Interlayer-expanded MWW-type zeolite catalysts with carbon filler in expanded micropores for efficient microwave heating

Recently, microwave (MW) heating has been applied to chemical reactions instead of conventional heating because heating only catalysts by MW radiation is more energy-efficient than heating reaction systems by conventional heating. However, zeolites, which are widely used as catalysts in the chemical industry, can hardly be heated by MW radiation. Here, zeolite catalysts suitable for MW heating were prepared by filling carbon in the interlayer-expanded micropores of MWW-type zeolites. The carbon in the pores was readily heated by MW radiation. When the catalyst was heated in a nitrogen stream by MW radiation at 50 W of consumed electric power, the temperature reached 450 °C for 300 s. However, the temperatures of the MWW-type zeolite and the physical mixture of the MWW-type zeolite and graphite powder were 140 °C and 260 °C, respectively. This indicated that the carbon-filled interlayer-expanded MWW was suitable for MW heating. The methylation of toluene with methanol catalyzed using a proton-type C@expanded MWW by MW heating proceeded at a lower reaction temperature, compared with that of the methylation catalyzed using the physical mixture of the MWW-type zeolite and graphite. This indicated that the carbon-incorporated catalysts were suitable for MW heating and that the internal temperature of the catalyst particles was higher than the external temperature. This enhanced the shape selectivity because the reaction preferentially proceeded inside the pores.