低钒和无钒基氧化物类NH_3-SCR催化剂研究进展

NH_3-SCR技术是脱硝领域中应用最多和最为成熟的技术。现已工业化应用的V_2O_5-WO_3(MoO_3)-TiO_2催化剂存在低温活性差、操作温度范围窄,活性组分V_2O_5具有生物毒性等缺陷。因此,开发高效、稳定且无毒的新型无钒基NH_3-SCR催化剂成为脱硝领域的研究热点。以不同活性基的氧化物催化剂为主线,综述了国内外低钒和无钒基氧化物类NH_3-SCR催化剂的研究进展,总结了原料配方和制备工艺对催化剂性能和反应机理的影响,并展望了脱硝领域未来可能的发展方向。     

臭氧催化氧化处理活性蓝染料废水及催化剂的研究

进行了臭氧化学氧化体系和臭氧催化氧化体系对活性蓝处理效果的比较。提出了常温常压下臭氧催化氧化预处理活性蓝染料废水的新方法。实验结果表明,臭氧催化氧化处理COD为13 800 mg/L的活性蓝染料废水时,最佳反应pH值为5～6,臭氧用量为80 mg/L时,反应时间约40 min,COD去除率大于80%,色度去除率大于90%,达到了预处理要求。     

湿式空气非均相催化氧化处理有机废水中难降解有机物的研究

湿式空气催化氧化是曩为经济的环境友好型高级氧化技术之一,在处理有机废水中难降解有机物方面极具前景.为提高氧化效率,钌（Ru）、铑（Rh）、铂（Pt）、钯（Pd）等贵金属及铜（Cu）、铈（Ce）、锰（Mn）、铁（Fe）、镍（Ni）、铝（Al）、铬（Cr）及钴（Co）等金属氧化物等常作为非均相催化剂应用到湿式空气催化氧化体系中.本文对非均相催化湿式空气氧化处理有机废水中难降解有机物的非均相催化剂、工艺条件及反应机理进行了探讨,最后指出了催化剂的失效、解决方法及技术发展方向.     

老化对钴铈基催化剂催化氧化丙烷的影响

采用柠檬酸络合法合成Co-CeO_x多活性中心催化剂,在不同温度进行加速老化处理,测试新鲜和老化后催化剂对丙烷的催化氧化性能,同时对其结构和性质进行表征.结果表明,当加速老化温度低于650℃时,丙烷转化率达50%的温度变化幅度小于10℃;加速老化温度高于750℃时,催化剂氧化丙烷的性能快速下降.表征结果显示,Co-CeO_x催化剂主要表现为尖晶石结构,老化后晶粒尺寸显著增大,Co³⁺的含量减少,氢还原峰温度升高.加速老化处理对Co-CeO_x催化剂物理结构的影响进而抑制了其化学特性及催化活性.测试Co-CeO_x催化剂对丙酮和甲苯的催化氧化性能,分别在179和244℃达到90%的脱除效率.因此,Co-CeO_x多活性中心催化剂具有良好的氧化性能,且表现出一定的稳定性.     

复合惰气在采空区遗煤中竞争吸附的分子动力学模拟研究*

为明确作用于采空区的复合惰气的竞争吸附,进行不同温度、压力及组分下烟煤对N2、O2、CO2多元气体竞争吸附分子的模拟研究。研究结果表明:当注入压力达到3 MPa后,竞争吸附效果不再明显,为高压注入提供一定的理论基础;随着CO2分压的增大,O2吸附量降低速度逐渐平缓,初步确定最佳注入配比范围为2∶1至3∶1,为进一步结合实际工程中成本等因素确定最佳注入配比提供参考;等量吸附热受吸附条件的影响较小,仅与吸附质本身有关;随着CO2分压的增大,范德华能升高56.9%,分子内能升高78.7%,静电能升高67.2%,CO2对整个系统内的吸附作用强度及吸附量有着较大的影响;随着CO2分压增大,N2竞争吸附能力逐渐弱于O2,竞争吸附能力大小顺序为CO2>O2>N2。     

过渡金属催化剂上CO还原NO反应性能的研究

在一系列负载型过渡金属催化剂上考察了ＣＯ－ＮＯ和ＣＯ－Ｏ２的反应性能。结果表明，催化剂的ＣＯ－Ｏ２反应活性高于ＣＯ－ＮＯ反应，催化剂表面ＮＯ解离是ＣＯ－ＮＯ反应的速率控制步骤。低温反庆有利于Ｎ２Ｏ的生成，高温有利于Ｎ２的生成。     

Effects of synthesis methods on catalytic activities of CoOx–TiO2 for low-temperature NH3-SCR of NO

A series of cobalt doped TiO_2(Co-TiO_2) and Co Oxloaded TiO_2(Co/TiO_2) catalysts prepared by sol–gel and impregnation methods respectively were investigated on selective catalytic reduction with NH_3(NH_3-SCR) of NO. It was found that Co-TiO_2 catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD,TEM, Raman and FT-IR, Co species were proved to be doped into TiO_2 lattice by replaced Ti atoms. After being characterized and analyzed by NH_3-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH_3-SCR activities of Co-TiO_2 catalysts, compared with Co/TiO_2 catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions(O-2). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates(NO-3) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH_3-SCR activity of Co-TiO_2 catalysts.     

甲基橙废水的常温常压催化湿式氧化实验研究

以Fe、Mn、Cu和Zn的金属氧化物为活性组分,以γ-Al2O3为载体,制备了负载型催化剂,并分别以H2O2和NaClO为氧化剂,对比了在常温常压条件下催化湿式氧化工艺中处理甲基橙模拟废水的效果.结果表明,Fe/y-Al2O3催化剂较其他催化剂表现出较好的催化活性和稳定性,H2O2为适宜的氧化剂.在Fe/γ-Al2O3加入量为10g/L,氧化剂H2O2加入量为5 mL/L的条件下,处理甲基橙质量浓度为500 mg/L的模拟废水,其脱色率和COD去除率在3 h内均能达到70%以上.与传统的Fenton试剂法相比,以Fe/γ-Al2O3为催化剂的催化湿式过氧化氢氧化工艺具有矿化程度高,催化剂易回收再用的优点.     

ZrxMg1-xO supported cobalt catalysts for methane decomposition into COx-free hydrogen and carbon nanotubes

Zirconia-magnesia supported cobalt catalysts with various Zr/Mg atomic ratios were prepared and evaluated for non-oxidative catalytic decomposition of methane to produce CO_x-free hydrogen and carbon nanotube. The catalytic performance of the catalysts was performed in a continuous fixed bed flow reactor at 700°C under atmospheric pressure. The fresh and spent catalysts were characterized by XRD, TPR, BET, TEM, and Raman spectroscopy. The results showed that the change in Zr/Mg ratio of the mixed oxide support has a significant effect on the catalytic performance of the active Co metal. The catalyst 30%Co/Zr_0.8Mg_0.2 showed the highest activity and stability within the used series of catalysts with hydrogen yield reached up to 79%. Both Co/Mg_1.0 and Co/Zr_1.0 showed poor stability due to strong Co-Mg interaction and aggregation of Co species on Zr support, respectively. All catalysts produced mainly MWCNTs with different diameters depending on the Zr/Mg ratio. The outer diameter increased with increasing Zr content in the catalyst due to the enlargement of the particle size of cobalt as a result of aggregation.     

载体特性对Pd-Cu/TiO2催化剂催化脱氮性能的影响

以Pd-Cu／TiO2为催化剂，采用催化加氢技术进行脱氮研究．结果表明：TiO2载体的特性对催化活性及N2选择性有显著影响，与773K和973K温度下焙烧得到的载体相比，以573K温度下焙烧得到的TiO2为载体制备的Pd（5wt％）-Cu（1．25wt％）／TiO2催化剂可显著提高催化效率及N2选择性．