JPH07108982B2 - Hydrorefining method of arsenic-containing hydrocarbon oil - Google Patents

Description

The present invention relates to a method for hydrorefining an arsenic-containing hydrocarbon oil.

[Conventional technology]

Benzene in cracked gasoline as a by-product during thermal cracking of naphtha, toluene, C ₆ -C ₈ aromatic hydrocarbons such as xylene is contained in a large amount, the organic sulfur as impurities in the hydrocarbon oil of this kind It contains polymerizable diolefins and styrenes as well as compounds and organic nitrogen compounds.
Conventionally, in order to obtain useful components such as benzene, toluene, and xylene by removing these impurities by hydrogenation, polymerizable diolefins and styrenes have been used with a catalyst having an activity at low temperature such as palladium. Is removed by hydrogenation (referred to as primary hydrogenation), and then an organic sulfur compound and an organic nitrogen compound are removed by hydrogenation using a catalyst effective at a relatively high temperature such as cobalt-molybdenum (secondary hydrogenation). Call) method is generally adopted.

[Problems to be solved by the invention]

However, a small amount of arsenic may be contained in naphtha, and as a result, the decomposed gasoline produced as a by-product during thermal decomposition often contains a concentrated arsenic component. The concentration is usually about 10 ppb to 500 ppb, though it depends on the type of naphtha used.

Arsenic is generally highly toxic to catalysts, and it is known that organic arsenic compounds such as arsine significantly reduce the hydrogenation activity of noble metal catalysts such as palladium and platinum even in a small amount.

Therefore, when arsenic is contained in the cracked gasoline, the activity of the palladium catalyst used for primary hydrogenation is significantly reduced, and the hydrogenation removal of the polymerizable diolefins and styrenes becomes incomplete, Since it becomes a big problem, conventionally,
As a primary hydrogenation catalyst, a method using a transition metal oxide catalyst such as cobalt-molybdenum, which is highly resistant to catalyst poisons, has been adopted.

However, when a transition metal oxide catalyst is used as the primary hydrogenation catalyst, its hydrogenation activity is weaker than that of a palladium catalyst and it is necessary to use it at a relatively high temperature. In such a case, diolefins and styrenes The thermal polymerization causes a polymer to be deposited on the upper part of the reactor, resulting in an increase in the differential pressure in the reactor and a decrease in the activity of the catalyst, which leaves a problem that stable operation becomes difficult.

As another method, a method using a palladium catalyst after previously removing or detoxifying the arsenic component in the raw material has been proposed.

As a method for removing arsenic in cracked gasoline, for example, a method using an adsorbent such as activated carbon, a method using an oxide catalyst such as copper or manganese, a method of treating an arsenic component with an oxide and separating it by distillation are known. However, not only do any of the methods require extra auxiliary equipment, but also polymerization of highly reactive diolefins or styrenes tends to cause troubles such as clogging of the reactor.

As another method, there is also known a method in which a palladium catalyst poisoned by arsenic is subjected to an oxidation treatment with a gas containing oxygen and is used while being reactivated (Japanese Patent Publication No. 60-5789).
7). However, in this case, it is necessary to frequently stop the feed of the raw material oil and reactivate the catalyst, which makes stable operation difficult.

[Means for solving problems]

In view of the above-mentioned problems of the prior art, the inventors of the present invention have conducted extensive studies on an effective low temperature active catalyst, and as a result, have a specific relationship between the radius R of the alumina carrier and the distance r of the palladium concentration center from the carrier surface. By using the palladium catalyst internally supported on the alumina carrier, the dienes and styrenes in the arsenic-containing hydrocarbon oil can be removed at low temperature and without any additional equipment for removing arsenic in the raw material. The present invention has been completed by finding that hydrogenation purification can be performed.

That is, the gist of the present invention is that when the hydrocarbon oil containing an arsenic component is hydrorefined using the alumina-supported palladium catalyst, the radius R of the alumina carrier is in the range of 0.5 to 2.5 mm,
An arsenic-containing carbonized catalyst characterized by using a palladium catalyst internally supported on an alumina carrier having a ratio r / R of the distance r of the concentration center of palladium from the carrier surface to the carrier radius R in the range of 0.02 to 0.4. It exists in the hydrogenation refining method of hydrogen oil.

Hereinafter, the present invention will be described in detail.

In the present invention, the radius R of the alumina carrier (where R = 0.5 mm
2.5 mm) and the distance r of the concentration center of palladium from the surface of the carrier have a relationship of r / R = 0.02 to 0.4, and a palladium catalyst internally supported on an alumina carrier is used.

As the alumina carrier, those having a relatively high surface area are preferable, a surface area of 50 m ² / g or more, a spherical volume mainly composed of γ-alumina having a pore volume of 0.3 cc / g or more, a columnar one is mainly used, and its radius Is in the range of 0.5 mm to 2.5 mm.
If the radius is less than 0.5 mm, it is difficult to control the palladium concentration distribution, and there is a problem that heat loss of the reactor is likely to occur, and if it is greater than 2.5 mm, sufficient hydrogenation activity is obtained. It is hard to be caught.

There is no particular limitation on the method of loading palladium on the inside of the alumina carrier, and a known general method can be used. For example, palladium chloride-hydrochloric acid aqueous solution is allowed to coexist with an organic acid such as citric acid, and alumina. After impregnating the carrier, the method of removing the liquid, drying and then calcining is preferable in that the concentration distribution of palladium can be easily controlled. For example, when citric acid is used as the organic acid, the impregnation liquid 1
By coexisting 1 to 30 g of citric acid,
The concentration center of palladium can be controlled at an appropriate position inside the alumina carrier.

When palladium is supported at a high concentration on the surface of an alumina carrier, the initial hydrogenation activity is high, but it is immediately poisoned by arsenic in the raw material, resulting in a significant decrease in activity. When palladium is supported on the central part of the alumina carrier so that the ratio r / R of the distance r of the concentration center of R to the radius R of the alumina carrier is larger than 0.4, the hydrogenation activity itself is sufficiently exerted. In addition, the removal of the dienes in the raw material becomes incomplete, which is not preferable.

The amount of palladium supported can be usually in the range of 0.05 to 2% by weight, but is preferably in the range of 0.1 to 1% by weight.

The arsenic-containing hydrocarbon oil hydrogenated and refined by the method of the present invention is not particularly limited, but ethylene, propylene, etc. are produced by cracking naphtha, cracked gasoline by-produced when producing propylene, and naphtha are catalytically reformed. There are obtained naphtha modified oils and the like, and usually, an arsenic concentration of 10 ppm or less can be used.

As impurities other than arsenic in these hydrocarbon oils, those having a sulfur content of 200 ppm or less and basic nitrogen of 10 ppm or less can be suitably used as they are for hydrorefining.

The conditions for hydrorefining are not particularly limited and can be carried out within the range of conventional operating conditions, but the reaction pressure is usually 10 to 10
The suitable range of 0 kg / cm ² G and LHSV is 1.0 to 5.0 hr ^-1 . The reaction temperature is usually in the range of 30 to 200 ° C., but it is preferably as low as possible in order to avoid polymerization of the dienes and styrenes in the raw materials.

The method for measuring the center of palladium concentration in the alumina carrier in the present invention is carried out by a conventionally known method, for example, a catalyst is fixed with a resin and cut in a radial direction to form a spherical cross section, and a scanning XM (X-ray microanalyzer) is used. And the peak position is defined as the center of palladium concentration.

〔Example〕

Next, the present invention will be described more specifically with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

In the following examples, the diene value was determined by the maleic anhydride method, and the hydrogenation reaction results were represented by the diene value and styrene concentration of the reactor outlet liquid.

Reference Example-1 A commercially available spherical alumina carrier (radius R = 0.8) in 1.000 ml of an aqueous solution containing 1.5 g of palladium chloride, 1 ml of hydrochloric acid and 6.0 g of citric acid.
mm, surface area 242 m ² / g, pore volume 0.605 cc / g γ-alumina) 300 g (500 ml) by immersion and immersion, 1 hour later, draining, drying at 120 ℃ for 15 hours, then at 500 ℃ It was calcined in air for 3 hours to prepare a 0.3% Pd / alumina catalyst (hereinafter referred to as A catalyst).

When the cross section of the catalyst A was analyzed by an optical microscope and an X-ray microanalyzer, the distance r of the concentration center of palladium from the surface of the carrier was 180 μm and the ratio with the radius R of the alumina carrier was r.
/R=0.23.

SUS-31 with 5 ml of A catalyst together with diluting filler (glass beads)
It was filled in a 6-made reactor and hydrogen-reduced at 200 ° C for 2 hours, and then the reaction pressure was 40 kg / cm ² G, H ₂ flow rate was ₂ Nl / hr, LHSV 2.0 hr ^-1 , temperature 40.
At the temperature of ℃, a continuous hydrogenation experiment was conducted by using arsenic-free cracked gasoline produced from ethylene plato having the composition shown in Table-1 as a raw material, and the diene number of the reactor outlet liquid was measured. The outlet liquid composition was analyzed.

The results after 200 hours of reaction are shown in Table 2.

By adding triethoxy arsine cracked gasoline as used in Example -1 Reference Example _{-1 (As (OC 2 H 5} ) 3), and the reaction was conducted using a raw material obtained by adjusting the arsenic content in 40ppb outside Was subjected to a continuous hydrogenation experiment in the same manner as in Reference Example-1.

By adding triethoxy arsine cracked gasoline used in Examples -2 Reference Example _{-1 (As (OC 2 H 5} ) 3), and the reaction was conducted using a raw material obtained by adjusting the arsenic content in 290ppb outside Was subjected to a continuous hydrogenation experiment in the same manner as in Reference Example-1.

Example 3 A reaction was performed using a raw material in which triethoxyarsine (As (OC ₂ H ₅ ) ₃ ) was added to the cracked gasoline used in Reference Example 1 to adjust the arsenic content to 1.3 ppb. A continuous hydrogenation experiment was conducted in the same manner as in Reference Example 1 except for the above.

By adding triethoxy arsine cracked gasoline used in Examples -4 Reference Example _{-1 (As (OC 2 H 5} ) 3), and the reaction was conducted using a raw material obtained by adjusting the arsenic content in 13ppm outside Was subjected to a continuous hydrogenation experiment in the same manner as in Reference Example-1.

Reference Example-2 Using 2 g of citric acid, a commercially available spherical alumina carrier (radius R =
0.5 mm, surface area 217 m ² / g, and pore volume 0.568 cc / g γ-alumina) except that the same as Reference Example-1, except that 0.3% p
A d / alumina catalyst (hereinafter referred to as B catalyst) was prepared.

When the cross section of the B catalyst was analyzed in the same manner as in Reference Example-1, it was r / R = 0.08.

A continuous hydrogenation experiment was conducted in the same manner as in Reference Example 1 using 5 ml of the B catalyst.

Example-5 to Example-8 Using the B catalyst in Reference Example-2, Example-1 was used.
In the same manner as in Example 4, continuous hydrogenation experiments were conducted using raw materials having different arsenic contents.

The results of Reference Examples-1 and 2 and Example-1 to Example-8 are summarized in Table-2.

Comparative Example-1 In the same manner as in Reference Example-1, except that citric acid was not used.
A 3% Pd / alumina catalyst (hereinafter referred to as C catalyst) was prepared.

When the cross section of the C catalyst was analyzed in the same manner as in Reference Example-1, palladium was concentrated and supported on the surface of the alumina carrier, and r / R was smaller than 0.01.

A continuous hydrogenation experiment was conducted in the same manner as in Reference Example 1 using 5 ml of C catalyst.

Comparative Example-2 to Comparative Example-5 A continuous hydrogenation experiment was conducted using the C catalyst of Comparative Example-1 and using raw materials having different arsenic contents in the same manner as in Example-1 to Example-4.

Comparative Example-6 In the same manner as in Reference Example-1, except that 18.5 g of citric acid was used.
A 0.3% Pd / alumina catalyst (hereinafter referred to as D catalyst) was prepared.

When the cross section of the D catalyst was analyzed in the same manner as in Reference Example-1, r / R = 0.44.

A continuous hydrogenation experiment was conducted in the same manner as in Reference Example 1 using 5 ml of D catalyst.

The results of Comparative Example-1 to Comparative Example-6 are summarized in Table-3.

[Effect of the invention] The method of hydrolyzing the polymerizable dienes and styrenes contained in the arsenic-containing hydrocarbon oil using the alumina-supported palladium catalyst of the present invention is more effective than the conventional method in the raw material. Since it can be carried out at relatively low temperature without any additional equipment for removing arsenic of arsenic, it is said that troubles such as clogging of the reactor due to polymerization of highly reactive dienes and styrenes can be reduced. It is excellent in that it has a remarkable effect that the arsenic-containing hydrocarbon oil can be hydrogenated and refined economically.

[Brief description of drawings]

FIG. 1 shows that the diene number of the reactor outlet liquid obtained from the continuous hydrogenation experiments in Example-1 to Example-8 and Comparative Example-1 to Comparative Example-5 was compared with the arsenic concentration in cracked gasoline. It is the figure plotted on the contrary. FIG. 2 shows the styrene concentration (wt) of the reactor outlet liquid obtained from the continuous hydrogenation reaction in Example-2 and Comparative Example-3.
It is a figure showing the time change of (%).

Claims (2)

[Claims] 1. When hydrogenating and refining a hydrocarbon oil containing an arsenic component using an alumina-supported palladium catalyst, the radius R of the alumina carrier is in the range of 0.5 to 2.5 mm, and palladium from the carrier surface is Method for hydrorefining arsenic-containing hydrocarbon oil characterized by using a palladium catalyst internally supported on an alumina carrier having a ratio r / R of the distance r of the concentration center to the carrier radius R in the range of 0.02 to 0.4 . 2. A method for hydrorefining an arsenic-containing hydrocarbon oil according to claim 1, wherein the hydrocarbon oil is an arsenic component.
A method which comprises 10 ppm or less, a sulfur content of 200 ppm or less, and basic nitrogen of 10 ppm or less.