阅读说明：本技术 一种稀硝酸还原转化用催化剂及其制备方法和应用 (Catalyst for reduction and conversion of dilute nitric acid and preparation method and application thereof ) 是由 梁必超 欧进永 钱宏义 骆念军 计扬 毛彦鹏 于 2018-08-22 设计创作，主要内容包括：本发明涉及一种稀硝酸还原转化用催化剂及其制备方法和应用,包括载体、活性组分和助剂,所述的载体为分子筛或硅胶；所述的活性组分为氧化铜,所述的助剂为Fe、Cs、La、Zr、Zn、Ca的氧化物中的一种或多种；其中,活性组分铜元素的总含量为载体质量的0.1％-10.0％,助剂元素的总含量为载体质量的0.1％-6.0％。该催化剂可以用于还原转化稀硝酸及回收氮元素,与现有技术相比,本发明以一氧化氮气体为还原剂,将溶液中的稀硝酸还原为亚硝酸甲酯(MN)。当溶液中稀硝酸浓度为1～10％时,转化后溶液中硝酸浓度不高于0.1％,硝酸转化率>95％。(The invention relates to a catalyst for reduction and conversion of dilute nitric acid and a preparation method and application thereof, and the catalyst comprises a carrier, an active component and an auxiliary agent, wherein the carrier is a molecular sieve or silica gel; the active component is copper oxide, and the auxiliary agent is one or more of oxides of Fe, Cs, La, Zr, Zn and Ca; wherein the total content of the active component copper element is 0.1-10.0% of the mass of the carrier, and the total content of the auxiliary agent element is 0.1-6.0% of the mass of the carrier. Compared with the prior art, the catalyst takes nitric oxide gas as a reducing agent to reduce the dilute nitric acid in the solution into Methyl Nitrite (MN). When the concentration of the dilute nitric acid in the solution is 1-10%, the concentration of the nitric acid in the converted solution is not higher than 0.1%, and the conversion rate of the nitric acid is more than 95%.)

1. The catalyst for the reduction and conversion of the dilute nitric acid is characterized by comprising a carrier, an active component and an auxiliary agent, wherein the carrier is a molecular sieve or silica gel; the active component is copper oxide, and the auxiliary agent is one or more of oxides of Fe, Cs, La, Zr, Zn and Ca; wherein the total content of the active component copper element is 0.1-10.0% of the mass of the carrier, and the total content of the auxiliary agent element is 0.1-6.0% of the mass of the carrier.

2. The catalyst for the reductive conversion of dilute nitric acid as claimed in claim 1, wherein the carrier is SBA-15 molecular sieve or water-resistant silica gel.

3. The catalyst for the reductive conversion of dilute nitric acid according to claim 1, wherein said carrier has a spherical shape of 3 to 8 mm.

4. The catalyst for the reductive conversion of dilute nitric acid according to claim 1, wherein the copper element precursor as the active component is copper sulfate, copper nitrate or copper chloride, preferably copper nitrate.

5. The catalyst for the reductive conversion of dilute nitric acid according to claim 1, wherein the precursor of the auxiliary element is a nitrate, a sulfate, a chloride, a fluoride or a carbonate, preferably a chloride.

6. The catalyst for the reduction and conversion of dilute nitric acid according to claim 1, wherein the total content of the copper element as the active component is 1-2% of the mass of the carrier, and the total content of the auxiliary element is 0.5-1.0% of the mass of the carrier.

7. The catalyst for the reductive conversion of dilute nitric acid according to claim 1, wherein the molar ratio of said promoter elements is Fe, Cs, La, Zr, Zn, Ca ═ 0.5 to 3.0: (0-3.0): (0-2.0): (0-2.0): (0-2.0): (0-1.0).

8. The catalyst for the reductive conversion of dilute nitric acid according to claim 1 or 7, wherein the molar ratio of said promoter element is preferably (0.9-1.1): (0.9-1.1): (0.9-1.1): (0.3-0.5): (0.3-0.5): (0.1-0.3).

9. A method of preparing a catalyst for the reductive conversion of dilute nitric acid according to claim 1, comprising the steps of: the active components and the auxiliary agents are loaded on the carrier by adopting an impregnation method, and then the carrier is dried and roasted to obtain the product, wherein the impregnation method is equivalent impregnation loading or excessive impregnation loading, and the impregnation method is one-time impregnation or step-by-step impregnation.

10. The use of the catalyst for the reductive conversion of dilute nitric acid according to claim 1, wherein the catalyst is used for the reductive conversion of nitric acid and the recovery of nitrogen elements in wastewater generated in the coal-based ethylene glycol oxidation and esterification stage.

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a nitric acid reduction and conversion catalyst, more preferably a catalyst for reducing and converting nitric acid in wastewater of a coal-based ethylene glycol project esterification workshop section and recovering nitrogen elements.

Background

Ethylene glycol is an important chemical raw material and strategic material, is used for manufacturing polyester (which can be further used for producing terylene, beverage bottles and films), explosive and glyoxal, and can be used as an antifreezing agent, a plasticizer, hydraulic fluid, a solvent and the like. The coal-made glycol is used for producing glycol by replacing petroleum ethylene with coal. Experts point out that the technical route conforms to the resource characteristics of oil shortage, gas shortage and relatively rich coal resources in China.

At present, the domestic route for preparing ethylene glycol from coal is mainly an oxalate method, wherein a key step is an esterification reaction: and carrying out esterification reaction on oxygen, methanol and nitric oxide to obtain Methyl Nitrite (MN). In the process, waste liquid containing nitric acid, water and methanol is generated due to side reaction, if the waste liquid is directly discharged after the methanol is recovered, the content of the nitric acid exceeds the environmental protection requirement, and nitrogen elements in the nitric acid are lost, so that the production cost is increased. If the waste water containing the dilute nitric acid is neutralized by alkali, a large amount of alkali is consumed, the problem of equipment corrosion is caused, and meanwhile, nitrogen elements cannot be recycled, so that the production cost is increased. If the nitric acid in the liquid can be converted into methyl nitrite for recycling, the discharged liquid can meet the environmental protection requirement, and the utilization rate of nitrogen elements can be improved, so that the method is the most economic and effective method so far.

At present, in coal-based ethylene glycol industrial devices, gas rich in nitric oxide in a system is used as reducing gas to reduce, convert, oxidize and esterify nitric acid in wastewater generated in a reduction stage, but the used catalyst is a carbon-based catalyst, so that the problems of large pressure drop and serious crushing exist in the using process, the pressure drop of a bed layer is further increased when the crushing is serious, and the problems of catalyst loss, nitric acid conversion rate reduction, deepening of discharged wastewater color and the like are caused. Therefore, the development of the nitric acid and water resistant non-carbon-based catalyst for the nitric acid reduction and conversion of the wastewater in the oxidative esterification section can solve a series of problems caused by the crushing of the catalyst in the using process, and has good industrial application prospect.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a catalyst for reducing and converting dilute nitric acid, a preparation method and application thereof. The catalyst can be used for reducing nitric acid in wastewater in a coal-based glycol esterification stage by nitric oxide to reduce the concentration of the nitric acid to be below 0.1% so as to meet the environmental-protection emission standard; meanwhile, the catalyst adopts a non-carbon-based carrier, and has better crushing resistance, lower pressure drop and longer service life.

The purpose of the invention can be realized by the following technical scheme: the catalyst for the reduction and conversion of the dilute nitric acid is characterized by comprising a carrier, an active component and an auxiliary agent, wherein the carrier is a molecular sieve or silica gel; the active component is copper oxide, and the auxiliary agent is one or more of oxides of Fe, Cs, La, Zr, Zn and Ca; wherein the total content of the active component copper element is 0.1-10.0% of the mass of the carrier, and the total content of the auxiliary agent element is 0.1-6.0% of the mass of the carrier.

Further, the carrier is an SBA-15 molecular sieve or water-resistant silica gel.

SBA-15 belongs to a mesoporous molecular sieve, the synthesis of which is another important chemical technology which is aroused in recent years, the SBA-15 has wide application prospects in the fields of catalysis, separation, biology, nano materials and the like, and the advantages of high hydrothermal stability and the like of the SBA-15 develop new research fields for the subjects of catalysis, adsorption separation, high-grade inorganic materials and the like. The synthesis condition of SBA-15 is mild, the surfactant is easy to remove, and the structure collapse is not easy to cause; the repulsive force between the neutral surfactant and the neutral inorganic precursor is much smaller than that between the ionic surfactant and the charged inorganic precursor, and a thicker hole wall can be formed, so that the thermal and hydrothermal stability of the framework structure of the molecular sieve is improved.

The water-resistant silica gel is white or gray microporous spherical particles, has a high microporous structure of common industrial silica gel, is insoluble in water and inorganic acid, is soluble in hydrofluoric acid and concentrated caustic alkali solution, and has high mechanical strength. The product is heterogeneous formed silica gel which is prepared by further processing general silica gel serving as a raw material.

The invention finds that SBA-15 and water-resistant silica gel are optimal in a plurality of carriers such as alumina, molecular sieves and silica gel, such as 5A, 13X, ZSM-5, SAPO-11, SAPO-17, SAPO-20, NaY, common silica gel, water-resistant silica gel, α -alumina, β -alumina, gamma-alumina and the like, not only the prepared catalyst has high catalytic activity, but also has the best water resistance and crushing resistance, small pressure drop and longest service life, and can well achieve the aim of the invention.

Further, the carrier is spherical with the diameter of 3-8 mm.

Further, the active component copper element precursor is copper sulfate, copper nitrate or copper chloride, and is preferably copper nitrate.

Further, the precursor of the auxiliary element is nitrate, sulfate, chloride, fluoride or carbonate, preferably chloride.

Furthermore, the total content of the active component copper element is 1-2% of the mass of the carrier, and the total content of the auxiliary agent element is 0.5-1.0% of the mass of the carrier.

The molar ratio of the auxiliary elements is Fe, Cs, La, Zr, Zn and Ca (0.5-3.0): (0-3.0): (0-2.0): (0-2.0): (0-2.0): (0-1.0).

Furthermore, the molar ratio of the auxiliary elements is preferably (0.9-1.1): (0.9-1.1): (0.9-1.1): (0.3-0.5): (0.3-0.5): (0.1-0.3).

A preparation method of a catalyst for reduction and conversion of dilute nitric acid is characterized by comprising the following steps: the active components and the auxiliary agents are loaded on the carrier by adopting an impregnation method, and then the carrier is dried and roasted to obtain the product, wherein the impregnation method is equivalent impregnation loading or excessive impregnation loading, and the impregnation method is one-time impregnation or step-by-step impregnation.

The application of the catalyst for reducing and converting the dilute nitric acid is characterized by being used for reducing and converting the nitric acid and recovering nitrogen elements in wastewater generated in the coal-based ethylene glycol project oxidation esterification stage.

The preparation method comprises the following specific steps:

(a) dissolving precursors of the active component and the auxiliary agent, such as nitrate, chlorate, fluoride, sulfate or carbonate, in a proper amount of water to prepare pure substance water solution or mixed water solution of the active component and various auxiliary agent precursors;

(b) soaking the spherical SBA-15 molecular sieve or the water-resistant silica gel in the active component and auxiliary agent precursor solution prepared in the step (a), and then drying;

if a one-time dipping method is adopted, the dipping solution is a mixed aqueous solution of active components and various auxiliaries, and the product is obtained by drying after one-time dipping; if the method is a distributed impregnation method, the impregnation liquid is a pure substance aqueous solution of the active components and various auxiliaries, firstly, a certain pure substance aqueous solution of the active components or the auxiliaries is impregnated, dried and dried, then, a second pure substance aqueous solution is continuously impregnated and dried, and the impregnation and the drying are sequentially carried out by the method until the impregnation loading of all the active components and the auxiliaries is completed;

(c) the loading amounts of the active components and the auxiliary agents are controlled by controlling the concentrations of the active components and the auxiliary agent precursor solution and the using amount of the impregnation liquid, and an equivalent impregnation method and a one-step impregnation method are preferred to ensure that the loading amounts of the active components and the auxiliary agents are easy to control;

and slowly heating the impregnated and dried catalyst from room temperature to the roasting temperature for roasting, and obtaining a finished catalyst product after roasting.

Compared with the prior art, the invention has the following advantages:

1. the invention selects SBA-15 molecular sieve or water-resistant silica gel as a carrier, wherein the SBA-15 has a two-dimensional hexagonal through hole structure and a P3mm space group. In the XRD diffraction pattern, the main peak is near about 1 degree, and is a (10) crystal plane peak. The second intense peak is (11) and (20) in this order. The other peaks are weak and not easily observed. In addition, silica on the SBA-15 skeleton is generally amorphous, and no significant diffraction peak is observed in wide-angle XRD diffraction. The mesoporous molecular sieve SBA-15 has large specific surface, uniform pore diameter distribution, adjustable pore diameter, wall thickness and high hydrothermal stability. The water-resistant silica gel is white or gray microporous spherical particles, has a high microporous structure of common industrial silica gel, is insoluble in water and inorganic acid, is soluble in hydrofluoric acid and concentrated caustic alkali solution, and has high mechanical strength. The product is heterogeneous formed silica gel which is prepared by further processing general silica gel serving as a raw material, has good adsorption performance and water resistance, and does not crack in water. The material is used as a carrier, so that the water resistance and the crushing resistance of the catalyst are greatly improved, the pressure drop is small, and the service life is long.

2. According to the invention, CuO is used as an active component, and can catalyze the main reaction, so that the reaction rate of reducing nitric acid into methyl nitrite is increased, and the conversion rate of nitric acid is improved.

3. The invention adopts one or more of Fe, Cs, La, Zr, Zn and Ca as an auxiliary agent, especially the combination of Fe, Cs, La, Zr, Zn and Ca which are matched according to a special proportion, and the combination has the following two effects: on one hand, the interaction between the auxiliary agent element and the active component improves the dispersion degree, stability and catalytic activity of the active component; on the other hand, the addition of these auxiliaries can increase the solubility of nitric oxide gas in the reaction solution, thereby increasing the nitric acid conversion rate.

4. The catalyst can be used for reducing and converting dilute nitric acid and recovering nitrogen elements, and reduces the dilute nitric acid in the solution into Methyl Nitrite (MN) by taking nitric oxide gas as a reducing agent. When the concentration of the dilute nitric acid in the solution is 1-10%, the concentration of the nitric acid in the converted solution is not higher than 0.1%, and the conversion rate of the nitric acid is more than 95%.

Drawings

FIG. 1 is a diagram of an apparatus for evaluating a catalyst for reductive conversion of dilute nitric acid according to the present invention.

In the figure, 1 is a raw material liquid containing dilute nitric acid; 2 is reaction liquid, 3 is raw material gas containing nitric oxide, 4 is methyl nitrite-rich tail gas, 5 is cooling upper water, and 6 is cooling return water; 1A is a raw material liquid pump, 2A is a fixed bed reactor, and 3A is a condenser.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.