A method for preparing solid phosphoric acid using lithium slag

Abstract

The invention discloses a method for preparing solid phosphoric acid by using lithium slag. The method comprises the following steps: S1, reacting lithium slag and sodium hydroxide solution in an environment of 60-80 DEG C for 48-96 hours, filtering and collecting filtrate; S2, adding hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose to the filtrate, adjusting the pH value of the solution to 7-9, filtering and obtaining hydroxypropyl methylcellulose / silicic acid hydrogel; S3, placing the hydrogel in an environment of 100-200 DEG C for drying for 4-24 hours, and then calcining at 350-550 DEG C for 10-12 hours under an anaerobic condition, washing and drying the calcined residue to obtain a C / SiO2 composite material; S4, placing the C / SiO2 composite material in an environment of 100-300 DEG C for drying for 4-24 hours; adding the dried C / SiO2 composite material to an excess phosphoric acid solution, stirring evenly and standing for 12-24 hours, filtering to remove excess phosphoric acid, and calcining at 350-650 DEG C for 12-60 hours under an aerobic environment to obtain solid phosphoric acid. The preparation method of the invention not only realizes the recycling and reuse of lithium slag, but also reduces the preparation cost of solid phosphoric acid.

Description

Technical Field

[0001] The invention relates to the technical field of solid phosphoric acid preparation, in particular to a method for preparing solid phosphoric acid by using lithium slag as a raw material. Background Art

[0002] Solid phosphoric acid is usually prepared by heat treatment of a mixture of phosphoric acid and diatomite, and is an important catalyst for ethylene hydration reaction, benzene and propylene alkylation to produce cumene. Diatomite is a sediment of diatom shells, mainly composed of amorphous silicon dioxide. Since the content of amorphous silicon dioxide in different diatomite is quite different, and the purity of silicon dioxide is not enough, the use effect of solid phosphoric acid is affected. The ideal carrier for loading solid phosphoric acid is a synthetic high-specific surface, high-purity amorphous silicon dioxide. Currently, the commonly used synthetic high-purity silicon dioxide is produced by using organosilicon (such as silicon tetrachloride) and methyltrichlorosilane as raw materials, and using gas phase method (white carbon black), sol-gel method, precipitation method and microemulsion method. The raw material cost is high, and the production environment and equipment requirements are high, which limits the application in the preparation of solid phosphoric acid.

[0003] Spodumene is the raw material for producing lithium carbonate. In the process of preparing lithium carbonate, it needs to be calcined at 1200℃ to convert α-type into β-type spodumene, and then various processes will be used to obtain lithium carbonate products. In this process, about 90% slag is produced. According to research and testing, the main component of lithium slag is amorphous silicon dioxide. If the raw material for preparing high-purity amorphous silicon dioxide is changed from expensive organosilicon to waste lithium slag, the production cost can be greatly reduced, and the high-value utilization of lithium slag can be achieved, solving the problem of difficult lithium slag treatment. Therefore, it is worth studying the preparation of high-purity amorphous silicon dioxide with lithium slag for the production of solid phosphoric acid. Summary of the invention

[0004] In order to solve the high cost problem of the existing high-purity amorphous silicon dioxide preparation method and the problem of difficult lithium slag treatment, the present invention provides a method for preparing solid phosphoric acid using lithium slag as a raw material, which not only realizes the recycling and reuse of lithium slag, but also reduces the preparation cost of high-purity amorphous silicon dioxide, thereby reducing the preparation cost of solid phosphoric acid.

[0005] The method for preparing solid phosphoric acid using lithium slag as a raw material provided by the present invention comprises the following steps:

[0006] S1. React lithium slag and sodium hydroxide solution in an environment of 60-80°C for 48-96h, filter after the reaction, and collect the filtrate. The mass ratio of sodium hydroxide to lithium slag is 1:4-6.

[0007] S2, add hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose to the filtrate, then adjust the pH of the solution to 7-9 with dilute hydrochloric acid, filter, and obtain hydroxypropyl methylcellulose / silicic acid hydrogel. Wherein, the mass ratio of hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose to lithium slag is controlled to be 1:4-6. The role of hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose is to mix evenly with silicic acid and form a hydrogel with silicic acid.

[0008] S3, drying the hydroxypropyl methylcellulose / silicic acid hydrogel at 100-200°C for 4-24h, and then calcining at 350-550°C for 10-12h under anaerobic conditions, and repeatedly washing the calcined residue with chloroform and deionized water, and drying to obtain a nano-scale C / SiO2 composite material. The specific surface area of ​​the composite material is 100-300m 2 / g. The contents of C and SiO2 in the composite material are between 92.15% and 96.58%.

[0009] S4. Place the C / SiO2 composite material in an environment of 100-300°C and dry it for 4-24h; then add the dried C / SiO2 composite material to an excess of phosphoric acid solution, stir it evenly and let it stand for 12-24h, filter out excess phosphoric acid, and calcine it at 350-650°C for 12-60h in an aerobic environment (air is introduced during calcination) to obtain solid phosphoric acid.

[0010] Preferably, in step S4, the content of phosphoric acid in the phosphoric acid solution is 85%. The weight of phosphoric acid added to the phosphoric acid solution is more than 4 times the weight of the C / SiO2 composite material.

[0011] Preferably, in step S4, the calcination temperature is 550-650° C., and the calcination time is 36-48 hours.

[0012] Compared with the prior art, the present invention is beneficial in that:

[0013] (1) The method for preparing solid phosphoric acid of the present invention uses lithium slag as raw material, and lithium slag is waste generated in the process of producing lithium carbonate. The present invention realizes the recycling and reuse of lithium slag, and solves the problem of difficult treatment of lithium slag.

[0014] (2) Since lithium slag is used as a raw material, the method for preparing solid phosphoric acid of the present invention reduces the preparation cost of amorphous silicon dioxide, thereby reducing the preparation cost of solid phosphoric acid.

[0015] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 , XRD comparison diagram of solid phosphoric acid prepared in Example 1 and Comparative Example. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0018] Example 1

[0019] A method for preparing solid phosphoric acid using lithium slag as a raw material, the steps are as follows:

[0020] (1) adding a solution containing 10 g of sodium hydroxide to 50 g of lithium slag, reacting at 70° C. for 48 h, filtering after the reaction is complete, and collecting the filtrate;

[0021] (2) 40 g of hydroxypropyl methylcellulose was added to the filtrate, and then the pH of the solution was adjusted to 7 with dilute hydrochloric acid, and filtered to obtain hydroxypropyl methylcellulose / silicic acid hydrogel.

[0022] (3) The obtained hydroxypropyl methylcellulose / silicic acid hydrogel was first placed in an environment at 150°C for 12 hours and then calcined in an oxygen-free muffle furnace at a temperature of 350°C for 12 hours. The calcined residue was repeatedly washed with chloroform and deionized water and dried to obtain 23.54 g of C / SiO2 composite material, which is a nano-scale composite material. The specific surface area of ​​the composite material is 152.42 m 2 / g, C and SiO2 contents are 94.26%.

[0023] (4) Preparation of solid phosphoric acid: 10 g of C / SiO2 composite material was placed in an environment of 120°C and dried for 12 h. The dried C / SiO2 composite material was then added to an excess amount of phosphoric acid solution, stirred evenly, and allowed to stand for 24 h. The excess phosphoric acid was filtered out, and the filter residue was heated and calcined at 650°C for 48 h. The calcined product was crushed in a mortar to obtain 25.12 g of solid phosphoric acid, which was then placed in a dryer and sealed for storage.

[0024] Example 2

[0025] A method for preparing solid phosphoric acid using lithium slag as a raw material, the steps are as follows:

[0026] (1) adding a solution containing 10 g of sodium hydroxide to 40 g of lithium slag, reacting at 60° C. for 48 h, filtering after the reaction is complete, and collecting the filtrate;

[0027] (2) Add 50 g of sodium hydroxypropyl methylcellulose to the filtrate, then adjust the pH of the solution to 8 with dilute hydrochloric acid, and filter to obtain hydroxypropyl methylcellulose / silicic acid hydrogel.

[0028] (3) The obtained hydroxypropyl methylcellulose / silicic acid hydrogel was first placed in an environment at 200°C for 12 hours, and then calcined in an oxygen-free muffle furnace at a temperature of 450°C for 12 hours. The calcined residue was repeatedly washed with chloroform and deionized water, and dried to obtain 21.64 g of C / SiO2 composite material with a specific surface area of ​​182.23 m 2 / g, C and SiO2 content is 95.34%.

[0029] (4) Preparation of solid phosphoric acid: 10 g of C / SiO2 composite material was placed in an environment of 150°C and dried for 12 h. The dried C / SiO2 composite material was then added to an excess amount of phosphoric acid solution, stirred evenly, and allowed to stand for 24 h. Excess phosphoric acid was removed by filtration. The filter residue was heated and calcined at 550°C for 48 h. The calcined product was crushed in a mortar to obtain 24.12 g of solid phosphoric acid, which was then placed in a dryer and sealed for storage.

[0030] Example 3

[0031] A method for preparing solid phosphoric acid using lithium slag as a raw material, the steps are as follows:

[0032] (1) adding a solution containing 10 g of sodium hydroxide to 60 g of lithium slag, reacting at 80° C. for 12 h, filtering after the reaction is complete, and collecting the filtrate;

[0033] (2) Add 60 g of hydroxypropyl methylcellulose to the filtrate, then adjust the pH of the solution to 9 with dilute hydrochloric acid, and filter to obtain hydroxypropyl methylcellulose / silicic acid hydrogel.

[0034] (3) The obtained hydroxypropyl methylcellulose / silicic acid hydrogel was first placed in an environment at 250°C for 12 hours and then calcined in an oxygen-free muffle furnace at a temperature of 550°C for 12 hours. The calcined residue was repeatedly washed with chloroform and deionized water and dried to obtain 20.64 g of C / SiO2 composite material with a specific surface area of ​​235.23 m 2 / g, C and SiO2 contents are 96.28%.

[0035] (4) Preparation of solid phosphoric acid: 10 g of C / SiO2 composite material was placed in an environment of 150°C and dried for 24 h. The dried C / SiO2 composite material was then added to an excess amount of phosphoric acid solution, stirred evenly, and allowed to stand for 24 h. Excess phosphoric acid was removed by filtration. The residue was heated and calcined at 650°C for 36 h. The calcined product was crushed in a mortar to obtain 26.35 g of solid phosphoric acid, which was then placed in a dryer and sealed for storage.

[0036] Comparative Example

[0037] A solid phosphoric acid prepared by using diatomaceous earth, the preparation steps are as follows: 5g of diatomaceous earth and 28.6g of phosphoric acid are evenly mixed, and the mixture is calcined at 573 degrees Celsius for 24 hours to obtain solid phosphoric acid.

[0038] The XRD spectra of the solid phosphoric acid prepared in Example 1 and the comparative example are shown in Figure 1 It can be seen from the XRD graph that the shapes of the spectra of the two solid phosphoric acids are basically the same, which proves that solid phosphoric acid is successfully prepared using lithium slag as a raw material by the method of the present invention.

[0039] The solid phosphoric acid prepared in Example 1 and the comparative example was used to liquefy bamboo chips in a polyol system (PEG400: glycerol = 3: 1), and the experimental conditions of the two solid phosphoric acids were exactly the same. 10g of bamboo chips were added to 80g of a mixed polyol system (PEG400: glycerol = 3: 1), and then 1.5g of a solid phosphoric acid catalyst was added, and liquefied at 170 degrees Celsius for 18 hours. The result obtained was that the solid phosphoric acid with diatomaceous earth as a carrier in Comparative Example 1 had a liquefaction rate of 74.52% for bamboo chips, and the solid phosphoric acid with lithium slag as a raw material in Example 1 had a liquefaction rate of 76.25% for bamboo chips. The catalytic efficiency of the solid phosphoric acid of the present invention is not much different from that of Comparative Example 1, and is even better than that of Comparative Example 1, thus indicating that it is feasible to prepare solid phosphoric acid using lithium slag as a raw material instead of diatomaceous earth.

[0040] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing solid phosphoric acid using lithium slag, characterized in that: Here are the steps: S1, reacting lithium slag and sodium hydroxide solution in an environment of 60-80°C for 48-96h, filtering after the reaction, and collecting the filtrate; S2, adding hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose to the filtrate, then adjusting the pH of the solution to 7-9 with dilute hydrochloric acid, filtering, and obtaining hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose / silicic acid hydrogel; the mass ratio of hydroxypropyl methylcellulose or sodium hydroxypropyl methylcellulose to lithium slag is 1:4-6; S3, drying the hydroxypropyl methylcellulose / silicic acid hydrogel at 100-200° C. for 4-24 h, and then calcining at 350-550° C. for 10-12 h under anaerobic conditions, and repeatedly washing the calcined residue with chloroform and deionized water, and drying to obtain a C / SiO2 composite material; S4. Dry the C / SiO2 composite material in an environment of 100-300°C for 4-24h; then add the dried C / SiO2 composite material into an excess phosphoric acid solution, stir evenly and let stand for 12-24h, filter to remove excess phosphoric acid, and calcine at 350-650°C for 12-60h in an aerobic environment to obtain solid phosphoric acid.

2. The method for preparing solid phosphoric acid using lithium slag according to claim 1, characterized in that: In step S1, the mass ratio of sodium hydroxide to lithium slag is 1:4-6.

3. The method for preparing solid phosphoric acid using lithium slag according to claim 1, characterized in that: In step S4, the content of phosphoric acid in the phosphoric acid solution is 85%.

4. The method for preparing solid phosphoric acid using lithium slag according to claim 3, characterized in that: In step S4, the weight of phosphoric acid in the added phosphoric acid solution is more than 4 times the weight of the C / SiO2 composite material.

5. The method for preparing solid phosphoric acid using lithium slag according to claim 4, characterized in that: In step S4, air is introduced during calcination.

6. The method for preparing solid phosphoric acid using lithium slag according to claim 4, characterized in that: In step S4, the calcination temperature is 550-650° C., and the calcination time is 36-48 hours.

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