AU685564B2

AU685564B2 - Use of tertiary-hexyl methyl ether as a motor gasoline additive

Info

Publication number: AU685564B2
Application number: AU13387/95A
Authority: AU
Inventors: Dan Eldon Hendriksen
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1993-12-15
Filing date: 1994-12-13
Publication date: 1998-01-22
Anticipated expiration: 2014-12-13
Also published as: EP0734429B1; SG67335A1; DE69427133D1; WO1995016763A1; JPH09506660A; AU1338795A; CA2178955A1; DE69427133T2; EP0734429A1

Description

WO 95/16763 PCT/US94/14234 -1- USE OF TERTIARY-HEXYL METHYL ETHER AS A MOTOR GASOLINE

ADDITIVE

This invention relates to the use of one isomer of tertiary-hexyl methyl ether, which is 2-methoxy-2,3-dimethylbutane, as an octane booster in motor gasoline.

Generally, any component that has a research octane number over 105 and a motor octane number over 95 is considered to be an octane booster for use in motor gasoline. It is well known in the art that ethers made from C 4 and C 5 olefins are excellent octane boosters. Methyl tertiarybutyl ether (MTBE) made from isobutene, a C 4 olefin, has a research octane number (RON) of 118 and a motor octane number (MON) of 100; and tertiary-amyl methyl ether (TAME) produced from C 5 olefins has a RON of 111 and a MON of 98 according to Unzelman, Oil Gas Journal, Volume 44, April 15, 1991.

It is also well known that these ethers have a higher octane booster number than their counterpart olefins. "Physical Constants of Hydrocarbon and Non-Hydrocarbon Compounds" ASTM data series publication DS 4B, 1991 states that the octane numbers for one of the parent olefins of TAME, 2-methyl-2-butene, is 97 for the RON and 82 for the MON. Etherification of this C 5 olefin increases the octane numbers to 111 for the RON and 98 for the MON. While the art teaches that ethers produced from C 4 and C olefins are excellent octane boosters, it teaches away from the use of ethers produced from C 6 and heavier olefins.

For example, in Pescarollo et al.'s article, "Etherify light gasolines", Hydrocarbon Processing, February 1993, pp 53-60, he states that ethers derived from C 6 and heavier olefins do not significantly enhance octane over the parent olefins".

Also, US-A-4,193,770, and its equivalent, DE-A-2,854,250 (1979) teaches that the octane numbers of the C 6 ethers are no higher than those of the parent olefins mixed with the same amount of methanol. The blending octane numbers for tertiary-hexyl methyl ether which is produced from a C 6 olefin are reported as being 100 for the RON and 90 for the MON, but no mention is made of any specific isomers, including 2-methoxy-2,3dimethylbutane (MDMB). Hence, there is no recognition or teaching that MDMB is effective as an octane booster. The reported numbers serve to WO 95/16763 PCTIUS94/14234 -2teach away from investigating the performance of ether produced from C 6 or

C

7 olefins.

This reference teaches the importance of etherifying C 4 and C olefins separately from each other because of the different reaction kinetics.

Also stressed is the importance of keeping each of these fractions separate from the C 6 olefin fraction, which forms tertiary hexyl methyl ether, because there is no improvement in octane rating as compared to the ethers from the

C

4 and C 5 olefins. The reference goes as far as saying that any reported increases in octane rating for ethers from C 6 and C 7 olefins, are "illusory".

See column 3, lines 5 to 13 and 26 to 37.

This reference sets up a major prejudice against using C 6 ethers as motor gasoline octane boosters. And there is absolutely no mention of

MDMB.

MICROLOG-88-03391 from Energy Res. Abstr., 13(22), Abstr. No.

5031, 1988, also teaches against the use of ethers produced from C 6 olefins in that "predictions for C 6 ethers were not carried out because there was virtually no improvement in octane number when compared with its precursors".

EP-A-0 036 260, discloses the use of ethers produced from a mixture of C 4 through C 7 olefins as components in a motor gasoline blend from a refinery catalytic cracker unit, with 7% being C 6 olefins, but reinforces the belief that the octane booster effect is due to the ethers produced from C 4 and C 5 olefins rather than those ethers produced from C 6 or C 7 olefins.

It would be desirable if ethers produced from C 6 olefins could be used as motor octane boosters. Current market predictions indicate that there will be a glut of propylene, which could be used to make C 6 olefins, in the market place within the next ten years. Currently, propylene is sent to the motor gasoline pool from refinery catalytic crackers, but the propylene does not boost the octane. It would be very profitable if one could determine a way to convert propylene into an octane booster.

SUMMARY OF THE INVENTION This invention relates to using an octane boosting amount of a tertiary hexyl methyl ether component comprising 2-methoxy-2,3-dimethyl butane (MDMB) which enables providing a blend comprising WO 95/16763 PCTIUS94/14234 -3motor gasoline or motor gasoline feedstock; and an octane boosting amount of a tertiary hexyl methyl ether component comprising 2-methoxy-2,3-dimethyl butane (MDMB) in an amount of at least 10% by weight based on the total weight of tertiary hexyl methyl ether, wherein composition has a Research Octane Number (RON) and/or a Motor Octane Number (MON) greater than those of composition One embodiment includes providing a blend wherein the tertiary hexyl methyl ether component of composition comprises in various amounts and ranges, including, greater than 10%, preferably from 20 to 100%, more preferably greater than 50%, even more preferably from 60% to 100%, and most preferably greater than 80% by weight of MDMB.

Another embodiment i lcludes providing a blend wherein composition contains greater than 50%, preferably from 60% to 100%, and more preferably greater than 80%, by weight of the tertiary hexyl methyl ether.

Yet another embodiment includes providing a method of increasing the octane number in motor gasoline comprising blending MDMB with the motor gasoline or with a motor gasoline feedstock to boost the octane number of the motor gasoline or motor gasoline feedstock which contains a sufficient amount of composition to boost the octane number of component by at least 1, preferably by at least 2, and more preferably by at least 3 units.

Still another embodiment includes the use of a tertiary hexyl methyl ether component comprising MDMB and having a blending RON greater than 100 and a blending MON greater than 90, as an octane booster for motor gasoline.

The tertiary hexyl methyl ether component comprising MDMB may be prepared by dimerizing propylenes and additional embodiments of the present invention include a blend wherein composition is made by a process comprising: dimerizing propylene to form dimethylbutenes; and (ii) etherifying the dimethyl butenes with methanol, to form the desired composition and/or a blend.

Additionally, another embodiment includes the further treatment wherein step (ii) comprises partial etherification and is followed by (iii) -s WO 95/16763 WO 9516763PCTIIJS94/1 4234 -4hydrogenation of unetherified dimethylbutenes to form a tertiary hexyl methyl ether composition comprising MD)MB and dimethyl butanes.

DETAILED DESCRIPTION OF THE INVENTION Not all c the isomers of tertiary-hexyl methyl ether produced from C 6 olefins, are suitable for use as octane boosters. The four isomers of tertiaryhexyl methyl ether (C 6

H

1 3

-OCH

3 are as follows: 1) 2-Methoxy-2,3-dimethylbutane (MMB)

CH

3

CH

3

CH

3 -CH C-OCH 3 GCl 3 2) 2-Methoxy-2-methylpentane (2MMI')

CH

3 GCl 3

-CH

2 -Gil 2 C OCH- 3 Gil 3 3) 3-Methoxy-3-methylpentane (3MMP)

OCH

3

GH

3

GH

2 -C -CH 2 Gil 3 Gil 3

I

WO 95/16763 WO 9516763PCTJUS94/1 4234 4) 1-Methoxy-1-methylcyclopentane (MMCP)

CH

2

CH

2

CI

2

CIT

2

C

OCH

3

CH

3 1-Methoxy-1-methylcyclopentane (MMCP) is considered an isomer of tertiary-hexyl-methyl ether even though it has two fewer hydrogen atoms.

One isomer of tertiary-hexyl methyl ether has been found to be a very useful high octane booster for use in motor gasoline. That particular isomer is 2-methoxy-2,3-dimethylbutane (MDM).

MDMIB may be prepared from propylene and methanol by first dimerizing the propylene to dimethylbutenes (2,3-dimethyl)-(1 and/or 2)butene), and then by etherifying the dimethylbutenes with methanol, as shown in the following reaction equations. Both 2,3-dimethyl-l-butene and 2,3-dimethyl-2-butene react with methanol to form the desired product ether.

CIT

3

CIT

3

CH

3 CH CH 2 4 CH 3 CHI- C CH.

2 propylene 2,3-dimethyl-l-butene

CIT

3

CH

3

CH

3 -CH C =CH 2

+CH

3 0H 4 2,3-dimethyl-I-butene methanol (DM13)

CIT

3

CIT

3 I I C1 3 -CH C-OCH 3

CH

3 2-methoxy-2,3dimethylbutane

(MDM[B)

U~~l WO 95/16763 PCT/US94/14234 -6- Olefin dimerization and codimerization processes are known in the art. The propylene may be dimerized to dimethylbutenes (DMB) using a tungsten catalyst, such as that disclosed in U.S. Patent 5,059,739. The dimethylbutenes (DMB) may also be produced using nickel with specific organo-phosphine ligands.

In the event, the tungsten catalyst is used, the ratio of olefin to tungsten should be such that a catalytic amount of the tungsten complex is used. The reaction may be run in either a batch or a continuous manner.

The reaction pressure is normally the pressure generated by the olefin at the reaction temperature, although the pressure may be increased with an inert gas. The reaction temperature may range, for example, from about 40 to 100P C, with 50 to C being preferred. The reaction or residence time may be, for example, from 5 minutes to about 3 hours, with 0.5 to 2.0 hours being preferred. The preferred embodiment uses a catalyst which is prepared by taking a tungsten salt and an aniline to form a complex of the tungsten salt and aniline. Substantially all of the hydrogen chloride produced in this reaction is removed from the solution during the course of the reaction.

After formation of the tungsten and aniline complex, an alkyl aluminum halide is added to the solution to form the active catalyst system of the invention. The preferred feedstock is refinery grade propylene, after sufficient removal of water and other catalyst poisons.

The etherification of the dimethylbutenes with methanol to prepare MDMB may take place in a manner similar to the preparation of methyl tertiary-butyl ether (MTBE) from isobutylene or the preparation of tertiaryamyl methyl ether (TAME) from isoamylenes. The reaction takes place over the acid form of an ion exchange resin.

The present invention involves the feeding of a mixture containing DMB and methanol into the feed zone of a reactor a fixed-bed guard reactor), and contacting the resultant mixture of DMB and methanol with a fixed bed acidic cation exchange resin Amberlyst@ 15) in the reaction zone, thereby catalytically reacting the DMB with the methanol under conditions which favor forming the resultant 2-methoxy-2,3-dimethylbutane

(MDMB).

Where the etherification step of the present invention is practiced in a catalytic distillation process, the catalytic material may be in any form which l WO 95/16763 PCT/US94/14234 -7permits its incorporation into a distillation tower, such as a fixed bed, but may also be in a form which serves as a distillation packing, for example, rings, saddles, balls, irregular pieces, sheets, tubes, spirals, packed in bags, plated on grills or screens, and reticulated polymer foams.

Catalysts which have been found to be suitable for use in the etherification step of the present invention are resin catalysts such as cation exchange resin catalysts, acidic resin catalysts, macroreticular sulfonic acid cation exchange resin catalysts, and solid acid catalysts. Still others have used a zeolite as an etherification catalyst. Preferred catalysts for purposes of the present invention, however, are acid catalysts, such as acidic resin catalysts.

A more preferred catalyst for purposes of the present invention is a macroreticular sulfonic acid cation exchange resin such as a sulfonated copolymer of polystyrene-divinyl-benzene. Such catalysts include Amberlyst 15 and 15C (marketed by Rohm and Haas), Lewatit SPC 118 and SPC 118 BG (marketed by Miles/Bayer), and Dowex M-31 and M-32 (marketed by the Dow Chemical A special version of this type of catalyst, Dowex DR-2040 (marketed by the Dow Chemical is used specifically for reactive distillation.

It has been found that equilibrium conversion to ether is only 50-60%, so it is expected that catalytic distillation will be advantageous in the etherification step. Catalytic distillation is commercially practiced in the production of MTBE and this process has be.n extensively explored with TAME. Therefore, there is every reason to expect that catalytic distillation would be advantageous when applied to the process for producing ethers from C 6 olefins.

When the ether is produced from a C 6 olefin which has been formed by dimerizing propylene, the composition of the resulting mixture of isomers may be as pure as 98 wt% MDMB, 2 wt% 2MMP, with negligible amounts of 3MMP and MMCP. When the C 6 olefin is produced in a refinery catalytic cracker, the isomer mixture is different, with more than 50% being 2MMP and approximately 7% being MDMB.

It is well known in the art that ethers are used as motor gasoline additives to enhance the quality of the motor gasoline due to environmental regulations, both existing and pending in the USA. By using an oxygenate rather than its counter part olefin in motor gasoline, less carbon monoxide pollution is produced upon combustion of the motor gasoline. Also, the rules WO 95/16763 PCT/US94/14234 -8regulating reformulated gasoline, which is a particular type of motor gasoline, require that a lower olefin content be present in the gasoline due to the fact that olefins contribute to ozone formation more than their counter part ethers. An additional advantage of using the ether rather than the olefin in motor gasoline is that the ether has a lower Reid vapor pressure, which reduces evaporative emissions which contribute to pollution.

The addition of the MDMB to the motor gasoline or motor gasoline feedstock to boost the octane may be accomplished in several ways. One method includes the preparation of a blend comprising the mixture of two compositions, and wherein composition consists of the motor gasoline or motor gasoline feedstock which is blended with composition (b) which comprises an octane boosting amount of a tertiary hexyl methyl ether component comprising 2-methoxy-2,3-dimethyl butane (MDMB) in an amount of at least 10% by weight based on the total weight of tertiary hexyl methyl ether, wherein the composition has a Research Octane Number (RON) and/or a Motor Octane Number (MON) greater than those of composition In addition to the tertiary hexyl methyl ethers and the MDIMB, composition may include other components. These additional 2 0 components may be any other hydrocarbons typically found in motor gasoline or motor gasoline feedstocks, including, but not limited to, aromatics, olefins, and saturates.

These additional hydrocarbons may or may not be considered useful as octane boosters. In the case where the other hydrocarbons are useful as octane boosters, composition may include either MTBE or TAME, or mixtures thereof.

Composition may have a RON greater than 95, preferably greater than 100, and/or a MON greater than 85, preferably greater than Optionally composition has a blending RON greater than 100, preferably greater than A.5 and/or a blending MON greater than preferably greater than The tertiary hexyl methyl ether component of composition may comprise greater than 10%, preferably from 20 to 100%, by weight of MDMB. Optionally, this tertiary hexyl methyl ether component of composition may comprise from 50 to 100%, preferably greater than by weight of MDMB.

I -I 96LKR618.DOC -9- The tertiary hexyl methyl ether component may have a RON greater than 100 and/or a MON greater than 90. Optionally, this tertiary hexyl methyl ether component may have a blending RON greater than 100 and/or a blending MON greater than The MDMB component of composition may have a RON greater than 105 and/or a MON greater than 95. Optionally, the MDMB component may have a blending RON greater than 105 and/or a blending MON greater than The resulting blend may have a RON greater than 90, preferably greater than 93, and/or a MON greater than 80, preferably greater than 83.

A sufficient amount of composition must be blended with composition such that the octane number of component is boosted by at least 1, preferably by at least 2, and more preferably by at least 3 units. The resulting blend may which comprise greater than preferably greater than and most preferably greater than 5 by volume of MDMB.

In addition to its use as an octane booster, MDMB has the added benefit of not significantly increasing the Reid vapor pressure (RVP) of the motor gasoline blend as is typical with other octane boosters, such as MTBE or

TAME.

For example, MTBE has a blending RVP of 57.9 kPa (8.4 psi) and 20 TAME has a blending RVP of 27.6 kPa (4.0 psi), both of which are higher than that of MDMB being 6.9 kPa (1 psi).

When the starting motor gasoline feedstock has a high RVP level, one could be limited on how much MTBE or TAME addition is possible to achieve the required octane requirements, while at the same time, not exceeding the 25 RVP limit.

Therefore, an additional embodiment of the present invention includes the use of more than one octane booster to achieve the maximum octane boosting effect and without the corresponding undesirable increase in RVP.

For example, one could make a blend comprising the addition of MTBE and/or TAME up to the maximum RVP limit of the motor gasoline product as set by an environmental standard. Then, MDMP, either alone or in mixture with the tertiary hexyl methyl ether, could be blended into the motor gasoline to achieve on even higher octane number without incurring any increase in the RVP of the final blend of motor gasoline.

RAi!, 'V Ix a I 1 WO 95/16763 PCT/US94/14234 One embodiment of the invention includes a blend which contains a sufficient amount of composition to boost the octane number of component by at least 1, while at the same time increasing the Ieaid vapor pressure of component by less than 13.8 kPa (2 psi), preferably by less than 6.9 kPa (1 psi), and more preferably by less than 3.4 kPa (0.5 psi).

The MDMB may be prepared using a process comprising (i) dimerizing propylene to form dimethylbutenes and (ii) etherifying the dimethyl butenes with methanol. Optionally, wherein step (ii) comprises partial etherification, the process may further comprise the additional step of (iii) hydrogenation of the unetherified dimethylbutenes to form a tertiary hexyl methyl ether composition comprising MDMB and dimethyl butanes.

Composition may contain dimethylbutenes and may also contain less than 1% methanol and/or less than 5% olefins. Composition may contain greater than 50%, preferably from 60% to 100%, and more preferably greater than 80%, by weight of the tertiary hexyl methyl ether.

By blending the prepared MDMB, with a motor gasoline or motor gasoline feedstock, the octane number of the blended gasoline may be increased by 1 or more units, preferably 2 or more units, and most preferably 3 or more units, over the original octane number of the motor gasoline or motor gasoline feedstock.

The foregoing invention will now be illustrated by, although not limited to, the following examples.

EXAMPLES

EXAMPLE I 2-MMP Comparative Example This comparative example illustrates that not all ethers produced from

C

6 olefins are useful as octane boosters.

An ion exchange resin in the acid form (Amberlyst R15, washed with methanol) was added to a 5000 mL round-bottom flask along with 1000 g of 2-methyl-l-pentene and 416 g methanol. The slurry of resin catalyst was stirred magnetically and refluxed at atmospheric pressure for 16 hours. In the refluxing process, the material boils at atmospheric pressure and condenses the vapors back into the boiling material. The resin catalyst was 96LKR618.DOC 11 filtered from the product mixture, and then unconverted methanol and methyl pentenes were distilled away from the product ether (2MMP). The unconverted materials were placed back in the reaction flask with the resin catalyst and refluxed again for another 16 hours. This procedure of reaction followed by removal of product ether was repeated three times. This was desirable in order to achieve good conversion of the starting material since the etherification reaction is equilibrium limited. The product ether was distilled again (boiling point 112 0 C) to yield product purity of 99.4% by GC analysis.

The octane numbers and Reid vapor pressure results were measured using the standard test methods well known in the art. The Research Octane Number (RON) was 88.3 and the Motor Octane Number (MON) was approximately 90. The precise MON could not be measured as the fuel/air ratio was set at the highest setting available on the test engine. In the standard test procedure, the fuel/air ratio is continually increased until maximum knock is obtained. The Reid vapor pressure was 8.6 kPa (1.25 psi).

These results are consistent with the reported octare numbers for ethers of C 6 olefins, and support the industry view (for example, as expressed in US- A-4,193,770) that such ethers are not useful as octane boosters for motor gasoline.

EXAMPLE I MDMB the Invention This example of the invention illustrates that one of the ethers produced 25 from C 6 olefins, specifically MDMB, is useful as an octane booster.

2-Methoxy-2,3-dimethyl butane (MDMB) was prepared from 2,3dimethyl-2-butene (2112 g) and methanol (879 g) in a similar manner as described for preparation of 2MMP in Example I. The product had a boiling point of 115 0 C and a product purity of 98.2% 2-methoxy-2,3-dimethylbutane with the balance being 2-methoxy-2-methyl pentane from 2-methylpentene impurity in the starting material. The Research Octane Number measured for this MDMB rich product was 108.1 and the Motor Octane Number was 96.8.

The Reid vapor pressure was 7.3 kPa (1.06 psi).

i-J' j 96LKR618.DOC -12- Analysis of Examples I and II The octane numbers from Examples I and II along with those of C 4 and

C

5 olefins are reproduced below in a table format for easy comparison.

Parent Olefin Ether RON MON C MTBE 118 100

C

5 TAME 111 98

C

6 MDMB 108.1 96.8 2MMP 88.3 approximately One can see that unexpectedly, and contrary to the prejudice arising from the prior art investigation of C 6 olefin ether, MDMB has RON and MON values which make it surprisingly good as an octane booster for motor gasoline.

EXAMPLE mI In addition to the component RON, MON, and Reid vapor pressure (RVP) numbers being determined, a set of corresponding blending values for MDMB was also ascertained. As it is well known to one of ordinary slcdl in the 15 art, the "blending" RON, MON, and RVP values vary based upon the base gasoline composition. Typically, the "Blending Values" (BV) are higher for RON and MON and are slightly lower for RVP.

Blends of approximately 14, 19, and 25% volume MDMB/volume gasoline, as synthesized in Example II, were prepared using two different 20 gasolines, A and B, as described below.

Gasoline A Gasoline B RON 93 97 MON 83 87 RVP, kPa 50.3 (7.3 psi) 53.8 (7.8 psi) The resulting RON, MON, and Reid vapor pressure numbers were measured for each of the blends with the following results.

sc ro a r r 1

I-

-c WO 95/16763 PCTI/S94/14234 -13- Gasoline MDMB RON MON RVP RVP Vol Blend Blend Blend, Blend, kPa psi A 13.8 95.6 85.2 45.5 6.6 A 18.7 96.3 85.8 43.4 6.3 A 24.3 97.3 87.0 37.9 Average A 96.4 86.0 42.1 6.1 B 14.2 98.8 88.2 42.7 6.2 B 19.2 99.4 88.8 46.2 6.7 B 24.9 99.9 89.6 40.7 5.9 Average B 99.4 88.7 43.4 6.3 The values of the blend were then used in the following manner to calculate the properties of the finished blend. RVP is used as an example.

VOL gasoline VOLMDMB R -end RVP gasoline BV RVP MDMB VOL gasoline VOL MDMB VOL gasoline VOL MDMB Even though this equation is not 100% accurate for calculating octane numbers, as the RON and MON do not blend linearly, it can be used to predict octane within 1 number for the narrow range of blends investigated.

This example illustrates that the blending values for the properties of MDMB for the RON and MON are somewhat higher with an average of 110 and 97 respectively, and the RVP is somewhat lower at 6.9 kPa (1 psi), which is typical, as compared to the component values for the RON, MON, and RVP of the MDMB component, which were 108, 97, and 7.3 kPa (1.06 psi) respectively. Also shown for reference are the typical blending values for MTBE, 10% ethanol and 12% TAME.

-I-1 WO 95/16763 PCT/JS9.1/14234 -14- COMPONENT RON BV MON BV RVP BV MDMB with 112 98 1 Gasoline A MDMB with 109 96 1 Gasoline B MTBE 117 98 8.4 ETHANOL 115 96 22 TAME 106 94 224 One can see that the blending RON and MON values of MDMB are comparable to those of MTBE, ethanol, and TAME, which makes MDMB attractive as an octane booster for motor gasoline. MDMB's low blending RVP value makes it especially attractive as an octane booster in comparison to MTBE, ethanol, and TAME, as it does not carry a high RVP debit as is typically associated with the other octane boosters.

Claims

1. A blend comprising motor gasoline or motor gasoline feedstock; and an octane boosting amount of a tertiary hexyl methyl ether component comprising 2-methoxy-2,3-dimethyl butane (MDMB) in an amount of at least 10% by weight based on the total weight of tertiary hexyl methyl ether, wherein the composition has a Research Octane Number (RON) and/or a Motor Octane Number (MON) greater than those of composition

2. A blend according to Claim 1, wherein the composition has a RON greater than 95 and/or a MON greater than

3. A blend according to Claim 1 or 2, wherein the composition has a RON greater than 100 and/or a MON greater than

4. A blend according to any one of the preceding claims, wherein the composition has a blending RON greater than 100 and/or a blending MON greater than 4 A blend according to any one of the preceding claims, wherein the composition has a RON greater than 105 and/or a MON greater than

6. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component of composition comprises greater than by weight of MDMB.

7. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component of composition comprises from 20 to 100% by weight of MDMB. 0,' 4 16

8. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component of composition comprises from 50 to 100% by weight of MDMB.

9. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component of composition comprises greater than by weight of MDMB. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component has a RON greater than 100 and/or a MON greater than

11. A blend according to any one of the preceding claims, wherein the tertiary hexyl methyl ether component has a blending RON greater than 100 and/or a blending MON greater than

12. A blend according to any one of the preceding claims, wherein the MDMB 6 0: component has a RON greater than 105 and/or a MON greater than

13. A blend according to any one of the preceding claims, wherein the MDMB S component has a blending RON greater than 105 and/or a blending MON greater than

14. A blend according to any one of the preceding claims, wherein the blend has a RON greater than 90 and/or a MON greater than :.1i 5. A blend according to any one of the preceding claims, wherein the blend has a RON greater than 93 and/or a MON greater than 83.

16. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 1 unit. "J ci-

17. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 2 units.

18. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 3 units.

19. A blend according to any one of the preceding claims, which comprises greater than 1% by volume of MDMB. A blend according to any one of the preceding claims, which comprises greater than 2% by volume of MDMB.

21. A blend according to any one of the preceding claims, which comprises greater than 5% by volume of MDMB. e

22. A blend according to any one of the preceding claims, wherein composition is made by a process comprising: dimerizing propylene to form dimethylbutenes; and (ii) etherifying the dimethyl butenes with methanol, to form the desired composition.

23. A blend according to Claim 22, wherein step (ii) comprises partial etherification and is followed by (iii) hydrogenation of unetherified dimethylbutenes to form a tertiary hexyl methyl ether composition comprising MDMB and dimethyl butanes.

24. A blend according to any one of the preceding claims, wherein composition also contains dimethylbutenes. 'i 18 A blend according to any one of the preceding claims, wherein composition also contains less than 1% methanol.

26. A blend according to any one of the preceding claims, wherein composition also contains less than 5% olefins.

27. A blend according to any one of the preceding claims, wherein composition contains greater than 50% by weight of the tertiary hexyl methyl ether.

28. A blend according to any one of the preceding claims, wherein composition contains from 60% to 100% by weight of the tertiary hexyl methyl ether.

29. A blend according to any one of the preceding claims, wherein composition contains greater than 80% by weight of the tertiary hexyl methyl S. .ether.

30. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 1 unit, while at the same time increasing the Reid vapor pressure of component by less than 13.8 kPa (2 psi).

31. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 1 unit, while at the same time increasing the Reid vapor pressure "I of component by less than 6.9 kPa (1 psi).

32. A blend according to any one of the preceding claims, which contains a sufficient amount of composition to boost the octane number of component by at least 1 unit, while at the same time increasing the Reid vapor pressure of component by less than 3.4 kPa (0.5 psi). Uj II P~ 19

33. The use of a tertiary hexyl methyl ether component comprising MDMB in an amount of at least 10% by weight based on the total weight of tertiary hexyl methyl ether component and having a blending RON greater than 100 and a blending MON greater than 90, as an octane booster for motor gasoline.

34. The use of a tertiary hexyl methyl ether component comprising MDMB in an amount of at least 10% by weight based on the total weight of tertiary hexyl methyl ether component, as an octane booster for motor gasoline wherein the blending RON and/or the blending MON of the tertiary hexyl methyl ether component is higher than the RON and/or Mon of the untreated motor gasoline. The use of a tertiary hexyl methyl ether component in accordance with Claim 33 or 34, wherein the Reid vapor pressure of the treated motor gasoline is higher by less than 13.8 kPa (2 psi).

36. The use of a tertiary hexyl methyl ether component in accordance with o. Claim 33 or 34, wherein the Reid vapor pressure of the treated motor gasoline is higher by less than 6.9 kPa (1 psi). 0*

37. The use of a tertiary hexyl methyl ether component in accordance with Claim 33 or 34, wherein the Reid vapor pressure of the treated motor gasoline is higher by less than 3.4 kPa (0.5 psi). DATED this 9th day of October, 1997. *CSo EXXON CHEMICAL PATENTS WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA ,LPS:AW DOC17 AU 1338795.WPC Uv, r INTERNATIONAL SEARCH REPORT'I Intrir il Application No PCT/US 94/14234 A. (I.ASSIICATION OF: SUIl(:I' MA'IT'liR IPC 6 C10L1/02 According to International Patent Classification (IPC) or to both national classification and IPC I. FIlil.)S SlARCIIIDI Minimum documentation searched (classificaton system followed by classificauon symbols) IPC 6 C1OL Documcntation scarchcd other than minimum documentation to the extent that such documents are included in the fields searched Ilectronic data base consulted during the intrnational search (name of data base and, where pracucal, search terms used) C. DOCUMINTS CONSIDERED I TO I1: Ril.HiVAN' Category Citation of document, with indication, where appropnate, of the relevant passages Relevant to claim No. A US,A,4 519 809 (EXXON) 28 May 1985 A EP,A,0 254 496 (MOBIL) 27 January 1988 A EP,A,0 036 260 BP) 23 September 1981 cited in the application A WO,A,89 11463 (MOBIL) 30 November 1989 F urther documents are listed in the connuation of box C. I Patent family members are listed in annex. Special categories of cited documcnts: later document published after the international fiing date document defining the general stae of the art whic' is not citd tority dte and tin cnflict o th the pdplication but considered to he of particular relevance invenuon *I"i earlier document hut published on or after the intcrnatonal 'X document of particular relevance; the claimed invention filing date cannot be considered novel or cannot be considered to document which may throw doubts on pnonty claim(s) or involve an invenuve step when the document is taken alone which is cited to establish the publication date of another document of particular relevance; the claimed invention citation or other special rcast i (as specified) canrot be considered to involve an inventive step when the document referring to an oral disclosure, use, exhibition or document is combined with one or more other such docu- other means ments, such combination being obvious to a person skilled document published pnor to the intcrnational filing date but in the a rt later than the pnority date claimed document member of the same patent family Date of the actual completion of the international search Date of mailing of the intcmauonal search report 26 April 1995 1 9 05 Name and mailing address of the ISA Authonzed officer European Patent Office, 5818 atcntlaan 2 NI. 2280 I1V Ritswilk Tel. 31-70) 340-2040, Tx. 31 651 epo nl De Herdt, 0 Fax (t 31-70) 340-3016 Form PCT ISA.'210 (econd sheet) (July 1992) i N1LRNATIO4A L SIiARC I UP~ORTi Inri, %Ii Application No oirmflioi ofl patent family mcmlicri PCT/US 94/14234 Patent. document Publit-aton Patent. family Publication cited in search report d ate Imember(s) Idate US-A-4519809 28-05-85 EP-A- 0160476 06-11-85 JP-A- 60233198 19-11-85 EP-A-254496 27-01-88 US-A- 4746761 24-05-88 US-A- 4684757 04-08-87 AU-B- 597692 07-06-90 AU-A- 7571787 21-01-88 CA-A- 1275420 23-10-90 NO-B- 174742 21-03-94 JP-A- 63066288 24-03-88 EP-A-36260 23-09-81 JP-A- 56139588 31-10-81 WO-A-8911463 30-11-89 US-A- 4886925 12-12-89 AU-B- 625062 02-07-92 AU-A- 3688589 12-12-89 EP-A- 0414800 06-03-91 JP-T- 3504136 12-09-91 US-A- 4957709 18-09-90 I rarm PCTAISA.210 (patenti family Xnnel (July 1992)