The catalytic conversion of pure glycerol to bio-aromatics (bio-BTX) over an un-modified H-ZSM-5 (SiO2/Al2O3 molar ratio of 23) via an ex-situ catalytic pyrolysis approach in a continuous tandem-micro reactor at a scale of 1 g glycerol h−1 was investigated. A BTX peak carbon yield of 28.1 ± 0.2 % was obtained at a pyrolysis temperature of 400 °C, catalytic upgrading temperature of 500 °C, atmospheric pressure and a WHSV of 1 h−1. About 70 % of the bound oxygen in glycerol was converted to water. The latter was mainly formed in the catalytic upgrading unit (70 %), though conversion of glycerol to other oxygenates with water formation was also observed in the pyrolysis unit. Catalyst deactivation occurs at a time scale of hours and is mainly due to coke deposition (12.0 wt.%) on the catalyst surface. An oxidative regeneration procedure to remove coke was applied and 5 cycles of reaction-regeneration were performed successfully, though a drop in activity was observed after each cycle due to irreversible catalyst deactivation. Characterization of the fresh, deactivated and regenerated catalysts by various techniques revealed dealumination of the H-ZSM-5 framework and resulted in a dramatic decrease in Brønsted acidity of the catalyst. Dealumination mainly occurred in the catalytic upgrading reactor and to a by far lesser extent during catalyst regeneration. This information is relevant for a better understanding of the process on a molecular level but also for scale-up studies, e.g. for the design of pilot plants.@en

The use of H-ZSM-5 with various binders (Al2O3, SiO2, and kaolinite, 10 wt% on catalyst formulation) for the catalytic conversion of glycerol to bio-based aromatics (GTA) was investigated in a continuous bench-scale unit at a pyrolysis temperature of 450 °C, catalytic upgrading temperature of 500 °C, WHSV of pure glycerol of 1 h−1, and atmospheric pressure, and their performance was compared to H-ZSM-5 (SiO2/Al2O3 molar ratio of 28). The latter gave a peak BTX carbon yield of ca. 31.1C.%, a life-time of ca. 220 min, and a total BTX productivity of ca. 312 mg BTX g−1H-ZSM-5. The introduction of binders affects catalyst performance, which is the most profound and promising for the H-ZSM-5/Al2O3 catalyst. It shows a prolonged catalyst life-time of ca. 320 min and a higher total BTX productivity of ca. 518 mg BTX g−1H-ZSM-5, compared to the H-ZSM-5 without a binder. Catalyst characterization studies show that the addition of the binder does not have a major effect on the specific surface area, total pore volume, and total acidity. Other relevant properties were affected, though, such as micropore volume (SiO2), a reduced Brønsted acidity (Al2O3, and SiO2), and reduced crystallinity (SiO2). Coke formation causes severe catalyst deactivation, ultimately leading to an inactive catalyst for BTX formation. Catalyst characterization studies after an oxidative regeneration showed that the textural properties of the regenerated catalysts were close to those of the original catalysts. However, some dealumination of H-ZSM-5 occurs, resulting in decreased crystallinity and acidity, causing irreversible deactivation, which needs attention in future catalyst development studies.@en

The catalytic conversion of glycerol to aromatics (GTA, e.g., benzene, toluene, and xylenes, BTX) over a shaped H-ZSM-5/Al2O3 (60/40 wt%) catalyst was investigated in a continuous fixed-bed reactor to study the addition of the Al2O3 binder in the catalyst formulation on catalyst performance. The experiments were performed under N2 at 550 °C, a WHSV of glycerol (pure) of 1 h−1, and atmospheric pressure. The spent H-ZSM-5/Al2O3 catalysts were reused after an oxidative regeneration at 680 °C and in total 5 reaction-regeneration cycles were performed. Catalyst characterization studies show that the addition of the Al2O3 binder does not affect the surface area and crystallinity of the formulation, but increases the total pore volume (mesopores in particular) and total acidity (Lewis acidity in particular). The H-ZSM-5/Al2O3 (60/40 wt%) catalyst shows a considerably prolonged catalyst life-time (8.5 vs. 6.5 h for H-ZSM-5), resulting in a significant increase in the total BTX productivity (710 vs. 556 mg g−1 H-ZSM-5). Besides, the addition of the Al2O3 binder retards irreversible deactivation. For instance, after 3 regenerations, catalyst performance is comparable to the fresh one. However, after 4 regenerations, some irreversible catalyst deactivation occurs, associated with a reduction in total pore volume, crystallinity, and acidity (Brønsted acidity in particular), and meso-porosity of the Al2O3 binder. This study shows that both the stability and reusability of H-ZSM-5-based catalysts for GTA are remarkably enhanced when using a suitable binder.@en