Sulfate Ester Formation for Alkylation Feedstock Purification
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Solution Overview
Problem
Existing alkylation processes in petroleum refining face challenges with the buildup of non-reactive C3-C5 n-alkanes, which require significant fractionation energy for removal, and often include inert aromatic compounds, necessitating a process to decrease the concentration of inert alkanes in alkylation feedstocks.
Innovation Solution
A process involving the contact of alkylation feedstocks with sulfuric or hydrofluoric acid to form sulfate esters or alkyl fluorides, followed by separation of n-alkanes and iso-alkanes from the acid and ester or fluoride products, with acid concentrations maintained below 75 weight percent to facilitate efficient separation and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional alkylation processes are used with high concentration sulfuric acid, then alkylation reaction efficiency is improved, but significant fractionation energy is required to remove non-reactive n-alkanes
Solution Approach 1:
The patent applies preliminary action by converting olefins to sulfate esters before the main alkylation reaction. This pre-treatment step selectively transforms reactive olefins into sulfate esters that can be easily separated from non-reactive n-alkanes, avoiding the need for energy-intensive fractionation later in the process
Solution Approach 2:
The patent changes the chemical state parameter of olefins by converting them to sulfate esters through reaction with sulfuric acid. This parameter change enables selective separation based on chemical properties rather than requiring energy-intensive physical fractionation based on boiling points
2Reliability
If high concentration sulfuric acid is used for alkylation, then catalyst activity is improved, but separation of n-alkanes from acid and products becomes more difficult
Solution Approach 1:
The patent performs preliminary conversion of olefins to sulfate esters before separation. This pre-treatment creates a distinct chemical form that separates easily from n-alkanes, solving the separation difficulty that would otherwise result from using high concentration sulfuric acid
Solution Approach 2:
The sulfate ester acts as an intermediary form between the olefin and the final alkylate product. This intermediate compound has properties that facilitate easy separation from n-alkanes while maintaining the benefits of high concentration sulfuric acid catalysis
3Device complexity
If conventional single-step alkylation is used, then process simplicity is maintained, but inert alkanes accumulate requiring considerable fractionation energy
Solution Approach 1:
The patent segments the alkylation process into two distinct steps: (1) olefin conversion to sulfate esters, and (2) alkylation reaction. This segmentation allows for selective removal of n-alkanes after the first step, preventing their accumulation and reducing the energy required for fractionation in the second step
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 effectively decreases the concentration of inert alkanes, reduces energy requirements, and enhances alkylation unit efficiency by allowing for increased reactor throughput and lower separation costs, while also providing a beneficial use for spent acid.
Implementation Method 1
contacting at least a portion of the alkylation feedstock with sulfuric acid in a reaction zone under conditions to form sulfate esters of the olefins
Implementation Method 2
separating the n-alkanes and the iso-alkanes from the sulfuric acid and the sulfate esters
Data Source
AI summary
A process for treating an alkylation feedstock comprising olefins, n-alkanes, and iso-alkanes, the process including: contacting at least a portion of the alkylation feedstock with sulfuric acid in a reaction zone under conditions to form sulfate esters of the olefins; separating the n-alkanes and the iso-alkanes from the sulfuric acid and the sulfate esters; recovering the n-alkanes and the iso-alkanes in a first product stream; and recovering the sulfate esters in a second product stream; wherein the sulfuric acid has a strength titrating as below 75 weight percent H2SO4/water mixtures.