1.1 Traditional methods
1.1.1 Reppe method
The Reppe method is an early preparation method, and the reaction process is roughly under the catalyst of Ru and Rh. At a temperature of 100-300°C and a pressure of 100-350 MPa, acetylene reacts with carbon monoxide to form 1,4-benzenediol. The process of this method is simple, but the required catalyst is expensive and difficult to recover.
1.1.2 Aniline oxidation method
Aniline oxidation is a traditional synthesis process. At present, some manufacturers in my country still use this method to produce 1,4-benzenediol. The reaction process of this method is as follows: Step 1. Under acidic conditions in the presence of sulfuric acid, aniline is oxidized to p-benzoquinone with manganese dioxide or sodium dichromate; in the second step, p-benzoquinone is under acidic conditions. It is reduced to 1,4-benzenediol with iron powder; step 3. The finished product is obtained by filtration, crystallization and decolorization. The reaction equation is as follows:
This method is mature, easy to control, and has a high yield, but generates a large amount of manganese salt, iron salt and ammonium sulfate waste liquid, etc., with low recovery rate, environmental pollution, large consumption of raw materials, and high cost of production equipment.
1.1.4 Phenol and acetone method
Phenol and acetone method (bisphenol A method) prepares 1,4-diphenol production method The reaction scheme is roughly: the 1st step, under the hydrochloric acid catalysis condition, phenol and acetone react to generate bisphenol A; the 2nd step, in the alkali Under the action of a natural catalyst, bisphenol A is decomposed into phenol and p-isopropyl phenol; in the third step, p-isopropyl phenol is oxidized to 1,4-benzenediphenol and acetone.
1.1.5 Benzene and Propylene Process
The process is roughly as follows: Benzene is alkylated with propylene to generate para-cumene and meta-cumene. Separation and oxidation of para-cumene to dicumene oxide, catalytic decomposition of 1,4-benzenediol and acetone.
1.2 Clean and environmentally friendly methods
with the development of economy. The requirements for environmental protection are also getting higher and higher, and the new environmental protection process has challenged the traditional synthesis process, and gradually matured.
1.2.1 Hydroxylation of phenol with hydrogen peroxide
The method was developed in the 1970s and is now industrialized. The reaction process is as follows: in the presence of a catalyst, phenol reacts with hydrogen peroxide to generate 1,4-benzenediol; dehydration and separation to obtain crude 1,4-benzenediol; finally, through dissolution, decolorization and recrystallization to obtain 1,4-benzenediol 4-Benzenediol.
1.2.2 Phenol hydroxylation-peroxyacid, peroxyketone oxidation
This method, also known as the Ube method, is the first example of the successful application of El Ben Ube Company. The reaction process is as follows: sulfuric acid, a certain amount of hydrogen peroxide and methyl isobutyl ketone are reacted to generate peroxyketone as a catalyst. Catalytic oxidation of phenol to produce 1,4-benzenediol and catechol: finally, the items are obtained by separation and purification.