(Anna Khlyustova, Nikolay Sirotkin, pp. 513‒521)
Benzoic acid is used in textiles, plastics, chemicals, powders, catalyst, and for wood bleaching. The solutions of benzoic acid are corrosive, toxic and poisonous and they should be removed from water. Plasma in contact with liquids is one of the methods of advanced oxidation processes. Plasma treatment can lead to destruction as well as synthesis processes. It was proved in the experiments with benzoic acid. At the small [Detail] ...
Research results regarding selective catalytic reduction (SCR) of NOx with ethanol and other C1-4 oxygenates as reductants over silver-alumina catalysts are summarized. The aspects of the process mechanism, nature of active sites, role of alumina and silver (especially in the formation of bifunctional active sites), effects of reductants and reaction conditions are discussed. It has been determined that key stages of the process include formation of reactive enolic species, their interaction with NOx and formation of nitroorganic compounds which transform to NCOads species and further to N2. The results obtained over various silver-alumina catalysts demonstrate the perspectives of their application for reducing the level of nitrogen oxides in engine emissions, including in the presence of water vapor and sulfur oxides. Ways to improve the catalysts for the SCR of NOx with C1-4 oxygenates are outlined.
Recently, the performance and fabrication of thin-film thermoelectric materials have been largely enhanced. Based on this enhancement, the thin-film thermoelectric cooler (TEC) is becoming a research hot topic, due to its high cooling flux and microchip level size. To fulfill a thin-film TEC, interfacial problems are unavoidable, as they may largely reduce the properties of a thin-film TEC. Moreover, the architecture of a thin-film TEC should also be properly designed. In this review, we introduced the enhancement of thermoelectric properties of (Bi,Sb)2(Te,Se)3 solid solution materials by chemical vapor deposition, physical vapor deposition and electrodeposition. Then, the interfacial problems, including contact resistance, interfacial diffusion and thermal contact resistance, were discussed. Furthermore, the design, fabrication, as well as the performance of thin-film TECs were summarized.
It has become the top priority for coking industry to rationally use and enlarge coking coal resources because of the shortage of the resources. This review focuses on the potential utilization of oil shale (OS) as a feedstock for coal-blending coking, in which the initial and basic step is pyrolysis. However, OS has a high ash content. If such OS is directly used for coal-blending coking, the coke product will not meet market demand. Therefore, this review firstly summarizes separation and beneficiation techniques for organic matter in OS, and provides an overview on coal and OS pyrolysis through several viewpoints (e.g., pyrolysis process, phenomena, and products). Then the exploratory studies on co-pyrolysis of coal with OS, including co-pyrolysis phenomena and process mechanism, are discussed. Finally, co-pyrolysis of different ranks of coals with OS in terms of coal-blending coking, where further research deserves to be performed, is suggested.
Plasma-assisted oxidation of organic compounds is one of the developing technologies for wastewater treatment. Plasmas effectively accelerate degradation processes due to plasma generated reactive species and ultra-violet radiation. Oxidation of BA in aqueous solutions by the atmospheric pressure glow discharge and underwater diaphragm discharge was studied and monitored by fluorescence and spectrophotometric methods. Discharge type and solution pH affect the formation rates of mono- and dihydroxybenzoic acids. Dihydroxyl derivatives were formed only by glow discharge action. The yields of hydroxyl radical were estimated on the kinetics data for the hydroxylation of benzoic acid. The steps of the hydroxylation processes and further oxidation were described.
A series of PdCu bimetallic catalysts with low Cu and Pd loadings and different Cu: Pd atomic ratios were prepared by conventionally sequential impregnation (CSI) and modified sequential impregnation (MSI) of Cu and Pd for selective hydrogenation of acetylene. Characterization indicates that the supported copper (II) nitrate in the PdCu bimetallic catalysts prepared by MSI can be directly reduced to Cu metal particles due to the hydrogen spillover from Pd to Cu(NO3)2 crystals. In addition, for the catalysts prepared by MSI, Pd atoms can form PdCu alloy on the surface of metal particles, however, for the catalysts prepared by CSI, Pd tends to migrate and exist below the surface layer of Cu. Reaction results indicate that compared with CSI, the MSI method enables samples to possess preferable stability as well as comparable reaction activity. This should be due to the MSI method in favor of the formation of PdCu alloy on the surface of metal particles. Moreover, even Pd loading is super low, <0.045 wt-% in this study, by through adjusting Cu loading to an appropriate value, attractive reactivity and selectivity still can be achieved.
In the last decades, many reports dealing with technology for the catalytic combustion of methane (CH4) have been published. Recently, attention has increasingly focused on the synthesis and catalytic activity of nickel oxides. In this paper, a NiO/CeO2 catalyst with high catalytic performance in methane combustion was synthesized via a facile impregnation method, and its catalytic activity, stability, and water-resistance during CH4 combustion were investigated. X-ray diffraction, low-temperature N2 adsorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, hydrogen temperature programmed reduction, methane temperature programmed surface reaction, Raman spectroscopy, electron paramagnetic resonance, and transmission electron microscope characterization of the catalyst were conducted to determine the origin of its high catalytic activity and stability in detail. The incorporation of NiO was found to enhance the concentration of oxygen vacancies, as well as the activity and amount of surface oxygen. As a result, the mobility of bulk oxygen in CeO2 was increased. The presence of CeO2 prevented the aggregation of NiO, enhanced reduction by NiO, and provided more oxygen species for the combustion of CH4. The results of a kinetics study indicated that the reaction order was about 1.07 for CH4 and about 0.10 for O2 over the NiO/CeO2 catalyst.
Catalysts for the desulfurization of gasoline samples were synthesized via the immobilization of well-dispersed phosphotungstic acid (HPW) on Mobil composition of matter-twenty-two (MWW) zeolite. Characterization results indicated that these catalysts possess a mesoporous structure with the retention of the Keggin structure of immobilized HPW. Relevant reaction parameters inﬂuencing sulfur removal were systematically investigated, including HPW loading, catalyst dosage, temperature, initial S-concentration, molar ratio of oxidant to sulfide (O/S), volume ratio of MeCN to model oil (Ext./oil), and sulfide species. The 40 wt-% HPW/MWW catalyst exhibited the highest catalytic activity with 99.6% dibenzothiophene sulfur removal from prepared samples. The 40 wt-% HPW/MWW catalyst was recycled four times and could be easily regenerated. Finally, as an exploratory study, straight-run-gasoline and fluid catalytic cracking gasoline were employed to accurately evaluate the desulfurization performance of 40 wt-% HPW/MWW. Our research provides new insights into the development and application of catalysts for desulfurization of gasoline.
Controlled growth of Bi2WO6 nanorods with exposed [0 0 1] facets and the fabrication of an Fe3O4-Bi2WO6 magnetic composite by a microwave-assisted polyol process, were achieved in this study. The adsorptivity and photocatalytic performance of the composite toward sunset yellow dye degradation were greatly enhanced by the β-cyclodextrin cavities on its surface, firmly anchored through a cetyltrimethylammonium bromide linkage. A series of examinations and characterizations were carried out to determine the influence of various factors on the morphological modulation-photocatalytic behavior of the pure Bi2WO6 prior to final functionalization. Changing the pH of the precursor solution impacted the formation of 0D, 2D, and 3D structures; however, the presence of hexamethylenetetramine surfactant induced the development of 1D nanorod structure. A reasonable crystal growth mechanism was proposed to elucidate the formation process. Conversely, the mechanism of the activity enhancement of β-cyclodextrin functionalized Fe3O4-Bi2WO6, compared to that of the non-functionalized samples, could be realized with the assistance of chemical trapping experiments on sunset yellow, and was confirmed on the colorless antibiotic (sulfamethoxazole). The high performance and durability of this composite can be attributed to the facet-dependent activity, large adsorption capacity due to inclusion interactions, enhanced visible light absorption, and efficient charge separation.
The room temperature synthesis of ZIF-8 micro- and nano-particles was investigated using a mixed methanol-water solvent system. ZIF-8 particles of good quality and high crystallinity were obtained. Response surface methodology was used to determine the effect of the synthesis conditions on the ZIF-8 yield, particle size distribution, and mean particle size. The ligand/metal salt molar ratio followed by the amount of sodium formate (the deprotonating agent) and then the amount of water (i.e., the composition of the mixed solvent) respectively had the largest effects on both the ZIF-8 yield and particle size. Results showed that mixing of solvents with different strengths in producing ZIF-8 crystals is a practical method to size-controlled synthesis of ZIF-8 particles. This method is more favorable for industrial-scale ZIF-8 synthesis than using excess amounts of ligands or chemical additives (like sodium formate). In addition, ZIF-8 samples with different mean particle sizes (100, 500, and 1000 nm) were used for CO adsorption and the mid-sized ZIF-8 particles had the highest adsorption capacity.
A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo2S4 material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo2S4 material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo2S4 material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g−1, the CuCo2S4 material shows an extremely high initial discharge capacity of 2510 mAh·g−1, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g−1. Furthermore, the discharge capacity can reach 269 mAh·g−1 at a current of 2000 mA·g−1. More importantly, when the current density comes back to 200 mA·g−1, the discharge capacity could be recovered to 1436 mAh·g−1, suggesting an excellent capacity recovery characteristics.
In the present work, ball milling was applied for the pretreatment of lignocellulose to obtain high conversion and bio-oil yield in supercritical ethanol. Ball milling substantially decreased the crystallinity and particle size of lignocellulose, thereby improving its accessibility in ethanol solvent. An increased bio-oil yield of 59.2% was obtained for the ball milled camphorwood sawdust at 300°C, compared with 39.6% for the original lignocellulose. Decreased crystallinity significantly benefited the conversion of the cellulose component from 60.8% to 91.7%, and decreased particle size was beneficial for the conversion of all components. The obtained bio-oil had a high phenolic content, as analyzed by gas chromatography-mass spectrometry. Methoxylation and retro-aldol condensation were observed during alcoholysis, and the reaction pathways of lignocellulose in supercritical ethanol were attributed to the action of free radicals.
Steam methane reforming (SMR)-based methanol synthesis plants utilizing a single CO2 feed represent one of the predominant technologies for improving methanol yield and CO2 utilization. However, SMR alone cannot achieve full CO2 utilization, and a high water content accumulates if CO2 is only fed into the methanol reactor. In this study, a process integrating SMR with dry methane reforming to improve the conversion of both methane and CO2 is proposed. We also propose an innovative methanol production approach in which captured CO2 is introduced into both the SMR process and the recycle gas of the methanol synthesis loop. This dual CO2 feed approach aims to optimize the stoichiometric ratio of the reactants. Comparative evaluations are carried out from a techno-economic point of view, and the proposed process is demonstrated to be more efficient in terms of both methanol productivity and CO2 utilization than the existing stand-alone natural gas-based methanol process.
Novel PdCoAg/C nanostructures were successfully synthesized by the polyol method in order to develop electrocatalysts, related to the glucose sensor performance of the high glycemic index in beverages. The characterization of this novel PdCoAg/C electrocatalyst was performed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy equipped with energy dispersive X-ray. The characterization results revealed that electronic state of the PdCoAg/C electrocatalyst was modified by the addition of the third metal. The electrochemical performances of the sensor were investigated by cyclic voltammetry and differential pulse voltammetry. The prepared enzyme-free sensor exhibited excellent catalytic activity against glucose with a wide detection range (0.005 to 0.35 mmol∙L−1), low limit of detection (0.003 mmol∙L−1), high sensitivity (4156.34 µA∙mmol−1∙L∙cm−2), and long-term stability (10 days) because of the synergistic effect between the ternary metals. The glucose contents of several energy drinks, fruit juices, and carbonated beverages were analyzed using the novel PdCoAg/NGCE/C sensor system. These results indicate the feasibility for applications in the foods industry.
In the production of lithium-ion batteries (LIBs) and recycling of spent LIBs, a large amount of low-concentration lithium-containing wastewater (LCW) is generated. The recovery of Li from this medium has attracted significant global attention from both the environmental and economic perspectives. To achieve effective Li recycling, the features of impurity removal and the interactions among different ions must be understood. However, it is generally difficult to ensure highly efficient removal of impurity ions while retaining Li in the solution for further recovery. In this study, the removal of typical impurity ions from LCW and the interactions between these species were systematically investigated from the thermodynamic and kinetics aspects. It was found that the main impurities (e.g., Fe3+, Al3+, Ca2+, and Mg2+) could be efficiently removed with high Li recovery by controlling the ionic strength of the solution. The mechanisms of Fe3+, Al3+, Ca2+, and Mg2+ removal were investigated to identify the controlling steps and reaction kinetics. It was found that the precipitates are formed by a zero-order reaction, and the activation energies tend to be low with a sequence of fast chemical reactions that reach equilibrium very quickly. Moreover, this study focused on Li loss during removal of the impurities, and the corresponding removal rates of Fe3+, Al3+, Ca2+, and Mg2+ were found to be 99.8%, 99.5%, 99%, and 99.7%, respectively. Consequently, high-purity Li3PO4 was obtained via one-step precipitation. Thus, this research demonstrates a potential route for the effective recovery of Li from low-concentration LCW and for the appropriate treatment of acidic LCW.
In this work, a thin zirconium-based UiO-66 membrane was successfully prepared on an alumina hollow fiber tube by flow synthesis, and was used in an attempt to remove p-nitrophenol from water through a nanofiltration process. Two main factors, including flow rate and synthesis time, were investigated to optimize the conditions for membrane growth. Under optimal synthesis conditions, a thin UiO-66 membrane of approximately 2 µm in thickness was fabricated at a flow rate of 4 mL·h−1 for 30 h. The p-nitrophenol rejection rate for the as-prepared UiO-66 membrane applied in the removal of p-nitrophenol from water was only 78.1% due to the existence of membrane defects caused by coordinative defects during membrane formation. Post-synthetic modification of the UiO-66 membrane was carried out using organic linkers with the same flow approach to further improve the nanofiltration performance. The result showed that the p-nitrophenol rejection for the post-modified membrane was greatly improved and reached over 95%. Moreover, the post-modified UiO-66 membrane exhibited remarkable long-term operational stability, which is vital for practical application.
The utilization of materials with a hierarchical porous structure as multi-functional additives is highly attractive in the preparation of hybrid membranes. In this study, novel hybrid membranes are designed by embedding hierarchical porous Santa Barbara Amorphous 15 (SBA-15) with a dual-pore architecture (micropores and mesopores) for pervaporation desulfurization. The SBA-15 with cylindrical mesopores provides molecular transport expressways to ensure improved permeability, while micropores on the wall have molecular sieving effects that are essential for the enhancement of permselectivity of thiophene molecules. Considering thiophene/n-octane mixture as a model system, the hybrid membrane with embedded 6 wt-% SBA-15 exhibits optimal pervaporation desulfurization performance with a permeation flux of 22.07 kg·m−2·h−1 and an enrichment factor of 6.76. Moreover, the detailed structure and properties of hybrid membranes are systematically characterized. This study demonstrates the immense potential of hierarchical porous materials as additives in membranes to simultaneously increase permeability and permselectivity.
Adsorptive polyethesulfone (PES) membranes were prepared by intercalation of powder activated carbon (PAC) with and without functionalization. Accordingly, PAC was aminated with 1,5-diamino-2-methylpentane, and the physicochemical properties of the functionalized PAC were analyzed. Intercalation of PAC within the PES scaffold changed the porosity and mean pore size of the aminated membrane (AC-NH2) from 52.6% to 92.5% and from 22.6 nm to 3.5 nm, respectively. The effect of temperature on the performance of the modified membranes was monitored by the flux and chemical oxygen demand (COD) removal of leachate. At ambient temperature, the COD removal of the neat, AC-containing, and AC-NH2 membranes was 47%, 52%, and 58.5%, respectively. A similar increment was obtained for the membrane flux, which was due to the synergistic effect of the high porosity and large number of hydrophilic functional groups. The experimental leachate adsorption data were analyzed by Langmuir, Freundlich, and Dubinin- Radushkevich isotherm models. For all membranes, the significant thermodynamic parameters (ΔH, ΔS, and ΔG) were calculated and compared. The isosteric heat of adsorption was lower than 80 kJ∙mol−1, indicating that the interaction between the membranes and the leachate is mainly physical, involving weak van der Waals forces.