A single-particle near-source HCl capturing spherical shell structure hydrogenation dechlorination catalyst, and a preparation method and application thereof

Abstract

This invention discloses a spherical shell-structured hydrodechlorination catalyst for near-source HCl capture in a single particle, its preparation method, and its applications. The catalyst comprises a core and an adsorption layer covering the outer surface of the core. The core contains a hydrodechlorination active metal component, and the adsorption layer primarily uses zinc oxide as the adsorbent component. During the reaction, chlorinated organic compounds preferentially enter the core and undergo hydrodechlorination to generate HCl. The generated HCl is immediately adsorbed and fixed by the outer shell adsorption layer during its outward diffusion, thereby constructing a controlled mass transfer pathway of "reaction first, capture later" at the single-particle scale. This invention can significantly improve the near-source capture efficiency of HCl, reduce the escape and migration of acidic products, mitigate catalyst deactivation, and reduce the risk of equipment corrosion. It is suitable for the hydrodechlorination treatment of chlorinated oils or chlorinated organic feedstocks.

Description

Technical Field

[0001] This invention relates to the field of dechlorination purification and hydrogenation conversion technology of chlorinated organic compounds, specifically to a spherical shell-structured hydrogenation dechlorination catalyst for near-source HCl capture by a single particle, its preparation method, and its application. Background Technology

[0002] Chlorinated organic compounds are widely present in various chemical feedstocks and petroleum systems, especially in pyrolysis oils generated during solid waste pyrolysis, chlorinated polymer cracking, and related recycling processes, often accompanied by different forms of organochlorides. These chlorinated feedstocks have potential value as fuel oils or chemical raw materials, but their chlorinated components easily cause a series of problems during subsequent processing and catalytic conversion: on the one hand, due to its extremely high electronegativity, chlorine readily undergoes strong adsorption reactions at the active metal sites of catalysts, leading to rapid catalyst deactivation; on the other hand, the hydrogenation product HCl from chlorinated compounds easily causes corrosion in reactors and downstream heat exchange and separation equipment, thereby reducing the overall safety and stability of the process.

[0003] To mitigate the adverse effects of chlorine on hydrogenation systems, existing technologies typically employ methods such as increasing the hydrogen-to-oil ratio, raising operating temperature or pressure, increasing metal loading, using more active catalysts, or shortening catalyst lifespan to maintain unit operation. However, these measures often lead to a significant increase in energy consumption and operating costs, and still fail to fundamentally prevent deactivation and corrosion caused by chlorine migration and accumulation within the system. Another approach attempts to incorporate adsorption units to immobilize the generated HCl and / or chlorine-containing species within the solid phase during hydrodechlorination, thereby reducing the release and migration of chlorine-containing species in the reaction phase, thus decreasing the poisoning of metal active sites by chlorine and reducing the downstream migration of corrosive chlorine.

[0004] Following the aforementioned "reaction-adsorption synergy" approach, patent CN120173644B physically combines a hydrodechlorination catalyst and an adsorbent in two powder or granular forms. For example, a composite bed is formed through simple mixing, kneading and granulation, or co-packing. This allows chlorine-containing compounds to undergo hydrodechlorination on the catalyst to generate HCl, which is then captured and fixed by the adsorbent in the bed. However, this type of "uniform mixing of two powders / granules" scheme still has the following shortcomings in actual operation: (1) The generation location of HCl and the spatial location of the adsorbent are randomly distributed. HCl needs to undergo diffusion and migration from the generation point to the adsorption site, which can easily form a local high-concentration acidic microenvironment. When the adsorbent and catalyst particles have insufficient contact probability or there are low-resistance channels in the mass transfer path within the bed, some HCl may migrate downstream with the flow before being adsorbed, making it difficult to achieve a high capture rate and stable "zero escape". The risk of equipment corrosion still exists.

[0005] (2) The consumption and saturation of the adsorbent exhibit obvious spatial non-uniformity, and local saturation and breakthrough are likely to occur. At the same time, the random mixing between powders / particles makes it difficult for the "reaction zone-adsorption zone" to be stably coupled at the microscale, resulting in low utilization of adsorption sites. It is often necessary to increase the amount of adsorbent added or replace it frequently to maintain the HCl control level. Summary of the Invention

[0006] Based on previous research and existing problems, this invention, after further research and analysis, proposes a spherical-shell structured hydrodechlorination catalyst for near-source HCl capture by a single particle, along with its preparation method and applications. The proposed core-shell integrated reaction and adsorption catalyst establishes a clear "reaction-then-capture" mass transfer pathway within the single particle by placing the hydrodechlorination active component in the core and constructing the adsorption component as the outer shell: chlorinated compounds preferentially diffuse inward into the core to undergo hydrodechlorination and generate HCl, which then diffuses outward and is immediately adsorbed and fixed in the shell. Compared to two uniform powder / particle mixing methods, this structure is beneficial for improving the near-source HCl capture efficiency, reducing the probability of HCl escape and migration, increasing the utilization rate of adsorption sites, and improving the stability and long-term reliability of the catalyst bed operation.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle includes a core and an outer shell adsorption layer covering the outer surface of the core. The core is loaded with hydrodechlorination active metal components, and the outer shell adsorption layer is mainly composed of zinc oxide. During the hydrodechlorination of chlorinated organic compounds, the chlorinated organic compounds diffuse inward to the core and undergo a hydrodechlorination reaction to generate HCl. The generated HCl diffuses outward and is adsorbed and fixed by the outer shell adsorption layer, forming a near-source HCl capture system at the single-particle scale, where the reaction occurs first and then the HCl is captured.

[0008] Preferably, the content of the active metal component for hydrodechlorination in the catalyst is 0.5 to 30 wt% based on oxides; the active metal component for hydrodechlorination is one or more of cobalt, molybdenum, nickel, and tungsten.

[0009] Preferably, the core also includes a support on which the hydrodechlorination active metal component is loaded. The support is alumina, silica, molecular sieve or a composite support thereof.

[0010] Preferably, the outer shell adsorption layer further comprises a structurally stabilizing component, which is one or more of Al2O3, SiO2, or ZrO2.

[0011] Preferably, the content of zinc oxide in the outer shell adsorption layer is 70-95 wt%, and the content of the structurally stable component in the outer shell adsorption layer is 5-30 wt%.

[0012] This invention also proposes a method for preparing a spherical shell-structured hydrodechlorination catalyst with single-particle near-source HCl capture as mentioned above, comprising the following steps: S1: Preparation of catalyst core supported with active metal components for hydrodechlorination; S2: Prepare shell powder with zinc oxide as the main adsorbent component; S3: The catalyst core and outer shell powder are formed under the action of a bonding medium, so that the outer shell powder covers the outer surface of the core, and the finished catalyst is obtained by drying and calcining.

[0013] Preferably, the process of preparing the catalyst core in step S1 is as follows: the precursor salt of the hydrodechlorination active metal component is prepared into an impregnation solution, which is loaded onto the support by an equal volume impregnation method. After standing, drying, calcining and grinding, the active metal supported catalyst powder is obtained. The powder is then rolled into shape under the action of a bonding medium to obtain the catalyst core. The precursor salt of the active metal component for hydrodechlorination is one or more of cobalt nitrate, ammonium molybdate tetrahydrate, nickel nitrate, and ammonium metatungstate.

[0014] Preferably, the process of preparing the shell powder in step S2 is as follows: the zinc oxide precursor and the structurally stable component precursor are mixed in a certain proportion, dried, calcined, pulverized and sieved to obtain the shell powder; Among them, the zinc oxide precursor is one or more of basic zinc carbonate, zinc nitrate, basic zinc acetate, and zinc hydroxide; The structurally stable component precursor is one or more of aluminum hydroxide, boehmite, silica sol, sodium silicate, and zirconium hydroxide.

[0015] Preferably, in step S3, the bonding medium is a mixture of aluminum sol and nitric acid aqueous solution, and the volume ratio of aluminum sol to nitric acid aqueous solution is 15:1. In steps S1-S3, the drying temperature is 100-120℃ and the drying time is 10-12h; the calcination temperature is 550-600℃ and the calcination time is 6-10h.

[0016] This invention also proposes a method for the hydrodechlorination of chlorinated organic feedstocks. The chlorinated organic feedstock and hydrogen are reacted in the presence of a spherical-shell hydrodechlorination catalyst as described above. A pre-reaction and post-capture system at the single-particle scale of the catalyst is used to achieve near-source capture of HCl, thus completing the hydrodechlorination of the chlorinated organic feedstock. The reaction conditions are: hydrogen partial pressure 2–16 MPa, reaction temperature 200–400 °C, and liquid hourly space velocity 0.3–2.0 h⁻¹. -1 .

[0017] Compared with the prior art, the present invention provides a spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle, its preparation method and application, which has the following beneficial effects: (1) In this invention, the active component for hydrodechlorination is placed in the core, and the adsorbent is constructed as a continuously coated outer shell adsorbent layer, forming a controlled mass transfer path of "reaction first, adsorption later" at the single particle scale: chlorine-containing compounds preferentially enter the core to undergo hydrodechlorination to generate HCl, and the generated HCl is immediately adsorbed and fixed by the outer shell adsorbent layer during the outward diffusion process. This can significantly reduce the probability of HCl migration, penetration and escape in the bed, improve the effective utilization rate and operational stability of the adsorbent layer, and thus reduce the risk of corrosion in downstream equipment.

[0018] (2) The immediate adsorption and fixation of HCl by the shell adsorption layer can weaken the fluctuation of acidic atmosphere outside the particles and in the bed, reduce the influence of acidic species on the active center of hydrodechlorination, thereby slowing down the activity decay caused by chlorination / acidity, which is conducive to extending the effective service life of the catalyst.

[0019] (3) Since the generated HCl is adsorbed and fixed in time, the present invention can effectively remove chlorine-containing compounds while reducing the residue and fluctuation of acidic chlorine-containing species in the product stream, which helps to improve the product acid value, total chlorine and other indicators, and enhance the long-term stable operation capability of the device, and reduce the overall operating cost caused by corrosion and frequent material replacement. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0021] S1. Preparation of catalyst core powder: Weigh an alumina support and prepare a mixed aqueous solution containing nickel nitrate and ammonium molybdate tetrahydrate as an impregnation solution, wherein the total content of Ni in the core is 3 wt% (based on oxides) and the total content of Mo in the core is 15 wt% (based on oxides). Impregnate the support with the impregnation solution using an equal-volume impregnation method, and let it stand for 6 hours after impregnation. Then, dry the impregnated sample at 110°C for 10 hours and calcine it at 550°C for 6 hours in air atmosphere to obtain an active metal supported catalyst powder.

[0022] The powder was added to a pelletizing machine and rolled into a catalyst core with an average particle size of 1 mm under the condition of atomized spraying of aluminum sol and nitric acid aqueous solution (volume ratio 15:1).

[0023] S2. Preparation of catalyst shell powder: Weigh basic zinc carbonate and boehmite according to the mass ratio, wherein basic zinc carbonate accounts for 90 wt% and boehmite accounts for 10 wt%. Add the two to a mixer for wet mixing, add an appropriate amount of deionized water, and mix thoroughly under stirring conditions to form a uniform precursor mixture.

[0024] The mixture was dried at 110°C for 12 hours, and then calcined in air at 550°C for 6 hours to decompose the precursor and form a porous ZnO–Al2O3 composite oxide. The calcined product was then pulverized and sieved to obtain a catalyst shell powder with a particle size suitable for roll forming.

[0025] S3. Forming of the core-shell structured catalyst: The catalyst core and shell powder prepared above are added together into a pelletizing machine and rolled under the condition of atomized adhesive spraying, so that the shell powder continuously coats the outer surface of the core (average shell thickness 1 mm). The formed particles are dried at 110℃ for 10 h and calcined at 550℃ for 6 h to obtain the core-shell type reaction-adsorption integrated catalyst A1. Example 2

[0026] S1. Preparation of catalyst core powder: Weigh a silica support and prepare a mixed aqueous solution containing nickel nitrate and ammonium metatungstate as an impregnation solution, wherein the total content of Ni in the core (based on oxides) is 3 wt%, and the total content of W in the core (based on oxides) is 17 wt%. Impregnate the support with the impregnation solution using an equal-volume impregnation method, and let it stand for 6 hours after impregnation. Then, dry the impregnated sample at 110°C for 10 hours and calcine it at 550°C in air for 6 hours to obtain an active metal supported catalyst powder.

[0027] The powder was added to a pelletizing machine and rolled into a catalyst core with an average particle size of 1 mm under the condition of atomized spraying of aluminum sol and nitric acid aqueous solution (volume ratio 15:1).

[0028] S2. Preparation of catalyst shell powder: Weigh basic zinc carbonate, silica sol, and zirconium hydroxide according to the following mass ratio, wherein basic zinc carbonate accounts for 90 wt%, silica sol accounts for 5 wt%, and zirconium hydroxide accounts for 5 wt%. Add the three to a mixer for wet mixing, add an appropriate amount of deionized water, and mix thoroughly under stirring conditions to form a uniform precursor mixture.

[0029] The mixture was dried at 110°C for 12 hours, and then calcined in air at 550°C for 6 hours to decompose the precursor and form a porous ZnO–SiO2-ZrO2 composite oxide. The calcined product was then pulverized and sieved to obtain a catalyst shell powder with a particle size suitable for roll forming.

[0030] S3. Forming of the core-shell catalyst: The catalyst core and shell powder prepared above are added together into a pelletizing machine and rolled under the condition of atomized adhesive spraying, so that the shell powder continuously coats the outer surface of the core (average shell thickness 1 mm). The formed particles are dried at 110℃ for 10 h and calcined at 550℃ for 6 h to obtain the core-shell integrated reaction-adsorption catalyst A2. Example 3

[0031] S1. Preparation of catalyst core powder: Weigh alumina and USY molecular sieve (mass ratio of alumina:USY molecular sieve = 9:1, the USY molecular sieve was purchased from Nankai Catalyst Factory). Prepare a mixed aqueous solution containing nickel nitrate and ammonium molybdate tetrahydrate as an impregnation solution, wherein the total content of Ni in the core is 3wt% as oxide and the total content of Mo in the core is 15wt% as oxide. Impregnate the carrier with the impregnation solution using an equal volume impregnation method, and let it stand for 6 hours after impregnation. Then, dry the impregnated sample at 110℃ for 10 hours and calcine it at 550℃ for 6 hours in air atmosphere to obtain active metal supported catalyst powder. Add the powder to a pelletizer and roll it under the condition of atomized spraying of aluminum sol and nitric acid aqueous solution (volume ratio 15:1) to obtain catalyst cores with an average particle size of 1 mm.

[0032] S2. Preparation of catalyst shell powder: Weigh basic zinc carbonate and boehmite according to the mass ratio, wherein basic zinc carbonate accounts for 70 wt% and boehmite accounts for 30 wt%. Add the two to a mixer for wet mixing, and add an appropriate amount of deionized water. Mix thoroughly under stirring conditions to form a uniform precursor mixture.

[0033] The mixture was dried at 110°C for 12 hours, and then calcined in air at 550°C for 6 hours to decompose the precursor and form a porous ZnO–Al2O3 composite oxide. The calcined product was then pulverized and sieved to obtain a catalyst shell powder with a particle size suitable for roll forming.

[0034] S3. Forming of the core-shell catalyst: The catalyst core and shell powder prepared above are added together into a pelletizing machine and rolled under the condition of atomized adhesive spraying, so that the shell powder continuously coats the outer surface of the core (average shell thickness 1 mm). The formed particles are dried at 110℃ for 10 h and calcined at 550℃ for 6 h to obtain the core-shell integrated reaction-adsorption catalyst A3.

[0035] Comparative Example 1 The nickel-molybdenum / alumina hydrodechlorination catalyst core powder was prepared using the same method as in Example 1; ZnO adsorbent powder obtained by calcining basic zinc carbonate was also prepared separately.

[0036] The above-mentioned hydrodechlorination catalyst powder and ZnO adsorption powder were mixed at a mass ratio of 1:1 and then extruded to obtain mechanically mixed catalyst B1.

[0037] Comparative Example 2 The nickel-molybdenum / alumina hydrodechlorination catalyst core powder was prepared using the same method as in Example 1; ZnO adsorbent powder obtained by calcining basic zinc carbonate was also prepared separately.

[0038] The above-mentioned hydrodechlorination catalyst powder and ZnO adsorbent powder were extruded separately and then graded and packed in a mass ratio of 1:1, with the hydrodechlorination catalyst in the upper bed and the ZnO adsorbent in the lower bed, to obtain graded catalyst B2.

[0039] Hydrochlorination experiments were conducted on chlorinated oils using the catalysts from the above embodiments and comparative examples: Raw materials: Chlorine-containing pyrolysis oil with a chlorine content of 448 μg / g and a sulfur content of 600 μg / g was selected as the experimental raw material; Reaction apparatus: Fixed-bed hydrogenation reactor, catalyst loading 100 mL; Reaction conditions: hydrogen partial pressure 8 MPa, reaction temperature 300℃, liquid hourly space velocity 1.0 h⁻¹ -1 The hydrogen-to-oil volume ratio is 500:1. Operating procedures: Chlorine-containing pyrolysis oil is preheated and mixed with hydrogen, then continuously fed into a reactor packed with catalyst. Under the above conditions, a hydrodechlorination reaction is carried out. The reaction products are collected after condensation and separation. The chlorine, sulfur, and nitrogen content in the products is detected using gas chromatography-mass spectrometry (GC-MS), and the bromine value is determined using a bromine titrator. A corrosion experiment using a coated substrate simulates equipment corrosion and simultaneously reflects the catalyst's ability to capture HCl. The catalyst deactivation cycle is recorded. The results are shown in Table 1.

[0040] a Small steel sheets of the same material as the equipment (316L stainless steel) were placed inside the catalyst bed to simulate equipment corrosion. b Deactivation is defined as a decrease of 20 wt% in any one of the desulfurization rate, denitrification rate, or dechlorination rate compared to the fresh catalyst. The results in Table 1 show that, compared with the mechanically mixed or graded packed catalysts used in the comparative examples, the core-shell integrated reaction-adsorption catalyst of this invention achieves near-source immediate adsorption and fixation of HCl by constructing a "reaction first, capture later" mass transfer pathway within a single particle. Under the reaction conditions defined in this invention, the dechlorination method using catalysts A1, A2, and A3 can reduce the chlorine content of the raw material to about 2 μg / g, which is far superior to the dechlorination effect of existing catalysts. Moreover, there is no equipment corrosion, and the catalyst deactivation cycle is >2000h, proving that the hydrodechlorination method of this invention has significant advantages in dechlorination efficiency, equipment protection, and long-term operation.

[0041] Compared with the prior art, the method for hydrodechlorination of chlorine-containing organic raw materials of the present invention has the following advantages: This method is highly compatible with the spherical shell structure catalyst of this invention. Through the synergistic effect of the catalyst's near-source capture mechanism and the defined reaction conditions, it achieves highly efficient dechlorination of chlorinated organic feedstocks, with a dechlorination rate of over 99.5%. During the reaction, HCl is captured near-source with no significant escape, effectively avoiding corrosion of the reactor and downstream equipment, reducing equipment maintenance costs. The defined reaction conditions are mild (temperature 200–400℃, pressure 2–16MPa), resulting in lower energy consumption compared to the high temperature and high pressure conditions of existing technologies. Furthermore, the catalyst has a long deactivation cycle, eliminating the need for frequent replacements and enhancing the industrial application value of the method. The method has a wide range of applications and can be used for the dechlorination and purification of various chlorinated organic feedstocks such as chlorinated oils and chlorinated chemical intermediates, demonstrating good versatility.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle, characterized in that, It includes a core and an outer shell adsorption layer covering the outer surface of the core; The core is loaded with hydrodechlorination active metal components, and the outer shell adsorption layer is mainly composed of zinc oxide. During the hydrodechlorination of chlorinated organic compounds, the chlorinated organic compounds diffuse inward to the core and undergo a hydrodechlorination reaction to generate HCl. The generated HCl diffuses outward and is adsorbed and fixed by the outer shell adsorption layer, forming a near-source HCl capture system at the single-particle scale, where the reaction occurs first and then the HCl is captured.

2. The spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle according to claim 1, characterized in that, The content of the active metal component for hydrodechlorination in the catalyst core is 0.5 to 30 wt% based on oxides; the active metal component for hydrodechlorination is one or more of cobalt, molybdenum, nickel, and tungsten.

3. The spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle according to claim 2, characterized in that, The core also includes a support on which the hydrodechlorination active metal component is loaded. The support is alumina, silica, molecular sieve or a composite support thereof.

4. The spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle according to claim 1, characterized in that, The outer shell adsorption layer also contains structurally stabilizing components, which are one or more of Al2O3, SiO2, or ZrO2.

5. The spherical shell-structured hydrodechlorination catalyst for near-source HCl capture by a single particle according to claim 4, characterized in that, The content of zinc oxide in the outer shell adsorption layer is 70-95 wt%, and the content of the structurally stable component in the outer shell adsorption layer is 5-30 wt%.

6. A method for preparing a spherical shell-structured hydrodechlorination catalyst with single-particle near-source HCl capture as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Preparation of catalyst core supported with active metal components for hydrodechlorination; S2: Prepare shell powder with zinc oxide as the main adsorbent component; S3: The catalyst core and outer shell powder are formed under the action of a bonding medium, so that the outer shell powder covers the outer surface of the core, and the finished catalyst is obtained by drying and calcining.

7. The method for preparing the spherical shell-structured hydrodechlorination catalyst with single-particle near-source HCl capture according to claim 6, characterized in that, The process of preparing the catalyst core in step S1 is as follows: the precursor salt of the hydrodechlorination active metal component is prepared into an impregnation solution, and loaded onto the support by the equal volume impregnation method. After standing, drying, calcining and grinding, the active metal supported catalyst powder is obtained. The powder is then rolled into shape under the action of a bonding medium to obtain the catalyst core. The precursor salt of the active metal component for hydrodechlorination is one or more of cobalt nitrate, ammonium molybdate tetrahydrate, nickel nitrate, and ammonium metatungstate.

8. The method for preparing the spherical shell-structured hydrodechlorination catalyst with single-particle near-source HCl capture according to claim 6, characterized in that, The process of preparing the shell powder in step S2 is as follows: the zinc oxide precursor and the structurally stable component precursor are mixed in a certain proportion, dried, calcined, crushed and sieved to obtain the shell powder. Among them, the zinc oxide precursor is one or more of basic zinc carbonate, zinc nitrate, basic zinc acetate, and zinc hydroxide; The structurally stable component precursor is one or more of aluminum hydroxide, boehmite, silica sol, sodium silicate, and zirconium hydroxide.

9. The method for preparing the spherical shell-structured hydrodechlorination catalyst with single-particle near-source HCl capture according to claim 6, characterized in that, In step S3, the bonding medium is a mixture of aluminum sol and nitric acid aqueous solution, with a volume ratio of aluminum sol to nitric acid aqueous solution of 15:

1. In steps S1-S3, the drying temperature is 100-120℃ and the drying time is 10-12h; the calcination temperature is 550-600℃ and the calcination time is 6-10h.

10. A method for the hydrodechlorination of chlorine-containing organic feedstock, characterized in that, The chlorinated organic feedstock is subjected to a hydrodechlorination reaction with hydrogen in the presence of a spherical-shell hydrodechlorination catalyst as described in any one of claims 1 to 5. A near-source capture of HCl is achieved using a single-particle-scale pre-reaction and post-capture system, thus completing the hydrodechlorination of the chlorinated organic feedstock. The reaction conditions are: hydrogen partial pressure 2–16 MPa, reaction temperature 200–400 °C, and liquid hourly space velocity 0.3–2.0 h⁻¹. -1 .

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