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Solid phosphoric acid (SPA) catalysts with different carriers were prepared and used for catalytic fast pyrolysis of poplar wood to produce levoglucosenone (LGO), a valuable anhydrosugar derivative that can be used in various organic synthesis applications. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to evaluate the catalytic capabilities of these catalysts under different reaction conditions. The results indicated that SPA catalyst prepared with the SBA-15 carrier exhibited the best catalytic capability for selectively producing LGO. Both the catalytic pyrolysis temperature and catalyst-to-biomass ratio affected the pyrolytic products greatly. The maximal LGO yield reached as high as 8.2 wt% from poplar wood, obtained at the pyrolysis temperature of 300°C and the catalyst-to-biomass ratio of 1. The by-products during the catalytic pyrolysis process were mainly acetic acid (AA) and furfural (FF). In addition, the SPA catalyst possessed better catalytic capability than the liquid phosphoric acid (H 3 PO 4 ) catalyst to produce LGO.

Activated carbon (AC) prepared by chemical activation with H 3 PO 4 (named AC-P) was employed for catalytic fast pyrolysis of cellulose and biomass to selectively produce levoglucosenone (LGO). The catalytic pyrolysis behaviors and product distributions were revealed via both analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale experiments. Moreover, the performance of AC-P catalyst was compared with previously reported strong acid catalysts and other ACs prepared by different activation methods. In addition, reusability and stability of the AC-P catalyst have been examined via recycling experiments. The results indicated that the AC-P catalyst was effective for selectively preparing LGO from both cellulose and biomass and performed better than other catalysts. Among the three biomass materials (pine wood, poplar wood, and bagasse), pine wood showed the best selectivity for producing LGO. The maximal LGO yields of 18.1 and 9.1 wt % were obtained from cellulose and pine wood, respectively, in Py-GC/MS experiments under a catalyst-to-feedstock ratio of 1:3 at 300 °C, whereas the lab-scale setup obtained the highest LGO yields of 14.7 and 7.8 wt % from cellulose and pine wood with selectivities of 76.3 and 43.0%, respectively, based on organic liquid products. Furthermore, granular AC-P catalyst exhibited good reusability and stability in the recycling experiments. Stable yields of LGO above 12.5 wt % from cellulose were obtained in six consecutive runs without any regeneration of the recycled granular AC-P catalyst.

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To help understand the pyrolysis mechanism of lignin, a non-phenolic lignin dimer model compound with b-O-4 linkage, namely 1-methoxy-2-(4-methoxyphenethoxy) benzene, was prepared. Its pyrolysis mechanism was investigated by density functional theory calculations and confirmed by the analytical pyrolysis-gas chromatography/mass spectrometry experiments. Possible pyrolytic pathways were proposed and analyzed based on three initial pyrolysis mechanisms of the model compound, including the C b -O homolytic mechanism, the C a -C b homolytic mechanism and the C b -O concerted decomposition mechanism. The results indicate that the lignin dimer model compound is thermally stable at low pyrolysis temperature (300°C), whereas at moderate pyrolysis temperature (500°C), four major pyrolytic products will be generated via the initial C b -O concerted decomposition and C b -O homolysis, including the 1-methoxy-4-vinylbenzene, 2-hydroxybenzaldehyde, 1-ethyl-4-methoxybenzene and 2-methoxyphenol. Products from the C a -C b homolysis can hardly be formed, due to the high-energy barriers and limitation of the available free hydrogen atoms. Secondary cracking of the primary pyrolytic products will take place to form some light compounds, which will be enhanced with the increase in pyrolysis temperature.

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Biomass fast pyrolysis liquefaction to obtain biological oil is a mixture of water and hundreds of organic compounds, can be used as liquid fuel or chemical raw materials used in different fields. In order to increase the application value of the bio-oil, on the one hand, the biological oil can be refined, on the other hand can target specific biomass raw materials, selective control pyrolysis reaction process, thereby gaining specific high grade oil. With the improvement of catalyst preparation, a variety of new king of catalysts were introduced to the field of biomass pyrolysis. Recently, some researches had reported that some chemicals can be selectively promoted by introducing specific technology during pyrolysis process. Using this technology, chemical-riched liquid would be produced and the following purification process would be greatly simplified. Hence, developing new kind of technique with high selectivity to realize a variety of chemical preparation will be an inexorable trend in the field of biomass pyrolysis.