US20020175107A1 - Gasoline product - Google Patents

Abstract

Aromatic blendstocks suitable for use in making an unleaded gasoline fuel for combustion in a spark ignition engine contain substantial amounts of diisopropylbenzene which provides relatively more energy for doing work while producing fewer carbon dioxide emissions as compared to current gasoline blendstocks. Unleaded gasolines made utilizing the foregoing aromatic blendstocks contain at least about 0.3 weight percent diisopropylbenzene, preferably about 0.3 to about 10 weight percent diisopropylbenzene.

Description

FIELD OF INVENTION
• This invention relates to automotive gasoline and blending stocks therefor. [0001]
BACKGROUND OF INVENTION
• When gasoline products are formulated, it is done by mixing various petroleum blending stocks. Different blending stocks have different properties known to refiners, and the properties of a particular gasoline product can be modified by varying the relative amounts of the different petroleum blending stocks that together make up the gasoline product. [0002]
• A major environmental problem in the United States as well as other countries of the world is atmospheric pollution caused by the emission of combustion products from automobiles. Because of such environmental considerations, refiners continuously strive to produce automotive gasoline with reduced combustion emissions. It has now been found that combustion emissions from automotive gasoline can be reduced by the use of gasoline and gasoline blendstocks having a certain composition that provides a more hydrogen-rich fuel with enhanced energy value and reduced carbon dioxide emission than currently available gasolines and blendstocks therefor. In particular, it has been found that diisopropylbenzene exhibits unique properties by providing energy for doing work while producing fewer carbon dioxide emissions than current gasoline blendstocks. [0003]
SUMMARY OF INVENTION
• A relatively higher energy value unleaded gasoline fuel, suitable for combustion in a spark ignition internal combustion engine and having relatively low undesirable emissions upon combustion, is produced by enriching the gasoline fuel with diisopropylbenzene. The diisopropylbenzene enriched unleaded gasoline fuel of this invention contains at least 0.3 weight percent diisopropylbenzene, and preferably contains about 0.3 to about 10 weight percent diisopropylbenzene. [0004]
• Unleaded gasoline fuels embodying the present invention can be produced utilizing aromatic blendstocks having a isopropylbenzene-to-diisopropylbenzene mole ratio in the range of about 0 to 20. Typically, isopropylbenzene-to-diisopropylbenzene mole ratio in the blendstock is in the range of about 1 to about 6.[0005]
BRIEF DESCRIPTION OF DRAWING
• In the drawing, [0006]
• The sole FIGURE is a flow diagram illustrating a process suitable for the production of high-energy aromatic blendstocks for unleaded gasolines.[0007]
DESCRIPTION OF PREFERRED EMBODIMENTS
• A relatively high energy aromatic blendstock, containing diisopropylbenzene and eminently well suited for making an unleaded gasoline fuel for combustion in an internal combustion engine with spark ignition can be produced as illustrated in the FIGURE. As shown in the flow diagram of the FIGURE, a light reformate from a naphtha reformer which contains benzene is charged to light reformate tower [0008] 10 where molecules containing five or six carbon atoms, for example isopentane, are removed and exit in an overhead C₅-stream 14 for further processing or blending. The light reformate preferably contains substantially no aromatic hydrocarbons other than benzene, toluene and xylene. More preferably, a relatively high concentration of benzene and toluene is present in the light reformate stream. The bottoms from light reformate tower 10 flow to light reformate tower 12 as stream 16. Distillation in light reformates tower 12 separates benzene from toluene. Substantially all of the benzene in the light reformates feed goes into the benzene-rich overhead products via overhead stream 18, along with other reformate molecules boiling at about the same temperature. Substantially all of the toluene, along with other reformate molecules boiling at about the same temperature as toluene, exit as the bottoms stream 20 from tower 12. This heavy portion of light reformate may be purified further to produce industrial grade toluene for use as commercial solvent or to make toluene diisocyanate (a precursor for polyurethane foams), or it can be blended to gasoline as produced, or together with other components, as desired.
• The benzene rich overhead stream [0009] 18 from tower 12 is combined with refinery grade propylene from stream 24 (usually a mixture of about 30% propane and 70% propylene produced by other units such as a fluid catalytic cracker) and charged to benzene conversion or aromatic alkylation's reactor 22 via stream 25. The feed to reactor 22 can also be relatively pure benzene and or relatively pure propylene. In this reactor 22 benzene and propylene combine in the presence of an acidic catalyst (solid phosphoric acid catalyst, zeolite catalyst, aluminum chloride catalyst, or the like) to form diisopropylbenzene, as well as isopropylbenzene and byproducts. The propane present in the refinery grade propylene is separated from the relatively higher boiling reactor effluent and is removed overhead as stream 26. The alkylation of aromatics with propylene in the presence of an acidic catalyst, e.g. a solid phosphoric acid catalyst, is well known in the art and is described, for example, in U.S. Pat. No. 5,792,894 to Huff, Jr. et al.
• The alkylated aromatic product from the benzene conversion reactor [0010] 22 is then charged as stream 28 to distillation tower 30 for high-energy blendstock recovery. Light materials boiling below the boiling point of isopropyl benzene are recovered in the overhead stream 32 of tower 30 and may be sent to gasoline blending. The bottoms stream 34 from this tower has a relatively high diisopropylbenzene content and is charged to high-energy blendstock recovery tower 36, where isopropylbenzene is recovered from the top of the tower 36 as stream 38, and diisopropylbenzene is recovered from the bottom of the tower as stream 40. These two high energy, low CO₂ emission generating products can then be segregated and blended into gasoline products in desired proportions. Alternatively, the bottoms stream 34 can be sufficiently rich in diisopropylbenzene to be used directly as aromatic gasoline blendstock.
• Gasoline fuels typically are composed of mixtures of aromatics, olefins and paraffins, and are produced by blending together several different, processed hydrocarbon streams, commonly referred to as blendstocks, into various grades of saleable products, e.g., unleaded regular and premium gasolines, each of which meets certain product specifications. From an emissions standpoint, olefins are the least desirable gasoline fuel constituents, and olefin content preferably is minimized. More preferably, the produced gasoline fuel is substantially olefin-free. [0011]
• For use in spark-ignition engines, most commercially available gasoline fuels conform to the requirements of ASTM D4814-89 specifications. Such gasolines fall into five different volatility classes as set forth in Table I below: [0012]

  TABLE I
  Gasoline Specifications

  Properties		Class A	Class B	Class C	Class D	Class E

  RVP	(psi) max	9.0	10.0	11.5	13.5	15.0
  	(atm) max	0.6	0.7	0.8	0.9	1.0
  	(kPa) max	62	69	80	93	104
  Dist. 10%	(° F.) max	158	149	140	131	122
  	(° C.) max	70	65	60	55	50
  Dist. 50%	(° F.) min-max	170-250	170-245	170-240	170-235	170-230
  	(° C.) min-max	77-121	77-118	77-116	77-113	77-110
  Dist. 90%	(° F.) max	374	374	365	365	365
  	(° C.) max	190	190	185	185	185
  End Point	(° F.) max	437	437	437	437	437
  	(° C.) max	225	225	225	225	225

• To produce the aforementioned grades of gasoline, the blendstocks include n-butane, iso-butane, reformates, light hydrocrackate, heavy hydrocrackate, alkylates, aromatics, straight-run gasoline, straight-run naphtha, cat-cracked gasoline and coker gasoline. The blend stocks are selected to produce a gasoline fuel with predetermined specifications to research octane number (RON), motor octane number (MON), and vapor pressure (usually specified as Reid Vapor Pressure or RVP). Diisopropylbenzene provides a convenient manner for adjusting the octane numbers even in gasolines that have a relatively high paraffin or naphthane content. [0013]
• The blendstocks embodying the present invention contain alkylated aromatics in which the aromatics content is at least 25 mole percent, the rest being constituted primarily by paraffin hydrocarbons, and preferably having substantially no light (C[0014] ₄ to C₆) olefin content. The diisopropylbenzene content of the present aromatic blendstocks is at least about 10 mole percent, preferably about 20 to about 30 mole percent, most preferably about 100 mole percent. Also, in the aromatic blendstocks of the present invention, the mole ratio of isopropylbenzene(cumene)-to-diisopropylbenzene is a significant characteristic. This mole ratio in the present aromatic blendstocks is in the range of about 0 to about 20, and preferably in the range of about 1 to about 6.
• The foregoing, aromatic blendstocks preferably have a relatively low benzene content, and are incorporated into unleaded gasoline fuels in an amount sufficient to provide a diisopropylbenzene content therein of at least about 0.3 weight percent, preferably about 0.3 to about 10 weight percent. The so constituted gasoline fuel preferably contains no more than about 1 weight percent, preferably no more than about 0.5 weight percent of benzene. The 90% distillation endpoint (T[0015] ₉₀ max.) preferably is no more than about 375□ F. (190□ C.), and the Reid Vapor Pressure is no more than about 1 atmosphere (104 kPa), preferably about 0.5 atmospheres (52 kPa) to about 0.9 atmospheres (93 kPa).
• The benefits attainable with gasoline fuel compositions enriched with diisopropylbenzene are illustrated below. It will be noted that diisopropylbenzene provides added energy for doing work while producing substantially less carbon dioxide emissions than other comparable gasoline blendstocks. [0016]
• The properties of common blendstock components, and of diisopropylbenzene, are compiled in Table II, below. [0017]

  TABLE II
  Properties of Blendstock Components

  			Liquid	Heat of	Heat of	Pounds
  		Carbon	Density	Combustion;	Combustion;	of CO2
  		Weight	Lbs/gal	BTU per	BTU per	Produced
  Component	RON	%	@ 60° F.	Pound(2)	Gallon(2)	Per Gallon

  Benzene	104.9	92.3	7.361	17,258(3)	127,036	24.9
  Toluene	110.0	91.2	7.289	17,423(3)	126,996	24.4
  3-Ethylpentane	65.0	83.9	5.871	19,156(3)	112,465	18.0
  Diisopropl	110.5	88.8	7.214	17,970(4)	129,635	23.5
  Benzene(1)

• Table III, below, illustrates the amounts of carbon dioxide generated by gasoline fuel blendstocks upon combustion. In these blendstocks, a relatively high octane aromatic component is combined with a relatively low octane component to produce a mixture having the same octane as a final target unleaded gasoline (92 Research Octane Number Unleaded Regular). 3-Ethylpentane is selected as a representative low octane component, having seven carbon atoms and an octane typical of those in naphtha blendstocks. [0018]

  TABLE III
  Blendstock Examples

  			Pounds	Heat of BTU
  		Volume	of CO2	Combustion,
  		Percent	Produced	Produced
  	RON	In Blend	Per Gallon	Per Gallon

  Blend 1

  Benzene	104.9	67.7	24.9	127,036
  3-Ethylpentane	65.0	32.3	18.0	112,465
  Blend	92.0	100%	22.7	122,330

  Pounds of CO2 per Million BTU delivered(5): 186

  Blend 2

  Diisopropyl Benzene	110.5	59.3	23.5	129,635
  3-Ethylpentane	65.0	40.7	18.0	112,465
  Blend	92.0	100%	21.3	122,647

  Pounds of CO2 per Million BTU delivered(5): 174

  Blend 3

  Toluene	110.0	60.0	24.4	126,996
  3-Ethylpentane	65.0	40.0	18.0	112,465
  Blend	92.0	100%	21.8	121,184

  Pounds of CO2 per Million BTU delivered(5): 180

  $\left(5\right)\mathrm{Calculated}\mathrm{as}\mathrm{follows}\text{:}\mathrm{lbs}{\mathrm{CO}}_2=\frac{\left(\mathrm{lbs}{\mathrm{CO}}_2\mathrm{per}\mathrm{gallon}\right)\times {10}^6}{\left(\mathrm{BTU}\mathrm{per}\mathrm{gallon}\right)}$

• The RON values in Table III above are the volume weighted average RON values of the individual components. [0019]
• The superior benefits attainable by diisopropylbenzene by reducing CO[0020] ₂ emissions are readily apparent. Whereas a benzene-containing blend is shown to emit 186 pounds of CO₂ per million BTU delivered, the diisopropylbenzene-containing blend is shown to limit only 174 pounds of CO₂ per million BTU delivered.
• The total achievable benefit is even more striking when the United States' annual consumption of gasoline is considered. This benefit is strikingly illustrated in Table IV below, if benzene or toluene, respectively, is replaced by diisopropylbenzene. In both of these examples, the blend is selected to contain sufficient 3-Ethylpentane to provide the target RON value of 92. Because a relatively larger volume of toluene-containing Blend 3 of Table III can be replaced by the diisopropylbenzene containing Blend 2, a significantly larger reduction in CO[0021] ₂ emissions is achievable.

  TABLE IV
  Annual CO2 Reduction Benefit Replacing Benzene
  Item	Value	Comment
  United States gasoline consumption, gallons/day	306,900,000	EIA Publication; Average Year 1999
  Benzene content of U.S. Gasoline pool	0.95%	NIPER Survey, Solomon Refining Survey
  Gallons of Benzene blended per day	2,915,550
  Gallons of Blend Number 1 blended per day	4,306,573	Gallons of Benzene Divided by 67.7%(6)
  Pounds of CO2 Per Gallon of Blend 1	22.7
  Pounds of CO2 Per Day Emitted via Blend 1	97,759,207	Gallons of Blend 1 Times 22.7
  BTU of Energy Per Day Obtained from Blend 1	526,823,075,090	Gallons of Blend 1 Times 122,330
  BTU of Energy Per Day Required from Blend 2	526,823,075,090
  Energy Content of Blend 2, BTU/Gallon	122,647	From Table III, data for Blend 2 =
  Gallons Per Day of Blend 2 to Deliver Energy	4,295,442	526,823,075,090/1 22,647
  Pounds of CO2 Per Gallon of Blend 2	21.3	From Table Ill, data for Blend 2 =
  Pounds Per Day of CO2 Emitted by Blend 2	91,492,915	21.3 times 4,295,442
  Pounds Per Day of CO2 Emitted by Blend 1	97,759,207
  Pounds Per Day of CO2 Emitted by Blend 2	91.492.915
  Reduction in Pounds Per Day of CO2	6,266,292
  Reduction in Tons Per Year of CO2	1,143,598

• [0022]

  TABLE V
  Annual CO2 Reduction Benefit Replacing Toluene
  Item	Value	Comment
  United States gasoline consumption, gallons/day	306,900,000	EIA Publication; Average Year 1999(7)
  Toluene to be replaced	7%
  Gallons of Toluene blended per day	21,483,000
  Gallons of Blend Number 3 blended per day	35,805,000	Gallons of Toluene Divided by 600%(8)
  Pounds of CO2 Per Gallon of Blend 3	21.8
  Pounds of CO2 Per Day Emitted via Blend 3	780,549,000	Gallons of Blend 3 Times 21.8
  BTU of Energy Per Day Obtained from Blend 3	4,338,993,120,000	Gallons of Blend 3 Times 121,184
  BTU of Energy Per Day Required from Blend 2	4,338,993,120,000
  Energy Content of Blend 2, BTU/Gallon	122,647	From Table III, data for Blend 2
  Gallons Per Day of Blend 2 to Deliver Energy	35,377,899	=4,338,993,120,000/1 22,647
  Pounds of C02 Per Gallon of Blend 2	21.3	From Table III, data for Blend 2
  Pounds Per Day of CO2 Emitted by Blend 2	753,549,249	=21.3 times 35,777,899
  Pounds Per Day of CO2 Emitted by Blend 3	780,549,000
  Pounds Per Day of CO2 Emitted by Blend 2	753.549.249
  Reduction in Pounds Per Day of CO2	26,999,751
  Reduction in Tons Per Year of CO2	4,927,455

• The foregoing specification and the examples therein are illustrative of the present invention, are not to be taken as limiting. Still other variants within the spirit and scope of the present invention are possible and will readily present themselves to those skilled in the art. [0023]

Claims (10)

That which is claimed is:

1. An unleaded gasoline fuel suitable for combustion in a spark ignition internal combustion engine and containing at least about 0.3 weight percent diisopropylbenzene.

2. The unleaded gasoline fuel in accordance with claim 1 containing about 0.3 to about 10 weight percent diisopropylbenzene.

3. The unleaded gasoline fuel in accordance with claim 1, containing no more than about 1 weight percent benzene.

4. The unleaded gasoline fuel in accordance with claim 1, containing no more than about 0.5 weight percent benzene.

5. The unleaded gasoline fuel in accordance with claim 1 and substantially free from olefins.

6. The unleaded gasoline fuel in accordance with claim 1 and having a Reid Vapor Pressure no greater than about 1 atmosphere.

7. The unleaded gasoline fuel in accordance with claim 1 and having a Reid Vapor Pressure of about 0.5 atmospheres to about 0.9 atmospheres.

8. The unleaded gasoline fuel in accordance with claim 1 and having a Reid Vapor Pressure no greater than about 1 atmosphere and a 90% D-86 Distillation Point no greater than about 375□ F.

9. An aromatic blendstock, suitable for making an unleaded gasoline fuel for combustion in a spark ignition internal combustion engine and comprising isopropylbenzene and diisopropylbenzene in a isopropylbenzene-to-diisopropylbenzene mole ratio in the range of about 0 to about 20.

10. The aromatic blendstock in accordance with claim 9 wherein the isopropylbenzene-to-diisopropylbenzene mole ratio is in the range of about 1 to about 6.