Recent Progress in the Steam Reforming of Bio-Oil for Hydrogen Production: A Review of Operating Parameters, Catalytic Systems and Technological Innovations

Distinct coking depth in steam reforming of oxygen-containing organics and hydrocarbons

In steam reforming of organics in a fixed-bed reactor, catalyst particles in varied location of catalyst bed will experience different history of contacting with reactants/products. This may affect accumulation of coke in varied section of catalyst bed, which are investigated in steam reforming of some typical oxygen-containing organics (acetic acid, acetone and ethanol) and hydrocarbons (n-hexane and toluene) in a fixed-bed reactor with double layers of catalyst bed for investigating coking depth at 650 °C over Ni/KIT-6 catalyst in this study. The results indicated that the intermediates derived from the oxygen-containing organics in steam reforming could hardly penetrate the upper-layer catalyst to form coke in the lower-layer catalyst. In converse, they reacted quickly over the upper-layer catalyst via gasification or coking, forming coke almost exclusively in the upper-layer catalyst. The hydrocarbon intermediates from the dissociation of hexane or toluene could easily penetrate and reach the lower-layer catalyst to form even more coke therein than the upper-layer catalyst. The characterization showed that the insufficient gasification of *C_xH_y species led to their aggregation/integration to form more aromatic coke, especially from n-hexane. The aromatic-ring containing intermediates from toluene tended to integrate with *OH species to form ketones that further involved in coking, forming coke of less aromatic nature than that from n-hexane. Steam reforming of oxygen-containing organics also produced oxygen-containing intermediates and coke of higher aliphatic nature, lower carbon to hydrogen (C/H) ratio, lower crystallinity and thermal stability.

Assessment of the Possibilities for the Use of Selected Waste in Terms of Biogas Yield and Further Use of Its Digestate in Agriculture

The utilization of municipal waste and sewage sludge as a source of energy is technically very difficult due to high variability of their physical and chemical properties. The aim of this study was to evaluate the efficiency of the conversion of biomass contained in the whitewater fraction of municipal waste and sewage sludge by means of methanogenesis. The second objective was to assess the chemical composition of the digestate in the context of its use for fertilizer purposes. The whitewater fraction of municipal waste and sewage sludge was subjected to methanogenesis under static experimental conditions, according to DIM DIN 38414 methodology. The methanogenesis of concentrated substrates used in agricultural biogas plants was taken as a reference to evaluate the efficiency of the process. The organic fraction of the municipal waste was characterized by approximately 30% lower value of the soluble COD, with a comparable level of total COD compared to other materials. The total biogas yield, i.e., 404 dm³ per 1 kg of dry weight of the batch, was measured in the facility with sewage sludge. In COD value, this is 0.232 dm³·g O₂ COD. In the case of corn, these values were, respectively, 324 dm³ and 0.193, and for the organic sub-sieve fraction of municipal waste, 287 dm³·kg⁻¹ dw or 0.178 dm³·g O₂ COD, respectively. The type of fermented material did not affect the intensity of biogas production. The maximum level of biogas production occurred between the 13th and 15th day of the process. The digestate obtained in the process of methanogenesis of corn silage and the organic fraction of municipal waste was characterized by good parameters in terms of possible use for fertilization purposes.