Two-Stage Hydrocracking for C2 and C3 Yield Control
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Solution Overview
Problem
Existing processes for converting naphtha to LPG suffer from unbalanced C3/C4 ratios and excessive methane production, which is undesirable for petrochemical applications, and lack control over C4 production and composition.
Innovation Solution
A two-stage hydrocracking process involving a mild first hydrocracking followed by a more severe C4 hydrocracking, optimized to convert C4 hydrocarbons into C3 hydrocarbons, using specific catalysts and conditions to achieve a high yield of C2 and C3 hydrocarbons while minimizing methane production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the severity of hydrocracking is increased to shift products to ethane and propane, then C2 and C3 hydrocarbon yield is improved, but methane production becomes excessive
Solution Approach 1:
The hydrocracking process is divided into two distinct stages: a first mild hydrocracking stage that converts naphtha to LPG with controlled C3/C4 ratio, followed by a second severe C4 hydrocracking stage that selectively converts C4 hydrocarbons to C3 hydrocarbons. This segmentation allows optimization of each stage for its specific function, achieving high C2/C3 yield while minimizing methane production by avoiding excessive severity in the first stage.
2Productivity
If single-stage hydrocracking is used to maximize ethane production, then C2 production is improved, but the recycle stream size becomes too large
Solution Approach 1:
The process separates ethane production from the main hydrocracking by using a dedicated second-stage C4 hydrocracking unit that feeds into the ethane production loop. This allows the first stage to operate independently with optimized LPG production, while the second stage handles C4 conversion to C3, thereby limiting the recycle stream size to only what is necessary for C4 conversion rather than the entire LPG stream.
3Quantity of substance
If C4 hydrocarbons are produced in high amounts, then LPG volume is increased, but the balance between C3 and C4 derivatives becomes unbalanced
Solution Approach 1:
The process dynamically adjusts the C3/C4 ratio by controlling the severity and conditions of the second-stage C4 hydrocracking. By optimizing this stage specifically for C4 to C3 conversion, the system can maintain a balanced C3/C4 ratio in the final LPG product while still achieving high overall LPG volume, thereby adapting the composition to match petrochemical demand.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the selective shifting of the LPG composition from C4 to C3, achieving a high yield of C2 and C3 hydrocarbons with controlled C4 production and reduced methane levels, aligning with petrochemical demand.
Implementation Method 1
subjecting a mixed hydrocarbon stream to first hydrocracking in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream
Implementation Method 2
subjecting the first hydrocarbon product stream to C4 hydrocracking optimized for converting C4 hydrocarbons into C3 hydrocarbons in the presence of a C4 hydrocracking catalyst
Data Source
AI summary
The invention relates to a process for producing C2 and C3 hydrocarbons, comprising a) subjecting a mixed hydrocarbon stream to first hydrocracking in the presence of a first hydrocracking catalyst to produce a first hydrocracking product stream; and b) subjecting the first hydrocarbon product stream to C4 hydrocracking optimized for converting C4 hydrocarbons into C3 hydrocarbons in the presence of a C4 hydrocracking catalyst to obtain a C4 hydrocracking product stream comprising C2 and C3 hydrocarbons.