Special fuel for thermomotor as well as preparation method and application of special fuel

Abstract

The invention relates to a preparation method of a special fuel for a coal-based heat engine. The method mainly comprises the following steps: 1) distilling a coal tar fraction under the pressure of 20KPa, and collecting a fraction with a boiling point of 240-340 DEG C under normal pressure to obtain the coal tar fraction; 2) carrying out selective hydrogenation ring opening on the coal tar fraction to obtain refined coal tar; 3) distilling the refined coal tar under the pressure of 20KPa, and collecting fractions with the boiling point of 240-340 DEG C under normal pressure to obtain refined coal tar fractions; 4) directly using the refined coal tar fraction as a special fuel for a thermomotor; or compounding the refined coal tar fraction with a special fuel for a petroleum-based hot-air engine to obtain the special fuel for the hot-air engine. The obtained fuel special for the hot-air engine is free of sulfur and nitrogen, high in cetane number, high in flash point and good in thermal oxidation stability, and is a high-performance fuel special for the hot-air engine.

Description

Technical Field

[0001] The present invention relates to a preparation method of a coal-based fuel, and more specifically to a preparation method of a special fuel for a coal-based hot air engine (coal as the initial raw material of the fuel). Background Art

[0002] The hot air engine not only has the advantages of high efficiency, small volume, light weight, etc., but also can be applied to various special scenarios. At present, the special fuel for the hot air engine is petroleum-based refined diesel, and the process is relatively complex. In addition, China's dependence on imported crude oil has far exceeded the internationally recognized safety warning line. Once international tensions occur or a war breaks out, the supply of diesel will be seriously threatened. It is urgent to expand the fuel security source. As a by-product of coking, coal tar is usually used as raw material oil for carbon black, fuel oil and asphalt blending oil, or separated into crude products such as naphthalene, anthracene, phenanthrene, carbazole, etc., but the comprehensive economy of these methods is poor, especially when it is consumed as low-grade fuel oil, which causes serious environmental pollution. Hydrofining of coal tar to produce high-performance coal-based fuel is an effective way for the clean utilization of tar, and it can also ensure fuel supply and optimize the fuel supply structure. Summary of the Invention

[0003] The present invention aims to provide a preparation method of a special fuel for a high-performance new hot air engine.

[0004] Based on the above object, the technical solution adopted by the present invention is as follows:

[0005] A) Distill coal tar under a pressure of 20 KPa and collect the fraction with a boiling point between 240 - 340 °C at normal pressure to obtain a coal tar fraction;

[0006] B) Perform selective hydrocracking on the coal tar fraction. The reaction conditions for selective hydrocracking are: reaction temperature 220 - 320 °C, reaction pressure 0.5 - 7 MPa, volumetric space velocity 0.5 - 5 h -1 , the volume ratio of hydrogen to the coal tar fraction is 200 - 2000, and the catalyst is a noble metal catalyst supported on molecular sieve to obtain refined coal tar;

[0007] C) Distill the refined coal tar under a pressure of 20 KPa and collect the fraction with a boiling point between 240 - 340 °C at normal pressure to obtain a refined coal tar fraction

[0008] D) Directly use the refined coal tar fraction as the special fuel for the hot air engine; or, compound the refined coal tar fraction with the special fuel for the petroleum-based hot air engine and use it as the special fuel for the hot air engine.

[0009] During the selective hydrocracking reaction in step B), the total conversion rate of the coal tar fraction is controlled at 25 - 75%.

[0010] In the noble metal catalyst supported on molecular sieve, the noble metal is one or more combinations of metals such as Pt and Pd, and the molecular sieve is one or more combinations of HY, NaY or USY.

[0011] In the special coal-based hot gas engine obtained in step D), the volume percentage of the selective hydrogenation ring-opening coal tar is 20-100%.

[0012] The advantages of the present invention are that through the selective hydrogenation ring-opening reaction of coal tar, the fuel hydrocarbon composition is adjusted. While maintaining a high yield, the physical and chemical properties of the fuel are improved, and a special fuel for coal-based hot gas engines with no sulfur, no nitrogen, high cetane number, high flash point and good thermal oxidation stability is obtained. The present invention reduces the dependence on petroleum-based fuels and broadens the fuel supply. Specific Embodiments

[0013] In order to further illustrate the present invention, the following examples are listed, but they do not limit the scope of the invention defined by the appended claims.

[0014] Example 1

[0015] Preparation of catalyst:

[0016] A) On a 20L distillation device (distillation column), fractionation of coal tar is carried out under a pressure of 20KPa, and the fraction of 220-320°C is collected to obtain a coal tar fraction;

[0017] B) Carry out a selective hydrogenation ring-opening reaction on 500 ml of the above coal tar fraction. The reaction conditions are: reaction temperature: 260°C, reaction pressure: 5MPa, volume space velocity: 3h -1 , hydrogen-oil volume ratio: 1000, the catalyst is Pt / USY (Pt mass loading is 1%, prepared by equal-volume impregnation method), and the conversion rate of the coal tar fraction is 53%.

[0018] C) Carry out fractionation of the selective hydrogenation ring-opening coal tar under a pressure of 20KPa (in the distillation column) and collect the fraction of 220-320°C to obtain a selective hydrogenation ring-opening coal tar fraction; At this time, the yield of the selective hydrogenation ring-opening coal tar fraction after distillation cutting (referring to the volume ratio of the liquid after removing the light components to the 220-320°C coal tar fraction) is 89.5%.

[0019] Example 2

[0020] Except that the reaction temperature is changed to 300°C in the raw material hydrogenation reaction step B), a selective hydrogenation ring-opening coal tar fraction obtained by the same method as in Example 1; the coal tar conversion rate is 75%, and the yield of the hydrogenation ring-opening coal tar fraction is 65.4%.

[0021] Example 3

[0022] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the reaction temperature in the raw material hydrogenation reaction step B) is changed to 220 °C; the coal tar conversion rate is 25%, and the yield of the hydrogenated ring-opening coal tar fraction is 95.4%.

[0023] Example 4

[0024] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the reaction pressure in the raw material hydrogenation reaction step B) is changed to 0.5 MPa; the coal tar conversion rate is 27%, and the yield of the hydrogenated ring-opening coal tar fraction is 94%.

[0025] Example 5

[0026] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the reaction pressure in the raw material hydrogenation reaction step B) is changed to 7 MPa; the coal tar conversion rate is 75%, and the yield of the hydrogenated ring-opening coal tar fraction is 65%.

[0027] Example 6

[0028] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the space velocity in the raw material hydrogenation reaction step B) is changed to 0.5 h -1 ; the coal tar conversion rate is 76%, and the yield of the hydrogenated ring-opening coal tar fraction is 63.4%.

[0029] Example 7

[0030] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the space velocity in the raw material hydrogenation reaction step B) is changed to 5 h -1 ; the coal tar conversion rate is 46%, and the yield of the hydrogenated ring-opening coal tar fraction is 90%.

[0031] Example 8

[0032] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the hydrogen-to-oil ratio in the raw material hydrogenation reaction step B) is changed to 200; the coal tar conversion rate is 37%, and the yield of the hydrogenated ring-opening coal tar fraction is 91%.

[0033] Example 9

[0034] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that the hydrogen-to-oil ratio in the raw material hydrogenation reaction step B) is changed to 2000; the coal tar conversion rate is 47%, and the yield of the hydrogenated ring-opening coal tar fraction is 90%.

[0035] Example 10

[0036] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that in the raw material hydrogenation reaction step B), the catalyst was changed to Pt / NaY (Pt mass loading of 1%, prepared by the incipient wetness impregnation method); the coal tar conversion rate was 48%, and the yield of the hydrogenated ring-opening coal tar fraction was 90%.

[0037] Example 11

[0038] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that in the raw material hydrogenation reaction step B), the catalyst was changed to Pt / HY (Pt mass loading of 1%, prepared by the incipient wetness impregnation method); the coal tar conversion rate was 68%, and the yield of the hydrogenated ring-opening coal tar fraction was 82%.

[0039] Example 12

[0040] A selectively hydrogenated ring-opening coal tar fraction obtained by the same method as described in Example 1, except that in the raw material hydrogenation reaction step B), the catalyst was changed to Pd / USY (Pt mass loading of 1%, prepared by the incipient wetness impregnation method); the coal tar conversion rate was 51%, and the yield of the hydrogenated ring-opening coal tar fraction was 89%.

[0041] Comparative Example 1

[0042] Using the existing petroleum-based hot gas engine special fuel as a comparison, the physical and chemical properties and thermal oxidation stability of the coal-based hot gas engine special fuel obtained by the preparation method of the present invention were investigated. The test results of the physical and chemical properties are shown in Table 1.

[0043] Table 1: Physical and chemical properties of the coal-based hot gas engine special fuel obtained under different conditions

[0044]

[0045]

[0046] In the selective hydrogenation ring-opening reaction of the coal tar, as the conversion rate of the raw material increases, the cetane number increases. When the conversion rate reaches a certain level, the cetane number no longer increases, but the cracking side reaction increases, resulting in a decrease in the yield of the target product.

Claims

1. A method for preparing a special fuel for a Stirling engine, characterized in that, The main steps are as follows: A) Distill coal tar under a pressure of (5 - 50) KPa and collect the fraction with a boiling point between 220 - 340 °C at atmospheric pressure to obtain a coal tar fraction; B) Carry out selective hydrocracking of the coal tar fraction. The reaction conditions for selective hydrocracking are as follows: reaction temperature 220 - 340 °C (preferably 230 - 300 °C, more preferably 240 - 280 °C), reaction pressure 0.5 - 7 MPa (preferably 4 - 6 MPa), space velocity 0.5 - 5 h -1 (preferably 2 - 5 h -1 ,), the volume ratio of hydrogen to the coal tar fraction is 200 - 2000 (preferably 500 - 1500), and the catalyst is a noble metal catalyst supported on molecular sieve to obtain refined coal tar; C) Distill the refined coal tar under a pressure of (5 - 50) KPa and collect the fraction with a boiling point between 220 - 340 °C at atmospheric pressure to obtain a refined coal tar fraction.

2. The preparation method according to claim 1, wherein: During the selective hydrogenation ring - opening reaction described in step B), the total conversion rate of the coal tar fraction is controlled at 25 - 75% (preferably 30 - 70%).

3. The preparation method according to claim 1, characterized in that: The noble metal in the noble - metal - loaded molecular sieve catalyst is one or a combination of two of metals such as Pt, Pd, etc., and its mass percentage is: 0.1% - 5%, preferably 0.5% - 3%; the molecular sieve is one or a combination of two or more of HY, NaY, or USY.

4. According to the preparation method described in claim 1, characterized in that: The refined coal tar fraction is directly used as a special fuel for a coal - based hot - air engine; or, the refined coal tar fraction is compounded with a special fuel for a petroleum - based hot - air engine and used as a special fuel for a coal - based hot - air engine; In the special fuel for a coal - based hot - air engine, the volume percentage of the refined coal tar fraction is 20 - 100%.

5. A special fuel for a hot - air engine prepared by the preparation method according to any one of claims 1 - 4.

6. Application of the special fuel for a coal - based hot - air engine according to claim 5 as a fuel in a hot - air engine.

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