Can crude oil be directly catalytically cracked?
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This post was last edited by Someone on 2019-6-19 23:18. I remember when I was studying petroleum refining processes in undergraduate courses, it was said that the atmospheric and vacuum distillation units in refineries are the most energy-intensive production facilities; however, their economic efficiency is not as good as that of chemical plants. As electric vehicles become more widespread, could there be an oversupply of oil products? So, is it possible to avoid atmospheric and vacuum distillation, and instead process the crude oil directly through pretreatment before sending it to catalytic cracking to produce chemical raw materials? Or through a simple distillation, the light ends are sent for reforming while the rest are sent for catalytic cracking? Would this help reduce the energy consumption of refineries and improve their economic efficiency? By the way, one more question: why are the prices of refined oil products set by the National Development and Reform Commission rather than determined by the market?
Catalytic cracking units also have requirements regarding the feedstock; firstly, the heavy metal content and alkaline nitrogen content in the feedstock must not be high, as this can cause the catalyst to become inactive； Next is the product distribution; the diesel component in crude oil goes through catalytic processing, and its economic viability is affected by the prices of diesel and gasoline. Generally speaking, processing diesel through catalysis results in losses.
Well, thank you for the reply. I know there are limits on the metal content of the raw materials; in addition, there is residual carbon, and high levels of residual carbon may pose a problem from a thermal balance perspective. Putting aside metal content and residual carbon, if diesel components are fed into catalytic cracking to produce low-carbon olefins, would that make it more economical?
In fact, 10 years ago, certain catalytic processes in China were already being used to process raw materials directly; it was only necessary to carry out the pretreatment process you mentioned, namely removing heavy metals and basic nitrogen compounds from the crude oil. As a supplementary note, the original design concept of the catalytic cracking process was to convert more diesel into gasoline components!
The target products of the catalytic unit are gasoline, diesel, and liquefied gas, with gasoline and diesel being the main ones; the by-products are dry gas, coke, and slurry. Direct catalytic cracking of crude oil reduces the yields of gasoline and diesel.
The high energy consumption of atmospheric and vacuum distillation is due to its large processing capacity; if catalytic processing reached the same scale as that of atmospheric and vacuum distillation, its energy consumption would be 3 to 5 times higher. The purpose of catalysis is to lighten heavy oils, primarily by processing vacuum distillates. The gasoline obtained through atmospheric and vacuum distillation, as well as the straight-run diesel, can be sold directly as products. If they are further processed catalytically, they turn into lighter gases and liquefied gases, which represents a depreciation and waste of high-quality fractions!
Is processing raw materials directly also considered blending? Or crude oil separately? What crude oil is being used? Why do we need to do this?
In the future, refineries might reduce the yields of gasoline and diesel; it seems that new energy vehicles are the trend of the times
It’s true that atmospheric and vacuum distillation can handle large volumes of feedstock. But what is the basis for your claim that catalytic cracking requires 3 to 5 times more energy for the same volume of feedstock? You also mentioned the depreciation and waste associated with high-quality distillates, but from a chemical engineering perspective, burning them directly is even more wasteful! Moreover, companies do not have the power to set prices for refined oil. . . My question is: as new energy vehicles continue to become more widespread, there will likely be an oversupply of refined oil capacity. In such a situation, if production plans are adjusted so that no oil is produced any longer, could it be possible to use simple distillation to process naphtha for reforming, while using catalytic cracking for the other components, in order to produce more low-carbon olefins? Could the gasoline and diesel fractions also be subjected to steam cracking?
Planes still need to be flown, and aviation fuel still relies on hydrogenation