Improving the catalyst stabilities under different conditions (water vapor, SO2, both water vapor and SO2) is important for industrial applications regarding catalytic NO deep oxidation by ozone.
Zeolitic-imidazolate framework precursors (ZIF-67) were synthesized in an inorganic solution with triethylamine as a deprotonating agent for N2O decomposition, and the catalytic activities of the pyrolysis products under different conditions were investigated. Among them, the Co/CoOx@carbon catalyst pyrolyzed at 650 °C in a N2 atmosphere (Co-650N) exhibited excellent low-temperature catalytic activity and stability, achieving 50% decomposition efficiency at 305 °C and ∼100% at 400 °C, which benefitted from its large specific surface area, great reduction performance, abundant cobalt active sites, and surface oxygen species. Further, utilizing temperature-programmed desorption (TPD) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) results, it was found that N2O molecules preferentially combined with oxygen species bound to cobalt sites. The absorbed N2O was decomposed into N2 and oxygen species, and the latter was subsequently transferred to carbon frameworks. Interestingly, the amorphous graphitic carbon frameworks played an important role in transferring/storing active oxygen and regenerating cobalt sites. Moreover, Co-650N exhibited better resistance to SO2, and the efficiency could be recovered via heating and finally stabilized at 100%. Finally, the mechanisms of N2O decomposition and sulfur poisoning-reactivation on Co/CoOx@carbon catalysts were proposed for the first time.
Cl-VOCs have become the most concerning pollutants in flue gas from industrial production and solid waste incineration process due to its strong toxicity and potential of dioxins formation. How to achieve efficient elimination of Cl-VOCs at low temperature and maintain high activity without Cl poisoning is crucial. This paper adopts a novel monolithic CoOx@Ni catalyst to attain efficient degradation of Cl-VOCs at 120 oC, which can be applied to industrial without further modification for the original process. O3 decomposition and Cl-VOC ozonation occur simultaneously but the active radicals and intermediates from O3 decomposition and Cl-VOC ozonation have competitive effects on oxygen vacancies. Most interestingly, presence of water vapor and NO, as well as lowering temperature to 50 oC further promote catalytic ozonation of Cl-VOCs. Moisture vapor facilitate desorption of surficial Cl species and deep oxidation by washing effect and additional H source to attain high conversion and less byproducts. NO ozonation generates NO3 related radicals with strong oxidability to promote Cl-VOC conversion and inhibit polychlorinated byproducts formation. Lower temperature promotes adsorption of the above-mentioned active radicals and intermediates to prolong the contact time, thus attaining higher conversion. SO2 and Ca caused severe deactivation on catalytic ozonation that required higher O3 input, which should attribute to the occupation of active sites and attenuation of acidity. XPS results showed NO introduction enhanced the content of high valent Co3+/Ni3+ and improved the generation of active oxygen species as well as oxygen vacancies while Ca addition and SO2 introduction exhibited negative effect. Above all, this paper reports an effective and practical approach for Cl-VOC elimination in flue gas with potential to simultaneous remove NO. The mineralization rate, byproducts formation, stability, and feasibility for multiple Cl-VOCs are evaluated to be excellent for industrial application.
Wet flue gas desulfurization (WFGD) provides highly efficient SO2 removal in industrial flue gas treatment. Although NO and NO2 are not readily absorbed in the traditional desulfurization wash tower, deep oxidation with ozone can promote the formation of N2O5 that is absorbed in the washing fluid, making possible simultaneous denitration and desulfurization in the WGFD unit. This paper presents a survey of operating parameters for NOx removal after ozone deep oxidation using a Na2CO3-based WFGD. The effects of preoxidation time, Na2CO3 aqueous solution concentration, spray liquid/gas ratio, gas residence time in wash tower, and SO2 concentration on NOx removal efficiency were investigated systematically in a variable-configuration experimental setup. The results demonstrate that preoxidation time was the most sensitive factor in N2O5 formation, although oxidation continued in the wash tower. Thus, one strategy for a system where physical constraints limit the volume of the oxidation chamber is to extend the flue gas residence time in the wash tower. Increasing the liquid/gas ratio and Na2CO3 solution concentration gave some enhancement on the wet absorption process. Under optimal laboratory conditions, 95% NOx removal efficiency was achieved. Addition of SO2 yielded a slight inhibition for NOx removal, and under industrial relevant operating conditions, 98% SO2 and 62% NOx removal was achieved during 50 min experimental runs.
Given China’s ambition to realize carbon peak by 2030 and carbon neutralization by 2060, hydrogen is gradually becoming the pivotal energy source for the needs of energy structure optimization and energy system transformation. Thus, hydrogen combined with renewable energy has received more and more attention. Nowadays, power-to-hydrogen, power-to-methanol, and power-to-ammonia are regarded as the most promising three hydrogen-driven power-to-X technologies due to the many commercial or demonstration projects in China. In this paper, these three hydrogen-driven power-to-X technologies and their application status in China are introduced and discussed. First, a general introduction of hydrogen energy policies in China is summarized, and then the basic principles, technical characteristics, trends, and challenges of the three hydrogen-driven power-to-X technologies are reviewed. Finally, several typical commercial or demonstration projects are selected and discussed in detail to illustrate the development of the power-to-X technologies in China.
Treatment of full-thickness skin defects still presents a significant challenge in clinical practice. There is a need for accurate patterning of living cells in pre-defined spatial positions, and the three-dimensional (3D) bioprinting technique offers a promising approach for fabricating skin substitutes. However, it is necessary to identify bioinks that have both sufficient mechanical properties to simulate the complex skin structure, and can provide a suitable microenvironment to support cell growth. In this study, we found that acellular dermal matrix (ADM) bioink preserved the main extracellular matrix (ECM) components of the skin to promote cell growth, and gelatine methacrylamide (GelMA) bioink with tunable and sufficient mechanical properties was strong and elastic for skin tissues. Here, we propose a new 3D structure to simulate natural full-thickness skin, which included 20% GelMA with HaCaTs as an epidermal layer, 1.5% ADM with fibroblasts as the dermis, and 10% GelMA mesh with human umbilical vein endothelial cells (HUVECs) as the vascular network. We demonstrated that this 3D bioprinting functional skin model (FSM) could not only maintain a moist microenvironment and barrier function, but also recreate the natural skin microenvironment to promote cell viability and proliferation in vitro. When transplanted in vivo, our FSM could maintain cell viability for at least 1 week. Furthermore, the FSM promoted wound healing and re-epithelization, stimulated dermal ECM secretion and angiogenesis, and enhanced wound healing quality. Therefore, the FSM may provide viable functional skin substitutes for future clinical applications.
Different Cr-based bimetallic oxides were prepared, and their catalytic performance was evaluated on the simultaneous removal of multi-VOCs mixtures (acetone, benzene, toluene, and o-xylene) by ozonation. Among them, Co-Cr catalyst stood out in catalytic ozonation of aromatic VOCs, and its activity on acetone conversion was promoted by raising the temperature and ozone concentrations, owing to lower crystallization, larger surface area, excellent redox and VOCs/CO2 desorption ability. Above 95% conversion of all multi-VOCs was achieved over the Co-Cr catalyst when the temperature was 100 oC and an excess ozone ratio λ (the ratio of actual moles of ozone to theoretical moles of ozone needed) was equal to 3. A competitive relationship was noticed during the removal process of four multiple VOCs, with significant inhibition of acetone conversion in the presence of aromatic VOCs, conceivably due to adsorption competition and byproducts accumulation. Effects of NO/SO2/H2O and respective reversibility were also investigated. The inhibition effects of NO/SO2/H2O on aromatic VOCs were far less than those on acetone. Further, the retarding effect of NO was reversible, attributing to physical adsorption competition, but the inhibition effect of SO2/H2O was irreversible, due to the blockage of active sites for VOCs removal. With the combination of scrubbing, multi-VOCs and NO/SO2 could be removed by catalytic ozonation simultaneously and efficiently. In-situ DRIFTS measurement was also conducted to investigate the adsorption and catalytic ozonation process of multi-VOCs mixtures, as well as under the presence of SO2/H2O, discovering the major intermediates, surface carboxylates and carboxylic acids.
Low temperature, high alkali metal, and water content flue gas in biomass boilers restrict the application of traditional NOx treatment technology (i.e., selective noncatalytic reduction and selective catalytic reduction). In this paper, the coupled ozonation and wet absorption technology was used in a 130 t/h biomass circulating fluid bed boiler. Key parameters, that is, O3/NO molar ratio, mixing uniformity, liquid/gas ratio, and O3 residual, were investigated with the industrial real case. The higher O3/NO molar ratio achieved better denitration efficiency, and the O3 residual started to increase once the O3/NO molar ratio exceeded 2.1. Mixing uniformity is a key factor for the diffusion of ozone in flue gas, and it would directly influence N2O5 formation and O3 decomposition process. In the slurry, NO3– and SO42– were the major byproducts after NOx and SO2 absorption. With the optimization of key parameters, the NOx emission was controlled below 50 mg/Nm3 under 34.8 kg/h O3 dosage.
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