JPH0248597B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for removing As from petroleum fractions. The petroleum fraction in this specification refers to straight-run naphtha,
Kerosene, gas oil, vacuum distillate, pyrolysis gasoline from ethylene plants, coffee, visbreakers,
Relatively light crude oil equivalents such as naphtha produced in catalytic cracking equipment, recycled oil, etc., distilled from crude oil, fractions produced by heat treatment, catalytic cracking, etc., and condensate (NGL) This is a general term for a wide range of hydrogen oils. Also As
is a general term for compounds containing As as one constituent element. Crude oil often contains As, although the amount varies depending on the region of production, and petroleum fractions made from crude oil containing As contain trace amounts of As. In the process of manufacturing petrochemical raw materials or petrochemical products from petroleum fractions, depending on the content of As, As can be toxic to catalysts or cause problems in various processes such as promoting coking during thermal decomposition. effect. For example, in the process of producing aromatic compounds benzene, toluene, and xylene from the gasoline by-products of the thermal decomposition of straight-run naphtha or the gasoline by-products of the thermal decomposition of kerosene, hydrogenation treatment converts the diolefins contained in the cracked gasoline into olefins. is carried out, but the palladium catalyst and
It acts as a severe catalyst poison for C ₂ and C ₃ acetylene hydrogenation catalysts (PD, PT), etc., and rapidly reduces catalytic activity. As is generally toxic to catalysts, but in particular, as mentioned above, it is extremely toxic to precious metal catalysts containing pt, pd, etc. used for hydrogenation, dehydrogenation, etc. even in minute amounts. Significantly reduces catalyst activity. Therefore, the As contained in the raw petroleum fraction used in the process using the noble metal catalyst must be removed in advance to a predetermined amount or less. For this reason, various As removal methods have been proposed and implemented in the past. For example, the method of removing S in hydrocarbons by catalytic hydrocracking and removing As together with S by hydrodesulfurization is difficult to apply to petroleum fractions that contain almost no S due to equipment costs, This causes the inconvenience of increased operating costs. In addition, the contact method with a basic compound, the contact method with copper and a salt of a metal whose electromotive force is lower than that of copper, and the contact method with a nitrogen compound containing three added groups and one unpaired electron are all different. Get rid of it too
The As capacity is low and a large amount of As removal agent is required, and these agents are not general-purpose products and are expensive, resulting in cost problems. Furthermore, the contact method with a precious metal catalyst using acid-impregnated alumina as a carrier may cause problems such as polymerization of olefins and diolefins and reactions with aromatic fractions when processing highly reactive petroleum fractions such as cracked gasoline. occurs. In addition, the method of contacting with lignite-based activated carbon is inefficient in order to reduce the As concentration in the petroleum fraction to below the permissible limit because the adsorption amount is small in equilibrium with the As concentration in the liquid. In the method of directly oxidizing As in oil using an oxidizing agent such as an organic peroxide, making it heavier, and separating it by distillation, the unsaturated hydrocarbons in the oil polymerize, resulting in equipment stains and blockages, etc. There are safety issues due to the introduction of oxygen-containing compounds into the process. As described above, each of the conventional As removal methods has its drawbacks, and there is a strong desire for the emergence of an easy and inexpensive As removal technology. In view of the above circumstances, the inventors of the present invention have conducted extensive research and found that by treating petroleum fractions using special activated carbon, the As contained in the petroleum fraction can be sufficiently removed to the extent that it does not poison the catalyst. It has been found that activated carbon, whose ability to remove As has deteriorated due to adsorption of As, can be easily regenerated by first washing it with a solvent that has both hydrophilicity and lipophilicity, and then washing it with water. The present invention was completed based on the above findings, and an object of the present invention is to provide a method for easily and inexpensively removing As from petroleum fractions. The present invention will be explained in detail below. Although As compounds in petroleum fractions vary somewhat depending on the fraction, they are usually contained as organic compounds and the amount thereof is very small. The present inventor has discovered that the above trace amount
As a result of various experiments to remove As by adsorption, it was found that activated carbon with a specific surface area of 1000 to 1800 m ² /g, average pore diameter of 25 to 40 Å, and pore volume of 1.0 to 1.5 cm ³ /g can absorb As. It was confirmed that it is extremely excellent for adsorption. In contrast to the above activated carbon, the properties of normal activated carbon are: specific surface area: 700 to 1800 m ² /g, average pore diameter:
12-40 Å, pore volume: 0.5-1.5 cm ³ /g. Generally, activated carbon has a large average pore diameter, a small specific surface area, and a large pore volume. However, although the activated carbon used in the present invention has a large average pore diameter, it has a special property of having a large specific surface area and a large pore volume. Therefore, large molecules such as As can be taken into the micropores, and since the specific surface area and pore volume are large, it is thought that a large amount of As molecules can be adsorbed. Activated carbon used for various adsorption treatments is usually reused after being subjected to appropriate regeneration treatments. However, there is still no known method for regenerating activated carbon that has adsorbed As. The present inventor adsorbed and removed As in petroleum fractions,
We investigated various methods for regenerating activated carbon whose removal ability has decreased. As a result, activated carbon, whose adsorption capacity had deteriorated due to adsorption of As, was washed with a solvent that has both hydrophilic and lipophilic properties and dissolves in considerable amounts in both water and oil, and then washed with water. By doing this, most of the adsorbed As is extracted and removed, and the activated carbon
It was found that the As adsorption capacity was easily regenerated. The above hydrophilic and lipophilic solvents include acetone, alcohols, (methanol, ethanol,
isopropyl alcohol, etc.) aldehydes (acetaldehyde), amines (ethanolamine, etc.)
These are either used alone or as a mixture, and the following water is used alone or as a mixture. The water used for the above-mentioned cleaning may be water, H ₂ O ₂ aqueous solution, acidic aqueous solution,
It means an alkaline aqueous solution alone or a mixture. The method of the present invention uses activated carbon with the above properties to easily remove As in petroleum fractions to the extent that it does not poison the catalyst, and the deteriorated activated carbon is sequentially washed with solvent and water. Therefore, it is a method that can restore almost the original state. The regeneration conditions for the adsorbent are (a) Regeneration solvent amount: 0.5 to 5 times the activated carbon capacity, (b) Regeneration water amount: 1 of the activated carbon capacity.
~5 times the amount, (c) Temperature: room temperature to boiling point, (d) Concentration of regeneration solvent (aqueous solution): 30 to 100%, (preferably 70 to 90%)
%) range. Next, the method of the present invention will be explained in more detail with reference to Examples. In the examples, naphtha was used as the petroleum fraction. In addition, the As concentration ratio, which indicates As adsorption capacity, the As desorption rate, which indicates regeneration capacity, and the repeated adsorption rate, which indicates whether or not adsorption capacity can be maintained through repeated adsorption and regeneration, are calculated using the following formula. will be shown. As concentration rate = As concentration in naphtha after activated carbon treatment (wt
ppb) / As concentration in naphtha before activated carbon treatment (wtppb) x 10
0 (%) As removal rate = Amount of As removed from activated carbon to cleaning solution (g) / Amount of As adsorbed from naphtha to activated carbon (g) x 10
0 (%) Repeated adsorption rate = current amount of As adsorption/previous amount of As adsorption x 10
0 (%) Further, the operation was performed at normal pressure and room temperature. [Example 1] Naphtha containing various adsorbents with As: 206wtppb
Table 1 shows a representative example of the results obtained when As was adsorbed by adding naphtha/adsorbent: 5 c.c./cc to 100 c.c.

[Example 2]

Using activated carbons with different specific surface areas, average pore diameters, and pore volumes, 4 g of each activated carbon was added to 112 c.c. of naphtha containing 539 wtppb of As, and the mixture was gently stirred for 20 minutes to adsorb As. The results are shown in Table 2.

【table】

[Example 3]

5g of activated carbon No. 4 of Example 2 was added to 298wtppb of As.
is added to 250 c.c. of naphtha containing Naphtha and stirred for 30 minutes to adsorb As.
The concentration was measured. Next, the activated carbon (5 g) that had adsorbed As was stirred and washed with a predetermined amount of various solvents for 30 minutes, and then stirred and washed with 45 c.c. of water for 30 minutes to remove As. The amount of desorption was measured. Note that the solvent and water used to wash the activated carbon do not contain As. The results are shown in Table 3.

[Table] If an appropriate solvent is selected, most of the As adsorbed on activated carbon can be removed by two-stage cleaning with solvent and water. [Example 4] Activated carbon 1 (170 g) used in Example 3 was
A 3.75 cm, 100 cm long tube was filled, and naphtha containing As was passed from the top to the bottom at SV = 3.3 for 16 hours, then 70% acetone aqueous solution was passed from the bottom to the top at SV = 1.6. Add more water for 2 hours
The activated carbon was regenerated for 2 hours at SV=1.4. Naphtha containing As is added to this recycled activated carbon again from above.
It ran for 16 hours at SV=3.3. In this way, As adsorption and activated carbon regeneration were repeated alternately to examine changes in adsorption capacity. The results are shown in Table 4.

[Table] As is clear from the table, sufficient playback is possible.
As can be adsorbed and removed by repeating the process. It was also confirmed that the naphtha from which As had been removed was not contaminated in any way. In addition, almost the same results were obtained by using kerosene as another petroleum fraction to remove As caused by the above distribution.

Claims (1)

[Claims] 1 As in petroleum fraction, specific surface area: 1000-1800
^m2 /g, average pore diameter: 25~40Å, pore volume: 1.0~
^The As
Hydrophilic activated carbon, which has a reduced ability to adsorb and remove
A method for removing As from petroleum fractions, which comprises washing with a solvent having lipophilic properties and then washing with water to regenerate and repeatedly use the activated carbon for adsorption and removal of As.