Catalyst for p-xylene production, method for producing catalyst for p-xylene production, and method for producing p-xylene

Abstract

Provided are: a catalyst for p-xylene production, the catalyst including a first catalyst that includes at least one of a ternary composite oxide of aluminum, zinc, and zirconium and a mixed metal oxide composed of aluminum oxide and a binary composite oxide of zinc and zirconium, and a second catalyst that includes an H-ZSM-5 zeolite coated with an oxide including amorphous silicon; a method for producing the same; and a method for producing p-xylene using the same.

Description

Catalyst for producing para-xylene, method for producing catalyst for producing para-xylene, and method for producing para-xylene

[0001] The present disclosure relates to a catalyst for producing para-xylene, a method for producing a catalyst for producing para-xylene, and a method for producing para-xylene.

[0002] In recent years, interest in global warming has been increasing. At the Conference of the Parties (COP), where international frameworks for greenhouse gas emission reduction and other matters are discussed, the goal is to keep the increase in average global temperature relative to the pre-industrial revolution level well below 2°C as a common long-term global goal, to curb the emission peak as early as possible, and to achieve rapid reductions in accordance with the latest scientific findings. The COP21 Paris Agreement states that all countries should strive to formulate and submit long-term low greenhouse gas emission development strategies, and Japan has established a long-term goal of reducing greenhouse gas emissions by 80% by 2050. Among anthropogenically emitted greenhouse gases, carbon dioxide is estimated to have the largest impact, and research and development of countermeasure technologies for reducing carbon dioxide are being vigorously carried out in various fields. As one of the countermeasure technologies, several attempts to convert emitted carbon dioxide into useful substances have been proposed. However, large amounts of energy are required to convert carbon dioxide into other substances, and development of effective catalysts to promote the reaction is desired.

[0003] Furthermore, in order for a technology to contribute to carbon dioxide reduction, it is necessary to produce highly demanded useful substances. Para-xylene is a compound useful as a raw material for polyethylene terephthalate (PET), which is a general-purpose resin. If such a compound can be efficiently produced from carbon dioxide and hydrogen, this can be a useful measure for carbon dioxide reduction.

[0004] Conventionally, para-xylene has been produced by reforming crude oil and naphtha. Additionally, a technique for producing para-xylene using a mixed gas of carbon monoxide and hydrogen, so-called synthesis gas, as a raw material has been proposed. Furthermore, a method for producing para-xylene from carbon dioxide and hydrogen is also disclosed. For example, Patent Document 1 discloses a catalyst for para-xylene production, which comprises a first catalyst containing chromium oxide for synthesizing para-xylene from carbon dioxide and hydrogen in one step, and a second catalyst containing H-ZSM-5 zeolite coated with silicalite-1. Patent Document 2 discloses a catalyst for para-xylene production, which comprises a first catalyst containing a ternary composite oxide of chromium, zinc, and zirconium, and a second catalyst containing H-ZSM-5 zeolite coated with an oxide containing amorphous silicon.

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-205969 Patent Document 2: International Publication No. WO 2024 / 203963

[0006] The Cr-containing catalyst (Cr-based catalyst) disclosed in Patent Documents 1 and 2 is effective in that it can efficiently produce para-xylene from carbon dioxide and hydrogen. However, part of the Cr-based catalyst may be converted into hexavalent chromium, so a catalyst with lower toxicity is desirable.

[0007] Accordingly, an object of the present disclosure is to provide a catalyst for para-xylene production that enables highly selective production of para-xylene or aromatics containing para-xylene using carbon dioxide and hydrogen as raw materials by means of a Cr-free catalyst, a method for producing the catalyst for para-xylene production, and a method for producing para-xylene.

[0008] The gist of this disclosure is as follows: <1> A catalyst for producing paraxylene, comprising: a first catalyst comprising at least one of a ternary composite oxide of aluminum, zinc, and zirconium, and a mixed metal oxide comprising a binary composite oxide of zinc and zirconium and aluminum oxide; and a second catalyst comprising H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide. <2> The catalyst for producing paraxylene according to <1>, wherein the first catalyst contains 1 mol% to 55 mol% of aluminum, 1 mol% to 35 mol% of zinc, and 10 mol% to 98 mol% of zirconium, based on the total amount of aluminum, zinc, and zirconium. <3> The catalyst for producing paraxylene according to <1> or <2>, wherein the second catalyst is contained in an amount of 10% to 1000% by mass relative to the first catalyst. <4> A method for producing paraxylene, comprising contacting a raw material gas containing carbon dioxide and hydrogen with a paraxylene production catalyst described in any one of <1> to <3> to synthesize paraxylene. <5> A method for producing a paraxylene production catalyst described in any one of <1> to <3>, comprising: obtaining a coprecipitation by a coprecipitation method to obtain a coprecipitation containing zinc and zirconium, or a coprecipitation containing aluminum, zinc, and zirconium, and drying and / or calcining the coprecipitation to obtain a composite oxide, and in the case of a binary composite oxide of zinc and zirconium, mixing with aluminum oxide to obtain the first catalyst; performing hydrothermal synthesis or heating in the presence of a silicon compound and H-ZSM-5 zeolite to obtain the second catalyst containing H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide; and mixing the first catalyst and the second catalyst.

[0009] According to this disclosure, it is possible to provide a catalyst for the production of paraxylene that can selectively produce aromatic compounds containing paraxylene using carbon dioxide and hydrogen as raw materials, a method for producing the catalyst for the production of paraxylene, and a method for producing paraxylene, using a Cr-free catalyst.

[0010] This figure shows an example of an SEM-EDS image of the first catalyst (a ternary composite oxide of Al, Zn, and Zr). It is a triangular diagram showing the molar ratios (mol%) of aluminum, zinc, and zirconium.

[0011] An embodiment, which is an example of this disclosure, will be described. In this disclosure, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. Regarding the element content contained in the catalyst, "%" means "mass %" unless otherwise specified. In numerical ranges described in stages in this disclosure, the upper limit of one stage of numerical range may be replaced with the upper limit of another stage of numerical range, or with the value shown in the example. Also, in numerical ranges described in stages in this disclosure, the lower limit of one stage of numerical range may be replaced with the lower limit of another stage of numerical range, or with the value shown in the example. The term "process" is included not only in the sense of an independent process, but also in the sense of a process that cannot be clearly distinguished from other processes, as long as the intended purpose of that process is achieved.

[0012] The inventors of this disclosure, in their diligent efforts to develop a Cr-free catalyst while maintaining the productivity of paraxylene produced from carbon dioxide and hydrogen, have developed a conventional CrZnZrO ｘ In catalysts, we screened for elements to replace Cr. CrZnZrO ｘ It has a structure in which Zn is partially substituted into a Cr-Zn composite oxide, and as alternative elements, we screened mainly Al and Ga, which, like Cr, can form composite oxides with Zn. As a result, AlZnZrO, which contains Al, was particularly selected. ｘ By using a catalyst (which may be referred to in this disclosure as "aluminum, zinc, and zirconium ternary composite oxide catalyst," "aluminum, zinc, and zirconium ternary composite oxide," etc.), CrZnZrO ｘWe found that it exhibits equally high paraxylene selectivity. Furthermore, from a mechanistic standpoint, it is considered that a metal oxide consisting of a binary complex oxide of zinc and zirconium and aluminum oxide (sometimes referred to as "mixed metal oxide" in this disclosure) also exhibits equally high paraxylene selectivity.

[0013] Preferred embodiments of this disclosure will be described in detail below.

[0014] <1. Catalyst for Paraxylene Production> First, preferred embodiments of the paraxylene production catalyst of the present disclosure will be described. The paraxylene production catalyst according to the present disclosure catalyzes the synthesis reaction of hydrocarbon compounds, particularly paraxylene, using carbon dioxide and hydrogen as raw materials. The paraxylene production catalyst according to the present disclosure comprises a first catalyst comprising at least one of a ternary composite oxide containing aluminum, zinc, and zirconium, and a mixed metal oxide consisting of a binary composite oxide of zinc and zirconium and aluminum oxide, and a second catalyst comprising H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide.

[0015] A first catalyst comprising at least one of a ternary composite oxide containing aluminum, zinc, and zirconium, and a mixed metal oxide consisting of a binary composite oxide of zinc and zirconium and aluminum oxide, catalyzes the conversion of carbon dioxide and hydrogen to methanol. On the other hand, a second catalyst comprising H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide catalyzes the conversion of methanol to paraxylene. In other words, the paraxylene production catalyst according to this disclosure is a catalyst composition (composite catalyst) comprising a first catalyst and a second catalyst having different functions.

[0016] (1.1. First Catalyst) The first catalyst is particles of a ternary composite oxide of aluminum, zinc, and zirconium, or particles of a mixed metal oxide obtained by adding aluminum oxide to a binary composite oxide of zinc and zirconium. The ternary composite oxide of aluminum, zinc, and zirconium catalyzes the conversion of carbon dioxide and hydrogen to methanol. Here, since the ternary composite oxide containing aluminum, zinc, and zirconium has oxygen vacancies, carbon dioxide is easily adsorbed on the surface of the ternary composite oxide containing aluminum, zinc, and zirconium, and the reaction between the carbon dioxide adsorbed on the ternary composite oxide containing aluminum, zinc, and zirconium and hydrogen occurs efficiently, and methanol is efficiently produced. Similarly, the binary composite oxide of zinc and zirconium also has oxygen vacancies, so carbon dioxide is easily adsorbed, and in addition, the presence of aluminum oxide can promote the synthesis of intermediates such as methanol produced from carbon dioxide and hydrogen, and aromatic compounds including paraxylene from hydrocarbons, so the same effect as the ternary composite oxide containing aluminum, zinc, and zirconium can be expected. Furthermore, the first catalyst in this disclosure can efficiently produce methanol even if carbon monoxide gas is present in the raw material gas, by recycling a portion of the reaction gas (including unreacted carbon dioxide gas and by-product carbon monoxide gas). As a result, the selectivity of paraxylene can be improved.

[0017] Figure 2 is a triangular diagram showing the molar ratios (mol%) of aluminum, zinc, and zirconium. From the viewpoint of paraxylene productivity, the content of aluminum, zinc, and zirconium in the first catalyst is preferably 1 mol% to 55 mol%, zinc 1 mol% to 35 mol%, and zirconium 10 mol% to 98 mol% (the region indicated by A in Figure 2), relative to the total amount of aluminum, zinc, and zirconium. More preferably, the content is 2 mol% to 53 mol%, zinc 2 mol% to 33 mol%, and zirconium 20 mol% to 95 mol%. Alternatively, the first catalyst may contain 1 mol% to 55 mol%, zinc 1 mol% to 35 mol%, and zirconium 30 mol% to 98 mol%.

[0018] The first catalyst can be identified from SEM-EDS and TEM images as particles of a ternary composite oxide of aluminum, zinc, and zirconium, or particles of a binary composite oxide of zinc and zirconium with added aluminum oxide. Figure 1 shows an example of an SEM-EDS image of the first catalyst (a ternary composite oxide of Al, Zn, and Zr). The presence of the elements Al, Zn, and Zr in a single particle indicates that it is a composite oxide. Similarly, it can be confirmed that the particles are of a binary composite oxide of zinc and zirconium with added aluminum oxide, and this morphology can be confirmed by the presence of aluminum oxide particles in the vicinity of the zinc and zirconium particles.

[0019] The catalyst in this disclosure may contain impurities introduced during the catalyst manufacturing process. However, from the viewpoint of improving catalytic activity, the less impurities there are, the better, and it is preferable to avoid introducing impurities as much as possible (for example, 1% by mass or less relative to the total mass of the first catalyst). Examples of impurities that may be introduced during the manufacturing process include N, Cl, C, etc.

[0020] Furthermore, the mass concentration of metals in the first catalyst can be quantified by scanning radio frequency inductively coupled plasma (ICP-AES) spectroscopy. Specifically, after grinding the sample, an alkaline fusion agent (e.g., sodium carbonate, sodium borate) is added and heated and melted in a platinum crucible. After cooling, the entire volume is dissolved in a hydrochloric acid solution under heating. When this solution is injected into an ICP analyzer, the sample solution is atomized and thermally excited in the high-temperature plasma state within the analyzer. As it returns to its ground state, it produces an emission spectrum with wavelengths specific to each element. From the emission wavelength and intensity, the types and amounts of elements contained can be qualitatively and quantitatively determined. The concentration of each metal element is defined as the molar concentration of each metal element, where the total concentration of all metals calculated by the ICP-AES method is set to 100 mol%, and the molar concentration of each metal element within that total is defined as the concentration of each metal element.

[0021] The form of the first catalyst is not particularly limited and, for example, it may be granular. The first catalyst is usually porous and therefore has pores for the reaction to take place, and has a relatively large specific surface area. The specific surface area and other properties when the first catalyst is porous will be described below.

[0022] The specific surface area of ​​the first catalyst is not particularly limited, but for example, 3 m² ２ / g or more 500m ２ / g or less, preferably 10m ２ / g or more 100m ２ The specific surface area is less than or equal to / g. This ensures a sufficient supply of active sites for the reaction between hydrogen and carbon dioxide. Furthermore, by keeping the specific surface area below the upper limit mentioned above, the pore diameter becomes excessively small, preventing a difference in the gas diffusion rates of carbon dioxide and hydrogen within the pores, and thus preventing a difference in the partial pressure of carbon dioxide and hydrogen within the first catalyst. As a result, the conversion of hydrogen and carbon dioxide to methanol is carried out efficiently. The specific surface area can be measured by the BET method.

[0023] Further, the average pore diameter of the first catalyst is not particularly limited, and is, for example, 0.5 nm or more and 100 nm or less, preferably 2 nm or more and 30 nm or less. This prevents the occurrence of a difference in gas diffusion rate between carbon dioxide and hydrogen within the pores, allows the specific surface area of the first catalyst to be increased, and makes it possible to sufficiently supply active sites. As a result, conversion of hydrogen and carbon dioxide into methanol is efficiently performed.

[0024] The pore diameter can be obtained by analyzing data obtained from the gas adsorption method (BET specific surface area measurement) according to the BJH (Barrett-Joyner-Halenda) method. The adsorption gas used for measurement is, for example, N ２ molecules can be used, and the specific surface area can be measured from the adsorption amount of gas molecules and the weight of the measurement sample. Furthermore, by performing this measurement at a temperature at which adsorbed molecules liquefy, the liquid adsorbed molecules filled in the pores can be measured, and the pore volume and pore diameter can be measured.

[0025] The pore volume of the first catalyst is not particularly limited, and is, for example, 0.1 cc / g or more and 5 cc / g or less, preferably 0.5 cc / g or more and 2 cc / g or less.

[0026] The pore volume can be obtained by mercury porosimetry. If mercury porosimetry cannot be used, measurement can be performed by the water titration method. Further, the average pore diameter can be measured by mercury porosimetry using a mercury porosimeter. If mercury porosimetry cannot be used, the average pore diameter can be obtained by the gas adsorption method described above.

[0027] Further, when the first catalyst is in a granular form, the average particle diameter of the first catalyst is, for example, 1 µm or more and 800 µm or less, preferably 10 µm or more and 200 µm or less. This accelerates mass transfer between the first catalyst and the second catalyst, and also reduces flow resistance of the raw material gas (reduction in pressure loss). In the present specification, "average particle diameter" refers to the volume-based 50% particle diameter (D50) measured by a wet laser diffraction / scattering method.

[0028] (1.2. Second Catalyst) As described above, the second catalyst includes H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide. The second catalyst catalyzes the conversion of methanol to paraxylene produced via the first catalyst. In the second catalyst, the H-ZSM-5 zeolite primarily catalyzes the selective conversion of methanol to paraxylene, while the amorphous silicon-containing oxide coating the surface of the H-ZSM-5 zeolite prevents the isomerization of paraxylene.

[0029] The second catalyst is mainly composed of H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide. However, the amorphous silicon-containing oxide in the second catalyst may contain trace amounts of other elements resulting from the manufacturing process or elements derived from the support used to support the second catalyst. Other elements that may be present include aluminum and magnesium.

[0030] The amorphous nature of silicon-containing oxides is determined by observing broad X-ray diffraction patterns. If the silicon-containing oxide is crystalline, then SiO ２ The peak intensity is high in SiO2, but in amorphous SiO2, it appears as a weak peak, making it distinguishable. Furthermore, crystalline and amorphous SiO2 can also be determined by the electron diffraction pattern obtained with a transmission electron microscope. In the case of crystalline SiO2, the periodicity of the structure yields strong diffraction and a clear electron diffraction pattern, while in the case of amorphous SiO2, the lack of periodicity in the structure results in weak diffraction and a halo-like image. Below is amorphous SiO2. ２ Simply "SiO ２ It is sometimes referred to as "[...]."

[0031] Specifically, within the 10-membered ring pores of H-ZSM-5 zeolite, numerous acid sites are present. These acid sites act as active sites, and an aromatic ring (benzene ring) is formed from methanol via dimethyl ether and light olefins. Furthermore, within the pores of H-ZSM-5 zeolite, the benzene ring is methylated at its 1 and 4 positions via a Friedel-Crafts reaction by further methanol. Here, the pore size of the 10-membered ring pores of H-ZSM-5 zeolite is such that paraxylene can pass through, but orthoxylene and metaxylene cannot. Therefore, paraxylene is preferentially formed due to the so-called spatial localization effect. The spatial localization effect refers to the phenomenon or effect in which, when a reaction proceeds within a certain space, the reaction is controlled or localized (restricted) according to the shape and size of the space, and a specific reaction or reaction at a specific site proceeds preferentially.

[0032] On the other hand, on the outer surface of the H-ZSM-5 zeolite, excluding the pores, there are no spatial limitations, and therefore the spatial localization effect does not occur. Consequently, there is a risk of orthoxylene, metaxylene, and trimethylbenzene being generated at acid sites on the outer surface. In contrast, in this disclosure, the surface (outer surface) of the H-ZSM-5 zeolite is coated with an amorphous silicon-containing oxide.

[0033] Amorphous silicon-containing oxides are oxides mainly composed of silica, and more preferably SiO ２ It is SiO ２ SiO has low acidity and basically does not have the function of catalyzing reactions with methanol or methanol-derived compounds. ２ By coating the outer surface of H-ZSM-5 zeolite with SiO2, the acid sites, which are active sites on the outer surface of H-ZSM-5 zeolite, are eliminated, and the isomerization of paraxylene to metaxylene and orthoxylene, and the methylation reaction to trimethylbenzene can be prevented. On the other hand, paraxylene generated in the pores of H-ZSM-5 zeolite is SiO2 ２ It is released to the outside of the second catalyst through its pores.

[0034] In the second catalyst, the amorphous silicon-containing oxide and the H-ZSM-5 zeolite can be in any positional relationship, as long as the amorphous silicon-containing oxide coats the surface of the H-ZSM-5 zeolite. For example, the second catalyst may have a so-called core-shell structure in which H-ZSM-5 zeolite particles form a core, and amorphous silicon-containing oxide coats the core as a shell.

[0035] Furthermore, in the second catalyst, the thickness of the amorphous silicon-containing oxide coating the surface of the H-ZSM-5 zeolite is not particularly limited, but is, for example, 0.01 μm or more and 200 μm or less, preferably 0.02 μm or more and 20 μm or less. This makes it possible to more reliably prevent the isomerization of paraxylene to metaxylene and orthoxylene, and also prevents a decrease in reaction efficiency due to insufficient methanol supply to the H-ZSM-5 zeolite caused by a thickness of amorphous silicon-containing oxide that is too large.

[0036] The thickness of the amorphous silicon-containing oxide film formed on the outer surface of H-ZSM-5 zeolite can be measured by observing the cross-section of the catalyst using a scanning electron microscope (SEM). One method for preparing a sample for observing the catalyst cross-section is to embed catalyst particles in resin and then polish it. The above thickness is an average value. When measuring by observing the catalyst cross-section with an SEM, if the thickness is uniform, only a few measurement points are needed. If it is not uniform, set up enough measurement points (for example, 16 points at approximately equal intervals in the circumferential direction) to calculate the average value. If the thickness differs for each particle, observe multiple particles (for example, 10 particles) as representatives and average the results. When selecting multiple representative particles, observe more particles than the representative particle, and then select particles with an average thickness after removing particles with extremely different thicknesses. If catalysts of different particle sizes are mixed, when observing as a representative as described above, select particles with a particle size approximately equal to the average particle size. To measure the average particle size, a laser diffraction particle size analyzer is used, which irradiates dispersed catalyst particles with laser light and measures the angular dependence of the scattered light intensity from the particles to determine the particle size distribution. In some cases, there may be defective areas where an amorphous silicon oxide film is not formed; however, in such cases, the defective areas are not included in the measurement, and the average value is taken from the areas where the amorphous silicon oxide is formed.

[0037] Furthermore, in the second catalyst, the mass ratio of the amorphous silicon-containing oxide is not particularly limited, but for example, it is 5% by mass or more and 100% by mass or less, preferably 10% by mass or more and 40% by mass or less, relative to the mass of H-ZSM-5 zeolite. This makes it possible to more reliably prevent the isomerization of paraxylene to metaxylene and orthoxylene, and also prevents a decrease in reaction efficiency due to insufficient methanol supply to the H-ZSM-5 zeolite because the film thickness of the amorphous silicon-containing oxide is too large.

[0038] The mass percentage of amorphous silicon-containing oxides in the second catalyst is determined by the following method. First, the silica (SiO₂) of the second catalyst is determined by scanning radio frequency inductively coupled plasma (ICP-AES) spectroscopy. ２The silica / alumina ratio of H-ZSM-5 (+H-ZSM-5) and alumina is quantitatively analyzed. Next, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) is used to obtain the silica / alumina ratio of H-ZSM-5 obtained from cross-sectional analysis. Then, considering the silica / alumina ratio of H-ZSM-5, the total silica quantified by ICP-AES is separated into amorphous silicon-containing oxide and H-ZSM-5, thereby calculating the mass percentage of amorphous silicon-containing oxide.

[0039] The average pore size of the second catalyst is not particularly limited, but is, for example, 0.1 nm to 2.5 nm, preferably 0.4 nm to 0.6 nm. This makes it possible to more reliably obtain the spatial localization effect within the pores described above, and the pore size becomes large enough for the paraxylene synthesized by H-ZSM-5 inside the second catalyst to pass through.

[0040] The specific surface area of ​​the second catalyst is not particularly limited, but for example, 20 m² ２ / g or more 1000m ２ / g or less, preferably 100m ２ / g or more 400m ２ The value is less than or equal to / g. This ensures a sufficient supply of active sites for the methanol reaction and the synthesis of paraxylene, and also allows the pore size of the second catalyst to be easily set to the aforementioned range.

[0041] The pore capacity of the second catalyst is not particularly limited, and is, for example, 0.1 cc / g or more and 5 cc / g or less, preferably 0.5 cc / g or more and 2 cc / g or less.

[0042] Furthermore, if the second catalyst is granular, the average particle size of the second catalyst can be, for example, 0.1 μm or more and 50 μm or less, preferably 0.5 μm or more and 5 μm or less. This accelerates mass transfer between the first catalyst and the second catalyst, and also reduces the flow resistance of the raw material gas (reduction of pressure loss).

[0043] (1.3. Positional relationship between the first catalyst and the second catalyst) As described above, in this disclosure, the catalyst for the production of paraxylene includes a first catalyst and a second catalyst. In this disclosure, the statement that the catalyst for the production of paraxylene includes a first catalyst and a second catalyst means that the first catalyst and the second catalyst are not physically separated by other elements such as glass wool. The positional relationship between the first catalyst and the second catalyst in the catalyst for the production of paraxylene is not particularly limited. For example, if the first catalyst and the second catalyst are granular, they may be physically mixed. Alternatively, if the first catalyst and the second catalyst each constitute layers, the layers of the first catalyst and the layers of the second catalyst may be stacked. In this case, the amorphous silicon-containing oxide of the second catalyst is arranged on the outer surface side of the catalyst for the production of paraxylene. Specifically, one example is a configuration in which the second catalyst is arranged around the first catalyst.

[0044] Furthermore, it is preferable that the first and second catalysts are in close proximity. Proximity can be achieved by granulation after physical mixing. This is because proximity suppresses other side reactions from the intermediate methanol, thereby improving the selectivity of paraxylene.

[0045] In the catalyst for the production of paraxylene, the amount of the second catalyst relative to the first catalyst is, for example, 10% to 1000% by mass (i.e., 10 to 1000 parts by mass of the second catalyst per 100 parts by mass of the first catalyst), preferably 50% to 200% by mass, from the viewpoint of improving the space-time yield. This makes it possible to make the methanol synthesis rate in the first catalyst and the methanol consumption rate in the second catalyst relatively similar, and prevents unintended side reactions from occurring due to excess compounds.

[0046] During the production of the paraxylene catalyst according to this disclosure, the ratio of the second catalyst to the first catalyst can be optimized by adjusting the respective masses (blending amounts) of the first and second catalysts when they are mixed. In the catalyst after the first and second catalysts have been mixed (including when they have been molded or granulated thereafter), this ratio can be determined, for example, using scanning radio frequency inductively coupled plasma (ICP-AES) spectroscopy. Specifically, after grinding the sample, an alkaline fusion agent (e.g., sodium carbonate, sodium borate, etc.) is added and heated and melted in a platinum crucible, and after cooling, the entire amount is dissolved in a hydrochloric acid solution under heating. When this solution is injected into an ICP analyzer, the sample solution is atomized and thermally excited in the high-temperature plasma state inside the analyzer, and when it returns to the ground state, it produces an emission spectrum of wavelengths specific to the elements. From the emission wavelength and intensity, the types and amounts of elements contained can be qualitatively and quantitatively determined. Then, considering the ratio of the quantified types of elements contained, the ratio of the first catalyst to the second catalyst can be calculated.

[0047] The catalyst for paraxylene production according to this disclosure has been described above. According to this disclosure, paraxylene can be efficiently produced using carbon dioxide and hydrogen as raw materials. Specifically, a ternary composite oxide of aluminum, zinc, and zirconium is used as the first catalyst, which readily adsorbs carbon dioxide and allows the reaction between carbon dioxide and hydrogen to proceed efficiently. As the second catalyst, H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide has a spatial limiting effect, allows for the selective and efficient synthesis of paraxylene, and enables this synthesis. Paraxylene can be synthesized efficiently and in high yield. It should be noted that carbon monoxide may be included in part of the raw material gas.

[0048] <2. Method for Producing a Catalyst for Paraxylene Production> Next, a method for producing a catalyst for paraxylene production according to this disclosure will be described. The method for producing a catalyst for paraxylene production according to this disclosure is not particularly limited, but for example, it includes a step (third step) of obtaining a second catalyst by performing hydrothermal synthesis or heating in the presence of at least a silicon compound and H-ZSM-5 zeolite to coat the surface of the H-ZSM-5 zeolite with an oxide containing amorphous silicon, and a step (fourth step) of mixing a first catalyst containing a ternary composite oxide of aluminum, zinc, and zirconium with the second catalyst. The first catalyst may be a metal oxide (mixed metal oxide) obtained by mixing a binary composite oxide of zinc and zirconium with aluminum oxide, or a mixture of a ternary composite oxide and a mixed metal oxide. The method for producing a paraxylene catalyst according to this disclosure may optionally include a step (second step) prior to the third step in which H-ZSM-5 zeolite is synthesized from a silicon compound and an aluminum compound by hydrothermal synthesis. Furthermore, the method for producing a paraxylene catalyst according to this disclosure may optionally include a step (first step) separate from the second and third steps in which a coprecipitation method is used to obtain a coprecipitation product (precipitate containing a complex hydroxide) containing aluminum, zinc, and zirconium, and the coprecipitation product is dried and / or calcined to obtain a first catalyst containing a ternary complex oxide of aluminum, zinc, and zirconium.

[0049] (2.1. First Step) First, in the first step, although not particularly limited, when producing a ternary composite oxide of aluminum, zinc, and zirconium, for example, a coprecipitation method is used to obtain a coprecipitation (precipitate containing a composite hydroxide) containing the ternary metals of aluminum, zinc, and zirconium. Alternatively, when producing a binary composite oxide of zinc and zirconium, for example, a coprecipitation method is used to obtain a coprecipitation method containing the binary metals of zinc and zirconium (precipitate containing a composite hydroxide).

[0050] Next, the obtained coprecipitate containing the ternary metal (precipitate containing the composite hydroxide) is dried and / or calcined to obtain a first catalyst containing a ternary composite oxide of aluminum, zinc, and zirconium. Alternatively, the obtained coprecipitate containing the binary metal (precipitate containing the composite hydroxide) is dried and / or calcined to obtain a binary composite oxide of zinc and zirconium, and aluminum oxide is mixed therein to obtain a first catalyst containing a binary composite oxide of zinc and zirconium and aluminum oxide. Note that the catalyst of the ternary composite oxide of aluminum, zinc, and zirconium and the catalyst of the mixed metal oxide containing a binary composite oxide of zinc and zirconium and aluminum oxide may be used in combination.

[0051] In the coprecipitation method, specifically, an aluminum compound, a zinc compound, and a zirconium compound are first dissolved in an aqueous solution, and a precipitating agent is added to precipitate a ternary complex hydroxide of zinc, aluminum, and zirconium. Alternatively, a zinc compound and a zirconium compound are dissolved in an aqueous solution, and a precipitating agent is added to precipitate a binary complex hydroxide of zinc and zirconium. The aluminum compound (aluminum source) is not particularly limited as long as it is soluble in aqueous solution, and for example, aluminum nitrate, aluminum acetate, aluminum chloride, aluminum bromide, etc. can be used. The zinc compound (zinc source) is not particularly limited as long as it is soluble in aqueous solution, and for example, zinc nitrate, zinc acetate, zinc chloride, zinc bromide, etc. can be used. The zirconium compound (zirconium source) is not particularly limited as long as it is soluble in aqueous solution, and for example, zirconium nitrate, zirconium acetate, zirconium chloride, zirconium bromide, etc. can be used.

[0052] Furthermore, the precipitating agent is not particularly limited as long as it can precipitate (settle) a ternary complex hydroxide of aluminum, zinc, and zirconium or a binary complex hydroxide of zinc and zirconium. For example, ammonium carbonate, sodium carbonate, sodium bicarbonate, urea, potassium carbonate, etc., can be used.

[0053] Furthermore, for the purpose of controlling the particle size and shape of ternary composite hydroxides of aluminum, zinc, and zirconium, or binary composite hydroxides of zinc and zirconium, a maturation treatment may be performed while the composite hydroxides have settled. The maturation treatment can be carried out, for example, by letting the mixture stand for 30 minutes to 12 hours.

[0054] In the above process, the temperature of the aqueous solution is not particularly limited, but can be, for example, 30°C or higher and 100°C or lower.

[0055] Next, the obtained ternary composite hydroxide of aluminum, zinc, and zirconium or binary composite hydroxide of zinc and zirconium is dried and / or calcined to obtain a ternary composite oxide of aluminum, zinc, and zirconium or a binary composite oxide of zinc and zirconium. Prior to drying and calcining, the ternary composite hydroxide of aluminum, zinc, and zirconium or the binary composite hydroxide of zinc and zirconium may be washed as appropriate.

[0056] Drying can be carried out, for example, in an atmospheric atmosphere at 100°C to 200°C for 30 minutes to 12 hours. Alternatively, it can be carried out using supercritical carbon dioxide at 50°C to 200°C for 20 minutes to 24 hours. Furthermore, calcination can be carried out, for example, in an atmospheric atmosphere at 400°C to 600°C for 30 minutes to 10 hours. In this way, a ternary composite oxide of aluminum, zinc, and zirconium or a binary composite oxide of zinc and zirconium is obtained. A first catalyst containing a ternary composite oxide of aluminum, zinc, and zirconium is obtained by the above method. Alternatively, the first catalyst can be obtained by mixing aluminum oxide with a binary composite oxide of zinc and zirconium. While the binary composite oxide of zinc and zirconium and aluminum oxide are effective even when simply mixed, a granulated form is more preferable. Furthermore, the method for adding aluminum oxide to the binary composite oxide of zinc and zirconium is not particularly limited, but preferably, it can be mixed physically using a mortar and pestle or a mixer, or by adding aluminum sol to the binary composite oxide of zinc and zirconium and mixing, drying for 30 minutes to 12 hours in an atmospheric atmosphere at 100°C to 200°C, for example, and then calcining for 30 minutes to 10 hours in an atmospheric atmosphere at 400°C to 600°C. In addition, the first catalyst can be used in powder form, but it may also be used after granulation, and granulation can be done using existing methods such as pelletization or briquetting, depending on the environment in which it is used.

[0057] (2.2. Second Step) In this step, H-ZSM-5 zeolite is synthesized from a silicon compound and an aluminum compound by hydrothermal synthesis. The formation of H-ZSM-5 zeolite is carried out, for example, by heating an aqueous solution (precursor solution) containing a silicon compound (silica source) and an aluminum compound (alumina source).

[0058] Examples of silicon compounds that can be used include tetramethyl orthosilicate and tetraethyl orthosilicate, and examples of aluminum compounds that can be used include aluminum nitrate and aluminum acetate, but the invention is not limited to these.

[0059] Furthermore, the precursor solution may contain amine compounds, such as tetrapropylammonium hydroxide or tetraethylammonium hydroxide, as a template agent (organic structure-determining agent). In addition, while the solvent of the precursor solution is mainly water, it may also contain alcohol-based solvents such as ethanol or methanol to control the hydrolysis rate of the silicon compound.

[0060] The temperature in hydrothermal synthesis is not particularly limited, but for example, it can be 150 to 200°C, preferably 170 to 190°C.

[0061] As the time of hydrothermal synthesis increases, the particle size of H-ZSM-5 zeolite increases. The time of hydrothermal synthesis is, for example, 1 hour or more and 168 hours or less, preferably 24 hours or more and 72 hours or less.

[0062] In addition, the reaction mixture may be stirred as needed during hydrothermal synthesis. The stirring conditions can be set as appropriate. Furthermore, the physical properties of H-ZSM-5 zeolite, such as particle size, pore size, and specific surface area, can be controlled by the hydrothermal synthesis conditions, such as time.

[0063] The H-ZSM-5 zeolite produced by hydrothermal synthesis is subjected to washing and drying as appropriate after the completion of hydrothermal synthesis. The drying time is not particularly limited, but can be, for example, 0.5 to 20 hours. The drying temperature is not particularly limited, but can be, for example, 50 to 150°C.

[0064] Next, the dried catalyst is subjected to calcination to remove organic matter present in the pores of the zeolite. This yields H-ZSM-5 zeolite. The calcination time is not particularly limited, but can be, for example, 0.5 to 15 hours. The calcination temperature is not particularly limited, but can be, for example, 400 to 600°C.

[0065] If H-ZSM-5 zeolite is available separately, this step may be omitted. Furthermore, notwithstanding the above explanation, H-ZSM-5 zeolite does not necessarily have to be manufactured by hydrothermal synthesis.

[0066] (2.3. Third Step) In this step, hydrothermal synthesis is performed in the presence of a compound containing at least silicon and H-ZSM-5 zeolite, or heating is performed in the presence of a compound containing silicon and H-ZSM-5 zeolite to form an amorphous silicon-containing oxide (preferably SiO₂) on the surface of the H-ZSM-5 zeolite. ２ A second catalyst is obtained by coating it with SiO. ２ The formation is carried out, for example, by adding tetraethoxysilane (TEOS) dropwise to an organic solvent in which H-ZSM-5 zeolite is dispersed, and then heating the mixture.

[0067] Also, SiO ２ When coating, hexane or the like is used as the organic solvent to disperse H-ZSM-5. Other organic solvents, alcohols, etc., may also be included.

[0068] Furthermore, stirring is performed to disperse H-ZSM-5 in the organic solvent, but the stirring speed is not particularly limited. For example, it can be 200 to 1000 rpm / min, preferably 300 to 800 rpm / min.

[0069] The heating temperature after adding TEOS dropwise to the H-ZSM-5 dispersed organic solvent is not particularly limited. For example, it can be 50 to 150°C, preferably 50 to 80°C.

[0070] TEOS is added dropwise to the H-ZSM-5 dispersed organic solvent, and then the organic solvent is removed while heating. The heating temperature at this time is not particularly limited, but for example, it can be 50 to 150°C, preferably 50 to 80°C.

[0071] As described above, SiO ２ The H-ZSM-5 zeolite coated with the coating is subjected to drying and calcination after heating, if necessary. The drying time is not particularly limited, but can be, for example, 0.5 to 20 hours. The drying temperature is not particularly limited, but can be, for example, 50 to 150°C.

[0072] Next, the dried catalyst is subjected to a calcination treatment to remove organic matter present in the pores of the zeolite. This results in SiO ２A coated H-ZSM-5 zeolite is obtained. The firing time is not particularly limited, but can be, for example, 0.5 to 15 hours. The firing temperature is not particularly limited, but can be, for example, 400 to 600°C.

[0073] (2.4. Fourth step) A first catalyst containing a ternary composite oxide of aluminum, zinc, and zirconium is physically mixed with a second catalyst containing H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide. This yields a catalyst for paraxylene production. The mixing can be carried out using, for example, a mortar and pestle, a ball mill, or an automatic kneader.

[0074] Furthermore, after mixing, in order to improve the adhesion between the first catalyst and the second catalyst, pellets of the catalyst for paraxylene production may be formed and these pellets may be crushed.

[0075] <3. Method for Producing Paraxylene> Next, a method for producing paraxylene using the above-described paraxylene production catalyst will be explained based on a preferred embodiment.

[0076] Paraxylene can be produced by contacting a raw material gas containing carbon dioxide and hydrogen with a paraxylene production catalyst according to this disclosure. Carbon dioxide and hydrogen may be supplied separately, but are usually supplied as a mixed gas.

[0077] For the carbon dioxide and hydrogen mixture used in the method described herein, a gas in which the total amount of carbon dioxide and hydrogen is 50% or more of the total is preferable from the standpoint of productivity, and in particular, a molar ratio of hydrogen to carbon dioxide (hydrogen / carbon dioxide) in the range of 0.5 to 4.0 is desirable. This is because if the molar ratio of hydrogen to carbon dioxide is less than 0.5, the amount of hydrogen present in the raw material gas is too small, making it difficult for the hydrogenation reaction of carbon dioxide to proceed and resulting in low productivity. On the other hand, if the molar ratio of hydrogen to carbon dioxide exceeds 4.0, the amount of carbon dioxide present in the raw material gas is too small, resulting in low productivity of liquid hydrocarbons regardless of catalytic activity.

[0078] Furthermore, the reactor used for contact between the mixed gas and the catalyst according to this disclosure is not particularly limited and includes, for example, general gas-phase synthesis reactors such as fixed-bed reactors, jet-bed reactors, and fluidized-bed reactors, liquid-phase synthesis reactors such as slurry-bed reactors, and microchannel reactors.

[0079] When carrying out the reaction to produce paraxylene, the ternary composite oxide of aluminum, zinc, and zirconium (the first catalyst) must be in a reduced state. Therefore, before supplying the mixed gas to produce paraxylene, a reducing gas such as hydrogen gas is passed through to reduce the catalyst for paraxylene production. Such a reduction treatment is not particularly limited, but can be carried out, for example, at a temperature of 300 to 500°C for 1 to 40 hours.

[0080] Furthermore, the catalyst for paraxylene production may be reduced after loading the reactor, or it may be reduced before loading. For example, it is possible to perform the reduction treatment before charging the reactor with the paraxylene production catalyst, and then load the reactor.

[0081] The conditions for the production of paraxylene are not particularly limited and can be set according to the type of reactor.

[0082] For example, the reaction temperature during the reaction to produce paraxylene is not particularly limited, but is 200 to 500°C, preferably 300 to 400°C. Also, the pressure in the system during the reaction is not particularly limited, but is, for example, 4.0 to 10.0 MPa, preferably 5.0 to 8.0 MPa.

[0083] If the activity decreases due to factors such as an extremely high conversion rate or a long reaction time, the catalyst for paraxylene production can be regenerated by supplying a gas containing air (regeneration gas) instead of the mixed gas. The air content of the regeneration gas is preferably 0.01% or more. However, the air content in the regeneration gas may be 100%. Furthermore, the regeneration gas may contain inert gases such as nitrogen or argon.

[0084] The conditions for regeneration of the paraxylene production catalyst are not particularly limited, as long as catalyst regeneration progresses. The catalyst regeneration mechanism by contacting the paraxylene production catalyst with a regeneration gas containing air is presumed to be due to the removal of precipitated carbon by the air.

[0085] The following describes in more detail the paraxylene production catalyst and the like related to this disclosure with reference to examples and comparative examples, but this disclosure is not limited to these examples and comparative examples.

[0086] [Example 1] (Production of a catalyst for paraxylene production) 1.4 g of zinc nitrate, 3.5 g of aluminum nitrate, and 2.5 g of zirconium nitrate were accurately weighed and dissolved in 200 mL of ultrapure water to make solution A. Furthermore, 6.3 g of ammonium carbonate was dissolved in 300 mL of ultrapure water to make solution B. 500 mL of ultrapure water was heated to 80°C and stirred to make solution C. Solution A was titrated against solution C, and immediately afterwards, solution B was also titrated, and the titration rate of solution B was adjusted so that the pH was 7 to 8. The precipitate obtained from the reaction of solution A and solution B was left to stand for 3 hours under heating at 80°C. After that, the precipitate was filtered and washed 5 times with 80°C warm water. The obtained filtrate was dried overnight at 120°C. The obtained solid was coarsely ground and then calcined (hereinafter also referred to as charring) in air at 500°C for 3 hours. This yielded a ternary composite oxide powder of aluminum, zinc, and zirconium as the first catalyst. The obtained ternary composite oxide powder of aluminum, zinc, and zirconium was N ２ The BET specific surface area due to adsorption and desorption is 199 m². ２ The average pore size was 3.4 nm per g.

[0087] Meanwhile, to produce H-ZSM-5 zeolite, tetramethyl orthosilicate, aluminum nitrate, water, tetrapropylammonium hydroxide, and ethanol were accurately weighed and dissolved in a molar ratio of 1:0.025:50:0.24:4. This solution was introduced into a Teflon® sealed autoclave, stirred with a magnetic stirrer for 4 hours, and then reacted at 180°C for 24 hours. The resulting product was washed with distilled water, dried overnight at 120°C, and then calcined in air at 550°C for 5 hours to decompose and remove organic matter present in the zeolite pores, thereby obtaining H-ZSM-5 zeolite powder. The obtained H-ZSM-5 zeolite powder is N ２ The BET specific surface area due to adsorption and desorption is 367.6 m². ２ The average pore size was 2.0 nm per g.

[0088] The 5 g of zeolite (H-ZSM-5) obtained in this way was added to 50 g of n-hexane and dispersed for 10 min using ultrasound. Next, 12 g of TEOS was added dropwise to this solvent. After adding TEOS, stirring was continued at a stirring speed of 300 rpm for 4 hours. Then, the solution was heated to 80°C while stirring to remove the n-hexane. The obtained sample was dried at 120°C for 16 hours and then calcined at 550°C for 6 hours to obtain amorphous SiO as a second catalyst. ２ H-ZSM-5 zeolite coated with (hereinafter referred to as "SiO ２ It is sometimes called a "coated zeolite." ) was obtained. The obtained SiO ２ Coated zeolite powder is N ２ The BET specific surface area due to adsorption and desorption is 263.7 m². ２ The average pore size was 2.4 nm per g. In Tables 1 and 2 described later, the second catalyst is referred to as "H-ZSM-5 + SiO ２ It is abbreviated as "".

[0089] The ternary composite oxide of aluminum, zinc, and zirconium obtained in this way (first catalyst) and SiO ２The coated zeolite (second catalyst) was weighed to a mass ratio of 1:1 and physically mixed in a mortar for 10 minutes to obtain a mixed powder. The mixed powder was then pressed into 3 mmφ tablets using a compression molder to obtain the tablet bodies, which were then crushed to a size of 20-40 mesh to obtain a catalyst for paraxylene production.

[0090] (Production of paraxylene) Using 0.5 g of the obtained paraxylene production catalyst, it was fixed with quartz wool so that it was located in the center of a SUS reaction tube with an inner diameter of 6 mm, a thermocouple was inserted in the center of the catalyst layer, and these fixed-bed reaction tubes were set in the predetermined position.

[0091] Before starting the synthesis reaction, the reactor was first heated under a nitrogen atmosphere at room temperature, with a hydrogen gas flow rate of 60 N mL / min, to 400°C, and then reduced for 2 hours. After that, it was cooled to room temperature and then treated with 18% CO2. ２ +12%CO+4%Ar+H ２ The remaining mixed gas was circulated at 70 N mL / min, pressurized to 5 MPa, and then heated to 360°C to initiate the reaction. Data was collected at 4 hours. After removing water from the reaction product, it was injected into two gas chromatographs (Shimadzu Corporation: GC-8A) and analyzed using a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0092] The degree of reaction in the synthesis reaction (the rate of paraxylene production) is CO ２ Conversion rate, CO selectivity, methane selectivity, C2-C4(O) selectivity from ethane, propane, and butane, C2-C4(=) selectivity from ethylene, propylene, and butylene, CH4 from methanol and dimethyl ether ３The selectivity for OH+DME, pentane, long-chain aliphatic hydrocarbons (C5+) and aromatics (Aromatics) from pentane onward, as well as the selectivity for benzene (B), toluene (T), ethylbenzene (E), orthoxylene (o-X), metaxylene (m-X), paraxylene (p-X), C9 aromatic hydrocarbons (cumene) (A(C9)), tetralin, aromatic hydrocarbons with 10 or more carbon atoms (A(C10+)), and p-X / X as the proportion of paraxylene in total xylene (orthoxylene, metaxylene, and paraxylene) were calculated from the concentrations of each component using the following formula. Of these, the aromatic selectivity, PX selectivity, and space-time yield are shown in Example 1 in Table 1.

[0093] CO ２ Conversion rate (%) = {1 - (CO after reaction) ２ (Amount of carbon molars derived) / (Supplied CO ２ (Molar amount of carbon derived from CO) × 100 CO selectivity (%) = (Molar amount of carbon derived from CO) / (Supplied CO ２ (Amount of carbon molars derived) - (CO after reaction) ２ (Amount of carbon molars derived) × 100 CO + CO ２ Conversion rate (%) = {1 - (CO after reaction) ２ (Molar amount of carbon derived from CO + Molar amount of carbon derived from CO after reaction) / (Supplied CO) ２ Hydrocarbon selectivity (%) = (Molar amount of carbon derived from hydrocarbons + Molar amount of carbon derived from supplied CO) × 100 ２ (Amount of carbon molars derived) - (CO after reaction) ２ (Molar amount of carbon derived) × 100 CH ４ Selection rate (%) = (CH ４ Ethane selectivity (%) = (moles of carbon derived from hydrocarbons) / (moles of carbon derived from hydrocarbons) × 100 Propane selectivity (%) = (moles of carbon derived from propane) / (moles of carbon derived from hydrocarbons) × 100 Butane selectivity (%) = (moles of carbon derived from butane) / (moles of carbon derived from hydrocarbons) × 100 C2-C4(O) selectivity (%) = (ethane selectivity) + (propane selectivity) + (butane selectivity)

[0094] Ethylene selectivity (%) = (moles of carbon derived from ethylene) / (moles of carbon derived from hydrocarbons) × 100 Propylene selectivity (%) = (moles of carbon derived from propylene) / (moles of carbon derived from hydrocarbons) × 100 Butylene selectivity (%) = (moles of carbon derived from butylene) / (moles of carbon derived from hydrocarbons) × 100 C2-C4 selectivity (%) = (ethylene selectivity) + (propylene selectivity) + (butylene selectivity)

[0095] CH ３ OH selectivity (%) = (CH ３ (Molar amount of carbon derived from OH) / (Molar amount of carbon derived from hydrocarbons) × 100 DME selectivity (%) = (Molar amount of carbon derived from DME) / (Molar amount of carbon derived from hydrocarbons) × 100 CH ３ OH + DME selectivity (%) = (CH ３ Pentane selectivity (%) = (moles of carbon derived from pentane) / (moles of carbon derived from hydrocarbons) × 100 Long-chain aliphatic hydrocarbon (C5+) selectivity (%) = (pentane selectivity) + (long-chain aliphatic hydrocarbon selectivity of C6 or higher)

[0096] Selectivity for B (%) = (moles of carbon derived from benzene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for T (%) = (moles of carbon derived from toluene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for E (%) = (moles of carbon derived from ethylbenzene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for o-X (%) = (moles of carbon derived from orthoxylene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for m-X (%) = (moles of carbon derived from metaxylene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for p-X (%) = (moles of carbon derived from paraxylene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for A (C9) (%) = (moles of carbon derived from cumene) / (moles of carbon derived from hydrocarbons) × 100 Selectivity for tetralin (%) = (moles of carbon derived from tetralin) / (moles of carbon derived from hydrocarbons) × 100 A(C10+) selectivity (%) = (tetraline selectivity) + (C11 or higher aromatic hydrocarbon selectivity) Aromatic selectivity (%) = (B selectivity) + (T selectivity) + (o-X selectivity) + (m-X selectivity) + (p-X selectivity) + (A(C9) selectivity) + (A(C10+) selectivity) Paraxylene content in total xylene (%) = (p-X selectivity) / ((o-X selectivity) + (m-X selectivity) + (p-X selectivity)) × 100 Space-time yield of paraxylene (unit catalyst mass, amount of paraxylene produced per unit time) (g / kg / h) = (CO + CO ２ (Conversion rate) × ((CO flow rate supplied (mol / h / g)) cat ) + supplied CO ２ Flow rate (mol / h / g cat ))) × p-X selectivity × 10⁶ / 8 (g / mol) × 1000 Note that the space-time yield of paraxylene (PX) is (CO + CO ２ This value is obtained by converting the amount of carbon consumed by the conversion to the amount of PX molars using the number of carbon atoms in PX (8), converting it to mass using the molecular weight of PX (106 g / mol), and further converting it to g / kg / h based on the catalyst mass.

[0097] [Example 2] 2.8 g of zinc nitrate, 3.5 g of aluminum nitrate, and 2.5 g of zirconium nitrate were accurately weighed and dissolved in 200 mL of ultrapure water to make solution A. Furthermore, 6.3 g of ammonium carbonate was dissolved in 300 mL of ultrapure water to make solution B. 500 mL of ultrapure water was heated to 80°C and stirred to make solution C. Solution A was titrated against solution C, and immediately afterwards, solution B was also titrated, adjusting the titration rate of solution B so that the pH was 7-8. The precipitate obtained from the reaction of solution A and solution B was allowed to stand for 3 hours under heating at 80°C. After that, the precipitate was filtered and washed 5 times with 80°C warm water. The obtained filtrate was dried overnight at 120°C. The obtained solid was coarsely ground and then calcined in air at 500°C for 3 hours. This yielded a ternary composite oxide powder of aluminum, zinc, and zirconium as the first catalyst. Paraxylene was synthesized using the obtained catalyst in the same manner as in Example 1. The results are shown in Example 2 in Table 1.

[0098] [Examples 3-5] Except for varying the amounts of zinc nitrate, aluminum nitrate, and zirconium nitrate to adjust the molar ratio of the metals contained in the resulting composite oxide to Al / Zn / Zr = 43 / 3 / 52 (Example 3), 3 / 3 / 94 (Example 4), and 52 / 3 / 45 (Example 5), the catalysts for paraxylene production were prepared in the same manner as in Example 1. Paraxylene was synthesized using each of the obtained paraxylene production catalysts in the same manner as in Example 1. The results are shown in Examples 3-5 in Table 1.

[0099] [Examples 6-20] Except for varying the amounts of zinc nitrate, aluminum nitrate, and zirconium nitrate to adjust the molar ratio of metals Al / Zn / Zr in the resulting composite oxide as shown in Table 1, catalysts for paraxylene production were prepared in the same manner as in Example 1. Paraxylene was synthesized using each of the obtained catalysts in the same manner as in Example 1. The results are shown in Examples 6-20 in Table 1.

[0100] [Comparative Example 1] 6.4 g of zinc nitrate, 8.6 g of chromium nitrate, and 5.7 g of zirconium nitrate were accurately weighed and dissolved in 100 mL of pure water. This aqueous solution was heated to 70°C, and an aqueous solution of ammonium carbonate was added to precipitate a ternary complex hydroxide of zinc, chromium, and zirconium, which was then thoroughly stirred with a stirrer. After that, stirring was continued for 3 hours while maintaining the temperature at 70°C for maturation, followed by filtration and thorough washing with pure water at 80°C. The obtained solid was coarsely ground and then calcined in air at 500°C for 3 hours. This prepared a ternary complex oxide powder of chromium, zinc, and zirconium as the first catalyst, and obtained a catalyst for the production of paraxylene. The obtained ternary complex oxide powder of chromium, zinc, and zirconium is N ２ The BET specific surface area due to adsorption and desorption is 115 m². ２ The average pore size was 3.0 nm per g.

[0101] Meanwhile, to produce H-ZSM-5 zeolite, tetramethyl orthosilicate, aluminum nitrate, water, tetrapropylammonium hydroxide, and ethanol were accurately weighed and dissolved in a molar ratio of 1:0.025:50:0.24:4. This solution was introduced into a Teflon® sealed autoclave, stirred with a magnetic stirrer for 4 hours, and then reacted at 180°C for 24 hours. The resulting product was washed with distilled water, dried overnight at 120°C, and then calcined in air at 550°C for 5 hours to decompose and remove organic matter present in the zeolite pores, thereby obtaining H-ZSM-5 zeolite powder. The obtained H-ZSM-5 zeolite powder is N ２ The BET specific surface area due to adsorption and desorption is 367.6 m². ２ The average pore size was 2.0 nm per g.

[0102] The 5 g of zeolite (H-ZSM-5) obtained in this way was added to 50 g of n-hexane and dispersed for 10 min using ultrasound. Next, 12 g of TEOS was added dropwise to this solvent. After adding TEOS, stirring was continued at a stirring speed of 300 rpm for 4 hours. Then, the solution was heated to 80°C while stirring to remove the n-hexane. The obtained sample was dried at 120°C for 16 hours and then calcined at 550°C for 6 hours to obtain amorphous SiO as a second catalyst. ２ H-ZSM-5 zeolite coated with (hereinafter referred to as "SiO ２ It is sometimes called a "coated zeolite." ) was obtained. The obtained SiO ２ Coated zeolite powder is N ２ The BET specific surface area due to adsorption and desorption is 263.7 m². ２ The average pore size was 2.4 nm per g. In Tables 1 and 2 described later, the second catalyst is referred to as "H-ZSM-5 + SiO ２ It is abbreviated as "".

[0103] The ternary composite oxide of zinc, chromium, and zirconium obtained in this way (first catalyst) and SiO ２ Coated zeolite (second catalyst) was accurately weighed to a mass ratio of 1:2 according to known conditions such as those described in Patent Document 2, and physically mixed in a mortar for 10 minutes to obtain a mixed powder. The mixed powder was then press-molded into 3 mmφ tablets using a compression molder to obtain the tablet bodies, which were then crushed to a size of 20-40 mesh to obtain a catalyst for paraxylene production. Paraxylene was synthesized using the obtained catalyst for paraxylene production in the same manner as in Example 1. The results are shown in Comparative Example 1 in Table 1.

[0104] [Comparative Example 2] A catalyst for paraxylene production was obtained in the same manner as in Example 1, except that 0.8 g of zinc nitrate and 5.7 g of zirconium nitrate were used to form a binary complex oxide of zinc and zirconium. Paraxylene was synthesized using the obtained catalyst for paraxylene production in the same manner as in Example 1. The results are shown in Comparative Example 2 in Table 1.

[0105] [Comparative Example 3] A catalyst for paraxylene production was obtained in the same manner as in Example 1, except that the amounts of zinc nitrate and zirconium nitrate were changed so that the molar ratio of the metals contained in the resulting composite oxide was adjusted to Zn / Zr = 1 / 2. Paraxylene was synthesized using the obtained paraxylene production catalyst in the same manner as in Example 1. The results are shown in Comparative Example 3 in Table 1.

[0106] [Comparative Example 4] A catalyst for paraxylene production was obtained in the same manner as in Example 1, except that 5.3 g of zinc nitrate and 3.3 g of aluminum nitrate were used to form a binary aluminum-zinc composite oxide. Paraxylene was synthesized using the obtained catalyst in the same manner as in Example 1. The results are shown in Comparative Example 4 in Table 1.

[0107]

[0108] In Examples 1, 3-5, 6, 11, 13, 14, and 18, by using a ternary composite oxide containing Al instead of Cr as the first catalyst of this disclosure, the aromatic selectivity or paraxylene selectivity was equivalent to that of the Cr-containing ternary composite oxide catalyst in Comparative Example 1. In contrast, in Comparative Examples 2-4, although the catalyst did not contain Cr, the paraxylene selectivity was significantly lower than in Comparative Example 1. In Examples 3, 5, 6, and 18, although the productivity (space-time yield) of paraxylene was low, the aromatic selectivity including paraxylene was high, making it easier to separate by-products when the reactor outlet gas components are recycled, and CO used in aromatic synthesis was also utilized. ２ and H ２ It is effective because it has the advantage of requiring a smaller amount.

[0109] Furthermore, while Examples 2, 8, 12, 15, 19, and 20 show slightly lower aromatic selectivity and paraxylene selectivity compared to the Cr-containing ternary composite oxide catalyst of Comparative Example 1, they show higher aromatic selectivity and paraxylene selectivity compared to Comparative Examples 2-4, which do not contain Cr in the first catalyst, indicating their superiority as Cr-free catalysts. Similarly, Example 7 shows higher paraxylene selectivity compared to Comparative Examples 2-4, which do not contain Cr in the first catalyst, indicating its superiority as a Cr-free catalyst. Also, Examples 9, 10, 16, and 17 show higher aromatic selectivity and paraxylene selectivity compared to Comparative Example 2, which does not contain Cr in the first catalyst, indicating their superiority as Cr-free catalysts. In Figure 2, the circular plots represent the molar ratios of Examples 1-20, and the triangular plots represent the molar ratios of Comparative Examples 1-4.

[0110] <Evaluation of the effect of the weight ratio of the first and second catalysts> In Examples 1 to 20, a catalyst for paraxylene production was prepared with a weight ratio of 1:1 between the first and second catalysts. However, the aromatic selectivity, paraxylene selectivity, and space-time yield were evaluated when paraxylene was synthesized using a paraxylene production catalyst with a different weight ratio between the first and second catalysts.

[0111] [Examples 21-23] The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 1 and SiO ２ A catalyst for paraxylene production was obtained by preparing the same procedure as in Example 1, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:10. The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 2 and SiO ２ A catalyst for paraxylene production was obtained by preparing the same procedure as in Example 2, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:10. The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 4 and SiO ２ A catalyst for paraxylene production was obtained by preparing the same procedure as in Example 4, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:10.

[0112] [Examples 24-26] The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 1 and SiO ２ A catalyst for paraxylene production was obtained in the same manner as in Example 1, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:0.25. The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 2 and SiO ２ A catalyst for paraxylene production was obtained in the same manner as in Example 2, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:0.25. The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 4 and SiO ２ A catalyst for paraxylene production was obtained by preparing the same procedure as in Example 4, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:0.25.

[0113] [Example 27] The ternary composite oxide of aluminum, zinc, and zirconium (first catalyst) prepared in Example 2 and SiO ２ A catalyst for paraxylene production was obtained by preparing the same procedure as in Example 2, except that the coated zeolite (second catalyst) was mixed in a mass ratio of 1:15.

[0114] Paraxylene was synthesized in the same manner as in Example 1 using the paraxylene production catalysts obtained in Examples 21 to 27. The results are shown in Table 2 for Examples 1, 2, and 4.

[0115]

[0116] As shown in Table 2, the space-time yield was better when the weight of the second catalyst relative to the first catalyst (100% by mass) was 25% by mass, 100% by mass, or 1000% by mass, compared to when the weight of the second catalyst relative to the first catalyst (1500% by mass). Thus, it can be seen that the catalysts shown in the examples exhibit performance at the same level or higher than conventional Cr-free catalysts (at least in terms of paraxylene selectivity), and in the preferred composition range, they exhibit performance at the same level or higher than conventional Cr-based catalysts.

[0117] While preferred embodiments and examples of the present disclosure have been described in detail above, the present disclosure is not limited to such embodiments. It is clear to any person with ordinary skill in the art to which the present disclosure pertains that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure.

[0118] The disclosure of Japanese Patent Application No. 2025-057253, filed on 28 March 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually described.

Claims

1. A catalyst for the production of paraxylene, comprising: a first catalyst comprising at least one of a ternary composite oxide of aluminum, zinc, and zirconium, and a mixed metal oxide comprising a binary composite oxide of zinc and zirconium and aluminum oxide; and a second catalyst comprising H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide.

2. The first catalyst for producing paraxylene according to claim 1, wherein, with respect to the total amount of aluminum, zinc, and zirconium, aluminum is contained in an amount of 1 mol% to 55 mol%, zinc in an amount of 1 mol% to 35 mol%, and zirconium in an amount of 10 mol% to 98 mol%.

3. The catalyst for producing paraxylene according to claim 1 or claim 2, wherein the second catalyst is contained in an amount of 10% by mass or more and 1000% by mass or less relative to the first catalyst.

4. A method for producing paraxylene, comprising contacting a raw material gas containing carbon dioxide and hydrogen with a paraxylene production catalyst according to any one of claims 1 to 3 to synthesize paraxylene.

5. A method for producing a paraxylene production catalyst according to any one of claims 1 to 3, comprising: obtaining a coprecipitation by coprecipitation of a coprecipitation containing zinc and zirconium, or a coprecipitation containing aluminum, zinc, and zirconium, and performing either drying and / or calcination of the coprecipitation to obtain a composite oxide, and in the case of a binary composite oxide of zinc and zirconium, mixing with aluminum oxide to obtain the first catalyst; performing hydrothermal synthesis or heating in the presence of a silicon compound and H-ZSM-5 zeolite to obtain the second catalyst containing H-ZSM-5 zeolite coated with an amorphous silicon-containing oxide; and mixing the first catalyst and the second catalyst.

Images