Search

In recent decades, supercritical fluid has gained increasing interest in various industries. One of its promising applications is the extraction of valuable compounds from solid materials such as various plant parts, known as supercritical fluid extraction (SFE). With growing interest to employ SFE commercially, it is vital to provide reliable and robust mathematical modeling for the SFE to optimize the process and achieve maximum extraction yield and to better understand the process mechanism. The present review aims to critically report and discuss different strategies proposed thus far for the mathematical modeling of the SFE process in packed bed columns. The main features, key assumptions and their validity, mathematical expressions, and applications of each modeling strategy are evaluated. Additionally, this manuscript covers a comprehensive review of the different studies carried out for SFE of plant matrices encompassing mathematical modeling part. The studied systems in each research (both solute and solid substrate) along with the employed models as well as the ranges of the operational conditions such as pressure, temperature, and solvent flow rate are also highlighted. This review assists the scientific community to identify the most suitable models and the appropriate operating conditions for different systems in the SFE process.

Pyrolysis oil from oil palm biomass can be a sustainable alternative to fossil fuels and the precursor for synthesizing petrochemical products due to its carbon-neutral properties and low sulfur and nitrogen content. This work investigated the effect of applying mesoporous acidic catalysts, Ni–Mo/TiO2 and Ni/Al2O3, in a catalytic co-pyrolysis of oil palm trunk (OPT) and polypropylene (PP) from 500 to 700 °C. The obtained oil yields varied between 12.67 and 19.50 wt.% and 12.33–17.17 wt.% for Ni–Mo/TiO2 and Ni/Al2O3, respectively. The hydrocarbon content in oil significantly increased up to 54.07–58.18% and 37.28–68.77% after adding Ni–Mo/TiO2 and Ni/Al2O3, respectively. The phenolic compounds content was substantially reduced to 8.46–20.16% for Ni–Mo/TiO2 and 2.93–14.56% for Ni/Al2O3. Minor reduction in oxygenated compounds was noticed from catalytic co-pyrolysis, though the parametric effects of temperature and catalyst type remain unclear. The enhanced deoxygenation and cracking of phenolic and oxygenated compounds and the PP decomposition resulted in increased hydrocarbon production in oil during catalytic co-pyrolysis. Catalyst addition also promoted the isomerization and oligomerization reactions, enhancing the formation of cyclic relative to aliphatic hydrocarbon.

Pyrolysis oil can be used as a precursor to synthesize value-added biochemicals. Co-pyrolysis of two or more feedstocks generally improves the selectivity and yield of the target compounds. In this work, oil palm trunk (OPT) was subjected to single-feed pyrolysis and co-pyrolysis with polypropylene (PP) from 500 to 700 °C. The highest pyrolysis oil yield of 26.33 wt.% was obtained from OPT at 700 °C, which mainly contributed by the lignin decomposition in OPT. Phenolics (51.77–57.78%) and oxygenates (36.31–46.99%) were the major compounds detected in the OPT-derived pyrolysis oil. The addition of PP enhanced the formation of hydrocarbons (5.19–10.22%) and decreased the contents of phenolics (34.01–41.85%) in the co-pyrolysis oil. In the case of co-pyrolysis, the intermolecular reactions between PP and OPT-derived radicals led to the formation of ketones and alcohols, which contributed to the increase of oxygenates content. The highest oil yield of 16.17 wt.% was obtained at 600 °C from co-pyrolysis, the oil of which contained mainly phenolic compounds, oxygenated compounds (i.e., ketones and furans), and hydrocarbons. These findings highlighted the potential of oil derived from the pyrolysis of OPT (single feed) and co-pyrolysis of OPT and PP (binary feed) for the production of value-added chemicals.

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) for in situ persistent organic pollutant (POP) remediation in aqueous solutions can be a promising technology. However, this technology is constrained by its high toxicity and cost of metal oxide and non-metal catalysts for PMS activation. Here, we investigated the catalytic performance of a widely available natural mineral, manganese ore (MO), for PMS activation. A series of natural MO samples in an aqueous solution were prepared via the Fenton-like reaction. The samples' crystalline structure, surface morphology, textural properties, and other surface characteristics of the selected MO were systematically characterized. The effects of PMS concentration and process parameters on the degradation performance of four chosen model pollutants, that is, phenol, tetrabromobisphenol A (TBBPA), rhodamine B (RhB), and methylene blue (MB), were evaluated. The experimental results showed that natural MO increased catalytic activity and enhanced the PMS oxidation processes, with 98%, 90%, and 75% removal efficiencies on phenol, TBBPA, and RhB, respectively, within 1.5 h. The reduction in the initial pH solution from 10 to 7 and the increase in temperature from 15 to 45°C enhanced the MB degradation rate (decolorization) by 55 and 46%, respectively, within 2 h. During the PMS activation process, SO4•−, •OH, and 1O2 species were generated, but only SO4•− and •OH radicals with strong oxidative potentials contributed to the catalytic degradation. The dissolved metals from the experiments were found well within the limit of drinking water standards, verifying that the MO + PMS catalytic system is suitable for commercial applications. This work provides insights into the development potential and prospects of using natural minerals for PMS activation and POP degradation, which can accelerate their industrial applications.

Mixed ionic-electronic conducting (MIEC) membranes have gained growing interest recently for various promising environmental and energy applications, such as H2 and O2 production, CO2 reduction, O2 and H2 separation, CO2 separation, membrane reactors for production of chemicals, cathode development for solid oxide fuel cells, solar-driven evaporation and energy-saving regeneration as well as electrolyzer cells for power-to-X technologies. The purpose of this roadmap, written by international specialists in their fields, is to present a snapshot of the state-of-the-art, and provide opinions on the future challenges and opportunities in this complex multidisciplinary research field. As the fundamentals of using MIEC membranes for various applications become increasingly challenging tasks, particularly in view of the growing interdisciplinary nature of this field, a better understanding of the underlying physical and chemical processes is also crucial to enable the career advancement of the next generation of researchers. As an integrated and combined article, it is hoped that this roadmap, covering all these aspects, will be informative to support further progress in academics as well as in the industry-oriented research toward commercialization of MIEC membranes for different applications.

Reverse water-gas shift reaction (RWGS) is important in the CO2 utilization cycle to convert carbon dioxide (CO2) and hydrogen (H2) to carbon monoxide (CO). In this work, the RWGS performance is evaluated by utilizing Ti4O7-doped SrCe0.9Y0.1O3-d (SCY-b) hollow fibre membrane reactor where H2 permeates through the SCY-b proton conducting membrane and reacts with CO2 feed gas. Upon increasing the temperature from 750 to 950 °C, the CO yield increased from a negligible value to 14.82 %, when the sweep gas flow rate was 50 mL min-1 H2-He (50:50 vol. ratio) and the feed gas flow rate was 100 mL min-1 CO2-N2 (5:95 vol. ratio). The CO yield increase with the temperature increase reflects the enhanced H2 permeation flux through the SCY-b membrane at higher temperatures. Higher CO2 concentration in the feed gas led to lower CO yield due to the higher amount of remaining CO2 in the outlet stream. The deposition of porous SCY or SCY-b surface layer onto the hollow fibre outer circumference surface also increased H2 flux through the fibre relative to the non-deposited one. Thermogravimetric and CO2-temperature programmed desorption results further reveal that SCY-b adsorbed CO2 at temperature above 500 °C due to the reaction between CO2 and SCY-b material. Despite the formation of SrCO3 during RWGS, the SCY-b hollow fibre membrane reactor still displayed a stable CO yield of around 14 % throughout the 6-day continuous membrane reactor test.

© 2019 Elsevier B.V. Direct conversion of natural gas-derived syngas into higher alcohols via the Fischer-Tropsch process offers a more sustainable pathway to address fuels and chemicals demands for various industries in the near future. Large scale application of this process nonetheless relies on the availability of a highly active and selective catalyst. In this work, tri-metallic Co-Ni-Cu catalyst derived from La0.9Sr0.1Co0.8Ni0.1Cu0.1O3 perovskite precursor with two different alkali promoters were prepared and tested for higher alcohol synthesis from syngas. Active components and catalyst performances were found to vary with same weight loading of Na and K. K-promoted catalyst demonstrated the best higher alcohol formation with the higher alcohol distribution of 82.2% and alcohol chain growth probability factor of 0.53 at 325 °C, followed by the Na-promoted and non-promoted counterparts. The rationale behind the alkali addition—performance relationship is two-fold. On one hand, the addition of alkali promotes the formation of stable Co2C; resulting in high Co2C/Co ratio that enhances the higher alcohol distribution but decreases the CO conversion. On the other hand, the increased catalyst basicity obtained from alkali promotion facilitates the carbon chain propagation of alcohols, especially for the conversion of methanol to ethanol. In addition, the alkali promoters, especially K, prevent the deactivation of catalyst Co-Ni-Cu by eliminating the carbon deposition during the reaction; resulting in a stable catalyst even at 340 °C.

Dense mixed ionic-electronic conducting (MIEC) dual-phase Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Al0.3Fe0.7O3-d (SDC-SSAF) represents one of the most attractive oxygen-selective membrane materials for oxygen separation from air above 700 °C. Its high phase stability in reducing atmosphere and CO2 resistance allows its potential direct integration into oxyfuel combustion and membrane reactor applications. In this work, the oxygen permeation parameters and properties of SDC-SSAF are evaluated theoretically using the Zhu model, which analyses the role of interfaces in electrochemical oxygen permeation. The model produced good correlation with the experimental data (R2 = 0.9990), with the calculated resistance constants indicating higher resistance encountered at the feed side interface as compared to the permeate side. An analysis of the characteristic thickness indicates increasing influence of surface exchange reactions with decreasing temperature, feed side pressure, and permeate side pressure. Although oxygen permeation is dependent upon various operating conditions, our parametric study reveals that temperature effect surpasses oxygen partial pressure difference effect in enhancing the oxygen permeation flux. Oxygen permeation is limited by surface reactions between 800 and 850 °C and mixed bulk diffusion and surface exchange reactions between 850 and 875 °C. Above 875 °C, the rate determining step shifts to bulk diffusion.

Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO 2 and RuO 2 ). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of La 1-x Sr x FeO 3-δ (x = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER-specific activities in alkaline solution increase in the order of LaFeO 3-δ (LF), La 0.8 Sr 0.2 FeO 3-δ (LSF-0.2), La 0.5 Sr 0.5 FeO 3-δ (LSF-0.5), SrFeO 3-δ (SF), and La 0.2 Sr 0.8 FeO 3-δ (LSF-0.8). We establish a direct correlation between the enhancement in the specific activity and the amount of surface oxygen vacancies as well as the surface Fe oxidation states. The improved specific activity for LSF-0.8 is clearly linked to the optimum amount of surface oxygen vacancies and surface Fe oxidation states. We also find that the OER performance stability is a function of the crystal structure and the deviation in the surface La and/or Sr composition(s) from their bulk stoichiometric compositions. The cubic structure and lower deviation, as is the case for LSF-0.8, led to a higher OER performance stability. These surface performance relations provide a promising guideline for constructing efficient water oxidation.

Because of their structural and compositional flexibility, perovskite oxides represent an attractive alternative electrocatalyst class to precious metals for the oxygen reduction reaction (ORR); an important reaction in fuel cells and metal–air batteries. Partial replacement of the original metal cation with another cation, namely, doping, can be used to tailor the ORR activity of perovskite, for which a metal has been exclusively used as the dopant component in the past. Herein, phosphorus is proposed as a non‐metal dopant for the cation site to develop a new perovskite family with the formula of La0.8Sr0.2Mn1−xPxO3−δ (x=0, 0.02, 0.05, and 0.1; denoted as LSM, LSMP0.02, LSMP0.05, and LSMP0.1, respectively). Powder XRD patterns reveal that the solubility of phosphorus in the perovskite structure is around 0.05. Rotating ring‐disk electrode experiments in the form of linear‐sweep voltammetry scans demonstrated the best ORR performance for LSMP0.05, and also revealed close to a four‐electron ORR pathway for all four compositions. A chronoamperometric test (9000 s) and 500 cycle accelerated durability test demonstrated higher durability for LSMP0.05 relative to that of LSM and the commercial 20 wt % Pt/C catalyst. The higher ORR activity for LSMP0.05 is attributed to the optimised average valence of Mn, as evidenced by combined X‐ray photoelectron spectroscopy and soft X‐ray absorption spectroscopy data. Doping phosphorus into perovskites is an effective way to develop high‐performance electrocatalysts for ORR.

In this work, we characterized and tested the oxygen permeation properties of BaCo 0.85 Bi 0.05 Zr 0.1 O 3-d (BCBZ) hollow fibre membranes fabricated by a combined phase inversion for spinning and sintering route using polyetherimide (PEI) as the polymer binder. The powder X-ray diffraction results showed that the BCBZ powder for spinning had to be calcined at around 950 °C to form a hexagonal phase structure, while the hollow fibre precursors were sintered at 1150–1200 °C to form the cubic perovskite structure for oxygen permeation. It displayed the highest oxygen flux of 7.3 cm 3 (STP) cm -2 min -1 at 950 °C under an air/He gradient. The theoretical correlation of the oxygen fluxes at different operating conditions showed that the oxygen permeation through BCBZ fibre was limited by surface exchange reactions. Carbon dioxide (CO 2 ) resistance of BCBZ hollow fibre was tested by exposing it to alternating different sweep gas containing helium (He), 20% CO 2 in He, 80% CO 2 in He, and pure He. Despite the significant reduction in oxygen fluxes upon subjected to CO 2 -containing sweep gases due to the strong CO 2 sorption on the membrane surface, no permanent damage on the membrane was detected and the original flux could be recovered at the end of the 105-h test once the sweep gas was switched back to helium. This result clearly highlights the high CO 2 resistance of BCBZ hollow fibre membrane due to the presence of Zr 4+ with higher acidity than Co 2+ in BCBZ perovskite lattice. High CO 2 tolerance enables the membrane use as membrane reactors for more advanced applications where the presence of CO 2 -containing atmosphere is unavoidable.

BACKGROUND: To date, none of the existing techno-economic analyses on natural gas dehydration via absorption using triethylene glycol takes into consideration the profit assessment. This work addresses this shortcoming by developing a techno-economic framework that evaluates the economic feasibility of three different dehydration processes, i.e., conventional dehydration process, stripping gas dehydration process using sale gas, and stripping gas dehydration process using nitrogen, which can meet the maximum water dew point requirement set by local authorities (e.g., Malaysia) for pipeline-transported natural gas. RESULTS: Our techno-economic analyses reveal that the maximum water dew point specification of -25 °C can only be achieved by using a stripping gas dehydration process that consumes more than 260 Nm3 h-1 of sale gas or 435 Nm3 h-1 of nitrogen. In particular, the use of sale gas as stripping gas with an optimum flow rate of 260 Nm3 h-1 generates the highest annual net profit margin, of about $29 million. Such a profit margin is higher with respect to the use of nitrogen as stripping gas and the conventional dehydration process by about $1.6 million and $300 000, respectively. The minimum water dew point specification of 5 °C, on the other hand, can be achieved by all three analysed dehydration processes. CONCLUSION: The use of sale gas as stripping gas becomes more justifiable economically relative to the conventional dehydration process and the other alternative (the use of nitrogen as stripping gas) and when a low water dew point specification of -25 °C is required for natural gas. © 2018 Society of Chemical Industry.

© 2018 Curtin University and John Wiley & Sons, Ltd. Dual-phase membrane is an attractive concept that combines the advantages of two different phases into single membrane matrix. The recently reported significant enhancement of oxygen surface kinetics on the La0.8Sr0.2CoO3-d (LSC)/(La0.5Sr0.5)2CoO4+d (LSC214) hetero-interface due to the formation of fast oxygen transport paths along hetero-interface is adopted into dual-phase membrane to achieve enhanced oxygen permeability. The 1300°C sintered LSC/LSC214 (4:1 weight ratio) hollow fiber displayed a maximum oxygen flux of 3.35 ml·min-1·cm-2 at 900°C and 200 ml min-1 helium sweep gas flow rate, which represents up to 80% enhancement relative to that of the 1300°C sintered LSC hollow fiber at the same experimental condition. Such enhancement is enabled by the enlargement of triple phase boundaries to larger areas across the membrane surface for dual-phase case as confirmed by the significantly lower area specific resistance for LSC/LSC214|Ce0.8Sm0.2O1.9 (SDC)|LSC/LSC214 relative to LSC|SDC|LSC symmetrical cell between 600°C and 800°C. This nominal dual-phase LSC/LSC214 hollow fiber also showed very stable fluxes of 3.3 and 2.3 ml·min-1·cm-2 during 300-hr permeation test at 900°C and 850°C, respectively.

© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Hydrogen production from renewable electricity relies upon the development of an efficient alkaline water electrolysis device and, ultimately, upon the availability of low cost and stable electrocatalysts that can promote oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Normally, different electrocatalysts are applied for HER and OER because of their different reaction intermediates and mechanisms. Here, the synthesis of a heterostructured CoP@a-CoOx plate, which constitutes the embedded crystalline cobalt phosphide (CoP) nanoclusters and amorphous cobalt oxides (CoOx) nanoplates matrix, via a combined solvothermal and low temperature phosphidation route is reported. Due to the presence of synergistic effect between CoP nanoclusters and amorphous CoOx nanoplates in the catalyst, created from the strong nanointerfaces electronic interactions between CoP and CoOx phases in its heterostructure, this composite displays very high OER activity in addition to favorable HER activity that is comparable to the performance of the IrO2OER benchmark and approached that of the Pt/C HER benchmark. More importantly, an efficient and stable alkaline water electrolysis operation is achieved using CoP@a-CoOx plate as both cathode and anode as evidenced by the obtainment of a relatively low potential of 1.660 V at a 10 mA cm-2current density and its marginal increase above 1.660 V over 30 h continuous operation.

© 2018 Elsevier B.V. Oxygen demand has continuously increased given its indispensable role as a raw material in various large-scale industries and clean energy production. The present cryogenic and pressure swing adsorption (PSA) technologies are either energy intensive or are unable to produce very high purity oxygen. Mixed ionic-electronic conducting (MIEC) membrane is a promising alternative technology to produce high-purity oxygen above 700 °C. The main attraction of MIEC membranes lies in the fact that only oxygen can permeate through the membrane under the presence of oxygen partial pressure driving force that endows this technology 100% oxygen selectivity; giving 99.99% pure oxygen. The past two decades has observed rapid progress in the research and development of dense MIEC ceramic membrane technology, mainly along the materials science and engineering direction that seeks to maximise the oxygen permeation flux. Modelling serves as an essential aid to support the experimental progress, mainly to simulate and predict the experimental results and behaviour and to provide insights on the effect of design and operation variables. This review seeks to cover the advances in the oxygen permeation modelling studies over the past two decades by discussing the existing models, their applications in oxygen permeation process, and their limitations as well as the future direction.

© 2018 Elsevier B.V. The glycol purity limit in conventional absorption-based natural gas dehydration process has led to the significant water vapour presence in the supposedly dry product gas. Several alternative processes have been developed to overcome this limitation that includes stripping gas injection using nitrogen, a portion of dry product gas, or volatile hydrocarbon (DRIZO process), stripping gas modified with Stahl column, and Coldfinger technology. This review summarises these different processes and elaborates on their mechanisms, process flow diagram, advantages, drawbacks, and current statuses. Relevant works from 1991 to 2017 were compiled and the existing gaps were highlighted as recommendation for future work.

© 2018 Elsevier B.V. CO2-resistant perovskite cathode has a significant role in solid oxide fuel cell (SOFC) application particularly for operation in an air atmosphere contains higher than normal amount of CO2such as in single-chamber SOFC (SC-SOFC). This work features a systematic study of the electrochemical performance of SrCo0.8Nb0.1Ta0.1O3-d(SCNT)-Ce0.9Gd0.1O2-d(GDC) composite cathode under CO2exposure for SOFC operation in low-temperature (LT, 500 °C and below) and intermediate-temperature (IT, 500–700 °C) ranges. The complementary results from powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, in situ high temperature XRD, electrochemical impedance spectroscopy, and the single cell test show that SCNT-GDC cathode exhibit slightly lower electrochemical performance but higher CO2resistance than SCNT, which enables practical SOFC application. At 550 °C, SCNT-GDC-based single cell has a peak power density of 630 mW cm-2and reduces to a stable power density of 525 mW cm-2after exposure to air containing 1 vol% CO2for 2 h. The collective characterization and electrochemical data presented here highlight the potential of SCNT-GDC composite cathode for use in SC-SOFC and to enhance the performance stability in LT and IT-SOFCs.

Hydrogen is considered a fuel of the future due to its diversified supply and zero greenhouse gas emission. The application of advanced membrane technology for hydrogen separation within the larger hydrogen production process context can substitute the use of more expensive and energy intensive cryogenic distillation and pressure swing adsorption technologies. This review overviews the basic aspects and progresses in perovskite-based proton conducting hydrogen separation membranes. Different configurations such as symmetric, asymmetric, hollow fiber, and surface modified perovskite membranes with various compositions are discussed and summarized. The challenges and future directions of such membranes are also elaborated.

The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portray a concerning image of our contemporary security of liquid transportation fuels in the event of a global crisis. Despite a vast amount of natural gas resources we have and the huge economic incentive, the conversion for gas-to-liquid fuels or chemicals is still very limited due to the high technological complexity and capital cost for facilities. However, with the anticipated depletion of liquid petroleum and the soaring price of crude oil, the conversion of natural gas to liquid feedstock or fuels will become more and more important. Higher alcohols are important feedstocks for chemical and pharmaceutical industries and have wide applications as the potential fuel additives or hydrogen carriers for fuel cells for clean energy delivery. There is a long-standing interest for higher alcohols synthesis from syngas, an important Fischer-Tropsch technology for natural gas conversion. The purpose of this article is to provide readers with an extensive account on catalytic higher alcohols synthesis from syngas using various catalysts, reviewed from a unique perspective-clarification of the active centers and reaction pathways. In light of the different sources to provide the active centers, three major classes of catalysts in terms of monometallic, bimetallic and trimetallic /multimetallic catalysts have been systemically reviewed and their respective performances are carefully compared. Finally, future works proposed to improve the catalyst design are described.

An abundant, highly active, and durable oxygen evolution reaction (OER) electrocatalyst is an enabling component for a more sustainable energy future. We report, herein, a molybdenum and niobium codoped B-site-ordered double perovskite oxide with a compositional formula of Ba2CoMo0.5Nb0.5O6-d(BCMN) as an active and robust catalyst for OER in an alkaline electrolyte. BCMN displayed a low overpotential of 445 mA at a current density of 10 mA cm-2disk. BCMN also showed long-term stability in an alkaline medium. This work hints toward the possibility of combining a codoping approach with double perovskite structure formation to achieve significant enhancement in the OER performance.

Large-scale utilization of hydro, solar, or wind-based electrochemical water splitting relies on the availability of low cost, highly active oxygen evolution reaction (OER) catalyst. Transition metal-containing perovskite oxide is attractive in this regard. The OER on such perovskite oxide in an alkaline solution is nonetheless often limited by proton transfer step. To overcome such limitation, here we apply mixed protonic-electronic conductor BaCo0.8-xFexZr0.1Y0.1O3(x = 0, 0.2, and 0.4) as an OER catalyst. Among these three, BaCo0.8Zr0.1Y0.1O3(BC0.8ZY) in particular shows the lowest OER overpotential, the lowest Tafel slope, the highest OER mass activity, and the highest OER specific activity, which surpass those of Ba0.5Sr0.5Co0.8Fe0.2O3-d(BSCF) benchmark. Using O2-temperature programmed desorption, impedance spectroscopy, and O1s X-ray photoelectron spectroscopy, we attribute such superior OER performance to the highest oxygen desorption capacity, the lowest charge transfer resistance, and the highest hydroxide species content for BC0.8ZY. We also demonstrate that the OER current of BC0.8ZY exhibits a first-reaction order dependence to the solution pH between 12.5 and 14, which confirms its proton transfer rate-determining step.

© 2017 Elsevier Ltd. We reported the direct electrochemical hydrogen peroxide detection on three-dimensionally ordered macroporous SmCoO 3 (3DOM-SmCoO 3 ) perovskite oxide electrode synthesized via a poly (methyl methacrylate) (PMMA) colloidal crystal templating route. The low-cost and simple 3DOM-SmCoO 3 sensor not only overcome the various disadvantages of enzyme- and noble metal-based sensors but also display a superior sensing performance for H 2 O 2 detection. More importantly, using 800 nm PMMA microspheres, a hexagonally ordered macroporous crystalline structure can be created, which features large surface area (20.14 m 2 g -1 ) and large, open, interconnected channels for facile reactants and ions diffusions. The resultant 3DOM-SmCoO 3 synthesized using 800 nm PMMA microspheres template (3D-SC-800) displayed higher sensitivity (715 and 460 µA mM -1 cm -2 ), lower limit of detection (0.004 µM), larger detection linear range (0.1–10,000 µM), and higher selectivity in the presence of interfering species (i.e., glucose, ascorbic acid, dopamine, and uric acid), for H 2 O 2 detection, relative to SmCoO 3 (SC) and SmCoO 3 synthesized using 200 nm PMMA template (3D-SC-200). Our comprehensive electrochemical characterization attributes the superior H 2 O 2 electrooxidation performance of 3D-SC-800 to its fast electron transfer kinetics and diffusion rate. What we demonstrated here bolsters the future opportunity to harness ordered macroporous perovskite oxide-based materials for highly active and selective non-enzymatic H 2 O 2 detection.

© 2018 Elsevier B.V. The efficient oxidative removal of persistent organic components in wastewater relies on low-cost heterogeneous catalysts that offer high catalytic activity, stability, and recyclability. Here, we designed a series of nanostructured Co-Mn containing perovskite catalysts, LaCo 1-x Mn x O 3+d (LCM, x = 0, 0.3, 0.5, 0.7, and 1.0), with over-stoichiometric oxygen (d > 0) to show superior catalytic activity for the degradation of a variety of persistent aqueous organic pollutants by activating peroxymonosulfate (PMS). The nature of LCM for catalysis was comprehensively investigated. A “volcano-shaped” correlation was observed between the catalytic activity and electron filling (e g ) of Co in LCM. Among these compounds, LaCo 0.5 Mn 0.5 O 3+d (LCM55) exhibited an excellent activity with e g = 1.27. The high interstitial oxygen ion diffusion rate (D O 2- = 1.58 ± 0.01 × 10 -13 cm 2 s -1 ) of LCM55 also contributes to its catalytic activity. The enhanced stability of LCM55 can be ascribed to its stronger relative acidity (3.22). Moreover, an increased solution pH (pH = 7) generated a faster organic degradation rate and a decrease in metal leaching (0.004 mM) for LCM55 perovskite, justifying it as a potential material for environmental remediation.

© 2017 Elsevier B.V. Mixed conducting perovskite membranes have attracted much research interest for use in air separation. However, the application of perovskite hollow fiber membranes is limited by their brittleness. Herein, the fiber bundling in a perovskite matrix is reported to overcome the physical weakness of the individual perovskite hollow fiber membranes. This has been achieved by binding these hollow fibers into one matrix using a porous binder made from the same membrane material, i.e., La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d (LSCF) perovskite. The bending force for one individual LSCF hollow fiber is 2.18 N for a fixed length of 4 cm; in contrast, the bending forces for the LSCF bundle in the same length including 3, 5, 8, and 10 single LSCF hollow fibers are 6.80, 11.77, 23.97, and 39.02 N, respectively. The membrane bundle was evaluated for air separation using a sweep gas mode by passing the air in the shell side and a rgon through the fiber lumen operated from 800 to 1000 °C. The oxygen flux through the single LSCF hollow fiber at 950 °C was 0.26 mL cm -2 min -1 (standard conditions) but the bundle gave a higher flux improved by 76% up to 0.46 mL cm -2 min -1 under similar testing conditions due to the porous matrix with enhanced surface reaction kinetics. The resultant membrane bundle demonstrates exceeding performance for air separation in terms of high oxygen flux, mechanical strength, and thermal stability for an easy scale-up.

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduce the cost and increase the lifetime, which relies upon the development of a cathode component with high oxygen reduction reaction (ORR) activity at a lower temperature. Herein, we report the characterization of high-performance BaSc x Co 1-x O 3-d (x=0, 0.125, 0.25, and 0.375) perovskite SOFC cathodes. Unlike BaCoO 3-d , which adopts 2H-hexagonal perovskite structure, the replacement of 25mol% of Co with Sc stabilizes the cubic structure, which also leads to the significant reduction in area specific resistances and their activation energies between 650 and 500°C (for BaSc 0.25 Co 0.75 O 3-d ) relative to the non-doped BaCoO 3-d . In this temperature range, BaSc 0.25 Co 0.75 O 3-d displayed a remarkably high ORR activity compared to Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d (BSCF), the current cathode benchmark. We attribute such superior ORR performance to the higher oxygen non-stoichiometries of BaSc 0.25 Co 0.75 O 3-d relative to BSCF, which also translates to the higher oxygen bulk diffusion and surface exchange coefficients for the former compared to the latter. As a result, a single fuel cell based on an anode-supported 20µm thick samarium-doped ceria electrolyte and BaSc 0.25 Co 0.75 O 3-d cathode achieved a very high peak power density of 1723mWcm -2 at 650°C. We also demonstrated the possibility to increase the ORR activity of the BaSc 0.25 Co 0.75 O 3-d cathode by impregnation of a low amount of silver.

In this work, hydrogen (H 2 ) permeation fluxes through 230 nm-thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H 2 permeation model. H 2 fluxes through such GO-YSZ hollow fiber membrane increased from 4.83 × 10 -8 mol cm -2 s -1 to 2.11 × 10 -7 mol cm -2 s -1 with temperature rise from 20 to 100 °C. The activation energy of H 2 permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H 2 fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H 2 partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications.

© 2018 Institution of Chemical Engineers Oxygen-selective perovskite hollow fiber membrane can be used to obtain an effective oxygen separation from air at high temperature (above 700 °C) for large scale application. Here, we display that oxygen permeation fluxes of La 0.6 Sr 0.4 CoO 3 (LSC 113 ) hollow fiber membrane was enhanced by macrostructure modification and (La,Sr) 2 CoO 4 (LSC 214 ) surface decoration. By changing the cross-section macrostructure from sandwich structure (for LSC-a fiber) to asymmetric structure (for LSC-b fiber), the oxygen flux was improved by up to 3.6-fold. Applying porous LSC 214 decoration on LSC 113 furthermore enhanced the oxygen fluxes for LSC-a and LSC-b, by up to 6.8-fold and 1.9-fold, respectively.

© 2018 Elsevier B.V. CO2-resistant oxygen selective ceramic membranes have wide applications in clean energy delivery and green chemical synthesis. In this work, CO2erosion and O2permeation behavior of BaCo0.85Bi0.05Zr0.1O3-d(BCBZ) perovskite hollow fibre membranes are investigated. The BCBZ hollow fibre was fabricated by a combined phase-inversion and sintering technique. Experimental results indicate that the O2permeation flux can reach 3.07 mL cm-2min-1at 1000 °C under the air/Ar gradient whereas the O2flux reduced significantly in CO2presence depending on the CO2concentration in the feed gas or sweep gas. The deteriorating effect of CO2on the membrane performance in the feed side was more significant than when it was present in the permeate side. One of the BCBZ hollow fibre samples had been tested for more than 190 h; undergoing six thermal cycles from 700 to 1000 °C in different CO2-containing gas streams. With high CO2concentrations up to 10 vol.% in both feed and permeate sides, no permeation was observed due to the strong CO2adsorption on the membrane surface; however, the O2flux can be completely recovered once the CO2became absent in the gas atmosphere. When the membrane test was continued up to 180 h, the O2flux value cannot be fully recovered and 9.6% of the original flux value was lost due to the carbonate salt formation. To get the quantitative information on the erosion rate, more membrane samples had been tested from 1 to -8 days in 10 vol.% CO2at 900 °C under the oxygen permeating conditions. We found that the erosion rate was relatively fast at the beginning stage with corrosion depth up to 3 µm for the first 3 days but slowed down to 1 µm depth for the subsequent 5 days. The significantly reduced erosion rate is due to the higher O2concentration in the locally uncontaminated membrane area (without the carbonate deposition). Inspired by such findings, one future strategy to protect the membrane is to deposit the membrane surface using more robust

© 2017 Elsevier B.V. Hydrogen (H 2 )-selective proton conducting perovskite membrane is the low cost alternative of palladium membrane. In this work, we report the preparation of an A-site deficient Zr-doped proton conductor composition of Ba 0.95 Ce 0.85 Tb 0.05 Zr 0.1 O 3-d (BCTZ) in the dual-layer hollow fiber configuration consisting of Ni-BCTZ inner porous layer and BCTZ outer dense layer, denoted as BCTZ/Ni-BCTZ hollow fiber via co-spinning, co-sintering, and reduction (in hydrogen) processes. The presence of Zr 4+ in BCTZ perovskite lattice leads to higher CO 2 resistance for BCTZ relative to Ba 0.95 Ce 0.95 Tb 0.05 O 3-d (BCT) as revealed by their CO 2 -temperature programmed desorption results. H 2 permeation flux of dual-layer BCTZ/Ni-BCTZ hollow fiber reaches a maximum of 0.41 mL min -1 cm -2 at 900 °C. When CO 2 was introduced in the permeate side, H 2 permeation flux was enhanced with respect to the CO 2 -absent case, which is attributed to the presence of reverse water-gas shift reaction that consumes the permeated H 2 to produce carbon monoxide and water. The dual-layer BCTZ/Ni-BCTZ hollow fiber showed stable H 2 permeation fluxes when operated at 800 °C in CO 2 -containing permeate atmosphere for 25 days. Its original morphology and structure were retained following this long term operational test; highlighting its potential use for H 2 separation in CO 2 -containing reactions and processes.

Fluorite oxide is an excellent material candidate for oxygen production from air with potentials in oxyfuel combustion for clean energy delivery and ceramic membrane reactor for chemical synthesis given its desirable CO 2 resistance and high oxygen ionic conductivity. However, its limited electronic conductivity restricts its practical applications in these technologies. In this work, we probed the use of transition metal (Co, Fe, and Cu) oxides as the sintering aid and the electronic conductivity enhancement agent. The presence of these transition metal oxides can lower the sintering temperature of GDC up to 300 °C. Oxygen fluxes were also enhanced in their presence; reaching the highest value of 0.112 mL min - 1 cm - 2 at 900 °C through a 0.8 mm-thick GDC membrane containing 2 mol% Co. Among the three sintering aids, C oO provided the maximum enhancement effect for oxygen fluxes. Such enhancement was primarily sourced from the improved electronic conductivities and the modified element distribution across the grain boundaries. In overcoming the electronic conductivity limitation of a predominantly ionic conducting phase, the use of sintering aid offers an attractive non-precious metal-based alternative that enables competitive performance enhancement with respect to the external short-circuit decoration.

CO 2 -resistant oxygen selective ceramic membranes show potential to be utilized in clean combustion and membrane-based reactions for greener chemical synthesis. In real applications, such membranes should have high mechanical strength as well as high oxygen flux and high stability in a CO 2 -containing atmosphere. In this work, a (La 0.8 Ca 0.2 ) 1.01 FeO 3-d (LCF) perovskite hollow fiber membrane was developed. Its oxygen permeation behavior was tested in different gas atmospheres, i.e., helium and carbon dioxide. Compared to the typical perovskite hollow fibers such as La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d (BSCF), the LCF hollow fiber displayed the highest mechanical strength as well as the largest oxygen fluxes and stability in a CO 2 -containing atmosphere, highlighting its attractiveness in oxyfuel combustion and syngas production from methane.

Hydrogen proton conducting perovskite-based hollow fiber membrane is an attractive hydrogen separation technology that shows higher stability relative to Pd-based membranes above 800 °C. One of the challenges towards high hydrogen (H2) permeability on such proton conducting membrane is enabling simultaneously high proton and electronic conductivities to be achieved in single phase membrane. This has been addressed by developing dual-phase membrane. Here, we showed another promising approach, i.e., exploitation of beneficial phase reactions to create new conductive phases along the grain boundaries. By doping up to 8 wt. % magneli Ti4O7 into SrCe0.9Y0.1O3-d (SCY), Ce-doped SrTiO3 and Y-doped CeO2 were created in-between SCY grains. Electrical conductivity tests confirmed higher conductivities for 5 and 8 wt. % Ti4O7-doped SCY relative to SCY between 750 and 950 °C. These higher conductivities manifested into higher H2 permeation fluxes for the doped SCY membranes. The highest flux of 0.17 mL min-1 cm-2 was observed for 5 wt. % Ti4O7-doped SCY at 900 °C when 50 vol. % H2/He and 100 vol. % N2 were used in the feed side and the permeate side, respectively. This is much higher than the flux of 0.05 mL min-1 cm-2 obtained from SrCe0.9Y0.1O3 membrane at identical condition. More essential is the fact that the doped SCY membranes displayed catalytic activity for the reverse water-gas shift (RWGS) reaction which consumed H2 in the permeate side; increasing the H2 flux up to 0.57 mL min-1 cm-2 at 900 °C. The 5 wt. % Ti4O7-doped SCY furthermore showed stable flux for more than 140 h at 850 °C despite the formation of minor amount of SrCO3 in H2-CO2-containing atmosphere; highlighting its potential application as membrane reactor for RWGS or dehydrogenation reaction.

Perovskite-like oxides SrCo1−xTixO3−δ (SCTx, x = 0.1, 0.2, 0.4, 0.6) were used as heterogeneous catalysts to activate peroxymonosulfate (PMS) for phenol degradation under a wide pH range, exhibiting more rapid phenol oxidation than Co3O4 and TiO2. The SCT0.4/PMS system produced a high activity at increased initial pH, achieving optimized performance at pH ≥ 7 in terms of total organic carbon removal, the minimum Co leaching and good catalytic stability. Kinetic studies showed that the phenol oxidation kinetics on SCT0.4/PMS system followed the pseudo-zero order kinetics and the rate on SCT0.4/PMS system decreased with increasing initial phenol concentration, decreased PMS amount, catalyst loading and solution temperature. Quenching tests using ethanol and tert-butyl alcohol demonstrated sulfate and hydroxyl radicals for phenol oxidation. This investigation suggested promising heterogeneous catalysts for organic oxidation with PMS, showing a breakthrough in the barriers of metal leaching, acidic pH, and low efficiency of heterogeneous catalysis.

Oxygen selective ceramic membranes have many important applications, not only for air separation but also as membrane reactors for cost-effective chemical synthesis. However, the prerequisite to realize these potentials is their stability in the presence of acid gases of CO2 and reducing atmosphere containing H2 and CH4. This work seeks to validate the applicability of robust triple layer hollow fiber membranes consisting of (Ag+YSZ)/YSZ/La0.8Sr0.2MnO3-δ (LSM)+YSZ to separate O2 from air in the presence of these unavoidable gases for more advanced applications. To prepare the triple layer hollow fiber, the dual-layer fiber was firstly synthesized via a combined phase inversion and sintering method where the dense YSZ layer was present on top of the porous LSM-YSZ layer. We further deposited either porous Ag or its mixture with YSZ layer above the dense YSZ surface. The final fiber consists of three layers in sequence from outside surface to inside surface of Ag+YSZ/YSZ/LSM+YSZ. The dense central YSZ layer acts as the ionic conducting phase to prevent gas diffusion while the other two porous layers serve as the electronic conducting phase with catalytic effect to enhance the surface reaction kinetics. To overcome the electronic conductivity limitation of YSZ, silver (Ag) short circuit paste was additionally used to seal the membrane and electronically connect the outer and inner surfaces for electron shuttle for the two surface O2 exchange reactions. Ag-YSZ coated fiber performed better than Ag coated fiber and showed increasing fluxes from 0.1 to 0.53 mL min−1 cm−2 upon increasing temperature from 700 to 900 °C. The O2 fluxes remained constant irrespective of changing the sweep gas from pure He to its mixtures containing CO2, H2, or CH4; mirroring the membrane robustness to tolerate these gases at high temperatures.

Hydrogen share in the energy market has increased significantly in line with greater demand for zero emission fuel and the development of novel production routes via renewable resources. The application of mixed protonic-electronic conducting (MPEC) ceramic membrane within the hydrogen production process is an innovative route that enables high purity hydrogen production with low cost. This review provides readers a brief summary of the research efforts on MPEC ceramic membrane for hydrogen separation as well as the membrane reactor for hydrogen production and dehydrogenation or hydrogenation reactions. Most of the existing MPEC ceramic membranes come from either a single-phase or a dual-phase membrane. We discuss the working principles, the performances, the advantages and disadvantages, and the main issues of all these membranes. Major emphasis of the review is to cover the literature published in the last ten years since the earlier progress has been well documented by the previously existing reviews. We also put forward recommendations for future research direction in this topic.

Perovskite oxides exhibit potential for use as electrocatalysts in the oxygen evolution reaction (OER). However, their low specific surface area is the main obstacle to realizing a high mass-specific activity that is required to be competitive against the state-of-the-art precious metal-based catalysts. We report the enhanced performance of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF) for the OER with intrinsic activity that is significantly higher than that of the benchmark IrO2, and this result was achieved via fabrication of an amorphous BSCF nanofilm on a surface-oxidized nickel substrate by magnetron sputtering. The surface nickel oxide layer of the Ni substrate and the thickness of the BSCF film were further used to tune the intrinsic OER activity and stability of the BSCF catalyst by optimizing the electronic configuration of the transition metal cations in BSCF via the interaction between the nanofilm and the surface nickel oxide, which enables up to 315-fold enhanced mass-specific activity compared to the crystalline BSCF bulk phase. Moreover, the amorphous BSCF-Ni foam anode coupled with the Pt-Ni foam cathode demonstrated an attractive small overpotential of 0.34 V at 10 mA cm(-2) for water electrolysis, with a BSCF loading as low as 154.8 µg cm(-2).

© 2017 Curtin University and John Wiley & Sons, Ltd. Refinery hydrogen network problem is highly nonlinear due to the equation that describes the power of new compressor. Most of the previous attempts to linearize this equation have been made by assuming constant suction and discharge pressure while taking the inlet flow rate as a variable. Such assumption may not be practical in real condition because the calculated power requirement for new compressor may not be compatible with the pressure ratio of the selected compressor. This work proposed a new linearization method for the power of new compressor that provides additional degree of freedom by allowing the solver to choose the optimum new compressor(s) that satisfied the pressure requirement of process sinks. Using our proposed model, mixed-integer nonlinear programming (MINLP) formulation can be converted into mixed-integer linear programming. The applicability of our model was validated using two different refinery case studies. Mixed-integer linear programming results obtained using our model require substantially lower computational cost than their MINLP counterparts where at least 60% savings in terms of iteration number and computational processing time were achieved. The approach demonstrated here can be potentially used to approach more complex refinery hydrogen network cases where the initial guess can be obtained from the linearized MINLP problem.