US20040060228A1

US20040060228A1 - Gasoline additive and method of making same

Info

Publication number: US20040060228A1
Application number: US10/260,755
Authority: US
Inventors: Kenneth Webber
Original assignee: Equistar Chemicals LP
Current assignee: Equistar Chemicals LP
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-01

Abstract

A gasoline additive composed of a plurality of isomers of at least one of dibutyloxide, dipentyloxide, and butylpetyloxide, methods of making same comprising reacting at least one monoolefin with at least one monoalcohol in the presence of an acid catalyst, and methods of using same.

Description

BACKGROUND OF THE INVENTION

This invention relates to an octane enhancing gasoline additive for a spark-induced internal combustion engine. It also relates to various methods for making said additive.

DESCRIPTION OF THE PRIOR ART

It is well known that certain hydrocarbons containing oxygen (oxygenates) can enhance (increase) the octane of spark-induced, internal combustion engine (automotive engine) gasoline when added thereto. Increasing the octane of a gasoline is also well known to enhance the performance of automotive engines.

Oxygenates also help improve the exhaust emission profiles of automotive engines. This is recognized by the Environmental Protection Agency, which requires up to 2 percent oxygen in automotive fuel in certain regions of the United States. Methyl-tert-butyl ether (MTBE) is widely employed as an oxygenate additive for automotive fuels for enhancing the octane number of a fuel, enhancing engine performance, and reducing undesired engine emissions such as NO _X, CO, and unburned fuel.

The term “octane” is meant to refer to either of Research Octane Number (RON) or Motor Octane Number (MON) which are based on isooctane as the standard with an octane number of 100. For example, regular automotive gasoline has an average octane number (RON/2 plus MON/2) of at least 87 and premium fuel an average octane number of at least 92.

The term “hydrocarbon” as used herein is meant to refer not only to an organic chemical molecule that contains hydrogen atoms and carbon atoms, but also such a molecule that may also contain oxygen atoms, as well. By this definition, certain classes of compounds such as alcohols (e.g., ethanol, butanol, etc.) and ethers (e.g., diethyl ether, dibutyl ether, etc.) are considered to be hydrocarbons.

Although widely employed as an oxygenate additive in automotive fuels, MTBE is quite soluble in water, and when dissolved in water in even low concentrations may impart to the water an odor and taste that people find objectionable. Some state governments are considering banning the use of MTBE in gasoline because of the potential for fugitive gasoline containing MTBE reaching water supplies, both surface and subsurface.

Ethanol has been suggested as a substitute for MTBE, but it has a vapor pressure greater than MTBE and can adversely impact the Reid Vapor Pressure of its host gasoline. Also, if ethanol contacts water after being blended into its host gasoline, it will be extracted into the water phase. This requires that ethanol be splash blended into gasoline at local gasoline distribution terminals rather than at the main gasoline blending facility.

Accordingly, it is desirable to find a substitute additive for MTBE that does not have the water solubility problem that MTBE has, and does not have the vapor pressure and blending problems that ethanol has.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided an oxygenate automotive gasoline additive which can serve as a substitute for MTBE and ethanol, and which does not suffer from the deficiencies of MTBE and ethanol as noted above.

The octane enhancing automotive gasoline additive of this invention contains a plurality of isomers of at least one of dibutyloxide, dipentyloxide, and butylpentyloxide.

The additives within this invention are not nearly as water soluble as MTBE. The additives are not as volatile as either MTBE or ethanol, and therefore, will not increase the Reid Vapor Pressure of their host gasoline. Further, the additives of this invention are much less water soluble than ethanol and will not require splash blending, but rather can readily be blended into the gasoline pool at the main blending facility.

This invention also provides a plurality of methods for using and making the additives of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Automotive gasolines are generally composed of a mixture of at least two hydrocarbon streams boiling at atmospheric pressure in a temperature 10 range of from about 77° F. to about 437° F. They typically are composed of mixtures of paraffins, aromatics, and olefins, and may contain numerous additives such as oxygenates, detergents, corrosion inhibitors, and the like. Currently gasolines suitable for use (combustion) in an automotive engine conform to the requirements of ASTM D4B14-89 specifications.

The additives of this invention contain a plurality (at least two) isomers of at least one of dibutyloxide (DBO), dipentyloxide (DPO), and/or butylpentyloxide (BPO).

Dibutyloxides (C4H90C4H9) include 2-2′ oxybisbutane [sec butyl ether] and both its stereo optical isomers (isomers), and oxybis(2,2 methylpropane) bis(2 butane) [sec-butyl-tert-butyl ether].

Dipentyloxides (C5H110C5H11) include 3,3′ oxybispentane[3 pentyl ether]; 3,2′ oxybispentane[3 pentyl, 2 pentyl ether]; 2,2′oxybispentane[2 pentyl ether]; oxybis(2,2 methylbutane)bis 2 pentane[2 pentyl isoamyl ether]; oxybis(2,2 methylbutane)bis 3 pentane[3 pentyl isoamyl ether]; and isomers thereof.

The additive(s) of this invention contain at least two, preferably more than two, of the foregoing compounds by themselves or in combination with other hydrocarbons suitable for use in an automotive engine. Such other hydrocarbons can be carriers for the additive of this invention, other additives for automotive gasoline, and the like.

The DBO, DPO, and BPO components of the additive(s) of this invention will tend to be less soluble in water than MTBE. Typically, as the number of carbon atoms increases in a homologous series of a particular species, e.g., dialkyl oxides, the water solubility decreases. For example, diethyl ether is shown to be slightly water soluble in “The Handbook of Chemistry and Physics” (Lide, David R, Editor-in-Chief, CRC Press, 1995). That same reference teaches that dibutyl ether is insoluble in water. Therefore, since the DBO, DPO and BPO molecules discussed in this invention all have more carbon atoms than does MTBE, one familiar with the art would anticipate the DBO, DPO and BPO molecules to be less soluble in water than is MTBE.

The additive(s) of this invention can individually contain at least one isomer from a plurality (two or more) of DBO, DPO, and BPO, and/or mixtures of 2 or more isomers of DBO, DPO, and/or BPO.

The additives of this invention can be blended in conventional manner with an automotive fuel to provide an automotive gasoline suitable for use (combustion) in a spark-induced, internal combustion engine. One or more additives of this invention will be blended into such gasolines in an effective octane enhancing amount, which amount will vary greatly depending on the particular composition of the host gasoline. Since gasoline is almost infinitely variable in its hydrocarbon make-up, it is impossible to quantify the amount of additive(s) to be employed other than to say the amount is sufficient to enhance the octane of the host gasoline. It can be also said that an effective amount of additive can be that which provides a measurable addition of oxygen to the host gasoline, preferably up to about two weight percent oxygen based on the total weight of the gasoline, or more if desired and economically feasible.

Accordingly this invention contemplates a method of operating and a method of enhancing the performance of an automotive engine by introducing into said engine an effective octane enhancing amount of at least one additive within this invention and/or an amount effective to make a measurable increase of oxygen in the gasoline used in said engine.

This invention also provides an automotive gasoline suitable for use in an automotive engine which contains an effective octane enhancing amount of at least one additive of this invention and/or an amount effective to provide a measurable increase of oxygen in the gasoline used in said engine.

This invention also includes a method for making automotive gasoline having an enhanced octane. Automotive fuels are normally made by blending or otherwise mixing a plurality, at least two, hydrocarbon-containing streams to produce an automotive gasoline as characterized hereinabove. Such blending produces a gasoline product that is suitable for combustion in an automotive engine as characterized hereinabove. Such blends can readily be made in or near an operating refinery in various ways well known in and obvious to the refining/blending art.

The additive of this invention can be prepared in a number of ways. One preferred approach to making the additive of this invention comprises providing a hydrocarbon stream containing at least in part at least one monoalcohol selected from the group having 4 and 5 carbon atoms per molecule (C4/C5 monoalcohol), and at least one monoolefin, either normal or branched, selected from the group having 4 and 5 carbon atoms per molecule (C4/C5 monoolefin), and reacting the at least one monoalcohol with the at least one monoolefin to form at least one of DBO, DPO, BPO to yield an additive containing in whole or in part a mixture of isomers of DBO, DPO and/or BPO.

Another preferred approach is to provide a hydrocarbon stream containing at least in part at least one, preferably a mixture, of C4/C5 monoolefins (normal and or branched) such as 1- or 2-butene, isobutylene, 1-, 2-, or 3-pentene, and isopentylene, and reacting a part of the monoolefins with water to form a monoalcohol while leaving a remainder of unhydrolyzed and unreacted monoolefin. Thereafter the monoalcohols are allowed to further react with at least a part of the remainder of the monoolefin to form at least one of DBO, DPO, and BPO. The product is an additive containing in whole or at least in part a rich mixture of octane enhancing isomers of DBO, DPO, and/or BPO.

It should be noted that when a mixture of molecules having four and five carbon atoms, e.g., monoolefins, is reacted with another mixture of molecules having four and five carbon atoms, e.g., monoalcohols, the resulting mixture of reaction products will contain not only isomers of DBO and DPO wherein the hydrocarbon chains on either side of the oxygen in a given molecule are the same in number, but also BPO wherein the hydrocarbon chains on either side of the oxygen in a given molecule are not the same in number. Examples of BPO reaction products useful in the additives of this invention are sec butyl 2 pentyl ether, sec butyl 3 pentyl ether, 2 pentyl tert butyl ether, sec butyl isoamyl ether, and the like.

The hydrolysis step described hereinabove can be carried out separately from the remaining reaction steps or can be carried out in the same mixture of reactants thus forming the alcohol reactant in situ in the original monoolefin mixture. When hydrolysis is carried out separately, a monoolefin mixture is hydrolyzed at least in part to the various monoalcohols corresponding to the monoolefins in the original mixture. Thereafter the hydrolysis reaction product mixture is reacted with normal monoolefins, iso-monoolefins, or a mixture of normal monoolefins and iso-monoolefins.

All the foregoing approaches for making the additives of this invention from the hydrolysis reaction through the final reactions that produce the desired isomers of DBO, DPO, and BPO can be carried out within the same range of reaction conditions using a catalyst or a number of catalysts from the same class of catalyst systems.

These reaction conditions are a temperature of from about 120 to about 250° F., a pressure of from about 25 to about 750 psig, a weight hourly space velocity of from about 0.25 to about 10 h ⁻¹(reciprocal hours), a mole ratio of monoolefin (normal or branched)/water of from about 0.4/1 to about 10/1, and a mole ratio of monoalcohol to iso-monoolefin of from about 0.25/1 to about 10/1.

The acid catalyst class is useful in the aforesaid reactions from hydrolysis through the final reactions that form the DBO, DPO and/or BPO products. The same acid catalyst can be used in all the reactions or different acid catalysts can be used in different reaction steps such as when hydrolysis is carried out physically separately. Suitable acid catalysts are well known and will be obvious to those skilled in the art, but generally will be acidic resins and acidic inorganic solids. Suitable specific catalysts include zeolites, amorphous silica aluminas, aluminophosphates (AIPO), silicoaluminophosphates (SAPO), metalloaluminophosphates (MeAPO) titanium aluminophosphates (TAPO), titanium silicophosphates (TASO), metallosilicoaluminophosphates (MeAPSO), silicas, aluminas, the acid form of ion exchange resins, and the acid form of perflourinated ion exchange resins.

When employing mixtures of C4/C5 monoolefins in the preparation of additives within this invention various refinery or petrochemical plant hydrocarbon streams can be used. Suitable streams include raffinate streams from ethylene stream cracking operations, isobutylene from tert-butyl alcohol dehydration, C4 streams from refinery catalytic cracking operations, and the like.

EXAMPLE 1

Five pounds per hour of a mixture of hydrocarbons comprising 36 weight % (wt%) normal 1- and 2-butenes, 44 wt % isobutylene, and 20 wt % normal and iso-butanes, all wt % based on the total weight of the mixture, are mixed with 0.7 pounds of water per hour in a reactor containing five pounds of an acid catalyst composed of sulfonic acid ion exchange resin. The reactor is operating at about 180° F. and about 500 psig. The weight hourly space velocity for the hydrocarbons is 1.0 and the weight hourly space velocity of the water is 0.14 h[0032] ⁻¹.
This process produces a reaction product containing 2.3 pounds of DBO; 1.3 pounds of incompletely reacted alcohols (tert butyl alcohol and sec butyl alcohol) which are separated and recycled to the reactor to complete their conversion into DBO; 0.8 pounds of unreacted normal and iso-butenes; and 1.0 pounds of normal and iso-butanes, 0.1 pounds unreacted water and 1.2 pounds of heavy by-product (mostly olefinic material with [0033] 8 carbon atoms per molecule).

EXAMPLE 2

A hydrocarbon stream consisting essentially of 1-butene and 2-butene is mixed at the rate of 3 pounds per hour with water at the rate of 1 pound per hour in the presence of 3 pounds of an acid catalyst composed of sulfonic acid ion exchange resin. The hydrolysis reactor operates at 190° F. and 500 psig, and produces a hydrocarbon stream product consisting essentially of sec butyl alcohol. This sec butanol stream is passed at the rate of 3 pounds/hour to an etherefication reactor which is at 160° F. and 500 psig, and contains 7 pounds of an acid catalyst composed of sulfonic acid ion exchange resin. A separate hydrocarbon mixture containing 44 wt. isobutylene and 36 wt % normal butene isomers, all wt % based on total weight of mixture, is passed at the rate of 5 pounds/hour into said etherefication reactor to mix and react with the sec butanol stream in the presence of the acid catalyst. The etherefication reactor produces a hydrocarbon stream comprising 50 wt % of a mixture of sec butyl ether (DBO) and sec butyl tert butyl ether (DBO), 10 wt % unreacted sec butanol, and 19 wt % of unreacted normal and iso-butenes (primarily n-butenes), all wt % based on total weight of the stream. This hydrocarbon stream is subjected to conventional distillation to separate the sec butanol and butenes. The sec butanol is returned to the etherefication reactor to form additional DBO. The distillation separated, unreacted normal butene isomers are returned to the hydrolysis reactor to form additional sec butanol. After the foregoing distillation operation, a DBO product remains which is composed of 26 wt % sec butyl ether and 61 wt % sec butyl tert butyl ether and 13 wt % heavy by-product (mostly olefinic material with 8 carbon atoms per molecule), all wt % based on the total weight of the DBO product. [0034]
Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention. [0035]

Claims

I claim:

1. An octane enhancing gasoline additive for combustion in a spark-induced, internal combustion engine, said additive consisting essentially of a plurality of isomers of at least one of dibutyloxide, dipentyloxide, and butylpentyloxide.

2. The additive of claim 1 wherein said additive consists essentially of at least one of a) at least one isomer of dibutyloxide, b) at least one isomer of dipentyloxide, and c) at least one isomer of butylpentyloxide.

3. The additive of claim 1 wherein said additive consists essentially of a mixture of isomers of dibutyloxide, dipentyloxide, and butylpentyloxide.

4. The additive of claim 3 wherein said additive consists essentially of at least one isomer of each of two or more of dibutyloxide, dipentyloxide, and butylpentyloxide.

5. In a method for operating a spark-induced, internal combustion engine, the improvement comprising introducing into said engine an effective octane enhancing amount of at least one additive of claim 1 or 3.

6. A method for making a gasoline having an enhanced octane for use in a spark-induced, internal combustion engine comprising mixing at least two hydrocarbon streams that boil in the range of from about 77° F. to about 437° F., and blending with said hydrocarbon streams at least one additive of claim 1 or 3.

7. The method of claim 6 wherein said additive is blended with said hydrocarbon streams in an effective octane enhancing amount.

8. The method of claim 7 wherein said effective octane enhancing amount is an amount sufficient to impart to said hydrocarbon stream mixture a measurable increase in oxygen content.

9. A method for making an octane enhancing gasoline additive suitable for use in a spark-induced, internal combustion engine comprising providing a hydrocarbon suitable for combustion in said engine which contains at least in part at least one monoolefin from the group having 4 and 5 carbon atoms per molecule and, hydrolyzing part of at least one of said monoolefin in the presence of an acid catalyst to the corresponding monoalcohol, leaving a remainder of unreacted monoolefins, reacting a portion of said monoalcohol with the remainder of said monoolefin in the presence of an acid catalyst to form a product containing at least one of dibutyloxide, dipentyloxide, and bulylpentyloxide, thereby rendering said hydrocarbon suitable for use as said gasoline additive.

10. The method of claim 9 wherein said monoolefin is at least one selected from the group consisting of 1-butene, 2-butene, iso-butene, 1-pentene, 2-pentene, iso-pentene and said corresponding monoalchol is at least one selected from the group consisting of normal butyl alcohol, sec butyl alcohol, isobutyl alcohol, normal pentyl alcohol, sec pentyl alcohol, and isopentyl alcohol.

11. The method of claim 9 wherein unreacted olefin is separated from said product and returned to said hydrolyzing step to form additional monoalcohol.

12. The method of claim 9 wherein the same acid catalyst is employed for all said reaction steps.

13. The method of claim 10 wherein said reaction steps are each carried out at a temperature of from about 120 to about 250° F., a pressure of from about 25 to about 750 psig, a weight hour space velocity of from about 0.25 to about 10 h⁻¹, a mole ratio of monoolefin to water of from about 0.4/1 to about 10/1, a mole ratio of monoalcohol to monoolefin of from about 0.25/1 to about 10/1, and a catalyst selected from the group consisting of acidic resins and acidic inorganic solids.

14. A method for making an octane enhancing gasoline additive suitable for use in a spark-induced, internal combustion engine comprising providing a hydrocarbon suitable for combustion in said engine which contains at least in part at least one monoalcohol selected from the group having 4 and 5 carbon atoms per molecule, and at least one iso-monoolefin selected from the group having 4 and 5 carbon atoms per molecule, reacting said at least one monoalcohol with said at least one iso-monoolefin in the presence of an acid catalyst to form at least one of dibutyloxide, dipentyloxide, and butylpentyloxide, whereby a mixture of isomers of same is formed in said hydrocarbon.

15. The method of claim 14 wherein said monoalcohol is at least one selected from the group consisting of normal butyl alcohol, sec butyl alcohol, iso-butyl alcohol, normal pentyl alcohol, sec pentyl alcohol, and iso-pentyl alcohol, and said at least one iso-monoolefin is at least one selected from the group consisting of iso-butylene and iso-pentylene.

16. The method of claim 14 wherein said reaction is carried out at a temperature of from about 120 to about 200° F., a pressure of from about 25 to about 750 psig, a weight hour space velocity of from about 0.25 to about 10 h⁻¹, a mole ratio of monoalcohol to iso-monoolefin of from about 0.25/1 to about 10/1, and a catalyst selected from the group consisting essentially of acidic resins and acidic in organic solids.

17. The method of claim 14 wherein said at least one monoalcohol is formed by first hydrolyzing at least part of said at least one monoolefin.

18. A method for making an octane enhancing gasoline additive comprising providing a mixture of at least one normal monoolefin, at least one iso-monoolefin, and at least one monoalcohol, and reacting same in the presence of an acidic catalyst to form at least one isomer of dibutyloxide, dipentayloxide, and butylpentyloxide.

19. The method of claim 18 wherein said at least one monoalcohol is formed by first hydrolyzing at least part of said at least one monoolefin.

20. A method for making an octane enhancing gasoline additive comprising providing a mixture of at least one normal monoolefin selected from the group having 4 and 5 carbon atoms per molecule, and at least one normal monoalcohol selected from the group having 4 and 5 carbon atoms per molecule, and reacting said monoolefin and monoalcohol in the presence of an acid catalyst to form at least one isomer from a plurality of dibutyloxide, dipentyloxide, and butylpentyloxide.

21. The method of claim 20 wherein said at least one monoalcohol is formed by first hydrolyzing at least part of said at least one monoolefin.

22. An automotive gasoline suitable for use in a spark-induced, internal combustion engine containing an effective octane enhancing amount of at least one additive of claim 1 or 3.

23. In a method for enhancing the performance of a spark-induced, internal combustion engine, the improvement comprising introducing into said engine an effective octane enhancing amount of at least one additive of claim 1 or 3.