A method for isomerization of methylphenol compounds

Abstract

This invention belongs to the field of chemical product synthesis technology and discloses a method for isomerization of methylphenolic compounds. Under certain reaction temperature and pressure conditions, methylphenolic compounds are vaporized and mixed with a carrier gas. The mixture passes through a fixed-bed reactor containing a bilayer modified ZSM-5 catalyst at a certain space velocity, where it undergoes an isomerization reaction to generate its isomer products. The ZSM-5 catalyst contains Si, Al, Fe, and Ge elements. This invention, by introducing metal heteroatom components into the ZSM-5 molecular sieve framework, effectively improves the pore structure and active sites of the molecular sieve, enhances the catalyst's resistance to carbon deposition, strengthens its activity and stability, and significantly extends its lifespan. Furthermore, it exhibits excellent catalytic effects on the isomerization of various methylphenolic compounds.

Description

Technical Field

[0001] This invention belongs to the field of chemical product synthesis technology, specifically relating to a method for isomerization of methylphenol compounds. Background Technology

[0002] Methylphenols are important chemical raw materials, including o-cresol, p-cresol, m-cresol, and various xylenols, widely used in pharmaceuticals, pesticides, dyes, fragrances, coatings, rubber, and plastics. In addition, cresols can also be used as solvents, preservatives, and disinfectants. Besides their wide range of applications, these compounds also have high added value.

[0003] Currently, the main route to obtain methylphenolic compounds is natural separation, i.e., separation from coal tar. However, due to limited resources, complex processes, and low product quality, natural separation equipment is being phased out. Chemical synthesis methods have emerged in recent years, with the main methods including phenol or cresol alkylation, chlorotoluene hydrolysis, and cresol isomerization.

[0004] However, existing catalysts used for the isomerization of methylphenols generally exhibit low activity, poor selectivity, and are prone to deactivation during the isomerization reaction. To suit fixed-bed reactors, catalysts with better activity and stability are needed. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for isomerization of methylphenolic compounds, the technical solution of which is as follows:

[0006] A method for isomerization of methylphenolic compounds involves the following steps: under specific reaction temperature and pressure conditions, the methylphenolic compound is vaporized and mixed with a carrier gas. When the mixture passes through a fixed-bed reactor containing a bilayer modified ZSM-5 catalyst at a specific space velocity, an isomerization reaction occurs, generating its isomer products. The ZSM-5 catalyst contains Si, Al, Fe, and Ge elements.

[0007] The methylphenolic compounds include one or more of o-cresol, p-cresol, m-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, and 3,5-dimethylphenol.

[0008] The reaction temperature is 270℃~400℃.

[0009] The reaction pressure is 0.1–2 MPa.

[0010] The space velocity is the feed space velocity of methylphenol compounds, and its range is 0.5 to 3 h. -1 .

[0011] The carrier gas is nitrogen or hydrogen, and the molar ratio of the carrier gas to the methylphenol compound is 0.5 to 5.

[0012] The bilayer modified ZSM-5 catalyst is a shaped iron-germanium bimetallic modified ZSM-5 molecular sieve catalyst. The elemental molar ratio of the catalyst packed in the upper layer of the reactor is Si:Al:Fe:Ge=50-100:1:0.5:0.5, and the elemental molar ratio of the catalyst packed in the lower layer of the reactor is Si:Al:Fe:Ge=20-50:1:0.5:0.5. The mass ratio of the two catalysts is 2:1 to 1:2.

[0013] The molding method includes: mixing modified ZSM-5 molecular sieve powder and binder in a certain proportion, extruding or pressing into sheets, and then drying and calcining to obtain the molded catalyst.

[0014] The binder is silica sol or boehmite, and the mass ratio of the binder to the molecular sieve powder is 5-30:100.

[0015] The drying temperature is 100-200℃, the drying time is 8-24h, the calcination temperature is 400-600℃, and the calcination time is 4-24h.

[0016] The advantages of this invention compared to the prior art are:

[0017] This invention, by introducing metal heteroatom components into the ZSM-5 molecular sieve framework, effectively improves the pore structure and active sites of the molecular sieve, enhances the catalyst's resistance to carbon deposition, and strengthens its activity and stability, significantly extending its lifetime. Furthermore, since the metal atoms introduced into the molecular sieve possess moderate hydrogenation properties, excessive hydrogenation of phenols is avoided during the hydroisomerization of cresols, while further inhibiting catalyst carbon deposition, thus further extending the catalyst's lifetime. In catalytic isomerization reactions, since catalysts with different silicon-to-aluminum ratios exhibit varying activities, combining catalysts with different silicon-to-aluminum ratios in the reactor can result in a more uniform reaction distribution, which is beneficial for improving reaction selectivity. Simultaneously, it demonstrates excellent catalytic effects on the isomerization of various methylphenolic compounds. Detailed Implementation

[0018] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0019] Example 1

[0020] The preparation method of iron-germanium modified ZSM-5 molecular sieve raw powder is as follows:

[0021] (1) Weigh 100g of silica sol (SiO2≥30wt%) and mix it with 100g of deionized water. Then, add 203g of 25% tetrapropylammonium hydroxide (TPAOH) solution while stirring. Continue stirring until the solution is clear to obtain solution A.

[0022] (2) Dissolve 5.7g of aluminum sulfate in 100g of deionized water and stir well to obtain solution B;

[0023] (3) Solution B is slowly added dropwise to solution A with stirring to obtain the initial gel C;

[0024] (4) Weigh 1.4g Na2GeO3 and dissolve it in 20g deionized water. Stir well to obtain solution D. Then slowly add solution D into the initial gel C while stirring to obtain gel E.

[0025] (5) Weigh 3.4g Fe(NO3)3·9H2O and dissolve it in 5g deionized water. After stirring evenly, solution F is obtained. Solution F is then slowly added dropwise into gel E under stirring to obtain a mixed gel. The pH of the gel solution is adjusted to 10 with 1mol / L sodium hydroxide and aged at 30℃ for 24h. The molar ratio of Si:Al:Fe:Ge:template in the obtained gel is 30:1:0.5:0.5:15.

[0026] (6) The above mixed gel was placed in a crystallization vessel and subjected to hydrothermal crystallization at 180°C and autogenous pressure for 24 hours to obtain Fe / Ge isomorphically substituted ZSM-5 molecular sieve;

[0027] (7) The obtained molecular sieve was filtered, washed, dried at 120℃ for 24h and calcined at 550℃ for 12h to remove the template agent, and then the molecular sieve raw powder was obtained.

[0028] (8) The molecular sieve raw powder was ion exchanged three times with 1 mol / L NH4NO3 solution at 70℃, and then filtered, washed, dried at 120℃ for 24 h and calcined at 550℃ for 8 h to obtain hydrogen-type Fe-Ge-ZSM-5 molecular sieve raw powder, which was denoted as CAT-30.

[0029] Using the same method, except changing Si:Al to 60:1, the resulting catalyst is denoted as CAT-60.

[0030] Example 2

[0031] Take 20g and 12g of CAT-30 and CAT-60 molecular sieve raw powder respectively, mix them evenly with 30% silica sol, extrude them into strips and air dry them naturally. Then dry them at 120℃ for 12h and calcine them at 550℃ for 6h to obtain catalysts denoted as CAT-30-1 and CAT-60-1.

[0032] Example 3

[0033] Take 20g of CAT-30 and CAT-60 molecular sieve raw powder and 5g of pseudoboehmite, mix them evenly, compress them into tablets, dry them at 120℃ for 12h, and then calcine them at 500℃ for 12h to obtain catalysts denoted as CAT-30-2 and CAT60-2.

[0034] Example 4

[0035] The catalytic performance of the catalysts in the o-cresol isomerization reaction was evaluated. 3g of catalyst CAT-30-1 was loaded into the lower layer of a fixed-bed reactor, and 2g of catalyst CAT-60-1 was loaded into the upper layer. Under nitrogen as the carrier gas, the temperature was raised to 280℃, and the o-cresol feed rate was 5g / h (space velocity 1h). -1 The reaction was carried out at a nitrogen flow rate of 30 mL / min and a reaction pressure of 0.2 MPa, and the reaction was carried out continuously at 280–380 °C for 2000 h. The products were analyzed by gas chromatography. The results showed that the average conversion rate of o-cresol was 47.1%, the average yield of m-cresol was 35.1%, the average yield of p-cresol was 11.4%, and the total selectivity of m- and p-cresol was 98.7%.

[0036] Comparative Example 1

[0037] The catalytic performance of the catalyst in the o-cresol isomerization reaction was evaluated. 5 g of catalyst CAT-60-1 was loaded into a fixed-bed reactor, and the reactor was heated to 280 °C under nitrogen as the carrier gas. The o-cresol feed rate was 5 g / h (space velocity 1 h⁻¹). -1 The reaction was carried out at a nitrogen flow rate of 30 mL / min and a reaction pressure of 0.2 MPa at 280–380 °C for 2000 h. The products were analyzed by gas chromatography. The results showed an average conversion rate of 35.9% for o-cresol, an average yield of 26.8% for m-cresol, an average yield of 8.4% for p-cresol, and a total selectivity of 98.1% for p-cresol. Using CAT-60-1 as the catalyst alone resulted in a relatively low conversion rate.

[0038] Comparative Example 2

[0039] The catalytic performance of the catalyst in the o-cresol isomerization reaction was evaluated. 5 g of catalyst CAT-30-1 was loaded into a fixed-bed reactor, and the reactor was heated to 280 °C under nitrogen as the carrier gas. The o-cresol feed rate was 5 g / h (space velocity 1 h⁻¹). -1 The reaction was carried out at a nitrogen flow rate of 30 mL / min and a reaction pressure of 0.2 MPa at 280–380 °C for 2000 h. The products were analyzed by gas chromatography. The results showed an average conversion of 45.3% for o-cresol, an average yield of 33.3% for m-cresol, an average yield of 10.4% for p-cresol, and a total selectivity of 96.4% for p-cresol. Using CAT-30-1 alone as a catalyst resulted in relatively low selectivity.

[0040] Example 5

[0041] The catalytic performance of 2,6-xylenol in the isomerization reaction was evaluated. 2.5 g of catalyst CAT-30-2 was loaded into the lower layer of a fixed-bed reactor, and 2.5 g of catalyst CAT-60-2 was loaded into the upper layer. Under hydrogen as the carrier gas, the temperature was raised to 280 °C, and the 2,6-xylenol feed rate was 8 g / h (space velocity 1.6 h⁻¹). -1 The reaction was carried out at a hydrogen flow rate of 50 mL / min and a reaction pressure of 0.4 MPa, under conditions of 280–360 °C for 2000 h. The products were analyzed by gas chromatography. The results showed that the average conversion rate of 2,6-xylenol was 56.2%, the average yield of 2,4-xylenol was 12.9%, the average yield of 2,5-xylenol was 23.7%, the average yield of 2,3-xylenol was 2.8%, the average yield of 3,4-xylenol was 7.5%, the average yield of 3,5-xylenol was 5.4%, and the total selectivity of xylenol was 92.9%.

[0042] Example 6

[0043] The catalytic performance of the catalysts in the isomerization reaction of p-cresol was evaluated. 2g of catalyst CAT-30-2 was loaded into the lower layer of a fixed-bed reactor, and 3g of catalyst CAT-60-2 was loaded into the upper layer. Under hydrogen as the carrier gas, the temperature was raised to 280℃, and the p-cresol feed rate was 5g / h (space velocity 1h). -1 The hydrogen flow rate was 30 mL / min, the reaction pressure was 0.6 MPa, and the reaction was carried out continuously at 280–340 °C for 2000 h. The products were analyzed by gas chromatography. The results showed that the average conversion rate of p-cresol was 53.3%, the average yield of o-cresol was 5.7%, the average yield of m-cresol was 46.5%, and the total selectivity of o- and m-cresol was 97.9%.

[0044] Example 7

[0045] The catalytic performance of the catalysts in the isomerization reaction of 2,4-xylenol was evaluated. 1.7 g of catalyst CAT-30-1 was loaded into the lower layer of a fixed-bed reactor, and 3.3 g of catalyst CAT-60-2 was loaded into the upper layer. Under nitrogen as the carrier gas, the temperature was raised to 280 °C, and the feed rate of 2,4-xylenol was 5 g / h (space velocity 1 h⁻¹). -1The reaction was carried out at a nitrogen flow rate of 20 mL / min and a reaction pressure of 0.4 MPa at 280–380 °C for 2000 h. The products were analyzed by gas chromatography. The results showed that the average conversion rate of 2,4-xylenol was 59.1%, the average yield of 2,6-xylenol was 3.0%, the average yield of 2,5-xylenol was 38.2%, the average yield of 2,3-xylenol was 2.1%, the average yield of 3,4-xylenol was 8.0%, the average yield of 3,5-xylenol was 5.3%, and the total selectivity of xylenol was 95.8%.

[0046] Example 8

[0047] The catalytic performance of the catalysts in the isomerization reaction of 2,3-xylenol was evaluated. 3g of catalyst CAT-30-2 was loaded into the lower layer of a fixed-bed reactor, and 2g of catalyst CAT-60-1 was loaded into the upper layer. Under hydrogen as the carrier gas, the temperature was raised to 280℃, and the 2,3-xylenol feed rate was 15g / h (space velocity 3h⁻¹). -1 The reaction was carried out at a hydrogen flow rate of 50 mL / min and a reaction pressure of 0.5 MPa, under conditions of 280–340 °C for 2000 h. The products were analyzed by gas chromatography. The results showed that the average conversion rate of 2,4-xylenol was 67.2%, the average yield of 2,6-xylenol was 3.3%, the average yield of 2,5-xylenol was 30.3%, the average yield of 2,4-xylenol was 15.7%, the average yield of 3,4-xylenol was 8.9%, the average yield of 3,5-xylenol was 6.1%, and the total selectivity of xylenol was 95.7%.

[0048] In summary, the product yield using the isomerization method for methylphenol compounds of this invention can reach over 95%, while the yield of existing methods is generally around 90%.

[0049] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for isomerization of methylphenolic compounds, characterized in that: Under certain reaction temperature and pressure conditions, methyl phenol compounds are isomerized to their isomers when they are vaporized and mixed with carrier gas, and then passed through a fixed bed reactor with double-layer combined modified ZSM-5 catalyst at a certain space velocity, the double-layer combined modified ZSM-5 catalyst is a shaped iron-germanium bimetallic modified ZSM-5 molecular sieve catalyst, wherein the element molar ratio of the catalyst loaded in the upper layer of the reactor is Si:Al:Fe:Ge=50-100:1:0.5:0.5, and the element molar ratio of the catalyst loaded in the lower layer of the reactor is Si:Al:Fe:Ge=20-50:1:0.5:0.5; the mass ratio of the loading amount of the two catalysts is 2:1-1:2; the methyl phenol compounds include one or more of o-cresol, p-cresol, m-cresol, 2,3-dimethyl phenol, 2,4-dimethyl phenol, 2,5-dimethyl phenol, 2,6-dimethyl phenol, 3,4-dimethyl phenol and 3,5-dimethyl phenol.

2. The method for isomerization of methylphenolic compounds according to claim 1, characterized in that: The reaction temperature is 270-400 DEG C.

3. The methyl phenol compound isomerization method according to claim 1, characterized in that the reaction pressure is 0.1-2 MPa.

4. The method for isomerization of methylphenolic compounds according to claim 1, characterized in that: The space velocity is the feed space velocity of the methylphenol compound, which ranges from 0.5 to 3 h -1 .

5. The method for isomerization of methylphenolic compounds according to claim 1, characterized in that: The carrier gas is nitrogen or hydrogen, and the molar ratio of the carrier gas to the methyl phenol compound is 0.5-5.

6. The method for isomerization of methylphenolic compounds according to claim 1, characterized in that: The ZSM-5 catalyst is a shaped catalyst, and the shaping method comprises: mixing modified ZSM-5 molecular sieve raw powder with a binder in a certain proportion, extruding or pressing into a tablet, and then drying and calcining.

7. The method of claim 6, wherein the methylphenol isomers are separated by a combination of distillation and crystallization. The binder is silica sol or pseudo-boehmite, and the mass ratio of the binder to the molecular sieve raw powder is 5-30:

100.

8. The method of claim 6, wherein the methylphenol isomers are separated by a combination of distillation and crystallization. The drying temperature is 100-200 DEG C, the drying time is 8-24 h, the calcination temperature is 400-600 DEG C, and the calcination time is 4-24 h.