Preparation method and application of a chitosan-based boron nitride adsorbent

Abstract

The present invention belongs to the field of fuel desulfurization and relates to a preparation method of a chitosan-based boron nitride adsorbent. First, the P123 template agent is dissolved in deionized water, and boric acid, low-molecular-weight chitosan, urea, and methanol are sequentially added under oil bath stirring. Stirring is continued until the solid completely precipitates. Finally, the precipitated solid is placed in a tube furnace and calcined under certain conditions to obtain the chitosan-based boron nitride adsorbent. In the present invention, boron nitride is prepared using biomass low-molecular-weight chitosan and urea as dual nitrogen sources. Chitosan is rich in sources, low in cost, green and non-toxic, and biodegradable. The prepared chitosan-based boron nitride adsorbent has good adsorption performance for dibenzothiophene in fuel and shows good application prospects in fuel adsorption desulfurization.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a chitosan-based boron nitride adsorbent, and belongs to the field of fuel oil desulfurization. Background Art

[0002] Sulfur oxides (SO x ) will not only cause metal catalyst poisoning and engine corrosion in automobile exhaust converters, but also SO x When discharged into the environment, sulfuric acid rain will be formed, causing serious air pollution and posing a huge threat to the environment and human health. Hydrodesulfurization (HDS) is the longest-studied and most sophisticated desulfurization technology. However, due to the influence of steric hindrance and electronic effects, the hydrogenation reaction activity of thiophene sulfides (such as dibenzothiophene and its derivatives) in fuel is low, resulting in extremely harsh conditions for their removal from fuel, high energy and hydrogen consumption, and increased desulfurization costs. Therefore, seeking other effective desulfurization methods to remove thiophene sulfides from fuel is of great significance to achieving the national strategic goal of "energy conservation and emission reduction".

[0003] Adsorption desulfurization (ADS) is a desulfurization process implemented under mild conditions. It is easy to operate, has low energy consumption, simple equipment, high desulfurization efficiency, few side reactions, and has almost no effect on the quality of fuel. In particular, adsorption desulfurization technology can effectively remove dibenzothiophene and its derivatives that are difficult to remove by catalytic hydrogenation. The core of the adsorption method is the selection of adsorbents. Boron nitride is considered to be a potential high-performance adsorbent because of its good chemical stability, resistance to high temperature, acid and alkali corrosion, and resistance to organic solvents. At present, the commonly used nitrogen sources for the preparation of boron nitride materials mainly include melamine, sodium azide, biuret, hydrazine hydrate, etc. However, the shortcomings of this type of inorganic nitrogen source limit its further application, such as sodium azide and hydrazine hydrate are explosive, and melamine is harmful to the human body. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing a chitosan-based boron nitride adsorbent. The chitosan-based boron nitride adsorbent is prepared using biomass low molecular weight chitosan and urea as dual nitrogen sources, and is used for the adsorption and removal of dibenzothiophene and its derivatives in fuel.

[0005] In order to achieve the above purpose, the specific steps of the present invention are as follows:

[0006] Firstly, the P123 template is dissolved in deionized water, and boric acid, low molecular weight chitosan, urea and methanol are added in sequence under stirring in an oil bath, and stirring is continued until the solid is completely precipitated; finally, the precipitated solid is placed in a tubular furnace and calcined under certain conditions to obtain a chitosan-based boron nitride adsorbent.

[0007] Preferably, in the above steps, the dosage ratio of the P123 template agent to deionized water is 0.3 - 0.8 g: 15 - 40 mL.

[0008] Preferably, in the above steps, the temperature of the oil bath stirring is 60 - 90 °C.

[0009] Preferably, in the above steps, the dosage ratio of the template agent, boric acid, low - molecular - weight chitosan, urea, and methanol is 0.3 - 0.8 g: 0.4 - 0.9 g: 0.2 - 0.5 g: 9.3 - 21 g: 15 - 40 mL.

[0010] Preferably, in the above steps, the molecular weight of the low - molecular - weight chitosan is 1500 - 3200.

[0011] Preferably, in the above steps, the calcination conditions are: temperature 800 - 1000 °C, time 1.5 - 3 h, and the calcination atmosphere is N2.

[0012] The present invention has the following remarkable advantages compared with the prior art:

[0013] (1) In the present invention, a chitosan - based boron nitride adsorbent is prepared by a calcination method using P123 as a template agent. The introduction of P123 helps to improve the pore structure characteristics of the boron nitride adsorbent and form a more regular and ordered morphology.

[0014] (2) In the present invention, boron nitride is prepared using biomass low - molecular - weight chitosan and urea as dual nitrogen sources. Compared with common inorganic nitrogen sources such as melamine, chitosan is rich in sources, low in cost, green and non - toxic, and biodegradable. In particular, the chitosan structure is rich in amino and hydroxyl active groups, which are easy to construct adsorption active sites.

[0015] (3) In the present invention, low - molecular - weight chitosan with a molecular weight of 1500 - 3200 is used as a nitrogen source. The molecular weight range of 1500 - 3200 can make the prepared boron nitride adsorbent expose the optimal number of adsorption active sites. Compared with high - molecular chitosan, low - molecular - weight chitosan not only retains the original functional characteristics of high - molecular chitosan but also has more unique physiological activities. Description of the Drawings

[0016] Figure 1 It is the scanning electron microscope image of the chitosan - based boron nitride adsorbent prepared in Example 1 of the present invention before and after adsorbing dibenzothiophene in fuel.

[0017] Figure 2 It is the EDS image of the chitosan - based boron nitride adsorbent prepared in Example 1 of the present invention after adsorbing dibenzothiophene in fuel.

[0018] Figure 3FT-IR spectra of the chitosan-based boron nitride adsorbent prepared in Example 1 of the present invention before and after adsorbing dibenzothiophene in fuel and of commercial-grade dibenzothiophene. Embodiment

[0019] The present invention will be further described below with reference to specific embodiments and the accompanying drawings. Example

[0020] First, 0.5 g of P123 template agent was dissolved in 25 mL of deionized water and continuously stirred in an oil bath at 70 °C. Subsequently, 0.6 g of boric acid, 0.3 g of low-molecular-weight chitosan (molecular weight of 2500), 14.4 g of urea, and 25 mL of methanol were added in sequence, and heating and stirring were continued until the solid completely precipitated. Finally, the precipitated solid was placed in a tubular furnace and calcined in an N2 atmosphere at 900 °C for 2 h to obtain the chitosan-based boron nitride adsorbent. Example

[0021] First, 0.3 g of P123 template agent was dissolved in 15 mL of deionized water and continuously stirred in an oil bath at 60 °C. Subsequently, 0.4 g of boric acid, 0.2 g of low-molecular-weight chitosan (molecular weight of 1500), 9.3 g of urea, and 15 mL of methanol were added in sequence, and heating and stirring were continued until the solid completely precipitated. Finally, the precipitated solid was placed in a tubular furnace and calcined in an N2 atmosphere at 800 °C for 1.5 h to obtain the chitosan-based boron nitride adsorbent. Example

[0022] First, 0.4 g of P123 template agent was dissolved in 20 mL of deionized water and continuously stirred in an oil bath at 65 °C. Subsequently, 0.5 g of boric acid, 0.25 g of low-molecular-weight chitosan (molecular weight of 2000), 11.7 g of urea, and 20 mL of methanol were added in sequence, and heating and stirring were continued until the solid completely precipitated. Finally, the precipitated solid was placed in a tubular furnace and calcined in an N2 atmosphere at 850 °C for 1.75 h to obtain the chitosan-based boron nitride adsorbent. Example

[0023] First, 0.7 g of P123 template agent was dissolved in 30 mL of deionized water and continuously stirred in an oil bath at 80 °C. Subsequently, 0.8 g of boric acid, 0.4 g of low-molecular-weight chitosan (molecular weight of 2750), 18.7 g of urea, and 30 mL of methanol were added in sequence, and heating and stirring were continued until the solid completely precipitated. Finally, the precipitated solid was placed in a tubular furnace and calcined in an N2 atmosphere at 950 °C for 2.5 h to obtain the chitosan-based boron nitride adsorbent. Example

[0024] First, 0.8 g of P123 template agent was dissolved in 40 mL of deionized water and continuously stirred in a 90 °C oil bath. Subsequently, 0.9 g of boric acid, 0.5 g of low molecular weight chitosan (molecular weight 3200), 21 g of urea, and 40 mL of methanol were added in sequence, and heating and stirring were continued until the solid completely precipitated. Finally, the precipitated solid was placed in a tubular furnace and calcined in an N2 atmosphere at 1000 °C for 3 h to obtain a chitosan-based boron nitride adsorbent. Example

[0025] Taking the chitosan-based boron nitride adsorbent prepared in Example 1 as an example, the adsorption activity of the boron nitride adsorbent prepared in Example 1 was evaluated; using dibenzothiophene (DBT) as the adsorption object, the adsorption capacity of the chitosan-based boron nitride adsorbent for DBT was measured.

[0026] The specific operation steps are as follows:

[0027] A simulated diesel of a single sulfur compound was prepared using n-octane as the solvent. Different masses of DBT were dissolved in n-octane respectively, and a certain amount of n-tetradecane was added as an internal standard to prepare simulated diesel with DBT contents of 100, 200, 300, 400, and 500 mg / L respectively. 0.0500 g of the chitosan-based boron nitride adsorbent was accurately weighed into a 50 mL conical flask, and 20.00 mL of simulated fuel with a sulfur content of 500 mg / L was added. At a certain temperature (298 K, 308 K, 318 K), it was placed in a constant temperature water bath oscillator and subjected to an adsorption experiment at 130 rpm. After a certain time, the supernatant was aspirated with a pipette, and the remaining sulfur content was detected by gas chromatography after centrifugation.

[0028] The detection method is as follows:

[0029] Detection was carried out using an Agilent 7890A gas chromatograph (hydrogen flame ionization detector). A mixture of N2, H2, and O2 was used as the gas source, and the gas flow rates were respectively: 30 mL / min (H2), 400 mL / min (O2), 25 mL / min (N2). The peak area at 6.375 min was integrated to obtain the remaining DBT content, and the adsorption capacity of the boron nitride adsorbent for DBT was calculated.

[0030] Figure 1 This is the scanning electron microscope image of the chitosan-based boron nitride adsorbent prepared in Example 1 of the present invention before and after adsorbing dibenzothiophene from fuel. It can be seen from the figure that the chitosan-based boron nitride adsorbent is mostly a multi-layered flaky structure formed by the stacking of single layers. In comparison, the chitosan-based boron nitride adsorbent still maintains a multi-layered flaky structure after adsorbing DBT, and the morphology has no significant change.

[0031] Figure 2EDS diagram of the chitosan-based boron nitride adsorbent prepared in Example 1 of the present invention after adsorbing dibenzothiophene in fuel. It can be seen that the presence of sulfur (S) element can be observed in the EDS diagram of chitosan-based boron nitride after adsorbing DBT. The S element is derived from the adsorbed DBT molecule, confirming that chitosan-based boron nitride can effectively adsorb DBT.

[0032] Figure 3 FT-IR diagrams of the chitosan-based boron nitride adsorbent prepared in Example 1 of the present invention before and after adsorbing dibenzothiophene in fuel. As can be seen from the figure, the infrared characteristic peak at 1386 cm -1 in the FT-IR spectrum of the chitosan-based boron nitride adsorbent belongs to the in-plane stretching vibration of B-N-B, while the absorption peak at 800 cm -1 corresponds to the out-of-plane bending vibration of B-N-B, and the infrared absorption peak at 3420 cm -1 belongs to the stretching vibration of -NH2. When the chitosan-based boron nitride adsorbent adsorbs DBT, a new infrared characteristic peak appears at 741 cm -1 . By comparing the infrared spectrum of commercial-grade DBT, it is found that this new infrared characteristic peak corresponds to the stretching vibration of DBT, proving that DBT can be effectively adsorbed by the prepared chitosan-based boron nitride adsorbent.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above respective embodiments, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a chitosan-based boron nitride adsorbent, characterized in that, The steps are as follows: Dissolve the P123 template agent in deionized water, and successively add boric acid, low molecular weight chitosan, urea and methanol under stirring in an oil bath, and continue stirring until the solid completely precipitates; place the precipitated solid in a tube furnace and calcine it under certain conditions to obtain a chitosan-based boron nitride adsorbent. The dosage ratio of the P123 template agent to deionized water is 0.3 - 0.8 g: 15 - 40 mL, the molecular weight of the low molecular weight chitosan is 1500 - 3200, and the dosage ratio of the P123 template agent, boric acid, low molecular weight chitosan, urea and methanol is: 0.3 - 0.8 g: 0.4 - 0.9 g: 0.2 - 0.5 g: 9.3 - 21 g: 15 - 40 mL. The calcination conditions are: temperature 800 - 1000 °C, time 1.5 - 3 h, and the calcination atmosphere is N2.

2. The preparation method of a chitosan-based boron nitride adsorbent according to claim 1, characterized in that: The temperature of the oil bath stirring is: 60 - 90 °C.

3. Application of the chitosan-based boron nitride adsorbent prepared by the preparation method according to any one of claims 1 - 2 in the adsorption and removal of dibenzothiophene and its derivatives in fuel oil.

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