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Raina Sharma, Speaker at Catalysis Conferences
Institute of Nano Science and Technology, India
Title : An investigation of the phosphate functionalization, kinetics, and mechanistic aspects of phosphorylated sporopollenin as sustainable catalyst for selective 5-hydroxymethylfurfural formation in water


The tremendous use of non-renewable fossil fuels causes global problems such as CO2 emission, hence it is imperative to switch to a renewable biomass resource. Nevertheless, utilizing biomass directly as a fuel poses significant challenges due to its intricate structure and low energy density. However, an alternative strategy involves the utilization of platform chemicals i.e., 5-HMF derived from cellulose, a degraded product of lignocellulosic biomass, which can be further processed for commercialization into liquid fuels, solvents, polymers, and bioplastics. Metal-free Brønsted acid catalysts in aqueous solution are recognized for their tendency to trigger unwanted side reactions, such as polymerization and formic acid synthesis, thereby posing challenges in the synthesis of 5-hydroxymethylfurfural (5-HMF) from C6 sugars. Consequently, there is significant interest in water-tolerant organic heterogeneous catalysts that exhibit high selectivity towards 5-HMF. In this investigation, sporopollenin (exine), a natural biopolymer biomass, serves as a heterogeneous support. We present, for the first time, the use of orthophosphoric acid to remove protoplasmic content from spores, resulting in empty sporopollenin (ESP-Phos) functionalized with mono- and di-phosphoesters (41:59). This material proves effective as a selective and sustainable catalyst for glucose conversion into 5-HMF. Notably, activation at 200°C leads to a significant increase in the phosphodiester ratio of ESP-Phos200 (29:71), observed through 31P NMR analysis. This augmentation correlates with enhanced activity (yield of 92%) and selectivity (96%) for 5-HMF synthesis. DFT calculations reveal stronger interactions between glucose and di-phosphoesters (–20.58 kcal mol–1) compared to mono-phosphoesters (–17.32 kcal mol–1), underscoring the synergistic effect of phosphodiesters in expediting 5-HMF catalysis. Kinetic analysis indicates a pseudo-first-order reaction mechanism. ESP-Phos200 under optimized conditions (180 oC, 12 h) increased the glucose to HMF formation rate 23-fold (rate constant k = 0.0046 min–1) higher than humin formation rate. Isotopic labelling, 13C NMR, and DFT calculations collectively support a glucose dehydration mechanism over fructose isomerization for ESP-Phos200. Although humin polymer deposition leads to catalyst deactivation after multiple cycles (up to 4 cycles), subsequent calcination of ESP-phos200 at 200°C restores its activity. The catalyst and methodology employed in this study for 5-HMF synthesis offer environmentally friendly, greener, and sustainable alternatives with promising potential for large-scale production.

Audience Takeaway Notes:

  • The study illuminates the catalytic potential of di-phosphoester Brønsted acid-based waste biomass biopolymer, namely sporopollenin, which exhibits water tolerance and thermal stability.
  • As sporopollenin, a natural biopolymer, comprises various functional groups, its further derivatization for specific catalytic reactions becomes feasible. Therefore, this research aids scientists in the field of heterogeneous catalysis in developing sustainable catalysts utilizing sporopollenin as an efficient, cheaper, and environmentally greener heterogeneous support.
  • Our investigation delves into how different types of phosphorylated groups can exhibit varying catalytic activities, offering insights for tailoring phosphorylated active sites based on specific catalytic reaction requirements.
  • This advancement holds promise for the practical and scalable production of 5-HMF in greener conditions, thereby advancing the field of sustainable catalysis.


Raina Sharma was born in Delhi, India, in 1997. She completed her BSc degree (Life Sciences) in 2017 from Delhi University and her MSc degree (Chemistry) in 2019 from Central University of Punjab, India (CUPB). Currently, she is doing PhD (joined in 2020) under the supervision of Prof. G. Jayamurugan at the Institute of Nano Science and Technology, Mohali, India (INST). Her research interests focus on the heterogenous catalytic biomass conversion to value-added chemicals. Since the beginning of her PhD, she has published 5 articles with her team, and others are in preparation for submission soon.