Catalytic Elimination of Oxygenated Byproducts in the Toluene Methylation Process  

作　　者：Hou Min Qi Xiaolan Zheng Junlin 

机构地区：[1]State Key Laboratory of Green Chemical Engineering and Industrial Catalysis,SINOPEC Shanghai Research Institute of Petrochemical Technology Co.,Ltd.,Shanghai 201208,China

出　　处：《China Petroleum Processing & Petrochemical Technology》2023年第2期65-73,共9页中国炼油与石油化工（英文版）

基　　金：We gratefully acknowledge the support from the National 973 Program of China(Grant No.2003CB615800).

摘　　要：Catalytic methylation of toluene with methanol is an important alternative pathway for xylene production.Previous studies have indicated that methanol always undergoes several side reactions on acidic zeolites,resulting in oxygencontaining byproducts such as dimethyl ethers,ketones,and carboxylic acids.Herein,the presence and distribution of the oxygenated compounds formed during toluene methylation were firstly examined by systematic chromatographic analysis.Plausible formation mechanisms for the various oxygenates are discussed.The most problematic byproduct is found to be acetic acid,which can lead to inferior product quality and damage downstream units.A feasible solution is presented for oxygenate removal after toluene methylation,in which acetic acid is eliminated by catalytic decomposition into low-boilingpoint acetone over a MgO catalyst.This process allows for all of the low-boiling-point oxygenates,including methanol,dimethyl ether,acetone,and butanone,to be removed from the aromatics phase,taking advantage of the temperature of the reaction effluent and standard distillation equipment.X-ray diffraction was used to characterize the crystal phase of the fresh and used MgO decarbonylation catalysts,while thermogravimetry/mass spectrometry and Fourier-transform infrared spectroscopy were applied to investigate the transformation mechanism of acetic acid over the decarbonylation catalyst.CO insertion and ketonization of acetic acid accounted for the formation and elimination of acetic acid,respectively.The combined methylation/decarbonylation process should enable the production of high-quality xylenes,an important industrial feedstock,by overcoming the main technical obstacles associated with the toluene methylation process.

关 键 词：XYLENE catalytic methylation DECARBONYLATION TOLUENE MgO catalyst 

分 类 号：TQ241.13[化学工程—有机化工] TQ426