Catalytic Gasification Process Research Articles

Characterization and mechanism of red-mud-catalyzed steam gasification of corn stover

Catalytic biomass gasification has received extensive attention from scholars worldwide. This study proposes steam gasification of corn stover using red mud (RM), an industrial solid waste, as a catalyst to produce high-quality reducing gas. Experiments were conducted at different reaction temperatures and gasification times. Characterization of RM and its three main components, Fe2O3, CaCO3, and Al2O3, in the catalytic steam gasification process of corn stover, was performed and its catalytic mechanism was explored by characterizing magnetic separation products. Results show that an increase in reaction temperature significantly promotes the production of CO, CO2, and H2. The promotion of steam to H2 production is caused by the gas-phase reaction and gasification of fixed carbon (FC). Fe2O3 promotes gas-phase reactions, such as the water–gas shift reaction, and effectively catalyzes the steam gasification of FC as an intermediate reactant. The addition of Al2O3 is beneficial for the production of CH4 and H2. The CO2 produced by the decomposition of CaCO3 inhibits the water–gas shift and methane-steam reforming reactions, thus reducing H2 output. The addition of RM is beneficial for the production of H2 and CO2 and inhibits the production of CO. Compared with pure Fe2O3, the superior pore structure and unique solid solution structure of RM provide Fe2O3 with more active surface lattice oxygen, higher redox performance, larger gas–solid contact area, superior ability to prevent carbon deposition, and better catalytic ability.

Ce/Pumice and Ni/Pumice as heterogeneous catalysts for syngas production from biomass gasification

This work presents a study of synthesis and characterization of catalysts-based cerium and nickel supported on the pumice stone (Ce/Pumice and Ni/Pumice) to be used in the gasification process of an invasive species present in the Canary Islands, such as Pennisetum setaceum to obtain syngas. Specifically, the effect of the metal impregnated on the pumice, and the effect of catalyst on the gasification process was studied. For this purpose, the composition of the gas was determined and the results obtained were compared with those obtained in non-catalytic thermochemical processes. Gasification tests were performed using a simultaneous thermal analyzer coupled with a mass spectrometer, providing a detailed analysis of the gases released during the process. The results showed that during the catalytic gasification process of the Pennisetum setaceum, the gases produced appear at lower temperatures in the catalytic process that in the non-catalytic process. Specifically, H2 appears at 640.42 °C and 641.84 °C when Ce/pumice and Ni/pumice were used as catalyst, respectively, compared to 697.41 °C for the non-catalytic process. Moreover, the reactivity at 50 % of char conversion for the catalytic process (0.34 and 0.38 min−1 for Ce/pumice and Ni/pumice, respectively) was higher than for the non-catalytic process (0.28 min−1), indicating that the incorporation of Ce and Ni on the pumitic material increases the gasification rate of the char compared to the pumitic support. Catalytic biomass gasification is an innovative technology that can provide new opportunities for research and development of renewable energy technologies, as well as for the creation of green jobs.

Experimental study on supercritical water gasification of oily sludge using a continuous two-step method

Supercritical water gasification (SCWG) technology can convert oily sludge into hydrogen-rich gas. To achieve high gasification efficiency of oily sludge with a high oil concentration under mild conditions, a two-step method involving a desorption process and a catalytic gasification process using Raney-Ni catalyst was investigated. High oil removal efficiency (99.57%) and carbon gasification efficiency (93.87%) were achieved. The lowest wastewater total organic carbon, oil content, and carbon content in the solid residues were 4.88 ppm, 0.08% and 0.88%, respectively, using a gasification temperature of 600 °C, treatment concentration of 1.11 wt%, gasification time of 70.7 s, and the optimal desorption temperature of 390 °C. The main organic carbon component in the solid residues was cellulose, which is environmentally safe. As the treatment concentration increased, the two-step method outperformed the single-step method. The mechanism for the two-step SCWG of oily sludge was revealed. In the first step, supercritical water is used in the desorption unit to achieve a high oil removal efficiency with few liquid products generated. In the second step, the Raney-Ni catalyst promotes efficient gasification of high-concentration oil at a low temperature. This research provides valuable insights into the effective SCWG of oily sludge at a low temperature.

Char structure evolution and behaviors of sodium species during catalytic gasification of sodium-rich direct coal liquefaction residue under CO2 atmosphere

In this work, to better understand catalytic gasification process of direct coal liquefaction residue rich in sodium species, char structure evolution and behaviors of sodium species during gasification under CO2 atmosphere were investigated in detail by N2 adsorption and desorption, FT-IR, XRD, SEM, and Raman analyses. The results show that sodium species developed pore structure of direct coal liquefaction residue during gasification, especially expanded mesoporous structures which increased from 0.05 to 0.16 cm3/g at maximum. With the increase of gasification time, different crystalline compounds were formed in chars. Most of the mineral matters identified by XRD were calcium-containing ones, whereas no obvious sodium-containing crystalline compounds were found. This was because that most of sodium species volatilized at high temperature and the crystalline forms of sodium-containing compounds had defects. Compared with sodium species, calcium species were more prone to react with aluminosilicates, which happened to make sodium species remain active during gasification process. The ratio of (GR + VL + VR)/D rose initially and then decreased, which could be explained as the dissociation of the large aromatic and the rearrangement of small aromatic rings into large aromatic structures. Moreover, release ratio of sodium species was closely related with gasification time and 49.8% of them released in the initial stage of gasification process (within 15 min). Compared with that of direct coal liquefaction residue reloaded with water-soluble sodium species, the release ratio of sodium species in the original direct coal liquefaction residue was on a lower level (85.2% versus 89.7%).

In-situ study of fractal properties of coal char particles during catalytic gasification

Interactions of potassium-based catalysts with Shenfu (SF) char during catalytic gasification was observed by an in-situ heating stage microscope. The effects of the gasification temperature (800–900 °C) and the catalyst loading (4.4%, 10%) on the reactivity of coal char were investigated. The heating stage microscopy was used to visualize the catalytic gasification process of coal char particles and the fractal theory was introduced to analyze the surface structure of coal char particles to reveal the gasification reactivity. The experimental results show that the fractal dimension of coal char particles is positively correlated with the carbon conversion rate, and the fractal dimension increases by increasing the gasification temperature and the catalyst loading. The relationship between the initial gasification reaction rate and the fractal dimension of coal char particles is consistent with that between the carbon conversion rate and the fractal dimension of coal char particles. There is an exponential relation between the fractal dimension of coal char and the char angle; the fractal dimension increases with the increase of coal char particle angle; and the fractal dimension of coal char particles can be used in the study of coal char catalytic gasification process.

Green ammonia production via microalgae steam catalytic gasification process over LaFeO3 perovskite

Ammonia (NH3) is a potential carbon-free energy carrier. This study proposed a green route for NH3 production via microalgae steam catalytic gasification process over LaFeO3 perovskite. The experiments of pyrolysis, catalytic pyrolysis, steam gasification, and steam catalytic gasification were compared in a fixed bed reactor. Compared with pyrolysis, steam is introduced as the gasifying agent for reforming volatile-N and gasifying char-N during steam gasification, thus promoting the fuel-nitrogen transfer into the gas phase. Synergistic effects of steam and LaFeO3 are able to promote the hydrogenation of char-N, the decomposition of proteins, and the deamination of amides, resulting in a remarkable release of NH3. More importantly, steam and LaFeO3 can significantly promote the conversion of HCN into NH3, which will enhance the selectivity of NH3. Proper steam concentration can provide considerable amounts of H radicals for enhanced NH3 production, whereas excessive steam is likely to facilitate the NH3 conversion to H2. Gasification temperature exerts positive effects on the NH3 yield at 700–800 °C, but further increase in temperature causes a reduction in NH3 production, as a result of its decomposition into N2. The highest conversion of nitrogen into NH3 (55.98 wt%) is obtained at 800 °C with a steam concentration of 54 vol% and the catalyst-to-feedstock ratio of 1. Moreover, the LaFeO3 perovskite also exhibits desirable stability during the long-term cycling both in the activity and structure aspect.

Catalytic performance of Na/Ca-based fluxes for coal char gasification

Abstract Flux, able to improve the ash fusibility, usually contains catalytic metal compounds. Unfortunately, the quantitative analysis of synergistic catalysis effects between different fluxing agents on coal gasification has not been investigated thoroughly. In this study, the effect of the kinds and content of Na/Ca-based fluxes on char gasification was investigated in thermogravimetry analyzer (TGA). The synergistic catalysis effects and mechanism between the two kinds of fluxes were also studied. Finally, based on the TGA tests, the kinetics models for char gasification with flux addition were developed. The results showed that all the four Na-based fluxes could increase the char reactivity. Na2CO3, which afforded the best activity, could increase the reactivity by 5.3 times when the content was 5%. The five Ca-based fluxes had a weaker catalysis effect compared with Na-based fluxes. CaCl2, exhibiting the best activity among the five Ca-based fluxes, could increase the reactivity by 2.3 times when the content was 5%. For composite fluxes, Na2CO3–CaO and Na2CO3–CaCO3 had a remarkable synergistic effect, whereas others had less effect. Na2CO3 could inhibit the aggregation of Ca, which might cause the synergistic effects between Na and Ca fluxes. The random pore model was more suitable to describe the catalytic gasification process.

Gas production Characteristics during Electrochemical Catalytic Coal Gasification

To study the influences of temperature and power on coal gasification in the electrochemical catalytic gasification (ECG) process, gasification experiments of FX coal in CO2 atmosphere were performed in ECG system. The effects of temperature and power (thermal electrons) on gas production characteristics during ECG of coal have been studied in detail. Experimental results showed that the combustible components (CO, CH4 and H2) increased with temperature and power. The heat value, gas yield and cold gas efficiency increased with temperature and power. The heat value, gas yield and cold gas efficiency in ECG are higher than those in CCG at the same temperature. In addition, compared with temperature, power (thermal electrons) has a greater impact on gas production characteristics.

Hydrogen-rich gas production via steam gasification of food waste over basic oxides (MgO/CaO/SrO) promoted-Ni/Al2O3 catalysts

Food waste, a renewable resource, was converted to H2-rich gas via a catalytic steam gasification process. The effects of basic oxides (MgO, CaO, and SrO) with 10 wt% Ni/Al2O3 on the gasification properties of food waste were investigated using a U-shaped gasifier. All catalysts prepared by the precipitation method were analyzed by X-ray diffraction, H2-temperature-programmed reduction, NH3-temperature-programmed desorption, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The Ni/Al2O3 catalyst was reduced incompletely, and low nickel concentrations were detected on the surface of the alumina. The basic oxides minimized the number of acid sites and suppressed the formation of nickel-aluminate (NiAlxOy) phase in catalyst. In addition, the basic oxides shifted nickel-aluminate reduction reaction to lower temperatures. It resulted in enhancing nickel concentration on the catalyst surface and increasing gas yield and hydrogen selectivity. The low gas yield of the Ni/Al2O3 catalyst was attributed to the low nickel concentration on the surface. The maximum gas yield (66.0 wt%) and hydrogen selectivity (63.8 vol%) of the 10 wt% SrO- 10 wt% Ni/Al2O3 catalyst correlated with the highly dispersed nickel on the surface and low acidity. Furthermore, coke deposition during steam gasification varied with the surface acidity of the catalysts and less coke was formed on 10 wt% SrO- 10 wt% Ni/Al2O3 due to efficient tar cracking. This study showed that the steam gasification efficiency of the Ni/Al2O3 catalyst could be improved significantly by the addition of SrO.

Chemical looping catalytic steam gasification (CLCSG) of algae over La1-xBaxFeO3 perovskites for syngas production

Multifunctional perovskite-type oxides (ABO3) with flexible chemical tailoring characteristics and unique physical properties, are attracting an ever-increasing attention of scientists in the field of biomass chemical looping gasification process. Barium substituted lanthanum ferrite La1-xBaxFeO3 (x = 0, 0.3, 0.5, 0.7, 0.9, 1.0) with perovskite structure was used as oxygen carrier for algae chemical looping catalytic steam gasification (CLCSG) process for the first time. The effects of the Ba-substitution, mass ratio of perovskite and algae (P/A), temperature and water injection rate on the gasification performance were investigated. Results showed that the activity of LaFeO3 was dramatically improved by Ba substitution due to the formation of Fe4+/Fe3+ and oxygen vacancies. Among all the doped LaFeO3 perovskites, La0.3Ba0.7FeO3 (L3B7F) exhibited the best performance and gave highest syngas yield, carbon conversion and gasification efficiency. A maximum syngas yield of 1.00 m3/kg-Algae, carbon conversion of 98.86% and gasification efficiency of 96.71% were obtained at 900 °C with a water injection rate of 0.3 ml/min. Continuous high syngas yield and carbon conversion were observed during the cyclic redox tests.

Chemical Looping Catalytic Steam Gasification (CLCSG) of Algae Over La <sub>1-X</sub>Ba <sub>x</sub>FeO <sub>3</sub> Perovskites for Syngas Production

Multifunctional perovskite-type oxides (ABO3) with flexible chemical tailoring characteristics and unique physical properties, are attracting an ever-increasing attention of scientists in the field of biomass chemical looping gasification process. Barium substituted lanthanum ferrite La1-xBaxFeO3 (x=0, 0.3, 0.5, 0.7, 0.9, 1.0) with perovskite structure was used as oxygen carrier for algae chemical looping catalytic steam gasification (CLCSG) process for the first time. The effects of the Ba-substitution, mass ratio of perovskite and algae (P/A), temperature and water injection rate on the gasification performance were investigated. Results showed that the activity of LaFeO3 was dramatically improved by Ba substitution due to the formation of Fe4+/Fe3+ and oxygen vacancies. Among all the doped LaFeO3 perovskites, La0.3Ba0.7FeO3 (L3B7F) exhibited the best performance and gave highest syngas yield, carbon conversion and gasification efficiency. A maximum syngas yield of 1.00 m3/kg‧Algae, carbon conversion of 98.86% and gasification efficiency of 96.71% were obtained at 900 oC with a water injection rate of 0.3 ml/min. Continuous high syngas yield and carbon conversion were observed during the cyclic redox tests.

Catalytic coal gasification for methane production: A review

Catalytic coal gasification for methane production is a promising technology in the clean coal utilization field. In this review, the technologies for coal-derived natural gas production, the catalytic coal gasification processes and the used reactors were compared. The compared catalysts mainly included single-component, composite, and disposable catalysts. The effects of catalyst properties included composition, preparation method, supporter and loading amount were further illustrated. The influences of coal properties included char preparation method, particle size, and ash content on catalytic performance were investigated. The effects of temperatures and pressures on gasification performance were discussed in details. The evaporation, melting, decomposition, and inactivation of catalyst under various temperatures and pressures were also analyzed. It is expected to provide comprehensive information on the researches of catalytic coal gasification for methane production.

Different impacts of magnesium on the catalytic activity of exchangeable calcium in coal gasification with CO2 and steam

Exchangeable calcium (Ca) in coal has excellent catalysis on gasification reaction. Magnesium (Mg) may have effects on this process, but the previous researches are limited and the influence mechanism is still unclear. Thus, this work aims to investigate the influence of Mg on Ca catalytic gasification process. A low-rank coal was demineralized and then loaded with Ca and Mg, separately or jointly, by ion exchange. Subsequently, the samples were gasified in CO2 or steam at 800 ℃–900 ℃ in a specially designed thermogravimetric reactor. The partially-gasified chars were collected and analyzed with scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption tests, and temperature-programmed desorption (TPD) with a mass spectrometer (MS). The results show that the exchangeable Ca and Mg in coal form Ca-containing particles (CaCO3 or CaO) and MgO particles, respectively. Moreover, Mg has different impacts on the catalytic activity of Ca during CO2 and steam gasification. In CO2, Mg has a promoting effect. It is rather evident at 800 ℃, resulting from that MgO inhibits the sintering of large CaCO3 particles. These particles are mainly on the char surface and the pore structure is less developed. On the contrary, in steam, Mg has an inhibiting effect. It reduces the calcium-carbon interface and inhibits the channeling reaction process.

Influence mechanism of alkali metals on CO2 gasification properties of metallurgical coke

In order to clarify the function mechanism of alkali metal on degradation of metallurgical coke in blast furnace, the influence of alkali metal potassium and sodium on carbon structure change was investigated by gaseous adsorption method, and also the catalytic gasification reaction behaviors of alkali metal adsorbed coke samples was further studied. The results showed that the alkali metal vapor absorbed on coke has significant degradation effect on high temperature metallurgical properties of coke, which has catalytic effect and significantly increases gasification reactivity, and the catalytic limit of potassium vapor and sodium vapor was about 5% and 3%, respectively. Besides, potassium adsorption could also cause more fine coke particles to be produced, further aggravating degradation of coke in blast furnace. The analysis of physicochemical structures of different samples shows that the destruction of aromatic ring structure with dense and stable carbon structure in coke by alkali metal vapor adsorption process was the essential cause of coke reactivity increase and fracture. Kinetics analysis study shows that the random pore model (RPM) has the best performance representing the catalytic gasification process, and for different samples the activation energy first increases and then decreases with the increase of alkali metal adsorption content. It was also confirmed that there existed the kinetic compensation effect in the gasification process.

Effects of Ionic Liquid-Assisted Pretreatment of Heavy Metal-Contaminated Biomass on the Yield and Composition of Syngas Production Using Noncatalytic and Catalytic Pyrolysis and Gasification Processes

In this research, noncatalytic and catalytic pyrolysis and gasification of heavy metal-contaminated biomass (HMCB)—untreated and pretreated using a low-cost ionic liquid (IL, triethylammonium hydro...

Studies of CO2 gasification of the Miscanthus giganteus biomass over Ni/Al2O3-SiO2 and Ni/Al2O3-SiO2 with K2O promoter as catalysts

An assessment of the catalytic and non-catalytic gasification process of the Miscanthus giganteus (MG) biomass in an atmosphere of carbon dioxide was performed on the basis of thermogravimetric and thermovolumetric analyses. In the first step, the thermal behavior of biomass was determined by analyzing the mass loss during non-catalytic gasification with the use of TGA. The results of thermogravimetric analysis were used to assess the course of the biomass heating process in the atmosphere of CO2 and to distinguish the individual phases of this process. Then, the thermovolumetric measurements of MG gasification were taken with the use of Ni/Al2O3-SiO2 and Ni/Al2O3-SiO2 with K2O promoter as catalysts. The obtained results allowed determining the process rate as well as composition of the resulting gas and yields of main gaseous products (CH4, CO, H2). The use of Ni/Al2O3-SiO2 as catalyst resulted in the highest conversion rate of MG gasification into gaseous products with considerably increased contents of H2 and CO. The second analyzed catalyst—Ni/Al2O3-SiO2 with K2O promoter—did not catalyze the gasification process. However, the use of both tested catalysts had a positive effect on reducing the methane content in the resulting gas. One can also suppose that it promotes the decomposition of the tar formed in the process.

The Characteristic of Coal Oil From Catalytic Coal Gasification

In this work, the catalytic gasification process of coal was studied at different operating temperatures and catalyst weights. The purpose of this study was to study the characteristics of coal oil produced through the gasification process using Nickel Molybdenum (NiMo) catalyst. The effect of adding NiMo catalyst with variations in weight of 0%, 5%, 10% and 15% for different gasification temperatures (375 – 385 °C, 430 – 440 °C, and 475 – 485 °C) were studied on coal with a calorific value of 6,400 kcal/kg. The process was done in fluidized bed reactor under atmospheric pressure and an air flow rate of 2 liters/minute was flow for 60 minutes. The results showed that NiMo is effective as a catalyst in the gasification of coal at 430 – 440 °C, the addition of 15% weight of catalysts produced coal oil with a yield of 9.35% and the composition of hydrocarbon consists of 59.75% of aromatics, 26.42% of aliphatics, and 7.34% of phenolics. Compared to coal oil without catalyst give a yield of 6.56% with 57.33% of aromatics, 17.44% of aliphatics, and 16.03% of phenolics. This showing that NiMo catalysts have a high selectivity to increase aromatic and aliphatic hydrocarbons in coal oil.

Highly dispersed nickel nanoparticles supported on hydrochar for hydrogen-rich syngas production from catalytic reforming of biomass

The synthesis of carbon-based nanomaterials, ideally produced via facile, inexpensive approaches, using sustainable resources as precursors, with modulated structures, morphologies and functionalities is still challenging for energy applications. This work developed a mild one-step hydrothermal synthesis route for the fabrication of highly dispersed metallic nickel nanoparticles on hydrothermal carbons derived from waste biomass. The roles of precursor nickel ion concentration and calcination temperature in modulating the morphology, location and crystalline size of the nickel nanoparticles as well as the metal-support interactions have been delineated. The average grain size of the metallic nickel nanocrystals on the resultant Ni0.5@HCOp nanocatalysts could be tuned to 8–13 nm by varying the preparation conditions. The catalytic abilities of the Ni-based nanocatalysts towards hydrogen-rich syngas production and tar reduction were then tested in a two-stage reactor system using sewage sludge as biomass feedstock. The catalytic tests showed that the Ni0.5@HCOp catalyst calcined at 700 °C was shown to have stronger metal-support interactions compared to other Ni-based nanocomposites, which provided better suppression of coke deposition and resistance of nickel agglomeration during the catalytic gasification process. This highly active catalyst promoted formation of hydrogen-rich syngas, with up to 109.2 g H2/kg sludge, and tar yields as low as 2.12 mg g−1.

Synergistic Mechanism of Ni Catalyst and Supercritical Water during Refractory Organic Wastewater Treatment

The synergistic mechanism of Ni catalyst and supercritical water (SCW) during the treatment of dibutyl phthalate (DBP), a representative component of refractory phthalic acid esters, has been investigated using the ReaxFF molecular dynamic simulations. During the catalytic SCW gasification process, Ni catalyst could facilitate the bond cleavage while the roles of SCW were to promote cracking and serve as H sources. As for the evolution of dissociated side chains, the cooperative effects greatly enhanced the cracking of long-chain fragments and generation of saturated products. Ni could help split H2O and the SCW accelerated β-scission as well as provided H and O atoms. For the aromatic ring-opening stage, a Ni-catalyzed process involved successive bond scission and migration of carbon chains into catalyst bulk was dominant while the SCW only offered marginal help. With regard to H2 production, the synergistic effects were supposed to improve H2 yield. Furthermore, the Ni catalyst was gradually deactivated...

Graphene-supported metal nanoparticles as novel catalysts for syngas production using supercritical water gasification of microalgae

In this study, biomass conversion of chlorella sp. microalgae was investigated in the catalytic supercritical water gasification (SCWG) process. The catalytic effect of five different graphene-supported metal nanoparticle catalysts (Ni/rGO, Cu/rGO, Co/rGO, Mn/rGO and Cr/rGO) were evaluated on the composition of syngas. The impact of main process factors including catalyst loading (40, 70, and 100wt%), and temperature (355–405 °C) was studied on the SCWG process over Ni/rGO catalyst as the most efficient catalyst among the selected metal nanoparticles. The findings showed that at the optimum Ni/rGO loading of 70wt% (at temperature of 380 °C), the hydrogen yield increased by a factor of 5.8 in comparison to absence of Ni/rGO catalyst. At the optimum temperature of 405 °C (Ni/rGO loading of 40wt%), hydrogen selectivity of 31.9% was obtained. The results revealed that increment of Ni/rGO catalyst loading extremely reduced the solid residue and tar formation, which is desired in the SCWG process. Moreover, Characterizations proved the stability of prepared catalysts at supercritical condition.