A method for recovering molybdic acid from waste catalyst

Abstract

The present invention discloses a method for recovering molybdic acid from waste catalysts, comprising the following contents: (1) de-oiling a waste molybdenum-containing hydrogenation catalyst to obtain a de-oiled material A; (2) uniformly mixing the de-oiled material A, ammonium bicarbonate and water, transferring the mixed material to a pressure-resistant container for hydrothermal treatment, and then performing solid-liquid separation to obtain a molybdenum-containing solution; (3) adjusting the pH of the molybdenum-containing solution with an acid solution to precipitate a precipitate B, and washing and removing impurities from the precipitate B to obtain molybdic acid. The method of the present invention has a simple recovery process, low energy consumption, and is green and environmentally friendly, and is conducive to industrial application and promotion.

Description

Technical Field

[0001] The invention relates to a method for recovering molybdic acid from waste catalyst. Background Art

[0002] A catalyst is a substance that can change the chemical reaction rate of other substances, but does not change the total standard Gibbs free energy of the reaction, and its own mass and chemical properties do not change before and after the reaction. According to statistics, more than 90% of the technical processes in the chemical industry currently have catalytic processes, and catalysts occupy a very important position in chemical production.

[0003] As the use time increases, the catalyst will experience thermal aging, which will cause the active component grains to grow and even sinter, and the catalytic activity to decrease. It may also be poisoned by certain poisons, losing some or all of its activity. The activity may also be reduced due to the accumulation of some pollutants on the catalyst surface or the blockage of pores. Or the catalyst may not be able to continue to be used because of its poor crushing strength and the increase in system resistance caused by particle breakage after repeated use, affecting the normal catalytic process and quality, and eventually it has to be replaced with a new catalyst.

[0004] The Co-Mo, Ni-Mo and Ni-W systems commonly used as residue oil hydrogenation catalysts have relatively high prices for their main metal elements. Since deactivated catalysts contain more metal elements, if these waste catalysts are not disposed of and randomly piled up, on the one hand, a large amount of land resources will be occupied. Some toxic and harmful substances adsorbed by the catalysts during use and some metal elements contained in the catalysts will enter the natural environment due to various effects, causing serious pollution to the environment. On the other hand, it will cause a waste of valuable metals.

[0005] CN108067245A discloses a method for recycling a hydroprocessing catalyst, comprising the following contents: (1) extracting, calcining and crushing a molybdenum-nickel waste catalyst; (2) mixing the crushed catalyst powder with an alkali, and then subjecting it to microwave treatment; (3) adding an acid solution to the molybdate solution in step (2) to obtain molybdic acid; (4) crushing the alumina filter residue in step (2), mixing it with an alkali again, calcining it, soaking it in hot water, and filtering it to obtain an aluminate solution and a nickel oxide solid; (5) introducing carbon dioxide into the aluminate solution in step (4), preparing pseudo-boehmite by carbonization, mixing the pseudo-boehmite with an adhesive, forming, drying and calcining it to prepare a carrier; (6) adding an acid to the nickel oxide in step (4) to prepare a nickel solution, and adding a carbonate to prepare a basic nickel carbonate; (7) preparing a molybdenum-nickel-phosphorus solution by mixing the molybdenum acid in step (3) and the basic nickel carbonate in step (6), and then impregnating it on the carrier in step (5), and preparing a catalyst by drying and calcining it.

[0006] CN109837393A discloses a method for selectively recovering valuable metals from a waste hydrogenation catalyst. The method comprises the following steps: firstly calcining the waste hydrogenation catalyst at high temperature and then crushing it to obtain a valuable metal recovery material, then subjecting the valuable metal recovery material to a first leaching with an ammonia-ammonium salt solution, subjecting the first solid-liquid separation to obtain a first leaching solution and a first leaching residue, adjusting the pH of the first leaching solution to a molybdenum precipitation value, subjecting the second solid-liquid separation to obtain molybdic acid and a second leaching solution, adding alkali to the second leaching solution to precipitate nickel, subjecting the first leaching residue to an alkali leaching with an ammonia-ammonium salt solution, subjecting the third solid-liquid separation to obtain an alumina residue and a third leaching solution, and adjusting the pH of the third leaching solution to a value for ammonium metavanadate precipitation.

[0007] When the existing technology recovers valuable metals from waste catalysts, it is usually necessary to subject the waste catalysts to high-temperature treatment to remove carbon deposits in the catalysts, which results in high cost and high energy consumption for recovering valuable metals, and is not in line with the concept of low carbon and environmental protection. In addition, the existing technology for recovering valuable metals from waste catalysts is relatively complicated and not easy to industrialize. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a method for recovering molybdic acid from waste catalysts. The molybdic acid recovery process of the method is simple, energy-saving and environmentally friendly.

[0009] The method for recovering molybdic acid from a waste catalyst of the present invention comprises the following contents:

[0010] (1) deoiling the molybdenum-containing waste hydrogenation catalyst to obtain deoiled material A;

[0011] (2) mixing the deoiled material A, ammonium bicarbonate and water uniformly, transferring the mixed material into a pressure-resistant container for hydrothermal treatment, and then performing solid-liquid separation to obtain a molybdenum-containing solution;

[0012] (3) The pH of the molybdenum-containing solution is adjusted to 1-3 with an acid solution to precipitate precipitate B. After washing and removing impurities from precipitate B, molybdic acid is obtained.

[0013] In the method of the present invention, the molybdenum-containing waste hydrogenation catalyst in step (1) refers to a molybdenum-containing catalyst that has failed to meet the reaction requirements. The catalyst may be a Ni-Mo or Co-Mo or Ni-Co-Mo catalyst. The catalyst may be a hydrogenation treatment catalyst such as wax oil and residual oil hydrodemetallization, hydrodesulfurization, denitrogenation, etc., or a gasoline and diesel hydrorefining catalyst. The waste catalyst is generally supported by alumina, and the molybdenum content in the catalyst is 1wt%-30wt% in terms of oxide, preferably 10wt%-25wt%. In addition to the molybdenum element, the waste catalyst may also contain Group VIII metals such as nickel, cobalt, etc., with a nickel and / or cobalt content of 1wt%-10wt% in terms of oxide, a carbon content of 1wt%-15wt% and other impurities.

[0014] In the method of the present invention, the de-oiling treatment described in step (1) is to remove the reaction oil raw material on the surface and in the pores of the waste catalyst, which can be treated by high-temperature nitrogen extraction or organic solvent extraction until there is no raw material oil on the surface and inside of the waste catalyst. When an organic solvent extraction treatment is used, the material is dried after the extraction treatment, which can be natural air drying at room temperature or drying in a blast oven, with a drying temperature of 80-120°C and a drying time of 4-10 hours, until the organic solvent in the material is completely volatilized.

[0015] In the method of the present invention, the de-oiled material A in step (2) can be the original form of the catalyst such as a clover-shaped, spherical, cylindrical strip, etc. The de-oiled material A is preferably crushed to a mesh size of 40 or more, more preferably 60 or more.

[0016] In the method of the present invention, the mass ratio of the ammonium bicarbonate to the de-oiled material A in step (2) is 4:1-8:1; the mass ratio of water to the sum of ammonium bicarbonate and material A is 2:1-4:1. The de-oiled material A, ammonium bicarbonate and water can be added and mixed in any order, and the mixing temperature is generally room temperature. In order to further facilitate the dissolution of ammonium bicarbonate in water, the temperature can be appropriately increased, but this operation is not necessary.

[0017] In the method of the present invention, in step (2), the mixture of ammonium bicarbonate, deoiled material A and water is preferably subjected to ultrasonic treatment before being transferred into an autoclave for hydrothermal treatment. The ultrasonic frequency is 20-40 kHz and the ultrasonic time is 0.5-3 hours.

[0018] In the method of the present invention, the hydrothermal treatment temperature in step (2) is 120-200° C., preferably 140-180° C., and the treatment time is 6-24 hours, preferably 10-18 hours. The pressure-resistant container is generally a high-pressure reactor.

[0019] In the method of the present invention, the solid-liquid separation method in step (2) can be filtration, centrifugation, etc.

[0020] In the method of the present invention, the acid solution in step (3) is nitric acid or sulfuric acid.

[0021] When the method of the present invention recovers the molybdenum metal from the waste catalyst, it is not necessary to carry out carbonization treatment on the waste catalyst. Compared with the previous method, the process flow is simplified and the cost of recovering valuable metals is reduced. The raw materials selected in the activation process are relatively cheap and the treatment process is simple, which is very easy to promote and apply in the recycling of waste catalysts. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with embodiments, but is not limited to the following embodiments.

[0023] Molybdenum recovery rate = (0.89 × m1) ÷ (m2 × c%), where m1: mass of molybdic acid, m2: mass of waste catalyst added during hydrothermal treatment, c%: mass percentage of molybdenum oxide in the waste catalyst.

[0024] XRF characterization: The sample composition was analyzed using a Rigaku ZSX100e X-ray fluorescence spectrometer. The target material was Rh. The optical path atmosphere was vacuum conditions.

[0025] The waste catalyst used in the embodiment is a waste catalyst from a fixed bed residue oil hydrogenation industrial device. After the oil in the catalyst is removed by extraction, the de-oiled material A contains MoO3: 22.3wt%, NiO: 7.9wt%, V2O5: 4.2wt%, Fe2O3: 0.6wt%, Al2O3: 53.4wt%, and C: 8.3wt%. Ammonium bicarbonate, analytical grade, is produced by Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0026] Example 1

[0027] (1) Crush the deoiled material A and sieve it to a size of 60 mesh or above.

[0028] (2) Weigh 100 grams of the above powder and 550 grams of ammonium bicarbonate, add 1900 grams of distilled water to the above materials and stir for 20 minutes. Then transfer the mixed material to an ultrasonic cleaner for ultrasonic treatment at an ultrasonic frequency of 25 kHz and an ultrasonic time of 1.2 hours. Transfer the mixed material after ultrasonic treatment to an autoclave and heat it to 155°C for hydrothermal treatment for 16 hours. After the hydrothermal treatment, the material is filtered to obtain a molybdenum-containing solution;

[0029] (3) Add concentrated nitric acid solution to the molybdenum-containing solution obtained in step (2), control the pH value of the solution to 1.3 to precipitate, wash and remove impurities from the precipitate, and determine by XRD that the precipitate is molybdic acid. The recovery rate of molybdenum in the waste catalyst is calculated to be 75.3%.

[0030] Example 2

[0031] The same as Example 1, except that the amount of ammonium bicarbonate added was 645 g, the ultrasonic frequency was 35 kHz, the ultrasonic time was 1 hour, the hydrothermal treatment temperature was 165° C., the treatment time was 14.5 hours, the concentrated nitric acid was changed to concentrated sulfuric acid, the pH value of the solution was controlled to be 1.8, and the recovery rate of molybdenum in the waste catalyst was calculated to be 77.9%.

[0032] Example 3

[0033] The same as Example 1, except that the amount of ammonium bicarbonate added was 730 g, the ultrasonic frequency was 30 kHz, the ultrasonic time was 1.5 hours, the hydrothermal treatment temperature was 175° C., the treatment time was 12 hours, and the recovery rate of molybdenum in the waste catalyst was calculated to be 79.4%.

[0034] Example 4

[0035] The same as Example 1, except that the amount of ammonium bicarbonate added was 450 g, the ultrasonic frequency was 30 kHz, the ultrasonic time was 1.3 hours, the hydrothermal treatment temperature was 145° C., the treatment time was 18 hours, the pH value of the solution was controlled to be 1.7, and the recovery rate of molybdenum in the waste catalyst was calculated to be 71.8%.

[0036] Example 5

[0037] The same as Example 1, except that the mixed material was not subjected to ultrasonic treatment, the recovery rate of molybdenum in the spent catalyst was calculated to be 63.2%.

[0038] Example 6

[0039] The same as Example 1, except that the de-oiled material A was subjected to roasting and decarbonization treatment, the roasting temperature was 500° C., the roasting time was 6 hours, and the recovery rate of molybdenum in the waste catalyst was calculated to be 90.3%.

[0040] Comparative Example 1

[0041] The same as Example 1, except that the amount of ammonium bicarbonate added in step (2) is 150 g, and the recovery rate of molybdenum in the waste catalyst is calculated to be 8.3%.

[0042] Comparative Example 2

[0043] The same as Example 1, except that the hydrothermal treatment temperature in step (2) is 100°C, the recovery rate of molybdenum in the waste catalyst is calculated to be 20.4%.

[0044] Comparative Example 3

[0045] The same as Example 1, except that the hydrothermal time in step (2) was 5 hours, the recovery rate of molybdenum in the waste catalyst was calculated to be 28.7%.

Claims

1. A method for recovering molybdic acid from a waste catalyst, characterized in that The method comprises the following contents: (1) de-oiling a molybdenum-containing waste hydrogenation catalyst to obtain a de-oiled material A; (2) uniformly mixing the de-oiled material A, ammonium bicarbonate and water, transferring the mixed material into a pressure-resistant container for hydrothermal treatment, and then performing solid-liquid separation to obtain a molybdenum-containing solution; (3) adjusting the pH value of the molybdenum-containing solution with an acid solution to precipitate a precipitate B, and washing and removing impurities from the precipitate B to obtain molybdic acid; The mass ratio of the ammonium bicarbonate to the de-oiled material A in step (2) is 4:1-8:1; the mass ratio of the water to the sum of the ammonium bicarbonate and the de-oiled material A in step (2) is 2:1-4:1; The hydrothermal treatment temperature in step (2) is 120-200°C and the treatment time is 6-24 hours; The molybdenum-containing spent hydrogenation catalyst in step (1) comprises an alumina carrier, and the molybdenum content in the catalyst is 1wt%-30wt% in terms of oxide.

2. The method according to claim 1, characterized in that: The de-oiling treatment in step (1) is to remove the reaction oil raw material from the surface and pores of the waste catalyst by high-temperature nitrogen extraction treatment or organic solvent extraction treatment until there is no raw material oil on the surface and inside of the waste catalyst.

3. The method according to claim 1, characterized in that: The de-oiled material A described in step (2) is crushed to a mesh size of 40 or more.

4. The method according to claim 3, characterized in that: The de-oiled material A in step (2) is crushed to a mesh size of 60 or more.

5. The method according to claim 2, characterized in that: Step (2) The mixture of ammonium bicarbonate, deoiled material A and water is subjected to ultrasonic treatment before being transferred into an autoclave for hydrothermal treatment. The ultrasonic frequency is 20-40 kHz and the ultrasonic time is 0.5-3 hours.

6. The method according to claim 1, characterized in that: The hydrothermal treatment temperature in step (2) is 140-180° C., and the treatment time is 10-18 hours.

7. The method according to claim 1, characterized in that: The acid solution in step (3) is nitric acid or sulfuric acid; the pH is adjusted to 1-3.