Hydrotreating Renewable Feedstocks Using Pretreatment to Manage Exotherms
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current processes for hydrotreating renewable feedstocks face challenges in effectively eliminating inorganic impurities and nitrogen compounds, leading to catalyst deactivation, pressure loss, and reduced yield of paraffinic hydrocarbons, particularly due to the high temperatures required for hydrodenitrogenation reactions and the presence of nitrogen inhibitors.
Innovation Solution
A process that integrates an advanced pretreatment step upstream of the catalytic zones, using a flow of hydrogen to eliminate inorganic impurities and partially hydrogenate unsaturations in the feedstocks, promoting hydrodeoxygenation reactions while maintaining low temperatures for hydrodeoxygenation and enabling effective hydrodenitrogenation, thus extending catalyst lifespan and improving product yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperatures are used to promote hydrodenitrogenation reactions, then nitrogen removal is improved, but catalyst deactivation and pressure loss increase
Solution Approach 1:
The patent applies preliminary action by implementing a pretreatment step before the main hydrotreatment process. In this pretreatment step, inorganic impurities are removed and unsaturations are partially hydrogenated at controlled conditions. This preliminary action prevents the formation of harmful substances during subsequent high-temperature hydrodenitrogenation, thereby resolving the contradiction between achieving nitrogen removal and avoiding catalyst deactivation.
2Reliability
If high temperatures are used for hydrodenitrogenation, then nitrogen compounds are removed, but CO/CO2 formation increases
Solution Approach 1:
The pretreatment step performs preliminary hydrogenation of unsaturations before the main treatment. This preliminary action modifies the chemical structure of the feedstock in a controlled manner, enabling subsequent nitrogen removal at lower temperatures and reducing unwanted decarboxylation reactions that produce CO/CO2, thus resolving the contradiction between nitrogen removal and minimizing carbon loss.
3Productivity
If inorganic impurities are present in feedstocks, then processing continues, but catalyst lifespan is reduced
Solution Approach 1:
The patent applies the extraction principle by implementing a pretreatment step that specifically removes inorganic impurities from the feedstock before it enters the main hydrotreatment process. This extraction of harmful substances prevents catalyst poisoning and deactivation, thereby extending catalyst lifespan while maintaining continuous processing capability.
4Device complexity
If unsaturations are not hydrogenated before hydrotreatment, then processing is simpler, but temperature control becomes difficult
Solution Approach 1:
The pretreatment step performs preliminary hydrogenation of unsaturations at controlled conditions before the main hydrotreatment process. This preliminary action reduces the overall exothermic heat generation during subsequent reactions, making temperature control easier and more stable throughout the process, while only adding a moderate level of process complexity.
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 enhances the yield of paraffinic hydrocarbons, reduces CO/CO2 formation, minimizes catalyst deactivation, and extends the lifespan of the hydrotreatment system by effectively managing temperature profiles and eliminating nitrogen compounds, resulting in improved fuel quality and reduced operating costs.
Implementation Method 1
a flow of hydrogen to eliminate inorganic impurities and partially hydrogenate unsaturations in the feedstocks
Implementation Method 2
hydrodeoxygenation (HDO) leading to the formation of water by consumption of hydrogen and to the formation of hydrocarbons
Implementation Method 3
The hydrogenation of unsaturations of hydrocarbon chains (carbon-carbon double bonds) is strongly exothermic and the increase in temperature caused by the release of heat
Implementation Method 4
decarboxylation/decarbonylation leading to the formation of carbon oxides (carbon monoxide and dioxide: CO and CO2) and the formation of hydrocarbons with one less carbon
Data Source
Figure 1
AI summary
The invention relates to a hydrotreating process for feedstock derived from renewable sources, such as vegetable oils, to produce paraffinic hydrocarbons. The process includes a pretreatment step involving crystallization and/or precipitation and pre-hydrogenation of the feedstock under hydrogen. This pretreatment eliminates inorganic impurities that are insoluble under hydrotreating conditions and improves the management of reaction exotherms. The total feedstock stream is divided into several partial streams, each corresponding to a number of catalytic zones in the reactor. These partial streams are injected into successive catalytic zones in increasing proportions to produce an effluent containing paraffinic hydrocarbons. The effluent then undergoes a separation step to separate a gaseous fraction from a liquid fraction containing the paraffinic hydrocarbons.At least a portion of said liquid fraction is recycled either to the pretreatment stage or to at least one catalytic zone such that the mass ratio between this recycle and the partial flow introduced into the first catalytic zone is greater than or equal to 10.