The pore-opening size of HZSM-5 was finely controlled by the chemical vapor deposition of Si(OCH~3)~4. After calcination a thin layer of silica was deposited on the external surface and narrowed the pore- opening of the zeolite effectively. A series of HZSM-5 zeolite samples with different amount of silica deposition (SiHZSM-5) were prepared and characterized by IR spectroscopy, NH~3-TPD and adsorption measurements. It was found that after deposition and calcination the zeolite framework structure, pore volume and internal surface properties were essentially unaltered. The shape-selective adsorption of xylene and cresol isomers on SiHZSM-5 was investigated. The separation of p-isomer from mixed isomers of xylene or cresol can be achieved successfully by using SiHZSM-5 with proper silica deposition extent, because the larger m-isomer molecules are refrained from adsorption due to the narrowed pore-opening while the total adsorption capacity of the zeolite keeps at a reasonably high level.

Key words: CRESOL, INFRARED SPECTROPHOTOMETRY, DIMETHYLBENZENE, SILICON OXIDE, STRUCTURE AND PROPERTY CORRELATION, VAPOR PHASE DEPOSITION, HZSM-5