Catalytic Cracking Of Tar Research Articles

Hydrogen-rich syngas production by catalytic cracking of tar in wastewater under supercritical condition

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al2O3 catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 °C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6–215.3 m2/g. The effect of Ni loading (5–30 wt%), reaction temperature (400–500 °C), and tar concentration (0.5–7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H2, were significantly enhanced with an addition of Ni/Al2O3 catalysts. With 20%Ni/Al2O3, the H2 yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al2O3 had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H2 yield of 46.8 mol/kgtar was achieved with 20%Ni/Al2O3 at 500 °C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al2O3 has a potential to improve H2 production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater.

Catalytic cracking of biomass tar together with syngas production over red brick powder-supported nickel catalysts

The catalytic cracking of biomass tar accompanied with syngas production was investigated over red brick powder (RBP) supported nickel (Ni/RBP) catalyst. The Ni/RBP catalysts demonstrated high catalytic performance on biomass tar removal and production of CO and H2. The tar conversion efficiency was 96.76% at 800 °C together with the yields of CO and H2 being 266.59 ml/g and 297.71 ml/g, respectively, when the nickel loading quantity accounted for 10.25 wt% of the catalyst. The increase in cracking temperatures from 500 °C to 800 °C showed a positive influence on tar removal and syngas production. The loading of nickel on RBP also contributed well to tar removal and syngas production. The Ni/RBP catalyst was beneficial to cracking some heavy molecular compounds into lighter species, and possessed a reasonable resistance to coke deposition. The results suggested that Ni/RBP catalyst would be a greatly potential catalyst for the efficient cracking of biomass tar into syngas.

Synergy of steam reforming and K2CO3 modification on wood biomass pyrolysis

The primary objective of this study was to investigate the synergistic effects of K2CO3 and steam reforming in the gasification process of woody biomass for hydrogen production. The experiment was carried out in a fixed-bed reactor with a continuous feeding system to investigate the effect of steam to biomass (S/B) molar ratio (0–0.4), K2CO3 loading amount (0–10 wt%) and reaction temperature (650–850 °C) as three main factors. The experimental results clearly indicated that both S/B and K2CO3 loadings promoted hydrogen production which could reach from 56 to 66% progressively as temperature increased from 650 to 750 °C, the role of potassium carbonate was mainly to change the path of catalytic cracking of tar and reduce the carbon deposit on the surface of the catalyst. While the role of water vapor mainly promoted shifting the reforming reaction in the direction of hydrogen generation. In addition, the water vapor itself could react with carbon to generate more hydrogen. The synergy of K2CO3 modification and steam reforming alleviated the deposited char and changed the components of tar simultaneously, and the optimum value for hydrogen production was acquired with 7.5% K2CO3 loading biomass while the value of S/B was 0.3 as the result of K2CO3 modification. The yield of rich-hydrogen syngas at 650 °C was similar with that of 850 °C, which evidenced that K2CO3 promoted the cracking of biomass at the low temperature region. It was concluded that K2CO3 modification of wood biomass with steam reforming promoted the hydrogen production and changed the path of catalytic cracking of tar and reduced the carbon deposit on the surface of the catalyst.

One-step synthesis of biomass activated char supported copper nanoparticles for catalytic cracking of biomass primary tar

Activated char supported copper nanocatalysts were synthesized directly by one-step pyrolysis of CuCl2 impregnated biomass together with ZnCl2 as activation agent and applied to the cracking of biomass primary tar in a dual-stage reactor. The characterization of the obtained catalysts using XRD, SEM-EDX, TEM and N2 adsorption-desorption indicated CuCl2 can be reduced to Cu0 nanoparticles as active sites, and the presence of ZnCl2 can significantly enlarge the surface area of biomass char to improve the dispersion of copper nanoparticles. A large number of micropores and mesopores were formed during the synthesis process, which also helps to adsorb tar molecules and prolong the reaction time. The prepared nanocatalysts exhibited excellent catalytic activity in the cracking of primary biomass tar as a result of the combining effect of CuCl2 and ZnCl2, and a high tar conversion efficiency of 94.5% was obtained using RHC-1.0Cu1·0Zn at 800 °C. The yields of H2, CH4, CO and the total gas product increased significantly as a result of the tar reforming reactions using the activated char supported catalysts. GC-MS analysis illustrated that the biomass primary tar was mainly decomposed into oxygenated aromatic compounds and light tar compounds over the biomass char supported copper nanocatalysts.

Study on Sulfur Conversion Characteristics in Catalytic Cracking of Coal Tar in the Presence of Dolomite-Supported Catalysts

To investigate sulfur redistribution in the process of tar catalytic cracking, nature dolomite, Ni-based dolomite, Fe-based dolomite, and Ni/Fe-based dolomite catalysts were prepared. The effect of...

Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds To Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures

The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chemical substances, and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodology unsuccessfully due to the blockage of separating particle filters, fuel line flow, and substantial transfer losses. Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, it is still highly desirable to enhance the catalysts’ activity kinetics, selectivity, stability, resistance to (ir)reversible coke deposition, and regeneration solutions. The purpose of this Review is to provide a comparative systematic evaluation of the various natural, synthetic, and hybrid ways to convert the model molecular compounds into benzene, toluene, xylene, (poly)aromatics, syngas, and others. The recent scientific progress, including calcite...

In-situ catalytic upgrading of coal pyrolysis tar over activated carbon supported nickel in CO2 reforming of methane

An integrated process of in-situ catalytic cracking of coal pyrolysis tar and CO2 reforming of methane (CRM) over activated carbon supported nickel (Ni/AC) was conducted to upgrade tar. The results show that a tar with more than 95 wt% light tar content can be obtained, and the light tar yield is increased by 52.5% at 650 °C over Ni/AC. In comparison to the non-upgrading tar, the content of light oil, phenol oil, naphthalene oil and wash oil over Ni/AC increases by 224%, 283%, 132% and 36%, respectively, and the average molecular weight of tar decreases from 279 to 160 amu. During the upgrading process, 3-ring and 4-ring arenes decline, accompanied by the remarkable increase of 1-ring and 2-ring arenes. Isotope trace method were used to explore the mechanism of the upgrading process. When CH4 was replaced by CD4 or 13CH4, D and 13C can be detected in the upgraded tar. The results reveal that Ni/AC catalyze both CRM and tar cracking simultaneously, the free radicals from CRM stabilize cracking fragments of coal tar to generate more light components. By comparing the fresh and spent catalysts, it can be confirmed there is no adsorption of heavy tar over Ni/AC during the upgrading process.

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

The catalytic activity of pyrolysis chars from bio-waste was investigated for the cracking of model tar compounds (ethylbenzene and benzene). Two pyrolysis chars were produced at 700 °C from (1) used wood pallets (UWP), and (2) a 50/50 dry% mixture of food waste (FW) and coagulation-flocculation sludge (CFS). Steam activation at 850 °C was used to study the influence of the porous structure. While coke deposition is known to be responsible for the deactivation of carbonaceous chars and metal catalysts during tar cracking reactions, the deactivation of complex materials such as bio-waste chars has scarcely been studied. For this reason, special attention was paid on the relationships between the physicochemical properties of the chars, the operating conditions, and the deactivation mechanisms. To this aim, the cracking tests were performed over a wide temperature range: 400–650 °C for the ethylbenzene cracking, and 850–950 °C for benzene cracking. After the ethylbenzene cracking tests at 650 °C, the characterisations performed with SEM, BET, FTIR and Raman revealed that coke deposition was responsible for the char’s deactivation. The high specific surface area of activated chars explained their higher catalytic activity, and mesoporous catalysts were proved to be more resistant to coke deactivation than microporous catalysts. For these reasons, the higher ethylbenzene conversion (85.8%) was reached with the activated char from food waste and sludge (ac.FW/CFS). For benzene cracking at higher temperature (850 and 950 °C), the chars from food waste and sludge (FW/CFS) were the most active catalysts, despite their deactivation by the melting, diffusion and sintering of the inorganic species. This original deactivation mechanism, reported for the first time, led to the formation of an inorganic layer composed of P and Ca species at the char surface, with some areas rich in KCl and NaCl. Non-activated char from food waste and sludge (c.FW/CFS) was surprisingly proved to be more resistant to deactivation by inorganic species than the activated char (ac.FW/CFS) during the benzene cracking tests at 950 °C. This extended catalytic activity was explained by the activation of the non-activated char (c.FW/CFS) with the CO2 contained in the syngas which simultaneously developed the porosity and created new available active sites. This study marks a step forward in the understanding of the relationships between the deactivation mechanisms, the physicochemical properties of the chars, and the cracking temperature. Finally, a proposal for process integration is presented to consider the possibility to valorise the chars as catalysts to decompose the tar generated in the same pyro-gasification process.

Catalytic gasification of refuse-derived fuel in a two-stage laboratory scale pyrolysis/gasification unit with catalyst based on clay minerals

Municipal solid waste (MSW) disposal is a serious environmental issue requiring immediate solution and good waste management strategy. Mechanical-biological treatment (MBT) plants offer the opportunity to reduce the amount of MSW that is, otherwise, disposed of in landfills. Up to 40% of MSW is converted to waste fuel, also called refuse-derived fuel (RDF). Gasification is a promising alternative of RDF processing. It can be defined as high temperature treatment of the feedstock with lower than stoichiometric amount of oxygen resulting mainly in a gaseous product (syngas). High hydrogen content, specific ratio of H2/CO, and low tar content are important parameters of syngas for its application in both energy production and chemical synthesis. Reduction of tar content in syngas can be achieved by catalytic tar cracking. In this work, a catalyst prepared from natural clay was characterised by thermogravimetric, specific surface area, X-ray diffraction, X-ray fluorescence and scanning electron microscopy (SEM) analyses. Catalyst activity was tested in two reactions, namely in decomposition of model tar constituent, p-xylene, and in cracking of tar produced in RDF gasification experiments. Influence of the reaction temperature and the amount of catalyst on the p-xylene conversion and products’ distribution was studied. The results proved high catalytic activity of the prepared catalyst in the decomposition of p-xylene. Coupled RDF pyrolysis and the produced volatiles gasification experiments were carried out in a two-stage laboratory scale reactor using a bed of tar cracking catalyst in the second stage. Tar decomposition experiments were carried out at the reactor temperatures of 700–850 °C applying different amounts of catalyst (0.75 g, 1 g, 1.25 g, 1.5 g, 2 g and 4 g) per 1 g of pyrolised RDF. Results indicate that the presence of catalyst had significant effect on both tar cracking efficiency and gas composition. Loss of the catalyst specific surface area was observed when the experiments were carried out at temperatures exceeding 800 °C.

Catalytic cracking of tar derived from the pyrolysis of municipal solid waste fractions over biochar

The tars derived from the pyrolysis of four typical municipal solid waste fractions at 600 °C, namely pine wood (PW), tryptone (TP), polyethylene (PE) and polyvinyl chloride (PVC), were characterized and then catalytically cracked by activated biochar catalyst (ABC) at 700–900 °C. The ABC was produced from the pyrolysis of pine wood at 800 °C for 1 h, then activated by CO2 at 900 °C for 20 min. The results showed that O-containing species, N-containing species, chain hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were the main products in the raw tar from the pyrolysis of PW, TP, PE and PVC, respectively. The tar cracking efficiency by ABC was ordered as PW>TP>PE>PVC, which indicated that the biomass tars were easier to be converted by ABC than plastic tars. The highest tar conversion of 98.7% was achieved for PW at 900 °C. Besides, N-containing tars were more stable than O-containing tars. The coke deposition on the ABC was more serious after the cracking of plastic tars (PE and PVC) than that of biomass tars (PW and TP). After the catalytic cracking of TP and PVC tars at 900 °C, the nitrogen and chlorine contents in ABC increased by 3 times and 10.5 times, respectively.

Catalytic cracking of biomass pyrolysis tar over char-supported catalysts

The work aims to investigate an effective method of catalytic reforming of tar during biomass high-temperature pyrolysis using rice husk char (RHC) and metal impregnated (Fe, Cu and K) char in a dual-stage reactor. The char and char-supported catalysts exhibited high catalytic performance, in terms of the high tar conversion efficiencies of 77.1% for RHC, 82.7% for K-RHC, 92.6% for Fe-RHC and 90.6% for Cu-RHC at 800 °C. Moreover, K-RHC and Cu-RHC catalysts after three cycles still exhibited high activity for tar removal. The catalytic tar conversion by char or char-supported catalysts contributes to improving the yield of syngas, particularly the combustible gases of H2, CO and CH4, corresponding to the syngas yield increasing from 196.6 mL/g for thermal reforming to 269.6 mL/g for K-RHC, 274.9 mL/g for Cu-RHC and 342.7 mL/g for Fe-RHC at 800 °C, respectively. The results from GC–MS analysis illustrated that the addition of char and char-supported catalysts promoted the transformation of larger polycyclic aromatic hydrocarbons into lighter tar compounds, leading to an increase in the proportion of single-ring tars. XRD results indicated that the most active phases of the fresh K-RHC, Cu-RHC and Fe-RHC for tar cracking and reforming were KCl, Cu and Fe, respectively. Textural characterization showed the addition of Fe and Cu was in favor of producing highly porous carbon materials and led to the increase in specific surface area and total pore volume.

Steam catalytic cracking of coal tar over iron‐containing mixed metal oxides

AbstractSteam catalytic cracking is deemed as a promising method for the catalytic cracking of coal tar. In this study, a serial of iron‐containing mixed metal oxides including ceria, zirconia, alumina, cobalt, nickel, and barium oxides were prepared for steam catalytic cracking of coal tar and characterized by N2 adsorption‐desorption, X‐ray diffraction, H2 temperature programmed reduction, and Raman spectroscopy, respectively. It was found that the specific surface area and pore volume increase while the crystal size decreases when Fe2O3 was doped with the investigated metal oxides. Among these, iron‐alumina mixed oxide (FeAl) shows the highest specific surface area and pore volume. The H2‐TPR analysis indicated that most of the mixed metal oxides have lower reduction temperature, especially for iron‐ceria mixed oxide (FeCe). The reduction temperature of FeCe is around 500 °C, and its reduction peak shifts to a lower temperature and becomes narrower as compared to other iron‐containing mixed metal oxides. The steam catalytic cracking of coal tar at 550 °C showed that the light tar content (below 360 °C) over FeCe, FeCo, and FeAl are 68.5, 67.0, and 66.5 %, respectively. The increase of CO2 and H2 over iron‐containing mixed metal oxides suggested that oxygen species from iron‐containing mixed metal oxides and steam could participate in the steam catalytic cracking of coal tar.

In-situ catalytic upgrading of coal pyrolysis tar coupled with CO2 reforming of methane over Ni-based catalysts

Tar was upgraded by integrating in-situ catalytic cracking of coal pyrolysis tar with CO2 reforming of methane (CRM) over Ni-based catalysts to improve light tar yield. The results showed that Ni-based catalysts can catalyze coal tar cracking and CRM simultaneously, and some radicals, like H and CHx, produced in CRM over Ni-based catalysts could combine with the radicals from catalytic cracking of tar to avoid excessive cracking of tar. The catalyst 5Ni/Al2O3 (Ni/Al2O3 with 5 wt% Ni) showed the best performance for tar upgrading owing to its appropriate activity of both tar cracking and CRM. Compared with non-upgrading tar, the average molecular weight of upgrading tar over 5Ni/Al2O3 decreases from 279 to 193 amu, and the content and yield of light tar (boiling point < 360 °C) over 5Ni/Al2O3 increase by 53% and 32% at 650 °C. The contents of light fractions increase and that of pitch decreases apparently. The light components, such as benzenes, phenols and naphthalenes, are all improved, and long aliphatic chains and aromatics with 3 or 4 rings have an obvious decrease. Active components in upgrading catalysts obviously affect the upgrading effect of coal tar. 5Ni/Al2O3 exhibits higher content and yield of light tar compared with 5Co/Al2O3 and 5Fe/Al2O3.

Catalytic cracking of biomass tar over char supported nickel catalyst

Catalytic cracking of biomass tar was investigated using steam gasification obtained char supported nickel catalyst in a lab-scale fixed bed reactor to determine the effects of catalytic cracking temperature, Ni loading and gas residence time on product distribution and gas composition. Results showed that the optimum catalytic cracking parameters were at 800 °C catalytic cracking temperature, 6 wt% Ni loading and 0.5 s gas residence time. The characterizations of tars were determined by ultimate analysis, FTIR and GC-MS. Compared with no catalyst cracking, the relative content of single-ring aromatics in tars obviously increases with the appreciably decreases in polycyclic aromatics, O-containing compounds and heterocyclic compounds after catalytic cracking, especially in Ni-6/char catalyst condition.The surface characteristics of Pre- and Post- char supported 6 wt% loading Ni catalysts were analyzed with BET, SEM, XRD and XPS. The BET and SEM results indicated that there was a slight deposition of coke on the surface of char after catalytic cracking. Meanwhile, XRD and XPS results indicated that NiO was transformed into Ni via carbothermal and hydrogenation reductions which contributed to the enhancement of tar conversion. These findings manifested that char supported nickel catalyst can be used as a low-cost catalyst to decompose tar.

Experimental investigation of catalytic cracking of rice husk tar for hydrogen production

The presence of tar content in the product gas is a major problem with the biomass gasification process as it prevents its further utilization. Heterogeneous cracking of tar using catalyst is the most effective way to overcome this problem. The present study provides specially a method for converting biomass to hydrogen-rich syngas in a two-stage process. The first stage refers to pyrolysis process and the second stage refers to gasification process. The heterogeneous experiments of rice husk tar cracking were performed in a two-stage gasifier using different catalysts such as char formed from pyrolysis of rice husk in the same reactor, commercial activated carbon, sand silica, and nickel containing stainless steel turnings obtained from mechanical workshop. The products of heterogeneous tar cracking were evaluated for optimizing hydrogen-rich syngas formation considering the effects such as temperature, carrier gas and quantity of catalyst. The mild steel turnings were found to be the best catalyst giving 0.31 vol% tar, 53.60 vol% of hydrogen, 22.73 vol% of carbon monoxide, 0.0 vol% of methane and 23.35 vol% of carbon dioxide in product gas at 900 °C.

Co-gasification of municipal solid waste with high alkali coal char in a three-stage gasifier

The commercial scale up of municipal solid waste (MSW) gasification system is restricted by the low quality of the syngas, especially due to the low heating value and high contents of tar and HCl. In this study, an innovative three-stage system for co-gasification of MSW with high alkali coal char was developed. The modeled MSW was pyrolyzed in the first stage and the raw syngas was partially oxidized in the second stage and then reduced with high alkali coal char in the final stage to produce high quality syngas. The effects of temperatures and equivalence ratios (ER) have been evaluated experimentally and the concentration of condensable tar species and HCl was examined carefully. In general, the two key pollutants in produced gas could be controlled as low as 11.3 mg/Nm3 (tar content) and 17.6 mg/Nm3 (HCl content). Meanwhile, the level of H2, CO, CH4 in synthesis gas reach a stable high level of 41.9 vol%, 29.3 vol% and 7.49 vol%, respectively, while the lower heating value (LHV) attains 12.2 MJ/Nm3, meeting the intake-gas conditions for internal combustion engines. The experimental results confirm that the highest pyrolysis temperature leads to the maximum gas yield from oxidation stage (i.e., 0.913 Nm3/kg at 650 °C), to be compared with 0.898 Nm3/kg (550 °C) and 0.747 Nm3/kg (450 °C). The lowest gasification temperature (800 °C) is indicated as most favorable for HCl removal from syngas, linked with the advancement of reversible reactions between HCl and Ca-based compounds. H2, tar and LHV all decrease with rising equivalence ratio. In summary, the high-quality syngas can be produced at a steady yield rate of 1.57 Nm3/kg from three-stage gasifier, due to dichlorination and catalytic tar cracking action of high alkali coal char at a low cost.

Pyrolysis behavior of thermally thick wood particles: Time-resolved characterization with laser based in-situ diagnostics

Infrared laser absorption spectroscopy (IRLAS) and laser-induced fluorescence spectroscopy (LIF) are applied in the present study for online in-situ characterization of volatiles products in the close vicinity of a single pyrolysing wood sphere. These advanced analytical techniques are combined with online measurements of temperature and mass evolutions in order to gain further insight into the complex processes occurring during slow pyrolysis of thermally thick wood particles. Three different heating rates (5, 10, 20°C/min) and two wood types (beech, pine) were used. Time-resolved absolute concentrations of the main permanent gases CO2, CO, CH4 and H2O were measured applying IRLAS. From the LIF measurements the qualitative temporal release of polycyclic aromatic hydrocarbons (PAHs) could be deduced. Different behaviors regarding the release of volatiles, temperature evolution and conversion rates were observed for both wood species, which could not be ascribed only to the different content of cellulose, hemicellulose and lignin. According to the measured volatiles evolution an enhancement of heterogeneous catalytic tar cracking seemed to be present with higher heating rates for both wood types. However, the evolution of exothermicity and PAH release differed for both wood types indicating different reaction pathways. An analysis of possible reaction pathways including secondary reactions is performed taking into account all experimental findings about the in-situ composition of the volatiles and the evolution of the PAHs as well as the exothermicity. The differences in the pyrolytic behavior of both species can be related to both the chemical and physical properties of the raw materials.

Selection of dolomite bed material for pressurized biomass gasification in BFB

Dolomite is considered advantageous as bed material in fluidized bed gasification processes, due to its catalytic tar cracking and anti-sintering properties. However, in case of pressurized fluidized bed gasifiers, the use of dolomite is challenging. High temperature in the presence of steam favors the production of clean syngas due to the intensified cracking of tar in the presence of CaO, whereas it simultaneously increases the tendency of fragmentation of dolomite particles after full calcination. The present study was carried out to examine the influence of the properties of dolomite on the stability of dolomite in a pressurized fluidized bed gasifier, with the aim of determining criteria for dolomite selection. Glanshammar dolomite exhibited a better stability in the mechanical strength after calcination, compared to Sala dolomite. The corresponding change of micro-structure that occurred during dolomite chemical transformation was presented. The crystal pattern and Si distribution in the crystal lattice are the possible explanations for the superior performance of the Glanshammar dolomite compared to the Sala dolomite.

Preparation of hydrogen-rich gas by heavy tar cracking with pyrolysis coke catalyst modified by plasma

ABSTRACTIn this paper, two pyrolysis furnace reactors were used, and pyrolysis tar was cracked by different types of pyrolysis coke and Mn-supported pyrolysis coke catalysts. The effect of pyrolysis coke prepared at different temperatures on the catalytic cracking of coal tar was studied. The optimum pyrolysis coke was used as the carrier, and the catalyst was prepared by low-temperature plasma. The effect of the catalyst on the catalytic cracking of tar was discussed. The composition of the pyrolysis gas was analyzed by gas chromatography, and the catalysts were characterized by XRD, BET, and SEM. The results showed that: 1) pyrolysis coke prepared at different temperatures could reduce tar yield and increase gas content, and the catalytic cracking effect of pyrolysis coke prepared at 500°C was obvious; 2) the catalyst prepared by plasma modification and roasting had the best effect on tar cracking, and hydrogen production increased by 1.07 times.

Selection of dolomite bed material for pressurized biomass gasification in BFB

Dolomite is considered advantageous as bed material in fluidized bed gasification processes, due to its catalytic tar cracking and anti-sintering properties. However, in case of pressurized fluidized bed gasifiers, the use of dolomite is challenging. High temperature in the presence of steam favors the production of clean syngas due to the intensified cracking of tar in the presence of CaO, whereas it simultaneously increases the tendency of fragmentation of dolomite particles after full calcination. The present study was carried out to examine the influence of the properties of dolomite on the stability of dolomite in a pressurized fluidized bed gasifier, with the aim of determining criteria for dolomite selection. Glanshammar dolomite exhibited a better stability in the mechanical strength after calcination, compared to Sala dolomite. The corresponding change of micro-structure that occurred during dolomite chemical transformation was presented. The crystal pattern and Si distribution in the crystal lattice are the possible explanations for the superior performance of the Glanshammar dolomite compared to the Sala dolomite.