Binderless Na-LSX zeolite synthesis for higher N2 adsorption

Abstract

The present invention relates to a method for synthesizing binderless Na-LSX zeolite without gel aging, which exhibits higher N2 adsorption from air containing 21% N2 and 79% O2.

Description

[Technical Field]

[0001] The present invention relates to binderless Na-LSX zeolites for higher N adsorption. In particular, the present invention relates to a method for synthesizing binderless Na-LSX zeolites without gel aging, which exhibit higher N adsorption from air containing 21% O and 79% N. [Background technology]

[0002] The separation of nitrogen from a mixture of various gases by adsorption techniques is a very important process in all industrial processes. Nitrogen is separated to obtain a nitrogen-rich or nitrogen-free product.

[0003] In the prior art of N2 adsorption, several techniques are available, such as cryogenic distillation, pressure swing adsorption (PSA), and vapor pressure swing adsorption (VPSA). Among them, the use of zeolites for N2 separation / adsorption is a widely used technique. Due to their high adsorption efficiency, zeolites are used to adsorb various gases, such as CO2, O2, and N2, from various mixtures, as well as oily / liquid materials. The various ratios of zeolite composition and its physical form play crucial roles in its adsorption efficiency. Therefore, its proper preparation has also become a very important and interesting research topic for scientists.

[0004] A paper titled "Synthesis and Characterization of NaX-Type Zeolites Prepared by Different Silica and Alumina Sources and Their CO2 Adsorption Properties" by K. Chayakul Chanapattharapol et al., published in the journal Microporous and Mesoporous Materials 310 (2021) 110632, reported the synthesis of zeolites using two pairs of silicon and aluminum sources: sodium silicate solution + Al(OH)3 and sodium silicate powder + sodium aluminate. This paper showed that the sodium silicate and sodium aluminate sources yielded zeolites with high surface area and pore volume. The CO2 adsorption capacity and selectivity of zeolite NaX were modified by using cetyltrimethylammonium bromide (CTAB) and heptane. The surface area and pore volume of the zeolite product increased due to smaller crystal size, which in turn led to a significant improvement in CO2 uptake of the synthesized zeolite NaX. This paper also showed that the role of additives on zeolite formation is to increase the rate and number of nucleation, which results in smaller zeolite crystals.

[0005] Another paper, "Effects of Na and K ions on the Crystallization of Low-silica X Zeolite and Its Catalytic Performance for Alkylation of Toluene with Methanol," by Kan Zhang et al., published in the journal J. Braz. Chem. Soc., Vol. 25, No. 1, pp. 65-74, 2014, showed that in the synthesis of LSX, the K / (Na+K) molar ratio affected the crystallization and composition of the final product. A higher K molar fraction corresponded to a lower crystallization rate, a higher Si concentration in the liquid phase, and a lower Si / Al ratio in the resulting LSX. The average size of the LSX product gradually increased with the replacement of Na with K, and the crystalline morphology of the LSX product gradually changed from spherical to octahedral.

[0006] Another paper, titled "Synthesis and Characterization of High Aluminum Zeolite X from Technical Grade Materials," by Seyed Kamal Masoudian et al., published in the journal "Bulletin of Chemical Reaction Engineering & Catalysis," 8(1), 2013, pp. 54-60, reported the preparation of high-aluminum zeolite X by mixing technical-grade sodium aluminate and sodium silicate solutions at temperatures between 70 and 100°C. The synthesized zeolite X was characterized by SEM and X-ray methods according to ASTM standard procedures. Results showed that aging the synthesis medium at room temperature significantly increased the selectivity of zeolite X formation. On the other hand, heating the reaction mixture during crystallization resulted in the formation of zeolite A in the product, thus decreasing the purity of zeolite X. Furthermore, it was found that increasing the HO / Na2O and decreasing the Na2O / SiO2 molar ratio in the reaction mixture resulted in a product with higher purity.

[0007] One U.S. patent publication, US9061918B2, reports a low-silica faujasite X-type zeolite, more precisely, zeolite LSX, having a Si / Al atomic ratio of 1.15 or less and a high degree of crystallinity. The crystals have a controlled particle size distribution and molar compositions of Na2O / (Na2O+K2O) ratio of 0.75 to 1; SiO2 / Al2O3 of 1.8 to 2.2; (Na2O+K2O) / Al2O3 of 4.8 to 6; and H2O / Al2O3 of 60 to 85. However, the molar gel composition and salt addition method covered by this U.S. patent are different from those of the present application and are completely undesirable, considering that they produce sodalite and other Na- or K-based impurities and therefore only provide a maximum crystallinity of 95% (rather than the desired maximum of 100%).

[0008] It can therefore be seen that there remains a need in the art to develop methods for producing zeolitic materials that can be effectively used for the separation and adsorption of various gases. Summary of the Invention [Problem to be solved by the invention]

[0009] The main objective of the present invention is to provide a binderless Na-LSX zeolite for higher N2 adsorption.

[0010] Another object of the present invention is to provide a method for synthesizing binderless Na-LSX zeolite for higher N2 adsorption.

[0011] Yet another object of the present invention is that the binderless Na-LSX zeolite is applicable for N2 adsorption from air by PSA / VPSA technology.

[0012] Yet another object of the present invention is a process for adsorbing N2 from air using said binderless Na-LSX zeolite by PSA / VPSA technique. [Means for solving the problem]

[0013] Therefore, to achieve the objective, the present invention provides a binderless Na-LSX zeolite for higher N2 adsorption.

[0014] In one embodiment, the present invention provides a binderless Na-LSX zeolite for higher N adsorption, the zeolite having a molgel composition of SiO / AlO=2.0; (NaO+KO) / SiO=3.0; NaO / NaO+KO=0.77; HO / NaO+KO=25, and a crystallinity of 100%.

[0015] Another embodiment of the present invention provides a method for synthesizing NaK-LSX zeolite in powder form and Na-LSX zeolite in powder form, said method comprising: (a) adding, under constant stirring, rapidly for a period of 5 minutes at a temperature in the range of 70-75°C (the temperature of solution B), solution A (prepared by dissolving 0.896 kg of sodium aluminate in 2.8 L of water under continuous stirring and continuing stirring until the sodium aluminate is completely dissolved) to solution B (prepared by dissolving 1.135 kg of NaOH in 4.1 L of water under constant stirring); (b) preparing solution C by adding sodium silicate solution (2.07 kg) to 4.1 kg of water, and then slowly adding solution C to the mixture of solutions A and B obtained in step (a) under vigorous continuous stirring at a temperature in the range of 30-40°C for a period of 60 minutes; (c) adding solution D (prepared by adding 0.878 kg of KOH to 0.8 L of water) to the mixture obtained in step (b) under vigorous stirring at a temperature in the range of 30-40°C for a period in the range of 1-2 hours; (d) transferring the gel obtained in step (c) into a 20 L SS autoclave and crystallizing it at 70-75°C for 17 hours; (e) filtering, washing with demineralized water until Na and K are removed, and drying at 100°C for 12 hours to obtain NaK LSX zeolite in powder form, which is confirmed as pure faujasite-type zeolite (NaK-LSX) by X-ray diffraction; (f) subjecting the thus obtained NaK-LSX to further ion exchange using a 2M sodium chloride solution (at a rate of 10 ml per gram of solid) at a pH of 9-10 for 5 hours at 95°C; (g) removing chloride ions from the solid obtained in step f) by washing excess salt with deionized water and drying the solid at 110°C for 12 hours to obtain Na-LSX zeolite in powder form; Includes:

[0016] Another aspect of one embodiment is to provide a method for preparing Na-LSX zeolite in extrudate, sphere, or tablet form. Specifically, the present invention discloses a method for preparing binderless Na-LSX zeolite in extrudate, sphere, or tablet form by converting binder-containing Na-LSX zeolite extrudates / spheres / tablets (e.g., kaolin clay, etc.) into zeolite, said method comprising: A) Mixing 70g of zeolite X powder (Na-LSX), 30g of kaolin (initial material 4) and 2g of lactose; B) preparing a dough of suitable consistency from the mixture obtained in step (A), wherein the dough is prepared in a twin-shaft mixer using 45 gm of a carboxymethylcellulose solution of sodium salt (2.5% by weight); C) forming the dough mixture obtained in step (B) into extrudates of 1 millimeter size in a screw extruder (VJ instrument); D) cutting the extrudates as obtained in step (C) after extrusion into lengths of 2-5 mm, drying at 110°C for 12 hours, and then annealing at 600°C for 4 hours; E) further processing the Na-LSX extrudate in a spheronizer to turn the extrudate into Na-LSX spheres or tablets; F) soaking 10 g of extrudates / spheres / tablets in 100 ml of deionized water for 60 minutes; G) After approximately a predetermined time, decanting the water from the reaction material obtained in step F) and replacing it with solution Z (the reaction solution consists of 100 ml of deionized water and 2 gm of NaOH in a flask); H) aging the impregnated extrudates in the solution obtained in step (G) for 1 hour at a temperature in the range of 25-35°C; I) heating the reaction mixture obtained in step (H) to a temperature in the range of 80-85°C and maintaining at 80-85°C for 17 hours; J) cooling the reaction material obtained in step (I), decanting the supernatant solution, washing with 100 ml of deionized water three times, filtering and drying at 100°C to obtain binderless Na-LSX zeolite in extrudate / sphere / tablet form; (The material thus produced exhibits a crystallinity (XRD) of 95% based on the initial zeolite powder.)

[0017] Another embodiment of the present invention is that the binderless Na-LSX zeolite is applicable for N2 adsorption. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a graph showing powder XRD patterns (x-axis: 2θ and y-axis: intensity) of 1a) NaK LSX zeolite in powder form, 1b) Na-LSX zeolite in powder form, 1c) Na-LSX zeolite in extrudate, sphere, and tablet (1 mm) forms, 1d) binderless Na-LSX extrudates / spheres / tablets (1 mm), and 1e) a commercial sample. [Figure 2] 1 is a graph showing N2 adsorption (9.39 ml / g) of Na-LSX powder. [Figure 3]1 is a graph showing N2 adsorption (9.34 ml / g) of binderless Na-LSX extrudates / spheres (1 mm). [Figure 4] 1 is a graph showing N2 adsorption (N2 adsorption - 19.52 ml / g) for Ca-exchanged LSX extrudates / spheres (CaLSX). [Figure 5] 1 is a graph showing N2 adsorption for Li-exchanged LSX extrudates / spheres (LiLSX) (N2 adsorption - 21.92 ml / g). DETAILED DESCRIPTION OF THE INVENTION

[0019] Abbreviations and definitions: Zeolite: The term "zeolite" may be defined as "any of a large group of minerals consisting of hydrated aluminosilicates of sodium, potassium, calcium, or barium, which can be readily dehydrated and rehydrated, and which are commonly used as cation exchangers and molecular sieves." Binderless Process: This process involves converting the binder into zeolite to create binder-free granules. Extrudate: Converting zeolite powder into extrudate form by adding a binder. 13X or NaX zeolite or phase: the sodium form of X-type zeolite LSX zeolite: low-silica X-type zeolite Na: Sodium K: Potassium NaK-LSX: Sodium-potassium LSX zeolite N2: Nitrogen Ca: Calcium Li: Lithium SiO2: silicon dioxide Al2O3: Aluminum oxide Na2O: Sodium oxide KO: Potassium oxide NaOH: Sodium hydroxide

[0020] It should be understood that the figures and descriptions of the present invention have been simplified to illustrate relevant elements for a clear understanding of the present invention. Hereinafter, a detailed description will be provided with reference to the accompanying drawings.

[0021] As used herein, the term "adsorption capacity" refers to nitrogen adsorption capacity.

[0022] The present invention provides binderless Na-LSX zeolite for higher N2 adsorption.

[0023] In one embodiment, the present invention provides a binderless Na-LSX zeolite for higher N adsorption, the zeolite having a molgel composition of SiO / AlO=2.0; (NaO+KO) / SiO=3.0; NaO / NaO+KO=0.77; HO / NaO+KO=25 with 100% crystallization.

[0024] In another embodiment, the present invention relates to a binderless zeolite for higher N2 adsorption comprising sodium LSX, wherein the molgel composition of the binderless zeolite comprises SiO2, Al2O3, Na2O, K2O, and H2O in a ratio of 1.9:0.9:4.52:1.28:140-2.1:1.1:4.72:1.48:150, and the molar concentrations of the binderless zeolite comprise SiO2 / Al2O3=1.9-2.1; (Na2O+K2O) / SiO2=2.9-3.1; Na2O / (Na2O+K2O)=0.67-0.87; and H2O / (Na2O+K2O)=24-26.

[0025] In another embodiment, the binderless zeolite has a molgel composition ratio of 2:1:4.62:1.3:150.

[0026] In another embodiment, the molar concentrations of the binderless zeolite include SiO2 / Al2O3=2.0; (Na2O+K2O) / SiO2=3.0; Na2O / (Na2O+K2O)=0.77; and H2O / (Na2O+K2O)=25.

[0027] In another embodiment, the binderless Na-LSX zeolite has 100% crystallinity of the pure 13X or NaX phase.

[0028] The molgel composition is crucial and important in order to have the optimum gel necessary to obtain a pure Na-LSX phase without the generation of impurities such as Na-A, sodalite and zeolite P and without gel aging.

[0029] Another embodiment of the present invention provides a method for synthesizing NaK LSX zeolite in powder form, said method comprising: (a) adding, under constant stirring, rapidly for a period of 5 minutes at a temperature in the range of 70-75°C (the temperature of solution B), solution A (prepared by dissolving 0.896 kg of sodium aluminate in 2.8 L of water under continuous stirring and continuing stirring until the sodium aluminate is completely dissolved) to solution B (prepared by dissolving 1.135 kg of NaOH in 4.1 L of water under constant stirring); (b) preparing solution C by adding sodium silicate solution (2.07 kg) to 4.1 kg of water, and then slowly adding solution C to the mixture of solution A and solution B obtained in step (a) under vigorous continuous stirring at a temperature in the range of 30-40°C for a period of 60 minutes; (c) adding solution D (prepared by adding 0.878 kg of KOH to 0.8 L of water) to the mixture obtained in step (b) under vigorous stirring at a temperature in the range of 30-40°C for a period in the range of 1-2 hours; (d) transferring the gel obtained in step (c) into a 20 L SS autoclave and crystallizing the gel at 70-75°C for 17 hours; (e) filtering the crystallized gel obtained in step d), washing with demineralized water until Na and K are removed, and drying at 100°C for 12 hours (confirmed as pure faujasite-type zeolite (NaK-LSX) by X-ray diffraction).

[0030] The present invention further provides a method for converting NaK-LSX into Na-LSX zeolite in powder form, said method comprising: i) subjecting the NaK-LSX thus obtained to further ion exchange using a 2M sodium chloride solution (at a rate of 10 ml per gram of solid) at a pH of 9-10 for 5 hours at 95°C; ii) removing chloride ions from the solid obtained in step i) by washing excess salt with deionized water and drying the solid at 110°C for 12 hours to obtain Na-LSX; Includes.

[0031] In another embodiment, the present invention provides a method for synthesizing NaK-LSX and Na-LSX zeolites in powder form, the method comprising: (a) adding a solution A, which is prepared by dissolving sodium aluminate in water, to a solution B, which is prepared by dissolving sodium hydroxide in water, rapidly under stirring at 220-280 rpm at a temperature in the range of 70-75°C for a period of 3-8 minutes; (b) preparing a solution C by dissolving sodium silicate in water, and then slowly adding said solution C to the mixture of solution A and solution B obtained in step (a) under rapid stirring at 220-280 rpm at a temperature in the range of 30-40°C for a period of 40-80 minutes; (c) adding a solution D, which is prepared by dissolving KOH in water, to the mixture obtained in step (b) under vigorous stirring at a temperature in the range of 30-40°C for a period in the range of 1-2 hours to obtain a gel; (d) transferring the gel obtained in step (c) into an autoclave, followed by crystallizing the gel at a temperature in the range of 70-75°C for a period in the range of 15-19 hours; (e) filtering the crystallized gel obtained in step d), followed by washing with demineralized water until Na and K are removed, and then drying at a temperature in the range of 90-110°C for a period in the range of 10-14 hours to obtain NaK-LSX zeolite in powder form; (f) subjecting the NaK-LSX zeolite powder form of step e) to an ion-exchange step at a temperature in the range of 90-100°C for a period in the range of 4-6 hours at a pH of 9-10 to obtain ion-exchanged zeolite; (g) washing the ion-exchanged zeolite of step f) with deionized water to remove excess salt and chloride ions, followed by drying at a temperature in the range of 100-120°C for a period of 10-14 hours to obtain Na-LSX zeolite in powder form; Includes.

[0032] In another embodiment, the stirring referred to in the above step is preferably 250 rpm.

[0033] In another embodiment, solution A is prepared by dissolving 0.5-2 kg of sodium aluminate in 2-6 L of water under continuous stirring at 220-280 rpm until the sodium aluminate is completely dissolved.

[0034] In a preferred embodiment, solution A is prepared by dissolving 0.896 kg of sodium aluminate in 2.8 L of water under continuous stirring at 250 rpm until the sodium aluminate is completely dissolved.

[0035] In another embodiment, solution B is prepared by dissolving 1.5-4 kg of NaOH in 3.5-7 L of water at a temperature in the range of 70-75° C. under constant stirring at 220-280 rpm.

[0036] In a preferred embodiment, solution B is prepared by dissolving 1.135 kg of NaOH in 4.1 L of water at a temperature in the range of 70-75° C. under constant stirring at 250 rpm.

[0037] In another embodiment, solution C is prepared by adding 1.5 to 3 kg of sodium silicate to 3.5 to 7 kg of water under stirring at 220 to 280 rpm.

[0038] In a preferred embodiment, solution C is prepared by adding 2.07 kg of sodium silicate to 4.1 kg of water under stirring at 250 rpm.

[0039] In another embodiment, solution D is prepared by adding 0.5-2 kg of KOH to 0.5-3 L of water under stirring at 220-280 rpm.

[0040] In a preferred embodiment, solution D is prepared by adding 0.878 kg of KOH to 0.8 L of water under stirring at 250 rpm.

[0041] In another embodiment, the method step of ion exchange is carried out using a 0.5-4 M sodium chloride solution at a rate of 10 ml per gram of solid.

[0042] In a preferred embodiment, the method step of ion exchange is carried out using a 2M sodium chloride solution at a rate of 10 ml per gram of solid.

[0043] Another embodiment of the present invention provides a method for preparing Na-LSX zeolite in extrudate (cylindrical), spherical, or tablet (pellet) form, said method comprising: A) Mixing 70g of zeolite X powder (Na-LSX), 30g of kaolin (initial material 4) and 2g of lactose; B) preparing dough of suitable consistency from the mixture obtained in step (A) in a twin-shaft mixer using 45 gm of a carboxymethylcellulose solution of sodium salt (2.5% by weight); C) forming the dough mixture obtained in step (B) into extrudates of 1 millimeter size in a screw extruder (VJ instrument); D) cutting the mixture obtained in step (C) after extrusion into lengths of 2-5 mm, drying at 110°C for 12 hours, and then annealing at 600°C for 4 hours; E) further processing the extrudate in a spheronizer to form the extrudate into spheres or tablets; Includes.

[0044] The present invention further provides a method for preparing binderless Na-LSX zeolite in extrudate, sphere or tablet form, said method comprising: I) soaking 10 g of extrudates / spheres / tablets in 100 ml of deionized water for 60 minutes; II) After approximately a predetermined time, decanting the water from the reaction material obtained in step I) and replacing it with a reaction solution (the reaction solution consists of 100 ml of deionized water and 2 gm of NaOH in a flask); III) aging the impregnated extrudates in the solution obtained in step (II) for 1 hour at a temperature in the range of 25-35°C; IV) heating the reaction mixture obtained in step (III) to a temperature in the range of 80-85°C and maintaining at 80-85°C for 17 hours; V) cooling the reaction material obtained in step (IV), decanting the supernatant solution, washing with 100 ml of deionized water three times, filtering and drying at 100°C; (The material thus produced exhibits a crystallinity (XRD) of 95% based on the initial zeolite powder.)

[0045] In another embodiment, the present invention provides a method for preparing Na-LSX zeolite in extrudate, sphere, or tablet form, and binderless Na-LSX zeolite in extrudate, sphere, and tablet form by converting binder-containing Na-LSX zeolite extrudates / spheres / tablets into binderless zeolite, said method comprising: a. Mixing 50-90 gm of Zeolite X powder (Na-LSX) as obtained in claim 1 with 10-50 gm of binder as initial material and 0.5-5 gm of additives; b. preparing dough of suitable consistency from the mixture obtained in step a) in a twin-shaft mixer using 30-60 gm of 1-10% by weight of a carboxymethylcellulose solution of sodium salt; c. The dough mixture as obtained in step b) is then formed into extrudates of 0.5-10 mm size in a screw extruder; d. cutting the extrudates as obtained in step c) after extrusion into lengths of 2-5 mm, then drying at a temperature in the range of 100-120°C for a period of 10-14 hours, followed by annealing at a temperature in the range of 500-650°C for a period of 3.5-4.5 hours to obtain Na-LSX extrudates; e. processing the Na-LSX extrudate of step d) in a spheronizer to form the extrudate into Na-LSX spheres or tablets; f. Immersing 10 gm to 100 kg of extrudates / spheres / tablets as obtained in either step d) or e) in 100 ml to 1000 L of deionized water for a period of 60 minutes; g. After approximately a predetermined time, decanting the water from the reaction material obtained in step f) and replacing it with solution Z containing NaOH solution; h. Aging the impregnated extrudates / spheres / tablets of step f) with solution Z as obtained in step g) for 0.5-1.5 hours at a temperature ranging from 25-35°C; i. heating the reaction mixture as obtained in step h) at a temperature in the range of 80-85°C for a period of 15-19 hours; j. cooling the reaction mixture obtained in step i), decanting the supernatant solution, followed by washing with 100 ml of deionized water three times, filtering and drying at a temperature in the range of 90-110°C to obtain binderless Na-LSX zeolite in extrudate, sphere or tablet form; Includes:

[0046] In a preferred embodiment, the amount of zeolite X powder (Na-LSX) used in step a) is 70 gm. In another preferred embodiment, the amount of binder is 30 gm. In another preferred embodiment, the amount of additive is 2 gm.

[0047] In a preferred embodiment, the amount of sodium salt carboxymethylcellulose solution is 45 gm at 2.5% by weight.

[0048] In a preferred embodiment, the size of the extrudate is 1 mm.

[0049] In another embodiment, solution Z is prepared by mixing and stirring 100 ml of deionized water with 2 gm of NaOH in a flask.

[0050] In another embodiment, the binderless Na-LSX zeolite in extrudate / sphere / tablet form exhibits about 100% crystallinity as measured using powder XRD.

[0051] In another embodiment, the binder is selected from kaolin clay, attapulgite clay, bentonite clay, montmorillonite clay, and / or mixtures thereof.

[0052] In another embodiment, the excipient is selected from lactose, polyacrylic acid, microcrystalline cellulose, polyvinyl alcohol, polylactic acid and / or mixtures thereof.

[0053] In another embodiment, the method further comprises treating the binderless Na-LSX zeolite in extrudate / sphere / tablet form with 0.5 M CaCl solution at a temperature in the range of 90-110°C for a period of 16-20 hours to obtain a Ca-exchanged binderless Na-LSX zeolite. Optionally, the Ca-exchanged binderless Na-LSX zeolite is washed and dried at a temperature of 90-110°C for a period of 10-14 hours, followed by activation at a temperature of 420-480°C for a period of 5-7 hours.

[0054] In another embodiment, the method further comprises treating the binderless Na-LSX zeolite in extrudate / sphere / tablet form with a 2 M LiCl solution at a temperature in the range of 85-105°C for a period of 4-6 hours to obtain a Li-exchanged binderless Na-LSX zeolite. Optionally, the Li-exchanged binderless Na-LSX zeolite is washed and dried at a temperature of 90-110°C for a period of 10-14 hours, followed by activation at a temperature of 380-420°C.

[0055] In a preferred embodiment, the zeolites obtained in the form of extrudates in the above process are cylindrical in shape, the spheres are spherical in shape and the tablets are pellet in shape.

[0056] In another embodiment, the addition order of the above method, particularly the addition of KOH as the last step, is unique and important as it helps to control the alkalinity or pH in the gel and also helps to obtain a homogenous gel.

[0057] Thus, the combination of the specific molgel composition and the order of addition of the alkaline solutions completely eliminated gel aging, as well as the simultaneous addition of NaOH+KOH, which is required with other molgel compositions (known in the literature).

[0058] In another embodiment, the particular gel composition as disclosed above serves to replace a two-step crystallization (a first nucleation step and a second crystallization step) with a one-step crystallization process in which nucleation and crystallization occur simultaneously.

[0059] In another embodiment, the present invention provides a method for adsorbing nitrogen from a sample, comprising the steps of: i) treating the sample containing air, oxygen and nitrogen with the binderless sodium LSX-based zeolite according to any one of the preceding claims; ii) measuring N adsorption in a Brunauer-Emmett-Teller (BET) instrument at atmospheric pressure; The present invention provides a method comprising:

[0060] In another embodiment, before said treatment step i), the sample is degassed at a temperature in the range of 300-360° C. for a period of 10-14 hours.

[0061] In a preferred embodiment, before said treatment step i), the sample is degassed at a temperature of 340° C. for a period of 12 hours.

[0062] Another embodiment of the present invention is that the binderless Na-LSX zeolite is applicable for N adsorption measured with a Brunauer-Emmett-Teller (BET) instrument at atmospheric pressure by degassing the sample at 340°C for 12 hours.

[0063] The zeolites and methods of the present invention are compared with those of the prior art literature, and the results are summarized in Table 1 below.

[0064] [Table 1]

[0065] FIG. 1e shows the powder XRD patterns of commercially available Na-LSX (obtained from Arkema Chemical Co.) and the Na-LSX extrudates of the present invention (FIG. 1d), demonstrating that the Na-LSX is more crystalline than the commercial sample. [Example]

[0066] Example 1: Synthesis of NaK LSX zeolite in powder form Solution A was prepared by dissolving 0.896 kg of sodium aluminate in 2.8 L of water under continuous stirring and continuing stirring until the sodium aluminate was completely dissolved. Solution B was prepared by dissolving 1.135 kg of NaOH in 4.1 L of water under constant stirring. Solution A was added to solution B under rapid stirring for a period of 5 minutes at a temperature ranging from 70 to 75 °C (the temperature of solution B). Solution C was prepared by adding sodium silicate solution (2.07 kg) to 4.1 kg of water, and then solution C was added slowly to the mixture of solutions A and B under vigorous stirring for a period of 60 minutes at a temperature ranging from 30 to 40 °C under vigorous continuous stirring. Solution D was prepared by adding 0.878 kg of KOH to 0.8 L of water and added to the reaction mixture under vigorous stirring for a period of 1 to 2 hours at a temperature ranging from 30 to 40 °C. The resulting gel was transferred into a 20 L SS autoclave and crystallized for 17 hours at 70-75°C, after which the solid was filtered, washed with demineralized water until Na and K were removed, and dried at 100°C for 12 hours.

[0067] The powder X-ray diagram (Figure 1a) shows well-resolved diffraction peaks, with a crystallinity of 100% for the pure NaK LSX phase, a characteristic pattern for faujasite-type zeolites. Chemical analysis revealed a Si / Al molar ratio of 1.04–1.08, which corresponds to the Si / Al molar ratio of LSX zeolite.

[0068] Example 2: Conversion of NaK-LSX to Na-LSX zeolite in powder form: The NaK-LSX thus obtained in Example 1 was further subjected to ion exchange using a 2 M sodium chloride solution (at a rate of 10 ml per gram of solid) at a pH of 9 to 10 for 5 hours at 95°C. Excess salt was washed with deionized water to remove chloride ions from the solid, and the solid was dried at 110°C for 12 hours to obtain Na-LSX.

[0069] The powder X-ray diagram of Na-LSX (Figure 1b) also clearly shows the well-resolved diffraction peaks of faujasite-type zeolite, and the crystallinity of the pure Na-LSX phase is 100%, indicating that the structural characteristics remained unchanged after the conversion of NaK-LSX to Na-LSX. The 100% crystallinity of the synthesized Na-LSX is further confirmed by comparison with the powder XRD data of commercially available Na-LSX (see Figure 1e), which clearly shows the lower intensity peak (y-axis) and the presence of amorphous powder along with impurities (given the unclear x-axis graph in Figure 1e). In contrast, the synthesized binderless Na-LSX of the present invention is free of impurities and 100% crystalline, given its higher intensity and clear x-ray graph (see Figure 1b).

[0070] Example 3: Preparation of Na-LSX zeolite in extrudate, sphere, and tablet form: 70 g of Na-LSX from Example 2 was mixed with 30 g of kaolin (initial material 4) and 2 g of lactose. 45 gm of a carboxymethylcellulose solution of sodium salt (2.5 wt%) was used to prepare a dough of the above mixture to a suitable consistency in a twin-screw mixer. The resulting dough mixture was then formed into 1-millimeter-sized extrudates in a screw extruder (VJ instrument). After extrusion, the mixture was cut into 2-5 mm lengths, dried at 110°C for 12 hours, and then annealed at 600°C for 4 hours.

[0071] (The wet form of extrudate obtained after the extruder was further processed in a spheronizer to make the extrudate into spheres or tablets.)

[0072] The XRD diagram (Fig. 1c) of the extrudate / sphere / tablet form of Na-LSX zeolite does not show any extra peaks due to any impurities. However, the peak intensity of the characteristic faujasite peak is lower than that of the parent Na-LSX in powder form. It is clear that the relative crystallinity decreases from 100% for the powder form of Na-LSX to 31% for the extrudate / sphere / tablet form of Na-LSX zeolite. The 30% decrease in crystallinity is due to the 30% contribution of kaolin.

[0073] Example 4: Preparation of binderless Na-LSX zeolite in extrudate, sphere and tablet form: 20 g of the Na-LSX extrudates from Example 3 were added to 200 ml of water and allowed to soak for 60 minutes. After 1 hour, the excess water was decanted, and the wet extrudates were then added to 200 ml of 2% NaOH solution. The mixture was aged at 25-35°C for 1 hour. Finally, the mixture was subjected to hydrothermal treatment at 80-85°C for 17 hours. The supernatant solution was then decanted to separate the extrudates / spheres / tablets, which were washed with 100 ml of deionized water, filtered, and dried at 100°C.

[0074] Compared with the parent Na-LSX in powder form, the Na-LSX extrudates / spheres / tablets (Fig. 1d) recovered % crystallinity to over 95% after binderless processing. The binderless Na-LSX zeolite as extrudate is relatively more crystalline than the commercial sample (Fig. 1e).

[0075] Example 5: N2 adsorption measurements on LSX zeolite: The N adsorption isotherms of Na-LSX extrudates / spheres / tablets were measured using a static volumetric measurement system (Micromeritics ASAP 2010 system). Prior to isotherm measurements, the samples were activated in vacuum at 340 °C for 8 h.

[0076] Figures 2 and 3 both show N2 adsorption isotherms of parent Na-LSX in powder form and binderless Na-LSX in extrudate / sphere / tablet form measured at room temperature.

[0077] The N2 adsorption of Na-LSX powder and binderless Na-LSX extrudates / spheres / tablets is 9.39 ml / g and 9.34 ml / g, respectively. The N2 uptake of parent Na-LSX and binderless Na-LSX is almost similar.

[0078] Example 6: Ca exchange of binderless Na-LSX zeolite extrudates / spheres / tablets 10 gm of binderless Na-LSX zeolite extrudates / spheres / tablets prepared in Example 4 are exchanged with Ca in a glass column using 0.5 M CaCl solution at a flow rate of 0.8 ml / min at 100° C. for 18 hours. After the exchange, Cl - The sample was washed until free of ions, dried at 100°C for 12 hours, and activated at 460°C for 6 hours.

[0079] The N2 adsorption isotherm of the Ca-exchanged sample was measured according to Example 5. Figure 4 shows the N2 isotherm of the Ca-exchanged sample, and the N2 adsorption capacity is 19.52 ml / g.

[0080] Example 7: Li-exchange of binderless Na-LSX zeolite extrudates / spheres / tablets 6 gm of binderless Na-LSX zeolite extrudates / spheres / tablets prepared in Example 4 are exchanged with Li in a glass column using 2 M LiCl solution at a flow rate of 0.9 ml / min at 95°C for 5 hours. After the exchange, Cl - The sample was washed until free of ions, dried at 100°C for 12 hours, and activated at 400°C.

[0081] Figure 5 shows the N2 adsorption isotherm of the Li-exchanged sample. The N2 adsorption capacity is 21.92 ml / g. [Industrial Applicability]

[0082] Advantages of the Invention - New synthesis process for 13X or Na-LSX zeolite - Highly crystalline Na-LSX with pure phases. - Separate addition of KOH allows better mixing of the alkali, improving mixing and crystallization. - Higher N2 adsorption was obtained by Na-LSX prepared as above. In the binderless process, only NaOH treatment is required, whereas the methods known in the literature require the addition of NaOH + sodium aluminate. The addition of KOH solution (solution D) to the mixture of solutions containing solutions A-C in the process of preparation of Na-LSX zeolite is unique and not disclosed in any of the methods known in the literature.

Claims

1. Higher N, including sodium LSX ２ A binderless zeolite for adsorption, wherein the molgel composition of the binderless zeolite is SiO ２ , Al ２ O ３ , Na ２ O.K. ２ O, and H ２ O in a ratio of 1.9:0.9:4.52:1.28:140 to 2.1:1.1:4.72:1.48:150, and the molar concentration of the binderless zeolite is ２ / Al ２ O ３ =1.9~2.1; (Na ２ O+K ２ O) / SiO ２ =2.9~3.1;Na ２ O / (Na ２ O+K ２ O) = 0.67 to 0.87; and H ２ O / (Na ２ O+K ２ Binderless zeolite, including zeolite having a molecular weight of 24 to 26.

2. 10. The binderless zeolite of claim 1 having 100% crystallinity of the pure 13X or NaX phase.

3. 10. A method for synthesizing sodium LSX according to claim 1, wherein the sodium LSX is in powder form, the method comprising: (a) adding a solution A comprising sodium aluminate dissolved in water to a solution B comprising sodium hydroxide dissolved in water rapidly under stirring at 220-280 rpm at a temperature in the range of 70-75°C for a period of 3-8 minutes; (b) preparing a solution C by dissolving sodium silicate in water, and then slowly adding said solution C to the mixture of solutions A and B obtained in step (a) under rapid stirring at 220-280 rpm at a temperature in the range of 30-40°C for a period of 40-80 minutes; (c) adding a solution D, which is prepared by dissolving KOH in water, to the mixture obtained in step (b) under vigorous stirring at a temperature ranging from 30 to 40°C for a period ranging from 1 to 2 hours to obtain a gel; (d) transferring the gel obtained in step (c) into an autoclave, followed by crystallizing the gel at a temperature in the range of 70-75°C for a period in the range of 15-19 hours; (e) filtering the crystallized gel obtained in step d), followed by washing with demineralized water until Na and K are removed, and then drying at a temperature ranging from 90 to 110°C for a period ranging from 10 to 14 hours to obtain NaK-LSX zeolite in powder form; (f) subjecting the NaK-LSX zeolite powder form of step e) to an ion-exchange step at a temperature in the range of 90-100°C for a period in the range of 4-6 hours at a pH of 9-10 to obtain ion-exchanged zeolite; (g) washing the ion-exchanged zeolite of step f) with deionized water to remove excess salt and chloride ions, followed by drying at a temperature in the range of 100-120°C for a period of 10-14 hours to obtain Na-LSX zeolite in powder form; A method comprising:

4. 4. The method of claim 3, wherein solution A is prepared by dissolving 0.5 to 2 kg of sodium aluminate in 2 to 6 L of water under continuous stirring at 220 to 280 rpm until the sodium aluminate is completely dissolved; solution B is prepared by dissolving 1.5 to 4 kg of NaOH in 3.5 to 7 L of water under constant stirring at 220 to 280 rpm at a temperature in the range of 70 to 75°C; solution C is prepared by adding 1.5 to 3 kg of sodium silicate to 3.5 to 7 kg of water under stirring at 220 to 280 rpm; and solution D is prepared by adding 0.5 to 2 kg of KOH to 0.5 to 3 L of water under stirring at 220 to 280 rpm.

5. 4. The method of claim 3, wherein the ion exchange step is carried out using a 0.5-4 M sodium chloride solution at a rate of 10 ml per gram of solid.

6. 1. A method for preparing Na-LSX zeolite in extrudate, sphere, or tablet form by converting a binder-containing Na-LSX zeolite into a binderless zeolite, wherein the Na-LSX zeolite is binderless Na-LSX zeolite, said method comprising: a. Mixing 50-90 gm of Zeolite X powder (Na-LSX) as obtained in claim 3 with 10-50 gm of binder as initial material and 0.5-5 gm of additives; b. preparing dough of suitable consistency from the mixture as obtained in step a) in a twin-shaft mixer using 30-60 gm of a carboxymethylcellulose solution of sodium salt having 1-10% by weight; c. The dough mixture as obtained in step b) is then formed into extrudates of 0.5-10 mm size in a screw extruder; d. Cutting the extrudates as obtained in step c) after extrusion into lengths of 2-5 mm, then drying at a temperature in the range of 100-120°C for a period of 10-14 hours, followed by annealing at a temperature in the range of 500-650°C for a period of 3.5-4.5 hours to obtain Na-LSX extrudates; e. processing the Na-LSX extrudate of step d) in a spheronizer to form the extrudate into Na-LSX spheres or tablets; f. Immersing 10 gm to 100 kg of extrudates / spheres / tablets as obtained in either step d) or e) in 100 ml to 1000 L of deionized water for a period of 60 minutes; g. After approximately a predetermined time, decanting the water from the reaction material obtained in step f) and replacing it with Solution Z containing the NaOH solution; h. Aging the impregnated extrudates / spheres / tablets of step f) with solution Z as obtained in step g) for 0.5 to 1.5 hours at a temperature ranging from 25 to 35°C; i. heating the reaction mixture as obtained in step h) at a temperature in the range of 80-85°C for a period of 15-19 hours; j. cooling the reaction mixture obtained in step i) and decanting the supernatant solution, followed by washing with 100 ml of deionized water three times, filtering and drying at a temperature in the range of 90-110°C to obtain binderless Na-LSX zeolite in extrudate, sphere or tablet form; A method comprising:

7. 7. The method of claim 6, wherein solution Z is prepared by mixing and stirring 100 ml of deionized water with 2 gm of NaOH in a flask; and the binderless Na-LSX zeolite in extrudate, sphere, or tablet form exhibits about 100% crystallinity as measured using powder XRD.

8. 7. The method of claim 6, wherein the binder is selected from kaolin clay, attapulgite clay, bentonite clay, montmorillonite clay, or a mixture thereof; and the additive is selected from lactose, polyacrylic acid, microcrystalline cellulose, polyvinyl alcohol, polylactic acid, or a mixture thereof.

9. The binderless Na-LSX zeolite is dissolved in 0.5 M CaCl at a temperature in the range of 90 to 110°C for a period of 16 to 20 hours. ２ 7. The method of claim 6, further comprising treating with a solution of 2 M LiCl at a temperature in the range of 85 to 105° C. for a period of 4 to 6 hours to obtain a Ca-exchanged binderless Na-LSX zeolite, or treating with a 2 M LiCl solution at a temperature in the range of 85 to 105° C. for a period of 4 to 6 hours to obtain a Li-exchanged binderless Na-LSX zeolite.

10. 1. A method for adsorbing nitrogen from a sample, comprising: i) treating the sample containing air, oxygen and nitrogen with the binderless sodium LSX-based zeolite according to any one of claims 1 to 9; ii) N in a Brunauer-Emmett-Teller (BET) instrument at atmospheric pressure ２ measuring the adsorption; A method comprising:

11. 11. The method of claim 10, wherein prior to treatment step i), the sample is degassed at a temperature in the range of 300-360°C for a period of 10-14 hours.

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