What are the catalytic conversion technologies for the preparation of 5-Hydroxymethylfurfural (HMF)?

5-Hydroxymethylfurfural (HMF) is a high-value platform compound converted from biomass sugars in the frontier field of green chemistry and biomass conversion, and is leading a revolution from renewable resources to fine chemicals. In the preparation of HMF, catalytic conversion technology is the core link, which determines the conversion efficiency, product selectivity and production cost. The following will discuss in depth several major catalytic conversion technologies used in the preparation of HMF.

1. Acid catalysis technology
Acid catalysis is one of the most classic and widely used methods for the preparation of HMF. By using inorganic acids (such as hydrochloric acid, sulfuric acid) or organic acids (such as formic acid, acetic acid) as catalysts, the dehydration reaction of hexose (mainly fructose) is promoted under appropriate conditions to generate HMF. This method is simple to operate, but there are problems such as equipment corrosion, difficulty in product separation and waste liquid treatment. In recent years, solid acid catalysts such as sulfonic acid functionalized carbon materials, metal oxides, etc. have gradually attracted attention because of their easy recovery, reusability and environmental friendliness.

2. Alkaline catalysis technology
Different from acid catalysis, alkaline catalysis technology uses alkaline conditions to promote the isomerization and dehydration reaction of fructose to produce HMF. This method usually has a high conversion rate and selectivity, but the alkaline environment easily leads to further degradation of HMF and reduces the product yield. The development of efficient and stable alkaline catalysts and the optimization of reaction conditions have become the research focus in this field.

3. Bifunctional catalysis technology
In order to overcome the limitations of a single catalyst, researchers have proposed a bifunctional catalytic strategy. This technology integrates two or more active sites with different catalytic functions into the same catalyst to achieve a one-pot method for fructose isomerization and dehydration reactions. Bifunctional catalysts can improve the yield and selectivity of HMF, simplify the process flow, and reduce costs. Some metal oxide-supported acid-base bifunctional catalysts show excellent performance in the preparation of HMF.

4. Biocatalysis technology
Biocatalysis technology has shown great potential in the preparation of HMF with its mild reaction conditions, high selectivity and environmental friendliness. By using microorganisms or enzymes as catalysts, the conversion of fructose to HMF can be achieved at room temperature and pressure. However, the stability and reaction rate of biocatalysts are still the main bottlenecks restricting their industrial application. At present, researchers are working on the transformation and optimization of biocatalysts through genetic engineering, protein engineering and other means.

There are many catalytic conversion technologies in HMF preparation, each of which has its unique advantages and challenges. With the continuous progress and innovation of science and technology, more efficient, environmentally friendly and economical catalytic conversion technologies will be developed in the future development, which will promote the HMF industry to a higher level. This will also promote the effective utilization and sustainable development of biomass resources, and bring more green and sustainable energy and chemical solutions to human society.