CN114806672A

CN114806672A - Method for preparing fuel for spark-ignition engine

Info

Publication number: CN114806672A
Application number: CN202210048708.9A
Authority: CN
Inventors: 新井琢真; 桥本公太郎; 松浦胜也; 葛冈浩平
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2021-01-20
Filing date: 2022-01-17
Publication date: 2022-07-29
Also published as: JP2022111454A; US20220228077A1; JP7171776B2

Abstract

The present invention provides a method for producing a fuel for a spark-ignition engine, which comprises mixing cyclopentane in light naphtha.

Description

Method for preparing fuel for spark-ignition engine

Technical Field

The present invention relates to a method for producing a fuel for a spark-ignition engine.

Background

Conventionally, a high octane gasoline using a catalytically reformed gasoline as a high octane base material has been known (for example, see patent document 1). The high-octane gasoline described in patent document 1 contains a gasoline base obtained from a catalytically reformed gasoline obtained by subjecting a naphtha fraction to a catalytic reforming treatment.

However, in order to obtain the high octane gasoline described in patent document 1, it is necessary to further charge energy to the naphtha fraction and perform catalytic reforming treatment, and therefore it is difficult to suppress the carbon emission amount (carbon strength) per energy of the finally produced fuel.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2007-246744 (JP 2007-246744A).

Disclosure of Invention

One technical scheme of the invention is a preparation method of a spark-ignition engine fuel for preparing the fuel for the spark-ignition engine, which comprises the step of mixing cyclopentane in light naphtha.

Drawings

The objects, features and advantages of the present invention are further clarified by the following description of embodiments in relation to the accompanying drawings.

Fig. 1 is a diagram for explaining an example of a renewable fuel produced using a renewable energy source;

fig. 2 is a graph showing an example of the octane number of a mixed fuel prepared by adding cyclopentane to a standard fuel;

FIG. 3 is a graph showing characteristics of octane addition versus a blend ratio of cyclopentane and octane number of a standard fuel;

fig. 4 is a graph showing characteristics of the octane number (measured value) of the mixed fuel with respect to the mixing ratio of cyclopentane and the octane number of the standard fuel;

fig. 5 is a diagram showing an example of a combustion test result of the mixed fuel;

fig. 6 is a graph showing characteristics of the ignition delay time of the mixed fuel with respect to the mixing ratio of cyclopentane and the octane number of the standard fuel;

fig. 7 is a diagram for explaining an example of a preferable mixing ratio of cyclopentane in producing reformed gasoline by adding cyclopentane to FT light naphtha;

fig. 8 is a diagram for explaining another example of a preferable mixing ratio of cyclopentane when cyclopentane is added to FT light naphtha to produce reformed gasoline;

fig. 9 is a diagram for explaining still another example of a preferable mixing ratio of cyclopentane when cyclopentane is added to FT light naphtha to produce reformed gasoline;

FIG. 10 is a graph for explaining the effect of addition of cyclopentane to paraffins;

FIG. 11 is a diagram for explaining a chemical reaction upon combustion of a general paraffin;

FIG. 12 is a diagram for explaining a chemical reaction upon combustion of cyclopentane;

fig. 13 is a diagram for explaining the OH radicals consumed and generated in the combustion process of each mixed fuel.

Detailed Description

Embodiments of the present invention are described below with reference to fig. 1 to 13. The method for producing a fuel for a spark ignition engine according to the embodiment of the present invention reforms light naphtha having a low octane number to produce reformed gasoline having an octane number usable for a spark ignition engine.

The average temperature of the earth is kept warm by greenhouse gases in the atmosphere, which is suitable for living things. Specifically, the greenhouse gas absorbs a part of heat radiated from the ground surface heated by the sunlight to the space, and radiates the heat to the ground surface again, thereby keeping the atmosphere warm. When the concentration of greenhouse gases in the atmosphere increases as described above, the average temperature of the earth rises (global warming).

The concentration of carbon dioxide in the atmosphere, which has a large influence on global warming, in greenhouse gases is determined by the balance between carbon fixed on the ground or underground in the form of plants or fossil fuels and carbon present in the atmosphere in the form of carbon dioxide. For example, when plants absorb carbon dioxide from the atmosphere through photosynthesis during growth, the concentration of carbon dioxide in the atmosphere decreases, and when fossil fuels are burned to release carbon dioxide into the atmosphere, the concentration of carbon dioxide in the atmosphere increases. In order to suppress global warming, renewable energy sources such as sunlight, wind power, and biomass need to be used instead of fossil fuels to reduce carbon emissions.

Fig. 1 is a diagram for explaining an example of a renewable fuel produced using a renewable energy source, and shows a renewable fuel produced via FT (fischer-tropsch) synthesis. As shown in fig. 1, renewable power is generated from renewable energy sources such as solar energy and wind energy by solar power generation, wind power generation, and the like, and water is electrolyzed using the renewable power to generate renewable hydrogen. Then, FT synthesis is performed using renewable hydrogen and carbon dioxide recovered from a plant off-gas or the like to produce FT crude oil.

The FT naphtha is fractionated according to boiling point ranges to separate FT diesel, jet fuel, and FT light naphtha. Among them, FT diesel oil can be used as fuel for diesel engines as it is, and jet fuel can be used as fuel for jet engines as it is. On the other hand, the FT light naphtha is mainly chain saturated hydrocarbons (paraffins) having 4 to 6 carbon atoms, and therefore has a research octane number of about 60 to 70, which is low, and if it is used as a fuel for a spark ignition gasoline engine, the combustion performance of the engine may be impaired.

In this connection, the inventors have found that if cyclopentane is added (mixed) to paraffin hydrocarbons, the octane number increases beyond the expected value depending on the octane numbers and the mixing ratio of the two. Therefore, in the present embodiment, a method for producing a spark ignition engine fuel by adding cyclopentane to FT light naphtha and reforming the mixture to produce reformed gasoline having an octane number usable for a spark ignition engine will be described.

Fig. 2 is a graph showing an example of the octane number of a mixed fuel prepared by adding cyclopentane (octane number 103.2) to a standard fuel (octane number (research octane number RON)65) while changing the mixing ratio x (capacity% in the standard state). The standard fuel is prepared by blending iso-octane (octane number 100) and n-heptane (octane number 0) as paraffinic hydrocarbons at an appropriate mixing ratio. In the present embodiment, the octane number of cyclopentane is an experimental value measured by a test in accordance with JIS standard. As shown by the broken line in fig. 2, the calculation value RONc of the octane number of the mixed fuel calculated by the following formula (i) based on the mixing ratio of the standard fuel to cyclopentane linearly increases according to the mixing ratio x of cyclopentane.

RONc＝65(100－x)/100+103.2x/100(i)

On the other hand, as shown by the graph and the solid line in fig. 2, the measured octane number RONa of the mixed fuel is higher than the calculated value RONc independently of the mixing ratio x of cyclopentane, and reaches the maximum when the mixing ratio x is 50%. Standard fuels with different octane numbers also show the same trend. It is thus believed that some interaction occurs between the alkane and cyclopentane. Hereinafter, the difference Δ RON between the measured octane number RONa and the calculated octane number RONc is referred to as "octane addition".

Thus, the octane addition Δ RON when cyclopentane is added to paraffin is maximized at a mixing ratio x of cyclopentane of 50%. Therefore, in the case of producing reformed gasoline by adding cyclopentane to FT light naphtha, the mixing ratio x of cyclopentane is preferably 50% or less from the viewpoint of effective use of FT light naphtha.

Fig. 3 is a graph showing characteristics of the octane addition Δ RON with respect to the mixing ratio x of cyclopentane and the octane number of standard fuel. As shown in fig. 3, the octane addition Δ RON shows a maximum value at a blending ratio x of cyclopentane of 50% regardless of the octane number of the standard fuel. The lower the octane number of the standard fuel, the greater the maximum value of octane addition Δ RON. By adjusting the mixing ratio x of cyclopentane in the range of octane number equivalent to FT light naphtha 60 to 70, the octane addition Δ RON can be made 15 or more. In the case of producing reformed gasoline by adding cyclopentane to FT light naphtha, it is preferable to set the mixing ratio x of cyclopentane in a range where the octane addition Δ RON becomes a predetermined value (for example, 15) or more, from the viewpoint of sufficiently utilizing the effect of adding cyclopentane.

Fig. 4 is a graph showing characteristics of the mixing ratio x of the octane number (measured value) RONa of the mixed fuel with respect to cyclopentane and the octane number of the standard fuel. As shown in fig. 4, the octane number RONa of the mixed fuel varies depending on the octane number of the standard fuel and the mixing ratio x of cyclopentane. Based on the test results, a calibration curve (predetermined characteristics) is set, and the blending ratio x of cyclopentane is set based on the calibration curve, whereby cyclopentane can be added to FT light naphtha to produce reformed gasoline having an appropriate octane number. For example, reformed gasoline with an octane number of 88 to 95 equivalent to that of standard gasoline can be produced.

Fig. 5 and 6 are diagrams showing an example of the combustion test results of the mixed fuel, and show the results of the combustion test using the rapid compression device. In a combustion test using a rapid compression device, an air-fuel mixture of fuel and air at a stoichiometric air-fuel ratio is introduced into a vacuum combustion chamber, the air-fuel mixture is compressed to a predetermined compression ratio, and the time (ignition delay time) ti [ ms ] from the time when the air-fuel mixture reaches the predetermined compression ratio to the time when autoignition starts is measured.

Fig. 5 shows the characteristic of the maximum heat efficiency [% ] with respect to the ignition delay time ti. As shown in fig. 5, on the one hand, when the ignition delay time ti is less than 10ms, the maximum thermal efficiency is significantly reduced, and on the other hand, in the range where the ignition delay time ti is 10ms or more, the maximum thermal efficiency tends to be stable. Therefore, in the case of producing reformed gasoline by adding cyclopentane to FT light naphtha, the blending ratio x of cyclopentane is preferably set so that the ignition delay time ti becomes 10ms or more, from the viewpoint of ensuring sufficient performance of the spark ignition engine used.

Fig. 6 shows the characteristics of the ignition delay time ti with respect to the mixing ratio x of cyclopentane and the octane number of the standard fuel. As shown in fig. 6, the larger the mixing ratio x of cyclopentane, the longer the ignition delay time ti; the larger the octane number of the standard fuel, the lower the blending ratio x of cyclopentane for the ignition delay time ti to reach 10 ms.

Fig. 7 to 9 are diagrams for explaining an example of a preferred blending ratio x of cyclopentane in the production of reformed gasoline by adding cyclopentane to FT light naphtha, and show an example of a range of the preferred blending ratio x with respect to the octane number of the FT light naphtha.

From the viewpoint of effective utilization of FT light naphtha, the mixing ratio x of cyclopentane is preferably 50% or less (fig. 2 and 3). From the viewpoint of ensuring sufficient performance of a spark ignition engine using reformed gasoline, it is preferable to set the ignition delay time ti to 10ms or more (fig. 5 and 6). That is, as shown in the example of fig. 7, the mixing ratio x of cyclopentane in producing reformed gasoline by adding cyclopentane to FT light naphtha is preferably set to 50% or less, and the ignition delay time ti is preferably set to 10ms or more.

From the viewpoint of sufficiently exerting the effect of adding cyclopentane, it is preferable to set the mixing ratio x of cyclopentane in a range where the octane addition Δ RON becomes equal to or greater than a predetermined value (for example, 15) (fig. 3). From the viewpoint of ensuring sufficient performance of a spark ignition engine using reformed gasoline, the mixing ratio x of cyclopentane is preferably set so that the ignition delay time ti becomes 10ms or more (fig. 5 and 6). That is, as shown in the example of fig. 8, the blending ratio x of cyclopentane is set so that the ignition delay time ti becomes 10ms or more in the range where the octane addition Δ RON becomes a predetermined value (for example, 15) or more.

The blending ratio x of cyclopentane in the production of reformed gasoline by adding cyclopentane to FT light naphtha can be set according to the desired octane number of reformed gasoline (fig. 4). For example, the octane number can be set based on a predetermined characteristic so as to achieve an octane number of 88 to 95 equivalent to standard gasoline. In this case, although the performance of the engine to which the reformed gasoline is applied can be ensured, from the viewpoint of effectively exerting the effect of addition, it is preferable to set the blending ratio x (fig. 3) of cyclopentane in a range where the octane addition Δ RON becomes equal to or greater than a predetermined value (for example, 15). That is, as shown in the example of fig. 9, it is preferable to set the blending ratio x of cyclopentane based on the characteristic set in advance such that the octane number RONa of the mixed fuel falls within a predetermined range in the range where the octane addition Δ RON falls within a predetermined value (for example, 15) or more.

Fig. 10 is a graph for explaining the effect of addition of cyclopentane to paraffins, showing the change in combustion temperature with time for different fuel components. As shown in fig. 10, the mixed fuel (standard fuel) of isooctane 50% and n-heptane 50% and the mixed fuel of cyclopentane 50% and n-heptane 50% show a large difference in time until reaching the low-temperature oxidation reaction in which the combustion temperature is increased. The low-temperature oxidation reaction is an exothermic reaction caused by a slow oxidation reaction of fuel molecules, and proceeds in a chain manner by generation and consumption of OH radicals.

Fig. 11 is a diagram for explaining a chemical reaction in combustion of a general paraffin. As a result of analyzing the chemical reaction, in the chemical reaction when general paraffin (RH) is burned, OH radicals less than 2 times the stoichiometric amount of the consumed OH radicals are generated. In general paraffin combustion, the chain reaction is easily performed because more OH radicals are generated than consumed, and the low-temperature oxidation reaction rapidly proceeds.

Fig. 12 is a diagram for explaining a chemical reaction in the combustion of cyclopentane. In the chemical reaction when cyclopentane is burned, less than 0.65 times as many OH radicals are generated as the consumed OH radicals. It was also confirmed that 35% of the product was stable cyclopentene, and the rate of termination reaction by radical elimination was high. Thus, in the combustion of cyclopentane, the OH radicals generated are less than the OH radicals consumed, and therefore, the chain reaction is not easily performed, and the low-temperature oxidation reaction is not easily performed rapidly.

Fig. 13 is a diagram for explaining the state of OH radicals consumed and generated during combustion of each mixed fuel, and shows the results of chemical reaction analysis. As shown in fig. 13, in the mixed fuel of isooctane 50% and n-heptane 50%, OH radicals (43%) consumed during the combustion of isooctane and generated OH radicals (40%) were almost equal, and OH radicals (57%) consumed during the combustion of n-heptane and generated OH radicals (60%) were almost equal. Therefore, the rate of the low-temperature oxidation reaction of n-heptane does not change due to the coexistence of isooctane.

On the other hand, in the mixed fuel of 50% cyclopentane and 50% n-heptane, more OH radicals (56%) are consumed than generated OH radicals (38%) during the combustion of cyclopentane, and less OH radicals (44%) are consumed than generated OH radicals (62%) during the combustion of n-heptane. That is, in the case where the low-temperature oxidation reaction of n-heptane and the low-temperature oxidation reaction of cyclopentane are performed in parallel, OH radicals generated during the combustion of n-heptane are consumed during the combustion of cyclopentane. Therefore, the low-temperature oxidation reaction of n-heptane is not easily performed due to the coexistence of cyclopentane.

As described above, cyclopentane is not easily oxidized as a monomer, and when it is added (mixed) to paraffin, OH radicals generated during combustion are consumed, so that the low-temperature oxidation reaction of the whole fuel mixture is not easily performed, and the combustion is slowed.

With this embodiment, the following effects can be achieved.

(1) A process for producing a spark-ignition engine fuel for reforming gasoline for a spark-ignition engine comprises blending cyclopentane in a light naphtha. By adding cyclopentane to light naphtha having a low octane number, reformed gasoline having an octane number that can be used in a spark ignition engine is produced, and therefore reformed gasoline having a low carbon strength can be produced without the need to input additional energy.

(2) The blending ratio x of cyclopentane is set so that the ignition delay time ti from the compression of the reformed gasoline to the autoignition after the compression of the reformed gasoline at the predetermined compression ratio when the reformed gasoline is combusted at the predetermined compression ratio becomes 10ms or more. Thereby, sufficient performance of the spark ignition engine to which reformed gasoline is applied can be ensured.

(3) The mixing ratio x of cyclopentane is less than 50% by volume. The light naphtha can be effectively used by setting the blending ratio x of cyclopentane to 50% or less at the maximum of the effect of adding cyclopentane due to the interaction between the light naphtha and cyclopentane.

(4) The blending ratio x of cyclopentane is set so that the difference Δ RON between a calculated value RONc of octane number of reformate, which is calculated based on the octane number of light naphtha, the octane number of cyclopentane, and the blending ratio of light naphtha to cyclopentane, and an actual measured value RONa of octane number of reformate, which is calculated based on the octane number of light naphtha, the octane number of cyclopentane, becomes a predetermined value (for example, 15) or more. By setting the mixing ratio x of cyclopentane in a range where the effect of adding cyclopentane by the interaction between light naphtha and cyclopentane is sufficiently large, the effect of adding cyclopentane can be sufficiently exhibited.

(5) The light naphtha is FT light naphtha obtained by FT synthesis. By using FT light naphtha, the carbon strength of the reformed gasoline can be further suppressed.

(6) The blending ratio x of cyclopentane is set based on a characteristic predetermined in advance so that the octane number of the reformed gasoline reaches a predetermined range, and is set so that the difference Δ RON between a calculated value RONc of the octane number of the reformed gasoline calculated based on the octane number of light naphtha, the octane number of cyclopentane, and the mixing ratio of light naphtha and cyclopentane reaches a predetermined value (for example, 15) or more.

By setting the mixing ratio x of cyclopentane in a range where the effect of adding cyclopentane due to the interaction between light naphtha and cyclopentane is sufficiently large, the effect of adding cyclopentane can be sufficiently exhibited, and reformed gasoline with a high octane number can be efficiently produced. Further, by setting the blending ratio x of cyclopentane based on the characteristics predetermined in advance in consideration of the interaction between the paraffin, which is the main component of the light naphtha, and cyclopentane, reformed gasoline having an appropriate octane number can be produced.

(7) The specified range is set according to the octane number of standard gasoline. In this case, the reformed gasoline can be preferably used for a gasoline engine that is supposed to be prepared using a standard gasoline.

In the above embodiment, the example in which cyclopentane is added to FT light naphtha as a renewable fuel was described, but cyclopentane may be added to naphtha derived from a fossil fuel. Additionally, cyclopentane can also be recycled cyclopentane from a renewable fuel. In this case, the carbon strength of the reformed gasoline can be further reduced.

One or more of the above-described embodiments and modifications may be combined as desired, and modifications may be combined with each other.

According to the present invention, a fuel for a spark ignition type engine having a low carbon strength can be produced.

While the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the disclosure of the following claims.

Claims

1. A process for producing a fuel for a spark-ignition engine, which is a process for producing a fuel for a spark-ignition engine,

comprising mixing cyclopentane in a light naphtha.

2. The method for producing a spark ignition engine fuel according to claim 1,

the mixing ratio of the cyclopentane is set so that an ignition delay time from compression of the fuel to autoignition after the fuel is compressed to a predetermined compression ratio when the fuel is combusted at the predetermined compression ratio becomes 10ms or more.

3. The method of producing a spark ignition engine fuel according to claim 2,

the mixing proportion of the cyclopentane is less than 50% by volume.

4. The method of producing a spark ignition engine fuel according to claim 2,

the blending ratio of the cyclopentane is set so that a difference between a calculated value of the octane number of the fuel, which is calculated based on the octane number of the light naphtha, the octane number of the cyclopentane, and the blending ratio of the light naphtha and the cyclopentane becomes equal to or greater than a predetermined value, and an actual measured value of the octane number of the fuel.

5. The method for producing a spark ignition type engine fuel according to any one of claims 1 to 4,

the light naphtha is FT light naphtha obtained by fischer-tropsch synthesis.

6. The method for producing a spark ignition engine fuel according to claim 1,

the blending ratio of the cyclopentane is set based on a characteristic predetermined in advance such that the octane number of the fuel falls within a predetermined range, and the difference between a calculated value of the octane number of the fuel calculated based on the octane number of the light naphtha, the octane number of the cyclopentane, and the blending ratio of the light naphtha and the cyclopentane is set such that the difference between the calculated value of the octane number of the fuel and the measured value of the octane number of the fuel becomes equal to or greater than a predetermined value.

7. The method for producing a spark ignition engine fuel according to claim 6,

the prescribed range is set according to the octane number of standard gasoline.