Boiling free fractionation of hydrocarbon streams utilizing a membrane cascade

Patent metadata

Field	Value
Publication number	US-2019367820-A1
Application number	US-201916423736-A
Country	US
Kind code	A1
Filing date	May 28, 2019
Priority date	Jun 1, 2018
Publication date	Dec 5, 2019
Grant date	—

Abstract

Methods and systems are provided herein utilizing a membrane cascade to separate a hydrocarbon feed into boiling point fractions. Also provided herein are methods for selecting membranes for said cascades to achieve the desired boiling point fraction separation.

First claim

1 . A process for fractionating a hydrocarbon stream into boiling point fractions, comprising:
providing a hydrocarbon stream; selecting a first stage membrane effective to separate a hydrocarbon feed into a first stage permeate and a first stage retentate; wherein the heaviest molecule in the first stage permeate has a boiling point in the kerosene boiling range; selecting a second stage membrane effective to separate a hydrocarbon feed into a second stage permeate and a second stage retentate; wherein the heaviest molecule in the second stage permeate has a boiling point in the diesel boiling range; selecting a third stage membrane effective to separate a hydrocarbon feed a third stage permeate and a third stage retentate; wherein the heaviest molecule in the third stage permeate has a boiling point in the gas oil boiling range; selecting a fourth stage membrane effective to separate a hydrocarbon feed into a fourth stage permeate and a fourth stage retentate; wherein the heaviest molecule in the fourth stage permeate has a boiling point in the naphtha boiling range; and feeding the hydrocarbon stream to one of the first, second, third, or fourth stage membranes under effective separation conditions; feeding the applicable stage permeate and retentate to either a downstream refinery process or to another membrane stage; and repeating the preceding act until each of the first, second, third, and fourth stage membranes has performed a separation on the hydrocarbon stream, permeate from a previous membrane stage, or retentate from a previous membrane stage.

2 . The process of claim 1 , wherein the selecting a membrane for any of the stages comprises:
obtaining compositional data of the hydrocarbon stream; said compositional data comprising one or more of API gravity, average molecular weight, aromaticity, average boiling point, density, total sulfur and nitrogen content, pour point, viscosity, metal content, total acid number (TAN), reid vapor pressure, Micro Carbon Residue content, C7 asphaltenes content, paraffin-naphthene-aromatic content, carbon to hydrogen ratio, and STAR-7 analysis; determining a desired diffusion of molecules through the membrane; selecting a membrane based on a relationship:

Diffusion



of



molecules

∝

kT

6

π



viscosity
*
Radius


function




(

Radius
,
MW

)

where k is the Boltzmann constant, T is temperature for separation, viscosity is the viscosity of the feed, radius is the radius of each molecule in the feed, and MW is the molecular weight of each molecule in the feed;
wherein determining the relationship comprises;
obtaining a hydrocarbon feed of known composition;
obtaining a membrane;
performing a separation experiment by contacting the hydrocarbon feed of known composition with the membrane thereby forming a control permeate and a control retentate;
analyzing the control permeate and the control retentate via one of simulated distillation, elemental analysis, and STAR7 analysis;
establishing at least one parameter unique to the membrane as an input to the function(Radius, MW).

3 . The process of claim 2 , wherein the relationship is based on the relationship:

Diffusion



of



molecules

∝

kT

6

π



viscosity



(

1
Radius

)

a



(

1
MW

)

b




or



Diffusion



of



molecules

∝

kT

6

π



viscosity
*
Radius



(

1
-

Radius
PoreRadius

)

a



(

1
MW

)

b

wherein PoreRadius is the pore size of the membrane, wherein a and b are the parameters unique to the membrane and are established via the relationship a, b∝function(MWCO).

4 . The process of claim 3 , wherein function(MWCO) is

1
MWCO

.

5 . The process of claim 1 , wherein the first stage membrane has a MWCO from about 100-500 Daltons.

6 . The process of claim 1 , wherein the first stage membrane separates via a reverse osmosis modality, a nanofiltration modality, or a combination thereof.

7 . The process of claim 1 , wherein the second stage m

Assignees

• Exxonmobil Res & Eng Co

Inventors

• Mccool Benjamin A
• Bhandari Dhaval A
• Joshi Yogesh V

Classifications

• B01D69/02

  characterised by their properties · CPC title

• C10G31/00 Primary

  Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for (by distillation C10G7/00) · CPC title

• B01D61/025

  Reverse osmosis; Hyperfiltration · CPC title

• C10G2400/06

  Gasoil · CPC title

• B01D2325/20

  Specific permeability or cut-off range · CPC title