Can hydrorefining be considered a part of hydrocracking?

There is a process known as hydroprocessing modification, which involves placing two cracking reactors in series after the hydrorefining reactor; it represents a combination of hydrorefining and hydrocracking. This process not only refines the diesel fraction but also reduces its pour point. I have seen this technology used in the refineries of the Yanchang Petroleum Group. . . It is more suitable for processing diesel and mixed components of normal third-line and reduced first/second-line light paraffin oils. . . :lol

Hydrocracking refers to a hydrogenation technique in which, during the hydrogenation process, more than 10% of the molecules in the feed oil become smaller. Hydrotreated API is defined as a hydrogenation process in which, under hydrogen pressure and in the presence of a catalyst, ≤10% of the feed oil is converted into products whose molecular size is smaller than that of the feed molecules. (In my opinion, this includes hydrogenation; the proportion of feed oil that undergoes conversion during refining should be smaller.) Generally, for a simple hydrogenation refining unit, the design pressure is lower than that of a hydrocracking unit, and the hydrogen-to-oil ratio is also smaller. Therefore, in my opinion, it can be said that hydrocracking units have a hydrofinishing process, but hydrofinishing cannot be considered to be part of hydrocracking

“The concept of \"hydrocracking\" refers to hydrogenation processes in which molecules in the feed oil that account for 10% or more are reduced in size through hydrogenation reactions; typical examples include high-pressure hydrocracking, mild hydrocracking, and medium-pressure hydrorefining. The “hydrorefining” process refers to a hydrogenation reaction aimed at removing impurities while keeping the molecular structure of the crude oil essentially unchanged or only slightly altered, thereby improving the quality of the oil. In other words, it involves the hydrogenation removal of non-hydrocarbon components such as sulfur, nitrogen, oxygen, and metals present in petroleum fractions, as well as the hydrogenation saturation of olefins and aromatics, all in the presence of a catalyst and hydrogen gas. ” Currently, there are combined units for hydrorefining and hydrocracking, that is, refining first and then cracking. I think the two are relatively independent; one is not a part of the other.

Hydrogenation processes are generally divided into hydrofining, hydrocracking, and hydroisomerization. The main purpose of hydrorefining is to remove sulfur and nitrogen from the feedstock, as well as to saturate olefins. Examples include diesel hydrorefining and wax oil hydrorefining. The purpose of hydrocracking is mainly to crack large-molecule feedstocks into smaller-molecule products in order to increase the yield of light oils. Hydroprocessing lies between the two approaches; it is primarily used to improve the quality of diesel, or more precisely, to increase its cetane number. The raw materials used are usually catalytic diesel or a mixture of catalytic diesel and coke diesel, and through hydroprocessing, the cetane number can be increased by 10 units. In hydrocracking and hydroreforming, since the cracking or reforming catalysts contain a certain amount of molecular sieve, the basic nitrogen in the feedstock can poison the molecular sieve, resulting in a loss of catalyst activity. Therefore, a hydrofining catalyst is placed before both the hydrocracking catalyst and the hydrorefining catalyst; the nitrogen present in the feedstock is first removed using this refining catalyst and converted into inorganic nitrogen, thereby ensuring that the cracking catalyst is not poisoned. Sometimes the refining catalyst and the cracking catalyst are installed in the same reactor, while sometimes another reactor is placed before the cracking reactor to house the refining catalyst. In summary, in a hydrocracking unit, hydrofining can be considered a part of hydrocracking.

In my opinion, refining is not part of cracking; however, the feedstock before cracking needs to be refined. The earliest forms of hydrocracking used only cracking catalysts, but as it evolved, it was found that adding some refining catalysts before the cracking catalysts not only improved the efficiency of those catalysts but also reduced costs. That’s the direction in which things have developed.

In my opinion, refining is part of cracking; its main purpose is to ensure that the nitrogen content in the feedstock for cracking is within acceptable limits and that the aromatics are sufficiently saturated

Hydrorefining and hydrocracking indicate differences in the degree of cracking.

They are not the same thing; refining is also not part of cracking.

I believe these two processes each have their own characteristics: hydrorefining can improve the quality of diesel by altering its color and removing nitrogen, oxygen, and sulfur compounds from it, while hydrocracking involves breaking down large molecules into smaller ones to increase the yield of light oils. Hydroisomerization, on the other hand, can reduce the density of diesel. Modification and refinement have great similarities in terms of the process, but their catalysts are different

Hydrorefining and hydrocracking are two different hydrogenation processes; hydrorefining is primarily used to remove impurities such as sulfur, nitrogen, oxygen, and metals, while hydrocracking involves breaking down large molecules into smaller ones.

What was said on the second floor is incorrect; the hydrogenation reforming unit also has two reactors. The first one is a hydrogenation refining reactor in which refining agents are used, while the second reactor is a reforming reactor that uses reforming agents. The difference between hydrogenation reforming and hydrocracking is that hydrogenation reforming is a milder process. What the original poster referred to as hydrogenation refining is actually part of hydrocracking; I think hydrogenation refining constitutes just a portion of hydrocracking, and its complexity is much lower than that of hydrocracking. It is merely a part of the hydrocracking reaction, with hydrogenation refining serving only to refine the product by removing sulfur and nitrogen and achieving hydrogen saturation, without any ring-opening or isomerization reactions taking place.

It seems that it is first necessary to distinguish between the hydrogenation refining of raw materials and that of products.

The main reactions in hydrorefining are the removal of sulfides and nitrides from the feed oil, as well as the saturation of olefins and polycyclic aromatic hydrocarbons, in order to provide a suitable feed for the cracking process. These reactions result in the production of hydrocarbons free from impurities, as well as hydrogen sulfide and ammonia (H2S and NH3). Other refining reactions include the removal of oxygen, metals, and halogens. In all of these reactions, hydrogen is consumed, and they are all exothermic. The main reaction types are hydrogenation and hydrodesorption reactions; hydrodesorption reactions are primarily used for desulfurization, denitration, and deoxygenation, while hydrogenation reactions are mainly used for the hydrogenation and saturation of unsaturated hydrocarbons such as olefins and aromatics, as well as nitrogen-containing compounds. The main reactions in hydrocracking include hydrogenation, cracking, isomerization, hydrodecomposition, and polymerization. (1) Under hydrocracking conditions, alkanes yield alkanes with lower molecular weights; the general formula for this process is: CnH2n+2 + H2 → CmH2m+2 + Cn-mH2(n-m)+2. The characteristic of the cracking of n-alkanes is that as the boiling point of these alkanes increases, the cracking reaction rate also increases significantly. This is because: ① Heavier components are more strongly adsorbed on the catalyst than lighter components, which results in a faster hydrocracking rate for the heavier components ； ②The C-C bond energies in the heavy fraction and the light fraction are different; the lighter the component, the higher the activation energy required. (2) Hydrocarbons are decomposed into alkanes and alkenes with lower molecular weights, and the resulting alkenes are then hydrogenated to saturation. Olefins can also cyclize. (3) Both alkanes and alkenes undergo isomerization reactions, resulting in a higher ratio of isomeric hydrocarbons to n-paraffins in the hydrogenation products. Cycloalkanes with two or more rings undergo ring-opening cleavage and isomerization, ultimately yielding monocyclic cycloalkanes and smaller alkane molecules ； (4) The main reactions of naphthenes in hydrocracking are dealkylation, hexagonal ring isomerization, and ring-opening reactions. (5) The main reactions of polycyclic aromatic hydrocarbons are a series of parallel and sequential reactions such as ring-by-ring hydrogenation, ring opening (including isomerization), and dealkylation. Polycyclic aromatic hydrocarbons are rapidly hydrogenated to form polycycloaromatic hydrocarbons (hydrogenation of the benzene ring itself occurs more slowly); the cycloalkane rings open, followed by isomerization and side-chain cleavage (dealkylation) reactions, resulting in a mixture of benzenes and small alkane molecules. (6) A small amount of oxygen-, nitrogen-, and sulfur-containing organic compounds that have been hydrogenated and refined undergo further hydrogenolysis. (7) Hydrocracking also involves some side reactions, such as the condensation of decomposition products and further condensation of polycyclic aromatics; these reactions lead to the deposition of coke on the catalyst. However, at higher hydrogen partial pressures, such reactions are inhibited to a certain extent.