CO2 hydrogenation can lead to the formation of various products, of which methanol, dimethyl ether (DME) and ethanol have received great attention. In this study, a comprehensive thermodynamic ...analysis of CO2 hydrogenation in binary (methanol/CO) and ternary product systems (methanol/CO with DME or ethanol) is conducted in Aspen Plus by the Gibbs free energy minimization method combined with phase equilibrium calculations. It is demonstrated that product condensation can be utilized to circumvent thermodynamic restrictions on product yield. Significant improvements in CO2 conversion can be achieved by operating at conditions favorable for product condensation, whereas the selectivity is mildly affected. The relevance of the results herein is discussed with regards to recent advances in catalysis and process design for CO2 hydrogenation. Our study highlights the importance of obtaining a thorough understanding of the thermodynamics of CO2 hydrogenation processes, which will be critical for developing potential breakthrough technology applicable at the industrial scale.
The Konggar massif, about 120km long and 13–18km wide, developed along the eastern segment of the Xianshuihe fault zone in East Tibet. It consists of two rock units: the Konggar granitic pluton and ...an elongate migmatite zone about 70km long and 1–3km wide. A metamorphic event was well recorded by the growth rims of zircons in the migmatite, their SHRIMP U–Pb dating of two rock samples taken from leucosome and melanosome yields respectively the ages of ca. 31.75Ma and ca. 26.9Ma. The SHRIMP U–Pb dating of zircons from two rock samples of the granitic pluton yields respectively the crystalline ages of 17.35Ma and 14.4Ma. These new data, together with the previously zircon U–Pb ages, the mica Ar–Ar dating ages and whole rock Rb–Sr age of the granitoid, allows to constraining the tectono-thermal evolution history of the Xianshuihe fault zone. It is inferred that this fault zone suffered along its eastern segment from high temperature metamorphism and migmatization during the Oligocene (in 32–27Ma), which was followed by magma intrusion during the Miocene (in 18–12Ma); sinistral shearing began to occur at about 10Ma and continues to present-day.
•SHRIMP zircon U-Pb dating of the migmatite along the Xianshuihe Fault zone.•Deciphering an Oligocene metamorphic event along this fault zone.•Confirming episodic emplacements of the Konggar granitic pluton at 18–12Ma.•Addressing the onset time (about 12–10Ma) of the sinistral strike-slip faulting.
To meet the practical demand of overall water splitting and regenerative metal–air batteries, highly efficient, low‐cost, and durable electrocatalysts for the oxygen reduction reaction (ORR), oxygen ...evolution reaction (OER), and hydrogen evolution reaction (HER) are required to displace noble metal catalysts. In this work, a facile solid‐state synthesis strategy is developed to construct the interfacial engineering of W2N/WC heterostructures, in which abundant interfaces are formed. Under high temperature (800 °C), volatile CNx species from dicyanodiamide are trapped by WO3 nanorods, followed by simultaneous nitridation and carbonization, to form W2N/WC heterostructure catalysts. The resultant W2N/WC heterostructure catalysts exhibit an efficient and stable electrocatalytic performance toward the ORR, OER, and HER, including a half‐wave potential of 0.81 V (ORR) and a low overpotential at 10 mA cm−2 for the OER (320 mV) and HER (148.5 mV). Furthermore, a W2N/WC‐based Zn–air battery shows outstanding high power density (172 mW cm−2). Density functional theory and X‐ray absorption fine structure analysis computations reveal that W2N/WC interfaces synergistically facilitate transport and separation of charge, thus accelerating the electrochemical ORR, OER, and HER. This work paves a novel avenue for constructing efficient and low‐cost electrocatalysts for electrochemical energy devices.
Interfacial engineering of W2N/WC heterostructures for ORR, OER, and HER via a facile and practical solid‐state synthesis strategy is investigated. W2N/WC heterostructures exhibit superior electrochemical activity and stability. Such W2N/WC heterostructures catalysts also exhibit remarkable performance for Zn–air batteries and overall water splitting. This work paves a new way for constructing the electrocatalyst in electrochemical energy devices.
•Property impacts on CCS processes have been reviewed.•Properties were ranked and priority of properties in model development was analyzed.•Relevant properties in the design and operation of CCS ...processes have been identified.•The studied CCS processes include CO2 capture, conditioning, transport and storage.
The knowledge of thermodynamic and transport properties of CO2-mixtures is important for designing and operating different processes in carbon capture and storage systems. A literature survey was conducted to review the impact of uncertainty in thermos-physical properties on the design and operation of components and processes involved in CO2 capture, conditioning, transport and storage. According to the existing studies on property impacts, liquid phase viscosity and diffusivity as well as gas phase diffusivity significantly impact the process simulation and absorber design for chemical absorption. Moreover, the phase equilibrium is important for regenerating energy estimation. For CO2 compression and pumping processes, thermos-physical properties have more obvious impacts on pumps than on compressors. Heat capacity, density, enthalpy and entropy are the most important properties in the pumping process, whereas the compression process is more sensitive to heat capacity and compressibility. In the condensation and liquefaction process, the impacts of density, enthalpy and entropy are low on heat exchangers. For the transport process, existing studies mainly focused on property impacts on the performance of pipeline steady flow processes. Among the properties, density and heat capacity are most important. In the storage process, density and viscosity have received the most attention in property impact studies and were regarded as the most important properties in terms of storage capacity and enhanced oil recovery rate. However, for physical absorption, physical adsorption and membrane separation, there has been a knowledge gap about the property impact. In addition, due to the lack of experimental data and process complexity, little information is available about the influence of liquid phase properties on the design of the absorber and desorber for chemical absorption process. In the CO2 conditioning process, knowledge of the impacts of properties beyond density and enthalpy is insufficient. In the transport process, greater attention should focus on property impacts on transient transport processes and ship transport systems. In the storage process, additional research is required on the dispersion process in enhanced oil recovery and the dissolution process in ocean and saline aquifer storage.
CeO2–TiO2 (CeTi) catalysts synthesized by an ultrasound-assisted impregnation method were employed to oxidize elemental mercury (Hg0) in simulated low-rank (sub-bituminous and lignite) coal ...combustion flue gas. The CeTi catalysts with a CeO2/TiO2 weight ratio of 1–2 exhibited high Hg0 oxidation activity from 150 to 250 °C. The high concentrations of surface cerium and oxygen were responsible for their superior performance. Hg0 oxidation over CeTi catalysts was proposed to follow the Langmuir–Hinshelwood mechanism whereby reactive species from adsorbed flue gas components react with adjacently adsorbed Hg0. In the presence of O2, a promotional effect of HCl, NO, and SO2 on Hg0 oxidation was observed. Without O2, HCl and NO still promoted Hg0 oxidation due to the surface oxygen, while SO2 inhibited Hg0 adsorption and subsequent oxidation. Water vapor also inhibited Hg0 oxidation. HCl was the most effective flue gas component responsible for Hg0 oxidation. However, the combination of SO2 and NO without HCl also resulted in high Hg0 oxidation efficiency. This superior oxidation capability is advantageous to Hg0 oxidation in low-rank coal combustion flue gas with low HCl concentration.
Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Compared with the majority of carbon materials, it has ...electron-rich properties, basic surface functionalities and H-bonding motifs due to the presence of N and H atoms. It is thus regarded as a potential candidate to complement carbon in material applications. In this review, a brief introduction to g-C3N4 is given, the methods used for synthesizing this material with different textural structures and surface morphologies are described, and its physicochemical properties are referred. In addition, four aspects of the applications of g-C3N4 in catalysis are discussed: (1) as a base metal-free catalyst for NO decomposition, (2) as a reference material in differentiating oxygen activation sites for oxidation reactions over supported catalysts, (3) as a functional material to synthesize nanosized metal particles, and (4) as a metal-free catalyst for photocatalysis. The reasons for the use of g-C3N4 for such applications are also given, and we expect that this paper will inspire readers to search for further new applications for this material in catalysis and in other fields.
The energy consumption of buildings accounts for a major share in the modern society. Accurate forecast of building thermal demand is of great significance to both building management systems and ...heat distribution networks. Machine learning models driven by abundant load data have demonstrated their great capability in predicting real-world consumption patterns and trends. A large number of input features have been considered in the literature for developing data-driven models. However, a thorough analysis regarding their importance is currently lacking. This work first presents a review on the commonly considered features in building thermal demand prediction models, and focuses particularly on their influences. To further facilitate investigating the impacts of various input features, based on a four-year dataset collected from a district heating system with 13 input features, a deep learning model, the long short-term memory (LSTM) network, is employed for a real-world case study. Our results suggest that the past load, outdoor temperature, and hour index have the greatest influence, and should be primarily considered in building thermal demand forecast models. For the studied case, they lead to an RMSE of 12.231 MW and a CV-RMSE of 5.814 %. Additionally involving wind speed and day index is also useful, which improves the RMSE to 11.971 MW and CV-RMSE to 5.691 %. On the contrary, including all available features does not achieve a bettery accuracy, in which RMSE and CV-RMSE are 12.349 MW and 5.871 %.
Perovskite oxides with formula ABO3 or A2BO4 are a very important class of functional materials that exhibit a range of stoichiometries and crystal structures. Because of the structural features, ...they could accommodate around 90% of the metallic natural elements of the Periodic Table that stand solely or partially at the A and/or B positions without destroying the matrix structure, offering a way of correlating solid state chemistry to catalytic properties. Moreover, their high thermal and hydrothermal stability enable them suitable catalytic materials either for gas or solid reactions carried out at high temperatures, or liquid reactions carried out at low temperatures. In this review, we addressed the preparation, characterization, and application of perovskite oxides in heterogeneous catalysis. Preparation is an important issue in catalysis by which materials with desired textural structure and physicochemical property could be achieved; characterization is the way to explore and understand the textural structures and physicochemical properties of the material; however, application reflects how and where the material could be used and what it can solve in practice, which is the ultimate goal of catalysis. This review is organized in five sections: (1) a brief introduction to perovskite oxides, (2) preparation of perovskite oxides with different textural structures and surface morphologies, (3) general characterizations applied to perovskite oxides, (4) application of perovskite oxides in heterogeneous catalysis, and (5) conclusions and perspectives. We expected that the overview on these achievements could lead to research on the nature of catalytic performances of perovskite oxides and finally commercialization of them for industrial use.
•Porewater salinity differs between macropores and the adjacent sediment matrix.•Crab burrows can significantly increase the intensity and duration of soil aeration.•Crab burrows can provide an ...efficient pathway for salt transport in coastal wetlands.•Crab burrows may limit the development of seepage faces in salt marshes.
Crab burrows can act as preferential flow conduits for pore water-surface water interactions in salt marshes, but the effect of preferential flow on subsurface transport in these tidally-influenced systems is not fully understood. We used numerical models based on salt marshes of North Inlet, South Carolina, to investigate the impacts of crab burrows on porewater salinity. This modeling effort was inspired by field results from North Inlet, where prior field studies that used a combination of tension samplers and passive diffusion samplers measure salinity in crab burrows and in the adjacent sediment matrix found that the minimum salinity (28 PSU) reported by the tension samplers was larger than the maximum salinity (26 PSU) reported by passive diffusion samplers. Two kinds of numerical models were developed to investigate the effect of crab burrows on tidally-driven groundwater flow and salt transport. In the equivalent-continuum model (ECM), crab burrows were included via a shallow surface layer with hydraulic properties representing a bulk average of sediment matrix and crab burrow properties. In the preferential flow model (PFM), an independent high-permeability material was embedded in the surface muddy layer to explicitly simulate preferential flow conduits. The simulated results showed that both models can depict the effect of crab burrow on soil saturation and salt transport in salt marshes. The presence of crab burrows can greatly increase tidally-driven water exchange, improve the intensity and duration of soil aeration and enhance salt transport in salt marshes. The effect of crab burrows on groundwater flow and salt transport varied spatially from the creek bank to marsh interior. PFM models demonstrated that salinity is likely to differ between crab burrows and the sediment matrix, which supports observed differences in results between tension samplers and passive diffusion samplers. These findings may have important implications for practical pore water sampling and hydrochemical investigation in coastal wetlands.
•Location of polluted nearshore waters coincided with SGD hotspots on a local scale.•SGD-driven nutrients were one order of magnitude higher than riverine inputs in China.•Nutrients via SGD ...contributed >50% of the total sources to Chinese coastal waters.•SGD influences coastal water quality and nutrient budgets at small and large scales.
Submarine groundwater discharge (SGD) can be a significant source of chemical pollutants from land to ocean. Here, we first estimated SGD using radium isotopes and related nutrient fluxes at the local scale in Jiaozhou Bay (JZB), a typical Chinese system that is experiencing rapid urban and industrial development. We then summarized SGD studies off China to assess the large-scale implications of SGD to nutrient budgets. In JZB, the location of contaminated nearshore waters revealed by an integrative water quality index (WQI) coincided with the SGD hotspots. The total (fresh and saline) SGD flux in JZB was estimated to be (0.64–1.67) × 107 m3/d or (2.12–5.59) cm/d based on 224Ra and 228Ra mass balance models. This was approximately 8 times the discharge rate of local rivers. By combining these JZB results with the literature data, we provide the first estimate of SGD and associated nutrient fluxes off China. The magnitude of SGD at the China-scale was (5.40–10.2) × 1012 m3/yr, accounting for 5–9% of the global SGD flux. SGD-derived nutrient fluxes summarized from ∼40 previous studies were one order of magnitude higher than riverine inputs. These nutrients fluxes from SGD contributed >50% of the total dissolved inorganic nitrogen (DIN), phosphorous (DIP) and silicate (DSi) inputs into Chinese coastal waters, which can explain about 60% of the phosphorus required by primary production. The mean DIN/DIP ratio (121) in SGD was significantly higher than the Redfield ratio, with important implications for phytoplankton growth and structure. SGD can influence water quality, dominate nutrient budgets, and drive primary production not only at the local scale, but also at the regional and global scales.
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