Synthesis of non-symmetrical alkyl carbonates from alcohols and DMC over the nanocrystalline ZSM-5 zeolite
A novel heterogeneous acid (nanocrystalline ZSM-5) catalyzed carboxymethylation of alcohols to non-symmetrical alkyl carbonates using DMC has been realized. Nanocrystalline ZSM-5 (NZSM-5) with a crystal size of 20–30 nm was synthesized by hydrothermal crystallization. The synthesized NZSM-5 was verified by X-ray diffraction, Fourier transformation infrared spectroscopy and solid state NMR. The morphology of NZSM-5 was confirmed by transmission electron microscopy and scanning electron microscopy, which revealed the formation of aggregates of the zeolite (100–200 nm) made by the nano-sized (20–30 nm) NZSM-5 particle packing. The physicochemical properties of NZSM-5 were measured by nitrogen adsorption and temperature programmed desorption of ammonia, which indicate the surface area of 465 m2 g−1 and the acidity of 0.936 mmol g−1. The present protocol provides an attractive approach to a variety of non-symmetrical alkyl carbonates in high yields. The catalyst was efficiently recycled for up to 5 consecutive cycles. This method broadens the series of possible utilization for DMC in green chemistry.