Thymol by-product water atmosphere cracking process

Abstract

The invention relates to a thymol byproduct water atmosphere cracking process which comprises the following steps: filling a molecular sieve catalyst in the middle of a bed layer of a fixed bed reactor, aging the catalyst, raising the temperature of the bed layer to 360 DEG C, continuously pumping thymol byproduct alkylated liquid by using a first liquid pump, pumping water by using a second liquid pump, and carrying out a catalytic dealkylation reaction; carrying out primary distillation on the obtained liquid to remove non-phenol substances such as benzene and methylbenzene, feeding the liquid into a mixed phenol separation workshop, feeding m-cresol obtained by rectification separation as a raw material into an alkylation workshop for producing thymol, and carrying out water atmosphere catalytic dealkylation treatment on the residual material again; according to the process, hydrogen atmosphere is not needed, and the thymol mass production alkylation liquid is subjected to catalytic cracking under the water atmosphere condition to generate m-cresol.

Description

Technical Field

[0001] The invention relates to a hydrous atmosphere cracking process of thymol byproduct. Background Art

[0002] In the thymol production process, during the step of alkylating meta-cresol with propylene to synthesize thymol, thymol isomers and homologues are produced as by-products. After the product thymol is extracted, these mixtures can be converted back into meta-cresol through dealkylation and returned to the reaction system. A large portion of thymol isomers will still become stable by-products, reducing the yield of thymol and increasing the consumption of the raw material meta-cresol. This phenomenon cannot be ignored.

[0003] The by-product is a mixture mainly composed of 5-isopropyl-3-methylphenol, which contains a certain proportion of unreacted meta-cresol, other isopropyl meta-cresol isomers and diisopropyl meta-cresol isomers, and a small amount of phenol.

[0004] The development of thymol isomer catalytic cracking process can further reduce the consumption of raw materials and the impact on the environment in the thymol synthesis process.

[0005] Traditionally, the catalytic dealkylation of alkylphenols is generally carried out under hydrogenation conditions. However, the hydrocracking of the liquid byproduct will produce a large amount of non-phenolic or even non-benzene small molecular liquid byproducts, which is not conducive to the subsequent separation and recovery of m-cresol. The literature (Shouyi Li, Beibei Lu, Yonggang Wang, Xiongchao Lin, Haiyong Zhang, Dealkylation of alkylphenols in phenol oil on acid zeolites, Journal of Analytical and Applied Pyrolysis, Volume 179, 2024, 106470, ISSN 0165-2370, https: / / doi.org / 10.1016 / j.jaap.2024.106470.) took 4-ethylphenol, 4-isopropylphenol and 4-tert-butylphenol and their mixtures as the research objects, studied their dealkylation reactions on ZSM-5 molecular sieves, and determined an appropriate reaction condition. However, ZSM-5 molecular sieve is not stable enough when catalyzing the dealkylation of alkylphenol, and mixed raw materials with complex components will further damage the stability of the catalyst and greatly increase the process cost. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a thymol byproduct hydrochloric acid cracking process, which does not require a hydrogen atmosphere and utilizes hydrochloric acid conditions to catalytically crack thymol mass production alkylation liquid to generate meta-cresol.

[0007] In order to solve the above technical problems, the present invention provides a thymol byproduct hydrochloric acid cracking process, comprising the following steps:

[0008] (1) a molecular sieve catalyst is loaded in the middle of a bed of a fixed bed reactor, and after the catalyst is aged, the bed temperature is raised to 360° C., an alkylation liquid of thymol byproduct is continuously pumped in by a first liquid pump, and water is pumped in by a second liquid pump to perform a catalytic dealkylation reaction;

[0009] (2) the liquid obtained from the reaction of step (1) is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, and then enters a mixed phenol separation workshop, the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C, the meta-cresol obtained by rectification separation is used as a raw material to enter an alkylation workshop for thymol production, the conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C, and the remaining material is subjected to water-atmosphere catalytic dealkylation treatment again;

[0010] The molecular sieve catalyst in step (1) is a HY / HMOR mixed crystal molecular sieve catalyst, the Y-type molecular sieve has a silicon-aluminum ratio of 5 to 7, and the MOR molecular sieve has a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mixing mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0011] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0012] The feed space velocity of the thymol byproduct alkylation liquid is controlled at 0.6-0.8h -1 ;

[0013] The mass ratio of water and thymol by-product alkylation liquid feed is 4:7;

[0014] In the step (1), the catalytic dealkylation reaction is carried out, the reaction temperature is controlled at 380-420° C., the reaction pressure is controlled at 1-1.2 MPa, and nitrogen is used for purging during the reaction, with a nitrogen flow rate of 50 ml / min.

[0015] Preferably, the HY / HMOR mixed crystal molecular sieve catalyst is in the form of strips with a diameter of 1.35-2 mm, which needs to be broken into small segments of 2-3 mm when used. The catalyst is loaded from the center of the fixed bed reaction tube to both sides, and the loading height does not exceed 2 / 3 of the tube length.

[0016] The advantages of the present invention are as follows: the process does not require a hydrogen atmosphere, but uses water atmosphere conditions to catalytically crack the alkylation liquid for mass production of thymol to generate meta-cresol. The catalyst type suitable for the water cracking process is determined, and the temperature, pressure, space velocity and other conditions required for cracking are clarified. The process flow is clear, and the steps are simple and controllable. The problem of liquid byproducts piling up and causing waste of raw materials in the thymol alkylation production process is solved. In the reaction, water vapor prevents the formation of diphenyl ether in the pores by shortening the life of phenolic substances at the active sites, and also offsets the balance of the phenolic condensation reaction. Under water atmosphere conditions, water vapor can compete with the hydroxyl groups on the isopropyl meta-cresol isomer molecules for adsorption, reducing the production rate of non-phenolic small molecule products, while reducing catalyst carbon deposition and improving the stability of the catalyst. DETAILED DESCRIPTION

[0017] Embodiment 1:

[0018] The thymol byproduct hydrochloric acid cracking process comprises the following steps:

[0019] (1) a molecular sieve catalyst is loaded in the middle of a fixed bed reactor bed, and after the catalyst is aged, the bed temperature is raised to 360° C., and a first liquid pump is used to continuously pump in thymol byproduct alkylation liquid, and a second liquid pump is used to pump in water to perform a catalytic dealkylation reaction for 30 hours;

[0020] (2) the liquid obtained from the reaction of step (1) is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, and then enters a mixed phenol separation workshop, the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C, the meta-cresol obtained by rectification separation is used as a raw material to enter an alkylation workshop for thymol production, the conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C, and the remaining material is subjected to water-atmosphere catalytic dealkylation treatment again;

[0021] The average yield of m-cresol is about 35%, the conversion rate of the target reactant 5-isopropyl-3-methylphenol is >50%, and the selectivity of m-cresol among cresol isomers is >83%;

[0022] The molecular sieve catalyst in step (1) is a HY / HMOR mixed crystal molecular sieve catalyst, the Y-type molecular sieve has a silicon-aluminum ratio of 5 to 7, and the MOR molecular sieve has a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mixing mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0023] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0024] The feed space velocity of the thymol byproduct alkylation liquid is controlled at 0.7 h -1 ; The water feed air velocity is controlled at 0.4h -1 ,

[0025] In the step (1), the catalytic dealkylation reaction is carried out, the reaction temperature is controlled at 380-390° C., the reaction pressure is controlled at 1 MPa, and nitrogen is used for purging during the reaction, with a nitrogen flow rate of 50 ml / min.

[0026] The HY / HMOR mixed crystal molecular sieve catalyst is in the form of strips with a diameter of 1.35-2 mm. It needs to be broken into small segments of 2-3 mm when used. The catalyst is loaded from the center of the fixed bed reaction tube to both sides, and the loading height does not exceed 2 / 3 of the tube length.

[0027] Embodiment 2:

[0028] The thymol byproduct hydrochloric acid cracking process comprises the following steps:

[0029] (1) a molecular sieve catalyst is loaded in the middle of a fixed bed reactor bed, and after the catalyst is aged, the bed temperature is raised to 360° C., and a first liquid pump is used to continuously pump in thymol byproduct alkylation liquid, and a second liquid pump is used to pump in water to perform a catalytic dealkylation reaction for 30 hours;

[0030] (2) the liquid obtained from the reaction of step (1) is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, and then enters a mixed phenol separation workshop, the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C, the meta-cresol obtained by rectification separation is used as a raw material to enter an alkylation workshop for thymol production, the conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C, and the remaining material is subjected to water-atmosphere catalytic dealkylation treatment again;

[0031] The average yield of m-cresol is about 36%, the conversion rate of the target reactant 5-isopropyl-3-methylphenol is >45%, and the selectivity of m-cresol among cresol isomers is >85%;

[0032] The molecular sieve catalyst in step (1) is a HY / HMOR mixed crystal molecular sieve catalyst, the Y-type molecular sieve has a silicon-aluminum ratio of 5 to 7, and the MOR molecular sieve has a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mixing mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0033] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0034] The feed space velocity of the thymol byproduct alkylation liquid is controlled at 0.7 h -1 ; The water feed air velocity is controlled at 0.4h -1 ,

[0035] In the step (1), the catalytic dealkylation reaction is carried out, the reaction temperature is controlled at 380-390° C., the reaction pressure is controlled at 1.2 MPa, and nitrogen is used for purging during the reaction, with a nitrogen flow rate of 50 ml / min.

[0036] The HY / HMOR mixed crystal molecular sieve catalyst is in the form of strips with a diameter of 1.35-2 mm. It needs to be broken into small segments of 2-3 mm when used. The catalyst is loaded from the center of the fixed bed reaction tube to both sides, and the loading height does not exceed 2 / 3 of the tube length.

[0037] Embodiment three:

[0038] The thymol byproduct hydrochloric acid cracking process comprises the following steps:

[0039] (1) a molecular sieve catalyst is loaded in the middle of a fixed bed reactor bed, and after the catalyst is aged, the bed temperature is raised to 360° C., and a first liquid pump is used to continuously pump in thymol byproduct alkylation liquid, and a second liquid pump is used to pump in water to perform a catalytic dealkylation reaction for 30 hours;

[0040] (2) the liquid obtained from the reaction of step (1) is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, and then enters a mixed phenol separation workshop, the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C, the meta-cresol obtained by rectification separation is used as a raw material to enter an alkylation workshop for thymol production, the conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C, and the remaining material is subjected to water-atmosphere catalytic dealkylation treatment again;

[0041] The average yield of m-cresol is about 35%, the conversion rate of the target reactant 5-isopropyl-3-methylphenol is >45%, and the selectivity of m-cresol among cresol isomers is >80%;

[0042] The molecular sieve catalyst in step (1) is a HY / HMOR mixed crystal molecular sieve catalyst, the Y-type molecular sieve has a silicon-aluminum ratio of 5 to 7, and the MOR molecular sieve has a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mixing mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0043] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0044] The feed space velocity of the thymol byproduct alkylation liquid is controlled at 0.7 h -1 ; The water feed air velocity is controlled at 0.4h -1 ,

[0045] In the step (1), the catalytic dealkylation reaction is carried out, the reaction temperature is controlled at 380-390° C., the reaction pressure is controlled at 1.1 MPa, and nitrogen is used for purging during the reaction, with a nitrogen flow rate of 50 ml / min.

[0046] The HY / HMOR mixed crystal molecular sieve catalyst is in the form of strips with a diameter of 1.35-2 mm. It needs to be broken into small segments of 2-3 mm when used. The catalyst is loaded from the center of the fixed bed reaction tube to both sides, and the loading height does not exceed 2 / 3 of the tube length.

[0047] In the above examples, the HY / HMOR mixed crystal molecular sieve catalyst was purchased from Raodong (Liaoning) New Materials Co., Ltd. The thymol byproduct alkylation liquid was from Anhui Haihua Technology Group Co., Ltd.

Claims

1. A process for cracking thymol byproduct water vapor, characterized in that: The following steps are involved: (1) a molecular sieve catalyst is loaded in the middle of a bed of a fixed bed reactor, and after the catalyst is aged, the bed temperature is raised to 360° C., an alkylation liquid of thymol byproduct is continuously pumped in by a first liquid pump, and water is pumped in by a second liquid pump to perform a catalytic dealkylation reaction; (2) the liquid obtained from the reaction of step (1) is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, and then enters a mixed phenol separation workshop, the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C, the meta-cresol obtained by rectification separation is used as a raw material to enter an alkylation workshop for thymol production, the conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C, and the remaining material is subjected to water-atmosphere catalytic dealkylation treatment again; The molecular sieve catalyst in step (1) is a HY / HMOR mixed crystal molecular sieve catalyst, the Y-type molecular sieve has a silicon-aluminum ratio of 5 to 7, and the MOR molecular sieve has a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mixing mass ratio of 2:1 and extruded with 40% silica sol as a binder. The molecular sieve catalyst aging conditions are 400° C., 3 h; The feed space velocity of the thymol byproduct alkylation liquid is controlled at 0.6-0.8h -1 ; The mass ratio of water and thymol by-product alkylation liquid feed is 4:7; In the step (1), the catalytic dealkylation reaction is carried out, the reaction temperature is controlled at 380-420° C., the reaction pressure is controlled at 1-1.2 MPa, and nitrogen is used for purging during the reaction, with a nitrogen flow rate of 50 ml / min.

2. The thymol byproduct water vapor cracking process according to claim 1, characterized in that: The HY / HMOR mixed crystal molecular sieve catalyst is in the form of strips with a diameter of 1.35-2 mm. It needs to be broken into small segments of 2-3 mm when used. The catalyst is loaded from the center of the fixed bed reaction tube to both sides, and the loading height does not exceed 2 / 3 of the tube length.