Catalysts fall into three working groups: metals such as iron, nickel and platinum, oxides such as vanadium pentoxide and manganese dioxide, and acids or bases such as concentrated sulfuric acid and lye. Solid metals and oxides sit in a bed while the gas or liquid flows past them; acids and bases dissolve in the reaction mixture and have to be removed afterward. Choose by the reaction and by what you can source: iron filings are easy, platinum is salvaged, vanadium is scarce.
Part of Industrial Chemistry
The three main classes of catalyst, where each is used in the corpus’s processes and how to source them.
Solid And Dissolved Catalysts Behave Differently
A solid (heterogeneous) catalyst is a different phase from the reactants, so the reactants flow over it and it stays put. Metals and oxides are the usual solids. A dissolved (homogeneous) catalyst, such as a strong acid or base, is mixed into the liquid and must be neutralised or washed out afterward.
The Carrier’s List And Where Each Is Used
| Catalyst | Used for | Source, per the carrier |
|---|---|---|
| Iron with promoters | Haber process (ammonia) | Iron filings plus ground limestone |
| Vanadium pentoxide | Contact process (sulfuric acid) | Vanadium ore or petroleum residues |
| Platinum | Multiple oxidation reactions | Salvage from catalytic converters and jewellery |
| Nickel | Hydrogenation | Salvage from stainless steel and coins |
| Manganese dioxide | Oxygen generation, batteries | Battery scrap, natural ore |
Two further catalysts appear elsewhere in this section. Concentrated sulfuric acid catalyses ester formation (Esterification), and lye (sodium or potassium hydroxide) catalyses the biodiesel reaction (Lye Catalyst). Both are consumed in part, since lye also reacts with free fatty acids, which is the point of Free Fatty Acid Problem.
Choosing By Reaction And By Hazard
- Metals need a clean feed (sulfur poisons them) and are best prepared as small uniform pieces. Finely divided nickel can ignite in air, and nickel reacting with carbon monoxide at moderate temperature can form nickel carbonyl, a very toxic gas (general toxicology, not a corpus figure). That matters near wood gas and other CO sources.
- Oxides such as vanadium pentoxide are toxic as dust and must be handled with a mask and gloves.
- Acid and base catalysts burn skin and eyes; see Protective Gear.
What You Need
- The reaction’s catalyst, identified from the table.
- A source (salvage, ore, scrap) that can be confirmed by test.
- Preparation tools: crusher, sieve of 3-10 mm for bed catalysts (Catalyst Beds).
- Protective equipment for dust and corrosives.
Method: Choosing And Sourcing
Step 1: Name the reaction.
Step 2: Pick the catalyst class from the table.
Step 3: Source and verify the material. An unknown metal can be wrong or contaminated.
Step 4: Prepare it to size and pack or dissolve as the reaction needs.
Worked Example: How Much Catalyst In A Bed
A solid catalyst bed is filled by volume. Suppose a steel tube of 10 cm internal diameter and 60 cm of catalyst depth, within the carrier’s tube ranges of 5-15 cm diameter and 30-100 cm length. Bed volume = π ÷ 4 × 0.10² × 0.60 = 0.785 × 0.01 × 0.60 = 0.00471 m³, 4.7 litres. At an assumed catalyst bulk density of 2 kg per litre (an illustrative figure, as bulk density varies widely with material), the bed holds 4.7 × 2 = 9.4 kg. The mass is what drives cost and sourcing: 9.4 kg of vanadium oxide is a different undertaking from 9.4 kg of iron filings.
Common Mistakes
- Using stainless steel scraps as “nickel”. Stainless steel holds nickel only as part of an alloy; recovering it is a separate chemistry task.
- Mixing up the catalyst and the reactant, then weighing for yield.
- Skipping the mask for oxide dust.
- Leaving lye in biodiesel. Wash it out.
Safety
Toxic dust, ignitable metal powder and corrosive catalysts
Vanadium pentoxide dust, finely divided nickel, nickel carbonyl (from nickel plus carbon monoxide), concentrated sulfuric acid and lye each demand specific precautions: mask, closed handling, no CO near nickel, eye and skin protection. Do not heat any catalyst past its range or pack and open beds with gas present.
What’s Next
- Learn next: Catalyst Beds — how a solid catalyst is housed
- Combine with: Contact Process — the vanadium oxide application