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Abstract
In this report, study of a diethyl ether production plant is done by considering, raw materials to use, equipment specifications, utilities needed, economic analysis and safety issues. It is supposed to provide the plant with 50000 metric tons of ethanol as a feed. Ethanol dehydration reaction is known to be a catalytic reaction so a packed bed reactor with alumina as a catalyst is used. The process starts by pre-heating the methanol feed up to the boiling point then re-heat up to 4000C and sent to the reactor. The feed is given as liquid Ethanol with 70 mol% in water. Since the ethanol dehydration reaction is an exothermic reaction, the temperature in the reactor increases up to 4500C approximately to give 80% conversion. Finally, the exit stream of the reactor is sent to separation towers in order to get the desired product (DEE) with 99.7 % wt.
1 INTRODUCTION
Diethyl ether (DEE) is an organic compound in the ether class with the formula (C2H5)2O. It is colour less volatile flammable liquid. This is commonly used as solvent and was once used as general anaesthetic. It is an important solvent in the production of cellulose acetate and other cellulose-based polymers. Other uses for DEE are as a starter fluid for diesel and gasoline engines and as a solvent for Grignard and other reactions involving organometallic reagents. [1]
Figure 1: 2D structure of DEE
1.1 CHEMICAL PROPERTIES
Molecular Formula: (C2H5)2O
Molecular Weight: 74.1216 g/mol
DEE is a clear colourless liquid with an anaesthetic odour. Less dense than water and slightly soluble in water. Hence floats on water. Vapours are heavier than air. It is a highly flammable and oxidizes readily in air to form unstable peroxide that may explode spontaneously. [2]
1.2 PHYSICAL PROPERTIES
Property Value
Melting Point -1160C
Boiling Point 34.60C
Density 0.714
Vapour Density 2.6 (vs air)
Vapour Pressure 28.69 psi (550C)
Freezing Point -116.30C
Flash Point -450C
Viscosity 0.2448cP (200C)
Heat of Combustion -8.807 kcal/g
Heat of Vaporization 89.80 cal/g (300C)
Table 1hysical Properties
1.3 PRODUCTION
Most diethyl ether is produces as a by-product of the vapour-phase hydration of ethylene to make ethanol. This process uses solid supported phosphoric acid catalyst and can be adjusted to make more of ether if the need arises. Vapour-phase dehydration of ethanol over some alumina catalyst can give diethyl ether yields up to 95%
Diethyl ether can be prepared both in laboratories and on industrial scale by the acid ether synthesis. Ethanol is mixed with a strong acid, H2SO4. The acid dissociates in the aqueous environment producing hydronium ions, H3O+. A hydrogen ion protonates the electronegative oxygen atom of the ethanol, giving the ethanol molecule a positive charge:
CH_3 CH_2 OH+H_3 O^+→CH_3 CH_2 O〖H_2〗^++H_2 O
A nucleophilic oxygen atom of unprotonated ethanol displaces a water molecule from the protonated (electrophilic) ethanol molecule, producing water, a hydrogen ion and diethyl ether. [3]
CH_3 CH_2 OH_2^++CH_3 CH_2 OH→H_2 O+H^+→CH_3 CH_2 OCH_2 CH_3
This reaction must be carried out at temperatures lower than 150 °C in order to ensure that an elimination product (ethylene) is not a product of the reaction. At higher temperatures, ethanol will dehydrate to form ethylene. The reaction to make diethyl ether is reversible, so eventually an equilibrium between reactants and products is achieved. Getting a good yield of ether requires that ether be distilled out of the reaction mixture before it reverts to ethanol, taking advantage of Le Chatelier's principle.
Another reaction that can be used for the preparation of ethers is the Williamson ether synthesis, in which an alkoxide (produced by dissolving an alkali metal in the alcohol to be used) performs a nucleophilic substitution upon an alkyl halide.
Import and Export
India is one of the major export destination for diethyl ether. The major importing countries are Egypt, Netherlands, Saudi Arabia, United States, France, Nepal etc. which generates a revenue of around INR. 4034,50,347. Apart from Exporting, India also imports diethyl ether from Germany
Process Description
Introduction
ThePlant that is considered to be revamped, has a capacity to produce 50,000 metric tons of DEE as a byproduct per year. Production method is vapor-phase dehydration of ethanol. A catalytic reactor (R-1201), may be either an isothermal fixed bed reactor with a heat transfer jacket, or two adiabatic fixed bed reactor stages with heat exchanger between stages.
Fresh ethanol, stream 1, consists of 70 mol% ethanol in water, is mixed with recycled ethanol, stream 29, in a feed vessel (V-1201). Then this mixture is vaporized and heated in heat exchanger (E-1201) and then it is fed to the packed bed reactor (R-1201) which operates at 450˚C. The reactor contains packed bed of alumina catalyst. The main reaction.
2C_2 H_5 OH→(C_2 H_5 )_2 O+H_2 O
Is exothermic reversible, and limited by equilibrium. The reaction occurs at medium temperature (400-600 K) and high pressure (1000-5000 kPa). The alumina catalyst minimizes side reactions at higher temperatures. The only side reaction that occurs in R-1201 is the dehydration of DEE to form ethylene.
(C_2 H_5 )_2 O→H_2 O+2C_2 H_4
The stream leaving reactor, stream-4, is then cooled (E-1202) using cooling water and enters a flash vessel (V-1202). The undesirable side reaction that contains all of the ethylene and small amounts of DEE and ethanol is sent to another process to be used as a fuel gas. The liquid in flash vessel is sent to the first of two distillation columns, T-1201 and T-1202. DEE product is taken overhead from the first column (stream-17). The second column separates the water from the unused ethanol. The ethanol, stream-29 is recycled back to the front end of the process, and the water is sent to wastewater treatment to remove trace amounts of organic compounds.