Is there any difference between top feeding and bottom feeding in a fixed-bed reactor?
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In a fixed-bed tubular reactor, where the catalyst is located in the tube side, what is the difference between the two types of feedstocks? Could an expert give some advice? I am extremely grateful
Is it related to the selectivity of the products? If the product is a recombinant component, from top to bottom; otherwise, from bottom to top
Thank you for your comment. The product is propylene oxide, the solvent is methanol; there is also an excess of propylene, along with residual hydrogen peroxide. As for propylene, it has a higher density, while the other substances have a lower density
Liquid-phase fixed beds generally use bottom feeding, while gas-phase ones use top feeding.
For liquid-phase reactions, a fixed bed is generally fed from the bottom, as feeding from the top can easily lead to channeling or side flow when the catalyst is present. Feeding from the bottom poses no major issues, as it ensures good distribution of the feed. It actually doesn’t matter for gas-phase reactions, because gravity has little effect on gas distribution and flow. Some people feed materials from the top for gas-phase reactions, but this is not common, as the residence time in gas-phase reactions is usually very short. In gas-liquid reactions, it is common to feed the gas from below the liquid, thereby enabling counter-current contact; the gas can lift the liquid and form a film on the packing, which improves the reaction efficiency. For gas-liquid reactions in microreactors, gas and liquid are generally fed in co-current fashion, which allows Taylor flow to be formed within the pipes, enabling the gas-liquid mass transfer process to be controlled in a predictable manner.
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