净化汽车尾气的三效催化剂

在我国，汽车尾气对大气的污染日趋严重，使用三效催化剂净化汽车尾气势在必行。介绍了几种主要的三效催化剂及其应用情况。     

Progress on metal-support interactions in Pd-based catalysts for automobile emission control

The interactions between metals and oxide supports, so-called metal-support interactions (MSI), are of great importance in heterogeneous catalysis. Pd-based automotive exhaust control catalysts, especially Pd-based three-way catalysts (TWCs), have received considerable research attention owing to its prominent oxidation activity of HCs/CO, as well as excellent thermal stability. For Pd-based TWCs, the dispersion, chemical state and thermal stability of Pd species, which are crucial to the catalytic performance, are closely associated with interactions between metal nanoparticles and their supporting matrix. Progress on the research about MSI and utilization of MSI in advanced Pd-based three-way catalysts are reviewed here. Along with the development of advanced synthesis approaches and engine control technology, the study on MSI would play a notable role in further development of catalysts for automobile exhaust control.     

P204f(D2EHPA)萃取分离回收催化剂母液中钴、锰

石油化工和化纤工业中大量使用钴,锰催化剂,应及时从各种废液中回收、再生,本文在25±1℃下研究了D_2EHPA-煤油从硫酸盐介质中萃取分离钴(Ⅱ)、锰(Ⅱ)的工艺,考察了萃取剂浓度、平衡pH值、相比对萃取的影响,求取了较适宜的工艺条件,利用五级逆流萃取模拟试验将钴、锰浓度比从1:1.5提高到1000:1,加入洗涤段后,又可获得金属含量比为1000的纯锰溶液,初步探索了用先进的液膜萃取新技术从溶液中分别富集、分离钴(Ⅱ)、锰(Ⅱ)的方法,找出了体系pH值对液膜萃取的影响,提出了从PTA氧化母液中回收废催化剂,萃取分离钴、锰,再生制备醋酸钴、醋酸锰和其他含钴、锰精细化工产品的工艺。     

Pd/ZrO【sub】2【/sub】-Al【sub】2【/sub】O【sub】3【/sub】催化剂加氢脱硫性能的研究

采用等体积浸渍法制备了一系列不同Zr含量的ZrO2-Al2O3复合载体和Pd/ZrO2-Al2O3催化剂,利用连续流动微反装置考察了Pd/ZrO2-Al2O3催化剂的噻吩加氢脱硫(HDS)性能,并运用程序升温还原(TPR),程序升温脱附(H2-TPD,NH3-TPD)和N2物理吸附等技术对载体及催化剂进行了表征.结果表明:ZrO2-Al2O3复合载体中Zr含量对Pd基催化剂的HDS性能有较大影响,加入适量Zr可增大Pd/Al2O3催化剂的分散度及H2吸附量和酸量,减弱活性组分与载体的相互作用,使活性中心和噻吩吸附位增多以及活化能降低,从而有利于Pd基催化剂HDS反应活性的提高,w(Zr)为9%时Pd/ZrO2-Al2O3催化剂的活性最好.     

负载TiO2的泡沫镍网光催化降解甲醛的膜厚优化

采用负载TiO2的泡沫镍网光催化降解甲醛,考虑内部和外部质量传递,建立了可预测优化催化剂膜厚的数学模型.分析了TiO2膜厚对光催化降解甲醛的影响,并在模型基础上分析了催化剂层内光的衰减系数和污染物的有效扩散系数对最优催化剂膜厚的影响.结果表明,随着催化剂膜厚的增加,甲醛的降解先增加而后趋于平缓;最优催化剂膜厚受UV光衰减系数的影响较大,受污染物的有效扩散系数的影响较小;由于TiO2催化剂对254nmUV光的强烈吸收,优化的催化剂膜厚只有80nm左右.该模型对实验数据拟合较好.     

Enhanced hydrolytic removal of tylosin in wastewater using polymer-based solid acid catalysts converted from polystyrene

Antibiotic production wastewater usually contains high concentrations of antibiotic residues, which can cause instability and deterioration of biological wastewater treatment units and also domestication and proliferation of antibiotic-resistance bacteria. An effective pretreatment on antibiotics production wastewater is expected to selectively reduce the concentration of antibiotics and decrease the toxicity, rather than mitigate organic and other contaminants before further treatments. In this work, two polymer-based solid acids, PS-S and CPS-S bearing high concentrations of -SOH₃ groups (up to 4.57 mmol/g), were prepared and successfully used for hydrolytic mitigation of 100 mg/L tylosin within 20 min. The co-existence of high concentrations of COD and humic substances did not affect the mitigation of tylosin obviously, while more than 500 mg/L of nitrogenous compounds suppressed the hydrolytic efficiency. Recycle and reuse experiments showed that the solid acids performed well in five cycles after regeneration. Three transformation products (P1, P2 and P3) were identified using UPLC-QTOF-MS/MS. Sugar moieties including mycarse, mycaminose, and mycinose detached and released simultaneously or in order from the 16-member lactone ring through desugarization, which led to a dramatic decrease in antibacterial activity as revealed by cytotoxicity evaluations using S. aureus. Ecotoxicity estimation indicated the acute toxicities of the hydrolyzed products to model species (e.g., fish, daphnid and green algae) were classified as “not harmful”. This work suggested an effective and selective method to pretreat tylosin-contained production wastewater by using polymer-based solid acids. These results will shed light on effective elimination of antibiotics pollution from pharmaceutical industries through strengthening the pretreatments.     

Ti-Cu-Mn复合物负载石墨烯催化剂制备及其降解二甲苯性能

采用水热法制备了4种不同摩尔比的Cu-Mn-Ti/GS复合物催化剂,利用固定式反应床评价了其对二甲苯的催化氧化性能,并对催化剂进行了BET、XRD、SEM、TEM、XPS等表征,探讨了其对二甲苯的降解动力学.结果表明,当催化剂的Cu、Mn含量增加时,其比表面积有所降低,总孔容也降低,降解活性减小.催化剂中Cu-Mn呈现Cu_(1.5)Mn_(1.5)O_4和CuMn_2O_4两种晶格,活性组分有Cu~+、CuMn O和TiO_2.石墨烯载体的稳定性较好,Ti-Cu-Mn/GS(1∶1∶1)催化剂的颗粒分布较均匀,粒径也较小,降解二甲苯的T50为97℃,表现出较好的低温催化降解性能.催化剂对二甲苯的催化氧化降解过程符合一级反应动力学方程.     

催化氧化NO催化剂Mn/ZrO2的制备与性能研究

以二氧化锆为载体负载锰氧化物,制备了MnO x/ZrO2催化剂用于催化氧化法(SCO)脱除烟气NO,考察了制备条件和反应条件对催化剂SCO活性的影响.同时,采用N2吸附、SEM、XRD及XPS等手段对催化剂理化性质进行了表征.结果表明,采用等体积浸渍法,以硝酸锰作为前驱体制备的Mn8/ZrO2/450催化剂在300℃、空速15000 h-1条件下,NO转化率可达84%,表现出较好的NO氧化活性.催化剂的主要活性组分为MnO2,在催化剂载体表面上呈现出较好的分散度.对催化剂进行了NO等温吸附与程序升温脱附,结合程序升温表面反应(TPSR)实验,探讨了催化剂表面NO催化氧化机理.研究发现,NO在该催化剂表面主要以吸附态反应,在含氧气氛中吸附态NO的氧化速率高于脱附速率,表面NO2的脱附峰温与最佳SCO活性温度相吻合.上述结果表明,NO转化过程速率受氧化产物NO2的脱附步骤控制,表面反应为快速步骤.     

多相催化臭氧氧化技术机理研究进展

多相催化臭氧氧化技术能够有效去除水中的微量有机物。尽管有越来越多的研究致力于多相催化臭氧氧化技术领域,以及各种新的催化剂的引入,但对于多相催化臭氧氧化技术机理尚不清楚。因此,本文针对多相催化臭氧氧化技术中常用的负载型金属、负载型金属氧化物以及活性炭三类催化剂的反应机理进行了探讨。此外还对机理研究中存在的问题进行了探讨。     

Oxidation of Toluene on γ-Al2O3 Supported Copper–Manganese Catalysts

Abstract Catalytic incineration of toluene over γ-Al2O3-supported copper–manganese oxide catalysts in the temperature range of 433?K–553?K was investigated using a fixed-bed flow reactor. Catalysts were characterized using Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, temperature-programmed reduction, temperature-programmed oxidation, X-ray photoelectron spectroscopy, and X-ray diffraction. Incineration of toluene was achieved at temperatures up to 553?K and it was found that the weight ratio of reactants (Cu:Mn) was optimized to be 15:10. Brunauer-Emmett-Teller surface area results had no correlation with the activity of the catalysts. Results of temperature-programmed reduction/temperature-programmed oxidation and X-ray photoelectron spectroscopy showed that the redox peak of the 15Cu-10Mn catalyst shifted at lower temperatures and the binding energy shifted toward higher oxidation levels. These results show that high binding energy and high redox capacity are the causes of...