Regeneration of waste SCR catalyst by air lift loop reactor

A solution of 0.1 mol/L to 1.0 mol/L H2SO4 can dissolve alkali metals and alkaline earth metals which weaken an active site of SCR catalyst. The waste catalyst washed with 0.5 mol/L H2SO4 regained the best catalytic activity. When a concentration of the sulfuric acid is less than 0.5 mol/L, sufficient cleaning effects cannot be obtained. In contrast, when the concentration is greater than 1.0 tool/L, the active components, vanadium and tungsten are undesirably eluted. The total BET surface of the catalyst regenerated by air lift loop reactor showed almost the same as that of fresh catalyst due to the removal of insoluble compounds which may be penetrated into pores of catalyst. The addition of a solution of 0.075 mol/L ammonium vanadate （NHnVO3） and 0.075 mol/L ammonium paratungstate （5（NH4）20· 12WO3-5H20） to 0.1 mol/L H2SO4 significantly increases the activity of the waste catalyst.

Catalytic effect in lithium metal batteries: From heterogeneous catalyst to homogenous catalyst

Lithium metal batteries are regarded as prominent contenders to address the pressing needs owing to the high theoretical capacity.Toward the broader implementation,the primary obstacle lies in the intricate multi-electron,multi-step redox reaction associated with sluggish conversion kinetics,subsequently giving rise to a cascade of parasitic issues.In order to smooth reaction kinetics,catalysts are widely introduced to accelerate reaction rate via modulating the energy barrier.Over past decades,a large amount of research has been devoted to the catalyst design and catalytic mechanism exploration,and thus the great progress in electrochemical performance has been realized.Therefore,it is necessary to make a comprehensive review toward key progress in catalyst design and future development pathway.In this review,the basic mechanism of lithium metal batteries is provided along with corresponding advantages and existing challenges detailly described.The main catalysts employed to accelerate cathode reaction with emphasis on their catalytic mechanism are summarized as well.Finally,the rational design and innovative direction toward efficient catalysts are suggested for future application in metal-sulfur/gas battery and beyond.This review is expected to drive and benefit future research on rational catalyst design with multi-parameter synergistic impacts on the activity and stability of next-generation metal battery,thus opening new avenue for sustainable solution to climate change,energy and environmental issues,and the potential industrial economy.

Influence of Ca/P ratio on the catalytic performance of hydroxyapatite for decarboxylation of itaconic acid to methacrylic acid

Methacrylic acid,an important organic chemical,is commercially manufactured starting from fossil feedstock.The decarboxylation of itaconic acid derived for biomass is a green route to the synthesis of methacrylic acid.In view of the problems existing in the researches on this route such as use of noble metal catalyst,harsh reaction conditions and low desired-product yield,we prepared a series of hydroxyapatite catalysts with different Ca/P molar ratios and evaluated their catalytic performance.The results showed that the hydroxyapatite catalyst with a Ca/P molar ratio of 1.58 had the best catalytic activity.The highest yield of MAA up to 61.2%was achieved with basically complete conversion of itaconic acid under the suitable reaction conditions of 1 equivalent of NaOH,2 MPa of N_(2),250℃,and 2 h.On this basis,a reaction network for the decarboxylation of itaconic acid to methacrylic acid catalyzed by hydroxyapatite was established.With the aid of catalyst characterization using X-ray powder diffraction,NH3/CO2 temperature-programmed desorption,N_(2)physisorption,inductively coupled plasma optical emission spectrometry,and scanning electron microscopy,we found that the distribution of surface acid sites and basic sites,crystal growth orientation,texture properties and morphology of hydroxyapatite varied with the Ca/P molar ratio.Furthermore,the change of the crystal growth orientation and its influence on the surface acidity and alkalinity were clarified.

A highly hydrothermal stable copper-based catalyst for catalytic wet air oxidation of m-cresol in coal chemical wastewater

Catalytic wet air oxidation(CWAO) can degrade some refractory pollutants at a low cost to improve the biodegradability of wastewater. However, in the presence of high temperature and high pressure and strong oxidizing free radicals, the stability of catalysts is often insufficient, which has become a bottleneck in the application of CWAO. In this paper, a copper-based catalyst with excellent hydrothermal stability was designed and prepared. TiO_(2) with excellent stability was used as the carrier to ensure the longterm anchoring of copper and reduce the leaching of the catalyst. The one pot sol–gel method was used to ensure the super dispersion and uniform distribution of copper nanoparticles on the carrier, so as to ensure that more active centers could be retained in a longer period. Experiments show that the catalyst prepared by this method has good stability and catalytic activity, and the catalytic effect is not significantly reduced after 10 cycles of use. The oxidation degradation experiment of m-cresol with the strongest biological toxicity and the most difficult to degrade in coal chemical wastewater was carried out with this catalyst. The results showed that under the conditions of 140℃, 2 MPa and 2 h, m-cresol with a concentration of up to 1000 mg·L^(-1) could be completely degraded, and the COD removal rate could reach 79.15%. The biological toxicity of wastewater was significantly reduced. The development of the catalyst system has greatly improved the feasibility of CWAO in the treatment of refractory wastewater such as coal chemical wastewater.

Effects of Temperature and Catalyst to Oil Weight Ratio on the Catalytic Conversion of Heavy Oil to Propylene Using ZSM-5 and USY Catalysts

It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC （fluid catalytic cracking）. The effects of temperature and C/O ratio （catalyst to oil weight ratio） on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil （VGO） was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas （LPG）, repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC （hydrogen transfer coefficient） and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/A1203 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.

Effects of total pressures and equivalence ratios on kerosene/air rotating detonation engines using a paralleling CE/SE method

In this paper,the kerosene/air rotating detonation engines(RDE)are numerically investigated,and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE including the initiation,instabilities,and propulsive performance.A hybrid MPI t OpenMP parallel computing model is applied and it is proved to be able to obtain a more effective parallel performance on high performance computing(HPC)systems.A series of cases with the total pressure of 1 MPa,1.5 MPa,2 MPa,and the equivalence ratio of 0.9,1,1.4 are simulated.On one hand,the total pressure shows a significant impact on the instabilities of rotating detonation waves.The instability phenomenon is observed in cases with low total pressure(1 MPa)and weakened with the increase of the total pressure.The total pressure has a small impact on the detonation wave velocity and the specific impulse.On the other hand,the equivalence ratio shows a negligible influence on the instabilities,while it affects the ignition process and accounts for the detonation velocity deficit.It is more difficult to initiate rotating detonation waves directly in the lean fuel operation condition.Little difference was observed in the thrust with different equivalence ratios of 0.9,1,and 1.4.The highest specific impulse was obtained in the lean fuel cases,which is around 2700 s.The findings could provide insights into the understanding of the operation characteristics of kerosene/air RDE.

Artificial neural network techniques to predict the moisture ratio content during hot air drying and vacuum drying of Radix isatidis extract

Background:To predict the moisture ratio of Radix isatidis extract during drying.Methods:Artificial neural networks were designed using the MATLAB neural network toolbox to produce a moisture ratio prediction model of Radix isatidis extract during hot air drying and vacuum drying,where regression values and mean squared error were used as evaluation indexes to optimize the number of hidden layer nodes and determine the topological structure of artificial neural networks model.In addition,the drying curves for the different drying parameters were analyzed.Results:The optimal topological structure of the moisture ratio prediction model for hot air drying and vacuum drying of Radix isatidis extract were“4-9-1”and“5-9-1”respectively,and the regression values between the predicted value and the experimental value is close to 1.This indicates that it has a high prediction accuracy.The moisture ratio gradually decreases with an increase in the drying time,reducing the loading,initial moisture content,increasing the temperature,and pressure can shorten the drying time and improve the drying efficiency.Conclusion:Artificial neural networks technology has the advantages of rapid and accurate prediction,and can provide a theoretical basis and technical support for online prediction during the drying process of the extract.

Study on the Environmental Quality Guarantee Ratio on the Basis of Total Air Pollutant Emission Amount Control

The hourly and daily air quality concentration in the total air pollutant emission amount control zone is not sure to be continuously up to national ambient air quality standard, even though the total annual air pollutant emission is permitted under the total air pollutant emission amount control (TAPEAC) on the basis of A-value method. So the concept of the environmental quality guarantee ratio (EQGR) for TAPEAC is advanced in this paper and its quantitative formula is figured out for both hourly and daily EQGR. It is concluded that the EQGR is related with the yearly arrangement of A-value besides the pollutant type. According to the meteorological data in a lower area along Yangtze River in 2000, the yearly A-value trend is analyzed. Based on the data, the hourly EQGR of SO 2 and NO 2 is respectively 97.4% and 90.2%, and daily EQGR respectively 90.2% and 79.5%.

Designing Oxide Catalysts for Oxygen Electrocatalysis: Insights from Mechanism to Application

The electrochemical oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal–air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O_(2) to water(H_2O) or from O_(2) to hydrogen peroxide(H_2O_(2)). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments(e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.

Strengthening absorption ability of Co-N-C as efficient bifunctional oxygen catalyst by modulating the d band center using MoC

Co-N-C is a promising oxygen electrochemical catalyst due to its high stability and good durability.However,due to the limited adsorption ability improvement for oxygen-containing intermediates,it usually exhibits inadequate catalytic activity with 2-electron pathway and high selectivity of hydrogen peroxide.Herein,the adsorption of Co-N-C to these intermediates is modulated by constructing heterostructures using transition metals and their derivatives based on d-band theory.The heterostructured nanobelts with MoC core and pomegranate-like carbon shell consisting of Co nanoparticles and N dopant(MoC/Co-N-C)are engineered to successfully modulate the d band center of active Co-N-C sites,resulting in a remarkably enhanced electrocatalysis performance.The optimally performing MoC/Co-N-C exhibits outstanding bi-catalytic activity and stability for the oxygen electrochemistry,featuring a high wave-half potential of 0.865 V for the oxygen reduction reaction(ORR)and low overpotential of 370 mV for the oxygen evolution reaction(OER)at 10 mA cm^(-2).The zinc air batteries with the MoC/Co-N-C catalyst demonstrate a large power density of 180 mW cm^(-2)and a long cycling lifespan(2000 cycles).The density functional theory calculations with Hubbard correction(DFT+U)reveal the electron transferring from Co to Mo atoms that effectively modulate the d band center of the active Co sites and achieve optimum adsorption ability with"single site double adsorption"mode.

Effect of Air Injector on the Performance of an Air-lift for Conveying River Sand

An air-lift has been more recently applied in the dredging, deep-seated beach placer mining and underground mining engineering. However, the influence and mechanism of various parameters on the air-lift performance are not quite clear, especially the influence of flow pattern on lifting efficiency. Focusing on the problems mentioned above, the key part of the air-lift （namely, the air injector） was proposed aimed to reduce friction loss in the inner pipe according to improving flow field performance, thus increase the lifting efficiency. The study of relative factors of the performance of an air-lift is performed and the river sand is used as simulation of underground ore bed. The total lifting height of the experimental system is 3 m, the water flux, mass flow of solid particles, concentration of particles and lifting efficiency are measured under the same submergence ratios by changing the air injector, which is divided into nine specifications of air injection in this research. The experimental results indicate that the optimal air flow rate corresponding to excellent performance of the air-lift can be obtained in the range of 35-40 m3/h. The air injection method has a great effect on the performance of the air-lift, the air injector with three nozzles is better than that in the case of one or two nozzles. Further more, the air injection angle and arrangement of air injection pipes also have great effect on the performance of an air-lift. The proposed research results have guiding significance for engineering application.

Catalytic wet air oxidation of phenol over RuO_2/γ-Al_2O_3 catalyst

A kind of CWAO catalyst, RuO_2/γ-Al_2O_3, was prepared by dipping Al_2O_3into the aqueous solution of RuCl_3·3H_2O. XRD, SEM and TEM were used to determine the catalyticstructure. Influences of the calcination temperature, the initial pH of the feed solution anddegradation temperature on the activity of the RuO_2/γ-Al_2O_3 catalyst were investigated and thereaction mechanism was preliminarily studied. Results showed that uniform dispersion of RuO_2crystallites was observed on the surface of the catalyst. The activity of the catalyst was higher atcalcination temperature of 300℃ for 3 h and the particle reunion occurred and some large RuO_2crystallites were abundant at high calcination temperature of 500℃ The activity of the catalyst wasbetter in the acid solution than in the alkaline solution. Increasing degradation temperature andusing the catalyst could shorten the induction periods so that the phenol and COD removal wereincreased. For RuO_2/γ-Al_2O_3 catalyst, the phenol and COD removal were respectively 98% and 80%in a temperature of 150℃, pH of 5.6 and pressure of 3 MPa after a 2 h reaction. This indicated thatRu/γ-Al_2O_3 catalyst had good activity.

Liquid penetration of freeze-drying and air-drying wood of plantation Chinese fir

A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution uptake by the capillary rise method was used to evaluate the liquid penetration properties of the treated wood. The pit aspiration ratio was determined by semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results showed that compared with air drying, the freeze drying had a significant effect on liquid penetration of sapwood and heartwood of Chinese fir. The liquid penetration of sapwood is significantly higher than that of the heartwood for both drying treatments. Low pit aspiration ratio and cracks of pits membrane of some bordered pits are the main reasons for increasing liquid penetration after freeze drying treatment.

Solar-assisted selective separation and recovery of precious group metals from deactivated air purification catalysts

The mitigation of environmental and energy crises could be advanced by reclaiming platinum group precious metals(PGMs) from decommissioned air purification catalysts. However, the complexity of catalyst composition and the high chemical inertness of PGMs significantly impede this process. Consequently,recovering PGMs from used industrial catalysts is crucial and challenging. This study delves into an environmentally friendly approach to selectively recover PGMs from commercial air purifiers using photocatalytic redox technology. Our investigation focuses on devising a comprehensive strategy for treating three-way catalysts employed in automotive exhaust treatment. By meticulously pretreating and modifying reaction conditions, we achieved noteworthy results, completely dissolving and separating rhodium(Rh), palladium(Pd), and platinum(Pt) within a 12-h time frame. Importantly, the solubility selectivity persists despite the remarkably similar physicochemical properties of Rh, Pd, and Pt. To bolster the environmental sustainability of our method, we harness sunlight as the energy source to activate the photocatalysts, facilitating the complete dissolution of precious metals under natural light irradiation. This ecofriendly recovery approach demonstrated on commercial air purifiers, exhibits promise for broader application to a diverse range of deactivated air purification catalysts, potentially enabling implementation on a large scale.

Structure, characterization, and dynamic performance of a wet air oxidation catalyst Cu–Fe–La/γ-Al_2O_3

A Cu–Fe–La/γ-Al_2O_3(CFLA) catalyst was prepared by the excessive impregnation method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that the catalyst contained mostly Cu^(2+), Fe^(3+), and La^(3+)and a small amount of Cu^+, Fe^(2+), and La. The active components were uniformly distributed in the catalyst, and the particle size of the components was approximately 7.5 nm. The CFLA catalyst was used for the treatment of methyl orange(MO) solution by catalytic wet air oxidation(CWAO), and it exhibited a high catalytic activity. The catalytic reaction involved variable valence states of metals and free-radical reaction mechanism. The CWAO reaction of MO solution was fitted by a segmented first-order dynamic model, and the rapid reaction apparent activation energy was 13.9 k J·mol^(-1).

Kinetics study on catalytic wet air oxidation of phenol by several metal oxide catalysts

Four metal oxide catalysts composed of copper(Cu), stannum(Sn), copper-stannum(Cu-Sn) and copper-cerium(Cu-Ce) respectively were prepared by the co-impregnation method, and γ-alumina(γ-Al 2O 3) is selected as support. A first-order kinetics model was established to study the catalytic wet air oxidation of phenol at different temperature when these catalysts were used. The model simulations are good agreement with present experimental data. Results showed that the reaction rate constants can be significantly increased when catalysts were used, and the catalyst of 6% Cu—10%Ce/γ-Al 2O 3 showed the best catalytic activity. This is consistent with the result of catalytic wet air oxidation of phenol and the COD removal can be arrived at 98.2% at temperature 210℃, oxygen partial pressure 3 MPa and reaction time 30 min. The activation energies of each reaction with different catalysts are nearly equal, which is found to be about 42 kJ/mol and the reaction in this study is proved to be kinetics control.

Design, Development and Testing of an Air Damper to Control the Resonant Response of a SDOF Quarter-Car Suspension System

An air damper possesses the advantages that there are no long term changes in the damping properties, there is no dependence on working temperature and additionally, it has less manufacturing and maintenance costs. As such, an air damper has been designed and developed based on the Maxwell type model concept in the approach of Nishihara and Asami [1]. The cylinder-piston and air-tank type damper characteristics such as air damping ratio and air spring rate have been studied by changing the length and diameter of the capillary pipe between the air cylinder and the air tank, operating air pressure and the air tank volume. A SDOF quarter-car vehicle suspension system using the developed air enclosed cylinder-piston and air-tank type damper has been analyzed for its motion transmissibility characteristics. Optimal values of the air damping ratio at various values of air spring rate have been determined for minimum motion transmissibility of the sprung mass. An experimental setup has been developed for SDOF quarter-car suspension system model using the developed air enclosed cylinder-piston and air-tank type damper to determine the motion transmissibility characteristics of the sprung mass. An attendant air pressure control system has been designed to vary air damping in the developed air damper. The results of the theoretical analysis have been compared with the experimental analysis.

Investigation of the Effects of a Large Percentage of Dried Sludge on the Operation of a Coal-Fired Boiler

A 600 MW coal-fired boiler with a four-corner tangential combustion mode is considered here to study the combustion features and pollutant emissions at different loads for large-percentages of blending dried sludges.The influence of the over-fired air(OFA)coefficient is examined and the impact of the blending ratio on the boiler operation is explored.The results show that for low blending ratios,a slight increase in the blending ratio can improve the combustion of bituminite,whereas a further increase leads to the deterioration of the combustion of blended fuels and thus reduces the boiler efficiency.Enhancing the supporting capability of the secondary air effectively reduces the slagging degree in the bottom ash hopper and improves the burnout rate of coals.For a large-percentage blending case at full load,it is found that the OFA coefficient must be reduced appropriately,otherwise,a secondary high-temperature combustion zone can be generated in the vicinity of the furnace arches,causing high temperature slagging and superheater tube bursting.Considering the influences of combustion and pollutant emissions,the recommended OFA coefficient is 0.2.Blending dried sludge under low loads increases the flue gas temperature at the furnace exit.While reducing the flue gas temperature in the main combustion region,which is beneficial to the safe operation of the denitrification system.Increasing the blending ratio and reducing load lead to an increase in NOx concentration at the furnace exit Sludges with low nitrogen content are suggested for the practical operation of boilers.

Development and experimental validation of a one-dimensional dynamic hygrothermal modeling based on air humidity ratio

A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials.The solution for the governing equations was obtained numerically by implementing the finite-difference scheme.To evaluate the accuracy of the model,a test system was built up to measure relative humidity and temperature within a porous wall and compare with the prediction of the model.The prediction results have good agreement with the experimental results.For the interface close to indoor side,the maximum deviation of temperature between calculated and test data is 1.87 K,and the average deviation is 0.95 K;the maximum deviation of relative humidity is 11.4%,and the average deviation is 5.7%.For the interface close to outdoor side,the maximum deviation of temperature between prediction and measurement is 1.78 K,and the average deviation is 1.1 K;the maximum deviation of relative humidity is 9.9%,and the average deviation is 4.2%.

Sensitivity and effect of key operational parameters on performance of a dual-cylinder free-piston engine generator

The free-piston engine generator(FPEG)is regarded as the next generation of energy conversion system which may replace traditional engines in the future.The effect of key operational parameters like excess air ratio of input mixture and ignition position on the engine performance of a dual-cylinder FPEG was investigated,and their sensitivity was analyzed in this paper.The operating compression ratio of the system is susceptible to changes in excess air ratio and ignition position.At the same time,it decreases from 15.8 to 6.6 when excess air ratio increases from 0.85 to 1.15,but it increases from 6.1 to 13.3 as ignition position increases from 15 mm to 20 mm.The operating frequency and indicated power are more sensitive to changes in excess air ratio than ignition position.But it is the opposite for the indicated thermal efficiency and friction loss.Excess air ratio and ignition position have a quite similar influence on heat transfer.Therefore,from the perspective of system operation and performance,it is preferable to keep excess air coefficient slightly below 1.0.In contrast,when selecting ignition position,it is of great importance to comprehensively consider the risk of structural damage caused by the increase in the compression ratio and in-cylinder gas pressure.