Propylene Selectivity via Catalyst Regeneration
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Solution Overview
Problem
The production of propylene through propane dehydrogenation is hindered by the need for high temperatures, which leads to catalyst deactivation due to coking and fouling, and requires additional heating that results in non-selective cracking and increased maintenance costs.
Innovation Solution
A process that recirculates partially coked catalyst through a regenerator at high velocity, where it is heated to at least 575°C by combustion of coke and supplemental fuel, eliminating the need for a charge heater and reducing thermal residence time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fuel fired charge heaters are used to provide additional heat for dehydrogenation, then the reaction temperature is maintained, but fouling or coking of the charge heater tubes occurs and propylene yield is lost due to non-selective cracking
Solution Approach 1:
The invention removes the charge heater from the system entirely. Instead of heating the feedstock before it enters the reactor, the catalyst itself is heated in a regenerator and then circulated to provide heat directly in the reactor. This extraction of the charge heater eliminates the source of fouling and coking while maintaining the necessary reaction temperature through catalyst-to-feed heat transfer.
Solution Approach 2:
The catalyst serves as an intermediary heat transfer medium. It is heated in the regenerator by combustion of regeneration gases and then circulated to the reactor where it transfers heat to the propane feedstock. This mediator approach allows heat transfer without direct contact between the heating source and the feedstock, eliminating thermal residence time and non-selective cracking.
2Productivity
If high temperature is used to proceed dehydrogenation reaction at satisfactory rate, then reaction rate is improved, but catalyst deactivation due to coking occurs
Solution Approach 1:
The catalyst undergoes periodic cycles of dehydrogenation in the reactor followed by regeneration in the regenerator. During regeneration, coke deposited on the catalyst is burned off, restoring catalyst activity. This periodic regeneration allows the catalyst to maintain high activity over extended periods despite operating at high temperatures that would otherwise cause permanent deactivation.
Solution Approach 2:
The catalyst is temporarily discarded from the reactor when it becomes coked and deactivated, transferred to the regenerator where it is recovered through combustion of the deposited coke. This recovery process restores the catalyst to its active state, allowing it to be reused in the dehydrogenation reaction.
3Use of energy by moving object
If thermal residence time in heater and heater transfer line is extended, then heating is sufficient, but non-selective cracking occurs and propylene yield is lost
Solution Approach 1:
The invention replaces the mechanical heating system (charge heater with tubes and transfer lines) with a catalyst-based heat transfer system. The heated catalyst particles directly contact the feedstock in the reactor, providing rapid and efficient heat transfer without the need for extended thermal residence time in separate heating equipment. This eliminates the conditions that lead to non-selective cracking.
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 increases catalyst circulation rate, improves propylene selectivity by up to 5 wt%, and reduces fouling and coking issues, while maintaining sufficient reaction temperature without the need for additional heating equipment.
Implementation Method 1
The catalyst and regeneration gases pass through the regenerator at a velocity of at least 1.2 m/s (4 ft/sec) in the regenerator. The regeneration gases burn off coke deposited on the catalyst. In addition, supplemental fuel is added to continue heating the catalyst to a temperature sufficient to provide the energy for the dehydrogenation reaction.
Implementation Method 2
The reaction is strongly endothermic, and requires a high temperature for the reaction to proceed at a satisfactory rate.
Data Source
AI summary
A process for catalyst regeneration is presented. The process regenerates a catalyst in a paraffin dehydrogenation process, where the reaction is endothermic. The regeneration process provides the heat for the process through heating the catalyst and removes the need for a charge heater to the dehydrogenation reactor, which in turn eliminates high temperature thermal residence time which eliminates thermal cracking of the feed and improves the overall product selectivity. In addition, plot area, equipment costs and operating complexity are reduced.