Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide

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1 International Journal of Scientific Research in Chemical Engineering, 1(1), pp. 1-8, 2014 Available online at ISSN: ; 2014 IJSRPUB Full Length Research Paper Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide Abhishek Sao 1*, Omprakash Sahu 2* 1 Department of Chemical Engineering, IT Guru Ghashi University, Bilaspur (CG), India. 2 Department of Chemical Engineering, KIOT, Wollo University, Kombolcha (SW), Ethiopia *Correspondence Author: ops0121@gmail.com; Tel: Received 02 April 2014; Accepted 02 May 2014 Abstract. Propylene oxide has major uses in different chemical product, with production of more than 6 million tons per year worldwide. The main goal of study is to compare the efficiency of the packed bed reactor and fluidized bed reactor for the production of propylene oxide. Currently two are applied for the production of propylene oxide first chlorohydrin process and second hydroperoxide process. For this study hydroperoxide process was used. It found that the conversion factor with respect catalysis loading and length of the tube found to be 100 % shown by packed bed reactor. By design and experiment it was found that packed bed reactor is more suitable as compared to fluidized bed reactor for production of propylene oxide. Keyword: Acid; Boiling point; Catalysis; Process; Time 1. INTRODUCTION Propylene oxide (PO) is a major industrial product with production of more than 6 million tons per year worldwide. Propylene oxide is a volatile, clear, colorless, and extremely flammable liquid with an ether-like odor (Creaser et al., 2000). Its molecular weight is 58.1, its melting point is C, and its boiling point is C. Propylene oxide has a specific gravity of at 20 C/20 C and an octanol-water partition coefficient of 0.03 (Sinha et al., 2003). It is soluble in water and miscible with acetone, benzene, carbon tetrachloride, diethyl ether, and ethanol. Propylene oxide is very reactive, particularly with chlorine, ammonia, strong oxidants, and acids. It may polymerize explosively when heated or involved in a fire (Buyevskaya et al., 2000). Propylene oxide is used primarily as a chemical intermediate in the production of polyurethane polyols (60% to 65%), propylene glycols (20% to 25%), glycol ethers (3% to 5%), and specialty chemicals (Greben et al., 2005). Polyurethane polyols are used to make polyurethane foams; whereas, propylene glycols are primarily used to make unsaturated polyester resins for the textile and construction industries (CEFIC, 2005). Propylene glycols are also used in drugs, cosmetics, solvents and emollients in food, plasticizers, heat transfer and hydraulic fluids, and antifreezes (Rihko-Struckmann et al., 2004). In 1 addition, propylene oxide may be used in fumigation chambers for the sterilization of packaged foods and as a pesticide. Approximately 70% of it is used as polypropylene glycol in the raw materials for urethane, and the remainder is used as propylene glycol in the raw materials for unsaturated polyesters, food product additives and cosmetics (Valbert et al., 1993). The major application of PO is shown in Fig. 1. PO production methods that have been industrialized up to this point can be roughly divided into two methodologies first chlorohydrins process and the second is hydroperoxide process. In 1999, the production capacity was distributed evenly between these two processes; however, because of the environmental impacts of the chlorohydrins process, the most recently built plants are all using hydroperoxide process technologies (Wang et al., 2004). However, a disadvantage of the hydroperoxide processes is the production, in a fixed ratio, of a coproduct (either styrene or tert-butyl alcohol, depending on which variant of the hydroperoxide process is applied) (Bartolome et al., 1975). Because these co-products are produced in a volume that is 3 times larger than that of propene oxide, the economy of the process is primarily dominated by the market of the co-product. A major research effort has been made in the development of alternative direct epoxidation

2 Sao and Sahu Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide processes for the production of propene oxide (Tullo, 2005). Due to lack of technical problem the production may be affected. In this study compared the efficiency of packed bed reactor with fluidized bed reactor for the production of propylene oxide. The effect of catalysis and length of tube was studied for packed bed reactor as well as cost estimation was also calculated. Fig. 1: Major application of propylene oxide 2. MATERIALS AND METHODS 2.1. Material Propylene oxide is an organic compound with the molecular formula CH 3 CHCH 2 O. Propylene oxide is a colourless, low-boiling, highly volatile liquid with a sweet, ether-like odour and moderately toxic. It is flammable and reactive, so storage and unloading areas must be specifically designed and monitored. This compound is sometimes called 1,2-propylene oxide to distinguish it from its isomer 1,3-propylene oxide, better known as oxetane. Its other common names are 1,2 Epoxypropane, Propene epoxide, Propene oxide. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics. It is chiral epoxide, although it commonly used as a racemic mixture (Trent, 2001) Methodology (Hydrogen peroxide) Propene oxide is currently produced using two different types of commercial processes: the 2 chlorohydrin process and the hydroperoxide process Hydroperoxide processes are based on the peroxidation of an alkane to an alkyl-hydroperoxide. These alkyl-hydroperoxides then react with propene, producing propene oxide and an alcohol. A characteristic of these processes is that, besides propene oxide, a coproduct is produced in a fixed ratio, usually 2-4 times the amount of propene oxide produced. Currently, two variants of this process are applied commercially. The first is the propene oxidestyrene monomer (PO-SM, also commonly abbreviated as SMPO) process (60% of the hydroperoxide plants use this version) (Pell and Korchak, 1969; Dubner and Cochran, 1993; Van and Sluis, 2003). In this process, ethylbenzene is oxidized to ethylbenzene hydroperoxide, which reacts with propene to produce propene oxide and R-phenyl ethanol. The R-phenyl ethanol is then dehydrated to produce styrene. The second process in use is the propene oxide-tert-butyl alcohol (PO-TBA) process. In this process, isobutane is oxidized to tert-butyl hydroperoxide (TBHP), which reacts with propene to produce propene oxide and tert-butyl alcohol. This can be dehydrated to isobutene or converted directly with methanol to methyl-tert-butyl ether (MTBE).

3 International Journal of Scientific Research in Chemical Engineering, 1(1), pp. 1-8, 2014 Although other combination processes are possible, no others have been applied so far (Richey, 1994). Other possibilities include, for example, acetaldehyde to acetic acid, 2-propanol to acetone, isopentane (via tert-pentyl alcohol) to isoprene, cumene (via dimethylphenyl methanol) to R-methylstyrene, and cyclohexene (via cyclohexanol) to cyclohexanone (Kalich et al., 1993). Characteristics of the hydroperoxide processes are that they are selective and produce far less waste than the chlorohydrin process. However, the major disadvantage of the hydroperoxide processes is that a fixed amount of coproduct is always produced. Because the markets for propene oxide and the coproducts are not linked, a problem could arise, should the demand for one of the products collapse. Since the use of MTBE as a fuel additive is becoming less favorable, the latest plants that have been built using a hydroperoxide process are all of the PO-SM type (Hayashi et al., 1998). Figure 2 schematically demonstrates the PO-SM process. The basic principle of the PO-TBA process is similar to that of the PO-SM process, so both processes are discussed simultaneously (Cisneros et al., 1995). The first reactor converts the ethylbenzene or isobutene noncatalytically to its corresponding hydroperoxide by direct liquid-phase oxidation, using oxygen or air. The oxidation is usually performed in a bubble column at 400 K and 30 bar when isobutane is used, or 423 K and 2 bars in the case of ethylbenzene. Fig. 2: Flow diagram for production of propylene oxide by hydrogen peroxide method (Nijhuis et al., 2006) 3. RESULTS AND DISCUSSIONS 3.1. Packed bed reactor Design of packed bed reactor It can be calculated by Where, W = Weight of catalyst, F 0 A = Molar Flow Rate, XA = Conversion, -ra = Rate of Reaction W/ F o A = x 10 6 W= weight of Catalyst = = Kg Weight of catalyst can be given by formula W= ρc V (1-ф) Where, ρc = Density of catalyst = Kg/m3, V = Volume of Reactor, ф = Porosity of Catalyst Bed = 0.3, W = ρc V (1- ф), = V (1-0.3), V = m3 =677 ft3 3

4 Sao and Sahu Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide schedule 80, the cross sectional area is ft2 the number of pipe necessary is It was decided to use a bank of 2 inch schedule 80 pipes in a parallel that are 60 ft in length. For pipe n= Volume of the Reactor Cross sectional Area x Length Number of tubes in the reactor is 550 m, μ = Viscosity of gas passing through bed = x10-3, z = Length of Reactor =60 ft = 18.3 m, ρc = Density of catalyst = , G = ρ x u = Superficial Mass Velocity = 2931 Kg / (m2 s), Therefore, β = (P/Po)=0.15 P=1.5atm Hence the pressure drop ( P) = 8.5 atm Pressure Drop in the Reactor Most gas phase reaction is takes place in packed bed reactor. Equation most used to calculate pressure drop in packed bed reactor is Ergun equation o P T FT dp o dw Ac bulk P To FTo o G G (1 ) 150(1 ) G o D p 3 Dp F i,o Effect of catalysis weight: The effect of catalysis weight on conversion is shown in Fig. 3. It was found that the conversion was increase with increase in increase in weight of catalysis. When the catalysis loading was 1, 2, 3, 4, the conversion was 12, 23, 30 and 45% was observed. Almost 98 percentage of conversion was found to at 5.5kg of catalysis. Then it maintained constant for the conversion of long time (Diakov et al., 2002). M Wi i Ac Where, P = Pressure, P0 = Inlet Pressure = 10 atm, ф = Porosity = (Volume of Void / Total Bed Volume) = 0.3, 1- ф = (Volume of Solid / Total Bed Volume) = 0.7, gc = Conversion Factor = 1 (in the metric system), dp = Diameter of Particle in the bed = Fig. 3: Effect of catalysis loading on conversion conversion was increase with increase in length of tube (Ramos et al., 2000). The maximum conversion was 90% found at 18 ft of tube length in reactor. The total number of tube in the reactor is Effect of length on conversion The effect of length of tube on the conversion of propylene is shown in Fig. 4. It was found that 4

5 International Journal of Scientific Research in Chemical Engineering, 1(1), pp. 1-8, Design of Fluidized Bed Reactor Fig. 4: Effect of tube length on conversion The design equation for Fluidized Bed Reactor is same as for CSTR By solving above equation analytically, we can find the concentration profile with respect to time constant. That concentration profile shown in figure below. Conversion in the packed bed reactor is, Weight of catalyst in the reactor calculated by formula W= ρc V (1-ф ) Assume Porosity = 0.6 W = (1-0.65) = Kg Effect of concentration on time The effect of concentration on the reaction time is shown in Fig. 5. It was found that the concentration of component C was 7.2 mole/liters maximum at 250min of reaction time. The concentration of component A was 3.5mole/liters at zero time and the concentration of component was 1.5 mole/liters at 250 min (Leveles, 2002). Fig. 5: Effect of concentration time 5

6 Sao and Sahu Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide 3.3. Cost estimation Packed Bed Reactor Weight of Material Required Tube = 2 π r L Thickness Density Number = lb Weight of Material Required Shell = 2 π r L Thickness Density = lb Weight of Material Required Head = 4090 lb Total weight of Material required = = lb = Kg Actual weight of Material required = % Extra weight = Kg Cost of Material required = tone 887 $/tones = $ = Rs Cost of Catalyst Required = W e i g h t of Catalyst Cost per kg of Catalyst = (Assume) = Rs Miscellaneous Cost = Rs/yr 1) Total Equipment Cost = = Rs ) Insulation Cost = 15 % Equipment Cost = Rs ) Piping and Instrumentation = Rs = 10% Equipment Cost Total Reactor Cost = = Rs Fluidized Bed Reactor Weight of Material Required Shell = 2 π r L Thickness Density = lb Weight of Material Required Head = lb Total weight of Material required = = lb = Kg Actual weight of Material required = % Extra weight 6 = Kg Cost of Material required = tone 887 $/tone = $ = Rs Cost of Catalyst Required = Weight of Catalyst Cost per kg of Catalyst = Kg 40 (assumed) = Rs Miscellaneous Cost = Rs/yr 1) Total Equipment Cost = Rs = Rs ) Insulation Cost = 15 % Equipment Cost = Rs ) Piping and Instrumentation = 10% Equipment Cost = Rs ) Land = Rs Total Reactor Cost = = Rs CONCLUSION This study demonstrated that packed bed reactor is more suitable as compared to fluidized bed reactor. The conversion factor with respect catalysis loading and length of the tube found to be approximately 100 percentages. Packed bed reactor shows good efficiency at 550 numbers of tubes, 8.5 Atm pressure drops, 98% of conversion at 5.5 Kg catalysis and 90% conversion 18feet. The fixed bed reactor shows upto 80% conversion. The hydroperoxide processed will maintain a very important position as long as there is a high demand for their coproducts. Considering the huge market for styrene, especially, the PO-SM process will be in use for a long time. The new processes developed fulfilled the requirement. Improvements are being made continuously and new processes to replace the two existing processes are beginning to be applied. REFERENCE Bartolome E, Koehler W, Stoeckelman G, May A, (1975). Continuous manufacture of propylene oxide from propylene chlorohydrine. (BASF Corporation) U.S. Patent No. 3,886,187. Buyevskaya OV, Wolf D, Baerns M, (2000). Ethylene and propene by oxidative dehydrogenation of ethane and propane Performance of rare-earth oxide based catalysts and development of redox-type catalytic materials by combinatorial methods, Catalysis today, 62: Cisneros MD, Holbrook MT, Ito LN, (1995).. Hydrodechlorination process and catalyst for

7 International Journal of Scientific Research in Chemical Engineering, 1(1), pp. 1-8, 2014 use therein. (Dow Chemical Co.) U.S. Patent No. 5,476, 984. Creaser DC, Andersson B, Hudgins RR, Silveston PL, (2000). Kinetic modeling of oxygen dependence in oxidative dehydrogenation of propane. The Canadian Journal of Chemical Engineering 78, Diakov V, Blackwell B, Varma A, (2002). Methanol oxidative dehydrogenation in a catalytic packed-bed membrane reactor: experiments and model, Chemical Engineering Science 57: Dubner WS, Cochran RN, (1993). Propylene oxidestyrene monomer process. (ARCO Corporation), U.S. Patent No. 5, 210, 354. European Chemical Industry Council (CEFIC) (2005). Propylene production, consumption and trade balance. Available via the Internet at Greben H.A., Maree J.P., Eloff E., Murray K., Improved sulphate removal rates at increased sulphide concentration in the sulphidogenic bioreactor. Water SA, 31, Hayashi T, Tanaka K, Haruta M, (1998). Selective Vapor-Phase Epoxidation of Propylene over Au/TiO 2 Catalysts in the Presence of Oxygen and Hydrogen. Journal of Catalysis, 178(2): Kalich D, Wiechern U, Linder J, (1993). Propylene Oxide. In Ullman s Encyclopedia of Industrial Chemistry, 5th Edition; Verlag Chemie: Weinheim, Germany. 22(A): Leveles L, (2002). Oxidative conversion of lower alkanes to olefins, Doctoral Thesis, Twente University, Enschede, the Netherlands. Nijhuis TA, Makkee M, Moulijn JA, Weckhuysen BM, (2006). The Production of Propene Oxide: Catalytic Processes and Recent Developments. Industrial Engineering Chemical Research, 45: (Figure Reff.) Pell M, Korchak EI, (1969). Epoxidation using ethylbenzene hydroperoxide with alkali or adsorbent treatment recycle ethylbenzene. (Halcon Corporation), U.S. Patent No. 3,439,001, Ramos R, Menendez M, Santamaría J, (2000). Oxidative dehydrogenation of propane in an inert membrane reactor, Catalysis Today 56: Richey WF, (1994). Chlorohydrins. In Kirk-Othmer: Encyclopedia of Chemical Technology, 4th Edition; Wiley: New York, 6: Rihko-Struckmann LK, Karinen RS, Krause AO, Jakobsson K, Aittamaa JR, (2004). Process configurations for the production of the 2- methoxy-2,4,4-trimethylpentane- a novel gasoline oxygenate, Chemical Engineering and Proceed, 43(1): Sinha AK, Seelan S, Akita T, Tsubota S, Haruta M, (2003).Vapor phase propylene epoxidation over Au/Ti-MCM-41 catalysts prepared by different Ti incorporation modes. Applied Catalysis A, 240(1-2): Trent DL, (2001). Propylene oxide. In Kirk-Othmer: Encyclopedia of Chemical Technology; Wiley: New York. Tullo A, (2005). BASF, Dow Plan More Propylene Oxide Units. Chemical Engineering News 83(44): 7-8. Valbert JR, Zajacek JG. Orenbuch DI, (1993). Propene oxide and glycol. In Encyclopedia of Chemical Processing and Design; Marcel Dekker: New York, Van D, Sluis JJ, (2003). Process for the preparation of styrene and propylene oxide. (Shell Corporation), U.S. Patent No. 6, 504, 038. Wang X, Zhang Q, Guo Q, Lou Y, Yang L, Wang Y, (2004). Ironcatalyzed propylene epoxidation by nitrous oxide: dramatic shift of allylic oxidation to epoxidation by the modification with alkali metal salts. Chemical Communication 2:

8 Sao and Sahu Comparative Study of Packed Bed Reactor and Fluidized Bed Reactor for the Production of Propylene Oxide Mr. Abhishek Sao was finial year Chemical Engineering student in department of chemical engineering, IT, Guru Ghasi Das University, Bilaspur (CG), India in His specialization is process engineering. Mr Omprakash Sahu was graduated from department of Chemical Engineering, ITGGV Bilaspur (CG) India in the year of 2003.His specialization in Chemical, Energy and Environment 8