Method for preparing synthesis gas by coupling ammonia gas with carbonate reaction

Abstract

The invention provides a method for preparing synthesis gas by coupling ammonia gas with carbonate reaction, and belongs to the field of carbonate pyrolysis. The ammonia gas is used for replacing hydrogen to serve as a hydrogen source to be used for carbonate thermal decomposition, the hydrogen source is introduced to reduce the thermal decomposition temperature, meanwhile, hydrogen and carbon monoxide are generated in the decomposition process, carbonate and ammonia gas are coupled in the carbonate decomposition process, multiple functions of reduction, nitridation, hydrogen supply and the like are achieved, the reaction system is simplified, carbon dioxide emission is greatly reduced, and the production cost is reduced. In the decomposition process, no extra catalyst needs to be added, the reaction process is green, environment-friendly, safe and non-toxic, the operation in the decomposition process is simple, hydrogen does not need to serve as a reducing agent, and the safety of thermal decomposition is improved.

Description

Technical Field

[0001] This invention relates to the field of carbonate pyrolysis, and more specifically to a method for preparing syngas using ammonia coupled with a carbonate reaction. Background Technology

[0002] Carbonate pyrolysis, as an important chemical process, is the most commonly used method in industry for producing metal oxides. This technology decomposes carbonates into metal oxides and carbon dioxide through high-temperature heating, and is widely used in industries such as cement manufacturing and metallurgy. However, the large amount of carbon dioxide emissions does not comply with carbon-related environmental regulations. The carbonate pyrolysis process generally requires high temperatures, consuming a large amount of energy and placing high demands on the equipment and safety involved. To address the carbon emissions problem associated with carbonate pyrolysis, existing technologies employ a method of reducing carbonates with hydrogen.

[0003] For example, patent CN118954980A discloses a method for hydrogenating bimetallic carbonate dolomite. The specific method involves introducing reducing gas into the dolomite to carry out a hydrogenation reaction. The method does not require the use of a catalyst and can reduce the refining temperature of the dolomite without the use of a catalyst. At the same time, the carbon in the dolomite is converted into carbon monoxide and methane, reducing the generation of carbon dioxide.

[0004] However, hydrogen is expensive and poses significant safety risks during transportation, storage, and high-temperature environments, significantly increasing the danger and cost of carbonate pyrolysis. Therefore, new alternative materials are needed. Patent CN110156048A discloses a method for preparing calcium cyanamide using calcium carbonate as a raw material. This method uses calcium carbonate and ammonia as raw materials in a tubular furnace, with porous solid materials containing acidic sites, such as molecular sieves, as catalysts, and performs a high-temperature, one-step reaction to prepare calcium cyanamide. Replacing hydrogen with ammonia in the decomposition of carbonates can effectively reduce the cost of carbonate decomposition and improve its safety.

[0005] In summary, existing carbonate decomposition processes result in significant carbon dioxide emissions. To address this issue, carbonates are often decomposed under hydrogen conditions by heating. However, due to the high cost and hazardous nature of hydrogen, this method of hydrogen pyrolysis of carbonates is not widely used in industry. Therefore, it is necessary to find alternative gases for carbonate decomposition. Summary of the Invention

[0006] To address the above problems, this invention provides a method for preparing syngas using ammonia coupled with a carbonate reaction. By using specific thermal decomposition temperatures, gas flow rates, and heating rates, carbonates are decomposed to generate nitrides and oxides, which in turn generate syngas, thus reducing carbon dioxide emissions.

[0007] This invention provides a method for preparing syngas using ammonia coupled with a carbonate reaction, comprising the following steps: Carbonates are fixed in a fixed-bed reactor with quartz wool. High-purity ammonia is introduced into the fixed-bed reactor at atmospheric pressure. The fixed-bed reactor is then heated and kept at that temperature until the carbonates are completely decomposed, yielding solid cyanamides and oxides, as well as gaseous hydrogen and carbon monoxide.

[0008] Furthermore, the carbonate has a mesh size of 40-60 mesh.

[0009] Furthermore, the carbonate is one or both of calcium carbonate and dolomite.

[0010] Furthermore, the thickness of the quartz wool is 1-3 μm.

[0011] Furthermore, the purity of the high-purity ammonia gas is ≥99.9%.

[0012] Furthermore, the flow rate of the high-purity ammonia gas is 10-100 mL / min.

[0013] Furthermore, the heating temperature of the fixed-bed reactor is 600-900℃.

[0014] Furthermore, the heating rate of the fixed-bed reactor is 10-40℃ / min.

[0015] Furthermore, the yield of the oxide is 10-90 / 500 mg carbonate, and the yield of the cyanamide is 10-90 / 500 mg carbonate.

[0016] Furthermore, the selectivity of the carbon monoxide is 76-96%, and the volume ratio of the hydrogen to the carbon monoxide is (3:1)-(9:1).

[0017] Furthermore, in addition to hydrogen and carbon monoxide, the gaseous products after the thermal decomposition of the carbonate also contain small amounts of methane and carbon dioxide gases.

[0018] Furthermore, the main reaction formula for the thermal decomposition of the carbonate under ammonia gas is as follows: MCO3 + NH3 → MCN2 + MO + H2 + CO.

[0019] The beneficial effects of this invention are: 1. This invention uses ammonia instead of hydrogen as a hydrogen source to thermally decompose carbonates. The traditional thermal decomposition temperature of carbonates in air is around 900℃. Introducing a hydrogen source lowers the decomposition temperature of carbonates. However, due to the high cost of hydrogen and the high hydrogen content required for carbonate decomposition, the high risk factor of decomposition under pure hydrogen makes the industrial decomposition process of carbonates difficult to carry out. Using ammonia for decomposition not only introduces a hydrogen source to lower the decomposition temperature but also reduces the risk factor of thermal decomposition. Moreover, the thermal decomposition of carbonates can also generate hydrogen and carbon monoxide. Utilizing ammonia as a gas to simultaneously complete multiple functions such as reduction, nitriding, and hydrogen supply significantly simplifies the reaction system and greatly reduces the carbon dioxide emissions from the original thermal decomposition of carbonates. 2. The thermal decomposition temperature of carbonates in this invention is 600-900℃. At this temperature, the coupled reaction of carbonates and ammonia under high-temperature conditions produces hydrogen amines and oxides in different proportions to meet the needs of different industrial applications. The preparation method in this invention does not require additional catalysts, and in the fixed-bed reactor, ammonia and carbonates are in full contact, maximizing the decomposition of carbonates. The resulting carbon monoxide has high selectivity. Carbonates are decomposed in a green, environmentally friendly, safe, and non-toxic environment, while carbon monoxide and hydrogen are produced simultaneously, which is highly efficient and promising. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the solid product in Example 1. Figure 2 This is the energy scattering spectrum of the solid product in Example 1. Figure 3 The X-ray diffraction (XRD) patterns of the solid products in Examples 8-10 are shown below. Figure 4 This is the X-ray diffraction (XRD) pattern of the solid product in Example 12. Figure 5 This is a scanning electron microscope image of the solid product in Example 12. Figure 6 The X-ray diffraction (XRD) patterns of the solid products in Examples 3-4 and Comparative Examples 1-2 are shown below. Figure 7 This is the decomposition route of the carbonate portion in this invention. Detailed Implementation

[0021] The invention will be described in detail below with reference to the embodiments: This invention provides a method for preparing syngas using ammonia coupled with a carbonate reaction. By decomposing carbonate under ammonia conditions, the amount of carbon dioxide released during carbonate decomposition is greatly reduced.

[0022] Example 1 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the fixed-bed reactor was heated to 900 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0023] The decomposition reaction formula of calcium carbonate under ammonia gas described in this embodiment is as follows: CaCO3+NH3→CaCN2+ CaO+ H2+CO.

[0024] like Figure 1 The image shows a scanning electron microscope (SEM) image of the solid product in Example 1. The crystals are uniformly distributed, exhibiting irregular agglomerations and layered or lamellar crystal planes.

[0025] like Figure 2 The image shows the energy scattering spectrum of the solid product in Example 1. The crystal composition in the image includes the elements Ca, N, C, and O.

[0026] Example 2 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the fixed-bed reactor was heated to 800 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0027] Example 3 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 700 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0028] Example 4 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0029] Example 5 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 40 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0030] Example 6 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 30 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0031] Example 7 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 10 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0032]

[0033] Example 8 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 100 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0034] Example 9 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 50 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0035] Example 10 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 20 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0036] like Figure 3 The X-ray diffraction (XRD) patterns of the solid products in Examples 8-10 are shown in the figure. The solid species include calcium cyanamide (CaCN2), calcium oxide (CaO), and a very small amount of undecomposed calcium carbonate (CaCO3).

[0037]

[0038] Example 11 500 mg of 60-mesh calcium carbonate was fixed in a fixed-bed reactor using 3 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0039] Example 12 500 mg of 40-mesh dolomite was fixed in a fixed-bed reactor using 3 μm silica wool. High-purity ammonia gas was introduced into the reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The dolomite underwent thermal decomposition within the reactor. The resulting gas was detected by a gas chromatograph until ammonia was the dominant gas, indicating complete decomposition of the dolomite. The resulting products were solid calcium cyanamide, calcium oxide, and magnesium oxide, as well as gaseous hydrogen and carbon monoxide. The oxide content in the table refers only to calcium oxide.

[0040] The decomposition reaction formula of dolomite under ammonia gas in this embodiment is as follows: CaMg(CO3)2+NH3→CaCN2+ CaO+MgO+CO+H2+CO.

[0041] like Figure 4 The image shows the X-ray diffraction (XRD) pattern of the solid product in Example 12. As can be seen from the image, the solid product includes calcium cyanamide, calcium oxide, and magnesium oxide.

[0042] like Figure 5 The image shows a scanning electron microscope (SEM) image of the solid product in Example 12. The crystals in the image are irregularly aggregated, with layered or lamellar crystal planes and a rough crystal surface.

[0043]

[0044] Comparative Example 1 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the fixed-bed reactor was heated to 500 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was detected by a gas chromatograph.

[0045] Comparative Example 2 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity ammonia gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the fixed-bed reactor was heated to 400 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was detected by a gas chromatograph.

[0046] like Figure 6 The figures show the X-ray diffraction (XRD) patterns of the solid products in Examples 3-4 and Comparative Examples 1-2. As shown, the solid species in Examples 3-4 include calcium cyanamide (CaCN2), calcium oxide (CaO), and a very small amount of undecomposed calcium carbonate (CaCO3), while the solid products in Comparative Examples 1 and 2 are still calcium carbonate, indicating that calcium carbonate did not decompose at 500 and 400 °C.

[0047]

[0048] Comparative Example 3 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. High-purity hydrogen gas was introduced into the fixed-bed reactor at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the fixed-bed reactor was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was hydrogen, yielding solid calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0049] Comparative Example 4 500 mg of 40-mesh calcium carbonate was fixed in a fixed-bed reactor using 1 μm quartz wool. Under normal pressure, air was introduced into the fixed-bed reactor at a rate of 10 mL / min. After 5 min, the fixed-bed reactor was heated to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the fixed-bed reactor. The gas obtained from the thermal decomposition was then passed into a gas chromatograph for detection.

[0050] Comparative Example 5 500 mg of 40-mesh calcium carbonate was fixed in a tubular furnace using 1 μm quartz wool. High-purity ammonia gas was introduced into the tubular furnace at a rate of 10 mL / min under normal pressure. After 5 min, the temperature of the tubular furnace was increased to 600 °C at a rate of 20 °C / min. The calcium carbonate underwent thermal decomposition in the tubular furnace. The gas obtained from the thermal decomposition was passed into a gas chromatograph for detection. The calcium carbonate was completely decomposed when the gas composition was ammonia, yielding solid calcium cyanamide and calcium oxide, as well as gaseous hydrogen and carbon monoxide.

[0051]

[0052] As shown in all the tables above, the specific hydrogen amines and oxides of this invention can be prepared under the decomposition temperature, gas flow rate, and heating rate specified in this invention. At the same time, ammonia is converted into hydrogen. However, in Comparative Examples 1 and 2, the carbonates failed to decompose due to the low thermal decomposition temperature. In Comparative Examples 3 and 4, the thermal decomposition gases were hydrogen and air. Under these conditions, carbonates could not decompose to generate hydrogen amines. In Comparative Example 5, the fixed-bed reactor was replaced with a tubular furnace, which resulted in insufficient contact between the carbonates and the gas during decomposition, leading to low selectivity of the final carbon monoxide.

[0053] like Figure 7 This diagram illustrates the partial decomposition route of carbonates in this invention. The carbonates decompose under ammonia gas, primarily producing nitrogen-fixing products (CaCN2) and CO, without generating CO2, thus reducing CO2 emissions. It should be noted that the attached diagram does not represent all products, but only highlights the key products of this invention.

[0054] As can be seen from the above, the preparation method for preparing metal compounds by thermal decomposition of carbonates described in this invention has a wide range of applications, is simple to operate, and has a very high market prospect.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing syngas using ammonia coupled with a carbonate reaction, characterized in that, The following steps are involved: Carbonates are fixed in a fixed-bed reactor with quartz wool. High-purity ammonia is introduced into the fixed-bed reactor at atmospheric pressure. The fixed-bed reactor is then heated and kept at that temperature until the carbonates are completely decomposed, yielding solid cyanamides and oxides, as well as gaseous hydrogen and carbon monoxide.

2. The method according to claim 1, characterized in that, The carbonate has a mesh size of 40-60.

3. The method according to claim 1, characterized in that, The carbonate is one or both of calcium carbonate and dolomite.

4. The method according to claim 1, characterized in that, The thickness of the quartz wool is 1-3 μm.

5. The method according to claim 1, characterized in that, The purity of the high-purity ammonia gas is ≥99.9%.

6. The method according to claim 1, characterized in that, The flow rate of the high-purity ammonia gas is 10-100 mL / min.

7. The method according to claim 1, characterized in that, The heating temperature of the fixed-bed reactor is 600-900℃.

8. The method according to claim 1, characterized in that, The heating rate of the fixed-bed reactor is 10-40℃ / min.

9. The method according to claim 1, characterized in that, The yield of the oxide is 10-90 / 500 mg carbonate, and the yield of the cyanamide is 10-90 / 500 mg carbonate.

10. The method according to claim 1, characterized in that, The selectivity of the carbon monoxide is 76-96%, and the volume ratio of the hydrogen to the carbon monoxide is (3:1)-(9:1).

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