MTBE process: What is a mixed-bed reactor, and what is an expanded-bed reactor?

http://www.docin.com/p-707608040.html – it provides a very detailed explanation of mixed-bed reactors, on Docin

https://wenku.baidu.com/view/9f5f56650b1c59eef8c7b47c.html, expanded bed

In a mixed-phase bed reactor, the term “mixed phase” refers to the phase state of the reaction materials. A mixed-phase bed is generally fed at the bubble point; the heat released by the reaction causes the material to vaporize, resulting in a phase change. The reaction bed thus contains both gas and liquid phases, which is what defines it as a mixed-phase bed. Mixed-bed reactors are generally used in applications where strict control over the reaction temperature is required. For example, the activity of the C4 feedstocks used in MTBE production is too high; any fluctuations in operation can lead to an increased exothermic reaction, which can cause the catalyst bed to overheat rapidly within a short period of time, resulting in the loss of catalyst activity. Using a mixed-bed reactor allows the temperature to be controlled by the latent heat of phase change. The disadvantage is that the presence of a gas phase in the reaction bed reduces the activity of the materials actually participating in the reaction, resulting in a low conversion rate. In a fluidized bed reactor, the term \"fluidization\" describes the state of the catalyst during the reaction process. The material flows in from below and out from above; under the action of the upward-flowing fluid, the catalyst bed in the reactor is in a fluidized state. The catalyst particles rotate irregularly and experience slight disturbances, while the pressure drop across the entire bed remains low and constant. The bed temperature distribution is uniform, with no local hot spots. The expansion bed reactor has a lower ability to control temperature compared to the mixed-phase bed; generally, a subcooled liquid is used as the feed, and no phase change occurs during the reaction, resulting in a higher conversion rate. If the reaction temperature rise is too high, external circulation for heat removal is required.