Catalysts for deoxygenation and NOx removal of organic hydrocarbons and their preparation methods

Abstract

This invention provides a catalyst for the deoxygenation and NOx removal of organic hydrocarbons and its preparation method. The method includes the preparation of a composite support, support modification, and loading of the active component. At least two of a noble metal nitrate and a chloroiridium acid are prepared into a mixed solution, and the pH is adjusted to 2-4 with sodium bicarbonate solution. MoO3-Pr6O... 11 / aTiO2-bSiO2-Al2O3 is added to the mixed solution, stirred evenly, and allowed to stand for 4–8 hours; after filtration, it is dried at 105℃ and calcined at 400–600℃ for 4–6 hours to obtain a semi-finished product. The semi-finished product is then reduced with sodium borohydride at 60–80℃ for 2–3 hours, or reduced with a mixture of 95% nitrogen and 5% hydrogen at 250–350℃ for 4–6 hours to obtain the finished product.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a catalyst for the deoxygenation and NOx removal of organic hydrocarbons and its preparation method. Background Technology

[0002] In recent years, the chemical industry has seen an increasing demand for syngas. Many industrial waste gases can be separated and purified to obtain suitable feedstock gases, such as H2, CO, C2H4, CH4, and CO2. These gases can be used to synthesize new materials and as energy sources. However, during the separation and purification process, depending on the requirements of different operating environments, it is often necessary to remove oxygen and NOx from the feedstock gases to certain standards. Gas separation and purification typically employs methods such as pressure swing adsorption (PSA), temperature swing adsorption (TSA), and cryogenic treatment, with the combination of purification methods usually chosen based on the composition of the feedstock gas. However, even after separation and purification, oxygen and NOx cannot be completely removed. Oxygen can affect many subsequent processes, and NOx accumulation in later processes poses an explosion risk. For deoxygenation, many catalysts are currently available on the market, commonly including palladium, platinum, copper, and cobalt-molybdenum catalysts; however, selective catalytic reduction (SCR) catalysts are currently the most commonly used for NOx removal. Currently, there is no catalyst on the market that can simultaneously remove oxygen and NOx in a mixed gas environment.

[0003] Therefore, a catalyst that can not only remove oxygen but also remove NOx has been developed for these application environments, shortening the gas separation and purification process and reducing the capital investment required for separate oxygen and NOx removal. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a catalyst for the deoxygenation and NOx removal of organic hydrocarbons and its preparation method.

[0005] The technical solution of the present invention is a method for preparing a catalyst for the deoxygenation and NOx removal of organic hydrocarbons, comprising the following steps:

[0006] Preparation of S1 composite carrier;

[0007] S2 support modification: The aTiO2-bSiO2-Al2O3 composite support was sequentially impregnated with ammonium heptamolybdate solution, praseodymium nitrate solution, or praseodymium oxalate solution, and then calcined at 380-550℃ for 3-6 hours to obtain the modified MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3;

[0008] Among them, MoO3 and Pr6O 11 They account for 0.3% to 2% and 0.01% to 0.5% of the carrier weight, respectively;

[0009] Loading of the active component S3: A mixed solution of palladium or / and platinum nitrate and chloroiridium acid was prepared, and the pH was adjusted to 2-4 with sodium bicarbonate solution. The MoO3-Pr6O in S2 was then loaded. 11 / aTiO2-bSiO2-Al2O3 is added to the mixed solution, stirred evenly, and then allowed to stand for 4 to 8 hours;

[0010] After filtration, drying at 105℃ and calcination at 400-600℃ for 4-6 hours, a semi-finished product is obtained. The semi-finished product is then reduced with sodium borohydride at 60-80℃ for 2-3 hours, or reduced with a mixture of 95% nitrogen and 5% hydrogen at 250-350℃ for 4-6 hours, to obtain the finished product.

[0011] The roasting conditions in S2 are 480–520°C for 4–6 hours.

[0012] In S3, chloroiridium acid is replaced by ammonium chloroiridium.

[0013] The preparation step of S1 is as follows: using tetrabutyl titanate as raw material, nano-titanium dioxide is prepared by sol-gel method. The obtained nano-titanium dioxide is mixed evenly with boehmite and silicon dioxide, and then additives are added. The mixture is pressed into shape by tablet press to obtain aTiO2-bSiO2-Al2O3 composite carrier with a specific surface area of ​​100-300㎡ / g, wherein the contents of a and b are 1%-5% and 2-8% of the total carrier mass, respectively.

[0014] The second technical solution of the present invention is a catalyst prepared by the aforementioned method, the chemical composition of which is:

[0015] xPd-yPt-zIrO2-MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3

[0016] Where: x = 0 to 0.21%, y = 0 to 0.1%, z = 0.03% to 0.3%, all of which are mass percentages.

[0017] In the third step (S3) of catalyst preparation, non-precious metals other than precious metals are selected, with a loading of 2%–15%, and are loaded using the equal-volume impregnation method for 2–4 hours, followed by calcination at 550–650℃. The non-precious metals are selected from copper, cobalt, nickel, and manganese.

[0018] The third technical solution of the present invention is a catalyst prepared by the aforementioned method, the chemical composition of which is:

[0019] xCu / Co / Ni / Mn-yBi-MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3

[0020] Where x = 2%–15%, y = 0.2%–1.5%.

[0021] Deoxygenation mechanism:

[0022] 2H₂ + O₂ = 2H₂O

[0023] 2CO + O2 = 2CO2

[0024] CnHm + O2 → CO2 + H2O

[0025] NOx removal mechanism:

[0026] NO x +H2→N2+H2O

[0027] NO x +CO→N2+CO2

[0028] CnHm+NO x →N2+CO2+H2O

[0029] This catalyst, operating in a gas source environment containing organic hydrocarbons, utilizes the reaction of hydrogen, oxygen, or hydrocarbons in the feed gas with oxygen to deoxygenate to <1 ppm. Simultaneously, it can remove trace amounts of NOx from the feed gas to <100 ppb. This catalyst is suitable for gas source environments such as catalytic cracking dry gas, semi-water gas, water gas, and calcium carbide tail gas. The gas contains one or more of H2, CnHm, and CO, and contains O2 or / and NOx, as well as inert gases such as N2.

[0030] This catalyst has a wide range of applications, high deoxygenation precision, and NOx removal capabilities. It also exhibits high selectivity and can suppress hydrogenation side reactions of unsaturated hydrocarbons in environments containing such hydrocarbons.

[0031] The catalyst's tolerance is improved through support modification, enabling it to adapt to various environments. Furthermore, the use of IrO2 as a co-catalyst to protect the noble metals Pd and / or Pt increases the catalyst's reducibility for NOx and enhances its selectivity. Attached Figure Description

[0032] Figure 1 This is the cross-section of the finished granules. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments and accompanying drawings.

[0034] Step 1: Preparation of the composite carrier: Using tetrabutyl titanate as raw material, nano-titanium dioxide is prepared by the sol-gel method. The obtained nano-titanium dioxide is mixed evenly with boehmite and silica, and then stearic acid, activated carbon, guar gum, etc. are added. The mixture is then pressed into shape using a tablet press to obtain an aTiO2-bSiO2-Al2O3 composite carrier with a specific surface area of ​​100-300 m² / g, wherein the contents of a and b are 1%-5% and 2%-8% of the total carrier mass, respectively. Alternatively, commercially available composite carriers can be purchased for this step.

[0035] Step 2: Support Modification: The aTiO2-bSiO2-Al2O3 composite support was sequentially impregnated with ammonium heptamolybdate solution, praseodymium nitrate solution, or praseodymium oxalate solution, and then calcined at 380–550℃ for 3–6 hours, with a preferred condition of 480–520℃ for 4–6 hours. This yielded the modified MoO3-Pr6O3. 11 / aTiO2-bSiO2-Al2O3. Where MoO3 and Pr6O... 11 They account for 0.3% to 2% and 0.01% to 0.5% of the carrier weight, respectively;

[0036] Step 3: Loading of the active component: Prepare a mixed solution of palladium and / or platinum nitrate and chloroiridium acid (ammonium chloroiridium acid can also be used instead of chloroiridium acid), adjust the pH to 2-4 with sodium bicarbonate solution, and load the MoO3-Pr6O from step 2. 11 / aTiO2-bSiO2-Al2O3 is added to the mixed solution, stirred evenly, and then allowed to stand for 4 to 8 hours;

[0037] After filtration, the product is dried at 105℃ and calcined at 400-600℃ for 4-6 hours to obtain a semi-finished product. The semi-finished product is then reduced with sodium borohydride at 60-80℃ for 2-3 hours, or reduced with a mixture of 95% nitrogen and 5% hydrogen at 250-350℃ for 4-6 hours to obtain the finished product.

[0038] The chemical composition of the catalyst is: xPd-yPt-zIrO2-MoO3-Pr6O11 / aTiO2-bSiO2-Al2O3

[0039] Where: x = 0 to 0.21%

[0040] y = 0 to 0.1%

[0041] z = 0.03% to 0.3%. All values ​​are mass percentages.

[0042] Example 1

[0043] Test gases: CO: balance gas, H2: 1.75%, C2H4: 0.5%, O2: 0.5%, NO: 9ppm

[0044] Catalyst: 0.05Pd-0.03Pt-0.1IrO2-MoO3-Pr6O 11 / 2TiO2-4SiO2-Al2O3

[0045] Test conditions: 0.5 MPa, air velocity 5000 h⁻¹ -1 .

[0046] Test results:

[0047] Residual oxygen content / ppm 5000 2276 27.8 1.37 0.6 0.3 NO content / ppm 9 8.9 8.9 8.6 5.2 0.08

[0048] Example 2

[0049] Test gases: C2H4: balance gas, H2: 1%, C2H6: 30%, O2: 0.05%, NO2: 6ppm, N2: 24%

[0050] Catalyst: 0.01Pd-0.05Pt-0.15IrO2-MoO3-Pr6O 11 / 3TiO2-5SiO2-Al2O3

[0051] Test conditions: 0.3 MPa, air velocity 5000 h⁻¹ -1 .

[0052] Test results:

[0053] Residual oxygen content / ppm 447 2.84 0.95 0.87 0.62 <![CDATA[NO2 content / ppm]]> 5.8 5.5 2.8 1.3 0.06

[0054] Example 3

[0055] Test gases: C2H4: 2.6%, H2: 36%, C2H6: 2%, O2: 0.6%, NO2: 6ppm, H2S: 20ppm, CH4: balance gas

[0056] Catalyst: 0.12Pd-0.18IrO2-MoO3-Pr6O 11 / 3TiO2-2SiO2-Al2O3

[0057] Test conditions: 0.8 MPa, air velocity 4000 h⁻¹ -1 .

[0058] Test results:

[0059] Residual oxygen content / ppm 5997 5.4 1.68 0.77 0.52 <![CDATA[NO2 content / ppm]]> 6 5.5 2.8 0.6 0.05

[0060] Figure 1 This is the cross-section of the finished granules.

[0061] In the third step of catalyst preparation, non-precious metals other than palladium and platinum, such as copper, cobalt, nickel, and manganese, can be selected with a loading of 2%–15%, but additives such as lead and bismuth are required. The catalyst is loaded using an equal-volume impregnation method for 2–4 hours, and calcined at 550–650℃. The non-precious metals selected are copper, cobalt, nickel, and manganese. The chemical composition of this catalyst is as follows:

[0062] xCu / Co / Ni / Mn-yBi-MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3

[0063] Where x = 2–15%, y = 0.2–1.5%.

[0064] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A method for preparing a catalyst containing organic hydrocarbon deoxygenation and NOx removal, characterized in that, Includes the following steps: Preparation of S1 composite carrier; S2 support modification: The aTiO2-bSiO2-Al2O3 composite support was sequentially impregnated with ammonium heptamolybdate solution, praseodymium nitrate solution, or praseodymium oxalate solution, and then calcined at 380~550℃ for 3~6 hours to obtain the modified MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3; Among them, MoO3 and Pr6O 11 These account for 0.3%~2% and 0.01%~0.5% of the carrier weight, respectively; Loading of the active component S3: A mixed solution of palladium and / or platinum nitrate and chloroiridium acid was prepared, and the pH was adjusted to 2-4 with sodium bicarbonate solution. This process was then used to load the MoO3-Pr6O3 component from S2. 11 Add / aTiO2-bSiO2-Al2O3 to the mixed solution, stir well, and let stand for 4-8 hours; After filtration and drying, the semi-finished product is obtained by calcination at 400-600℃ for 4-6 hours. The semi-finished product is then reduced by sodium borohydride at 60-80℃ for 2-3 hours, or by a mixture of 95% nitrogen and 5% hydrogen at 250-350℃ for 4-6 hours, to obtain the catalyst.

2. The method according to claim 1, characterized in that, The roasting conditions in S2 are 480~520℃ and roasting for 4~6 hours.

3. The method according to claim 1, characterized in that, The preparation step of S1 is as follows: using tetrabutyl titanate as raw material, nano-titanium dioxide is prepared by sol-gel method. The obtained nano-titanium dioxide is mixed evenly with boehmite and silicon dioxide, and then additives are added. The mixture is pressed into shape by tablet press to obtain aTiO2-bSiO2-Al2O3 composite carrier with a specific surface area of ​​100~300㎡ / g, wherein the contents of a and b are 1%~5% and 2%~8% of the total carrier mass, respectively.

4. The method according to claim 1, characterized in that, The precious metal in S3 is selected from palladium and platinum.

5. The catalyst prepared by the method according to any one of claims 1 to 3, wherein the chemical composition of the catalyst is: xPd-yPt-zIrO2-MoO3-Pr6O 11 / aTiO2-bSiO2-Al2O3 in: x=0~0.21%, y=0~0.1%, z=0.03%~0.3% x, y, and z are all mass percentages.

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