Gasification Of Glucose Research Articles

Kinetics study of total organic carbon destruction during supercritical water gasification of glucose

AbstractThe kinetics of total organic carbon (TOC) destruction during supercritical water gasification (SCWG) of glucose were studied at 400–500°C and 25 MPa in a 600 mL batch reactor. Both TOC and water concentrations are critical for the conversion of TOC in supercritical water, especially at longer residence times. Initially, it was assumed that the TOC destruction reaction followed first‐order kinetics ignoring the water concentration. However, experimental results showed that the feed‐to‐water ratio had a significant effect on TOC decomposition. Considering the water concentration in the reaction, the reaction orders of TOC (2.35) and water (1.45) were calculated using nonlinear regression analysis (the Runge‐Kutta method). The estimated pre‐exponential factor (k’) and activation energy (E) were calculated to be 8.1 ± 2/min and 90.37 ± 9.38 kJ/mol respectively.

Reaction characteristics of homogeneous and heterogenous reactions for glucose gasification in supercritical water using ruthenium catalyst supported on carbon nanotube

In this study, a spherical, Ru-based catalyst with a Carbon nanotube (CNT) support was used in a continuous-flow system, where homogeneous and heterogeneous reactions occurred simultaneously. Therefore, determining the homogeneous and heterogeneous reaction rates is important. Glucose (5 and 10) wt%, a typical model biomass compound, was chosen as the feedstock, and the reaction temperature was set at (500 and 600) ℃. The weight hourly space velocity was changed (40, 80, or 160) h−1 by maintaining the catalyst loading at 0.15 g and altering the flow rate (2, 4, or 8) mL/min. A reaction model where homogeneous and heterogeneous reactions proceed in parallel was developed, and the reaction rates were determined. The homogeneous reaction rate constants were (0.00968 and 0.0194) /s for (500 and 600) ℃, respectively, and the heterogeneous ones for Ru-based catalyst with a CNT support were (0.0137 and 0.0420) m3/(kg s) for (500 and 600) ℃, respectively.

Simulation of the Catalytic Gasification of Banana Biomass in the Production of Hydrogen, Using Glucose as a Model Compound

In the face of the climate change problem caused by fossil fuels, it is essential to seek efficient alternative energies with a lower environmental impact that are derived from renewable resources. Biomass gasification technology continues to generate significant interest in sustainable energy research as an alternative to traditional combustion technology. Gasification involves the thermochemical conversion of raw materials, resulting in a highly valuable gaseous product known as synthesis gas, commonly used as a fuel. Its numerous advantages include the availability of raw materials, the reduction in harmful emission streams, performance, and costs. As this topic gains momentum in the global energy framework, it is imperative to advance the maturity of this technology by addressing its weaknesses, primarily in terms of efficiency. The objective of this project was to investigate the hydrogen production process through the simulation of glucose gasification as a representative compound for biomass. This was achieved by conducting an integrated simulation of glucose gasification, encompassing both the heat transfer in the external system and the conversion of glucose into hydrogen gas, using the results obtained in the external system as initial conditions. Interrelated aspects of this complex process, including heat transfer and the kinetics of the gasification process, were modeled. Glucose was selected as the model compound due to its availability, simplicity, fundamental understanding, reproducibility, comparability, knowledge of reaction pathways, and simplification of mathematical models. The simulation resulted in a H2:CO ratio of 2.2, and molar fluxes were obtained for H2, CO, CO2, CH4, and H2O consistent with those typically observed in the gasification process of organic matter. These models were constructed, laying the foundation for the adaptability of subsequent optimization studies.

Hydrothermal gasification of glucose for H2 production using Ni–Al2O3 nanocatalyst

Hydrothermal gasification is a promising technology for converting biomass into syngas (H2/CO). A substantial challenge of hydrothermal gasification for producing hydrogen is the unwanted deposition of graphitic coke and metal particle agglomeration on the catalyst active sites. In this contribution, we hypothesize and examine controlling the active site nickel nanoparticle size (2, 9, 23 and 32 nm) through synthesis on supported mesoporous alumina (Al2O3). Nanoparticles were synthesized from nickel acetylacetonate (Ni(acac)2) by varying the molar ratio of oleylamine (OA) to trioctylphosphine (TOP) which gave controlled sizes of nanoparticles. Based on catalyst analysis, the 11 wt% Ni–Al2O3 containing 2 nm Ni was further evaluated for hydrothermal gasification of glucose for the production of syngas (H2/CO) at 500 °C temperature and 30 min reaction time. This nanocatalyst was found to significantly increase H2 yield compared to a previously prepared impregnated catalyst having larger Ni active sites. Graphitic coke deposition was minimized while the total organic carbon destruction (TOC) and carbon gasification efficiency (CGE) were both enhanced with the nanocatalyst. Almost double the yield of H2 (1.94 times higher) was achieved compared to the impregnated catalyst. This is attributed to the larger surface area, higher percentage of metal dispersion and uniform size distribution of active metal nanoparticles on the support.

Calculations of complex chemical reaction equilibria using stoichiometric and non‐stoichiometric approaches in combination with arc‐length continuation

AbstractChemical equilibrium calculations—as they are required to evaluate the evolution limits of any reactive system—are fundamentally performed using either a reaction based stoichiometric (S) approach or a non‐stoichiometric (NS) method. One objective of the present paper is to check and discuss whether both methods lead to comparable solutions in the case of complex chemical equilibria encountered in high temperature and pressure combustion of hydrazine and propane and in steam gasification of glucose and cellulose. Within both calculation models various numerical methods can be used. We apply several techniques for each approach and discuss their easiness of implementation and usage, in particular when chemical equilibria are computed for reacting systems under a multitude of temperature and pressure conditions and feed compositions. In addition, we present a novel approach to perform sensitivity analyses based on a combination of S or NS methods and arc‐length continuation technique. For this purpose, three industrially relevant case studies are exposed: (1) synthesis of ammonia using the Haber process, (2) steam gasification of a typical biomass surrogate, glucose, and (3) steam gasification of cellulose. For all the above reacting systems, our results are benchmarked against their counterparts obtained either from the ubiquitous process simulator: ASPEN‐Plus® or from data available in the open literature.

Catalytic supercritical water gasification of glucose with in-situ generated nickel nanoparticles for hydrogen production

Hydrogen production from catalytic supercritical water gasification of glucose with in-situ generated nickel nanoparticles in a quartz tube reactor is demonstrated. The effects of various operating parameters such as the presence of catalyst, resident time, reaction temperature and feed concentration on the gasification performances are studied. The results show that both the carbon gasification efficiency and the hydrogen gasification efficiency of glucose in supercritical water were improved with in-situ generated nickel nanoparticles as catalyst compared to those without catalyst. The catalyst promotes the water-gas shift reaction and CO methanation reaction, resulting in increased yields of H2, CH4 and CO2 and decreased yield of CO. At the presence of catalyst, 10 wt% glucose solution exhibits the best gasification performances at 500 °C. Highly dispersed nickel nanoparticles identified by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) are assumed to be generated via supercritical hydrothermal synthesis through hydrolysis, dehydration and in-situ reduction. However, the in-situ generated nano-nickel catalyst underwent an activation to deactivation transition due to carbon deposition on the surface of nickel nanoparticles. Regeneration strategies of the deactivated catalysts need further study for practical application.

Effect of surface acidity of Al2O3 supported metal catalysts on catalytic activity and carbon deposition during SCWG of glucose

In this study, the impact of a catalyst's surface acidity on supercritical water gasification (SCWG) of glucose is investigated. Four different catalysts including Ni, Ru0·2Ni, Ru0·5Ni and NiLa were prepared on an Al2O3 support via an incipient impregnation method. NH3-TPD and pyridine-FTIR results of the fresh catalysts showed that NiLa was the least acidic amongst the four investigated catalysts. Although the BET surface area for all four catalysts were similar, the NiLa and Ru0·5Ni catalysts were found to significantly reduce carbon deposition during SCWG of glucose, attributed to their lower acidic nature. Production of H2 was also increased by 1.52 and 1.21 × using the NiLa and Ru0·5Ni compared to Ni. The carbon deposition was characterized by TG-DTA, TPO, XRD and Raman spectroscopy, showing that the higher the acidic nature of the catalyst, the higher the tendency for carbon deposition. Using a lower acidic catalyst for SCWG helped minimize the catalyst's deactivation, while improving the catalyst lifetime This study shows that the acidic nature of the catalyst is an important consideration towards a better understanding of the SCWG mechanism.

Numerical modelling of char formation during glucose gasification in supercritical water

Supercritical water gasification is an efficient thermochemical conversion process to convert wet biomass into a high grade fuel. However, char formation during the conversion might influence the process efficiency and operational stability. Providing insight into char formation behavior during the gasification process will facilitate the utilization of this technology. Computational fluid dynamic modelling is used to study the supercritical water gasification of glucose in a tubular helical reactor, which includes an injector tube to mix glucose feed with pre-heated water to provide fast heating. Validation against experimental data confirms that the developed model performs well. An average discrepancy of 4% is obtained for the total feed conversion whereas the gas yield at high temperature is computed with 15% difference. The char yield trend is also captured well. Sensitivity analysis reveals that the presence of low temperature zone at the injection point plays a significant role in char formation.

Fluidizable Ni/Ce-meso-Al2O3 for gasification of glucose: Effect of catalyst reduction on hydrogen selectivity

A new template-free technique is applied to develop fluidizable Ce-Al2O3 support and impregnated with nickel. The Ni(x)/Ce-Al2O3 catalysts are evaluated in a fluidized CREC Riser Simulator using glucose as biomass surrogate. XRD shows that nickel is well-dispersed on Ce-Al2O3. The acidity of the catalysts decreased from 0.317 to 0.202mmol NH3/g-sample as the nickel loading was increased. In catalyst evaluation, it is found that the reduced catalysts favor bond cleavage, promotes water gas shift and steam reforming reactions to give hydrogen/syngas as more selective products. Ni(20)/Ce-Al2O3 exhibited lowest extent of coking and produced hydrogen rich syngas with H2/CO≈1.75:1.

Kinetics of Steam Gasification of Glucose as a Biomass Surrogate over Ni/Ce–Mesoporous Al2O3 in a Fluidized Bed Reactor

This study reports the kinetics of steam gasification of glucose as a biomass surrogate over a new Ni(x)/Ce-doped Al2O3 (x = 5, 10, 15, and 20 wt %) catalyst in a fluidized bed reactor. The presence of ceria plus successive nickel impregnation helped in conserving the catalyst’s high surface area (i.e., 102 m2/g at 20 wt % nickel loading). Incorporation of ceria dopant suppressed coke formation during steam gasification of 15 wt % glucose in the fluidized bed reactor at 650 °C and 1 atm in the order Ni(20) < Ni(15) < Ni(10) < Ni(5)/Ce-doped Al2O3. The detailed kinetic model comprises reactant adsorption, surface reaction, and product desorption steps, involving the water gas shift reaction (WGS), steam reforming of methane (SRM), and reverse dry reforming of methane (RDRM). Ni(20)/Ce-doped Al2O3 with the best performance in terms of syngas production, and the least tendency for coking, was used for the kinetic studies (for T = 550–700 °C and t = 5–25 s). The results of the model simulation indicate that t...

La-based catalysts to enhance hydrogen production during supercritical water gasification of glucose

Controlling hydrogen production during supercritical water gasification (SCWG) of biomass is challenging using conventional mono-metallic catalysts. This work examines the role of Lanthanum (La) both as a catalyst and co-catalyst with Nickel (Ni), for enhancing the Water-Gas Shift (WGS) reaction to maximize hydrogen production. A stirred tank batch reactor was used with glucose as feed (model compound for biomass), from T = 400 to 500 °C, residence time = 5–120 min and P = 28 MPa. Compared to non-catalytic gasification, the La2O3/Al2O3 catalyst enhanced both the H2 and CO2 production by 1.9-fold and 2.0-fold respectively. Ni-La2O3/Al2O3 catalyst increased hydrogen production (3.95 mol/mol feed) to almost thermodynamic equilibrium composition (4.15 mol/mol feed) at 120 min reaction time. By examining the fresh and spent catalysts by various physico-chemical techniques, this enhancement is attributed to the Ni promoting tar cracking, while La promoted the WGS reaction and inhibits the methanation reactions. A parametric study was used to optimize reaction conditions, finding that H2 production and carbon conversion to gaseous products increased significantly with higher reaction time and temperatures and lower feed concentrations. Almost 98% carbon was gasified at 120 min reaction time using Ni-La2O3/Al2O3 as catalyst. Using a controlled feedstock of CO and H2 to further examine the catalytic mechanism, adding La onto the Ni/Al2O3 enhanced CO2 and H2 production with negligible CH4 production, showing the importance of the WGS reaction to maximizing H2 production in SCWG.

Steam gasification of a cellulosic biomass surrogate using a Ni/La2O3-γAl2O3 catalyst in a CREC fluidized riser simulator. Kinetics and model validation

This study describes a Langmuir-Hinshelwood based mechanistic kinetic model for the catalytic steam gasification of glucose, a biomass surrogate. This model accounts for the algebraic addition of dominant reactions: water gas-shift, the steam reforming of methane and the reverse dry reforming of methane. Reaction runs are developed in a mini-fluidized CREC Riser Simulator reactor using a highly performing Ni/La2O3-γ-Al2O3 catalyst. H2, CO, CO2, CH4 and H2O are the major product species observed with negligible coke and tar being formed. For adequate parameter estimation and model validation, two experimental data sets are considered. The first data set includes runs at different temperatures and reaction times. This data set is used to establish intrinsic kinetic parameters with narrow 95% confidence spans and low cross-correlation. The proposed model is validated using a second data set obtained by varying S/B ratio and reaction time. Thus, the proposed model includes phenomenologically based parameters that can successfully account for various observable chemical species in a wide range of operating conditions.

Process simulation and energetic analysis of different supercritical water gasification systems for the valorisation of biomass

The energetic efficiency for the supercritical gasification of biomass is studied for three cases: hydrogen and methane production, heat and electricity cogeneration. Experimental results from the gasification of glucose are used to represent the gasifier. The other unit operations are simulated using the software ProsimPlus through thermodynamic equilibrium calculations. Simulations are conducted at different pressure, temperature and initial biomass concentration. The energetic and exergetic yields are calculated, as well as the minimum heat requirement estimated from a pinch analysis. All the results are then exploited to determine optimal conditions for two systems: adiabatic and isothermal. The optimal temperature ranges from 584 to 626°C, whereas the optimal initial concentration ranges from 51 to 87gL−1. The system giving the best result in term of global energetic optimisation is methane production in isothermal conditions, followed by methane production in adiabatic conditions. The optimal energy efficiencies are 94% and 91% respectively.

Supercritical water gasification of glucose using bimetallic aerogel Ru-Ni-Al2O3 catalyst for H2 production

Hydrogen production from biomass using supercritical water gasification (SCWG) is gaining considerable attention as a sustainable source for emerging energy needs. A significant problem with SCWG is the low activity of conventional catalysts with simultaneous graphitic coke formation on the catalyst surface. In this contribution, novel bimetallic nickel-ruthenium supported on alumina catalysts were synthesized via a sol–gel process followed by scCO2 drying (aerogel catalyst). In order to investigate the effect of both Ru and the drying step, both supercritical and conventional drying (xerogel catalyst) were compared with and without Ru. All catalyst types were examined for glucose gasification in supercritical water using a 600 cm3 batch reactor from 400 to 500 °C at 25 to 35 MPa. The fresh and spent catalysts were then characterized by various physico-chemical techniques to understand the role of Ru and the deactivation mechanism. Ru-Ni-Al2O3 aerogel catalyst reduced graphitic coke formation, significantly enhancing H2 formation while also increasing the carbon gasification efficiency (CGE) and total organic carbon (TOC) destruction, respectively. H2 yield was increased 1.7 times higher for Ru-Ni-Al2O3 aerogel compared to the xerogel. Ni-Al2O3 aerogel and impregnated catalyst provided 1.26 and 1.55 times lower H2 yield compared to Ru-Ni-Al2O3 aerogel catalyst. This is attributed to the Ru-Ni-Al2O3 aerogel catalyst having a higher BET surface area as well as larger pore volume, smaller active metal crystallite sizes, and a higher degree of active metal dispersion.

Hydrogen production by biomass gasification in a supercritical water fluidized bed reactor: A CFD-DEM study

In this study, we used CFD-DEM model to simulate glucose gasification in a supercritical water fluidized bed reactor (SCWFBR). Simplified reaction kinetic model, including glucose decomposition, water gas shift reaction and methanation reaction, was used. Particle distributions, gas composition and reaction rate profiles were analyzed. Moreover, the influence of chemical reaction on flow behavior, and the effects of operation parameters, such as wall temperature, flow rates and initial bed height were investigated. The results show that high wall temperature, low flow rate and high initial bed height are in favor of gasification. However, lower H2 yield, gasification efficiency (GE) are found at flow rate below the minimum fluidization velocity. The simulation results show good agreement with the experimental results, demonstrating the validity of this model. The information obtained by the numerical study is useful for the operation and optimization of the gasification reactor.

Enhancement of glucose gasification by Ni/La2O3-Al2O3 towards the thermodynamic extremum at supercritical water conditions

This communication presents the promotional effects of La on Ni/La-Al2O3 catalyst for biomass gasification in supercritical water using glucose as a biomass surrogate. The experimental findings were also compared with the product compositions predicted by the thermodynamic model. In modeling, the equations of state (EoS) by Peng–Robinson, as well as by Duan, were separately used to derive the residual Gibbs' free energy and compressibility factor, Z. Results, obtained by both EoS showed close agreement. The accuracy of our calculation was checked by comparing the compressibility factor, Z of the gaseous products, with those obtained from Aspen-HYSYS. In all cases considered, the percentage error in Z was less than 10%. Moreover, we have found that water to glucose (W/G) ratio affects the syngas composition. For example, at 600 °C and 25 MPa, an increase in W/G ratio from 6 to 9 led to an increase in H2/CO ratio from ∼3.2 to ∼4.7. On the other hand, operating pressure has little effect on syngas composition. This finding could be useful in the design and optimization of supercritical water gasification (SCWG) plants. Finally, we also observed that lanthanum helped to drive the hydrogen yield towards the thermodynamic extremum, while at the same time scavenging CO2 and coke, and retarding the methanation reaction.

Hydrothermal gasification of glucose and starch in a batch and continuous reactor

A batch reactor was used for the gasification of glucose and starch as carbohydrate model compounds. The effects of H2O in various states (low-pressure hot compressed water (LP-HCW, 300 °C and 10 MPa), high-pressure hot compressed water (HP-HCW, 360 °C and 20 MPa), high-temperature steam (HTS, 400 °C and 10 MPa), and supercritical water (SCW, 400 °C and 25 MPa)), as well as reaction time (10, 30, and 60 min), sample concentration (10, 20, and 30 wt%), and catalyst (mixture of Ca(OH)2 and Na2CO3) on gas production were investigated in the hydrothermal gasification. In addition, using a continuous reactor, the hydrothermal gasification of glucose was examined with LP-HCW (200 °C and 5 MPa), HP-HCW (200 °C and 25 MPa), HTS (600 °C, 5 MPa), and SCW (600 °C, 25 MPa) in order to study the productions of gases and tar, and the mass balance. The reaction temperature affected gasification considerably, but pressure had little effect. In the batch experiments, the characteristics of the produced gases were almost identical after a reaction time of 10 min, and addition of Ca(OH)2 and Na2CO3 as catalysts in a molar ratio of 7:3 led to selective production of H2 in the SCW gasification of 10 wt% glucose for 30 min. In a continuous experiment under the SCW conditions, the conversion efficiency of glucose to gas was 26% and the composition of the produced gas was 29 vol% CO, 23 vol% H2, and 16 vol% CH4. Under the hydrothermal conditions, glucose was mainly converted to char and suspended components of high-molecular-weight compounds such as fat, whereas starch was mainly converted to gas and liquid.

Transition Metal Oxides as Catalysts for Hydrogen Production from Supercritical Water Gasification of Glucose

In the present study, 12 kinds of metal oxides (V2O5, Cr2O3, MnO2, Fe2O3, Co2O3, CuO, ZnO, ZrO2, MoO3, SnO2, WO3 and CeO2) were tested in supercritical water gasification of glucose at 600 °C. Quartz capillary reactor was used to eliminate the potential catalytic effect of the reactor wall. The influence of metal oxides on the gasification efficiency, gas composition and yield was studied. Most metal oxides improved the gasification efficiency, and Cr2O3, CuO, WO3 and V2O5 were the most effective ones. Most oxides had little influence on H2 fraction but showed significant influence on CO fraction. The lowest CO fraction was achieved with MnO2 and CuO. The catalytic activity of the metal oxides was summarized and compared based on their impacts on the gas composition and yield. Through the visualization of the reactor, CuO was found to be reduced into Cu metal during gasification. Both the presence of Cu metal and released oxygen were supposed to enhance the gasification. Further study on the valence state of metal oxides after gasification may help to reveal the catalytic mechanism of the metal oxides.

Supercritical water gasification of glucose in fluidized bed reactor: A numerical study

Supercritical water fluidized bed (SCWFB) is a new reactor concept for gasification of biomass and coal in supercritical water. In this paper, physical fields, residence time and gas yield in a SCWFB reactor were investigated numerically based on the Eulerian two-fluid method with the kinetic theory of granular flow. A three-step reaction model including steam reforming, water-gas shift and methanation was used to describe the supercritical water gasification of glucose. Distributions of velocity and temperature were obtained, and the results show that the mixing of preheated water and cold glucose solution at the bottom in the bed leads to a region with low solid volume fraction and local swirl flow. In the freeboard, most of reactants flow near the wall and with a velocity much higher than the superficial velocity. The reaction rates and conversion ratio of glucose at different regions in the reactor were also obtained. Distribution of residence time was found to be non-uniform, and its effect on glucose gasification was analyzed. In addition, the effects of operation condition and reactor structure on gas yield and residence time were studied to explore best operation rules for increasing gas yield. The results from this work may be of interest to operators attempting to obtain more information in the reactor and provide instruction for the design of SCWFB reactor.

Effect of mesoporosity of bimetallic Ni-Ru-Al2O3 catalysts for hydrogen production during supercritical water gasification of glucose

A well-known problem with metal supported alumina catalysts during gasification processes for H2 formation is catalyst deactivation by coke formation and pore plugging. Poorly controlled catalyst structure with low surface area and microporous structure also accounts for low catalyst activity. This work investigated bimetallic Ni-Ru/Al2O3 catalysts that are both effective and durable for glucose gasification in supercritical water with minimal coke formation. Both non-ionic (Pluronic P-123) and cationic (CTAB) templates were examined for mesoporous alumina synthesis with Ni and Ru loadings and compared with a conventional incipient impregnation method. Gas formation during SCWG catalysis was monitored for hydrogen formation while the catalysts were examined both before and after reaction by a variety of physico-chemical techniques including BET surface area, BJH pore size analysis, XRD, TG-DTA, TPR, TPO, Raman spectroscopy & TEM microscopy. The results showed that templating helped disperse both Ni and Ru particles homogeneously inside the pores of mesoporous Al2O3 catalysts; whereas the impregnated catalyst gave poorer dispersion. Comparing with the impregnation method, a six-fold increase of BET surface area was observed using the one-pot synthesis method. Hydrogen production during glucose gasification increased by 25mol% for both templated catalysts, with the CTAB catalyst showing slightly higher activity. This method provided insignificant coke deposition indicating that the new Ru-Ni/Al2O3 templated catalyst is promising for the development of hydrogen production for an emerging biorefinery.