Incinerating volatile organic compounds with ferrospinel catalyst MnFe2O4: an example with isopropyl alcohol

This paper concerns the incineration of isopropyl alcohol (IPA) using the ferrospinel catalyst MnFe2O4. It covers the preparation of the ferrospinel catalyst, the screening of catalytic activity, catalytic incineration testing, and 72-hr decay testing of the catalyst. The experimental results of catalyst screening reveal that the Mn/Fe catalyst is the best of five prepared catalysts (chromium/iron [Cr/Fe], manganese/iron [Mn/Fe], zinc/iron [Zn/Fe], nickel/iron [Ni/Fe], and pure magnetite [Fe3O4]). In tests of the catalytic incineration system used to convert IPA, 98% conversion was obtained at a space velocity of 24,000 hr(-1), an oxygen (O2) content of 21%, 1700 ppm of IPA, and a reaction temperature of 200 degrees C.     

The promoter effect and a rate expression of the catalytic incineration of (CH3)2S2 over an improved CuO-MoO3/gamma-Al2O3 catalyst

The CuO-MoO3/gamma-Al2O3 catalyst, confirmed previously as having good activity in the catalytic incineration of (CH3)2S2, was employed as the principal catalyst in this study. With the aim of improving catalyst activity and resistance to deactivation by sulfur compounds, a promoter was added either before adding the precursors of Cu and Mo or together with Cu and Mo onto the gamma-Al2O3. Promoters included transition metals and elements from groups IA-VIIA in the chemical periodic table. Experimental results reveal Cr2O3 as the most effective promoter, with an optimal composition of 5 wt.% Cu, 6 wt.% Mo and 4 wt.% Cr (designated as Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3). Knowing that higher acidity can improve activity, we further investigated the effect of acid treatment on the performance of the Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3 catalyst. Experimental results indicate the H2SO4-treated catalyst (Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3) has a better activity and durability. A study for finding an appropriate rate expression for the catalytic incineration of (CH3)2S2 by Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3 was carried out in a differential reactor. The results show that the Mars-Van Krevelen model is applicable to this destructive oxidation reaction. Results additionally reveal that competitive adsorption of CH4 reduces conversion of (CH3)2S2.     

CuCoOx／TiO2催化氧化NO性能研究

采用浸渍法制备了CuCoOx／TiO2催化剂，考察了焙烧温度、反应温度、氧含量、NO浓度和空间速度对催化剂催化氧化NO性能的影响，并考察了催化剂的抗硫抗水性能。XRD、TPR和BET分析表明，350℃焙烧的催化剂具有CuCo2O4尖晶石结构，比表面积大，对NO的氧化效果好。在空速为5000h^-1，NO进口浓度500mg／m^3，含氧量10％的条件下，反应温度300℃时NO转化率可达79．5％，250℃时NO转化率接近50％。该催化剂具有良好的单独抗SO2、抗H2O毒化性能，H2O和SO2同时存在时很快失活。该催化剂可用于不同时含H2O和SO2的含NO气体催化氧化后再吸收处理。     

Catalytic destruction of pentachlorobenzene in simulated flue gas by a V2O5-WO3/TiO2 catalyst

Pentachlorobenzene (PeCB) in simulated flue gas was destructed by a commercial V₂O₅-WO₃/TiO₂ catalyst in this study. The effects of reaction temperature, oxygen concentration, space velocity and some co-existing pollutants on PeCB conversion were investigated. Furthermore, a possible mechanism for the oxidation of PeCB over the vanadium oxide on the catalysts was proposed. Results show that the increase of gas hourly space velocity (GHSV) and the decrease of operating temperature both resulted in the decrease of PeCB removal over the catalyst, while the effect of the oxygen content in the range of 5-20% (v/v) on PeCB conversion was negligible. PeCB decomposition could be obviously affected by the denitration reactions under the conditions because of the positive effect of NO but negative effect of NH₃. The introduction of SO₂ caused the catalyst poisoning, probably due to the sulfur-containing species formed and deposited on the catalyst surface. The PeCB molecules were first adsorbed on the catalyst surface, and then oxidized into the non-aromatic acyclic intermediates, low chlorinated aromatics and maleic anhydride.     

Mn的氧化价态对Mn／γ-Al2O3催化剂催化臭氧氧化气相低浓度甲苯的影响

采用共沉淀法，以Al2O3为载体制备Mn／γ-Al2O3和Mn—Ce／Mn／γ-Al2O3催化剂，并分别在N2气氛和O2气氛下焙烧。采用固定床连续流动反应器，研究所制备催化剂在室温条件下催化臭氧氧化甲苯的性能。通过XRD、XPS和FTIR等手段对催化剂的结构和组成进行表征。结果表明，Mn／Mn／γ-Al2O3催化剂具有良好的催化臭氧氧化甲苯和催化臭氧自身分解的性能，共沉淀法制备催化剂的最佳Mn负载量为20％。O2气氛焙烧和Ce的加入，可以有效提高催化剂的活性和寿命。原因是O2气氛焙烧和Ce的加入可以提高Mn的氧化价态。催化剂失活的主要原因是有机副产物在催化剂表面吸附堆积，失活催化剂在550℃、空气气氛下焙烧可恢复催化性能。     

双氧水催化氧化中Cu/γ-Al_2O_3催化剂的稳定性研究

针对废水湿式双氧水催化氧化,采用浸渍法制备Cu催化剂,研究非均相Cu催化剂在常温常压湿式双氧水催化氧化中的稳定性与失活问题。研究表明,催化剂制备条件及催化氧化反应条件对催化剂中Cu2＋溶出均有影响。研究同时表明,催化剂失活与活性组分流失和活性组分被有机中间产物覆盖有关,高温焙烧可对催化剂再生。     

CeO2-CoO／ACF低温SCR烟气脱氮性能的研究

活性炭纤维（ACF）经硝酸处理后采用浸渍法制备了CeO2-CoO／ACF复合催化剂，测试了其在以氨气为还原剂的低温SCR过程中的催化活性，同时研究了金属氧化物浸渍顺序及负载量、催化剂煅烧温度、空速比（SV）、NH，／NO（摩尔比）、O2含量等因素对NO转化效率的影响。研究发现，负载量为10％的CeO2-CoO／ACF复合催化剂经煅烧后在120—240℃时具有很高的催化活性，并且在N0初始浓度为1000mg／m3、空速比（SV）为6000h～、NH3／NO为1．05、O：体积分数在3．0％时具有较高的NO转化效率。     

铈改性Al2O3担载Pd催化剂的CO氧化性能研究

浸渍法制备了Al2O3＋CeO2为载体的Pd催化剂，对制备中各因素对催化剂效果的影响作了初步研究。考察了活性组分含量与催化剂性能的关系以及焙烧温度、水蒸气对催化剂活性的影响。结果表明，稀土Ce元素的存在使催化剂的性能得到明显改善。制备过程中焙烧步骤对催化剂的活性影响很大，催化剂制备必须高于600℃焙烧。     

Catalytic reduction of N2O over Ag-Pd/Al2O3 bimetallic catalysts

A study of the catalytic conversion of N2O to N2 over a bimetallic Ag-Pd catalyst is described in this article. Several Ag-Pd catalytic systems were prepared supported on Al2O3 with different ratios and their catalytic activity for the direct decomposition of N2O and their reduction with CO was measured. Based on the experimental results, it was observed that Ag-Pd bimetallic catalyst (5-0.5%) was the most active for both nitrous oxide reduction and direct decomposition. This high activity seems to be connected with a synergistic effect between Ag and Pd.     

Catalytic destruction of 1,2-dichlorobenzene on V2O5-WO3/Al2O3-TiO2 catalyst

Studies on the catalytic destruction of 1,2-dichlorobenzene were carried out on a specially constructed semi-technical equipment whose most important element was a catalytic reactor with a monolithic catalyst in the form of 150 x 150 x 100 mm cubes. A catalyst made from cordierite with an active layer composed of Al2O3 - 64 wt%, TiO2 - 26 wt%, V2O5 - 6.6 wt% and WO3 - 3.4 wt% was used. The reactor made it possible to carry out the process in the temperature range 150-350 degrees C, at variable catalyst loading and different velocities of gas flow through the reactor. The content of 1,2-dichlorobenzene in the air was analysed by a chromatographic method. A significant effect of catalyst loading and temperature on 1,2-dichlorobenzene destruction efficiency was observed and no effect of the linear flow velocity through the catalyst on o-dichlorobenzene destruction efficiency was reported. The applied vanadium-tungsten catalyst on a monolithic carrier made from TiO2/gamma-Al2O3 revealed very good activity that resulted in an over 80% efficiency of 1,2-dichlorobenzene destruction at the temperature around 250 degrees C at a very high catalyst loading reaching ca. 8200 h(-1). Additionally, in this study the kinetics of 1,2-dichlorobenzene decomposition was determined, specifying the order of reaction and dependence of the decomposition rate constant on temperature, using a simple power-rate law model.     

Characterization and reactivity of natural manganese ore catalysts in the selective catalytic oxidation of ammonia to nitrogen

Natural manganese ore (NMO) catalysts were characterized and tested in the selective catalytic oxidation of ammonia to nitrogen oxides under dilute conditions. Also, the oxidation of ammonia (NH(3)) was carried out using pure MnO(2), Mn(2)O(3) for comparing with the activity. It is found that the activity of NMO was similar to that of MnO(2) at low temperature below 150 degrees C but above this temperature, the activity of these catalysts showed the difference. In the course of NH(3) oxidation, N(2), NO, N(2)O and H(2)O were produced. But the quantity of NO(2) produced in this experiment was negligible. At temperature below 250 degrees C, selectivity into N(2) from NH(3) oxidation was in the order, NMO > MnO(2) > Mn(2)O(3). This is the reverse of activity of these manganese oxides. Also the characterization of NH(3) oxidation was proposed and supported by the effect of space velocity, inlet O(2) and NH(3) concentration. The increase of space velocity remarkably influenced not only the conversion but also selectivity into N(2). The higher the reaction temperature was, the higher the effect of inlet O(2) and NH(3) concentration on the reaction rate was. By introducing NO during NH(3) oxidation reaction, the possibility of NMO as selective catalytic reduction catalyst at low temperature was studied and showed positive results.     

Incinerating Volatile Organic Compounds with Ferrospinel Catalyst MnFe2O4: An Example with Isopropyl Alcohol

Abstract

This paper concerns the incineration of isopropyl alcohol (IPA) using the ferrospinel catalyst MnFe₂O₄. It covers the preparation of the ferrospinel catalyst, the screening of catalytic activity, catalytic incineration testing, and 72-hr decay testing of the catalyst. The experimental results of catalyst screening reveal that the Mn/Fe catalyst is the best of five prepared catalysts (chromium/iron [Cr/Fe], manganese/iron [Mn/Fe], zinc/iron [Zn/Fe], nickel/iron [Ni/Fe], and pure magnetite [Fe₃O₄]). In tests of the catalytic incineration system used to convert IPA, 98% conversion was obtained at a space velocity of 24,000 hr^?1, an oxygen (O₂) content of 21%, 1700 ppm of IPA, and a reaction temperature of 200 °C.     

Selective catalytic oxidation of ammonia over copper-cerium composite catalyst

This work considers the oxidation of ammonia (NH3) by selective catalytic oxidation (SCO) over a copper (Cu)-cerium (Ce) composite catalyst at temperatures between 150 and 400 degrees C. A Cu-Ce composite catalyst was prepared by coprecipitation of copper nitrate and cerium nitrate at various molar concentrations. This study also considers how the concentration of influent NH3 (500-1000 ppm), the space velocity (72,000-110,000 hr(-1)), the relative humidity (12-18%) and the concentration of oxygen (4-20%) affect the operational stability and the capacity for removing NH3. The effects of the O2 and NH3 content of the carrier gas on the catalyst's reaction rate also are considered. The experimental results show that the extent of conversion of NH3 by SCO in the presence of the Cu-Ce composite catalyst was a function of the molar ratio. The NH3 was removed by oxidation in the absence of Cu-Ce composite catalyst, and approximately 99.2% NH3 reduction was achieved during catalytic oxidation over the Cu-Ce (6:4, molar/molar) catalyst at 400 degrees C with an O2 content of 4%. Moreover, the effect of the initial concentration and reaction temperature on the removal of NH3 in the gaseous phase was also monitored at a gas hourly space velocity of less than 92,000 hr(-1).     

Fe2O3-Cr2O3/TiO2系列催化剂的结构和脱硝性能

研究以纳米TiO2为载体,浸渍负载过渡金属氧化物,以CO为还原剂的脱硝催化剂的脱硝性能。实验中以计算量的Ni（NO3）2和Fe（NO3）3混合溶液浸渍纳米TiO2粉末,室温下搅拌30 min至混合均匀,放入旋转蒸发器中,70℃下至水分蒸干为止;所得粉末在550℃下、空气气氛中焙烧4 h即得所需催化剂。用以上方法分别制备2%Fe2O3-10%Cr2O3/TiO2、4%Fe2O3-8%Cr2O3/TiO2、6%Fe2O3-6%Cr2O3/TiO2、8%Fe2O3-4%Cr2O3/TiO2与10%Fe2O3-2%Cr2O3/TiO2等5种催化剂样品。实验结果表明,制备的催化剂具有较好的结构,分散较为均匀。对于CO＋NO反应,Fe2O3-Cr2O3/TiO2系列催化剂具有较好的催化活性,NO的转化率都达到了100%。其中,10%Fe2O3-2%Cr2O3/TiO2样品具有最好的低温活性,H2-TPR结果表明,这是由于10%Fe2O3-2%Cr2O3/TiO2催化剂更易于被CO预还原。     

CeO_2-CoO/ACF低温SCR烟气脱氮性能的研究

活性炭纤维(ACF)经硝酸处理后采用浸渍法制备了CeO2-CoO/ACF复合催化剂,测试了其在以氨气为还原剂的低温SCR过程中的催化活性,同时研究了金属氧化物浸渍顺序及负载量、催化剂煅烧温度、空速比(SV)、NH3/NO(摩尔比)、O2含量等因素对NO转化效率的影响。研究发现,负载量为10%的CeO2-CoO/ACF复合催化剂经煅烧后在120~240℃时具有很高的催化活性,并且在NO初始浓度为1 000 mg/m3、空速比(SV)为6 000 h-1、NH3/NO为1.05、O2体积分数在3.0%时具有较高的NO转化效率。     

Catalytic activity of Ru/Al2O3 for ozonation of dimethyl phthalate in aqueous solution

With dimethyl phthalate as the model pollutant and Ru/Al(2)O(3) as catalyst, this paper systemically investigates the removal of total organic carbon (TOC) of system. Our results have confirmed that Ru/Al(2)O(3) can significantly increase the effect of ozonation. TOC removal in 120 min can reach 72% while only 24% with ozone alone. The optimal catalyst preparing condition was 0.1 wt% Ru content, 600 degrees C calcination temperature, 0.5-1.0mm particle diameter, which is characterized by a high surface area and a large population of surface active sites. The contrasting experiments of ozone alone, catalyst adsorption after ozonation, and catalytic ozonation confirmed that catalytic reaction was the most important process to TOC removal in system with Ru/Al(2)O(3) as catalyst.     

Al2O3-supported transition-metal oxide catalysts for catalytic incineration of toluene

The catalytic incineration of toluene over gamma-Al2O3-supported transition-metal oxide catalysts in the temperature range of 200-380 degrees C was investigated employing a fixed bed flow reactor. CuO/gamma-Al2O3 was found to be the most active of seven catalysts tested. Using this catalyst with different wt% Cu in the incineration of toluene, we found that the optimal Cu content was 5 wt%. X-ray diffraction, BET surface area and hydrogen-temperature-programmed reduction showed that it was mainly the formation of large CuO crystals that caused declines in catalyst activity at Cu content above 5 wt%. Addition of water vapor or CO2 inhibited catalyst activity, but this effect was reversible. Although coexistence of toluene and n-hexane resulted in a reduction in n-hexane conversion, the impact on toluene oxidation was only negligible. Temperature-programmed desorption revealed that this differential effect was due to more competitive adsorption of toluene onto active sites of the catalyst.     

Innovative PCDD/F-containing gas stream generating system applied in catalytic decomposition of gaseous dioxins over V2O5-WO3/TiO2-based catalysts

Development of effective PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran) control technologies is essential for environmental engineers and researchers. In this study, a PCDD/F-containing gas stream generating system was developed to investigate the efficiency and effectiveness of innovative PCDD/F control technologies. The system designed and constructed can stably generate the gas stream with the PCDD/F concentration ranging from 1.0 to 100ng TEQ Nm(-3) while reproducibility test indicates that the PCDD/F recovery efficiencies are between 93% and 112%. This new PCDD/F-containing gas stream generating device is first applied in the investigation of the catalytic PCDD/F control technology. The catalytic decomposition of PCDD/Fs was evaluated with two types of commercial V(2)O(5)-WO(3)/TiO(2)-based catalysts (catalyst A and catalyst B) at controlled temperature, water vapor content, and space velocity. 84% and 91% PCDD/F destruction efficiencies are achieved with catalysts A and B, respectively, at 280 degrees C with the space velocity of 5000h(-1). The results also indicate that the presence of water vapor inhibits PCDD/F decomposition due to its competition with PCDD/F molecules for adsorption on the active vanadia sites for both catalysts. In addition, this study combined integral reaction and Mars-Van Krevelen model to calculate the activation energies of OCDD and OCDF decomposition. The activation energies of OCDD and OCDF decomposition via catalysis are calculated as 24.8kJmol(-1) and 25.2kJmol(-1), respectively.     

铁氧化物复合氧化铝催化臭氧化过程中溴酸盐的生成控制

以市售活性炭、硅藻土和氧化铝小球为载体，考察了负载铁基活性组分对催化臭氧化过程中溴酸盐的控制情况，其中，铁基复合氧化铝小球体现出更好的溴酸盐还原特性和催化剂稳定性，证实催化剂中铁氧化物是溴酸盐得到有效控制的主要活性组分。进一步考察了铁基复合氧化铝小球催化臭氧化处理实际原水过程中对溴酸盐的生成控制，以及反应过程中溶解性有机碳（DOC）的去除情况。结果表明，与单独臭氧化相比，该催化剂既能有效去除水中的溶解性有机物，又能明显抑制溴酸盐的生成，反应50h，其活性并没有明显下降。催化剂失活主要归因于吸附位点数量的下降，可以通过负载铁氧化物来实现催化剂的再生。     

Photocatalytic oxidation of gaseous DMF using thin film TiO2 photocatalyst

The heterogeneous photocatalytic oxidation of gaseous N,N'-dimethylformamide (DMF) widely used in the manufacture of synthetic leather and synthetic textile was investigated. The experiments were carried out in a plug flow annular photoreactor coated with Degussa P-25 TiO2. The oxidation rate was dependent on DMF concentration, reaction temperature, water vapor, and oxygen content. Photocatalytic deactivation was observed in these reactions. The Levenspiel deactivation kinetic model was used to describe the decay of catalyst activity. Fourier transform infrared (FTIR) was used to characterize the surface and the deactivation mechanism of the photocatalyst. Results revealed that carbonylic acids, aldehydes, amines, carbonate and nitrate were adsorbed on the TiO2 surface during the photocatalytic reaction. The ions, NH4+ and NO3-, causing the deactivation of catalysts were detected on the TiO2 surface. Several treatment processes were applied to find a suitable procedure for the regeneration of catalytic activity. Among these procedures, the best one was found to be the H2O2/UV process.