Reclamation Of Acid Pickling Waste:Controllable Preparation Of Nano α-Fe₂O₃ And Its Catalytic Performance In Alkylation Reaction

During the processing of iron and steel products, hydrochloric acid is usually used for removing oxide coating on the surface, resulting in a lot of pickling waste, which is mainly composed of hydrogen chloride, ferrous chloride, water and small amounts of other impurities. Discharging of waste acid directly may cause environmental pollution. In this paper, nano-iron oxide materials was prepared from acid pickling waste using nonionic surfactant polyethylene glycol(PEG-400) as dispersant and ultrasonic enhancement by the sol-gel method, as proved by scanning electron microscopy(SEM), X-ray diffraction(XRD), transmission electron microscopy(TEM), UV-vis, and inductively coupled plasma mass spectrometry(ICP-MS), respectively. The results showed that high purity(96.89%) α-Fe2O3 nanoparticles were well-crystallized with different size and morphology, mainly including a web-like structure linked by about 25 nm spherical particles(Fe-w), a nanorod with about a 45 nm width diameter(Fe-r), and daylily bud-like materials with a 50 nm width leaf(Fe-l). The effect of reaction conditions such as the solution pH and ultrasonic time on the preparation of nano iron oxide was studied. The optimal reaction conditions are obtained: polyethylene glycol as a dispersant, reaction temperature 85 oC, reaction time 8h, calcined temperature 500 oC, calcined time 2h.The catalytic performance of nano α-Fe2O3 for benzylation of aniline with benzyl chloride to yield N-benzyl aniline was explored. The results showed that the nano α-Fe2O3 exhibited excellent activity with TOF of 65.1 h-1. The effect of several reaction conditions, such as reaction temperature, time, molar ratio of aniline to benzyl chloride and amount of catalyst on the benzylation was investigated. The optimal operating conditions were obtained: reaction temperature 60 oC, reaction time 1 h, molar ratio of phenol to benzyl chloride 4:1, amount of nano-iron oxide 0.1 g. Under these conditions, the conversion of benzyl chloride was 99.69%, the selectivity to N-benzyl aniline was 92.54%. The catalyst could be recycled at least three times without appreciable loss of catalytic activity.Simultaneously, the catalytic performance of nano α-Fe2O3 for benzylation of phenol with benzyl chloride to yield 2-benzylphenol and 4-benzylphenol was also explored. The results showed that the nano α-Fe2O3 exhibited excellent activity with TOF of 33.3 h-1. The effect of several reaction conditions, such as reaction temperature, time, molar ratio of phenol to Benzyl chloride and amount of catalyst on the benzylation was investigated. The optimal operating conditions was obtained: reaction temperature 60 oC, reaction time 1 h, molar ratio of phenol to benzyl chloride 3:1, amount of nano-iron oxide 0.1 g. Under these conditions, the conversion of benzyl chloride was 97.09%, the selectivity to 2-benzylphenol was 42.85% and the selectivity to 4-benzylphenol was 42.16%. However, the catalyst could be recycled at least three times without appreciable loss of catalytic activity.Furthermore, the proposed mechanism of the benzylation of aniline and phenol with benzyl chloride was investigated according to the reports on literatures and our experimental results.