Fixed-bed Reactor Experiments Research Articles

Assessing bioenergy prospects of algal biomass and yard waste using an integrated hydrothermal carbonization and pyrolysis (HTC–PY): A detailed emission–to–ash characterization via diverse hyphenated analytical techniques and modelling strategies

Hydrothermal carbonization (HTC) presents a promising method for converting carbonaceous waste into renewable fuels, facilitating energy recovery. This study focuses on the HTC pretreatment of microalgae (Chlorella sorokiniana) and yard waste, examining their physicochemical structural changes, component migration, and potential for valorization via integrated HTC and pyrolysis processes. HTC notably enhances the carbon content while reducing oxygen and nitrogen levels in these feedstocks, producing a clean solid fuel with high energy density. The study investigates the pyrolytic behavior of hydrochars and their blends using different analytical techniques, kinetic modeling, and fixed–bed reactor experiments. The blends with 90% and 70% of microalgae hydrochar (CSH) exhibited the most significant synergistic effects during co–pyrolysis, evident in its devolatilization behaviors and reduced activation energies. Integrating artificial neural networks and response surface methodology models facilitated optimization of pyrolysis parameters and accurate prediction of bio–oil, biochar, and gas yields. The analytical techniques enabled characterization of pyrolysis products, revealing notable changes in bio–oil and biochar compositions, suggesting potential enhancements. The study comprehensively evaluates the HTC–pyrolysis approach’s potential for converting microalgae and lignocellulosic biomass into eco–friendly biofuels for industrial applications.

N-N self-inhibition effect of aromatic N-heterocyclic compounds on NiWS supported γ-Al2O3 hydrotreating catalyst

The reason for high-difficulty nitrogen removal of aromatic N-heterocyclic compounds in petroleum fractions was investigated from the main thought of “NiWS property - Reaction behavior - DFT calculation”. The properties of the used catalyst were characterized by a series of techniques with the aim of providing the basis for model construction in the DFT calculations. The kinetic experiments in fixed-bed reactor revealed that although 1,2,3,4-tetrahydroquinoline (THQ1) and decahydroquinoline (DHQ), o-ethylaniline (OEA) exhibited relatively high yields in the HDN reaction of quinoline and indole respectively, they were all able to show high conversions and HDN rates when reacted as feedstocks alone. The study of product normalizations in the reaction system of the mixed feedstocks demonstrated that the difficulty of conversion of THQ1 and DHQ in quinoline HDN was mainly due to the inhibition effect of quinoline feedstock. While in the HDN of indole, the presence of the intermediate product OEA was the main factor for the low conversion of indole. This phenomenon of inhibition originating from within the molecular reaction network was proposed as N-N self-inhibition effect for the first time. The DFT calculations suggested that the inhibition of quinoline on THQ1 could be attributed to the adsorption advantage of quinoline, while the inhibition on DHQ was mainly due to the steric hindrance effect of DHQ itself. And the inhibition effect of OEA on indole can be mainly attributed to its greater nucleophilicity and stronger adsorption ability on the active sites compared with IND.

Thermally Modified Palygorskite Usage as Adsorbent in Fixed-Bed Reactor for High Concentration NH4+-N Removal and Further Application as N-Fertilizer in Hydroponic Cultivation.

Palygorskite sample (Pal) underwent thermal treatment at 400 °C (T-Pal) to be used as adsorbent for the removal of 200 mg NH4+-N/L from artificial solution. After thermal treatment, the sample was characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). For NH4+-N removal, T-Pal was added as a bed matrix in fixed-bed reactor experiments and the effect of flow rate was determined. It was indicated that with the flow rate increase from 10 mL/min to 50 mL/min, fewer liters of the solution were purified, rendering a longer residual time of interactions, which is optimal for NH4+-N removal from T-Pal. The maximum removed amount was calculated at 978 mg NH4+-N (qtotal), suggesting T-Pal is a promising ammonium adsorbent. The data of kinetic experiments were applied to Clark, Yoon–Nelson, and Thomas kinetic models, with Clark having the best fit, highlighting a heterogenous adsorption. At the end of kinetic experiments, T-Pal applied in hydroponic cultivations and presented a sufficient release rate, which was found utilizable for saturated T-Pal usage as N fertilizer that satisfactory results were deemed concerning lettuces characteristics and growth.

The reaction characteristics and mechanism of pine sawdust chemical-looping gasification based on CoFe2O4 oxygen carrier

Biomass chemical-looping gasification (BCLG) is a promising technology for high quality syngas production. CoFe2O4 with good redox stability and synergistically enhanced performance is considered as a better oxygen carrier. Herein, the gasification characteristic and mechanism between pine sawdust and CoFe2O4 were studied by using the thermodynamic calculation, thermogravimetric analysis (TGA) and fixed bed reactor experiments. Thermodynamic calculation reveals that the oxygen carrier to pine sawdust ratio, H2O volume fraction and reaction temperature of 0.08, 50%, and 900 °C, respectively, could be optimal for obtaining syngas with high quality and biomass conversion efficiency. CoFe2O4 can provide lattice oxygen for pine sawdust gasification and accelerate the carbon conversion rate of pine sawdust. The existence of Co in CoFe2O4 can synergistically improve the activity of Fe3+ and promote the further reduction of Fe3+ to Fe0. Experimental results verify that pine sawdust gasification process with an oxygen carrier to pine sawdust ratio of 0.08, reaction temperature of 900 °C, and H2O volume fraction of 50% has the highest syngas quality and biomass conversion. After five redox cycles, CoFe2O4 still maintains good reactivity and redox stability. These results can offer useful information for the utilization of biomass energy and can be used to improve the BCLG process.

Kinetic studies in pyrolysis of garden waste in the context of downdraft gasification: Experiments and modeling

The disposal and management of dry leaves litter (biomass) from roads and gardens in urban areas is a challenging task. It is beneficial to use this waste as an energy source in thermal applications through pyrolysis and gasification. Downdraft gasifier is one such promising reactor that can be employed to achieve this task in a decentralized manner. A distinct pyrolysis zone is established in the gasifier during its operation, and it influences the performance significantly. Hence, the present work is undertaken to study the kinetics of pyrolysis in conditions that prevail in gasifier. A fixed-bed laboratory reactor that uses biomass pellets is employed to analyze the gases generated during pyrolysis process. Carbon dioxide and carbon monoxide evolve at relatively lower temperatures while methane and hydrogen form at higher temperatures. A simplified single-step power law kinetic model is used to fit the experimental data for the gas evolution in fixed bed reactor experiments and the respective kinetic parameters are estimated. The model thus developed is used successfully to predict the flow rate and the composition of gas leaving the pyrolysis zone of gasifier, showing the utility of this approach to obtain an insight into the gasifier operation.

Pyrolysis of municipal solid waste with iron-based additives: A study on the kinetic, product distribution and catalytic mechanisms

To realize highly efficient and environmentally friendly utilization of municipal solid waste (MSW) and iron ore, we proposed a novel method for combining MSW pyrolysis and iron ore reduction. The effects of two iron-based additives (iron ore and iron oxide) on the pyrolysis characteristics of MSW were first investigated by using TGA, and the kinetic results illustrated that the average activation energy of MSW pyrolysis was 180.32 kJ/mol. By adding iron ore and iron oxide, the activation energy decreased to 151.76 and 150.18 kJ/mol, respectively. Then, the product yield and product composition of MSW were analyzed by a fixed-bed reactor, GC-MS and GC. The fixed-bed reactor experiments of MSW pyrolysis indicated that the iron ore and iron oxide acted as catalysts to change the yield and composition of pyrolysis gas and tar, thereby promoting thermal cracking of MSW and showing a high conversion rate for MSW pyrolysis (55.81 and 55.05%). The GC-MS and GC analyses demonstrated that the two additives could significantly reduce the heteroatomic compounds of pyrolysis tar and increase H2, CO and CO2 production. Furthermore, the reduction of iron ore and the catalytic mechanism were analyzed by H2-TPR, XPS and BET. The H2-TPR results showed that compared with the peak of iron oxide, the characteristic peaks of iron ore shifted to a high temperature due to being suppressed by minerals in the iron ore. XPS suggested that the MSW volatiles led to an increase in the binding energy of Fe 2p3/2 and Fe 2p1/2 and a decrease in the binding energy of O 1s during the reduction of iron ore. BET analysis indicated that the high activity of the catalyst might be attributed to its high surface area.

Effect of metal doping on multi-step electron transfer and oxygen species of silicon-based nanocomposite aerogel supported Pd catalysts in oxidative carbonylation of phenol

A series of new metal/silicon-based nanocomposite aerogel supported Pd catalysts were prepared using ambient pressure drying method with low energy consumption, which was applied in the synthesis of diphenyl carbonate (DPC) by oxidative carbonylation. New PS-MnCe nanocomposite areogel catalyst with better activity and stability than traditional metal oxide, which the single pass yield of DPC reached 34.2% with selectivity above 99.2% and TOF (turnover frequency) 100.6 molDPC/molPd h−1. The regeneration of the catalyst maintained the yield 16.6% in the third run with selectivity 97.9%. The prepared nanocomposite areogel catalysts were characterized by power X-ray diffraction pattern, FTIR spectrum, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller and Transmission electron microscopy, in order to make clear the effects of metal doping on multi-step electron transfer, oxygen species and active Pd2+ in the oxidative carbonylation of phenol by as-prepared nanocomposite aerogel supported Pd catalysts. The results showed that this kind of catalyst had a typical structure of aerogel stereoscopic three-dimensional network with high specific surface area and high metal dispersion, which effectively increased the number of active site (Pd2+). Different kinds of metal complexes can adjust the ratio of oxygen species, raise the efficiency of multi-step electron transfer and improve the performance of oxidation properties at low temperatures of the catalyst. The strong SMSI effect between the active center Pd and the support can effectively promote the recycling of Pd2+ so as to improve the activity and stability of the catalyst which may suite for industrial experiments in fixed-bed reactor in future.

Lactic acid recovery from a model of Thermotoga neapolitana fermentation broth using ion exchange resins in batch and fixed-bed reactors

ABSTRACTThis study focused on the integration of lactic acid adsorption and desorption onto commercially available resins in batch reactors with consequent scale-up in fixed-bed reactors. Amberlite® IRA-900, IRA-400, IRA-96 and IRA-67 were used as adsorbents for lactic acid recovery from solutions that mimic the fermentation broth of Thermotoga neapolitana. The best resins were further tested in adsorption–desorption batch experiments, over 13 cycles, with IRA-67 showing an average removal efficiency of 97%. IRA-67 was tested in fixed-bed reactor experiments and an average desorption efficiency of 68% was achieved using three bed volumes of 0.5 M NaOH as the desorbing agent.

FTIR as an easy and fast analytical approach to follow up microbial growth during fungal pretreatment of poplar wood with Phanerochaete chrysosporium

Since the determination of the fermentation kinetics is one of the main challenges in solid state fermentation, the quantitative measurement of biomass growth during microbial pretreatment by FTIR spectroscopy in Attenuated Total Reflectance mode was evaluated.Peaks at wave numbers of 1651 cm−1 and 1593 cm−1 showed to be affected during pretreatment of poplar wood particles by Phanerochaete chrysosporium MUCL 19343. Samples with different microbial biomass fractions were obtained from two different experiments, i.e., shake flask and fixed-bed reactor experiments. The glucosamine concentration was compared to the normalized absorbance ratio of the 1651 cm−1 to 1593 cm−1 peak, measured by FTIR-ATR, and resulted in a linear relationship. The application of a normalized absorbance ratio in function of time provided a graph that was similar to the microbial growth curve.Application of FTIR in ATR mode to follow-up kinetics during solid state fermentation seems to be a fast and easy alternative to laborious measurement techniques, such as glucosamine determination.

Experimental investigation of the influence of reaction atmosphere on the pyrolysis of printed circuit boards

Printed circuit boards (PCB) are one of the most challenging fractions of waste electrical and electronic equipment (WEEE) in terms of recycling due to their complexity and diversity. Pyrolysis seems to be a promising alternative for production of energy carriers from its organic fraction with simultaneous recovery of metals. Reaction atmosphere is among the process parameters that affects the thermal decomposition as well as the products’ formation and distribution. In this study, the decomposition of two different PCB fractions in inert and steam atmospheres has been investigated by means of thermogravimetric analysis (TGA) and lab scale fixed bed reactor experiments. It was found that the decomposition of the tested materials in steam atmosphere starts at lower temperatures and proceeds slower compared to the N2 atmosphere. Moreover, a two-step decomposition has been observed on the PCB sockets fraction due to the fact that high amount of antimony oxide was present, a common additive for improving the flame retardancy, which have been also observed on previous studies (Wu et al., 2014). The presence of steam influence the pyrolysis gas composition and promotes additional vaporisation of antimony as verified by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Finally, the liquid fraction has been qualitatively analysed using a GC/MS in order to determine the brominated compounds as well as other compounds that are produced from this process.

Surface barriers as dominant mechanism to transport limitations in hierarchically structured catalysts – Application to the zeolite-catalyzed alkylation of benzene with ethylene

The meso-macropore network of a hierarchically structured zeolite catalyst is numerically optimized to maximize the volume-integrated reaction yield in the ethylation of benzene to produce ethylbenzene over zeolite H-ZSM-5. A hierarchical approach is used at multiple length scales to determine the optimal pore network properties. The maximum volume-integrated reaction yield of the hierarchically structured zeolite catalyst containing meso- and macropores is nearly twice the yield of a zeolite pellet containing only macropores, at the same macroporosity. To bridge the gap between modeling and experiments, a series of physical mixtures of ZSM-5 crystals and mesoporous silica, containing different weight fractions of zeolite is synthesized and used in fixed bed reactor experiments to determine the optimal pellet structure to maximize the conversion of ethylene. Comparison with reactor simulations of the zeolite composites shows that the performance of the zeolite composites might be limited by surface barriers at the external surface of the zeolite crystals, rather than by diffusion limitations within the meso-macropore network of the pellets.

Sulphated zirconia catalysed conversion of high density polyethylene to value-added products using a fixed-bed reactor

A sulphated zirconia catalyst (SZ) was investigated for catalytic conversion of high density polyethylene (HDPE) to liquid and gaseous hydrocarbons using a fixed-bed reactor. The SZ catalyst reduced the onset of degradation from 337°C for HDPE alone to 187°C with 10wt% SZ added. At 450°C a complete weight loss was obtained with the SZ addition against only 4wt% loss for HDPE only. Fixed-bed reactor experiments using 2g of HDPE with 10wt% SZ catalyst with a 30min residence time showed a 98.0wt% conversion at temperature as low as 380°C. The liquid yield obtained was 39.0wt% with a composition of 16wt% paraffins, 21wt% olefins, 5wt% naphthenes and 58wt% aromatics. The carbon number distribution of the liquid was C7–C12, which is within the gasoline range. Equally, gaseous products ranging from methane up to different isomers of pentane which contained more paraffinic and naphthenic hydrocarbon were obtained. The sulphated zirconia catalyst was found to have high ammonia desorption (337.0μmolNH3g−1), BET surface area (116.0m2g−1), external surface area (112.0m2g−1) and mesoporous structure. The overall results indicate that sulphated zirconia had excellent properties for catalytic conversion at temperature as low as 380°C with significant liquid yield which could offer a solution to plastic waste problem by converting the waste back into value-added chemicals and fuel.

Evaluating the Activity and Stability of CaO-based Sorbents for Post-combustion CO2 Capture in Fixed-bed Reactor Experiments

Carbonate Looping is a post-combustion CO2 capture technology in which CO2 is captured by a CaO-based sorbent. In this work, we report the development, preliminary evaluation and bench-scale testing of synthetic and natural sorbents. After preliminary screening, the most promising materials were studied in a fixed bed reactor under realistic flue gas feed composition. Zr and Al-doped synthetic CaO based sorbents exhibited very high sorption capacity and stability, due to their porous structure that is retained after 20 consecutive carbonation/calcination cycles. The natural sorbents presented inferior results, however their regeneration via hydration seems possible. The presence of steam in the flue gases seems to enhance sorption capacity and stability.

Carbon dioxide removal using calcium aluminate carbonates on titanic oxide under warm-gas conditions

This study presents a scale-up production method for Ti including Ca/Al sorbents and their CO2 sorption test under warm gas conditions by thermogravimetric (TG) analysis and fixed-bed reactor experiments. The Ca/Al/Tix sorbents are made by the precipitation-and-deposition method where Ca2+ and Al3+ ions are deposited via an alkaline solution of OH−/CO32− on TiO2 powder. The titanium dioxide binder facilitates CO2 capture and enhances the CO2 capacity and multicycle stability by adjusting the Ti/Ca ratio. The results showed that these sorbents exhibited excellent CO2 capture stability of 96–98% after ten cycles at 750°C by TG analysis. Characterization by XRD indicated that the reduction in the deterioration of the sorbent during the cycle test could possibly result from the formation of an anti-sintering compound such as CaTiO3 along with calcium aluminate hydroxides related to katoite. Using a reactor as test rig, the amount of sorbent and total capture weight was significantly increased. This TiO2-coated sample of Ca/Al/O–TiO2 provides a feasible route for the manufacture of cheap CO2 sorbents.

Continuous catalytic deoxygenation of model and algal lipids to fuel-like hydrocarbons over Ni–Al layered double hydroxide

The deoxygenation of lipid-based feeds to diesel-like hydrocarbons was investigated over a series of oxide-supported Ni catalysts. Catalyst screening in a semi-batch reactor revealed that a Ni–Al layered double hydroxide formulation afforded a higher yield of hydrocarbons in the diesel range than 20wt% Ni/Al2O3, 20wt% Ni/ZrO2, 20wt% and Ni/La-CeO2 (lanthanum-stabilized ceria). Through a series of fixed bed reactor experiments involving model lipids in which reaction conditions – including temperature, hydrogen partial pressure and feed to catalyst ratio – were systematically changed, the effects of these variables on catalyst performance were elucidated. Based on the results of these experiments the optimum set of conditions was identified and applied to the conversion of realistic feeds, including the oil extracted from algae cultured using flue gas from a coal-fired power plant. Catalyst stability studies showed Ni–Al layered double hydroxide to be a stable formulation, no significant loss of activity being observed between 6 and 72h on stream under conditions known to promote catalyst deactivation, namely the use of an unsaturated feed – comprising both a triglyceride and a considerable amount of free fatty acids – in high concentration.

Study of catalytic post-treatment of the vapours from sewage sludge pyrolysis by means of γ-Al2O3

The present work describes an experimental study on sewage sludge pyrolysis in a Fluidised Bed Reactor (FluBR) and the effect on the pyrolysis liquid product of passing the hot exhaust (pyrolysis) vapours through a Fixed Bed Reactor (FixBR) filled with gamma-alumina (γ-Al2O3). Experiments have been done at temperatures of 450 and 550°C (FluBR) and 400 and 500°C (FixBR). In the FixBR experiments, the bed was filled with inert sand and two different bed quantities of γ-Al2O3 (97.3g, 194.6g) giving a weight hour space velocity (WHSV) of between 0.6 and 1.8h−1. By means of this treatment, the pyrolysis liquid phase separation was improved, obtaining a liquid with two phases (organic and aqueous) instead of the three (two organic and an aqueous phase) usually obtained in sewage sludge pyrolysis without applying γ-Al2O3. This organic phase is quite interesting from the point of view of a possible application as bio-oil. Although the product distribution results using γ-Al2O3 show a slight liquid yield decrease for both temperatures (compared to sewage sludge pyrolysis without applying γ-Al2O3), there is a clear increase in the organic phase yield at 450°C. Therefore, γ-Al2O3 application makes it possible to lower the pyrolysis temperature in order to maximise the organic phase in the sewage sludge pyrolysis liquid. Furthermore, a general improvement in the higher heating value of the organic phases has been achieved.

Preparation and performance of Cu-based monoliths for methanol synthesis

Methanol synthesis from syngas could be carried out in steel monoliths coated with CuO/ZnO/Al 2O 3 catalysts. The Cu-based coatings were prepared using different techniques: slurry coating of CuO/ZnO/Al 2O 3 obtained via 2-stage co-precipitation, sol–gel coating of Al 2O 3 followed by Cu–Zn impregnation, colloid coating of Al 2O 3 followed by Cu–Zn impregnation, and colloid coating of Al 2O 3 followed by deposition–precipitation of Cu–Zn. The coated monoliths were characterized (XRD, BET, N 2O titration) and studied in the methanol synthesis reaction at 80 bar. Comparison was made to similarly prepared powder catalysts subjected to characterization and laboratory scale fixed bed reactor (FBR) experiments. Monoliths with high activity for the methanol synthesis reaction were obtained with slurry coating of CuO/ZnO/Al 2O 3, whereas the impregnation and deposition–precipitation methods gave insufficient Cu dispersion. Higher activity of the monolith relative to FBR experiments with the same catalyst was ascribed to the thermal properties of the steel monolith.

Evaluation of published kinetic models for tert-amyl ethyl ether synthesis

The published kinetic models for liquid phase synthesis of tert-amyl ethyl ether (TAEE) by addition of ethanol to isoamylenes on acidic ion exchange resins were evaluated by comparison with own experimental data. Fixed bed and batch reactor experiments were carried out in liquid phase on Amberlyst-35 ion exchange resin as catalyst. Among the published kinetic models, our experimental data fits the best with the model published by [J.A. Linnekoski, A.O. Krause, L.K. Rihko, Kinetics of the heterogeneously catalyzed formation of tert-amyl ethyl ether, Ind. Eng. Chem. Res. 36 (1997) 310–316.]. In the simulation study for the fixed bed reactor experiments, the influences of axial mixing, liquid–solid mass transfer and internal diffusion steps on the overall process kinetics were theoretically evaluated. The results evidenced that on the working temperature domain, significant kinetic limitations by internal diffusion can appear for catalyst pellets size over 1 mm. The external mass transfer step has a weak influence on the process kinetics and can be important only at lower limit of the flow rates domain. Our computations evidenced also a negligible influence of the axial mixing on the reactants conversion in the experimental fixed bed reactor, on the working domain investigated.

Origin of ligand acceleration in heterogeneous ethyl pyruvate hydrogenation

Ethyl pyruvate (EP) was hydrogenated in the presence and absence of cinchonidine (CD) over a broad concentration range of EP (0.01–2.0 mol L −1) using a commercial 5% Pt/Al 2O 3 catalyst (Strem). Ligand acceleration (LA) could be observed at a higher concentration (0.3–2.0 mol L −1), whereas at lower concentration, both enantioselective and racemic reactions have very similar reaction rates. Regardless of LA, a constant ( 84 ± 2 % ) enantiomeric excess (ee) could be obtained. As CD concentration was increased, the ee increased from 0 to 80%, while the hydrogenation rate remained constant at a low EP concentration (0.01 mol L −1). Continuous fixed-bed reactor experiments revealed that LA can be linked to catalyst deactivation. In particular, EP causes catalyst deactivation, which is faster at higher reactant concentrations. CD restores catalyst activity and suppresses catalyst deactivation, resulting in higher reaction rates compared with racemic reactions carried out without CD.

Methanol oxidative dehydrogenation in a catalytic packed-bed membrane reactor: experiments and model

Methanol oxidative dehydrogenation to formaldehyde over a Fe–Mo oxide catalyst was studied experimentally in three reactor configurations: the conventional fixed-bed reactor (FBR) and the packed-bed membrane reactor (PBMR), with either methanol (PBMR-M) or oxygen (PBMR-O) as the permeating component. The kinetics of methanol and formaldehyde partial oxidation reactions were determined independently from FBR experiments. A steady state plug-flow PBMR model, utilizing these kinetics and no adjustable parameters, fit the experiments accurately. It is shown experimentally and in accordance with the model that for given overall feed conditions, the reactor performance for methanol conversion and formaldehyde yield is in the order PBMR-M < FBR < PBMR-O.