Modified molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to a modified molecular sieve and a preparation method and application thereof, and the preparation method comprises the following steps: alkali modification: obtaining an alkali modified ultra-stable Y molecular sieve; performing nickel ion exchange for many times to obtain a nickel ion loaded ultra-stable Y molecular sieve; and carrying out cerium ion exchange to obtain the nickel-cerium double-loaded ultra-stable Y molecular sieve. On the basis of an ultra-stable Y-type molecular sieve, a novel modified molecular sieve is prepared through further modification treatment, so that the adsorption performance of the novel modified molecular sieve on organic sulfides such as mercaptan and thioether in oily sewage and oily waste gas is improved, and a more efficient, economical and environment-friendly technical solution is provided for VOCs emission treatment in the petrochemical industry; the method has important application value and market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and particularly relates to a modified molecular sieve, a preparation method thereof, and an application thereof. Background Art

[0002] Organic sulfides are a class of complex organic compounds, covering a variety of different types. Among them, thiols belong to polar organic sulfides. In their molecular structure, sulfur atoms are connected to hydrogen atoms, showing strong polar characteristics; while sulfides, thiophenols, thiocarbonates, carbon disulfide, thiophenes, etc. belong to non-polar organic sulfides. These compounds have different molecular structures and chemical properties, but all pose potential hazards to the environment and human health.

[0003] Among current various desulfurization technical methods, adsorption desulfurization, as an emerging technical means, has shown relatively significant advantages and broad application prospects, and is considered to be one of the most potential methods for solving the problem of deep desulfurization of fuels such as gasoline and diesel. Adsorption desulfurization technology has many outstanding advantages. First of all, compared with traditional desulfurization technologies, the investment cost of adsorption desulfurization equipment is relatively low, which reduces the economic burden of enterprises to a certain extent; secondly, its desulfurization efficiency is high, and it can effectively remove sulfides in fuels, meeting the increasingly strict environmental protection emission standards; furthermore, the adsorption desulfurization process does not consume hydrogen, avoiding the related costs and safety risks of hydrogen preparation and use; in addition, the price of the adsorbent is relatively low, and the entire adsorption desulfurization operation process is simple, convenient, fast, and economical, and is easy to realize industrial large-scale application. Therefore, it has received extensive attention and research in the desulfurization field of the petrochemical industry.

[0004] Among the numerous materials available for adsorptive desulfurization, zeolite molecular sieves have stood out and become a hot research topic and commonly used adsorbent materials. Zeolite molecular sieves are porous substances with a regular pore structure. Their pore sizes are uniform, usually in the nanometer to micrometer range. This unique pore structure endows them with a high specific surface area, providing a large number of active sites for adsorption reactions. At the same time, zeolite molecular sieves also have excellent ion exchange properties and can interact with sulfides in fuels through ion exchange, thereby achieving effective adsorption and removal of sulfides. Among various types of zeolite molecular sieves, ultrastable Y zeolite is favored due to its unique performance advantages. Ultrastable Y zeolite has undergone special stabilization treatment and has good hydrothermal stability, capable of maintaining the stability of its structure and performance under harsh industrial conditions such as high temperature and high humidity. Its micropore size is moderate and matches the sizes of fuel molecules and sulfide molecules, which is conducive to the selectivity and efficiency of the adsorption process. Moreover, the ion exchange performance of ultrastable Y zeolite is also very excellent, capable of effectively adsorbing and fixing sulfide ions. Therefore, it is widely used as a basic adsorbent material in the research of adsorptive desulfurization, providing a good foundation for the further development of high-performance adsorptive desulfurization agents.

[0005] Through research and analysis of the existing technology, although certain progress has been made in the field of adsorptive desulfurization, the research on the preparation and application of high-performance adsorbents still has important practical significance and broad development space. Based on ultrastable Y zeolite, through further modification treatment, a new type of modified molecular sieve is prepared to improve its adsorption performance for organic sulfides such as thiols and thioethers in oily wastewater and oily waste gas, providing a more efficient, economical, and environmentally friendly technical solution for the treatment of VOCs emissions in the petrochemical industry, which has important application value and market prospects. Summary of the Invention

[0006] (1) Technical Problems to be Solved

[0007] The technical problem to be solved by the present invention is to provide a modified molecular sieve and its preparation method and application to improve its adsorption performance for organic sulfides such as thiols and thioethers in oily wastewater and oily waste gas.

[0008] (2) Technical Solutions

[0009] To solve the above problems, the present invention provides a preparation method of a modified molecular sieve, including the following steps:

[0010] Alkali modification to obtain alkali-modified ultrastable Y zeolite;

[0011] Multiple nickel ion exchanges to obtain nickel-loaded ultrastable Y zeolite;

[0012] Cerium ion exchange is carried out to obtain nickel-cerium double-loaded ultrastable Y zeolite.

[0013] Among them, the multiple nickel ion exchanges are two nickel ion exchanges.

[0014] Among them, the two nickel ion exchanges include:

[0015] Primary nickel ion exchange: The alkali-modified ultrastable Y zeolite and the nickel ion exchange solution are mixed at a mass ratio of 1:10 and stirred; vacuum filtration and drying are carried out to obtain the ultrastable Y zeolite loaded with primary nickel ions;

[0016] Secondary nickel ion exchange: The ultrastable Y zeolite loaded with primary nickel ions and the nickel ion exchange solution are mixed at a mass ratio of 1:10 and stirred; vacuum filtration and drying are carried out to obtain the ultrastable Y zeolite loaded with nickel ions.

[0017] Among them, between the steps of primary nickel ion exchange and secondary nickel ion exchange, there is also included:

[0018] Calcination: The dried ultrastable Y zeolite loaded with primary nickel ions is placed in a muffle furnace for calcination, the calcination temperature is 500 °C, and the time is 5 h.

[0019] Among them, the nickel ion exchange solution is an aqueous solution of nickel nitrate with a concentration of 0.1 mol / L.

[0020] Among them, the cerium ion exchange includes:

[0021] The ultrastable Y zeolite loaded with nickel ions and the aqueous solution of cerium nitrate are mixed at a mass ratio of 1:10 and stirred;

[0022] Vacuum filtration and drying are carried out to obtain the nickel-cerium double-loaded ultrastable Y zeolite.

[0023] Among them, there is also included:

[0024] Molecular sieve activation: The nickel-cerium double-loaded ultrastable Y zeolite is placed in a muffle furnace for calcination, the calcination temperature is 500 °C, and the time is 5 h.

[0025] The present invention also provides a modified molecular sieve prepared by the above preparation method.

[0026] The present invention also provides the application of the modified molecular sieve prepared by the above preparation method in the adsorption of mercaptan and / or thioether in oily sewage.

[0027] The present invention also provides the application of the modified molecular sieve prepared by the above preparation method in the adsorption of mercaptan and / or thioether in oily waste gas.

[0028] (III) Beneficial effects

[0029] The above technical solution of the present invention has the following advantages: In the preparation method of the modified molecular sieve, through alkali modification, multiple nickel ion exchanges and cerium ion exchanges, the prepared nickel-cerium double-loaded ultrastable Y molecular sieve has excellent adsorption performance for thiols and thioethers in oily sewage and waste gas, can efficiently remove sulfides, and meets environmental protection standards. It has good hydrothermal and chemical stability and can operate stably for a long time under complex working conditions. The preparation cost is low, the operation is simple, the adsorbent can be recycled, and it is economical and practical. At the same time, it reduces sulfide emissions and energy consumption, and has significant environmental benefits. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] A preparation method of a modified molecular sieve provided by an embodiment of the present invention includes the following steps:

[0032] Molecular sieve pretreatment: Weigh the ultrastable Y molecular sieve, and the model can be selected as: USY, SiO 2 / Al2O 3 molar ratio ≥ 30, specific surface area ≥ 600 m 2 / g. Use a blast drying oven of model DHG-9070A to raise the temperature to 110 °C at a heating rate of 2 °C / min and dry for 6 h. After drying, transfer it to a dryer with silica gel desiccant inside and cool it to room temperature to prevent secondary moisture absorption.

[0033] Alkali modification treatment: Add the dried ultrastable Y molecular sieve and 0.2 mol / L NaOH aqueous solution to a high-pressure reaction kettle, and keep it at room temperature for 18 h. Stirring parameters: mechanical stirring speed 300 rpm, temperature control accuracy ±0.5 °C. The high-pressure reaction kettle is a magnetic stirring reaction kettle with a polytetrafluoroethylene lining, the volume is 500 mL, and the pressure tolerance ≥ 3 MPa. The liquid-solid ratio is controlled at 5:1. For example, 20 g of molecular sieve requires 100 mL of 0.2 mol / L NaOH solution.

[0034] Perform three-stage countercurrent washing with hot deionized water at 60 °C, and the amount of washing liquid used each time is 3 times the solid weight until the pH value of the filtrate is 7.

[0035] Dry at 393 K for 6 h. When drying, introduce N 2 protection, N 2 flow rate 50 mL / min.

[0036] Calcination: Select a box furnace SX2-4-10 muffle furnace and use three-stage heating: heat from room temperature to 673K at a rate of 5°C / min, hold for 2h at 673K, heat from 673K to 723K at a rate of 3°C / min, and hold for 4h at 723K. Cool down at a rate of 3°C / min. During the holding period, the temperature fluctuation does not exceed ±5°C.

[0037] Finally, the alkali-modified ultrastable Y zeolite is obtained, and the framework structure is verified by XRD, with characteristic peaks at 2θ = 6.2°, 15.6°, and 23.6°.

[0038] Prepare nickel ion exchange solution: Weigh nickel nitrate solution, then add deionized water to prepare a nickel nitrate aqueous solution with a concentration of 0.1mol / L, stir well to obtain a nickel ion exchange solution.

[0039] Among them: Use analytical pure nickel nitrate (Ni(NO 3 ) 2 ·6H 2 O, purity ≥ 99.0%); The conductivity of deionized water should be ≤ 1μS / cm. After preparation, disperse ultrasonically for 10min, with a power of 300W and a frequency of 40kHz; Control the solution pH value at 2.5 - 3.0.

[0040] Primary nickel ion exchange: Mix the alkali-modified ultrastable Y zeolite and the nickel ion exchange solution at a mass ratio of 1:10 and stir for 5h; Filter by vacuum suction and dry to obtain the ultrastable Y zeolite with primary nickel ion loading;

[0041] Among them, a constant temperature magnetic stirrer is used during the stirring process. The size of the stirring bar is Φ8×30mm, and the rotation speed is 800rpm. Temperature control: 90 ± 1°C. A condensing reflux device is used during the reaction process to prevent the solution from evaporating. Use ICP-OES to sample and detect every 1h to monitor the nickel ion concentration in real time.

[0042] When filtering by vacuum suction, use a Φ100mm Buchner funnel and cooperate with a 0.45μm mixed cellulose ester filter membrane for suction filtration. Standard of washing water volume: Each time use 50mL of 60°C deionized water, wash until the conductivity of the filtrate ≤ 10μS / cm and the pH is neutral. When drying, use a DZF-6020 type vacuum drying oven, set the vacuum degree at -0.08MPa, and dry at 110°C for 2h.

[0043] Calcination: Place the dried ultrastable Y zeolite with primary nickel ion loading in a muffle furnace for calcination, with a calcination temperature of 500°C and a time of 5h.

[0044] Secondary nickel ion exchange: Mix the ultrastable Y zeolite loaded with primary nickel ions and the nickel ion exchange solution at a mass ratio of 1:10 and stir for 6 h. The Ni content detected by XRF should reach 4.0 - 5.5 wt%. Perform vacuum filtration and drying to obtain the ultrastable Y zeolite loaded with nickel ions. The BET specific surface area should be ≥ 550 m 2 / g, and the pore volume should be ≥ 0.35 cm 3 / g.

[0045] Among them, a constant temperature magnetic stirrer is used during the stirring process. The size of the stir bar is Φ8×30 mm, and the rotation speed is 800 rpm. Temperature control: 90 ± 1 °C. A condensing reflux device is used during the reaction process to prevent the solution from evaporating. ICP - OES is used to sample and detect every 1 h to monitor the nickel ion concentration in real - time. During vacuum filtration, a Φ100 mm Buchner funnel is used in combination with a 0.45 μm mixed cellulose ester filter membrane for filtration. Standard for washing water volume: Each time, use 50 mL of deionized water at 60 °C and wash until the conductivity of the filtrate is ≤ 10 μS / cm and the pH is neutral. During drying, a DZF - 6020 type vacuum drying oven is used, with a vacuum degree of - 0.08 MPa and drying at 110 °C for 2 h.

[0046] Prepare cerium nitrate solution: Weigh cerium nitrate solution with a purity of ≥ 99.5%, and then add deionized water to prepare an aqueous cerium nitrate solution with a concentration of 0.05 mol / L, and stir well.

[0047] Cerium ion exchange: Mix the ultrastable Y zeolite loaded with nickel ions and the aqueous cerium nitrate solution at a mass ratio of 1:10 and stir; Use gradient heating: Keep at 80 °C for the first 2 h, and increase the stirring speed to 800 rpm. Raise the temperature to 95 °C in the next 2 h, and increase the stirring speed to 1000 rpm to promote diffusion. End - point determination: When the change rate of Ce 3 + concentration is < 0.5% / h, terminate the reaction.

[0048] Perform vacuum filtration and drying to obtain the Ni - Ce dual - loaded ultrastable Y zeolite. Analyze the metal dispersion by TPR. The reduction peak temperature of NiO is ≤ 400 °C, and the reduction peak temperature of CeO 2 is ≤ 500 °C.

[0049] Molecular sieve activation: Place the Ni - Ce dual - loaded ultrastable Y zeolite in a muffle furnace for roasting. The roasting temperature is 500 °C and the time is 5 h.

[0050] The activated Ni - Ce dual - loaded ultrastable Y zeolite can be put into subsequent use.

[0051] The present invention provides a modified molecular sieve prepared by the above - mentioned preparation method.

[0052] The modified molecular sieve prepared by the above preparation method can be applied to the adsorption of thiols and / or thioethers in oil-containing waste gas. It can also be applied to the adsorption of thiols and / or thioethers in oil-containing sewage.

[0053] Adsorption application of thiols and / or thioethers in oil-containing waste gas:

[0054] Oil-containing waste gas is usually a complex gas mixture generated during oil exploration, refining, and related chemical production processes. Sulfur-containing compounds such as thiols and thioethers are one of the main pollutants. These sulfur-containing compounds not only have an unpleasant odor but also pose serious hazards to the environment and human health. For example, thiol substances have a strong stench and can be perceived by people even at very low concentrations, affecting the quality of life of surrounding residents; thioethers will undergo photochemical reactions in the atmosphere to generate harmful secondary pollutants, damaging air quality.

[0055] The modified molecular sieve prepared in the present invention has significant advantages in the adsorption of thiols and / or thioethers in oil-containing waste gas. First of all, the molecular sieve itself has a regular pore structure and a large specific surface area, which provides a large number of adsorption active sites for it. The molecular sieve impregnated with NaOH solution has a higher peak intensity and better relative crystallinity because after the molecular sieve is treated with alkali, its framework silicon-aluminum ratio changes and the surface acidity changes. When loading metal ions, the framework is not easily damaged, so the crystallinity is better. During the alkali modification process, the ultrastable Y molecular sieve reacts with the NaOH solution, enhancing the surface basicity of the molecular sieve, which is helpful for the adsorption of thiol and thioether molecules. Because the sulfur atoms in thiol and thioether molecules have a certain electron density and can interact with the basic sites on the surface of the molecular sieve, they are adsorbed into the pores of the molecular sieve.

[0056] An adsorbent of Ni and Ce bimetallic Y molecular sieve modified with NaOH solution was prepared. Alkali modification not only increased the specific surface area of the Y molecular sieve but also introduced more mesoporous structures, and the pore diameter increased, which was beneficial for larger-diameter sulfide molecules such as dibenzothiophene to enter the pores for adsorption. The nickel ion exchange step further improved the adsorption performance of the molecular sieve for thiols and thioethers. Nickel ions have a certain polarity and can form coordination bonds with the sulfur atoms in thiol and thioether molecules, enhancing the adsorption. Through the primary nickel ion exchange and the secondary nickel ion exchange, sufficient adsorption active sites were ensured. Cerium ion exchange endows the molecular sieve with unique redox properties. During the adsorption process, cerium ions can undergo redox reactions with thiol and thioether molecules, promoting their adsorption and conversion on the surface of the molecular sieve. At the same time, the presence of cerium ions can also improve the thermal stability and water resistance of the molecular sieve, enabling it to maintain good adsorption performance in the complex environment of oil-containing waste gas.

[0057] The results of the dynamic adsorption desulfurization experiment show that the bimetallic adsorbent has the best desulfurization performance. Because it can combine organic sulfides through two types of adsorption modes, the desulfurization performance is greatly improved. In practical applications, the oily waste gas can be treated by contacting with the modified molecular sieve. For example, the waste gas can be passed through an adsorption tower filled with the modified molecular sieve, and the mercaptan and thioether molecules in the waste gas are removed under the adsorption of the molecular sieve, thus realizing the purification of the waste gas. By regularly replacing or regenerating the molecular sieve, the continuous and effective operation of the adsorption system can be ensured.

[0058] Adsorption application of mercaptan and / or thioether in oily wastewater

[0059] Oily wastewater is one of the main types of wastewater generated in the petrochemical industry and contains a large amount of organic matter, oil, and sulfur-containing pollutants such as mercaptan and thioether. The presence of these sulfur-containing pollutants not only increases the difficulty of wastewater treatment but also causes serious harm to the water ecological environment and wastewater treatment facilities.

[0060] The modified molecular sieve of the present invention also performs excellently in the adsorption of mercaptan and / or thioether in oily wastewater. Because the molecular sieve has good water stability and can maintain the stability of its structure and performance in the water-containing environment of oily wastewater. Its large specific surface area and special pore structure enable it to effectively adsorb mercaptan and thioether molecules in the wastewater. During the alkali modification process, the basic sites on the surface of the molecular sieve can interact with mercaptan and thioether molecules to promote their adsorption. The exchange of nickel ions and cerium ions further enhances the adsorption performance of the molecular sieve. The coordination of nickel ions with mercaptan and thioether molecules and the redox properties of cerium ions both contribute to improving the removal efficiency of the molecular sieve for these sulfur-containing pollutants.

[0061] In the process of treating oily wastewater, the modified molecular sieve can be fully contacted with the wastewater by using a fixed-bed adsorption column or stirring adsorption. For example, in a fixed-bed adsorption column, the wastewater enters from the top of the column and flows through the adsorption layer filled with the modified molecular sieve, and the mercaptan and thioether molecules therein are adsorbed onto the molecular sieve, thus realizing the purification of the wastewater. In addition, because the molecular sieve is renewable, after a certain period of adsorption, the mercaptan and thioether molecules adsorbed on the molecular sieve can be removed by appropriate regeneration methods such as heating and washing, so that the molecular sieve restores its adsorption performance, thus realizing the recycling of the molecular sieve and reducing the cost of wastewater treatment.

[0062] In summary, the modified molecular sieve prepared by the present invention has broad application prospects in the adsorption of thiols and / or thioethers in oil-containing waste gas and oil-containing sewage due to its unique structure and properties. By reasonably utilizing this modified molecular sieve, thiol and thioether pollutants in oil-containing waste gas and oil-containing sewage can be effectively removed, reducing environmental pollution, which has important environmental and economic significance. In future petrochemical and other related industries, this modified molecular sieve is expected to become an important environmental protection material, providing an effective solution to the problems in the treatment of oil-containing waste gas and oil-containing sewage.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that not every embodiment only contains an independent technical solution. In the case of no conflict between the solutions, the technical features mentioned in each embodiment can be combined in any way to form other embodiments that can be understood by those skilled in the art.

[0064] In addition, without departing from the scope of the present invention, modifying the technical solutions described in the foregoing embodiments or equivalently replacing some of the technical features does not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims

1. A method for preparing a modified molecular sieve, characterized in that: The steps include: Alkali modification to obtain alkali-modified ultra-stable Y molecular sieve; Multiple nickel ion exchanges to obtain ultra-stable Y molecular sieve loaded with nickel ions; Cerium ion exchange to obtain nickel-cerium dual-loaded ultra-stable Y molecular sieve.

2. The method for preparing a modified molecular sieve according to claim 1, characterized in that: The multiple nickel ion exchanges are two nickel ion exchanges.

3. The method for preparing a modified molecular sieve according to claim 2, characterized in that: The two nickel ion exchanges include: Initial nickel ion exchange: the alkali-modified ultra-stable Y molecular sieve and the nickel ion exchange liquid are mixed and stirred at a mass ratio of 1:10; vacuum filtered and dried to obtain the ultra-stable Y molecular sieve loaded with the initial nickel ion; Secondary nickel ion exchange: The ultra-stable Y molecular sieve loaded with nickel ions for the first time is mixed with the nickel ion exchange liquid at a mass ratio of 1:10 and stirred; vacuum filtered and dried to obtain the ultra-stable Y molecular sieve loaded with nickel ions.

4. The method for preparing a modified molecular sieve according to claim 3, characterized in that: Between the steps of the primary nickel ion exchange and the secondary nickel ion exchange also include: Calcination: The dried ultra-stable Y molecular sieve loaded with primary nickel ions was placed in a muffle furnace and calcined at a temperature of 500°C for 5 hours.

5. The method for preparing a modified molecular sieve according to claim 4, characterized in that: The nickel ion exchange solution is a nickel nitrate aqueous solution with a concentration of 0.1 mol / L.

6. The method for preparing a modified molecular sieve according to claim 5, characterized in that: The cerium ion exchange comprises: The nickel ion-loaded ultrastable Y molecular sieve and the cerium nitrate aqueous solution were mixed in a mass ratio of 1:10 and stirred; The nickel-cerium dual-loaded ultra-stable Y molecular sieve was obtained by vacuum filtration and drying.

7. The method for preparing a modified molecular sieve according to claim 6, characterized in that: Also includes: Molecular sieve activation: The nickel-cerium dual-loaded ultra-stable Y molecular sieve was calcined in a muffle furnace at a temperature of 500°C for 5 hours.

8. A modified molecular sieve, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. The modified molecular sieve prepared by the preparation method according to any one of claims 1 to 7, which is used for adsorption of mercaptans and / or thioethers in oily wastewater.

10. The modified molecular sieve prepared by the preparation method according to any one of claims 1 to 7, which is used for adsorption of mercaptans and / or sulfides in oily waste gas.