High-value utilization process for liquid-phase byproducts in thymol synthesis alkylation workshop

Abstract

The invention relates to a high-valued utilization process for liquid-phase byproducts in a thymol synthesis alkylation workshop, which comprises the following steps: distilling and decoloring alkylated liquid from which thymol is extracted, and crystallizing and extracting 4-isopropyl-3-methylphenol; rectifying the crystallization mother liquor to respectively obtain a raw material A taking 4, 6-diisopropyl-3-methylphenol as a main component and a raw material B taking 5-isopropyl-3-methylphenol as a main component, distilling and decoloring the raw material A, mixing with m-cresol, and performing catalytic transalkylation reaction crystallization to extract the 4-isopropyl-3-methylphenol, mixing the residual liquid with the raw material B to obtain a raw material C, performing catalytic dealkylation reaction under a water atmosphere condition after distillation decoloration to obtain mixed phenol, performing distillation to remove non-phenol substances, performing rectification to obtain m-cresol, feeding the m-cresol as a raw material into an alkylation workshop, mixing the residual alkylation liquid with the raw material C, and performing water atmosphere catalytic dealkylation treatment again; according to the process, high-valued products can be obtained to the greatest extent, and the effects of reducing the cost and improving the economic value of the process are achieved.

Description

Technical Field

[0001] The invention relates to a high-value utilization process of liquid phase by-products in a thymol synthesis alkylation workshop. Background Art

[0002] The synthesis process of thymol is divided into three steps: (1) alkylation, (2) distillation, and (3) solvent crystallization, see Chinese patent CN105315133B for details. The problem of the prior art is that in the step of synthesizing thymol by alkylation of meta-cresol and propylene in the production process, a large amount of liquid by-products will be produced. After extracting the product thymol, these by-products accumulate in the waste tank, which seriously affects the efficiency of the use of the raw material meta-cresol and also causes environmental hazards. There are still a lot of technical gaps in the treatment and disposal of the liquid by-products. The liquid by-products can be used as chemical fuels for relatively extensive harmless disposal, or they can be harmlessly disposed of after recovering low-content meta-cresol, phenol and other chemical raw materials after distillation separation. However, these treatment methods are difficult to maximize the economic value of these liquid by-products, and are not conducive to energy saving and efficiency improvement in the thymol production industry. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a high-value utilization process for liquid by-products in a thymol synthesis alkylation workshop, which can obtain high-value products to the greatest extent and reduce the comprehensive recycling method of raw material consumption, thereby reducing the by-product treatment cost and improving the economic value of the process.

[0004] In order to solve the above technical problems, the present invention provides a high-value utilization process of liquid by-products in a thymol synthesis alkylation workshop, comprising the following steps:

[0005] (1) distilling and decolorizing the alkylated liquid after thymol is extracted at 110-120° C., and the treated alkylated liquid enters a glass crystallization kettle, and performs secondary solvent crystallization using 30% and 45% ethanol, respectively, to extract 4-isopropyl-3-methylphenol;

[0006] (2) The crystallization mother liquor produced in step (1) is subjected to rectification to obtain: a raw material A with 4,6-diisopropyl-3-methylphenol as a main component, and a raw material B with 5-isopropyl-3-methylphenol as a main component, wherein: the raw material B is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 125° C., and a tower bottom temperature of 160° C., and the raw material A is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 130° C., and a tower bottom temperature of 165° C.;

[0007] (3) The raw material A obtained in step (2) is distilled and decolorized at 110-120° C., mixed with an equal mass of m-cresol, and introduced into a fixed bed reactor to perform a catalytic transalkylation reaction under the action of a HZSM-5 molecular sieve catalyst, and then transferred into a glass crystallization kettle to perform secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol, and then the remaining liquid is added to the raw material B to mix into the raw material C;

[0008] (4) After the raw material C is distilled and decolorized at 110-120° C., it enters a fixed bed reactor and uses a HY / HMOR mixed crystal molecular sieve catalyst under water atmosphere to catalyze a dealkylation reaction to obtain a mixed phenol with a high content of m-cresol;

[0009] (5) After the mixed phenol is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, it enters the mixed phenol separation workshop, and the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C. The meta-cresol obtained by distillation separation is used as a raw material and enters the alkylation workshop. The conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C. The remaining alkylation liquid is mixed with raw material C and subjected to water-atomization catalytic dealkylation treatment again;

[0010] The catalyst needs to be aged before the catalytic reaction in step (3) and step (4), and the aging conditions are 400° C. for 3 h;

[0011] The catalytic transalkylation reaction in step (3) is carried out under normal pressure, wherein the feed space velocity of raw material A 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.

[0012] In the water-atmosphere catalytic dealkylation reaction in step (4), the mass ratio of water to raw material C is 4:7, and the feed space velocity of raw material C is 0.6 to 0.8 h -1 , the temperature is between 380 and 420°C, the reaction pressure is controlled at 1 to 1.2 MPa, and nitrogen is continuously introduced at 50 ml / min during the reaction.

[0013] Preferably, the HZSM-5 molecular sieve catalyst in step (3) has a silicon-aluminum ratio of 120 and is extruded using pseudo-boehmite powder and 8% by mass dilute nitric acid as a binder;

[0014] In the step (4), the HY / HMOR mixed crystal molecular sieve catalyst has a Y-type molecular sieve with a silicon-aluminum ratio of 5 to 7 and a MOR molecular sieve with a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0015] Preferably, the HZSM-5 molecular sieve catalyst and HY / HMOR mixed crystal molecular sieve catalyst are both in the form of strips with a diameter of 1.35 to 2 mm. When used, they need to be broken into small segments of 2 to 3 mm. 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 invention has the following advantages: the mass fraction of 4,6-diisopropyl-3-methylphenol in the raw material A obtained in step (2) is not less than 55%, the mass fraction of 5-isopropyl-3-methylphenol in the raw material B is not less than 53%, after the reaction in step (3), the maximum yield of the high-value product 4-isopropyl-3-methylphenol is 22%, and the conversion rate of 4,6-diisopropyl-3-methylphenol is about 60%, after the reaction in step (4), the conversion rate of 5-isopropyl-3-methylphenol is about 60%, the yield of meta-cresol is between 35-45%, and the selectivity of cresol to meta-cresol is greater than 80%.

[0017] The liquid by-products produced in the thymol synthesis alkylation workshop have the characteristics of large production volume and strong reusability. Compared with the current conventional treatment methods, the present invention provides a comprehensive recycling method that can obtain high-value products to the greatest extent and reduce raw material consumption, which has the effect of reducing the cost of by-product treatment and improving the economic value of the process. The reaction principle involved in the present invention is clear, the steps are simple, the equipment and catalyst are easy to obtain, and it has strong practicality and can become a powerful supplement to the thymol synthesis industry. DETAILED DESCRIPTION

[0018] The high-value utilization process of the liquid by-product of the thymol synthesis alkylation workshop comprises the following steps:

[0019] (1) distilling and decolorizing the alkylated liquid after thymol is extracted at 110-120° C., and the treated alkylated liquid enters a glass crystallization kettle, and performs secondary solvent crystallization using 30% and 45% ethanol, respectively, to extract 4-isopropyl-3-methylphenol;

[0020] (2) The crystallization mother liquor produced in step (1) is subjected to rectification to obtain: a raw material A with 4,6-diisopropyl-3-methylphenol as a main component, and a raw material B with 5-isopropyl-3-methylphenol as a main component, wherein: the raw material B is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 125° C., and a tower bottom temperature of 160° C., and the raw material A is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 130° C., and a tower bottom temperature of 165° C.;

[0021] (3) The raw material A obtained in step (2) is distilled and decolorized at 110-120° C., mixed with an equal mass of m-cresol, and introduced into a fixed bed reactor to perform a catalytic transalkylation reaction under the action of a HZSM-5 molecular sieve catalyst, and then transferred into a glass crystallization kettle to perform secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol, and then the remaining liquid is added to the raw material B to mix into the raw material C;

[0022] (4) After the raw material C is distilled and decolorized at 110-120° C., it enters a fixed bed reactor and uses a HY / HMOR mixed crystal molecular sieve catalyst under water atmosphere to catalyze a dealkylation reaction to obtain a mixed phenol with a high content of m-cresol;

[0023] (5) After the mixed phenol is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, it enters the mixed phenol separation workshop, and the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C. The meta-cresol obtained by distillation separation is used as a raw material and enters the alkylation workshop. The conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C. The remaining alkylation liquid is mixed with raw material C and subjected to water-atomization catalytic dealkylation treatment again;

[0024] The catalyst needs to be aged before the catalytic reaction in step (3) and step (4), and the aging conditions are 400° C. for 3 h;

[0025] The catalytic transalkylation reaction in step (3) is carried out under normal pressure, wherein the feed space velocity of raw material A 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.

[0026] In the water-atmosphere catalytic dealkylation reaction in step (4), the mass ratio of water to raw material C is 4:7, and the feed space velocity of raw material C is 0.6 to 0.8 h -1 , the temperature is between 380 and 420°C, the reaction pressure is controlled at 1 to 1.2 MPa, and nitrogen is continuously introduced at 50 ml / min during the reaction.

[0027] The HZSM-5 molecular sieve catalyst in step (3) has a silicon-aluminum ratio of 120 and is extruded using pseudo-boehmite powder and 8% by mass dilute nitric acid as a binder;

[0028] In the step (4), the HY / HMOR mixed crystal molecular sieve catalyst has a Y-type molecular sieve with a silicon-aluminum ratio of 5 to 7 and a MOR molecular sieve with a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mass ratio of 2:1 and extruded with 40% silica sol as a binder.

[0029] The HZSM-5 molecular sieve catalyst and HY / HMOR mixed crystal molecular sieve catalyst are both in strip shape with a diameter of 1.35-2 mm. They need 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.

[0030] In the above examples, HZSM-5 molecular sieve catalyst and HY / HMOR mixed crystal molecular sieve catalyst were purchased from Raodong (Liaoning) New Materials Co., Ltd. Thymol byproduct alkylation liquid was from Anhui Haihua Technology Group Co., Ltd.

Claims

1. A process for high-value utilization of liquid by-products in a thymol synthesis alkylation workshop, characterized in that: The following steps are involved: (1) distilling and decolorizing the alkylated liquid after thymol is extracted at 110-120° C., and the treated alkylated liquid enters a glass crystallization kettle, and performs secondary solvent crystallization using 30% and 45% ethanol, respectively, to extract 4-isopropyl-3-methylphenol; (2) The crystallization mother liquor produced in step (1) is subjected to rectification to obtain: a raw material A with 4,6-diisopropyl-3-methylphenol as a main component, and a raw material B with 5-isopropyl-3-methylphenol as a main component, wherein: the raw material B is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 125° C., and a tower bottom temperature of 160° C., and the raw material A is distilled under the conditions of a vacuum degree of -98 kPa, a tower top temperature of 130° C., and a tower bottom temperature of 165° C.; (3) The raw material A obtained in step (2) is distilled and decolorized at 110-120° C., mixed with an equal mass of m-cresol, and introduced into a fixed bed reactor to perform a catalytic transalkylation reaction under the action of a HZSM-5 molecular sieve catalyst, and then transferred into a glass crystallization kettle to perform secondary solvent crystallization using 30% and 45% ethanol to extract 4-isopropyl-3-methylphenol, and then the remaining liquid is added to the raw material B to mix into the raw material C; (4) After the raw material C is distilled and decolorized at 110-120° C., it enters a fixed bed reactor and uses a HY / HMOR mixed crystal molecular sieve catalyst under water atmosphere to catalyze a dealkylation reaction to obtain a mixed phenol with a high content of m-cresol; (5) After the mixed phenol is subjected to preliminary distillation to remove non-phenolic substances such as benzene and toluene, it enters the mixed phenol separation workshop, and the distillation conditions are vacuum degree -80 kPa, tower top temperature 80°C, and tower bottom temperature 165°C. The meta-cresol obtained by distillation separation is used as a raw material and enters the alkylation workshop. The conditions for separating the meta-cresol are vacuum degree -98 kPa, tower top temperature 110°C, and tower bottom temperature 130°C. The remaining alkylation liquid is mixed with raw material C and subjected to water-atomization catalytic dealkylation treatment again; The catalyst needs to be aged before the catalytic reaction in step (3) and step (4), and the aging conditions are 400° C. for 3 h; The catalytic transalkylation reaction in step (3) is carried out under normal pressure, wherein the feed space velocity of raw material A 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. In the water-atmosphere catalytic dealkylation reaction in step (4), the mass ratio of water to raw material C is 4:7, and the feed space velocity of raw material C is 0.6 to 0.8 h -1 , the temperature is between 380 and 420°C, the reaction pressure is controlled at 1 to 1.2 MPa, and nitrogen is continuously introduced at 50 ml / min during the reaction.

2. The high-value utilization process of liquid by-products in the thymol synthesis alkylation workshop according to claim 1, characterized in that: The HZSM-5 molecular sieve catalyst in step (3) has a silicon-aluminum ratio of 120 and is extruded using pseudo-boehmite powder and 8% by mass dilute nitric acid as a binder; In the step (4), the HY / HMOR mixed crystal molecular sieve catalyst has a Y-type molecular sieve with a silicon-aluminum ratio of 5 to 7 and a MOR molecular sieve with a silicon-aluminum ratio of 10 to 12. The catalyst is mechanically mixed at a mass ratio of 2:1 and extruded with 40% silica sol as a binder.

3. The high-value utilization process of liquid phase byproducts in the thymol synthesis alkylation workshop according to claim 1, characterized in that: The HZSM-5 molecular sieve catalyst and HY / HMOR mixed crystal molecular sieve catalyst are both in strip shape with a diameter of 1.35-2 mm. They need 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.