CL 452 – Design Project
Spring 2019
Group 22
Production of Acetaldehyde
Report - Evaluation stage I
Members:
Dhrumil Shah : 150020009
Harsh Prasad : 150110013
Prajakta Gajbhiye : 150020102
Cheeranesh Ganeshamoorthy: 150020109
Jayprakash Ghritlahre: 150020039
Department of Chemical Engineering
Indian Institute of Technology Bombay
1
Table of Contents
1. Introduction
4-8
1.1. About acetaldehyde
4
1.2. Properties
4-5
1.3 Hazards and handling practices
5-6
1.4 Uses
6
1.5 Market survey
6-8
1.6 Production pathway
8
2. Production process
9-13
2.1. Reactions
9
2.2. Process flow diagram
10
2.3. Catalyst regeneration process
10
2.4. Selection of reactor
11-13
2.5. Separation processes
13
3. Mass balances
14-16
3.1 Overall balance
14
3.2 Balance around reactor
14
3.3 Balance around scrubber
14-15
3.4 Balance around distillation column
15-16
4. References
17
2
List of tables
Content
Page no.
Table 1.a - Physical properties :
Table 2.a -Membrane reactor vs Bubble Column Reactor
4
13
List of figures
Content
Page no.
Figure 1.a - 2 D structure of acetaldehyde
4
Figure 1.b - Geography wise split of acetaldehyde consumption as of 2016
7
Figure 1.c - Price trends of acetaldehyde
8
Figure 2.a - Reaction mechanism for production through Wacker-Hoechst process. ..... 9
Figure 2.b - Process Flow Diagram
10
Figure 2.c - Schematic diagram for Membrane Reactor
11
Figure 2.d - Conc. vs. residence time results of silicone rubber membrane reactor
11
Figure 2.e - Conc. vs residence time results of polypropylene membrane reactor
12
Figure 2.f - Schematic diagram for Bubble column Reactor
14
Figure 3.a - Mass balance around reactor
14
Figure 3.b - Mass balance around scrubber
15
Figure 3.c - Mass balance around extractive distillation column
16
Figure 3.d - Mass balance around distillation column
16
3
Chapter 1
INTRODUCTION
1.1 About acetaldehyde
Acetaldehyde is one of the most used organic chemicals in the world. It’s colourless,
miscible with water and is flammable in nature. The chemical formula of acetaldehyde is
C2H4O. It is a common substance naturally found in coffee, ripe fruits, breads ,
vegetables, gasoline , cigarette smoke and diesel exhaust. It is widely used in the
manufacturing a downstream chemicals. Acetaldehyde has been flagged as a ‘Group 1
carcinogen’ by ‘The International Agency for Research on Cancer’. Acetaldehyde is
also produced by the partial oxidation of ethanol in the liver and is a contributing cause
of hangover after alcohol consumption. One can be exposed to acetaldehyde through
both air(smoke) and water(groundwater).
Fig. 1a : 2D structure of acetaldehyde
1.2 Properties
1.2.1 Physical Properties
Table 1a - Physical properties
Property
Values
Colour
Colourless
Odour
Pungent choking odour
Solubility
Miscible with organic solvents and water
Molar mass
44.05 g /mol
Density
0.784 g/cm3 (at 20 oC)
Melting pt.
-127.37 oC
Boiling pt.
20.2 oC
4
1.2.2 Chemical properties
Acetaldehyde is a highly reactive compound. It is flammable ,toxic and corrosive
in nature and is a very dangerous fire hazards when exposed to heat or flames.It
is a strong reducing agent which undergoes number of condensation, addition
and polymerization reactions.
● Decomposition - Acetaldehyde decomposes into a methane and carbon
monoxide at temperature greater than a 400 degree celsius through a
radical basis process
● Oxidation - Acetaldehyde is rapidly oxidized with air(oxygen) and form a
acetic acid, acetic anhydride, and peracetic acid . The main products from
above are depends on a reaction conditions. For example acetic acid is
produced commercially by the liq. Phase oxidation of acetaldehyde at a
65°C with with cobalt or manganese acetate as catalyst
● Reduction- Acetaldehyde is rapidly reduced to a ethanol . Before 1940’s
when petrochemical didn’t came into picture this method is used for
production of ethanol
● Polymerization- When acetaldehyde is reacted with acids such as
sulphuric, mineral, hydrochloric acid it polymerize into a
Paraldehyde,2,4,6- trimethyl – 1,3,5 – trioxane, a cyclic trimer of
acetaldehyde.Paraldehyde may also be formed by continuously feeding of
acetaldehyde at room temperature over an acidic medium
● Reaction with nitrogen compound - Acetaldehyde rapidly react with
ammonia to form a acetaldehyde ammonia. Pyridine and many pyridine
derivatives are formed from a paraldehyde and aqueous ammonia in the
presence of a catalyst at elevated temperature (450 to 550 0F)
1.3 Hazards and handlings
● Potential health effects - Hazardous in case of direct eye contact (irritant), of
ingestion, of inhalation (lung irritant). Slightly hazardous in case of skin contact
(irritant, permeator)
Levels reported for acute exposure25-200 ppm concentration in air --→ eye irritation , upper respiratory infection
Concentration greater than 300 ppm --→ Asthma and cancer
● Potential Chronic Health Effects - Acetaldehyde is reported as group 1
carcinogenic compound in nature . In risk assessment is found that cancer risk is
one in a millions
5
Precautions- At plants for workers safety
1. Exposure must be avoided and adequate ventilation and suction at critical
points must be available
2. Must be kept away from alkalis , strong acids and oxidizing agents
1.4 Uses
Acetaldehyde is mainly used for production of downstream chemicals viz acetic acid,
acetic anhydride, ethyl acetate( used as a solvent in glue), chloral ( used as a sedative)
and 1,3-butadiene (used in rubbers) besides a variety a dyes and drugs.
Globally, the top revenue generating uses of acetaldehyde are:
A. Pyridine
Acetaldehyde with ammonia leads to the formation of pyridine. Pyridine is used as
precursors for many agrochemical and pharmaceutical products, widely used as solvent
and reagent in reactions
B. Pentaerythritol
Formed by the condensation of acetaldehyde with formaldehyde. Pentaerythritol is used
in various products such as alkyd resins, rosin esters, synthetic lubricants, antioxidants,
and explosives.
C. Acetic acid
Produced by oxidation of acetaldehyde, it is used as a reagent to produce various
compounds such as vinyl acetate monomers and esters. In the form of vinegar, it finds
application in foods and beverages
1.4.1 Specifications for industrial use
1. Practically colourless
2. Conc. : more than 99% by wt.
3. Acid(as acetic acid): less than 0.1% by wt.
4. Water : less than 0.02% by wt.
1.5 Market survey
1.5.1 Overview
Globally, the major source of acetaldehyde production is ethylene. However, a
small portion of it is produced from ethanol and acetylene as well. In the past
decade, the growth in the acetaldehyde market has slowed down primarily due to
a declining demand from acetic acid producing plants which no longer use
acetaldehyde as a raw material since a more efficient process has been
discovered. However, rising demand from paper and pulp; pharmaceuticals; food
and beverages and waste water treatment industries have arrested the decline in
6
demand and have ensured enough demand growth to set up a new plant
viabally.
1.5.2 Growth trends
The acetaldehyde demand is expected to grow at a CAGR of 6.3% for the next 5
years and reach $2Bn in value by 2024. Manufacturing facilities have been able
to keep up with the rising demand and the global production capacity of
acetaldehyde is expected to reach 1.4Mn T.P.A. by 2022.
1.5.3 Geographical distribution
Asia is currently the major producer and consumer of acetaldehyde with India
and China together accounting for more than 50% of the global production as
well as consumption. While the western economies have phased out production
of acetic acid using acetaldehyde, India and China continue to do so. As a result
their share in the global market has jumped over the past couple of decades.
Fig. 1b - Geography wise split of acetaldehyde consumption as of 2016
Source : Chemical Economics Handbook (Ref. item 13)
1.5.4 Major players and price trends
The price of acetaldehyde has declined over the past few years. The prices
shown in the graph below have been calculated using the import/export data of
the total quantity shipped and the overall worth of trade.
7
Fig 1c - Price trends of acetaldehyde
Source: UN Comtrade website(Ref. Item 14)
Celanese Corp., LCY Chemicals, EuroChem are among the many major players
of acetaldehyde globally. Most of the plants manufacture multiple chemicals and
not just acetaldehyde. This gives them an opportunity to exploit economies of
scale and its associated synergies. Acetaldehyde is consumed in-house for
producing downstream chemicals in most of the chemical plants producing it in
bulk.In India, a few players like Trichy Distilleries and Kumaka Industries
manufacture acetaldehyde with annual capacities of around 5000 TPA.
1.6 Production pathway
There are 3 major methods in production of acetaldehyde● Production from ethylene (oxidation of ethylene) (Chosen pathway)
● Production from ethanol(oxidation of ethanol/ethyl alcohol)
● Production from acetylene
Lower cost, better conversion and comparatively lesser environmental damage lead us
to choose production from ethylene using the Wacker-Hoechst process as the desired
pathway. The required raw materials are ethylene which can be obtained from a
petrochemical plant and pure oxygen to get high selectivity and better conversion.
Aqueous palladium chloride solution is used as catalyst for this process.This process is
called Wacker-Hoech.
8
Chapter 2
Process Flow Diagram
2.1 Reactions
2.1.1 Reaction mechanism:
Fig 2a: Reaction mechanism for production through Wacker-Hoechst process
In the Wacker-Hoechst process, ethylene is oxidized in a bubble column reactor
with the catalyst being CuCl2, CuCl and PdCl2. The operating temperature is
around 400 K and pressure is 3 bar. The gaseous stream consists of steam,
acetaldehyde, ethylene and small amounts of oxygen, carbon dioxide, acetic acid,
crotonaldehyde and chlorinated compounds (such as methyl chloride, ethyl
chloride and chloro acetaldehyde). The stream is later separated into following
streams: light streams (ethyl chloride, methyl chloride etc), acetaldehyde,
crotonaldehyde and waste water stream (consisting of acetic acid,
chloroacetaldehyde and water).
2.1.2 Main Reaction:
C2H4 + ½ O2 → CH3CHO
ΔH= -240 KJ/mol
2.1.3 Side Reactions :
CH3CHO + ½ O2 → CH3COOH
C2H4 + HCl → C2H5Cl
2CH3CHO → CH3CH=CHCHO + H2O
9
2.2 Process Flow Diagram
Fig. 2b - Process Flow Diagram
2.3 Catalyst regeneration process
2.3.1 Brief explanation
Catalyst particles are carried up by the gaseous mixture. Then, they are
separated using separating vessel(flash).Further, the stream is split into two one directly fed back to the reactor and the other sent through a catalyst
regeneration process
2.3.2 Reactions involved
Pd + 2CuCl2 → PdCl 2+ 2CuCl
2CuCl + ½ O2 + 2HCl → 2CuCl2 + H2O
Here,we are using HCl and oxygen to convert Pd back to PdCl2 which is then fed
back to the reactor.
2.3.3 Physical conditions
Typical flash temperatures are around 50 to 100 deg C. The liquid needs to be
dried of water and HCl is later added to the spent catalyst to regenerate it.
Devices which work under reduced pressure, e.g. rotary evaporators are
considered. Catalyst solids are preferred to be dehydrated.
Source : Ref. item 1 and 2
10
2.4 Selection of reactor
2.4.1 Membrane Reactor
Fig 2c: Schematic diagram for Membrane Reactor
The design is similar to shell and tube heat exchanger. The catalyst solution
containing PdCl2, CuCl and CuCl2 fills the shell side and the reactants fill the tube
side while the tubes are made of membrane.The following steps occur in the
reactor:
1)
Permeation of reactants from tube to shell
2)
Diffusion of reactants and products in the liquid phase (shell)
3)
Chemical reaction in the liquid phase
4)
Permeation of gas products back to the gas phase
There are two single-bundle membrane reactors, one with non porous silicone
rubber (SR) and the other with porous polypropylene (PP). Tygon tubing is used
as outer shell.
Fig 2d: Conversion vs. residence time results of the silicone rubber membrane reactor.
11
Fig 2e: Conversion vs residence time results of the polypropylene membrane reactor
Source for fig. 2d and 2e : Ref. item 15
2.4.2 Bubble Column Reactor
The bubble column reactor contains catalyst solution through which the reactor
gas is bubbled. A gas dispersion tube could be used to ensure an even
distribution of bubbles. Reaction occurs at 130 deg C and pressure of 400 kPa.
The reactors are passed co-currently in a reaction tower which is bubble column
reactor.
Fig 2f: Schematic diagram for Bubble column Reactor
12
Table 2a : Membrane reactor vs Bubble Column Reactor
Parameters
Membrane Reactor
Bubble Column reactor
Mass Transfer area
3000-5000 m2/m3
50-1000 m2/m3
Low flow rates
Higher conversion
Lower conversion
High flow rates
Lower conversion
Higher conversion
Need for catalyst and
product separation
No
Yes
With high rate of production of acetaldehyde, we will have high flow rates and hence,
we will go with Bubble Column Reactor.
Source : Ref. item 15
2.5 Separation processes
In the Scrubber, unreacted ethene and oxygen is separated and recycled back to
reactor. The remaining products undergo extractive distillation to separate light
products like Chloromethane,Chloroethane and Carbon dioxide from heavy impurities
like acetaldehyde and other impurities which is followed by distillation where
acetaldehyde, Crotonaldehyde and acetic acid+water is separated out to give our final
product.
Source : Ref. item 1
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Chapter 3
Mass Balance
3.1 Quantities of major reactants and products
The targeted plant capacity is 5000 T.P.A. and assuming 8000 annual operating hours,
the hourly production rate required is 625kg. To achieve this, nearly 1200 kg of
ethylene and 320 kg of oxygen is needed. Oxygen used is of 99.5% purity with the
remainder gases being argon and other inerts. Some extra amount of oxygen is added
as compared to that calculated stoichiometrically to account for the side reactions and
the impurities present in the oxygen being fed in.
3.2 Mass balance around reactor+regenerator system
Ethylene and oxygen are the main reactants and HCl is added to help in the catalyst
regeneration. The presence of chlorine in the catalyst also leads to the formation of alkyl
chlorides. To make up for this,chlorine is supplied through HCl. The main reaction has a
single pass conversion of 35% and ethylene has a selectivity of 94% towards the main
reaction. The catalyst regeneration process is included in this step itself. Make up water
needs to be added since the reaction is exothermic. Using patent (Ref. item 5) water
required is calculated. 15 tons of water is required as make-up for every 13 tons of
acetaldehyde produced.
Fig. 3a - Mass balance around the reactor
3.3 Balance around scrubber
The effluents from the reactor are sent through a knock out drum wherein the entrained
liquid water is removed. The gases left after that are sent through a cooler to a scrubber
14
wherein water is added to separate the water soluble components.
Amount of water added in scrubber = 77.5/13 * 625
= 3726 kg/hr
The following figures were used with reference to a patent( Ref. item 5) wherein a
thumb rule for scrubbing was explained as 77.5 tons of scrubbing liquid for every 13
tons of acetaldehyde produced.
Ethylene(unreacted), oxygen(unreacted), carbon dioxide and crotonaldehyde are the
gaseous products which are later separated into the recycle and purge streams
.
Fig. 3b- Mass balance around the scrubber
3.4 Balance around distillation columns
Similar to the thumb rule followed for the scrubbing process, 1.5 tons of water is added
for every 13 tons of acetaldehyde produced in the extractive distillation column. Acetic
acid, acetaldehyde,crotonaldehyde and water form the crude aldehyde end which are
further separated using distillation.
Final distillate composition : 99.88% acetaldehyde
: 0.1% acetic acid
: 0.02% water
15
Fig. 3c Mass balance around extractive distillation column
Fig 3d- Mass balance around the distillation column.
16
References
1. Ullman’s Encyclopaedia of Industrial Chemistry, Vol. 1; Pg. no. 192-207 article
by Marc Eckert & Gerald Fleischmann
2. Shioyama, T. K., & Straw, J. J., U.S. Patent 4,419,525, 1983
3. California Office of Environmental Health Hazard Assessment’s website
4. https://pubs.acs.org/doi/pdf/10.1021/ja01232a023. Article contributed by J. Carrel
Morris, Harvard University. Reviewed on 20/1/19
5. Steppich, W., & Sartorius, R., U.S. Patent 4,237,073, 1980
6. Van Leeuwen, P. W. N. M. (2004). Homogeneous Catalysis, Page no. 53-90.
7. https://www.wacker.com/cms/media/documents/wacker_group/sustainability_1/g
ps_product_summaries.pdf Safety summary of acetaldehyde on wacker.com
(Date of publishing : 19/03/12)
8. Annual report 2018 ( http://www.airproducts.com/ Date reviewed: 20/01/2019)
9. Jira R et al; Chloroacetaldehydes. Ullmann's Encyclopedia of Industrial
Chemistry 7th ed. (1999-2013). New York, NY: John Wiley & Sons. Online
Posting Date: July 15, 2007
10. https://www.researchandmarkets.com/research/lc8hz5/acetaldehyde
Market research report by researchandmarkets.com reviewed on 11/1/19
11. https://www.techsciresearch.com/report/global-acetaldehyde-market/2266.html
Market research report by techsciresearch.com reviewed on 11/1/19
12. https://www.scribd.com/doc/122192768/acetaldehyde-doc
Article by Er Bali Pandhare reviewed on 20/1/19
13. https://ihsmarkit.com/products/acetaldehyde-chemical-economics-handbook.html
Chemical Economics handbook published on ihsmarkit.com
14. https://comtrade.un.org (UN Comtrade)
15. Chen, S., & Kao, Y. DIRECT OXIDATION OF ETHYLENE TO ACETALDEHYDE
IN A HOLLOW FIBER MEMBRANE REACTOR (2010).
https://doi.org/10.1080/00986449008940545
17