Alkene/Alkane Separations in Fixed Bed Adsorbers скачать в хорошем качестве

Alkene/Alkane Separations in Fixed Bed Adsorbers

For production of alkene feedstocks of 99.95%+ purity required for polymerization reactors, cryogenic distillation columns operated at high pressures and high reflux ratios are commonly employed for large scale separations of C2H4/C2H6, and C3H6/C3H8 mixtures. Many MOF developments have targeted alkene/alkane separations with the objective of eventually supplanting the energy-intensive distillation technologies.1-7 Each of the unsaturated alkenes C2H4, and C3H6 possesses a -bond, and the preferential adsorption of the alkene from the corresponding alkane with the same number of C atoms can be achieved by choosing zeolitic adsorbents with extra-framework cations (e.g. LTA-4A, LTA-5A, and NaX (= 13X) zeolites), or MOFs with unsaturated “open” metal sites (e.g. M2(dobdc) [M = Mg, Mn, Co, Ni, Zn, Fe; dobdc4- = 2,5- dioxido-1,4-benzenedicarboxylate], M2(m-dobdc) [M = Mn, Fe, Co, Ni; m-dobdc4- = 4,6-dioxido-1,3-benzenedicarboxylate] and CuBTC8). An alternative is employ NbOFFIVE-1-Ni (= KAUST-7) or Co-gallate, that almost completely exclude the saturated alkane from the pores due to diffusional limitations. To attain higher C3H6 purities that are required for polymerization feedstocks, we need to operate with multiple beds involving five different steps, consisting of (i) Pressurization with C3H6/C3H8 feed mixture (ii) High pressure adsorption separation with withdrawal of purified C3H8 (iii) Co-current purge with a portion of the product C3H6 (iv) co-current blowdown, and (v) counter-current vacuum blowdown