Ammonia synthesis catalyst

Types of ammonia synthesis catalyst

The ammonia synthesis catalyst is necessary to produce ammonia in the Haber process. Different types or forms of these catalysts are available, and they include:

• Iron-based catalysts

  Iron-based catalysts are the most commonly used ammonia synthesis catalysts. They are normally in granular form, and their main element is iron. However, some have small quantities of potassium and alumina or other substances that enhance the catalyst's activity. The catalysts are often utilized in large-scale ammonia production. Even though their activity is lower than the newer types, they are preferred due to their durability and ability to function for long periods.

• Ruthenium-based catalysts

  Ruthenium is commonly dispersed on an activated carbon support and used as a catalyst in ammonia synthesis at lower hydrogen pressures. It is effective on a molar basis but more expensive than other catalysts. Even though suppliers offer iron-based catalysts in bulk and at affordable prices, ruthenium-based catalysts are highly preferred for their efficiency at low temperatures, significantly cutting costs in small production setups.

• Nickel-based catalysts

  Nickel is usually dispersed on supports like alumina and used as a catalyst in ammonia synthesis at lower pressures. It is effective in the reaction since it comprises a transition metal. However, it is less stable and can be easily deactivated by impurities in the feed gases. Buyers who are working on small projects where they would be handling the catalysts manually prefer bulk catalysts since they are easy to handle.

• Cobalt-based catalysts

  Similarly, cobalt is usually dispersed on supports like silica or alumina and used as a catalyst in ammonia synthesis. It is usually preferred over nickel for its stability and activity. However, like nickel, it is deactivated by impurities in the feed gases. Cobalt-based catalysts are ideal for small chemical companies since they are easy to handle and store.

• Molybdenum-based catalysts

  For one, molybdenum promotes iron catalysis for ammonia synthesis. Often, it is incorporated in small amounts into iron-based catalysts. Occasionally, it can also be used in other non-haber processes to create catalysts. Molybdenum is ideal for extending the life of iron-based catalysts since it enhances their activity and keeps them stable. Chemicals that are hard to find and expensive, such as ammonia synthesis catalysts, are ideal for small chemical companies and distributors to buy in bulk.

How to use ammonia synthesis catalyst

The ammonia synthesis catalyst breaks down reactants and helps form ammonia. The iron-based ammonia synthesis catalyst is mixed with hydrogen and nitrogen gases in the Haber process. The gases then flow through a reactor containing the catalyst. The reaction then occurs under specific temperature and pressure conditions, usually around 450 degrees Celsius and 200 atmospheres.

The iron catalyst helps bind the nitrogen atoms and hydrogen atoms together. This forms ammonia gas. The ammonia gas is then cooled, allowing it to liquify and separate from the unreacted gases. The unreacted gases are recycled and passed through the reactor again to keep the process efficient.

The iron-based catalyst used must be active enough to drive the equilibrium toward product formation. The ammonia conversion rate is the percentage of reactants converted into products in a chemical reaction. The ammonia conversion rate in the Haber process ranges between 10 and 20%. However, in smaller setups with lower pressure and temperature, the rate can be less than five. Note that the conversion rate may vary depending on the feed composition, catalyst condition, and operating parameters.

Ammonia synthesis catalyst details and specs

When buying the catalysts, business owners should consider these aspects:

• Composition: Iron-based catalysts are often composed of iron and potassium supported on alumina. The ruthenium catalysts are usually ruthenium dispersed on activated carbon supports. Nickel catalysts are also supported on other materials like alumina, while cobalt is also supported on materials like silica or alumina. Molybdenum is often added in small amounts to other catalysts.
• Form: Most of the ammonia synthesis catalysts are in bulk form. However, some are in the form of thin films or monoliths. Recently, more catalysts are being developed as pellets, powder, and membrane to improve efficiency.
• Porosity: The catalysts are highly porous, which increases their surface area and enhances their ability to adsorb reactants.
• Pore size and distribution: Note that the pore size and distribution significantly affect the catalyst's activity. Newer methods, like 3D printing, enable one to control the pore size and distribution to enhance the catalyst's effectiveness.
• Particle size: The particle size normally influences the ammonia conversion rate. Small particles provide more surface area and shorten diffusion distances. However, smaller particle sizes also mean increased pressure drop and reduced mass transfer. Balance is critical, and prospective buyers should check if the suppliers have a variety of particle sizes to choose from.
• Mechanical strength: It is vital for catalysts used in fixed bed reactors. If the catalyst particles are too small, they may break and lead to catalyst deactivation.

Ammonia synthesis catalyst QC and aftercare

When launching the product, business owners should ensure the quality is high. To achieve this, they should carry out the following QA processes:

• Particle size distribution: They should check if the catalyst particles are of the required size using laser diffraction or screening methods. They should also ensure the particles are distributed evenly.
• Surface area: They should check the surface area of the ammonia synthesis catalysts using BET analysis. Large surface areas are ideal as they provide more active sites for the reactants to adsorb.
• Mechanical strength testing: The rocks should be strong enough not to create fines during transport and storage. Buyers can test the rocks' strength by measuring their fracture or crushing resistance. If they use small particles, they should ensure the particles are agglomerized to avoid fines.
• Temperature and pressure stability checks: Buyers should keep the catalysts in temperature and pressure stability storages to ensure they work well during shipping. The iron-based catalysts are usually stable at 450 degrees Celsius and 200 bars. Make sure the ammonia synthesis catalysts do not lose their activity or strength when exposed to these conditions.
• Impurity analysis: The catalysts should be free of significant amounts of sulfur, carbon monoxide, or other impurities. Buyers can use techniques like X-ray fluorescence or scanning electron microscopy to check for impurities. They should also check that the metal supports are homogenous and do not contain uneven elemental concentrations.
• Typical maintenance and care for ammonia synthesis catalysts

  Since the catalysts are often used in ammonia production, buyers are always on the lookout for the catalysts' conditions. They normally look for signs of deactivation, like decreased conversion rates or changes in product composition. Frequent inspections help them catch issues before they affect production adversely. One of the most effective methods to reduce deactivation is by taking preventive maintenance measures. One is purchasing high-quality catalysts and replacing them promptly.

• How to store

  To maintain efficiency, store the catalysts in optimum conditions. Store them in dry, cool places and avoid exposure to high temperatures and humidity. Also, avoid direct sunlight as it can demobilize the catalysts and make them less effective. Iron-based catalysts can easily oxidize when exposed to moisture. Therefore, store them in dry environments and use moisture-resistant containers. Additionally, store them in low-temperature areas to maintain particle size and surface area. Ruthenium and other precious metal catalysts are also sensitive to moisture. Thus, store them in secure and dry locations.

Q&A

What should buyers pay attention to when purchasing the ammonia synthesis catalysts?

Buyers should focus on key elements like composition, activity, selectivity, and stability when purchasing ammonia synthesis catalysts. They should also check where the catalyst comes from. Suppliers stock those that are produced using eco-friendly techniques. They should also order catalysts that have been suitable for large and small-scale production. If the buyer does not use the catalysts themselves, they could consider purchasing customizable catalysts. They also should look for news of any advances in ammonia group catalysts as they may improve the stability and efficiency of the older ones.

What are some ways buyers can keep their ammonia synthesis catalysts in optimal condition?

To keep their ammonia catalysts in good condition, buyers should avoid exposing them to high temperatures, humidity, or harsh chemical environments. High temperatures can demobilize the catalysts, making them less useful. Also, high humidity can lead to oxidation, especially on iron and ruthenium-based catalysts. Keep the catalysts in dry environments and avoid direct sunlight. If the catalysts come into contact with ammonia, clean them promptly using mild detergents, water, or alcohol-based wipes. Avoid using harsh chemicals as they could potentially corrode or damage the catalyst material.

Do catalysts have to be replaced once they are deactivated?

Catalysts can be regenerated to restore their catalytic activity. For example, one can recover ruthenium from ammonia synthesis catalysts and reuse it in making new ones. They can also be reactivated by removing the substances that poisoned them. However, if the structure of the catalysts changes or wears out, it becomes impossible to reactivate them. Ammonia synthesis catalysts come deactivated after long use. However, many can be regenerated. Buyers should be keen on those that can be regenerated easily.

What are the signs that ammonia synthesis catalysts are deactivated?

There are several indicators that one should look for to determine if the catalyst is deactivating. One of the easiest signs is checking the conversion rates. Low conversion rates usually indicate that the catalyst might be deactivated. Thermal stability is another one. If the temperature drastically fluctuates, it may indicate that the catalyst is deactivated. One can also conduct an analysis to check if there are any coking deposits on the catalysts. Lastly, changes in product composition are also a sign of deactivation.