Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite
Round 1
Reviewer 1 Report
The article is written on an urgent topic! I have no significant comments on the work, so I believe that it can be published in this form!
Author Response
Thank you very much for kindly review our manuscript.
Reviewer 2 Report
This study investigated the glucose conversion of 5-HM5 with acidic catalyst. The catalyst is quite new and the study is well-performed. The writing is also quite clear. Some minor comments are:
- Fig. 2C (TEM) is not included in the figure. Please check.
- Please add the original NH3 TPD curves in the SI.
Author Response
This study investigated the glucose conversion of 5-HM5 with acidic catalyst. The catalyst is quite new and the study is well-performed. The writing is also quite clear.
Some minor comments are:
Comment (1): Fig. 2C (TEM) is not included in the figure. Please check.
Response to Comment (1):
Thank you for your comment. On Page 7, we added the TEM images of representative Nb/HMS and Nb/MCS catalysts in the revised manuscript according to the comment already.
Comment (2): Please add the original NH3-TPD curves in the SI.
Response to Comment (2):
Thank you for your suggestion. We added the original NH3-TPD profiles as Fig. S3 in the revised SI.
Reviewer 3 Report
The authors showed the synthesis of Nb/MCS catalysts and their application in HMF synthesis. The catalyst synthesis method is very interesting since it was used a renewable elastomer (natural rubber) for the preparation of polymer/silica nanocomposites. As Thailand is one of the world leading producers of natural rubber it seems a very useful version for the production of value-added chemicals. The HMF is produced via one-pot glucose conversion in a biphasic solvent. The 10-Nb/MCS material achieved a superior glucose conversion (up to 93.2 %) and HMF yield (up to 57.5 %) when compared to the pure silica HMS-supported Nb catalyst. The catalyst also showed good stability. Therefore, I do recommend the publication of this article after minor revisions.
# Questions and suggestions:
- Have the authors tried to use the method for other sugars? The application in other sugars could improve the work.
- Have the pressure effects been studied?
- The use of reaction illustrations would improve the article.
- Have other solvents been tested?
# Corrections:
-Line 190- 0.36 g- what is the concentration?
-Lines 218-215 text with different sizes.
-Lines 251-252 text with different sizes.
-Table 2- The concentration is missing.
-The sustainable advantages of the method should be highlighted in the conclusion to improve the article.
-Reference 12: The page numbers are missing.
-Reference 15: The page numbers are missing.
-Reference 16: The page numbers are missing.
Author Response
The authors showed the synthesis of Nb/MCS catalysts and their application in HMF synthesis. The catalyst synthesis method is very interesting since it was used a renewable elastomer (natural rubber) for the preparation of polymer/silica nanocomposites. As Thailand is one of the world leading producers of natural rubber it seems a very useful version for the production of value-added chemicals. The HMF is produced via one-pot glucose conversion in a biphasic solvent. The 10-Nb/MCS material achieved a superior glucose conversion (up to 93.2 %) and HMF yield (up to 57.5 %) when compared to the pure silica HMS-supported Nb catalyst. The catalyst also showed good stability. Therefore, I do recommend the publication of this article after minor revisions.
Comment (1): Have the authors tried to use the method for other sugars? The application in other sugars could improve the work.
Response to Comment (1):
We have not tried other sugars in this work. The use of fructose as substrate for HMF synthesis provides the highest HMF yield. However, using fructose as substrate is not economical due to its low availability and high cost. According to the previous reports, the highest HMF yield was obtained when using glucose as substrate among different types of sugars (sucrose, cellobiose, insulin, and xylose).
- Zhang, Y.; Wang, J.; Li, X.; Liu, X.; Xia, Y.; Hu, B.; Lu, G.; Wang, Y. Direct conversion of biomass-derived carbohydrates to 5-hydroxymethylfurural over water-tolerant niobium-based catalysts. Fuel 2015, 139, 301-307, doi:https://doi.org/10.1016/ j.fuel.2014.08.047.
- Li, X.; Xia, Q.; Nguyen, V.C.; Peng, K.; Liu, X.; Essayem, N.; Wang, Y. High yield production of HMF from carbohydrates over silica–alumina composite catalysts. Catalysis Science & Technology 2016, 6, 7586-7596, doi:10.1039/C6CY01628F.
Furthermore, using xylose as substrate promoted the furfural formation more than HMF formation. Thus, glucose being considered a more desirable substrate for the synthesis of HMF.
Comment (2): Have the pressure effects been studied?
Response to Comment (2):
Yes, we also studied the effects of reaction pressure on the glucose conversion and HMF yield. The N2 pressure will keep both solvent in liquid phase. As shown in figure below, the glucose conversion increased around 10%, and the HMF yield increased from 25.8% to 32.6% when increasing the atmosphere pressure to 10 bar. Moreover, pressure did not affect the humins yield (constant at 41%). Therefore, the reaction pressure of 10 bar was used for HMF synthesis in this work.
Effect of pressure on glucose conversion, HMF yield and humins yield. (Reaction conditions: catalyst amount, 0.1 g; glucose concentration, 0.07 M; solvent volume (1: 2 v/v water saturated with NaCl: THF), 30 mL; temperature, 190 °C; time, 1 h).
Comment (3): The use of reaction illustrations would improve the article.
Response to Comment (3):
Thank you for your suggestion. On Page 11, we added the reaction illustration as Scheme 1 according to your suggestion.
Comment (4): Have other solvents been tested?
Response to Comment (4):
We have not tried other solvents in this work because biphasic system provided the glucose conversion and HMF yield better than pure aqueous system. It is because a large amount of water is not favorable for dehydration of glucose and can promote the side reactions. The use of biphasic system has a positive effect on the fructose dehydration to HMF. Because of low solubility of HMF in aqueous phase, the generated HMF product is gradually transferred into the upper organic phase to avoid the side reaction. For the biphasic system, the highest yield of HMF was obtained in the THF-H2O biphasic system as compared with other solvents (MIBK, 1-4,dioxane, toluene, 2-butanal and acetone) as demonstrated in the references below. Therefore, the use of THF/H2O biphasic reaction system is promising and provides a step further towards achieving an efficient reaction medium for this study.
- Li, X.; Xia, Q.; Nguyen, V.C.; Peng, K.; Liu, X.; Essayem, N.; Wang, Y. High yield production of HMF from carbohydrates over silica–alumina composite catalysts. Catalysis Science & Technology 2016, 6, 7586-7596, doi:10.1039/C6CY01628F.
- Hong, Z.; Xinxin, Y.; Rui, Y.; Xiaohui, L.; Yong, G.; Yanqin, W. Direct conversion of glucose to 5-hydroxymethylfurfural over zirconium phosphate catalyst in a biphasic system. China Petroleum Processing and Petrochemical Technology 2018, 20, 6-14.
Comment (5): Line 190- 0.36 g- what is the concentration?
Response to Comment (5):
Thank you for your comment. The concentration of glucose in the reaction was 0.07 M. We added this information in the revised manuscript according to the comment already.
Comment (6): Lines 218-215 text with different sizes.
Response to Comment (6):
Thank you for your comment. We revised the manuscript according to the comments already.
Comment (7): Lines 251-252 text with different sizes.
Response to Comment (7):
Thank you for your comment. We revised the manuscript according to the comment already.
Comment (8): Table 2- The concentration is missing.
Response to Comment (8):
Thank you for your comment. We revised the manuscript according to the comment already.
Comment (9): The sustainable advantages of the method should be highlighted in the conclusion to improve the article.
Response to Comment (9):
Thank you for your comment. In the Conclusions (Page 14), we highlighted the potential application of natural rubber to the MCS preparation and the practical use of 10-Nb/MCS in the catalytic conversion of glucose into HMF at a high concentration of glucose substrate.
Comment (10): Reference 12: The page numbers are missing.
Response to Comment (10):
Thank you for your comment. We revised the manuscript according to the comment already.
Comment (11): Reference 15: The page numbers are missing.
Response to Comment (11):
Thank you for your comment. We revised the manuscript according to the comment already.
Comment (12): Reference 16: The page numbers are missing.
Response to Comment (12):
Thank you for your comment. We revised the manuscript according to the comment already.
