Controlling guest conformation for efficient purification of butadiene

• Published in: Science (American Association for the Advancement of Science) Vol. 356; no. 6343; pp. 1193 - 1196
• Main Authors: Liao, Pei-Qin, Huang, Ning-Yu, Zhang, Wei-Xiong, Zhang, Jie-Peng, Chen, Xiao-Ming
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 16.06.2017
• Subjects: Butadienes - isolation & purification; Chemistry Techniques, Analytical - methods; Computer Simulation; Crystallography, X-Ray; Metal-Organic Frameworks - chemistry; Molecular Conformation; Temperature
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.aam7232

Conventional adsorbents preferentially adsorb the small, high-polarity, and unsaturated 1,3-butadiene molecule over the other C₄ hydrocarbons from which it must be separated. We show from single-crystal x-ray diffraction and computational simulation that a hydrophilic metal-organic framework, [Zn₂(btm)₂], where H₂btm is bis(5-methyl-1H-1,2,4-triazol-3-yl)methane, has quasi-discrete pores that can induce conformational changes in the flexible guest molecules, weakening 1,3-butadiene adsorption through a large bending energy penalty. In a breakthrough operation at ambient temperature and pressure, this guest conformation–controlling adsorbent eluted 1,3-butadiene first, then butane, butene, and isobutene. Thus, 1,3-butadiene can be efficiently purified (≥99.5%) while avoiding high-temperature conditions that can lead to its undesirable polymerization.