Data di Pubblicazione:
2018
Citazione:
Process design and cost evaluation for H2 and ethylene production from bioethanol / G. Ramis, A. Tripodi, M. Compagnoni, I.G. Rossetti. ((Intervento presentato al 4. convegno International Conference on Catalysis for Biorefineries tenutosi a Lione nel 2017.
Abstract:
1. Introduction
The steam reforming of bioethanol gained growing attention as a pathway towards renewable hydrogen production. Bioethanol is being produced mainly from the fermentation of “first generation” raw materials, e.g. sugar cane and corn, which compete with the feed and food chain. However, also second generation production processes are becoming available, producing bioethanol from lignocellulosic biomass. During the last 10 years our group focused on process development for the production of hydrogen from second generation bioethanol, which was kindly supplied by the Biochemtex group through the Proesa technology. More recently we also turned our attention to ethylene production through ethanol dehydration under unconventional reaction conditions1. For both applications we focused on the use of diluted bioethanol solutions, i.e. obtainable after simple flash separation of excess water and fermentation residua (in which ethanol concentration is ca. 50 wt%). This substrate is particularly interesting for steam reforming since it already contains the water amount that should be co-fed in the steam reformer. On the other hand heavy dehydration of ethanol (commonly accomplished after a flash unit with a rectification columns and molecular sieves) is an energy waste in this case. For ethylene production cofeeding water may inhibit the thermodynamic conversion, but it helps improving catalyst life preventing coking. So, for both applications, the possibility to exploit diluted bioethanol solutions is intriguing. Therefore, in this work we explored the effect of possible impurities contained in raw bioethanol (S-containing compounds, acids and higher alcohols) on catalyst durability for both reactions. Then we designed and simulated the performance of a fully integrated and optimized plant for hydrogen production. One layout was dedicated to centralized hydrogen production, sized to transform 40kton/year bioethanol (Biochemtex plant capacity installed in Crescentino (VC), Italy). For this plant we performed a full economic assessment of the plant. The other layout was designed for distributed micro-cogeneration, so that a fuel processor with 6 integrated reactors for hydrogen production and purification was coupled with a fuel cell. The plant capacity was set to achieve 5 kWelectrical + 5 kWthermal energy output2.
2. Experimental
Home prepared catalysts were tested for bioethanol steam reforming (ESR) and ethylene production using diluted bioethanol solutions: 50 wt% and 90 wt%, compared with 99.9 vol% ethanol. The catalysts were 10 wt% Ni/ZrO2/9 wt% K2O, prepared by flame pyrolysis in our lab, while for ethanol dehydration we used an H-BEA zeolite, with tuned Si/Al = 17 atomic ratio, kindly supplied by Prof. S. Dzwigaj (Pierre et Marie Curie University, Paris).
ESR was carried out at atmospheric pressure, temperature between 300 and 625°C and with overall water/ethanol ratio = 3 mol/mol. Ethanol dehydration reaction was performed at atmospheric pressure, temperature ranging from 300 to 500 °C and water/ethanol ratio from 0 to 3 mol/mol.
The materials were characterized by N2 adsorption-desorption, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and temperature programmed reduction/oxidation (TPR/TPO) and FT-IR of adsorbed pyridine for acidity. Spent samples were analysed through TPO, microRaman, FESEM and TEM.
Process simulation was carried out using the Aspen Plus process simulator, under steady state conditions. The economic evaluation was performed through the Aspen Economic Evaluator tool.
3. Results and discussion
The effect of impurities concentration for both reactions was negligible. This allowed to exploit the potential of 50 wt% second generation bioethanol as poorly expensive
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
G. Ramis, A. Tripodi, M. Compagnoni, I.G. Rossetti
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