Multistage Renewable Diesel Process Reduces Catalyst Coking
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Solution Overview
Problem
The formation of high molecular weight compounds and catalyst coking in the production of renewable diesel from renewable feedstocks, particularly those containing more than 5% free fatty acids, leads to reduced product quality and catalyst deactivation.
Innovation Solution
A process involving hydrogenation, decarboxylation, decarbonylation, and hydrodeoxygenation in a reaction zone with a liquid recycle stream before the first reactor, where the most reactive species are reacted initially to reduce maximum reaction temperatures and side reactions, using a low activity catalyst and high liquid hourly space velocity to minimize FFA and heavy molecule formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogenation, decarboxylation, decarbonylation, and hydrodeoxygenation are performed in a single reaction zone with high recycle ratio to process feedstocks containing more than 5% free fatty acids, then the conversion of free fatty acids is improved, but the formation of high molecular weight compounds and catalyst coking is significantly increased
Solution Approach 1:
The reaction zone is divided into two separate reactors: a first reactor for partial conversion and a second reactor for complete conversion. This segmentation allows the first reactor to handle the most reactive species (free fatty acids) at lower temperatures, reducing side reactions, while the second reactor completes the conversion at higher temperatures, thereby resolving the contradiction between conversion efficiency and harmful byproduct formation
Solution Approach 2:
The first reactor performs preliminary conversion of the most reactive species (free fatty acids) before the feed enters the second reactor. This preliminary action removes the most problematic components that cause coking and high molecular weight compound formation, allowing the second reactor to operate more efficiently with reduced harmful effects
2Productivity
If maximum reaction temperatures are used in the main reaction zone to improve conversion efficiency, then the productivity is improved, but side reactions leading to high molecular weight compound formation are increased
Solution Approach 1:
The reaction process is segmented into two temperature zones: the first reactor operates at lower temperatures for partial conversion, minimizing side reactions, while the second reactor operates at higher temperatures for complete conversion. This segmentation allows each reactor to operate at optimal temperatures for its specific function, resolving the contradiction between conversion efficiency and side reaction suppression
Solution Approach 2:
Different parts of the reaction system operate under different conditions: the first reactor uses lower temperatures and higher LHSV to minimize coking, while the second reactor uses higher temperatures to maximize conversion. This local differentiation of operating conditions allows each zone to optimize for its specific purpose, resolving the temperature-related contradiction
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 reduces catalyst coking, extends catalyst life, and improves product quality by limiting side reactions and heavy molecule formation, allowing the primary reactor to operate at higher temperatures with reduced FFA concentrations.
Implementation Method 1
hydrogenation, decarboxylation, decarbonylation, and/or hydrodeoxygenation in a reaction zone
Implementation Method 2
hydrogenation, decarboxylation, decarbonylation, and/or hydrodeoxygenation in a reaction zone
Implementation Method 3
hydrogenation, decarboxylation, decarbonylation, and/or hydrodeoxygenation in a reaction zone
Implementation Method 4
hydrogenation, decarboxylation, decarbonylation, and/or hydrodeoxygenation in a reaction zone
Implementation Method 5
a liquid recycle stream is used before the first reactor and/or bed where partial conversion takes palace
Data Source
AI summary
The invention relates to a method to reduce the formation of high molecular weight compounds and catalyst coking in the production of renewable diesel. Renewable diesel is produced using hydrogenation, decarboxylation, decarbonylation, and/or hydrodeoxygenation of renewable feedstocks such as animal and/or plant fats, oils, and/or greases (FOG). By first reacting the most reactive species in the FOG in an initial reaction zone prior to the main reaction zone, maximum reaction temperatures and side reactions that lead to the formation of high molecular weight compounds are reduced. This reduces catalyst coking (extends catalyst life) and improves product quality.