以ZIF-8衍生NC和活性炭为载体的金铜双金属催化剂对乙炔氢氯化反应性能研究
发布时间：2018-07-22 15:48
【摘要】：氯乙烯(VCM)是生产重要化工产品聚氯乙烯(PVC)的单体。全球每年生产PVC逾4000万吨,中国占其中的60%以上。基于我国富煤、贫油、少气的能源现状,我国75%以上的PVC采用以煤炭为原料的乙炔氢氯化法生产。目前全球有超过70个国家和地区签署了《水俣公约》,规定从2020年起,凡签署了《公约》的国家均禁止生产及进出口含汞产品,所以研究开发新型高效的无汞催化剂是PVC生产行业亟待解决的问题。本文探讨了三种不同载体或不同活性组分的催化剂,具体工作如下:(1)金属-有机框架化合物(MOFs)是一类多孔、比表面积超高的配位聚合物。本文选择其中结构稳定、合成简便的ZIF-8作为前驱体,将其经过焙烧碳化制成氮掺杂的碳结构(NC),其中在950℃下碳化而成的NC-950对乙炔氢氯化反应活性最好。将其用酸进行进一步改性,发现经王水改性的NC-950活性最高,在GHSV(C_2H_2)为50 h-1,反应温度为180℃时,NC-950)(王水)催化剂的乙炔转化率可达50%以上,表现出较高的催化活性。且在研究中,经XPS表征发现,吡咯型N在反应中起明显的催化作用,且随着反应的进行,吡咯型N会逐渐转化为吡啶型N,使催化效果逐渐降低。(2)以NC-950为载体制备的Au1Cu1/NC-950催化剂和载体为活性炭的Au1Cu1/AC催化剂,在C_2H_2空速为600 h-1、V(HCl):V(C_2H_2)=1.15:1、温度为180oC的条件下,在20 h内,Au1Cu1/NC-950催化剂的乙炔转化率维持在90%以上,而Au1Cu1/AC催化剂的乙炔转化率在达到最高值95%后逐渐下降至68%。可知Au1Cu1/NC-950催化剂活性明显优于Au1Cu1/AC催化剂。其原因是NC-950载体中的N能够促进反应气体C_2H_2在催化剂上的吸附,同时还能够诱导活性中心Au与HCl形成Au-Cl键,并且发生极化,从而使催化剂活性增强。(3)S的改性能够有效提高AuCu/AC催化剂的催化活性。在未用S改性时,活性组分Au NPs和Cu NPs由于其较高的表面能而发生团聚,导致催化剂失活;但经S改性后,能够有效促进活性纳米粒子的分散,从而减弱了由于团聚而导致失活的影响。在C_2H_2空速为180 h-1、V(HCl):V(C_2H_2)=1.15:1、温度为180 oC的条件下,在长达520 h(21天)的时间里,Au1Cu2-S1/AC催化剂的C_2H_2转化率及VCM选择性均保持在99%以上,且未有明显的下降趋势。此外,S的加入能够使活性炭载体层状分离,使其比表面积增大,有效提升了催化剂的活性及稳定性。
[Abstract]:Vinyl chloride (VCM) is a monomer that produces polyvinyl chloride (PVC), an important chemical product. China accounts for more than 60 per cent of the world's annual production of more than 40 million tons of PVC. Based on the energy status of rich coal, lean oil and less gas in China, over 75% of PVC in China is produced by acetylene hydrochlorination with coal as raw material. At present, more than 70 countries and territories worldwide have signed the Minamata Convention, which provides for a ban on the production, import and export of mercury-containing products from 2020 in all countries that have signed the Convention, Therefore, the research and development of new and effective mercury-free catalysts is an urgent problem in PVC production industry. In this paper, three kinds of catalysts with different supports or active components are studied. The main works are as follows: (1) Metallic organic framework compounds (MOFs) are a kind of porous coordination polymers with high specific surface area. In this paper, ZIF-8, which has stable structure and simple synthesis, is selected as precursor, and calcined to form nitrogen-doped carbon structure (NC). NC-950, which is carbonized at 950 鈩，
本文编号：2137961
[Abstract]:Vinyl chloride (VCM) is a monomer that produces polyvinyl chloride (PVC), an important chemical product. China accounts for more than 60 per cent of the world's annual production of more than 40 million tons of PVC. Based on the energy status of rich coal, lean oil and less gas in China, over 75% of PVC in China is produced by acetylene hydrochlorination with coal as raw material. At present, more than 70 countries and territories worldwide have signed the Minamata Convention, which provides for a ban on the production, import and export of mercury-containing products from 2020 in all countries that have signed the Convention, Therefore, the research and development of new and effective mercury-free catalysts is an urgent problem in PVC production industry. In this paper, three kinds of catalysts with different supports or active components are studied. The main works are as follows: (1) Metallic organic framework compounds (MOFs) are a kind of porous coordination polymers with high specific surface area. In this paper, ZIF-8, which has stable structure and simple synthesis, is selected as precursor, and calcined to form nitrogen-doped carbon structure (NC). NC-950, which is carbonized at 950 鈩，
本文编号：2137961
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