Problems with hydrocracking and hydrorefining
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Colleagues: In hydrocracking units, hydrogenation refining catalysts are generally used in the first reactor, while cracking catalysts are used in the second reactor. Why not use cracking catalysts directly from the start?
This post was last edited by “Strive to Live Each Day Well” on December 22, 2016, at 15:25. It serves to remove impurities such as sulfur, nitrogen, and oxygen from raw materials, as well as to saturate olefins, etc. The original poster can search for posts related to hydrogenation.
Their functions are different; some modified catalysts have requirements regarding nitrogen content.
My personal understanding: First of all, you need to understand the functions of hydrogenation refining and hydrocracking catalysts; hydrogenation refining is primarily used for desulfurization, denitration, and deoxygenation. Demetallization. To saturate olefins and dienes, cracking catalysts serve the purpose of cracking, mainly by breaking down molecular chains. Another key reason is that hydrocracking catalysts are sensitive to nitrogen and metals present in the feedstock. This can lead to catalyst poisoning and subsequent deactivation; therefore, hydrorefining is carried out first to remove such substances, followed by the cracking reaction.
That will destroy the cracking agent!
The direct cracking catalyst will be wasted. . .
The hydrocracking process actually consists of two reaction steps. The first is hydrogenation, in which the feed oil (usually a heavier-type oil) is subjected to appropriate hydrogenation to remove most of the sulfur and nitrogen impurities, and the unsaturated components are saturated to an appropriate extent (depending on the degree of hydrogenation). The hydrogenated oil undergoes cracking to break down large-molecule hydrocarbons into smaller ones, thereby obtaining lighter oils.
The function of hydrorefining is to remove SNO from the feed oil, converting it into H2S, NH3, and H2O that are easier to remove. The hydrogenation of unsaturated hydrocarbons leads to their saturation, while hydrocracking involves the breaking of carbon chains in order to lighten heavy oils. Alkanes and alkenes undergo cracking, isomerization, and a small amount of cyclization reactions; in addition, naphthenes and aromatics experience side-chain cleavage, ring opening, and other such reactions.
Hydrorefining involves first removing impurities, followed by appropriate hydrogenation to eliminate most sulfur and nitrogen impurities, as well as saturating the unsaturated components appropriately.