Production of Acetone

5. 1 MANUFACTURING PROCESSES: Acetone is produced directly or indirectly by propylene. Early processes for the manufacture of acetone were based on the thermal decomposition of calcium acetate or the carbohydrate fermentation of corn starch or molasses. The ready availability of propylene in the 1960s led to routes based on the dehydrogenation of isopropyl alcohol or cumene peroxidation. (1) By Cumene Oxidation (Hock Process). Propene is added to benzene [71-43-2] to form cumene [98-82-8], which is then oxidized by air to cumene hydroperoxide, and cleaved in the presence of an acid catalyst like zeolite. Phenol [108-95-2] and acetone [67-64-1] produced in the process are recovered by distillation. Ratio of phenol to acetone is 1:0. 6. (2) By Dehydrogenation of 2-proponal The hydration of propene [115-07-1] gives 2-propanol [67-63-0], which is then dehydrogenated to acetone. In the United States a C3 stream containing 40 – 60 % propene is used for the manufacture of 2-propanol. A large number of catalysts for 2-propanol dehydrogenation have been studied, including copper, zinc, and lead metals, as well as metal oxides, e. g. , zinc oxide, copper oxide, chromium-activated copper oxide, manganese oxide, and magnesium oxide. Inert supports, such as pumice, may be used. CH3CH=CH2 CH3CH(OH)CH3 CH3COCH3 +H2 (3) By catalytic oxidation of Propene (Wacker-Hoechst). The process is analogous to the oxidation of ethylene to acetaldehyde by theWacker process. The catalyst solution typically contains 0. 045M Palladium (II) chloride, 1. 8M Copper (II) Chloride, and acetic acid. The reaction usually is carried out in two alternating stages. In the first stage, air is used to oxidize the metal ions to the +2 oxidation state. In the second, air is removed and propene added. Palladium (II) oxidizes propene, and the resulting Palladium (I) is reoxidized by the pool of copper (II). Besides propionaldehyde, chlorinated carbonyl compounds and carbon dioxide also are formed. Acetone and the byproducts are removed from the catalyst solution by flash evaporation with steam and separated by fractional distillation. A mixture of acetone (92 % selectivity) and propionaldehyde (2 – 4 % selectivity) is produced. CH3CH=CH2 + ? O2 CH3COCH3 + CH3CH2CHO (4) By oxidation of p-Disisopropyl Benzene (Goodyear Process). Acetone is coproduced with hydroquinone [123-31-9] from p-diisopropylbenzene [100-18-5] in a process analogous to the phenol – acetone production from cumene. In the Goodyear process p-diisopropylbenzene is oxidized by oxygen in the presence of caustic. The p-diisopropylbenzene dihydroperoxide [3159-98-6] formed is crystallized and washed with benzene. It is then dissolved in acetone and cleaved to hydroquinone and acetone in the presence of sulfuric acid. Next the acid is neutralized with ammonia and the ammonium sulfate formed is filtered. Acetone is recovered by distillation from the reaction mixture. 5) By distillation of Calcium Acetate. Manufacture of Acetone from Acetate of Lime, etc. – Acetone is produced commercially by the dry distillation of various acetates, calcium acetate (commercial grey acetate of lime) or barium acetate being generally used. The single acetate is usually employed, although mixtures of two acetates have been recommended. Grey calcium ace tate usually contains about 80 per cent calcium acetate, the remaining 20 per cent consisting of water and various impurities, including small quantities of calcium formate and propionate as well as salts of other organic acids. Calcium acetate when heated at a temperature of about 380Â ° C. decomposes, giving acetone and a residue of calcium carbonate, but at the same time the accompanying calcium salts present as impurities also react and acetaldehyde and various higher ketones are formed together with the condensation products. In addition other impurities (such as dumasin) and tar-like bodies are formed. Ca(CH? -COO)? CH? -CO-CH? + CaCO? (6) By fermentation of Corn Products by selected Bacteria. The process was started during World War II to provide acetone needed for the manufacture of cordite. The last operating plant in the United States (Publicker Industries) closed in 1977. The fermentation of cornmeal or molasses by various members of the Clostridium genus yields a mixture of 1-butanol, acetone, and ethanol in 2 % overall concentration. The products are recovered by steam distillation and then fractionated. 5. 2 SELECTION OF PROCESSES: Sr NoProcessesParameterCatalystAdvantages/ Disadvantages 1Cumene OxidationYield:- 40% Selectivity:- 90% 1)For Cumene hydroperoxide Temp:- 120 0C Pressure:- 1 atm 2) For acetone Temp:- 60-65 0CAcid catalyst like zeoliteAdvantage:- Valuable main product phenol Disadvantage: – ) Higher operating cost. 2) Acetone is as a byproduct. 2Dehydrogenation of 2-proponalYield:- 90% Selectivity:- 98% Temp:- 300-500 0C Pressure:- 3 atm Dehydrogenation Catalyst:- ZnO, CuAdvantages:- 1) The primary advantage of this process is that the acetone produced is free from trace aromatic compounds, particularly benzene. 2) Less operating cost 3) Valuable byproduct Hydrogen which is 99% pure. 4) High Yield 3Catalytic oxidation of PropeneYield:- 97-99% Selectivity:-92% Temp:- 140 0C Pressure:- 14 atmPalladium Chloride – Cupric ChlorideAdvantage:- 1) Single stage Disadvantages:- 1) High capital & operating cost. 2) Corrosion problem. 4Oxidation of p-Di-isopropyl BenzeneYield:- 20% Temp:- 80-90 0CSulfuric acidDisadvantage: – 1) Higher operating cost. 2) Acetone is as a byproduct. 3) Lower yield 5Distillation of Calcium AcetateYield:- 75% Temp:- 380 0C Disadvantage: – 1) Higher operating cost 2) Lower yield 6Fermentation processYield:- 28-30% Temp:- 35-450CClostridium Madisonii VacteriaDisadvantages: – 1) Lower yield. 2) Higher processing cost due to increase in price of petrochemical feedstock which is used for extracting the acetone. On the above discussion between various methods we are choosing the IPA route to produce Acetone. 5. 3 PROCESSES DESCRIPTION: The production of acetone is divided in two parts. 1)Production of IPA through Feed drum is a kind of tank used for the mixing of the recycle stream and feed stream. Recycle stream concentration was assumed to be same with the feed stream. The temperature of the feed stream is assumed to be 25 0C at 2 bar pressure, which is assumed to be constant. The temperature of recycle stream was calculated as 111. 5 0C. The temperature of the leaving stream was calculated as 32. 9 0C, by the energy balance around feed drum. In the vaporizer molten salt was used for heating. The temperature at the entrance of the unit is the temperature of the mixture leaving the feed drum, which is 32. 89 0C. And the leaving temperature is the bubble point temperature of the mixture, which is 109. 5 0C. The pressure is 2 bars, and assumed to be constant. Since the temperature leaving the vaporizer is not enough for the reaction a pre-heater was used. The unit is working at 2 bars, and assumed to be constant. The entrance and leaving temperatures are 109. 50 0C and 325 0C. The reactor was the starting point for the calculations. The temperature values for the entering and leaving streams were found from literature, which are 325 0C and 350 0C, respectively. The reaction taken place inside is endothermic, for this reason the reactor has to be heated. For heating, molten salt was used. The pressure is 1. 8 bar, and assumed to be constant. The entrance temperature of the cooler is 350 0C and leaving is 94. 70 0C. For cooling, water was used. Instead of water a refrigerant may be used. Better results may get. But since it costs too much, it wasn’t chosen as the cooling material. From the temperature values it’s easily seen that the load is on the cooler not on the condenser, for this process. But in reality the unit cannot cool that much, and the load is mostly on the condenser. In this process, the mixture cooled down to its dew point. The pressure is 1. 5 bar, and assumed to be constant. The temperature of the entering stream is the dew point and the leaving temperature is the bubble point of the mixture. In the condenser water was used as cooling material. In the calculation of the dew and bubble points Antoine Equation was used. Trial and error was used with the help of Excel. The mixture includes acetone, i-propyl-alcohol, water and hydrogen. But hydrogen was not taken into consideration in the calculations. Since the condensation temperature of hydrogen is very low, it is not condense in the condenser. It stays in this for this reasons it has no effect on bubble and dew point calculations. Also since it does not affect the temperature calculations it’s not taken into consideration on mole and mass fraction calculations. The leaving and entering temperatures are 94. 70 0C and 81 0C, respectively. The pressure is 1. 5 bar, and assumed to be constant. Flash unit was assumed to be isothermal, for this reason temperature was not changed. It is 81 0C in the entrance and exit. The pressure is 1. 5 bar, and assumed to be constant. By trial and error method, (V / F) value was found to be 0. 2. The entrance temperature of the unit is the bubble point of the mixture, but if it was its dew point the (V/F) value would be much higher. Scrubber was assumed to be adiabatic. The temperature of water entering the unit was assumed to be 25 0C. The temperature of the off gas, including hydrogen and a very little amount of acetone, was assumed to 70 0C. But this assumption is too high, a lower temperature should have been assumed, since a lot of water is used in the unit. It should have been around 40 0C – 50 0C. The temperature of the leaving stream was found to be 28. 10 0C. The pressure of the unit is 1.. 5 bar, and assumed to be constant. The streams leaving the scrubber and flash unit are mixed together before entering the acetone column. The temperature leaving the flash unit and scrubber are 81 0C and 28. 10 0C, respectively. The temperature of the mixture was found to be 45 0C. This result was getting by using energy balance around the mixing point. The acetone column is used to separate the acetone from the mixture. The entrance temperature is 45 0C. The leaving temperatures for the top and bottom product are 102. 3 and 105, respectively, which are the bubble and dew points. Top product of the unit includes acetone i-propyl-alcohol and 99wt% of the product is acetone. This amount is assumed to be the desired acetone production rate, which is 115000 ton/year. From the bottom i-propylalcohol water and a very little amount of, 0,1 %, acetone is discharged. The pressure is 1. 1 bar, and assumed to be constant. In the distillation column, i-propyl-alcohol and water are separated. The entrance temperature is 105 0C. The leaving temperatures of the top and bottom products are both 111. 50 0C. The top product is recycled to the feed drum. For this reason it’s assumed to have the same concentration with the feed stream. But in reality a very little amount of acetone exists in the stream. It’s calculated but neglected on the recycle stream calculations. The bottom product is assumed to be pure water and it’s thrown away. Since its temperature is very high it cannot be recycled to the scrubber. But if a cooler is used, a recycle can be used. The pressure is 1. 1 bar, and assumed to be constant.