The production methods of o-phenylphenol currently mainly include separation method and synthesis method. The production methods of o-phenylphenol (OPP) can be divided into two types: isolation method and synthesis method.
The separation method is used to recover the distillation residue of phenol produced by the sulfonation method
The process is as follows: the distillation residue of phenol contains about 40% of phenylphenol, and other components are phenol, inorganic Salt, water, etc. After vacuum distillation, the mixed phenylphenol fraction is separated. The vacuum degree is 400~500mm mercury. The temperature starts to intercept above 100℃ at 65~75℃, but must not exceed 135℃. Then the mixture (mainly 2-hydroxybiphenyl and 4-hydroxybiphenyl) is heated and dissolved in trichlorethylene. After cooling, the 4-hydroxybiphenyl crystals are separated, and the 4-hydroxybiphenyl is obtained by centrifugal filtration and drying. The mother liquor is washed with sodium carbonate solution, and dilute alkali solution is added to form a salt of 2-hydroxybiphenyl. After static separation, take the upper layer 2-hydroxybiphenyl sodium salt and dehydrate it under reduced pressure to obtain the finished sodium salt. Due to resource constraints, the output of o-phenylphenol produced by separation methods is very limited. The process of producing o-phenylphenol from cyclohexanone as raw material is as follows:
The basic reaction equation is shown in the figure below
The condensation of cyclohexanone adopts multi-kettle series continuous technology. The ketone and catalyst are continuously added to the first reactor for reaction, and then enter the second and third reactors in sequence. The generated water is taken out by the water-carrying agent. After phase separation, the water-carrying agent is returned to each kettle. The water generated by the reaction After being collected, it enters the water washing device for continuous water washing. The separated catalyst is recycled into the first reactor, and the washed reaction product continuously enters the continuous distillation device, where unreacted cyclohexanone is steamed out and recycled into the first reactor for reaction. After the precise dimer is measured, it enters the dehydrogenation reactor for reaction. After the crude OPP is distilled to remove the light components, more than 99% of the OPP is added with a stabilizer in the mixing kettle and then continuously sliced ??and packaged. The other part needs to be recrystallized. , centrifuge and dry to obtain more than 99.5% OPP products. The o-phenylphenol production technology has the following key technologies and innovations:
(a) Cyclohexanone condensation uses super strong solid acid catalyst and multi-kettle series continuous technology
Cyclohexanone condensation In general patent documents for ketone condensation reactions, concentrated sulfuric acid is used as a catalyst. The reaction temperature is 120°C, the single-pass conversion rate is about 50%, and the total yield is 85%. After the reaction is completed, alkali is used to neutralize the reaction solution. The equipment is seriously corroded, and there are A large amount of waste water causes serious environmental pollution.
O-phenylphenol uses a super strong solid acid as a catalyst, with a dosage of 2-3%, a reaction temperature of about 120°C, a single-pass conversion rate of 60%, and a total yield of more than 90%. The catalyst can be repeated The use is a completely clean production process, which solves the problem of waste water generation.
The use of multi-kettle series continuous technology overcomes the current shortcomings of troublesome production operations and large equipment investment, and can achieve fully automatic continuous production.
(b) Efficient dehydrogenation catalyst
The dehydrogenation catalyst uses platinum as the main catalyst, adding 2-3 kinds of cocatalysts, one of which is a rare earth element, which is carried on a special carrier Pt0.5%-rare earth 5% catalyst, using hydrogen as carrier gas, reaction temperature 350-370°C, dimer liquid phase space velocity at high load of 0.2-0.4h-1, dimer conversion rate It reaches 98%, the selectivity reaches more than 93%, and the o-phenylphenol yield remains above 90% after continuous operation for more than 5,000 hours. According to domestic patent information, the catalyst load is 0.2h-1 and the o-phenylphenol efficiency has dropped significantly after 200 hours of continuous operation.
(c) Continuous product refining technology
The cyclohexanone condensation product adopts thin film evaporation + two-tower continuous distillation refining technology.
The dehydrogenation product adopts high vacuum molecular distillation technology and continuous recrystallization technology. Continuous recrystallization combines recrystallization, centrifugal separation, drying and packaging into a continuous system to meet the requirements of high product purity, production safety and automation. requirements.
(d) High-purity products
The purity of o-phenylphenol can be as high as 99.5% or more, meeting the needs of exports and the fields of sterilization, anti-mold and preservatives.
(e) Special product stabilizer
Added 0.05-0.2% special stabilizer to the refined product to ensure the color of the product is white flaky crystals, which meets the export requirements needs. Without adding the above-mentioned stabilizer, the product turns light red in less than a month.
Comparison of main parameters of similar technologies and products at home and abroad
O-phenylphenol is produced by the synthesis method of cyclohexanone condensation and dehydrogenation. Although a few domestic units have published a small number of research papers , but there have been no reports of industrial production. For the production technology of o-phenylphenol synthesized from cyclohexanone, Yancheng Huaye Pharmaceutical Chemical Co., Ltd. was the first in China to build a pilot plant with an annual output of 200 tons of o-phenylphenol. It was successfully tested in December 2002 and filled the gap. A domestic blank, the condensation of cyclohexanone uses super strong solid acid as the catalyst and cyclohexane as the water-carrying agent. The total yield reaches more than 90%, and the catalyst can be recycled and reused. The dehydrogenation reaction is catalyzed by Pt-K-rare earth/Al2O3. The dehydrogenation conversion rate reaches 98-100% and the yield reaches more than 90%. The current catalyst can operate stably for more than 9,000 hours. The purity of the OPP product reaches 99.5%. The product has been exported. The United States, Germany, Japan, India, Taiwan and other countries and regions.
Abroad, the main company that uses cyclohexanone to synthesize o-phenylphenol is the German company Bayer, with a production capacity of 20,000t/a. There are no reports on the industrialization technology and level. After communicating with Yancheng Huaye Pharmaceutical Chemical Co., Ltd., Bayer Company uses sulfuric acid as a catalyst for the condensation of cyclohexanone, which produces a large amount of waste water. It also uses a precious metal platinum catalyst for dehydrogenation, with a lifespan of about 10 months and product purity ≥99.5%. The by-product hydrogen has been utilized. The comparison of the quality and technical level of o-phenylphenol produced by Yancheng Huaye Pharmaceutical Chemical Co., Ltd. with domestic and foreign products is shown in Table 2-1, Table 2-2 and Table 2-3 below.
Table 2-1 Comparison table between OPP main quality indicators and foreign products
Serial number
Indicator name
Unit
Yancheng Huaye OPP
Germany Bayer OPP
1
Appearance
/
White flake crystal
White flaky crystals
2
OPP content
%
99.5
99.5
3
Melting point range
℃
56-58
54-58
4
Clarity
0.1mol/l
Colorless transparent liquid
Colorless transparent liquid
5
Chloride ion
ppm
<50
<50
6
Sulfate
ppm
<50
<150
Table 2-2 OPP production process comparison table< /p>
Serial number
Indicator name
Yancheng Huaye
Germany Bayer
Japan Sanko
1
Processing route
Cyclohexanone synthesis method
Cyclohexanone synthesis method
Phenol chlorobenzene condensation method
2
Cost
Low
Low
High
3
< p>Three wastesNone
There is waste water
There is waste water
4
Condensation catalyst
Solid super acid
Concentrated sulfuric acid
None
Table 2-3 Comparison of the technical levels of Yancheng Huaye Company and Bayer Company
< p>Huaye CompanyBayer Company
Cyclohexanone unit consumption
1.6-1.65
1.5-1.55
Cyclohexanone condensation catalyst
Solid super acid
Concentrated sulfuric acid
Wastewater
No wastewater
With wastewater
Dehydrogenation catalyst usage time
9000 hours
16000 hours
Utilization of by-product hydrogen
Not fully utilized
Completely utilized
O-phenylphenol content
≥99.5%
≥99.5%
< p>OPP colorWhite flake crystal
White flake crystal
Production scale (t/a)
10000
p>20000
Price (10,000 yuan/t)
5.0
6.5
Sales
Global
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