改进钒基SCR脱硝催化剂的抗碱金属中毒性能

以锐钛矿型二氧化钛和钛钨粉(5%WO3-TiO2)为载体,制备了系列钒和钨负载量不同的钒钛催化剂,考察碱金属和碱土金属(钾、钠和钙)对催化剂在氨选择性催化还原(NH3-SCR)氮氧化物反应中催化活性的影响。钾、钠和钙对钒钛催化剂的中毒影响大小顺序为钾钠钙。提高钒钛催化剂中钒的含量可显著提高催化剂的SCR活性和抗碱金属中毒性能,但高钒负载量(4.5%V2O5)造成催化剂氮气选择性明显下降,氧化亚氮生成显著增加。钨的添加有利于提高钒钛催化剂的低温活性和抗碱金属中毒性能,对氮气选择性无明显影响。     

SO2对MnOx/PG催化剂低温脱硝的影响机理研究

采用等体积浸渍法制备了锰氧化物负载凹凸棒石(MnO_x/PG)低温SCR催化剂,通过SO₂暂态响应、程序升温表面反应(TPSR)等实验技术研究了烟气中SO₂对催化剂SCR脱硝活性的影响行为.采用程序升温脱附(TPD)、BET比表面及孔径分布测定、XPS等表征技术对催化剂硫中毒的机理及化学本质进行了深入分析.结果表明,低温下烟气中SO₂对MnO_x/PG催化剂的SCR脱硝活性存在显著的抑制作用,催化剂中毒主要由烟气中SO₂的催化氧化引起.一方面SO₂氧化为SO₃后与NH₃及H₂O竞争反应形成复杂的硫酸铵盐堵塞催化剂孔道,另一方面与活性组分MnO₂结合形成MnSO₄使得部分活性组分形态发生变迁.其中硫酸铵盐的形成可通过适当的热处理得以去除,而MnSO₄则不可恢复,但催化剂SCR活性却显著增加,表明MnSO₄的形成不是催化剂失活的主要因素.吸附态的硫可显著增加催化剂表面酸性,因此对SCR活性有促进作用.催化剂失活主要机理为:由气相SO₂的连续氧化并与NH₃相结合形成硫酸铵盐,并且在低温下难以分解,以致堵塞催化剂活性中心.     

Synergistic effect of Pt nanoparticles and micro-mesoporous ZSM-5 in VOCs low-temperature removal

Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide (TPAOH) solution with different concentration. The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature. The catalyst treated with TPAOH of 0.1 mol/L (Pt/ZSM-5(0.1)) shows the lowest degradation temperature (T_90%) of 128 and 142°C, respectively for benzene and n-hexane. Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal. More importantly, the existence of H₂O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128°C, which is very important for VOCs low-temperature removal in the future practical applications.     

Co- or Ni-modified Sn-MnOx low-dimensional multi-oxides for high-efficient NH3-SCR De-NOx: Performance optimization and reaction mechanism

NH₃-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis method.Due to its strong oxidation performance,Sn-MnOx was prone to side reactions between NO,NH₃ and O₂,resulting in the generation of more NO₂ and N₂ O,here most of N₂ O was driven from the non-selective oxidation of NH₃,while ...     

粉煤灰基催化剂深度处理印染废水的研究

采用粉煤灰基催化剂催化臭氧氧化深度处理印染废水。通过正交试验考察了O3输出体积分数、催化剂的投加量、pH值、反应时间对处理效果的影响,影响程度从大到小依次为:O3输出体积分数>pH值>催化剂投加量>反应时间。并通过单因素实验确定在最佳反应条件下:O3的输出体积分数为40%(即质量浓度为9.22 mg/L),催化剂的投加量为4 g,pH值为6.5,反应时间为60 min;COD的去除率能从单独臭氧氧化的41.44%提高到73.87%,色度去除率也能达到98%。各项指标均达到了印染废水的回用要求。     

A comparative investigation of NdSrCu_(1-x)Co_xO_(4-δ) and Sm_(1.8)Ce_(0.2)CU_(1-x)Co_xO_(4-δ) (x: 0-0.4) for NO decomposition

A series of single-phase T-structured NdSrCu_(1-x)Co_xO_(4-δ) with oxygen vacancies and T'-structured Sm_(1.8)Ce_(0.2)Cu_(1-x)Co_xO_(4-δ) (x:0-0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-progranuned desorption (NO-TPD). The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCut_xCoxO4_b catalysts were of oxygen vacancies whereas the Sm_(1.8)Ce_(0.2)CU_(1-x)Co_xO_(4-δ) ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level,the oxygen vacancy density of NdSrCu_(1-x)Co_xO_(4-δ) decreased while the over-stoichiometric oxygen amount of Sm_(1.8)Ce_(0.2)CU_(1-x)Co_xO_(4-δ)increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO_(3.702) catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr~(-1), and 600-900℃, the catalytic activity of NO decomposition followed the order of NdSrCuO_(3.702)> NdSrCu_(0.8)Co_(0.2)O_(3.736) > NdSrCu_(0.6)Co_(0.4)O_(3.789) > Sm_(1.8)Ce_(0.2)Cu_(0.6)Co_(0.4)O_(4.187)> Sm_(1.8)Ce_(0.2)Cu_(0.8)Co_(0.2)O_(4.104)> Sm_(1.8)Ce_(0.2)CuO_(4.045), in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu~(3+)/Cu~(2+) redox ability of NdSrCu_(1-x)Co_xO_(4-δ) account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.     

金属催化剂对油漆板材催化热解产物的影响

研究使用CaCO3、CaO、Fe2O3、还原铁粉、Na2CO35种金属催化剂对油漆板材进行热解,收集固、液两相产物进行产率计算和检测分析.结果表明,5种催化剂都有效提高了热解固相产物的产率,CaCO3、Na2CO3以及还原铁粉可以增加液相产品产率.钛元素在所有催化热解固相产物含量均较高,可能造成潜在的环境污染.热解液相...     

Mn1-yNiyOx的制备及其催化燃烧甲苯性能的研究

通过水热共沉淀法制备了Mn_1-yNi_yO_x复合氧化物催化剂(y=0.1~0.5),考察掺杂Ni对Mn基氧化物在甲苯燃烧中的影响,在获得最优锰镍比例后,对其热稳定性与耐久性进行测试,然后通过XRD、N₂吸脱附、SEM、H₂-TPR以及XPS对其物理结构和氧化还原性能进行表征.结果表明,Mn和Ni在甲苯吸附和活化中产生相互作用,生成更多的Mn⁴⁺以及表面吸附氧,提供大量的反应活性位点,增强了催化氧化性能.Mn_0.8Ni_0.2O_x在甲苯催化燃烧中表现出的催化性能最好,其热稳定性与耐久性也表现优异,与MnO_x在甲苯催化燃烧中相比,其T₅₀、T₉₀分别下降12和11 ℃,在238℃即可将甲苯完全氧化,并且碳平衡值约为99%,无二次污染产生,该研究成果可为挥发性有机化合物(VOCs)催化燃烧提供更好的方式和材料.     

Ru/ZrO2催化剂高温焙烧对NO催化氧化反应性能的影响

采用浸渍法制备了一系列负载Ru催化剂,并将其应用于NO催化氧化反应.同时,对Ru/ZrO2样品在不同温度下进行焙烧处理,并通过X-射线衍射(XRD)、程序升温还原(TPR)和透射电子显微镜(TEM)等技术对不同温度焙烧的Ru/ZrO2进行表征,根据表征结果对导致Ru/ZrO2催化活性下降的原因进行了探讨.结果表明,Ru/ZrO2催化剂具有很好的催化活性,在空速为180000h-1条件下,275℃时即可获得93%的NO转化率.高温焙烧会导致Ru/ZrO2催化活性明显下降.     

Removal of Cinnamic Acid Derivatives from Aqueous Effluents by Fenton and Fenton-like Processes as an Alternative to Direct Biological Treatment

The removal of various phenolic acids (p-coumaric, caffeic and ferulic acids), typically found in wastewaters of agricultural origin, from model effluents by chemical and biological means has been investigated. Chemical oxidation processes comprising hydrogen peroxide and a homogeneous or heterogeneous copper or iron catalyst were employed over a wide range of experimental conditions. Chemical oxidation is capable of removing most of the total organic carbon initially present in the effluent at relatively mild treatment conditions (i.e. reaction times up to 120 min and temperatures up to 80°C), while removal rates generally increase with increasing temperature, H₂O₂ and catalyst concentrations. The anaerobic degradability and toxicity of p-coumaric acid has been assessed using the biochemical methane potential and anaerobic toxicity assay respectively. p-Coumaric acid, at concentrations below about 1 g/L, is not toxic against methanogens and slowly degrades over a period of about 35 days at 35°C. In light of this, chemical oxidation may provide a promising alternative to direct biological treatment for either the partial or complete removal of phenolic acids at reasonable treatment times; the implications for wastewater treatment are discussed.