Abstract
Paper sludge is a solid waste by-product abundantly produced in the paper industry and contains fine minerals and lignocellulosic biomass. In this contribution, the ex-situ catalytic fast pyrolysis of paper sludge with a high mineral content of ca. 71 wt% is reported for the first time and demonstrated in a pilot-scale unit (feeding rate of 11.3 kg h−1) using a granular Na2CO3/γ-Al2O3 catalyst (loading of 650 g) to produce a high-grade bio-oil at a fast pyrolysis temperature of 475 ± 5 °C (pre-screened using a pyroprobe) and a catalytic upgrading temperature of 500 °C. Besides, > 99 wt% minerals in the paper sludge could be recovered, including paper fillers such as CaCO3 (major) and talc. The bio-oil obtained at a carbon yield of 21 C.% has a low oxygen content of 3.2 wt%, a low total acidity number of 5.2 mg KOH g−1, low H2O content of 0.7 wt%, and a high higher heating value of 40.9 MJ kg−1. It consists of value-added bio-based chemicals such as paraffins, olefins, and low molecular weight aromatics. The results demonstrate that the use of paper sludge to recover minerals and to obtain fuels and chemicals using ex-situ catalytic pyrolysis is technically feasible at a pilot plant scale, which will be of importance for the development of future bio-based economy.
Highlights
The increasing fossil energy uses and demands, as well as the aggravation of the associated environmental pollution, urge a substantial effort for the search of alternative renewable resources
To improve the efficiency of glucose conversion to HMF, the strategy of combining Lewis and Brønsted acid catalysts was extensively developed.[14−16] A typical work was reported by Davis and his co-workers,[16] where they first revealed that the Sn-Beta zeolite was effective for glucose isomerization to fructose owing to its Lewis acidic Sn4+ site, and 56.9% yield of HMF with a glucose conversion of 72% could be achieved in a 35 wt % NaCl-H2O/THF biphasic system after combining with HCl as a dehydration catalyst
The surface of the modified SAPO-34 zeolite became rougher accompanied by a decrease in structural regularity (Figure 1b−d)
Summary
The increasing fossil energy uses and demands, as well as the aggravation of the associated environmental pollution, urge a substantial effort for the search of alternative renewable resources. To improve the efficiency of glucose conversion to HMF, the strategy of combining Lewis and Brønsted acid catalysts was extensively developed.[14−16] A typical work was reported by Davis and his co-workers,[16] where they first revealed that the Sn-Beta zeolite was effective for glucose isomerization to fructose owing to its Lewis acidic Sn4+ site, and 56.9% yield of HMF with a glucose conversion of 72% could be achieved in a 35 wt % NaCl-H2O/THF biphasic system after combining with HCl as a dehydration catalyst.
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