Separation and Purification of C4∼C6 Hydrocarbons Using Metal-organic Frameworks

As important chemical raw materials and energy source, C-4 similar to C-6 hydrocarbons are mainly used to produce polymer rubber, plastics and high-quality gasoline, which requires high purity of the raw materials. For example, the purity requirement in 1,3-butadiene polymerization reactor is higher than 99.5%. When producing butyl rubber, tert-butylamine, pivalic acid, etc., the purity of isobutylene should surpass 99%. In the traditional petrochemical industry, C-4 similar to C-6 hydrocarbons are mostly separated and purified through distillation, yet suffering from large energy consumption, high equipment cost and poor economic benefits. Adsorption separation with solid adsorbents can not only reduce energy cost and environmental footprints, but also improve separation efficiency. Metal-organic frameworks (MOFs) are a class of crystalline porous materials assembled from metal ions or clusters and organic linkers. Compared with zeolite, activated carbon and silica gel, MOFs feature high porosity, well-defined open channels, rich functional groups and diverse structures, showing great potentials in gas storage and separation, sensing, catalysis, photoelectric devices, drug release and delivery. Up to now, there have been many reports on separation and purification of C-4 similar to C-6 hydrocarbons using MOFs by different mechanisms. Specifically, highly selective separation can be achieved by precisely adjusting the size and shape of the MOF channels to match the size of the target molecule. Besides, selecting MOFs with specific functional groups, open metal sites or flexible skeletons to regulate the interactions between the gas molecules and backbone, can also achieve efficient separation. This review introduced the importance of C-4 similar to C-6 hydrocarbons separation and summarized the current research progress of using MOFs to separate and purify C-4 similar to C-6 hydrocarbons. In addition, we also summed up the challenges of using MOFs as industrial adsorbents and pointed out the possible research directions in the future, which may provide ideas for designing new MOFs with high performance for crucial separation processes.