JPH0137437B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for thermally decomposing heavy oil, and more specifically, the present invention relates to a method for thermally decomposing heavy oil, and more specifically, it generates gas by thermally decomposing heavy oil using carbon monoxide and steam in the presence of a specific catalyst and under a specific temperature and pressure. The present invention also relates to a method for obtaining middle distillates such as kerosene and gas oil in high yield while suppressing the production of pitches and cokes. Lightening of heavy oil by cracking is becoming an important issue with the recent tendency for crude oil to become heavier. Various methods have been developed to lighten heavy oil, but the most common method is nickel-oil.
This is a hydrogenolysis method that uses a molybdenum-silica-alumina solid acid catalyst and reacts with high-pressure hydrogen at 400-450°C. However, this method requires (1) a deasphalt process depending on the type of feedstock oil because asphaltene in the feedstock does not decompose and easily deteriorates into pitch or coke, resulting in asphalt being produced as a by-product; 2) While the amount of light distillates such as gas and gasoline is large, the amount of middle distillates such as kerosene and diesel oil is small; (3) Skeletal isomerization progresses in parallel with thermal decomposition. (4) Since the precipitation of coke and the like on the catalyst surface is significant, it has various problems and drawbacks such as a high deterioration rate of the catalyst. The present inventors have conducted extensive research in order to overcome the drawbacks of the above-mentioned conventional techniques and to develop a method for decomposing heavy oils such as kerosene and gas oil with a high yield of middle distillates. As a result, when heavy oil is pyrolyzed using a carbon monoxide-containing gas such as synthesis gas under a specific temperature and pressure in the presence of a specific catalyst and water vapor, a water gas shift reaction occurs. (CO＋ _H2O →
It has been found that the hydrogen produced by CO ₂ +2H) is active and suppresses the production of coke and the like, as well as controlling excessive decomposition, thereby increasing the yield of the desired middle distillate. The present invention was completed based on this knowledge. That is, in the present invention, heavy oil is treated with carbon monoxide and steam in the presence of an alkali metal compound,
Reaction temperature 400-470℃, reaction pressure 50-130Kg/cm ² −
This invention provides a method for thermally decomposing heavy oil, which is characterized by thermally decomposing it under the conditions of G. The heavy oil to be thermally decomposed by the method of the present invention is not particularly limited and may include various oils such as atmospheric residual oil and vacuum residual oil. Next, the hydrogenating agent used in the method of the present invention is not hydrogen gas itself, but hydrogen obtained by causing a shift reaction (CO+H ₂ O→CO ₂ +2H) with carbon monoxide and water vapor. In addition, various gases can be considered as sources of carbon monoxide used here.
Further, this gas may also contain hydrogen gas. As the gas as the carbon monoxide source, it is common and convenient to use synthesis gas, that is, the product gas of the so-called steam reforming reaction of hydrocarbons during hydrogen production. The method of the present invention is economically very advantageous because such synthesis gas can be used as a hydrogenating agent without undergoing any treatment such as CO conversion or purification. In the method of the present invention, the ratio of carbon monoxide and water vapor to be present in the thermal decomposition reaction system is not particularly limited and may be adjusted so that the shift reaction sufficiently proceeds and a large amount of active hydrogen is generated. Although stoichiometrically they should be equimolar, it is usually preferable to have a slight excess of water vapor. In addition, the supply ratio of carbon monoxide and steam to heavy oil, which is a raw material, can be selected appropriately depending on various conditions and cannot be unambiguously determined, but for example, the ratio of steam to heavy oil is 0.05 to 0.5. (weight ratio) is preferable. When the amount of water vapor supplied increases, the yield of the target middle distillate increases, but the reaction rate itself decreases, so it is preferable to set it within the above range depending on the purpose, taking into account the balance between the two. Become. In addition, when synthesis gas is used as a carbon monoxide source in the method of the present invention, hydrogen gas (molecular hydrogen) is supplied into the reaction system in an approximately equimolar ratio to carbon monoxide. Since this molecular hydrogen has a lower activity than the hydrogen produced in the shift reaction, it is thought that it hardly participates in the thermal decomposition reaction. Therefore, it seems that the presence of this hydrogen gas does not substantially affect the thermal decomposition reaction of the present invention. Furthermore, the method of the invention is carried out in the presence of an alkali metal compound. The method of the present invention carries out a thermal decomposition reaction of heavy oil using active hydrogen obtained by a shift reaction between carbon monoxide and steam as a hydrogen source. It plays the role of facilitating smooth promotion. The alkali metal compounds used as catalysts for this shift reaction include various compounds such as lithium, sodium, and potassium, such as carbonates,
Examples include hydroxide. Specific examples include potassium carbonate, lithium carbonate, sodium carbonate, potassium hydroxide, and the like. Furthermore, it is of course possible to use these compounds by fixing them on solids such as silica gel, alumina, and activated carbon. Furthermore, in the method of the present invention, the temperature of the pyrolysis reaction is 400-470°C, preferably 430-460°C, and the pressure is 50°C.
~130Kg/ ^cm2 -G, preferably 90-130Kg/cm2 ^- G
Should be. In the present invention, the reaction temperature is 400℃.
The yield of middle distillates is high at low temperatures below ℃;
The reaction rate becomes extremely low, and high temperatures exceeding 470° C., although the reaction rate is high, are undesirable because the yield of middle distillates decreases and the yield of light fractions and coke increases. In addition, the reaction pressure is 50Kg/cm ²
If it is less than -G or exceeds 130 Kg/cm ² -G, the yield of the middle distillate will be low and undesirable. The method of the present invention can be implemented in various embodiments, and one embodiment will be explained below based on FIG. First, after dispersing powder of an alkali metal compound, which is a shift reaction catalyst, into heavy oil, which is a feedstock oil,
It is preheated in a preheater 1 and introduced into a reactor 2. Further, into this reactor 2 are introduced a synthesis gas (a gas whose main components are carbon monoxide and hydrogen gas) from a gasifier 3 and water from a water washing step 4 and others. Then, in this reactor 2, a shift reaction (CO + H ₂ O→
CO ₂ +2H) occurs, and then the generated hydrogen causes the thermal decomposition reaction of heavy oil to proceed. Note that reactors that can be used here include those of various shapes, such as empty columns, tubes, and packed columns (up flow type and down flow type). This reactor 2
The oil produced in the column is led to the fractionating column 5, where naphtha fractions or middle distillates such as kerosene and light oil are separated, and unreacted oil is extracted from the bottom of the fractionating column 5 as residual oil. Served. Note that this residual oil contains a used shift reaction catalyst. Most of this residual oil is recycled to the reactor 2 while still containing the shift reaction catalyst, but a portion is used as fuel or a raw material for synthesis gas. If the presence of the shift catalyst is undesirable for the gasification reaction, the shift catalyst may be separated from the residue by washing with water or dilute acid. Further, when the shift catalyst is supported on a solid, the catalyst may be separated by filtration or other known solid-liquid separation methods. When separated by water washing, the washing liquid can be fed again to the reactor 2 for the purpose of supplying the catalyst and water. If the method of the present invention is carried out in the manner described above, unreacted heavy oil will be recycled to the reactor as residual oil, resulting in a high reaction rate and a shift reaction catalyst. Since it is constructed as a closed system, it can be reused and is extremely economical. As mentioned above, the method of the present invention does not use expensive high-pressure hydrogen as a hydrogenating agent, but instead uses highly active hydrogen produced by a shift reaction between inexpensive synthesis gas and steam, making it extremely economical. At the same time, it is possible to suppress the production of pitches and cokes and obtain middle distillates in high yield. Furthermore, the method of the present invention is basically a thermal decomposition reaction, and unlike the case of using a normal solid acid catalyst, skeletal isomerization does not occur. Therefore, when linear paraffins are decomposed, the products are low molecular weight linear paraffins and α-olefins, and the molecular weight of these products can be changed significantly by controlling the reaction temperature, reaction time, etc. It is. Therefore, the method of the present invention can be used very effectively industrially. Next, the method of the present invention will be explained more specifically and in detail based on Examples. Example 1 and Comparative Example (Using high-grade paraffin as raw material oil) A 150 ml induction stirring autoclave (made of stainless steel) was used as a reaction vessel, and a model compound of heavy oil with the composition shown in Fig. 2 was used as raw material oil. high-grade paraffin (manufactured by Koizumi Chemicals, melting point 58~
60℃, average molecular weight 395) approx. 25.0g (6.3×10 ^-2 mol)
Injected and further shifted K ₂ CO ₃ as a reaction catalyst
About 1.25 g of powder was dispersed, and water was added thereto at a ratio of 0 to 0.15 (weight ratio) to the above-mentioned high paraffin. Next, a gas selected from synthesis gas (equimolar mixture of CO and H ₂ gas), nitrogen gas, or hydrogen gas is introduced into this system to give an initial pressure of 50 Kg/cm ² -G, and the operating pressure is further increased to 90 ~ It was selected in the range of 130Kg/cm ² -G. The reaction temperature is set in the range of 400 to 460℃,
The reaction time starts from the time when the reaction system reaches the specified temperature.
The duration was 15 to 45 minutes. Note that it took about 30 minutes to raise the temperature. In addition, from the time when the temperature reached 100℃ after the start of temperature rise, stirring was continued at 100℃ during the reaction and after the reaction was completed.
It was carried out at 300 rpm until the temperature dropped below ℃. It took about 60 minutes to let it cool. The reaction was carried out in the above order, and the obtained product was analyzed by the following method. (A) Gas: After the autoclave was allowed to cool to room temperature, the final pressure was measured, and the gas in the autoclave was collected and analyzed for its composition. Quantification of CO, CO ₂ , N ₂ , CH ₄ It was carried out using a thermal conductivity gas chromatograph using a 2 m activated carbon column. Quantification of _H2 : 3m molecular sieve 13×
The thermal conductivity was measured using a gas chromatograph using a column and a nitrogen carrier. Quantification of gaseous hydrocarbons Measurement was performed by hydrogen flame gas chromatography using a 2m activated alumina column at elevated temperatures of 60 to 140°C. Standard gas was used for quantitative determination. (B) Liquid: After the liquid was weighed, it was analyzed by hydrogen flame gas chromatography using a 2m Dexyl 300GC column and heating from room temperature to 380°C at a rate of 5°C/min. (C) Bromine number: The bromine number of the liquid hydrocarbon was measured according to JISK-2543, and the olefin content was calculated from the average molecular weight of the hydrocarbon. (D) Reaction rate and selectivity of each fraction The reaction rate was calculated using the following formula. Reaction rate = Amount of product having 1 to 19 carbon atoms/Amount of raw oil supplied x 100 (
%) The selectivity of each fraction is, for example, carbon number 1
For products with carbon numbers of 1 to 4, the selectivity of products with 1 to 4 carbon atoms was calculated as follows: Amount of products with 1 to 4 carbon atoms/Amount of products with 1 to 19 carbon atoms x 100 (%) . The results of the reaction conducted under the above conditions are shown below. (1) Effect of filling gas Table 1 shows the reaction results with various filling gases.

[Table] As can be seen from Table 1 above, the reaction rate is H ₂
The order is system > N ₂ system > synthesis gas (CO + H ₂ ) system > synthesis gas - water vapor (CO + H ₂ + H ₂ O) system, and H ₂
The reaction in the system was particularly effective in accelerating decomposition. However, when looking at the selectivity, the H ₂ system produces a large amount of C ₁ to C ₄ gas, while the synthesis gas-steam system produces a large amount of C ₁ to C 4 gas.
~ The amount of C ₄ gas produced is extremely small, and C ₁₀ ~ C ₁₄ ,
It can be seen that the amount of C ₁₅ to C ₁₉ produced is increasing. Moreover, in this synthesis gas-steam system, the olefin content in the produced liquid is extremely small. Therefore, taking these things into consideration, it can be seen that the yield of so-called middle distillates increases significantly when a syngas-steam-based filling gas is used. (2) Effect of reaction time The reaction was carried out under the conditions of filling gas CO+H ₂ , water supply amount H ₂ O/raw material paraffin=1 (molar ratio), and reaction temperature 450° C. while changing the reaction time. The weight distribution of the obtained decomposition products is shown in FIG. As can be seen from FIG. 3, secondary and tertiary decomposition of the decomposition products progresses as the reaction time increases, and the distribution shifts to the lower carbon atom number side. (3) Effect of reaction temperature The reaction was carried out under the conditions of filling gas CO+H ₂ , water supply amount H ₂ O/raw material paraffin=1 (molar ratio), and reaction time 30 minutes while varying the temperature. The molar distribution of the decomposition products obtained is shown in FIG. (4) Effect of water supply amount The reaction was carried out under the conditions of filling gas CO + H ₂ , reaction temperature 450° C., and reaction time 30 minutes while changing the water supply amount. Figure 5 shows the amount of CO consumed and the amount of CO ₂ produced during the reaction. Moreover, FIG. 6 shows the molar distribution of the decomposition products obtained in the above reaction. Example 2 (Using Daqing atmospheric residual oil as raw material oil) A 150 ml induction stirring autoclave (made of stainless steel) was used as a reaction vessel, and Daqing atmospheric residual oil (average molecular weight 612, elemental analysis value: C85.03%, H13.90%, N0.24%, S0.16%,
Inject 25g or 35g of O0.67%), further disperse K ₂ CO ₃ powder as a shift reaction catalyst at a ratio of 5% by weight based on the feedstock oil, and add water to this at a rate of 10% by weight based on the feedstock oil. added at the rate of Next, synthesis gas (equimolar mixture of CO and _H2 ) was introduced into the system to give an initial pressure of 50Kg/cm2-G, and the operating pressure was further increased to 90Kg/ ^cm2 -G.
It was selected in the range of ~130Kg/cm ² -G. The reaction temperature is
The temperature was set in the range of 400 to 460°C, and the reaction time was 15 to 45 minutes from the time the reaction system reached the predetermined temperature. Note that it took about 30 minutes to raise the temperature. In addition, stirring was carried out at 300 r.pm from the point when the temperature reached 100℃ after the start of temperature rise until the temperature reached 100℃ or less during the reaction and after the reaction was completed.
I did it at Note that cooling required approximately 10 minutes. The reaction was carried out in the above order, and the obtained product was analyzed by the following method. (A) Gas: Basically, the analysis method is the same as that of the gas obtained by thermal decomposition of high-grade paraffin described above. (B) Liquid: The distillation curve was measured in a N ₂ stream using a thermal balance. We also conducted measurements using GPC. The above was used as a guideline for decomposition. Note that coke refers to the solid content in the liquid that does not dissolve in benzene. The results of the reaction conducted under the above conditions are shown below. (1) Effect of coexistence of synthesis gas and steam The reaction was carried out under the conditions of 35.0 g of Daqing atmospheric residual oil, reaction temperature of 440° C., and reaction time of 30 minutes while varying the amount of steam added. The reaction results obtained are shown in Table 2. Moreover, the weight distribution of the decomposition products obtained by the reaction under different atmospheres is shown in FIG. Furthermore, the seventh
The reaction temperature for the reaction shown in the figure was selected to be 440°C. As can be seen from Table 2, there is no significant difference in the amount of gas or liquid produced depending on whether or not steam is added, but the amount of coke produced is significantly reduced by increasing the amount of steam added. The reaction progresses more and more hydrogen is produced than is consumed. Furthermore, as is clear from Figure 7, in the reaction in an atmosphere of synthesis gas + steam, the decomposition reaction itself is slightly slower than the reaction in a hydrogen atmosphere, but it is an inert gas. The reaction is comparable to that under a nitrogen atmosphere, and the production of coke is significantly lower than in either atmosphere. In other words, it can be seen that according to the method of the present invention, residual oil can be efficiently decomposed while suppressing the production of coke to a minimum.

[Table] (2) Effect of reaction time The reaction was carried out under the conditions of 25.0 g of Daqing atmospheric residual oil and a reaction temperature of 450°C, while varying the reaction time. The reaction results obtained are shown in Table 3, and the weight distribution of the decomposition products is shown in FIG. Furthermore, the results of molecular weight distribution of the product obtained using gel permeation chromatography are shown in FIG. In FIG. 9, PS indicates the molecular weight in terms of polystyrene. The results shown in Table 3 and FIG. 8 show that when cracking is carried out by the method of the present invention, a cracking rate of 70 to 80% is easily achieved, while at the same time the yields of gas and coke are extremely low. It can be seen that by appropriately adjusting the reaction time, the main product can be controlled to be kerosene or gas oil fraction. Also, from the results shown in Figure 9, the molecular weight of the reaction product shifts to the lower molecular weight side compared to the raw material residual oil, but in particular, high molecular weight substances with a molecular weight of 10,000 or more are preferentially decomposed, resulting in light I know it will take a minute.

[Table] (3) Effect of reaction temperature The reaction was carried out under the conditions of 35.0 g of Daqing atmospheric residual oil and 30 minutes of reaction time while varying the reaction temperature. The reaction results obtained are shown in Table 4, and the weight distribution of the decomposition products is shown in FIG. From the results shown in Figure 10, the reaction temperature was 400°C.
It can be seen that although decomposition hardly progresses in this case, the decomposition rate increases as the temperature rises. In particular, it can be seen that at a reaction temperature of 460°C, most of the residual oil is decomposed, but the production of gas and coke increases.

[Table] Example 3 and comparative example (Kuwait atmospheric residual oil was used as feedstock oil) Kuwait atmospheric residual oil was used as feedstock oil (sulfur content 3.84
%, specific gravity 0.910, residual carbon 10.5%) was used in the same manner as in Example 2. The results of the reaction with gas filling are shown in Table 5.

[Table] As is clear from Table 5, the reaction rates are almost the same for both the N ₂ system and the (CO+H ₂ O) system. However, looking at the distribution of products, in the _N2 system _C1 to _C4
The amount of gas and coke produced is large, while (CO+
It can be seen that in the H ₂ O) system, the amount of C ₁ to _{C 4} gas and coke produced is small (in particular, coke is less than half of that in the N ₂ system), and the kerosene fraction is increased. Example 4 and Comparative Example (Daqing atmospheric residual oil used as raw material oil) A 150 ml induction stirring autoclave (made of stainless steel) was used as the reaction vessel, and 35 g of Daqing atmospheric residual oil (average molecular weight 612) was used as the raw material oil. was injected, and furthermore, K ₂ CO ₃ powder was dispersed as a shift reaction catalyst at a ratio of 5% by weight based on the raw oil, and water was added thereto at a ratio of 10% by weight based on the raw oil. Subsequently, a synthesis gas (equimolar mixed gas of CO and H ₂ ) was introduced into the system to give an initial pressure of 50 Kg/cm ² -G, and an operating pressure of 90 Kg/cm ² -G. The reaction temperature is
The temperature was 440°C, and the reaction time was 30 minutes from the time when the reaction system reached a predetermined temperature. Note that it took about 30 minutes to raise the temperature. In addition, stirring is performed from the point when the temperature reaches 100℃ after the start of temperature rise, during the reaction and after the completion of the reaction by water cooling.
It was carried out at 300 rpm until the temperature dropped to below 100°C. Note that cooling required 10 minutes. Table 6 shows the reaction results depending on the difference in reaction pressure.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the method of the present invention. FIG. 2 shows the composition distribution of higher paraffin used in the examples. 3, 4 and 6 to 10 show the composition distribution of the decomposition products obtained by the method of the present invention. FIG. 5 shows the amount of CO consumed and the amount of CO ₂ produced when the method of the present invention is carried out. In FIG. 1, 1 is a preheater, 2 is a reactor, 3 is a gasifier, 4 is a water washing step, 5 is a fractionation column, and 6 is a gas scrubber.

Claims (1)

[Claims] 1. Heavy oil is treated with carbon monoxide and steam in the presence of an alkali metal compound at a reaction temperature of 400 to 470.
A method for thermally decomposing heavy oil, characterized by thermally decomposing it under conditions of temperature and reaction pressure of 50 to 130 kg/cm ² -G. 2. The method according to claim 1, in which synthesis gas is used as the carbon monoxide source.