Esterification Simulation with Aspen HYSYS
Welcome to the esterification
simulation guide with Aspen HYSYS. Before we get into the simulation, let us
further understand what esterification is and why it is important in the
chemical industry.
What is Esterification?
Esterification is a chemical
reaction that involves combining acids and alcohols to form compounds known as
esters and water. Esters are a type of chemical compound that belongs to the
class of organic compounds. These compounds have a standard chemical structure
characterized by a bond between an acyl group (-CO-) and an alkoxy group (-OR),
where "R" is an alkyl or aryl group (a hydrocarbon group linked to an
aromatic chain or ring). These groups are often found in a variety of natural
materials, includinn various types of essential oils, fruits, and flowers that
give them their distinctive aroma. Esters are also widely used in the food and
beverage industry to provide preferred flavors and aromas in products such as
candies, alcoholic beverages, and desserts.
In esters, the characteristic aroma and flavor are due to the functional groups attached to the central carbon atom in the ester molecule. Due to their characteristic aromas, esters are often used as important components in perfumes, beverages, food, and other consumer products. It is one of the very important reaction types in organic chemistry and has a wide range of industrial applications, including:
- Food Industry: Many esters have pleasant aromas and flavors and are used in the manufacture of food and beverages. Examples include ethyl acetate esters that have a fruity aroma, which are used in candies and beverages.
- Perfume Industry: Esters are also used in perfume manufacturing due to their pleasant aromas. For example, methyl salicylate esters are used for floral scents.
- Plastics Industry: Some types of esters are used in the production of plastics, such as polyethylene terephthalate (PET) used in plastic bottles.
- Pharmaceutical Industry: Many ester compounds are significant components in pharmaceuticals.
Esterification Reaction Mechanism
- Esterification reactions involve the reaction between an acid and an alcohol under certain conditions, often with a catalyst. The mechanism of this reaction involves several stages:
- Acid Protonation: The acid initially accepts a proton from another acid molecule, forming a hydronium ion (H3O+).
- Nucleophilic Attack: The hydronium ion attacks the oxygen atom of the alcohol, forming an intermediate compound.
- Water Elimination: The intermediate compound loses water through an elimination reaction.
- Ester Formation: The final yield structure is an ester, which has a carbon-oxygen double bond.
Case Study
It is desired to produce 375
kg/hr of ethyl acetate product from a feed stream consisting of 13 mol% acetic
acid, 35 mol% ethanol, and 52 mol% water. This feed stream is available with a
capacity of 100,000 kg/day. A single-tube plug single-tube flow reactor with a
length of 10 meters and a diameter of 1 m is available for use in an existing
chemical plant. Determine if it is feasible to achieve the desired product
using this reactor.
Aspen HSYSY Completion
Open Aspen HYSYS and create a New
Case
Enter the components that will be
used. In the Component List folder select Add. Add acetic acid,
ethanol, ethyl acetate, and water.
Define the property package used,
and click Add in the Fluid Package folder. Select NRTL as
the property package.
Define the reaction. Select Add
in the Reactions folder and add a new Reaction Set. In Set-1
click Add Reaction and select Kinetic to add a new kinetic
reaction.
Double-click on Rxn-1 to
define the reaction kinetics. Enter the information below. Make sure to select the
Aqueous Phase as the Rxn Phase.
Next, click Add to FP and
select Basis-1
Click Simulation on the bottom left of the
screen
Double-click on Reactor (PFR-10).
Define Inlet stream
as FEED and Outlet stream as PRODUCT
On the Reactions tab
select Set-1 as the Reaction Set
In the Rating tab, enter
the value of Length 10 meters and Diameter 1 meter
In the Parameters section
under the Design tab, enter Delta P 0
We are now defining the FEED
stream. Go to the Worksheet tab. Enter Temperature 25 oC, Pressure 1
bar, and Mass Flow 100,000 kg/day (4167 kg/h).
In the Composition section
enter Mole Fraction values of 0.13
for acetic acid, 0.35 for ethanol, 0 for ethyl
acetate, and 0.52 for water. After defining it, the feed stream
should be resolved.
Check the results. Right-click on
the Product stream and select Show Table. The table will appear
in the flowsheet Double click on the table and select Add Variable.
Select Master Comp Mass Flow
and select component E-Acetate.
The mass flow value of ethyl
acetate will be added to the table.
The mass flow value of ethyl
acetate in the product stream is 453.4 kg/h.
Conclusion
The use of a 10-meter reactor and
supplied feedstock to produce 375 kg/h is feasible. Aspen HYSYS can be used to
model existing equipment in addition to designing new equipment. Modeling
existing equipment allows engineers to decide if they can reuse equipment and
improve performance by changing state variables.