Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.18 No.2 (June 2017) 109 - 123 

ISSN: 1997-4884 

 
 
 
 
 

Improving of Design Parameters of an Industrial Continuous 

Catalytic Reforming Reactors 

 
Shymaa Ali Hameed  

Chemical Engineering Department, College of Engineering, Tikrit University 

Email: sh.a.hamed@tu.edu.iq   

 

Abstract 

Catalytic reforming of naphtha occupies an important issue in refineries for obtaining 

high octane gasoline and aromatic compounds, which are the basic materials of 

petrochemical industries. In this study, a novel of design parameters for industrial 

continuous catalytic reforming reactors of naphtha is proposed to increase the 

aromatics and hydrogen productions. Improving a rigorous mathematical model for 

industrial catalytic reactors of naphtha is studied here based on industrial data 

applying a new kinetic and deactivation model. The optimal design variables are 

obtained utilizing the optimization process in order to build the model with high 

accuracy and such design parameters are then applied to get the best configuration of 

this process by new design variables. New results related to aromatic and hydrogen 

production have been obtained (the highest hydrogen and aromatic) in comparison 

with those reported in the literature and with the conventional method. 

 

Key words: naphtha reforming, continuous catalytic reactors, kinetic model, 

regeneration. 

 

Introduction  

In order to achieve environmental 

regulations, octane number of the 

produced gasoline should be increment 

to an acceptable level. Continuous 

catalytic reforming (CCR) operation is 

regarded as a proper choice to fulfill 

this goal. Continuous catalytic 

reforming (CCR) of naphtha is a 

significant operation to produce high 

octane gasoline called reformate, 

aromatic feedstock and hydrogen in 

petrochemical industries [1-3]. For 

designing new plants and optimizing 

the existing ones, a suitable 

mathematical model to simulate the 

industrial CCR reactor is required. The 

naphtha feedstock is a very complex 

containing many components and each 

of them undergoes different reactions. 

A detailed model with taking into 

accounts all the components and 

reactions in addition to the catalyst 

deactivation is a hard task and thus an 

appropriate lumping of the components 

by carbon number based on similar 

properties and kinetic behavior should 

be more convenient [4-6]. Therefore, 

efforts have made for modelling CCR 

reactors of naphtha by considering 

kinetic lumps (groups of components) 

in reforming reactions. Such progress 

is observed in illustrating better kinetic 

University of Baghdad 
College of Engineering 

Iraqi Journal of Chemical and 
Petroleum Engineering 

 

mailto:a.t.jarullah@tu.edu.iq


Improving of Design Parameters of an Industrial Continuous Catalytic Reforming Reactors 

  

  

110                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

and deactivation mechanisms with 

higher predictive ability and presenting 

more efficient reactor setups to 

improve the production yield and 

operating conditions [7-10]. 

The aim of the present study is to 

improve the design parameters for 

naphtha continuous catalytic reforming 

(CCR) reactors based on the industrial 

data obtained by a real plant to achieve 

the optimal design and operations of 

such process. The model introduced is 

firstly investigated by employing the 

optimization process to obtain the 

optimum decision variables with a big 

challenge, which is getting a high 

agreement between industrial data and 

the model results (with average 

absolute error less than 1% among all 

results). Secondly, the model is then 

used to maximize the production rate 

(higher hydrogen and aromatic 

production than those reported in the 

literature and obtained in the industrial 

plant). Modeling, simulation and 

optimal design via optimization of the 

industrial CCR reactor are carried out 

by gPROMS (general PRocess 

Modeling System) package. 

 

Process Description of CCR Reactor 

An industrial scheme of a continuous 

catalytic reforming process is shown in 

Figure 1. The industrial process 

consists of a series of four separate 

reactors (the first one is the smallest 

and the last reactor is the largest) and a 

regeneration system. Regenerated 

catalysts is entered the top of the 1
st
 

reactor and is moved axially through 

the reactor then exit from the bottom of 

the reactor. The catalyst is moved from 

the bottom of the 1
st
 reactor to the top 

of the next reactor and such behavior is 

repeated up to the last reactor. The 

catalyst will be withdrawn from the 

last reactor and is sent to the 

regenerator. After that, the regenerated 

catalyst is sent to the 1
st
 reactor again, 

where gas-lift method is employed for 

catalyst circulation between the 

reactors and the regenerator. 

 

R
e
a
c
to

r
 1

R
e
a
c
to

r
 2

R
e
a
c
to

r
 3

R
e
a
c
to

r
 4

R
e
g
e
n

e
r
a
to

r

S
ta

b
il

iz
e
r

Reformate

Off Gas

Net 

Hydrogen

Gas 

Separator

Compressor

Hydrogen 

recycle gas
Naphtha 

Heat 

Exchanger

N
a
p

h
th

a
 

S
tr

e
a
m

 

Heater

C
a
ta

ly
s
t 

s
tr

e
a
m

Regenerated Catalyst 

 Fig. 1: Industrial scheme of a continuous catalytic reforming process 

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-Available online at: www.iasj.net                      IJCPE Vol.18 No.2 (June 2017)                        111 
 

The feedstock is passed through all 

reactors and the liquid product 

obtained by the last reactor will be sent 

to the separator (where hydrogen rich 

gas is separated from hydrocarbons). 

Then, products are passed to the 

stabilizer and the exit reformate 

obtained via the bottom of the 

stabilizer will be sent to storage for 

gasoline blending. Table 1 shows the 

characterization of the industrial CCR 

process (feedstock, catalyst, reactors) 

taken from a real industrial CCR plant 

reported in the literature [11]. 

 
Table 1: Characterization of the Industrial CCR Process 

Property Values  

Feedstock  

Feed (naphtha) 233637.01 (kg/hr) 

Hydrogen to hydrocarbon (mole ratio) 2.193 

H2 in recycle (mole %) 0.83 

Catalyst  

Particle diameter  1.8 (mm) 

Specific surface area 220 (m
2
/g) 

Void fraction  0.36 

Bulk density 680 (kg/m
3
) 

Platinum (Pt) 0.3 (wt %) 

Tin (Sn) 0.3 (wt %) 

Industrial Reactors  

 First  

Reactor  

Second 

Reactor 

Third 

Reactor 

Fourth 

Reactor 

Catalyst distribution (wt %) 12 18 25 45 

Reactor length to reactor diameter (L/D) 3.88 4.40 4.78 5.33 

Outlet temperature (◦C) 434 452 470 488 

Outlet pressure (kPa) 581 535 490 446 

Hydrogen production (kg/h) 14030 16435 18560 20340 

Aromatic production (kg/h) 69230 107785 142660 174600 

Naphthene production (kg/h) 23000 12036 7172 3960 

Paraffine production (kg/h) 164085 128780 89790 52220 

 

Mathematical Modeling 

In this study, hard efforts have been 

made to improve the design parameters 

to obtain an accurate mathematical 

model of the industrial continuous 

catalytic reforming reactors of naphtha 

based on the industrial data reported in 

the literature [12, 13]. In order to 

develop the industrial reactor model 

for CCR process with high accuracy, 

mass and energy balances are required 

in addition to the catalyst deactivation, 

pressure drop, thermodynamic and 

kinetic relations. The overall 

continuous catalytic reforming reactors 

model introduced in this work are 

assembling the mass and energy 

balance on the system of reforming 

reactions, kinetic models for reforming 

reaction and catalyst deactivation 

model that has not been taken widely 

into considerations  for such reactors 

as well as Ergun's equation to calculate 

the pressure drop in the differential 

format. The following assumptions are 

made during the modelling of such 

reactors: The reactors are operated in 

steady-state conditions, heat loss is 

negligible, a homogeneous catalyst 

moving bed is considered and the gas 

mixtures are considered to be ideal. 

 

Mass Balance 

The mass flow rate of each component 

through the CCR reactor containing 

catalyst is calculated by the following 

equation: 

 
   

  
 ∑     

  
     ,i= 1,2,3 …., 26  …(1) 

 

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112                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

Where, nr is the number of reactions, 

Fi is the molar flow rate of the 

component i (kmol/h),    s the rate of 

reaction j (          
      ), W is the 

catalyst weight (kg),      is the 
stochiometry coefficients of species i 

in reaction j. 

 

Energy Balance 

The energy balance equation for the 

CCR reactor containing catalyst is 

evaluated by the following correlation: 

 

  

  
 

∑       
 

  
   

  

∑        
  
   

                        …(2) 

 

Where, T is the temperature (K), Cpi is 

the heat capacity of component i 

(kJ/kmol.K), ΔHj is the heat of reaction 

of reaction j (kJ/kmol). 

 

Pressure Drop 

The pressure drop through the reactors 

can be calculated by using the Ergun's 

equation as presented in the following 

equation [3]: 

 
  

  
  

 

    
 
 
         

  
 

       
 

    
                                  …(3) 

 

Where, P is the total  reactor  pressure  

(bar), ρ is the density  of  the  gas  

mixture  (kg/m
3
),  Ac is the cross 

sectional area of the bed (m
2
), μ is the 

viscosity of the gas mixture (cP), dp is 

the diameter of the catalyst particle 

(m), ρc is the density of the catalyst 

(kg/m
3
),   is the void fraction of 

catalyst bed (-), G is the superficial 

mass velocity of gas mixture (kg/m
2
.s). 

 

Chemical Reaction Network 

The naphtha  feedstock  and  reforming  

products are included as 26 

hydrocarbon lumps characterized by 

naphthenes (alkylcyclohexanes (ACH) 

and alkylcyclopentanes (ACP)), 

normal paraffins (NP), isoparaffins 

(IP), and aromatic (A) lumps with 

carbon numbers ranging from C6 to C9
+
 

with 47 reforming reactions. The 

impact of pressure drop is also 

considered
 
[4, 8]. In this model, the 

lumps of hydrocarbons related to the 

main reforming reactions network can 

be described as follows [1,5,11,14]: 

 Dehydrogenation  Reactions 
The formation of aromatics by 

dehydrogenation of cyclohexanes is an 

endothermic reaction leading to an 

increase in the octane number. Such 

reaction is the fastest among all the 

reforming reactions, therefore 

equilibrium state is quickly occurred. 

The reaction rate equations for this 

reaction are stated as: 

 

               
 

       (       
       

 

   
)       …(4) 

 

              
              

   (   
 

  
)                               …(5) 

 

       
       (    

 

 
)        …(6) 

 

 Dehydrocyclization Reactions 
In the reforming process, 

dehydrocyclization of paraffins to 

naphthenes and aromatics is a desirable 

reaction due to induce the most 

considerable increment in octane 

number among the naphtha reforming 

reactions. The most reactions of 

dehydrocyclization are endothermic 

and promoted by high temperature, 

low pressure and by both metallic and 

acidic functions of the catalyst. The 

needed reactions with the reaction rate 

equations are written as follows: 

 

               
    

       (          
   

   
)       …(7) 

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-Available online at: www.iasj.net                      IJCPE Vol.18 No.2 (June 2017)                        113 
 

              
              

   (   
 

  
)                               …(8) 

 

        
        (   

 

 
)       …(9) 

 

                
   

       (          
    

   
)    …(10) 

 

              
              

   (   
 

  
)                             …(11) 

 

       
        (   

 

 
)      …(12) 

 

               
   

       (      
        

   
)    …(13) 

 

              
              

   (   
 

  
)                             …(14) 

  

             (   
 

 
)          …(15) 

 

               
   

       (      
        

   
)     …(16) 

 

              
              

   (   
 

  
)                             …(17) 

 

             (   
 

 
)          …(18) 

 

 Isomerization Reactions 
Isomerization reactions are regarded as 

important reactions owing to the 

branched hydrocarbons that have a 

high octane number compared with 

others and such reactions are promoted 

via acid catalyst function. In the 

reforming process, the isomerization 

reactions are endothermic reaction and 

paraffins and naphthenes compounds 

are isomerized. The following 

equations are used to describe the 

isomerization reactions: 

  

            
   

       (       
     

   
)        …(19) 

 

              
               

   (   
 

  
)                             …(20) 

 

           (   
 

 
)              …(21) 

 

             
 

       (      
    

   
)            …(22) 

 

              
              

   (   
 

  
)                             …(23) 

 

            (   
 

 
)             …(24) 

 

 Paraffins and Naphthenes Cracking 
Reactions 

In this process, carbons bonds are 

breaking in the reformer reactors at 

any positions along the hydrocarbon 

chain. The aim of these reactions is to 

reduce the low octane number paraffins 

and naphthenes from reformate leading 

to produce lighter hydrocarbons having 

higher octane in the products. Such 

reactions are catalyzed via acidic or 

metallic function of the catalyst. 

Reaction with the rate equations for 

hydrocracking of paraffins are shown 

below as follows: 

 

     
   

 
    

 

  
 ∑   

 
        

 

       ( 
    

  
)                       …(25) 

 

              
        

   (   
 

  
)                             …(26) 

 

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114                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

     
   

 
    

 

  
 ∑   

 
      

   

       ( 
    

  
)                        …(27) 

 

              
         

   (   
 

  
)                              ...(28) 

 

      
 

 
    

 

  
 ∑   

 
      

   

         ( 
     

  
)                  …(29) 

 

               
        

   (   
 

  
)                             …(30) 

 

      
 

 
    

 

  
 ∑   

 
      

   

         ( 
     

  
)                   …(31) 

 

               
        

   (   
 

  
)                             …(32) 

 

 Hydrodealkylation Reactions 
In these reactions, the branched radical 

of aromatic ring is cleavage in the 

presence of hydrogen. This reaction is 

considered the slowest of the 

reforming reactions, which is catalyzed 

by the metallic function of the catalyst 

and is favored at high temperature and 

pressure reactions. The needed 

chemical reactions with the rate 

equation for hydrodealkylation process 

are given as follows: 

 

                  
  

         (         
   )            …(33) 

 

               
                

   (   
 

  
)                             …(34) 

 

Catalyst Deactivation 
Coke deposition on the catalyst is an 

undesirable by-product in the CCR 

process and coke formation is a 

significant issue for catalyst 

deactivation. Catalyst deactivation is 

primarily a function of coke deposition 

on the catalyst leading to block the 

active sites and reducing the yield of 

product therefore controlling coke 

deposition is equivalent to control the 

catalyst deactivation [15]. This 

deactivation effect is compensated by 

increasing the operating temperature so 

that the yields of primary products are 

kept constant. However, there is a limit 

for increasing the temperature after a 

certain value that can not yield 

reformate of desired quality. Then the 

catalyst has to be regenerated for using 

in the next cycle of operation [4]. The 

perfect model should accurately be 

predicted the rates of coke formation 

and the catalyst deactivation on the 

reactor performance as a function of 

operating conditions [16-

18]. Therefore, the following equations 

related to the catalyst deactivation have 

taken into accounts in this work as 

presented below, where the rate of 

reaction over a spent catalyst can be 

evaluated via multiplying the activity 

of the catalyst and the rate of reaction 

over fresh catalyst: 

 

        
                           …(35) 

 

                                      …(36) 

 

Where,   
 is the rate of i

th
 reaction of 

fresh catalyst (coke content is zero),    
is the rate of i

th
 reaction of spent 

catalyst,    is the catalyst activity 
(which is a function of deposited 

coke),     is the deactivation constant, 
    is the coke weight fraction. 

The related reaction rate constants, 

equilibrium constants, activation 

energies, frequency factors, heat of 

reactions, heat capacities, etc.) can be 

found elsewhere [1, 4, 12, 19]. 

 

 

 

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Case Studies 

Case 1: The minimization of the sum 

of the squared production (SSP) 

between the industrial data and 

estimated yields of hydrogen, 

aromatics, naphthene and paraffine 

components at the end of each reactor 

under the same characterization of the 

industrial CCR reactors (operating 

conditions, catalyst distribution and 

properties, feedstock, reactors) is used 

as an objective function in the 

optimization process to evaluate the 

optimal decision variables. Non-linear 

regression is employed to optimize the 

control variables (inlet reaction 

temperature and pressure for each 

reactor simultaneously) including the 

outlet temperature, the outlet pressure, 

hydrogen production, aromatic 

production, naphthene production and 

paraffine production of the industrial 

unit as process constraints and the 

average absolute error must not exceed 

1% among all results. The following 

equation is employed for this purpose: 

  

    ∑    
      

               …(37) 
 

Case 2: The optimization process in 

case 2 is aimed to maximize the 

productivity of hydrogen and 

aromatics, where the optimal outlet 

temperature and pressure, catalyst 

distribution and hydrogen to 

hydrocarbon ratio for each reactor is 

obtained. The optimal design 

parameters obtained in case 1. are 

utilized in case 2 as constraints. The 

following objective function for case 2 

can be introduced as follows: 

 

                       

                                              ...(38) 
 

Optimization Problem Formulation 

Mathematically, the optimization 

problem for case 1 can be described as: 
Min      SSP 

Tin,i,  Pin,i  ,      i=1,..no. of reactors 

Subject to                y(w, m(w), u(w), 

g(w), q)= 0, 

                Tin,i
 L

 ≤ Tin,i
 
≤ Tin,i

 U
 

                Pin,i
 L

 ≤ Pin,i
 
≤ Pin,i

 U
 

               Tout,i
 L

 ≤ Tout,i
 
≤ Tout,i 

U
 

               Pout,i 
L
 ≤ Pout,i ≤ Pout,i 

U
 

              PRH2
L
 ≤ PRH2≤ PRH2

U
 

  PRaromatic
L
 ≤ PRaromatic≤ PRaromatic

U
 

PRNaphthene
 L

 ≤ PRNaphthene ≤ PRNaphthene
 U

 

PRParaffine
 L

 ≤ PRParaffine≤ PRParaffine
U 

 

While, the optimization problem for 

case 2 is stated as: 

Max     PR 

Tout,I , Pout,i , Catdis ,     i=1,..no. of 

reactors 

                 Tout,i
 L

 ≤ Tout,i
 
≤ Tout,i

 U
 

                 Pout,i
 L

 ≤ Pout,i
 
≤ Pout,i

 U
 

               Catdis
L
 ≤ Catdis ≤ Catdis 

U
 

                      H2/Hc
 
  H2/Hc

 *
 

               Catact
L
 ≤ Catact≤ Catact

U
 

[PR1(in) – PR4(out)]   [PR1(in) – PR4(out)]
*
 

                   PRH2  PRH2
*
 

             PRaromatic   PRaromatic
*
 

y(w, m(w), u(w), g(w), q)= 0 represents 

the system model described above, 

where w is the independent variable 

(catalyst distribution), m(w) denotes 

the set of all differential and algebraic 

variables, u(w) represents the 

derivative of differential variables with 

respect to catalyst distribution, q gives 

the design variables, and g(w) is the 

control variables. PRi is the 

productivity of component i, Catdis is 

the catalyst distribution, Catact is the 

catalyst activity, PR is the reactor 

pressure, L and U is the lower and 

upper bound, respectively. 
 

Results and Discussion 
 

Optimal Design Parameters for Case 

1 

The effect of optimized parameters of 

the industrial CCR reactor has been 

investigated here. The optimal design 

parameters for the industrial 

continuous catalytic reforming (CCR) 

reactors are reported in Table 2 based 

on the industrial data obtained by a real 

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116                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

plant for getting the optimal design and operations of such process. 
 

Table 2: Optimization problem results for case study 1 

Decision variables Optimal Values 

 1
st
 Reactor  2

nd
 Reactor 3

rd
 Reactor 4

th
  Reactor 

Inlet temperature (◦C)  Tin1=518.03 Tin2=516.31 Tin3=515.07 Tin4=514.11 

Inlet pressure (kPa) Pin1=595.02 Pin2=550.21 Pin3=505.34 Pin4=460.15 

Outlet temperature (◦C) Tout1=434.01 Tout2=451.98 Tout3=470.11 Tout4=488.09 

Outlet pressure (kPa) Pout1=580.8 Pout2=535.6 Pout3=490.4 Pout4=445.7 

Hydrogen production (kg/h) 14033.202 16430.400 18591.453 20342.362 

Aromatic production (kg/h) 69234.866 107786.297 142668.738 174600.000 

Naphthene production (kg/h) 23000.279 12036.027 7172.520 3961.580 

Paraffine production (kg/h) 164087.056 128780.230 89788.789 52219.1360 

Catalyst activity (%) 0.950 0.943 0.938 0.918 

Absolute Error of the Industrial Product Compositions and Present Study  

Hydrogen production (%) 0.023 0.028 0.169 0.012 

Aromatic production (%) 0.007 0.001 0.006 0.000 

Naphthene production (%) 0.001 0.008 0.007 0.039 

Paraffine production (%) 0.001 0.000 0.001 0.002 

 

As can be seen from these results, a 

very good agreement is obtained by 

using the optimization process. Where, 

the optimum decision variables with 

the target values among all results 

between the industrial data and model 

results have been achieved with 

average absolute error less than 1% 

under process conditions and 

constraints. The best inlet reaction 

temperature that should be applied for 

getting the actual temperature of the 

industrial naphtha CCR reactors are 

optimized to be 518.03  C, 516.31  C, 
515.07  C and 514.11  C for reactor 1, 
2, 3 and 4, respectively. Whereas, The 

best inlet reaction pressure that should 

be utilized for getting the actual 

pressure for the industrial naphtha 

CCR reactors are optimized to be 

595.02 kPa, 550.21 kPa, 505.34 kPa, 

and 460.15 kPa, for reactor 1, 2, 3 and 

4, respectively. 

The optimal decision variables 

presented above have been obtained 

under process limitations for each 

reactor (outlet temperature, outlet 

pressure, Hydrogen production, 

aromatic production, naphthene 

production and paraffine production). 

Such new results can be attributed to 

the accuracy of the model studied here 

under process conditions and 

constraints, where all the necessary 

design parameters, reaction rate 

equations as a function of operating 

conditions (obtained based on the 

experimental data, mass and energy 

balance, hydrodynamic parameters, 

physiochemical properties in addition 

to the catalyst activity that ignored in 

the literature) have taken into 

considerations here. Such design and 

kinetic parameters can effect on the 

process leading to reduce the 

sensitivity analysis of the process and 

giving high deviation and as a results 

the performance and the behaviour of 

the process can not be predicted 

confidently in addition to the advanced 

solution method utilized here 

(Successive quadratic Programming 

(SQP)).  

Based on the results presented above, a 

clear indication is observed that the 

accuracy of the mathematical model 

related to the design parameters can 

now be applied with high trusted for 

modifying such design parameters by 

changing the decision variables in 

order to improve quality and quantity 

of the process via maximizing the 

hydrogen and aromatic production. 
 

 

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Optimal Design Parameters for Case 

2  

After getting the optimal results of 

case 1, the optimization process is 

applied for case 2 in order to obtain the 

maximum productivity of hydrogen 

and aromatic. The optimal results 

related to case study 2 are given in 

Table 3. As noted from this table, the 

highest hydrogen production is 

optimized to be 20821.857 kg/h (while 

20342.362 kg/h for conventional 

process) and aromatic production of 

191428.973 kg/h (whereas 174600.0 

kg/h for conventional process). Such 

new results have got utilizing the 

optimization technique of the decision 

variables simultaneously (not 

individually for each variable as 

presented in the literature). Where, the 

best outlet temperature and pressure is 

444  C and 476.4 kPa, 462  C and 
544.2 kPa, 482  C and 496.6 kPa, and 
497  C and 451.3 kPa for reactor 1, 2, 
3 and 4, respectively. Also, the new 

catalyst distribution and H2/Hc should 

be ordered simultaneously beside 

temperature and pressure as follows: 

21.4 wt% and 2.193, 22.2 wt% and 

2.898, 26.8 wt% and 3.491, and 29.6 

wt% and 4.857 for reactor 1, 2, 3 and 

4, respectively, under process 

constraints (the catalyst activity, 

pressure difference and the 

productivity of hydrogen and 

aromatic).   

Table 4 shows the comparison results 

obtained from this study and those 

obtained by previous studies related to 

the production increasing of hydrogen 

and aromatic. It is clearly observed 

from this table that the production 

increasing of hydrogen (by 481.857 

kg/h) and aromatic (16828.973) is 

higher than conventional method and 

those obtained in the literature, which 

becomes a considerable amount per 

year. This new results is attributed to 

the improvement of design parameters 

investigated here (outlet temperature, 

outlet pressure, catalyst distribution 

and process constraints) in addition to 

the solution method (SQP) employed 

in this study depending on the 

modified model. Where, this method 

used here to maximize the production 

of hydrogen and aromatic is better than 

the methods used with all previous 

works (that used different solution 

methods for maximizing the objective 

function to get the optimal design of 

CCR reactor) in this field. Such 

approach utilized having high accuracy 

in evaluating the control variables of 

the process within gPROMS package 

(advanced languages and formalisms 

for model improvement, which allow 

the description of difficult differential 

and algebraic models and has several 

features that make it an attractive tool 

and suitable for the modelling, 

simulation and optimization of any 

plant process). Furthermore, this 

approach is a highly trusted method for 

solution of such mathematical models, 

which means that this model can be 

applied confidently to reactor design, 

operation and control leading to get 

higher profit (higher quality and 

quantity). 
 

Table 3: Optimization problem results for case study 2 

Decision variables Optimal Values 

1
st
 Reactor  2

nd
 Reactor 3

rd
 Reactor 4

th
  Reactor 

Outlet temperature (◦C) Tout1=444.0 Tout2=462.0 Tout3=482.0 Tout4=497.0 

Outlet pressure (kPa) Pout1=576.40 Pout2=544.2 Pout3=496.6 Pout4=451.3 

Catalyst distribution (wt %) 21.4 22.2 26.8 29.6 

H2/Hc 2.193 2.898 3.491 4.857 

Catalyst activity (%) 0.943 0.937 0.927 0.912 

PR1(in) – PR4 (out) (kPa) 147.8 

Hydrogen production (kg/h) 14673.069 17606.492 19768.371 20821.857 

Aromatic production (kg/h) 86759.027 136484.659 173364.538 191428.973 

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118                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

Table 4: Comparison results between this work and previous studies 

Authors (year) Production Increasing 

of Hydrogen (kg/h) 

Production Increasing of 

Aromatic (kg/h) 

Rahimpour et al. (2011) 54.432 414.600 

Iranshahi et al. (2013) 322.560 6633.600 

Karimi et al. (2014) 383.040 9535.800 

This study (2016) 481.857 16828.973 

 

The Performance of the Industrial 

CCR Reactor 

The effect of optimized parameters on 

industrial CCR performance has been 

investigated and compared with the 

performance of the non-optimized 

operations in the Figures 2-8. The 

reaction side temperature profiles of 

industrial (conventional) and 

recuperative reactors are illustrated in 

Figure 2. Owing to the predominant 

reactions in the naphtha reforming 

process are highly endothermic, 

temperature drop along the reaction 

side is expected and the temperature 

drops using the optimized parameters 

(case 2) are lower than the industrial 

method (case 1). 

 

 
Fig. 2: Temperature profiles along four CCR 

reactors for case studies 
 

This reduction in temperature drop can 

be attributed to heat transfer from 

exothermic side. In the first reactors, 

concentration of naphthenes is high 

and dehydrogenation, which is very 

rapid and endothermic reaction, takes 

place. Hence, very sharp temperature 

drop occurs in this reactor. While in 

the last reactors, naphthenes 

concentration decrease and 

hydrocracking and hydrodealkylations 

occur, which are very slow and 

exothermic reactions, thus, temperature 

drop is lower. As well as, the hydrogen 

content of the recycled gas decreases 

in the optimized configurations and the 

molar flow rate of the recycled gas will 

be increased by increasing in H2/HC 

molar ratio. Using the optimized 

design parameters, more recycled gas 

enters the reactors, which acts as a 

thermal source and leading to less 

temperature drop. Due to the 

relationship between the temperature 

gradient and the molar flow rate, the 

sum of the fresh naphtha feed and 

recycled gas, the temperature drop 

along the optimized reactors is the 

least due to an increase in the molar 

flow rate [1, 12].    

One of the advantages of the CCR 

reactor is to reduce the pressure drops 

in the reactors allowing to use of 

smaller catalyst particle with high 

efficiency and the reaction rate and 

conversion increase with decreasing 

the pressure drop. So, other significant 

design parameter that influences the 

performance of naphtha reforming 

process is operating pressure. Figure 3 

shows the pressure profile for 

industrial and both case studies. As can 

be observed from this Fig., the 

pressure drop in the industrial reactors 

is higher than the optimized reactors 

(case 2) due to the design parameters 

of such reactor in which the catalyst 

distribution reactors is longer than that 

of conventional process. The sudden 

pressure drops during the passage of 

stream through the reactors are due to 

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piping and employing intermediate 

instruments such as furnaces [11]. 

 

Catalyst Weight (%)

0 10 20 30 40 50 60 70 80 90 100

P
r
e
s
s
u

r
e
 (

k
P

a
)

420

440

460

480

500

520

540

560

580

600

620

Industrial

Case 1

Case 2

Fig. 3: Pressure profiles along four CCR 

reactors for case studies 
 

The hydrogen and aromatic yield vs. 

the catalyst distribution for both case 

studies is illustrated in Figure 4 and 5, 

respectively. One of the positive 

impacts of the proposed modifications 

can clearly be observed in these 

figures. Hydrogen is regarded the most 

the source of hydrocracking, 

hydrotreating and hydroprocessing 

units in the refineries.  

Hydrogen is a product in the 

dehydrogenation and 

dehydrocyclization reactions in 

addition to the reactant in the 

hydrocracking and hydrodealkylation 

reactions.  

 

 
Fig. 4: Hydrogen production along four CCR 

reactors for case studies 

Catalyst Weight (%)

0 10 20 30 40 50 60 70 80 90 100

A
r
o
m

a
t
ic

 P
r
o
d

u
c
t
io

n
 (

k
g
/h

)

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

Industrial

Case 1

Case 2

Fig. 5: Aromatic production along four CCR 

reactors for case studies  
 

In the first two reactors, the high 

production rate is observed, because 

dehydrogenation and 

dehydrocyclization are dominant 

reactions, while in the last two 

reactors, production rate decreases 

owing to presence of hydrogen 

consumer reactions. As noticed, in the 

optimized configuration owing to 

supply the copious heat for 

dehydrogenation and 

dehydrocyclization reactions, hydrogen 

production rate has increased, which is 

one of the main goals in the modified 

configuration.  

Aromatic production with high octane 

number is the main aim of reforming 

process hence, the aromatic yield 

should be increased in the proposed 

configuration. Almost all reactions 

proceed more rapidly at higher 

temperatures hence, the aromatics and 

hydrogen yields increase in both 

optimized reactors due to a lower 

temperature drop compared with 

conventional method. Moreover, the 

pressure drop in the reactors is 

considerably less than that in the 

conventional, so that the product yield 

increases as a result of increasing in 

reaction rates. These factors lead to 

higher aromatic production in the 

modified process configuration (case 

2) compared with the traditional 

process (case 1). The amount of 

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120                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

aromatic flow rate has increased as the 

stream passes through the reactors 

owing to aromatic producing reactions 

such as dehydrogenation and 

dehydrocyclization of paraffins to 

aromatics. As well as, higher aromatic 

production is achieved employing case 

2 configuration and consequently, high 

octane gasoline can also be produced 

in this configuration. Where, the rate of 

aromatics production is higher than 

those produced by the conventional 

method due to the dehydrogenation of 

naphthenes to aromatics [1].  

The naphthenes and paraffins 

production rates are illustrated in 

Figure 6 and 7, respectively for both 

case studies. Naphthenes and paraffins 

constitute the main part of naphtha. 

Since dehydrogenation of naphthene is 

the major source of aromatic 

production and octane number 

enhancement, naphthenes play a very 

important role in naphtha reforming 

process. Since naphthenes are 

consumed in the naphtha reforming 

process and their flow rates decline 

along the catalyst distribution of the 

reactors. Owing to hydrogenation 

reaction in naphtha reforming reactors, 

more heat is available for the 

dehydrogenation of naphthens, which 

is endothermic and its yield increases 

by consuming more heat. 

 

Catalyst Weight (%)

0 10 20 30 40 50 60 70 80 90 100

N
a
p

h
th

e
n

e
 P

r
o
d

u
c
ti

o
n

 (
k

g
/h

)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

Industrial

Case 1

Case 2

Fig. 6: Naphthene production along four CCR 

reactors for case studies 

Catalyst Weight (%)

0 10 20 30 40 50 60 70 80 90 100

P
a
r
a
ff

in
e
 P

r
o
d

u
c
t
io

n
 (

k
g
/h

)

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

Industrial

Case 1

Case 2

Fig. 7: Paraffin production along four CCR 

reactors for case studies 

 

Also, hydrocracking as another 

naphthene consumer reaction is 

favored at high temperature thus, the 

highest conversion of naphthene is 

observed in optimized design 

parameters (modified configuration – 

case 2) that operate at higher 

temperature. As well as, the paraffins 

production declines continuously along 

the catalyst distribution inside the 

reactors owing to dehydrocyclization 

and hydrocracking reactions. Using the 

optimized parameters, more heat is 

accessible leading the 

dehydrocyclization toward consuming 

more paraffins. On the other hand, 

hydrocracking is favored at high 

temperature and it can progress further 

in the modified configuration having a 

higher operating temperature. 

Therefore, a lower position in 

comparison with the conventional 

configuration [11, 12] is observed. 

The catalyst activity along the catalyst 

distribution for both case studies is 

shown in Figure 8. The catalyst 

activity has a reverse relationship with 

temperature and the catalyst activity is 

increased as proceeding along the 

reactors due to a decrease in 

temperature. As clearly observed, the 

catalyst activity deteriorates 

considerably owing to coke deposition 

on the catalyst surfaces and sintering 

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Shymaa Ali Hameed 

 

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phenomena. It is worth mentioning that 

the catalyst activity itself does not 

convey any independent judgment, and 

its effect on the production rate should 

be investigated. One of the main goals 

is to keep the catalyst activity as high 

as possible under process conditions 

with taking into considerations the 

optimal design parameters that should 

be modified. 

 

Catalyst Weight (%)

0 10 20 30 40 50 60 70 80 90 100

C
a
t
a
ly

s
t
 A

c
t
iv

it
y

0.89

0.90

0.91

0.92

0.93

0.94

0.95

0.96

Case 1

Case 2

Fig. 8: Catalyst activity along four CCR 

reactors for case 1 and case 2 

 

Conclusions 

A new configuration of industrial 

continuous catalytic reforming reactors 

of naphtha is studied by improving the 

design parameters of such process in 

order to boost the aromatics and 

hydrogen productions as a result of 

increasing the efficiency of the 

reformers. A rigorous mathematical 

model for CCR reactors of naphtha is 

investigated here depending on 

industrial data with taking into account 

the deactivation model. The optimal 

design variables have obtained 

employing the optimization process in 

order to build the model with high 

accuracy (with average absolute error 

less that 1% among all results between 

the industrial data and model results). 

Then, such design parameters have 

been employed for getting the best 

configuration of the process by 

improving the design parameters. The 

results of the modified design 

parameters showed about 16828.973 

and 481.857 kg/h have increase in the 

aromatics and hydrogen production, 

respectively, compared with those 

reported in the literature and obtained 

with the conventional method. Such 

new results have clearly indicated that 

the modified design parameters of 

CCR reactors can cause excellent 

configuration in comparison with the 

conventional system.  

 

Nomenclature 

a  constant 

A constant 

B constant 

CCR continuous catalytic reactor 

n number of carbon atom 

Pt  total pressure (kPa) 

PAn  partial pressure of n carbon 

aromatic (kPa) 

PACHn partial pressure of n carbon 

alkyl- cyclohexane (kPa) 

PACPn  partial pressure of n carbon 

alkyl-cyclopentane (kPa) 

PH2  partial pressure of hydrogen 

(kPa) 

PIPn  partial pressure of n carbon iso-

paraffin (kPa) 

PNPn  partial pressure of n carbon 

normal-paraffin (kPa) 

SQP successive quadratic 

programming  

SSP sum of the squared production 

.3 

R gas constant (J mol
-1

K
-1

) 

T temperature (K) 

* the target final value 

in inlet 

out outlet 

 

References 

1- Iranshahi, D.; Rafiei, R.; Jafari, M.; 
Amiri, Sh.; Karimi, M.; Rahimpour, 

M.R., (2013), “Applying new 

kinetic and deactivation models in 

simulation of a novel thermally 

coupled reactor in continuous 

catalytic regenerative naphtha 

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Improving of Design Parameters of an Industrial Continuous Catalytic Reforming Reactors 

  

  

122                                  IJCPE Vol.18 No.2 (June 2017)                -Available online at: www.iasj.net 
 

process”, Chemical Engineering 

Journal, Vol. 229, pp. 153. 

2- Maria, S.; Kravtsov, A.V.; 
Ivanchina, E.D.; Korolenko, MV.; 

Chekantsev, NV., (2011), “Reactor 

modeling and simulation of 

moving-bed catalytic reforming 

process”, Chemical Engineering 

Journal, Vol. 176–177, pp. 134. 

3- Taskar, U.M., (1996), “Modeling 
and optimization of a catalytic 

naphtha reformer”, PhD Thesis, 

Texas University. 

4- Padmavathi, G.; Chaudhuri, K.K., 
(1997), “Modeling and simulation 

of commercial catalytic naphtha 

reformers”, Canadian Journal of 

Chemical Engineering, Vol. 75, pp. 

930. 

5- Behin, J.; Kavianpour H.R., (2009), 
“A Comparative Study for the 

Simulation of Industrial Naphtha 

Reforming Reactors With 

Considering Pressure Drop on 

Catalyst”, Petroleum and Coal, Vol. 

51, pp. 208. 

6- Askari A.; Karimi, H.; Rahimi, 
M.R.; Ghanbari, M., (2012), 

“Simulation and Modeling of 

Catalytic Reforming Process”, and 

Coal, Vol. 54, pp. 76. 

7- Weifen, H.; Hongye, S.; Yongyou, 
H.; Jian, C., (2006), “Modeling, 

Simulation and Optimization of  a 

Whole Industrial Catalytic Naphtha 

Reforming Process on Aspen Plus 

Platform”, Chinese Journal of 

Chemical Engineering, Vol. 14, pp. 

584. 

8- Hongjun, Z.; Mingliang, S.; Huixin, 
W.; Zeji, L.; Hongbo J., (2010), 

“Modeling and Simulation of 

Moving Bed Reactor for Catalytic 

Naphtha Reforming”, Petroleum 

Science and Technology, Vol. 28, 

pp. 667. 

9- Taghavi, B.; Fatemi, S., (2014), 
“Modeling and Application of 

Response Surface Methodology in 

Optimization of a Commercial 

Continuous Catalytic Reforming 

Process”, Chemical Engineering 

Communication, Vol. 201, pp. 171. 

10- Rodríguez, M.A.; Ancheyta, J., 
(2011), “Detailed description of 

kinetic and reactor modeling for 

naphtha catalytic reforming”, Fuel, 

Vol. 90, pp. 3492. 

11- Iranshahi, D.; Karimi, M.; Amiri, 
Sh.; Jafari, M.; Rafiei, R.; 

Rahimpour, M.R., (2014), 

“Modeling of Naphtha Reforming 

Unit Applying detailed description 

of kinetic in continuous catalytic 

regeneration process”, Chemical 

Engineering Research and Design, 

Vol. 92, pp. 1704. 

12- Iranshahi, D.; Amiri, Sh.; 
Karimi, M.; Rahimpour, M.R.; 

Rafiei, R.; Jafari, M.;  Rahimpour, 

M.R., (2013), “Modeling and 

Simulation of a Novel Membrane 

Reactor in a Continuous Catalytic 

Regenerative Naphtha Reformer 

Accompanied with a Detailed 

Description of Kinetics”, Energy 

and Fuels, Vol. 27, pp. 4048. 

13- Iranshahi, D.; Karimi, M.; Amiri, 
Sh.; Jafari, M.; Rafiei, R.; 

Rahimpour, M.R., (2013), 

“Modeling and Simulation of a 

Novel Membrane Reactor in a 

Continuous Catalytic Regenerative 

Naphtha Reformer Accompanied 

with a Detailed Description of 

Kinetics”, Energy and Fuels, Vol. 

27, pp. 4048.  

14- Saidi, M.; Mostoufi, N.; 
SotudehGharebagh, R., (2011), 

“Modeling and Simulation of 

Continuous Catalytic Regeneration 

(CCR) Process”, International 

Journal of Applied Engineering 

Dindigul, Vol. 2, pp. 115. 

15- Antos, G.A.; Aitani, A.M., 
(1995), “Catalytic Naphtha 

Reforming”, 2
nd

 ed., New York, 

Marcel Dekker. 

16- Ren, X.H.; Bertmer, M.; Stapf, 
S.; Demco, D.E.; Blümich, B.; 

http://www.iasj.net/
http://www.sciencedirect.com/science/journal/0926860X


Shymaa Ali Hameed 

 

-Available online at: www.iasj.net                      IJCPE Vol.18 No.2 (June 2017)                        123 
 

Kern, C.; Jess, A., (2002), 

“Deactivation and regeneration of a 

naphtha reforming catalyst”, 

Applied Catalysis A: General, Vol. 

228, pp. 39. 

17- De Pauw, R.P.; Froment, G.F., 
(1975), “Deactivation of a platinum 

reforming catalyst in a tubular 

reactor”, Chemical Engineering 

Science, Vol. 30, pp.789. 

 

 

 

 

 

 

18- Van Trimpont, P.A.; Marin, 
G.B.; Froment, G.F., (1988), 

“Reforming of C7 hydrocarbons on 

a sulfided commercial Pt/Al2O3 

catalyst”, Industrial and 

Engineering Chemistry Research, 

Vol. 27 pp.51. 

19- Reid, R.C.; Prausnitz, J.M.; 
Poling, B.E., (1987), “The 

Properties of Gases and Liquids”, 

4
th

 ed., New York, McGraw-Hill. 

 

 
 

 

 

 

 

 
 

 

 

 

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