阅读说明：本技术 一种新型钛硅分子筛的制备方法及应用 (Preparation method and application of novel titanium silicalite molecular sieve ) 是由 王冰 肖琪琳 景欢旺 冯辉霞 史亮 刘亚飞 夏浩天 汪强强 于 2020-11-24 设计创作，主要内容包括：本发明属于新能源材料技术领域,尤其涉及一种新型钛硅分子筛的制备方法及应用。本发明方法通过十六烷基三甲基溴化铵(CTABr)、去离子水、盐酸,溶于异丙醇的钛酸四丁酯(TBOT)溶液、正硅酸乙酯等组分进行一系列合成反应后,进行抽滤、洗涤、烘干机煅烧得Ti-SBA-1,并通过金属元素掺杂或有机官能团修饰进一步提高催化性能。本发明在强酸条件下,直接合成了一种三维立方结构的钛硅分子筛,该分子筛具有介孔和比表面积大的特点,从而拥有较强的吸附性能；本发明制备的钛硅分子筛通过光电联合催化CO-2还原反应,可成功实现CO-2到甲醇,乙醇的转变。通过新型钛硅分子筛催化苯乙烯的环氧化反应,成功制备出苯甲醛和环氧苯乙烷,可在一定程度上缓解石油资源短缺的压力。(The invention belongs to the technical field of new energy materials, and particularly relates to a preparation method and application of a novel titanium silicalite molecular sieve. The method comprises the steps of carrying out a series of synthetic reactions on components such as cetyl trimethyl ammonium bromide (CTABr), deionized water, hydrochloric acid, tetrabutyl titanate (TBOT) solution dissolved in isopropanol, ethyl orthosilicate and the like, carrying out suction filtration, washing and drying machine calcination to obtain Ti-SBA-1, and further improving the catalytic performance through metal element doping or organic functional group modification. Under the strong acid condition, the titanium silicalite molecular sieve with a three-dimensional cubic structure is directly synthesized, and has the characteristics of mesopores and large specific surface area, so that the molecular sieve has strong adsorption performance; the titanium silicalite molecular sieve prepared by the invention catalyzes CO by photoelectricity combination 2 Reduction reaction can successfully realize CO 2 Conversion to methanol, ethanol. The benzaldehyde and styrene oxide are successfully prepared by the epoxidation reaction of styrene under the catalysis of the novel titanium silicalite molecular sieve, and the pressure of shortage of petroleum resources can be relieved to a certain extent.)

1. A preparation method of a novel titanium silicalite molecular sieve; the method is characterized in that: the method comprises the following steps:

(1) and (3) synthesis of Ti-SBA-1: dissolving cetyl trimethyl ammonium bromide (CTABr) in deionized water, and carrying out ultrasonic treatment for 15 minutes at 313K; obtaining a homogeneous clear solution, adding hydrochloric acid, dropwise adding a tetrabutyl titanate (TBOT) solution dissolved in isopropanol into the solution under mechanical stirring, and cooling to 273 k;

after 30 minutes, slowly dripping tetraethoxysilane which is cooled to 273k in advance into the solution under the condition of vigorous stirring, stopping stirring after 5 minutes, crystallizing for 6 hours under the condition of standing, carrying out suction filtration on the solution, and washing with acetone;

placing the mixture in a drying oven, setting the temperature at 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain a Ti-SBA-1 product;

(2) doping of metal elements: adding the titanium silicalite molecular sieve Ti-SBA-1 obtained in the step (1) into a metal salt solution, and performing ultrasonic treatment for 30 minutes to uniformly disperse metal ions in the Ti-SBA-1; carrying out suction filtration on the solution, and placing the obtained solid in an oven for drying treatment; after drying, transferring the mixture into a muffle furnace for calcining to obtain a metal-doped titanium-silicon molecular sieve material;

(3) modification of organic functional groups: adding the molecular sieve obtained in the step (1) into a sodium hydroxide solution for activation for 6 hours, filtering the solution, and placing the solution in an oven for drying; transferring the mixture into a container containing absolute ethyl alcohol solution, carrying out oil bath, dripping 3-aminopropyl triethoxysilane when the temperature is raised to 70 ℃, taking out the mixture after 6 hours, washing the mixture with ethyl alcohol, putting the mixture into an oven, and drying the mixture for 12 to 18 hours; taking out, adding absolute ethyl alcohol and salicylaldehyde into the solution, and placing the solution in an oil bath pan for oil bath; setting the temperature at 80 ℃ and refluxing for 6 hours; and washing with propanol, placing in an oven, and drying for 12-18 hours to obtain the titanium silicalite molecular sieve material modified by the organic functional group.

2. The process of claim 1, wherein the process comprises: the molar ratio of the raw material components in the step (1) is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCI: 250H₂O。

3. The process of claim 1, wherein the process comprises: the concentration of the hydrochloric acid solution in the step (1) is 37%.

4. The process of claim 1, wherein the process comprises: and (3) doping the metal element in the step (2) by Pd doping or Au doping.

5. The process of claim 4, wherein: in the step (2), a palladium source is a palladium chloride solution when Pd is doped, the drying temperature of an oven is 80 ℃, and the drying time is 12-18 h; the calcination adopts 2 hours of temperature programming to 500 ℃, and the calcination time is 2 hours.

6. The process of claim 4, wherein: in the step (2), the gold source is chloroauric acid solution during Au doping; before pumping filtration, the pH value of the solution needs to be adjusted to 9-10 by using ammonia water; the drying temperature of the oven is 80 ℃, and the drying time is 12-18 h; the calcination adopts 2 hours of temperature programming to 600 ℃, and the calcination time is 2 hours.

7. The process of claim 1, wherein the process comprises: the mass ratio of each raw material component in the step (3) is as follows: NaOH: Ti-SBA-1: ethanol: 3-aminopropyltriethoxysilane: salicylaldehyde = 0.48: 1: 39.45: 2.37: 4.68.

8. the method of any one of claims 1 to 7, wherein the method comprises the following steps: the novel titanium silicalite molecular sieve is of a three-dimensional cubic structure, the size of a mesoporous is 2-3 nm, and the specific surface area is more than or equal to 500m²/g。

9. The application of the novel titanium silicalite molecular sieve is characterized in that: for photoelectrocatalytic reductionCrude CO₂Or styrene and hydrogen peroxide are catalyzed to synthesize benzaldehyde and styrene oxide.

Technical Field

The invention belongs to the technical field of new energy materials, and particularly relates to a preparation method and application of a novel titanium silicalite molecular sieve.

Background

The rapid development of the economy in the world nowadays greatly improves the productivity and brings many negative problems. The development of descendants of us and the descendants of us is seriously restricted by a series of global crises of environmental pollution, ecological damage, energy shortage and the like.

Benzaldehyde and styrene oxide are important intermediates of a plurality of industrially important reactions and have great industrial value, but the traditional industrial synthesis methods of the two products consume crude oil, the production steps are complicated, the conditions are very harsh, and the pollution to the environment is serious.

Only a small part of the energy radiated from the sun reaches the earth's surface, and then only a small part of the energy reaching the earth is absorbed in the form of short-wavelength light, and most of the energy is dissipated as long-wavelength heat radiation, so as to maintain the earth's temperature balance and stability. However, when the amount of endothermic gas increases, the energy that is lost is retained by the gas, which is equivalent to a layer of heat insulation film covering the earth's periphery, resulting in the rise of the surface temperature, which is known as the greenhouse effect. These endothermic gases include methane, nitrogen oxides, chlorofluorocarbons, sulfur hexafluoride, and carbon dioxide. Among them, carbon dioxide is the main greenhouse gas, accounting for 55%. According to latest data, in 2016, China consumed 36.5 million tons of coal and emitted about 100 million tons of carbon dioxide. On the premise of not reducing economic development, the conversion of a resource-saving and environment-friendly society is realized, and the emission of carbon is reduced, so that great challenges are provided for people.

Among various mature renewable energy sources at present, the catalytic conversion and reduction of carbon dioxide are the hot spots of the present research, and the technology can not only effectively reduce CO in the air₂The content of (a) and the ability to produce value-added chemicals at the same time are considered as one of the top-end technologies. Catalytic conversion of carbon dioxide requires a catalyst to achieve rapid carbon dioxide conversion. Titanium silicalite is an important milestone in the field of catalysis due to its good selective activity, catalytic activity, and high hydrothermal stability. Since its discovery, it has attracted a great deal of attention from many researchers. And systematically studied it. It is found through research that it has excellent catalytic performance in oxidation of straight chain hydrocarbon, ethanol, paraffin, etc. For titanium silicalite molecular sieves, only titanium entering a silica framework has catalytic activity, most of the currently synthesized titanium silicalite molecular sieves exist in a free anatase form, and the defects of mesopores and small specific surface exist, so that the titanium silicalite molecular sieves have weak catalytic activity and low carbon dioxide conversion efficiency.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a preparation method of a novel titanium silicalite molecular sieve which has strong catalytic activity and can obviously improve the conversion efficiency of carbon dioxide and a method for preparing the same in the photoelectrocatalysis reduction of CO₂And the application of styrene and hydrogen peroxide in the aspect of catalytic synthesis of benzaldehyde and styrene oxide.

The technical scheme for realizing the purpose of the invention is as follows: a preparation method of a novel titanium silicalite molecular sieve; the method comprises the following steps:

(1) and (3) synthesis of Ti-SBA-1: dissolving cetyl trimethyl ammonium bromide (CTABr) in deionized water, and carrying out ultrasonic treatment for 15 minutes at 313K; obtaining a homogeneous clear solution, adding hydrochloric acid, dropwise adding a tetrabutyl titanate (TBOT) solution dissolved in isopropanol into the solution under mechanical stirring, and cooling to 273 k;

after 30 minutes, slowly dripping tetraethoxysilane which is cooled to 273k in advance into the solution under the condition of vigorous stirring, stopping stirring after 5 minutes, crystallizing for 6 hours under the condition of standing, carrying out suction filtration on the solution, and washing with acetone;

placing the mixture in a drying oven, setting the temperature at 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain a Ti-SBA-1 product;

(2) doping of metal elements: adding the titanium silicalite molecular sieve Ti-SBA-1 obtained in the step (1) into a metal salt solution, and performing ultrasonic treatment for 30 minutes to uniformly disperse metal ions in the Ti-SBA-1; carrying out suction filtration on the solution, and placing the obtained solid in an oven for drying treatment; after drying, transferring the mixture into a muffle furnace for calcining to obtain a metal-doped titanium-silicon molecular sieve material;

(3) modification of organic functional groups: adding the molecular sieve obtained in the step (1) into a sodium hydroxide solution for activation for 6 hours, filtering the solution, and placing the solution in an oven for drying; transferring the mixture into a container containing absolute ethyl alcohol solution, carrying out oil bath, dripping 3-aminopropyl triethoxysilane when the temperature is raised to 70 ℃, taking out the mixture after 6 hours, washing the mixture with ethyl alcohol, putting the mixture into an oven, and drying the mixture for 12 to 18 hours; taking out, adding absolute ethyl alcohol and salicylaldehyde into the solution, and placing the solution in an oil bath pan for oil bath; setting the temperature at 80 ℃ and refluxing for 6 hours; and washing with propanol, placing in an oven, and drying for 12-18 hours to obtain the titanium silicalite molecular sieve material modified by the organic functional group.

According to the technical scheme, the molar ratio of the raw material components in the step (1) is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCl: 250H₂O。

According to the technical scheme, the concentration of the hydrochloric acid solution in the step (1) is 37%.

In the above technical scheme, the metal element doping in the step (2) is Pd doping or Au doping.

According to the technical scheme, a palladium source is a palladium chloride solution when Pd is doped in the step (2), the drying temperature of an oven is 80 ℃, and the drying time is 12-18 h; the calcination adopts 2 hours of temperature programming to 500 ℃, and the calcination time is 2 hours.

According to the technical scheme, the gold source is chloroauric acid solution when Au is doped in the step (2); before pumping filtration, the pH value of the solution needs to be adjusted to 9-10 by using ammonia water; the drying temperature of the oven is 80 ℃, and the drying time is 12-18 h; the calcination adopts 2 hours of temperature programming to 600 ℃, and the calcination time is 2 hours.

According to the technical scheme, the mass ratio of each raw material component in the step (3) is as follows: NaOH: Ti-SBA-1: ethanol: 3-aminopropyltriethoxysilane: salicylaldehyde 0.48: 1: 39.45: 2.37: 4.68.

according to the technical scheme, the novel titanium silicalite molecular sieve is of a three-dimensional cubic structure, the size of a mesoporous is 2-3 nm, and the specific surface area is more than or equal to 500m²/g。

The invention also comprises the application of the novel titanium silicalite molecular sieve in the photoelectrocatalysis reduction of CO₂Or styrene and hydrogen peroxide are catalyzed to synthesize benzaldehyde and styrene oxide.

After the technical scheme is adopted, the invention has the following positive effects:

(1) under the strong acid condition, the titanium silicalite molecular sieve with a three-dimensional cubic structure is directly synthesized, and has the characteristics of mesopores and large specific surface area, so that the molecular sieve has strong adsorption performance; meanwhile, the molecular sieve is subjected to multi-scale modification through metal doping and organic functional groups, so that the catalytic performance of the titanium silicalite molecular sieve is further improved;

(2) the titanium silicon molecule has a large specific surface area, provides a large number of active sites for loading titanium, has a smooth spherical shape and uniform particles, and the porous structure determines that the molecular sieve has strong adsorption performance, carbon dioxide molecules are adsorbed in the pore channel, carbon dioxide can be directly reduced under the participation of electricity and light, the conversion efficiency is high, and the conversion speed is high;

(3) the invention modifies the molecular sieve by doping palladium and gold and modifies organic functional groups, and can more effectively capture protons and adsorb CO without destroying the original titanium-silicon molecular sieve structure₂Thereby further improving the catalytic performance;

(4) the novel titanium silicalite molecular sieve catalyzes CO through the photoelectric combination₂Reduction reaction can successfully realize CO₂Conversion to methanol, ethanol. In addition, the novel titanium silicalite molecular sieve is used for catalyzing the epoxidation reaction of styrene to successfully prepare benzaldehyde and styrene oxide, and the pressure of shortage of petroleum resources can be relieved to a certain extent.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which

FIG. 1 is an XRD spectrum of SBA-1 and Ti-SBA-1, and modified molecular sieves;

FIG. 2 is an SEM image of SBA-1 and Ti-SBA-1, and modified molecular sieves.

Detailed Description

Example 1

Preferably, 5.28g of cetyltrimethylammonium bromide (CTABr) is weighed out and dissolved in 325.7ml of deionized water, sonicated for 15 minutes at 313K. A homogeneous clear solution is obtained, 167.2ml of 37% hydrochloric acid are added, and a defined amount of tetrabutyl titanate (TBOT) solution in isopropanol is slowly added dropwise to this solution with vigorous mechanical stirringAnd then cooled to 273 k. After 30 minutes, under vigorous stirring, a certain amount of tetraethoxysilane which is cooled to 273k in advance is slowly dripped into the solution, after 5 minutes, the stirring is stopped, crystallization is carried out for 6 hours under the standing condition, then the solution is filtered by suction and washed by acetone. And (3) placing the mixture in an oven, setting the temperature to be 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain the Ti-SBA-1 product. The molar ratio of each raw material component of the product is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCl: 250H₂O。

The SBA-1 is prepared by the same method as Ti-SBA-1 except that tetrabutyl titanate (TBOT) is not added.

Example 2

Preferably, (1) 5.28g of cetyltrimethylammonium bromide (CTABr) is weighed out and dissolved in 325.7ml of deionized water, sonicated for 15 minutes at a temperature of 313K. A homogeneous clear solution is obtained, 167.2ml of 37% hydrochloric acid are added, and a defined amount of tetrabutyl titanate (TBOT) solution in isopropanol is added dropwise slowly to this solution, with vigorous mechanical stirring, and cooled to 273 k. After 30 minutes, under vigorous stirring, a certain amount of tetraethoxysilane which is cooled to 273k in advance is slowly dripped into the solution, after 5 minutes, the stirring is stopped, crystallization is carried out for 6 hours under the standing condition, then the solution is filtered by suction and washed by acetone. And (3) placing the mixture in an oven, setting the temperature to be 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain the Ti-SBA-1 product. The molar ratio of each raw material component of the product is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCl: 250H₂O；

(2) Modification of organic functional groups: and adding Ti-SBA-151 g into 40ml of 3mol/L sodium hydroxide solution for activation for 6 hours, filtering the solution, and placing the solution in an oven for drying. And then transferring the mixture into a 100mL beaker containing 50mL of absolute ethanol solution, carrying out oil bath, dripping 2.5mL of 3-aminopropyltriethoxysilane when the temperature is raised to 70 ℃, taking out the mixture after 6 hours, washing the mixture with ethanol, putting the mixture into an oven, and drying the mixture for one night. The next day, the mixture was taken out and put into a 100mL round-bottomed flask, 50mL of absolute ethanol and 4mL of salicylaldehyde were added to the flask, and the mixture was put into an oil bath pan at a set temperature of 80 ℃ and refluxed for 6 hours. And washing with propanol, placing in an oven, and drying for one night to obtain the product Ti-SBA-1-CHO.

Example 3

Preferably, (1) 5.28g of cetyltrimethylammonium bromide (CTABr) is weighed out and dissolved in 325.7ml of deionized water, sonicated for 15 minutes at a temperature of 313K. A homogeneous clear solution is obtained, 167.2ml of 37% hydrochloric acid are added, and a defined amount of tetrabutyl titanate (TBOT) solution in isopropanol is added dropwise slowly to this solution, with vigorous mechanical stirring, and cooled to 273 k. After 30 minutes, under vigorous stirring, a certain amount of tetraethoxysilane which is cooled to 273k in advance is slowly dripped into the solution, after 5 minutes, the stirring is stopped, crystallization is carried out for 6 hours under the standing condition, then the solution is filtered by suction and washed by acetone. And (3) placing the mixture in an oven, setting the temperature to be 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain the Ti-SBA-1 product. The molar ratio of each raw material component of the product is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCl: 250H₂O；

(2) Pd doping

And adding 10.5 g of Ti-SBA into 10ml of 2g/L palladium chloride solution, and performing ultrasonic treatment for 30 minutes to uniformly disperse palladium ions in the Ti-SBA-1. And carrying out suction filtration on the solution, and placing the obtained solid in an oven, wherein the temperature is 80 ℃, and drying for one night. And then transferring the mixture into a muffle furnace, carrying out programmed heating to 500 ℃ for two hours, and calcining for 2 hours to obtain the product Ti-SBA-1-Pd.

Example 4

Preferably, (1) 5.28g of cetyltrimethylammonium bromide (CTABr) is weighed out and dissolved in 325.7ml of deionized water, sonicated for 15 minutes at a temperature of 313K. A homogeneous clear solution is obtained, 167.2ml of 37% hydrochloric acid are added, and a defined amount of tetrabutyl titanate (TBOT) solution in isopropanol is added dropwise slowly to this solution, with vigorous mechanical stirring, and cooled to 273 k. After 30 minutes, a further quantity of tetraethyl orthosilicate, which had been cooled to 273k beforehand, was slowly added dropwise to the solution with vigorous stirring, 5 minutes laterStopping stirring, standing for crystallization for 6 hours, suction-filtering the solution, and washing with acetone. And (3) placing the mixture in an oven, setting the temperature to be 100 ℃, taking the mixture out to a mortar after 4 hours, grinding the mixture into uniform powder, placing the powder into a muffle furnace, and carrying out two-hour programmed temperature rise to 873k for calcination for 4 hours to obtain the Ti-SBA-1 product. The molar ratio of each raw material component of the product is 1.0 TEOS: 0.13 CTABr: 0.2 TBOT: 20 HCl: 250H₂O；

(2) Au doping

And adding 10.5 g of Ti-SBA into 10ml of 2g/L chloroauric acid solution, and performing ultrasonic treatment for 30 minutes to uniformly disperse gold in the Ti-SBA-1. Adjusting the pH of the solution to 9-10 by using ammonia water, carrying out suction filtration on the solution, and placing the obtained solid in an oven, wherein the temperature is 80 ℃, and drying for one night. And then transferring the mixture into a muffle furnace, carrying out programmed heating to 600 ℃ for two hours, and calcining for 2 hours to obtain the product Ti-SBA-1-Au.

FIG. 1 shows XRD spectra of SBA-1 and Ti-SBA-1, and modified molecular sieves, wherein FIG. 1(a) shows XRD spectra of SBA-1, FIG. 1(b) shows XRD spectra of Ti-SBA-1, and XRD spectra of metal-doped molecular sieves of Au and Pt and modified molecular sieves of organic functional groups are shown in FIG. 1(c), FIG. 1(d) and FIG. 1 (e). As shown in fig. 1, almost all samples have three distinct absorption peaks in the range of 2 θ ═ 2.5 to 3.5 °, which are (200), (210), and (211), respectively. Indicating that the sample is of a typical three-dimensional cubic structure. The crystal structure of the titanium-silicon molecular sieve is not changed after the modification of Au, Pt and organic functional groups.

FIG. 2 is SEM pictures of SBA-1, Ti-SBA-1 and modified molecular sieves, wherein FIG. 2a is an XRD spectrum of SBA-1, FIG. 2b is an XRD spectrum of Ti-SBA-1, and XRD spectrums of metal-doped molecular sieves of Au and Pt and modified molecular sieves of organic functional groups are shown in FIG. 2c, FIG. 2d and FIG. 2 e. As shown in the figure, the particle size distribution of the samples is 1.2-3.5 μm, all the samples are in a spherical shape, the particle size of the samples is increased by doping metal, the surface of the samples modified by organic functional groups is covered by a layer of flocculent substances, and organic molecules can grow on the surface of the samples.

Table 1 shows the product distribution of SBA-1 and Ti-SBA-1, and modified molecular sieves, the product distribution of the catalytic reaction of each sample is shown in the table, no corresponding liquid phase product is detected in SBA-1 and Ti-SBA-1, and the Au and Pt doped molecular sieves have methanol formation. And the liquid phase product of the organic modified molecular sieve catalytic reaction is generated by methanol and ethanol.

TABLE 1 product distribution Table for SBA-1, Ti-SBA-1 and modified molecular sieves

Table 2 shows the activity of SBA-1 and Ti-SBA-1, and the epoxidation reaction of modified molecular sieve styrene. It can be seen from the table that the pure molecular sieve has the lowest catalytic activity (3.9%) for the epoxidation of styrene, while the titanium silicalite Ti-SBA-1 has improved catalytic activity for the epoxidation of styrene and improved selectivity for styrene oxide, and the metal-doped sample has higher selectivity for the reaction, especially significantly improved selectivity for ethylene oxide, wherein the gold-doped sample exhibits the highest selectivity (38.9%). The conversion rate and selectivity of the organic modified sample are remarkably reduced, a large number of organic molecules cover the surface of the molecule, part of reactive active sites are covered, and the reduction of the specific surface area also plays a role in inhibiting the reaction.

TABLE 2 SBA-1, Ti-SBA-1 and modified molecular sieves styrene epoxidation reactivity Table

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.