Hydrotreatment Process for Aromatic Nitrogen Removal
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Solution Overview
Problem
The efficient removal of nitrogen from hydrocarbons derived from aromatic feedstocks, such as pyrolysis oil, is challenging due to the difficulty in denitrogenation, especially when the nitrogen compounds are in aromatic forms, which are stable at high temperatures.
Innovation Solution
A process involving initial hydrotreatment at high temperatures followed by a second hydrotreatment step with conditions adjusted to favor the conversion of aromatic nitrogen compounds to non-aromatic nitrogen-free compounds, utilizing catalysts like platinum, palladium, nickel, cobalt, tungsten, and molybdenum on refractory supports, and employing techniques like temperature reduction, ammonia removal, and pressure changes to shift thermodynamic equilibria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature hydrotreatment is used to remove nitrogen from aromatic compounds, then nitrogen removal efficiency is improved, but aromatic stability prevents complete denitrogenation
Solution Approach 1:
The process is divided into two distinct stages: first, hydrotreatment at high temperature to remove easily removable nitrogen; second, hydrodearomatization at lower temperature to convert aromatic nitrogen compounds to non-aromatic forms for complete denitrogenation. This segmentation allows each stage to operate under optimal conditions for its specific function.
Solution Approach 2:
The process changes temperature parameters between stages: high temperature (350-450°C) in the first stage for initial denitrogenation, then lower temperature (200-350°C) in the second stage for hydrodearomatization. This parameter change exploits the thermodynamic equilibrium shift that favors non-aromatic structures at moderate temperatures.
2Manufacturing precision
If severe hydrotreatment conditions are applied to achieve high denitrogenation, then nitrogen content is reduced, but process complexity and cost increase
Solution Approach 1:
The complex denitrogenation task is segmented into two simpler sequential processes: hydrotreatment followed by hydrodearomatization. Each process uses different catalysts and operates under different conditions, allowing optimization of each individual step rather than requiring one extremely severe process.
Solution Approach 2:
The first hydrotreatment stage acts as an intermediary that removes easily removable nitrogen and prepares the feedstock for the second stage. This intermediate step prevents the second stage from having to handle all nitrogen removal tasks, reducing its complexity requirements.
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 process achieves significant denitrogenation, potentially up to 90% or more, by converting aromatic nitrogen compounds to non-aromatic forms, thereby improving the quality of pyrolysis oil and making the process cost-effective and efficient.
Implementation Method 1
contact a material catalytically active in hydrotreatment under active hydrotreatment conditions
Implementation Method 2
adjusting one or more conditions of the hydrotreated intermediate stream to active hydrodearomatization conditions where the equilibrium between aromatic nitrogen compounds and non-aromatic nitrogen-free compounds is shifted towards non-aromatic nitrogen-free compounds
Implementation Method 3
removal of ammonia by washing with water, benefiting from the fact that the thermodynamic equilibrium favors non-aromatic structures at moderate temperatures and that removal of ammonia product favors the reaction forming ammonia
Data Source
AI summary
A process for conversion of a feedstock originating from thermal decomposition of solids, containing from at least 0.5 wt % nitrogen and less than 15 wt % nitrogen, including the steps of directing the feedstock to contact a material catalytically active in hydrotreatment under active hydrotreatment conditions in the presence of dihydrogen, to provide a hydrotreated intermediate, adjusting one or more conditions of the hydrotreated intermediate stream to active hydrodearomatization conditions where the equilibrium between aromatic nitrogen compounds and non-aromatic nitrogen-free compounds is shifted towards non-aromatic nitrogen-free compounds, directing at least an amount of the hydrotreated intermediate to contact a material catalytically active in hydrodearomatization under the active hydrodearomatization conditions, in the presence of dihydrogen, to provide a further converted intermediate. This has the associated benefit of providing a pyrolysis plant with the ability to remove aromatic nitrogen efficiently from the pyrolysis oil.