Influence of the Surface and Structural Characteristics of Activated Carbons on Adsorptive Removal of Halo-Olefinic Impurities from 1,1,1,3,3-Pentafluoropropane

Halo-olefinic impurities in 1,1,1,3,3-pentafluoropropane (HFC-245fa) product used as blowing agents, etc. could damage the human body and must be removed. Activated carbon was treated by HCl, HNO3 and NaOH, respectively. The adsorptive performance of unmodified and modified activated carbons for the removal of a low content of 1-chloro-3,3,3-trifluoro-1-propene (HCFC-1233zd), 1,3,3,3-tetrafluoro-1-propene (HFC-1234ze), 1-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224zb) and 2-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224xe) halo-olefins in the 1,1,1,3,3-pentafluoropropane (HFC-245fa) product was investigated. These halo-olefinic impurities could be substantially removed from the HFC-245fa product via the adsorption over activated carbon when the adsorption temperature was under 333 K, which can be attributed to the π–π dispersion interactions between the halo-olefins and carbon graphite layer. The basic surface groups of activated carbon could catalyze the decomposition of HFC-245fa to form HFC-1234ze. However, the significant increase in the amount of surface acidic groups of activated carbon led to a distinct decrease of adsorption capacity due to the reduction in the micropore volume of adsorbent and a decrease in the strength of the π–π dispersive interactions between halo-olefin molecules and carbon basal. The breakthrough time of halo-olefinic impurities on activated carbon increased with the increase of molecular mass and the decrease of molecular symmetry.

Halo-olefinic impurities can be substantially removed from the HFC-245fa product via the adsorption over activated carbon. The surface acidities/basicities of adsorbents have an important role in their catalytic/adsorptive behaviors.Figure optionsDownload as PowerPoint slide