Conversion of waste to high-value products by pyrolysis is a suitable and harmless disposal technology for the abundant waste generated in the tobacco industry. To determine the optimum operational parameters for biomass pyrolytic polygeneration using tobacco waste as the feedstock, the product characteristics and nitrogen transformation were investigated from 250 to 950 °C. The highest low calorific values of gas and char were 13 MJ/m 3 at 750 °C and 15 MJ/kg at 450 °C, respectively. The optimum operating temperature recommended for biomass pyrolytic polygeneration of tobacco waste is 650 °C when the three products (char, oil, and gas) are balanced. The char formation process is divided into three stages: degradation (250−450 °C), reforming (450−650 °C), and condensation (>650 °C). Three types of N-containing structures are formed in chars: pyridinic N, pyrrolic/pyridine N, and quaternary N. Pyridinic N is dominant at low temperatures, whereas quaternary N becomes dominant at high temperatures. N-containing volatiles escape from chars with increasing temperature and are primarily found in oil below 550 °C and in gas above 650 °C. N-containing compounds are the major components (up to 45%) in the organic portion of oil, with pyridines, pyrroles, and piperidines as the dominant forms. In the gas product, NH 3 and HCN are the major N-containing compounds released above 650 °C. This study is expected to be beneficial for the comprehensive utilization of tobacco waste.

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Co-doping of heteroatoms into the support of metal-supported catalysts is a prevalent method to improve the catalytic performance by adjusting metal–support interactions. This paper investigated the catalytic performances of Ru supported on biomass-derived char (Ru@Char), N-doped char (Ru@N-Char), and N,P-co-doped char (Ru@NP-Char) in the emerging lignin-first depolymerization for both poplar (hardwood) and pine (softwood) samples, with an emphasis on the production of phenolic monomers. Various characterizations of the prepared catalysts showed that the codoping of N,P not only facilitated the formation of micropores in the char but also introduced weak and moderate acid sites. Furthermore, the sizes of Ru nanoparticles on the codoped char became smaller, and the proportion of metallic Ru species was increased, resulting from electron transfer from Ru to the codoped char. The yields of the phenolic monomers from poplar and pine over Ru@NP-Char were as high as 57.98 and 17.53 wt % Klason lignin, respectively, which were improved by factors of 1.4–2.5 in comparison to Ru@Char and Ru@N-Char. Full delignification during the depolymerization of both poplar and pine was also achieved over Ru@NP-Char.

To explore the influence of Fe-, Zr-, and Co-modified zeolites on bio-oil characteristics, the catalytic fast pyrolysis of cellulose combined with sawdust and cotton stalk was investigated using a pyrolyzer reactor. The results indicate that Feloaded zeolite favors naphthalene and 1-methylnaphthalene formation through catalytic deoxygenation and hydrocarbon formation. Zr-modified zeolite enhances the contents of ketones and aromatics with higher benzene and p-xylene selectivity. Co leads to higher production of anhydrous sugars but suppresses the progress of aromatics evolution, whereas the selectivity of Co for toluene and p-xylene is the highest. A comprehensive reaction network is also proposed to describe the cellulose catalytic pyrolysis process. Considering the catalytic adaptability, catalytic pyrolysis of typical biomass samples with Fe/HZSM-5 was investigated. The total contents of aromatic hydrocarbons are in the following order: sawdust > cellulose > cotton stalk. The selectivities of naphthalene and 2-methylnaphthalene in cellulose are the highest, while the selectivities of benzene and its derivatives in sawdust and cotton stalk are higher.