Hydrogen production from cheese whey by catalytic steam reforming: Preliminary study using lactose as a model compound

Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. Before dealing with real cheese whey, this work addresses the production of a rich hydrogen gas from lactose (the largest organic constituent of this waste) by catalytic steam reforming. This reforming process has been theoretically and experimentally studied. The theoretical study examines the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and N2 (0-80 cm3 STP/min) and liquid flow (0.1-0.5 mL/min) rates on the thermodynamic composition of the gas. The results show that the temperature and lactose concentration exerted the greatest influence on the thermodynamics. The experimental study, conducted in a fixed bed reactor using a Ni-based catalyst, considers the effect of the temperature (300-600 °C), lactose concentration (1-10 wt.%) and spatial time (4-16 g catalyst min/g lactose) on the global lactose conversion, product distribution on a carbon basis (gas, liquid and solid) and the compositions of the gas and liquid phases. Complete lactose conversion was achieved under all the experimental conditions. The carbon converted into gas, liquid and solid was 2-97%, 0-66% and 0-94%, respectively. The gas phase was made up of a mixture of H2 (0-70 vol.%), CO2 (20-70 vol.%), CO (2-34 vol.%) and CH4 (0-3 vol.%). The liquid phase consisted of a mixture of aldehydes, ketones, carboxylic acids, sugars, furans, alcohols and phenols. Optimal conditions for cheese whey valorisation were sought considering the energetic aspects of the process. Using a lactose concentration similar to that of cheese whey (5.5 wt.%), maxima for the CC gas (88%) and the proportion of H2 (67 vol.%) in the gas together with a carbon-free liquid stream can be achieved at 586 °C using a spatial time of 16 g catalyst min/g lactose. Theoretically, the combustion of 20% of this gas provides the energy necessary for the process enabling the transformation of 68% of the carbon present in the initial effluent into a H2 rich gas (67 vol.%) with a global H2 yield of 16 mol H2/mol lactose. In a real case it would be necessary to increase the amount of gas combusted to compensate for heat losses

An insight into the separation of 1, 2-propanediol, ethylene glycol, acetol and glycerol from an aqueous solution by adsorption on activated carbon

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1, 2-propanediol, acetol, ethylene glycol and glycerol onto activated carbon were determined by batch adsorption experiments. These isotherms were fitted slightly better to the Freundlich equation than to the Langmuir equation. Acetol is the compound with the highest adsorption at concentrations smaller than 1 M. Properties of the adsorbate such as the -OH group number, chain length, molecular size and dipole moment, besides characteristics of the adsorbent such as the surface area, oxygen and ash content, are considered to explain the observed results. Moreover, adsorption experiments were performed with mixtures of compounds and it was determined that the molar amount adsorbed is less than predicted from the adsorption isotherms of the individual compounds treated separately. In addition, the influence of the activated carbon thermal pretreatment temperature on the adsorption capacity has been studied, the optimum being 800¿C. An analysis of the influence of the activated carbon characteristics showed that the most important parameters are the total pore volume and the ash content. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Effect of biodiesel-derived impurities (acetic acid, methanol and potassium hydroxide) on the aqueous phase reforming of glycerol

This work analyses the influence of three biodiesel-derived impurities (CH3OH, CH3COOH and KOH) on the aqueous phase reforming of glycerol at 220 °C and 44 bar using a Ni-La/Al2O3 catalyst. The experiments were planed according to a factorial 2k design and analysed by means of an analysis of variance (ANOVA) test to identify the effect of each impurity and all possible binary and ternary combinations. The presence of CH3OH decreased the glycerol conversion, while CH3COOH and KOH decreased and increased the gas production, respectively. Catalyst deactivation took place under acidic conditions due to the loss of part of the active phase of the catalyst through leaching. The gas phase was made up of H2, CO2, CO and CH4. KOH exerted the greatest influence on the gas composition, increasing H2 production due to the greater gas production and the lower H2 consumption in the hydrogenation reactions. The liquid phase was made up of aldehydes, monohydric and polyhydric alcohols, C3 and C4 ketones and esters. CH3OH increased the proportion of monohydric alcohols, while CH3COOH promoted dehydration reactions, leading to an increase in the relative amount of C3-ketones

Cheese whey valorisation: Production of valuable gaseous and liquid chemicals from lactose by aqueous phase reforming

Cheese effluent management has become an important issue owing to its high biochemical oxygen demand and chemical oxygen demand values. Given this scenario, this work addresses the valorisation of lactose (the largest organic constituent of this waste) by aqueous phase reforming, analysing the influence of the most important operating variables (temperature, pressure, lactose concentration and mass of catalyst/lactose mass flow rate ratio) as well as optimising the process for the production of either gaseous or liquid value-added chemicals. The carbon converted into gas, liquid and solid products varied as follows: 5–41%, 33–97% and 0–59%, respectively. The gas phase was made up of a mixture of H2 (8–58 vol.%), CO2 (33–85 vol.%), CO (0–15 vol.%) and CH4 (0–14 vol.%). The liquid phase consisted of a mixture of aldehydes: 0–11%, carboxylic acids: 0–22%, monohydric alcohols: 0–23%, polyhydric-alcohols: 0–48%, C3-ketones: 4–100%, C4-ketones: 0–18%, cyclic-ketones: 0–15% and furans: 0–85%. H2 production is favoured at high pressure, elevated temperature, employing a high amount of catalyst and a concentrated lactose solution. Liquid production is preferential using diluted lactose solutions. At high pressure, the production of C3-ketones is preferential using a high temperature and a low amount of catalyst, while a medium temperature and a high amount of catalyst favours the production of furans. The production of alcohols is preferential using medium temperature and pressure and a low amount of catalyst

Study of ni/al-fe catalyst stability in the aqueous phase hydrogenolysis of glycerol

The present work studied the stability and reusability of Ni/Al-Fe catalyst in the aqueous phase hydrogenolysis of glycerol without external hydrogen addition. The catalyst based on 28 molar % of Ni with 3/1 molar ratio of Al/Fe was prepared through co-precipitation. This catalyst presented the best performance in our last study which compares several Ni/Al-Fe catalysts with different molar ratios of Al/Fe. To see the influence of the pressurized water on the physicochemical characteristics of Ni/Al-Fe catalyst, a test of up to 9 h has been carried out. Fresh and used catalysts were characterized by various techniques: X-ray Diffraction (XRD), N2-physisorption, field emission scanning electron microscopy (FESEM) and STEM. Glycerol conversion and carbon yield to gases and liquids did not vary significantly when compared at 3 h and 9 h. Furthermore, the morphology of the catalyst remains stable after continuous recycling under severe hydrothermal conditions. The nickel rich phase of the catalyst, which was determined by XRD and scanning transmission electron microscopy (STEM) techniques, showed a stable size after 9 h under reaction

Influence of the Ni-Co/Al-Mg catalyst loading in the continuous aqueous phase reforming of the bio-oil aqueous fraction

The effect of catalyst loading in the Aqueous Phase Reforming (APR) of bio-oil aqueous fraction has been studied with a Ni-Co/Al-Mg coprecipitated catalyst. Because of the high content of water in the bio-oil aqueous fraction, APR could be a useful process to convert this fraction into valuable products. Experiments of APR with continuous feeding of aqueous solution of acetol, butanol and acetic acid as the only compound, together with a simulated and a real aqueous fraction of bio-oil, were carried out. Liquid products in the liquid effluent of the APR model compounds were quantified and the reaction pathways were revised. The increase of catalyst loading produced an increase of gas production and a gas with higher alkanes content. Acetol was the compound with the highest reactivity while the conversion of acetic acid was very low. The presence of acetic acid in the feed caused catalyst deactivation

Combustion characteristics of hydrochar and pyrochar derived from digested sewage sludge

In this paper, hydrochars and pyrochars were produced at 260 ºC under different residence times (2 and 4 h) using anaerobic digested sewage sludge (SSL) as initial feedstock. The effect of reaction time on the fuel properties of hydrochars and pyrochars was evaluated. Moreover, the combustion kinetics of raw SSL and the derived pyrochars and hydrochars without coal blending were determined at two different air flows (20 and 90 mL/min) and compared. In the same conditions, the yield of hydrochar was significantly lower than that of pyrochar, confirming the different reaction pathways followed in each process. The results showed hydrochars have lower carbon recovery and energy yield than pyrochars, making the latter more suitable for energy purposes. The thermogravimetric combustion study showed that both thermochemical treatments increased the ignition temperature but decreased the burnout temperature, which results in higher stability during handling and storage. However, raw SSL is better for combustion than hydrochar according to the combustibility index. In addition, the kinetic study showed that the activation energy of the combustion of biochars, especially pyrochar, is lower than that of raw SSL, which is advantageous for their combustion

Valorización de biomasa: pirólisis de biomasa con un alto rendimiento a líquido y posterior reformado catalítico de éste en busca de un gas con un alto contenido en H2

Los líquidos de pirólisis de biomasa son una mezcla compleja de un gran número decompuestos obtenidos tras someter a la biomasa a un proceso de pirólisis rápida. Mediante laadición de agua sobre estos líquidos se obtienen dos fases, una fracción insoluble que contienelos compuestos derivados de la lignina y una fracción soluble o fracción acuosa, consistente enuna mezcla de ácidos carboxílicos, aldehídos, cetonas, alcoholes, azúcares, oligómeros de bajamasa molecular y carbohidratos complejos. Las propiedades químicas de estas fraccionesacuosas dependen de los líquidos de pirólisis utilizados, dependientes a su vez de la fuente debiomasa y de la tecnología y condiciones de pirólisis. Una alternativa prometedora para laproducción de un gas con un alto contenido en H2 (hasta un 70% v/v) consiste en el reformadocatalítico de la fracción acuosa estos líquidos. En este contexto, en el presente trabajo gracias ala financiación recibida por parte del MICINN (ENE-2010-18985) y a la ayuda FPI (BES-2011-044856) concedida a Javier Remón, se ha estudiado el efecto de la tecnología de pirólisis,el catalizador y contacto gás-sólido durante la reacción de reformado mediante un diseño deexperimentos factorial. Con respecto al catalizador, se obtuvo la siguiente estabilidad:NiCoAlMg>NiAlMg=NiCuAlMg. La fracción acuosa alimentada influyó significativamente enel proceso, obteniéndose el mayor rendimiento a H2 con la fracción acuosa obtenida en elreactor de cono rotatorio. El tipo de reactor tiene una influencia significativa, lográndose unamenor desactivación en lecho fluidizado