Processing of C4‐Fraction Contained in the Waste Gases of Refineries by Catalytic Isomerisation to Isobutane on Pd/Sulfated Zirconia
Доклады на конференциях
The increase in the depth of oil refining and the shift to heavier oil processing is inevitably accompanied by an increase in the formation of waste oil refinery gases. In this case, light alkanes, in particular n-butane fraction (C4 fraction), do not find an equivalent market. Processing of C4 fraction aimed at the production of high-octane oxygen-containing components of motor fuels, in particular, tert-butyl alcohol (TBA) is regarded as a promising solution to improve economic issues. The technological process to solve this problem was proposed in . It includes two consecutive stages, the first is n-butane isomerization to isobutane , and the second is oxidation of isobutane to tert-butyl hydroperoxide (TBHP), followed by the decomposition of the formed TBHP to the targeted TBA.
Thermodynamic equilibria for the branched paraffin isomers are generally favored by low temperatures. Efficient catalysts for n-butane isomerization should be active well below 200℃. At 120°C, the equilibrium conversion of n-butane to isobutane is appx. 67%, then it drops to 60% with an increase in temperature to 160°C. The effect of the n-butane isomerization process conditions such as temperature, WHSV of n-butane, and hydrogen/butane molar ratio on the performance of Pd-SO4/ZrO2 catalyst was investigated within the ranges indicated above. It is determined that at a given temperature, conversion of n-butane strongly depends on the molar ratio H2/C4 and grows substantially with its decrease approaching the equilibrium values; also, it declines with the increase in WHSV of n-butane, that is, with the decrease in residence time. With the temperature increase, conversion of n-butane grows in all cases. Selectivity towards isobutane decreases slightly with the temperature rise; however, it increases with the increase in both WHSV and molar ratio H2/C4. The presence of relatively small isobutane impurities in the inlet reaction mixture reduces its equilibrium yield in isomerization and the observed conversion of n-butane.
This work was supported by the Ministry of Education and Science of the Russian Federation, the unique project identifier RFMEFI60717X0169