Solvent Dewaxing Near Miscibility Limit
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Solution Overview
Problem
Conventional solvent dewaxing methods are limited by low dewaxing rates due to the inability to pass the oil phase through filters without disrupting the wax filter cake or damaging the membrane, and the formation of additional liquid phases can reduce dewaxed oil yield and filtration efficiency.
Innovation Solution
Operating with a dewaxing solvent mixture that is beyond the miscibility limit, specifically a combination of ketone solvents like methyl ethyl ketone and toluene, allows for increased dewaxing rates and reduced pour point differences, facilitating higher filtration temperatures and oil recovery by forming a solvent-rich phase that aids in phase transport through the wax cake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional miscible solvents are used for dewaxing, then filtration can be performed without disrupting the wax filter cake, but the dewaxing rate is limited due to inability to pass oil phase through filter quickly
Solution Approach 1:
The patent changes the miscibility parameter of the solvent system by using a partially immiscible solvent combination (e.g., n-heptane and methyl ethyl ketone) where the solvents are immiscible or partially miscible with each other. This parameter change allows the formation of a solvent-rich phase that can transport oil through the filter cake more effectively, increasing dewaxing rate while maintaining filter cake integrity through proper phase separation.
2Productivity
If partially immiscible solvent is used to increase dewaxing rate, then filtration speed improves, but additional third oil phase forms causing decrease in filtration rate and increase in oil content in wax
Solution Approach 1:
The patent optimizes the composition ratio of the partially immiscible solvent system to control phase formation. By adjusting the proportions of immiscible solvents (e.g., n-heptane and methyl ethyl ketone in specific ratios), the system achieves sufficient phase separation to transport oil effectively while minimizing the formation of excessive third phases that would trap oil in the wax product.
Solution Approach 2:
The patent creates different local phases within the filtration system: a solvent-rich phase for oil transport, a wax-rich phase for separation, and controls the interface between phases. This local quality differentiation allows the solvent-rich phase to move oil through the filter cake while the wax-rich phase maintains separation efficiency, preventing excessive oil content in the wax product.
3Productivity
If conventional solvent systems are used, then wax separation is effective, but the difference between filtration temperature and pour point is large reducing processing efficiency
Solution Approach 1:
The patent changes the solvent system composition to partially immiscible solvents, which alters the phase behavior and temperature characteristics of the dewaxing process. This parameter change reduces the temperature difference between filtration and pour point by creating a solvent-rich phase that maintains better solubility characteristics at filtration temperature, thereby improving processing efficiency.
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 significantly enhances dewaxing rates and reduces the difference between filtration and pour points of the dewaxed oil, enabling higher processing volumes and improved oil yield while maintaining or improving wax separation efficiency.
Implementation Method 1
mixing a dewaxing solvent comprising a first solvent and a second solvent with a feedstock to form a dewaxing mixture; performing solvent dewaxing on the dewaxing mixture to form dewaxed oil and wax cake
Implementation Method 2
forming a solvent-rich phase that aids in phase transport through the wax cake
Data Source
AI summary
Systems and methods are provided for performing solvent dewaxing using a dewaxing solvent that is not fully miscible with the feed being dewaxed. It has been unexpectedly discovered that by operating with a ketone solvent mixture that is beyond the miscibility limit by a small amount, the rate of solvent dewaxing can be substantially increased. Additionally, the difference between the filtration temperature during solvent dewaxing and the pour point of the resulting dewaxed product is unexpectedly reduced. The dewaxing solvent beyond the miscibility limit can correspond to, for example, a solvent mixture where the weight percent of methyl ethyl ketone is beyond the miscibility limit by 0.1 vol % to 5.0 vol %.