Activated carbon for mercury adsorption

Abstract

Provided is an activated carbon for adsorbing mercury that can adsorb mercury more efficiently without utilizing the properties of inorganic compounds such as halogen or sulfur compounds that are suitable for adsorbing mercury. The activated carbon for mercury adsorption in petroleum refining has a BET specific surface area of ​​1200 m2 calculated by the BET method from the nitrogen adsorption isotherm. 2 / g or less, the average pore diameter calculated by the following formula (i) using the pore volume calculated from the nitrogen adsorption isotherm by the BET method is 1.75 nm or less, and the pore volume of pores with a diameter of 0.6 nm or less calculated from the nitrogen adsorption isotherm by the MP method is 0.14 cm 3 / g or more, and the pore size distribution calculated by the MP method from the nitrogen adsorption isotherm (vertical axis: log differential pore volume dV / dlogD (cm 3 / g), horizontal axis: pore diameter D (nm), the maximum peak position of the pore diameter is in the range of 0.5 to 0.7 nm.

Description

[Technical Field]

[0001] The present invention relates to activated carbon for mercury adsorption in petroleum refining. [Background technology]

[0002] When refining petroleum from feedstock oils such as naphtha, the feedstock oil contains impurities such as sulfur, heavy metals, and other elements or compounds, and it is therefore necessary to remove these impurities during the refining process. Among the impurities contained in the feedstock oils, for example, mercury-based impurities are known to have a significant impact on productivity and the environment, for example, by acting as a catalyst poison for precious metal catalysts such as palladium used in the petroleum refining process and by causing environmental pollution.

[0003] Therefore, in petroleum refining, activated carbon for mercury adsorption, which is activated carbon loaded with halogen compounds, metal sulfides, etc., is used as a method for removing mercury from liquid hydrocarbons such as feed oil (see, for example, Patent Document 1). In this type of activated carbon for mercury adsorption, halogen compounds and sulfur compounds suitable for mercury adsorption are loaded on the activated carbon as an adsorbent, because halogens and sulfur have a strong chemical bonding force with mercury. This improves the mercury adsorption performance of the activated carbon.

[0004] In petroleum refining, large volumes of feedstock oil are processed in plants such as refineries, requiring enormous quantities of mercury-adsorbing activated carbon to remove mercury from liquid hydrocarbons such as feedstock oil. Therefore, by further improving the mercury adsorption performance of mercury-adsorbing activated carbon, it is expected that the total amount of mercury removed in petroleum refining can be significantly increased. However, conventional mercury-adsorbing activated carbon has problems in that inorganic compounds, such as halogen compounds and sulfur compounds, supported on the activated carbon can leach into liquid hydrocarbons during petroleum refining, reducing the amount of mercury adsorbed, causing corrosion of equipment, and potentially remaining as impurities. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-168288 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been proposed in view of the above-mentioned points, and aims to provide an activated carbon for adsorbing mercury that can adsorb mercury more efficiently without utilizing the properties of inorganic compounds such as halogen or sulfur compounds that are suitable for mercury adsorption. [Means for solving the problem]

[0007] That is, the first invention is an activated carbon for adsorbing mercury in petroleum refining, which has a BET specific surface area of ​​1200 m2 calculated by the BET method from a nitrogen adsorption isotherm. 2 / g or less, the average pore diameter calculated by the following formula (i) using the pore volume calculated by the BET method from the nitrogen adsorption isotherm is 1.75 nm or less, and the pore volume of pores with a diameter of 0.6 nm or less calculated by the MP method from the nitrogen adsorption isotherm is 0.14 cm 3 / g or more, and the pore size distribution calculated by the MP method from the nitrogen adsorption isotherm (vertical axis: log differential pore volume dV / dlogD (cm 3 / g, horizontal axis: pore diameter D (nm)), the maximum peak position of the pore diameter is in the range of 0.5 to 0.7 nm.

[0008]

number

[0009] The second invention relates to the activated carbon for adsorbing mercury according to the first invention, which has an ultramicropore volume ratio of 0.25 or more, which is the ratio of the volume of pores having a diameter of 0.6 nm or less calculated by the MP method from a nitrogen adsorption isotherm to the volume of pores having a diameter of 2 nm or less calculated by the MP method.

[0010] A third invention relates to the activated carbon for adsorbing mercury according to the second invention, wherein the ultramicropore volume ratio is 0.4 or more.

[0011] The fourth invention is the first or second invention, wherein the BET specific surface area is 1000 m 2 / g.

[0012] The fifth invention is the third invention, wherein the BET specific surface area is 1000 m 2 / g.

[0013] A sixth aspect of the present invention relates to the activated carbon for adsorbing mercury according to the first or second aspect of the present invention, wherein the average pore diameter is less than 1.70 nm.

[0014] A seventh aspect of the present invention relates to the activated carbon for adsorbing mercury according to the third aspect of the present invention, wherein the average pore diameter is less than 1.70 nm.

[0015] An eighth aspect of the present invention relates to the activated carbon for adsorbing mercury according to the fourth aspect of the present invention, wherein the average pore diameter is less than 1.70 nm.

[0016] A ninth aspect of the present invention relates to the activated carbon for adsorbing mercury according to the fifth aspect of the present invention, wherein the average pore diameter is less than 1.70 nm. [Effects of the Invention]

[0017] The activated carbon adsorbent according to the first aspect of the present invention is an activated carbon for adsorbing mercury in petroleum refining, and has a BET specific surface area of ​​1200 m2 calculated by the BET method from a nitrogen adsorption isotherm. 2 / g or less, the average pore diameter calculated by the following formula (i) using the pore volume calculated by the BET method from the nitrogen adsorption isotherm is 1.75 nm or less, and the pore volume of pores with a diameter of 0.6 nm or less calculated by the MP method from the nitrogen adsorption isotherm is 0.14 cm 3 / g or more, and the pore size distribution calculated by the MP method from the nitrogen adsorption isotherm (vertical axis: log differential pore volume dV / dlogD (cm 3 / g), horizontal axis: pore diameter D (nm)), the maximum peak position of the pore diameter is in the range of 0.5 to 0.7 nm. Therefore, it is possible to efficiently adsorb mercury in feed oil during petroleum refining without utilizing the properties of inorganic compounds such as halogen or sulfur compounds that are suitable for mercury adsorption.

[0018] The activated carbon adsorbent according to the second aspect of the present invention has an ultramicropore volume ratio of 0.25 or more, which is the ratio of the volume of pores having a diameter of 0.6 nm or less calculated by the MP method from the nitrogen adsorption isotherm to the volume of pores having a diameter of 2 nm or less calculated by the MP method in the first aspect of the present invention. This enables improved mercury adsorption performance.

[0019] According to the activated carbon adsorbent of the third invention, since the ultramicropore volume fraction in the second invention is 0.4 or more, the mercury adsorption performance can be more effectively improved.

[0020] According to the fourth aspect of the present invention, in the first or second aspect of the present invention, the BET specific surface area is 1000 m 2 / g, which results in better mercury adsorption performance.

[0021] According to the fifth aspect of the present invention, in the third aspect of the present invention, the BET specific surface area is 1000 m 2 / g, which results in better mercury adsorption performance.

[0022] According to the activated carbon adsorbent of the sixth aspect of the present invention, in the first or second aspect of the present invention, the average pore diameter is less than 1.70 nm, and therefore better mercury adsorption performance can be obtained.

[0023] According to the activated carbon adsorbent of the seventh invention, since the average pore diameter in the third invention is less than 1.70 nm, better mercury adsorption performance can be obtained.

[0024] According to the activated carbon adsorbent of the eighth invention, in the fourth invention, the average pore diameter is less than 1.70 nm, so that better mercury adsorption performance can be obtained.

[0025] According to the activated carbon adsorbent of the ninth aspect of the present invention, since the average pore diameter in the fifth aspect is less than 1.70 nm, better mercury adsorption performance can be obtained. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a pore distribution diagram of activated carbons of prototypes 1 and 2. [Figure 2] FIG. 1 is a pore distribution diagram of activated carbons of Samples 3 and 4. [Figure 3] FIG. 1 is a pore distribution diagram of activated carbons of Samples 5 and 6. [Figure 4] FIG. 1 is a pore distribution diagram of activated carbons of Prototype Examples 7 and 8. DETAILED DESCRIPTION OF THE INVENTION

[0027] The activated carbon for mercury adsorption according to one embodiment of the present invention is activated carbon for adsorbing mercury-based impurities contained in feedstock oils such as naphtha when petroleum is refined from the feedstock oils. Examples of mercury-based impurities include elemental mercury and mercury compounds such as inorganic mercury and organic mercury.

[0028] Activated carbon can be in any suitable form, such as granular activated carbon or fibrous activated carbon, and is obtained by carbonizing and activating activated carbon raw materials. Examples of raw materials for activated carbon include, for example, wood (waste wood, thinned wood, sawdust), coffee grounds, rice husks, coconut shells, bark, and fruit kernels. These naturally occurring raw materials are prone to developing pores upon carbonization and activation, and coconut shells are preferred because they are readily available. Furthermore, because they are a secondary waste product, they can be procured inexpensively. Other raw materials that can be used include tires, petroleum pitch, burned synthetic resins such as urethane resins and phenolic resins, and even coal. Granular activated carbon is easy to handle because its usage form can be appropriately determined.

[0029] The fibrous activated carbon is obtained by carbonizing and activating suitable fibers, and examples of the raw materials include phenolic resins, acrylic resins, cellulose, coal pitch, etc. The fiber length and cross-sectional diameter of the fibrous activated carbon are appropriate.

[0030] Activated carbon is produced by heating and carbonizing an activated carbon raw material, followed by an activation treatment. Heating and carbonizing the activated carbon raw material is carried out when carbonization of the raw material is necessary. The conditions for heating and carbonizing are preferably, for example, a temperature range of 200 to 900°C. After carbonization, the raw material is subjected to an activation treatment to become activated carbon with various pores developed. In the activation treatment, for example, steam activation is carried out in a temperature range of 600 to 1200°C. Alternatively, carbon dioxide gas activation, zinc chloride activation, etc., can also be used. The activation time varies depending on the production scale, equipment, etc., but is generally 0.5 to 50 hours.

[0031] The activated carbon after activation is washed with dilute hydrochloric acid. After washing with dilute hydrochloric acid, the activated carbon adsorbent is washed with water until the pH reaches 5 to 7, as measured in accordance with JIS K 1474 (2014). After washing with dilute hydrochloric acid, the activated carbon is optionally heat-treated in a mixed gas of oxygen and nitrogen and washed with water to remove impurities such as ash. Residual hydrochloric acid and other components are removed by the heat treatment.

[0032] In activated carbon for mercury adsorption, it has been common to improve mercury adsorption performance by supporting inorganic compounds suitable for mercury adsorption, such as halogen compounds and sulfur compounds, which have excellent mercury-binding properties. However, the inorganic compounds suitable for mercury adsorption supported on activated carbon may leach into the feed oil during petroleum refining, potentially reducing mercury adsorption performance. Therefore, the present inventors have intensively investigated a method for achieving better mercury adsorption performance without supporting inorganic compounds such as halogen compounds and sulfur compounds, which have excellent mercury-binding properties, on activated carbon. Note that the support of inorganic compounds such as halogen compounds and sulfur compounds refers to a process in which the inorganic compounds are supported on activated carbon with the aim of improving mercury adsorption performance, and does not include processes such as acid washing, which may unintentionally support trace amounts of inorganic compounds.

[0033] As a result, the present inventors found that the physical properties of activated carbon suitable for mercury adsorption in petroleum refining can be expressed using the BET specific surface area, the average pore diameter, the pore volume of pores with a diameter of 0.6 nm or less, and the maximum peak position of the pore diameter in a pore distribution diagram. That is, the activated carbon for mercury adsorption of the present invention has a BET specific surface area of ​​1200 m 2 / g or less, the average pore diameter is 1.75 nm or less, and the pore volume of pores with a diameter of 0.6 nm or less is 0.14 cm 3 / g or more, and the maximum peak position of the pore diameter in the pore distribution diagram must be in the range of 0.5 to 0.7 nm.

[0034] BET specific surface area (m 2 / g) is a value calculated from the straight line in the region of the obtained curve at a relative pressure of 0.35 or less, measured by a multipoint analysis based on the BET equation after measuring the nitrogen adsorption isotherm at 77K. The BET specific surface area is used as an index showing the amount of pores formed in activated carbon, and can be used to define the adsorption performance of activated carbon. The preferred specific surface area for mercury adsorption activated carbon is 1200 m 2 / g or less, more preferably 1000m 2If this specific surface area is too large, it is thought that not only will the strength of the activated carbon decrease, but large pores that are not suitable for mercury adsorption will develop.

[0035] The average pore diameter (nm) is a value obtained using the pore volume calculated from the nitrogen adsorption isotherm by the BET method, and is an index showing the tendency of the development of the pores formed in the activated carbon. Specifically, assuming that the shape of the pores is cylindrical, the pore volume (mL / g) calculated by the BET method from the nitrogen adsorption isotherm measured at 77 K and the specific surface area (m 2 / g) according to the following formula (i). Because the atomic diameter of mercury to be adsorbed is approximately 0.3 nm, it is considered preferable that the activated carbon have many pores with relatively small pore diameters. Therefore, the average pore diameter of activated carbon for mercury adsorption is preferably 1.75 nm or less, more preferably less than 1.70 nm. If the average pore diameter is too large, it may be easier to adsorb substances other than the target, which may result in clogging of pores of a size suitable for mercury adsorption and a decrease in mercury adsorption performance. By keeping the average pore diameter within the above range, the target mercury-based compounds are easily adsorbed, resulting in good mercury adsorption performance.

[0036]

number

[0037] Pore ​​volume (cm) with a pore diameter of 0.6 nm or less 3The adsorption capacity (kJ / g) is a value calculated by analyzing the t-plot of the nitrogen adsorption isotherm at 77K using the MP method. The pores within the measurement range of the MP method are micropores (pores with a pore diameter of 2 nm or less), and the pore volume calculated by the MP method corresponds to the pore volume of micropores, of which the pore volume with a pore diameter of 0.6 nm or less corresponds to the pore volume of ultramicropores. Since the atomic diameter of mercury, which is the target for adsorption, is approximately 0.3 nm, pores with relatively small pore diameters are effective for mercury adsorption, and the pore volume of pores with a diameter of 0.6 nm or less is particularly suitable as an index of adsorption performance for mercury-based compounds. The preferred pore volume of activated carbon for mercury adsorption is 0.14 cm 3 / g or more, more preferably 0.16 cm 3 If the pore volume of pores with diameters of 0.6 nm or less is too small, the ultramicropores formed in the activated carbon may not be sufficiently developed, making it difficult to ensure the adsorption performance of mercury-based compounds.

[0038] The maximum peak position of the pore diameter in the pore distribution diagram is an index that represents the pore diameter of the pores that are most abundant in the activated carbon. The pore distribution diagram (vertical axis is log differential pore volume dV / dlogD (cm)) calculated by the MP method from the nitrogen adsorption isotherm is 3 / g) and the horizontal axis is the pore diameter D (nm). In the pore distribution diagram, the vertical axis is the log differential pore volume dV / dlogD (cm 3 The value of (m / g) is calculated by analyzing the t-plot of the nitrogen adsorption isotherm at 77 K using the MP method. The pore volume value at which the log differential pore volume value is maximized in this pore distribution diagram is taken as the maximum peak position of the pore diameter. The maximum peak position of the pore diameter of the activated carbon for mercury adsorption is preferably in the range of 0.5 to 0.7 nm. If the maximum peak position of the pore diameter in the pore distribution diagram is outside this range, there may be insufficient pores with a pore diameter suitable for adsorption of mercury-based compounds, making it difficult to ensure adsorption performance.

[0039] Furthermore, since the pore volume of pores with diameters of 0.6 nm or less effectively functions for mercury adsorption in the activated carbon for mercury adsorption of the present invention, it is believed that the mercury adsorption performance improves as the pore volume of pores with diameters of 0.6 nm or less increases. Therefore, based on the examples described below, the ratio of the pore volume (B) with pore diameters of 0.6 nm or less to the pore volume (A) with pore diameters of 2 nm or less was calculated as the ultramicropore volume ratio (B / A). The pore volumes of pores with diameters of 2 nm or less and pore volumes of pores with diameters of 0.6 nm or less were calculated by analyzing the t-plot of the nitrogen adsorption isotherm at 77 K using the MP method.

[0040] The ultramicropore volume ratio (B / A) is the ratio of the pore volume of pores suitable for mercury adsorption (ultramicropores with a pore diameter of 0.6 nm or less) to the pore volume of micropores (pores with a pore diameter of 2 nm or less) within the measurement range of the MP method. It is an index showing the amount of pore volume in activated carbon that is effective for mercury adsorption, and a larger value indicates a tendency for the mercury adsorption capacity to increase. Therefore, it can be suitably used as an index of mercury adsorption performance. The preferred ultramicropore volume ratio of activated carbon for mercury adsorption is 0.25 or more, more preferably 0.4 or more. If the ultramicropore volume ratio is too low, the mercury adsorption performance may be insufficient. An ultramicropore volume ratio of 0.25 or more can improve mercury adsorption performance.

[0041] As described above, the activated carbon for mercury adsorption of the present invention has various properties suitable for mercury adsorption in petroleum refining, particularly a pore volume with a pore diameter of 0.6 nm or less and a maximum peak position of the pore diameter in the range of 0.5 to 0.7 nm, and therefore the specific surface area, which indicates the adsorption performance of the activated carbon, is not expected to be very large. In other words, activated carbon with a smaller specific surface area than activated carbon adsorbents generally considered to have high adsorption performance is considered to be suitable. [Example]

[0042] [Preparation of activated carbon] To produce the activated carbons of Samples 1 to 8, coconut shells were used as the raw material for activated carbon, which was then heated and carbonized at 400 to 600°C to obtain a carbonized product. This carbonized product was then heated to approximately 800 to 900°C, maintained at this temperature, and then activated by introducing steam. The activation time was varied for each sample. After activation, the product was allowed to cool naturally to near room temperature and sieved through a 10 to 30 mesh sieve to obtain the activated carbons of Samples 1 to 8 with particle sizes of approximately 0.50 to 1.70 mm.

[0043] [Measurement of activated carbon] The BET specific surface area (m 2 / g), average pore diameter (nm), pore volume of pores with a diameter of 2 nm or less (cm 3 / g), pore volume (cm) of pores with a diameter of 0.6 nm or less 3 The adsorption capacity (kJ / g), ultramicropore volume fraction, and maximum peak position of pore diameter (nm) were determined. A mercury adsorption test was also conducted on each of Prototypes 1 to 8 to evaluate their adsorption performance for mercury compounds in the feedstock oil. The measurement results for each Prototype are shown in Table 1 below.

[0044] [BET specific surface area] For the activated carbons of Samples 1 to 8, a specific surface area / pore size distribution measuring device (Microtrac-Bel Corporation's "BELSORP-mini II") was used to measure the nitrogen adsorption isotherm at 77 K, and the specific surface area (m 2 / g) was calculated.

[0045] [Average pore diameter] For the activated carbons of Samples 1 to 8, the pore volume (cm) was calculated by the BET method from the nitrogen adsorption isotherm obtained by measuring the BET specific surface area. 3 / g) was calculated, and the specific surface area (m 2 / g) and pore volume (cm 3 The average pore diameter (nm) was calculated from the above formula (i) using the value of (μm / g).

[0046] [Volume of pores with diameters of 2 nm or less] For the activated carbons of Samples 1 to 8, a specific surface area / pore size distribution measuring device (Microtrack BEL Corporation's "BELSORP-mini II") was used to measure the pore volume (cm) in the range of pore diameters of 2 nm or less from the t-plot of the nitrogen adsorption isotherm at 77 K using the MP method. 3 / g) was analyzed and determined.

[0047] [Volume of pores with diameters of 0.6 nm or less] For the activated carbons of Samples 1 to 8, a specific surface area / pore size distribution measuring device (Microtrac BEL Corporation's "BELSORP-mini II") was used to measure the pore volume (cm) in the range of pore diameters of 0.6 nm or less from the t-plot of the nitrogen adsorption isotherm at 77 K using the MP method. 3 / g) was analyzed and determined.

[0048] [Ultramicropore volume ratio] For the activated carbons of Prototype Examples 1 to 8, the ultramicropore volume ratio (B / A) was calculated from the pore volume (A) of pores with a diameter of 2 nm or less and the pore volume (B) of pores with a diameter of 0.6 nm or less.

[0049] [Position of maximum peak of pore diameter] For the activated carbons of Samples 1 to 8, the t-plot of the nitrogen adsorption isotherm at 77 K was analyzed using the MP method, and the vertical axis was the log differential pore volume dV / dlogD (cm 3 A pore distribution diagram was calculated in which the horizontal axis represents the pore diameter D (nm) and the log differential pore volume dV / dlogD was plotted against the horizontal axis, and the pore diameter value (position) at which the log differential pore volume dV / dlogD was maximum was determined for each of Prototype Examples 1 to 8. Figures 1 to 4 are pore distribution diagrams for each of Prototype Examples 1 to 8, and symbols P1 to P8 in the diagrams represent the maximum peaks for each of Prototype Examples 1 to 8.

[0050] [Mercury adsorption test] For the mercury adsorption test, a hydrocarbon oil containing elemental mercury was prepared as a test solution simulating the feedstock oil used in petroleum refining. Elemental mercury was placed in a screw-cap bottle containing a stirrer, and 500 ml of normal hexane, which had been bubbled with argon gas, was added. The gas phase was then replaced with argon gas and the bottle was capped. The bottle was then stirred for 5 days using a magnetic stirrer. The mercury concentration in the hexane at this time was approximately 1500 μg / L. This hexane solution was diluted approximately twice with hexane to prepare the test solution, a hydrocarbon oil containing elemental mercury. The mercury concentration in the resulting hydrocarbon oil was 582 μg / L. The mercury concentration was measured using a general-purpose, fully automated petroleum mercury analyzer (Nippon Instruments Co., Ltd., "PE-1000").

[0051] Next, 50 ml of test liquid (hydrocarbon oil) was prepared for each prototype in a screw bottle containing a stirrer. Each prototype 1 to 8 was crushed to form a 0.01 g test specimen, which was then added to the test liquid and left to stand for 140 hours while stirring. After 140 hours, the test liquid was removed and the mercury concentration in the test liquid was measured. The mercury adsorption amount per unit weight of the test specimen (μg / g) was calculated from the difference between the mercury concentration before and after adding the specimen (582 μg / L). For each prototype 1 to 8, a mercury adsorption amount of 2700 μg / g or greater was evaluated as "Good" (○), and a mercury adsorption amount of less than 2700 μg / g was evaluated as "Poor" (×).

[0052] [Table 1]

[0053] [Results and Discussion] As shown in Table 1, the activated carbons of prototypes 1, 3, and 7 exhibited good mercury adsorption performance with mercury adsorption amounts of 2700 μg / g or more, while the activated carbons of prototypes 2, 4 to 6, and 8 exhibited insufficient mercury adsorption performance with mercury adsorption amounts of less than 2700 μg / g.

[0054] First, we will examine the pore size distribution diagrams of Prototype Examples 1 to 8 shown in Figures 1 to 4. In Prototype Examples 1, 3, and 7, which had good mercury adsorption performance, the maximum peaks P1, P3, and P7 were all located at a pore diameter of 0.6 nm. On the other hand, in Prototype Examples 2, 4 to 6, and 8, which had insufficient mercury adsorption performance, the maximum peaks P2, P4, P6, and P8 were located at a pore diameter of 0.8 nm. This suggests that activated carbons with maximum pore diameter peaks located around 0.6 nm generally have good mercury adsorption performance.

[0055] Thus, activated carbon with good mercury adsorption performance (Prototype Examples 1, 3, and 7) and activated carbon with poor mercury adsorption performance (Prototype Examples 2, 4, 6, and 8) tended to have different maximum pore diameter peak positions in the pore distribution diagram. The maximum pore diameter peak position in the pore distribution diagram corresponds to the pore diameter of the pores most abundant in the activated carbon, and based on the results of each prototype, it is believed that a range of 0.5 to 0.7 nm is preferable. Since the maximum pore diameter peak positions in the pore distribution diagrams of Prototype Examples 1, 3, and 7 are around 0.6 nm, it is believed that the pore diameter of activated carbon effective for adsorbing mercury in feed oil is around 0.6 nm. Therefore, it is believed that using the pore volume of pores with diameters of 0.6 nm or less as an indicator of mercury adsorption performance is effective.

[0056] On the other hand, among the prototypes with insufficient mercury adsorption performance, the maximum peak P5 of prototype 5 was at a pore diameter of 0.6 nm. Comparing prototype 5 with prototypes 1, 3, and 7, which had good mercury adsorption performance, the pore volume of prototype 7 with a pore diameter of 0.6 nm or less, which is considered effective for mercury adsorption in feed oil, was 0.1695 m for prototype 7, which had a mercury adsorption capacity of 2850 μg / g. 3 / g, 2750μg / g of prototype 1 is 0.1500, m 3 / g, 2720μg / g of prototype 3 is 0.1466m 3 / g, while prototype 5 was 0.1321m 3 / g. Therefore, it is thought that activated carbon with a maximum peak position of pore diameter around 0.6 nm requires a certain amount of pore volume with a pore diameter of 0.6 nm or less. From the above results, it is considered that the preferred pore volume of pore diameters of 0.6 nm or less is 0.14 m3 / g.

[0057] The BET specific surface area and average pore diameter of activated carbon are generally used as indicators of basic performance. From the measurement results of prototypes 1, 3, and 7, which have good mercury adsorption performance, it was found that activated carbon for mercury adsorption in petroleum refining has a BET specific surface area of ​​1200 m 2 / g or less and an average pore diameter of 1.75 nm or less are considered to be sufficient. If the specific surface area or average pore diameter is too large, it is thought that large pores that are not suitable for mercury adsorption will develop.

[0058] In general, the larger the BET specific surface area and the pore volume of micropores (pores with a diameter of 2 nm or less) that contribute to physical adsorption, the higher the adsorption performance for the adsorbed substance. However, in Prototype Examples 1 to 8, the larger the BET specific surface area and the pore volume of micropores with a diameter of 2 nm or less, the lower the amount of mercury adsorption. On the other hand, the larger the pore volume of micropores with a diameter of 0.6 nm or less, which is considered to be an effective index of mercury adsorption performance, the higher the amount of mercury adsorption.

[0059] Focusing on the ultramicropore volume ratio, Prototypes 1 to 8 showed a tendency for the mercury adsorption amount to increase as the ultramicropore volume ratio increased. This ultramicropore volume ratio is the ratio of the volume of pores with a diameter of 0.6 nm or less to the volume of pores with a diameter of 2 nm or less, which is the measurement range of the MP method, and can therefore be understood as the amount of pore volume in activated carbon that is effective for mercury adsorption. Based on the results of the mercury adsorption amount and ultramicropore volume ratio for Prototypes 1, 3, and 7, which had good mercury adsorption performance, and Prototypes 2, 4 to 6, and 8, which had insufficient mercury adsorption performance, it is believed that a preferable ultramicropore volume ratio is 0.25 or more.

[0060] As described above, the activated carbon for mercury adsorption of the present invention has a BET specific surface area of ​​1200 m 2 / g or less, the average pore diameter is 1.75 nm or less, and the pore volume of pores with a diameter of 0.6 nm or less is 0.14 cm 3 / g or more, and the pore distribution diagram (vertical axis: log differential pore volume dV / dlogD (cm 3 The maximum peak position of pore diameters on the graph (axis: pore diameter D (nm)) is in the range of 0.5 to 0.7 nm, which enables efficient adsorption of mercury in feedstock oil during petroleum refining. Furthermore, by increasing the ultramicropore volume ratio (the ratio of the volume of pores with a diameter of 0.6 nm or less to the volume of pores with a diameter of 2 nm or less) to 0.25 or more, mercury adsorption performance can be improved.

[0061] In particular, the activated carbon for mercury adsorption of the present invention does not support inorganic compounds suitable for mercury adsorption, such as halogen or sulfur compounds, which are commonly used in conventional activated carbons for mercury adsorption, and therefore does not cause problems such as the elution of the inorganic compounds supported on the activated carbon into liquid hydrocarbons during petroleum refining, and there is no risk of a decrease in mercury adsorption performance or corrosion of equipment due to the elution of the inorganic compounds. Therefore, the activated carbon for mercury adsorption of the present invention can contribute to more efficient petroleum refining than conventional methods, by eliminating the need for the laborious removal of impurities derived from the adsorbent while maintaining excellent mercury adsorption performance. [Industrial Applicability]

[0062] Because the amount of activated carbon used for mercury removal in petroleum refining is enormous, improving the mercury adsorption performance of activated carbon dramatically increases the total amount of mercury removed during the refining process. The activated carbon for mercury adsorption of the present invention has improved mercury adsorption performance compared to conventional activated carbons without supporting inorganic compounds suitable for mercury adsorption, such as halogens or sulfur compounds. This not only eliminates problems such as the elution of inorganic compounds supported on the activated carbon during petroleum refining, but is also expected to remove larger amounts of mercury than conventional activated carbons. Therefore, the activated carbon for mercury adsorption of the present invention is a promising alternative to conventional activated carbons for mercury adsorption. [Explanation of symbols]

[0063] P1~P8 Maximum peaks of prototypes 1~8

Claims

1. 1. An activated carbon for mercury adsorption for petroleum refining, comprising: The BET specific surface area calculated from the nitrogen adsorption isotherm using the BET method is 1200 m ２ / g or less, The average pore diameter obtained by formula (i) below, using the pore volume calculated by the BET method from nitrogen adsorption isotherms, is 1.75 nm or less. The pore volume of pores with a diameter of 0.6 nm or less calculated by the MP method from the nitrogen adsorption isotherm was 0.14 cm ３ / g or more, Pore ​​distribution map calculated from nitrogen adsorption isotherms using the MP method (vertical axis: log differential pore volume dV / dlogD (cm) ３ The maximum peak position of the pore diameter in the graph (g / m², horizontal axis: pore diameter D (nm)) is in the range of 0.5 to 0.7 nm. Activated carbon for mercury adsorption characterized by: [Equation 1]

2. The activated carbon for mercury adsorption according to claim 1, wherein the ultramicropore volume ratio, which is the ratio of the pore volume with a pore diameter of 0.6 nm or less calculated by the MP method to the pore volume with a pore diameter of 2 nm or less calculated by the MP method from nitrogen adsorption isotherms, is 0.25 or more.

3. 3. The activated carbon for adsorbing mercury according to claim 2, wherein the ultramicropore volume fraction is 0.4 or more.

4. The BET specific surface area is 1000 m ２ 3. The activated carbon for adsorbing mercury according to claim 1, wherein the activated carbon has a mercury adsorption capacity of less than 1000 kJ / g.

5. The BET specific surface area is 1000 m ２ The activated carbon for mercury adsorption according to claim 3, wherein the amount is less than / g.

6. 3. The activated carbon for adsorbing mercury according to claim 1, wherein the average pore diameter is less than 1.70 nm.

7. 4. The activated carbon for adsorbing mercury according to claim 3, wherein the average pore diameter is less than 1.70 nm.

8. 5. The activated carbon for adsorbing mercury according to claim 4, wherein the average pore diameter is less than 1.70 nm.

9. 6. The activated carbon for adsorbing mercury according to claim 5, wherein the average pore diameter is less than 1.70 nm.

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