A method for preparing a vocs adsorbent from catalytic cracking spent catalyst

Abstract

A method for preparing a VOCs adsorbent from catalytic cracking waste catalysts, comprising the following steps: 1) mixing the waste catalysts with a demetallizing agent, calcining, stirring and dissolving, filtering the slurry, washing and drying the filter cake to obtain a first demetallized sample; 2) uniformly mixing the sample with a demetallizing agent, calcining, mixing with a dilute acid solution, stirring, and then filtering, washing and drying to obtain a second demetallized sample; 3) treating the sample under high-temperature steam conditions, dissolving the treated sample in an acid solution, stirring, filtering, washing and drying to obtain enriched molecular sieves; 4) mixing the enriched molecular sieves, tetrapropylammonium hydroxide and silica sol, adjusting the pH for hydrothermal crystallization, and then filtering, washing, drying and calcining to obtain modified molecular sieves; and 5) mixing the modified molecular sieves with an additive, shaping, and preparing a VOCs adsorbent. The present application has the advantages of simple and smooth operation, a substantial reduction in waste liquid volume, low processing cost, and good environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of solid waste, specifically to a method for preparing VOCs adsorbent from catalytic cracking waste catalyst. Background Technology

[0002] Preparing VOCs adsorbents from spent catalytic cracking catalysts requires the removal of deposited metals such as iron and nickel, matrix alumina, and non-framework and framework aluminum from the molecular sieve. Removal of deposited metals like iron and nickel effectively restores the rich pore structure of the spent catalyst, thereby improving its adsorption performance. Residual aluminum causes the spent catalyst to retain high hygroscopic and acidic properties due to the presence of polar aluminum. The hygroscopic properties of the spent catalyst compete with VOCs for adsorption, while the residual acidic properties cause carbon deposition during VOCs desorption from the molecular sieve surface, affecting the adsorption-desorption recycling performance of the adsorbent.

[0003] CN113731512A discloses a method for the demetallization, reactivation, and reuse of spent hydrocarbon catalytic cracking catalysts, which includes the following steps:

[0004] (1) The spent catalyst was subjected to high-temperature roasting and decarbonization treatment in an air / oxygen atmosphere, and then mixed evenly with the separating agent and roasted.

[0005] (2) The calcined catalyst is hydrothermally dissolved in deionized water at a certain temperature, and then solid-liquid separation is performed.

[0006] (3) The obtained solid phase was washed until neutral and dried, and then calcined to obtain a demetallized catalyst. The filtrate was used to extract and recover rare earth metals.

[0007] (4) The demetallized catalyst obtained in step (3) is demetallized using a segmented roasting method, and the obtained demetallized catalyst is elementally modified to obtain a demetallized revitalized catalyst. This invention achieves the removal of deposited metals and part of the alumina matrix from the spent catalyst of catalytic cracking through roasting with a separating agent, thereby realizing the revitalization and regeneration of the spent catalyst. However, roasting with a separating agent alone cannot completely remove the alumina matrix, especially the non-framework aluminum and framework aluminum of molecular sieves, from the spent catalyst, and cannot realize the preparation of VOCs adsorbent from spent catalyst of catalytic cracking.

[0008] Apart from the aforementioned applications concerning the resource utilization of spent catalysts from catalytic cracking, there are currently very few reports on related catalyst recycling technologies.

[0009] In existing technologies, waste catalysts from heavy hydrocarbon catalytic cracking rich in ZSM-5 molecular sieves are often rendered harmless and then landfilled. This simplistic and crude treatment method results in a huge waste of resources and environmental pressure. Meanwhile, because VOCs adsorbents require high silica-to-alumina ratios, simply using acid treatment or roasting of extractants cannot effectively remove various forms of aluminum from waste catalytic cracking catalysts. Summary of the Invention

[0010] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing VOCs adsorbent from catalytic cracking waste catalyst. This method has the characteristics of simple and stable preparation process, significant reduction of waste liquid volume, low treatment cost, and good environmental benefits.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A method for preparing VOCs adsorbent from catalytic cracking waste catalyst includes the following steps;

[0013] 1) The waste catalyst was carbonized at 550-700℃ in air atmosphere. After carbonization, the sample was mixed with the demetallizing agent and roasted at 300-600℃ for 2-6 hours. After roasting, the mixture was stirred and dissolved in water at 60-90℃. The slurry was filtered, and the filter cake was washed until neutral and then dried to obtain the first demetallized sample.

[0014] 2) The first demetallized sample is uniformly mixed with the demetallizing agent and calcined at 300-600°C for 2-6 hours. The calcined solid powder is then thoroughly mixed with a dilute acid solution and stirred at 60-90°C for 2 hours to dissolve the powder. The second demetallized sample is then obtained by filtration, washing, and drying.

[0015] 3) The second demetallized sample was treated under high temperature steam conditions. After treatment, the sample was dissolved in an acid solution and stirred for 6-8 hours. Then, it was filtered, washed, and dried to obtain the enriched molecular sieve.

[0016] 4) The enriched molecular sieve, tetrapropylammonium hydroxide and silica sol are mixed, the pH is adjusted and hydrothermal crystallization is carried out. The crystallized product is filtered, washed, dried and calcined to obtain the modified molecular sieve.

[0017] 5) The modified molecular sieve and additives are mixed evenly and then molded to finally prepare the VOCs adsorbent.

[0018] The spent catalysts include, but are not limited to, spent catalysts from light hydrocarbon catalytic cracking, spent catalysts from heavy hydrocarbon catalytic cracking, and spent catalysts containing ZSM-5 molecular sieves in other application fields.

[0019] To define the scope of recycling spent catalysts, this applies to spent catalysts containing ZSM-5 type molecular sieves.

[0020] The demetallizing agent in steps 1) and 2) includes one or a mixture of several ammonium salts selected from ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium chloride, and ammonium acetate.

[0021] In step 1), the mass ratio of the demetallizing agent to the spent catalyst is 1.0 to 3.0.

[0022] In step 2), the mass ratio of the demetallizing agent to the spent catalyst is between 0.2 and 1.5.

[0023] The dilute acid solution in step 2) is a mixture of organic and inorganic acids, wherein the organic acids include one or more of citric acid and oxalic acid, and the inorganic acids include one or more of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid. The concentration of the dilute acid solution is 0.001 to 1.0 mol / L, and the volume ratio of solid powder to dilute acid solution is 1:(5 to 15).

[0024] Based on the original step (1) to remove some of the deposited metal and alumina matrix, a secondary treatment using acid is carried out to completely remove the deposited metal and alumina matrix from the waste catalyst. The standard for parameter selection is to mix a large volume of low-concentration dilute acid with the first metal sample to prevent the acid from being too strong and causing damage to the pore structure.

[0025] The high-temperature hydrothermal treatment in step 3) involves a temperature of 500–900°C, a water vapor content of ≤10%, and a treatment time of 8–24 hours. The purpose of high-temperature hydrothermal treatment is to remove framework and non-framework aluminum within the MFI molecular sieve, building upon the existing removal of deposited metals and alumina matrix. High-temperature hydrothermal treatment is essentially a pretreatment process; therefore, using a lower concentration of hydrothermal gas is also to prevent the collapse of the molecular sieve pore structure due to excessively high water vapor content and treatment temperature.

[0026] The acid solution in step 3) is one or more of fluorosilicic acid, ammonium fluorosilicate, fluoroboric acid and ammonium fluoroborate; the concentration is 0.001 to 1.0 mol / L.

[0027] In step 4), the mass ratio of silica sol (calculated as SiO2) to enriched molecular sieve is (5-20):(80-95); the molar ratio of silica sol (calculated as SiO2) to tetrapropylammonium hydroxide is 5:(0.5-5).

[0028] In step 4), the pH is adjusted to 9-12, and hydrothermal crystallization is carried out at 170℃ for 8-24 hours.

[0029] The additive in step 5) is one or more of alumina sol, silica sol, kaolin, and boehmite, and the proportion of the additive is 10% to 30% of the mass of the VOCs adsorbent.

[0030] The beneficial effects of this invention are:

[0031] (1) This invention utilizes a technical route of “multi-step dealumination and small-dose silicon replenishment” to sequentially remove matrix alumina, non-framework aluminum of molecular sieve and framework aluminum, thereby increasing the overall silicon-aluminum ratio of the waste catalyst and realizing the enrichment and recycling of ZSM-5 molecular sieve in the catalytic cracking waste catalyst. This technical route effectively improves the efficiency of aluminum removal from the waste catalyst and reduces the amount of acid waste liquid used in the acid-base treatment of the waste catalyst. It has the advantages of safety, environmental protection and green economy.

[0032] (2) The ZSM-5 molecular sieve recovered by the method of the present invention has excellent adsorption performance and low price. Using it as a VOCs adsorbent in the original preparation for VOCs treatment can effectively reduce the cost of VOCs adsorbents, promote the development of VOCs treatment, and have good environmental benefits. Attached image description:

[0033] Figure 1 The XRD pattern of the molecular sieve after enrichment in Example 2 of this invention is shown.

[0034] Figure 2 The nitrogen adsorption-desorption curve of the molecular sieve after enrichment in Example 2 of this invention is shown.

[0035] Figure 3 This is a comparison chart of the toluene adsorption performance of Example 2 and Comparative Example 1 of the present invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings.

[0037] Example 1

[0038] 1) The waste catalyst of heavy hydrocarbon catalytic cracking was carbonized at 700℃ in air atmosphere. Ammonium carbonate and the carbonized sample were mixed at 500℃ and roasted for 6 hours at a mass ratio of 1:1. After roasting, the mixture was stirred and dissolved in water at 80℃ for 2 hours. The slurry was filtered, and the filter cake was washed until neutral and then dried to obtain the first demetallized sample.

[0039] 2) Mix ammonium carbonate and the first demetallized sample uniformly at a mass ratio of 0.5:1, calcine at 500℃ for 4 hours, mix the calcined solid powder with 0.2mol / L dilute nitric acid at a ratio of 1:5, stir and dissolve at 70℃ for 2 hours, and then obtain the second demetallized sample by filtration, washing and drying.

[0040] 3) The second demetallized sample was treated with 10% water vapor at 700 degrees Celsius for 12 hours. The treated sample was then dissolved in 0.001 mol / L fluorosilicic acid and stirred for 8 hours. The sample was then filtered, washed, and dried to obtain the enriched molecular sieve.

[0041] 4) The enriched molecular sieve was mixed with tetrapropylammonium hydroxide and silica sol, and the pH was adjusted to 11. The mass ratio of silica sol (calculated as SiO2) to enriched molecular sieve was 10:90, and the molar ratio of silica sol (calculated as SiO2) to tetrapropylammonium hydroxide was 5:1. Hydrothermal crystallization was carried out at 170℃ for 18h. The crystallized product was filtered, washed, dried and calcined to obtain the modified molecular sieve.

[0042] 5) The modified molecular sieve and silica sol are mixed evenly and molded according to the proportion of silica sol of 30% to finally prepare VOCs adsorbent.

[0043] Example 2

[0044] 1) The waste catalyst of heavy hydrocarbon catalytic cracking was carbonized at 600℃ in air atmosphere. Ammonium acetate and the carbonized sample were mixed and roasted at 400℃ for 6 hours at a mass ratio of 2:1. After roasting, the mixture was stirred and dissolved in water at 70℃ for 2 hours. The slurry was filtered, and the filter cake was washed until neutral and then dried to obtain the first demetallized sample.

[0045] 2) Mix ammonium acetate and the first demetallized sample at a mass ratio of 0.3:1 and calcine at 400℃ for 4 hours. Mix the calcined solid powder with 0.1mol / L dilute hydrochloric acid at a ratio of 1:10 and stir at 85℃ for 2 hours to dissolve. Then, obtain the second demetallized sample by filtration, washing and drying.

[0046] 3) The second demetallized sample was treated with 5% water vapor at 600 degrees Celsius for 18 hours. The treated sample was dissolved and stirred in 0.01 mol / L fluoroboric acid for 6 hours. Then it was filtered, washed and dried to obtain the enriched molecular sieve.

[0047] 4) The enriched molecular sieve, tetrapropylammonium hydroxide and silica sol were mixed and the pH was adjusted to 12. The mass ratio of silica sol (as SiO2) to enriched molecular sieve was 15:85 and the molar ratio of silica sol (as SiO2) to tetrapropylammonium hydroxide was 2:1. Hydrothermal crystallization was carried out at 170℃ for 24h. The crystallized product was filtered, washed, dried and calcined to obtain the modified molecular sieve.

[0048] 5) The modified molecular sieve and silica sol are mixed evenly and molded according to the proportion of silica sol of 20% to finally prepare VOCs adsorbent.

[0049] Example 3

[0050] 1) The waste catalyst of heavy hydrocarbon catalytic cracking was carbonized at 650℃ in air atmosphere. Ammonium sulfate and the carbonized sample were mixed at 500℃ and roasted for 4 hours at a mass ratio of 1:1. After roasting, the mixture was stirred and dissolved in water at 90℃ for 2 hours. The slurry was filtered, and the filter cake was washed until neutral and dried to obtain the first demetallized sample.

[0051] 2) Mix ammonium acetate and the first demetallized sample at a mass ratio of 0.8:1 and calcine at 500℃ for 4 hours. Mix the calcined solid powder with 0.1mol / L dilute nitric acid at a ratio of 1:10 and stir at 85℃ for 2 hours to dissolve. Then, obtain the second demetallized sample by filtration, washing and drying.

[0052] 3) The second demetallization sample was treated with 10% water vapor at 600 degrees Celsius for 24 hours. The treated sample was dissolved in a 0.03 mol / L mixed solution of fluorosilicic acid and ammonium fluorosilicate and stirred for 6 hours. Then, it was filtered, washed and dried to obtain the enriched molecular sieve.

[0053] 4) The enriched molecular sieve, tetrapropylammonium hydroxide and silica sol were mixed. The mass ratio of silica sol (calculated as SiO2) to modified molecular sieve was 20:80 and the molar ratio of silica sol (calculated as SiO2) to tetrapropylammonium hydroxide was 1:1. The mixture was subjected to hydrothermal crystallization at 170℃ for 18h. The crystallized product was filtered, washed, dried and calcined to obtain the modified molecular sieve.

[0054] 5) The modified molecular sieve and silica sol are mixed evenly and molded according to the proportion of silica sol of 25% to finally prepare VOCs adsorbent.

[0055] Comparative Example 1

[0056] Commercially available ZSM-5 molecular sieves are produced by the catalyst factory of Nankai University. Aluminum sol is added at a mass ratio of 10% and mixed and molded to prepare VOCs adsorbents.

[0057] Specific implementation effects

[0058] Depend on Figure 1 As shown, compared with the waste catalyst from heavy hydrocarbon catalytic cracking, the crystallinity of ZSM-5 in Example 2 increased by 160%, indicating that the waste catalyst treated by this patented technology effectively enriched the ZSM-5 molecular sieve. Figure 2 As shown in Table 1, the pore structure of the samples modified with molecular sieves was effectively restored, providing an effective guarantee for their adsorption of VOCs.

[0059] Table 1. Pore structure data of the modified molecular sieve

[0060] Sample Information <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Aperture (nm) Waste catalyst 129 0.152 4.72 Modified molecular sieve in Example 1 298 0.328 4.94 Modified molecular sieve in Example 2 312 0.352 5.03 Modified molecular sieve in Example 3 309 0.358 5.02

[0061] As shown in Table 2, compared with the waste catalyst of heavy hydrocarbon catalytic cracking, the deposited metal and alumina matrix of the sample in the example were effectively removed, and the removal rate of aluminum reached more than 95%, effectively removing various metal components.

[0062] Table 2 Elemental composition data of the modified molecular sieves

[0063] sample DCC waste catalyst Example 1 Example 2 Example 3 V 0.062 0.008 0.002 0.005 Ti 0.058 0.044 0.022 0.014 Si 22.42 41.99 43.771 44.013 S 0.174 1.250 1.026 0.783 P 1.60 0.517 0.304 0.264 O 49.8 53.09 53.33 54.00 Ni 0.263 0.011 0.009 0.006 K 0.187 0.026 0.008 0.003 Fe 0.899 0.110 0.052 0.011 Ce 0.209 0.031 0.012 0.004 Ca 0.151 0.014 0.008 0.007 Al 23.81 2.900 1.007 0.858

[0064] The VOCs adsorbents prepared in Examples 1, 2, 3, and the comparative examples were subjected to toluene adsorption experiments. The toluene adsorption results (e.g.) were obtained through toluene adsorption experiments. Figure 3 The adsorbents prepared from the solid enriched by molecular sieves have similar totoluene adsorption capacities to those prepared from commercial molecular sieves, especially the toluene adsorption performance of Examples 2 and 3, which is better than that of Comparative Example 1.

Claims

1. A method for preparing VOCs adsorbent from catalytic cracking waste catalyst, characterized in that, Includes the following steps; 1) The waste catalyst was carbonized at 550~700℃ in air atmosphere. After carbonization, the sample and the demetallizing agent were mixed and roasted at 300~600℃ for 2~6h. After roasting, the mixture was stirred and dissolved in water at 60~90℃. The slurry was filtered, and the filter cake was washed until neutral and then dried to obtain the first demetallized sample. 2) The first demetallized sample is uniformly mixed with the demetallizing agent and calcined at 300~600℃ for 2~6h. The calcined solid powder is thoroughly mixed with dilute acid solution and stirred at 60~90℃ to dissolve. Then, the second demetallized sample is obtained by filtration, washing and drying. 3) The second demetallized sample was treated under high temperature steam conditions. After treatment, the sample was dissolved in an acid solution and stirred for 6-8 hours. Then, it was filtered, washed, and dried to obtain the enriched molecular sieve. The acid solution in step 3) is one or more of fluorosilicic acid, ammonium fluorosilicate, fluoroboric acid, and ammonium fluoroborate; 4) The enriched molecular sieve, tetrapropylammonium hydroxide and silica sol are mixed, the pH is adjusted and hydrothermal crystallization is carried out. The crystallized product is filtered, washed, dried and calcined to obtain the modified molecular sieve. 5) The modified molecular sieve and additives are mixed evenly and then molded to finally prepare the VOCs adsorbent. The demetallizing agent in steps 1) and 2) includes one or a mixture of several ammonium salts selected from ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonium chloride, and ammonium acetate. In step 1), the mass ratio of the demetallizing agent to the spent catalyst is 1.0 to 3.

0. In step 4), the mass ratio of silica sol (based on SiO2) to enriched molecular sieve is (5~20):(80~95); the molar ratio of silica sol (based on SiO2) to tetrapropylammonium hydroxide is 5:(0.5~5). In step 4), the pH is adjusted to 9-12, and hydrothermal crystallization is carried out at 170℃ for 8-24 hours. The spent catalyst is a molecular sieve spent catalyst containing ZSM-5.

2. The method for preparing VOCs adsorbent from catalytic cracking waste catalyst according to claim 1, characterized in that, In step 2), the mass ratio of the demetallizing agent to the waste catalyst is 0.2 to 1.

5.

3. The method for preparing VOCs adsorbent from catalytic cracking waste catalyst according to claim 1, characterized in that, The dilute acid solution in step 2) is a mixture of organic and inorganic acids, wherein the organic acids include one or more of citric acid and oxalic acid, and the inorganic acids include one or more of nitric acid, sulfuric acid, hydrochloric acid and phosphoric acid. The concentration of the dilute acid solution is 0.001~1.0 mol / L, and the volume ratio of solid powder to dilute acid solution is 1:(5~15).

4. The method for preparing VOCs adsorbent from catalytic cracking waste catalyst according to claim 1, characterized in that, The high-temperature steam treatment in step 3) is performed at a temperature of 500~900℃, with a steam content of ≤10%, and a treatment time of 8~24h.

5. The method for preparing VOCs adsorbent from catalytic cracking waste catalyst according to claim 1, characterized in that, The concentration of the acid solution in step 3) is 0.001~1.0 mol / L.

6. The method for preparing VOCs adsorbent from catalytic cracking waste catalyst according to claim 1, characterized in that, The additive in step 5) is one or more of alumina sol, silica sol, kaolin, and boehmite, and the proportion of the additive is 10% to 30% of the mass of the VOCs adsorbent.

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