Novel mercaptan removal catalyst as well as preparation method and application thereof

Abstract

The invention discloses a novel mercaptan removal catalyst as well as a preparation method and application thereof, the catalyst takes potassium-containing solution modified activated carbon as a carrier and one or a combination of more of CH3COOCs, CH3COOK, Cs2CO3 and Rb2CO3 as an active component, and the mass ratio of the active component substance to the modified activated carbon is 3-5%. The preparation method comprises the following steps: (1) modifying activated carbon by using a potassium-containing solution with the concentration of 15-20%, soaking the activated carbon for 2-4 hours by using the potassium-containing solution, then cleaning the activated carbon by using deionized water until the pH value is weakly alkaline, and drying the activated carbon for later use; (2) carrying out vacuum drying on the modified activated carbon at a certain temperature, and dipping a certain amount of active component-containing solution at 20-60 DEG C for 4-12 hours; and (3) carrying out vacuum drying on the active carbon impregnated with the active component, and roasting under the protection of N2 to obtain the mercaptan removal catalyst. The preparation method is simple, the prepared mercaptan removal catalyst has the characteristics of large specific surface and pore volume and the like, and compared with existing patents, the mercaptan removal catalyst is more favorable for maintaining the active center of the catalyst, maintaining the activity stability of the catalyst and improving the mercaptan removal rate.

Description

Technical Field

[0001] The invention relates to the technical field of desulfurization catalysts, and in particular to a novel desulfurization catalyst and a preparation method and application thereof. Background Art

[0002] Mercaptan is an organic compound in which a sulfhydryl group or a thiol group -SH is connected to an aliphatic hydrocarbon group. It has an extremely strong odor and obviously stimulates the sense of smell when the concentration is 0.01ppm. It is currently recognized as a substance that is harmful to the human body. In the process of petroleum refining, the liquefied petroleum gas produced by the coking unit, the atmospheric and vacuum unit, the catalytic cracking unit, etc. often contains a large amount of sulfides, such as hydrogen sulfide, carbonyl sulfide, methyl mercaptan, ethyl mercaptan, etc., among which methyl mercaptan and ethyl mercaptan are the main ones, which will cause catalyst poisoning in the subsequent processing. The latest standard for automotive ethanol gasoline has been released, which requires that oxygen-containing organic compounds, such as methyl tert-butyl ether (MTBE) and other etherification components, shall not be added artificially, which means that the MTBE unit will be reduced or stopped, and the construction of alkylation units will increase. As a raw material, the demand and processing scale of liquefied gas will increase. As a raw material for alkylation and aromatization, liquefied gas has a higher sulfur content and has a greater impact on subsequent processing. Therefore, liquefied gas must be deeply desulfurized, and desulfurization technology is indispensable.

[0003] At present, the commonly used desulfurization technologies at home and abroad mainly include alkaline washing process technology, Merox extraction-oxidation process technology, fiber membrane process technology, adsorption desulfurization method, catalytic oxidation-adsorption method, etc. Among them, the alkali washing process can effectively remove the mercaptans with low boiling points in liquefied gas, but the disadvantage is that the consumption of alkali solution is large, which is easy to cause environmental pollution, and the sodium sulfide produced in the purification process is not easy to reuse, resulting in high waste residue treatment costs; the catalyst of the Merox extraction-oxidation process is easy to aggregate and deactivate, the total desulfurization rate is not high, and liquid sodium hydroxide will produce a certain amount of alkali residue after use; the fiber membrane desulfurization process has the advantage that the reaction between the oil and its impurities and the alkali solution is carried out on a special fiber membrane, which improves the quality and economic benefits of the product. The disadvantage is that the material of the metal fiber membrane is extremely fine, the investment is large, and impurities are easy to block the pipeline; the adsorption desulfurization method uses the differences in composition and configuration between hydrocarbon molecules and mercaptan molecules to desulfurize the mercaptan compounds in light oil products, but has the disadvantages of high operating temperature and high energy consumption; the catalytic oxidation-adsorption desulfurization technology combines activated carbon adsorbents with metal oxides for catalytic-oxidation, and has the advantage of a simple process and no waste of alkali residue; the disadvantage is that the catalytic adsorbent has an adsorption capacity limit for sulfides.

[0004] Chinese patent CN103316705A discloses a catalyst for removing mercaptans from catalytic cracking gasoline at low temperature, using nano ZSM-5 molecular sieve and alumina composite solid acid as carriers, iron oxide, zinc oxide, lanthanum oxide and phosphorus oxide as active components, and this catalyst is used to remove mercaptans from catalytic cracking gasoline, which can avoid the use of caustic alkali, but has the disadvantages of needing to be used under hydrogenation conditions, high equipment investment, low specific surface area and pore volume of the catalyst, and low mercaptan removal rate. Chinese patent CN113522347A discloses a desulfurization catalyst and a preparation method thereof and a method for a desulfurizer, and the provided desulfurization catalyst utilizes the special crystal structure of the active phase to achieve the purification of mercaptans by adsorption combined with catalytic conversion, and has the advantages of low cost, high desulfurization accuracy, high sulfur capacity, and high single-pass conversion rate, and the disadvantages of a complex catalyst preparation process and high preparation requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a novel desulfurization catalyst and a preparation method and application thereof, so as to solve the technical problems that the existing desulfurization catalyst has a complicated preparation process, high cost, needs to be used under hydrogenation conditions, has high equipment investment, has low specific surface area and pore volume of the catalyst, and has a low mercaptan removal rate.

[0006] To this end, the technical solution adopted in the present invention is:

[0007] A novel desulfurization catalyst uses modified activated carbon as a carrier, wherein the active component is at least one of CH3COOCs, CH3COOK, Cs2CO3, and Rb2CO3, the mass ratio of the active component to the modified activated carbon is 3-5%, and the modified activated carbon is prepared by modifying a potassium-containing solution with a mass fraction of 15-20%.

[0008] Preferably, the potassium-containing solution is a K2CO3 solution or / and a KHCO3 solution.

[0009] Preferably, the activated carbon is coconut shell activated carbon, wood activated carbon or coal activated carbon.

[0010] The preparation method of any one of the novel desulfurization catalysts described above comprises the following steps:

[0011] (1) soaking the activated carbon in a potassium-containing solution with a mass fraction of 15 to 20% for 3 to 5 hours, then washing with deionized water until the pH value is weakly alkaline, and drying to obtain modified activated carbon;

[0012] (2) immersing the modified activated carbon obtained in step (1) in an aqueous solution containing an active component having a mass fraction of 1 to 5% at 20 to 60° C. for 4 to 12 hours,

[0013] (3) vacuum drying the modified activated carbon impregnated with the active component in step (2), and calcining under nitrogen protection to obtain a desulfurization catalyst.

[0014] Preferably, in step (1), the pH value is 7.0-8.0.

[0015] Preferably, in step (1), the drying temperature is 80 to 150° C., and the drying time is 4 to 24 hours.

[0016] Preferably, in step (3), the vacuum drying temperature is 50 to 150° C., and the drying time is 4 to 24 hours.

[0017] Preferably, in step (3), the calcination temperature is 300-600°C.

[0018] A method for removing mercaptan from raw gas, using a fixed bed reactor, the catalyst is any one of the above-mentioned novel mercaptan removal catalysts, and the reaction process conditions are: reaction temperature 40-100°C, normal pressure, volume space velocity 500-2500h -1 .

[0019] Preferably, the concentration of CH3SH and / or CH3CH2SH in the raw gas is 100-200 ppm.

[0020] Beneficial effects of the present invention:

[0021] (1) The preparation cost is low and the process is relatively simple.

[0022] (2) The modified activated carbon maintains weak alkalinity, which is beneficial to maintaining the active center of the desulfurization catalyst, keeping the catalyst activity stable, and continuously achieving high desulfurization efficiency.

[0023] (3) The catalyst of the present invention has simple use conditions and does not need to be used under hydrogenation conditions.

[0024] (4) The catalyst has high specific surface area and pore volume, and high mercaptan removal rate. DETAILED DESCRIPTION

[0025] The technical features of the present invention are further described below in conjunction with embodiments, but are not limited to the embodiments.

[0026] Example 1

[0027] (1) Take 5 g of 40-60 mesh wood activated carbon, soak it in 15% KOH solution for 4 h, then wash it with deionized water until the pH value is 7.5, and dry it in a vacuum oven at 70°C for 6 h.

[0028] (2) The modified activated carbon carrier was impregnated with 6 g of 3% CH3COOK solution for 20 h.

[0029] (3) The carrier impregnated with the active component is dried in a vacuum oven at 70°C for 6 h, and then calcined in a tubular furnace at 300°C for 2 h while introducing N2 to obtain an activated carbon-based desulfurization catalyst.

[0030] The active component of the obtained activated carbon-based desulfurization catalyst is CH3COOK, and the mass ratio of the active component to the modified activated carbon is 3.6%.

[0031] The specific surface area, pore volume and pore size of the activated carbon-based desulfurization catalyst obtained are shown in Table 6.

[0032] The obtained activated carbon-based desulfurization catalyst is used to remove CH3SH from the raw gas:

[0033] 0.5 g of catalyst was loaded into a Φ6 mm*120 mm fixed bed reactor. The reaction conditions were: temperature 80 °C, normal pressure, volumetric space velocity 1000 h -1 , CH3SH concentration 200ppm.

[0034] The removal rate of CH3SH is as follows in Table 1:

[0035] Table 1 CH3SH removal rate

[0036] Time (h) 1 2 4 6 8 10 <![CDATA[CH3SH removal rate]]> 100 100 99.95 99.90 99.82 99.71

[0037] Example 2

[0038] (1) Take 5 g of 40-60 mesh coal-based activated carbon, soak it in 20% K2CO3 solution for 4 h, then wash it with deionized water to a pH of 7.2, and dry it in a vacuum oven at 70°C for 6 h.

[0039] (2) Mix 3 g of 3% by mass CH3COOK solution and 3 g of 5% by mass Cs2CO3 solution, and use the mixed solution to impregnate the modified activated carbon support for 10 h.

[0040] (3) The carrier impregnated with the active component is dried in a vacuum oven at 70°C for 6 h, and then calcined at 500°C for 3 h in a tubular furnace under N2 to obtain an activated carbon-based desulfurization catalyst.

[0041] The active components of the obtained activated carbon-based desulfurization catalyst are CH3COOK and Cs2CO3, and the mass ratio of the active components to the modified activated carbon is 4.8%.

[0042] The specific surface area and pore volume of the activated carbon-based desulfurization catalyst obtained are shown in Table 6.

[0043] The obtained activated carbon-based desulfurization catalyst is used to remove CH3CH2SH from the raw gas:

[0044] 0.5 g of catalyst was loaded into a Φ6 mm*120 mm fixed bed reactor. The reaction conditions were: temperature 80 °C, normal pressure, volume space velocity 500 h -1 , CH3CH2SH concentration 100ppm.

[0045] The removal rate of CH3CH2SH is as shown in Table 2:

[0046] Table 2 CH3CH2SH removal rate

[0047] Time (h) 1 2 4 6 8 10 <![CDATA[Removal rate of CH3CH2SH]]> 100 100 99.99 99.96 99.93 99.90

[0048] Example 3

[0049] (1) Take 5 g of 40-60 mesh coal-based activated carbon, soak it in a mixture of 20% KHCO3 solution and 20% K2CO3 for 4 h, then wash it with deionized water until the pH value is 7.3, and dry it in a vacuum oven at 80°C for 8 h.

[0050] (2) Mix 5 g of 1% Rb2CO3 solution and 5 g of 3% Cs2CO3 solution, and use the mixed solution to impregnate the modified activated carbon support for 15 h.

[0051] (3) The carrier impregnated with the active component is dried in a vacuum oven at 70°C for 6 h, and then calcined at 600°C for 3 h in a tubular furnace with N2 flowing therethrough to obtain an activated carbon-based desulfurization catalyst.

[0052] The active components of the obtained activated carbon-based desulfurization catalyst are Rb2CO3 and Cs2CO3, and the mass ratio of the active components to the modified activated carbon is 4%.

[0053] The specific surface area and pore volume of the activated carbon-based desulfurization catalyst obtained are shown in Table 6.

[0054] When CH3SH is removed by using the obtained activated carbon-based desulfurization catalyst,

[0055] 0.5 g of catalyst was loaded into a Φ6 mm*120 mm fixed bed reactor. The reaction conditions were: temperature 80 °C, normal pressure, volume space velocity 1000 h -1 , CH3SH concentration 100ppm.

[0056] The removal rate of CH3SH is as shown in Table 3:

[0057] Table 3 CH3SH removal rate

[0058] Time (h) 1 2 4 6 8 10 <![CDATA[CH3SH removal rate]]> 100 100 99.99 99.96 99.93 99.88

[0059] Example 4

[0060] (1) Take 5 g of 40-60 mesh coal-based activated carbon, soak it in a 20% KHCO3 solution mixture for 4 h, then wash it with deionized water to a pH of 7.4, and dry it in a vacuum oven at 60°C for 8 h.

[0061] (2) Mix 3 g of 3% Rb2CO3 solution and 3 g of 3% CH3COOK solution, and use the mixed solution to impregnate the modified activated carbon support for 15 h.

[0062] (3) The carrier impregnated with the active component is dried in a vacuum oven at 70°C for 6 h, and then calcined in a tubular furnace at 600°C for 3 h under nitrogen to obtain an activated carbon-based carbonyl sulfide hydrolysis catalyst.

[0063] The active components of the obtained activated carbon-based desulfurization catalyst are Rb2CO3 and CH3COOK, and the mass ratio of the active components to the modified activated carbon is 3.6%.

[0064] The specific surface area and pore volume of the activated carbon-based desulfurization catalyst obtained are shown in Table 6.

[0065] The obtained activated carbon-based carbonyl sulfide hydrolysis catalyst is used to remove CH3SH from the feed gas:

[0066] 0.5 g of catalyst was loaded into a Φ6 mm*120 mm fixed bed reactor. The reaction conditions were: temperature 80 °C, normal pressure, volumetric space velocity 2500 h -1 , CH3SH concentration 200ppm.

[0067] The removal rate of CH3SH is as shown in Table 4:

[0068] Table 4 CH3SH removal rate

[0069] Time (h) 1 2 4 6 8 10 <![CDATA[CH3SH removal rate]]> 99.84 99.80 98.72 97.83 95.76 94.02

[0070] Comparative Example 1

[0071] The comparative example adopts the method of Chinese patent CN103316705A (desulfurization catalyst).

[0072] Weigh 11.0g of ferric nitrate and 4.0g of zinc nitrate, mix with 15ml of deionized water to obtain a co-impregnation solution containing iron and zinc, impregnate 20g of alumina carrier with the above impregnation solution at room temperature for 12h, dry at 100℃ for 12h, and calcine at 540℃ for 4h, then mix 0.8g of lanthanum nitrate, 0.7g of diammonium phosphate and 15ml of deionized water. Place the above catalyst in the impregnation solution for 12h, dry at 100℃ for 12h, and calcine at 540℃ for 4h to obtain a desulfurization catalyst.

[0073] The specific surface area and pore volume of the activated carbon-based desulfurization catalyst obtained are shown in Table 6.

[0074] 0.5 g of the catalyst was loaded into a Φ6 mm*120 mm fixed bed reactor. The reaction conditions were: temperature 80 °C, normal pressure, volume space velocity 1000 h -1 , CH3SH concentration 100ppm.

[0075] The removal rate of CH3SH is as shown in Table 5:

[0076] Table 5 CH3SH removal rate

[0077] Time (h) 1 2 4 6 8 10 <![CDATA[CH3SH removal rate]]> 94.38 93.72 92.84 91.91 90.26 89.89

[0078] Table 6 Specific surface area and pore volume of catalysts prepared in Examples 1-4 and Comparative Example 1

[0079] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 <![CDATA[Specific surface area m 2 / g]]> 929 954 938 896 146 <![CDATA[Pore volume cm 3 / g]]> 0.24 0.26 0.24 0.23 0.19

[0080] It can be seen from Tables 1 to 6 that the specific surface area and pore volume of the desulfurization catalyst prepared by the present invention are higher than those of the prior art, and the CH3SH removal rate of the desulfurization catalyst of the present invention is 94%, and the initial activity is above 99%, which is much higher than that of the prior art.

Claims

1. A novel desulfurization catalyst, characterized in that: The novel desulfurization catalyst uses modified activated carbon as a carrier, and its active component is at least one of CH3COOCs, CH3COOK, Cs2CO3, and Rb2CO3. The mass ratio of the active component material to the modified activated carbon is 3-5%. The modified activated carbon is modified by a potassium-containing solution with a mass fraction of 15-20%.

2. A novel desulfurization catalyst according to claim 1, characterized in that: The potassium-containing solution is a K2CO3 solution or / and a KHCO3 solution.

3. A novel desulfurization catalyst according to claim 1, characterized in that: The activated carbon is coconut shell activated carbon, wood activated carbon or coal activated carbon.

4. The method for preparing a novel desulfurization catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) soaking the activated carbon in a potassium-containing solution with a mass fraction of 15 to 20% for 3 to 5 hours, then washing with deionized water until the pH value is weakly alkaline, and drying to obtain modified activated carbon; (2) immersing the modified activated carbon obtained in step (1) in an aqueous solution containing an active component having a mass fraction of 1 to 5% at 20 to 60° C. for 4 to 12 hours, (3) vacuum drying the modified activated carbon impregnated with the active component in step (2), and calcining under nitrogen protection to obtain a desulfurization catalyst.

5. The method for preparing a novel desulfurization catalyst according to claim 4, characterized in that: In step (1), the pH value is 7.0-8.

0.

6. The method for preparing a novel desulfurization catalyst according to claim 4, characterized in that: In step (1), the drying temperature is 80 to 150° C. and the drying time is 4 to 24 hours.

7. The method for preparing a novel desulfurization catalyst according to claim 4, characterized in that: In step (3), the vacuum drying temperature is 50 to 150° C., and the drying time is 4 to 24 hours.

8. The method for preparing a novel desulfurization catalyst according to claim 4, characterized in that: In step (3), the calcination temperature is 300-600°C.

9. A method for removing mercaptans from raw gas, characterized in that: A fixed bed reactor is used, the catalyst is a novel desulfurization catalyst as described in any one of claims 1 to 3, and the reaction process conditions are: reaction temperature 40 to 100°C, normal pressure, volume space velocity 500 to 2500 h -1 .

10. The method according to claim 9, characterized in that The concentration of CH3SH and / or CH3CH2SH in the raw gas is 100 to 200 ppm.