Field enhanced separation of hydrocarbon fractions

Abstract

Systems and methods are provided for using field enhanced separations to produce multiple fractions from a petroleum input. A liquid thermal diffusion and/or electric field separation is used to produce the fractions. The fractions can then be used to form multiple outputs that share a first feature while being different with regard to a second feature. For example, a first fraction from the plurality of fractions can have a desired value for a first property such as viscosity index. Two or more additional fractions from the plurality of fractions can then be blended together to make a blended fraction or output. The blended fraction can have a value for the first property that is substantially similar to the value for the first fraction. However, for a second property, the first fraction and the blended fraction can have distinct values. As a result, multiple output fractions can be formed that share a first feature but differ in a second feature.

What is claimed is: 
     
         1 . A method for separating a lubricant boiling range feedstock, comprising:
 passing a feedstock with an initial boiling point of at least 200° C. into a gap between a first surface and a second surface in a thermal diffusion separator;   performing thermal diffusion separation by maintaining the feedstock in the gap with a temperature differential between the first surface and the second surface of at least 5° C. for a residence time;   withdrawing a plurality of fractions from the thermal diffusion separator including a first fraction, a second fraction, and a third fraction, the first fraction having a first value for a first property and a second value for a second property; and   blending at least a portion of the second fraction and at least a portion of the third fraction to form a blended fraction, the blended fraction having a third value for the first property that differs from the first value by 2.5% or less and a fourth value for the second property that differs from the second value by at least 5.0%.   
     
     
         2 . The method of  claim 1 , wherein the plurality of fractions are withdrawn from the thermal diffusion separator at a plurality of heights, the second fraction being withdrawn at a height greater than a height for the first fraction and the third fraction being withdrawn at a height lower than the height for the first fraction. 
     
     
         3 . The method of  claim 1 , wherein the first property is viscosity index, viscosity at 100° C., viscosity at 40° C., pour point, cloud point, weight percentage of sulfur, weight percentage of nitrogen, or weight percentage of aromatics. 
     
     
         4 . The method of  claim 1 , wherein the second property is product volume, viscosity index, viscosity at 100° C., viscosity at 40° C., pour point, cloud point, oxidation stability, deposit tendency, Noack volatility, weight percentage of sulfur, weight percentage of nitrogen, or weight percentage of aromatics. 
     
     
         5 . The method of  claim 1 , wherein the plurality of fractions further comprises a fourth fraction, the fourth fraction being withdrawn from the thermal diffusion separator at a location between the first fraction and the third fraction. 
     
     
         6 . The method of  claim 5 , wherein the blended fraction is a non-contiguous blend fraction. 
     
     
         7 . The method of  claim 1 , wherein maintaining the feedstock in the gap for a residence time comprises flowing feedstock through the gap in a continuous manner, the residence time corresponding to a time required for the feedstock to flow across a length of the gap. 
     
     
         8 . The method of  claim 1 , wherein the feedstock is a lubricant boiling range feedstock with a T5 boiling point of at least 350° C. and a final boiling point of 600° C. or less. 
     
     
         9 . The method of  claim 1 , wherein the feedstock is maintained in the gap in the presence of an electric field. 
     
     
         10 . The method of  claim 9 , wherein the electric field varies spatially. 
     
     
         11 . A method for separating a lubricant boiling range feedstock, comprising:
 passing a feedstock with a T5 boiling point of at least 350° C. into a gap between a first surface and a second surface in a thermal diffusion separator;   performing thermal diffusion separation by maintaining the feedstock in the gap with a temperature differential between the first surface and the second surface of at least 5° C. for a residence time;   withdrawing a plurality of fractions from the thermal diffusion separator including a first fraction, a second fraction, a third fraction, and a fourth fraction withdrawn from a height between the first fraction and the third fraction, the first fraction having a first value for a first property; and   blending at least a portion of the second fraction and at least a portion of the third fraction to form a blended fraction, the blended fraction excluding at least a portion of the fourth fraction, the blended fraction having a second value for the first property that differs from the first value by 2.5% or less,   wherein a yield of product for a combination of the first fraction plus the blended fraction is greater than a yield for a contiguous blend of fractions from the plurality of fractions that has a value for the first property that differs from the first value by 2.5% or less.   
     
     
         12 . The method of  claim 11 , wherein the first property is viscosity index, viscosity at 100° C., viscosity at 40° C., pour point, cloud point, weight percentage of sulfur, weight percentage of nitrogen, or weight percentage of aromatics. 
     
     
         13 . The method of  claim 11 , wherein the blended fraction excludes the fourth fraction. 
     
     
         14 . A system for performing hydroprocessing comprising:
 a separation volume formed by a first surface and a second surface aligned to face each other and define a separation volume width of the separation volume, the separation volume having a separation volume height defined by a top surface and a bottom surface and a separation volume length, the separation volume width being from 0.25 mm to 6.0 mm, the separation volume height being at least 0.25 m, and a ratio of the separation volume width to the separation volume height being less than 500;   one or more heating elements configured to maintain the first surface at a temperature;   one or more first electrodes associated with the first surface and one or more second electrodes associated with the second surface;   an input manifold in fluid communication with the separation volume; and   a plurality of output channels in fluid communication with the separation volume, the plurality of output channels being at two or more different heights relative to the height of the separation volume.   
     
     
         15 . The separation unit of  claim 14 , wherein the first surface and the second surface are parallel planar surfaces or wherein the first surface and the second surface define a closed path. 
     
     
         16 . The separation unit of  claim 14 , further comprising one or more additional heating elements to maintain the second surface at a temperature. 
     
     
         17 . The separation unit of  claim 14 , wherein the first surface comprises a surface of a non-reactive layer in thermal contact with a bulk material. 
     
     
         18 . The separation unit of  claim 17 , wherein the non-reactive layer comprises polyethyl ether ketone. 
     
     
         19 . The separation unit of  claim 14 , further comprising at least one adjustable spacer, the separation volume width being determined based on a width of the at least one adjustable spacer. 
     
     
         20 . The separation unit of  claim 14 , wherein the plurality of output channels comprise channels corresponding to at least three different heights relative to the height of the separation volume.