A method for polymerizing phenol using a nickel-based catalyst

Abstract

The present invention provides a method for polymerizing phenol using a nickel-based catalyst, and belongs to the technical field of wastewater treatment. The method is as follows: a nickel-based catalyst dispersion, a potassium persulfate solution, and a phenol aqueous solution are adjusted to the same pH, respectively, and then mixed to react. After the reaction is completed, the system is separated to obtain a solid phase, and the solid phase is dissolved using an acid solution, and the undissolved solid is a phenol polymer; the pH of the system is kept constant during the reaction. The method disclosed by the present invention has a high phenol removal rate and a low oxidant consumption, and can be directly used for the treatment of alkaline phenol-containing wastewater; active free radicals are not used as the main oxidation method, so the possibility of secondary pollution can be reduced. The nickel-based catalyst of the present invention can be recycled, and can still maintain a high removal rate after multiple uses, and has very high economic benefits.

Description

Technical Field

[0001] The invention relates to the field of wastewater treatment, and in particular to a method for polymerizing phenol using a nickel-based catalyst. Background Art

[0002] As a precursor of many chemical materials and compounds, phenol is widely used in oil refining, wood preservation, resin and plastic production, petrochemical and pharmaceutical industries. In the above industrial production processes, phenolic wastewater of different quantities and properties can be generated. Phenolic wastewater is a common type of toxic and difficult to degrade organic polluted wastewater. Its main pollutant, phenol, is volatile, difficult to degrade, and has teratogenic, carcinogenic and mutagenic properties. Phenolic wastewater with a concentration of only 100ppm entering the field can cause crops to die or reduce production. Low-dose intake of phenolic substances by the human body will lead to anemia; inhalation of high-concentration phenolic substances can lead to acute poisoning shock and other phenomena. Therefore, there is an urgent need to effectively treat phenolic wastewater.

[0003] At present, the treatment methods for phenol-containing wastewater are mainly physical, biological and chemical. The physical method mainly separates phenol and water according to the different relative volatility, molecular structure and similar dissolution principle by means of steam stripping, physical adsorption and solvent extraction. It generally has the problems of high energy consumption, high material cost and secondary pollution of organic solvents. The biological method is to add microorganisms that can decompose phenolic substances into phenol-containing wastewater to remove phenol through the decomposition of microorganisms. The biological method has the advantages of no secondary pollution and low treatment cost, but the microbial wastewater treatment cycle is long and has high requirements for the environmental conditions of wastewater. It must be able to meet the survival requirements of microorganisms, so it is difficult to be widely used. The chemical method is a method of removing phenol by chemical reaction between phenol and other chemical substances. There are mainly incineration, precipitation and oxidation. The combustion process of phenolic substances is prone to produce toxic and harmful gases. The precipitation method usually leads to a large amount of chemical flocculation sludge, while the oxidation method has the advantages of fast decomposition speed and strong wastewater purification ability. It is a method with broad prospects for treating difficult-to-degrade phenol-containing wastewater. Common oxidants include permanganate, ozone, Fenton's reagent, persulfate, etc. The oxidation process mainly relies on the production of active free radicals with higher redox potential to attack phenol molecules, thereby causing the ring opening and bond breaking of phenol, and finally generating carbon dioxide and water which are removed.

[0004] However, the current methods for treating phenol-containing wastewater by chemical oxidation based on active free radicals still have obvious shortcomings. (1) The existing technology mainly focuses on treating phenol-containing wastewater under acidic conditions. The oxidizing ability of active free radicals will decrease rapidly with the increase of pH value. The phenol treatment efficiency under alkaline conditions is significantly lower than that under acidic conditions, which limits the application of this technology in the field of alkaline phenol-containing wastewater. (2) The existing technology generally removes phenol in the wastewater by completely decomposing it to generate carbon dioxide and water. Determined by the chemical reaction stoichiometry, it is very expensive. Taking potassium persulfate (K2S2O8) as an oxidant as an example, 14 mol (3784.5 g) of potassium persulfate is consumed for every 1 mol (94 g) of phenol treated. (3) Studies have shown that after phenol is attacked by hydroxyl radicals, it will form dicarbonyl intermediates that are more toxic than phenol, thereby causing secondary pollution.

[0005] In view of this, there is an urgent need for a phenol-containing wastewater treatment method that can directly treat alkaline phenol-containing wastewater, has low oxidant consumption, and does not use active free radicals as the main oxidation method to solve the above-mentioned shortcomings. Summary of the invention

[0006] The object of the present invention is to provide a method for polymerizing phenol using a nickel-based catalyst, so as to solve the problem that the prior art cannot directly treat phenol-containing wastewater and has high oxidant consumption, resulting in secondary pollution.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for polymerizing phenol using a nickel-based catalyst, and the method is as follows:

[0009] The nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are adjusted to the same pH respectively, and then mixed to react, and after the reaction is completed, the system is separated to obtain a solid phase, and the solid phase is dissolved with an acid solution, and the undissolved solid is a phenol polymer;

[0010] The pH of the system was kept constant during the reaction.

[0011] Preferably, the pH is adjusted to the same range of 8 to 12; the pH adjusting agent is sulfuric acid or potassium hydroxide, and the concentration is 0.1 to 2 mol / L.

[0012] Preferably, in the mixed system, the concentration of the nickel-based catalyst is 0.5-1.5 g / L, the concentration of potassium persulfate is 0.2-5 mmol / L, and the concentration of phenol is 50-200 mg / L.

[0013] Preferably, the reaction is carried out under stirring at a rate of 100 to 150 r / min for 0.5 to 3 h.

[0014] Preferably, the preparation of the nickel-based catalyst dispersion comprises the following steps: adding ammonia water to the nickel salt solution to adjust the pH, adding alkaline solution for precipitation, and then performing solid-liquid separation, and the obtained solid is the nickel-based catalyst;

[0015] The obtained nickel-based catalyst is dispersed in water to obtain a nickel-based catalyst dispersion.

[0016] Preferably, the nickel salt solution is a nickel nitrate solution or a nickel chloride solution, with a concentration of 1 to 5 mol / L;

[0017] The mass concentration of the ammonia water is 15-30%, and the pH is adjusted to 8-12.

[0018] Preferably, the alkali solution is sodium hydroxide or potassium hydroxide solution with a concentration of 0.5 to 1 mol / L;

[0019] In the system after adding the alkali solution, the molar content ratio of nickel ions to hydroxide ions is 0.3-6.0:1.

[0020] Preferably, the adding of the alkali solution is carried out under heating and stirring conditions, the heating temperature is 25 to 95° C., the stirring rate is 100 to 300 r / min, and the time is 1 to 2 h.

[0021] The present invention has at least the following beneficial effects:

[0022] The method disclosed by the invention has a high phenol removal rate and low oxidant consumption, and can be directly used for the treatment of alkaline phenol-containing wastewater; it does not use active free radicals as the main oxidation method, so the possibility of secondary pollution can be reduced. In addition, the nickel-based catalyst of the invention can be recycled and can still maintain a high removal rate after multiple uses, and has very high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a molecular weight detection diagram of the product after the reaction of Example 2;

[0024] Figure 2 The phenol removal effect diagram of Examples 1 to 5 at different potassium persulfide concentrations;

[0025] Figure 3 The phenol removal effect diagram at different pH values ​​of Examples 1, 6 to 9 is shown;

[0026] Figure 4 The phenol removal effect diagram of the repeated experiments of Example 1 and Examples 10 to 14 is shown, and the serial numbers 1 to 6 in the figure correspond to Example 1 and Examples 10 to 14 respectively;

[0027] Figure 5 The phenol removal effect diagram of Example 1 and Test Examples 1-2 is shown. DETAILED DESCRIPTION

[0028] The present invention provides a method for polymerizing phenol using a nickel-based catalyst, and the method is as follows:

[0029] The nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are adjusted to the same pH respectively, and then mixed to react, and after the reaction is completed, the system is separated to obtain a solid phase, and the solid phase is dissolved with an acid solution, and the undissolved solid is a phenol polymer;

[0030] The pH of the system was kept constant during the reaction.

[0031] In the present invention, after the separated solid phase is dispersed in water, it can be directly used for the polymerization of phenol in the phenol aqueous solution without further treatment.

[0032] In the present invention, the range for adjusting to the same pH is preferably 8 to 12, more preferably 9 to 11, and more preferably 9; the pH adjusting agent is preferably sulfuric acid or potassium hydroxide, and the concentration is preferably 0.1 to 2 mol / L, more preferably 0.5 to 1.5 mol / L, and more preferably 0.8 to 1.2 mol / L.

[0033] In the present invention, the concentration of the nickel-based catalyst in the mixed system is preferably 0.5 to 1.5 g / L, more preferably 0.8 to 1.2 g / L, and more preferably 1 g / L; the concentration of potassium persulfate is preferably 0.2 to 5 mmol / L, more preferably 0.5 to 4 mmol / L, and more preferably 1 to 3 mmol / L; the concentration of phenol is preferably 50 to 200 mg / L, more preferably 80 to 180 mg / L, and more preferably 50 to 150 mg / L;

[0034] The acid solution is preferably a hydrochloric acid solution with a concentration of 10 to 37%.

[0035] In the present invention, the reaction is preferably carried out under stirring conditions, and the stirring rate is preferably 100-150 r / min, more preferably 110-140 r / min, more preferably 120-130 r / min; the time is preferably 0.5-3 h, more preferably 1-2.5 h, more preferably 1.5-2 h.

[0036] In the present invention, the preparation of the nickel-based catalyst dispersion comprises the following steps: adding ammonia water to the nickel salt solution to adjust the pH, adding alkali solution for precipitation, and then performing solid-liquid separation, and the obtained solid is the nickel-based catalyst;

[0037] The obtained nickel-based catalyst is dispersed in water to obtain a nickel-based catalyst dispersion.

[0038] In the present invention, the nickel salt solution is preferably a nickel nitrate solution or a nickel chloride solution, and the concentration is preferably 1 to 5 mol / L, more preferably 2 to 4 mol / L, and more preferably 3 mol / L;

[0039] The mass concentration of the ammonia water is preferably 15-30%, more preferably 15-25%, and more preferably 20%; the pH is preferably adjusted to 8-12, more preferably 9-11, and more preferably 10.

[0040] In the present invention, the alkali solution is preferably a sodium hydroxide solution or a potassium hydroxide solution, and the concentration is preferably 0.5 to 1 mol / L, more preferably 0.6 to 0.9 mol / L, and more preferably 0.7 to 0.8 mol / L;

[0041] In the system after adding the alkali solution, the molar ratio of nickel ions to hydroxide ions is preferably 0.3 to 6.0:1, more preferably 0.5 to 5:1, and even more preferably 1 to 3:1.

[0042] In the present invention, the addition of alkali solution is preferably carried out under heating and stirring conditions, the heating temperature is preferably 25-95°C, more preferably 40-80°C, more preferably 50-70°C; the stirring rate is preferably 100-300r / min, more preferably 150-250r / min, more preferably 180-220r / min; the time is preferably 1-2h, more preferably 1.2-1.8h, more preferably 1.5h.

[0043] In the present invention, the solid-liquid separation step includes centrifugation and washing, and the centrifugal speed is preferably 6000-12000 r / min, more preferably 7000-11000 r / min, and more preferably 8000-10000 r / min; the washing standard is that the pH of the water after washing is preferably 6.5-7.5, and more preferably 7.

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] 1) Add 25% ammonia to 50 mL of 1 mol / L Ni(NO3)2 solution, adjust to pH=8.0, add 125 mL of 1 mol / L NaOH solution, stir magnetically at 25°C and 150 r / min for 1 h. Centrifuge at 12000 r / min to separate solid precipitate, wash with water to pH=7.25, obtain nickel-based catalyst, and disperse it in water.

[0047] 2) A 3 g / L nickel-based catalyst dispersion was prepared, and the pH was adjusted to 9 using a pH adjusting reagent (potassium hydroxide reagent, concentration of 1 mol / L), which was recorded as dispersion a; a potassium persulfate solution with a concentration of 6 mmol / L was adjusted to pH 9 using a potassium hydroxide reagent (1 mol / L), which was recorded as solution b; a phenol aqueous solution with a phenol concentration of 300 mg / L was adjusted to pH 9 using a potassium hydroxide reagent (1 mol / L), which was recorded as solution c.

[0048] 3) The dispersion a, solution b and solution c obtained in step 2) are mixed in a volume ratio of 1:1:1 (the concentration of potassium persulfate in the system after mixing is 2 mmol / L), and the mixture is reacted for 2.5 hours at room temperature and 150 r / min. During the reaction, a pH regulator is used to control the pH of the system to 9 (as the reaction proceeds, the system gradually becomes acidic and the pH decreases. The pH regulator will automatically add the same pH adjusting reagent as in step 2) to make the pH 9); then, the solid and liquid are separated, and after quantitative analysis of the liquid phase, a phenol removal rate is calculated to be 93.8%.

[0049] Example 2

[0050] The other steps are the same as those in Example 1, except that the concentration of the potassium persulfate solution in step 2) is 15 mmol / L (the concentration of potassium persulfate in the system after mixing is 5 mmol / L). After the experiment, the solid phase after solid-liquid separation is dissolved with 30% hydrochloric acid, and the insoluble matter is dissolved with methanol, and the molecular weight of the dissolved product is tested.

[0051] After quantitative analysis of the liquid phase, the phenol removal rate was calculated to be 99.7%; Figure 1 This is the molecular weight detection diagram of the product after the reaction. It can be seen from the figure that the m / z values ​​between two adjacent peaks are both 92, which is consistent with the m / z value of a phenoxy unit, indicating that there are multiple phenoxy polymerization units in the compound, thereby indicating that polyphenol is generated.

[0052] Example 3

[0053] The other steps are the same as those in Example 1, except that the concentration of the potassium persulfate solution in step 2) is 3 mmol / L (the concentration of potassium persulfate in the system after mixing is 1 mmol / L). After quantitative analysis, the phenol removal rate was calculated to be 63.3%.

[0054] Example 4

[0055] The other steps are the same as those in Example 1, except that the concentration of the potassium persulfate solution in step 2) is 0.6 mmol / L (the concentration of potassium persulfate in the system after mixing is 0.2 mmol / L). After quantitative analysis, the phenol removal rate was calculated to be 25.6%.

[0056] Example 5

[0057] The other steps are the same as those in Example 1, except that the concentration of the potassium persulfate solution in step 2) is 1.5 mmol / L (the concentration of potassium persulfate in the system after mixing is 0.5 mmol / L). After quantitative analysis, the phenol removal rate was calculated to be 40.9%.

[0058] Figure 2 The phenol removal effect diagram under different potassium persulfate concentrations of Examples 1 to 5 shows that: as the potassium persulfate concentration increases, the reaction rate and final removal rate of phenol removal gradually increase; at low potassium persulfate concentrations, due to insufficient potassium persulfate, a relatively high amount of phenol remains after it is consumed; at high potassium persulfate concentrations, phenol can be removed rapidly and in large quantities.

[0059] Example 6

[0060] The other steps are the same as those in Example 1, except that in step 2), the pH of the nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are all adjusted to 10, and in step 3), a pH regulator is used to control the system pH to 10. After quantitative analysis, the phenol removal rate is calculated to be 85.9%.

[0061] Example 7

[0062] The other steps are the same as those in Example 1, except that in step 2), the pH of the nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are all adjusted to 8, and in step 3), a pH regulator is used to control the system pH to 8. After quantitative analysis, the phenol removal rate is calculated to be 80.7%.

[0063] Example 8

[0064] The other steps are the same as those in Example 1, except that in step 2), the pH of the nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are all adjusted to 11, and in step 3), a pH regulator is used to control the system pH to 11. After quantitative analysis, the phenol removal rate is calculated to be 70.1%.

[0065] Example 9

[0066] The other steps are the same as those in Example 1, except that in step 2), the pH of the nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are all adjusted to 12, and in step 3), a pH regulator is used to control the system pH to 12. After quantitative analysis, the phenol removal rate is calculated to be 41.9%.

[0067] Figure 3 The phenol removal effect diagram of Examples 1, 6 to 9 at different pH values ​​is shown in the figure. It can be seen from the figure that pH has a significant effect on the reaction process. The reaction rate and phenol removal rate are different under different pH conditions, and pH = 9 is the optimal pH condition for the reaction system.

[0068] Example 10

[0069] Following the protocol of Example 1, the first repetition was performed.

[0070] First repetition: The other steps are the same as those in Example 1, except that the dispersion a1 is: the solid phase separated in Example 1 is washed three times with water and then dispersed in water to prepare a dispersion a1 having a nickel-based catalyst content of 3 g / L.

[0071] After quantitative analysis, the phenol removal rate was 93.6%.

[0072] Embodiment 11

[0073] After the first repetition according to the protocol of Example 10, the second repetition was performed.

[0074] Second repetition: The other steps are the same as those in Example 1, except that dispersion a2 is prepared by washing the solid phase separated in Example 10 three times with water and then dispersing it in water to obtain dispersion a2 having a nickel-based catalyst content of 3 g / L.

[0075] After quantitative analysis, the phenol removal rate was 93.3%.

[0076] Example 12

[0077] After the second repetition according to the protocol of Example 11, the third repetition was performed.

[0078] The third repetition: the other steps are the same as those in Example 1, except that the dispersion a3 is prepared by washing the solid phase separated in Example 11 three times with water and then dispersing it in water to obtain a dispersion a3 having a nickel-based catalyst content of 3 g / L.

[0079] After quantitative analysis, the phenol removal rate was 93.1%.

[0080] Embodiment 13

[0081] After the third repetition according to the protocol of Example 12, the fourth repetition was performed.

[0082] Fourth repetition: The other steps are the same as those in Example 1, except that dispersion a4 is prepared by washing the solid phase separated in Example 12 three times with water and then dispersing it in water to obtain dispersion a4 having a nickel-based catalyst content of 3 g / L.

[0083] After quantitative analysis, the phenol removal rate was 92.6%.

[0084] Embodiment 14

[0085] After the fourth repetition according to the scheme of Example 13, the fifth repetition was performed.

[0086] Fifth repetition: The other steps are the same as those in Example 1, except that dispersion a5 is prepared by washing the solid phase separated in Example 13 three times with water and then dispersing it in water to obtain dispersion a5 having a nickel-based catalyst content of 3 g / L.

[0087] After quantitative analysis, the phenol removal rate was 92.2%.

[0088] Figure 4 The phenol removal effect diagram of the repeated experiments of Example 1 and Examples 10 to 14 is shown. In the figure, serial numbers 1 to 6 correspond to Example 1 and Examples 10 to 14 respectively. It can be seen from the figure that after recycling, the phenol removal rate of Example 14 is only 1.6% lower than that of Example 1, which proves that the nickel-based catalyst of the present invention has good repeatability and high economic benefits.

[0089] Test Example 1

[0090] 1) The other steps are the same as those in Example 1, except that 0.2 g / mL of the nickel-based catalyst aqueous dispersion is diluted to 3 g / L using 3 mol / L tert-butanol, and is used to replace the dispersion a in step 2) of Example 1.

[0091] After quantitative analysis, the phenol removal rate was calculated to be 86.1%.

[0092] Test Example 2

[0093] 1) The other steps are the same as those in Example 1, except that 0.2 g / mL of the nickel-based catalyst aqueous dispersion is diluted to 3 g / L using 3 mol / L methanol, and is used to replace the dispersion a in step 2) of Example 1.

[0094] After quantitative analysis, the phenol removal rate was calculated to be 80.3%.

[0095] Figure 5The phenol removal effect diagram of Example 1 and Test Examples 1 to 2 shows that: because tert-butyl alcohol is a strong binder of sulfate radicals and methanol is a strong binder of hydroxyl radicals and sulfate radicals, the addition of the two substances only slightly affects the removal rate of phenol (<15%), indicating that the common hydroxyl radical and sulfate radical oxidation in the potassium persulfate oxidation system are not the main mechanisms of the reaction process of the present invention.

[0096] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0097] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for polymerizing phenol using a nickel-based catalyst, characterized in that: The method is as follows: The nickel-based catalyst dispersion, potassium persulfate solution and phenol aqueous solution are adjusted to the same pH respectively, and then mixed to react. After the reaction is completed, the system is separated to obtain a solid phase, and the solid phase is dissolved with an acid solution, and the undissolved solid is a phenol polymer; the pH range of the same pH is adjusted to 8-12; the pH adjusting agent is sulfuric acid or potassium hydroxide, and the concentration is 0.1-2 mol / L; During the reaction, the pH of the system is kept constant; After mixing, the concentration of the nickel-based catalyst in the system is 0.5-1.5 g / L, the concentration of potassium persulfate is 0.2-5 mmol / L, and the concentration of phenol is 50-200 mg / L; The preparation of the nickel-based catalyst dispersion comprises the following steps: adding ammonia water to the nickel salt solution to adjust the pH, adding alkaline solution for precipitation, and then performing solid-liquid separation, and the obtained solid is the nickel-based catalyst; dispersing the obtained nickel-based catalyst into water to obtain a nickel-based catalyst dispersion; In the system after adding the alkali solution, the molar ratio of nickel ion to hydroxide ion is 0.3~6.0:1; The nickel salt solution is a nickel nitrate solution or a nickel chloride solution with a concentration of 1-5 mol / L; The mass concentration of the ammonia water is 15-30%, and the pH is adjusted to 8-12; The alkali solution is sodium hydroxide or potassium hydroxide solution with a concentration of 0.5-1 mol / L.

2. The method for polymerizing phenol using a nickel-based catalyst according to claim 1, wherein: The reaction is carried out under stirring conditions at a stirring rate of 100-150 r / min for a time of 0.5-3 h.

3. The method for polymerizing phenol using a nickel-based catalyst according to claim 1, characterized in that: The adding of the alkali solution is carried out under the conditions of heating and stirring, the heating temperature is 25-95° C., the stirring rate is 100-300 r / min, and the time is 1-2 h.

Images