Cu–Mn–Ce ternary mixed-oxide catalysts for catalytic combustion of toluene

Cu–Mn, Cu–Mn–Ce, and Cu–Ce mixed-oxide catalysts were prepared by a citric acid sol–gel method and then characterized by XRD, BET, H₂-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu–Mn–Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu–Mn–Ce catalyst, a portion of Cu and Mn species entered into the CeO₂ fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu–Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu–Mn and Cu–Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.     

椰壳活性炭吸附消除VOCs

对一种椰壳活性炭对甲基丙烯酸甲酯的吸附消除行为进行了研究,重点考察了甲基丙烯酸甲酯的浓度、流速和吸附温度等条件以及水汽存在时对活性炭吸附行为的影响。结果表明,该颗粒活性炭对甲基丙烯酸甲酯有良好的吸附效果,甲基丙烯酸甲酯进口浓度和进气量的改变均会影响吸附饱和时间,导致其增加或减少。通过变温吸附实验确定降低环境温度对其吸附有促进作用。湿度为50%时吸附量相对干气饱和吸附量影响较小,说明该活性炭抗水汽能力较好。经多次重复再生实验,其饱和吸附量未见明显下降。     

Groundwater geochemical signatures and implication for sustainable development in a typical endorheic watershed on Tibetan plateau

Environmental Science and Pollution Research - Groundwater resource is significantly important for sustainable development of the world, especially for arid endorheic watersheds. A total of 28...     

MgAlFe复合氧化物氧化吸附SO_2的性质

MgAlFe水滑石在 6 0 0℃以上焙烧后脱去表面水和层间水形成MgAlFe复合氧化物 通过对MgAlFe复合氧化物BET、XRD表征和测定它的吸附硫容 ,发现它对SO2 有优良的氧化吸附性能 吸附SO2 后MgO和尖晶石相消失 ,形成硫酸盐晶相 用氢气对饱和吸附SO2 后的MgAlFe复合氧化物进行还原再生 ,发现它经过 10次吸附还原循环后 ,MgO和尖晶石的晶相依然存在 ,是一种可循环利用脱除SO2 的环境催化材料     

Cu-Mn-Ce ternary mixed-oxide catalysts for catalytic combustion of toluene

Cu–Mn, Cu–Mn–Ce, and Cu–Ce mixed-oxide catalysts were prepared by a citric acid sol–gel method and then characterized by XRD, BET, H_2-TPR and XPS analyses. Their catalytic properties were investigated in the toluene combustion reaction. Results showed that the Cu–Mn–Ce ternary mixed-oxide catalyst with 1:2:4 mole ratios had the highest catalytic activity, and 99% toluene conversion was achieved at temperatures below 220°C. In the Cu–Mn–Ce catalyst, a portion of Cu and Mn species entered into the Ce O_2 fluorite lattice, which led to the formation of a ceria-based solid solution. Excess Cu and Mn oxides existed on the surface of the ceria-based solid solution. The coexistence of Cu–Mn mixed oxides and the ceria-based solid solution resulted in a better synergetic interaction than the Cu–Mn and Cu–Ce catalysts, which promoted catalyst reducibility, increased oxygen mobility, and enhanced the formation of abundant active oxygen species.     

水蒸气对改性椰壳活性炭吸附VOCs的影响

选取甲苯、甲基丙烯酸甲酯、吡啶3种不同极性的有机物作为吸附质,改性椰壳活性炭作为吸附剂,使用穿透曲线法研究了水蒸气对这3种VOCs在活性炭上吸附行为的影响,并同时讨论了水蒸气预处理对活性炭吸附的影响。结果表明,改性椰壳活性炭对3种有机废气均具有良好的吸附性能,但水蒸气的存在对极性小的甲苯吸附影响较大,尤其当甲苯浓度较低时,水分子易与甲苯产生竞争吸附。在对活性炭吸湿预处理后发现,吡啶、甲基丙烯酸甲酯分子可以置换出活性炭预先吸附的水分子,并且通过低温水蒸气加热再生法可以方便地完成活性炭再生过程,重复再生率可以维持在85%。     

催化氧化还原吸收法脱除工业含湿废气中NOx

基于精细化工、制药行业排出 NOx 废气氧化度低、氧气含量高的特点,提出以改性活性炭(MAC)为催化剂的催化氧化-还原吸收脱除 NOx 的方法.考察了相对湿度、氧化温度、氧化时间对 NO 催化氧化以及还原液种类对 NOx 吸收的影响.结果表明,随着相对湿度的增加 NO 转化率急剧下降,但随着氧化时间的延长有所提高;干气条件下,随着温度升高,NO 转化率下降;湿气条件下,NO 氧化反应最佳反应温度范围为 50～70℃,实验条件下的 NO 最高转化率可达 51%;还原液种类中以尿素-碱液对 NOx 和 NO 的吸收效果最好,亚硫酸铵-碱液对 NOx 的吸收效果最好.通过催化氧化-还原吸收的多级组合可实现 NOx 的有效脱除与达标排放.     

VOCs和水在Y型分子筛表面的竞争吸附

采用水热处理方法合成了具有不同硅铝比的超稳Y型分子筛,考察了苯、甲苯、二甲苯、苯乙烯和乙酸乙酯与水在Y分子筛表面的竞争吸附。结果表明,随着Si/Al比的增加,Y分子筛表面的有机分子选择性吸附位数量增加,有机分子竞争吸附能力增加。低硅Y型分子筛只有在吸附偶极距>1.0的高极性有机分子时才能与水分子产生有力的竞争吸附,而高硅超稳Y分子筛则对偶极距在0～0.5范围的有机分子就表现出很强的竞争吸附能力。     

全硅β分子筛催化氧化NO性能研究

针对NO氧化催化剂抗水汽性差、活性温度高等问题,本研究采用疏水型全硅β分子筛为催化剂,在NO进口浓度为0.05%(体积分数)、O2浓度为20.7%(体积分数)条件下,考察了反应温度(20~60℃)、相对湿度(0%~100%)、空速(360 h-1~20 000 h-1)等因素对NO催化氧化的影响。研究结果表明,随着反应温度升高,干气和湿气下NO氧化率都下降,低温有利于NO氧化;在20℃,空速为20 000 h-1条件下,相对湿度从0%增大到100%时,NO氧化率从49%下降到34%。反应温度升高会抑制水汽对NO氧化的影响。240 h催化剂稳定性实验结果表明,在30℃,NO进口浓度为0.05%,空速为7 200 h-1时,干气和饱和水汽下的NO氧化率分别能稳定地维持在67%和56%水平,说明全硅β分子筛即使在饱和水汽下也具有良好的稳定性及抗水汽性。     

一种可循环吸附SO2的复合氧化物

研究了一种从水滑石类材料制得的ＭｇＡｌＦｅ复合氧化物脱除低浓度ＳＯ２的性能，发现它对ＳＯ２具有有很高的吸附速率，吸附容量可达每克材料吸附ＳＯ２ １．４ｇ以上，是一种性能优良的ＳＯ２吸附剂。研究中发现这类材料饱和吸附ＳＯ２后可以用氢气还原再生。氢气的浓度在１５％－１００％范围内不影响再速率。