Hydrodesiliconization catalyst for crude benzene

Abstract

The invention discloses a crude benzene hydrodesiliconization catalyst. The hydrodesiliconization catalyst comprises a carrier and hydrogenation active components, the carrier is K, Zr and C modified sepiolite, and the hydrogenation active components are Mo and a group VIII element. The modified sepiolite carrier comprises the following components in percentage by weight: 2-4% of K2O, 2-5% of ZrO2, 20-30% of C and the balance of sepiolite. The content of MoO3 in the hydrodesilication catalyst active component is 9.2-14.6% by weight, and the content of the group VIII element is 3.0-4.5% by weight based on oxide. According to the present invention, with the catalyst, the silicon in the crude benzene raw material can be removed to less than 0.5 ppm, the aromatic hydrocarbon loss rate is less than 0.5%, and the silicon capacity of the catalyst is not less than 25%, such that the subsequent crude benzene hydrogenation catalyst can be effectively protected, the operation period of the device can be effectively prolonged, and the reduction of the triphenyl yield due to the high aromatic hydrocarbon loss can be avoided.

Description

Technical Field

[0001] The invention relates to a desiliconization catalyst, in particular to a hydrogenation desiliconization catalyst used in a crude benzene hydrogenation process and capable of effectively removing silicon impurities in raw crude benzene to protect a subsequent hydrogenation catalyst. Background Art

[0002] Crude benzene contains a variety of impurities, especially high sulfur and nitride content, which must be refined before being used in the production of chemicals. Currently, the main method used is hydrogenation refining. In the past two years, the silicon impurities in crude benzene raw materials have increased significantly, and the silicon content is usually 10~200ppm. The silicon impurities in crude benzene basically exist in the form of organosilicon compounds, which cannot be effectively removed during the fractionation and vaporization of crude benzene, but decompose into elemental silicon and corresponding alkanes during the hydrogenation process. The elemental silicon will be deposited in the pores of the catalyst, blocking the pores and covering the active centers of the catalyst, thereby causing the catalyst activity to decrease, seriously affecting the service life of the catalyst and the product indicators of the hydrogenation unit. For hydrogenation catalysts that have been poisoned by silicon, the traditional charring regeneration method cannot restore the catalyst activity, because during the charring regeneration process, the elemental silicon will be converted into silicon dioxide and retained in the catalyst pores, causing the catalyst to be permanently inactivated.

[0003] CN104419452 A discloses a desiliconizing agent for coking fraction oil: alumina and MCM-41 molecular sieve are used as carriers, the pore volume is 0.7-1.2 mL / g, the specific surface area is 500-800 m 2 / g, the content of MCM-41 molecular sieve in the carrier is 5 ~20wt%; the loaded metal Ni and W, WO 3 The content is 1~5wt% of the carrier, and the NiO content is 1~5wt% of the carrier.

[0004] CN103920524A discloses an oil desiliconizer and its preparation method and application. The desiliconizer contains a carrier and a hydrogenation active metal component loaded on the carrier, the carrier is pseudo-boehmite and mesoporous Y-type molecular sieve, and is used for deep desiliconization of coking gasoline to protect the coking gasoline hydrorefining catalyst from permanent deactivation caused by silicon poisoning.

[0005] CN116159569A discloses a waste lubricating oil desiliconizing agent, which includes a carrier and an active component. The carrier is a composite oxide carrier of Al2O3-SiO2-activated carbon, and the active component is Fe and Mo loaded on the surface of the composite carrier. The catalyst can effectively remove silicon from waste lubricating oil under certain conditions, protect the subsequent hydrogenation catalyst, and ensure the long-term operation of the subsequent hydrogenation device.

[0006] In the above patents, the desiliconization catalysts are basically applied to the hydrogenation devices of coking naphtha, coking diesel, and waste lubricating oil, and have not been reported in the field of crude benzene hydrogenation. The crude benzene hydrogenation desiliconization agent provided by the present invention can remove silicon in the crude benzene raw material to below 0.5ppm under the conditions of low temperature and high space velocity, and the adsorbed silicon capacity is not less than 25%, which is conducive to extending the service life of the subsequent hydrogenation catalyst and ensuring the operation cycle of the device. At the same time, by regulating the acidity of the carrier and the active components, the aromatic saturation rate is guaranteed to be less than 0.5% during the hydrogenation process, avoiding the economic losses caused by excessive aromatic saturation. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a crude benzene hydrodesiliconization catalyst, which can remove silicon in the crude benzene raw material to below 0.5 ppm, with a silicon content of not less than 25%, and an aromatic hydrocarbon saturation rate of less than 0.5%.

[0008] The catalyst provided by the present invention comprises a carrier and a hydrogenation active component, wherein the carrier is a sepiolite modified by K, Zr and C, the hydrogenation active component is Mo and a Group VIII element; the Group VIII element active component is Fe and X, wherein X is Ni and / or Co; the catalyst is weakly acidic, the total acid content of the catalyst is 0.31-0.45 mmol / g, wherein the weak acid content at 25-200°C is 0.22-0.34 mmol / g, the pore volume is 0.85-1.0 mL / g, and the average pore diameter is 18-22 nm. The modified sepiolite carrier, in terms of weight percentage, is K 2 O content is 2~4%, ZrO 2 The content of MoO is 2-5%, the content of C is 20-30%, and the balance is sepiolite. The carrier needs to be calcined under high temperature ammonia water conditions. The hydrogenation active component is calculated by weight percentage. 3 The content is 9.2~14.6%, the content of Group VIII elements in terms of oxides is 3.0~4.5%, and the active components of Group VIII elements are Fe 2 O 3 The content of Ni is 33~66%, the content of X is 34~67%, and NiO and CoO in the X component can be mixed in any proportion.

[0009] The present invention also provides a method for preparing the above catalyst, which comprises: (1) Weigh a certain amount of sepiolite and potassium nitrate, add them into water, stir evenly, then add 10% 3-aminopropyltrimethoxysilane ethanol solution, heat and reflux at 60°C for 6-8h, filter, wash and dry to obtain K-modified sepiolite.

[0010] (2) The K-modified sepiolite, zirconium source and carbon source are mixed evenly, and then a binder and a pore expander are added. After mixing and rolling evenly, the mixture is extruded and formed. After drying, the mixture is first calcined in air at 800-1000°C for 2-4 hours, and then a 2% ammonia solution is introduced, with the volume ratio of water vapor to air being 15-25%. The mixture is further calcined at 800-1000°C for 2-4 hours to obtain a weakly acidic, large-pore-diameter and large-pore-volume modified sepiolite carrier.

[0011] (3) The modified sepiolite carrier is impregnated with precursors of Mo and Group VIII elements, left to stand for 24 hours, dried, and then calcined at 450-550° C. for 4-6 hours to obtain a crude benzene hydrodesiliconization catalyst.

[0012] In the preparation method of the above catalyst, the zirconium source is zirconium nitrate or zirconium oxychloride, the carbon source is activated carbon, the molybdenum precursor is ammonium heptamolybdate or ammonium tetramolybdate, the iron precursor is ferric nitrate or ferric chloride, the nickel precursor is nickel nitrate or nickel acetate, and the cobalt precursor is cobalt nitrate or cobalt acetate.

[0013] The catalyst provided by the present invention is used for hydrogenation and desilication of crude benzene. The hydrogenation process conditions are temperature 250-280°C, pressure 2.0-3.0MPa, and space velocity 4-6h -1 , the hydrogen-oil volume ratio is 400:1~800:1, which can remove silicon in the crude benzene raw material to below 0.5ppm, the silicon content is not less than 25%, and the aromatic saturation rate is less than 0.5%.

[0014] The catalyst provided by the present invention has the following advantages compared with the prior art: (1) Sepiolite contains a large amount of inorganic ions, so it has strong hydrophilicity and oleophobicity. When used as a hydrogenation catalyst carrier, it will affect the diffusion and adsorption of the organic phase in its pores, thereby reducing the hydrogenation activity of the catalyst. Therefore, the present invention uses a 10% concentration of 3-aminopropyltrimethoxysilane ethanol solution to modify it, which can enhance the diffusion and adsorption of the organic phase in it during the hydrogenation process, thereby improving the hydrogenation activity of the catalyst.

[0015] (2) The organosilicon in the crude benzene raw material decomposes into elemental silicon and corresponding alkanes during the hydrogenation process. The elemental silicon will be deposited in the pores of the catalyst, blocking the pore openings and covering the active centers of the catalyst, thereby causing a decrease in the activity of the catalyst, seriously affecting the service life of the catalyst and the product indicators of the hydrogenation device. Therefore, the desiliconizer must have a larger pore size and pore volume to ensure that after adsorbing a certain amount of silicon, its active center can still function and ensure the stability of the hydrogenation activity. The carrier provided by the present invention is calcined under high-temperature ammonia atmosphere. Compared with calcination in an air atmosphere, the movement of oxygen ions on the surface of alumina increases, and particle sintering and growth can proceed more rapidly, so that the pore size distribution of the obtained carrier is concentrated on a larger pore size and a larger pore volume. The present invention adopts sepiolite with large pore volume and pore diameter as a carrier, supplemented by modified neutral activated carbon with large pore volume and pore diameter, and prepares a macroporous carrier with a pore volume of 0.85-1.0 mL / g and an average pore diameter of 18-22 nm by roasting in a high-temperature water-ammonia atmosphere. The macroporous carrier can effectively improve the silicon capacity of the catalyst, so that the silicon capacity of the catalyst is not less than 25%, which is conducive to the long-term operation of the device.

[0016] (3) In addition to ensuring the desiliconization activity, the hydrogenation saturation of components such as benzene and toluene must be minimized during the hydrogenation process to avoid the generation of a large amount of cyclohexane and methylcyclohexane, which will reduce the economic value of the hydrogenation product. The desiliconization catalyst provided by the present invention uses sepiolite with weakly acidic silica as the main component, and after K modification and ammonia calcination under high temperature conditions, it can effectively eliminate the strong acid center in the carrier and increase the medium and weak acid centers of the carrier. The strong acid center will enhance the adsorption capacity of unsaturated hydrocarbons in the active center, thereby making it easier to carry out the hydrogenation saturation reaction of aromatic hydrocarbons. Therefore, the catalyst prepared by the modified sepiolite carrier provided by the present invention is weakly acidic by regulating the acid center, and the total acid content of the catalyst is 0.31~0.45mmol / g, of which the weak acid content at 25~200℃ is 0.22~0.34mmol / g. While ensuring the hydrogenation desiliconization activity, it also effectively avoids the occurrence of hydrogenation saturation side reactions of benzene and toluene, ensuring that the aromatic hydrocarbon saturation rate is less than 0.5%.

[0017] (4) Since the modified sepiolite carrier is calcined at 800-1000°C, high temperature calcination will cause the carrier to undergo phase change, resulting in a decrease in specific surface area and pore volume. Adding a certain amount of Zr can significantly improve the thermal stability of the carrier, allowing the carrier to maintain a high specific surface area and pore volume at high temperatures.

[0018] (5) The Mo and Fe components in the hydrogenation active components ensure that the catalyst has a certain hydrogenation desiliconization ability. The Ni and Co components as additives can not only improve the desiliconization ability of the catalyst, but also limit the Ni and Co content to prevent the catalyst from having an excessively strong hydrogenation saturation ability, thereby causing a large amount of hydrogenation saturation of benzene and toluene. DETAILED DESCRIPTION

[0019] The characteristics, preparation method and catalytic performance of the catalyst of the present invention are described in detail below in conjunction with specific embodiments. However, the present invention is not limited to these examples, nor do they constitute any limitation on the scope of implementation of the present invention. Example 1

[0020] Weigh 73g of sepiolite and 4.28g of potassium nitrate and add them to water. After stirring evenly, add 10% 3-aminopropyltrimethoxysilane ethanol solution, heat and reflux at 60°C for 6h, filter, wash and dry to obtain K-modified sepiolite. Stir the above-mentioned K-modified sepiolite, 17.42g of zirconium nitrate and 20g of activated carbon evenly, add adhesive and pore expander, stir and roll evenly, and then extrude into shape. After drying, first bake at 800°C in air for 4h, then pass 2% ammonia solution, the volume ratio of water vapor to air is 15%, and continue to bake at 800°C for 2h to obtain a weakly acidic, large-pore, large-pore volume modified sepiolite carrier, in which K is 2.34% by weight. 2 O content is 2%, ZrO 2 The content is 5%, the C content is 20%, and the balance is sepiolite. Take 84.5g of the above carrier and impregnate 14.59g of ammonium heptamolybdate, 7.99g of nickel acetate, and 6.07g of ferric nitrate, let it stand for 24h, dry it, and then roast it at 500℃ for 4h to obtain 1# crude benzene hydrogenation desiliconization catalyst. Example 2

[0021] Weigh 67.5g of sepiolite and 8.56g of potassium nitrate and add them to water. After stirring evenly, add 10% 3-aminopropyltrimethoxysilane ethanol solution, heat and reflux at 60°C for 8h, filter, wash and dry to obtain K-modified sepiolite carrier. Stir the above-mentioned K-modified sepiolite, 9.15g zirconium oxychloride and 25g activated carbon source evenly, add adhesive and pore expander, stir and roll evenly and extrude into shape, after drying, first roast at 1000°C in air for 3h, then pass 2% ammonia solution, the volume ratio of water vapor to air is 25%, continue to roast at 1000°C for 3h, and obtain a weakly acidic, large-pore-diameter, large-pore-volume modified sepiolite carrier, in which K is 2.5% by weight. 2 O content is 4%, ZrO 2 The content is 3.5%, the C content is 25%, and the balance is sepiolite. 86.3g of the above carrier was impregnated with 10.61g of ammonium tetramolybdate, 8.93g of cobalt nitrate, and 4.46g of ferric chloride, and allowed to stand for 24h. After drying, it was calcined at 450℃ for 5h to obtain 2# crude benzene hydrodesiliconization catalyst. Example 3

[0022] Weigh 65g of sepiolite and 6.43g of potassium nitrate and add them to water. After stirring evenly, add 10% 3-aminopropyltrimethoxysilane ethanol solution, heat and reflux at 60°C for 7h, filter, wash and dry to obtain K-modified sepiolite. Stir the above-mentioned K-modified sepiolite, 5.23g of zirconium oxychloride and 30g of activated carbon source evenly, add adhesive and pore expander, stir and roll evenly and extrude into shape, after drying, first roast at 900°C in air for 2h, then pass 2% ammonia solution, the volume ratio of water vapor to air is 20%, continue to roast at 900°C for 4h, and obtain a weakly acidic, large-pore-diameter, large-pore-volume modified sepiolite carrier, in which K is 2.5% by weight. 2 O content is 3%, ZrO 2 The content is 2%, the C content is 30%, and the balance is sepiolite. Take 82.4g of the above carrier and impregnate it with 16.83g of ammonium tetramolybdate, 1.98g of nickel nitrate, 1.69g of cobalt acetate, and 4.02g of ferric chloride, let it stand for 24h, dry it, and then calcine it at 550℃ for 6h to obtain 3# crude benzene hydrodesiliconization catalyst.

[0023] Comparative Example 1 Weigh 73g of sepiolite and 4.28g of potassium nitrate into water, stir evenly, heat under reflux at 60°C for 6h, filter, wash and dry to obtain K-modified sepiolite. The remaining steps are the same as in Example 1 to obtain 4# crude benzene hydrodesiliconization catalyst.

[0024] Comparative Example 2 73g of sepiolite and 4.28g of potassium nitrate were weighed and added to water, and stirred evenly, and then a 10% ethanol solution of 3-aminopropyltrimethoxysilane was added, and heated under reflux at 60°C for 6h, and then filtered, washed, and dried to obtain K-modified sepiolite. The above-mentioned K-modified sepiolite and 17.42g of zirconium nitrate were stirred evenly, and then a binder and a pore-enlarging agent were added, and the mixture was stirred and rolled evenly, and then extruded and formed. After drying, the mixture was calcined at 550°C in air for 6h to obtain a modified sepiolite carrier. The remaining steps were the same as those in Example 1 to obtain a 5# crude benzene hydrodesiliconization catalyst.

[0025] Comparative Example 3 Weigh 73g of sepiolite, add 10% 3-aminopropyltrimethoxysilane ethanol solution, heat and reflux at 60°C for 6h, filter, wash and dry to obtain organic modified sepiolite. Stir the modified sepiolite, 17.42g zirconium nitrate and 20g activated carbon evenly, add binder and pore expander, stir and roll evenly, and then extrude and mold. After drying, calcine at 550°C in air for 6h to obtain modified sepiolite carrier. The remaining steps are the same as those in Example 1 to obtain 6# crude benzene hydrodesiliconization catalyst.

[0026] Comparative Example 4 The preparation method of the modified sepiolite carrier is the same as that in Example 1. 84.5 g of the above carrier is impregnated with 14.59 g of ammonium heptamolybdate and 11.94 g of nickel acetate, and allowed to stand for 24 h. After drying, the catalyst is calcined at 500° C. for 4 h to obtain 7# crude benzene hydrodesiliconization catalyst.

[0027] The physical and chemical properties of the different catalysts in the examples and comparative examples were analyzed, and the results are shown in Table 1.

[0028] Table 1 Physicochemical properties of different catalysts

[0029] Using crude benzene as raw material, the hydrodesiliconization performance of catalyst 1# was evaluated under different process conditions. The results are shown in Table 2: Table 2 Catalyst desiliconization performance under different process conditions

[0030] Using crude benzene as raw material, its silicon content is 32.4ppm, under pressure 2.5MPa, temperature 280℃, hydrogen oil volume ratio 600:1, space velocity 4h -1 The desiliconization performance of different catalysts was evaluated under the process conditions. The silicon content and aromatic saturation rate of hydrogenated oil after running for 1 day were measured to determine the initial desiliconization activity and aromatic saturation rate of each catalyst. Then tetramethoxysilane was added to the crude benzene raw material to make the silicon content in the crude benzene reach 500ppm. The process was continued under the above process conditions until the desiliconization rate was lower than 90%, which was considered as silicon breakthrough. The silicon capacity was calculated. The results are shown in Table 3: Table 3 Comparison of desiliconization performance of different catalysts

[0031] It can be seen from the above table that the 1-3# catalyst provided by the present invention has a high efficiency at a pressure of 2.5MPa, a temperature of 280°C, a hydrogen-to-oil volume ratio of 600:1, and a space velocity of 4h -1It has good desiliconization ability under the process conditions, which can ensure that the silicon content at the hydrogenation outlet is less than 0.5ppm, the aromatic saturation rate is less than 0.5%, and the silicon content is greater than 25%. Compared with the 1# catalyst, the 4# catalyst has poor desiliconization accuracy, with an outlet silicon content of 0.56ppm and a silicon content of only 21.8%. Although the acid center, pore size, and pore volume of the 4# catalyst are basically equivalent to those of the 1# catalyst, the sepiolite used in it has not been modified by organic matter, which affects the diffusion and adsorption of the crude benzene organic phase inside it, reduces the hydrogenation activity, and leads to insufficient desiliconization activity and a decrease in silicon content. The initial desiliconization activity of the 5-6# catalyst is equivalent to that of the 1# catalyst, but because the carriers of the 5-6# catalyst are all calcined at 550℃ in air, the pore size and pore volume of the catalyst are significantly lower than those of the 1# catalyst, but the total acid content of the catalyst is significantly higher than that of the 1# catalyst, resulting in the silicon content of the 5-6# catalyst being significantly lower than that of the 1# catalyst, but the aromatic saturation rate is higher than that of the 1# catalyst. Comparing 5# and 6# catalysts, 5# catalyst has lower total acid content and strong acid content than 6# catalyst due to the modification of sepiolite by K, so it shows lower aromatic saturation rate; 6# catalyst has larger pore volume and pore diameter due to the pore expansion effect of activated carbon, so it shows higher silicon capacity. 7# catalyst has higher hydrogenation activity than 1# catalyst due to its active component NiMo, so it shows higher aromatic saturation rate, and its desiliconization activity and silicon capacity are equivalent to 1# catalyst.

Claims

1. A crude benzene hydrodesiliconization catalyst, characterized in that: The catalyst comprises a carrier and a hydrogenation active component, wherein the carrier is sepiolite modified by K, Zr and C, and the hydrogenation active component is Mo and a group VIII element; the group VIII element active component is Fe and X, wherein X is Ni and / or Co; the catalyst is weakly acidic, the total acid content of the catalyst is 0.31-0.45 mmol / g, wherein the weak acid content at 25-200°C is 0.22-0.34 mmol / g, the pore volume is 0.85-1.0 mL / g, and the average pore diameter is 18-22 nm; the catalyst is used for crude benzene hydrogenation desiliconization, and the silicon in the crude benzene raw material can be removed to below 0.5 ppm, the silicon content is not less than 25%, and the aromatic saturation rate is less than 0.5%.

2. The catalyst according to claim 1, characterized in that: The modified sepiolite carrier has a K2O content of 2-4%, a ZrO2 content of 2-5%, a C content of 20-30% by weight, and the remainder is sepiolite. The carrier needs to be calcined under high-temperature ammonia conditions.

3. The catalyst according to claim 1, characterized in that: The active component of the hydrodesiliconization catalyst has a MoO3 content of 9.2-14.6% by weight and a Group VIII element content of 3.0-4.5% by weight in terms of oxide.

4. The catalyst according to claim 1, characterized in that: The content of Fe2O3 in the Group VIII element active component is 33-66%, the content of X is 34-67%, and NiO and CoO in the X component can be mixed in any proportion.

5. The catalyst according to claim 2, characterized in that: The modified sepiolite carrier is firstly calcined in air at 800-1000°C, then a 2% ammonia solution is introduced, and the calcination is continued at 800-1000°C.

6. The catalyst according to any one of claims 1 to 5, characterized in that: The preparation method of the catalyst is as follows: (1) Weigh a certain amount of sepiolite and potassium nitrate, add them into water, stir them evenly, then add a 10% ethanol solution of 3-aminopropyltrimethoxysilane, heat and reflux at 60° C. for 6 to 8 hours, filter, wash and dry to obtain K-modified sepiolite; (2) The K-modified sepiolite, zirconium source and carbon source are uniformly stirred, and then a binder and a pore-enlarging agent are added. After stirring and rolling, the mixture is extruded and formed. After drying, the mixture is first calcined in air at 800-1000° C. for 2-4 hours, and then a 2% ammonia solution is introduced, with a volume ratio of water vapor to air of 15-25%. The mixture is further calcined at 800-1000° C. for 2-4 hours to obtain a weakly acidic, large-pore-diameter, large-pore-volume modified sepiolite carrier. (3) The modified sepiolite carrier is impregnated with precursors of Mo and Group VIII elements, left to stand for 24 hours, dried, and then calcined at 450-550°C for 4-6 hours to obtain a crude benzene hydrodesiliconization catalyst.

7. The catalyst according to claim 6, characterized in that: The zirconium source in step (2) is zirconium nitrate or zirconium oxychloride, and the carbon source is activated carbon.

8. The catalyst according to claim 6, characterized in that: The precursor of molybdenum in step (3) is ammonium heptamolybdate or ammonium tetramolybdate; the precursor of iron in Group VIII is ferric nitrate or ferric chloride, the precursor of nickel is nickel nitrate or nickel acetate, and the precursor of cobalt is cobalt nitrate or cobalt acetate.

9. The catalyst according to claim 1, characterized in that: The catalyst is used for hydrogenation and desiliconization of crude benzene. The hydrogenation process conditions are temperature 250~280℃, pressure 2.0~3.0MPa, and space velocity 4~6h -1 , hydrogen-oil volume ratio 400:1~800:1.

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