JP2007246755A - Unleaded gasoline - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an unleaded gasoline which is excellent in cleaning property of interior of an engine and reducing CO and THC contents in exhaust gas. <P>SOLUTION: The unleaded gasoline is obtained by compounding 2-40 vol.% gasoline base material, 0.5-10.0 vol.% ethanol (EtOH), and 0.5-15.0 vol.% ethyl tertiary butylether (ETBT), wherein the gasoline base material is obtained from a catalytically reformed gasoline which has a polycyclic aromatic content index Y represented by a definite formula of ≤20 and is obtained by a catalytic reforming treatment of a desulfurized heavy naphtha fraction having definite properties which is obtained by a desulfurization treatment of a heavy straight-run naphtha having definite properties. The unleaded gasoline has a definite research octane number, a definite motor octane number, a definite 50 vol.% distillation temperature, a definite 90 vol.% distillation temperature and a definite Reid vapor pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to unleaded gasoline, and more particularly, to provide unleaded gasoline that has excellent cleanliness in an engine such as a combustion chamber and an intake valve, and can further reduce CO and THC in exhaust gas. is there.

In recent years, environmental pollution due to exhaust gas from automobiles and the like has been attracting attention from the viewpoint of environmental improvement, and various efforts have been made to reduce exhaust gas from the fuel surface. Specifically, it is considered effective to reduce engine exhaust gas or evaporated gas from a fuel tank.
The engine exhaust gas contains CO and THC (Total Hydro Carbon: hydrocarbon). When CO is absorbed even by the human body, it binds with hemoglobin and inhibits oxygen transport of red blood cells, causing a great adverse effect. It has been known. On the other hand, methane in THC is thought to contribute to global warming, and non-methane components are thought to contribute to the generation of photochemical smog. For this reason, it is important to reduce the exhaust gas from the automobile engine.

  In general, in order to reduce exhaust gas, it is known that installation of an exhaust gas purification catalyst system in an automobile is effective. It is also known that reducing the sulfur content of the fuel leads to a longer life of the exhaust gas purification catalyst system and is effective in reducing exhaust gas. On the other hand, keeping the inside of the engine clean by improving the fuel oil is also considered effective in reducing exhaust gas. Specifically, it is considered effective to suppress intake valve deposit (IVD) and combustion chamber deposit (CCD).

  Furthermore, in the production of unleaded gasoline, the reformed gasoline used as the high octane base material contains a large amount of aromatic components, but it is known that IVD tends to increase when a large amount of aromatic components are contained ( For example, refer nonpatent literature 1). Generally, a detergent such as polyetheramine or polyisobutene is added to reduce the IVD, but the CCD tends to increase when the detergent is added. In view of this, as a fuel that suppresses both IVD and CCD of a gasoline engine, a fuel that defines the aromatic content and the distillation property of gasoline has been proposed (see, for example, Patent Document 1). However, this technique has a problem in that the gasoline yield decreases because the blending amount of the heavy fraction is reduced in order to make the distillation property of gasoline light.

  Therefore, in order to prevent the gasoline yield from decreasing, the intake valve deposit (IVD (Inlet Valve Deposit)) and the combustion chamber deposit (CCD (Combustion Chamber Deposit)) are suppressed while blending heavy fractions. In addition, it is desired to provide unleaded gasoline that can further reduce CO and THC in the exhaust gas.

  Furthermore, in consideration of the recent global warming problem, in addition to the above, provision of fuel with reduced CO2 emissions is also desired. As measures against CO2 emissions, it is conceivable to mix ethanol derived from biomass or ETBE derived from it into gasoline. However, in order to increase the amount of CO2 reduction, if you try to add ethanol to gasoline more, the azeotropic phenomenon of hydrocarbon and ethanol becomes remarkable and the distillation curve becomes distorted, which may deteriorate the drivability. It has been known. In order to avoid this, ETBE obtained by reacting ethanol with isobutylene may be blended with gasoline, but from the viewpoint of CO2 reduction by mixing biomass, it is necessary to blend a very large amount of ETBE. It will be inferior to the economics of production.

SAE Paper, Society of Automotive Engineers 922217 JP 2000-204383 A

  An object of the present invention is to produce unleaded gasoline that can suppress both IVD and CCD of a gasoline engine and can further reduce CO and THC in exhaust gas while using a heavy fraction as a high octane base material. It is to provide a catalytic reformed gasoline that makes it possible, and an unleaded gasoline obtained by using this.

  As a result of intensive studies, the present inventors have obtained catalytic reformed gasoline using a desulfurized heavy naphtha fraction having a constant property, and further, the polycyclic aromatic content of the catalytic reformed gasoline is within a certain range. In order to ensure a reduction in CO2 emissions, the amount of the ring is adjusted so that the content is gradually reduced to a lower level, and ethanol and ethyl tertiary butyl ether are added to this. It has been found that even if it is blended, gasoline can be economically prescribed without causing deterioration in drivability. In addition, the mixture of ethanol and ETBE has excellent properties as an octane booster, and increasing the amount of these blends often has a positive impact on vehicle practical performance such as good driving performance and cleanliness. I found out.

That is, the present invention provides the following catalytic reformed gasoline and unleaded gasoline. (1) A desulfurized heavy naphtha fraction having a sulfur concentration of 5 mass ppm or less and a nitrogen concentration of 5 mass ppm or less obtained by desulfurizing a heavy straight-run naphtha having a 90% by volume distillation temperature of 160 ° C. or less. 2 to 40% by volume of a gasoline base material obtained from catalytically reformed gasoline obtained by catalytic reforming treatment and having a polycyclic aromatic content index Y represented by the following formula (I) of 20 or less, ethanol (EtOH) Containing 0.5 to 10.0% by volume, ethyl tertiary butyl ether (ETBE) 0.5 to 15.0% by volume, and satisfying the following properties 1) to 5): .
Y = (0.002 × 3R-A) + (0.01 × 4R-A) + (0.07 × 5R-A) + (0.2 × 6R + -A)… (I)
[In the formula, 3R-A is the tricyclic aromatic content, 4R-A is the 4-ring aromatic content, 5R-A is the 5-ring aromatic content, 6R + -A is the 6-ring or more aromatic content (both in gasoline) (Ppm by mass)
1) Research octane number of 89-97,
2) Motor method octane number is 79-85,
3) 50 volume% distillation temperature is 75-110 degreeC,
4) 90 volume% distillation temperature is 180 degrees C or less,
5) Reed vapor pressure is 45 to 93 kPa,
(2) The unleaded gasoline as described in (1) above, further satisfying the properties listed in 1) to 7) below.
1) Distillation at 70 ° C is 18-40% by volume
2) Aromatic content 40% or less 3) Olefin content 30% or less 4) Benzene content 1% or less 5) Sulfur content 10 mass ppm or less 6) Gas-liquid at 60 ° C Ratio (V / L) is 30-70
7) Density at 15 ° C is 0.68 to 0.78g / cm3
(3) The unleaded gasoline as described in (1) or (2) above, wherein the gasoline base material is obtained by debenzene treatment of the catalytic reformed gasoline.

  According to the unleaded gasoline of the present invention, it is possible to simultaneously suppress the generation of deposits in the combustion chamber and the intake valve in the engine without reducing the gasoline, thereby improving the cleanliness in the engine. Furthermore, the amount of harmful components such as CO and THC contained in the exhaust gas can be further reduced, and the air environment can be preserved.

Hereinafter, the contents of the present invention will be described in more detail.
The catalytically reformed gasoline used for the unleaded gasoline of the present invention is a desulfurization treatment of heavy straight run naphtha having a 90% by volume distillation temperature of 160 ° C. or less obtained by an atmospheric distillation apparatus, and the sulfur concentration is 5 mass ppm or less. The desulfurized heavy naphtha having a nitrogen concentration of 5 mass ppm or less is subjected to catalytic reforming treatment, and the polycyclic aromatic content index Y represented by the following formula (I) is set to 20 or less.
Y = (0.002 × 3R-A) + (0.01 × 4R-A) + (0.07 × 5R-A) + (0.2 × 6R + -A)… (I)
[In the formula, 3R-A is the tricyclic aromatic content, 4R-A is the 4-ring aromatic content, 5R-A is the 5-ring aromatic content, 6R + -A is the 6-ring or more aromatic content (both in gasoline) (Ppm by mass)

  The formula (I) of the polycyclic aromatic content index is an empirical formula determined from the relationship between the content of the polycyclic aromatic content and the amount of deposit in the engine, and includes three rings, four rings, five rings, and six rings. The higher the value, the higher the value. This indicates that the increase of harmful components in the exhaust gas and the generation of deposits in the engine become higher as the polycycle increases. The polycyclic aromatic content index Y in the catalytically modified gasoline is 20 or less, preferably 15 or less, more preferably 12 or less. If it is 20 or less, an increase in harmful components in exhaust gas and an increase in engine deposits can be prevented.

  The polycyclic aromatic content is a value obtained by quantification according to the number of rings by the gas chromatographic method shown below, and the quantification method is an absolute calibration curve method using a typical standard sample according to the number of rings. . That is, a capillary column of dimethyl silicon having a length of 30 m and an inner diameter of 0.25 mm is used for the column, the detector is a hydrogen ionization detector (FID), the carrier gas is 1.3 ml / min helium, splitless injection, injection It is a value measured by raising the column temperature from the initial temperature of 50 ° C. to the final temperature of 350 ° C. under the conditions of the inlet temperature of 300 ° C. and the detector temperature of 350 ° C.

  The 90 vol% distillation temperature range of the heavy straight-run naphtha used for obtaining desulfurized heavy naphtha in the present invention is 160 ° C or lower, preferably 135 to 160 ° C, more preferably 140 to 150 ° C. By setting the 90 vol% distillation temperature to 160 ° C or less, it is possible to prevent the catalytic reformed gasoline from becoming heavy. Furthermore, by setting the 90% by volume distillation temperature range to 135 ° C. or higher, the catalytic reformed gasoline when the benzene fraction is removed can be increased in octane number, which is more preferable. This distillation property is a value measured according to JIS K 2254.

In addition, desulfurization treatment of heavy straight-run naphtha is generally performed in the presence of a desulfurization catalyst in which a group VI or group VIII metal is supported on an inorganic carrier, with a reaction pressure of 0.1 to 10 MPa, preferably 1 to 3 MPa, and a reaction temperature. The desulfurization reaction is performed at 200 to 450 ° C., preferably 250 to 350 ° C., and the liquid space velocity (LHSV) is 0.1 to 20 hr ⁻¹ , preferably 0.5 to 10 hr ⁻¹ .
The sulfur concentration of the resulting desulfurized heavy naphtha is 5 ppm by mass or less, preferably 1 ppm by mass or less, and the nitrogen concentration is 5 ppm by mass or less, preferably 1 ppm by mass or less. If the sulfur concentration and the nitrogen concentration are each 5 ppm by mass or less, deactivation of the catalytic reforming catalyst can be prevented. The sulfur concentration is a value measured according to JIS K2541 microcoulometric titration method, and the nitrogen concentration is a value measured according to JIS K2609 chemiluminescence method.

  Contact reforming treatment of desulfurized heavy naphtha is performed by various contact reforming methods (Platform forming method, Magna forming method, Aromaizing method, Reni forming method, Food reforming method, Ultra forming method, Power forming method, etc.) The desulfurized heavy naphtha can be subjected to contact treatment with a catalyst (for example, a material in which platinum, rhodium and chlorine are supported on an alumina carrier) in a hydrogen stream under high temperature and pressure.

The unleaded gasoline of the present invention is produced using the catalytic reformed gasoline obtained by the catalytic reforming treatment of the desulfurized heavy naphtha as a base material. Although a manufacturing method in particular is not restrict | limited, Generally, it can manufacture using the following various fractions. Ie;
(A) Debenzene-catalyzed reformed gasoline obtained by removing a benzene fraction from the catalytic reformed gasoline of the present invention by distillation;
(B) The catalytic reformed gasoline of the present invention is divided into a light fraction, a benzene fraction, and a heavy fraction by distillation, and a light fraction (debenzene light catalytic reformed gasoline) and a heavy fraction (dehydrated) are separated. Benzene heavy contact reforming gasoline),
(C) Aromatic main catalytic reformed gasoline mainly composed of toluene or aromatics having 9 or more carbon atoms, obtained by distillation or extraction of the catalytic reformed gasoline of the present invention,
(D) Petroleum fractions ranging from kerosene / light oil to atmospheric residual oil, preferably heavy gas oil or vacuum gas oil, are conventionally known catalytic cracking methods, especially fluid catalytic cracking methods (UOP method, shell two-stage type) Decomposition with a solid acid catalyst (eg, silica / alumina blended with zeolite) by the method, flexi cracking method, ultra ortho flow method, texaco method, Gulf method, ultra cat cracking method, RCC method, HOC method, etc. Catalytic cracking gasoline,
(E) an alkylate obtained by reacting isobutane with a lower olefin (butene, propylene, etc.) in the presence of an acid catalyst (sulfuric acid, hydrogen fluoride, aluminum chloride, etc.),
(F) C4 fraction mainly composed of butane and butenes obtained by distillation at the time of atmospheric distillation of crude oil, crude oil or the like, during the production of reformed gasoline, or during the production of cracked gasoline,
(G) Isomerate obtained by isomerization of linear lower paraffinic hydrocarbon, light naphtha, preferably desulfurized light naphtha, or isopentane obtained by precision distillation of isomerate,
Etc. are used as gasoline base materials.

  The unleaded gasoline of the present invention further contains ethyl tertiary butyl ether (ETBE) and ethanol (EtOH). Ethanol (EtOH) has a purity of 92.0% by volume or more, preferably 95.0% by volume or more, and more preferably 99.5% by volume or more. As ETBE and ethanol, all those obtained from known production methods can be used, and the production method is not particularly limited.

The following examples are given as specific examples for producing the unleaded gasoline of the present invention by appropriately selecting and using the above various fractions. Ie;
(A ′) Research method octane number is 92 or more, motor method octane number is 82 or more, reed vapor pressure is 28 kPa or more, and boiling range is 28 to 215 ° C. b ') i) 0 to 25% by volume of debenzene light catalytic reformed gasoline having a research octane number of 78 or higher, a motor octane number of 70 or higher, a Reed vapor pressure of 85 kPa or higher, and a boiling point range of 26 to 80 ° C. And ii) 2 to 20% by volume of debenzene heavy catalytic reformed gasoline having a research octane number of 101 or higher, a motor octane number of 89 or higher, a Reid vapor pressure of 3 kPa or higher, and a boiling point range of 90 to 215 ° C., or (C ′) Aromatic substance mainly composed of toluene or aromatics having 9 or more carbon atoms, obtained by distillation or extraction of the catalytically modified gasoline or debenzene-heavy catalytically modified gasoline of the present invention 2-20% by volume of catalytic reformed gasoline, (b ') i) and (d') Research method octane number 87 or more, motor method octane number 76 or more, Reed vapor pressure 40 kPa or more, boiling range 30 10 to 70% by volume of catalytically cracked gasoline at ~ 215 ° C,
(G ′) 10-30% by volume of desulfurized light naphtha with a research octane number of 65 or more, a motor octane number of 62 or more, a reed vapor pressure of 80 kPa or more, and a boiling point range of 25 to 110 ° C.
The unleaded gasoline of the present invention can be produced by blending these so as to have the predetermined properties described later.
In addition, in the formulation of each substrate as described above,
(E ′) 0 to 30% by volume of an alkylate having a research octane number of 93 or higher, a motor octane number of 90 or higher, a lead vapor pressure of 40 kPa or higher, a boiling range of 30 to 210 ° C., and a C8 fraction of 65% by volume or higher. ,
May be further blended.

The unleaded gasoline of the present invention is a gasoline base obtained from the catalytic reformed gasoline, that is, at least one fraction of the above examples (a) to (c) (or (a ′) to (c ′)). It is included as an essential fraction so that the total amount is 2 to 40% by volume, preferably 10 to 40% by volume. If the content is 2% by volume or more, the octane number of the unleaded gasoline can be improved, and if it is 40% by volume or less, the unleaded gasoline can be prevented from becoming heavy.
The unleaded gasoline of the present invention further contains ethanol. The ethanol content is in the range of 1% to 15% by volume, preferably 3% to 15% by volume, based on the total gasoline. If it is 1% by volume or more, the advantage of improving the octane number by blending with ethanol can be obtained, and if it is 15% by volume or less, the evaporation characteristics do not change significantly due to the azeotropic phenomenon with other gasoline base materials. The proper drivability can be secured.
The unleaded gasoline of the present invention further contains 1 to 25% by volume, preferably 3 to 20% by volume, more preferably 5 to 18% by volume of ETBE. If the blending amount of ETBE is within the above range, it is possible to reduce CO, THC, etc. in the exhaust gas without fear of an adverse effect on fuel consumption due to a decrease in calorific value.
The other undiluted fractions are appropriately selected, and the unleaded gasoline of the present invention is blended by appropriately setting the blending amounts according to the properties of the respective fractions so that the unleaded gasoline obtained has a predetermined property. Gasoline can be produced.

  The unleaded gasoline produced using the catalytic reformed gasoline of the present invention has a research octane number of 89 to 97, preferably 89 to 95, and a motor octane number of 79 to 85, preferably 80 to 84. If RON is 89 to 97, it is possible to maintain high driving performance as a so-called regular-class octane gasoline, and if the motor method octane number is 79 to 85, it prevents deterioration of anti-knock properties at high speeds. Can do. The research method octane number and the motor method octane number are values measured in accordance with JIS K 2280.

  The unleaded gasoline of the present invention has a 50% by volume distillation temperature (T50) of 75 to 110 ° C, preferably 85 to 100 ° C, and a 90% by volume distillation temperature (T90) of 180 ° C or less, preferably 110 to 170. ° C. When the distillation temperature is within the above range, it is possible to prevent a problem in starting performance, operability, and acceleration. These distillation properties are values measured in accordance with JIS K 2254.

  The unleaded gasoline of the present invention has a 70 ° C. distillate (E70) of 18 to 40% by volume, preferably 20 to 40% by volume. If E70 is within the above range, it is possible to prevent a problem in starting performance, drivability and acceleration. These distillation properties are values measured in accordance with JIS K 2254.

  The lead vapor pressure of the unleaded gasoline of the present invention is 45 to 93 kPa, preferably 66 to 93 kPa. By setting the RVP to 93 kPa or less, the amount of evaporating gas can be reduced, and by setting it to 45 kPa or more, it is possible to prevent the low-temperature startability and the warm-up property from being deteriorated. The reed vapor pressure is a value measured according to JIS K 2258.

The density of the unleaded gasoline of the present invention at 15 ° C. is 0.68 to 0.78 g / cm ³ , preferably 0.69 to 0.76 g / cm ³ . When this density is 0.68 g / cm ³ or more, good fuel consumption can be ensured. Further, by setting the density to 0.78 g / cm ³ or less, high-density aromatics can be reduced, and the amount of aromatics discharged into the atmosphere by exhaust gas can be reduced. This density is a value measured in accordance with JIS K 2249.

  The aromatic content of the unleaded gasoline of the present invention is 40% by volume or less, preferably 5 to 35% by volume. If the aromatic content is within 40% by volume, an increase in harmful components in the exhaust gas can be prevented. The aromatic content is a value measured according to the Petroleum Institute method JPI-5S-33-90 (gas chromatographic method).

  The olefin content of the unleaded gasoline of the present invention is 30% by volume or less, preferably 5 to 27% by volume. When the olefin content is within 30% by volume, it is possible to prevent a decrease in oxidation stability. The olefin content is a value measured according to the Japan Petroleum Institute method JPI-5S-33-90 (gas chromatographic method).

  The benzene content of the unleaded gasoline of the present invention is 1% by volume or less, preferably 0.8% by volume or less. If the benzene content is within 1% by volume, there is a possibility that the increase in benzene concentration in the atmosphere can be prevented and environmental pollution can be reduced. The benzene content is a value measured according to the Petroleum Institute method JPI-5S-33-90 (gas chromatographic method).

  The sulfur content of the unleaded gasoline of the present invention is 10 mass ppm or less, preferably 8 mass ppm or less. If the sulfur content is 10 mass ppm or less, there is a possibility that the exhaust gas purification catalyst capacity can be prevented from being lowered and the concentration of THC and CO in the exhaust gas can be prevented from increasing. The sulfur content is a value measured in accordance with JIS K2541.

  The gas-liquid ratio (V / L) at 60 ° C. of the unleaded gasoline of the present invention is 30 to 70, preferably 30 to 60. When this V / L is 30 or more, good startability can be ensured. In addition, by setting V / L to 70 or less, there is a possibility that defects in acceleration and drivability can be reduced. The V / L is a value measured according to ASTM D 2533-93a.

  In the unleaded gasoline of the present invention, the ratio of aromatics having 9 or more carbon atoms to the total aromatics (hereinafter also referred to as (C9 + A) / TA) is 0.80 or less, preferably 0.10 to 0.80. is there. It is preferable that the ratio of the aromatic component having 9 or more carbon atoms and the total aromatic component is 0.80 or less because it is possible to prevent the smoldering property of the plug from being lowered. The aromatic content is a value measured in accordance with the Petroleum Institute Method JPI-5S-33-90 (gas chromatographic method).

  In the unleaded gasoline of the present invention, various additives can be appropriately blended as necessary. Such additives include phenolic and amine antioxidants, metal deactivators such as thioamide compounds, surface ignition inhibitors such as organophosphorus compounds, succinimides, polyalkylamines, polyetheramines. , Detergent dispersants such as polyisobutyleneamine, friction modifiers (FM) such as long chain alkylamines, amides, imides and derivatives thereof, anti-icing agents such as polyhydric alcohols and ethers thereof, alkali metals and alkaline earths of organic acids Metal salts, auxiliary agents such as sulfates of higher alcohols, anionic surfactants, cationic surfactants, antistatic agents such as amphoteric surfactants, rust inhibitors such as alkenyl succinates, and azo dyes Known fuel additives such as colorants are included. These can be added singly or in combination. The addition amount of these fuel additives is arbitrary, but usually the total addition amount is preferably 0.1% by mass or less.

  The content of the present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto.

Examples and Comparative Examples Table 1 shows properties of desulfurized heavy naphtha, and Table 2 shows properties of catalytic reformed gasoline obtained by catalytic reforming of the desulfurized heavy naphtha. In Tables 1 and 2, desulfurized heavy naphtha α and catalytically reformed gasoline 1 obtained therefrom satisfy the properties of the present invention. On the other hand, desulfurized heavy naphtha β and catalytically reformed gasoline 2 obtained therefrom deviate from the properties of the present invention.
And each gasoline base material shown in Table 3 and 4 was mixed in the ratio shown in Table 5, the unleaded gasoline was manufactured, and the various performance evaluation tests described below were done.
The density in the table was measured by JIS K 2249, and the aromatic content, olefin content, and benzene content were measured by the Petroleum Institute method JPI-5S-33-90 (gas chromatographic method).

  Intake valve deposit (IVD) test and combustion chamber deposit (CCD) test using a 1.5L displacement, multipoint injection (MPI) type vehicle with 60-100km / h acceleration / deceleration x 1,500 cycles The test was conducted under the condition of (8,000km travel). The method is described below, and the results are shown in Table 5.

(IVD test)
Evaluation was made based on the weight of the deposit (IVD) attached to the intake valve and the IVD score (Rating: CRC No. 16) obtained by weighing the intake valve weight before and after operation. The rating value indicates that the larger the numerical value, the smaller the IVD amount.
(CCD test)
After the IVD test, the deposit (CCD) adhered to the cylinder head and the piston top was collected and weighed.

(Plug smoldering test)
Using a vehicle with a total displacement of 2L, MPI method, automatic transmission (AT), and a test temperature condition of -10 ° C, about 30 minutes per cycle (engine start ⇒ 10-20 km / h acceleration / deceleration repeated 10 times ⇒ 28 The degree of fouling of the plug was measured by measuring the insulation resistance of the plug. It was determined that plug smoldering occurred when the plug insulation resistance value was 100 MΩ or less.

(Exhaust gas test)
The exhaust gas test was conducted using a domestic passenger car (total displacement 2 L, MPI system, automatic transmission (AT), three-way catalyst installed), chassis dynamometer, acceleration / deceleration of 60-100 km / h x 1,500 cycles ( After running for 8,000 km), an exhaust gas test in 11 mode was conducted to measure carbon monoxide (CO) and total hydrocarbons (THC).

  As specifically shown in the examples, deposits are particularly prevented from adhering to the intake valves. Therefore, the present invention is excellent in cleanliness inside the engine and can maintain the air environment while using heavy contact reformed gasoline as a high octane base material.

Claims (3)

Catalytic reforming of a desulfurized heavy naphtha fraction having a sulfur concentration of 5 mass ppm or less and a nitrogen concentration of 5 mass ppm or less, obtained by desulfurizing a heavy straight-run naphtha having a 90 vol% distillation temperature of 160 ° C or less. 2 to 40% by volume of a gasoline base material obtained from a catalytically reformed gasoline having a polycyclic aromatic content index Y represented by the following formula (I) obtained by the treatment and having a value of 20 or less; An unleaded gasoline characterized by containing 5 to 10.0% by volume, 0.5 to 15.0% by volume of ethyl tertiary butyl ether (ETBE), and satisfying the properties listed in 1) to 5) below.
Y = (0.002 × 3R-A) + (0.01 × 4R-A) + (0.07 × 5R-A) + (0.2 × 6R + -A)… (I)
[In the formula, 3R-A is the tricyclic aromatic content, 4R-A is the 4-ring aromatic content, 5R-A is the 5-ring aromatic content, 6R + -A is the 6-ring or more aromatic content (both in gasoline) (Ppm by mass)
1) Research octane number of 89-97,
2) Motor method octane number is 79-85,
3) 50 volume% distillation temperature is 75-110 degreeC,
4) 90 volume% distillation temperature is 180 degrees C or less,
5) Reed vapor pressure is 45 to 93 kPa, The unleaded gasoline according to claim 1, further satisfying the following properties 1) to 7).
1) Distillation at 70 ° C is 18-40% by volume
2) Aromatic content 40% or less 3) Olefin content 30% or less
4) Benzene content is 1 vol% or less 5) Sulfur content is 10 mass ppm or less 6) Gas-liquid ratio (V / L) at 60 ° C is 30 to 70
7) Density at 15 ° C is 0.68 to 0.78 g / cm ³ The unleaded gasoline according to claim 1 or 2, wherein the gasoline base material is obtained by debenzene treatment of the catalytic reformed gasoline.