Showing papers in "Industrial & Engineering Chemistry Process Design and Development in 2021"

Catalytic Combustion of Propane over MnNbOx Composite Oxides: The Promotional Role of Niobium

Abstract: Metal-doping is an efficient strategy to develop high-activity composite metal oxides catalysts for VOCs abatement. Herein, MnNbOₓ composite oxides were prepared using niobium element as a modification additive, finding that niobium addition presented a promotional effect on boosting the catalytic activity of MnOₓ for propane combustion. It was demonstrated that niobium insertion into manganese oxides was in favor of the formation of Mn₃O₄ crystalline phase and concurrently caused higher redox ability, more abundant surface oxygen species, and acid sites. All these properties were considered to be crucial parameters for catalytic activity enhancement. Among all, the catalyst of Mn₀.₈₅Nb₀.₁₅Oₓ (simply designated as M₀.₈₅N₀.₁₅) showed the highest propane conversion efficiency and relatively good catalytic durability under CO₂-containing atmospheres. Moreover, the in situ DRIFTs analysis highlighted the important role of surface acidity in the surface catalytic pathways of propane adsorption, activation, and oxidation.

Screening Transition Metals (Mn, Fe, Co, and Cu) Promoted Ni-Based CO2 Methanation Bimetal Catalysts with Advanced Low-Temperature Activities

Abstract: The Ni monometallic catalyst usually exhibits poor CO₂ methanation activity, although its low cost is beneficial for conducting large-scale application in industries Herein, the transition metal (Mn, Fe, Co, and Cu)-doped Ni-based bimetallic catalysts loaded on mesoporous Ce₀₈Zr₀₂O₂ solid solution were prepared to address this challenge in CO₂ methanation We found that the Co-doped catalysts exhibited much higher activity than the corresponding counterparts Therefore, the relationship between the Co/Ni ratio and activity was further investigated to acquire the optimum ratio The obtained catalysts were characterized by various measurements The results demonstrated that doping the second transition metals could promote Ni dispersion and strengthen metal–support interaction Resultantly, serious agglomeration of the metallic active sites was successfully inhibited Besides, we also carried out the in situ diffuse reflectance infrared spectroscopy and online temperature-programmed surface reaction of CO₂ methanation to study the possible reaction intermediates and pathways over the Ni–Co bimetallic catalysts A dynamic study was also conducted to further study the effect of the doped transition metals on the apparent activation energies Besides, the present research also revealed that the Ni–Co synergistic effect significantly improved the low-temperature activity by regulating the reaction intermediates As a result, the Ni–Co bimetallic catalysts supported by mesoporous Ce₀₈Zr₀₂O₂ solid solution were considered as a series of promising and efficient low-temperature CO₂ methanation catalysts

Flexible Electrothermal Laminate Films Based on Tannic Acid-Modified Carbon Nanotube/Thermoplastic Polyurethane Composite

Abstract: Carbon nanomaterials are ideal fillers in composites for electrothermal applications due to their ultrahigh electrical conductivity, thermal conductivity, and excellent mechanical property. In this study, high-performance electrothermal laminate films were prepared by a layer-by-layer process, which used tannic acid-functionalized multiwalled carbon nanotubes as filler and thermoplastic polyurethane as substrate. The prepared electrothermal laminate films exhibit excellent mechanical property, electrical heating property, and high electrothermal performance, which can reach steady-state temperature in about 120 s. Additionally, the maximum steady-state temperature can reach ∼150 °C at 20 V. During 10 different cycles of experiments and 5 h aging time, no significant change in temperature was observed. Moreover, from the results, it is clear that the performance of the samples is related to the amount of filler added and the applied voltage, and we can precisely control the sample performance by regulating the amount of filler addition and applied voltage. We believe that these electrothermal laminate films could be widely used in wearable heating cotton fabric, controllable electric heating module, floor heating, and deicing devices.

Nanofibrous Mats for Particulate Matter Filtration

Abstract: Biomass consumption and fossil fuel combustion are key contributors to particulate matter (PM) pollution, resulting in ecological disturbances, climate change, and an increase in serious global health problems, related to common respiratory and cardiovascular diseases. Strategies have been initiated to curb the filtration of PM. Specifically, nanofibrous mats render high filtration efficiency for removing PM from the gas stream due to their low basis weight, wide area to volume ratio, and small pore size. In this review, we holistically took into account the raw materials and fabrication techniques of nanofibrous filters constituting electrospinning, blow spinning, and natural/freeze-drying. We highlighted the mechanism of PM capture and the basic parameters for PM filtration which entail efficiency removal, pressure drop, quality factor, and reusability. Additionally, challenges in filter cleaning, low airflow rate, and filtration efficiencies, coupled with future perspectives using biobased nanofiber mats still need to be addressed going forward.

Biocrude Upgrading in Different Solvents after Microalgae Hydrothermal Liquefaction

Abstract: Hydrothermal liquefaction of the third-generation biomass represented by microalgae can produce biocrude. However, the directly obtained biocrude has a high heteroatom content and a low higher heating value (HHV), which cannot meet the standards of biofuel. In this work, water-insoluble biocrude which was directly gained from microalgae hydrothermal liquefaction (HTL) was upgraded under four kinds of solvents (i.e., methanol, ethanol, acetone, and H₂O) and one type of catalyst (H₂O + Ru/C) at 240–400 °C for 1 h. The results show that the HHV and C and H contents of upgraded bio-oil increased and the O/C ratio decreased significantly after solvent upgrading. The highest upgraded bio-oil yield appeared in the case of ethanol upgrading and reached the maximum value of 82.8 wt % at 360 °C. The upgraded bio-oil yield of acetone upgrading increased from 45.8 to 68.2 wt % as the temperature increased within 240–400 °C. Also, esterification reactions between alcohol and acid in the supercritical system remarkably reduced the content of carboxyl-containing organic matter.

Sorption and Diffusion of Methane, Carbon Dioxide, and Their Mixture in Amorphous Polyethylene at High Pressures and Temperatures

Abstract: Molecular dynamics (MD) simulations are performed to study the sorption and transport properties of CH₄ and CO₂ in amorphous polyethylene at temperatures from 350 to 600 K and pressures up to 500 bar. The uptake of CH₄ and CO₂ by polyethylene generally increased with increasing pressure and decreasing temperature. However, at high pressures, for example, the uptake of methane by polyethylene increases with temperature. The self-diffusion coefficients of methane and carbon dioxide generally increase with pressure. These results are, in general, consistent with the swelling behavior of the polymer. Interestingly, for the penetrants, the activation barrier of diffusion decreases with pressure. MD simulations are also carried out for the CH₄/CO₂ mixture in amorphous polyethylene. Here, the overall sorption and transport properties were similar to those reported for pure CH₄ and pure CO₂ in polyethylene. The sorption selectivity of CO₂/CH₄ decreases with increasing pressure and temperature and was mostly independent of the bulk mole fraction of methane. Importantly, at high pressures, the mobility of methane found here is higher than that of the corresponding pure methane in polyethylene and the opposite trend is observed in the case of carbon dioxide. These results might be due to the fact that the swelling of the polymer in the presence of carbon dioxide is significantly higher than that in the presence of methane, especially at high pressures. The diffusion and membrane selectivities of carbon dioxide/methane show a similar trend to the sorption selectivity data. Furthermore, the simulation data were in good agreement with the theoretical calculations based on the PC-SAFT equation of state.

SPICE_MARS: A Process Synthesis Framework for Membrane-Assisted Reactive Separations

Abstract: A membrane reactor (MR) combines reaction and separation phenomena in a single unit and offers an energy-efficient, cost-effective, compact, modular, and sustainable design compared to conventional designs. A systematic design framework can yield such benefits of MRs and increase their adoption in the chemical process industry. To this end, we present SPICE_MARS (synthesis and process intensification of chemical enterprises involving membrane-assisted reactive separations), a software prototype for conceptual design, simulation, synthesis, and optimization of MRs for different process applications. At the conceptual level, we can determine whether MR is desired or not and select which species to convert/separate. At the equipment level, we obtain optimal MR configurations considering different flow arrangements, intensification strategies, membrane types, sweep gases, reactor lengths, membrane areas, and catalyst amounts. Additionally, we can generate rank-ordered lists of optimal reactor configurations for different design objectives. These enabling capabilities are demonstrated using two case studies involving methanol synthesis and methane partial oxidation. In both cases, novel MR designs—achieving drastic improvement compared to current industrial practice—are found.

Characterization of 14-Crown-4 Ethers for the Extraction of Lithium from Natural Brines: Synthesis, Solubility Measurements in Supercritical Carbon Dioxide, and Thermodynamic Modeling

Abstract: Improving lithium mining methods is key to furthering lithium’s use as an energy metal. Current mining methods from brines are slow and inefficient and have significant environmental impacts, providing an avenue of research toward developing more effective and less environmentally damaging methods. Supercritical fluid extraction has been evaluated in earlier research for the extraction of metals such as uranium, mercury, and several alkali and earth alkaline metals from aqueous solutions but not for lithium. This study documents the synthesis and preliminary testing of two lithium extractants for possible application in a supercritical carbon dioxide fluid extraction process to recover lithium from natural brines. Based on their high solubility in supercritical carbon dioxide and their desirable structural properties, two 14-crown-4 ethers with different functional groups were selected. In this work, solubility measurements and thermodynamic modeling were carried out to characterize their solubility behavior in the range of P = 100–300 bar with T = 60 °C and T = 85 °C. The main conclusion from this work is the experimental observation of sufficiently high solubilities of the synthesized crown ethers in supercritical carbon dioxide. The highest measured solubility of M14C4, the nonfluorinated 14-crown-4 ether, was 0.30 mol/L at 60 °C and 205 bar, and the highest measured solubility of F14C4, the fluorinated 14-crown-4 ether, was 0.27 mol/L at 60 °C and 285 bar. Another major conclusion was the observed higher solubility of M14C4 than F14C4. We also showed that equation of state modeling provides insight into the factors affecting the crown ether solubility in supercritical carbon dioxide.

Synthesis of C3-Symmetric Triazine-Based Derivatives: Study of their AIEE, Mechanochromic Behaviors, and Detection of Picric Acid and Uric Acid in Aqueous Medium

Abstract: A smart accessible D-A with a tripod shape of triazine derivatives such as TZOME, TZSET, and TZNET was synthesized through simple Suzuki–Miyaura coupling and cyano cyclization reaction. Remarkably, TZNET has excellent optical properties compared to TZOME and TZSET. In particular, TZNET exhibits enhanced emission, induced through aggregation and mechanochromic luminescence. More interestingly, AIEE-fluorescent TZNET has a turnoff fluorescence sensor for picric acid with an LOD of 203 nM and a turn-on sensor for uric acid with an LOD of 209 nM. To the best of our knowledge, this is the first dual-coupled sensor for picric acid and uric acid in an aqueous medium.