Module 2: Industrial Chemistry

CHALLENGESOFINDUSTRIALCHEMISTRY

Chemistry on industrial (large) scale has three major challenges: 1. Chemistry • Optimise reaction conditions

2. Engineering • Extract products, control flow of material and heat

3. Logistic • Sourcing sufficient starting materials and properly disposing of waste

EUGENEHOUDRY–CATALYTIC‘CRACKING’OFOIL

Product Petrol: Complex mixture of hydrocarbons with 40 < MW < 170 Problem Crude oil contains only around 14% petrol – far less than demand

Extraction/Production

Different components of crude oil have different boiling points and separated by distillation. Longer chained hydrocarbons such as oil need to be broken down to be used as petrol.

Solution Eugene Houdry discovered clay called ‘Fuller’s Earth’ catalysed the breaking of carbon-carbon bonds in petroleum products in 1920. This is known as ‘cracking’ – breaking down large carbon compounds into smaller molecules that makeup petrol without need for high temperatures.

Implications Now can increase yield of petrol from crude oil – doubled the amount of petrol obtained from each barrel of oil. Improved fuel quality – distillation process made easier because can guess certain probabilities of where molecules may fracture.

Example Cracking Butane:

There are 3 places where molecule might split. Each has distinct likelihood: i.e. red bond is 48%

Final products are mixture of short alkanes, alkenes and some H2 reflecting probability of different reactions.

WILLIAMPERKIN–INVENTIONOFMAUVE

Product Mauve – one of the 1st synthetic dyes Problem Logistical problem - The need to source starting materials in large and regular

quantities. Extraction/Production

Needed to use solvents, coal and oil

Solution William Perkin accidentally made mauve when trying to synthesise the drug quinine.

Implications 1. Pioneered use of coal and oil as starting materials for organic chemistry

2. Synthetic dyes led to large loss of market for agriculture of natural dyes in countries such as India

3. Able to tailor make dyes – used to stain bacteria and cells contributing to development of microbiology

4. Inspired other developments of dye-derivatives trypan red which helped sleeping sickness; started pharmaceutical industry

FIXATIONOFNITROGEN–HABER-BOSCHPROCESS

Product Ammonia and synthetic fixation of nitrogen Converting free inert nitrogen in air to combine chemically with other elements to form more-reactive compounds/form that can be used by living organisms such as ammonia, nitrates etc.

Problem Until 1913, abundant supply of nitrogen in atmosphere was inaccessible due to stability of N2. World supply of nitrates came from Chilean saltpetre mines in form of guano.

Ammonia is the starting point for synthesis of many important materials: fertilisers, polymers, nitric acid, explosives

Extraction/Production N2 – from atmosphere H2 – from natural gas reserves

1. Gases are placed through compressor to increase pressure 2. Reaction occurs over catalyst bed à speed up reaction 3. Produces ammonia and 60% of reactants left over 4. Bosch introduces ammonia condenser – works because of difference in

boiling points. NH3 has higher boiling point and condensed out. 5. Reactants are recycled.

• NH3 condensed out of gas phase and unreacted N2 and H2 are recycled

back to reaction chamber o Increases yield o Reuses unreacted reactants – makes process sustainable and

efficient Solution Developed during WWII – due to embargo on products.

Fritz Haber – Solved chemical problem to optimize yield of ammonia by designing high pressure reaction vessels. Carl Bosch – Scaled up Haber process for industry.

Implications 1. Voted most important invention of 20th Century 2. Substantially increased ability to produce food 3. 80% of nitrogen in each human alive today comes from nitrogen fixed

by Haber-Bosch process 4. Allowed for world exponential growth

Optimising conditions Temperature à 400oC use catalyst Pressure à compromise of high and low pressure at 70-200atm This gives 40% yield of NH3. Yield further increased by removing NH3 as produced.

METALLURGY

Metallurgy: Ores to metals. We are interested in the chemical processes.

We want metal ores to be in oxide form before extracting. i.e. convert metal sulfides and phosphates (pre-treatment) to oxides. Mineral to Compound “Roast in air” – heating to react with oxygen into a more uniform chemical compound.

CaCO3(s) + heat à CaO(s) + CO2(g) 2ZnS(s) + 3O2(g) + heat à 2ZnO(s) + 2SO2(g)

Production of undesirable gases: CO2 and SO2 – Use acidic scrubbers to recycle back into sulfuric acid. Compound to Metal Depending on reactivity of metal:

1. Reduction a. Reduction with carbon (smelting) b. Reduction with hydrogen (avoid carbide formation) c. Reduction with more active metal (when hydride formation is a problem)

2. Electrochemical reduction – energy intensive and not preferred