Reactant Composition Research Articles

Recent Advances and Current Developments of Molten Pool Temperature Measurement for Laser Additive Manufacturing Processes

Background: Molten pool temperature in Laser Additive Manufacturing (LAM) will affect powder efficiency, structural compositions of reactants and products in the molten pool, thus determining the microstructure evolutions and mechanical properties of the final part. An interest in molten pool temperature measurement has been around for a long time since the appearance of LAM. However, a comprehensive summary of the existing methods and their applications does not exist in the literature. Objective: The state-of-the-art of the existed devices and methods for molten pool temperature measurement in various of LAM processes is reviewed in this paper. Methods: The existing temperature measurement methods for molten pool monitoring in LAM processes are discussed. For each method, the existed patents, detailed procedures, advantages and disadvantages, specific applications are specified. In the end, comparisons among the current temperature measurement techniques are made according to data accuracy, operation complexity and cost of implementation. Results: Four methods are currently being used for the molten pool temperature measurement in LAM processes, including (i) Thermocouples, (ii) Infrared pyrometers, (iii) Infrared cameras, and (iv) Charge-coupled-device cameras. Conclusion: Different measurement methods represent different characteristics of the signal, and each has merits and defects. Selecting suitable measurement method according to different process characteristics will be helpful to achieve a preferable and more convincing results.

A consecutive methanation scheme for conversion of CO2 – A study on Ni3Fe catalyst in a short-contact time micro packed bed reactor

In this work, the kinetics of CO2 methanation reaction is investigated on a 17 wt% Ni3Fe/ɣ-Al2O3 catalyst under technical operation conditions of Power-to-Gas processes. A short-contact time microstructured packed bed reactor with internal cross-flow cooling channel was designed particularly for kinetic studies of the highly exothermic methanation reaction. The influence of temperature, pressure, reactant and product composition as well as residence time on the product composition and conversion of the reactants was carefully studied. In total more than 160 data points were collected and fitted to three literature models applying a non-isothermal reactor model. Based on the state-of-the-art kinetic models and the experimental observations, a new LHHW rate equation for the consecutive CO2 methanation reaction was developed. This new model has reasonably lower number of parameters and improves description of the reaction compared to literature models with regard to the Ni3Fe catalyst system. Special attention was paid to the selectivity behavior and the influence of carbon monoxide and water on the reaction.

Evolution of Reaction‐Induced Phase Segregations in Bi‐Soft Segment Urethane Oligomers

AbstractOligomeric bi‐soft segment isocyanate‐terminated polyurethanes (ITPUs) are semi‐finished goods crucial for the fabrication of various polyurethane (PU) products such as foams, thermoplastics, adhesives, dispersions, and elastomers. Incompatibilities and thus phase segregation phenomena play an essential role in tailoring the properties of the final products. In this work, the evolution of reaction‐induced phase segregation (RIPS) in ITPUs is explored in terms of composition and morphology of the phase segregated products as well as competing second order kinetics of the reaction. The results suggest that mechanism and extent of the phase segregation are thermodynamically controlled following the ternary phase diagram of the reactants. A comprehensive description of the phase behavior during the reaction is provided demonstrating excellent control over the morphology of ITPUs by means of appropriate adjustment of the initial reactant composition. These results are fundamental for tailored morphology design as it is employed for instance in membrane synthesis.

Dry reforming of CH4 over stabilized Ni-La@KCC-1 catalyst: Effects of La promoter and optimization studies using RSM

A bimetallic Ni-La catalyst supported on fibrous silica KCC-1 (KAUST Catalysis Centre 1) was prepared by in situ one-pot hydrothermal method. The catalyst was characterized by XRD, BET, FESEM-EDX, TEM, H2-TPR, FTIR-pyrrole, O2-TPO and XPS. The H2-TPR result revealed that the addition of La2O3 enhanced the reducibility of Ni2+, as observed by the 25.1 % increase in H2 consumption. This is an evidence of improved dispersion as also indicated in the TEM images. Extra affinity for CO2 chemisorption and activation was provided by the La promoted catalyst with strong and intense basic sites to improve product selectivity. Therefore, the activity of catalyst was improved with significant enhancement in CO2 conversion and H2/CO selectivity. As a result, the activation energy for CO2 and CH4 conversions were reduced by a margin of 10.4 kJ/mol and 2.2 kJ/mol respectively. Ni-La@KCC-1 catalyst showed no sign of deactivation throughout the 22 h time on stream while Ni@KCC-1 deactivated after 15 h at a higher reactant feed composition. From ANOVA analysis, the reaction temperature is the most significant variable that influence CH4 conversion. The reaction operating condition was obtained that gives the optimum CH4 conversion. The model predicted response was 98.2 % fitted to the observed experimental values.

Experimental Study on Dry Reforming of Biogas for Syngas Production over Ni-Based Catalysts.

Syngas production from dry reforming of biogas (DRB) is studied experimentally in this work. Ni/Al2O3, Pt/Al2O3, and Pt-Ni/Al2O3 are used as catalysts to examine the effect of CO2 content in biogas and H2O addition on DRB performance for reaction temperatures in the 600–800 °C range. It is found that the bimetallic Pt–Ni catalyst exhibits the best activity and thermal stability among the three types of catalysts studied due to better carbon deposition resistance. Because CO2 functions as the oxidant in combustion, CH4 conversion is enhanced when the biogas contains more CO2. One hundred percent CO2 conversion can be reached for biogas containing a less amount of CO2 at high temperatures. With H2O addition in DRB, the steam reforming of methane (SRM) reaction is the dominant reaction, resulting in higher H2 and CO yields with biogas containing lesser amounts of CO2. However, lower CH4 conversion and negative CO2 conversion do result. With higher CO2 content in the biogas, higher CH4 and CO2 conversions can be obtained. Lower yields of H2 and CO are obtained due to less SRM dominance. With H2O addition in biogas, the H2/CO ratio with a value greater than 1 can be obtained from DRB. It is also found that the H2/CO ratio with a value of 2.1 can be obtained for reactant composition with a molar ratio of CH4/CO2/H2O = 1:0.25:1 and reaction temperature of 800 °C.

Effect of LiPO2F2 Electrolyte Additive on Surface Electrical Properties of LiNi0.6Co0.2Mn0.2O2 Cathode

The electrolyte additive of LiPO2F2 was injected into 18,650 Li ion battery cells composed of LiNi0.6Co0.2Mn0.2O2/graphite at 25 °C to avoid the formation of the undesirable solid electrolyte interface (SEI) layer. The potential distribution on the cathode surface was studied using electric force microscopy. The average potential distribution on the surface of the cathode in the cell where the additive LiPO2F2 was injected showed ~ 100 mV higher potential than the average potential on the surface of the cathode in the cell without the additive. X-ray photoemission spectroscopy results showed that the average potential distribution characteristics were correlated with the chemical composition of the surface reactants. These results indicate that the LiPO2F2 additive controls the formation of the SEI layer on the surface of the LiNi0.6Co0.2Mn0.2O2 cathode during the electrochemical reaction in the cell and has the decisive effect of inhibiting the decomposition of LiPF6, which is the main component of the electrolyte solution. In this study, the addition of the LiPO2F2 additive to the electrolyte improves the electrochemical performance of the Li ion battery by improving the surface potential of the cathode surface and controlling the formation of the SEI layer on the surface of the LiNi0.6Co0.2Mn0.2O2 cathode.

Single-Component Solid Electrolyte Interphases on Lithium

The ability to utilize Li metal anodes in rechargeable batteries would be an enabling breakthrough in the quest to increase energy density and meet current aggressive performance targets (> 350 Wh/kg) for electric vehicles. However, Li anodes face several persistent challenges:1 ,2 (1) Large volume expansion upon cycling, leading to rapid mechanical degradation; (2) Poor Coulombic efficiencies during cycling, which leads to loss of active Li and formation of so-called “dead Li”; and (3) Evolution of dendritic structures upon Li deposition, which grow rapidly and ultimately short-circuit the cell. The origins of these problems can be traced back to the chemical, ionic, and mechanical properties of the solid electrolyte interphase (SEI)3- consisting of ionically conductive, physically blocking solid inorganic and organic phases derived from the reaction of Li with the electrolyte - and the electrochemical processes that break down this layer. After decades of study, however, the native SEI, which is highly chemically nonuniform and nanoscopically thin (< 100 nm), remains notoriously difficult to experimentally probe. Consequently, there remains a need for improved understanding of which Li-derived phases are desirable or undesirable in the SEI, their precise roles, and how to manipulate or modify the SEI properties for improved function and stability. In this talk, we present our recent studies of single-component artificial interfaces on Li, which we have conducted to gain deeper insights into the possible roles of common interfacial constituents found in nearly all Li SEI.4,5We have developed synthetic approaches based on gas-phase reactions with oxide- and fluoride-donating reactants that permit introduction of single phases with high spatial uniformity. We first show results of controllable growth (10 – 100’s of nm thickness) of targeted ionic materials Li2O and LiF, which is achieved through judicious selection of the reactant gas composition and reaction conditions. The formed layers are conformal, compact, polycrystalline, and chemically stabile in carbonate electrolytes, and thus serve as model all-ionic interphases useful for further qualitative and quantitative study. Following the establishment of these “ionically enriched” Li anodes, we subject these interphases to electrochemical measurements including electrochemical impedance, galvanostatic cycling (relevant to practical battery operating conditions), as well as softer electrochemical techniques such as chronoamperometry, which allow the minimal overpotentials and current densities driving deposition through the layers to be determined. We find evidence that there exist maximum sustainable overpotentials and current densities in the all-ionic layers, above which degradation mechanisms are activated within the films, leading to breakage. Using defect and transport modeling applied to the electrochemical results, we are able to quantify transport parameters including Li+vacancy carrier concentrations and diffusion coefficients, and compare these to the bulk materials. Our results show that interfacially-formed Li2O and LiF have unique properties when they are formed on Li metal. Current understanding of SEI behavior, which is largely based on knowledge of bulk properties of Li2O and LiF formed under drastically different thermochemical conditions, should be updated to reflect the unique structural, chemical and electrochemical properties occurring at interphases derived directly from Li. Tikekar, M. D.; Choudhury, S.; Tu, Z. Y.; Archer, L. A., Nat Energy 2016, 1, 1-7. Lin, D.; Liu, Y.; Cui, Y. Nat. Nanotechnol. 2017, 12, 194–206. Peled, E. J. Electrochem. Soc. 1979,126(12), 2047. Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H. Solid State Ionics 2002, 148(3–4), 405–416. Wang, C.; Meng, Y. S.; Xu, K. J. Electrochem. Soc. 2019, 166(3), A5184–A5186.

Solventless ketalization of glycerol to solketal with acetone over the ionic liquid [P(C4H9)3C14H29][TsO

Abstract The ketalization of glycerol with acetone was conducted over an ionic liquid [P(C4H9)3C14H29][TsO] (TTPT) in a batch reactor. A scheme to obtain the purified product using TTPT as a homogeneous catalyst is proposed and a maximum solketal yield of 86% is achieved at acetone/glycerol molar ratio of 6/1, reaction time of 0.5 h, reaction temperature of 303 K, catalyst amount of 5 wt% of glycerol. TTPT was recycled and reused for ten times without obvious losses in terms of quantity and activity. Furthermore, effects of various experimental parameters (stirring speed, catalyst loadings, temperature and reactant composition) on the reaction kinetics are investigated. In terms of kinetics modeling, Kγ is fitted by reactant composition at the temperature range 298 K–323 K, which was a concise strategy that showed good precision in the kinetics fitting. The activation energy for this ketalization reaction was evaluated to be 28.2 kJ·mol−1. In addition, the kinetics of the reaction at a temperature exceeding the boiling point of acetone were also studied. We believe that all the results are important for further development of a technology for the continuous synthesis of solketal.

NiAl–TiC–Al2O3 composite formed by self-propagation high-temperature synthesis process: Combustion behaviour, microstructure, and properties

Intermetallic-ceramic composites formed by the self-propagation high-temperature synthesis (SHS) process have attracted much interest in research development since they offer low-cost production and mechanical properties that have characteristically high performance. The objective of this work was to study the effect of reactant compositions on the combustion behaviour, microstructure and mechanical properties of the synthesized product of NiAl–TiC–Al2O3 composite. The reaction mechanism of the synthesized products was discussed based on the observations of the combustion reaction and the microstructure characterization. The results provided information on the relationship between the reactant composition, microstructure and the properties of the products of NiAl–TiC–Al2O3 composites formed by the SHS process.

Performance evaluation of SOEC for CO2/H2O co-electrolysis: Considering the effect of cathode thickness

Solid oxide electrolysis cells (SOECs) provide a great opportunity to stabilize carbon dioxide (CO2) emissions by converting CO2/H2O into synthetic fuels with high energy conversion efficiency. Nevertheless, the performance of state-of-the-art Ni-cermet supported SOEC is limited by the interfacial polarization resistance. This study presents a simple approach to minimize the cathodic polarization resistances by reducing its thickness. The effect of cathode thickness on the electrochemical performance of SOECs for CO2/H2O co-electrolysis are investigated at 750–850 °C for variable reactant gas composition. Electrochemical measurements like current density-voltage (i-V) curves and electrochemical impedance spectroscopy (EIS) are performed to characterize the performances of the cells. Impedance spectra are recorded under open circuit voltage (OCV) and polarization (1.4 V) to deeply study the influence of cathode thickness on polarization loss processes. The EIS results confirm that when reducing the cathode thickness, the cathode activation polarization is slightly decreased, whereas, the concentration polarization is significantly reduced, improving the reactant gas diffusion and the performance of SOEC. A similar effect is observed by increasing the CO2 mole fraction in the feed. Furthermore, the variation of cathode thickness and gas composition greatly affected the cell performance at high temperature, due to large reactants utilization. The results reveal that SOEC performance for co-electrolysis of CO2/H2O could considerably be improved by reducing the cathode thickness and improving the transport processes within the fuel-electrode. These results aid the optimization of cell design to improve the gaseous transport to the electrode/electrolyte interface and enhance the performance of SOEC for CO2/H2O reduction.

Tuning 1-hexene/n-hexane adsorption on MOF-74 via constructing Co-Mg bimetallic frameworks

A series of bimetallic CoxMg1-x-MOF-74 (x = 0, 0.12, 0.30, 0.57, 0.78, 1) structures were synthesized by using facile solvothermal systems having different binary metal compositions. All MOF samples were characterized carefully. Both adsorption affinity to n-hexane and 1-hexene and adsorption selectivity of 1-hexene over n-hexane were evaluated by static adsorption test coupled with computer simulation. It is indicated that the CoMg bimetallic MOF-74 frameworks can be successfully constructed via using well-designed reactant compositions. All bimetallic MOF-74 retain almost the same crystalline structure but higher porosity as compared to their monometallic samples. In addition, both of the adsorption capacity and selectivity of CoMg bimetallic MOF-74 samples are found strongly dependent on their metal compositions. Specifically, Co0.30Mg0.70-MOF-74 exhibits the largest 1-hexene adsorption capacity of 152.7 mg/g and the highest 1-hexene/n-hexane selectivity of 9.74, which are 2.1–2.3 and 4.1–8.9 times higher than those of monometallic Co or Mg-MOF-74 samples. Such improvement on adsorption ability and selectivity for olefin molecules can be attributed to the incorporation of more stable coordinatively unsaturated sites (CUS) within Mg-MOF-74 framework, leading to the synergetic effect of pore structure evolution as well as higher density of CUS metal sites in bimetallic frameworks. The tunable adsorption affinity to olefin/paraffin on MOF-74 by means of metal modification provides an approach to the efficient separation of olefins and paraffins from liquid hydrocarbon mixtures.

Formation of 3-deoxyglucosone in the malting process

3-Deoxyglucosone (3-DG) is a metabolite from sugar degradation obtained by the Maillard reaction. It is an important precursor compound in Strecker reactionism that directly leads to known beer aging indicators and can influence the final sensory beer quality. However, the conditions of 3-DG formation in the malting process have not yet been described.To investigate the reaction pathways of 3-DG formation, we varied the composition of reactants (sugars, amino acids) by using different malting modification levels (germination time 5–7 d; steeping degree 42–45%; germination temperature 12–14 °C); final kilning temperature (60 °C to 100 °C).After its derivatization with ortho-phenylenediamine, we analyzed 3-DG with HPLC-UV. 3-DG concentration was between 5 and 120 µmol/100 g dry weight. The formation of 3-DG increased for high malt modification levels and high final kilning temperature.The abundant formation of 3-DG in the malting process is already comparable to the occurred brewing process concentration.

Synthesis of non-porous and nanocrystalline lanthana-doped zirconia layers by MOCVD method at low temperatures and pressure

Amorphous and nanocrystalline lathana-doped zirconia layers were synthesized by the MOCVD method using La(tmhd)3 and Zr(tmhd)4 as reactants on planar and tubular quartz glass substrates. The synthesis temperature was in the range of 500–700 °C. The gas pressure in the CVD reactor was modified between 3 × 103 and 6 × 103 Pa. Argon and air were used as carrier gases. Air was also necessary for oxidation of carbon, which is a solid by-product of reactant pyrolysis. Other synthesis parameters were selected in order to obtain a value of the extended criterion Grx/Rex2 below 0.01. Then, laminar gas flow in the CVD reactor will be maintained. The surface, as well as the cross-section of deposited layers were observed using a scanning electron microscope (SEM). Their chemical composition was investigated by means of EDS analysis. XRD investigations on obtained layers were also performed. There was correlation between the chemical composition of reactants and obtained layers when the synthesis process was controlled by reactant diffusion to the substrate. The phenomenon of La3+ ion segregation in obtained layers was also observed. The layers exhibited good adhesion to the substrate.

Nanostructured ceramic composite rods: Synthesis, properties and application

The nanostructured ceramic composites based on TiCTiB2 have attracted a great interest during recent years because they exhibit superior properties combining high hardness and good wear resistance. Here we demonstrate the possibility of producing TiCTiB2ZrO2Al2O3 based ceramic composites via self-propagating high-temperature synthesis by extrusion method (SHS-extrusion). The effect of reactant composition on the microstructure of obtained composites was studied. According to X-ray diffraction (XRD) the synthesized ceramic composites consist of TiC, TiB2, ZrO2 (monoclinic and tetragonal), and Al2O3 phases. ZrO2 and Al2O3 phases form eutectic consisting of extended filaments up to 100 nm in thickness and 2–3 μm in length. TiC and TiB2 grains with sizes of 1–2 μm surround the filaments. The composite materials were used as electrodes for electric-spark deposition. The deposited coatings have high wear resistance (1 × 10−5 mm3/N/m) and low friction coefficient (0.2).

Mass Balance Simulation for Steam Reformer in Direct Reduction of Iron Ore by Hyl III Process.

HYL direct reduction of iron ore process uses a reducing gas composed of a mixture of H2 and CO in order to reduce iron oxide pellets to metallic iron (DRI). This process is mainly dependent on a reformer to supply the reducing gas. In the reformer, natural gas is catalytically converted into reducing gas by reaction with steam at a temperature of 800 to 850°C and pressure between 8 and 8.5 bars in the presence of Nickel based catalyst. In order to analyze the reformer operation, it is necessary to estimate the reformed gas composition for some specific process conditions.The present work is based on the solution of a set of non-linear equations describing mass balances of carbon, hydrogen, oxygen and higher hydrocarbons, to enable the calculation of reformed gas composition for a steam reformer. The procedure can assist both process engineers tackling the problem of estimating output from a primary reformer at the design stage and plant operating engineers. The mass balance equations are solved by using the equilibrium constants for the reforming and water gas shift reactions. This includes simultaneously solving non-linear equations relating to the composition of reactants and other variables as temperature and pressure at which reactions take place. In addition, amount of carbon contained in natural gas compared to amount of steam used in steam reforming reaction is also considered during calculations. The basic requirements to establish the model are a set of reactions and values of equilibrium constants for the reforming and water gas shift reactions.

Modeling mafic carbonation efficiency using mafic rock chemistries from Nevada, USA

Mineral carbonation is one of the many ways that are being actively investigated to sequester point-source carbon dioxide emissions. However, relations between reaction conditions, variations in reactant mineral composition, and carbon sequestration potential are poorly understood. In this study we used reaction path geochemical modeling to evaluate carbon sequestration potential during ex-situ mineral carbonation of ten mafic rock samples from Nevada, USA. Models were run using arbitrary dissolution kinetics at temperatures between 0 and 200 °C. A subset of models were run using true dissolution kinetics. In the models, carbon is sequestered in 5 mineral phases: magnesite, siderite, dolomite, calcite, and dawsonite, with magnesite and dolomite the most abundant. Dawsonite sequesters carbon at T > 150 °C in most of the arbitrary kinetics models but is not a significant carbon sink in the models using true dissolution kinetics. The arbitrary kinetics models resulted in 4.5–13 mol of carbon sequestered per kg of reacted mafic rock. True kinetics models only resulted in 1–2 mol of carbon sequestered, but the models only reacted 12.5 to 15 wt percent of the mafic rock inputs. Product minerals using the arbitrary kinetics model have volumes 150%–470% larger than the reactant volumes, whereas using true kinetics the models have a modest increase. Modeling presented herein confirms several areas of Nevada as having potential for mafic rock carbonation, some of which are located near existing coal- and natural gas-fired power plants. As shown in this study, reaction path modeling is a vital and inexpensive tool to help optimize costs and reaction conditions for ex-situ mafic rock carbonation projects.

Structure-reactivity study of model and Biodiesel soot in model DPF regeneration conditions

The aim of the present work is to investigate and compare the non-catalytic and catalytic reactivities of real and model soot samples through temperature-programmed oxidation (TPO). Such reactivity was furthermore correlated with soot structural properties, determined by laser granulometry, XRD, Raman and HRTEM. Biodiesel soot samples were obtained through the combustion of different fuels in a real engine, whereas model soot samples were produced in a laminar burner. TPO evidenced that the soot generated with 100% Biodiesel (methyl ester) was more reactive than real soot generated with 7% Biodiesel (7% methyl ester). The model soot from the diesel surrogate (Aref) containing 7% oxygenate additive (C11H22O2) exhibited higher reactivity than the model soot containing 30% additive, whereas a carbon black (Degussa Printex U) showed the poorest reactivity of this series. The presence of NO2 promoted the non-catalytic oxidation of real soot. In the presence of the MnOx-CeO2 catalyst, soot reactivity depended both on reactant gas composition and on soot-catalyst contact.

Ultrafast post-synthesis treatment to prepare ZSM-5@Silicalite-1 as a core-shell structured zeolite catalyst

Abstract Post-synthesis treatment is an effective way to modify zeolites to acquire desirable properties. Here, we present an ultrafast post-synthesis treatment to prepare core-shell structured zeolite, which is composed of a ZSM-5 core and a silicalite-1 shell. The pure silica shell, which is aimed to remove the Bronsted acid sites associated with the framework Al on the external surface of aluminosilicate core, was formed unprecedentedly within several minutes by our method. Complementary techniques, such as XRD, TG/DTA, SEM, TEM, ICP, and XPS, were employed to verify the successful coverage of the silicalite-1 shell onto the ZSM-5 core. By adjusting the treating period, temperature, and reactant compositions, the thickness of the shell can be easily tuned. Further, this ultrafast process enabled the establishment of a continuous flow reaction system, which could allow the mass production of core-shell structured zeolite catalysts.

Tracing olivine carbonation and serpentinization in CO2-rich fluids via magnesium exchange and isotopic fractionation

Chemical exchange between seawater and the oceanic crust is thought to play a significant role in the regulation of the global magnesium (Mg) cycle, yet relatively little is known about the rates and mechanisms of Mg exchange in these crustal environments. In this study we experimentally characterize the extent, and nature, of Mg isotope fractionation during the carbonation and serpentinization of olivine (one of the principal minerals found in ultramafic rocks) under hydrothermal conditions. Olivine alteration was found to be incongruent, with the reactant fluid composition varying according to the extent of olivine dissolution and the precipitation of secondary minerals. In mildly acid water (pH ∼ 6.5), olivine dissolved to form Mg-Fe carbonate solid solutions and minor chrysotile. Upon carbonation and a decrease of CO2 in the water, the pH increased to >8, with chrysotile and brucite becoming the dominant alteration minerals. The Mg-rich carbonates preferentially incorporated lighter Mg isotopes, resulting in a ∼0.5‰ increase of the δ26Mg composition of the fluid relative to olivine during the initial carbonation and serpentinization reactions. This was followed by a decrease in δ26Mg under higher pH conditions associated with the formation of brucite. Our experimental and modeling results therefore demonstrate that the δ26Mg composition of fluids involved in olivine alteration reflect the type and quantity of secondary Mg minerals formed, which in turn depend on the pH and CO2 concentration of the water. Comparison of these results with natural groundwaters and geothermal waters from basaltic terrains indicate that the δ26Mg composition of natural waters are likely to also be controlled by mafic rock dissolution and the preferential incorporation of isotopically light Mg into carbonates and isotopically heavy Mg into Mg-Si minerals. Together, these findings improve our understanding of Mg isotope systematics during water-rock interaction, and suggest that δ26Mg may be a useful tool for tracing reactions that are critical to geological CO2 sequestration.

Rational Design of High Surface Area Mesoporous Ni/CeO2 for Partial Oxidation of Propane

A Ni loaded catalyst on mesoporous ceria, with a large surface area, prepared through the surfactant-assisted precipitation and impregnation method was investigated as an efficient catalyst for propane partial oxidation to produce synthesis gas. The results show that 2.5 wt% Ni/CeO2 had the optimum Ni loading, exhibiting the highest catalytic propane conversion. It also showed excellent stability, with no obvious activity drop after a 10 h time-on-stream reaction and slightly decreased in H2 and CO yields. The investigation of the reactant composition effect on carbon formation showed that by decreasing the C/O2 ratio the content of accumulated carbon decreased and propane conversion increased. The good activity of the Ni/CeO2 can be ascribed to the high surface area and rich surface defects of the ceria support and a high dispersion of active sites (Ni nanoparticles).