A method for hydroprocessing of a double metal carbonate dolomite

Abstract

The present application relates to the field of carbonate decomposition, in particular to a method for hydrogen refining dolomite double metal carbonate, the specific method is to pass reducing gas into dolomite for hydrogenation reaction, the method does not need to use catalyst;The crystal structure of dolomite is: in X-ray diffraction spectrum, there are two characteristics: (1) d104=2.88Å;(2) superstructure (h0l) and (0kl) diffraction line (l is odd) appears on the spectrum, at 2θ angle 22.05 o 、30.9 o 、35.3 o 、41.1 o 、44.9°, dolomite has the characteristic diffraction peak of (101), (104), (015), (113), (202). The present application can reduce the refining temperature of dolomite without using catalyst by preparing dolomite with specific crystal structure, at the same time, carbon in dolomite is converted into carbon monoxide and methane, and the generation of carbon dioxide is reduced, therefore, the present application reduces energy consumption and the processing cost of carbon dioxide, and the overall scheme has high economic value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of carbonate decomposition, in particular to a method for hydrogen refining of double-metal carbonate dolomite. BACKGROUND

[0002] China is the world's largest magnesium producer and exporter, with an annual raw magnesium production of about 900,000 tons, accounting for more than 85% of the world's raw magnesium production. Dolomite is a mineral containing calcium and magnesium elements, with a chemical formula of CaMg(CO3)2. Dolomite ore has abundant reserves in China, with proven reserves of up to 20 billion tons. Dolomite is also easy to mine and relatively inexpensive, making it an important raw material for producing calcium and magnesium products.

[0003] Currently, the thermal reduction method is one of the main magnesium refining processes. The thermal reduction method represented by the Pidgeon process is the main method for producing raw magnesium in China, accounting for more than 90% of China's total raw magnesium production. The Pidgeon process for refining magnesium uses dolomite as raw material to produce calcined dolomite, and then uses ferrosilicon as a reducing agent to reduce magnesium in calcined dolomite to magnesium vapor under vacuum and high temperature conditions, and then condenses to obtain metallic magnesium. However, the pyrolysis process of the Pidgeon method involves high temperature conditions, which not only increases production costs, but also emits large amounts of carbon dioxide, causing serious environmental damage.

[0004] CN115583665B discloses a method for co-production of calcium carbonate and magnesium building material raw material from dolomite ore. The method uses dolomite ore to obtain calcium oxide and magnesium oxide, which are subjected to a selective precipitation reaction. The filtrate after filtration is subjected to carbonation treatment to obtain calcium carbonate products, and the filter residue is used as a raw material for preparing magnesium building materials. However, dolomite ore needs to be refined at 950°C, and the generated carbon dioxide also needs to be recovered and treated, increasing the preparation cost.

[0005] Therefore, how to reduce the refining temperature of dolomite and reduce the emission of carbon dioxide after refining is a technical problem that needs to be solved. SUMMARY

[0006] To solve the above technical problems, the present application provides a method for hydrogen refining of double-metal carbonate dolomite. The method uses dolomite with a specific crystal structure to reduce the refining temperature of dolomite without using a catalyst, and converts the carbon in dolomite into carbon monoxide and methane, reducing the generation of carbon dioxide.

[0007] The application provides a method for hydrogenation refining of double-metal carbonate dolomite, which comprises the following steps: introducing reducing gas into the dolomite to perform hydrogenation reaction, and the method does not need to use a catalyst; the crystal structure of the dolomite is as follows: two characteristics are present in the X-ray diffraction spectrum, namely (1) d104=2.88Å; (2) superstructure (h0l) and (0kl) diffraction lines (l is an odd number) appear on the spectrum at 2θ angles of 22.05 o , 30.9 o , 35.3 o , 41.1 o , 44.9°, and the dolomite has characteristic diffraction peaks of (101), (104), (015), (113) and (202).

[0008] Further, the preparation method of the dolomite is as follows: magnesium chloride and calcium chloride with a molar ratio of (0.5-2):1 are dissolved in deionized water to prepare a mixed solution with a concentration of 1.5-3mol / L, 1-3g of calcium carbonate is first added into a polytetrafluoroethylene liner, then 150-450ml of the mixed solution is added, and the mixture is placed in a blast drying oven for crystallization; after crystallization, centrifugal separation is performed and deionized water is used for washing, and finally drying is performed.

[0009] Further, the temperature of the crystallization treatment is 200-260 o C.

[0010] Further, the time of the crystallization treatment is 24-60h.

[0011] Further, the rotation speed of the centrifugal treatment is 8000-15000r / min.

[0012] Further, the temperature of the drying treatment is 60-80 o C.

[0013] Further, the reducing gas comprises hydrogen, and the volume of the hydrogen is 20-100% of the total volume of the reducing gas based on the total volume of the reducing gas.

[0014] Further, the reducing gas further comprises nitrogen or argon.

[0015] Further, the flow rate of the reducing gas is 30-100ml / min.

[0016] Further, the pressure of the reducing gas is 1-5bar.

[0017] Further, the temperature of the hydrogenation refining of the dolomite is 400-600 o C.

[0018] Further, the refining product of the dolomite after hydrogenation includes calcium oxide, magnesium oxide, carbon monoxide, methane and carbon dioxide.

[0019] Further, the decomposition rate of the dolomite is the ratio of the moles of carbon monoxide to the moles of carbon in the dolomite, and the decomposition rate of the dolomite is 87-100%.

[0020] Further, the selectivity of the carbon monoxide is the ratio of the moles of carbon monoxide to the total moles of gas in the refining product, and the selectivity of the carbon monoxide is 80-96%.

[0021] Further, the excess reducing gas is introduced in the hydrogenation refining process of the dolomite, and the molar ratio of the unreacted hydrogen to the carbon monoxide is (4-8):1.

[0022] Advantages of the present application

[0023] 1. The prior art generally uses high temperature to refine dolomite, and a large amount of carbon dioxide is generated after refining. The present application can reduce the refining temperature of dolomite without using a catalyst by preparing dolomite with a specific crystal structure, and can convert carbon in dolomite into carbon monoxide and methane, thereby reducing the generation of carbon dioxide. Therefore, the present application not only reduces energy consumption, but also reduces the processing cost of carbon dioxide, and the overall scheme has high economic value.

[0024] 2. In the present application, excess reducing gas is introduced in the refining process of dolomite, and the unreacted hydrogen and the generated carbon monoxide can produce different by-products under different conditions, for example, (1) Fischer-Tropsch synthesis reaction: using cobalt or iron as a catalyst, hydrogen and carbon monoxide react to produce hydrocarbon products, including straight-chain alkanes and low-carbon olefins; (2) alcohol synthesis reaction: using copper as a catalyst, hydrogen and carbon monoxide react to produce alcohol products, mainly low-carbon alcohols; (3) methanation reaction: using nickel as a catalyst, hydrogen and carbon monoxide react to produce methane and water. Therefore, the generation of by-products can further improve the economic value of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 X-ray diffraction patterns of self-made dolomite with different proportions in Examples 1-3;

[0026] Figure 2 X-ray diffraction patterns of self-made dolomite in Example 1, natural dolomite in Comparative Example 1 and calcium carbonate in Comparative Example 2;

[0027] Figures 3a-3c Scanning electron microscope images of self-made dolomite in Example 1, natural dolomite in Comparative Example 1 and calcium carbonate in Comparative Example 2. DETAILED DESCRIPTION

[0028]

[0028] Example 1

[0029] A method for hydrogenolysis of a double metal carbonate dolomite, comprising the following steps:

[0030] Step 1: Preparation of dolomite: 0.5 moles of magnesium chloride and 1 mole of calcium chloride were dissolved in deionized water to prepare a mixed solution with a concentration of 1.5 mol / L. 1 g of calcium carbonate was first added to a polytetrafluoroethylene liner, and then 150 ml of the mixed solution was added. The mixture was placed in a forced air drying oven for crystallization. The crystallization temperature was 200 o C, and the crystallization time was 24 h. After crystallization, centrifugation and washing with deionized water were performed. The centrifugation speed was 8000 r / min. Finally, drying was performed at a temperature of 60 o C. Dolomite was obtained. The crystal structure of the dolomite was trigonal.

[0031] Step 2: Hydrogenolysis of dolomite: 1000 mg of dolomite was placed in a quartz tube with a diameter of 40 mm. Reducing gas was introduced for hydrogenolysis. The volume of hydrogen was 20% of the total volume of the reducing gas, and the rest was argon. The flow rate of the reducing gas was 30 ml / min, the pressure was 1 bar, and the hydrogenolysis temperature was 400 o C. The hydrogenolysis time was 30 min. The hydrogenolysis products were calcium oxide, magnesium oxide, carbon monoxide, methane, and carbon dioxide. The end of the quartz tube was connected to a silica gel drying device. The dried gas was introduced into a mass spectrometer for detection. The decomposition rate of dolomite was 87%, the selectivity of carbon monoxide was 80%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 8:1.

[0032] Example 2

[0033] A method for hydrogenolysis of a double metal carbonate dolomite, comprising the following steps:

[0034] Step 1: Preparation of dolomite: 1 mole of magnesium chloride and 1 mole of calcium chloride were dissolved in deionized water to prepare a mixed solution with a concentration of 2 mol / L. 2 g of calcium carbonate was first added to a polytetrafluoroethylene liner, and then 300 ml of the mixed solution was added. The mixture was placed in a forced air drying oven for crystallization. The crystallization temperature was 230 o C, and the crystallization time was 40 h. After crystallization, centrifugation and washing with deionized water were performed. The centrifugation speed was 12000 r / min. Finally, drying was performed at a temperature of 70 o C. Dolomite was obtained. The crystal structure of the dolomite was trigonal.

[0035] Step 2: Refining dolomite: 1000 mg of dolomite was placed in a quartz tube with a diameter of 40 mm, and reducing gas was introduced for refining. The volume of hydrogen was 50% of the total volume of the reducing gas, and the rest was argon. The flow rate of the reducing gas was 50 ml / min, the pressure was 3 bar, the refining temperature was 500 o C, and the time was 30 min. The refining products were calcium oxide, magnesium oxide, carbon monoxide, methane, and carbon dioxide. The end of the quartz tube was connected to a silica gel drying device. The dried gas was introduced into a mass spectrometer for detection. The decomposition rate of dolomite was 94%, the selectivity of carbon monoxide was 89%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 6:1.

[0036] Example 3

[0037] A method for hydrogen refining of a double-metal carbonate dolomite, comprising the following steps:

[0038] Step 1: Preparation of dolomite: 2 moles of magnesium chloride and 1 mole of calcium chloride were dissolved in deionized water to prepare a mixed solution with a concentration of 3 mol / L. First, 3 g of calcium carbonate was added to a polytetrafluoroethylene liner, and then 450 ml of the mixed solution was added. The mixture was placed in a forced air drying oven for crystallization. The crystallization temperature was 260 o C, and the time was 60 h. After crystallization, centrifugation and washing with deionized water were performed at a speed of 15000 r / min. Finally, drying was performed at a temperature of 80 o C. The obtained dolomite had a crystal structure of the trigonal system.

[0039] Step 2: Refining dolomite: 1000 mg of dolomite was placed in a quartz tube with a diameter of 40 mm, and reducing gas was introduced for refining. The volume of hydrogen was 100% of the total volume of the reducing gas, and the rest was argon. The flow rate of the reducing gas was 100 ml / min, the pressure was 5 bar, the refining temperature was 600 o C, and the time was 30 min. The refining products were calcium oxide, magnesium oxide, carbon monoxide, methane, and carbon dioxide. The end of the quartz tube was connected to a silica gel drying device. The dried gas was introduced into a mass spectrometer for detection. The decomposition rate of dolomite was 100%, the selectivity of carbon monoxide was 96%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 4:1.

[0040] Comparative Example 1

[0041] Step 1: Refining natural dolomite: 1000 mg of natural dolomite from Hunan Huahuan was placed in a quartz tube with a diameter of 40 mm, and reducing gas was introduced for refining. The volume of hydrogen was 20% of the total volume of the reducing gas, and the rest was argon. The flow rate of the reducing gas was 30 ml / min, the pressure was 1 bar, and the refining temperature was 600o C, the time was 30 min, the calcined product was calcium oxide, magnesium oxide, carbon monoxide, methane and carbon dioxide, the end of the quartz tube was connected to a silica gel drying device, the dried gas entered a mass spectrometer for detection, the decomposition rate of the dolomite was 64%, the selectivity of carbon monoxide was 73%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 10:1.

[0042] Comparative Example 2

[0043] Step 1: Calcination of calcium carbonate: 100 mg of calcium carbonate powder was placed in a glass tube reactor body, and reducing gas was introduced from the bottom for calcination, the volume of hydrogen was 20% of the total volume of the reducing gas, and the rest was argon,

[0044] The flow rate of the reducing gas was 50 ml / min, the pressure was 1 bar, the calcium carbonate powder was in a suspended state, the calcination temperature was 700℃, the time was 30 min, the calcined product was calcium oxide, carbon monoxide, methane and carbon dioxide, the end of the quartz tube was connected to a silica gel drying device, the dried gas entered a mass spectrometer for detection, the decomposition rate of the calcium carbonate powder was 55%, the selectivity of carbon monoxide was 62%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 10:1.

[0045] In summary, it is generally expected in the prior art that the decomposition rate of natural dolomite is about 60% and the selectivity of carbon monoxide is about 70% under the condition that the calcination temperature is 600℃ and the calcination time is 30 min; the decomposition rate of calcium carbonate is about 50% and the selectivity of carbon monoxide is about 60% under the condition that the calcination temperature is 700℃ and the calcination time is 30 min, that is, the decomposition rate of natural dolomite and calcium carbonate and the selectivity of carbon monoxide in Comparative Examples 1-2 are lower than those in Example 1-3 under the condition that the temperature is higher than or equal to that of the example, and the molar ratio of unreacted hydrogen to generated carbon monoxide in Comparative Examples 1-2 is higher than that in Example 1-3, because the dolomite with a specific crystal structure [having two characteristics in the X-ray diffraction spectrum: (1) d104=2.88Å; (2) superstructure (h0l) and (0kl) diffraction lines (l is an odd number) appear on the spectrum at 2θ angles of 22.05 o , 30.9 o , 35.3 o , 41.1 o , 44.9°] is prepared, thereby producing unexpected technical effects, that is, without using a catalyst, the calcination temperature of dolomite can be reduced, the decomposition rate of dolomite and the selectivity of carbon monoxide can be improved, and the overall scheme has high economic value.

[0046] The above descriptions are only the preferred embodiments of the present application, not intended to limit the present application in any manner. Any modification or equivalent variation made according to the technical essence of the present application shall still fall within the scope of the present application.

Claims

1. A method for the hydroprocessing of a double metal carbonate dolomite, characterized in that, The method is to introduce reducing gas into the dolomite for hydrogenation reaction, and the method does not need to use a catalyst; the crystal structure of the dolomite is that in an X-ray diffraction spectrum, two characteristics are: (1) d104=2.88Å; (2) superstructure (h0l) and (0kl) diffraction lines appear on the spectrum, l is an odd number, and the 2θ angle is 22.05 o , 30.9 o , 35.3 o , 41.1 o , 44.9 o ; the dolomite has characteristic diffraction peaks of (101), (104), (015), (113), (202); the temperature of the dolomite hydrogenation refining is 400-600 ℃; the decomposition rate of the dolomite is the ratio of the number of moles of carbon monoxide to the number of moles of carbon in the dolomite, and the decomposition rate of the dolomite is 87-100%; the selectivity of the carbon monoxide is the ratio of the number of moles of carbon monoxide to the total number of moles of gas in the refining product, and the selectivity of the carbon monoxide is 80-96%; the preparation method of the dolomite is: dissolving magnesium chloride and calcium chloride with a molar ratio of (0.5-2):1 in deionized water to prepare a mixed solution with a concentration of 1.5-3mol / L, first taking 1-3g of calcium carbonate into a polytetrafluoroethylene liner, then adding 150-450ml of the mixed solution, putting into a forced air drying oven for crystallization, centrifuging and washing with deionized water after crystallization, and finally drying; The temperature of the crystallization treatment is 200-260℃, and the time of the crystallization treatment is 24-60h; The white dolomite hydrogen refining process is passed through excess reducing gas, the reducing gas includes hydrogen, and the volume of the hydrogen is 20-100% of the total volume of the reducing gas on the basis of percentage; the molar ratio of unreacted hydrogen to the carbon monoxide is (4-8):

1.

2. The method of claim 1, wherein, The flow rate of the reducing gas is 30-100ml / min.

3. The method of claim 1, wherein, The method comprises the following steps: Step 1: Preparation of white dolomite: 0.5 moles of magnesium chloride and 1 mole of calcium chloride are dissolved in deionized water to prepare a mixed solution with a concentration of 1.5 mol / L, 1g of calcium carbonate is first added to a polytetrafluoroethylene liner, and then 150ml of the mixed solution is added, and the crystallization is carried out in a forced air drying oven, the crystallization temperature is 200℃, and the crystallization time is 24h, after crystallization, centrifugation and washing with deionized water are carried out, the centrifugal speed is 8000r / min, and finally drying is carried out, the drying temperature is 60℃, white dolomite is obtained, and the crystal structure of the white dolomite is trigonal system; Step 2: Refining white dolomite: 1000mg of white dolomite is placed in a quartz tube with a diameter of 40mm, and reducing gas is introduced for refining, the volume of hydrogen is 20% of the total volume of the reducing gas on the basis of percentage, the rest is argon, the flow rate of the reducing gas is 30ml / min, the pressure is 1bar, the refining temperature is 400℃, the refining time is 30min, the end of the quartz tube is connected to a silica gel drying device, the dried gas is introduced into a mass spectrometer for detection, the decomposition rate of the white dolomite is 87%, the selectivity of carbon monoxide is 80%, and the molar ratio of unreacted hydrogen to generated carbon monoxide is 8:

1.

4. The method of claim 1, wherein, The method comprises the following steps: Step 1: Preparation of white dolomite: 1 mole of magnesium chloride and 1 mole of calcium chloride are dissolved in deionized water to prepare a mixed solution with a concentration of 2mol / L, 2g of calcium carbonate is first added to a polytetrafluoroethylene liner, and then 300ml of the mixed solution is added, and the crystallization is carried out in a forced air drying oven, the crystallization temperature is 230℃, and the crystallization time is 40h, after crystallization, centrifugation and washing with deionized water are carried out, the centrifugal speed is 12000r / min, and finally drying is carried out, the drying temperature is 70℃, white dolomite is obtained, and the crystal structure of the white dolomite is trigonal system; Step 2: Refining white dolomite: 1000mg of white dolomite is placed in a quartz tube with a diameter of 40mm, and reducing gas is introduced for refining, the volume of hydrogen is 50% of the total volume of the reducing gas on the basis of percentage, the rest is argon, the flow rate of the reducing gas is 50ml / min, the pressure is 3bar, the refining temperature is 500℃, the refining time is 30min, the end of the quartz tube is connected to a silica gel drying device, the dried gas is introduced into a mass spectrometer for detection, the decomposition rate of the white dolomite is 94%, the selectivity of carbon monoxide is 89%, and the molar ratio of unreacted hydrogen to generated carbon monoxide is 6:

1.

5. The method of claim 1, wherein, The method comprises the following steps: Step 1: Preparation of dolomite: 2 moles of magnesium chloride and 1 mole of calcium chloride were dissolved in deionized water to prepare a mixed solution with a concentration of 3 mol / L. 3 g of calcium carbonate was first added to a polytetrafluoroethylene liner, and then 450 ml of the mixed solution was added. The mixture was placed in a blast drying oven for crystallization at a temperature of 260°C for 60 h. After crystallization, centrifugation and washing with deionized water were performed at a speed of 15000 r / min. Finally, drying was performed at a temperature of 80°C to obtain dolomite. The crystal structure of the dolomite was trigonal. Step 2: Refining of dolomite: 1000 mg of dolomite was placed in a quartz tube with a diameter of 40 mm. Reducing gas was introduced for refining. The volume of hydrogen gas was 100% of the total volume of the reducing gas, and the rest was argon. The flow rate of the reducing gas was 100 ml / min, the pressure was 5 bar, the refining temperature was 600°C, and the refining time was 30 min. The end of the quartz tube was connected to a silica gel drying device. The dried gas was introduced into a mass spectrometer for detection. The decomposition rate of the dolomite was 100%, the selectivity of carbon monoxide was 96%, and the molar ratio of unreacted hydrogen to generated carbon monoxide was 4:1.

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