chemical processes

Iso-octane (IO) is produced by reacting iso-butane (IB) with butylene (B) in an emulsion with concentrated sulfuric acid (A):

i-C4H10 + C4H8 →i-C8H18

or

IB + B → IO

The acid catalyzes the reaction and is not consumed. The process flow diagram is provided in the Figure below.

The sulfuric acid solution contains 91% H2SO4 by mass; the balance is water. The aqueous acid is immiscible with the hydrocarbons. Vigorous mixing disperses the acid as small droplets within the organic phase to form the emulsion in the reactor. The emulsion will separate into an organic phase on top of an aqueous phase when mixing stops. A decanter is used to hold the reactor effluent and allow phase separation to occur. All of the acid is separated from the organic in the decanter and recycled to the reactor feed.

The fresh feed to the process contains 25% IB and 25% B on a molar basis; the balance is a non-reactive inert. All of the B is consumed in the reactor. A portion of the reactor effluent is recycled to the reactor feed to form stream 4. The remainder of stream 5 is sent to the decanter from which the hydrocarbon-free acid is recovered and recycled to the reactor feed to form stream 3. The acid -free hydrocarbons removed from the decanter are sent to a distillation column. The bottoms product from the column contains only IB and is recycled to the reactor feed to form stream 2. The top product contains IO and the inert.

The stream entering the reactor (stream 4) contains 200 moles IB per mole of B and 660 moles A per mole of B. The stream produced by mixing the fresh feed with the isobutane recycle (stream 2) contains 5 moles IB per mole B.

Assuming a basis of 100 kmol/h of the fresh feed, determine the component flow rates for each stream. Submit all of your calculations and complete the following table to report your answers. Remember the streams that enter and leave a split all have the same composition which implies the ratio of flow rates for any two components also is the same. It is recommended that you start by first determining which components are in each process stream – if a component is absent its flow rate in the solution table will be zero.

Solution Table

Please return with your calculations.

Stream 11

reactor recycle

Stream 1Stream 2Stream 3Stream 4ReactorStream 5Stream 6DecanterStream 7DistillationStream 8

Stream 10

acid recycle

Stream 9

isobutane recycle