JPS6041615B2 - Method for recovering valuables from petroleum hydrodesulfurization waste catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering cobalt, molybdenum, nickel, and vanadine from cobalt-molybdenum waste catalysts generated in hydrodesulfurization steps in the petroleum refining industry.

The deoxidized cobalt-molybdenum waste catalyst conventionally used in the hydrodesulfurization process, i.e., the deoxidized metal components such as Co, Mo) vanadine, and nickel supported on an inert carrier such as alumina, silica, clay, etc. The recovery method is to oxidize and roast the waste catalyst while passing it through secondary air, burn off the attached tar and carbon, and convert metals in the form of sulfides into oxides, which are then converted into (1 ) acid extraction, (2) alkaline roasting-water extraction, and (3) high-pressure alkaline extraction. That is, the proposed conventional method consists of (1) oxidative roasting-acid extraction method, (2) oxidative roasting-mono-alkali roasting-water extraction method, and (3) oxidative roasting-high-pressure alkaline extraction method, and some of them have not been implemented. ing.

All of these conventional extraction methods agree that oxidative roasting is the starting point, and this idea is the simplest method to burn off the oil and tar attached to the waste catalyst. It is something.

This method has the following drawbacks: 1 Catalytic metals are dispersed in fine particles on activated alumina carriers in order to increase catalytic activity, so when they become oxides, they easily combine with the carrier alumina to form stable mineralized substances, allowing them to react with acids and alkalis. tends to be insoluble in

Therefore, although the extraction operation is easy in the above-mentioned method of carrying out acid extraction after oxidative roasting, the extraction rate is extremely low and cannot be put to practical use. Also, in method (2), MONV is extracted, but N
i) Co remains. Furthermore, a considerable amount of aluminum constituting the carrier is extracted, making separation work difficult. Furthermore, although the method (3) extracts the entire amount of Mo), V), Ni, Co), etc., the process is complicated, and the separation process is very extensive because the aluminum of the support is completely dissolved. Since most of the products produced are cheap alumina, they are currently unprofitable. 2. Since all the sulfur compounds in the spent catalyst turn into sulfur dioxide gas, it is impossible to release it into the atmosphere due to pollution regulations, and a large-scale flue gas desulfurization process is required to treat it.

That is, since the spent catalyst usually contains 5 to 10% sulfur, about 35 to 70 sulfur dioxide gas is generated per ton of the spent catalyst. The present invention uses reductive roasting to oxidize and extract sulfides produced by the sulfur content in the waste catalyst, whereas the conventional method extracts oxides produced by oxidative roasting. This is based on the discovery that it is possible to significantly improve the extraction rate. The catalysts contemplated by the present invention are MOI, Ni, . The catalyst includes any metal component that can be sulfurized, such as COI, and an optional inert support such as alumina.

That is, the present invention consists of the following two steps.

1st step: Convert catalyst metal into sulfide. Second step: Sulfides are leached using a combination of an oxidizing agent and an acid.

That is, in the present invention, the catalytic metal is converted into a sulfide by reducing roasting, which is less susceptible to the stabilizing effect of the aluminum or silica carrier at high temperatures, and then the metal is extracted using a combination of an oxidizing agent and an acid. do.

It is said that when activated, the metals in the catalyst become sulfides and become activated by the sulfur content in petroleum, as described in "Petrochemical Roo 2" (Published by Koshobo, 196 reviews), page 89.
When the waste catalyst is taken out of the tower, it is converted into oxides by air oxidation.

This reaction generates heat and sometimes causes ignition, ``industrial pollution'' (published by the Industrial Pollution Prevention Association, Vol. 2, No. 12).
(See page 9). Therefore, the catalytic metal becomes an oxide not only by roasting in air but also by leaving it alone.

In the present invention, reduction roasting is performed as a means of converting these oxides into sulfides, and this mechanism is presumed to be based on the following mechanism.

A▼ν1VJVBχノ
-Here X. , y are numerical values unique to each catalyst metal, and H. ．． C. ．． S is derived from an organic matter attached to the material or a decomposed product thereof.

That is, in sulfidization by reduction roasting, there is no need to add a reducing agent or sulfur source from the outside, and the materials involved in the reaction are available, such as hydrocarbons and sulfur-containing compounds in the deposits.

Inert gases such as argon and nitrogen are effective as the reducing atmosphere for this reaction, but in principle, volatile gases generated from deposits, twisting gases such as natural gas, and water vapor can also be used. .

The roasting temperature is 500℃ if only the attached organic matter is removed.
The purpose is almost achieved at 700°C, but the sulfurization reaction of the metal hardly progresses at this temperature, and at 700°C, about 50% of the oxide is removed.
% becomes sulfide and 90% is required for the reaction to completely terminate.
A temperature of 0°C or higher is required. Furthermore, at temperatures above 700°C, the sulfide dispersed in the catalyst undergoes migration and diffusion, and the particles of metal sulfide become coarse and the activity decreases, so there is almost no heat generation due to air oxidation and the generation of sulfur dioxide gas, making it difficult to handle. It becomes convenient. The relationship between temperature and extraction rate is almost constant above 900°C, but from around 1000°C the carrier alumina undergoes a transition and becomes a chemically stable alpha state.

As a result, the amount of aluminum extracted during extraction is reduced, which is advantageous because less aluminum hydroxide, which is difficult to precipitate and difficult to filter, is generated in the subsequent separation step.

However, since this purpose can be almost achieved by raising the temperature to 1100℃, there is no need to raise the temperature any further.
Rather, it is disadvantageous from a thermoeconomic standpoint, and even considering the material of the furnace, it is appropriate to limit the heating to 1100°C.

Of the reduction roasting mechanisms that are a component of the present invention, special mention must be made of the treatment of sulfur, which is contained in the spent catalyst in an amount of 5 to 12%.

In other words, the tar contained in the spent catalyst contains complex sulfur compounds, which are decomposed into low-boiling point thiols through reduction roasting and collected as oil by cooling at the exhaust port. Ru.

Since 4500-500℃ is sufficient for tar decomposition,
It is also possible to process the spent catalyst in advance in this step and then reprocess it at a predetermined temperature. Since the catalytic metal sulfide thus obtained has strong chemical activity, a high extraction rate can be obtained at room temperature and pressure by using an oxidizing agent in combination.

The extraction mechanism is shown by Equations 3 and 4.

In addition to commonly used oxidizing agents such as hydrogen peroxide, hypochlorite, and chlorine, blowing air, oxygen, and ozone are also effective, and electrolytic oxidation can also be used.

Any inorganic acid can be used as the acid, but sulfuric acid is particularly suitable, and the acid concentration is practically 1 to 10%.
A range of 1 is particularly preferred, but oxidation of sulfur produces sulfuric acid, which can also be substituted. The present invention will be described below with reference to Examples.

Example 1 A waste catalyst used for petroleum hydrodesulfurization with a mesh size of 2
After sifting through the sieve and removing alumina balls,
In an electric rotary kiln with an inner diameter of 8cyf0n1 and a soaking zone length of 400w0n, nitrogen was passed through at 2'/min.
It was calcined at ~500°C and then heated at 950~1000°C in the same rotary kiln.

The cooled sample is crushed to 100 mesh or less, and the 20
0y was extracted with an aqueous solution 1e containing 5f of sulfuric acid and 20q of hydrogen peroxide. After the solid content was filtered, the solid content was suspended in 1' water, the pH was adjusted to 8 with caustic soda, and the suspension was filtered again.

The results are shown in Table 1, where the initial liquid extract is referred to as the acid extraction liquid and the residual liquid is referred to as the alkaline extraction liquid, and the ratio of the eluted metals to the metals in the roasted raw material is expressed as extraction rate %.

Example 2 The same waste catalyst as in Example 1, which had been sieved to remove alumina holes, was heated to 100% in a rotary kiln under argon gas ventilation.
A sample of 200V roasted at 00C and ground to 100 mesh or less was suspended in water 1e, and while keeping the pH at 1, an effective electrode area 1 with an anode made of platinum steel or the like and an ion exchange membrane was prepared.
．． Electrolytic oxidation was carried out in the anode chamber of a 54 square decimeter electrolytic cell.

The following treatment was carried out according to Example 1, and the extraction rate of acid extraction was shown in Table 2.
Shown below.

Example 3 Add 1' of water to 500 y of the roasted waste catalyst obtained in Example 1, keep it at 150°C, and increase the oxygen pressure to 20"K9l while stirring.
d.

The pH of the aqueous solution was 6.5 at the start of the experiment, but it immediately dropped to 3.2, indicating the production of acid.

The oxygen pressure was maintained at 20k91Cf1L, and when the influx of oxygen ceased, it was cooled to room temperature, the oxygen pressure was lowered, the contents were taken out and filtered, and the extraction rate was determined by analysis. The results are shown in Table-3. As described above, according to the present invention, a high extraction rate can be obtained with a simple extraction method even under normal temperature and normal pressure, which was completely unthinkable with conventional methods.

That is, in the conventional oxidative roasting monoacid extraction method, the extraction rate does not exceed 60%, and in the oxidizing roasting-alkali roasting monohydric extraction method, the Ni. ．． CO cannot be extracted.

The fact that the oxidation roasting-high-pressure alkaline extraction method is unprofitable due to the high cost of equipment and energy is also evident from the fact that although this method has been attracting attention for a long time, it has not yet been commercially implemented. Furthermore, the reduction roasting method employed in this method does not generate sulfur dioxide gas, as mentioned above, and is extremely advantageous in terms of pollution control. It can be applied as is to waste catalysts that use alumina, silica, etc. as a carrier and is contaminated with sulfur-containing compounds, and if it does not contain sulfur-containing compounds, the catalyst metal can be converted to sulfide by roasting. If a substance that can be added is added, the method for recovering valuable materials according to the present invention can be applied, and the present invention has great industrial significance.

Claims (1)

[Claims] 1 A waste petroleum hydrodesulfurization catalyst was heated for 70 minutes in an inert gas atmosphere.
A method for recovering valuables from a waste catalyst, which comprises roasting at a temperature of 0° C. or higher and 1100° C. or lower, and then leaching useful metals using an acid aqueous solution in combination with an oxidizing agent.