JPS6057897B2 - Catalyst regeneration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating platinum or palladium catalysts poisoned by arsenic contained in petroleum fractions.

The inventors of the present application have previously proposed a method for removing arsenic and a method for rendering it harmless since trace amounts of arsenic become a harmful component when manufacturing various petrochemical products using petroleum fractions containing trace amounts of arsenic as raw materials. invented.

These inventions were filed in Japanese Patent Application No. 52-121001,
-55511 and Japanese Patent Application No. 52-125103. As a result of further intensive research, the present inventor discovered that platinum or palladium catalysts poisoned by arsenic contained in petroleum fractions can be reactivated by a surprisingly simple method, and completed the present invention. . The structure of the present invention is as described in claim 1, and its purpose is to regenerate a catalyst that has been poisoned by arsenic contained in petroleum fractions.

Further, the effects of the present invention are as follows. That is, if a palladium or platinum catalyst is used for scaling, reforming, etc. using a petroleum fraction containing arsenic as a raw material, these catalysts will be poisoned and the process will not proceed smoothly. In this case, if the present invention is implemented to regenerate these catalysts, it is possible to stabilize the scale (for example, the scale of diolefins using a Pd catalyst) and the reforming process (for example, the production of aroma from naphthenes using a platinum catalyst). As a result, even if a trace amount of arsenic is contained in the raw petroleum fraction, it is advantageous that it does not necessarily have to be removed. The petroleum fractions described in this specification include petroleum, straight-run naphtha, kerosene, light oil, vacuum distillate, atmospheric residual oil, etc., as well as pyrolysis gasoline by-produced in the pyrolysis equipment of an ethylene plant, and A wide range of hydrocarbons, including hydrocarbon oils that have been heat-treated by cokers and visbreakers, naphtha fractions produced in catalytic crackers, recycled oil, etc., as well as Joule oil, tar sands, and synthetic petroleum from coal. means oil.

Furthermore, the term "arsenic" as used herein refers to a compound containing elemental arsenic as one of its constituent elements.

However, the following words stated in the specification of the present application, namely, elemental arsenic,
Arsenic in the arsenic compound and arsenic concentration, of course, means arsenic itself and does not mean an arsenic compound. Many petroleum distillates contain trace amounts of arsenic.

Its form varies depending on the fraction, but it is thought to be arsine and organic arsenic compounds. In the process of manufacturing various petrochemical raw materials or petrochemical products from petroleum fractions, this trace amount of arsenic may act as a catalyst poison, depending on its content, or may cause coking during steam pyrolysis. It often interferes with various processes, such as promoting. For example, in the process of producing aromatic compounds benzene, toluene, and xylene from direct-run naphtha or kerosene byproduct gasoline (hereinafter referred to as cracked gasoline), arsenic is converted to olefins of diolefins contained in cracked gasoline. It appears to act as a catalyst poison for the palladium catalyst used in the hydrogenation process, rapidly reducing its activity. Arsenic is generally highly toxic to catalysts, especially Pd, which is used for hydrogenation, dehydrogenation, etc. It significantly reduces the activity of noble metal catalysts such as Pt. Therefore, in the past, especially in treatment processes using noble metal catalysts, it has been essential to remove or detoxify the arsenic in the raw materials in advance. However, as already mentioned, if the present invention is carried out, it is possible to easily regenerate the activity of a catalyst that has been poisoned by arsenic contained in the petroleum fraction and whose activity has significantly decreased. Contained in minutes. It is no longer necessary to remove or detoxify the arsenic used in the process in advance. Rather, it is generally advantageous to adopt the method of the present invention and continue the process by repeating catalyst regeneration. Next, we will discuss prior art similar to the present invention! Ru.

East German Patent No. 120589 "Activation method for steam and Pd catalyst" uses a gas mixture of chlorine (Cl.) and air and dry hydrogen chloride (HCl) at 300 to 350°C.
The method for activating or reactivating a PtlPd/alumina or alumina-silica catalyst, which is characterized by a 30-7 treatment, is similar to the present invention, in particular, the method uses an oxidizing gas to reactivate the catalyst. However, it is different from the technology of the present invention, which is characterized in that it is reactivated by oxidation treatment at a temperature range from room temperature to 250°C, and does not suggest this. Also, so-called decoking is a process that is often performed to regenerate catalysts, and this is a process in which carbon or tar-like substances on a catalyst that has been used for a long time are removed by passing air and steam at a temperature of about 400°C or higher. However, there is a clear difference in temperature from the method of the present invention, and this does not imply the present invention.

In the method of the present invention, a gas containing oxygen and oxygen, such as air, is used as the oxidation means.This method will be explained below.

The cracked gasoline containing arsenic is treated with a Pd/Al2O3 catalyst (
For example, PGC catalyst manufactured by Nippon Engelhard Co., Ltd.) is brought into contact with diolefin under hydrogenation reaction conditions.

The hydrogenation reaction conditions are 50 to 2 in the case of Pd/Al2O3 catalyst.
00℃, 30-70kgICTiG,. 100-300
It is about the range of e-H2le-01L. Catalytic activity decreases with hydrogenation treatment of cracked gasoline, and the degree of decrease in catalyst activity depends on the amount of arsenic contained in cracked gasoline.
After purging the oil contained in the catalyst whose activity has decreased in this way, the catalyst is brought into contact with air at a temperature ranging from room temperature to 250°C. The contact time and supply rate with air are arbitrary, but if the contact is too small, arsenic will be sufficiently oxidized, and if the contact is too large, time will be wasted. In addition, if the oxidation treatment temperature is too low, the oxidation reaction rate will be slow; if it is too high, local overheating will occur due to the combustion reaction of the attached carbon, causing Pd to aggregate,
Requires expensive equipment for heating heat source (e.g. heating furnace)
In addition, it becomes necessary to make the reactor resistant to high temperatures, which increases the cost, which is undesirable.

Furthermore, if steam at a temperature of 100 to 250°C is available, regeneration gas, which is a mixture of steam and air, can be used to perform regeneration processing in an extremely easy way without requiring special equipment or ingenuity. It becomes possible.

The activity of the catalyst thus oxidized and regenerated is recovered to almost the level of the new catalyst. The arsenic element content in the catalyst before and after regeneration is almost at the same level. The present invention will be specifically explained below with reference to Examples. Example 1 The following series of experiments were conducted for the purpose of examining the regeneration effect of oxidation treatment on a catalyst poisoned with an organic arsenic compound.

Experiment 1 (comparative example) In a 500 ml flask, 150 TnL of cyclohexane and 2*6-dimethyloctatriene 1-1-1-1-(hereinafter simply abbreviated as DMOT) were added.

) 2ml, and then Pd catalyst (PdO.3wt%,
γ-Al2O3) 0.4y was added, and the mixture was heated in a stream of air at normal pressure.
The hydrogenation reaction of DMOT was carried out under conditions of 70° C. and stirring for 10 minutes. DMOT in hydrotreated oil after reaction completion
The amount of DMOT was measured and the reduction rate of DMOT was determined. Note that the reduction rate is defined by the following formula. CO: DMOT concentration before reaction C: DMOT concentration after reaction Experiment 2 (comparative example) 150 mL of toluene was charged into a 500 mt flask.
Furthermore, triphenylarsine (Asφ3) was added so that the arsenic element concentration in the toluene solution was 3.5 weight Ppm, and then 0.4y of Pd catalyst (same as in Experiment 1) was added, and the mixture was heated at 70°C in a hydrogen stream. The catalyst was poisoned while stirring for 2 hours.

Next, after completely removing the triphenylarsine-toluene solution from the flask, 150 mt of cyclohexane was removed. ．． D
2ml of M0T was charged and the same hydrogenation reaction as in Experiment 1 was performed.

After the reaction was completed, the rate of decrease in DMOT was determined. Experiment 3 (Example) After poisoning the catalyst in the same manner as in Experiment 2, the triphenylarsine-toluene solution was completely extracted and 100%
The poisoned catalyst was oxidized by blowing air heated to 'C into the flask for 60 minutes.

Next, as in Experiments 1 and 2, cyclohexane 150
ml, 2ml of DMOT was charged, hydrogenation reaction was carried out, and DMO
The rate of decrease in T was determined. Continuing with the above-mentioned experimental method, only the oxidation treatment temperature of the poisoned catalyst was changed to 150'Cl2OO℃.
, 250°C was carried out.

After all experiments were completed, the arsenic concentration of the catalyst used in each experiment was measured, and the results and DMOT obtained in each experiment were measured.
The reduction rates are summarized in Table 1.

The above results show that the temperature of the catalyst poisoned with arsenic is 100 to 150℃.
It has been shown that the activity is significantly recovered by oxidation treatment with air at a relatively low temperature.

Furthermore, the arsenic element on the catalyst hardly decreases even after the oxidation treatment. Example 2 A continuous hydrogenation experiment using a palladium catalyst was conducted using arsenic-free pyrolyzed gasoline produced from an ethylene plant, and during the course of this experiment, an organic arsenic compound was added to the raw cracked gasoline as a model. The behavior of arsenic on catalysts was confirmed.

The properties of the pyrolysis gasoline used in the experiment were determined by the diene value (DV
)16. Bromine number 30, benzene 35% by weight, toluene 2
Weight%, C8 aromatics 20.5% by weight, total sulfur content 14
5 Ppml arsenic was detected, and the hydrogenation conditions were as follows.

Note that the diene value was determined by the maleic acid method. Same below.

Reactor: Flow-type high-pressure reactor (made of SUS) Catalyst: Palladium catalyst (PdO.3% by weight γ-Al2O
3) Reaction temperature: 90°C Reaction pressure: 50 kg Icd-G (in H2 gas flow) LHS■
The activity of the :3Hr1 catalyst tended to decrease slightly at the beginning of operation, but after about the 5th day it stabilized at an almost constant level.

From 10 days after the start of operation, Mφ3 corresponding to an arsenic element concentration of 5 weight Ppm was continuously added to the raw cracked gasoline.
I drove for a day. The diene value of the hydrogenated oil immediately before the addition of Asφ3 was 2.1, but due to the decrease in catalytic activity over time after the addition of Asφ, the diene value of the hydrogenated oil decreased to 8 on the 5th day after the addition. It rose to .0. Next, the operation of the reactor was stopped and steam was pumped in for 2 hours to remove oil adhering to the catalyst.
The feed was carried out under conditions of time, normal pressure, and 120°C.

Subsequently, air was fed at 130° C. for 3 hours to oxidize the catalyst. Then feed pyrolysis gasoline again,
It was returned to its original operating condition.

The diene value of the hydrogenated oil after restarting the operation was 2.4, and no significant change in the diene value was observed during subsequent operations. The above experimental results indicate that a catalyst poisoned by arsenic can be sufficiently regenerated by oxidation treatment with air even if the treatment temperature is relatively low.

After the experiment was completed, the amount of arsenic in the catalyst used was measured, and the measured value was 50 Ppm, which was calculated from the difference in arsenic concentration before and after hydrogenation in pyrolyzed gasoline to which triphenylarsine was added. This almost coincided with the calculated amount of arsenic adsorbed on the catalyst. This means that the arsenic element on the catalyst is not removed even during the catalyst oxidation regeneration treatment and subsequent operation. Example 3 Using pyrolyzed gasoline containing arsenic produced from an ethylene plant, a continuous hydrogenation reaction incorporating catalyst regeneration treatment using a Pd catalyst was carried out, and arsenic-containing pyrolysis was performed. The effectiveness of regeneration treatment for poisoned catalysts was confirmed.

The properties of the pyrolysis gasoline used in the experiment were as follows: diene value 2, bromine number 42, benzene 3%, toluene 2%, C
8 aromatic 18.5% by weight, total sulfur content 1 group weight Ppm
l Arsenic element content 1. The heel amount is Ppm. The conditions for the continuous hydrogenation treatment were as follows. Reactor: Flow-type high-pressure reactor (made of SUS) Catalyst: Palladium catalyst (PdO.3% by weight γ-Al2O
3) Reaction temperature: 90℃ Reaction pressure 50k9kI-G (in H2 gas flow) LHSV:
Changes in catalyst activity over time from the start of 3Hr1 operation, treatment effects of catalyst regeneration, and changes in catalyst activity after regeneration are determined from the diene value (DVO) of the feedstock pyrolysis gasoline and the diene value (DV) of the hydrogenated oil. Decrease rate of diene value [(DVO-
DV)/DVO].

The experiment was conducted continuously according to the following schedule. All hydrogenation experiments were conducted under the same reaction conditions, and for catalyst regeneration treatment, after the hydrogenation experiment was interrupted, steam was fed for 2 hours at normal pressure and 120°C to remove oil adhering to the catalyst. First, using water vapor containing about 15V0L% of air.
The second regeneration was carried out under normal pressure and 120°C for 4 hours, and the third regeneration was carried out under normal pressure and 400°C for 7 hours. The conditions for the third regeneration process correspond to the conditions for a catalyst decoking operation that is generally widely used for the purpose of burning off carbon-like substances adhering to the catalyst. Table 2 shows the data obtained from each hydrogen experiment 5 days, 10 days, 15 days, and 30 days after the start of each operation (5 days and 10 days after the 3rd and 4th hydrogenation experiments only).
Decrease rate of diene value in DVO-D■.

Claims (1)

[Claims] 1. In the hydrogenation and conversion reaction of petroleum mills, platinum or palladium catalysts poisoned by arsenic contained in petroleum mills are oxidized with oxygen-containing gas at a temperature range from room temperature to 250°C. 1. A method for regenerating a platinum or palladium catalyst, which comprises reactivating a platinum or palladium catalyst.