Dual-Stage Bio-Based LPG Synthesis for Lower CO2 Loss
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Solution Overview
Problem
Existing methods for synthesizing liquefied petroleum gas (LPG) from bio-based sources face challenges such as high loss of valuable synthesis gas components like H2, CO, and CO2, significant energy costs in hydrogen recycling, and inefficiencies in the conversion process, which hinder high LPG yields.
Innovation Solution
A dual-stage process involving an oxygenate synthesis reaction zone and an oxygenate conversion reaction zone, using specific catalysts like SSZ-13, to convert bio-based synthesis gas into LPG while recycling unreacted components efficiently, minimizing losses through liquid and solid absorption zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional recycling processes are used to recycle hydrogen from exit gas, then hydrogen can be recovered and reused, but significant energy costs are incurred due to recompression
Solution Approach 1:
The patent extracts and removes hydrogen from the exit gas stream using a membrane separator before recycling. This extraction approach allows hydrogen to be separated and recovered without requiring energy-intensive compression of the entire gas stream, thereby reducing the energy cost while maintaining effective hydrogen recovery
Solution Approach 2:
The patent introduces a membrane separator as an intermediary device between the reactor and the recycle stream. This intermediary component enables selective hydrogen permeation and separation, facilitating hydrogen recovery without direct compression of the bulk gas, thus resolving the contradiction between recovery efficiency and energy consumption
2Productivity
If conventional processing is used, then synthesis gas can be converted to LPG, but over 10% of the carbon introduced as reaction feedstock is produced as carbon dioxide representing a waste of valuable carbon monoxide
Solution Approach 1:
The patent modifies the reaction parameters by introducing a two-stage process with specific temperature zones and catalyst configurations. This parameter optimization shifts the reaction pathways to favor LPG formation over CO2 generation, thereby maintaining high productivity while reducing carbon monoxide loss
Solution Approach 2:
The patent employs composite catalyst systems in the two-stage process that combine multiple functional components. These composite catalysts are designed to promote selective hydrocarbon formation while suppressing unwanted CO2 production, enabling high LPG yields with minimized carbon monoxide waste
3Productivity
If a dual-stage process with catalysts like SSZ-13 is used, then LPG yields are improved and losses of synthesis gas components are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the synthesis process into two distinct stages with different catalysts and operating conditions. This segmentation allows each stage to be optimized for specific reactions, improving overall LPG yield while managing complexity through modular design where each stage can be independently controlled and maintained
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 achieves high LPG yields with reduced losses of H2, CO, and CO2, optimizing the recovery of valuable reaction byproducts and minimizing environmental impact.
Implementation Method 1
reacting a blended bio-based synthesis gas comprising CO, CO2 and H2 in an oxygenate synthesis reaction zone containing an oxygenate synthesis catalyst and forming a first effluent containing oxygenates
Implementation Method 2
reacting at least a portion of the first effluent in an oxygenate conversion reaction zone containing an oxygenate conversion catalyst and forming a second effluent comprising C2− hydrocarbons, bio-based LPG, and C5+ hydrocarbons
Implementation Method 3
removing C3+ hydrocarbons from a third effluent by contacting at least a portion of the third effluent with a liquid absorption solvent in an absorption zone, absorbing C3+ hydrocarbons from the third effluent
Implementation Method 4
removing light gases, including C2− hydrocarbons, CO, and CO2, from a fourth effluent by contacting at least a portion of the fourth effluent with a solid adsorbent for adsorbing at least a portion of the light gases
Data Source
AI summary
A method is provided for synthesizing bio-based LPG from renewable sources via a bio-based synthetic gas feedstock, in a dual-stage reaction system comprising an oxygenate synthesis reaction zone and an oxygenate conversion reaction zone that are configured for producing and converting a methanol intermediate for reduced CO2 selectivity. The method includes recovering LPG from either the full reaction zone effluent or from a purge stream separated from the full reaction zone effluent for LPG recovery.