Fe-Beta zeolite for selective catalytic reduction of NO_x with NH_3:Influence of Fe content

Fe doped Beta zeolite with different Fe contents were prepared by ion exchange by changing the volume or the concentration of a Fe salt solution. For a particular mass of Fe salt precursor, the concentration of the metal salt solution during ion exchange influenced the ion exchange capacity of Fe, and resulted in different activities of the Fe-Beta catalyst. Fe-Beta catalysts with the Fe contents of （2.6, 6.3 and 9） wt% were synthesized using different amounts of 0.02 mol/L Fe salt solution. These catalysts were studied by various characterization techniques and their NH3-SCR activities were evaluated. The Fe-Beta catalyst with the Fe content of 6.3 wt% exhibited the highest activity, with a temperature range of 202-616℃ where the NOx conversion was 〉 80%. The Fe content in Beta zeolite did not influence the structure of Beta zeolite and valence state of Fe. Compared with the Fe-Beta catalysts with low Fe content （2.6 wt%）, Fe-Beta catalysts with 6.3 wt% Fe content possessed more isolated Fe3. active sites which led to its higher NH3-SCR activity. A high capacity for NH3 and NO adsorption, and a high activity for NO oxidation also contributed to the high NH3-SCR activity of the Fe-Beta catalyst with 6.3 wt%. However, when the Fe content was further increased to 9.0 wt%, the amount of FexOy nanoparticles increased while the amount of isolated Fe3＋ active sites was unchanged, which promoted NH3 oxidation and decreased the NH3-SCR activity at high temperature.

Investigation of low-temperature hydrothermal stability of Cu-SAPO-34 for selective catalytic reduction of NO_x with NH_3

The low‐temperature hydrothermal stabilities of Cu‐SAPO‐34samples with various Si contents and Cu loadings were systematically investigated.The NH3oxidation activities and NH3‐selective catalytic reduction(SCR)activities(mainly the low‐temperature activities)of all the Cu‐SAPO‐34catalysts declined after low‐temperature steam treatment(LTST).These results show that the texture and acid density of Cu‐SAPO‐34can be better preserved by increasing the Cu loading,although the hydrolysis of Si-O-Al bonds is inevitable.The stability of Cu ions and the stability of the SAPO framework were positively correlated at relatively low Cu loadings.However,a high Cu loading(e.g.,3.67wt%)resulted in a significant decrease in the number of isolated Cu ions.Aggregation of CuO particles also occurred during the LTST,which accounts for the decreasing NH3oxidation activities of the catalysts.Among the catalysts,Cu‐SAPO‐34with a high Si content and medium Cu content(1.37wt%)showed the lowest decrease in NH3‐SCR because its Cu2+content was well retained and its acid density was well preserved.

Low-Temperature Selective Catalytic Reduction of NO with NH_3 over Fe–Ce–O_x Catalysts

In this study, we used a simple impregnation method to prepare Fe-Ce-O x catalysts and tested them regarding their low-temperature (200-300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94-99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h−1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80-98% between 200 and 300 °C at a space velocity of 204,000 h−1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200-300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.

Kinetics of selective catalytic reduction of NO by NH_3 on Fe-Mo/ZSM-5 catalyst

The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction （SCR） of nitric oxide （NO） with NH3. The kinetics of the SCR reaction in the presence of O2 was studied in this work. The results showed that the observed reaction orders were 0.74-0.99, 0.01-0.13, and 0 for NO, O2 and NH3 at 350-450℃, respectively. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst. The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N2 and H2O. Gaseous O2 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process. It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH3.

In situ preparation of mesoporous Fe/TiO_2 catalyst using Pluronic F127-assisted sol-gel process for mid-temperature NH_3 selective catalytic reduction

An Fe/TiO2catalyst with uniform mesopores was synthesized using Pluronic F127as a structuredirecting agent.This catalyst was used for selective catalytic reduction of NO with NH3.The catalytic activity and resistance to H2O and SO2of Fe/TiO2prepared by a template method were better than those of catalysts synthesized using impregnation and coprecipitation.The samples were characterized using N2‐physisorption,transmission electron microscopy,ultraviolet‐visibl spectroscopy,X‐ray photoelectron spectroscopy,and in situ diffuse reflectance infrared Fouriertransform spectroscopy.The results showed that Pluronic F127acted as a structural and chemical promoter;it not only promoted the formation of a uniform mesoporous structure,leading to a higher surface area,but also improved dispersion of the active phase.In addition,the larger number of Lewis acidic sites,indicated by the presence of coordinated NH3species(1188cm-1)and the N–H stretching modes of coordinated NH3(3242and3388cm-1),were beneficial to mid‐temperature selective catalytic reduction reactions.

Enhanced selective catalytic reduction of NO with NH3 via porous micro-spherical aggregates of Mn–Ce–Fe–Ti mixed oxide nanoparticles

We rationally designed a high performance denitration(De-NOx) catalyst based on a micrometer-sized spherical Mn–Ce–Fe–Ti(CP-SD)catalyst for selective catalytic reduction(SCR). This was prepared by a co-precipitation and spray drying(CP-SD) method. The catalyst was systematically characterized, and its morphological structure and surface properties were identified. Compare with conventional Mn–Ce–Fe–Ti(CP) catalysts, the Mn–Ce–Fe–Ti(CP-SD) catalyst had superior surface-adsorbed oxygen leading to enhanced 'fast NH3-SCR' reaction. The asobtained Mn–Ce–Fe–Ti(CP-SD) catalyst offered excellent NO conversion and N2 selectivity of 100.0% and 84.8% at 250℃, respectively, with a gas hourly space velocity(GHSV) of 40,000 h-1. The porous micro-spherical structure provides a larger surface area and more active sites to adsorb and activate the reaction gases. In addition, the uniform distribution and strong interaction of manganese, iron, cerium, and titanium oxide species improved H2O and SO2 resistance. The results showed that the Mn–Ce–Fe–Ti(CP-SD) catalyst could be used prospectively as a denitration(De-NOx) catalyst.

Low-Temperature Denitrification Performance of Cu2O/Activated Carbon Catalysts for Selective Catalytic Reduction of NOx by CO

To improve the denitrification performance of carbon-based materials for sintering flue gas,we prepared a composite catalyst comprising coconut shell activated carbon(AC)modified by thermal oxidation air.The microstructure,the specific surface area,the pore volume,the crystal structure,and functional groups presented in the prepared Cu2O/AC catalysts were thoroughly characterized.By using scanning electron microscopy(SEM),nitrogen adsorption/desorption isotherms,Fourier-transform infrared(FTIR)spectroscopy and X-ray diffractometry(XRD),the effects of Cu2O loading and calcination temperature on Cu2O/AC catalysts were investigated at low temperature(150℃).The research shows that Cu on the Cu2O/AC catalyst is in the form of Cu2O with good crystalline performance and is spherical and uniformly dispersed on the AC surface.The loading of Cu2O increases the active sites and the specific surface area of the reaction gas contact,which is conducive to the rapid progress of the carbon monoxide selective catalytic reduction(CO-SCR)reaction.When the loading of Cu2O was 8%and the calcination temperature was 500℃,the removal rate of NOx facilitated by the Cu2O/AC catalyst reached 97.9%.These findings provide a theoretical basis for understanding the denitrification of sintering flue gas.

Cu-SAPO-17:A novel catalyst for selective catalytic reduction of NOx

The high-temperature(HT) and low-temperature(LT) hydrothermal stabilities of molecular-sieve-based catalysts are important for the selective catalytic reduction of NOx with ammonia(NH3-SCR). In this paper, we report a catalyst, Cu2+ loading SAPO-17, synthesized using cyclohexylamine(CHA), which is commercially available and inexpensive and is utilized in NH3-SCR reduction for the first time. After systematic investigations on the optimization of Si and Cu2+ contents, it was concluded that Cu-SAPO-17-8.0%-0.22 displays favorable catalytic performance, even after being heated at 353 K for 24 h and at 973 K for 16 h. Moreover, the locations of CHAs, host–guest interaction and the Bronsted acid sites were explored by Rietveld refinement against powder X-ray diffraction data of as-made SAPO-17-8.0%. The refinement results showed that two CHAs exist within one eri cage and that the protonated CHA forms a hydrogen bond with O4, which indicates that the proton bonding with O4 will form the Bronsted acid site after the calcination.

Catalytic reductive dechlorination of p-chlorophenol in water using Ni/Fe nanoscale particles

Nanoscale bimetallic Ni/Fe particles were synthesized from the reaction of sodium borohydride （NaBH4） with reduction of Ni^2＋ and Fe^2＋ in aqueous solution. The obtained Ni/Fe particles were characterized by TEM （transmission electron microscope）, XRD （X-ray diffractometer）, and N2-BET. The dechlorination activity of the Ni/Fe was investigated using p-chlorophenol （p-CP） as a probe agent. Results demonstrated that the nanoscale Ni/Fe could effectively dechlorinate p-CP at relatively low metal to solution ratio of 0.4 g/L （Ni 5 wt%）. The target with initial concentration ofp-CP 0.625 mmol/L was dechlorinted completely in 60 rain under ambient temperature and pressure. Factors affecting dechlorination efficiency, including reaction temperature, pH, Ni loading percentage over Fe, and metal to solution ratio, were investigated. The possible mechanism of dechlorination ofp-CP was proposed and discussed. The pseudo-first- order reaction took place on the surface of the Ni/Fe bimetallic particles, and the activation energy of the dechlorination reaction was determined to be 21.2 kJ/mol at the temperature rang of 287-313 K.

Electrochemical reduction characteristics and mechanism of nitrobenzene compounds in the catalyzed Fe-Cu process

The reduction of the nitrobenzene compounds （NBCs） by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium（pH=11）. The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder＇s iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order： nitrobenzene 〉4-chloro-nitrobenzene ≥m-dinitrobenzene ：〉 4-nitrophenol ≥2,4-dinitrotoluene 〉2-nitrophenol. The reduction rate by Master Builder＇s iron decreased in the following order： m-dinitrobenzene ≥4-chloro-nitrobenzene 〉4-nitrophenol 〉2,4-dinitrotoluene ≈nitrobenzene 〉2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe（OH）2 in Master Builder＇s iron, It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC＇s electron withdrawing ability.

In-situ Infrared Study on Surface Species in Selective Catalytic Reduction of NO with Hydrocarbon over Copper ZSM-5 Zeolite

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Low-temperature Catalytic Reduction of Nitrogen Monoxide with Carbon Monoxide on Copper Iron and Copper Cobalt Composite Oxides

Copper iron composite oxides （CuO/Fe2O3） and copper cobalt composite oxides （CuO/Co3O4） for the catalytic reduction of NO with CO at low temperature were prepared by co-precipitation. The catalytic activity and thermal stability of the catalysts were evaluated by a microreactor-GC system. The 100% conversion temperatures of NO are 80 ℃ for CuO/Fe2O3 and 90 ℃ for CuO/Co3O4. The catalysts possess high catalytic activity and favorable thermal stability for NO reduction with CO in a wide temperature range and long time range. A systematic study of the molar ratios of the reactants, the volume of NaOH, aging time, and calcination temperature/time was carried out to investigate the influence preparation conditions on the catalytic activity of the catalysts.

Cu改性MIL-100(Fe)催化剂的SCR-C_(3)H_(6)脱硝特性

烃类化合物选择性催化还原氮氧化物(SCR-HC)是一种很有发展前景的脱硝技术。催化剂有效的氧化-还原能力是影响其活性的关键因素。利用水热法制备了新型有机金属骨架MIL-100(Fe),通过超声浸渍法合成不同Cu含量的m Cu-MIL-100(Fe)催化剂,在固定床微反应器中对其催化C_(3)H_(6)选择性还原NO的特性进行了实验研究。结果表明Cu的引入使MIL-100(Fe)催化活性得到改善。2.3Cu-MIL-100(Fe)的NO转化率在275℃下可达到100%,275~400℃范围内可维持85%以上NO转化率及90%以上N_(2)选择性,且具有较好抗SO_(2)的能力。通过各种技术手段对催化剂的微观结构及物化性质进行了表征,并对反应机理作了进一步讨论。N_(2)吸附-脱附结果表明,加入适量Cu可以增大催化剂的比表面积,并增强催化剂表面对反应气体的吸附能力;XPS研究结果表明,Cu可以提高催化剂表面的氧空位数目。Cu与Fe之间具有协同作用,二者之间存在电子转移现象。H_(2)-TPR曲线表明Cu使催化剂的还原特征峰向低温方向移动,增强了其还原性能。

Fe和Cu分子筛催化剂同时催化NO_(x)还原和N_(2)O分解

采用离子交换法制备了Fe-Beta和Cu-SSZ-13催化剂并采用不同混合方式制备了复合催化剂,考察了催化剂同时催化NO_(x)还原和N_(2)O分解的性能.以实现NO_(x)和N_(2)O同时高效去除、拓宽活性温度窗口为目标,优选出了上Fe下Cu分层填充、Fe-Beta和Cu-SSZ-13质量比为4:1的Fe_(0.4)Cu_(0.1)催化剂,进一步考察了进气组成对NO_(x)、N_(2)O和NH_(3)转化率的影响,并采用N_(2)吸脱附、XRD、NH_(3)-TPD、UV-Vis DRS和H_(2)-TPR等手段对催化剂理化特性进行了表征.结果表明,Cu-SSZ-13和Fe-Beta分别具有更优的催化NO_(x)还原和N_(2)O分解性能.采用Fe_(0.4)Cu_(0.1)催化剂、[NH_(3)]/[NO_(x)]为1时考察的温度范围内NH_(3)仅还原NO_(x),而N_(2)O通过分解去除,450℃时NO_(x)和N_(2)O转化率分别为93.4%和100%.高温(>350℃)下NH_(3)被O_(2)氧化导致NO_(x)转化率随温度升高而降低;高温(≥350℃)下N_(2)O分解形成的氧物种可使NO_(x)在进气中无O_(2)条件下实现高效还原.进气中含2%H_(2)O对高温(450℃)下Fe_(0.4)Cu_(0.1)表面NO_(x)的还原和NH_(3)的氧化无显著影响,但对N_(2)O的转化存在一定的可逆抑制作用.Cu-SSZ-13表面存在大量孤立的Cu^(2+)离子,可为NH_(3)-SCR反应提供充足的活性中心.Fe-Beta表面同时存在能够催化NO氧化的孤立Fe^(3+)离子和催化N_(2)O分解的Fe_(x)O_(y)物种.采用上Fe下Cu分层填充的混合方式时Fe-Beta表面NO氧化过程会消耗N_(2)O分解形成的氧物种,从而有利于低温(≤450℃)下N_(2)O的转化.但由于N_(2)O分解的温度范围内NO_(x)转化率本身较高,NO氧化对于脱硝的促进作用不显著.

Catalytic Dechlorination of Chlorobenzene in Water by Pd/Fe System

Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min-1.

In situ preparation of well-dispersed CuO nanocatalysts in heavy oil for catalytic aquathermolysis

We developed an in situ synthesis strategy for preparing well-dispersed CuO nanoparticles as aquathermolysis catalyst for viscosity reduction in Shengli heavy oil(China). A Cu(OH)_2-contained microemulsion was employed as a carrier to disperse the precursor Cu(OH)_2 to the heavy oil phase. Under aquathermolysis condition(240 ℃, 2.5 MPa of N_2), the Cu(OH)_2 precursors would first be converted in situ to well-crystallized and size-homogeneous CuO nanoparticles naturally, catalyzed by which the viscosity of Shengli heavy oil could be reduced as much as 94.6%; simultaneously, 22.4% of asphaltenes were converted to light components. The agglomeration of the in situ prepared monoclinic CuO nanoparticles could be negligible throughout the catalytic reaction. Based on the characterization results of ~1 H NMR, elemental analysis and GC-MS of oil samples before and after catalytic aquathermolysis, the mechanism for viscosity reduction of heavy oil in the catalytic system was investigated.

Catalytic Dechlorination and Kinetics of o-Dichlorobenzene by Pd/Fe

o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water throughcatalytic reduction. The dechlorination reaction is believed to take place on the surface site ofthe catalyst via a pseuclo-first-order reaction. The final reduction product of o-DCB is benzene.The dechlorination rate increases with the increase of bulk loading of palladium due to the increaseof both the surface loading of palladium and the total surface area. Dechlorination efficiencyaccounts for 90% at Pd/Fe mass ratio 0.02% and metal to solution ratio about 53.3g · L^(-1) in 120minutes. Dechlorination is affected by the reaction temperature, pH, Pd/Fe ratio and the addition ofPd/Fe. E_a is found to be 102.5 kJ · mol^(-1) in the temperature range of 287—313 K.

A Comparison of Hydrothermal Aging, SO2 and Propene Poisoning Effects on NH3-SCR over Cu-ZSM-5 and Cu-SAPO-34 Catalysts

This study was aimed to investigate the effects of hydrothermal aging, propene and SO2 poisoning on the ammonia-selective catalytic reduction (NH3-SCR) performance of both Cu-SAPO-34 and Cu-ZSM-5. The catalytic activities of fresh, aged and poisoned samples were tested in ammonia-selective catalytic reduction (NH3-SCR) of NOx conditions. The XRD, TG and N2-desorption results showed that the structures of the Cu-SAPO-34 and Cu-ZSM-5 remained intact after 750˚C hydrothermally aged, SO2 and propene poisoned. After hydrothermal aging at 750˚C for 12 h, the NO reduction performance of Cu-ZSM-5 was significantly reduced at lower temperatures, while that of Cu-SAPO-34 was less affected. Moreover, Cu-SAPO-34 catalyst showed high NO conversion with SO2 or propene compared to Cu-ZSM-5. However, Cu-ZSM-5 showed a larger drop in catalytic activity with SO2 or propene compared to Cu-SAPO-34 catalyst. The H2-TPR results showed that Cu2 ions could be reduced to Cu and Cu0 for Cu-ZSM-5, while no significant transformation of copper species was observed for Cu-SAPO-34. Meanwhile, the UV-vis DRS results showed that CuO species were formed in Cu-ZSM-5, while little changes were observed for the Cu-SAPO-34. Cu-SAPO-34 showed high sulfur and hydrocarbon poison resistance compared to Cu-ZSM-5. In summary, Cu-SAPO-34 with small-pore zeolite showed higher hydrothermal stability and better hydrocarbon and sulfur poison resistant than Cu-ZSM-5 with medium-pore.

Fe/Cu催化还原去除饮用水消毒副产物三氯乙酸

以高致癌风险的饮用水卤化消毒副产物(halogenated disinfection by-products,HDBPs)三氯乙酸(TCAA)为去除目标物,研究了Fe/Cu催化还原去除TCAA的效果,包括Fe/Cu质量比、Fe/Cu混合物投加量、pH值、有机物浓度和摇床转速等因素对Fe/Cu催化还原去除TCAA的影响.结果表明,Fe/Cu能够有效脱除TCAA,m(Fe)∶m(Cu)为10∶1时的TCAA去除效果最佳;Fe/Cu最佳投加量为30 g.L-1;Fe/Cu还原脱氯去除TCAA最佳pH值在4～8之间;有机物浓度对Fe/Cu还原脱氯存在负面影响;在摇床转速、反应时间、投加量、pH值和UV254分别为200 r.min-1,160min,30 g.L-1,6.82和0.117 cm-1的条件下,Fe/Cu催化还原对TCAA的去除率达到97.39%,并且Cu未被消耗,外扩散Fe/Cu催化还原反应的影响可以忽略,Fe/Cu对TCAA的催化还原脱氯降解过程符合拟一级反应.

非均相UV/Fe-Cu-Mn-Y/H_2O_2反应催化降解4BS染料废水

制备了负载在Na Y分子筛上的Fe Cu Mn Y复合催化剂,并对其在非均相UV Fe Cu Mn Y H2O2体系中催化氧化4BS染料废水进行了研究.结果表明,非均相UV Fe Cu Mn Y H2O2体系对4BS染料废水的处理具有很高的效率.在基准条件下,反应时间为20min时,废水中4BS的去除率达到了93 7%.与均相UV Fenton体系不同,非均相UV Fe Cu Mn Y H2O2体系在碱性条件下(pH=10 5)仍可高效去除CODCr.动力学研究得到催化氧化4BS废水的模型方程,该模型可以为非均相UV Fe Cu Mn Y H2O2体系处理高色度的实际染料废水提供指导.