Cumene reactor simulation using kinetic RPlug reactor model in Aspen Plus

To produce cumene from benzene and propylene a reactor model of RPlug (Rigorous plug flow reactor with rate controlled reactions based on know kinetics) type is used in Aspen plus process simulation software to find the behaviour of the available kinetics date. Using the power law (molarity basis), the kinetic factor and activation energy are applied in reaction menu.

Assumption made for cumene reactor simulation:

  • SRK property method is used for the simulation.
  • Adiabatic reactor model type is used.
  • Only the reactor behavior is tested neglecting the packing materials, void fraction, heat transfer effects.
  • Trans-alkylation reaction is not considered.
  • No recycle stream is considered.
  • Feed rate is 2 kmol/hr of benzene and 1.05 kmol/hr propylene stream (0.95% propylene) i.e totally 3.05 kmol/hr (200.51 kg/hr).

 Operating conditions used of cumene reactor simulation:

  • Reactor temperature: 350 o C
  • Reactor pressure:  25 atm
  • Length: 0.9 m
  • Diameter: 0.2m
Packed bed reactor aspen plus model for cumene reactor simulation

Aspen Plus Rplug Model

No other equipments are subjected for simulation study as shown in simulation flow sheet. A rough attempt is made to find the component mole fraction and temperature along the adiabatic reactor. The feed ratio is about 2:1 benzene to propylene. The results are available without any errors are present here to show how Aspen can simplify the calculation and designing the process. With less input data, the required information about the process operation condition can be obtained.

Reactions kinetics used in cumene reactor simulation rate model:

Propylene + Benzene →  Cumene   ——————— R1

R1=k1CpCb
k10 = 2.8 × 107
E = 104174

Propylene + Cumene →  p-diisoproyl benzene  —————— R2

R2= k2CpC
k20 = 2.32 × 109
E = 146742

Rates = kmol s-1 m-3,E = kJ/kmol

Reference:  Turton (2003), Analysis, Synthesis, and Design of Chemical Processes, 2 nd Edition.

Results of cumene reactor simulation :

Block PBR composition graph show how the reactants are react as well as the product formation along the adiabatic reactor model blue line shows the drop of propylene.

Component profile along the length of cumene reactor

Components molefraction profile

  • PROPY-01 = propylene
  • BENZE-01= benzene
  • ISOPR-01= Isopropyl benzene
  • P-DII-01 = p-diisopropylbezene (DIPB)
  • PROPA-01= Propane

100% conversion is considered so the output from the reactor contains:

  • cumene 0.9267 kmol/hr
  •  DIPB 0.351 kmol/hr
  • unreacted benzene 1.038 kmol/hr along with tie component propane with 0.525 kmol/hr.
  • Total output with 2.052 kmol/hr (200.51 kg/hr)

 

The graph Block PBR: Temperature show the reactor temperature profile along the length of the reactor which increases and stabilizes as per the reaction. The final temperature obtained is about 540 oC. Overall temperature increase is 190 oC.

Packed bed reactor temperature profile