Abstract
Background2,6-dimethylphenol (2,6-DMP) is a product of phenol methylation, especially important for the plastics industry. The process of phenol methylation in the gas phase is strongly exothermic. In order to ensure good temperature equalization in the catalyst bed, the process was carried out using a catalyst in the form of a fluidized bed - in particular, the commercial iron-chromium catalyst TZC-3/1.ResultsSynthesis of 2,6-dimethylphenol from phenol and methanol in fluidized bed of iron-chromium catalyst was carried out and the fluidization of the catalyst was examined. Stable state of fluidized bed of iron-chromium catalyst was achieved. The measured velocities allowed to determine the minimum flow of reactants, ensuring introduction of the catalyst bed in the reactor into the state of fluidization. Due to a high content of o-cresol in products of 2,6-dimethylphenol synthesis, circulation in the technological node was proposed. A series of syntheses with variable amount of o-cresol in the feedstock allowed to determine the parameters of stationary states.ConclusionA stable work of technological node with o-cresol circulation is possible in the temperature range of350-380°C, and o-cresolin/phenolin molar ratio of more than 0.48. Synthesis of 2,6-DMP over the iron-chromium catalyst is characterized by more than 90% degree of phenol conversion. Moreover, the O-alkylation did not occur (which was confirmed by GC-MS analysis). By applying o-cresol circulation in the 2,6-DMP process, selectivity of more than 85% degree of 2,6-DMP was achieved. The participation levels of by-products: 2,4-DMP and 2,4,6-TMP were low. In the optimal conditions based on the highest yield of 2,6-DMP achieved in the technological node applying o-cresol circulation, there are 2%mol. of 2,4-DMP and 6%mol. of 2,4,6-TMP in the final mixture, whereas 2,4,6-TMP can be useful as a chain stopper and polymer’s molar mass regulator during the polymerization of 2,6-DMP.
Highlights
IntroductionA wide range of applications of products of phenol methylation makes that the process of their preparation the subject of numerous studies [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]
The purpose of this study is to investigate the influence of process parameters on the synthesis of 2,6-dimethylphenol, and to identify the main and simultaneous reactions, as well as to develop a method for on-line monitoring of the reaction extents and to define the parameters of a stable work of 2,6-DMP node with a o-cresol circulation
The problem of high o-cresol content in the products of the 2,6-dimethylphenol synthesis can be solved by development of a technological node with o-cresol circulating in the system
Summary
A wide range of applications of products of phenol methylation makes that the process of their preparation the subject of numerous studies [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. Strong bacteriostatic [24], bacteriocidal [25] and fungicidal properties [26] result in methyl-substituted derivatives of phenol being used as preservatives in the food industry [27], antimicrobial agents in the pharmaceutical industry [28], in decontamination and disinfection agents, such as Lysol, creolin [29] and in the production pesticides [30]. 2,6-dimethylphenol (2,6-DMP) is an important product of phenol methylation, especially for the plastics industry. The oxidative polymerization of this derivative of phenol leads to the formation of polyphenylene oxide (PPO) [31], possessing excellent mechanical, dielectric and chemical properties [32]. Apart from the production of PPO, 2,6-dimethylphenol is used in the production of medicaments [36,37], pigments [38] and antioxidants [39]
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