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Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution of 5 wt.% of glycerol, obtaining gas and liquid products. The catalysts were prepared by the co-precipitation method, calcined at different temperatures, and characterized before and after their use by several techniques (XRD, ICP-OES, H2-TPR, NH3-TPD, CO2-TPD, FESEM, and N2-physisorption). Increasing the calcination temperature and adding Ca decreased the surface area from 256 to 188 m2/g, and its value after the APR changed depending on the feedstock used. The properties of the acid and basic sites of the catalysts influenced the H2 yield also depending on the feed used. The Ni crystallite was between 6 and 20 nm. In general, the incorporation of Ca into Ni-based catalysts and the increase of the calcination temperature improved H2 production, obtaining 188 mg H2/mol C fed during the APR of refined crude glycerol over Ni/AlCa-675 catalyst, which was calcined at 675 °C. This is a promising result from the point of view of enhancing the economic viability of biodiesel.

Currently, most plastic waste stems from packaging materials, with a large proportion of this waste either discarded by incineration or used to derive fuel. Accordingly, there is growing interest in the use of pyrolysis to chemically recycle non-recyclable (i.e., via mechanical means) plastic waste into petrochemical feedstock. This comparative study compared pyrolysis characteristics of two types of reactors, namely fixed and fluidized bed reactors. Kinetic analysis for pyrolysis of SRF was also performed. Based on the kinetic analysis of the pyrolytic reactions using differential and integral methods applied to the TGA results, it was seen that the activation energy was lower in the initial stage of pyrolysis. This trend can be mainly attributed to the initial decomposition of PP components, which was subsequently followed by the decomposition of PE. From the kinetic analysis, the activation energy corresponding to the rate of pyrolysis reaction conversion was obtained. In conclusion, pyrolysis carried out using the fluidized bed reactor resulted in a more active decomposition of SRF. The relatively superior performance of this reactor can be attributed to the increased mass and heat transfer effects caused by fluidizing gases, which result in greater gas yields. Regarding the characteristics of liquid products generated during pyrolysis, it was seen that the hydrogen content in the liquid products obtained from the fluidized bed reactor decreased, leading to the formation of oils with higher molecular weights and higher C/H ratios, because the pyrolysis of SRF in the fluidized bed reactor progressed more rapidly than that in the fixed bed reactor.

In this study, we develop physics-informed neural networks (PINNs) to solve an isothermal fixed-bed (IFB) model for catalytic CO2 methanation. The PINN includes a feed-forward artificial neural network (FF-ANN) and physics-informed constraints, such as governing equations, boundary conditions, and reaction kinetics. The most effective PINN structure consists of 5–7 hidden layers, 256 neurons per layer, and a hyperbolic tangent (tanh) activation function. The forward PINN model solves the plug-flow reactor model of the IFB, whereas the inverse PINN model reveals an unknown effectiveness factor involved in the reaction kinetics. The forward PINN shows excellent extrapolation performance with an accuracy of 88.1% when concentrations outside the training domain are predicted using only one-sixth of the entire domain. The inverse PINN model identifies an unknown effectiveness factor with an error of 0.3%, even for a small number of observation datasets (e.g., 20 sets). These results suggest that forward and inverse PINNs can be used in the solution and system identification of fixed-bed models with chemical reaction kinetics.

Artificial photosynthesis offers a promising strategy to produce hydrogen peroxide (H 2 O 2 )—an environmentally friendly oxidant and a clean fuel. However, the low activity and selectivity of the two-electron oxygen reduction reaction (ORR) in the photocatalytic process greatly restricts the H 2 O 2 production efficiency. Here we show a robust antimony single-atom photocatalyst (Sb-SAPC, single Sb atoms dispersed on carbon nitride) for the synthesis of H 2 O 2 in a simple water and oxygen mixture under visible light irradiation. An apparent quantum yield of 17.6% at 420 nm together with a solar-to-chemical conversion efficiency of 0.61% for H 2 O 2 synthesis was achieved. On the basis of time-dependent density function theory calculations, isotopic experiments and advanced spectroscopic characterizations, the photocatalytic performance is ascribed to the notably promoted two-electron ORR by forming μ -peroxide at the Sb sites and highly concentrated holes at the neighbouring N atoms. The in situ generated O 2 via water oxidation is rapidly consumed by ORR, leading to boosted overall reaction kinetics. Hydrogen peroxide is an interesting target for artificial photosynthesis, although its actual production via the two-electron oxygen reduction reaction remains limited. Now, a carbon nitride-supported antimony single atom photocatalyst has been developed with a superior performance for this process.

Gasification of biomass in fixed bed gasifiers is a well-known technology, with its origins dating back to the beginning of 20th century. It is a technology with good prospects, in terms of small scale, decentralized power co-generation. However, the understanding of the process is still not fully developed. Therefore, assessment of the changes in the design of a gasifier is typically performed with extensive prototyping stage, thus introducing significant cost. This study presents experimental results of gasification of a single pellet and bed of particles of raw and torrefied wood. The procedure can be used for obtaining design parameters of a fixed bed gasifier. Results of two suits of experiments, namely pyrolysis and CO2 gasification are presented. Moreover, results of pyrolysis of pellets are compared against a numerical model, developed for thermally thick particles. Pyrolysis time, predicted by model, was in good agreement with experimental results, despite some differences in the time when half of the initial mass was converted. Conversion times for CO2 gasification were much longer, despite higher temperature of the process, indicating importance of the reduction reactions. Overall, the obtained results could be helpful in developing a complete model of gasification of thermally thick particles in a fixed bed.

A plug‐flow fixed‐bed cell for synchrotron powder X‐ray diffraction (PXRD) and X‐ray absorption fine structure (XAFS) idoneous for the study of heterogeneous catalysts at high temperature, pressure and under gas flow is designed, constructed and demonstrated. The operating conditions up to 1000°C and 50 bar are ensured by a set of mass flow controllers, pressure regulators and two infra‐red lamps that constitute a robust and ultra‐fast heating and cooling method. The performance of the system and cell for carbon dioxide hydrogenation reactions under specified temperatures, gas flows and pressures is demonstrated both for PXRD and XAFS at the P02.1 (PXRD) and the P64 (XAFS) beamlines of the Deutsches Elektronen‐Synchrotron (DESY). A plug‐flow fixed‐bed cell for synchrotron powder X‐ray diffraction (PXRD) and X‐ray absorption fine‐structure (XAFS) idoneous for the study of heterogeneous catalysts at high temperature, pressure and under gas flow is designed, constructed and demonstrated. The operating conditions up to 1000°C and 50 bar are ensured by a set of mass flow controllers, pressure regulators and two infra‐red lamps that constitute a robust and ultra‐fast heating and cooling method.

The objective of the present study was to carry out a technical study of the gasification of almond shells and husks at different temperatures and, subsequently, an economic analysis for the in situ installation of a decentralized unit to produce electricity, through a syngas generator, that would overcome the use of fossil fuels used in this agroindustry. The gasification tests were carried out at three different temperatures (700, 750 and 800 °C) and the results for the tests carried out were as follows: a 50:50 mixture of almond husks and shells was found to have a lower heating value of value of 6.4 MJ/Nm3, a flow rate of 187.3 Nm3/h, a syngas yield of 1.9 Nm3/kg, cold gas efficiency of 68.9% and carbon conversion efficiency of 70.2%. Based on all the assumptions, a 100 kg/h (100 kWh) installation was proposed, located near the raw material processing industries studied, for an economic analysis. The technical–economic analysis indicated that the project was economically viable, under current market conditions, with a calculated net present value of k€204.3, an internal rate of return of 20.84% and a payback period of 5.7 years. It was concluded that thermal gasification is a perfectly suitable technology for the recovery of raw materials of lignocellulosic origin, presenting very interesting data in terms of economic viability for the fixed bed gasification system.

This study investigated the removal of a typical organic pollutant methylene blue (MB) dye from wastewater by a prepared mesoporous SBA-15 adsorbent in a continuous adsorption system (fixed-bed column). The structural and textural properties of the SBA-15 adsorbent were determined using different characterization techniques. The adsorption of continuous system experiments assessed the bed height effect, initial concentration, and flow rate on a breakthrough curve. The kinetic constants and breakthrough curves were obtained using the Thomas and Yan models. The breakthrough results revealed that SBA-15 has an excellent adsorption efficiency for use in the continuous adsorption system. The findings explain that MB removal achieved the maximum uptake (84 mg/g) at 6 cm of bed height, 0.5 mL/min of flow rate, and 30 mg/L initial concentration of MB. SBA-15 can be efficiently regenerated by calcination and re-employed 5 times in a fixed-bed system without a significant loss in its adsorption capacity of MB from MB solutions. As a result, SBA-15 was determined as the appropriate media to be adsorbent for MB. This study suggests that the prepared SBA-15 is feasible to use effectively for MB removal from the wastewater.

This work focuses on the impact of carrier gas on the quantity and quality of pyrolytic products received from intermediate pyrolysis of the brewer’s spent grain. In this study, three types of carrier gases were tested: argon, nitrogen, and carbon dioxide at three temperatures of 500, 600, and 700 °C. On the basis of the process conditions, the yield of products was determined. The ultimate analysis of the char was performed, and for selected chars, the combustion properties were determined. Gas chromatography of the organic fraction of oil was performed, and the compounds were determined. Additionally, microscale investigation of the spent grain pyrolysis was performed by thermogravimetric analysis. The results showed that there were no significant differences in product yields in various atmospheres. Char yield changed only with temperature from 28% at 500 °C up to 19% at 700 °C. According to ultimate analysis, the char from CO2 pyrolysis was approximately 2% richer in carbon and this fact did not influence on the combustion properties of the char. The oil fraction was characterized mainly by acids with a maximum content of 68% at 600 °C in an argon atmosphere and the acid concentration depended on the carrier gas as follows line: Ar > N2 > CO2.

Energy recovery from biomass by gasification technology has attracted significant interest because it satisfies a key requirement of environmental sustainability by producing near zero emissions. Though it is not a new technology, studies on its integrated process simulation and analysis are limited, in particular for municipal solid waste (MSW) gasification. This paper develops an integrated fixed bed gasifier model of biomass gasification using the Advanced System for Process ENngineering (Aspen) Plus software for its performance analysis. A computational model was developed on the basis of Gibbs free energy minimization. The model is validated with experimental data of MSW and food waste gasification available in the literature. A reasonable agreement between measured and predicted syngas composition was found. Using the validated model, the effects of operating conditions, namely air-fuel ratio and gasifier temperature, on syngas production are studied. Performance analyses have been done for four different feedstocks, namely wood, coffee bean husks, green wastes and MSWs. The ultimate and proximate analysis data for each feedstock was used for model development. It was found that operating parameters have a significant influence on syngas composition. An air-fuel ratio of 0.3 and gasifier temperature of 700 °C provides optimum performance for a fixed bed gasifier for MSWs, wood wastes, green wastes and coffee bean husks. The developed model can be useful for gasification of other biomasses (e.g., food wastes, rice husks, poultry wastes and sugarcane bagasse) to predict the syngas composition. Therefore, the study provides an integrated gasification model which can be used for different biomass feedstocks.