Densities isobutane alkylation

The process layout consists of two consecutive static mixers (Fig. 28). To the first mixer, the olefin feedstock is cofed with a recycled isobutane/alkylate stream. The stream coming out the first static mixer is then combined with the recycled IL-based composite catalyst and fed into the second static mixer where the alkylation reaction takes place at a reaction temperature around 15°C and a total pressure of 0.4 MPa. The reaction products are then sent to a settler where the composite catalyst is collected from the bottom, due to its higher density, and recycled. The supernatant is later split into a recycle (isobutane -I- alkylate) to the first static mixer upstream and a product effluent, which constitutes the incoming to the fractionation unit downstream. Total reaction time, considering residence times in the second static mixer and in the settler, is 10 min while the overall I/O ratio in the reactor is set to a value as high as 500. No details on catalyst regeneration or replacement have been disclosed (257). 

The primary process variables affecting the economics of sulfuric acid alkylation are the reaction temperature, isobutane recycle rate, reactor space velocity, and spent acid strength. To control fresh acid makeup, spent acid could be monitored by continuously measuring its density, the flow rate, and its temperature. This can reduce the acid usage in alkyla-tion units. 

Table 15. Influence of Supercritical Phase Density on the Alkylation Performance of a K2.6H0.4PW Catalyst in a Continuous Flow Fixed Bed Reactor (Isobutane/Butenes Molar Ratio of 20, Temperature of 145°C)...

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