Catalyst activity

1# snowdfr: Generally, when the process requirements can be met, keeping the inlet temperature close to the activation temperature allows the hotspot temperature to be maintained at a lower level, which is beneficial for preserving the catalyst’s activity. However, the factor of energy consumption must also be fully considered. For example, if a synthetic catalyst operates at low temperatures with high pressure and a low ammonia yield, it is certainly not appropriate to use low temperatures in such a situation; on the other hand, in systems that operate at high temperatures with low pressure and a high ammonia yield, using low temperatures is also inappropriate. Therefore, there is no strict absolute requirement for determining the optimal operating temperature; however, catalyst manufacturers tend to prefer lower operating temperatures

This statement is correct; catalysts should strive to maximize their low-temperature activity. The usage time has been extended. But this also depends on determining the inlet temperature based on actual production conditions.

This post was last edited by shiguomiao on 2010-1-1 02:53. The starting temperature for ammonia synthesis catalysts is between 280°C and 300°C. If only chemical equilibrium is taken into consideration, there is no need to carry out production; the lower the temperature, the slower the chemical reaction rate, and with a very low space velocity, it’s impossible to achieve any significant yield. Based on what’s in the book, it seems that considerations should be taken from multiple aspects

The low-temperature activity of a catalyst refers to its ability to perform catalytic functions effectively at lower temperatures, maintaining high activity; this is what indicates good low-temperature activity. If it has good activity at low temperatures, its onset activity temperature should also be lower ； Conversely, the onset activity temperature is a bit higher. Even if the inlet temperature of the catalyst bed should be as close as possible to the initial activity temperature, this does not necessarily mean that its activity at low temperatures is good. Therefore, to fully utilize the low-temperature activity of the catalyst, the inlet temperature of the catalyst bed should be as close as possible to the initial activity temperature. ”This statement is at least incomplete.

To extend the catalyst's service life, its activity at low temperatures should be maximized.

Under normal circumstances, the reactions carried out by the catalysts used in ammonia synthesis and ammonia purification processes are exothermic reactions. Therefore, once the catalysts are put into use, their low-temperature activity must be taken into consideration, that is, the reactions should take place at lower temperatures. If the inlet temperature is set close to that of the catalyst bed, the heat released during the shift or ammonia synthesis reactions will gradually increase, thereby affecting the catalyst’s low-temperature activity; hence this approach is incorrect.

Study the book \"Chemical Reaction Engineering\" carefully.

From the perspective of saving energy in the production process and extending the catalyst’s lifespan, the lower the temperature, the better. However, if the temperature is too low, the strength of the synthesis tower decreases, and the ammonia production rate per hour drops, which is not conducive to production and results in no economic benefit. After all, all production activities are carried out with the aim of generating economic benefits

1: The reaction rate increases at higher temperatures, but the equilibrium concentration decreases. A catalyst can exhibit its catalytic activity only within a certain temperature range, namely the onset activity temperature； 2: The catalyst exhibits good activity at lower temperatures; in other words, it has high activity at low temperatures. Low temperatures help to extend the catalyst’s lifespan and reduce corrosion of the equipment ； But the initial activity temperature of the catalyst cannot be taken as an indication of good low-temperature performance ； 3: To prevent the growth and merging of active crystals at high temperatures, which would lead to a reduction in the active surface area and a decrease in activity, and to make full use of the catalyst’s activity at low temperatures, the inlet temperature of the catalyst bed should be determined based on the reaction rate and equilibrium concentration.