07-03-2011, 04:54 PM
Presented By:
B. Rajasekhar
Ch.Madhubabu
M. Ramya
N.Ganesh varma
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LIQUID PHASE CATALYSIS OF MtBE USING SULFURIC ACID AS CATALYST
Problem statement
The purpose of this project is to determine the feasibility of constructing a chemical plant to manufacture 1,00,000 ton/y of MTBE by liquid phase catalysis of methanol and isobutylene using sulfuric acid catalyst.
Both methanol and isobutylene are pure and available from natural gas and refinery cuts respectively.
This project includes
Simulation of flowsheet using chemcad- Simulation of PFR using MATLAB (or) spreadsheet.
Specific equipment design for Heatexchanger Preliminary cost estimation and Plant design &layout.
INTRODUCTION
MTBE(methyl tertiary butyl ether) belongs to oxygenates family eg: ethers, alcohols.
It is a gasoline additive that boosts the oxygen content of gasoline which is also called as “an octane enhancer”.
Results in significant reduction in air pollution from vehicle exhausts as it replaces TEL and TML.
Can be used in concentrations on average of 8-10 weight % in gasoline.
history
MTBE production started and shooted up between 1970 -1999 in US since the phase out of ‘lead’ in1970.
US EPA ordered to stop its production in 1999 due to ground water contamination and to replace with ethanol.
But EU of MTBE ,Europe studies concluded that
It does not pose danger to human health but tight controls are required on handling and storage .
US EPA studies might be faulty.
In Europe production approximately equals the demand and firmly stable in next few years.
8 Asian countries like Japan, China etc already phased out lead and started MTBE production. INDIA is in progress
COMMON NAMES AND STRUCTURE
Chemical Name: 2-methoxy-2- methyl-propane (IUPAC)
Chemical Family: Alkyl ethers
Form: At room temperature it is a highly volatile, flammable and colorless liquid.
Common Names: MTBE
Methyl tert-butyl ether
tert-Butyl methyl ether
CAS# : 1634-04-4
Formula: C5H12O
Chemical Structure:
physical ,chemical and thermal properties of mtbe
Molecular weight : 88.15
Elemental analysis
Carbon content, wt% : 68.1
Hydrogen content, wt% :13.7
Oxygen content, wt% :18.2
C/H ratio :5.0
Density, g/cc
at 25° :0.7352
at 30°C :0.7299
Reid vapor pressure
at 25°C, psi- : 7.8
Boiling point, °C :55.0
Freezing point, °C : -108.6
Critical properties:
temperature(Tc),°K: : 510
pressure (Pc) ,Pa :3.31*e5
volume(Vc),m3\kmol :0.329
Solubility of MTBE in water at 25°C, wt%: :<5
Viscosity at 37.8°C, cSt :11.7
Refractive index at 20°C :1.3694
Surface tension, din/sqrcm :19.4
Latent heat of vaporization
at 25°C, Cal/g :81.7
Specific heat at 25°C, Cal/g°C :0.51
Flammability limits in air
Lower limit, vol% :1.5
Upper limit, vol% :8.5
Auto ignition temperature, °C :425
Flash point, °C : -30
Blending octane number
RON :117
MON :101
(RON+MON)/2 :110
applications
90% of total production of MTBE is used as an antiknocking agent.
Remaining 10%
To produce highly reactive polyisobutylene, butylrubber, methylmethacrylate.
As a solvent replaced with diethyl ethers to improve the miscibility of other solvents.
In clinical medicine to dissolve the cholesterol gall stones.
Advantages of mtbe over other OXYGENATES
Other oxygenates are
Ethers: TAME,TAEE,ETBE,
Alcohols: ethanol, methanol.
Ethers have comparatively:
low RVP
low vaporization temperature
low flame temperature and
high octane number.
Among ethers MTBE is proven to be economically effective as its physical, chemical properties are compatible with gasoline especially its boiling range.
Higher octane number than other ethers.
Literature survey
There are three types of MTBE production plants:
Refinery/Petrochemical plants: uses Isobutylene, produced as a byproduct in refinery catalytic crackers.
Merchant plants: Merchant plants uses normal butane to isobutane, dehydrogenate isobutane to isobutylene
TBA plants: TBA plants uses tertiary butyl alcohol (TBA) as a byproduct of the propylene oxide production process.
Another raw material is methanol for all plants
Comparison of the processes
Selection of the process
Refinery plants are proven to be least expensive which can also work on less purity raw materials.
Operated in only liquid phase with either solid or liquid phase acid catalysts.
Chemical reaction and kinetics
Pfr conversion with length
process Flowsheet
Material balances
Basis :100,000 ton/y of MTBE with on-stream factor of 0.9.
Reactants mole ratio (CH3OH to C4H8):- 1.1
Product in kmol/h : 100,000*1000/(328*24*88.15)=144.1
Feed requirements to produce 144.1kmol/h of mtbe:
C4H8 == 162.46 kmol/h (144.1/0.895)
CH3OH == 178.7 kmol/h (1.1*162.46)
Sulfuric acid== 7.57 kmol/h (5wt% of reaction mixture)
Molecular weights(kg/kmol):
C4H8: 56.1
CH3OH: 32.04
Sulfuric acid: 98
MTBE: 88.15
Material balance equipment
Reactor
Separator 1
Washer
Separator 2
Distillation column 1
Distillation column 2
Mixers-1,2,3
Reactor mass balance
Conversion= 89.5%
1 mole of isobutene requires 1mole of methanol to produce 1mole of product(from reaction stoichiometry)
SEPERATOR-1 MASS BALANCE
Total mass flow rate in = 15623.37kg/h
Total mass flow rate out=741.59+14881.78 = 15623.78kg/hr
IN RATE = OUT RATE
Sulfuric acid recovery= 97% and methanol=2% from bottom
WASHER MASS BALANCE
Total mass flow rate in= seperator1 top+ fresh water in=
= 14881.78+594.495=15476.28 kg/hr
Total mass rate out= 15476.28 kg/hr
Seperator-2 mass balance
99.8% of MTBE 100% of isobutene is removed from the top. Water and methanol from the bottom.
Total mass in =15476.28 kg/hr
Total mass out = 13832.88+164.398=15476.28 kg/hr
Distilation column-1
Distillate purity xd = 91.05%
bottom product purity: 99.97%
Total feed= 13832.8 kg/hr outlet=D+B=13832.8 kg/hr
Distillation column 2
Total feed (SEP 2 bottoms),F =1643.398 kg/hr
Dstillate purity.xd= 0.9977,
Feed F = 1643.398 kg/hr =(D+B)= (1024.618+618.772)kg/hr
mass balances of mixer 1,2,3.
Mixer 1:
Inlet streams: fresh methanol + recycle stream from distillation column 2: 4657.9468+1024.61 =5682.07 kg/hr
Outlet stream flow rate =5682.07 kg/hr.
Mixer 2:
Inlet streams= mixer1 outlet +fresh isobutene+ recycle stream from distillation column 1: =5682.08+8153.845+1023.43 =14859.36 kg/hr
Outlet flow rate =14859.36 kg/hr
Mixer 3:
future implementation
Energy balances
Simulation of PFR
Specific equipment design
Plant location and layout
Health and safety factors
Preliminary cost estimation etc