Electrosynthesisby Class 11, Kendriya Vidyalaya 2, Kalpakkam

Done by

Krishnaprasad K.A.

D.J. Vineeth

L. Narayanan

Antriksh Rathore

What is Electrosynthesis?

• Electrosynthesis in organic chemistry is the synthesis of chemical compounds in an electrochemical cell.

• The main advantage of electrosynthesis over an ordinary redox reaction is avoidance of the potential wasteful other half-reaction and the ability to precisely tune the required

potential.

Experimental Setup

• The basic setup:

1)A Galvanic cell

2)A Potentiostat and

3)Two electrodes.

Good electrosynthetic conditions use a solvent and electrolyte combination that minimizes electrical resistance.

• Electrodes are selected which provide favorable electron transfer properties towards the substrate while maximizing the activation energy for side reactions.

Experimental Setup

Experimental Setup

• Two basic cell types: undivided cell & divided cell type• In divided cells the cathode and anode chambers are separated with

a semiporous membrane.• Divided cell permits the diffusion of ions while restricting the flow of

the products and reactants. This is important when unwanted side reactions are possible.

REACTIONS INVOLVED

•Anodic Oxidations•Cathodic Reductions

Anodic Oxidations

• The most well-known electrosynthesis is the Kolbe electrolysis.

• A variation is called the non-Kolbe reaction when a heteroatom (nitrogen or oxygen) is present at the α-position. The intermediate oxonium ion is trapped by a nucleophile usually solvent.

Anodic Oxidations

• In the so-called Crum Brown–Walker reaction an aliphatic dicarboxylic acid is oxidized forming the elongated di-acid.

• Amides can be oxidized through a N-acyliminium ion which can be captured by a nucleophile.

This reaction type is called a Shono oxidation. An example is the α-methoxylation of N-carbomethoxypyrrolidine.

Cathodic Reductions

• In the Markó-Lam deoxygenation, an alcohol could be almost instantaneously deoxygenated by electroreducing their toluate ester.

Cathodic Reduction

• The cathodic hydroisomerization of activated olefins is applied industrially in the synthesis of adiponitrile from 2 equivalents of acrylonitrile:

Cathodic Reduction

• The Tafel rearrangement (Julius Tafel, 1907) at one time was relevant to the synthesis of certain hydrocarbons from alkylated ethyl acetoacetate, a reaction accompanied by the rearrangement reaction of the alkyl group:

APPLICATIONS OF ELECTROSYNTHESIS

Research & Development

• Electrochemical expertise in electrosynthesis includes the following fields: – Electrosynthesis of inorganic and organic (including pharmaceuticals) compounds – Energy Storage – Batteries and fuel cells – Electrodialysis– Membrane separation processes including salt splitting – Sensors– Environmental electrotechnology: water purification; metal recovery; pollutant

destruction; recovery, recycle and reuse

Inorganic Compounds Synthesis

• Electrochemical synthesis of inorganic compounds offers several advantages over conventional synthesis and often provides the only viable route.

• Electrosynthetic processes can often be run under milder operating conditions with fewer chemical reagents.

• Examples: – Chlor-alkali manufacture– Aluminum Refining – Water Electrolysis to produce hydrogen and oxygen– Manufacture of bromine, chlorate, perchlorate, ferrate, etc.– Metals extraction and refining: Al, Na, Mg, Li, etc.– Metal oxides manufacture

Organic Compound Synthesis

• Industrial scale electrochemical processing of organic chemicals : In practice for almost 100 years. An estimated 120 different processes – piloted .

At least 60 are now commercial.

Other examples of reactions that can be carried out electrochemically include:– Nitro Reduction– Halogenation – Methoxylation– Acetoxylation – Hydrogenation – Carboxylation – Coupling Reactions– Acetamidation– Dehalogenation– Cyanation

Energy Storage Using electrosynthesis

Energy Storage

• This technology was based on a polysulfide/bromide system.• The Redox Flow Battery : Form of rechargeable battery in which electrolyte

flows through an electrochemical cell.• On charge, it converts electricity into chemical energy. • The electrolyte, and therefore energy, is stored externally in tanks until the

energy is required when the solution is pumped back into the electrochemical cell discharging the chemical energy as electrical energy.

Advantages of E.S

Advantages:• This is one of only a few technologies that can separate energy and

power requirements. Power is determined by the size of the electrochemical cell whereas the energy is proportional to the size of the storage tanks.

• Large amounts of energy (up to hundreds of MWh) can be stored until required with little loss.

• High efficiency conversion from electrical to chemical energy• Long cycle life with quick response times.

Applications of E.S

Applications:

• Large (1 kWh - many MWh) stationary applications. • Load leveling: Store energy during times of low demand

and provide electricity during peak time.• Storing energy from renewable sources such as wind or

solar to supply power during low generation periods.• Uninterrupted power supply (UPS), to provide power

when main power fails.

Electro Dialysis

Electro Dialysis

• Electrodialysis (ED) is a very versatile technology for the separation of difficult mixtures.

• Electrodialysis is an electromembrane process in which ions are transported through ion permeable membranes from one solution to another under the influence of a potential gradient.

• The electrical charges on the ions allow them to be driven through the membranes fabricated from ion exchange polymers.

• Types of Membranes used:– Ion Permeable Membranes– Bipolar membranes

Ion Permeable Membrane

• The ion permeable membranes used in electrodialysis are essentially sheets of ion-exchange resins.

• They usually also contain other polymers to improve mechanical strength and flexibility.

• The resin component of a cation-exchange membrane would have negatively charged groups (e.g., -SO3

-) chemically attached to the polymer chains.

Bipolar Membrane

• Bipolar membranes consist of an anion-permeable membrane and a cation permeable membrane laminated together. 

• When this composite structure is oriented such that the cation-exchange layer faces the anode it is possibleto spit water into proton and hydroxyl ions by imposing a potential field.

• Multiple bipolar membranes along with other ion permeable membranes can be placed between a single pair of electrodes.

Salt Splitting

• Salt splitting is a relatively new technology dependent on the availability of modern membranes.

• Its development has usually been driven by two major factors,– The first is the desire to produce caustic soda without the co-

production of chlorine.– The second is the increased cost of disposing of heavily laden

salt solutions.

Sodium Sulphate for Salt Splitting

Caustic Soda production

Salt splitting with Bipolar Membranes

No chlorine produced.!

Salt Splitting

• With the demand for Chlorine predicted to fall down, the need for using production of NaOH without Chlorine has to be done.

• Electrosynthesis of Sodium Sulphate can be done to give Caustic Soda.

• A successful technology for treatment of sodium sulfate wastes will likely require additional economic incentives such as the coproduction of a saleable product (for example ammonium sulfate), or credits for the elimination of a waste stream.

• Technologies for the production of commodity quantities of caustic will need to rely on very low power costs and an increasing imbalance in causticchlorine production.

• Modular on-site production of chemicals will facilitate the implementation of electrochemical technologies.

Electrosynthesis Inc.

• Electrosynthesis Company, Inc. specializes in the development of electrochemical technologies for energy storage systems, fuel cells, electrodialysis, separations, sensors, synthesis of inorganic and organic chemicals and recycling of waste streams.

• Achievements:– New method for production of Potassium Ferrate by

electrosynthesis which has reduced its price from $100/g to $2/g. – New methods for synthesising Caustic Soda without Chlorine as

a byproduct.– Developing large scale energy storage systems using

electrosynthesis.