There are a number of efficient methods available for biomass conversion into chemicals and fuels. One such method is catalytic hydrolysis of cellulose using solid acid catalysts. This article discusses the testing of the catalytic activity of a novel silica catalyst synthesized by an evaporation-induced self-assembly method (EISA) for cellulose conversion to glucose by catalytic selective hydrolysis.
The silica catalyst showed superior catalytic activity to other oxides, including Al2O3, TiO2, and ZrO2, which are produced using the same method. Under hydrothermal conditions, it converted 73.3% cellulose and yielded 50.1% glucose without using hydrogen gas (Table 1).
Table 1. Cellulose conversion and yield of products over different catalysts at 433K for 12h
| Entry |
Catalyst |
Conversion (%) |
Yield (%) |
| Cellohexose |
Callopentaose |
Cellotetraose |
Cellotriose |
Cellobiose |
Glucose |
Unknown products |
| 1 |
Blank |
4.5 |
1.3 |
- |
- |
0.3 |
0.2 |
- |
2.7 |
| 2 |
ZrO2b |
15.8 |
- |
- |
- |
0.1 |
0.3 |
9.0 |
6.4 |
| 3 |
TiO2b |
15.4 |
1.9 |
- |
0.8 |
1.0 |
2.0 |
2.2 |
7.5 |
| 4 |
Al2O3b |
17.0 |
5.3 |
- |
1.2 |
0.1 |
1.3 |
0.1 |
9.0 |
| 5 |
SBA-15 |
4.0 |
1.2 |
- |
0.2 |
0.3 |
0.5 |
1.4 |
0.4 |
| 6 |
HZSM-5 (25) |
12.8 |
- |
1.9 |
1.5 |
1.1 |
0.8 |
1.6 |
5.9 |
| 7 |
HZSM-5 (38) |
12.3 |
- |
1.9 |
1.4 |
1.1 |
0.8 |
1.8 |
5.3 |
| 8 |
SiO2 |
73.3 |
1.8 |
- |
1.0 |
1.8 |
4.0 |
50.1 |
14.6 |
a. Reaction conditions: 12 hr reaction time, 10 mL H2O, 0.05 g cellulose, 0.15 g catalyst.
b. The preparation of catalysts were carried out under the identical experimental conditions to that of entry 8.
Instrumentation and Experimental Results
The study used the HPR-20 QIC Real time Gas Analyzer, a mass spectrometer from Hiden Analytical, for temperature-programmed desorption of ammonia (NH3-TPD) to determine the acidic properties of the samples of interest. The conventional acid–base titration method was used to estimate the amount of acid sites.
Figure 1 presents the results of NH3-TPD, showing the much stronger acidic properties of the SiO2 sample when compared to other samples. Moreover, the acid amount of the SiO2 sample was much higher than other samples.
From the textural properties (BET), it has been revealed that the average pore diameter of the SiO2 sample is 3.512nm, which is suitable enough to facilitate oligosaccharide transportation, thereby improving the probability of interaction of oligosaccharides with acid sites.
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Figure 1. Temperature-programmed desorption of ammonia (NH3-TPD) profiles for various samples of (a) ZrO2, (b) TiO2, (c) Al2O3, (d) HZSM-5(25), (e) HZSM-5(38), (f) SBA-15, and (g) SiO2 (EISA).
Conclusion
From the results, it has been shown that the novel silica catalyst has a suitable pore diameter and strong acidity and the synergistic effect between these characteristics of the silica catalyst causes it to exhibit a high catalytic activity. Furthermore, the catalyst was stable during recycle catalytic runs. Recyclability is another advantage of this silica catalyst.
Reference
Project Summary by: WANG Huayu, ZHANG Changbin, HE Hong, WANG Lian State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 China
Paper Reference: Wang H., Zhang C., He H., Wang L. (2012) “Glucose production from hydrolysis of cellulose over a novel silica catalyst under hydrothermal conditions” Journal of Environmental Sciences 24 (3), 473-478
Hiden Product: HPR-20 QIC Real time Gas Analyzer
This information has been sourced, reviewed and adapted from materials provided by Hiden Analytical.
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