Two-Stage Hydrodesulfurization for Low-Sulfur Petrol
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Solution Overview
Problem
Current processes for producing low-sulfur gasoline, particularly from catalytic cracking, face challenges in reducing mercaptans content while minimizing loss of octane number and hydrogen consumption.
Innovation Solution
A multi-stage hydrodesulfurization process involving specific catalysts and conditions to convert sulfur compounds into H2S, separate H2S, and then treat the effluent at lower hydrogen flow rates and higher temperatures to minimize mercaptans formation, using catalysts like CoMo and Ni-based catalysts to preserve octane number and reduce hydrogenation of olefins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional nonselective catalytic hydrodesulfurization is used to reduce sulfur content, then sulfur content is decreased, but octane number is significantly lost and hydrogen consumption is high
Solution Approach 1:
The hydrodesulfurization process is divided into two sequential stages: a first stage using a CoMo catalyst at lower temperature (200-300°C) to remove most sulfur compounds, and a second stage using a Ni catalyst at higher temperature (300-400°C) to remove residual sulfur. This segmentation allows selective desulfurization while preserving olefins and maintaining octane number, avoiding the need for severe single-stage conditions that cause excessive hydrogenation.
Solution Approach 2:
The invention changes operating parameters between stages: the first stage operates at lower temperature (200-300°C) and higher pressure (3-10 MPa) with high hydrogen flow rate to maximize sulfur removal, while the second stage operates at higher temperature (300-400°C) and lower pressure (1-5 MPa) with lower hydrogen flow rate to remove residual sulfur without excessive hydrogenation. This parameter optimization resolves the contradiction between sulfur removal efficiency and octane preservation.
2Quantity of substance
If conventional hydrodesulfurization processes are used to reduce sulfur content, then sulfur content is decreased, but hydrogen consumption is high
Solution Approach 1:
The two-stage process segments hydrogen consumption: the first stage consumes high hydrogen flow rate to remove the bulk of sulfur compounds (80-90% removal), while the second stage consumes lower hydrogen flow rate to remove residual sulfur. This segmentation reduces total hydrogen consumption compared to single-stage severe conditions, as the majority of sulfur is removed under optimized conditions rather than requiring continuously severe conditions throughout.
Solution Approach 2:
By changing pressure and temperature parameters between stages, the invention optimizes hydrogen utilization: the first stage uses high pressure (3-10 MPa) to enhance hydrogen solubility and reaction rate for bulk sulfur removal, while the second stage uses lower pressure (1-5 MPa) since less hydrogen is needed for residual sulfur removal. This parameter adjustment reduces overall hydrogen consumption while maintaining effective desulfurization.
3Quantity of substance
If severe operating conditions are applied to achieve very low sulfur content, then sulfur content is reduced below 10 ppm, but octane number is significantly lost
Solution Approach 1:
The two-stage process achieves severe desulfurization (below 10 ppm) without severe operating conditions by segmentation: the first stage removes most sulfur under moderate conditions (200-300°C, 3-10 MPa) preserving olefins, and the second stage removes residual sulfur under milder conditions (300-400°C, 1-5 MPa). This avoids the need for continuously severe single-stage conditions that would cause excessive hydrogenation and octane loss.
Solution Approach 2:
The invention uses optimized parameter changes to achieve deep desulfurization without severe conditions: the first stage operates at moderate temperature (200-300°C) and high pressure (3-10 MPa) for efficient sulfur removal, then the second stage operates at higher temperature (300-400°C) and lower pressure (1-5 MPa) to remove residual sulfur. This parameter optimization achieves below 10 ppm sulfur while minimizing olefin hydrogenation and preserving octane number.
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
The process effectively reduces mercaptans content to less than 10 ppm, minimizes octane loss, and decreases hydrogen consumption, making it suitable for meeting stringent environmental standards without requiring severe operating conditions.
Implementation Method 1
a) the gasoline, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase comprising a metal from group VIB and a metal from group VIII are brought into contact in at least one reactor... to convert at least a portion of the sulfur compounds into H2S
Implementation Method 2
conventional processes desulfurize gasolines in a nonselective manner by hydrogenating a large part of the monoolefins
Implementation Method 3
b) a stage of separation of the H2S formed and present in the effluent resulting from stage a) is carried out
Data Source
AI summary
The present invention concerns a method for processing a petrol containing sulfur and olefin compounds, comprising the following steps: a) a step of hydrodesulfurisation in the presence of a catalyst comprising an oxide support and an active phase comprising a metal from group VIB and a metal from group VIII, b) a step of separating the H2S formed, c) a step of hydrodesulfurisation at a higher temperature than that of step a), with a hydrogen/feedstock ratio less than that of step a), and in the presence of a hydrodesulfurisation catalyst comprising an oxide support and an active phase consisting of at least one metal from group VIII, d) a step of separating the H2S formed.