Special Report
Methyl Ethyl Ketone: Ketone: A Technoechno-Commercial Commercial Profle INTRODUCTION ethyl ethyl ketone [1] (MEK) (CAS No.: 78-93-3), is a ammable, colourless liquid with a sharp, sweet butterscotch odour reminiscent of acetone. It is soluble in four parts water and miscible with al cohol, ether, acetone, and benzene. It is lighter than water and may be expected to oat while rapidly dissolving .
M
It is unsymmetrical or mixed ali phatic ketone. Its IUPAC IUPAC name is 2-Butanone. Other names are: Methylacetone and Meetco. MEK is the second link in the ho mologous series of aliphatic ketones and next to acetone, the most important commercially produced ketone.
of MEK in the environment are exhaust from jet and internal combustion enen gines, and industrial activities such as gasication of coal. It is also found in substantial amounts in tobacco smoke.
DIVYESH ARORA & MOHIT SHARMA Jaypee Institute of Engineering & Technology E-mail:
[email protected] [email protected]
Properties Physical properties[1] MEK is a colourless liquid. Its odor resembles that of acetone. It is only partially miscible with water and it is completely miscible with most organic solvents. In fact, it forms binary and ternary azeotropic mixtures in combination with water and several other organic solvents (Table 1). Chemical properties[1] MEK is stable under normal condicondi tions and in absence of air. It is unsa poniable and does not form for m corrosive products under hydrolysis. hydrolysis . It is heat and light stable. It only decomposes after prolonged exposure of UV.
Self-condensation Aldol condensation of 2 moles of MEK yields a hydroxyketone, which readily dehydrates to an unsaturated ketone: O
II CH3CCH2CH3 + H2O2
OH
I CH3CCH2CH3 I OOH
Condensation with other compounds Reaction with aldehydes gives higher ketone, as well as ketals and cy clic compounds, depending on reaction conditions. Ketones are produced by the condensation of MEK with aliphatic esters. Sec-Butyl Sec-Butyl amine is formed by reacting MEK with aqueous ammonia and hydrogen:
It is produced in large quantities. Nearly half of it is used in paints and other coatings. It dissolves many subsub stances and is used as a solvent in propro cesses involving gums, resins, cellulose It can be widely utilized in chemical acetate, nitrocellulose coatings, in vinyl lms, in the synthetic rubber industry, synthesis. Its reactivity O NH2 plastics, textiles, in the production of centres on the carbonyl II I Ni parafn wax, and in household pro- group and its adjacent CH3CCH2CH3 + NH3 +H2 CH3CHCH2CH3 + H 2O Conducts such as lacquer, varnishes, paint hydrogen atoms. Conremover, a denaturing agent for de- densation, ammonolysis, halogenations An excess of MEK in this reaction natured alcohol, glues and as a cleaning and oxidation can be carried out under will produce di- sec- butylamine. butylamine. ReactReactre - ing MEK with acetylene gives methyl agent. MEK is also used in dry erase the proper conditions. Some typical rebelow. markers as the solvent of the erasable actions are described below. pentynol, a hypnotic hypnotic compound. dye and in synthesis of Table 1 MEK peroxide, a catalyst Applications[1] Physical properties of MEK for some polymerization MEK is consumed in large quantiquantireactions. ties in a variety of industries and appliappli Value Natural occurrence[g] MEK occurs naturally in volcanoes, forest res, and products of biologibiological degradation. It is made by some trees and found in some fruits and vegetables in small amounts. Sources
Molecular weight Boiling point Melting point Vapour pressure Vapour density Density/specic gravity
Chemical Weekly April 27, 2010
72.10 o
79.6 C o
-86.35 C o
90.6 mm Hg at 25 C 2.41 (air = 1) o
0.805 at -20/4 C
cations (Table 2). Environmental impact[g] When released into the soil, MEK may leach into groundwater & may evaporate to a moderate extent. When released into water, it may biodegrade to a moderate extent, may evaporate to a moderate extent & is expected to have a 189
Special Report Table 2 How MEK is used in industries
Sector
Industry
Application
Adhesives manufacture
Carpet adhesive solvents
Electroplating
Cold-cleaning solvents
Electroplating
Vapour degreasing solvents
Laboratory chemicals
Solvents - extraction
Machinery manufacture and repair
Solvents
Metal degreasing
Solvents
Paint manufacture
Solvents
Paint stripping
Solvents
Paper coating
Solvents Solvents for exography & gravure printing
half-life between 10 and 30 days. MEK is not expected to signicantly bio-accumulate. When released into the air, this ma terial is expected to be readily degraded by reaction with photochemically produced hydroxyl radicals & is expected to have a half-life between 1 and 10 days. Global scenario In 2007, publicly available sources reported global production for MEK reached 1,141-kt (kilotons) (2.5 billion pounds). Global demand for MEK was 1,100-kt (2.4 billion pounds).
Worldwide[h] MEK demand is forecast to grow at 3.5% over next ve years, to 1.3-mt (million tons) by 2010, according to SRI Consulting. Demand growth will be driven by China, the largest single consumer. Chinese demand is projected to grow at 8.5%/year,
while demand in the rest of Asia, excluding Japan, is expected to increase at about 2.6%/year. Growth in Western Europe will be almost at over the next four years (Table 3). Application-wise consumption pattern[h] Coating solvents are the largest enduse for MEK, accounting for almost half of worldwide demand. Adhesives are the second-largest end use, accounting for almost 20% of demand (Table 4,5). Indian Scenario[j] The current demand in India for MEK is around 10,000-11,000 tons. India is not self-sufcient to meet its demand, so it imports MEK from various countries (Table 6). Cetex Petrochemicals Ltd. is the only producer of MEK in the country.
Table 3 MEK growth prospects Country
China Rest of Asia (excluding China & Japan) Western Europe North America
190
Coatings/solvents Adhesives Printing inks Chemicals & pharmaceuticals Magnetic tapes Lube oil dewaxing Others Total
Share of demand [%] 58 11 8 7
4 2 10 100
Table 5 Major companies producing MEK [i]
Pesticide manufacturing (insecticides) Solvents Printing
Table 4 Applications of MEK by end-use
Growth (%)
8.5
Processes available[2] There are a few processes listed for the production of MEK.
Catalytic dehydro2.6 genation of secondary 0.0 butyl alcohol in gaseous phase 1.0 MEK is prepared by
Country / Company
Capacity (ktpa)
USA
Shell
136
Exxon Mobil
135
Idemitsu Petrochem
135
Japan
Toren Chemical
70
Maruzen Petrochem
40
Brazil
Oxiteno
90
Germany
Sasol Solvents
65
Taiwan
Tasco Chemical
60
Taiwan Synthetic
15
France
Atona
50
Romania
Petro Brazi
40
Thailand
Bangkok Synt.
20
South Korea
SK Corp.
15
vapor phase dehydrogenation of 2-butanol. The dehydrogenation of 2-butanol is an exothermic reaction (51 KJ/ Kg mol). Chemical Weekly April 27, 2010
Special Report Table 6 Imports of MEK into India [2007-08] [Tons] Country
Import
Taiwan
672
Japan
2,036
China
1,467
South Africa
3,286
Singapore UK
39 1,087
Netherlands
Advantages of the process are:
High conversion of 2-butanol; High selectivity of MEK of about 95 mole %; Better yield; Longer catalyst life; Simple production separation; and Lower energy consumption.
The disadvantages are:
Less economic advantage than liquid phase oxidation of n-Butane.
Liquid phase oxidation of n-Butane MEK is produced as a by-product in the liquid phase oxidation of n-butane to acetic acid. Autoxidation of n-butane takes place in the liquid phase accord ing to the radical mechanism yielding MEK as an intermediate and acetic acid as end-product with mass ratio 0.2:1.0 by non-catalyzed liquid phase oxidao tion at 180 C and 53 bars with remixing. Continuous oxidation under plug
Chemical Weekly April 27, 2010
350
2002 296
s 300 n o T c 250 i r t e M 200 f o s 150 d n a s 100 u o h T 50
296
2007 254
245
234
234
170
62
170
62
39 0
45
This is a primary process. The MEK concentration in the reaction mixture increases and reaches its o maximum at approximately 350 C. Copper, zinc or bronze are used as catalysts in gas phase dehydrogena tion. Commercially used catalysts are reactivated by oxidation, after 3 to 6 months use. They have a life expect ance of several years.
Global production of MEK
0
e p o r u E n r e t s e W
a c i r e m A h t r o N
0
t s a E e l d d i M
e p o r a u c E i r n f A r e & t s a E
39
n a p a J
n s a e i s i r A t r n e u h o t C O
h t u o a S i c & r l e a m r t n A e C
Global consumption of MEK 600 s n o T 500 c i r t e M400 f o s d n 300 a s u o h 200 T
2002 2007
490
400
213
220
180
193
129
100 14 0 a c i r e m A h t r o N
e p o r u E n r e t s e W
17
e p o r a u c E i r f n r A e t & s a E
o
ow conditions at 150 C, 65 bars and a residence time of 2-7 minutes forms MEK and acetic acid at a mass ratio of 3:1. This process has slight economic advantage over the dehydrogenation of 2-butanol. But the key factor is availability and price of butane. Direct oxidation of n-Butenes (Hoechst-Wacker process) In direct oxidation of n-butanes
36
133
47
t s a E e l d d i M
25 n a p a J
n s a e i s i r A t r n e u o h t C O
28
h t u o a S i c & r l e a m r A t n e C
by Hoechst-Wacker process, oxygen is transferred in a homogenous phase on to n-butenes using redox salt pair, PdCl2 / CuCl2. 95 per cent conversion of n-butanes can be obtained with MEK selectivity of about 86 per cent. Disadvantages of the process are:
Formation of chlorinated butanone and n-butryaldehyde; and Causes corrosion due to free acids.
191
Special Report Table 7 Comparative study of all the processes Catalytic dehydrogenation
Liquid phase oxidation
Direct oxidation Direct oxidation
Sec-Butyl benzene hydro peroxide
Raw material/(s)
Sec-Butyl alcohol
Butane
Butenes
Butenes
Sec-Butyl benzene
Main products
MEK
Acetic acid
MEK
MEK
MEK
Chlorinated butanone and n butryaldehyde
Chlorinated butanone and n-butryaldehyde
—
By-products
Phenol & MEK
Current status
88-90%
10-12%
Not accepted.
Not accepted
Uneconomical.
Catalysts
Copper, zinc or bronze
Non-catalysed
PdCl2 / CuCl 2
Palladium sulphate & ferric sulphate
Zeolite beta
Conversion
Higher conversion rate; 80-95%
Low conversion
95%
95%
—
Catalyst life
Several years
—
Small
Small
—
Selectivity
95%
—
86%
90%
—
Yield
Very high
Very low
High
High
Equivalent to phenol
Energy consumption
Very low
Very low
—
—
High
Economical feasi bility
Less than liquid phase oxidation
Very high
—
Not known
Uneconomical
Process separation
Very simple
—
Not known as process is patented
Not known as process is patented.
Phenol & MEK are both produced
Direct oxidation of n-Butanes, Maruzen process The Maruzen process is similar to the Hoechst-Wacker process except that oxygen is transferred by an aqueous solution of palladium sulphate and ferric sulphate.
The process is commercially good to get MEK via direct oxidation of n butenes, but is generally not accepted due to formation of undesirable by products. The process is patented and not much information is available. 192
Sec-Butylbenzene hydroperoxide process This process comprises the steps of oxidizing sec-butylbenzene to obtain a reaction liquid containing sec butylbenzene hydroperoxide as the main product, concentrating the reaction liquid by means of a distillation column to obtain a bottom liquid con taining sec-butylbenzene hydroperoxide as the main component from the column bottom and decomposing the bottom liquid to obtain phenol and MEK.
This process is good in that it manufactures both phenol and MEK, which are important products in chemical industry. However, the disadvantage is that the process is uneco nomical. Detailed process description catalytic dehydrogenation of SBA in gaseous phase Preheater (Steam Heater) In the dehydrogenation of 2-butanol, the cold feed of SBA is mixed with Chemical Weekly April 27, 2010
Special Report
Figure 1: Flow sheet of preparation of MEK from SBA
recycle stream and then pumped from the feed tank to a steam heater and heat ed up to 374°K (Stream 1), the heating medium being used is dry saturated steam at 160°C. Vaporizer This Stream 1 is further fed to ther mosyphon vaporizer which is heated by the reactor vapor. The heating medium in vaporizer is heated reaction products discharged from the reactor at 673°K i.e. (Stream 5) and itself gets cooled down to 425°K. Knockout drum Stream 2 is further fed to knock out drum to remove entrained liquid. Knockout drum consists of a hollow vertical drum having inclined sieve plates known as demister for the passage of clean gas. Separation in knock Chemical Weekly April 27, 2010
out drum is based on the principle of density difference of the liquid and the clean gas.
we need to supply heat from outside and that is being supplied by the ue gas, which is produced in the furnace.
Super heaters The liquid separated will be recycled and the dry alcohol (Stream 3) will be fed to super heaters steam and stream attains a temperature of 673°K (Stream 4). The combustion reaction of hydrogen takes place in a furnace and the hydrogen is taken from the absorption column. The heat of combustion of hydrogen is very high so its heat is being utilized here.
The MEK concentration in the reaction mixture increases and reaches o its maximum at approximately 500 C. Copper, zinc or bronze are used as catalysts in gas phase dehydrogenation. Commercially used catalysts are reactivated by oxidation, after 3 to 6 months use. They have a life expectance of several years.
Reactor (Multi-Tubed Reactor) Stream 4 is fed to the multi-tubed reactor where dehydrogenation reaction takes place. The reaction is endo thermic and the reactor is isothermal, so in order to maintain 400°C temperature
Condenser In the condenser about 80% MEK and SBA are condensed (Stream 7), which is sent for storage while the other stream (Stream 8), which contains satu rated non-condensable hydrogen along with MEK and SBA at the temperature of 358°K. 193
Special Report Absorption column The vapour is passed on to the bottom of the packed bed absorption column where MEK and SBA are absorbed in water. Absorption of MEK is 98% and SBA is 96% in water. The water (Stream 9) is recycled from the extraction column and its rate is con trolled to provide an aqueous efuent containing 10% MEK. Extraction column The aqueous efuent (Stream 10) from the absorber is pumped into an extraction column where it is contact ed with solvent 1,1,2-trichlorethane (Stream 11) to extract MEK and SBA. This solvent is selected because it has the maximum partition coefcient (3.44), in comparison to other solvents. The rafnate comprises of mainly water, which is fed back to the absorption column. Solvent recovery column The trichloroethane extract phase (Stream 14) is pumped to a distillation column for the separation of solvent. Initially it is preheated to 371°K. The bottom product is solvent, i.e. 1,1,2-trichloroethane and the distillate from this column (Stream 15) is MEK and
194
alcohol. The recovery of solvent is 99.5%. The solvent is rst cooled down to room temperature and then fed to the extraction column. MEK product still The distillate from the Solvent Recovery Column is fed to this distillation column along with the liquid from the condenser (Stream 7), which is mixed rst and then preheated to 354°K and then fed into the column (Stream 16). The distillate is MEK and the bottom product is SBA. The SBA discharged from the bottom of this column (Stream 19) will be sent back to alcohol feed tank; therefore it is cooled and then stored (Stream 20). The MEK product will be cooled and stored in a storage tank (Stream 18). The MEK produced is 99% pure. REFERENCES 1. Ullmann’s Encyclopaedia Industrial Organic Chemicals, Volume 2, (pp. 971- 981). 2. John J McKetta, William A. Cun ningham, Encyclopaedia Chemical Processes, (pp. 32-49). 3. Distillation, in Robert E. Treybal, Mass Transfer Operations, pp. 435-441.
4.
Liquid Liquid Extraction, in Robert E. Treybal, Mass Transfer Operations, pp. 505.
WEBSITES a. MEK sales specications, www. exxonmek.com/publicfiles/fluids/ aliphatic/northAmerica/sales_specications_pdf, as on 2nd July 2009. b. Chemical Prole, MEK; www. scorecard.org; as on 4th July 2009. c. PERP Program, www.nexant.com, as on 5th July 2009. d. MEK, www.weblakes.com, as on 7th July 2009. e. Production sec-Butyl alcohol via n butane hydration, www.fripps.com, as on 8th July 2009. f. Unit operations, www.chemistryreact.org, as on 10th July. g. Dr. R.B. Williams, International programs of chemical safety, www. inchem.org , as on 12th July. h. Eluira Greiner, MEK, Chemical Weekly, January 17th, 2007. i. ICB, Global MEK capacity, www. ICIS.com, as on 13th July. j. Subhadip Sarkar, Cetex Petrochemicals, www.expressindia.com; as on 15 July.
Chemical Weekly April 27, 2010
