JPH0123532B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for obtaining an aqueous solution containing nickel, cobalt, vanadium, and molybdenum when recovering valuables from a waste hydrodesulfurization catalyst. Catalysts made by combining one or more of nickel, cobalt, molybdenum, etc. on a catalyst carrier made of alumina or alumina and silica are used mainly as hydrodesulfurization catalysts for heavy oil, and are widely used in the organic chemical industry. It is used. After these catalysts have been used for a certain period of time, their functionality deteriorates and they are discarded as waste catalysts. This hydrodesulfurization waste catalyst (hereinafter abbreviated as waste catalyst)
Including the above metals originally present in the catalyst,
Contains metals found in heavy oil such as vanadium. Any attempt to recover these metals is
Although this method has been used for a long time, all of the methods so far have advantages and disadvantages. For example, this waste catalyst normally contains a considerable amount of water and oil, but in order to remove this and convert the vanadium and molybdenum contained in the waste catalyst into highly reactive oxides, There is a method of oxidative roasting at 700℃. However, in this case, the oil contained in the waste catalyst is also burned, so a local temperature rise is unavoidable, and as a result, the actual roasting temperature becomes high, and nickel and cobalt also turn into oxides and become water. It becomes difficult to elute with dilute acids, etc. Vanadium and molybdenum are also extracted by treating them with alkali, but in this case too, so-called soda roasting is performed at a temperature of 700°C or higher to improve the metal extraction rate, or another method is used. ,
There is a pressure oxidation method using an autoclave, etc.
When soda roasting is performed, nickel and cobalt form a solid solution with aluminum and become insoluble in water, making it impossible to recover nickel and the like. Therefore, the spent catalyst is placed in an autoclave either as is or after drying, and oxidized under pressure at over 100℃.
Nickel and cobalt are made into sulfates, vanadium,
A method of separating molybdenum and the like as oxides has been proposed. However, even with this method, the high-boiling point organic compounds contained in the waste catalyst are partially decomposed and burned in the autoclave, and alumina, which has similar properties to abrasives, must be stirred. There were problems in terms of cost, such as severe wear on the autoclave body and the inability to sufficiently extract nickel and cobalt without high-temperature and high-pressure treatment. An object of the present invention is to eliminate the drawbacks of conventional methods and to provide a method for extracting valuables from waste catalysts at a lower cost and with simple operations. In order to achieve this objective, the present inventor conducted intensive research on a method for simultaneously extracting all the valuable substances contained in the waste catalyst. Nickel, cobalt, molybdenum, and some vanadium in the waste catalyst can be removed in water or a weak sulfuric acid solution by removing them without affecting the valuables in the catalyst and then roasting them at appropriate temperatures. It has been experimentally discovered that the compound can be made into an extremely easily soluble form. Based on this knowledge, a more detailed study revealed that when the above treatment is performed, nickel and cobalt are essentially converted into sulfates, and molybdenum and some vanadium are converted into tetravalent oxides. It is estimated that the substance becomes the easily soluble substance mentioned above. From the above results, the method of the present invention is capable of converting waste catalyst to 5 to 50 Torr (Torr) of 200°C or higher, preferably 10 to 30 Torr.
After undergoing a process of vacuum distillation at 250 to 300°C for 2 hours or more, or treatment in a neutral atmosphere such as nitrogen gas at 300 to 700°C, preferably 400 to 500°C for 1 hour or more, the treated product is air-treated. 350 to 550℃, preferably 400℃ in medium or in air enriched with oxygen of about 10% by volume
Roast at ~500℃. Next, the roasted product is preferably cooled to room temperature, then water is added to form a slurry, and a reducing agent of 0.6 equivalent or more, preferably 0.8 equivalent or more relative to the amount of vanadium contained in the slurry is added to reduce the pH to 2.5 or less, preferably teeth
By processing at pH 0.5 to 1.0, nickel, cobalt, vanadium, and molybdenum are efficiently extracted and separated from undissolved residues. In the present invention, the reason why vacuum distillation or neutral atmosphere treatment is performed at a predetermined temperature in the first step is to remove moisture and oil without affecting the form of valuable substances, such as sulfides, in the spent catalyst. Next, this treated product is roasted at 350 to 550℃, preferably 400 to 500℃ in air or air enriched with a small amount of oxygen, so that only nickel and cobalt are converted into sulfates, and molybdenum and vanadium are converted into sulfates. This is to make it a preferable oxide. The above-mentioned preferred oxides mean molybdenum which is substantially tetravalent and vanadium which is a mixture of tetravalent and pentavalent oxides; It's about things. To explain this roasting condition in more detail,
Among the valuable substances in the waste catalyst, the extraction rate of nickel and cobalt is determined by the roasting temperature, while the atmosphere during roasting affects the extraction rate of vanadium and molybdenum. In other words, even if the roasting temperature is lower than 350℃, it is still 550℃.
Even if it becomes higher, the extraction rate of nickel and cobalt will decrease. On the other hand, when the atmosphere during roasting has a high oxygen concentration, vanadium becomes a stable pentavalent oxide, and molybdenum also becomes a hexavalent oxide, so even if a sufficient reducing agent is added, it cannot be extracted. rate decreases. The processed material that has undergone the above-mentioned roasting process is made into a slurry by adding an appropriate amount of water or a dilute aqueous sulfuric acid solution, and the pH of the slurry is preferably 2.5 or less. The reason is that the extraction rate of valuable substances decreases at pH 2.5 or higher. However, if you want to prevent the elution of aluminum, which is the carrier of the waste catalyst, the pH should be set to 0.5.
It is better to stop it at ~1.0. As for the reducing agent to be added to this slurry, sodium sulfite, sodium hydrogen sulfite, sulfur dioxide gas, hydrazine, etc. can be used, although it is not specified. The reason why the amount of the reducing agent added is 0.6 equivalent or more, preferably 0.8 equivalent or more relative to the amount of vanadium contained is that in the method of the present invention, only 60% to 80% of the vanadium is pentavalent. This is because vanadium and molybdenum other than that are obtained as oxides, and although their forms are not clear, they are tetravalent and easily soluble in water or weak acids. The reducing agent may be added gradually or all at once, but it is necessary to keep the pH of the aqueous solution constant. It is efficient to perform the operation of adding a reducing agent to the slurry and extracting valuable substances all at once at a temperature of 60°C or higher, preferably 80°C or higher. Most of the nickel, cobalt, vanadium, and molybdenum contained in the raw materials are dissolved in the extract obtained in this way, but recovery of each metal from this extract is well known. This can be easily done by the following method. For example, molybdenum is selectively extracted by a solvent extraction method by adding a solvent prepared by diluting tri-normal octylamine (TNOA) with kerosene to the extract, and then back-extracting the molybdenum with an aqueous solution of alkali hydroxide or ammonia. This is concentrated to obtain molybdate. The remaining mother liquor from which molybdenum has been extracted has a pH of 1.5.
While maintaining the temperature at ~1.8, add an oxidizing agent such as sodium chlorate or chlorine to precipitate vanadium as pentavalent and separate and recover from the mother liquor. The mother liquor from which molybdenum and vanadium have been separated is adjusted to a pH of 4 to 5 by adding an aqueous solution of alkali hydroxide, etc. After separating the formed aluminum precipitate, the pH of the mother liquor is brought to about 10.0, and nickel and cobalt are hydroxylated, respectively. Since it precipitates as a solid substance, it can be almost completely recovered. As explained above, according to the method of the present invention, waste catalyst can be treated at a relatively low temperature and with simple operations, and valuable substances in the waste catalyst can be efficiently extracted into an aqueous solution. The method of the present invention can also be applied to waste catalysts containing titanium. Examples will be described below. Example When 1 kg of the waste catalyst shown in Table 1 was treated in a siliconite furnace at 400 to 450 DEG C. for 1 hour in a nitrogen stream, 871 g of the treated product was obtained. As shown in Table 1, most of the oil adhering to the waste catalyst was removed.

[Table] Weighed 850g of the processed material in Table 1 and roasted it for 4 hours at 400-450℃ in air supplemented with 10% by volume of oxygen using the same silicone furnace to obtain 809g of roasted material. Ta. Next, 500 g of this roasted product was taken into a beaker No. 5, and when deionized water No. 2 was added thereto and stirred, the supernatant liquid of this slurry showed weak acidity (PH3.4). Next, this slurry was heated and kept at 80℃, and then 1+1 sulfuric acid was added to adjust the pH to 1.0.
While maintaining the pH, gradually add 0.8 equivalent of 250 g of sodium sulfite aqueous solution to the amount of vanadium in the slurry, and after the first addition of this reducing agent.
After treatment for 90 minutes with gentle stirring, filtration and washing were performed by vacuum filtration. The amount of undissolved residue obtained was 283 g, and the amount of extracted liquid was 2.3 g. The composition of this insoluble residue is shown in Table 2, and the extraction rate of valuable substances is shown in Table 3.

【table】

[Table] As is clear from Table 3, all of the valuable substances contained in the waste catalyst showed an extraction rate of 90% or more. Although there are some differences in the recovery of each metal from this extract depending on the procedure, it is possible to separate and recover each metal with a yield of 95% or more.

Claims (1)

[Claims] 1 Process of treating the spent hydrodesulfurization catalyst at 200°C or higher for 1 hour or more under reduced pressure or in a neutral atmosphere, and the treated product is heated at 350°C or more in air or air enriched with a small amount of oxygen.
In the process of roasting at 550℃, water is added to the roasted material to form a slurry, and then a reducing agent of 0.6 equivalent or more is added to the amount of vanadium contained, and the process is carried out at a pH of 2.5 or lower to substantially reduce the A method for extracting valuable metals from a desulfurization waste catalyst, comprising the steps of preparing a slurry containing nickel, cobalt, vanadium, and molybdenum as an aqueous solution, and separating this into an aqueous solution and an insoluble residue.