A coking crude benzol hydrodechlorination catalyst and a coking crude benzol hydrodechlorination method using the same

Abstract

The present application relates to a coking crude benzene hydrodechlorination catalyst and a coking crude benzene hydrodechlorination method using the same. The catalyst comprises: an Al2O3-SiO2 carrier as a catalyst carrier; a mixture of nickel oxide, palladium oxide and molybdenum trioxide as an active component; and a mixture of P2O5, B2O3 and MgO as a catalytic aid. The present application also relates to a coking crude benzene hydrodechlorination method, which comprises carrying out a coking crude benzene hydrodechlorination reaction in a fixed bed reactor loaded with the catalyst under the following reaction conditions: a reaction temperature of 80-290°C, a pressure of 2.0-3.0 MPa, a volume ratio of hydrogen to hydrogen sulfide of 150:1-2000:1, a liquid volume space velocity of 0.5-3 h ‑1 -1, and a hydrogen oil volume ratio of 400-900. The method of the present application can ensure that the total chlorine content of the coking crude benzene after dechlorination is less than 10 ppm.

Description

Technical Field

[0001] This invention relates to the field of coal chemical industry, specifically to a catalyst for the hydrodechlorination of crude benzene from coking and a method for the hydrodechlorination of crude benzene from coking using the catalyst. Background Technology

[0002] The high-temperature carbonization of coal to produce coke yields byproducts such as coal gas, coal tar, ammonia, and crude benzene. Coking crude benzene refining involves using coking crude benzene as raw material and removing harmful substances such as sulfur and nitrogen through physical or chemical methods to obtain high-purity benzene, toluene, xylene, etc., which can be used as raw materials. Currently, my country's industry mainly uses acid washing and catalytic hydrogenation methods to refine crude benzene.

[0003] Catalytic hydrogenation generally involves two steps. The first step is a pre-hydrogenation reaction, which mainly uses conventional catalysts to remove unstable substances from crude benzene from coking plants, and may also remove some sulfur-containing substances. The second step is the main hydrogenation reaction, which removes major sulfides such as thiophene and carbon disulfide, as well as organic nitrogen compounds, from the crude benzene from coking plants. Crude benzene hydrogenation processes are classified into high-temperature hydrogenation and low-temperature hydrogenation processes based on the catalytic reaction temperature.

[0004] Because the high-temperature method requires operation under high temperature and high pressure, and involves hydrogen embrittlement (under high temperature and high pressure, hydrogen atoms from the decomposition of hydrogen gas penetrate into the steel grains, reducing the atomic bonding force between the steel grains, thereby reducing the elongation and reduction of area of ​​the steel) and hydrogen corrosion (under high temperature and high pressure, hydrogen molecules and hydrogen atoms slowly penetrate into the defects of the steel material, agglomerate into molecular defects, and then undergo a hydrogenation reaction with the surrounding carbon compounds), the equipment requirements are high, the manufacturing is difficult, and it is necessary to import the entire set from abroad.

[0005] Among existing crude benzene hydrorefining technologies, the low-temperature hydrogenation process can yield high-quality benzene, toluene, and xylene products while also addressing environmental pollution issues. It also boasts advantages such as simple operation, low equipment and material requirements, and good economic benefits, leading to its widespread application in China. However, the catalysts used in this process have very strict requirements regarding the chlorine content of the crude benzene feedstock, generally requiring it to be below 10 ppm. Furthermore, with the gradual saturation of domestic crude benzene hydrogenation plants, competition for crude benzene feedstock is intensifying, resulting in inconsistent quality. Some plants are even resorting to purchasing coal-based naphtha, which directly leads to excessive chlorine content in the feedstock.

[0006] Therefore, how to provide a hydrodechlorination process that can effectively control the chlorine content of coking crude benzene products to below 10 ppm under low energy consumption conditions to meet its application standards is a challenge in this field.

[0007] US3864243 describes a method for removing chlorides and other impurities from hydrocarbon components, such as using pore sizes at room temperature and atmospheric pressure. 13X or 10X zeolite molecular sieves can remove chlorides from hydrocarbon components via adsorption. Although adsorption is a simple method for removing chlorides, it suffers from poor selectivity of the adsorbent, low adsorption capacity, and difficulties in regeneration and recycling.

[0008] CN1095702A discloses a method for the reductive dehalogenation of haloalkanes and the dehalogenation of ortho-dihaloalkanes to olefins under mild conditions, characterized by the use of highly active alkali metal hydrides synthesized by complexation catalysis as reducing agents. The reaction is carried out at atmospheric pressure, low temperature (-40~100℃), and in aprotic solvents. Although the above-mentioned renewable adsorbent and reducing agent provide mild reaction conditions, the catalyst is expensive and the preparation conditions are demanding.

[0009] CN101695663A discloses a catalyst for dechlorination in the pre-hydrogenation refining of naphtha reforming, comprising 3-5% nickel oxide, 15-20% molybdenum trioxide, 5-10% boron oxide, and the balance being alumina. Applying this catalyst can extend the production cycle of the reforming unit.

[0010] CN103611566A discloses a catalyst for removing organochlorines from naphtha. Its composition includes a molecular sieve MgAl2O3-Al2O3 as a composite support, nickel or cobalt and molybdenum / tungsten as active components, and phosphorus and rare earth cerium as additives. Applying this catalyst can extend the production cycle of reforming units.

[0011] CN1084547A relates to a catalyst for the hydroremoval of chlorine from naphtha under high temperature and high pressure conditions, which provides protection for the hydrorefining and dearomatization catalyst of naphtha in the later stage and extends the service life of the catalyst.

[0012] The hydrodechlorination methods described in the three patent documents CN101695663A, CN103611566A, and CN1084547A all involve reaction temperatures above 200℃. Given the current operating conditions of crude benzene hydrogenation plants in China, it is difficult to generate economic benefits. Therefore, a low-energy-consumption crude benzene dechlorination method is needed. Summary of the Invention

[0013] The purpose of this invention is to provide a catalyst and method for the hydrodechlorination of coking crude benzene. Using the catalyst, the total chlorine content in coking crude benzene can be reduced to below 10 ppm, and as low as 0 ppm, under conditions of 80 to 290°C, thereby meeting the application requirements of the product.

[0014] To achieve this objective, on the one hand, the present invention provides a hydrodechlorination catalyst for coking crude benzene, the catalyst comprising:

[0015] Al2O3-SiO2 support was used as the catalyst support;

[0016] A mixture of nickel oxide, palladium oxide, and molybdenum trioxide is used as the active component, and the molar ratio of nickel oxide, palladium oxide, and molybdenum trioxide is 1:(0.1–0.2):(1.5–2.5); and

[0017] A mixture of P2O5, B2O3 and MgO is used as a catalyst aid.

[0018] In a specific embodiment, the carrier is a strip-shaped Al2O3-SiO2 carrier.

[0019] In a specific embodiment, the content of the active component is 2% to 10% of the weight of the carrier, preferably 3% to 8%. For example, the content of the active component can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% of the weight of the carrier.

[0020] In a specific embodiment, the molar ratio of nickel oxide, palladium oxide, and molybdenum trioxide is 1:(0.12-0.17):(1.8-2.2), preferably 1:0.15:2. The inventors of this application have discovered that different mixing ratios of nickel oxide, palladium oxide, and molybdenum trioxide affect the hydrodechlorination effect of coking crude benzene. The inventors have also discovered that when the molar ratio of nickel oxide, palladium oxide, and molybdenum trioxide is 1:(0.1-0.2):(1.5-2.5), the chlorine content in coking crude benzene can be removed to a level below 10 ppm. That is, the three active components of this invention only exhibit a synergistic effect when the molar ratio is 1:(0.1-0.2):(1.5-2.5). When the molar ratio is outside the aforementioned range, or when any component is omitted or replaced, the synergistic effect cannot be achieved.

[0021] In specific embodiments, the ratio of P2O5, B2O3, and MgO in the catalyst is not particularly limited, as long as the content of each of P2O5, B2O3, and MgO reaches an effective amount. Preferably, the content of each of P2O5, B2O3, and MgO used in this invention is 1-4% of the weight of the carrier, more preferably 2-3%.

[0022] Although there are no specific ratio requirements among the catalytic promoters described in this invention, each promoter must reach an effective amount, that is, be able to play the role of a catalytic promoter, for example, 1 to 4% of the carrier weight. During the selection process, it was found that omitting or replacing one or more of the promoters would not achieve the technical effect of this invention; that is, there are specific synergistic relationships among the catalytic promoters of this invention.

[0023] In a specific embodiment, the catalyst undergoes pre-sulfurization activation treatment before use. Pre-sulfurization conditions can employ various methods known to those skilled in the art.

[0024] The preparation method of the catalyst in this application is not particularly limited, and conventional impregnation methods and other alternative methods can be used. Those skilled in the art can freely choose according to their existing technology. The preparation of the catalyst support is also not particularly limited, for example, extrusion molding, which is conventional in the art, can be used.

[0025] On the other hand, the present invention provides a method for the hydrodechlorination of coking crude benzene, which includes the following steps:

[0026] Crude benzene from coking, hydrogen, and hydrogen sulfide are fed into a fixed-bed reactor for reaction. The fixed-bed reactor is packed with the aforementioned hydrodechlorination catalyst that has been pre-sulfurized. The reaction temperature is 80–290 °C, the pressure is 2.0–3.0 MPa, the volume ratio of hydrogen to hydrogen sulfide is 150:1–2000:1, and the liquid hourly space velocity is 0.5–3 h⁻¹. -1 The hydrogen-to-oil volume ratio (i.e., the volume ratio of hydrogen to crude benzene) is 400–900.

[0027] In a specific embodiment, the reaction conditions of the fixed-bed reactor are as follows: reaction temperature 120–200°C; hydrogenation pressure 2.5–2.8 MPa; hydrogen to hydrogen sulfide volume ratio 500:1–1000:1; liquid hourly space velocity 1.5–2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 600–800.

[0028] In a specific embodiment, the fixed-bed reactor includes 1 to 5 catalyst beds, more preferably 2 to 3 catalyst beds.

[0029] The method described above in this invention can reduce the total chlorine content of the crude benzene product after fixed-bed hydrogenation reaction to below 10 ppm.

[0030] In addition, it should be noted that the coking crude benzene hydrodechlorination method used in this invention can be directly connected to the catalytic hydrorefining process before it, without affecting the original process design of catalytic hydrorefining.

[0031] In a specific embodiment, the hydrogen sulfide gas can be generated by the high-temperature decomposition of dimethyl disulfide, or high-purity hydrogen sulfide gas can be directly introduced.

[0032] In this invention, the volume ratio of hydrogen to hydrogen sulfide should not exceed 2000:1. The inventors of this application have discovered that when the volume ratio of hydrogen to hydrogen sulfide is too high, the dechlorination effect of the catalyst is significantly reduced. This is because the active materials molybdenum, palladium, nickel, etc., in the new catalyst (or regenerated catalyst) are in the oxidized state, while hydrogenation catalysts only exhibit high activity, stability, and selectivity in the sulfided state, and also possess strong resistance to toxicity and a long lifespan, thus meeting the requirements of the hydrogenation reaction. Therefore, the catalyst must be sulfided before contacting crude benzene, allowing it to contact and react with sulfides to transform into the sulfided state.

[0033] The sulfidation reaction formula for the catalytic action in this application is as follows:

[0034] 3NiO + H₂ + 2H₂S → Ni₃S₂ + 3H₂O

[0035] MoO3 + H2 + 2H2S → MoS2 + 3H2O

[0036] During the hydrogenation reaction, a certain concentration of hydrogen sulfide must be maintained to ensure that the catalyst remains in a sulfidated state.

[0037] The hydrogenation reaction formula of this invention is as follows:

[0038] C4H4S + 4H2 = H2S + C4H 10

[0039] CH3SCH3 + 2H2 = H2S + 2CH4

[0040] C6H5Cl + H2 = HCl + C6H6

[0041] In crude benzene feedstock, chlorine is attached to organic matter by single bonds, while sulfur mainly appears in the form of thiophene. Chlorine is more easily removed by hydrogenation than sulfur. This results in a severe shortage of hydrogen sulfide production during hydrogenation at reaction temperatures of 80–200°C, requiring external supplementation of hydrogen sulfide gas to prevent catalyst deactivation due to desulfurization.

[0042] In another aspect, the present invention provides the use of the catalyst described above in the hydrodechlorination of coking crude benzene.

[0043] Beneficial effects

[0044] The coking crude benzene hydrodechlorination process adopted in this invention can reduce the dechlorination reaction temperature to 80-290°C, especially to below 200°C, under continuous hydrogen sulfide introduction, and can ensure that the total chlorine content of coking crude benzene after dechlorination is less than 10 ppm. This effectively solves the problem of excessive chlorine content in the raw material crude benzene used in crude benzene hydrorefining. Furthermore, this process can be directly connected to the catalytic hydrorefining process before it, without affecting the original process design of catalytic hydrorefining. Attached Figure Description

[0045] Figure 1 A flowchart illustrating the process method of this application is shown.

[0046] like Figure 1 As shown, according to the method of this application, hydrogen and hydrogen sulfide are supplied to a fixed-bed reactor filled with the catalyst of this application through different feed pipes equipped with gas flow meters. Coking crude benzene with a high chlorine content is supplied to the fixed-bed reactor through a feed pipe equipped with a reciprocating pump and a liquid flow meter, and reacts therein. Temperature controllers are also installed at different locations in the fixed-bed reactor to monitor the temperature. After the reaction, crude benzene with a chlorine content of less than 10 ppm is obtained. The mixed gas discharged from the reaction can be used to absorb the acidic gas with an alkaline aqueous solution, and the remaining gas is reused or vented. Detailed Implementation

[0047] The technical solutions of this application are described in detail below through specific embodiments to enable those skilled in the art to better understand this application; however, these embodiments are not intended to limit the scope of this application. This application also includes various equivalent or substitution forms made by those skilled in the art based on their understanding of this application.

[0048] Example

[0049] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0050] In the following embodiments, the reactor tubes used were made of stainless steel with an inner diameter of 20 mm. The catalyst bed temperature was measured using an AL-type temperature controller from Xiamen Yudian Automation Technology Co., Ltd. The raw material, crude benzene from coking, was supplied by Hohhot Xuyang Zhongran Energy Co., Ltd., and its composition included 90% benzene, toluene, xylene, 0.3% thiophene, and 3% naphthalene, etc. It was continuously delivered by a Series II plunger pump manufactured by Connolly, USA. Hydrogen was supplied by a high-pressure gas cylinder and the flow rate was controlled by a Beijing Qixing Huachuang D07-11A / ZM gas mass flow meter.

[0051] In the following examples, the total chlorine and total sulfur of the coking crude benzene feedstock and the low-chlorine crude benzene product were determined using the method described in standard YB / T5022-2016.

[0052] Example 1

[0053] A process for hydrodechlorination of crude benzene from coking plants includes the following steps:

[0054] Step 1: The catalyst was prepared by the following impregnation method:

[0055] The measured amounts of nickel salt, palladium salt, molybdenum salt, phosphate salt, boron salt, and magnesium salt are dissolved in an appropriate amount of deionized water and stirred evenly to form an active component solution. Then, the strip-shaped Al2O3-SiO2 support is immersed in the prepared active component solution for 8–10 hours. After impregnation, the catalyst is dried at 110℃–150℃ for 4–6 hours. Finally, the dried catalyst is calcined at 550℃ for 5 hours and cooled to room temperature to obtain the catalyst.

[0056] The catalyst was prepared using a strip-shaped Al₂O₃-SiO₂ support. The active component was a mixture of nickel oxide, palladium oxide, and molybdenum trioxide; the total content of the active component was 5% of the support weight, and the molar ratio of nickel oxide, palladium oxide, and molybdenum trioxide was 1:0.15:2. The catalyst also contained a catalyst promoter, which was a mixture of P₂O₅, B₂O₃, and MgO, with each of the P₂O₅, B₂O₃, and MgO accounting for 1% of the support mass.

[0057] Step 2: The catalyst obtained in Step 1 is loaded into a fixed-bed reactor. The catalyst loading amount is 20g, and pre-sulfurization in the reactor is carried out by the following operations: hydrogen gas is introduced, the system pressure is adjusted to 2.5MPa, the hydrogen flow rate is 90ml / min, and solvent oil containing 2% dimethyl disulfide is continuously injected at a rate of 3g / h. Then, the temperature is increased to 220℃ at 10℃ / min and held at the temperature for 2h. Finally, the temperature is increased to 300℃ at the same rate and held at the temperature for 8h to complete the pre-sulfurization of the catalyst.

[0058] Step 3: Crude coking benzene with a total chlorine content of 103 ppm is pumped in using a plunger pump and mixed with hydrogen and hydrogen sulfide in the feed pipeline. The mixture then enters a fixed-bed reactor, which is loaded with the pre-sulfurized catalyst from Step 2. The reaction temperature is 140°C, the hydrogenation pressure is 2.5 MPa, and the liquid hourly space velocity (LHSV) is 2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 700, and the volume ratio of hydrogen to hydrogen sulfide is 700:1.

[0059] Example 2

[0060] The process steps are the same as in Example 1, except that in step 3, the total chlorine content of the coking crude benzene is 57 ppm, the hydrogenation pressure is 2.0 MPa, and the volume ratio of hydrogen to hydrogen sulfide is 500:1.

[0061] Example 3

[0062] The process steps are the same as in Example 1, except that in step 1, the contents of P2O5, B2O3 and MgO are 3% of the carrier weight; and in step 3, the hydrogen-oil volume ratio is 800.

[0063] Example 4

[0064] The process steps are the same as in Example 1, except that in step 1, the contents of P2O5, B2O3 and MgO are 3% of the carrier mass, respectively; and in step 3, the reaction temperature is 100℃.

[0065] Example 5

[0066] The process steps are the same as in Example 1, except that in step 1, the contents of P2O5, B2O3, and MgO are 3% of the carrier mass; and in step 3, the liquid hourly space velocity is 2.5 h⁻¹. -1 .

[0067] Example 6

[0068] The process steps are the same as in Example 1, except that in step 1, the molar ratio of nickel oxide, palladium oxide and molybdenum trioxide is 1:0.15:2.5, and the contents of P2O5, B2O3 and MgO are 3% of the carrier mass.

[0069] Example 7

[0070] The process steps are the same as in Example 1, except that in step 1, the molar ratio of nickel oxide, palladium oxide and molybdenum trioxide is 1:0.1:2.

[0071] Comparative Example 1

[0072] The process steps are the same as in Example 1, except that in step 1, the molar ratio of the active components nickel oxide, palladium oxide and molybdenum trioxide mixture is 1:0.15:3.

[0073] Comparative Example 2

[0074] The process steps are the same as in Example 2, except that the reaction temperature of the fixed bed in Example 2 is changed to 70°C.

[0075] Comparative Example 3

[0076] The process steps are the same as in Example 3, except that the volume ratio of hydrogen to hydrogen sulfide in Example 3 is changed to 4000:1.

[0077] Comparative Example 4

[0078] The process steps are the same as in Example 4, except that the liquid volume hourly space velocity (LHSV) of the fixed bed in Example 4 is changed to 5 h⁻¹. -1 .

[0079] Comparative Example 5

[0080] The process steps are the same as in Example 5, except that the hydrogen-to-oil volume ratio of the fixed bed in Example 5 is changed to 200.

[0081] Comparative Example 6

[0082] The process steps are the same as in Example 6, except that the total content of the active component in the carrier in Example 6 is changed to 1%.

[0083] Comparative Example 7

[0084] The process steps are the same as in Example 6, except that in step 1, the catalyst does not contain any catalytic aids.

[0085] The chlorine and sulfur content of the hydrodechlorinated products of Examples 1-7 and Comparative Examples 1-7 were tested, and the results are summarized in Table 1 below.

[0086] Table 1

[0087]

[0088]

[0089] As can be seen from the data in Table 1 above, most of the chlorine in the crude benzene has been removed, while the sulfur content remains essentially unchanged (the total sulfur content in the crude benzene feedstock is between 4000 and 4500 ppm). This is because chlorine is attached to organic compounds via single bonds, while sulfur mainly exists in the crude benzene feedstock in the form of thiophene. Chlorine is more easily removed by hydrogenation than sulfur. This results in a severe shortage of hydrogen sulfide production during the hydrogenation process at reaction temperatures of 80–200°C, necessitating external supplementation of hydrogen sulfide gas to prevent catalyst deactivation due to desulfurization.

[0090] Compared with the comparative examples, the efficient removal of chlorine from the raw material crude benzene was achieved in Examples 1-6 of this application by using a specific catalyst and controlling the process parameters of the hydrodechlorination reaction.

[0091] In summary, the coking crude benzene hydrodechlorination process adopted in this invention can reduce the total chlorine content in coking crude benzene to below 10 ppm under conditions of 80–290°C. This effectively solves the problem of excessive chlorine content in the raw material crude benzene used in crude benzene hydrorefining, and can be directly connected to the catalytic hydrorefining process without affecting the original process design of catalytic hydrorefining.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydrodechlorination catalyst for coking crude benzene, said catalyst comprising: Al2O3-SiO2 support was used as the catalyst support; A mixture of nickel oxide, palladium oxide, and molybdenum trioxide is used as the active component, and the molar ratio of nickel oxide, palladium oxide, and molybdenum trioxide is 1:(0.1~0.2):(1.5~2.5); and A mixture of P2O5, B2O3 and MgO is used as a catalyst aid.

2. The catalyst according to claim 1, wherein, The carrier is a strip-shaped Al2O3-SiO2 carrier.

3. The catalyst according to claim 1, wherein, The content of the active component is 2% to 10% of the weight of the carrier.

4. The catalyst according to claim 1, wherein, In the catalyst, the contents of P2O5, B2O3 and MgO are each 1 to 4% of the carrier weight.

5. A method for hydrodechlorination of crude benzene from coking plants, comprising the following steps: Crude benzene from coking, hydrogen, and hydrogen sulfide are supplied to a fixed-bed reactor for reaction. The fixed-bed reactor is packed with a pre-sulfurized hydrodechlorination catalyst as described in claim 1. The reaction temperature is 80–200°C, the pressure is 2.0–3.0 MPa, the volume ratio of hydrogen to hydrogen sulfide is 150:1–2000:1, and the liquid hourly space velocity is 0.5–3 h⁻¹. -1 The hydrogen-to-oil volume ratio is 400-900.

6. The method according to claim 5, wherein, The reaction conditions in the fixed-bed reactor are as follows: reaction temperature 120~200℃; hydrogen addition pressure 2.5~2.8MPa; hydrogen to hydrogen sulfide volume ratio 500:1~1000:1; liquid hourly space velocity 1.5~2h⁻¹. -1 The hydrogen-to-oil volume ratio is 600-800.

7. The method according to claim 5, wherein, The fixed-bed reactor comprises 1 to 5 catalyst beds.

8. Use of the catalyst as described in claim 1 in the hydrodechlorination of coking crude benzene.

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