Oil shale is an important alternative resource for coal , oil and natural gas . Its resource reserves are huge. If oil shale is converted into shale oil, the world can reach more than 400 billion tons, equivalent to 5.4 reserves of petroleum resources. Times. Therefore, the development of oil shale has important strategic significance. The proven reserves of oil shale in China are 32.789 billion tons, mainly distributed in Huadian, Jin'an, Jilin, Maoming, Fushun, Liaoning, Liaoning Fushun, Liaoning Fushun is also a famous oil shale processing base in China.
Oil shale has important economic value. At present, the main utilization methods of oil shale are refining shale oil, gas production and direct combustion power generation. However, since most of the oil shale is inorganic minerals, a large amount of ash is generated after use. There are major environmental problems with slag and harmful substances. The comprehensive utilization of oil shale solid waste has been studied at home and abroad. For example, white carbon black is prepared from oil shale deoil residue, and oil shale ash is used as adsorbent.
Since the inorganic mineral oil shale mainly of silicon aluminates, the content of SiO 2 and Al 2 O 3 accounts for the majority. Therefore, the extraction of these two valuable elements, the preparation of silica and Al 2 O 3 is a feasible method. A1 2 O 3 is an important industrial raw material that is discarded using high alumina solids.
Matter - Preparation of fly ash, coal gangue and other A1 2 O 3 more, and has entered the stage of industrialization, from Oil Shale Residue Preparation A1 2 O 3 have not been reported. Silica is also known as hydrated silica, rubber, plastic indispensable reinforcing agent, is also an important chemical raw materials, non-metallic mineral in recent years for the study of the process feedstream is quite active. Therefore, oil shale slag is used as raw material. First, A1 2 O 3 is prepared by acid leaching method, and then the residue is prepared by alkali dissolution method. It not only improves the comprehensive utilization degree of oil shale slag, but also solves the problem of environmental pollution and achieves the purpose of ecologically utilizing oil shale resources.
   First, the experiment
(1) Experimental materials and instruments
The oil shale slag is from Fushun shale oil plant. The main composition is shown in Table 1. It can be seen from the table that the content of SiO 2 and A1 2 O 3 in oil shale slag accounts for more than 85%, which belongs to high silicon aluminum solid. Waste.
Table 1 Chemical composition of oil shale slag (mass fraction) /%
SiO 2 | Al 2 O 3 | Fe 2 O 3 | K 2 O | MgO | TiO 2 | Na 2 O | CaO |
64.8 | 20.6 | 8.20 | 1.26 | 1.09 | 0.962 | 0.934 | 0.777 |
The experimental instruments are: PW3040/60 X-ray diffractometer (PANALYTICAL, the Netherlands), S3400 scanning electron microscope (Japan Hitachi), ZXS100e X-ray fluorescence spectrometer (Nippon Science), Nicolet 380 FT-IR spectrometer (USA) TA company), H800 transmission electron microscope (Japan Hitachi).
(two) experimental process
1. Extraction of A1 2 O 3 After crushing the oil shale slag, it is sieved to collect a portion having a particle diameter of less than 0.15 mm. First, 15.0 g of oil shale slag, a certain amount of concentrated hydrochloric acid, and 100 mL of water were placed in a three-necked flask, heated to a set temperature, and reacted at a constant temperature for a certain period of time. Then, it was naturally cooled to 60 ° C to filter, and a filtrate and a cake were obtained. The filtrate was adjusted to pH=5 by dropwise addition of 10 mol/L NaOH solution, and after filtration again, the filter cake was placed in a beaker and dissolved in 30.0 mL of 10.0 mol/L NaOH solution, and the insoluble matter was removed by filtration to obtain pure meta-aluminate. Sodium solution. Finally, the solution was titrated with HCl until pH=8-9, and after standing for a while, it was filtered and washed to obtain Al(OH) 3 , and then fired to 800 °C in a gradient furnace to obtain γ-Al 2 O 3 .
2. Extraction of white carbon black Weigh 10 g of the filter cake after extracting Al 2 O 3 into a three-necked flask, and add 100 mL of water and a certain amount of NaOH solution, start stirring and heat to a set temperature, and keep the reaction for a certain period of time. The Na 2 SiO 3 filtrate was obtained by filtration. After the filtrate was allowed to stand for a certain period of time, HCl was slowly added dropwise to acidify, and the pH was stopped at 8 to 9 to obtain a white precipitate. After filtration and drying, a white carbon black product was obtained.
   Second, the results and discussion
(1) Oil shale slag extraction alumina experimental part
1. Effect of calcination activation on the extraction rate of Al 2 O 3 From the general high-aluminum solid waste, especially the process of extracting Al 2 O 3 from fly ash, since Al 2 O 3 mainly exists in the structure, the structure is relatively stable. In the stone or glass phase, it exists in the form of a Si-Al-O space network structure, so that the activity is low. Therefore, the extraction of Al 2 O 3 must be activated by calcination to convert the mullite structure into a more active nepheline structure, and then Al 2 O 3 can be extracted by acid leaching.
However, the oil shale slag is a residue after dry distillation at 510-550 ° C. The composition granules are fine and have a porous structure, which is different from the fly ash structure which has been calcined at a high temperature and has great activity. In order to analyze the activity of the oil shale slag, the oil shale ash was obtained by firing at 1000 ° C, and the structure of the two was compared, as shown in FIG. 1 .
Figure 1 XRD pattern of oil shale slag and oil shale ash
It can be seen from Fig. 1 that no mullite crystal phase appears in the oil shale slag structure before and after calcination activation. In the oil shale slag structure, Al 2 O 3 is mainly present in the form of kaolinite and nepheline. The kaolinite in the oil shale slag is activated by dry distillation and has high chemical reactivity; and nepheline is a substance soluble in acid, which is beneficial to the extraction of Al 2 O 3 . After activation temperature, oil shale into oil shale ash residue, Al 2 O 3 is present in the form of mainly kaolinite, kaolinite content decreases but, nepheline crystal phase disappears, hematite iron oxide high-temperature oxidation This indicates that although the activity of oil shale ash exists, it is reduced. Comparing the two structures, it can be shown that it is feasible to extract Al 2 O 3 from oil shale ash or oil shale slag by acid leaching, but it is more suitable to prepare Al 2 O 3 directly from oil shale slag.
2. Effect of temperature on the leaching extraction of Al 2 O 3 ratio of the examined extraction Al 2 O 3 at different temperatures, other conditions were: 15.0g shale residue, 40.0 mL hydrochloric acid leaching time of 2.0h, The experimental results are shown in Figure 2.
Figure 2 Relationship between acid leaching temperature and Al 2 O 3 extraction rate
It can be seen from Fig. 2 that the influence of temperature on the extraction rate is very obvious, and increasing the reaction temperature can greatly increase the extraction rate. However, when the acid leaching temperature reaches 100 ° C or higher, the extraction rate is no longer obvious with temperature, so the optimum acid immersion temperature is 100 ° C, and the extraction rate of Al 2 O 3 is 90.6%.
3. Effect of the amount of hydrochloric acid on the extraction rate of Al 2 O 3 Take 1 part of 15.0 g of oil shale slag sample, add different concentrated hydrochloric acid, and treat at 100 ° C for 2 h. The experimental results are shown in Figure 3.
Figure 3 Relationship between the amount of hydrochloric acid and the extraction rate of Al 2 O 3
As shown in Fig. 3, the extraction rate of Al 2 O 3 gradually increases as the amount of hydrochloric acid increases. When the amount of hydrochloric acid was increased to 40 mL, the active Al 2 O 3 reaction was substantially complete, and therefore, the amount of hydrochloric acid used was 40 mL.
4. Effect of acid leaching time on the extraction rate of Al 2 O 3 Take 5 parts of 15.0 g oil shale slag sample and treat it in 40 mL of concentrated hydrochloric acid at 100 ° C with different acid leaching time. The experimental results are shown in Figure 4. Show.
Figure 4 Relationship between acid leaching time and Al 2 O 3 extraction rate
It can be seen from Fig. 4 that in the initial stage, the active Al 2 O 3 dissolves faster because of the higher concentration of hydrochloric acid, so the extraction rate increases rapidly, but as the acid leaching time increases, the hydrochloric acid concentration decreases and the chemical reaction rate decreases. The extraction rate of Al 2 O 3 also slowed down. When the acid leaching time reached 2.0 h, the extraction rate of Al 2 O 3 hardly increased, so the suitable acid leaching time was 2.0 h.
5. Al 2 O 3 detection analysis The XRD pattern of Al 2 O 3 prepared by acid leaching method is shown in Fig. 5. The apparent γ-Al 2 O 3 diffraction peak appears in the figure, so it can be proved that the product is γ-Al. 2 O 3 In addition, since the Al(OH) 3 was flocculated and precipitated, the impurities were not completely removed, and after firing to prepare γ-Al 2 O 3 , a small amount of NaCl crystal was mixed.
Figure 5 XRD pattern of Al 2 O 3
The purity of the crude γ-Al 2 O 3 product was determined by X-ray fluorescence spectrometry to be 91.7%. Experiments show that higher purity γ-Al 2 O 3 can be obtained by recrystallization, but this method has problems such as high energy consumption and cumbersome process, so further research and improvement are needed.
Fig. 6 is an SEM image of γ-Al 2 O 3 . It is clearly seen from the figure that γ-Al 2 O 3 is a cubic closely packed crystal, and the average particle size is about 2 μm.
Figure 6 SEM image of Al 2 O 3
(II) Oil shale slag extraction of white carbon black experimental part
In the process of oil shale slag preparation of Al 2 O 3 by acid leaching, other substances such as Fe 2 O 3 are also dissolved in the acid leaching process, and the main components of the oil shale residue are changed, among which SiO 2 The content reaches more than 90%. Therefore, the residue is treated by alkali dissolution to prepare a white carbon black product with higher purity, which will greatly improve the comprehensive utilization value of oil shale slag.
1. The effect of reaction temperature on the extraction rate of white carbon black The fixed reaction time was 6.0h and the alkali concentration was 6.0mo1/L. The extraction rate of white carbon black at different temperatures was examined. The experimental results are shown in Fig. 7.
Figure 7 Relationship between reaction temperature and extraction rate of silica
As can be seen from Fig. 7, as the reaction temperature increases, the extraction rate of the product increases. However, when the reaction temperature reaches 100 ° C or more, the extraction rate increases less. Therefore, the optimum reaction temperature is 100 ° C, and the extraction rate of white carbon black reaches 80.5%.
2, the reaction time of the white carbon black extraction rate of the fixed reaction temperature of 100 ° C, alkali concentration of 6mol / L, respectively, using different reaction time treatment, the experimental results shown in Figure 8.
Figure 8 Relationship between acid leaching time and white carbon black extraction rate
It can be seen from the figure that as the alkali treatment time is prolonged, the extraction rate of white carbon black increases. When the reaction time is less than 6.0 h, the white carbon black increases faster. However, when the reaction time exceeds 6.0 h, the extraction rate of white carbon black increases slowly. A suitable base treatment time is therefore 6.0 h.
3. Effect of alkali concentration on the extraction rate of white carbon black The fixed reaction temperature was 100 ° C and the reaction time was 6.0 h. The treatment was carried out with different alkali concentrations. The experimental results are shown in Fig. 9.
Figure 9 Relationship between alkali concentration and extraction rate of silica
As can be seen from Fig. 9, the extraction rate of white carbon black increases as the alkali concentration increases. When the alkali concentration is low, the yield is low and there is no practical production significance; when the concentration reaches 6 mol/L, the extraction rate does not change much. Therefore, from the economic point of view, the alkali concentration is 6 mol/L.
4. Analysis of white carbon black The XRD pattern of white carbon black prepared by alkali dissolution method is shown in Fig. 10. There is no sharp crystal diffraction peak in the figure, but only in the range of diffraction angle (2θ) 15° to 40°. The amorphous peak appears and the product is amorphous amorphous structure and does not contain other crystalline phases.
Figure 10 XRD pattern of white carbon black
FIG 11 is a silica infrared spectrum of the product, in FIG 3450cm - 1 a SiO-H stretching vibration and the physical adsorption of HO-H bond absorption, 1635 cm - 1 bending vibration is physically adsorbed water absorption, 1090 cm --1 to bond Si-O-Si antisymmetric stretching vibration at 968 cm - a weak absorption peak appears 1, a stretching vibration of Si-OH absorption; 796 cm - 1 bending vibration absorption is -OH, 467 cm - 1 for the Si-O bond stretching vibration absorption; thus may determine that the product is a hydrated silica.
Figure 11 FT-IR diagram of white carbon black
Fig. 12 is a TEM image of white carbon black. It can be clearly seen from the figure that the white carbon black particles are approximately spherical, and most of the particles have a particle diameter of 50 nm or less. The specific surface area of ​​the silica measured by the BET method was 110.5 m 2 /g. The SiO 2 content in the white carbon black product was determined by X-ray fluorescence spectrometry to be 95.9%.
Figure 12 TEM image of white carbon black
The test results of the industry standard HG/T3061-1999 (rubber compounding agent, precipitated hydrated silica technical conditions) and other physical and chemical indicators of silica are shown in Table 2. The preparation of white carbon black products from oil shale slag by precipitation method meets the requirements of industry standard HG/T061-1999.
Table 2 Determination results of physical and chemical properties of silica
project | HG/T3061-1999 | The measurement results |
Specific surface area (BET method) / (m 2 ·g -1 ) SiO 2 purity /% Heating loss /% 1000 ° C ignition loss /% pH | 70~200 ≥90 4.0～8.0 ≤7.0 5.0～8.0 | 110.5 95.9 5.15 5.78 5.5～6.0 |
After the alumina shale residue is used to prepare alumina and silica, the residual amount of ash is less than 5%, which achieves the environmental protection and comprehensive utilization of waste.
Third, the conclusion
(1) Oil shale slag does not require high-temperature roasting activation, and γ-Al 2 O 3 with higher purity can be directly prepared by acid leaching. The product is verified by XRD, SEM and X-ray fluorescence analysis.
(2) The residue after preparation of γ-Al 2 O 3 is prepared by alkali treatment, and the product is verified by XRD, TEM, FT-IR and X-ray fluorescence analysis, and the white carbon black product conforms to HG. /T061-1999 standard.
(3) After using alumina shale slag to prepare alumina and silica, the residual amount of ash is less than 5%, which achieves the purpose of environmental protection and comprehensive utilization of waste.
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