氧化铝改性高铈铈锆复合氧化物的制备及其负载钯催化性能

通过共沉淀法制备高比表面积、高孔容的氧化铝改性高铈铈锆复合氧化物,并研究氧化铝改性、前驱体含水焙烧等因素对铈锆复合氧化物结构及负载钯催化性能的影响。研究结果表明:氧化铝改性能够大幅度提升高铈铈锆复合氧化物的比表面积、孔容和高温稳定性。改性样品的新鲜比表面积为122.01 m^(2)/g,孔容为0.4750 mL/g;经1000℃、4 h高温老化后样品的比表面积为66.28 m^(2)/g。前驱体含水焙烧可以提高氧化铝改性铈锆复合氧化物的储氧能力,增强铈锆复合氧化物的高温稳定性;焙烧样品经1000℃、4 h高温老化后的比表面积比常规铈锆复合氧化物提高2.28 m^(2)/g,比常规铈锆铝复合氧化物提高2.75 m^(2)/g。此外,氧化铝改性还可以增大新鲜负载Pd催化剂的空燃比窗口,对催化剂的C_(3)H_(8)、NO催化性能具有促进作用;而前驱体含水焙烧对老化态氧化铝改性负载Pd催化剂的CO、C_(3)H_(8)、NO催化性能均有明显促进作用。

Occurrence and vertical distribution of aluminum and rare earths in weathered crust elution-deposited rare earth ore:Effect of soil solution pH and clay minerals

Weathered crust elution-deposited rare earth ore is crucial source of medium and heavy rare earths,with in-situ leaching being the most common mining method.The high contents of impurity of aluminum in the leach solution are a significant challenge for the subsequent enrichment process of rare earths.A comprehensive understanding of the occurrences and vertical distribution of aluminum and rare earths within typical vertical profiles can provide valuable insights into entire design of the in-situ leaching.This paper improves a five-step sequential extraction method to analyze the occurrence and vertical distribution of rare earths and aluminum in vertical profiles from Chongzuo and Longyan.Experimental results demonstrate that soil solution pH is the main factor affecting the vertical distribution of ionexchangeable rare earths.Both samples have distinct areas of enrichment for ion-exchangeable rare earths or aluminum.Ion-exchangeable rare earths are primary concentrated in the middle and lower parts of the ore layer(4-13 m in Chongzuo,14-22 m in Longyan),while the ion-exchangeable aluminum is mainly enriched in the upper part of the ore layer(1-5 m in Chongzuo,and 2-14 m in Longyan).The vertical distribution of inorganic hydroxy aluminum is likely influenced by the micromorphology and particle size of the clay minerals.The inorganic hydroxy aluminum concentration in Chongzuo samples decreases continuously from 415.65 to 120.95 mg/kg with increasing sampling depth,whereas the concentration in Longyan samples(110.55-171.27 mg/kg)is almost independence with sampling depth.These results provide direct guidance for the entire design of the injection well depth and the leaching parameters,thereby inhibiting the leaching of impurity of aluminum and lower the consumption of leaching agent.

等离子区域熔炼提纯金属Y过程中的杂质迁移规律

利用等离子体区域熔炼提纯金属钇,获得了区熔提纯过程中Al、Si、Fe、Ni、Cu和Mo等杂质的迁移规律。计算结果表明,金属钇中Al、Si、Fe、Ni、Cu和Mo等常见杂质的平衡分配系数分别是0.2173、0.2201、0.5065、0.1586、0.1742和0.8576。由于上述杂质平衡分配系数小于1,杂质在液相中的溶解度大于固相溶解度,所以从理论上可判断出Al、Si、Fe、Ni、Cu和Mo等杂质将随着熔区移动富集在金属钇锭的尾端,也就是最后凝固区。实验结果证明了该理论预判的准确性。此外,探究了区熔次数与杂质迁移的内在联系,结果表明:随着区熔次数由5次增加至10次,杂质在金属钇锭尾端富集程度增加,即去除率升高。10次区熔后,Al、Si、Fe、Ni、Cu和Mo等杂质的去除率分别为45.71%、61.54%、33.98%、64.15%、52.14%和46.28%。由于上述杂质饱和蒸气压与金属钇接近,所以很难通过常规方法予以去除。等离子体区域熔炼提纯金属钇的研究为制备高纯钇提供了一种新方向。