Influence of preparation methods on the physicochemical properties and catalytic performance of MnO_x-CeO_2 catalysts for NH_3-SCR at low temperature

This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.

Preparation of Ultrafine and High Dispersion Pd/C Catalyst and Its Electrocatalytic Performance for Formic Acid Oxidation

A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.

Porous palladium phosphide nanotubes for formic acid electrooxidation

The development of an efficient catalyst for formic acid electrocatalytic oxidation reaction(FAEOR)is of great significance to accelerate the commercial application of direct formic acid fuel cells(DFAFC).Herein,palladium phosphide(PdxPy)porous nanotubes(PNTs)with different phosphide content(i.e.,Pd3P and Pd5P2)are prepared by combining the self-template reduction method of dimethylglyoxime-Pd(II)complex nanorods and succedent phosphating treatment.During the reduction process,the self-removal of the template and the continual inside-outside Ostwald ripening phenomenon are responsible for the generation of the one-dimensional hollow and porous architecture.On the basis of the unique synthetic procedure and structural advantages,Pd3P PNTs with optimized phos phide content show outstanding electroactivity and stability for FAEOR.Im portantly,the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction,which effectively enhances the FAEOR electroactivity of Pd3P PNTs.In view of the facial synthesis,excellent electroactivity,high stability,and unordinary selectivity,Pd3P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC.

Preparation of Spherical Tungsten Particles Assisted by Hydrothermal Method

We presented a strategy to prepare spherical tungsten powder by the combination of hydrothermal method and H2reduction process.In hydrothermal process,the micelle of tetraethylammonium bromide(TEAB)act as spherical templates for the deposition of tungsten oxide,whereas the excessive TEAB inhibit the formation of spherical tungsten oxide due to the dense molecular layer of TEAB on the tungsten oxide particles.Citric acid(CA)can control the formation rate and structure of the tungsten oxide when its concentration is more than 0.2 mol/L,because of its ability to coordinate with tungsten atoms.The synergistic effect of TEAB and CA facilitates the formation of spherical tungsten oxide with nanorod crown.After being treated by H_(2)at 600 and 650℃,the tungsten oxide particles are reduced to tungsten particles,which maintain the spherical structure of tungsten oxide and have porous structure.

基于过氧乙酸处理水中新污染物的研究进展

为了解决新污染物(emerging contaminants,ECs)在地表水和饮用水中威胁人类健康的问题,探讨了过氧乙酸(PAA)处理水中有机污染物的高级氧化技术(AOPs)。活化PAA有多种方式,包括光催化(紫外线UV)、超声活化(US)、过渡金属离子(Fe、Co、Mn和Cu)活化等。综述了基于PAA的AOPs去除水中有机污染物的相关研究成果,探讨了联用技术存在的问题与发展前景,为开发活化PAA技术处理水中新污染物提供了参考。

化学氧化法处理含甲酸废水实验研究

含甲酸废水直接排放不仅会造成严重的环境污染,还会造成一定的资源浪费。因此,以某化工企业含甲酸废水为研究对象,以废水中COD的去除率为评价指标,采用化学氧化法对其进行了处理,并重点评价了氧化剂类型、氧化剂加量、废水p H值、废水矿化度、氧化反应时间和氧化反应温度对含甲酸废水处理效果的影响。结果表明:在相同的实验条件下,6种不同类型的氧化剂中复合氧化剂FO-2的COD去除率最大,对目标含甲酸废水的处理效果最好。氧化剂的加量越大,氧化反应时间越长,COD去除率相对就越大;废水矿化度越高,COD去除率相对就越小;酸性至中性条件更有利于COD去除率的提高;氧化反应温度对COD去除率的影响相对较小。当复合氧化剂FO-2的加量为30 mg·L^(-1)、废水p H值为7、废水矿化度为2 000 mg·L^(-1)、氧化反应时间为50 min、氧化反应温度为30℃时,含甲酸废水经过化学氧化处理后的COD去除率可以达到90.4%。研究结果表明,化学氧化法能够满足低浓度甲酸废水处理的需求。

石灰铁盐法处理高砷废酸应用研究

选择工业具有代表性的高砷污酸,研究了石灰铁盐法控制性因素,如反应终点pH、Fe/As摩尔比、反应时间及氧化方式对除砷及固砷的影响。结合工业应用实际情况,在pH=1.2、石膏晶种比1∶1、反应时间2 h的条件下,优先产出合格石膏产品。再以H_(2)O_(2)为氧化剂,H_(2)O_(2)/As摩尔比1.5,反应终点pH=8,晶种比例1∶1,Fe/As摩尔比4.5,反应时间3 h进行除砷,除砷后液As浓度0.12 mg/L,小于标准值(0.5 mg/L),除砷率接近100%,除砷渣TCLP浸出毒性为2.25 mg/L,小于标准值(3 mg/L)。该工业应用工艺方法流程简单、操作方便、成本低廉,是一种可靠安全除砷固砷工艺。

焙烧工艺参数对酸再生系统和氧化铁粉的影响

介绍了喷雾焙烧法酸再生的工艺流程,通过控制变量法研究了焙烧工艺参数,如焙烧炉温度、负压、氧含量、酸枪压力,对酸再生系统和氧化铁粉的影响,讨论并分析了这几个工艺参数影响酸再生系统和氧化铁粉的原因,在此基础上提出了工艺参数优化的建议。

An improved Hummers method to synthesize graphene oxide using much less concentrated sulfuric acid

The production of graphene oxide with less acid is beneficial to reduce the costs and lower the impact on the environment,but it is still a great challenge.In this work,a relatively simple,safe method for synthesizing graphene oxide with much less acid(decrease∼40%)is proposed.With assistance of the heat absorbed from environment and reaction system,the temperature of reaction system of low acid can be well controlled.More interestingly,the graphite can be completely oxidized into graphite oxide by using much less acid,with lowering the production of high-concentration aqueous waste acid(>1 mol/L,decrease∼40%).A series of characterizations show that the prepared graphene oxide has similar yield and functional groups compared with that of using the conventional method.This work provides a safe and environmentally friendly choice for the large-scale production of graphene oxide and its derivative materials.

Preparation and Catalytic Performance of Potassium Titanate Used as Soot Oxidation Catalyst

To prepare potassium titanate catalyst, a novel citrate acid complex-combustion method using CH3COOK and Ti（OC4H9）4 as raw materials was developed. The crystalline phase and surface morphology of K2Ti205 were investigated by X-ray diffraction （XRD）, field emission scanning electron microscope （FE-SEM） and transmission electron microscope （TEM）. The impact of some factors, such as the type of contact between K2Ti205 and soot, the content of water vapor and SO2 in exhaust, and the repeated use on catalytic activity of K2Ti205 were studied by temperature programmed reaction （TPR）. A comparison between the new method and the reported ones on catalytic activity of potassium titanate was investigated. The results showed that K2Ti205 had high catalytic activity and good stability.

焙烧温度对不同硅铝比的硅铝复合氧化物酸性质的影响

用溶胶-凝胶法制备硅铝复合氧化物,利用热重-差热分析(TG-DTA)、傅立叶变换红外光谱(FTIR)、氨程序升温脱附(NH3-TPD)、吸附吡啶红外光谱(Py-IR)等表征手段探讨焙烧温度变化对硅铝复合氧化物酸强度、酸量和酸类型等性质的影响。结果表明:焙烧温度在500~900℃的考察范围内,硅铝复合氧化物样品均显示出弱酸和中强酸性;随处理温度升高,硅铝复合氧化物样品呈现硅、铝物种复合程度增加(Si—O—Al键增多),B酸中心数量逐渐减少,且总酸量递减的趋势,这可归因于高温条件下硅铝复合氧化物羟基数量的减少。与Al/Si原子数之比为0.05的硅铝复合氧化物相比,Al/Si原子数之比为0.5的硅铝复合氧化物具有更多的Si—O—Al键,且存在少量强酸位。

Fenton铁泥资源化利用

Fenton铁泥是指Fenton法处理废水后产生的污泥,经检测含有大量铁元素和有机物,如果不经过良好的处理,不仅污染环境,而且更是一种资源的浪费。将铁泥中的铁回收,制备铁系产品,可以实现资源化利用。本文针对Fenton铁泥的特性,选择废酸浸液还原法制备硫酸亚铁,并研究其制备条件和影响因素,主要包括废酸浓度、废铁屑粒径、反应温度等。

盐酸法钛白粉新工艺副产氯化亚铁制备四氧化三铁

探索了一种以盐酸法钛白粉新工艺副产氯化亚铁为原料制备四氧化三铁磁粉的放大试验工艺,把副产危废氯化亚铁制备成用途广泛的四氧化三铁磁粉,实现资源的综合利用。研究结果表明:选用氧化钙为沉淀剂与氯化亚铁反应得到氢氧化亚铁,在分散剂辅助作用下通入空气使氢氧化亚铁被氧化成三价氢氧化铁,控制氧化钙及分散剂加料时间间隔为1.5 h、氧化温度为80℃、氧化时间为8.5 h,将氢氧化铁与氢氧化亚铁以物质的量比为2∶1均匀混合,通过正压分离得到固体,控制分离前pH为6.5,最后通过烘干、研磨等后处理得到四氧化三铁磁粉。进行50 kg级别放大试验得到四氧化三铁产品,收率达到97%。该工艺将副产危废转化为有一定经济效益的产品,进一步完善了盐酸法钛白粉新工艺。

真菌六胺银染色技术的优化

目的探索真菌六胺银染色的优化方案,寻求染色效果佳且环保简便的染色试剂。方法选取已知真菌感染的阳性病理组织,分别制作成蜡块,通过对比试验,比较不同氧化剂、六胺银染液不同配制方法、不同衬染试剂对六胺银染色质量的影响。结果真菌感染组织切片使用2%高碘酸水溶液氧化,染色步骤较使用三氧化铬溶液氧化简便,且三氧化铬为高毒致癌物,高碘酸毒性较低,故选择2%高碘酸溶液作为氧化剂更优;六胺银改良配制重复利用法配制六胺银液较传统配制法简便,对染液的利用率高,可以重复回收使用,较节约成本;1%亮绿染液与苏木素染液均是教材推荐的衬染剂,但亮绿染液的染色效果显著优于苏木素染液。结论真菌感染组织切片使用2%高碘酸水溶液作为氧化剂、六胺银改良配制重复利用法配制的六胺银液染色、1%亮绿染液衬染为较佳方案。

镧和氧化石墨烯掺杂对TiO_(2)光催化性能的影响

采用一步溶胶-凝胶法将镧、氧化石墨烯(GO)和TiO_(2)三种物质复合,制备出一种高效的具有可见光响应的光催化材料。借助X射线衍射仪、X射线光电子能谱分析仪、扫描电镜等手段对该催化剂的晶体结构和形貌进行了表征,并以酸性红B作为目标污染物,研究了该复合材料在模拟日光辐照下的光降解性能。实验结果表明,镧和GO的掺杂显著提高了TiO_(2)的光催化活性,当镧掺杂量为0.5%(wt,质量分数,下同),GO掺杂量为0.2%时,对酸性红B的光降解率为95.6%。

液相氧化-喷雾干燥法制备高纯超细二氧化锡颗粒

为了减少反应中氮氧化物(NO_(x))排放对环境造成的影响,提高二氧化锡产品纯度、减小粒径,以金属锡粒和稀硝酸为原料,采用液相硝酸氧化法与喷雾干燥工艺结合制备高纯超细二氧化锡颗粒。考察锡源类型、硝酸浓度及滴加速度、反应温度及煅烧温度等参数对产物的影响,并利用X射线衍射仪、电感耦合等离子体发射光谱仪、扫描电子显微镜、激光粒度仪、比表面积分析仪等对所制备的偏锡酸(H_(2)SnO_(3))和二氧化锡进行结构和性能表征。结果表明:以锡粒为锡源、硝酸质量分数为25%、滴加速度为30 m L/min、反应温度为80℃,经喷雾干燥工艺处理,再经950℃煅烧,最终制得纯度为99.997%、D_(50)为1.15μm、D_(90)为2.44μm、比表面积为3.86 m^(2)/g的二氧化锡,该产品在屏幕显示技术领域有重要应用,可用于制备氧化铟锡粉体材料(ITO)。

难溶锰矿石中锰含量测定方法研究

文章研究了采用酸溶后残渣回收,高氯酸氧化,硫酸亚铁铵滴定的方式测定难溶锰矿中的锰含量。试验证明,本法具有很好的回收率和精密度,分析结果稳定,解决了难溶锰矿中锰含量分析的难题,应用效果良好。

利用实验室废硫酸制备聚合硫酸铁及处理效果的研究

实验室每年都会产生较多的废硫酸,废硫酸的处理也会产生不少的费用,储存在实验室也会产生安全隐患,本文主要研究利用实验室废硫酸与工业硫酸按照一定比例混合采用氯酸钠氧化法来制备聚合硫酸铁,将废硫酸加以利用变废为宝,不但对环境没有影响而且将废硫酸变成了净水剂,达到了以废治废的目的。自制聚合硫酸铁通过检测分析Fe^(3+),盐基度,Fe^(2+)等指标来判断自制聚合硫酸铁的可行性,结果显示检测指标均可满足国家对聚合硫酸铁生产的各项要求。通过应用自制聚合硫酸铁与市售聚合硫酸铁对污水的处理效果的各项指标来对比分析自制聚合硫酸铁对污水处理效果的可行性。结果显示:自制聚合硫酸铁与市售聚合硫酸铁对污水处理的各项指标的去除率基本相同,对污水的处理效果是一样的。

乙二醛阳极氧化制乙醛酸过程的化学分析方法

乙二醛阳极氧化制乙醛酸的电解液可用简便的化学分析法测定 ,其中草酸的定量可用钙盐沉淀后用高锰酸钾法测定 ;乙二醛的定量用坎尼查罗反应后用标准酸测定 ;醛总量用亚硫酸钠法测定 ,乙醛酸的定量用醛总量减乙二醛的量。

二氧化钛基固体超强酸的结构及其光催化氧化性能

采用 溶 胶凝 胶 法 制 备 了 多 孔 性 、大 比 表 面 积 的 Ｓ Ｏ２ －４ ／ Ｔｉ Ｏ２ 固 体 超 强 酸 催 化 剂， 运 用 Ｘ Ｒ Ｄ ， Ｂ Ｅ Ｔ 比表面 积测定 ， Ｘ Ｐ Ｓ 和 Ｕ Ｖ Ｖｉｓ 反 射光 谱等 技 术对 该 催化 剂 的结 构、表 面状 态 以 及半导体特 性进行了 表征，并 通过 Ｃ Ｈ３ Ｂｒ ， Ｃ６ Ｈ６ 和 Ｃ２ Ｈ４ 等典型有 机物的 气相光催 化氧 化反 应，考 察了 Ｓ Ｏ２ －４ ／ Ｔｉ Ｏ２ 催化剂 的光 催 化 反 应 性 能． 结 果 表 明， Ｓ Ｏ２ －４ ／ Ｔｉ Ｏ２ 催 化 剂 具 有 较 高 的 结 构 稳 定 性， Ｔｉ Ｏ２ 的超强 酸化有效 地抑制 了晶相转 变、晶粒 度增加和 比表 面积 下降． 与 Ｔｉ Ｏ２ 相 比， Ｓ Ｏ２ －４ ／ Ｔｉ Ｏ２的吸收 边蓝移 及禁带宽 度增加， 产生了较 大的氧 化还原势 ，导致光 催化效率 提高．