Evaluating cubic equations of state for calculation of vapor–liquid equilibrium of CO2 and CO2-mixtures for CO2 capture and storage processes

Proper solution of vapor liquid equilibrium (VLE) is essential to the design and operation of CO₂ capture and storage system (CCS). According to the requirements of engineering applications, cubic equations of state (EOS) are preferable to predict VLE properties. This paper evaluates the reliabilities of five cubic EOSs, including PR, PT, RK, SRK and 3P1T for predicting VLE of CO₂ and binary CO₂-mixtures containing CH₄, H₂S, SO₂, Ar, N₂ or O₂, based on the comparisons with the collected experimental data. Results show that SRK is superior in the calculations about the saturated pressure of pure CO₂; while for the VLE properties of binary CO₂-mixtures, PR, PT and SRK are generally superior to RK and 3P1T. The impacts of binary interaction parameter k_ij were also analyzed. k_ij has very clear effects on the calculating accuracy of an EOS in the property calculations of CO₂-mixtures. In order to improve the calculation accuracy, the binary interaction parameter was calibrated for all of the studied EOSs regarding every binary CO₂-mixture.     

Electrodeposition of CuIn alloys for preparing CuInS2 thin films

Copper-indium alloys were prepared by electroplating from citric acid (C₆H₈O₇·H₂O) baths onto Ti substrate. Formation of the alloys was carried out by direct codeposition of the elements and by sequential electrodeposition of copper and indium. Studies of the alloy formation by electrochemical measurements and X-ray diffraction were performed. The presence of Cu₇In₄ in direct deposit as well as in sequentially electrodeposited material was observed during the alloy formation. The as-deposited layers were heated in H₂S. X-ray diffraction showed the annealed layers to be CuInS₂ with the chalcopyrite structure, where the CuIn₅S₈ phase was included during the annealing process.Photoelectrochemical characterization of the samples allowed us to determine the photoconductivity which is related with the Cu/In ratio in the samples. The energy gap for CuInS₂ photoelectrodes in polysulphide solution was 1.57 eV.     

Recyclable CeO2–ZrO2 and CeO2–TiO2 mixed oxides based Pt catalyst for aqueous-phase reforming of the low-boiling fraction of bio-oil

In this study, a series of CeO₂–ZrO₂ and CeO₂–TiO₂ materials with different composition were prepared, characterized by BET and XRD analysis, and their hydrothermal stability was studied by subjecting the samples to acetic acid solutions at 533 K. All of the materials, especially C1Z1 (50 mol% CeO₂ with 50 mol% ZrO₂) and C1T1 (50 mol% CeO₂ with 50 mol% TiO₂), exhibited excellent stability with no phase transformation and minimal decrease in their specific surface area (SSA) was observed even after 16 h. After being loaded by Pt, these catalysts were used for the aqueous phase reforming (APR) of the low-boiling fraction of bio-oil (LBF) to investigate their catalytic performance. Among these catalysts Pt/C1Z1 and Pt/C1T1 showed superior catalytic activity, probably due to their lowest reduction temperature and the largest amount of O vacancies generated by the reduction of the surface oxygen of well-dispersed CeO₂. Thus, Pt/C1Z1 and Pt/C1T1 were chosen to investigate their recyclability. The catalytic activity and H₂ selectivity of Pt/C1Z1 and Pt/C1T1 can be almost recovered after being calcined in air at 773 K for regeneration. After three cycles, the particle size of Pt/C1Z1 and Pt/C1T1 only experienced a slight increase, while for Pt/Al₂O₃ it increased from 2.9 nm to 7.8 nm. So, compared with Pt/Al₂O₃, the Pt/C1Z1 and Pt/C1T1 catalysts were identified as effective and recyclable candidates for the production of H₂ rich fuel gas from APR of LBF.     

Synergistic effect of organic-inorganic hybrid electrolyte for ultra-long Zn–I2 batteries

Hydrogel electrolytes are widely used in wearable aqueous zinc-ion batteries (ZIBs) which are considered as the most promising candidate for future energy storage systems. However, traditional organic hydrogel ions have the disadvantages of low ionic conductivity and poor mechanical properties. To conquer this, an organic-inorganic hybrid hydrogel electrolyte (PVA/CNC–C/sepiolite) is developed to improve ionic conductivity and reduce side reactions in ZIBs simultaneously. In this system, hydrogen bonds are formed between sulfonic acid groups in the polymer and the hydroxyl groups in sepiolite. The existence of these hydrogen bonds enhances the binding force between the organic and inorganic components, thus improving the ionic conductivity and mechanical properties of the electrolyte. Also, sulfonic acid groups in this hydrogel electrolyte can induce homogeneous deposition of Zn²⁺. The pores between the multilayer structures in sepiolite further optimize the ion transport channel and improve the transfer kinetics of Zn²⁺. Due to the synergistic effect of organic-inorganic compositions in this electrolyte, the Zn/Zn cell operates for more than 2000 h and Zn/I₂ cell full exhibits an ultra-stable lifespan for 10,000 cycles. This work opens up a new avenue for the design of hydrogel electrolytes in ZIBs.     

Paper-structured catalyst containing CeO2–Ni flowers for dry reforming of methane

In this paper, ceria flowers containing nano-sized catalyst Ni particles were prepared on alumina-silica fiber network for production of hydrogen from biogas. The CeO₂ flowers were prepared using hydrothermal method and then NiO was loaded on the CeO₂ flowers by impregnation method. The Paper-structured catalysts (PSCs) were prepared from alumina-silica fibers and the CeO₂–NiO flowers using conventional paper making method. The loaded NiO particles were uniformly dispersed on the CeO₂ flowers with the use of polyvinylpyrrolidone as a dispersion enhancer, which was observed by FE-SEM and EDX analysis. The NiO particles were then reduced into Ni by using H₂. The PSCs containing CeO₂–Ni flowers with various Ni contents (2.1, 3.4, and 4.6%) were used for dry reforming of CH₄. It was found that 3.4% amount of Ni on the PSC was suitable for reforming reaction, and the higher amount of Ni (4.6%) did not increase the CH₄ conversion. The PSC with the CeO₂ flowers had porous structure and large surface area leading to the better dispersion of the Ni particles with smaller size. This helped increase in catalytic performance, prevention of agglomerated particle catalysts at high temperature and coke forming after a long time operation. The CH₄ conversion of the PSCs containing CeO₂–NiO flowers in the dry reforming of CH₄ was much higher (nearly 90%) with a smaller Ni content in comparison with the PSC without the CeO₂ flowers (with higher Ni content of 8.6%). Moreover, the PSCs with the flowers exhibited an excellent catalytic stability with the degradation of CH₄ conversion of only 3.1% after 50 h of reforming. In addition, the high oxygen storage capacity and oxygen mobility of CeO₂ resulted in a partial removal of coke forming on the catalyst particles during reforming. This indicated that the catalytic activity of the Ni particles dispersed on the CeO₂ flowers for dry reforming of CH₄ was superior to that of various Ni-based catalyst systems which had much higher Ni contents. Therefore, it is possible to use the PSCs containing CeO₂–Ni flowers to generate hydrogen for use as fuels from dry reforming of CH₄.     

The deactivation effect of Na2O and NaCl on CeO2–TiO2 catalysts for selective catalytic reduction of NO with NH3

The effect of Na₂O and NaCl on CeO₂–TiO₂ catalyst for the selective catalytic reduction of NO with NH₃ was investigated with BET, XRD, XPS, NH₃-TPD, H₂-TPR, in-situ DRIFT and catalytic activity measurements. The results showed that both Na species could deactivate the CeO₂–TiO₂ catalyst and Na₂O had a stronger effect than NaCl. The more serious deactivation by Na₂O could be ascribed to smaller surface area, fewer surface Ce³⁺ and chemical adsorbed oxygen, lower surface acidity, and worse reducibility. The introduction of NaCl and Na₂O facilitated the formation of new surface NO_x adspecies, but were inactive in NH₃-SCR reaction. The adsorption of NH₃ were inhibited. The NH₃-SCR reaction over the CeO₂–TiO₂ catalyst was governed by both E-R and L-H mechanisms. The introduction of NaCl and Na₂O didn't change the NH₃-SCR reaction mechanisms.     

Effects of CaO addition on Ni/CeO2–ZrO2–Al2O3 coated monolith catalysts for steam reforming of N-decane

A series of 10 wt%Ni/CeO₂–ZrO₂–Al₂O₃ (10%Ni/CZA) coated monolith catalysts modified by CaO with the addition amount of 1 wt%~7 wt% are prepared by incipient-wetness co-impregnation method. Effects of CaO promoter on the catalytic activity and anti-coking ability of 10%Ni/CZA for steam reforming of n-decane are investigated. The catalysts are characterized by N₂ adsorption-desorption, XRD, SEM-EDS, TEM, NH₃-TPD, XPS, H₂-TPR and Raman. The results show that specific surface area and pore volume of as-prepared catalysts decrease to some extent with the increasing addition of CaO. However, the proper amounts of CaO (≤3 wt%) significantly enhance the catalytic activity in terms of n-decane conversion and H₂ selectivity mainly due to the improved dispersion of NiO particles (precursor of Ni particles). As for anti-coking performance, reducibility of CeO₂ in composite oxide support CZA is promoted by CaO resulting in providing more lattice oxygen, which favors suppressing coke formation. Moreover, the addition of CaO reduces the acidity of 10%Ni/CZA, especially the medium and strong acidity. But far more importantly, a better dispersion of NiO particles obtained by proper amounts of CaO addition is dominant for the lower carbon formation, as well as the higher catalytic activity. For the spent catalysts, amorphous carbon is the main type of coke over 10%Ni–3%CaO/CZA, while abundant filamentous carbon is found over the others.     

Comparison of Performances of Turbines for Wave Energy Conversion

The Wells turbine for a wave power generator is a self-rectifying air turbine that is available for an energy conversion in an oscillating water-air column without any rectifying valve. The objective of this paper is to compare the performances of the Wells turbines in which the profile of blade are NACA0020, NACA0015, CA9 and HSIM15-262123-1576 in the small-scale model testing. The running characteristics in the steady flow, the start and running characteristics in the sinusoidal flow and the hysteretic characteristics in the sinusoidal flow were investigated for four kinds of turbine. As a conclusion, the turbine in which the profile of blade is NACA0020 has the best performances among 4 turbines for the running and starting characteristics in the small-scale model testing.     

Thermodynamic models for H2O–CO2–H2 mixtures in near-critical and supercritical regions of water

The PVTx properties of the H₂O–CO₂–H₂ mixtures have significant applications in the technology of supercritical water gasification of coal. Here, we first carry out the molecular dynamics simulations of the PVTx properties of the H₂O–CO₂–H₂ mixtures in the near-critical and supercritical regions of water to generate 600 datasets at 750–1150 K and 4.0–443.5 MPa. The molar fraction of each composition in the ternary mixtures ranges from 10% to 80%. Later we investigate the applicability of a well-known thermodynamic model for the ternary mixtures, namely the Duan-Møller-Weare equation of state (DMW EOS). It is observed that the DMW EOS shows great potential in the prediction of the PVTx properties of the ternary mixtures. However, it is noted that the mixing parameters describing the binary interactions of H₂O–H₂ and CO₂–H₂ are still unknown in the DMW EOS. By determining the missing mixing parameters using the Levenberg-Marquardt algorithm, the accuracy of the original DMW EOS is improved for the ternary mixtures. Moreover, optimizing the coefficients in the DMW EOS further promotes the accuracy of the model for the H₂O–CO₂–H₂ mixtures. The results from this work may facilitate the development of supercritical water gasification of coal.     

Influence of coexisting Al2O3 on the activity of copper catalyst for water–gas-shift reaction

Influence of coexisting Al₂O₃ on the catalytic activity for low-temperature water–gas-shift (LT-WGS) reaction over Cu catalyst was investigated. The catalytic activity of Cu/Al₂O₃ catalyst increased with decreasing mesopore size when S/C ratio was 2.2, whereas the catalytic activity with S/C ratio = 4.6 increased with increasing mesopore size. IR measurement combined with kinetic study suggested that the low catalytic activity of Cu/CeO₂ catalyst comes from the restriction of CO adsorption on Cu⁰ by bidentate-type carbonate formed on the strong basic site of CeO₂ support. On the other hand, it was found that bidentate-type carbonate was not formed on Cu/Al₂O₃ showing high catalytic activity for LT-WGS reaction.     

Mg/SiO2–Al2O3 supported nickel catalysts for the production of naphthenic hydrocarbon fuel by hydro-de-oxygenation of eugenol

Ni–Mg supported on both mesoporous Al₂O₃–SiO₂ (10) and γ-Al₂O₃ with Al₂O₃–SiO₂/Mg = 10 and γ-Al₂O₃/Mg = 10 ratio were prepared via wet impregnation method. The synthesized materials were characterized by XRD, N₂-sorption study, NH₃-TPD/H₂-TPR, FT-IR, DRS-UV and used in hydrodeoxygenation (HDO) of eugenol to produce hydrocarbons in a high pressure reactor. The reactant molecules could be facilitated to yield hydrocarbon fuel by active nickel active sites. The high oxygen removal efficiency of 75% was achieved with C9 hydrocarbon selectivity. Evaluation of catalytic properties such as high hydrogen consumption of 145 μmol/g (H₂-TPR) and enriched surface acidity of 2.35 mmol g⁻¹ (NH₃-TPD) was done. Ni/Mg-SA (10) exhibited the highest catalytic activity of 6.7 × 10⁻⁴ mol g⁻¹ s⁻¹ SRR and 10.27 s⁻¹ TOF respectively. The stability of catalysts was found to be 185 mg/g for Ni/Mg-SA (10) catalyst by TGA analysis. The structure-activity relationship was studied and the product distributions were also discussed in detail.     

Effect of Vibration on Forced Convection Heat Transfer for SiO2–Water Nanofluids

In the process of heat transfer, the fluid type and external parameters have a significant impact on heat transfer performance. For this reason, the physical properties, pressure differences, and heat transfer rates of SiO₂–water nanofluids have been experimentally investigated in a straight circular pipe. Experimental results revealed a great difference in physical properties between SiO₂–water nanofluids and purified water. The friction factor of low-volume-concentration nanofluids was slightly increased for laminar flow and tended to be almost independent of the Reynolds number for turbulent flow. The heat transfer coefficient can be enhanced either by adding nanoparticles to purified water or by imposing a transverse vibration on the heat transfer surface. Using these two methods at the same time (compound heat transfer enhancement), heat transfer performance is much better than that with either method alone. The largest increase of about 182% was observed under conditions of compound heat transfer enhancement.     

Utilizing waste heat of the flue gas for post-combustion CO2 capture—A comparative study for different process layouts

The inlet flue gas entering the absorber column must be ~40°C and hence needs cooling. In this article, it is proposed that waste heat be recovered from the flue gas using a condensing heat exchanger. This recovered heat is utilized as partial supplement to subsequent heating in stripper during CO₂ capture. System layouts—one for base case and two others—have been conceptualized. ASPEN Plus^® simulation results for the other two layouts are discussed for energy savings with respect to the base case. Results show that, for the other two layouts, reboiler heat duty decreases though carbon capture efficiency also decreases.     

Ultrasonic-assisted synthesis of highly active catalyst Au/MnOx–CeO2 used for the preferential oxidation of CO in H2-rich stream

A series of nano-gold catalysts supported on binary oxides MO_x–CeO₂ (atomic ratio M/Ce = 1:1, M = Mn, Fe, Co, Ni) are prepared by deposition–precipitation (DP). An innovative and rather convenient ultrasonic pretreatment of the support is employed for Au/MnO_x–CeO₂ preparation. It is found that for preferential CO oxidation Au/MnO_x–CeO₂ is more active than Au/CeO₂. Ultrasonic pretreatment of MnO_x–CeO₂ further promotes the performance of Au/MnO_x–CeO₂, with CO conversion increased by 24 % at 120 °C. Meanwhile, the selectivity of oxygen to CO₂ is promoted in the whole temperature range, especially in 80–120 °C, the selectivity is increased by 15–21%. HR-TEM and XRD results indicate that ultrasonic pretreatment is favorable to the formation of much smaller gold nanoparticles (<5 nm). The characterization of XPS, UV–vis DRS, H₂-TPR and CO-TPR confirms that the strong interaction between Au and the support effectively inhibits the dissociation and oxidation of H₂ over the ultrasonically pretreated catalyst Au/MnO_x–CeO₂, making it highly selective to CO oxidation.     

Experimental Study of Thermo-Physical Properties of Nanofluids Based on γ-Fe2O3 Nanoparticles for Heat Transfer Applications

The main goal of the present study was to prepare and also to investigate the effects of both temperature and weight concentration on the thermo-physical properties of γ-Fe₂O₃/water nanofluids. The γ-Fe₂O₃ nanoparticles were synthesized by laser pyrolysis technique and characterized using TEM, XRD, and EDX techniques. Thermal conductivity, viscosity and surface tension of γ-Fe₂O₃/water nanofluids were investigated within the range of the temperature of 20°C to 70°C for various weight concentrations of nanoparticles (0.5, 1.0, 2.0, and 4.0 wt%). The experimental results show that the thermal conductivity ratio is much higher than of thermal conductivity of base fluid. Thus, the relative thermal conductivity was 59% for a concentration of 4.0 wt% and a temperature of 50°C. Also, it has been observed that the influence of weight concentration of nanoparticles on viscosity was lower at temperatures over 55°C. At standard temperature of 25°C and 2.0 wt.% concentration of nanoparticles, the relative dynamic viscosity was 5.61%. Experimental results show that the surface tension increases with increase of weight concentrations and decreases with increase of temperatures. For a temperature of 70°C and 2.0 wt.% concentration of nanoparticles, the relative surface tension was 46%. The experimental results were compared with data available in literature.     

Effect of sulfur–carbon interaction on sulfur poisoning of Ni/Al2O3 catalysts for hydrogenation

The poisoning effects of two types of carbon-containing sulfides (CS₂ and CH₃SSCH₃) on Ni/Al₂O₃ catalysts for the hydrogenation of benzene and cyclohexene were systematically investigated via experiments and DFT calculations. The toxicity of CH₃SSCH₃ is two and three times greater than that of CS₂ for the hydrogenation of cyclohexene and benzene, respectively. The characterization and DFT results reveal that CH₃SSCH₃ dissociates easily during hydrogenation and releases CH₄, allowing sulfur atoms to poison the Ni sites. However, the presence of CS₂ in the hydrogenation step slows the decline in the catalytic performance, because of resistance to the direct dissociation of the strong CS bond of CS₂. The chemisorbed CS₂ molecules and their incomplete dissociation weaken the strength of NiS bond and decrease the poisoning effect of sulfur. The poisoning processes of two sulfides are also discussed following a DFT study. This work opens up promising possibilities for the industrial study of S-poisoning resistance in supported Ni catalysts.     

Studies on electrochemical performance of partially reduced MnO2 used as cathode for MH–MnO2 rechargeable battery

Cyclic voltammograms show that the reversibility of the manganese dioxide (MnO₂) electrode is improved by means of using partially reduced samples. The crystal lattice of the intermediate is transformed by reduction. Formation of the manganous ion is very limited before the electrode potential reaches −0.4 V (versus Hg/HgO), thus the formation of Mn₃O₄ is prevented.The addition of Ni(OH)₂ to partially reduced samples can further improve the reversibility of the MnO₂ electrode, Ni(OH)₂ delays the 2e⁻ discharge step and decreases the opportunity for the co-existence of Mn(III) and Mn(II) ions and, thereby, prevents the formation of Mn₃O₄. The capacity retention of a cathode of partially reduced MnO₂ (pr-MnO₂) or pr-MnO₂+Ni(OH)₂ is much better than that of the MnO₂ cathode. This demonstrates the feasibility of using pr-MnO₂ as a cathode material.     

Cooperative effect of Pt and Cu on CeO2 for the CO-PROX reaction under CO2–H2O feed stream

Catalyst improvement for the preferential oxidation of CO (CO-PROX) is essential in developing efficient fuel cell technologies. Here, we investigate the promotion of the Cu/CeO₂ system with Pt, prepared by impregnation and alcohol-reduction methods, in the CO-PROX reaction under ideal and realistic feed compositions. The high Pt dispersion in PtCu/CeO₂ prepared by impregnation led to a CO conversion of 62% and CO₂ selectivity of 83% at 50 °C under a feed stream composed of H₂/CO/O₂, while monometallic Cu/CeO₂ and Pt/CeO₂ showed negligible activity at these conditions. By adding CO₂–H₂O to the feed stream, PtCu/CeO₂ catalysts prepared by both methods presented similar activity. The maximum CO conversion temperature was shifted to 100 °C. Under these conditions, Cu/CeO₂ was inactive, and Pt/CeO₂ showed identical conversion but lower CO₂ selectivity. In-situ XANES revealed that fast oxidation of Cu species at low temperatures is responsible for Cu/CeO₂ deactivation, while preferential adsorption of CO on Pt⁰ sites in PtCu/CeO₂ avoided deactivation. The use of deactivation-resistant Pt sites as complimentary sites for CO activation associated with improved oxygen mobility over Cu–CeO₂ surface proved to be an effective strategy for CO-PROX under H₂O/CO₂ feed stream at low temperatures.     

High-performance Ni–SiO2 for pressurized carbon dioxide reforming of methane

The SiO₂ and Ni–SiO₂ were synthesized via the complex-decomposition method by using different organic acids as the complexing agent and fuel. The Ni-supported SiO₂ from different sources was prepared by the incipient impregnation method. The Ni–SiO₂ and Ni/SiO₂ were comparatively evaluated for carbon dioxide reforming of methane (CDR) under severe conditions of CH₄/CO₂ = 1.0, T = 750 °C, GHSV = 53200 mL g⁻¹ h⁻¹, and P = 0.1–1.0 MPa. The materials were fully characterized by XRD, XPS, TEM, TG-DSC, H₂-TPR, and N₂ adsorption-desorption at −196 °C. It was found that the complexing agent and preparation method of the catalyst significantly affected its surface area, the size and dispersion of Ni, the reduction behavior, and the coking and sintering properties, which determine the activity and stability of the catalyst for CDR. As a result, a highly active and stable Ni–SiO₂ for pressurized CDR was obtained by optimizing the complexing agent.     

Effective fabrication method of rod-shaped γ-LiAlO2 particles for molten carbonate fuel cell matrices

An effective fabrication method for rod-shaped γ-LiA1O₂ particles for molten carbonate fuel cell matrices via the synthesis of porous β-LiAlO₂ agglomerates that are easily washed and dispersed with deionized water has been investigated. In order to make large pores and high porosity in the reaction mixture, powder types of carbon and ammonium carbonate that make little ash and undesired material during the whole process are utilized. Regardless of the kind of pore-formers used, most of the rod-shaped β-/γ-LiAlO₂ particles are 1 μm in diameter and 10–15 μm long (aspect ratio of 10–15). The crystal structure of rod-shaped γ-LiAlO₂ particles synthesized from the reaction mixture with pore-formers coincides exactly with that of commercial γ-LiAlO₂ powders. As a consequence, cell performance using rod-shaped γ-LiAlO₂ particle reinforced matrices is highly improved in comparison with non-reinforced standard matrices.