# Sn- and Mo-Modified Sulfonated Carbons: Properties and Evaluation as Catalysts for Fructose Conversion in Water and DMSO

## TL;DR

This paper studies how modifying sulfonated carbon materials with tin and molybdenum affects their ability to convert fructose into useful products like 5-HMF and organic acids.

## Contribution

The study introduces Sn- and Mo-modified sulfonated carbons as efficient heterogeneous catalysts for fructose conversion.

## Key findings

- CSn3Mo3 achieved the highest fructose conversion rate of 92.1% after 6 hours.
- Mo incorporation significantly improved catalytic performance compared to Sn alone.
- Lewis acid sites were crucial for forming intermediates like lactic acid and pyruvaldehyde.

## Abstract

Sulfonated carbon-based materials produced from residual
glycerol
from biodiesel were modified with metallic species (Sn and Mo) to
modulate their acidic properties. The materials C, CSn3, CMo3, and
CSn3Mo3 presented surface areas of 46.8, 29.3, 67.7, and 43.8 m2 g–1, respectively. The presence of Sn and
Mo, which impart Lewis acidity to the systems, can be evidenced by
ICP-OES and XRD, while the presence of groups acting as Brønsted
acids is clearly observed through FTIR. Their application as heterogeneous
catalysts for fructose conversion in water or DMSO revealed that varying
the Sn content had a minimal effect on the conversion rates. However,
since the CSn3 system stood out for presenting slightly better performance
despite having the lowest Sn content among the tested materials (conversion
of 41.8% after 6 h), it was chosen to be modified with Mo. The incorporation
of Mo into the materials significantly improved the conversion rates,
reaching 84.9% for CMo3 and 92.1% for CSn3Mo3 after 6 h. This suggests
that the nature of the acidic sites present in the materials played
a more critical role in the reaction efficiency than their textural
properties. For systems modified with Mo, the reaction produced not
only 5-HMF but also intermediates of the retro-aldol pathway (lactic
acid (AL), pyruvaldehyde (PYR), and glyceraldehyde (GAA), highlighting
the importance of Lewis acid sites in the formation of these species.
Additionally, organic acids, such as levulinic acid (LEV) and formic
acid (AF), were also detected. In the reuse tests, the observed loss
of catalytic activity was attributed to a reduction in the number
of Brønsted acid sites and the formation of humins during fructose
conversion.