MSECT-4 MOLECULAR SIEVES WITH OFF AND ERI TOPOLOGIES, PREPARATION METHOD THEREFOR, AND APPLICATIONS THEREOF

Abstract

The present disclosure provides msect-4 molecular sieves with OFF and ERI topologies, a preparation method therefor, and applications thereof. An eight-membered ring small pore molecular sieve used as a raw material is dispersed in an aqueous phase. Following that, caustic potash, an aluminum source, and an organic structure-directing agent (OSDA) are added. The pH value is then adjusted to be greater than 10, and a silicon source is introduced to attain the desired silicon-aluminum ratio, followed by stirring reaction, aging, crystallization, filtration, washing, ammonia exchange reaction, drying, and calcination. The msect-4 molecular sieves with OFF and ERI topologies, the preparation method therefor, and applications exhibit excellent hydrothermal stability, a plurality of adsorption sites exposed by a regular bone-like structure, and a large specific surface area. Consequently, this molecular sieves find applicability across various technical fields including selective catalytic reduction, passive adsorption, and catalytic cracking, and has broad application prospects.

Claims

1. A method for preparing msect-4 molecular sieves with OFF and ERI topologies, wherein the msect-4 molecular sieves with OFF and ERI topologies are intergrown, and the msect-4 molecular sieves exhibit a regular bone-like morphology; the method comprises the following steps: dispersing an eight-membered ring small pore molecular sieve used as a raw material in an aqueous phase with stirring, adding caustic potash, adjusting pH to be greater than 10, adding an Organic Structure-Directing Agent (OSDA), and adding a silicon source to adjust a silicon-aluminum ratio, followed by shear stirring, aging, crystallization reaction, filtration, washing, ammonia exchange reaction, drying, and calcination; main X-ray characteristic diffraction peak positions 20 of the msect-4 molecular sieve are 7.89±0.1°, 11.9±0.1°, 13.56±0.1°, 14.23±0.1°, 15.64±0.1°, 16.26±0.1°, 16.67±0.1°, 19.62±0.1°, 20.68±0.1°, 21.51±0.1°, 23.46±0.1°, 23.86±0.1°, 25.03±0.1°, 26.32±0.1°, 27.13±0.1°, 27.4±0.1°, 28.25±0.1°, 28.51±0.1°, 30.7±0.1°, 31.4±0.1°, 31.63±0.1°, 31.96±0.1°, 33.63±0.1°, 36.09±0.1°, 36.35±0.1°, 39.49±0.1°, 41.1±0.1°, 42.89±0.1°, 43.27±0.1°, 43.65±0.1°, 45.88±0.1°, 46.53±0.1°, 48.43±0.1°, 49.181±0.1°, 49.86±0.1°, 50.67±0.1°, 51.72±0.1°, 52.52±0.1°, 54.03±0.1°, 55.73±0.1°, 56.37±0.1°, 58.34±0.1°, 59.64±0.1°, 61.23±0.1°, 61.77±0.1°, 63.7±0.1°, 65.3±0.1°, 65.72±0.1°, 66.61±0.1°, 67.97±0.1°, 68.79±0.1°, 70.43±0.1°, 70.72±0.1°, 72.38±0.1°, 74.7±0.1°, 75.321±0.1°, 76.8±0.1°, and 78.56±0.1′; and the msect-4 molecular sieves have at least two framework types of OFF and ERI, with a silicon-aluminum atomic molar ratio range of 1-200.

2. The method according to claim 1, wherein the eight-membered ring small pore molecular sieve specifically comprises one or more molecular sieves with an AEI, AFX, CHA, DDR, EEI, ESV, ERI, LEV, LTN, LTA, KFI, RHO, RTH, SAS, or SFW topology; the silicon source is one or more of sodium silicate, silica sol, fumed silica, coal gangue, metasilicic acid, potassium silicate, and ethyl orthosilicate; and the OSDA is at least one of N, N, N-trimethylamantadine, benzyltrimethylammonium, choline chloride, 1,6-hexanediamine, tetramethylammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropylammonium hydroxide, and N, N-dimethylpiperidine hydroxide.

3. The method according to claim 1, wherein an ammonium exchange solution in the ammonia exchange reaction is at least one of ammonium nitrate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, and ammonium sulfate; an ammonium exchange reaction time is 1 h-24 h, and an ammonium exchange temperature is less than 120° C.

4. The method according to claim 1, wherein a molar ratio of the raw materials Al.sub.2O.sub.3: SiO.sub.2: OSDA:K.sub.2O:H.sub.2O=1: (5-50): (1-10): (0.5-10): (60-200); a stirring reaction temperature is not more than 100° C.; an aging time is 5 h-100 h; the crystallization is conducted at a constant temperature selected from a range of 140° C.-220° C. for 6 h-240 h; and the calcination is conducted at a constant temperature selected from a range of 450° C.-550° C. for 3 h-9 h; and oxygen content in the calcination atmosphere is more than 20%.

5. The method according to claim 1, wherein a promoter is further added in the process of adding the caustic potash, the aluminum source, and the OSDA; the promoter specifically comprises at least one of a small molecule organic alcohol, a fluorine element, nitrate, triethylamine, and diethylamine; and the small molecule organic alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol.

6. Use of msect-4 molecular sieves prepared by the method according to claim 1, wherein the msect-4 molecular sieves carry metal elements Cu, Fe, Co, Mo, Mn, La, Y, Ce, Sm, Pd, Pt, Rh, Au, Ag, Ru, Ni, Nb, Cr, Ag, Pr, Nd, and V, and a prepared msect-4 molecular sieve based catalytic material is suitable for selective catalytic reduction technology, passive adsorption technology, methanol-to-olefin technology, and catalytic cracking technology; and active metal elements account for 0.05%-35% by mass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a photo of a micro morphology showing H-msect-4 molecular sieves with OFF and ERI topologies prepared in Example 1, presenting a regular bone-like structure with a magnification of 2,000×;

[0035] FIG. 2 is a photo of a micro morphology showing H-msect-4 molecular sieve products prepared in Example 1, with a magnification of 5,000×;

[0036] FIG. 3 is an X-Ray Diffraction (XRD) pattern showing H-msect-4 molecular sieve products prepared in Example 1, with characteristic diffraction peaks attributed to molecular sieves with OFF and ERI topologies;

[0037] FIG. 4 shows a nitrogen adsorption-desorption isothermal curve of H-msect-4 molecular sieve products prepared in Example 1, where a microporous material can be judged through its hysteresis loop characteristics;

[0038] FIG. 5 is a photo of a micro morphology showing msect-4 molecular sieve products prepared in Example 2, where the morphology is formed by lamellar stacking, with a magnification of 20,000×;

[0039] FIG. 6 is a photo of a micro morphology showing msect-4 molecular sieve products prepared in Example 3, where the two ends are thick and the middle is thin, with a magnification of 10,000×;

[0040] FIG. 7 is a photo of a micro morphology showing H-msect-4 molecular sieve products prepared in Example 4, where a flat end face and a hexagonal shape is shown, with a magnification of 100,000×;

[0041] FIG. 8 shows a NO.sub.x conversion rate curve in a catalytic performance verification example, where a nitrogen oxide ignition temperature (T.sub.50) is 142° C., an active temperature window (T.sub.90) is 170° C.-580° C., and test conditions are [NH.sub.3]=[NO]=500 ppm, [O.sub.2]=10 vol. %, with N.sub.2 as a balance gas, a total flow rate of 1,000 ml/min, and a space velocity of 30,000 h.sup.−1;

[0042] FIG. 9 shows byproduct production curves in a catalytic performance verification example, where the production of N.sub.2O is less than 10 ppm and the production of NO.sub.2 at high temperatures is less than 15 ppm; and

[0043] FIG. 10 shows elements in a catalytic performance verification example, with a copper content of 3.26 wt %.

DESCRIPTION OF THE ERIBODIMENTS

[0044] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those commonly understood by a person skilled in the art to which the present disclosure belongs. Test reagents used in the following examples are all conventional biochemical reagents, unless otherwise specified; and the experimental methods are conventional methods, unless otherwise specified.

[0045] The present disclosure will be explained in detail below in conjunction with examples and the accompanying drawings.

[0046] In the present disclosure, a simulated flue gas used for NH.sub.3-SCR performance test includes 500 ppm NO, 500 ppm NH.sub.3, and 10% O.sub.2, and N.sub.2 is a balance gas, with a total flow rate of 1,000 ml/min and a reaction space velocity of 30,000 h.sup.−1.

[0047] In the present disclosure, the low-temperature performance index T.sub.50 represents a corresponding temperature when the NO.sub.x conversion rate reaches 50%; and the temperature window index T.sub.90 represents a corresponding temperature range when the NO.sub.x conversion rate exceeds 90%.

[0048] Unless otherwise specified, all numerical values in the specification and claims of the present disclosure, such as temperature, time, and material contribution percentage by mass, should not be understood as absolute accurate values, but are within the error ranges understood by those of ordinary skill in the art and allowed by the common knowledge.

[0049] This patent will be further described below in conjunction with examples, but the protection scope of the present disclosure is not limited thereto.

[0050] Examples of msect-4 molecular sieve synthesis are Examples 1-5, and corresponding comparative examples are Comparative Examples 1-3.

Example 1

[0051] 3.28 g of NaAlO.sub.2 and 2 g of KOH are weighed separately and dissolved in 20 g of water, the solution is stirred for 1 h until the solution is clear, 20 g of N, N, N-trimethylamantadine is added, the stirring is continued for 2 h until the solution is well-mixed, and then a solution with pH>11.9 is obtained. Subsequently, 60 g of silica sol is added and the stirring is continued for 4 h to form a well-mixed sol. Aging is conducted for 10 h, followed by crystallization at a constant temperature of 160° C. for 8 h. Then, drying and calcination are performed at a constant temperature of 550° C. for 3 h. The prepared molecular sieve is labeled as K-msect-4. A 0.5 M solution of NH.sub.4NO.sub.3 is prepared, 5 g of the K-msect-4 molecular sieve and 500 ml of the solution are mixed with stirring for 12 h, and drying and calcination are performed after repeating the previous operation for three times, where the calcination is performed at a temperature of 550° C. for 3 h. The prepared molecular sieve is labeled as H-msect-4.

[0052] FIG. 1 and FIG. 2 are two photos of a micro morphology showing H-msect-4 molecular sieves with OFF and ERI topologies prepared in Example 1, presenting a regular bone-like structure.

[0053] FIG. 3 is an XRD pattern showing H-msect-4 molecular sieve products prepared in Example 1, with characteristic diffraction peaks attributed to molecular sieves with OFF and ERI topologies. XRD characterization results show that the foregoing solid products have intergrown phases of ERI and OFF topologies; and Scanning Electron Microscope (SERI) characterization shows that the products exhibit a regular bone-like morphology. FIG. 4 shows a nitrogen adsorption-desorption isothermal curve of H-msect-4 molecular sieve products prepared in Example 1, wherei a microporous material can be judged through its hysteresis loop characteristics.

Example 2

[0054] The preparation conditions and preparation process of this example are the same as those of Example 1, except that a small amount of H-SSZ-13 molecular sieves is added into the well-mixed sol-gel as seed crystals. FIG. 5 is a photo of a micro morphology showing msect-4 molecular sieve products prepared in Example 2, where the morphology is formed by lamellar stacking.

Example 3

[0055] The preparation conditions and preparation process of this example are the same as those of Example 1, except that the OSDA is not added.

[0056] FIG. 6 is a photo of a micro morphology showing msect-4 molecular sieve products prepared in Example 3, where the two ends are thick and the middle is thin. SERI characterization shows that the product exhibits a regular bone-like morphology.

Example 4

[0057] 5 g of H-SSZ-13, 2 g of KOH, and 20 g of H.sub.2O are weighed and added into 20 g of N, N, N-trimethylamantadine, then 10 g of silica sol with a solid content of 30% is added, and stirring is performed for 3 h until the solution is well-mixed, followed by putting it aside to age for 12 h. Crystallization reaction at a constant temperature of 160° C. for 8 h is performed. Subsequently, drying and calcination are performed, where the calcination is performed at a temperature of 550° C. for 6 h; and H-msect-4 molecular sieves are prepared.

[0058] FIG. 7 is a photo of a micro morphology showing msect-4 molecular sieve products prepared in Example 4, where a flat end face and a hexagonal shape is shown. SERI characterization shows that the product exhibits a regular bone-like morphology.

Example 5

[0059] The preparation conditions and preparation process of this example are the same as those of Example 4, except that the H-SSZ-13 molecular sieves are replaced with Y-type molecular sieves.

Comparative Example 1

[0060] Refer to the preparation conditions and preparation process of H-msect-4 molecular sieve preparation in Example 1. The difference is that the pH value of the solution is adjusted to be less than 10 with KOH.

[0061] Experimental results indicate that the products are mainly amorphous SiO.sub.2.

Comparative Example 2

[0062] Refer to the preparation conditions and preparation process of H-msect-4 molecular sieve preparation in Example 1. The difference is that crystallization reaction at a constant temperature takes 4 h.

[0063] Experimental results indicate that the products are mainly amorphous SiO.sub.2.

Comparative Example 3

[0064] Refer to the preparation conditions and preparation process of H-msect-4 molecular sieve preparation in Example 1. The difference is that the crystallization is performed at a constant temperature of 100° C.

[0065] Experimental results indicate that the products are mainly amorphous SiO.sub.2.

[0066] Msect-4 molecular sieve catalysts prepared from Example 1 The catalysts are prepared by using an ion exchange method. 0.5 M solution of Fe(NO.sub.3).sub.3, 0.5 M solution of Cu(NO.sub.3).sub.2, 0.5 M solution of Mn(NO.sub.3).sub.2, 0.5 M solution of (NH.sub.4).sub.2MoO.sub.4, and 0.5 M solution of (NH.sub.4).sub.6W.sub.7O.sub.24 are prepared separately, 1 g of the H-msect-4 is added into 200 ml of each solution, and the solutions are heated at 80° C. for 12 h with stirring, followed by drying and calcination at a constant temperature of 550° C. for 3 h. The prepared catalysts are labeled as Fe/msect-4, Cu/msect-4, Mn/msect-4, Mo/msect-4, and W/msect-4, respectively.

[0067] Msect-4 molecular sieve catalysts prepared from Example 2 The catalysts are prepared by using an ion exchange method. 0.9 g of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 0.47 g of Cu(NO.sub.3).sub.2.Math.3H.sub.2O, 1.63 g of Mn(NO.sub.3).sub.2, 0.18 g of (NH.sub.4).sub.2MoO.sub.4.Math.6H.sub.2O, and 3.68 g of (NH.sub.4).sub.6W.sub.7O.sub.24.Math.6H.sub.2O are weighed separately, 1 g of the H-msect-4 is mixed with each of the metal sources, deionized water is added dropwise until the solution is viscous, and the solution is heated at 50° C. for ultrasound for 2 h, followed by drying and calcination at a constant temperature of 550° C. for 3 h. The prepared catalysts are labeled as Fe/msect-4-2, Cu/msect-4-2, Mn/msect-4-2, Mo/msect-4-2, and W/msect-4-2, respectively.

[0068] Msect-4 molecular sieve catalyst prepared from Example 3 Refer to the preparation conditions and preparation process of msect-4 molecular sieve catalyst in Example 2. The difference is that 0.9 g of Fe(NO.sub.3).sub.3.Math.9H.sub.2O and 0.47 g of Cu(NO.sub.3).sub.2.Math.3H.sub.2O are added simultaneously to obtain a catalyst labeled as Cu—Fe/msect-4-2.

[0069] Msect-4 molecular sieve catalyst prepared from Example 4 0.9 g of Fe(NO.sub.3).sub.3.Math.9H.sub.2O, 0.47 g of Cu(NO.sub.3).sub.2.Math.3H.sub.2O, 1.63 g of Mn(NO.sub.3).sub.2, 0.18 g of (NH.sub.4).sub.2MoO.sub.4.Math.6H.sub.2O, and 3.68 g of (NH.sub.4).sub.6W.sub.7O.sub.24.Math.6H.sub.2O are weighed separately, each of the metal sources is dissolved in 500 ml of deionized water to obtain a solution of metal sources, and 1 g of the H-msect-4 is mixed with the solution, followed by rotary evaporation at 70° C., drying and calcination at a constant temperature of 550° C. for 3 h. The prepared catalysts are labeled as Fe/msect-4-3, Cu/msect-4-3, Mn/msect-4-3, Mo/msect-4-3, and W/msect-4-3, respectively. Msect-4 molecular sieve catalyst prepared from Example 5 2.5 g of Pd(NO.sub.3).sub.2, 2.5 g of Pt(NO.sub.3).sub.2, and 2.5 g of Rh(NO.sub.3)3 are weighed separately, 5 g of the H-msect-4 is mixed with each of the metal sources, and deionized water is added dropwise until the solution is viscous, followed by ultrasound for 2 h, drying and calcination at a constant temperature of 550° C. for 3 h. The prepared catalysts are labeled as Pt-msect-4, Pd-msect-4, and Rh-msect-4, respectively.

Catalytic Performance Verification Example

[0070] The catalyst sample Cu/msect-4 of the H-msect-4 molecular sieve catalysts prepared in Example 1 is pressed and sieved to prepare a 40-60 mesh solid to-be-tested sample. NH.sub.3-SCR reaction performance is tested on an activity evaluation device by using simulated exhaust gas. A quartz reaction tube with a size of 15 mm is used, and a heating rate of 5° C./min is applied in the evaluation test. The simulated gas includes 500 ppm NO, 500 ppm NH.sub.3, and 10% O.sub.2, and N.sub.2 is a balance gas, with a total flow rate of 1,000 ml/min and a reaction space velocity of 30,000 h.sup.−1. The test results are shown in FIG. 8. FIG. 9 shows byproduct production curves in the catalytic performance verification example, where the production of N.sub.20 is less than 10 ppm and the production of NO.sub.2 at high temperatures is less than 15 ppm.

[0071] FIG. 10 shows elements in the catalytic performance verification example, with a copper content of 3.26 wt %.

[0072] The test results show that the foregoing catalysts have a NO.sub.x ignition temperature T.sub.50 of 142° C. and an active temperature window T.sub.90 of 175° C.-580° C.

[0073] The above descriptions are only preferred examples of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present disclosure is included in the protection scope of the present disclosure.