Breakthrough behavior of 17.5 mol% water in methanol, ethanol, isopropanol, and t‐butanol vapors passed over corn grits

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Abstract
Ground corn is now used in industry as an adsorbent to remove water from ethanol vapors. It is stable and inexpensive at 10 cents/lb (22 cents/kg). For regeneration it requires less than 2000 Btu/gal of 190 proof ethanol processed. If necessary, it could be readily saccharified and fermented into ethanol after use. This renewable resource has further exciting potential as an inexpensive adsorbent for water removal from other alcohols, including methanol, isopropanol, and t-butanol. Water sorption capacity in a fixed bed, nonisothermal adsorption column appears to be a function of the heat capacity of the non-adsorbed alcohol vapor, relative to the heat capacity of the corn adsorbent. Methanol, ethanol, isopropanol, and t-butanol containing 17.5 mol% water gave 105,151, 284, and 358 g anhydrous product/kg adsorbent, respectively, per adsorption cycle. This adsorbent, having operational temperature ranges between 80 and 100°C, is indicated to be of potential utility in solvent recycle processes using these industrially important alcohols. Observed adsorption characteristics are discussed in terms of the alcohol properties of molecular size, heat capacity, and diffusivity. The adsorption mechanism is hypothesized to include transport of water molecules into the structure of adjacent starch molecules present in small spherical bodies (diameter of several microns) immobilized on the surface of the corn grit particles.