Studies On Catalysts For Hydroxylation Of 4-tert-butyl-phenol

4-tert-butylcatechol (4-TBC) is an important fine chemical product and widely used in industry. It can be synthesized by using catechol alkylation method, which requires long reaction time, high energy consuming. This technology also demands highly for the equipments and cause environmental pollution in separation process. All of the characters mentioned above do not suit to the demand of industrial production and green chemicals. Phenols hydroxylation reaction, due to the cheap raw material and mild reaction condition, is recognized as environmental friendly. Phenol hydroxylation reaction has already been realized industrialization and benzene hydroxylation reaction also has been the studied fairly mature. However, there are not so many reports on directly hydroxylate 4-tert-butylcatechol (PTBP) to synthesize 4-TBC. The industrial value can be found from a market research that the price of 4-TBC is ten times of the price of PTBP. Several reports from patents of US or Japan, neither selectivity nor technology could reach the requirement of modern industry. Studies on PTBP hydroxylation reaction in china is just in the initial stage. In this paper, PTBP hydroxylation reaction is investigated by using iron based catalyst, reaction conditions is optimized and reaction mechanism is discussed preliminarily. The whole work is based on phenol and benzene hydroxylation reaction. The main contents are the following:1. PTBP hydroxylation reaction can be catalyzed by spinel type magnesium ferrite (MgFe2O4). MgFe2O4 catalyst is characterized by XRD, FT-IR and TG-DTA. The effects of reaction temperature, catalyst amount, the molar ratio of H2O2 to PTBP, solvent volume and catalyst roasting temperature on PTBP hydroxylation are investigated. The results showed that a long induction period exist in PTBP hydroxylation. The study on reaction induction period showed that iron species form, iron species valence states and catalyst particle size all have effect on reaction induction period. Under the condition that:PTBP 3.00g, the molar ratio of H2O2 to PTBP 1:1, acetonitrile volume 5mL, reaction temperature 80℃, the conversion of PTBP reaches to 34.3%, the selectivity to 4-TBC is 57.3%.2. PTBP hydroxylation reaction showed good result when using Fe (OH) 3 as catalyst and catechol as cocatalyst. Effects of reaction time, reaction temperature, and catalyst dosage, n (H2O2): n (PTBP), reaction solvents and so on are investigated. The results showed that reaction solvents and n (H2O2):n (PTBP) acted important role for catalyst catalytic activity. Under the condition:PTBP 0.80g, n(H2O2):n(PTBP)=1:1, acetonitrile mixing water(V:V=2:1) 30mL, Fe(OH)3 and Catechol 0.05g respectively, reaction temperature 55℃and reaction time 60 min, PTBP conversion reaches 18.5%, the selectivity to 4-TBC is 89.2%.3. In addition, the discussions of reaction mechanism showed that PTBP hydroxylation reaction with MgFe2O4 as catalyst follows free radical mechanism. The hydroxyl radical (OH) formed in reaction process is oxidant. Thus, When PTBP hydroxylation is carried out in Fe(OH)3+catechol+H2C)2 system, an active iron oxide complex is formed, the reaction mechanism is no longer abiding by free radical mechanism.