Liquefied petroleum gas synthesis method

Abstract

Provided is a liquefied petroleum gas synthesis method with which it is possible to synthesize a liquefied petroleum gas stably over a long period of time while suppressing deterioration of a liquefied petroleum gas synthesis catalyst. This liquefied petroleum gas synthesis method is for synthesizing a liquefied petroleum gas from a raw material gas containing carbon monoxide and hydrogen by using a liquefied petroleum gas synthesis catalyst, the method comprising a coupling step for coupling the yield of the liquefied petroleum gas with the synthesis temperature for the liquefied petroleum gas.

Description

Method for synthesizing liquefied petroleum gas

[0001] The present disclosure relates to a method for synthesizing liquefied petroleum gas.

[0002] A method for synthesizing liquefied petroleum gas from synthesis gas using a catalyst for liquefied petroleum gas synthesis is known. In this synthesis method, when synthesizing propane-rich liquefied petroleum gas from synthesis gas, the synthesis temperature is 350 to 600°C, and it is known that the higher the synthesis temperature, the higher the yield of propane (Patent Document 1).

[0003] Thus, the synthesis temperature of liquefied petroleum gas affects the yield of propane, and a higher synthesis temperature of liquefied petroleum gas increases the yield of propane. However, if the synthesis temperature of liquefied petroleum gas is maintained at a high temperature, the catalyst for liquefied petroleum gas synthesis gradually deteriorates, and as a result, the yield of liquefied petroleum gas decreases significantly before the specified synthesis time is reached.

[0004] International Publication No. 2008 / 015995

[0005] An object of the present disclosure is to provide a method for synthesizing liquefied petroleum gas that can synthesize liquefied petroleum gas stably over a long period of time while suppressing deterioration of a catalyst for synthesizing liquefied petroleum gas.

[0006] [1] A method for synthesizing liquefied petroleum gas from a feedstock gas containing carbon monoxide and hydrogen using a catalyst for liquefied petroleum gas synthesis, the method comprising a linking step of linking the yield of liquefied petroleum gas with the synthesis temperature of the liquefied petroleum gas. [2] The method for synthesizing liquefied petroleum gas described in [1] above, wherein the linking step involves gradually increasing the synthesis temperature of the liquefied petroleum gas. [3] The method for synthesizing liquefied petroleum gas described in [1] above, wherein the linking step involves gradually increasing the yield of the liquefied petroleum gas with the synthesis temperature of the liquefied petroleum gas, and also gradually increasing the selectivity of propane with the synthesis temperature of the liquefied petroleum gas. [4] The method for synthesizing liquefied petroleum gas described in [3] above, wherein the linking step involves gradually increasing the synthesis temperature of the liquefied petroleum gas. [5] The method for synthesizing liquefied petroleum gas described in [3] above, wherein the linking step involves gradually decreasing the synthesis temperature of the liquefied petroleum gas. [6] The method for synthesizing liquefied petroleum gas according to any one of [1] to [4] above, wherein, in the interlocking step, when the yield of the liquefied petroleum gas falls below a predetermined range, the synthesis temperature of the liquefied petroleum gas is increased at a rate of 0.05°C / day or more and 5.00°C / day or less. [7] The method for synthesizing liquefied petroleum gas according to any one of [3] to [4] and [6] above, wherein, in the interlocking step, when the selectivity of propane falls below a predetermined range, the synthesis temperature of the liquefied petroleum gas is increased at a rate of 0.05°C / day or more and 5.00°C / day or less. [8] The method for synthesizing liquefied petroleum gas according to any one of [1] to [7] above, wherein the synthesis temperature of the liquefied petroleum gas is 280°C or more and 350°C or less. [9] The method for synthesizing liquefied petroleum gas according to any one of [6] to [8] above, wherein, in the interlocking step, the lower limit of the predetermined range for the yield of the liquefied petroleum gas is 25 Cmol% or more.

[10] The method for synthesizing a liquefied petroleum gas according to any one of [7] to [9] above, wherein in the interlocking step, the lower limit of the predetermined range for the selectivity of the propane is 70% by volume or more.

[11] The method for synthesizing a liquefied petroleum gas according to any one of [1] to

[10] above, wherein the catalyst for synthesizing a liquefied petroleum gas does not contain any one of the metal elements Fe, Co, and Ru.

[12] The method for synthesizing liquefied petroleum gas according to any one of [1] to

[11] above, further comprising a combustion step of contacting the liquefied petroleum gas synthesis catalyst with an oxygen-containing gas that is higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C, and a reduction step of contacting the liquefied petroleum gas synthesis catalyst with a reducing gas that is higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C after the combustion step.

[0007] According to the present disclosure, it is possible to provide a method for synthesizing liquefied petroleum gas, which can synthesize liquefied petroleum gas stably over a long period of time while suppressing deterioration of a catalyst for synthesizing liquefied petroleum gas.

[0008] Fig. 1 is a graph showing the liquefied petroleum gas synthesis temperature before and after linking the liquefied petroleum gas yield with the liquefied petroleum gas synthesis temperature in Example 1. Fig. 2 is a graph showing the liquefied petroleum gas, propane, and butane yields before and after linking the liquefied petroleum gas yield with the liquefied petroleum gas synthesis temperature in Example 1. Fig. 3 is a graph showing the propane selectivity before and after linking the liquefied petroleum gas yield with the liquefied petroleum gas synthesis temperature in Example 1.

[0009] Hereinafter, a detailed description will be given based on an embodiment.

[0010] As a result of extensive research, the inventors have discovered that by linking the liquefied petroleum gas yield during liquefied petroleum gas synthesis with the liquefied petroleum gas synthesis temperature, it is possible to synthesize liquefied petroleum gas stably over a long period of time while suppressing deterioration of the liquefied petroleum gas synthesis catalyst, and have completed the present disclosure based on this finding.

[0011] The liquefied petroleum gas synthesis method of the embodiment is a liquefied petroleum gas synthesis method that synthesizes liquefied petroleum gas from a raw material gas containing carbon monoxide and hydrogen using a liquefied petroleum gas synthesis catalyst, and has a linking process that links the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature.

[0012] The liquefied petroleum gas synthesis method of the above embodiment synthesizes liquefied petroleum gas from a feedstock gas containing carbon monoxide and hydrogen using a liquefied petroleum gas synthesis catalyst. In the liquefied petroleum gas synthesis method, the synthesis of liquefied petroleum gas is started at an initial setting temperature, and the yield of the synthesized liquefied petroleum gas is measured during the synthesis, and the synthesis temperature of the liquefied petroleum gas can be adjusted during the synthesis. The measurement of the liquefied petroleum gas yield may be continuous or intermittent over the synthesis time. Furthermore, the adjustment of the liquefied petroleum gas synthesis temperature may be continuous or intermittent over the synthesis time. The liquefied petroleum gas synthesis method further includes a linking step of linking the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature during the synthesis of the liquefied petroleum gas.

[0013] In this application, "linkage" means that a parameter and another parameter change in a unified manner, or that a parameter is changed by another parameter, or that a change in a parameter is predicted and another parameter is changed in a unified manner based on the prediction.

[0014] Some parameters may be of one type or of multiple types, and other parameters may be of one type or of multiple types.

[0015] Change refers to increase, decrease, or maintenance over time.

[0016] In this application, the "synthesis temperature" refers to the catalyst bed temperature of the catalyst for synthesizing liquefied petroleum gas.

[0017] For example, if the liquefied petroleum gas yield is higher than the predetermined range, the high synthesis temperature of the liquefied petroleum gas causes rapid deterioration of the liquefied petroleum gas synthesis catalyst, leading to a rapid decrease in the liquefied petroleum gas yield as the synthesis of the liquefied petroleum gas progresses. In such a situation, by lowering the synthesis temperature of the liquefied petroleum gas below the initial setting temperature in the interlocking process so that the liquefied petroleum gas yield falls within the predetermined range, it is possible to synthesize liquefied petroleum gas stably at a yield within the predetermined range while suppressing the rate of deterioration of the liquefied petroleum gas synthesis catalyst. If the synthesis temperature of the liquefied petroleum gas is lowered to the point where the liquefied petroleum gas yield falls below the predetermined range, it will no longer be possible to synthesize liquefied petroleum gas at a yield within the predetermined range.

[0018] Furthermore, as the synthesis of liquefied petroleum gas progresses and the liquefied petroleum gas yield gradually drops below the predetermined range, it becomes impossible to synthesize liquefied petroleum gas at a yield within the predetermined range. In such a situation, by raising the liquefied petroleum gas synthesis temperature above the initial setting temperature in the interlocking process so that the liquefied petroleum gas yield increases to within the predetermined range, it is possible to synthesize liquefied petroleum gas stably at a yield within the predetermined range while suppressing the rate of deterioration of the liquefied petroleum gas synthesis catalyst. If the liquefied petroleum gas synthesis temperature is raised until the liquefied petroleum gas yield exceeds the predetermined range, the deterioration of the liquefied petroleum gas synthesis catalyst will progress rapidly, leading to a rapid drop in the liquefied petroleum gas yield.

[0019] In this way, in the linking process, liquefied petroleum gas is synthesized while linking the yield of the liquefied petroleum gas being synthesized with the synthesis temperature of the liquefied petroleum gas so that the yield of the liquefied petroleum gas falls within a predetermined range, and liquefied petroleum gas can be synthesized stably over a long period of time while suppressing deterioration of the liquefied petroleum gas synthesis catalyst.

[0020] The link between the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature does not need to be always performed during the synthesis of liquefied petroleum gas, but is performed, for example, when the liquefied petroleum gas yield falls outside the specified range, as described above. Increasing the liquefied petroleum gas synthesis temperature can increase the liquefied petroleum gas yield, and decreasing the liquefied petroleum gas synthesis temperature can decrease the liquefied petroleum gas yield. In this way, the link between the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature can be controlled.

[0021] In particular, when the liquefied petroleum gas yield is lower than a predetermined range, it is preferable to gradually increase the liquefied petroleum gas synthesis temperature in accordance with the liquefied petroleum gas yield in the interlocking process. In this way, gradually increasing the liquefied petroleum gas synthesis temperature relative to the liquefied petroleum gas synthesis time can suppress deterioration of the liquefied petroleum gas synthesis catalyst due to coke coating and deterioration due to active metal aggregation, which are associated with a sudden increase in synthesis temperature, as well as suppressing a decrease in the liquefied petroleum gas yield due to excessive cracking of the target product. In particular, in the interlocking process, when the liquefied petroleum gas yield is lower than a predetermined range, it is preferable to increase the liquefied petroleum gas synthesis temperature at a rate of 0.05°C / day or more and 5.00°C / day or less.

[0022] Furthermore, when the synthesis temperature of liquefied petroleum gas is increased to increase the yield of liquefied petroleum gas, from the viewpoint of suppressing deterioration of the catalyst for synthesizing liquefied petroleum gas, the upper limit of the synthesis temperature of liquefied petroleum gas is preferably 350° C. or less, more preferably 340° C. or less, even more preferably 330° C. or less, still more preferably 320° C. or less, and most preferably 310° C. or less. Furthermore, if the lower limit of the synthesis temperature of liquefied petroleum gas is preferably 280° C. or more, more preferably 290° C. or more, even more preferably 300° C. or more, and still more preferably 305° C. or more, liquefied petroleum gas can be synthesized stably.

[0023] In particular, when the liquefied petroleum gas yield is higher than a predetermined range, it is preferable to gradually lower the liquefied petroleum gas synthesis temperature, which is linked to the liquefied petroleum gas yield, in the interlocking process. In this way, gradually lowering the liquefied petroleum gas synthesis temperature relative to the liquefied petroleum gas synthesis time can suppress a decrease in the liquefied petroleum gas yield. Furthermore, suppressing coke coating contributes to extending the catalyst life. In particular, in the interlocking process, when the liquefied petroleum gas yield is higher than a predetermined range, it is preferable to gradually lower the liquefied petroleum gas synthesis temperature at a rate of 0.05°C / day or more and 5.00°C / day or less.

[0024] In the interlocking step, the lower limit of the predetermined range of the liquefied petroleum gas yield is 25 Cmol% or more, more preferably 30 Cmol% or more, and even more preferably 35 Cmol% or more, and the upper limit is, for example, 40 Cmol% or less. After starting the synthesis of liquefied petroleum gas at the initial setting temperature, the interlocking step can be performed if the liquefied petroleum gas yield falls outside the predetermined range.

[0025] The initial setting temperature is the temperature at which liquefied petroleum gas can be produced as a main component at the start of liquefied petroleum gas synthesis. The initial setting temperature refers to, for example, the temperature at which at least 20 Cmol%, 30 Cmol%, or 40 Cmol% of liquefied petroleum gas can be produced at the start of liquefied petroleum gas synthesis. The initial setting temperature varies depending on the liquefied petroleum gas synthesis catalyst used, so it is preferable to clarify it through prior experiments. Although it varies depending on the liquefied petroleum gas synthesis catalyst used, the initial setting temperature can be preferably 300°C or higher, more preferably above 300°C, and even more preferably 310°C or higher.

[0026] In addition, instead of detecting the yield of liquefied petroleum gas, it is also possible to detect the amount of synthesis gas (carbon monoxide and / or hydrogen) that is an unreacted product in the synthesis of liquefied petroleum gas. In the interlocking process, if the amount of synthesis gas after synthesis is greater than a predetermined range, it can be estimated that the yield of liquefied petroleum gas is low, and if the amount of synthesis gas after synthesis is less than a predetermined range, it can be estimated that the yield of liquefied petroleum gas is high.

[0027] In addition, substances other than synthetic gas that can be used as substitutes for the yield of liquefied petroleum gas include methane, ethane, hydrocarbons of C5 or higher, methanol, and dimethyl ether, which are produced by the synthesis of liquefied petroleum gas. For these gases, including synthetic gas, the amount of a single gas may be detected, or the total amount of multiple gases may be detected.

[0028] Furthermore, in the linking step, it is preferable that the yield of liquefied petroleum gas and the synthesis temperature of the liquefied petroleum gas are linked during the synthesis of the liquefied petroleum gas, and that the selectivity of propane and the synthesis temperature of the liquefied petroleum gas are linked. In the method for synthesizing liquefied petroleum gas having such a configuration, the selectivity of propane contained in the synthesized liquefied petroleum gas is measured during the synthesis. The measurement of the selectivity of propane may be continuous or intermittent with respect to the synthesis time.

[0029] For example, if the propane selectivity is higher than the predetermined range, the high synthesis temperature of the liquefied petroleum gas causes rapid deterioration of the liquefied petroleum gas synthesis catalyst, leading to a rapid decline in propane selectivity as the synthesis of the liquefied petroleum gas progresses. In such a situation, by lowering the synthesis temperature of the liquefied petroleum gas below the initial setting temperature in the interlocking process so that the propane selectivity falls within the predetermined range, it is possible to synthesize liquefied petroleum gas stably with a propane selectivity within the predetermined range while suppressing the rate of deterioration of the liquefied petroleum gas synthesis catalyst. If the synthesis temperature of the liquefied petroleum gas is lowered to the point where the propane selectivity falls below the predetermined range, it becomes impossible to synthesize liquefied petroleum gas with a propane selectivity within the predetermined range.

[0030] Furthermore, if the propane selectivity gradually drops below the predetermined range as the synthesis of liquefied petroleum gas progresses, it becomes impossible to synthesize liquefied petroleum gas with a propane selectivity within the predetermined range. In such a situation, by raising the liquefied petroleum gas synthesis temperature above the initial setting temperature in the interlocking process so that the propane selectivity increases to within the predetermined range, it is possible to synthesize liquefied petroleum gas stably with a propane selectivity within the predetermined range while suppressing the degradation rate of the liquefied petroleum gas synthesis catalyst. If the liquefied petroleum gas synthesis temperature is raised to the point where the propane selectivity exceeds the predetermined range, the degradation of the liquefied petroleum gas synthesis catalyst will progress rapidly, leading to a rapid drop in propane selectivity.

[0031] In this way, in the linking process, liquefied petroleum gas is synthesized while linking the selectivity of propane in the liquefied petroleum gas being synthesized with the synthesis temperature of the liquefied petroleum gas so that the selectivity of propane falls within a predetermined range, thereby making it possible to synthesize liquefied petroleum gas and propane stably over a long period of time while suppressing deterioration of the liquefied petroleum gas synthesis catalyst.

[0032] The linking of the propane selectivity and the synthesis temperature of liquefied petroleum gas does not need to be performed all the time during the synthesis of liquefied petroleum gas, but is performed, for example, when the propane selectivity falls outside the predetermined range as described above. Increasing the synthesis temperature of liquefied petroleum gas can increase the propane selectivity, and decreasing the synthesis temperature of liquefied petroleum gas can decrease the propane selectivity. In this way, the linking of the propane selectivity and the synthesis temperature of liquefied petroleum gas can be controlled.

[0033] In particular, when the propane selectivity is lower than a predetermined range, it is preferable to gradually increase the liquefied petroleum gas synthesis temperature in accordance with the propane selectivity in the interlocking step. In this way, gradually increasing the liquefied petroleum gas synthesis temperature relative to the liquefied petroleum gas synthesis time can suppress deterioration of the liquefied petroleum gas synthesis catalyst due to coke coating and active metal aggregation, which are associated with a sudden increase in synthesis temperature, as well as a decrease in the liquefied petroleum gas yield due to excessive cracking of the target product. In particular, in the interlocking step, when the propane selectivity is lower than a predetermined range, it is preferable to increase the liquefied petroleum gas synthesis temperature at a rate of 0.05°C / day or more and 5.00°C / day or less.

[0034] Furthermore, when the synthesis temperature of liquefied petroleum gas is increased to increase the selectivity of propane, from the viewpoint of suppressing deterioration of the catalyst for synthesizing liquefied petroleum gas, the upper limit of the synthesis temperature of liquefied petroleum gas is preferably 350° C. or less, more preferably 340° C. or less, even more preferably 330° C. or less, still more preferably 320° C. or less, and most preferably 310° C. or less. Furthermore, if the lower limit of the synthesis temperature of liquefied petroleum gas is preferably 280° C. or more, more preferably 290° C. or more, even more preferably 300° C. or more, and still more preferably 305° C. or more, liquefied petroleum gas and propane can be synthesized stably.

[0035] Furthermore, when the propane selectivity is higher than a predetermined range, it is preferable to gradually decrease the liquefied petroleum gas synthesis temperature, which is linked to the propane selectivity, in the interlocking process. In this way, gradually decreasing the liquefied petroleum gas synthesis temperature relative to the liquefied petroleum gas synthesis time can suppress a decrease in the liquefied petroleum gas yield that would otherwise be associated with a sudden decrease in synthesis temperature. Furthermore, suppressing coke coating contributes to extending the catalyst life. In particular, when the propane selectivity is higher than a predetermined range in the interlocking process, it is preferable to gradually decrease the liquefied petroleum gas synthesis temperature at a rate of 0.05°C / day or more and 5.00°C / day or less.

[0036] In the interlocking step, the lower limit of the predetermined range of the selectivity of propane is 70% by volume or more, and the upper limit is 90% by volume or less.

[0037] Furthermore, instead of detecting the selectivity of propane, it is also possible to detect the yield of butane, which is synthesized simultaneously with propane. In the interlocking process, if the yield of butane after synthesis is higher than a predetermined range, it can be estimated that the selectivity of propane is low, and if the yield of butane after synthesis is lower than the predetermined range, it can be estimated that the selectivity of propane is high.

[0038] Furthermore, the deterioration of the liquefied petroleum gas synthesis catalyst caused by raising the synthesis temperature of liquefied petroleum gas is caused by the deposition of carbonaceous material (coke) on the surface of the liquefied petroleum gas synthesis catalyst, which covers the active sites on the surface of the liquefied petroleum gas synthesis catalyst. Therefore, if the method for synthesizing liquefied petroleum gas further includes a combustion step in which the liquefied petroleum gas synthesis catalyst, whose catalytic activity has deteriorated, is brought into contact with an oxygen-containing gas that is higher than the synthesis temperature of liquefied petroleum gas but lower than 360°C, and a reduction step in which the liquefied petroleum gas synthesis catalyst is brought into contact with a reducing gas that is higher than the synthesis temperature of liquefied petroleum gas but lower than 360°C after the combustion step, the catalytic activity of the liquefied petroleum gas synthesis catalyst, whose catalytic activity has deteriorated, can be regenerated.

[0039] In the regeneration of such a liquefied petroleum gas synthesis catalyst, first, in a combustion step, the liquefied petroleum gas synthesis catalyst whose catalytic activity has deteriorated is brought into contact with an oxygen-containing gas at a temperature higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C, thereby burning and removing coke deposited on the surface of the liquefied petroleum gas synthesis catalyst. The oxygen-containing gas is preferably air. When the liquefied petroleum gas synthesis catalyst comes into contact with an oxygen-containing gas at 360°C or higher, metals contained in the liquefied petroleum gas synthesis catalyst, such as Cu and Zn contained in the methanol synthesis catalyst described below, aggregate, reducing the catalytic activity of the liquefied petroleum gas synthesis catalyst.

[0040] Although the coke present on the surface of the liquefied petroleum gas synthesis catalyst is removed by the oxygen-containing gas, the liquefied petroleum gas synthesis catalyst is oxidized because it is exposed to the oxygen-containing gas. The liquefied petroleum gas synthesis catalyst in the oxidized state has low catalytic activity.

[0041] Therefore, in the reduction step, the liquefied petroleum gas synthesis catalyst after being exposed to the oxygen-containing gas is brought into contact with a reducing gas that is higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C, thereby reducing the oxidized liquefied petroleum gas synthesis catalyst and improving the catalytic activity of the liquefied petroleum gas synthesis catalyst. In this way, the catalytic activity of the liquefied petroleum gas synthesis catalyst can be regenerated. The reducing gas is preferably a gas containing hydrogen, and the higher the hydrogen concentration, the more preferable, and hydrogen is even more preferable. When the liquefied petroleum gas synthesis catalyst comes into contact with a reducing gas at 360°C or higher, metals contained in the liquefied petroleum gas synthesis catalyst, such as Cu and Zn contained in the methanol synthesis catalyst described below, aggregate, reducing the catalytic activity of the liquefied petroleum gas synthesis catalyst.

[0042] Furthermore, in the combustion process, when a liquefied petroleum gas synthesis catalyst with deteriorated catalytic activity is brought into contact with an oxygen-containing gas at a temperature higher than the synthesis temperature of liquefied petroleum gas and lower than 360°C, it is preferable to bring the liquefied petroleum gas synthesis catalyst into contact with an oxygen-containing gas at a temperature higher than 310°C and lower than 360°C for 0.1 hours or more and within 48.0 hours in order to efficiently remove coke covering the surface of the liquefied petroleum gas synthesis catalyst.

[0043] Furthermore, in the reduction step, when the oxidized liquefied petroleum gas synthesis catalyst after exposure to the oxygen-containing gas is contacted with a reducing gas having a temperature higher than the synthesis temperature of liquefied petroleum gas but lower than 360°C, it is preferable to contact the liquefied petroleum gas synthesis catalyst with a reducing gas having a temperature of 320°C or higher but lower than 360°C for 0.1 hours or more but not exceeding 48.0 hours in order to efficiently reduce the oxidized liquefied petroleum gas synthesis catalyst.

[0044] Furthermore, if the regeneration of the catalyst for liquefied petroleum gas synthesis, i.e., the combustion step and reduction step, is carried out in the reactor used for the synthesis of liquefied petroleum gas, the interlocking step, the combustion step and the reduction step can be carried out in the same reactor, which is convenient.

[0045] In addition, it is preferable to regenerate the liquefied petroleum gas synthesis catalyst until the ratio of the yield of liquefied petroleum gas when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately after regeneration (immediately after the reduction step) to the yield of liquefied petroleum gas when liquefied petroleum gas is synthesized using an unused liquefied petroleum gas synthesis catalyst is 75% or more.

[0046] It is also preferable to regenerate the liquefied petroleum gas synthesis catalyst until the ratio of the carbon monoxide and / or hydrogen conversion rate when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately after regeneration to the carbon monoxide and / or hydrogen conversion rate when liquefied petroleum gas is synthesized using an unused liquefied petroleum gas synthesis catalyst is 75% or more.

[0047] In addition, it is preferable to regenerate the liquefied petroleum gas synthesis catalyst until the ratio of the yield of liquefied petroleum gas when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately after regeneration to the yield of liquefied petroleum gas when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately before regeneration (immediately before the combustion process) is 101% or more.

[0048] It is also preferable to regenerate the liquefied petroleum gas synthesis catalyst until the ratio of the carbon monoxide and / or hydrogen conversion rate when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately after regeneration to the carbon monoxide and / or hydrogen conversion rate when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately before regeneration is 101% or more.

[0049] The LPG yield when liquefied petroleum gas is synthesized using the liquefied petroleum gas synthesis catalyst immediately after regeneration is preferably 25 Cmol% or more, more preferably 27 Cmol% or more, and particularly preferably 30 Cmol% or more. The upper limit of the LPG yield is not particularly limited, but is, for example, about 50 Cmol%.

[0050] In the synthesis of liquefied petroleum gas, the interlocking process and the regeneration process (the combustion process and the reduction process carried out after the combustion process) can be carried out in combination. By combining the two, the catalyst for synthesizing liquefied petroleum gas can be used for a longer period of time.

[0051] The above-described method for regenerating a catalyst for synthesizing liquefied petroleum gas, which comprises a combustion step of contacting the catalyst for synthesizing liquefied petroleum gas with an oxygen-containing gas that is higher than the synthesis temperature of liquefied petroleum gas but lower than 360°C, and a reduction step of contacting the catalyst for synthesizing liquefied petroleum gas with a reducing gas that is higher than the synthesis temperature of liquefied petroleum gas but lower than 360°C, after the combustion step, is particularly effective when a Cu-Zn-based catalyst, as described below, is used as the catalyst for synthesizing liquefied petroleum gas.

[0052] Generally, metal compounds (elementary metals, metal oxides, etc.) contained in catalysts aggregate when heated during various reactions or regeneration processes, and the reduction in active sites due to aggregation has a negative effect on catalytic activity. Furthermore, since it is difficult to redisperse metal compounds that have aggregated once, how to prevent aggregation is an important issue for businesses.

[0053] Fe-based catalysts used in the Fischer-Tropsch synthesis process (FT synthesis) are known as catalysts for synthesizing hydrocarbons such as liquefied petroleum gas (JP 2022-102703 A). Fe-based catalysts contain iron and / or iron oxide as their primary components, with iron having a melting point of 1538°C and iron oxide having a melting point of 1565°C. Meanwhile, the melting point of copper in Cu-Zn-based catalysts after hydrogen reduction treatment is 1085°C, which is lower than that of iron or iron oxide. The melting point correlates with the degree of agglomeration, with higher melting points being less likely to agglomerate and lower melting points being more likely to agglomerate. Furthermore, copper has a lower activation energy for surface diffusion than iron, allowing copper atoms to migrate more easily across the surface of catalyst particles even at relatively low temperatures. Because copper atoms are more mobile on the surface, atomic mobility increases at low temperatures, promoting the growth of larger copper particles from smaller ones. Therefore, the lower the melting point and the lower the activation energy for surface diffusion of a metal, the more the reaction temperature and temperature adjustment of the regeneration process affect catalytic activity. In the above-mentioned known literature, it was unclear how activity could be regenerated while preventing aggregation when a metal having a lower melting point and a lower activation energy for surface diffusion than iron or iron oxide was used.

[0054] In addition to the above-mentioned issues related to melting point, atomic mobility, and agglomeration, a certain degree of high temperature is required for the removal of coke (oxidation treatment).

[0055] In other words, compared to Fe-based catalysts, Co-based catalysts, and Ru-based catalysts (FT synthesis catalysts), which are well-known catalysts for synthesizing hydrocarbons, Cu-Zn-based catalysts tend to be more susceptible to high-temperature regeneration processes. The inventors have addressed this special situation, which arises with metals that have lower melting points and lower activation energies for surface diffusion than iron or iron oxide, particularly Cu-Zn-based catalysts, by setting the temperatures of the oxidation and reduction processes above the synthesis temperature of liquefied petroleum gas but below 360°C, and have succeeded in restoring activity to the same level as that of an unused catalyst.

[0056] Therefore, it is preferable that the melting point of the metal contained in the liquefied petroleum gas synthesis catalyst used in the interlocking step, combustion step, and reduction step is 1600°C or lower. The upper limit of the melting point may be 1500°C, 1400°C, 1300°C, 1200°C, 1100°C, 1000°C, 900°C, 800°C, 700°C, 600°C, 500°C, or 400°C. The lower limit of the melting point is not limited as long as it is higher than the synthesis temperature of liquefied petroleum gas, but may be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, or 1500°C.

[0057] Therefore, it is preferable that the liquefied petroleum gas synthesis catalyst used in the combustion step and the reduction step (and the linked step described below) is not an FT synthesis catalyst. In other words, it is preferable that the liquefied petroleum gas synthesis catalyst does not contain any one of the metal elements Fe, Co, and Ru.

[0058] Furthermore, from the viewpoint of efficiently synthesizing liquefied petroleum gas from a feed gas containing carbon monoxide and hydrogen, the liquefied petroleum gas synthesis catalyst preferably includes a methanol synthesis catalyst and a dehydration catalyst. Methanol is synthesized from carbon monoxide and hydrogen using the methanol synthesis catalyst, and then the methanol synthesized by the methanol synthesis catalyst is dehydrated and condensed using the dehydration catalyst, followed by cracking and hydrogenation reactions, to synthesize liquefied petroleum gas containing propane.

[0059] The methanol synthesis catalyst is preferably a Cu—Zn catalyst, which contains copper oxide and zinc oxide as main components, and further contains aluminum oxide and zirconium oxide, which can improve the CO addition rate and enable efficient production of methanol from carbon monoxide and hydrogen.

[0060] The Cu—Zn catalyst may further contain gallium oxide and indium oxide, which improves the dispersibility of copper oxide and zinc oxide.

[0061] The Cu-Zn catalyst is preferably in the form of a powder or a compact. －９ ~10－４ m.) or granules having a particle size larger than that of the powder, but when the Cu—Zn-based catalyst is a molded body containing the Cu—Zn-based catalyst, the CO conversion rate can be further improved.

[0062] For a molded body containing a Cu—Zn-based catalyst, the content of the Cu—Zn-based catalyst in the molded body is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. When the content is 80% by mass or more, methanol can be efficiently synthesized from carbon monoxide and hydrogen. The content of the Cu—Zn-based catalyst in the molded body may be 100% by mass, i.e., the molded body may be composed solely of the Cu—Zn-based catalyst. Furthermore, the content is preferably 98% by mass or less, more preferably 96% by mass or less, and even more preferably 94% by mass or less. When the content is 98% by mass or less, the moldability and mechanical strength of the molded body can be improved while maintaining efficient synthesis of methanol from carbon monoxide and hydrogen.

[0063] The molded body containing the Cu—Zn-based catalyst may contain, in addition to the Cu—Zn-based catalyst, various additives that improve moldability and mechanical strength, such as molding binders such as graphite and carbon black.

[0064] Furthermore, the dehydration catalyst is preferably a zeolite catalyst carrying a noble metal (hereinafter simply referred to as a zeolite catalyst). The zeolite constituting the zeolite catalyst has a zeolite skeleton, which gives it high water resistance and prevents deterioration due to water produced as a by-product in Cu-Zn catalysts. Therefore, the zeolite catalyst has excellent long-term stability and a long life.

[0065] Furthermore, since the precious metal supported on the zeolite that constitutes the zeolite catalyst is Pt, the zeolite catalyst can efficiently convert intermediates such as methanol synthesized using a Cu-Zn catalyst and dimethyl ether produced as a by-product using a Cu-Zn catalyst into liquefied petroleum gas, thereby increasing the yield of liquefied petroleum gas.

[0066] The noble metal supported on the zeolite is preferably a platinum group element such as Pt, Pd, Rh, or Ru. The noble metal may be one type or two or more types. When two or more types of noble metals are supported on the zeolite, the state of the noble metals supported on the zeolite is not particularly limited. For example, the noble metals may be mixed as simple metals, may be alloyed, or may be mixed as simple metals and alloys.

[0067] The precious metal supported on the zeolite may be only Pt, only Pd, or may contain Pt and Pd. From the viewpoint of efficiently reacting methanol, the precious metal supported on the zeolite is preferably Pt and Pd, and more preferably Pt alone. Regarding the state of Pt and Pd supported on the zeolite, a mixture of metal Pt and metal Pd may be present, or Pt and Pd may be alloyed, or at least one of metal Pt and Pd may be present as a mixture with an alloy of Pt and Pd.

[0068] Furthermore, the zeolite constituting the zeolite catalyst preferably contains P (phosphorus). That is, the zeolite catalyst preferably contains P. When the zeolite contains P, it is presumed that P will bond to O (oxygen) that bonds with Si and O that bonds with Al present on the surface of the zeolite (zeolite catalyst), as shown in the following formula (1). As a result, the acid sites (solid acid sites) of the zeolite increase and change to weak acid sites, so the zeolite catalyst can increase the yield of liquefied petroleum gas.

[0069]

[0070] The lower limit of the mass of P contained in the zeolite catalyst, relative to the mass of the zeolite catalyst, is preferably more than 0 mass%, more preferably 0.5 mass% or more, and even more preferably 1.0 mass% or more, and the upper limit is preferably less than 5.0 mass%, more preferably 4.0 mass% or less, and even more preferably 3.0 mass% or less.

[0071] When the mass of P is more than 0% by mass relative to the mass of the zeolite catalyst, the yield of liquefied petroleum gas can be increased. Also, when the mass of P is less than 5.0% by mass relative to the mass of the zeolite catalyst, a decrease in the surface area of ​​zeolite due to an increase in the P content can be suppressed for zeolites having a porous structure, thereby enabling efficient production of liquefied petroleum gas.

[0072] The zeolite catalyst may contain Y (yttrium). By including Y in the zeolite catalyst, it is possible to suppress the generation of coke during the synthesis of liquefied petroleum gas. A zeolite catalyst with suppressed coke generation can sufficiently burn the coke without requiring high temperatures for regeneration treatment, thereby suppressing the aggregation of Cu-Zn catalyst and precious metal particles and enabling the catalyst to be used for a longer period of time.

[0073] The zeolite catalyst is preferably in the form of a powder or a molded body. －９ ~10 －４ m.) or granules having a particle size larger than that of the powder, but when the zeolite catalyst is a molded body containing the zeolite catalyst, the yield of liquefied petroleum gas can be further improved.

[0074] Although various known zeolites can be used as the zeolite constituting the zeolite catalyst, MFI zeolite, CHA zeolite, BEA zeolite, TON zeolite, MWW zeolite, FAU zeolite, FER zeolite, ERI zeolite, and MOR zeolite are preferred. In particular, when the zeolite constituting the zeolite catalyst is MFI zeolite or CHA zeolite, the yield of liquefied petroleum gas can be further improved.

[0075] The zeolite constituting the zeolite catalyst can be replaced with various known porous materials. Examples include SAPO, ELAPO, ALPO, alumina (Al ２ O ３ ) etc.

[0076] For a molded body containing a zeolite catalyst, the content of the zeolite catalyst contained in the molded body is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. When the content is 70% by mass or more, liquefied petroleum gas can be efficiently synthesized from methanol. The content of the zeolite catalyst contained in the molded body may be 100% by mass, i.e., the molded body may be composed solely of zeolite catalyst. Furthermore, the content is preferably 98% by mass or less, more preferably 96% by mass or less, and even more preferably 94% by mass or less. When the content is 98% by mass or less, the moldability and mechanical strength of the molded body can be improved while maintaining efficient synthesis of liquefied petroleum gas from methanol.

[0077] The molded body containing the zeolite catalyst may contain, in addition to the zeolite catalyst, various additives that improve moldability and mechanical strength. Examples of the various additives include molding binders such as various clay binders, alumina-based binders, and silica-based binders. Preferred clay binders are kaolin-based, bentonite-based, talc-based, pyrophyllite-based, molysite-based, verculolite-based, montmorillonite-based, chlorite-based, and halloysite-based binders. The molding binder is preferably a silica-based binder, as it efficiently improves the catalytic activity of the zeolite catalyst and suppresses the formation of catalyst-poisoning substances such as coke.

[0078] When the Cu—Zn-based catalyst and the zeolite catalyst are in the form of a molded body, the shape of these molded bodies is not particularly limited, and a desired shape can be selected, for example, a cylindrical, cloverleaf, ring-like, spherical, multi-hole, etc. In the case of a cylindrical or cloverleaf-like molded body, it is preferable that it is an extrusion molded product.

[0079] The particle size of the molded body containing a Cu-Zn catalyst and the molded body containing a zeolite catalyst preferably has a lower limit of 200 μm or more, more preferably 300 μm or more, and an upper limit of 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. If the particle size is 200 μm or more, pressure loss in the reactor can be prevented during synthesis of liquefied petroleum gas. Furthermore, if the particle size is 10 mm or less, the contact efficiency between these catalysts and the reaction raw materials can be increased.

[0080] It is also preferable that the methanol synthesis catalyst or the liquefied petroleum synthesis catalyst be subjected to a further hydrogen reduction treatment immediately before use.

[0081] According to the embodiment described above, by linking the liquefied petroleum gas yield during liquefied petroleum gas synthesis with the liquefied petroleum gas synthesis temperature, it is possible to synthesize liquefied petroleum gas stably over a long period of time while suppressing deterioration of the liquefied petroleum gas synthesis catalyst. Thus, in the liquefied petroleum gas synthesis method of the above embodiment, the problem of liquefied petroleum gas synthesis catalyst deterioration when the liquefied petroleum gas synthesis temperature is addressed by not using a liquefied petroleum gas synthesis catalyst that is more resistant to deterioration at high temperatures than conventional catalysts, but by linking the liquefied petroleum gas yield during synthesis with the liquefied petroleum gas synthesis temperature, it is possible to synthesize liquefied petroleum gas stably over a long period of time while suppressing rapid deterioration of the liquefied petroleum gas synthesis catalyst.

[0082] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure.

[0083] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0084] (Example 1-1) A Cu-Zn catalyst (CuOZnOZrO) was used as a methanol synthesis catalyst for liquefied petroleum gas synthesis. ２ Al ２ O ３) (chemical composition: copper oxide 62.6 mass%, zinc oxide 27.2 mass%, zirconium oxide 4.9 mass%, aluminum oxide 5.3 mass%) was used, and a zeolite catalyst (Pt 0.5% / P 2% ZSM-5 (ZSM-5(SiO ２ / Al ２ O ３ Pt was supported on the zeolite catalyst (ratio 40), and P was contained in the ZSM-5. The mass of Pt contained in the zeolite catalyst was 0.5%, and the mass of P was 2%. ) was used. After placing the liquefied petroleum gas synthesis catalyst in a reactor, a feed gas containing carbon monoxide and hydrogen was supplied into the reactor, and liquefied petroleum gas was synthesized at the liquefied petroleum gas synthesis temperature shown in Figure 1. Then, at the time indicated by the arrows in Figure 1 and Figures 2 and 3 described below (around 60 days into synthesis), the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature were linked by increasing the liquefied petroleum gas synthesis temperature as shown in Figure 1. Figure 2 shows the results of the liquefied petroleum gas, propane, and butane yields before and after linking the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature. Figure 3 also shows the results of the propane selectivity before and after linking the liquefied petroleum gas yield and the liquefied petroleum gas synthesis temperature.

[0085] As shown in Figure 2, during the period from about 5 days to about 60 days of synthesis before interlocking, the yield of liquefied petroleum gas gradually decreased as the synthesis of liquefied petroleum gas progressed. Furthermore, by increasing the synthesis temperature and interlocking the liquefied petroleum gas yield with the liquefied petroleum gas synthesis temperature as shown in Figure 1, the liquefied petroleum gas yield, which tended to decline before interlocking, was able to maintain around 30 Cmol% even after 140 days of liquefied petroleum gas synthesis. Furthermore, as shown in Figure 3, even after 140 days of liquefied petroleum gas synthesis, the propane selectivity was able to be maintained around 75 vol%. Thus, while suppressing degradation of the liquefied petroleum gas synthesis catalyst, the liquefied petroleum gas yield was maintained around 30 Cmol% and the propane selectivity was maintained around 75 vol%, and liquefied petroleum gas was stably synthesized for 140 days.

[0086] Furthermore, the inventors discovered an unexpected effect in Example 1-1. According to Examples 1 and 2 in Table 1 of Patent Document 1, the yields of propane and butane varied with reaction temperature. Specifically, as the reaction temperature increased, the yield of propane increased and the yield of butane decreased. In other words, the common general knowledge at the time of filing was that, even when the same catalyst was used, an increase in reaction temperature would change the product composition (selectivity). However, according to the present invention, as shown in Figure 3, the propane selectivity remained nearly constant even when the synthesis temperature was increased. In other words, even if the reaction temperature was gradually increased to maintain the liquefied petroleum gas yield, the product composition remained almost constant. This effect provides an economic benefit to liquefied petroleum gas producers, allowing them to operate production plants while predicting the propane yield. This effect could not have been discovered in experiments in which liquefied petroleum gas was synthesized at various reaction temperatures. This discovery led to the invention of a method for synthesizing liquefied petroleum gas that allows the catalyst to be used for a long period of time while maintaining selectivity for propane, which is particularly useful among liquefied petroleum gases.

[0087] (Examples 2-1 to 2-4, Comparative Examples 2-1 to 2-2) Here, the catalyst for liquefied petroleum gas synthesis (immediately before regeneration treatment) after 38 days of liquefied petroleum gas synthesis using a reactor was subjected to regeneration treatment under the conditions shown in Table 1. The details are as follows.

[0088] First, in Examples 2-1 to 2-3 and Comparative Example 2-1, the liquefied petroleum gas synthesis catalyst immediately before the regeneration treatment after 38 days of liquefied petroleum gas synthesis using a reactor had a CO conversion of 93%, a liquefied petroleum gas yield of 27 / C-mol%, a propane yield of 17 / C-mol%, and a butane yield of 10 / C-mol%. Also, in Example 2-4 and Comparative Example 2-2, the liquefied petroleum gas synthesis catalyst immediately before the regeneration treatment after 38 days of liquefied petroleum gas synthesis using a reactor had a CO conversion of 89%, a liquefied petroleum gas yield of 26 / C-mol%, a propane yield of 18 / C-mol%, and a butane yield of 9 / C-mol%.

[0089] In Examples 2-1 to 2-3 and Comparative Example 2-1, a catalyst for synthesizing liquefied petroleum gas having the same composition as in Example 1-1 was used. In Example 2-4 and Comparative Example 2-2, a catalyst for synthesizing liquefied petroleum gas similar to that in Example 1-1 was used, except that the P content was 1.5%.

[0090] (Examples 2-5 to 2-7, Comparative Example 2-3) Deteriorated catalysts for liquefied petroleum gas synthesis with the same catalytic activity were subjected to the following regeneration of catalytic activity. Here, the same catalysts as in Example 2-1 were used as the methanol synthesis catalyst for the liquefied petroleum gas synthesis catalyst and the dehydration catalyst for the liquefied petroleum gas synthesis catalyst.

[0091]

[0092]

[0093] The catalyst for liquefied petroleum gas synthesis in the reactor immediately before regeneration treatment was regenerated under the conditions shown in Tables 1 and 2, and then the pressure was increased to 280°C and 5 MPa in a stream of carbon monoxide and hydrogen. Subsequently, the temperature was increased from 280°C to 310°C at a rate of 1°C / min, and the synthesis of liquefied petroleum gas was resumed. The molar ratio of hydrogen to carbon monoxide was set to 2.

[0094] After maintaining 310 ° C. and 6 hours, the CO conversion (%), liquefied petroleum gas yield (C-mol%), propane yield (C-mol%), and butane yield (C-mol%) of Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3 were calculated. Furthermore, as a reference example, the molar amount of hydrogen relative to carbon monoxide was set to 2 as above, and an unused liquefied petroleum gas synthesis catalyst of the same composition as in Examples 2-1 to 2-3 was used. After 6 hours at 310 ° C., the CO conversion, liquefied petroleum gas yield, propane yield, and butane yield were calculated.

[0095] Tables 3 to 5 show the CO conversion rates, liquefied petroleum gas yields, propane yields, and butane yields of each Example and Comparative Example, when the CO conversion rate, liquefied petroleum gas yield, propane yield, and butane yield of the Reference Example are each set to 100.

[0096] CO conversion rate (%)=[(CO flow rate at inlet (μmol / min)−CO flow rate at outlet (μmol / min)) / CO flow rate at inlet (μmol / min)]×100

[0097] The CO conversion rate indicates the rate at which carbon monoxide (CO) in the feed gas is converted into hydrocarbons and the like.

[0098] Propane yield (C mol %)=[(C3 production rate×3) / (inlet CO flow rate)×106 / 22400]×100

[0099] The unit of the C3 production rate is C μmol / min, and the unit of the inlet CO flow rate is ml (Normal) / min. C3 is propane.

[0100] Butane yield (C mol%)=[(C4 production rate×4) / (inlet CO flow rate)×106 / 22400]×100

[0101] The unit of the C4 production rate is C μmol / min, and the unit of the inlet CO flow rate is ml (Normal) / min. C4 is butane.

[0102] Liquefied petroleum gas yield (C mol %) = propane yield (C mol %) + butane yield (C mol %)

[0103] Selectivity of propane (volume %)=number of moles of propane produced / (number of moles of propane produced+number of moles of butane produced)×100

[0104]

[0105]

[0106]

[0107] As can be seen from Table 3, the liquefied petroleum gas synthesis catalysts of Examples 2-1 to 2-3 exhibited a CO conversion recovery rate of 97% or more compared to the Reference Example. They also exhibited a liquefied petroleum gas yield recovery rate of 75% or more. They also exhibited a propane yield recovery rate of 69% or more. They also exhibited a butane yield recovery rate of 90% or more.

[0108] As shown in Table 4, the catalysts for liquefied petroleum gas synthesis in Examples 2-4 exhibited a CO conversion recovery rate of 96% or more compared to the Reference Example. They also exhibited a liquefied petroleum gas yield recovery rate of 82% or more. They also exhibited a propane yield recovery rate of 74% or more.

[0109] Furthermore, as shown in Table 5, the catalysts for liquefied petroleum gas synthesis in Examples 2-5 to 2-7 exhibited a CO conversion recovery rate of 95% or more compared to the Reference Example. They also exhibited a liquefied petroleum gas yield recovery rate of 73% or more. They also exhibited a propane yield recovery rate of 67% or more.

[0110] On the other hand, Comparative Example 2-1 showed a CO conversion recovery rate of 96% or less compared to the Reference Example. It also showed a liquefied petroleum gas yield recovery rate of 74% or less. It also showed a propane yield recovery rate of 68% or less. It also showed a butane yield recovery rate of 89% or less.

[0111] Furthermore, in Comparative Example 2-2, the CO conversion recovery rate was 95% or less compared to the Reference Example, the LPG yield recovery rate was 81% or less, and the propane yield recovery rate was 73% or less.

[0112] Furthermore, in Comparative Example 2-3, the CO conversion recovery rate was 94% or less compared to the Reference Example, the LPG yield recovery rate was 72% or less, and the propane yield recovery rate was 66% or less.

[0113] Thus, the catalyst for synthesizing liquefied petroleum gas regenerated by the above-mentioned regeneration treatment exhibits a high regeneration rate and can be used for a long period of time.

Claims

1. A method for synthesizing liquefied petroleum gas from a raw material gas containing carbon monoxide and hydrogen using a catalyst for synthesizing liquefied petroleum gas, the method comprising a linking step for linking the yield of liquefied petroleum gas with the synthesis temperature of the liquefied petroleum gas.

2. A method for synthesizing liquefied petroleum gas as described in claim 1, wherein in the interlocking step, the synthesis temperature of the liquefied petroleum gas is increased in stages.

3. A method for synthesizing liquefied petroleum gas as described in claim 1, wherein in the linking process, the yield of the liquefied petroleum gas is linked to the synthesis temperature of the liquefied petroleum gas, and the selectivity of propane is linked to the synthesis temperature of the liquefied petroleum gas.

4. A method for synthesizing liquefied petroleum gas as described in claim 3, wherein the synthesis temperature of the liquefied petroleum gas is increased in stages in the interlocking process.

5. A method for synthesizing liquefied petroleum gas as described in claim 3, wherein the synthesis temperature of the liquefied petroleum gas is gradually lowered in the interlocking step.

6. A method for synthesizing liquefied petroleum gas as described in claim 1, wherein in the linking step, when the yield of the liquefied petroleum gas falls below a predetermined range, the synthesis temperature of the liquefied petroleum gas is increased at a rate of 0.05°C / day or more and 5.00°C / day or less.

7. A method for synthesizing liquefied petroleum gas as described in claim 3, wherein in the interlocking step, when the selectivity of propane becomes lower than a predetermined range, the synthesis temperature of the liquefied petroleum gas is increased at a rate of 0.05°C / day or more and 5.00°C / day or less.

8. A method for synthesizing liquefied petroleum gas as described in claim 1, wherein the synthesis temperature of the liquefied petroleum gas is 280°C or higher and 350°C or lower.

9. A method for synthesizing liquefied petroleum gas as described in claim 6, wherein in the interlocking process, the lower limit of the specified range for the yield of liquefied petroleum gas is 25 Cmol% or more.

10. A method for synthesizing liquefied petroleum gas as described in claim 7, wherein in the interlocking process, the lower limit of the specified range for the selectivity of the propane is 70 volume % or more.

11. The method for synthesizing liquefied petroleum gas according to claim 1, wherein the catalyst for synthesizing liquefied petroleum gas does not contain any one of the metal elements Fe, Co, and Ru.

12. A method for synthesizing liquefied petroleum gas according to any one of claims 1 to 11, further comprising a combustion step of contacting the liquefied petroleum gas synthesis catalyst with an oxygen-containing gas at a temperature higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C, and after the combustion step, a reduction step of contacting the liquefied petroleum gas synthesis catalyst with a reducing gas at a temperature higher than the synthesis temperature of the liquefied petroleum gas but lower than 360°C.

Images