Boiling free fractionation of hydrocarbon streams utilizing a membrane cascade

Patent metadata

Field	Value
Publication number	US-11084985-B2
Application number	US-201916423736-A
Country	US
Kind code	B2
Filing date	May 28, 2019
Priority date	Jun 1, 2018
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

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

The invention claimed is:

1. A process for fractionating a liquid hydrocarbon stream into boiling point fractions, comprising:
providing a liquid hydrocarbon stream;
selecting a first stage membrane effective to separate a liquid 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 liquid 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 liquid 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 liquid 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 liquid hydrocarbon stream to one of the first, second, third, and 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 liquid hydrocarbon stream, permeate from a previous membrane stage, or retentate from a previous membrane stage; and
wherein the selecting a membrane for any of the stages comprises:
obtaining compositional data of the liquid 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 of diffusion of molecules through membrane based on temperature, viscosity of the feed, molecular weight and size/radius of molecules;
wherein determining the relationship comprises;
obtaining a liquid hydrocarbon feed of known composition;
obtaining a membrane;
performing a separation experiment by contacting the liquid 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 START analysis; and
establishing at least one parameter unique to the membrane as an input to relationship of diffusion of molecules on temperature, viscosity, molecular weight and size/radius of molecules.

2. The process of claim 1 , wherein the relationship of diffusion of molecules through the membrane 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 of a, b to Molecular Weight Cut Off (MWCO) of the membrane.

3. The process of claim 2 , wherein the relationship of a, b to MWCO is

∝

1
MWCO

.

4. The process of claim 1 , wherein the first stage membrane has a Molecular Weight Cut Off from about 100-500 Daltons.

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

6. The process of claim 1 , wherein the second stage membrane has a Molecular Weight Cut Off from about 500-2000 Daltons.

7. The process of claim 1 , wherein the second stage membrane separates via a nanofiltration modality, an ultrafiltration modality, or a combination thereof.

8. The process of claim 1 , wherein the third stage membrane has a Molecular Weight Cut Off from about 2-500 kDaltons, a pore size from 1.5-20 nm, or a combination thereof.

9. The process of claim 1 , wherein the third stage membrane has a Molecular Weight Cut Off from about 2-300 kDaltons.

10. The process of claim 1 , wherein the third stage membrane has a Molecular Weight Cut Off from ab

Assignees

• Exxonmobil Res & Eng Co

Inventors

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

Classifications

• B01D61/029

  Multistep processes comprising different kinds of membrane processes selected from reverse osmosis, hyperfiltration or nanofiltration · CPC title

• B01D61/362

  Pervaporation · CPC title

• C10G53/02

  plural serial stages only · CPC title

• B01D69/02

  characterised by their properties · CPC title

• B01D2317/08

  Use of membrane modules of different kinds · CPC title