction (ORR) activity of BaCoO

Supercritical CO2 (S-CO2) Brayton cycle is one of the alternative energy conversion technologies for generation IV nuclear energy systems. Printed circuit heat exchanger (PCHE) is one of the key co...

Oxygen-ion conducting perovskite oxides are important functional materials for solid oxide fuel cells and oxygen permeable membranes operating at high temperatures (> 500 ºC). Co-doped perovskites have recently shown their potential to boost oxygen-related kinetics, but challenges remain to understand the underlying mechanisms. This work unveils the local cation arrangement as a new key factor controlling oxygen kinetics in perovskite oxides. By single- and co-doping Nb5+ and Ta5+ into SrCoO3-δ, we control dominant factors affecting oxygen kinetics such as lattice geometry, cobalt states, and oxygen vacancies, which are confirmed by neutron and synchrotron X-ray diffraction as well as high-temperature X-ray absorption spectroscopy. Our combined experimental and theoretical study unveils that co-doping likely leads to higher cation dispersion at the B-site compared to single-doping. Consequently, a high-entropy configuration enhances oxygen ion migration in the lattice, translating to improved oxygen reduction activity.

The methodology of artificial intelligence (AI), particularly artificial neural network (ANN), would be in favor of nuclear energy system development. These ANN simulators may provide more efficient means than the traditional nuclear design codes, especially for the design of the key parameters, such as core geometry and layout, material composition. In this paper, a neutronics calculation code SARAX and the corresponding multilayer perceptron (MLP) surrogate model were used as simulators for core parameters optimization of a reference lead based fast reactor. The pellet radius, enrichments and active height are the interested core parameters, and core burnup and power distribution are the target characteristics in the study. The training of structure and weight parameters in MLP network are based on about 5000 calculations of SARAX code. Test results of neural network show a good agreement between MLP surrogate model and SARAX code. The feasibility of the MLP surrogate model to be used in core parameters optimization was also discussed. Results showed that, the core surrogate model based on MLP could be quickly constructed and regulated, and be a more efficient simulators in a innovate reactor optimization. The above work is completed in Sinan Platform, a multidisciplinary intelligent design platform developed by China Nuclear Power Technology Research Institute Co. Ltd.

Grazing and mowing are two dominant management regimes used in grasslands. Although many studies have focused on the effects of grazing intensity on plant community structure, far fewer test how grazing impacts the soil microbial community. Furthermore, the effects of long-term grazing and mowing on plant and microbial community structure are poorly understood. To elucidate how these management regimes affect plant and microbial communities, we collected data from 280 quadrats in a semiarid steppe after 12-year of grazing and mowing treatments. We measured plant species abundance, height, coverage, plant species diversity, microbial biomass, and microbial community composition (G+ and G− bacteria; arbuscular mycorrhizal and saprotrophic fungi; G+/G− and Fungi/Bacteria). In addition, we determined the soil’s physical and chemical properties, including soil hardness, moisture, pH, organic carbon, total nitrogen, and total phosphorus. This is a long-term and multifactorial dataset with plant, soil, and microbial attributes which can be used to answer questions regarding the mechanisms of sustainable grassland management in terms of plant and microbial community structure., Measurement(s) microbial community • plant trait • Abundance • composition of soil • Microbial DNA • acidity of soil • phosphorus • organic material • plant canopy cover • plant height • humidity of soil • hardness of soil • concentration of carbon atom in soil • concentration of nitrogen atom in soil • fungi phospholipid fatty acids • bacteria phospholipid fatty acids Technology Type(s) field work • DNA sequencing • pH meter • ultraviolet spectrometer • chloroform-extraction method • visual observation method • oven drying • soil hardness tester • Walkley-black method • colorimetry • gas chromatography • micro-Kjeldahl digestion Factor Type(s) long-term grazing • long-term mowing Sample Characteristic - Organism Bacteria • Fungi • Embryophyta Sample Characteristic - Environment steppe • grassland area Sample Characteristic - Location Inner Mongolia Autonomous Region Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.13162052

Arbuscular mycorrhizal fungi (AMF), common symbiotic root-associated soil biota, play a key role in maintaining ecosystem function and stability. However, how AMF are affected by livestock grazing in grassland\ud ecosystem is variable, and this uncertainty in mycorrhizal responses to grazing is mainly due to the contextdependent nature of the AMF symbiosis association. The effects of grazing on AMF are through grazing-induced\ud changes in the environment experienced by the mycorrhizal fungi and this includes both plant and soil-related\ud factors. Here, we introduce a conceptual framework that highlights potential drivers and mechanistic pathways\ud through which long-term grazing impacts AMF. We focus on known drivers of AMF abundance and diversity that\ud are expected to be influenced by grazing including plant above-ground biomass and diversity, nutrient availability (soil available nitrogen and phosphorus) and edaphic properties (soil organic carbon, soil pH, soil bulk\ud density and soil moisture). Given that the identity and relative importance of each of these drivers may differ\ud across different ecosystems, the application of our framework of potential environmental drivers allows us to\ud generalize, organize and help formulate hypotheses for testing the impact of various grazing management approaches on AMF. We also argue the herbivory-AMF relationship can be moderated by climate, seasonality and\ud topography. We reviewed the current state of knowledge of livestock grazing impacts on AMF and discussed\ud some of the reasons behind conflicting results among empirical studies. We also provide suggestions for future\ud research aimed at improving experimental design to unravel underlying mechanisms determining the impacts of\ud grazing on AMF.

Ongoing climate change, as well as long-term overgrazing, is threatening biodiversity and ecosystem functioning in grasslands worldwide. Climate change and grazing could directly alter ecosystem functioning and stability, or indirectly by changing species diversity, composition and plant functional traits. By synthesizing results from publications of the most recent 30-years, we found that effects of climate change and grazing on biodiversity and ecosystem functioning varied from positive to negative, depending on different scenarios. Generally, aboveground net primary production (ANPP), belowground net primary production (BNPP), and species richness showed strong negative responses to 4°C warming, 50% precipitation decrease, and high grazing intensity. Responses of ANPP, BNPP and species richness to precipitation increase were mostly positive, whereas their responses to 2°C warming and low-to-moderate grazing intensity varied from positive to negative. Negative effects of 2°C warming on ANPP were substantially greater in grasslands that had been grazed than those that had not been grazed, and larger in arid and semi-arid grasslands than those in sub-humid and humid grasslands. Under 50% precipitation increase, ANPP responses were larger in grazed than ungrazed grasslands, and bigger in arid and semi-arid than sub-humid and humid grasslands. High levels of grazing intensity had greater effects on productivity and species richness than did warming and precipitation decrease. Currently, although there are increasing number of experiments which have included both climate change and grazing factors, more studies are needed to test the joint effects of climate change (e.g. warming, changes in precipitation patterns) and grazing (grazing intensity and livestock type) on biodiversity and multiple ecosystem functions. Multi-factor experiments would provide a more comprehensive understanding for sustainable grassland management in future.

Although many studies have demonstrated that N deposition decreases biodiversity and alters ecosystem functioning, fewer studies have tested how N enrichment affect plant N and P limitation, N: P stoichiometry and ecosystem functioning. We examined the independent and interactive effects of N and P enrichment on plant N: P stoichiometry, nutrient limitation, and thereby ecosystem functioning based on two N, P, and N + P addition experiments in a typical steppe. At the species level, N enrichment increased leaf N: P ratio and P limitation of dominant species. The responses of plant tissue N: P ratio tend to saturate at soil available N: P supply ratio of approximately 20 for leaf N: P and 10 for root N: P ratio. At the community level, patterns of N and P limitation shifted from N limitation in a normal year to N and P co-limitation in a wet year, triggered mainly by inter-annual changes in soil N and P availability. The homoeostasis of N: P stoichiometry increases from plant leaves to roots and to microbes although the available N: P supply ratio varied by 56-fold in soil. Given that N deposition rates are projected to increase in upcoming decades, N deposition may further alter the stoichiometric balance of N and P and intensify P limitation of steppe ecosystems in future.

Summary Overgrazing has resulted in widespread decline in biodiversity and ecosystem functioning in grasslands world-wide in recent decades. However, few studies have examined the patterns and thresholds of grazing-induced changes in community structure and ecosystem functioning along a grazing gradient and based on species-level responses and plant functional traits. To identify the thresholds of grazing intensity (GI) at both species and community levels, we conducted a grazing manipulation experiment with seven levels of GI (0–9 sheep ha−1) and two topographies (flat vs. slope) in a typical steppe. Four plant functional traits were measured, including specific leaf area (SLA), plant height, leaf nitrogen content (LNC) and stem: leaf ratio. The threshold of GI that significantly altered community composition was at 3·75 sheep ha−1 for the flat system and 3·0 sheep ha−1 for the slope system. For both flat and slope systems, the threshold GI for changes in primary productivity was at 3·0 sheep ha−1, beyond which the productivity decreased substantially. At the species level, the abundances of common species, most of which are perennial grasses, declined at moderate grazing intensities (3·0–4·5 sheep ha−1). The abundances of most rare species, which are perennial forbs, declined at low grazing intensities (1·5–3·0 sheep ha−1). SLA and LNC are good predictors of species-level responses to grazing. Low SLA and high LNC species are negatively affected by high GI, while high SLA and low LNC species are little affected by grazing. The negative effect of GI on species’ abundance was greater in the slope system than in the flat system. Synthesis and applications. Our results indicate that the structural and functioning thresholds of grazing intensity depend on plant traits and species composition, which is mediated by topographic location. These findings, integrating plant functional traits and threshold approaches, have important implications for determining sustainable grazing intensity in grassland management and biodiversity conservation in semi-arid regions.

Keystone root symbiotic arbuscular mycorrhizal fungi play a major role in maintaining plant biodiversity, increasing plant productivity and enhancing storage of carbon in soil. AM fungi are ubiquitous and found in most ecosystems including grasslands currently experiencing increasing pressures form human activity. Grazing is known to impact AM fungi but very little is known about how AM fungi are affected by different levels of grazing intensity. Here we report on results from a long-term experimental site in a typical steppe in the north of China, containing seven levels of field-manipulated grazing intensities maintained for over 13 years. We assessed arbuscular mycorrhizal fungal abundance, represented by soil hyphal length density and mycorrhizal root colonization (mycorrhizal root frequency, intensity and arbuscule intensity) within the farm-scale field experiment. We also measured environmental variables to explain the responses of mycorrhizal fungi to grazing intensity. Our results showed that with an increase in grazing intensity, soil hyphal length density linearly decreased. There was, however, no significant trend for mycorrhizal root colonization variables in relation to grazing intensity. Mycorrhizal root frequency was negatively correlated with topographic-induced changes in soil nitrogen and phosphorus, while arbuscule intensity was marginally negatively correlated with soil available phosphorus. Further, we found a possible hump-shaped relationship between the ratio of external to internal AM fungal structures and grazing intensity. Our finding showed that external AM fungal structure was clearly impacted by grazing intensity but that this was not the case for internal mycorrhizal structures. This indicated that mycorrhizal functioning was impacted by the intensity of grazing as the mycorrhizal structures responded differently. Indeed the ratio of the foraging extra-radical mycorrhizal hyphae to intra-radical mycorrhizal structures was highest at moderate grazing intensity but strongly decreased by high grazing intensity. Our study suggests that the impacts of grazing intensity on the plant-AMF association could lead to further knock-on effects on the plant-soil system via the feedbacks that exist between plant and AMF communities.

Summary 1. Although extensive studies demonstrate that nitrogen (N) enrichment frequently reduces plant diversity within small quadrats (0.5– 4m 2 ), only a few studies have evaluated N effects on biodiversity across different spatial scales. 2. We conducted the first experimental test of the scale dependence of N effects on species richness from a 10-year N treatment (1.75–28 g N m � 2 year � 1 ) in a typical steppe. We used species–area relationship (SAR) to analyse the scale dependence of species loss with power model S = cA z (S is species number, A is area, c is intercept, and z is slope). 3. Absolute species loss decreased at sampling area > 8 m 2 . Proportional species loss (compared to control) decreased and critical threshold (Ncrit) for biodiversity losses increased with sampling areas. 4. These scale dependences were quantified as increasing slope (z-value) of SAR with N addition. Through SAR decomposition, we found that this overall positive effect was in response to positive effects of changes to the species abundance distribution over negative effects of overall species richness losses. 5. Synthesis. As nitrogen (N) enrichment typically occurs at scales much larger than individual plots, understanding how N enrichment affects the scaling patterns of biodiversity is necessary for biodiversity conservation and ecosystem management in response to anthropogenic N deposition.

Context Although many studies have demonstrated that grazing may increase or decrease plant diversity of grasslands at small scales, few studies have examined the patterns and mechanisms of grazing effects on biodiversity across multiple scales.

A novel carbon modified Fe–Mn–K catalyst for light olefin synthesis from CO hydrogenation was prepared by the sol–gel method. The effect of carbon contents on the structure and performance of the catalysts was investigated. With the incorporation of carbon, the catalysts showed much different morphology from that prepared by co-precipitation. At the carbon contents between 0.23 and 6.66 wt%, the catalyst particles were around 10 nm while the carbon phase was amorphous. The activity test results indicated that the catalysts (Fe/Mn/K molar ratio = 60/20/1) with carbon modification showed high conversion of CO and selectivity to light olefins with low CH4 selectivity. At the carbon content of 2.43 wt%, the total C2–C4 content in all hydrocarbons and O/P (olefin/paraffin) in the C2–C4 fraction was 49 wt% and 4.89, respectively. Furthermore, when the K content in the catalyst was reduced by half, the C2–C4 olefin yield raised from 60 to 71 g/Nm3 syngas. The formation of carbon provided a more hydrophobic surface, which inhibited the water gas shift reaction (WGSR) and caused a decrease in CO2 selectivity. The dispersion of carbon favored the formation and stabilization of small particles, and promoted the production of light olefins via suppressing the chain propagation.

The VO x –TiO 2 (VT) catalysts were prepared by the rapid combustion (RC) method and characterized by SEM, XRD, Raman, XPS, NH 3 -TPD and H 2 -TPR techniques. The catalytic performance was evaluated in the methanol oxidation reaction. The SEM result showed that the VT catalysts were consisted of nanoparticle with mean grain size about 30 nm. The RC process enhanced the formation of Ti (1− x ) V x O 2 . The XRD and Raman results revealed that the vanadia transformed from the isolated VO x to polymeric VO x and then as crystalline V 2 O 5 on the surface of V x Ti (1− x ) O 2 . The polymeric VO x was predominant when V 2 O 5 content was 30 wt.%. The H 2 -TPR and NH 3 -TPD results showed that the polymeric VO x exhibited more acidic sites and stronger reducibility than isolated VO x and crystalline V 2 O 5 . The catalytic activity result showed that the polymeric VO x was more active in methanol oxidation. The product distribution showed that the VT catalysts had redox-acidity bifunctional properties suitable for dimethoxymethane (DMM) synthesis, and the DMM selectivity was closely related to the reducibility and acidic sites.

Plant functional traits have been widely used to study the linkage between environmental drivers, trade-offs among different functions within a plant, and ecosystem structure and functioning. Here, the whole-plant traits, leaf morphological and physiological traits of two dominant species, Leymus chinensis (C3 perennial rhizome grass) and Cleistogenes squarrosa (C4 perennial bunchgrass), were studied in the Inner Mongolia grassland of China, with a grazing experiment including five stocking rates (0, 3.0, 4.5, 7.5, and 9.0 sheep/ha) in 2008 (wet year) and 2009 (dry year). Our results demonstrated that, for both species, the effects of stocking rate, year, and stocking rate × year on whole-plant traits and leaf morphological and physiological traits were highly significant in most cases. The differential responses of plant trait to variation in precipitation were caused by trait trade-offs between the wet and dry years. L. chinensis adopted the high N content and net photosynthetic rate (Pn) in the wet year but both the low N content and Pn in the dry year under grazed conditions. The trait trade-offs of C. squarrosa were characterized by high specific leaf area (SLA) and Pn in the dry year vs. low SLA and Pn in the wet year. Our findings also indicate that C. squarrosa is more resistant to grazing than L. chinensis in terms of avoidance and tolerance traits, particularly under heavy grazing pressure and in the dry year.

The VO x -TiO2 (VT-RC) and sulfated VO x -TiO2 (VTS-RC) catalysts were prepared by rapid combustion method (RC) and evaluated by the one-step oxidation of methanol to dimethoxymethane (DMM). The results showed that the VT-RC and VTS-RC catalysts were consisted of nano-particles and exhibited pore structure. Compared with the coprecipitated VO x -TiO2 (VT-CP) catalyst, the VT-RC catalyst showed more acidic sites and stronger reducibility. The addition of sulfate into VT catalyst further increased the number of acidic sites and had little effect on the reducibility. The catalytic test showed that the VT-RC catalyst exhibited high DMM selectivity (89.96% at 35% methanol conversion), which was further increased on VTS-RC catalyst (91.76% at 48% methanol conversion), and that was due to the larger number of acidic sites and stronger reducibility on these catalysts. Compared with the VT-CP catalyst, the VT-RC catalyst exhibited higher methanol conversion and DMM selectivity, which were further increased on VTS-RC catalyst.

The sulfated VOx–TiO2 catalysts were synthesized by rapid combustion method. The catalytic properties were evaluated by the one-step oxidation of methanol to dimethoxymethane. It was found that the sulfate was highly dispersed on the catalyst surface as the sulfate content below 4 mol%, and aggregated as it was above 4 mol%. The former contributed to the increased number of acidic sites, while the latter decreased the number of acidic sites. The highest DMM selectivity (91.76%) was obtained with the sulfate content at 4 mol%, which should be attributed to its largest number of acidic sites and stronger reducibility.

ZSM-5 zeolites were synthesized by adding Zn(NO 3 ) 2 aqueous solution into the gel precursor. The materials were characterized by XRD, ICP, nitrogen adsorption, FT–IR, SEM, 27 Al MAS NMR, NH 3 –TPD and Py–IR. After adding zinc salt into the gel precursor at synthesis, the products crystal size decreased obviously and the ratio of Lewis/Bronsted acid increased significantly. All the ZSM-5 samples synthesized in presence of zinc salt contained a small amount of zinc, the maximum was 0.026 wt%. Catalytic tests of alkylation of benzene with ethanol were investigated over these materials and the zinc containing catalysts showed higher ethylbenzene selectivity. The increased ethylbenzene selectivity was attributed to the change of acidity and crystal size.

Nickel and potassium co-modified β-Mo2C catalysts were prepared and used for CO hydrogenation reaction. The major products over β-Mo2C were C1–C4 hydrocarbons, only few alcohols were obtained. Addition of potassium resulted in remarkable selectivity shift from hydrocarbons to alcohols at the expense of CO conversion over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation with a higher C2+OH production. Modified by nickel, β-Mo2C showed a relatively high CO conversion, however, the products were similar to those of pure β-Mo2C. When co-modified by nickel and potassium, β-Mo2C exhibited high activity and selectivity towards mixed alcohols synthesis, and also the whole chain propagation to produce alcohols especially for the stage of C1OH to C2OH was remarkably enhanced. It was concluded that the Ni and K had, to some extent, synergistic effect on CO conversion.

Lanthanum oxides were real time modified to ZSM-5 during the hydrothermal synthesis of the zeolite. The addition of lanthanum oxides does not change the basic structure of ZSM-5, but obviously decrease the crystallinity and BrOnsted acid amount. The catalysis tests show that modification of ZSM-5 with lanthanum oxides significantly suppresses the coke formation on the catalyst surface and improves the catalyst stability, which is likely associated with the decrease of BrOnsted acid amounts and a promotional function of lanthanum oxides for the reaction between coke and water.

High performance iron-manganese catalysts dispersed with carbon to produce light olefins from CO hydrogenation were prepared by sol-gel method using citric acid as precursor. The effects of carbon content on the bulk structure, the water gas shift reaction, the chain propagation ability and the activity and selectivity of the catalysts were investigated. The results showed that the catalysts were gradually reduced during the decomposition of the precursor when calcined under pure N2. The formation of iron-manganese mixed crystallites was favored and stabilized because of the enhanced interaction of iron and manganese with increasing carbon content. During the subsequent CO hydrogenation reaction, all the catalysts showed high activity and olefin selectivity. With increasing carbon content, the water gas shift (WGS) reaction was restrained and the chain propagation ability was inhibited. Catalysts with higher carbon content showed much lighter hydrocarbon products; however, the selectivity of CH4 was almost unchanged.

A series of SBA-15 supported H3PMo12O40 catalysts were prepared for the one-step oxidation of methanol to dimethoxymethane (DMM). The evaluation and characterization revealed that higher DMM selectivity obtained on the incipient wetness impregnation (IM) catalyst was related to the instability of H3PMo12O40 on it. Raman spectra showed that 12-molybdophosphoric acid was more stable on the direct synthesis (DS) catalyst than on the IM catalyst and the existence of SBA-15 support enhanced the stability of H3PMo12O40. Moreover, higher H3PMo12O40 loading resulted in more acid sites and low DMM selectivity, furthermore the thermal pretreatment on H3PMo12O40 influenced its structure and thus affected DMM selectivity.

Fischer–Tropsch elements (Fe, Co and Ni) modified K/β-Mo2C catalysts were prepared and investigated for their performance in CO hydrogenation. The results revealed that Ni or Co modified K/β-Mo2C catalysts were shown to be highly active and selective towards the synthesis of mixed alcohols, especially for the C 2 + OH production, but Fe caused a negative effect. Ni or Co led to a decrease in apparent activation energies for C1–C4 alcohols, whereas Fe caused a slight increase for methanol and the decrease for C2–C4 alcohols. As a result, the promotion effects of Fischer–Tropsch elements were different and followed the sequence: Ni ≫ Co > Fe for the activity and Ni > Co > Fe for the C 2 + OH alcohol selectivity.

Nickel and potassium promoted β-Mo2C catalysts were prepared for CO hydrogenation to higher alcohols synthesis. The results revealed that β-Mo2C produced mainly hydrocarbons, but the addition of potassium resulted in a remarkable selectivity shift from hydrocarbons to alcohols over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation of β-Mo2C catalyst and led to a higher selectivity to C2+OH. The addition of nickel further enhanced higher alcohols synthesis, which showed the optimum at 1/8–1/6 of Ni/Mo molar ratios. The characterization suggested that there might be a synergistic effect of potassium and nickel on β-Mo2C, which favored the alcohols synthesis. The production of alcohols appeared to be relevant to the presence of Mo4+ species, whereas the formation of hydrocarbons was closely associated with Mo2+ and/or Mo0 species on the surface of β-Mo2C-based catalysts.

Potassium-promoted β-Mo 2 C catalysts were prepared and their performances in CO hydrogenation were investigated. The main products over β-Mo 2 C catalyst were C 1 –C 4 hydrocarbons, only ∼4 C-atom% alcohols were obtained. The products of hydrocarbons and alcohols obeyed traditional linear Anderson–Schultz–Flory (A–S–F) distribution. However, modification with K 2 CO 3 resulted in a remarkable selectivity shift from hydrocarbons to alcohols. Moreover, it was found that potassium promoter enhanced the ability of chain propagation of β-Mo 2 C catalysts and resulted in a higher selectivity to C 2+ OH. For K/β-Mo 2 C catalysts, the hydrocarbon products also obeyed traditional linear A–S–F plots, whereas alcohols gave a unique linear A–S–F distribution with remarkable deviation of methanol compared with that on β-Mo 2 C catalyst. It could be concluded that potassium promoter might exert a prominent function on the whole chain propagation to produce alcohols. A surface phase on the K/β-Mo 2 C catalysts such as the “K–Mo–C” explained the higher value for C 2+ OH, especially could promote the step of C 1 OH to C 2 OH, or could have a role in producing directly C 2 OH, but again this would be speculative. At the same time, the influence of the loadings of K 2 CO 3 on the performances of β-Mo 2 C catalyst was investigated and the results revealed that the maximum yield of alcohol was obtained at K/Mo molar ratio of 0.2.

Potassium and nickel doped β-Mo 2 C catalysts were prepared and their performances of CO hydrogenation were investigated. The main products over β-Mo 2 C catalyst were hydrocarbons, and only few alcohols were obtained. The potassium promoter resulted in remarkable selectivity shift from hydrocarbons to alcohols over β-Mo 2 C. Moreover, it was found that the potassium promoter enhanced the ability of chain propagation of β-Mo 2 C catalyst and resulted in a higher selectivity to C 2+ OH. When doped by potassium and nickel, β-Mo 2 C catalyst showed high activity and selectivity for mixed alcohols synthesis, the Ni promoter further enhanced the whole chain propagation to produce alcohols especially for the step of C 1 OH–C 2 OH. From the XPS analysis, it had been proved that the formation of higher alcohols might be attributable to the presence of Mo IV species, whereas the formation of hydrocarbons was closely associated with the presence of Mo II species on the surface of the catalysts.

K/Co/β-Mo 2 C catalysts were prepared and tested for higher alcohols (C 2+ OH) synthesis (HAS). The catalysts exhibited high catalytic activity and selectivity to C 2+ OH. The effect of Co/Mo molar ratio in the catalysts upon the catalytic performance of HAS was investigated and the best one was at Co/Mo molar ratio of 1/8–1/6. It could be concluded that the Co promoter exerted strong promotion for carbon chain growth, especially for the stage of C 1 OH to C 2 OH. The XPS spectra revealed that there was a strong synergistic interaction between Co and Mo, and it depended strongly on the Co/Mo molar ratio. The new phases “Co 3 Mo 3 C” and “Co 2 C” formed over Co promoted K/β-Mo 2 C catalysts, which might be responsible for the high activity of higher alcohols and hydrocarbons synthesis, respectively.

Abundant evidence has shown that grazing alters plant functional traits, community structure and ecosystem functioning of grasslands. Few studies, however, have tested how plant responses to grazing are mediated by resource availability and plant functional group identity. We examined the effects of grazing on functional traits across a broad range of species along a soil moisture gradient in Inner Mongolia grassland. Our results showed that trait syndromes of plant size (individual biomass) and shoot growth (leaf N content and leaf density) distinguished plant species responses to grazing. The effects of grazing on functional traits were mediated by soil moisture and dependent on functional group identity. For most species, grazing decreased plant height but increased leaf N and specific leaf area (SLA) along the moisture gradient. Grazing enhanced the community-weighted attributes (leaf NCWM and SLACWM), which were triggered mainly by the positive trait responses of annuals and biennials and perennial grasses and increased relative abundance of perennial forbs. Our results suggest that grazing-induced species turnover and increased intraspecific trait variability are two drivers for the observed changes in community weighted attributes. The dominant perennial bunchgrasses exhibited mixed tolerance–resistance strategies to grazing and mixed acquisitive–conservative strategies in resource utilization.

Molybdenum carbides, β-Mo 2 C and α-MoC 1− X , promoted by K 2 CO 3 were studied as catalysts for CO hydrogenation reactions at T = 573 K, P = 8.0 MPa, GHSV = 2000 h −1 , H 2 /CO = 1.0. Unpromoted molybdenum carbides produced mainly light hydrocarbons under these conditions. Addition of K 2 CO 3 as a promoter, however, both β-Mo 2 C and α-MoC 1− X resulted in remarkable selectivity shift from hydrocarbons to alcohols. Moreover, the promoter of potassium enhanced the ability of chain propagation of β-Mo 2 C and α-MoC 1− X with higher selectivity to C 2+ OH. Meanwhile, the investigation of the loadings of K 2 CO 3 in β-Mo 2 C and α-MoC 1− X revealed that the maximum of yield of alcohol was obtained at K/Mo (molar ratio) of 0.2 and 0.1, respectively. On K/β-Mo 2 C catalysts, the distribution of hydrocarbons obeyed traditional linear A–S–F plot, while alcohols gave a unique linear A–S–F distribution with remarkable deviation of methanol compared with that of on β-Mo 2 C catalyst. However, there was no significant difference between α-MoC 1− X and K/α-MoC 1− X catalysts about the distributions of alcohols and hydrocarbons; they both have similar linear A–S–F plots. Thus, the potassium promoter played a different role over β-Mo 2 C and α-MoC 1− X catalysts upon the catalytic performance of mixed alcohols synthesis.

As an effective promoter for K/MoS2 catalyst, the addition of nickel would result in a higher selectivity of hydrocarbons due to the presence of separated NiSx phase. In the present paper, a highly homogeneous and dispersed US-Ni/K/MoS2 catalyst was prepared by ultrasonic technology under non-water environment. Compared with conversional Ni/K/MoS2 catalyst prepared by co-precipitation method, US-Ni/K/MoS2 catalyst showed higher productivity of alcohols with the lower selectivity of hydrocarbons. The inhibition of methanation of Ni promoter should be ascribed to the high homogeneity of US-Ni/K/MoS2 catalyst, in which the formation of separated nickel sulfides was impressed remarkably. 2005 Elsevier B.V. All rights reserved.

The structure and catalytic performance of CuMnZrO2 and Fe-CuMnZrO2 catalysts, which were calcined at different temperature, were investigated by BET, XRD, N2O-titration, XANES, EXAFS and TPR. It was found that the calcination temperature strongly influenced the interaction between the active species and support and hence the structure and catalytic performance. Low calcination temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)(2)-like structure. The presence of iron could suppress crystallization of amorphous zirconia and increased the dispersion of copper due to the iron-zirconia interaction within the rise of calcination temperature from 623 to 873 K. However, the addition of iron resulted in the decrease of catalytic activity and selectivity. This could be explained by strong iron-zirconia interaction. It led to the decrease of copper-zirconia interaction, which was responsible for the methanol synthesis, and the decrease of copper-iron interaction, which was responsible for the formation of higher alcohols. (c) 2005 Elsevier B.V. All rights reserved.

Cu/ZrO2 catalysts with amorphous, monoclinic and tetragonal zirconia as supports were prepared and characterized by XRD, H2-TPR, N2O-titration, FT-IR and CO hydrogenation techniques. It was found that zirconia polymorphs had a great influence on the interaction of Cu and ZrO2. Though it had the lowest surface area, tetragonal zirconia supported copper catalyst showed the highest copper dispersion and the best catalytic performance for methanol synthesis from CO hydrogenation. The formate and methoxyl species were evidenced as intermediates by FT-IR in the case of CO hydrogenation, and the formate-to-methoxyl mechanism was suggested for methanol synthesis on Cu/ZrO2 catalyst.

In the present paper alkali-doped molybdenum sulfide (ADM) catalysts modified by Ni were prepared and Ni promoter showed an effective promotion on the activity and C2+OH selectivity. At Ni:Mo molar ratio of 0.5, the percentage of methanol decreased sharply from 53(C-atom) to 11(C-atom) and the ratio of C2+OH/C1OH reached the maximum (8.75), which was about 10 times compared with that of traditional ADM catalyst (0.87). Calculation revealed that the additions of Ni caused the apparent activation energies for C1–3 alcohols decreased, especially for ethanol. The great deviation of methanol from the linear A-S-F distribution indicated a different reaction route which might caused by the bi-functionality of nickel, namely, the formation of corresponding precursor of alcohol (CH x ) and the strong ability of CO insertion. Characterization suggested that such a promotion was closely related to the structure of nickel of the catalyst, the simultaneous presences of aggregated particles and high-dispersed Ni.

FT-IR spectroscopy and TPD profiles were performed to determine and compare the surface properties of amorphous, monoclinic and tetragonal zirconia polymorphs. It was found that zirconia polymorphs exhibited different surface hydroxyl and acid–base properties. These differences had great influence on the behavior of CO adsorption and reaction. Formate species could be formed at higher temperature via CO reaction with hydroxyl groups on the surface of amorphous and monoclinic zirconia, while bicarbonate and carbonate species were detected on tetragonal zirconia, whether hydrogen introduced or not.

The effect of iron on the structural and catalytic properties of CuMnZrO2 catalysts used for higher alcohols synthesis has been investigated by several techniques (BET, X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), temperature program reduction (TPR), CO-FTIR and CO hydrogenation). It was found that the presence of iron resulted in substantial changes in both structure properties and catalytic performance. The copper dispersion increased and the catalyst stabilization was improved. The role of iron was dependent on the method of catalyst preparation. The co-precipitation method produced highly dispersed copper species, which favored the synthesis of methanol and branched alcohols. However, the wetness impregnation method gave rise to highly dispersed copper and copper-iron phase, which showed a good performance for synthesis of straight-chain alcohols. Such differences in the performance of catalysts could be attributed to the extent of iron oxide-support interaction, which led to the presence of metallic iron phases in the reduced catalyst. (C) 2004 Elsevier B.V. All rights reserved.