Abstract
Lactic acid can not only be used to produce multiple chemicals, but can also be the building block for biodegradable and biocompatible polylactic acid identified as a renewable resource. As a by-product in biodiesel production, the glycerol yield increases with a rapid expansion of biodiesel. However, in the chemical and environmental fields it is still a great challenge to produce lactic acid or methyl lactate from glycerol. Herein, Sn-Beta zeolite was prepared through solid-state ion exchange (Sn-Beta SSIE) and was tested for base-free one-pot catalytic selective oxidation of glycerol into methyl lactate in methanol. The results showed that a maximum selectivity of up to 56.7% was achieved with a 36.8% conversion rate at 433 K within 4 h under an initial oxygen pressure of 0.1 MPa. In addition, the methyl lactate yield is not high because of its decomposition in the presence of oxygen. This study aims to contribute to the development of the polylactic acid industry.
Highlights
The fast development of renewable polylactic acid has greatly increased the demand for quantities of lactic acid (LA), as it offers an alternative to fossil resources and benefits the environment [1, 2]
Because too much Sn will destroy the formation of the crystal structure of Beta zeolite in the HT method, and will block the molecular sieve pore in the WI method
Sn-Beta zeolite prepared by SSIE was applied for basefree one-pot catalytic conversion of glycerol into methyl lactate (ML) in methanol
Summary
The fast development of renewable polylactic acid has greatly increased the demand for quantities of lactic acid (LA), as it offers an alternative to fossil resources and benefits the environment [1, 2]. The main route to produce LA is the biological fermentation of carbohydrates, which has many disadvantages such as complex downstream processing, low efficiency and high cost [3]. To solve these problems, an ideal choice is to produce lactic acid or methyl lactate (ML) by utilizing biomass or wastes through a one-pot chemical method [4,5,6]. Taarning et al first reported the conversion of dioxyacetone (DHA) and glyceraldehyde (GLA) into LA (90% selectivity) or ML (99% selectivity) using Sn-Beta zeolite obtained by hydrothermal synthesis [7].
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