Influence of the Moisture Content of Mesoporous Silica Gel on the Efficiency of the Chromatographic Recovery of Vanadyl Petroporphyrins with Benzene

Abstract— Benzene proved to be a more effective eluent compared to chlorinated organic solvents traditionally used for chromatographic recovery of vanadyl petroporphyrins from the dimethylformamide (DMF) extract of asphaltenes on a column packed with mesoporous silica gel. Low eluting power of benzene can be compensated by moistening of the silica gel adsorbent. An increase in the silica gel moisture content from 0 to 7.7% does not lead to a decrease in the efficiency of the separation of vanadyl porphyrins from nonporphyrin components but leads to a tenfold decrease in the eluent consumption. A decrease in the eluent flow rate from 0.8 to 0.12 mL min^–1 (per gram of the adsorbent) leads to a 1.5-fold increase in the yield of vanadyl porphyrins of required purity. An increase in the adsorbate : adsorbent weight ratio from 1 : 833 to 1 : 83 does not lead to a decrease in the efficiency of the vanadyl porphyrin recovery. Elution with benzene under optimum conditions (adsorbent moisture content, eluent flow rate, adsorbate : adsorbent ratio) allows the recovery of 3 times larger amount of petroleum vanadyl porphyrins from the DMF extract of asphaltenes than when using chloroform and dried silica gel under equal other conditions.