See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/281608354 Simulation of Propane Dehydrogenation to Propylene through a Radial Flow Reactor over the Pt-Sn/Al2O3 Catalyst Article in Chemical Engineering & Technology · September 2015 DOI: 10.1002/ceat.201500082 CITATIONS READS 10 1,406 4 authors: Seyed Mohammadreza Miraboutalebi 4 PUBLICATIONS 214 CITATIONS Leila Vafajoo Islamic Azad University, Tehran South Branch 65 PUBLICATIONS 581 CITATIONS SEE PROFILE SEE PROFILE Mohammad Kazemeini Moslem Fattahi Sharif University of Technology Abadan Faculty of Petroleum Engineering 148 PUBLICATIONS 2,780 CITATIONS 81 PUBLICATIONS 2,412 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Propane Dehydrogenation View project Heat and Fluid Flow in MicroChannel (Microfluidic) View project All content following this page was uploaded by Leila Vafajoo on 04 June 2018. The user has requested enhancement of the downloaded file. SEE PROFILE These are not the final page numbers! (( Research Article Seyed M. Miraboutalebi1,2 Leila Vafajoo1 Mohammad Kazemeini3 Moslem Fattahi4 1 Simulation of Propane Dehydrogenation to Propylene in a Radial-Flow Reactor over Pt-Sn/Al2O3 as the Catalyst 1 Department of Chemical Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran. 2 Young Researchers and Elite Club, South Tehran Branch, Islamic Azad University, Tehran, Iran. 3 Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran. 4 Department of Chemical Engineering, Abadan Faculty of Petroleum Engineering, Petroleum University of Technology, Abadan, Iran. 1 Catalytic paraffin dehydrogenation for manufacturing olefins is considered to be one of the most significant production routes in the petrochemical industries. A reactor kinetic model for the dehydrogenation of propane to propylene in a radial-flow reactor over Pt-Sn/Al2O3 as the catalyst was investigated here. The model showed that the catalyst activity was highly time dependent. In addition, the component concentrations and the temperature varied along the reactor radius owing to the occurring endothermic reaction. Moreover, a similar trend was noticed for the propane conversion as for the propylene selectivity, with both of them decreasing over the time period studied. Furthermore, a reversal of this trend was also revealed when the feed temperature was enhanced or when argon was added into the feed as an inert gas. Keywords: Catalyst, Propane dehydrogenation, Propylene, Radial-flow reactor, Simulation Received: February 9, 2015; revised: April 16, 2015; accepted: September 3, 2015 DOI: 10.1002/ceat.201500082 Introduction Catalytic dehydrogenation of paraffins to olefins has been performed commercially since the late 1930s. During World War II, catalytic dehydrogenation of butane over Cr/Al2O3 as the catalyst was utilized for the production of butene to enhance the octane number of aircraft fuel [1, 2]. In general, dehydrogenation reactions are carried out through a multistep mechanism. Meanwhile, other reactions including coking usually occurred, leading to catalyst deactivation, thereby lowering the reaction rate over a period of time [3, 4]. In addition, coke formation and the dehydrogenation reaction unavoidably affected each other. Thus, semi-experimental models were utilized for catalyst deactivation descriptions. These were based on introducing a deactivation function in terms of measurable variables [5]. Olefins have been considered as the feed of many industries including petrochemical plants [6]. On the other hand, lightalkane dehydrogenation is usually considered as an industrialized manufacturing method of olefins [7]. It ought to be mentioned that, due to the harsh operating conditions required for the reaction, catalyst deactivation normally occurred very quickly; hence, continuous regenerative techniques for the catalyst were needed. In this venue, moving-bed reactors with continuous regenerative systems were employed in some cases – Correspondence: Dr. Mohammad Kazemeini (kazemini@sharif.edu), Department of Chemical and Petroleum Engineering, Sharif University of Technology, P.O. Box 11365-9465, Tehran, Iran. Chem. Eng. Technol. 2015, 38, No. 00, 1–10 [8]. In another study, the catalyst regeneration was carried out periodically in fixed-bed reactors. Here, the bed temperature was increased to burn out the coke, thus renewing the catalyst for the endothermic propane dehydrogenation (PDH) [9, 10]. Yet another research article [11] presented the combination of exothermic and endothermic reactions of this kind. Other researchers compared simultaneous and sequential methods to combine non-oxidative PDH and the methane–propane burning reaction on a Pt catalyst in fixed-bed reactors [12, 13]. Propylene has always been mentioned as one of the most important light olefins according to its usage in petrochemical plants and its valuable role in downstream chemical products. This species possesses higher added-value than other petrochemical raw materials like natural gas and naphtha. Besides, both the economic terms of supply and demand being on the positive side provided an added advantage for this material [7]. In addition, the increasing demand for light olefins (like this) due to their environmental impacts drew even more attention to this chemical [3]. Meanwhile, propylene has been produced through many different routes. All of these methods were employed to fill up the gap between its demand and supply [3]. Some of these commercial routes are: steam cracking, catalytic cracking in a fluidized bed, deep catalytic cracking, metathesis, propyl alcohol dehydration, and propane catalytic dehydrogenation. In the first and second methods, propylene is produced as a byproduct [7]. Light-paraffin dehydrogenation is considered as common practice in olefin production. The processes of paraffin dehydrogenation can be divided into two major categories: ordinary paraffin dehydrogenation and oxidative paraffin dehydrogenation. While oxidative dehydrogenation is an exothermic reaction and is accompanied by water production, ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com ’’ These are not the final page numbers! Research Article 2 ordinary dehydrogenation is an endothermic reaction [4, 14–16]. As a consequence of many side reactions affecting the appropriate yield and catalyst activity, extensive research has been carried out in recent years on the appropriate catalyst selection, the optimum operation conditions, and on suitable reactors [17–21]. On the other hand, radial-flow reactors have been widely used in processes such as paraffin and ethyl benzene dehydrogenation. Furthermore, their lower pressure drops and smaller reactor volumes might be counted as their advantages in comparison with conventional tubular reactors [1, 22]. In this regard, PDH reactors are commonly operated at 525–625 C and around atmospheric pressure, assisted by platinum or chromia catalyst supports [3, 23]. Although there are some research studies on the kinetics of PDH in different reactors, investigations on the impact of pressure, temperature, and inert gases on the PDH reaction in a radial-flow reactor have not been published yet. In the present study, the simulation of PDH aiming towards propylene production in a radial-flow reactor over Pt-Sn/Al2O3 as the catalyst was investigated. For this purpose, a kinetic model was proposed to predict the propane conversion and the propylene selectivity as a function of the inlet feed temperature. Moreover, the catalyst deactivation and process temperature profiles in terms of the reaction time and reactor radius were studied. for the present study since it most consistently describes the considered experimental data. Moreover, it was assumed that propane absorption was negligible, as confirmed in previous researches [3, 5]. In addition, the proposed rate expressions for the reactions of cracking and ethylene hydrogenation are shown in Tab. 2 [3, 5]. 2.3 Radial-Flow Reactor Model In the present study, the PDH reaction in a radial-flow fixedbed reactor (RFBR) was considered. Accordingly [24], the reactor model for an RFBR is provided in Eq. (4): dnT;i ¼ rb r i dVreactor ði ¼ 1; 2; . . . ; kÞ (4) where i indicates the i-th chemical component. Eq. (4) was simplified for a cylindrical fixed-bed reactor at a fixed length as follows: dyi 2prL ¼ r r nT b i dr (5) 2.4 Material and Energy Balances for Components 2 Reactor Modeling and Simulation With respect to the initial concentration of the participating components and the inert material in the RFBR, the material balances for nT ; yC3 H8 ; yH2 ; yC2 H4 and yAr are written as below: 2.1 PDH and Side Reactions Propylene production reactions in the presence of a platinum catalyst based on alumina have been investigated experimentally [5]. The following reactions were suggested. The main reaction of PDH to propylene is as follows [3, 5]: nT ¼ C3H8 > C3H6 + H2 yC3 H8 ¼ (1) While the above reaction is an equilibrium reaction, other reactions like cracking and ethylene hydrogenation affecting the main product formation are in the center of the modeling approaches and simulations carried out in this study [3, 5]. Cracking reaction: C3H8 fi CH4 + C2H4 0 þ 2y0 0 0 yC0 3 H8 þ yH C2 H6 þ yC2 H4 þ yAr 2 1 yC3 H6 yCH4 þ yC2 H6 0 Þn0 ðyC0 3 H8 þ yC0 3 H6 þ yCH T 4 nT Model Power law LHHW-1 Ethylene hydrogenation: (3) rC3 H8 ¼ k1 PC3 H8 rC3 H8 ¼ LHHW-2 www.cet-journal.com PC3 H6 PH2 Keq ! k1 KC3 H8 ðPC3 H8 ðKC3 H6 =KC3 H8 ÞðPC3 H6 PH2 =Keq ÞÞ 1 þ PC3 H8 =KC3 H8 þ ðPC3 H6 =KC3 H6 Þ k1 ðPC3 H8 1þð PC3 H6 PH2 PC3 H6 KC3 H6 Three different models have been proposed for the main PDH reaction rate [5] and are provided in Tab. 1. Out of these, the Langmuir-HinshelwoodHougen-Watson 2 (LHHW-2) model was chosen (7) Kinetic equation r1 ¼ 2.2 Proposed Mechanism and Kinetics of the PDH Reaction yC3 H6 yCH4 (6) Table 1. Proposed models for the PDH reaction. (2) C2H4 + H2 fi C2H6 n0T Keq Þ Þ Table 2. Reaction rate expressions for the cracking and ethylene hydrogenation reactions. Cracking reaction r2 ¼ k2 PC3 H8 Ethylene hydrogenation r3 ¼ k3 PC2 H4 PH2 ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eng. Technol. 2015, 38, No. 00, 1–10 These are not the final page numbers! (( Research Article yH2 ¼ 0 y0 0 0 ðyH C3 H6 þ yC2 H6 ÞnT 2 yC2 H4 ¼ yAr nT 3 where þ yC3 H6 yC2 H6 0 ðyC0 2 H4 yCH þ yC0 2 H6 Þn0T 4 nT (8) Cm ¼ þ yCH4 yC2 H6 (9) y 0 n0 ¼ Ar T nT (10) Moreover, the material balances for other components [24] are provided as: dyC3 H6 2prLrb ¼ 1 yC3 H6 ar1 yC3 H6 r2 þ 2 yC3 H6 r3 dr nT (11) dyCH4 2prLrb yCH4 ar1 þ ð1 yCH4 Þr2 yCH4 r3 ¼ dr nT (12) dyC2 H6 2prLrb ¼ yC2 H6 ar1 yC2 H6 r2 þ 1 yC2 H6 r3 dr nT (13) (14) where DH1, DH2, and DH3 are the reaction enthalpies of the corresponding reactions (1), (2), and (3), respectively. 2.5 Coke Formation and Deactivation Model Several authors have developed different models for the coke formation of the PDH reaction. A rather popular mechanistic model is called the monolayer-multilayer coke growth model (MMCGM) [25]. This was generalized and modified [26], has been employed by many authors [3, 5, 27–29], and was also utilized in the present study. Tab. 3 indicates three catalyst activity models for the PDH reaction that have been investigated previously [5]. The D3 model was chosen for the catalyst activity [3–5] in the present model, owing to the lower errors resulting from its implementation: C a ¼ ð1 g1 Cm Þ þ g2 Cm exp g3 M Cm Table 3. Catalyst activity models. Model Activity D1 a =(1 – aCm)2 D2 a = (1 – g1Cm) + g2(Cm/(Cm + CM)) D3 a = (1 – g1Cm)+g2Cm exp[–g3(CM/Cm)] Chem. Eng. Technol. 2015, 38, No. 00, 1–10 k1c t 1 þ Cmax k1c t (16) CM ¼ k2c t (17) Eag1 1 1 g1 ¼ g01 exp R T T0 (18) and Eaic 1 1 kic ¼ k0ic exp T T0 R (19) 2.6 Reaction Kinetic Constants and DH Correlations According to the Arrhenius equation chemical kinetics and results available in the literature, the reaction and equilibrium constants can be written as in Eqs. (20)–(22) [3, 5, 24]. ki ¼ k0i exp Furthermore, the energy balance for the reactor regarding the three considered reactions was determined as follows: dT 2prLrb ¼ ½ðDH1 ar1 Þ þ ðDH2 r2 Þ þ ðDH3 r3 Þ dr nT CP;mix 2 Cmax Eai 1 1 T T0 R (20) DH 1 1 kC3 H8 ¼ k0 exp R T T0 (21) 15394 148728 Keq ¼ exp 16:858 · 105 þ T T2 (22) In accordance with classical thermodynamics, the final reaction heat involved at temperature T can be written as Eq. (23) [30]. DHR;T ¼ DHR;298 þ DaðT 298Þ þ þ in which DHR;298 ¼ Da ¼ Db ¼ (15) Dg ¼ X X X Db 2 T 2982 2 Dg 3 T 2983 3 X (23) Wi DHf;i;298 (24) Wi ai (25) Wi bi (26) W i gi (27) Values of the thermodynamic parameters and components of the model are presented in Tabs. 4 and 5. 3 Solution Method and Procedure The developed model was solved utilizing the 4th-order Runge-Kutta technique in the radial direction with appropriate ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com ’’ These are not the final page numbers! Research Article 4 Table 4. Values of a, b, and g for different materials participating in the considered reaction, obtained from [30, 31]. a b [·103] g [·106] C3H8 1.213 28.785 –8.824 C3H6 1.637 22.706 –6.915 H2 3.249 0.422 – CH4 1.702 9.081 –2.164 C2H4 1.424 14.394 –4.392 C2H6 1.131 19.225 –5.561 2.5 – – Component Ar Table 5. Model values used in the present simulation [4, 5, 12, 21, 23, 24]. Parameter Value L [m] 15 –1 a0 [kgcatkgcoke ] –1 a2 [kgcatkgcoke ] –1 Cmax [kgcokekgcat ] Tm [K] 700 394 1.04 ·10–3 793.15 –1 Ea1 [J mol ] 34 570 Ea2 [J mol–1] 137 310 Ea3 [J mol–1] 154 540 Ea1c [J mol–1] 38 430 Ea2c [J mol–1] 125 510 Eag1 [J mol–1] 9610 k01 [mol kg–1s–1P–1] 8.74 ·10–8 k02 [mol kg–1s–1P–1] 7.75 ·10–10 k03 [mol kg–1s–1P–1] 3.9 ·10–11 k01c [kgcokekgcat–1s–1] 3.9 –1 –1 k02c [kgcokekgcat s ] k C3 H 6 2.42 ·10–8 3.46 –1 DHC3 H6 [J mol ] –85,817 –1 124 260 –1 81 280 –1 DH3 [J mol ] –136 960 R [m] 0.75–1.5 DH1 [J mol ] DH2 [J mol ] –1 nT0[mol s ] 237.5 T [K] 813/848/873 P [Pa] 105 initial conditions. It ought to be noted that the temperature and the component concentrations as well as all other variable www.cet-journal.com parameters involved needed updating over the reactor radius increments for each iteration cycle. Additionally, at the end of each iteration cycle, the step size was halved until the convergence criterion was reached. The calculation flow chart as well as the appropriate initial and boundary conditions for the system used in this research are provided in Tab. 5 and Fig. 1. 4 Results and Discussion As a key step in any simulation work, after developing a mathematical model, it has to be verified. This was done for the present work through a comparison of the results generated by the model with those available in the open literature [29, 32, 33]. The results are shown in the parity plot of Fig. 2. It can be concluded that this model was verified utilizing independently obtained experimental data, with a maximum error of 8 %. It is worth mentioning that the preparation parameters of the catalysts in references [29, 32, 33] are not the same, which may have led to different particle sizes and catalytic performances. To clarify the aforementioned fact, the utilized model in this study predicted the experimental results for the different catalyst structures with good accuracy rather than reconfirming the robustness of the present model. Fig. 3 illustrates the catalyst activity as a function of the reactor radius and time. It reveals that the catalyst activity diminished over time due to the coke formation progressing from roughly 1 to 0.3 U (i.e., 100 % down to 30 %) in about 2 h. Moreover, as a result of the occurring endothermic reaction and the temperature drop in the radial direction during this period of time, the rate of the reactions kept decreasing. Nonetheless, a slight increase in activity towards the end of the reactor was observed at the end of this time period. As mentioned above, the PDH reaction was endothermic, due to which the reactants were converted in the radial directions while the temperature fell. Fig. 4 shows the temperature profile in the radial direction of the reactor, falling gradually from 820 to 750 K. It was a predictable conclusion (from both Figs. 3 and 4) that the maximum reaction rate would be observed in the reactor radius range of 0.7–1 m, where the maximum temperature drop occurred. Fig. 5 reveals the unsteady-state profiles of the propane conversion and the propylene selectivity, respectively. It is shown in Fig. 5 a that the propane conversion grew modestly from > 9 % to about 10 % over time, at a pressure of 100 kPa and a temperature of 813 K. On the one hand, the behavior revealed in Fig. 5 a was a consequence of the cumulative conversion of all involved species mentioned earlier in this paper. In addition, the slope of the graph in this figure declined over time, emphasizing the catalyst deactivation and showing that other undesired reactions became more pronounced compared to the main one. On the other hand, as the reactants were converted along the radius, the bed temperature decreased due to the endothermic nature of the reaction, resulting in a reduction of the rate constants and thus lowering the reaction rates; in turn, reaction progress occurred. Meanwhile, Fig. 5 b demonstrates that the propylene selectivity decreased from approximately 77 % to 70 % over time. As the rationale for this behavior it can once again be ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eng. Technol. 2015, 38, No. 00, 1–10 These are not the final page numbers! (( Research Article 5 lene selectivity. In other words, the yield was not the exact criterion for decision making in order to investigate the performance of the reaction system or for achieving an extremely stable catalytic performance. In the present model, considering the catalyst deactivations, the sharp changes in the propane conversion and propylene selectivity seem to be rational. Both trends observed in Fig. 5 a, b were repeated as the feed temperature was enhanced. The results of raising the temperature to 848 and 873 K at 100 kPa pressure are shown in Fig. 5. It is noteworthy that PDH is a highly endothermic reaction; hence, it was to be expected that the propane conversion increased while the propylene selectivity dropped with respect to the input feed temperature enhancement. This latter phenomenon can be attributed to the rate enhancements of the side reactions. In other words, progress of the undesired side reactions became pronounced compared with that of the main one. As such, the unsteady behaviors of the propane conversion and the propylene selectivity were explained. These trends were revealed at all temperatures varying from 813 to 873 K (Fig. 5). Fig. 6 demonstrates the effect of the inert gases (e.g., argon) on the propane conversion and propylene selectivity. It is displayed that the inert gases helped to increase the propane conversion even though the propylene selectivity decreased. This was attributed to the argon gas increasing the heat capacity of the mixture. This was in turn revealed to be a consequence of the endothermicity of the reaction requiring more energy input at higher temperatures. Thus, utilizing an inert gas led to a lower reaction temperature drop compared with an inert gas-free system. 5 Conclusions A mathematical model for PDH towards propylene production in a radial-flow reactor over commercial Pt-Sn/Al2O3 as the catalyst was developed. The results demonstrated that parameters such as the activity of the catalyst, the reactor temperature, and the feed composition were pronouncedly dependent on the time and on the radial spatial direction. In addition, it was noteworthy that these variables influenced each other rather dramatically. Furthermore, the developed model showed that the propane conversion decreased over time while it inFigure 1. Scheme of the process calculation for the model developed in this creased when the feed temperature was enhanced. study. On the other hand, the propylene selectivity revealed the reverse behavior as a result of the progressing side pointed out that this was due to the side (i.e. undesired) reacand undesired reactions. In other words, the model predicted a tions taking place more pronouncedly compared with the main decrease of the selectivity towards propylene as a function of one in this system. Besides, the propylene yield almost did not the feed temperature with progressing time. In addition, adding change with the reaction time due to the fact that the propylene an inert gas into the feed caused an enhancement of the proyield is the product of the propane conversion and the propy- Chem. Eng. Technol. 2015, 38, No. 00, 1–10 ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com ’’ These are not the final page numbers! Research Article 6 Model Propane Conversion (mol.%) 60 R² = 0,9446 50 40 30 20 10 0 0 10 20 30 40 Propane Conversion from the References (mol.%) 50 60 Figure 2. Parity plot of the propane conversion data from the developed model versus the experimental values obtained from [29, 32, 33]. 0.9 0.8 1 0.7 0.9 Activity 0.8 0.6 0.7 0.6 0 0.5 2000 0.4 0.4 4000 0.3 t (s) 0.2 1.5 0.5 0.3 6000 1.4 1.3 1.2 1.1 r (m) 1 0.9 0.8 0.7 8000 Figure 3. Impact of the time and the reactor radius on the catalyst activity in the studied system. pane conversion while reducing the propylene selectivity. This was attributed to the increased heat capacity of the resulting mixture. In the future, it might be interesting to add some material(s) of nonreactive nature (with the feed) possessing a high heat capacity and to observe the propane conversion and propylene selectivity behaviors, further investigating this idea of inert gas addition. The authors have declared no conflict of interest. www.cet-journal.com Symbols used a CM Cm E DH k kic [–] [kgcokekgcat–1] [kgcokekgcat–1] [J mol–1] [J mol–1] [mol kg–1s–1Pa–1] [kgcokekgcat–1s–1] Keq L nT [Pa] [m] [mol s–1] ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim activity multilayer coke monolayer coke activation energy reaction enthalpy reaction constant kinetic constant of coke formation reaction equilibrium constant reactor length gas molar flow Chem. Eng. Technol. 2015, 38, No. 00, 1–10 These are not the final page numbers! (( Research Article 7 810 820 800 810 T (K) 800 790 790 780 780 770 770 760 750 0 1000 2000 3000 t (s) 4000 5000 6000 7000 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 760 r (m) Figure 4. Unsteady variations of the temperature along the reactor radius for the studied system. a) b) Figure 5. Unsteady-state profile of (a) the propane conversion and (b) the propylene selectivity at P = 100 kPa, generated by the model. Chem. Eng. Technol. 2015, 38, No. 00, 1–10 ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com ’’ These are not the final page numbers! Research Article 8 68.5 9.8 68 9.7 67.5 9.65 67 9.6 66.5 9.55 9.5 0 P R r r T Vreactor y 1000 [Pa] [m] [kg m–3] [m] [K] [m3] [–] 2000 3000 4000 Time(s) 5000 pressure reactor radius density reactor radial distance temperature reactor volume component mole fraction Subscripts b c eq f max mix m M 6000 7000 [7] [8] [9] [10] [11] bed coke equilibrium fraction maximum mixture monolayer multilayer [12] [13] [14] [15] [16] References [1] [2] [3] [4] [5] [6] Propylene Selectivity (mol.%) Propane Conversion (mol.%) 9.75 G. Zahedi, H. Yaqubi, M. Ba-Shammakh, Appl. Catal., A 2009, 358 (1), 1–6. M. M. Bhasin, J. H. 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Research Article 10 www.cet-journal.com View publication stats Simulation of Propane Dehydrogenation to Propylene in a Radial-Flow Reactor over Pt-Sn/Al2O3 as the Catalyst 0.9 0.8 1 0.7 0.9 0.8 Activity Research Article: Modeling of the dehydrogenation of propane to propylene in a radial-flow reactor over Pt-Sn/Al2O3 shows that the catalyst activity, reactor temperature, and feed composition highly depend on the time and the radial position. Adding an inert gas into the feed enhances the propane conversion and reduces the propylene selectivity, probably due to the increased heat capacity of the resulting mixture. 0.6 0.7 0.6 0 0.5 S. M. Miraboutalebi, L. Vafajoo, M. Kazemeini*, M. Fattahi 2000 0.4 t (s) 0.2 1.5 0.5 0.4 4000 0.3 0.3 6000 1.4 1.3 1.2 1.1 r (m) 1 0.9 0.8 0.7 8000 Chem. Eng. Technol. 2015, 38 (XX), XXX K XXX DOI: 10.1002/ceat.201500082 ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eng. Technol. 2015, 38, No. 00, 1–10