Processes and systems for separate, parallel methane and higher alkanes' bromination
Process and systems for alkane bromination and, in one or more embodiments, to separate, parallel methane and higher alkanes bromination in a bromine-based process. An embodiment discloses a bromine-based process for converting alkanes to liquid hydrocarbons that includes alkanes bromination, the process comprising: brominating a methane stream comprising methane and having less than about 2 mol % of ethane to form methane bromination products comprising brominated methane and a first fraction of hydrogen bromide; separately brominating a C2+ alkane stream comprising an alkane having 2 or more carbon atoms to form C2+ methane bromination products comprising brominated alkanes having 2 or more carbon atoms and a second fraction of hydrogen bromide; and catalytically reacting at least a portion of the brominated methane and the brominated alkanes to form higher molecular hydrocarbons.
1. A bromine-based process for converting alkanes to liquid hydrocarbons that includes alkane bromination, the process comprising:
brominating a methane stream comprising methane and having less than about 2 mol % of ethane to form methane bromination products comprising brominated methane and a first fraction of hydrogen bromide;
separately brominating a C2+ alkane stream comprising an alkane having 2 or more carbon atoms to form C2+ methane bromination products comprising brominated alkanes having 2 or more carbon atoms and a second fraction of hydrogen bromide; and
combining and catalytically reacting at least a portion of the brominated methane and the brominated alkanes to form higher molecular hydrocarbons.
2. The process of claim 1 wherein the step of brominating the methane stream occurs at a temperature of greater than about 400° C.
3. The process of claim 1 wherein the step of separately brominating the C2+ alkane stream occurs at a temperature in a range of about 250° C. to about 450° C.
4. The process of claim 1 wherein the step of brominating the methane stream occurs at a temperature in a range of from about 490° C. to about 570° C., and wherein the step of separately brominating the C2+ alkane stream occurs at a temperature in a range of about 250° C. to about 375° C.
5. The process of claim 1 wherein bromination of the methane stream results in selectivity to mono-bromomethane for the brominated C1 alkanes of at least about 90 mol %.
6. The process of claim 1 wherein the methane-to-bromine ratio in the step of brominating the methane stream is at least about 2.5:1, and wherein the C2+ alkane-to-bromine ratio in the step of brominating the C2+ alkane stream is in a range of about 1.33:1 to about 2.5:1.
7. The process of claim 1 wherein the step of separately brominating a C2+ alkane stream comprises:
separately brominating an ethane stream comprising ethane to form an ethane bromination stream comprising brominated ethane and a third fraction of hydrogen bromine; and
separately brominating a C3+ alkane stream comprising propane and butane to form the C2+ methane bromination product stream, the brominated alkanes having 2 or more carbon atoms comprising brominated propane and brominated butane.
8. The process of claim 7 wherein the ethane stream comprises alkanes having 3 or more carbon atoms in an amount of less than about 1 mol %.
9. The process of claim 7 wherein residence times in a methane bromination reactor for the step of brominating the methane stream are in a range of from about 15 seconds to about 60 seconds, residence times in an ethane bromination reactor for the step of brominating the ethane stream are in a range of from about 15 seconds to about 45 seconds, and residence times in a C3+ bromination reactor the step of brominating the C3+ alkane stream are in a range of from about 15 seconds to about 45 seconds.
10. The process of claim 1 wherein the C2+ alkane stream comprises propane and butane, and wherein ethane is separated from the methane stream and C2+ alkane stream for use as a fuel.
11. The process of claim 1 wherein the higher molecular weight hydrocarbons comprise hydrocarbons having 5 or more carbon atoms.
12. The process of claim 1 comprising deriving elemental bromine from the first, second, and third fractions of hydrogen bromide, wherein the elemental bromine is recycled for use in the step of brominating the methane stream and brominating the C2+ alkane stream.
13. The process of claim 1 wherein the step of deriving elemental bromine comprises adsorbing the first, second, and third fractions of hydrogen bromide into an aqueous stream and oxidizing the resulting stream to form the elemental bromine.
14. The process of claim 1 further comprising separating the C2+ alkane stream from a stream comprising the higher molecular hydrocarbons.
15. A bromine-based process for converting alkanes to liquid hydrocarbons that includes alkane bromination, the process comprising:
brominating a methane stream in a bromination reactor to form methane bromination products comprising brominated methane and a first fraction of hydrogen bromide, the methane stream comprising methane and having less than about 1 mol % of ethane and less than about 0.10 mol % of hydrocarbons having 3 or more carbon atoms;
separately brominating a C2+ alkane stream in a C2+ bromination reactor to form C2+ methane bromination products comprising brominated alkanes having 2 or more carbon atoms and a second fraction of hydrogen bromide, the C2+ alkane stream comprising ethane, propane, and butane; and
combining and catalytically reacting at least a portion of the brominated methane and the brominated alkanes in a synthesis reactor to form higher molecular weight hydrocarbons and a third fraction of hydrogen bromide.
16. The process of claim 15 further comprising:
feeding a feed gas stream and an effluent stream from the synthesis reactor into an HBr removal unit, the feed gas stream comprising lower molecular weight hydrocarbons, the effluent stream comprising the higher molecular weight hydrocarbons and the first, second, and third fractions of hydrogen bromide;
recovering methane from the HBr removal unit and recycling at least a portion of the methane to the bromination reactor via the methane stream;
recovering ethane and propane from the HBr removal unit and recycling at least a portion of the ethane and propane to the C2+ bromination reactor via the C2+ bromination stream;
recovering a liquid product stream from the HBr removal unit, the liquid product stream comprising hydrocarbons having 4 or more carbon atoms; and
recovering an HBr stream from the HBr removal unit, the HBr stream comprising the first, second, and third fractions of hydrogen bromide.
17. The process of claim 16 further comprising oxidizing the HBr stream to form elemental bromine and recycling the elemental bromine to the bromination reactor and the C2+ bromination reactor.
18. The process of claim 15 wherein the step of brominating the methane stream occurs at a temperature in a range of from about 490° C. to about 570° C., wherein the step of separately brominating the C2+ alkane stream occurs at a temperature in a range of about 250° C. to about 375° C., wherein bromination of the methane stream results in selectivity to mono-bromomethane for the brominated alkanes of at least about 90 mol %, wherein the methane-to-bromine ratio in the step of brominating the methane stream is at least about 2.5:1, and wherein the C2+ alkane-to-bromine ratio in the step of brominating the C2+ alkane stream is in a range of about 1.33:1 to about 2.5:1.
19. The method of claim 1 further comprising processing the higher molecular weight hydrocarbons to at least one product selected from the group consisting of a gasoline grade fuel, a diesel grade fuel, and a fuel additive.
20. The method of claim 1 wherein the higher molecular weight hydrocarbons comprise C2 and C3 olefins.