Cu-MOFs的生长调控及其催化水解羰基硫的性能

羰基硫(COS)广泛存在于以煤、焦炭、渣油和天然气等为原料生产的化工原料气中,不仅腐蚀管道设备,使下游催化剂发生硫中毒,而且还会造成环境污染.因此,COS脱除具有重要意义.在各种方法中,催化水解COS(COS+H2O→CO2+H2S)由于具有反应条件温和、转化率高和副反应少等优点越来越受重视.其关键在于发展高效的催化剂.近年来,金属-有机骨架材料(metal-organic frameworks,MOFs)由于其独特的物理化学性质引起人们广泛关注.与传统材料相比,MOFs不仅拥有超高的比表面积和规则的孔道结构,而且其结构具有可设计性强和易调变等特点,是一类非常有潜力的多相催化剂.然而,目前MOFs在催化水解COS方面的研究应用未见报道.此外,MOFs的合成方法主要有水/溶剂热法、扩散法和微波辅助加热法等.近年来新发展的电化学法具有合成效率高、操作方便和环境友好等优点,在材料合成中显示出巨大的优越性,但利用电化学法合成MOFs相关研究还较少. 本文采用快速温和的电化学方法制备了典型的Cu-MOFs(HKUST-1).该方法可以有效缩短反应时间,通过调节反应电压(15–30 V),在室温下电解3 h,可得到一系列HKUST-1样品.根据合成中设置的电压值,样品分别命名为HKUST-1-E15,HKUST-1-E20,HKUST-1-E25和HKUST-1-E30.XRD表征结果显示,不同电压下合成样品的XRD谱图与通过晶体数据拟合的HKUST-1图出峰位置基本一致.SEM结果表明,合成电压对样品形貌的影响很大.HKUST-1-E15主要呈长棒状结构,长约为15μm.随着电压的增大,HKUST-1-E20的形貌逐渐转变为较短的四棱柱体.当电压为25 V时,所得HKUST-1-E25呈八面体状.进一步提高合成电压,HKUST-1-E30颗粒变小,没有特殊形貌,并出现明显的团聚.COS水解测试结果显示,不同电压下合成样品的活性差异大,这主要是由于样品的形貌及比表面积差异引起的.其中,HKUST-1-E25样品的活性较好.在150°C下,该样品对COS的转化率接近100%,比水热法合成的HKUST-1-Hy的活性更高.在此基础上,进一步对活性测试过程的条件进行优化,发现当原料气流速为30 mL/min,水温为40°C时,催化剂的COS水解性能最优.此外,样品的活性稳定性测试结果显示,相比传统的氧化铜材料,HKUST-1是一类较稳定的COS水解催化剂.

Tuning the growth of Cu-MOFs for efficient catalytic hydrolysis of carbonyl sulfide

Development of the high activity, promoter-free catalysts for carbonyl sulfide (COS) hydrolysis is important for the efficient utilization of various feedstocks. In this study, the Cu-based met-al-organic framework HKUST-1 is synthesized by a simple and mild anodic-dissolution electro-chemical method. The physical and chemical properties of the samples are characterized by several techniques, including scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis and X-ray photoelectron spectroscopy. The results reveal that the synthesis voltage plays a crucial role in controlling the morphology of the resulting HKUST-1. The obtained samples function as novel catalysts for the hydrolysis of COS. A high efficiency, approaching 100%, can be achieved for the conversion of COS at 150 oC over the optimal HKUST-1 synthesized at 25 V. This is signifi-cantly higher than that of the sample prepared by the traditional hydrothermal method. Additional-ly, the effects of the water temperature and the flow velocity on the hydrolysis of COS are also inves-tigated in detail. Finally, a possible reaction pathway of COS hydrolysis over HKUST-1 is also pro-posed. This work represents the first example of MOFs applied to the catalytic hydrolysis of COS. The results presented in this study can be anticipated to give a feasible impetus to design novel catalysts for removing the sulfur-containing compounds.