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An Ab Initio Study of N_2O Decomposition on mgo catalyst

Chinese Chemical Letters 1998年第6期9卷 583-586页

作者： Xin LU Xin XU Nan Qin WANG and Qian Er ZHANG(State Key Laboratory for Physical Chemistry of Solid Surfaces, Institute of Physical Chemistry,Department of Chemistry, Xiamen University, Xiamen 361005) State Key Lab. Phys. Chem. Solid S. Institute of Physical Chemistry Xiamen University Xiamen 361005 China

Ab initio calculations based on density functional theory have been used to study thedecompsition of N_2O on mgo. The reaction is predicted to occur on O_3c and O_(4c) atoms, but not onO_(5c) atoms, with an activation barrier of 25-27 kcal/mol, in agreement with the experimental valueof 35 kcal/mol. Natural bond orbital analysis shows that the reaction leaves O ad-atoms on thosesurface O anions to form a peroxide-like 'O^2_(2-)' species. The )O-O bond stretching frequency ispredicted to be in the range from 820 cm(-1) to 825 cm(-1).

关键词： Ab initio calculation N_2O decomposition mgo catalyst

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Catalytic Elimination of Oxygenated Byproducts in the Toluene Methylation Process

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China Petroleum Processing & Petrochemical Technology 2023年第2期25卷 65-73页

作者： Hou Min Qi Xiaolan Zheng Junlin State Key Laboratory of Green Chemical Engineering and Industrial Catalysis SINOPEC Shanghai Research Institute of Petrochemical Technology Co.Ltd.Shanghai 201208China

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

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