Propylene Sulfate Ester Alkylation Process
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Solution Overview
Problem
Conventional sulfuric acid-catalyzed alkylation of propylene is inefficient due to slow reaction rates and excessive oligomerization, leading to high energy consumption and maintenance-intensive processes, particularly in converting propylene into gasoline range components.
Innovation Solution
A process involving the formation of propylene sulfate esters by contacting a propylene and propane stream with sulfuric acid, followed by reaction with isobutane in an alkylation zone to produce C7 and C8 alkylate products, while maintaining specific temperature and acid ratios to minimize heavies formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sulfuric acid-catalyzed alkylation is used to convert propylene into gasoline range components, then the process can produce alkylate products, but the reaction rate is slow and excessive oligomerization occurs leading to high energy consumption and maintenance-intensive operations
Solution Approach 1:
The process is divided into two distinct reaction zones: a first reaction zone where propylene is absorbed by sulfuric acid to form propylene sulfate esters, and a second reaction zone where the propylene sulfate esters react with isobutane to form alkylate. This segmentation allows optimization of each zone for its specific function, improving overall reaction efficiency while controlling unwanted oligomerization.
Solution Approach 2:
The patent introduces an intermediate compound, propylene sulfate ester, formed by the absorption of propylene by sulfuric acid in the first reaction zone. This intermediate then serves as the actual alkylating agent in the second reaction zone, rather than using free propylene directly. This intermediary mechanism accelerates the reaction rate and reduces oligomerization by controlling the reactivity of the propylene derivative.
2Reliability
If sulfuric acid is used to absorb propylene for alkylation, then the alkylation reaction can proceed, but the absorbed propylene is very stable and reacts slowly with isobutane
Solution Approach 1:
The patent performs preliminary conversion of propylene to propylene sulfate ester in the first reaction zone before the alkylation step. This preliminary action transforms the stable absorbed propylene into a more reactive intermediate that will subsequently react faster with isobutane in the second reaction zone, thus resolving the contradiction between stability and reactivity.
Solution Approach 2:
The patent changes the chemical state of propylene from absorbed form to sulfate ester form, altering its reactivity parameters. The propylene sulfate ester has different chemical properties compared to absorbed propylene, enabling faster reaction with isobutane while maintaining process reliability through controlled transformation.
3Productivity
If conventional alkylation processes are used, then gasoline components can be produced, but high energy use and acid regeneration are required due to heavy compound buildup
Solution Approach 1:
The patent extracts and removes the problematic heavy compounds (oligomers and polymers) at the outlet of the first reaction zone before they can cause acid deactivation and require regeneration. By taking out these harmful byproducts early in the process, the sulfuric acid maintains its catalytic activity longer, reducing energy consumption for acid regeneration and improving overall gasoline production efficiency.
Solution Approach 2:
The patent converts the potentially harmful absorption of propylene by sulfuric acid, which normally leads to stable but unreactive complexes, into a beneficial process by controlling the absorption to form specific sulfate ester intermediates. These intermediates are then easily converted to desired alkylate products, turning what was previously a source of problems into an advantageous reaction pathway that reduces energy consumption.
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 promotes propylene alkylation with isobutane, reducing oligomerization and polymerization, thereby increasing gasoline production efficiency and providing a cost-effective alternative for 'stranded' refiners, while also utilizing spent sulfuric acid effectively.
Implementation Method 1
contacting a stream comprising propylene and propane with sulfuric acid in a first reaction zone under conditions to form propylene sulfate esters
Implementation Method 2
contacting the propylene sulfate esters with isoparaffin and sulfuric acid in an alkylation reaction zone under conditions to react the propylene sulfate esters and the isoparaffin to form a reactor effluent comprising an acid phase and a hydrocarbon phase comprising unreacted isoparaffin and alkylate product
Data Source
AI summary
A process for alkylation of propylene, the process including: contacting a stream comprising propylene and propane with sulfuric acid in a first reaction zone under conditions to form propylene sulfate esters; contacting the propylene sulfate esters with isoparaffin and sulfuric acid in an alkylation reaction zone under conditions to react the propylene sulfate esters and the isoparaffin to form a reactor effluent comprising an acid phase and a hydrocarbon phase comprising unreacted isoparaffin and alkylate product; separating the hydrocarbon phase from the sulfuric acid; separating the hydrocarbon phase to form a fraction comprising unreacted isoparaffin and a fraction comprising the alkylate product.