How does the dry gas yield change when the reaction pressure is increased?

In catalytic cracking units, increasing the reaction pressure prolongs the reaction time and raises the dry gas yield.

When the pressure is high, the reaction rate increases; the line speed should decrease, and the reaction time lengthens. The yield of dry gas should increase. Pressure affects catalytic cracking reactions, so chemical equilibrium does not need to be considered

High pressure increases the reaction depth and raises the dry gas yield

Reply 1# chengkang: Why increase the pressure during operation? As the pressure in the catalytic reaction increases, the coke yield and dry gas yield rise, while the total liquid yield decreases. The pressure development trend in catalytic reaction systems is moving toward lower pressures; of course, increasing the system pressure is a good approach when upgrading existing facilities to increase production capacity

The DCC process operates at the lowest pressure in catalytic cracking units, with the aim of producing more low-carbon olefins. Increasing the reaction pressure (the vapor pressure of hydrocarbons) reduces the yields of liquefied gas and propylene, while simultaneously increasing the yields of dry gas and coke. The same principle applies to catalytic cracking units; however, the reaction pressure is not optimal when it is too low, nor when it is too high. Low pressure is favorable for the reaction, but it increases the power consumption of the compressor ； High pressure is beneficial for the power consumption of the compressor, but it also increases the yields of dry gas and coke~~~ Therefore, when selecting the reaction pressure for different catalytic cracking processes, in addition to considering the characteristics of those processes, engineering factors such as energy savings must also be taken into account~~~

Increasing the reaction pressure prolongs the time that the feed materials spend in the riser reactor, which in turn increases the reaction rate. This leads to a decrease in the yields of gasoline and diesel, as well as an increase in the ratio of dry gas to coke. However, the reaction pressure cannot be adjusted arbitrarily – it is determined by the design of the main fan and the compressor. For example, when using a backup unit, the regeneration pressure is 0.14–0.16 MPa, while it is 0.16–0.18 MPa when using the main unit; accordingly, the reaction pressure also changes

It seems everyone shares the same view; it’s my understanding that is incorrect. Over the years, I have always believed that by increasing the reaction pressure, the coke yield increases while the dry gas yield decreases; whereas by reducing the reaction pressure, the coke yield decreases and the dry gas yield increases.