Recovery of distillation residue from sulfonated phenol production by separation method
The technological process is as follows: the residue of phenol distillation contains about 40% phenylphenol, and other components are phenol, inorganic salts, water and so on. After vacuum distillation, the mixed phenylphenol fraction is separated, the vacuum degree is 400 ~ 500 mm Hg, the temperature is 65 ~ 75℃, and the cut-off temperature is above 100℃, but it shall not exceed 135℃. Then the mixture (mainly 2- hydroxybiphenyl and 4- hydroxybiphenyl) is heated and dissolved in trichloroethylene, cooled, and 4- hydroxybiphenyl crystals are separated, centrifugally filtered and dried to obtain 4- hydroxybiphenyl. Washing mother liquor with sodium carbonate solution, and then adding dilute alkali solution to salify 2- hydroxybiphenyl. After static separation, the upper layer of 2- hydroxybiphenyl sodium salt is decompressed and dehydrated to obtain the sodium salt finished product. Due to the limitation of resources, the production of o-phenylphenol by separation method is very limited. The method for producing o-phenylphenol from cyclohexanone is as follows:
The basic reaction equation is shown in the following figure.
Cyclohexanone condensation adopts multi-kettle series continuous process. Cyclohexanone and catalyst are continuously added into the first kettle for reaction, and then sequentially enter the second kettle and the third kettle. The generated water is carried out by the water-carrying agent, and the water-carrying agent returns to each kettle after phase separation. The water generated by the reaction is collected and then enters a water washing device to continue water washing. The separated catalyst is recycled to the first reaction kettle, the reaction product after water washing continues to enter the continuous rectification device, and unreacted cyclohexanone is distilled out and recycled to the first reaction kettle for reaction. After the refined dimer is metered, it enters the dehydrogenation reactor for reaction. After light components are removed from crude OPP by rectification, more than 99% of OPP is added with stabilizer in the mixing kettle and then sliced and packaged, and the other part needs recrystallization, centrifugation and drying to obtain more than 99.5% of OPP products. The production technology of o-phenylphenol has the following key technologies and innovations:
(a) Cyclohexanone condensation adopts super-strong solid acid catalyst and multi-kettle series continuous technology.
The general patent literature of cyclohexanone condensation reaction uses concentrated sulfuric acid as catalyst, the reaction temperature is 120℃, the single-pass conversion is about 50%, and the total yield is 85%. After the reaction, the reaction solution was neutralized with alkali, which led to serious equipment corrosion, a large amount of wastewater and serious environmental pollution.
O-phenylphenol uses a super-strong solid acid as catalyst, the dosage is 2-3%, the reaction temperature is about 120℃, the one-way conversion rate is 60%, and the total yield is over 90%. The catalyst can be reused, which is a clean production process and solves the problem of wastewater generation.
The adoption of multi-kettle series continuous technology overcomes the shortcomings of complicated production operation and large equipment investment, and can realize full automatic continuous operation.
(b) high-efficiency dehydrogenation catalyst
The dehydrogenation catalyst takes platinum as the main catalyst, and 2-3 kinds of cocatalysts are added, one of which is rare earth element. The catalyst of 0.5% Pt and 5% rare earth is loaded on a special carrier, and hydrogen is used as the carrier gas. Under the high load of reaction temperature of 350-370℃ and liquid phase space velocity of dimer of 0.2-0.4h- 1, the conversion rate of dimer reaches 98%. However, according to the domestic patent data, the catalyst loading is 0.2h- 1, and the efficiency of o-phenylphenol decreases obviously after continuous operation for 200 hours.
(c) continuous product refining technology
Cyclohexanone condensation products were refined by thin film evaporation and continuous distillation in two towers.
Dehydrogenation products adopt high vacuum molecular distillation technology and continuous recrystallization technology, which consists of recrystallization, centrifugal separation, drying and packaging, meeting the requirements of high purity, production safety and automation.
High purity product
The purity of o-phenylphenol can reach above 99.5%, which meets the needs of export and sterilization, mildew prevention and corrosion protection.
(e) stabilizers for special products.
0.05-0.2% special stabilizer is added to the refined product, which ensures that the color of the product is white flake crystals and meets the needs of export. Without the above stabilizer, the product will turn pale red in less than one month.
Comparison of main parameters of similar technologies and products at home and abroad
O-phenylphenol is produced by condensation and dehydrogenation of cyclohexanone. Although a few domestic units have published some research papers, there is no report on industrial production. The production technology of synthesizing o-phenylphenol from cyclohexanone was first built in China by Yancheng Huaye Pharmaceutical and Chemical Co., Ltd., with an annual output of 200 tons. It was successfully put into trial operation in February 2002, which filled the domestic gap. Cyclohexanone condensation takes solid superacid as catalyst and cyclohexane as water-carrying agent. The total yield is over 90%, and the catalyst can be recycled. The dehydrogenation reaction was catalyzed by Pt-K- rare earth /Al2O3. The dehydrogenation conversion rate was 98- 100% and the yield was over 90%. At present, the catalyst can run stably for more than 9000 hours, and the purity of OPP products is 99.5%. Products have been exported to the United States, German, Japanese, Indian and Taiwan Province provinces and other countries and regions.
The synthesis of o-phenylphenol from cyclohexanone abroad is mainly produced by Bayer company in Germany, with a production capacity of 20 thousand t/a, and the industrialization technology and level have not been reported. Through the communication between Yancheng Huaye Pharmaceutical and Chemical Co., Ltd. and Bayer Company, cyclohexanone condensation uses sulfuric acid as catalyst, and there is a lot of wastewater. Precious metal platinum catalysts are also used for dehydrogenation. The service life is about 10 month, the product purity is ≥99.5%, and the by-product hydrogen has been utilized. See Table 2- 1, Table 2-2 and Table 2-3 for the comparison of the quality and technical level of o-phenylphenol produced by Yancheng Huaye Pharmaceutical Chemical Co., Ltd. with domestic and foreign products.
Table 2- 1 OPP Comparison Table with Main Quality Indicators of Foreign Products
serial number
Indicator name
unit
Yancheng huaye OPP
Bayer OPP Germany
1
external
/
White flake crystal
White flake crystal
2
OPP content
%
99.5
99.5
three
Melting point range
℃
56-58
54-58
four
clear
0. 1 mol/l
Colorless transparent liquid
Colorless transparent liquid
five
chlorion
parts per million
& lt50
& lt50
six
sulphate
parts per million
& lt50
& lt 150
Table 2-2 OPP Production Process Comparison Table
serial number
Indicator name
Yancheng huaye
Bayer
Japanese Three Lamps District.
1
process route
Synthesis of cyclohexanone
Synthesis of cyclohexanone
Phenol chlorobenzene condensation method
2
expense
low
low
high
three
Three wastes in industrial production
not have
There is wastewater
There is wastewater
four
Condensation catalyst
Solid superacid
concentrated sulfuric acid
not have
Table 2-3 Comparison Table of Technical Level between Yancheng Huaye Company and Bayer Company
Huaye company
Bayer Corp.
Cyclohexanone unit consumption
1.6- 1.65
1.5- 1.55
Cyclohexanone condensation catalyst
Solid superacid
concentrated sulfuric acid
waste water
No waste water
There is wastewater
Service time of dehydrogenation catalyst
9000 hours
16000 hours
Utilization of by-product hydrogen
Underutilized
make the most of/take full advantage of
O-phenylphenol content
≥99.5%
≥99.5%
OPP color
White flake crystal
White flake crystal
Production scale (ton/year)
10000
20000
Price (ten thousand yuan/ton)
5.0
6.5
sell
the four seas—the whole country
This European and American project has strong cost performance, broad market prospects and obvious market competitive advantages.