Three-Phase Reactor Selective Hydrogenation Thermal Control
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Solution Overview
Problem
The existing methods for selective hydrogenation of pyrolysis gasoline in fixed-bed reactors face challenges with thermal control of exothermic reactions, catalyst deactivation, and the need for frequent regeneration, leading to inefficiencies and increased costs.
Innovation Solution
The method involves performing selective hydrogenation in a three-phase reactor with a dispersed catalyst, where hydrogen is introduced in a gaseous phase with the liquid feedstock, allowing for better thermal control through quasi-isothermal operation and higher mean operating temperatures, reducing catalyst consumption, and eliminating the need for tempering boxes and secondary reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective hydrogenation is performed in a fixed-bed reactor, then the reaction can be carried out with a stationary catalyst bed, but thermal control of highly exothermic reactions becomes difficult leading to heat runaways and selectivity drops
Solution Approach 1:
The patent uses a slurry bubble column reactor where hydrogen gas is bubbled through a liquid slurry containing dispersed catalyst particles. This pneumatic-hydraulic system provides excellent heat and mass transfer, preventing thermal runaways while maintaining simple reactor structure without tempering boxes or complex internal configurations.
Solution Approach 2:
The patent changes the physical state of the catalyst from fixed-bed (stationary) to slurry phase (dispersed in liquid). This parameter change enables superior thermal control through the high heat capacity and heat transfer coefficient of the liquid phase, eliminating heat runaway problems while maintaining catalytic activity.
2Stress or pressure
If fixed-bed reactors are used with large catalyst diameters to limit pressure drops, then pressure control is improved, but diffusional limitations and catalyst deactivation increase
Solution Approach 1:
The patent uses fine catalyst particles (1-100 μm) dispersed in liquid slurry instead of large fixed-bed catalyst pellets. The liquid phase ensures uniform distribution and eliminates diffusional limitations within catalyst grains, while the slurry flow maintains low pressure drops. This resolves the contradiction between pressure control and catalyst activity stability.
Solution Approach 2:
The slurry bubble column reactor uses gas-liquid-solid three-phase flow to maintain catalyst particles in suspension. This hydraulic system ensures uniform catalyst distribution, eliminates channeling and hot spots, and maintains low pressure drops while preventing catalyst deactivation through continuous movement and fresh catalyst contact.
3Device complexity
If fixed-bed reactors operate with stationary catalyst beds, then reactor structure is simple, but catalyst regeneration requires shutdown and secondary reactors
Solution Approach 1:
The patent uses a dynamic slurry system where catalyst particles are continuously circulated between the reaction zone and regeneration zone. This dynamic configuration allows online catalyst regeneration without shutdown, maintaining continuous productivity while using a relatively simple reactor structure compared to dual fixed-bed systems.
Solution Approach 2:
The patent divides the catalyst system into separate reaction and regeneration zones that operate in parallel. The slurry circulates between these zones, allowing continuous catalyst regeneration. This segmentation enables continuous operation without requiring complex multi-reactor fixed-bed systems with alternating operation modes.
4Reliability
If tempering boxes and multiple reactors are used for thermal control and regeneration, then thermal stability and continuous operation are improved, but device complexity and operational costs increase
Solution Approach 1:
The slurry bubble column reactor uses gas-liquid-solid three-phase flow to achieve superior thermal control without tempering boxes. The high heat transfer coefficient of the bubbling slurry system prevents thermal runaways, maintaining thermal stability with a single simple reactor vessel and minimal internal components.
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 deolefination process, reduces catalyst consumption, and extends catalyst life, while providing better thermal management and flexibility in handling difficult feedstocks, thereby improving the overall efficiency and reducing operational costs.
Implementation Method 1
in the presence of a selective hydrogenation catalyst that is dispersed in the liquid phase
Implementation Method 2
selective hydrogenation of diolefinic components and alkenylaromatic components into monoolefins and corresponding alkylaromatic compounds
Data Source
AI summary
This invention has as its object a method for selective hydrogenation of a feedstock comprising a pyrolysis gasoline carried out in a three-phase reactor.