Thymol by-product transalkylation process

Abstract

The invention relates to a thymol by-product transalkylation process, which comprises: preparing a raw material, adding a co-reactant m-cresol and a solvent cyclohexane to a thymol by-product alkylation liquid, filling a molecular sieve catalyst in the middle of the bed layer of a fixed bed reactor, aging the catalyst, increasing the temperature of the bed layer to 260 DEG C, continuously pumping the prepared raw material, and carrying out a reaction to obtain the thymol by-product alkylation liquid. Carrying out a catalytic transalkylation reaction by adopting an HZSM-5 molecular sieve catalyst; and transferring the catalytic transalkylation reaction product into a glass crystallization kettle, carrying out secondary solvent crystallization by using 30% and 45% ethanol, extracting 4-isopropyl-3-methylphenol, and returning the residual liquid-phase product to the catalytic transalkylation or water catalytic dealkylation process for further harmless and resourceful treatment. According to the process, the 4, 6-diisopropyl-3-methylphenol in the thymol byproduct alkylated liquid is utilized, and the high-value product 4-isopropyl-3-methylphenol which is relatively high in production content and can be extracted is produced.

Description

Technical Field

[0001] The invention relates to a thymol byproduct transalkylation process. Background Art

[0002] The thymol synthesis process is divided into three steps: (1) alkylation, (2) distillation, and (3) solvent crystallization. For details, see Chinese patent CN105315133B. In the thymol production process, a large amount of liquid by-products will be produced in the step of synthesizing thymol by alkylation of m-cresol and propylene. After extracting the product thymol, these by-products accumulate in the waste tank, which seriously affects the utilization efficiency of the raw material m-cresol and also causes environmental hazards. There are still a lot of technical gaps in the treatment and disposal of these liquid by-products. After testing, it was found that most of these liquid by-products are isomers or homologues of thymol, among which 4,6-diisopropyl-3-methylphenol is the most serious. To solve this problem, a molecular sieve catalyst can be used to catalyze the alkylation of this thymol homologue. The catalytic dealkylation reaction can occur on the surface of the molecular sieve catalyst at a temperature of 300 to 400°C, and 4,6-diisopropyl-3-methylphenol is cracked into m-cresol and propylene. However, this process generally requires the reaction to be carried out in a water vapor atmosphere to prevent the rapid deactivation of the catalyst. In addition, under high temperature conditions, the molecular isomerization reaction of isopropyl meta-cresol isomers is significant, which will produce more 5-isopropyl-3-methylphenol, which is more difficult to handle, reducing the overall yield of high-value products. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a thymol byproduct alkylation process, and to produce a high-value product 4-isopropyl-3-methylphenol with a high content and capable of being extracted by utilizing 4,6-diisopropyl-3-methylphenol in the thymol byproduct alkylation liquid.

[0004] In order to solve the above technical problems, the present invention provides a thymol byproduct alkyl transalkylation process, comprising the following steps:

[0005] (1) preparing raw materials: adding a coreactant m-cresol and a solvent cyclohexane to the thymol byproduct alkylation liquid, wherein the mass fraction of m-cresol is 10% of the thymol byproduct alkylation liquid, and the mass fraction of cyclohexane is 40% of the thymol byproduct alkylation liquid;

[0006] (2) loading a molecular sieve catalyst in the middle of the bed of a fixed bed reactor, raising the bed temperature to 260° C. after aging the catalyst, and continuously pumping the raw material prepared in step (1) into the fixed bed reactor using a liquid pump to perform a catalytic transalkylation reaction;

[0007] (3) The reaction product of step (2) is transferred to a glass crystallization kettle and subjected to secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol. The remaining liquid product is returned to the catalytic transalkylation or water-catalytic dealkylation process for further harmless and resourceful treatment.

[0008] The molecular sieve catalyst in step (2) is HZSM-5 molecular sieve catalyst, with a silicon-aluminum ratio of 120, and is extruded using pseudo-boehmite powder and 8% by mass of dilute nitric acid as a binder;

[0009] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0010] The catalytic transalkylation reaction in step (2) is carried out under normal pressure, wherein the feed space velocity of the thymol byproduct alkylation liquid is 0.5 to 0.6 h -1 The reaction temperature was between 260 and 320°C, and nitrogen was continuously introduced at 50 ml / min during the reaction.

[0011] Preferably, the HZSM-5 molecular sieve catalyst is in the form of strips with a diameter of 1.35 to 2 mm. It needs to be broken into small segments of 2 to 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.

[0012] Advantages of the present invention: In view of the problem of liquid byproducts piling up and causing waste of raw materials in the production process of thymol, the present invention explores a catalytic transalkylation process with the addition of a co-reactant, meta-cresol, determines the type of catalyst suitable for the process, clarifies the process conditions required for cracking, and has a clear process flow with simple and controllable steps. The process can effectively dispose of the liquid byproducts produced in the alkylation step of meta-cresol and propylene in the large-scale industrial production of thymol, and under appropriate temperature conditions, produces a high-value product 4-isopropyl-3-methylphenol with a high content and extractable content, providing certain economic value. DETAILED DESCRIPTION

[0013] Embodiment 1:

[0014] The thymol byproduct alkylation process comprises the following steps:

[0015] (1) preparing raw materials: adding a coreactant m-cresol and a solvent cyclohexane to the thymol byproduct alkylation liquid, wherein the mass fraction of m-cresol is 10% of the thymol byproduct alkylation liquid, and the mass fraction of cyclohexane is 40% of the thymol byproduct alkylation liquid;

[0016] (2) loading a molecular sieve catalyst in the middle of the bed of a fixed bed reactor, raising the bed temperature to 260° C. after aging the catalyst, and continuously pumping the raw material prepared in step (1) into the fixed bed reactor using a liquid pump to perform a catalytic transalkylation reaction for 120 hours, wherein the conversion rate of 4,6-diisopropyl-5-methylphenol exceeds 40%;

[0017] (3) The reaction product of step (2) is transferred to a glass crystallization kettle and subjected to secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol. The remaining liquid product is returned to the catalytic transalkylation or water-catalytic dealkylation process for further harmless and resourceful treatment.

[0018] The molecular sieve catalyst in step (2) is HZSM-5 molecular sieve catalyst, with a silicon-aluminum ratio of 120, and is extruded using pseudo-boehmite powder and 8% by mass of dilute nitric acid as a binder;

[0019] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0020] The catalytic transalkylation reaction in step (2) is carried out under normal pressure, wherein the feed space velocity of the thymol byproduct alkylation liquid is 0.6h -1 The reaction temperature was between 265 and 290°C, and nitrogen was continuously introduced at 50 ml / min during the reaction.

[0021] The HZSM-5 molecular sieve catalyst is in the form of strips with a diameter of 1.35 to 2 mm. It needs to be broken into small segments of 2 to 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.

[0022] Embodiment 2:

[0023] The thymol byproduct alkylation process comprises the following steps:

[0024] (1) preparing raw materials: adding a coreactant m-cresol and a solvent cyclohexane to the thymol byproduct alkylation liquid, wherein the mass fraction of m-cresol is 10% of the thymol byproduct alkylation liquid, and the mass fraction of cyclohexane is 40% of the thymol byproduct alkylation liquid;

[0025] (2) loading a molecular sieve catalyst in the middle of the bed of a fixed bed reactor, raising the bed temperature to 260° C. after aging the catalyst, and continuously pumping the raw material prepared in step (1) into the reactor using a liquid pump to perform a catalytic transalkylation reaction for 120 h, wherein the conversion rate of 4,6-diisopropyl-5-methylphenol exceeds 60%;

[0026] (3) The reaction product of step (2) is transferred to a glass crystallization kettle and subjected to secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol. The remaining liquid product is returned to the catalytic transalkylation or water-catalytic dealkylation process for further harmless and resourceful treatment.

[0027] The molecular sieve catalyst in step (2) is HZSM-5 molecular sieve catalyst, with a silicon-aluminum ratio of 120, and is extruded using pseudo-boehmite powder and 8% by mass of dilute nitric acid as a binder;

[0028] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0029] The catalytic transalkylation reaction in step (2) is carried out under normal pressure, wherein the feed space velocity of the thymol byproduct alkylation liquid is 0.5h -1 The reaction temperature was between 260 and 300°C, and nitrogen was continuously introduced at 50 ml / min during the reaction.

[0030] The HZSM-5 molecular sieve catalyst is in the form of strips with a diameter of 1.35 to 2 mm. It needs to be broken into small segments of 2 to 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.

[0031] Embodiment three:

[0032] The thymol byproduct alkylation process comprises the following steps:

[0033] (1) preparing raw materials: adding a coreactant m-cresol and a solvent cyclohexane to the thymol byproduct alkylation liquid, wherein the mass fraction of m-cresol is 10% of the thymol byproduct alkylation liquid, and the mass fraction of cyclohexane is 40% of the thymol byproduct alkylation liquid;

[0034] (2) loading a molecular sieve catalyst in the middle of the bed of a fixed bed reactor, raising the bed temperature to 260° C. after aging the catalyst, and continuously pumping the raw material prepared in step (1) into the reactor using a liquid pump to perform a catalytic transalkylation reaction for 120 h, wherein the conversion rate of 4,6-diisopropyl-5-methylphenol exceeds 60%;

[0035] (3) The reaction product of step (2) is transferred to a glass crystallization kettle and subjected to secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol. The remaining liquid product is returned to the catalytic transalkylation or water-catalytic dealkylation process for further harmless and resourceful treatment.

[0036] The molecular sieve catalyst in step (2) is HZSM-5 molecular sieve catalyst, with a silicon-aluminum ratio of 120, and is extruded using pseudo-boehmite powder and 8% by mass of dilute nitric acid as a binder;

[0037] The molecular sieve catalyst aging conditions are 400° C., 3 h;

[0038] The catalytic transalkylation reaction in step (2) is carried out under normal pressure, wherein the feed space velocity of the thymol byproduct alkylation liquid is 0.55h -1 The reaction temperature was between 285 and 300°C, and nitrogen was continuously introduced at 50 ml / min during the reaction.

[0039] The HZSM-5 molecular sieve catalyst is in the form of strips with a diameter of 1.35 to 2 mm. It needs to be broken into small segments of 2 to 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.

[0040] In the above examples, the HZSM-5 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 thymol byproduct transalkylation process, characterized in that: The following steps are involved: (1) preparing raw materials: adding a coreactant m-cresol and a solvent cyclohexane to the thymol byproduct alkylation liquid, wherein the mass fraction of m-cresol is 10% of the thymol byproduct alkylation liquid, and the mass fraction of cyclohexane is 40% of the thymol byproduct alkylation liquid; (2) loading a molecular sieve catalyst in the middle of the bed of a fixed bed reactor, raising the bed temperature to 260° C. after aging the catalyst, and continuously pumping the raw material prepared in step (1) into the fixed bed reactor using a liquid pump to perform a catalytic transalkylation reaction; (3) The reaction product of step (2) is transferred to a glass crystallization kettle and subjected to secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol. The remaining liquid product is returned to the catalytic transalkylation or water-catalytic dealkylation process for further harmless and resourceful treatment. The molecular sieve catalyst in step (2) is HZSM-5 molecular sieve catalyst, with a silicon-aluminum ratio of 120, and is extruded using pseudo-boehmite powder and 8% by mass of dilute nitric acid as a binder; The molecular sieve catalyst aging conditions are 400° C., 3 h; The catalytic transalkylation reaction in step (2) is carried out under normal pressure, wherein the feed space velocity of the thymol byproduct alkylation liquid is 0.5 to 0.6 h -1 The reaction temperature was between 260 and 320°C, and nitrogen was continuously introduced at 50 ml / min during the reaction.

2. The thymol byproduct transalkylation process according to claim 1, characterized in that: The HZSM-5 molecular sieve catalyst is in the form of strips with a diameter of 1.35 to 2 mm. It needs to be broken into small segments of 2 to 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.