Pyrolysis liquids from lignocellulosic biomass have the potential to be used as a feed for aromatics such as benzene, toluene, and xylenes (BTX) using catalytic upgrading with zeolites. We here report an experimental study on the conversion of various pyrolysis oil fractions to determine the most suitable one for BTX synthesis. For this purpose, the pyrolysis liquid was fractionated using several extraction/distillation steps to give four fractions with different chemical compositions. The fractions were analyzed in detail using nuclear magnetic resonance spectroscopy, elemental analysis, gas chromatography-mass spectroscopy, thermogravimetric analysis, Karl-Fischer titration, and gel permeation chromatography. Catalytic pyrolysis experiments were carried out using a tandem microreactor with H-ZSM-5 (23) as the catalyst. The highest BTX yield of 24% (on a carbon and dry basis) was obtained using the fractions enriched in phenolics, whereas all others gave far lower yields (4.4-9%, on a carbon and dry basis). Correlations were established between the chemical composition of the feed fraction and the BTX yield. These findings support the concept of a pyrolysis biorefinery, where the pyrolysis liquid is separated into well-defined fractions before further dedicated catalytic conversions to biobased chemicals and biofuels using tailored catalysts.
Sustainable production of aromatics, especially benzene, toluene and xylenes (BTX), is essential considering their broad applications and the current global transition away from crude oil utilization. Aromatization of lower olefins, particularly ethene and propene, offers great potential if they are derived from more circular alternative carbon feedstocks such as biomass and waste plastics. This work aims to identify the preferred olefin feed, ethene or propene, for BTX production in a fixed-bed reactor. A commercial H-ZSM-5 (Si/Al = 23) catalyst was used as a reference catalyst, as well as a Ga-ZSM-5 catalyst, prepared by Ga ion-exchange of the H-ZSM-5 catalyst. At 773 K, 1 bar, 45 vol % olefin, 6.75 h−1, propene aromatization over the Ga-ZSM-5 catalyst exhibited higher BTX selectivity of 55 % and resulted in slower catalyst deactivation compared to ethene aromatization.
A process for the prepn. of arom. compds. from a feed stream contg. biomass or mixts. of biomass, the process comprising: a) subjecting a feed stream contg. biomass or mixts. of biomass to a process to afford a conversion product comprising arom. compds.; b) recovering the arom. compds. from said conversion product; c) sepg. a higher mol. wt. fraction comprising polyarom. hydrocarbons (PAH) from a lower mol. wt. fraction comprising benzene, toluene and xylene (BTX) by distn.; d) reducing at least part of said higher mol. wt. fraction to obtain a reduced fraction comprising polycyclic aliphatics (PCA); and e) subjecting the higher mol. wt. fraction obtained in step c), the reduced fraction obtained in step d), or a mixt. thereof, to a process to obtain lower mol. wt. aroms. (BTX). [on SciFinder(R)]
Paper sludge contains papermaking mineral additives and fibers, which could be reused or recycled, thus enhancing the circularity. One of the promising technologies is the fast pyrolysis of paper sludge, which is capable of recovering > 99 wt.% of the fine minerals in the paper sludge and also affording a bio-liquid. The fine minerals (e.g., ‘circular’ CaCO3) can be reused as filler in consumer products thereby reducing the required primary resources. However, the bio-liquid has a lower quality compared to fossil fuels, and only a limited application, e.g., for heat generation, has been applied. This could be significantly improved by catalytic upgrading of the fast pyrolysis vapor, known as an ex-situ catalytic pyrolysis approach. We have recently found that a high-quality bio-oil (mainly ‘bio-based’ paraffins and low-molecular-weight aromatics, carbon yield of 21%, and HHV of 41.1 MJ kg-1) was produced (Chem. Eng. J., 420 (2021), 129714). Nevertheless, catalyst deactivation occurred after a few hours’ of reaction. As such, catalyst stability and regenerability are of research interest and also of high relevance for industrial implementation. This project aims to study the potential of the add-on catalytic upgrading step to the industrial fast pyrolysis of paper sludge process. One important performance metric for sustainable catalysis in the industry is the level of catalyst consumption (kgcat tprod-1) for catalytic pyrolysis of paper sludge. Another important research topic is to establish the correlation between yield and selectivity of the bio-chemicals and the catalyst characteristics. For this, different types of catalysts (e.g., FCC-type E-Cat) will be tested and several reaction-regeneration cycles will be performed. These studies will determine under which conditions catalytic fast pyrolysis of paper sludge is technically and economically viable.
