Industrial and Laboratory Production of Fertilisers

Using resources • The Haber process and fertilisers

Flashcards

Test your knowledge with interactive flashcards

How is ammonia commonly prepared in the laboratory?

Click to reveal answer

Ammonia is prepared by heating an ammonium salt with a strong alkali (e.g., ammonium chloride with sodium hydroxide) to release NH3 gas.

Key concepts

What you'll likely be quizzed about

Haber process (industrial ammonia production)

The Haber process synthesises ammonia from nitrogen and hydrogen at high pressure and moderate temperature in the presence of an iron catalyst. High pressure shifts the equilibrium toward ammonia, causing higher yield; elevated temperature increases rate but shifts equilibrium toward reactants, so a compromise temperature is used. Continuous recycling of unreacted gases increases overall conversion and economic efficiency. Industrial design uses large reactors, gas compressors and heat exchangers to recover energy, which reduces operating cost. Scale and optimisation cause high ammonia output suitable for fertiliser manufacture but require large capital investment and strict safety and corrosion control.

Laboratory preparation of ammonia

Laboratory ammonia production uses thermal decomposition or displacement reactions such as heating an ammonium salt (e.g., ammonium chloride) with a strong alkali (e.g., sodium hydroxide). Low pressure and modest heating make the method safe and suitable for producing small quantities. Laboratory methods produce ammonia with impurities and limited yield compared with industrial synthesis. The reactions occur in batch setup without catalysts or high-pressure equipment, which reduces complexity but prevents the high throughput needed for fertiliser manufacture.

Nitric acid and ammonium salts (manufacture of nitrate fertilisers)

Industrial nitric acid production uses the contact process: ammonia oxidises to nitrogen oxides, which convert to nitric acid after absorption. High temperature and a vanadium(V) oxide catalyst provide fast rates and acceptable yields. Neutralisation of nitric acid with ammonia produces ammonium nitrate; control of concentration and temperature prevents decomposition and explosion hazards. Laboratory nitric acid preparation commonly involves reacting sodium nitrate with concentrated sulfuric acid and distilling the resulting acidic vapour. Neutralisation in the lab produces small samples of ammonium salts for analysis or demonstration, with lower concentration and higher impurity levels than industrial products.

Phosphate fertilisers: industrial versus laboratory

Industrial production of soluble phosphate fertilisers treats phosphate rock with sulfuric or phosphoric acid to produce single or triple superphosphate and other products. Large-scale acid handling and solid–liquid separation produce high volumes for agriculture. Laboratory preparation of phosphate salts uses small quantities of reagents and simple neutralisation or precipitation techniques. The lab focus lies on demonstrating reactions and analysing composition rather than supplying field-scale nutrient requirements.

Process design: continuous industrial vs batch laboratory

Industrial plants favour continuous operation to maintain steady state, improve energy efficiency and maximise throughput. Continuous flow allows heat recovery and recycling, which reduces raw material waste and operating cost. Laboratory work uses batch methods for flexibility, safety and educational clarity. Batch processes require simpler equipment but cause variable product quality and greater per-unit energy use, which limits scalability.

Limiting factors: equilibrium, kinetics, cost and safety

Equilibrium positions and reaction rates govern reachable yields. Industrial processes apply high pressure, catalysts and temperature optimisation to shift equilibria and accelerate reactions, which increases yield and productivity. Cost, safety and environmental limits determine feasible conditions. High-pressure and high-temperature equipment increases capital cost and hazard potential, requiring engineering controls in industry. Laboratory methods choose milder conditions to reduce risk and cost, while accepting lower yields and lower purity.

Key notes

Important points to keep in mind

Industrial processes prioritise yield, throughput and energy efficiency; laboratory methods prioritise safety and simplicity.

High pressure shifts equilibrium toward fewer gas molecules; high temperature increases rate but can lower yield for exothermic reactions.

Catalysts increase rate but do not change equilibrium composition.

Continuous operation enables heat recovery and reagent recycling, reducing per-unit cost.

Laboratory preparations use batch methods, lower pressures and no specialised catalysts, producing smaller quantities with more impurities.

Neutralisation of acids with ammonia produces ammonium fertilisers; control of concentration and temperature prevents hazards.

Environmental and safety regulations influence industrial design, requiring emission controls and safe storage.

Scale-up requires engineering (reactors, compressors, heat exchangers) that is impractical for laboratory setups.

Product purity affects fertiliser performance and handling requirements.

Economic constraints (capital and energy) limit achievable pressure and temperature in commercial plants.