Iron-based catalyst and method for hydrogenating carbon dioxide

Abstract

An iron-based catalyst and a method of hydrogenating carbon dioxide, the method of hydrogenating carbon dioxide comprising contacting hydrogen and carbon dioxide with an iron-based catalyst to form a liquid and a gas, where the liquid comprises CnH2n, CnH2n + 2, or a combination thereof, with water, and n is from 5 to 18, where the gas comprises CH4, CmH2m, CmH2m + 2, or a combination thereof, hydrogen, and carbon dioxide, where m is from 2 to 9, and n is from 5 to 18. Wherein the iron-based catalyst comprises: from 70 mol% to 97 mol% of porous FeO (OH) x, where 1 lt; xlt; 2; and 3 mol% to 30 mol% of an alkali metal compound supported on the porous FeO (OH) x.

Description

Technical Field

[0001] The present invention relates to an iron-based catalyst for directly converting carbon dioxide into olefins and paraffins. Background Art

[0002] Traditional processes use CO as the main raw material and react with H 2 (or syngas (CO / H 2 )) to form petrochemical olefins and paraffins such as gasoline and diesel. Currently, there is no commercial process for directly converting carbon dioxide into olefins and paraffins. If CO 2 is to be converted into olefins and paraffins, it is usually necessary to first convert CO 2 into CO, and then react CO with hydrogen to form olefins and paraffins.

[0003] In summary, there is an urgent need for new catalysts and corresponding conversion conditions to directly convert carbon dioxide and hydrogen into olefins and paraffins instead of first converting carbon dioxide into carbon monoxide and then into olefins and paraffins. Summary of the Invention

[0004] An iron-based catalyst provided by an embodiment of the present invention includes: 70 mol% to 97 mol% of porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of an alkali metal compound, supported on the porous FeO(OH) x .

[0005] A method for hydrogenating carbon dioxide provided by an embodiment of the present invention includes: (i) contacting hydrogen and carbon dioxide with an iron-based catalyst to form a liquid and a gas, where the liquid contains C n H 2n , C n H 2n+2 , or a combination thereof, and water, and n is from 5 to 18, where the gas contains CH 4 , C m H 2m , C m H 2m+2 , or a combination thereof, hydrogen, and carbon dioxide, where m is from 2 to 9; where the iron-based catalyst includes: 70 mol% to 97 mol% of porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of an alkali metal compound, supported on the porous FeO(OH) x .

[0006] In some embodiments, the above method further includes: (ii) separating the gas and the liquid; and (iii) contacting the gas with another iron-based catalyst to form another liquid and another gas, where the other liquid contains C n H 2n , C n H2n+2 , or a combination of the above, and water, where n is from 5 to 18, and the other gas contains CH 4 , C m H 2m , C m H 2m+2 , or a combination of the above, hydrogen, and carbon dioxide, where m is from 2 to 9, and the other iron-based catalyst includes: 70 mol% to 97 mol% of another porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of another alkali metal compound, supported on the other porous FeO(OH) x . BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is the Raman spectrum of the iron-based support in an embodiment of the present invention.

[0008] Figure 2 It is the Raman spectrum of the iron-based support in an embodiment of the present invention.

[0009] Figure 3 It is the Raman spectrum of the iron-based support in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The iron-based catalyst provided in an embodiment of the present invention includes: 70 mol% to 97 mol% of porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of an alkali metal compound, supported on the porous FeO(OH) x . If x = 0, the iron-based support is FeO (i.e., iron oxide), and the iron-based catalyst has no function of directly hydrogenating carbon dioxide into alkanes and alkenes. If the proportion of the alkali metal compound is too high, the carbon dioxide conversion rate is too low to be effectively converted into alkanes and alkenes. If the proportion of the alkali metal compound is too low, the content of the intermediate product carbon monoxide is too high. Generally, the above iron-based support substantially does not contain iron oxides such as FeO, Fe 2 O 3 , Fe 3 O 4 , or the like, which can be confirmed by Raman spectroscopy. Generally, iron oxide will deteriorate the effect of the iron-based catalyst in directly converting carbon dioxide into alkanes and alkenes.

[0011] In some embodiments, the specific surface area of the porous FeO(OH) x is 100 m 2 / g or more, such as 100 m 2 / g to 300 m 2 / g. If the porous FeO(OH) xIf the specific surface area is too small, the reaction surface area will be too small, resulting in insufficient catalyst efficiency. 2 / g porous FeO(OH) x In some embodiments, the porous FeO(OH) x The pore volume is 0.2 cm 3 / g to 0.5cm 3 / g. If porous FeO(OH) x If the pore volume is too small, the surface area and activity will decrease. In some embodiments, the porous FeO(OH) x The average pore size is to If FeO(OH) x If the average pore size is too large, the surface area and activity will decrease.

[0012] In some embodiments, the alkali metal compound includes sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, or a combination thereof. Generally speaking, the alkali metal compound is a common alkali such as sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, or a combination thereof. However, during the heating process, part of the carbonate may decompose into carbon dioxide and oxides, and part of the hydroxide may dehydrate into oxides.

[0013] In some embodiments, the formation method of the iron-based catalyst is as follows. First, an alkali solution such as ammonia water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution or potassium carbonate aqueous solution can be taken first, and quickly mixed with an aqueous solution of an iron salt solution such as an aqueous solution of ferric nitrate or ferric hydroxide. For example, the alkali solution and the iron salt aqueous solution can be stirred at high speed (such as>1000rpm) in a short time (such as less than 5 minutes) to make them quickly mixed. In other embodiments, other methods of rapid mixing can be used, and are not limited to high-speed stirring. If the effect of rapid mixing is poor, the specific surface area of ​​the iron-based carrier formed is too low, the pore volume is too small, and the average pore size is too large.

[0014] The pH value of the mixture is then adjusted to 8 to 10 (e.g., 9) and maintained for 1 to 3 hours to produce a precipitate. If the pH value of the mixture is too low, the precipitate particles and average pore size are too large. If the pH value of the mixture is too high, the precipitate cannot be effectively produced. The filter cake is then filtered and washed with water, and the filter cake is dried to obtain an iron-based carrier such as FeO(OH) x, and the drying temperature is about 100°C to 110°C. If the alkali solution used is ammonia water, the iron-based carrier needs to be soaked in an aqueous solution of an alkali metal compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate and dried so that the alkali metal compound is loaded on the iron-based carrier. If the alkali solution used is an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of sodium carbonate, or an aqueous solution of potassium carbonate, this loading step can be omitted as appropriate. Finally, the iron-based carrier loaded with the alkali metal compound is dried and formed to obtain the above-mentioned iron-based catalyst. If the above-mentioned drying temperature is too high, Fe 2 O 3 or Fe 3 O 4 If the drying temperature is too low, FeO(OH) cannot be effectively generated. x .

[0015] Generally speaking, iron salts react with alkali to form iron hydroxide (Fe(OH) 3 ). When iron hydroxide is heated, it undergoes an intramolecular dehydration reaction to form Fe 2 O(OH) 4 , which can further dehydrate to form FeO(OH) x .FeO(OH) x Further dehydration will form Fe 2 O 3 or Fe 3 O 4 According to the TGA analysis, heating of ferric hydroxide (Fe(OH) 3 ) to 50°C, where intramolecular dehydration occurs to form Fe 2 O(OH) 4 Further heating to about 100°C to 110°C forms FeO(OH) x From the Raman spectrum, we can see that there is almost no Fe 2 O 3 with Fe 3 O 4 If FeO(OH) is further heated x (If it exceeds 200℃), Fe 2 O 3 or Fe 3 O 4 The initial weight of the iron salt can be used to calculate the number of moles of Fe and the FeO(OH) formed. x For example, if the mole of Fe is 1 and the product is all FeO(OH), the product weight should be 88.85g; if the product is all FeO(OH) 2 , the product weight should be 105.86g. Therefore, when the actual product weight is 97.35g, it can be known that FeO(OH)x The x value is about 1.5, that is, FeO(OH) and FeO(OH) 2 About half each.

[0016] An embodiment of the present invention provides a method for hydrogenating carbon dioxide, comprising: (i) contacting hydrogen and carbon dioxide with an iron-based catalyst to form a liquid and a gas, wherein the liquid comprises C n H 2n , C n H 2n+2 , or a combination thereof, and water, and n is 5 to 18, wherein the gas comprises CH 4 , C m H 2m , C m H 2m+2 , or a combination thereof, hydrogen, and carbon dioxide, wherein m is 2 to 9. In some embodiments, the ratio of hydrogen to carbon dioxide is 2:1 to 4:1, and the total space velocity (GHSV) of hydrogen and carbon dioxide is 300 to 3000 hr -1 If the hydrogen ratio is too high, the amount of unreacted hydrogen is too high, wasting resources. If the hydrogen ratio is too low, the amount of hydrogen is insufficient, resulting in a low carbon dioxide conversion rate. If the total space velocity of hydrogen and carbon dioxide is too high, the contact time is insufficient to form alkanes and alkenes. If the total space velocity of hydrogen and carbon dioxide is too low, the unit catalyst efficiency is low and the economic benefits are insufficient.

[0017] In some embodiments, the pressure of contacting hydrogen and carbon dioxide with the iron-based catalyst is 50 psi to 400 psi, and the temperature is 260° C. to 360° C. If the pressure is too high, the energy loss is high. If the pressure is too low, multi-carbon alkanes cannot be effectively formed. If the temperature is too high, carbon monoxide is easily formed. If the temperature is too low, carbon dioxide cannot react effectively.

[0018] In some embodiments, the conversion of carbon dioxide is 50% to 80%, and C n H 2n , C n H 2n+2 , or a combination thereof and CH 4 , C m H 2m , C m H 2m+2 , or a combination thereof, with a yield of 45% to 75%. It is worth noting that direct conversion of carbon dioxide (not carbon monoxide) into alkanes (C n H 2n , C n H 2n+2 , or a combination thereof and CH 4 , C m H 2m , Cm H 2m+2 The conversion rate of (or the combination of the above) is usually much lower than 50%.

[0019] In another embodiment of the present invention, the above method may further include (ii) separating the gas and the liquid; and (iii) contacting the gas with another iron-based catalyst to form another liquid and another gas. The other liquid contains C n H 2n 、C n H 2n+2 、or the combination of the above, and water, and n is from 5 to 18. The other gas contains CH 4 、C m H 2m 、C m H 2m+2 、or the combination of the above, hydrogen, and carbon dioxide, where m is from 2 to 9. The other iron-based catalyst includes: 70 mol% to 97 mol% of another porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of another alkali metal compound, supported on the another porous FeO(OH) x .

[0020] Compared with the method that only performs step (i), the method that performs steps (i) to (iii) can further increase the conversion rate of carbon dioxide and hydrogen. For example, the conversion rate of carbon dioxide that only performs step (i) is at most 80%, but the conversion rate of carbon dioxide that performs steps (i) to (iii) can exceed 80%, and even exceed 95%. The method that only performs step (i) requires further separation of unreacted CO 2 and H 2 and the gas product CH 4 、C m H 2m 、C m H 2m+2 、or the combination of the above, which will increase the separation cost. The method that performs steps (i) to (iii) can greatly reduce unreacted CO 2 and H 2 , thus reducing the separation cost. In addition, the product produced by the method that only performs step (i) is mainly the gaseous CH 4 、C m H 2m 、C m H 2m+2 、or the combination of the above (m is mainly from 2 to 3). The method that performs steps (i) to (iii) can greatly increase the liquid product C with a high carbon number n H 2n 、C n H 2n+2, or a combination thereof (n is 5 to 18) and a high carbon number gas product C m H 2m , C m H 2m+2 , or a combination of the above (m>4).

[0021] In some embodiments, step (ii) uses a gas-liquid separation tank to separate the gas and the liquid. In some embodiments, step (ii) can cool the gas and the liquid produced in step (i) to below 100°C (e.g., 5°C to 80°C) to separate the liquid (e.g., water and C n H 2n , C n H 2n+2 , or a combination thereof) with gases (such as unreacted CO 2 With H 2 and CH 4 , C m H 2m , C m H 2m+2 , or a combination thereof). The liquid is then collected, and the separated gas is contacted with another iron-based catalyst in the next reactor to produce another gas and another liquid as in step (iii).

[0022] In some embodiments, the type and amount of the iron-based catalyst, the reaction temperature, and the reaction pressure of step (iii) are the same or similar to those of step (i). In some embodiments, the type and amount of the iron-based catalyst, the reaction temperature, and the reaction pressure of step (iii) are different from those of step (i). For example, the carbon dioxide conversion rate of step (iii) is greater than or equal to the carbon dioxide conversion rate of step (i) to further increase the high carbon number liquid product C n H 2n , C n H 2n+2 , or a combination thereof (n is 5 to 18) and a high carbon number gas product C m H 2m , C m H 2m+2 , or a combination of the above (m>4).

[0023] In some embodiments, the above method may repeat steps (ii) and (iii) multiple times. For example, after separating the liquid and the gas, the gas may be contacted with an iron-based catalyst in the next reactor to generate new liquid and gas. Step (ii) of separating the liquid and the gas and step (iii) of contacting the separated gas with an iron-based catalyst in the next reaction gas may be repeated multiple times until the generated gas is substantially free of carbon dioxide and hydrogen.

[0024] As can be seen from the above, the method of preparing the iron-based catalyst of the present invention is simple and large-scale, and can effectively convert carbon dioxide directly into alkanes and alkenes.

[0025] In order to make the above contents and other purposes, features, and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description as follows:

[0026] [Example]

[0027] Preparation Example 1

[0028] After 2.2 mol of ferric nitrate aqueous solution and ammonia water were stirred at high speed for 3 minutes, the pH value of the mixture was adjusted to 9 and stirred for 120 minutes. After filtering, the filter cake was washed with water and dried to obtain an iron-based carrier such as porous FeO(OH) x After drying the iron-based carrier at 110°C and measuring its weight (200 g), it can be inferred that the content of FeO(OH) is 77 mol%. 2 The content of FeO(OH) is 23 mol%. x x=1.23.

[0029] Preparation Example 2

[0030] After 3.6 mol of ferric nitrate aqueous solution and ammonia water were stirred at high speed for 3 minutes, the pH value of the mixture was adjusted to 9 and stirred for 120 minutes. After filtering, the filter cake was washed with water and dried to obtain an iron-based carrier such as porous FeO(OH) x After drying the iron-based carrier at 110°C and measuring its weight (332 g), it can be inferred that the content of FeO(OH) is 63 mol%. 2 The content of FeO(OH) is 37 mol%. x x=1.37.

[0031] Preparation Example 3

[0032] After 18.5 mol of ferric nitrate aqueous solution and ammonia water were stirred at high speed for 3 minutes, the pH value of the mixture was adjusted to 9 and stirred for 120 minutes. After filtering, the filter cake was washed with water and dried to obtain an iron-based carrier such as porous FeO(OH) x After drying the iron-based carrier at 110°C and measuring its weight (1730 g), it can be inferred that the content of FeO(OH) is 48 mol%. 2 The content of FeO(OH) is 52 mol%. x x=1.52.

[0033] Preparation Example 4

[0034] After 60 mol of ferric nitrate aqueous solution and ammonia water were stirred at high speed for 3 minutes, the pH value of the mixture was adjusted to 9 and stirred for 120 minutes. After filtering, the filter cake was washed with water and dried to obtain an iron-based carrier such as porous FeO(OH) x After drying the iron-based carrier at 110°C and measuring its weight (5620 g), it can be inferred that the content of FeO(OH) is 46 mol%. 2 The content of FeO(OH) is 54 mol%. x x=1.54.

[0035] Example 1

[0036] The iron-based carrier of Preparation Example 3 was re-taken, and its Raman spectrum was as follows: Figure 1 As shown, there is almost no Fe 2 O 3 with Fe 3 O 4 Iron-based supports such as porous FeO(OH) x The specific surface area is 249m 2 / g (measured and calculated by constant temperature nitrogen adsorption method - BET method), the pore volume is 0.39cm 3 / g (measured and calculated by constant temperature nitrogen adsorption method - BJH method), and the average pore size is (Measured and calculated by constant temperature nitrogen adsorption method - BJH method). Then the porous FeO(OH) x Add potassium carbonate aqueous solution to load potassium carbonate on porous FeO(OH) x Then, it is dried at 110℃ to obtain an iron-based catalyst, wherein FeO(OH) x It accounts for 95 mol% (x=1.52), while potassium carbonate accounts for 5 mol%.

[0037] After sieving the above iron-based catalyst, 9 mL of 12-20 mesh iron-based catalyst powder was taken and filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2=4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 350°C, and the reaction pressure was 200 psi. From the analysis of the gas composition after the reaction (using gas chromatography, and using a column Carboxen-1010PLOT, 30m x 0.53mmID with a TCD detector, and a column VB-1, 30m x 0.53mmID with a FID detector for simultaneous measurement and calculation. The following analysis methods are the same), it can be seen that the conversion rate of carbon dioxide is 66.0%, the yield of carbon monoxide is 1.5%, the yield of methane is 32.1%, and the yield of ethylene (C 2 H 4 ) was 11.4%, ethane (C 2 H 6 ) was 3.6%, while the yield of propylene / propane (C 3 H 6 / C 3 H 8 ) with a yield of 17.5%. 1-3 The yield of alkane-olefin was 64.6%.

[0038] Example 2-1

[0039] The iron-based carrier of Preparation Example 3, such as porous FeO(OH) x Add potassium carbonate aqueous solution to load potassium carbonate on porous FeO(OH) x Then, it is dried at 110℃ to obtain an iron-based catalyst, wherein FeO(OH) x It accounts for 75 mol% (x=1.52), while potassium carbonate accounts for 25 mol%.

[0040] After sieving the above iron-based catalyst, 9 mL of 12-20 mesh iron-based catalyst powder was taken and filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 74.0%, the yield of carbon monoxide was 1.9%, the yield of methane was 35.4%, the yield of ethylene was 14.1%, the yield of ethane was 4.5%, and the yield of propylene / propane was 16.4%. 1-3 The yield of alkene was 70.4%.

[0041] Example 2-2 (H 2 / CO 2 Lower limit)

[0042] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =2 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 43.0%, the yield of carbon monoxide was 4.3%, the yield of methane was 19.8%, the yield of ethylene was 6.8%, the yield of ethane was 2.6%, and the yield of propylene / propane was 9.5%. 1-3 The yield of alkane-olefin was 38.7%.

[0043] Example 2-3 (H 2 / CO 2 Too high)

[0044] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =6 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 84.7%, the yield of carbon monoxide was 0.7%, the yield of methane was 51.2%, the yield of ethylene was 6.1%, the yield of ethane was 9.2%, and the yield of propylene / propane was 17.5%. 1-3 The yield of alkane olefins was 84.0%.

[0045] Example 2-4 (H 2 / CO 2 Too low)

[0046] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =1 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 15.3%, the yield of carbon monoxide was 6.7%, the yield of methane was 5.9%, the yield of ethylene was 0.7%, the yield of ethane was 0.4%, and the yield of propylene / propane was 1.6%.1-3 The yield of alkene was 8.6%.

[0047] Example 2-5 (Upper limit of reaction temperature)

[0048] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 360°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 79.4%, the yield of carbon monoxide was 2.8%, the yield of methane was 37.3%, the yield of ethylene was 13.7%, the yield of ethane was 5.5%, and the yield of propylene / propane was 20.1%. 1-3 The yield of alkene was 76.6%.

[0049] Example 2-6 (lower limit of reaction temperature)

[0050] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 260°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 26.8%, the yield of carbon monoxide was 3.7%, the yield of methane was 6.7%, the yield of ethylene was 2.6%, the yield of ethane was 1.1%, and the yield of propylene / propane was 12.8%. 1-3 The yield of alkene was 23.1%.

[0051] Example 2-7 (reaction temperature is too high)

[0052] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2=4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 400°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 74.2%, the yield of carbon monoxide was 8.0%, the yield of methane was 41.3%, the yield of ethylene was 7.4%, the yield of ethane was 5.6%, and the yield of propylene / propane was 11.6%. 1-3 The yield of alkene was 65.9%.

[0053] Example 2-8 (reaction temperature is too low)

[0054] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 240°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 13.3%, the yield of carbon monoxide was 7.0%, the yield of methane was 4.1%, the yield of ethylene was 0.7%, the yield of ethane was 0.4%, and the yield of propylene / propane was 1.1%. 1-3 The yield of alkene was 6.3%.

[0055] Example 2-9 (Upper limit of reaction pressure)

[0056] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 400psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 68.0%, the yield of carbon monoxide was 1.0%, the yield of methane was 27.1%, the yield of ethylene was 15.7%, the yield of ethane was 3.4%, and the yield of propylene / propane was 20.8%. 1-3 The yield of alkane-olefin was 67.0%.

[0057] Example 2-10 (lower limit of reaction pressure)

[0058] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 50psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 50.8%, the yield of carbon monoxide was 5.8%, the yield of methane was 18.7%, the yield of ethylene was 10.6%, the yield of ethane was 1.9%, and the yield of propylene / propane was 13.9%. 1-3 The yield of alkane-olefin was 45.0%.

[0059] Example 2-11 (reaction pressure is too low)

[0060] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was about 0 psi (gauge pressure). The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 30.2%, the yield of carbon monoxide was 4.8%, the yield of methane was 16.7%, the yield of ethylene was 4.2%, the yield of ethane was 1.5%, and the yield of propylene / propane was 3.0%. 1-3 The yield of alkane olefins was 25.4%.

[0061] Example 2-12 (Upper limit of total space flow rate)

[0062] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space velocity was 3000 hr. -1 The hydrogen and carbon dioxide (H 2 / CO 2 =3.5 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 52.5%, the yield of carbon monoxide was 2.2%, the yield of methane was 22.0%, the yield of ethylene was 9.5%, the yield of ethane was 3.2%, and the yield of propylene / propane was 15.9%. 1-3 The yield of alkene was 50.6%.

[0063] Example 2-13 (Lower limit of total space flow rate)

[0064] After sieving the iron-based catalyst of Example 2-1, 9 mL of 12-20 mesh iron-based catalyst powder was filled into a 3 / 8 inch reactor. The total space flow rate was 300 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =3.5 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 59.5%, the yield of carbon monoxide was 2.1%, the yield of methane was 26.9%, the yield of ethylene was 11.3%, the yield of ethane was 3.8%, and the yield of propylene / propane was 15.4%. 1-3 The yield of alkene was 57.4%.

[0065] Example 2-14 (without potassium carbonate)

[0066] The iron-based carrier of Example 1, such as porous FeO(OH) x After sieving (without potassium carbonate loading), take 9 mL of 12-20 mesh porous FeO(OH) x The powder was filled in a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 14.8%, the yield of carbon monoxide was 0.1%, the yield of methane was 14.4%, the yield of ethylene was 0.0%, the yield of ethane was 0.2%, and the yield of propylene / propane was 0.1%. 1-3 The yield of alkene was 14.7%.

[0067] Example 2-15 (Too much potassium carbonate)

[0068] The iron-based carrier of Example 1, such as porous FeO(OH) x Add potassium carbonate aqueous solution to load potassium carbonate on porous FeO(OH) x Then, it is dried and molded to obtain an iron-based catalyst, wherein FeO(OH) x It accounts for 60 mol%, while potassium carbonate accounts for 40 mol%.

[0069] After sieving the above iron-based catalyst, 9 mL of 12-20 mesh iron-based catalyst powder was taken and filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 320°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 16.5%, the yield of carbon monoxide was 7.1%, the yield of methane was 5.3%, the yield of ethylene was 1.2%, the yield of ethane was 0.8%, and the yield of propylene / propane was 2.2%. 1-3 The yield of alkene was 9.4%.

[0070] Comparative Example 1

[0071] The pH value of the mixture of the aqueous solution of ferric nitrate and ammonia is adjusted to 9 and maintained for 120 minutes. After filtration, the filter cake is washed with water and dried at 110°C to obtain a porous iron-based carrier (such as FeO(OH) x , Fe 2 O 3 , and Fe 3 O 4 ). The Raman spectrum of the iron-based carrier is as follows Figure 2 As shown, it contains a lot of Fe 2 O 3 with Fe 3 O 4 The specific surface area of ​​the iron-based carrier is 41.6 m 2 / g (measured and calculated by constant temperature nitrogen adsorption method - BETmethod), the pore volume is 0.24cm 3 / g (measured and calculated by constant temperature nitrogen adsorption method - BJH method), and the average pore size is (Measured and calculated by constant temperature nitrogen adsorption method - BJH method). Then, the iron-based carrier (such as FeO(OH) x , Fe 2 O 3 , and Fe 3 O 4 ) is added with an aqueous solution of potassium carbonate to load the potassium carbonate on the iron-based carrier. Then, the iron-based catalyst is obtained by drying and forming. The iron-based carrier (such as FeO(OH) x , Fe 2 O 3 , and Fe 3 O 4 ) accounts for 95 mol%, and potassium carbonate accounts for 5 mol%.

[0072] After sieving the above iron-based catalyst, 9 mL of 12-20 mesh iron-based catalyst powder was taken and filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2=4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 350°C, and the reaction pressure was 200psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 22.2%, the yield of carbon monoxide was 20.9%, the yield of methane was 0.9%, the yield of ethylene was 0.3%, the yield of ethane was 0.2%, and the yield of propylene / propane was 0. 1-3 The yield of alkene was 1.4%.

[0073] Comparative Example 2

[0074] A16267 (iron(III)hydroxide, alpha-phase, 99+%FeO(OH), CAS: 20334-49-4) purchased from Alfa was used as an iron-based carrier. Its Raman spectrum is shown in Figure 3 As shown, it contains porous FeO(OH) x , Fe 2 O 3 , and Fe 3 O 4 The specific surface area of ​​the iron-based support purchased from Alfa is 14.3 m 2 / g (measured and calculated by constant temperature nitrogen adsorption method - BET method), the pore volume is 0.06cm 3 / g (measured and calculated by constant temperature nitrogen adsorption method - BJH method), and the average pore size is (Measured and calculated by constant temperature nitrogen adsorption method - BJH method). The iron-based carrier is added to the aqueous solution of potassium carbonate to load the potassium carbonate on the iron-based carrier. After that, it is dried and formed to obtain an iron-based catalyst, in which FeO(OH) x , Fe 2 O 3 , and Fe 3 O 4 It accounts for 95 mol%, while potassium carbonate accounts for 5 mol%.

[0075] After sieving the above iron-based catalyst, 9 mL of 12-20 mesh iron-based catalyst powder was taken and filled into a 3 / 8 inch reactor. The total space flow rate was 1800 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =4 / 1, mol / mol) was introduced into the reactor, the reaction temperature was 400°C, and the reaction pressure was 200 psi. The gas composition analysis after the reaction showed that the conversion rate of carbon dioxide was 25.7%, the yield of carbon monoxide was 24.5%, the yield of methane was 0.6%, the yield of ethylene was 0.4%, the yield of ethane was 0%, and the yield of propylene / propane was 0.2%. 1-3The yield of alkane-olefins was 1.2%. The above experiment was repeated, but the reaction temperature was reduced to 350°C, and the conversion of carbon dioxide was <10%.

[0076] Example 3-1

[0077] The iron-based catalyst (FeO(OH) x After sieving, 4.5 mL of 12-20 mesh iron-based catalyst powder was filled into the 3 / 8 inch first reactor, and 4.5 mL of 12-20 mesh iron-based catalyst powder was filled into the 3 / 8 inch second reactor. A gas-liquid separation tank was set up between the first reactor and the second reactor, which was mainly used to separate the gas and liquid produced in the first reactor and introduce the separated gas into the second reactor. The temperature of the gas-liquid separation tank was 50°C.

[0078] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =2.8 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 320°C, and the reaction pressure is 290psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 96.0%, the yield of carbon monoxide is 0.5%, the yield of methane is 29.5%, the yield of ethylene is 11.5%, the yield of ethane is 5.5%, and the yield of propylene / propane is 19.8%. 4 The yield of alkane-olefins was 11.9%, and the gaseous alkane-olefins with carbon number greater than 4 (C 4+ The yield of ) is 14.7%, and the yield of liquid alkane olefins with carbon number ≥ 5 is 2.68%. 2-4 The total yield of gaseous alkanes and alkenes was 48.7%.

[0079] Example 3-2

[0080] The first reactor, gas-liquid separation tank, and second reactor used in Example 3-2 are the same as those in Example 3-1.

[0081] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2=3.0 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 320°C, and the reaction pressure is 290psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 97.6%, the yield of carbon monoxide is 0.3%, the yield of methane is 30.4%, the yield of ethylene is 11.4%, the yield of ethane is 6.4%, and the yield of propylene / propane is 21%. 4 The yield of alkane olefins was 12.4%, and the gaseous alkane olefins with carbon number greater than 4 (C 4+ The yield of ) is 14.1%, and the yield of liquid alkane olefins with carbon number ≥ 5 is 1.74%. 2-4 The total yield of gaseous alkanes and alkenes was 51.2%.

[0082] Example 3-3

[0083] The first reactor, gas-liquid separation tank, and second reactor used in Example 3-3 are the same as those in Example 3-1.

[0084] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =3.4 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 320°C, and the reaction pressure is 290psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 98.0%, the yield of carbon monoxide is 0.1%, the yield of methane is 31.2%, the yield of ethylene is 11.5%, the yield of ethane is 6.6%, and the yield of propylene / propane is 21.4%. 4 The yield of alkane-olefins was 12.7%, and the gaseous alkane-olefins with carbon number greater than 4 (C 4+ The yield of ) is 14.5%, and the yield of liquid alkane olefins with carbon number ≥ 5 is 0%. 2-4 The total yield of gaseous alkanes and alkenes was 52.2%.

[0085] Embodiment 3-4

[0086] The first reactor, gas-liquid separation tank, and second reactor used in Example 3-4 are the same as those in Example 3-1.

[0087] The total space velocity is 1500 hr -1The hydrogen and carbon dioxide (H 2 / CO 2 =4.0 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 320°C, and the reaction pressure is 290psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 99.5%, the yield of carbon monoxide is 0%, the yield of methane is 33.1%, the yield of ethylene is 11.1%, the yield of ethane is 7.1%, and the yield of propylene / propane is 21.1%. 4 The yield of alkane-olefins was 12.3%, and the gaseous alkane-olefins with carbon number greater than 4 (C 4+ The yield of ) was 14.9%, and the yield of liquid alkanes with carbon number ≥ 5 was 0%. 2-4 The total yield of gaseous alkanes and alkenes was 51.6%.

[0088] Example 4-1

[0089] The iron-based catalyst (FeO(OH) x After sieving, 4.5 mL of 12-20 mesh iron-based catalyst powder was filled into the 3 / 8 inch first reactor, and 4.5 mL of 12-20 mesh iron-based catalyst powder was filled into the 3 / 8 inch second reactor. A gas-liquid separation tank was set up between the first reactor and the second reactor, which was mainly used to separate the gas and liquid produced in the first reactor and introduce the separated gas into the second reactor. The temperature of the gas-liquid separation tank was 50°C.

[0090] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =3.0 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 310°C, and the reaction pressure is 200psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 83.6%, the yield of carbon monoxide is 0.9%, the yield of methane is 19.8%, the yield of ethylene is 6.3%, the yield of ethane is 6.0%, and the yield of propylene / propane is 15.8%. 4 The yield of alkane-olefins was 9.1%, and the gaseous alkane-olefins with carbon number greater than 4 (C4+ The yield of ) is 6.2%, and the yield of liquid alkane olefins with carbon number ≥ 5 is 19.5%. 2-4 The total yield of gaseous alkanes and alkenes was 37.2%.

[0091] Example 4-2

[0092] The first reactor, gas-liquid separation tank, and second reactor used in Example 4-2 are the same as those in Example 4-1.

[0093] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2 =3.5 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 310°C, and the reaction pressure is 200psi. From the composition analysis of the liquid separated by the gas-liquid separation tank (after water removal) and the gas and liquid produced by the second reactor (after water removal), it can be seen that the conversion rate of carbon dioxide is 94.6%, the yield of carbon monoxide is 1.3%, the yield of methane is 20.8%, the yield of ethylene is 8.9%, the yield of ethane is 4.7%, and the yield of propylene / propane is 17.6%. 4 The yield of alkane-olefins was 10.7%, and the gaseous alkane-olefins with carbon number greater than 4 (C 4+ The yield of ) is 7.8%, and the yield of liquid alkane olefins with carbon number ≥ 5 is 22.8%. 2-4 The total yield of gaseous alkanes and alkenes was 41.9%.

[0094] Example 4-3

[0095] The first reactor, gas-liquid separation tank, and second reactor used in Example 4-3 are the same as those in Example 4-1.

[0096] The total space velocity is 1500 hr -1 The hydrogen and carbon dioxide (H 2 / CO 2=3.5 / 1, mol / mol) is passed into the first reactor to produce liquid and gas, and the gas is passed into the second reactor after separation in the gas-liquid separation tank to produce liquid and gas products. The reaction temperature of the first reactor and the second reactor is 310°C, and the reaction pressure is 200psi. After 2008 hours of continuous reaction, the composition analysis of the liquid separated by the gas-liquid separation tank (after dehydration) and the gas and liquid produced by the second reactor (after dehydration) shows that the conversion rate of carbon dioxide is 94.9%, the yield of carbon monoxide is 1.2%, the yield of methane is 21.7%, the yield of ethylene is 9.0%, the yield of ethane is 4.7%, and the yield of propylene / propane is 17.6%. 4 The yield of alkane-olefins was 10.5%, and the gaseous alkane-olefins with carbon number greater than 4 (C 4+ The yield of ) is 7.4%, and the yield of liquid alkanes with carbon number ≥ 5 is 22.8%. 2-4 The total yield of gaseous alkanes and alkenes was 41.8%.

[0097] Although the present invention has been disclosed as above with several embodiments, they are not intended to limit the present invention. Anyone with common knowledge in the technical field can make any changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the attached claims.

Claims

1. An iron-based catalyst comprising: 70mol% to 97mol% of a porous FeO(OH) x , where 1 <x<2; as well as 3 mol% to 30 mol% of an alkali metal compound is loaded on the porous FeO(OH) x superior.

2. The iron-based catalyst according to claim 1, wherein the porous FeO(OH) x The specific surface area is 100m 2 / g or above.

3. The iron-based catalyst according to claim 1, wherein the porous FeO(OH) x The pore volume is 0.2 cm 3 / g to 0.5cm 3 / g.

4. The iron-based catalyst according to claim 1, wherein the porous FeO(OH) x The average pore size is to 5. The iron-based catalyst according to claim 1, wherein the alkali metal compound comprises sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, or a combination thereof.

6. A method for hydrogenating carbon dioxide, comprising: (i) contacting hydrogen and carbon dioxide with an iron-based catalyst to form a liquid and a gas, The liquid contains C n H 2n , C n H 2n+2 , or a combination thereof, and water, wherein n is 5 to 18, The gas contains CH4, C m H 2m , C m H 2m+2 , or a combination thereof, hydrogen, and carbon dioxide, wherein m is 2 to 9; The iron-based catalyst comprises: 70 mol% to 97 mol% of a porous FeO(OH) x , where 1 < x < 2; and 3 mol% to 30 mol% of an alkali metal compound is loaded on the porous FeO(OH) x superior.

7. The method for hydrogenating carbon dioxide according to claim 6, wherein the ratio of the hydrogen gas to the carbon dioxide contacting the iron-based catalyst is 2:1 to 4:1, and the total space velocity of the hydrogen gas and the carbon dioxide contacting the iron-based catalyst is 300 hr -1 Up to 3000hr -1 .

8. The method for hydrogenating carbon dioxide according to claim 6, wherein the pressure of the hydrogen and the carbon dioxide contacting the iron-based catalyst is 50 psi to 400 psi, and the temperature is 260°C to 360°C.

9. The method for hydrogenating carbon dioxide according to claim 6, further comprising: (ii) separating the gas from the liquid; as well as (iii) contacting the gas with another iron-based catalyst to form another liquid and another gas, wherein the other liquid comprises C n H 2n , C n H 2n+2 , or a combination thereof, and water, wherein n is 5 to 18, The other gas comprises CH4, C m H 2m , C m H 2m+2 , or a combination thereof, hydrogen, and carbon dioxide, wherein m is 2 to 9, The other iron-based catalyst comprises: 70 mol % to 97 mol % of another porous FeO(OH) x , where 1 <x<2; as well as 3 mol % to 30 mol % of another alkali metal compound, supported on the other porous FeO(OH) x superior.

10. The method for hydrogenating carbon dioxide according to claim 9, wherein the carbon dioxide conversion rate in step (iii) is greater than or equal to the carbon dioxide conversion rate in step (i).

11. The method for hydrogenating carbon dioxide according to claim 9, further comprising repeating steps (ii) and (iii) multiple times.

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