Resourceful treatment process for alkylation byproduct low-boiling-point substances in BHT (butylated hydroxytoluene) production process

Abstract

The invention relates to a resourceful treatment process for an alkylation byproduct low-boiling-point substance in a BHT production process. The process mainly comprises three steps of preheating depolymerization, multi-stage water washing and phase separation purification, wherein firstly, low-boiling-point substances are preheated and depolymerized at the temperature of 50-60 DEG C, and residual isobutene is recovered; then, through three times of countercurrent water washing, TBA is transferred to a water phase by utilizing the hydrophilicity of TBA, and DIB is retained in an oil phase; and finally, concentrating and purifying the water phase by adopting a stripping tower to obtain industrial grade TBA with the concentration of more than or equal to 98wt%, rectifying the oil phase by adopting normal pressure to obtain industrial grade DIB with the concentration of more than or equal to 95wt%, and carrying out incineration treatment on residual liquid. According to the method, thermal activation and water washing are combined, the TBA / DIB azeotropic separation problem is effectively solved, high-energy-consumption azeotropic distillation is replaced, the technological process is simple, the operation condition is mild, the equipment requirement is low, the amount of hazardous waste can be reduced by 90% or above, the recycled product meets the relevant national standard, the resource utilization rate is high, economical efficiency is good, and industrial application and popularization are easy.

Description

Technical Field

[0001] This invention relates to a process for the resource recovery of low-boiling-point byproducts of alkylation during BHT production. Background Technology

[0002] The BHT production process includes an alkylation stage, as detailed in Chinese patent CN202111341381.6.

[0003] In a BHT production unit with an annual output of 20,000 tons, the alkyl chemical section (reaction of m-p-cresol and isobutylene) generates approximately 1,000 tons of low-boiling-point byproducts annually.

[0004] This low-boiling-point substance mainly contains tert-butanol (TBA) and diisobutylene (DIB), which form an azeotrope (azeotropic point of about 82°C), and cannot be effectively separated by conventional distillation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a resource utilization process for low-boiling-point byproducts of alkylation in the BHT production process, which can separate tert-butanol (TBA) and diisobutylene (DIB) from the low-boiling-point byproducts, reduce hazardous waste, and improve the economic efficiency of the process.

[0006] To address the aforementioned technical problems, this invention provides a process for the resource recovery of low-boiling-point byproducts of alkylation during BHT production, comprising the following steps:

[0007] (1) Preheating and depolymerization: The low-boiling-point byproduct of alkylation in the BHT production process is put into the preheating kettle, heated to 50~60℃, and kept at a constant temperature for 1~3h to dissociate the residual isobutylene monomer from the liquid phase. After condensation and recovery, it is returned to the alkylation workshop for reuse.

[0008] (2) Multi-stage water washing: Add pure water to the depolymerized material and perform three countercurrent water washings with a water-to-oil ratio of 0.8 to 1.2:1. Perform three countercurrent washings at 20 to 40°C. TBA will be transferred to the aqueous phase due to its hydrophilicity, while DIB will remain in the oil phase.

[0009] (3) Phase separation and purification: The oil phase and the aqueous phase are separated into liquid and liquid phases. After separation:

[0010] Aqueous phase treatment: Trace organic impurities are removed by stripping tower at 80~95℃, and concentrated to obtain ≥98wt% industrial grade TBA;

[0011] Oil phase treatment: Separate the oil phase using a single-stage distillation column at 100~120℃ / atmospheric pressure to obtain ≥95wt% industrial grade DIB;

[0012] The remaining liquid will be directly incinerated.

[0013] Advantages of this invention: This invention solves the TBA / DIB azeotropic problem through a combination of thermal activation and water washing, replacing energy-intensive azeotropic distillation. It can separate tert-butanol (TBA) and diisobutylene (DIB) from low-boiling-point byproducts of alkylation during BHT production. The entire process requires no special equipment, operates under mild conditions (atmospheric pressure, <120℃), has a low threshold for industrial implementation, reduces hazardous waste by ≥90%, and the recovered products meet the standards of GB / T 7814-2017 (industrial tert-butanol) and SH / T 1786-2015 (industrial diisobutylene). It improves resource utilization and process economy, can be directly integrated into existing BHT production lines, and has a short payback period for retrofitting investments. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0015] A process for the resource recovery of low-boiling-point substances produced as a byproduct of alkylation in BHT production includes the following steps, taking the processing of 100 kg of low-boiling-point substances as an example:

[0016] (1) Preheating and depolymerization: The low-boiling-point byproduct of alkylation in the BHT production process is put into the preheating kettle, heated to 55°C, and kept at a constant temperature for 2 hours to dissociate the residual isobutylene monomer from the liquid phase. After condensation and recovery, it is returned to the alkylation workshop for reuse, and 8.2 kg of isobutylene (purity 92%) is recovered.

[0017] (2) Multi-stage water washing: Add 80kg of pure water to the depolymerized material and perform three countercurrent water washings with a water-oil ratio of 1:1. Perform three countercurrent washings at 30℃. TBA is transferred to the aqueous phase due to its hydrophilicity, while DIB remains in the oil phase.

[0018] (3) Phase separation and purification: The oil phase and the aqueous phase are separated into liquid and liquid phases. After separation:

[0019] Aqueous phase (containing 32kg of TBA) treatment: Trace organic impurities were removed by stripping at 85℃, and the product was concentrated to obtain 30.1kg of TBA product (purity 98.5%).

[0020] Oil phase (containing 58 kg of DIB) processing: separated by a single-stage distillation column at 110℃ / atmospheric pressure to obtain 55.3 kg of DIB product (purity 98.2%).

[0021] If the residual liquid volume is less than 2kg, it can be directly incinerated.

Claims

1. A process for the resource utilization of low-boiling-point byproducts of alkylation during BHT production, characterized in that, Includes the following steps: (1) Preheating and depolymerization: The low-boiling-point byproduct of alkylation in the BHT production process is put into the preheating kettle, heated to 50~60℃, and kept at a constant temperature for 1~3h to dissociate the residual isobutylene monomer from the liquid phase. After condensation and recovery, it is returned to the alkylation workshop for reuse. (2) Multi-stage water washing: Add pure water to the depolymerized material and perform three countercurrent water washings with a water-to-oil ratio of 0.8 to 1.2:

1. Perform three countercurrent washings at 20 to 40°C. TBA will be transferred to the aqueous phase due to its hydrophilicity, while DIB will remain in the oil phase. (3) Phase separation and purification: The oil phase and the aqueous phase are separated into liquid and liquid phases. After separation: Aqueous phase treatment: Trace organic impurities are removed by stripping tower at 80~95℃, and concentrated to obtain ≥98wt% industrial grade TBA; Oil phase treatment: Separate the oil phase using a single-stage distillation column at 100~120℃ / atmospheric pressure to obtain ≥95wt% industrial grade DIB; The remaining liquid will be directly incinerated.

Images