Tar Mixture Research Articles

Hydroconversion of sawdust in a mixture with oil tar in the presence of nanosized cracking catalysts

The hydroconversion of oil tar and its mixture with pine sawdust was studied in an autoclave with the continuous removal of a vapor—gas phase at a hydrogen pressure of 7 MPa in the presence of aluminum nitrate and zirconium oxychloride as the precursor of a nanosized cracking catalyst. It was found that the greatest yield of hydrogenate and gaseous products was observed at aluminum nitrate and zirconium oxychloride concentrations of 0.35 and 0.09 wt %, respectively. In this case, 40.1 wt % liquid C5–C26 hydrocarbons, 16.3 wt % gases, and 5.2 wt % coke were formed upon the hydroconversion of oil tar at a temperature of 400°C for 2 h, whereas the yields of the products with the use of a mixture of oil tar with pine sawdust (18.0 wt %) in the process were 36.8, 18.8, and 21.2 wt %, respectively.L

Co-pyrolysis of biomass tar and iron ore fines for the production of direct reduced iron

Biomass tar can be used as reducing agent for reduction of iron oxide, and simultaneously iron is a good catalyst for tar cracking. Thus, an iron ore reduction system integrated tar cracking and iron ore reduction was proposed. The influences of raw material characteristics, the equivalence ratio of tar to iron ore fines as well as reduction conditions on the reduction behaviors of iron ore fines were discussed. Also, the co-pyrolysis of mixture of tar and iron ore fines was investigated. The results show that the iron ore reduction using tar is reliable with a high tar cracking efficiency and a high reduction degree. Due to the formation of porous structures, preheated iron ore fines showed an excellent reduction behavior than those without preheating. At the initial stage, iron oxide did not exert any obvious effect on tar destruction, while as reaction temperature raised above 600 °C, a noticeable decline of tar content was observed, which was attributed to the enhanced reduction consumption and catalytic decomposition by the reduced iron. Increasing the ratio of tar to iron ore was favorable for the reduction of iron oxide, while, when the ratio exceeding 0.6, the effect became less notable. The introduction of proper amount of steam can improve tar cracking and further improve iron oxide reduction. At optimum conditions (iron ore fines was first preheated at 400 °C and then mixed with tar according to tar/iron ore fines 0.6, reacted at 900 °C for 30 min under the steam atmosphere with the mass ratio of steam/tar 0.87), the reduced iron product with metallization rate 94.1% was achieved.

Analysis of pure tar substances (polycyclic aromatic hydrocarbons) in the gas stream using ultraviolet visible (UV-Vis) spectroscopy and multivariate curve resolution (MCR).

The analysis of tar, mostly characterized as polycyclic aromatic hydrocarbons (PAHs), describes a topic that has been researched for years. An online analysis of tar in the gas stream in particular is needed to characterize the tar conversion or formation in the biomass gasification process. The online analysis in the gas is carried out with ultraviolet-visible (UV-Vis) spectroscopy (190-720 nm). This online analysis is performed with a measuring cell developed by the Fraunhofer Institute for Chemical Technology (ICT). To this day, online tar measurements using UV-Vis spectroscopy have not been carried out in detail. Therefore, PAHs are analyzed as follows. The measurements are split into different steps. The first step to prove the online method is to vaporize single tar substances. These experiments show that a qualitative analysis of PAHs in the gas stream with the used measurement setup is possible. Furthermore, it is shown that the method provides very exact results, so that a differentiation of various PAHs is possible. The next step is to vaporize a PAH mixture. This step consists of vaporizing five pure substances almost simultaneously. The interpretation of the resulting data is made using a chemometric interpretation method, the multivariate curve resolution (MCR). The verification of the calculated results is the main aim of this experiment. It has been shown that the tar mixture can be analyzed qualitatively and quantitatively (in arbitrary units) in detail using the MCR. Finally it is the main goal of this paper to show the first steps in the applicability of the UV-Vis spectroscopy and the measurement setup on online tar analysis in view of characterizing the biomass gasification process. Due to that, the gasification plant (at the laboratory scale), developed and constructed by the Fraunhofer ICT, has been used to vaporize these substances. Using this gasification plant for the experiments enables the usage of the measurement setup also for the spectroscopic analysis of the tar formation during the biomass gasification.

Optimization of Products Yields from the Pyrolysis of Palm Kernel Shells Using Response Surface Methodology

This work focussed on the optimisation of product yields from the pyrolysis of palm kernel shells (PKS). 479g of dried PKS were loaded into the retort and then placed inside the furnace chamber and this was pyrolysed at 300, 400, 500, 600 and 700°C. The pyrolysis products obtained are char, tar (pyro oil and pyroligneous acid) and gas. A full factorial design (FFD) consisting two factors (Temperature and duration of pyrolysis) at three level was used to study the pattern of product yields from the pyrolysis of PKS. Char, tar and gas were evaluated as the responses. Thirteen experimental runs resulted from the FFD with a minimum product yield of 0.9wt% and maximum product yield of 99wt%. Response surface methodology was used to analyse the results of the FFD of the product yields of PKS. The optimum conversion yields expressed as a percentage of oven-dried weight of palm kernel shells of char, tar and gas products at their respective pyrolysing temperatures were 99wt% char at 304°C, 35wt% tar at 700°C and 39% gas at 700°C. The duration for the pyrolysis process was 20mins for 479g of dried palm kernel shells. The results of the work show that palm kernel shells can be readily pyrolised to obtain optimum yield of gas, tar (mixture of pyrolitic oil and pyroligneous acid) and char.

Assessment of the Solid-Phase Adsorption Method for Sampling Biomass-Derived Tar in Industrial Environments

Low-temperature gasification of biomass is a primary process step for production of biofuels or electricity using gas-fired engines or turbines. In addition to the desired product gas, the raw gas produced through gasification inevitably contains condensable hydrocarbons, known collectively as tar. The amount and composition of the tar have relevance for the efficiencies of the downstream processes. Tar can be measured using both online and off-line methods. However, many of these methods currently lack information regarding their implementation and accuracy levels for large-scale systems. In this work, the Solid-Phase Adsorption (SPA) method for measuring tar in industrial applications is evaluated. The individual steps of the method were examined for their effects on the overall performance of the analysis. Sample collection was found to be the most prominent source of error, and this was mainly due to human factors. Omitting to determine the temperature and pressure of the sampled gas contributed to this error, as the sampled volume of gas under normal conditions could not be correctly calculated. Inconsistencies in the treatment and storage of the collected samples were shown to affect the more volatile species with boiling points similar to that of benzene. The gas chromatography (GC) analysis was performed with satisfying accuracy. However, the reliability of the estimations of the average composition and dew-point of the tar mixture were dependent upon the amount of the identified species. The current implementation of the SPA method yields values with a relative standard deviation within 10% for the majority of the compounds in a given sample. However, in line with the result of previous studies, the tar species with boiling points between those of benzene and xylene (i.e., the BTX compounds) were measured with a lower accuracy than those of heavier tars.

Steam reforming of ethanol–phenol mixture on Ni/Al2O3: Effect of magnesium and boron on catalytic activity in the presence and absence of sulphur

The steam reforming of ethanol/phenol mixture (168gTOT/Nm3, ethanol: phenol 2:1mol), assumed as a model for tar mixtures, has been studied over Ni/Al2O3, Ni-Mg/Al2O3 and Ni-B/Al2O3 catalysts. The effects of reaction temperature and of the presence of sulphur have been investigated. Catalysts have been characterized by XRD, IR of adsorbed CO, TPR, UV–vis spectroscopies. IR studies of adsorbed water and phenol have also been performed.The addition of Magnesium shows an activating effect on Ni/Al2O3 but also increases sensitivity to sulphur poisoning. This has been associated to the formation of large Ni metal particles over the MgxAl2O3+x support surface formed by the penetration of Mg ions in the subsurface of alumina, and to the low activity of the surface of such a modified support in the conversion of the organic reactants. A possible role of Mg in a different, possibly more efficient, activation of water is envisaged. The addition of boron in small amounts reduces activity, mainly if boron is added to the support before impregnation of Ni. A slight positive effect in reducing the deactivation due to sulphur is observed when boron is added after nickel.

A study of the deactivation of low loading Ni/Al2O3 steam reforming catalyst by tetrahydrothiophene

The steam reforming (SR) of ethanol/phenol mixture (168 gTOT/N m3, ethanol:phenol 2:1 mol, GHSV = 54,000 h− 1), assumed as a model for tar mixtures, has been studied over a 5% Ni/Al2O3 catalyst (155 m2/g), in the presence and in the absence of 210 ppm tetrahydrothiophene (THT) as a sulphur containing contaminant. The sulphidation of the catalyst by THT has been studied by IR spectroscopy. Infrared spectra of CO adsorbed at low temperature over the oxidized, the reduced and the sulphurized catalyst have also been recorded. The catalyst acts as a bifunctional one, with the behaviour attributed to the uncovered support (alumina modified by nickel ions) at 773 K (dehydration of ethanol to ethylene, dehydrogenation to acetaldehyde and alkylation of phenol with ethanol) that fully disappears at 973 K when steam reforming occurs very selectively. By lowering back the reaction temperature, the support behaviour reappears. THT poisons selectively the Ni component, thus causing the appearance of the support behaviour also at 973 K. IR experiments show that THT deposes sulphur at the catalyst surface with the production of gas-phase 1,3-butadiene, thus converting the catalyst into a “sulphided” SR-inactive state. The steam reforming activity of the poisoned catalyst progressively reappears upon feeding back S-free feed at 973 K. IR study suggests that steam “cleans” the catalyst surface by sulphur, generating a “disordered” surface with dispersed Ni2 + and Ni0 species, that could slowly re-approach the initial active state.

The influence of temperature and steam on the yields of tar and light hydrocarbon compounds during devolatilization of dried sewage sludge in a fluidized bed

The influence of temperature and steam concentration over the yields of tar and light hydrocarbon compounds generated during devolatilization of batches of dried sewage sludge in a laboratory fluidized bed reactor was investigated. Tests were conducted in the temperature range of 600–900°C with gas residence time of 1.5s. Thirty-six aromatic tar compounds (from benzene to perylene) were analyzed by GC/MS and light hydrocarbons (CH4,C2H6,C2H4,C2H2,C3H8 and C3H6) by GC/thermal conductivity. The content of C, H, N and S in the gravimetric residue of the tar sample (that obtained after vacuum distillation of the original sample) was also analyzed. It was found that increasing the steam concentration (up to 30% molar) did neither modify the aromatic tar composition nor the yield of light hydrocarbons, only slightly affecting the yield of gravimetric tar. Detailed analyses of tar composition and light hydrocarbons enabled us to relate the yields of these compounds at different temperatures, shedding light on the mechanisms of tar conversion into light hydrocarbon species. It also provides shortcut methods for the estimation of tar mixture properties, such as the yields of heavy aromatic compounds and the aromaticity of the tar mixture, from light hydrocarbon measurements at different temperatures.

Characterisation of tars from biomass gasification: Effect of the operating conditions

Tars formation remains the main technical hurdle in the development of biomass gasification at commercial scale, due to its associated operating problems (condensation, catalyst deactivation, polymerisation). This work aims to study the effect of the operating conditions (biomass/air ratio, temperature and gasifying agent) on the production and the technical and environmental hazard (tar dew point and carcinogenic potential) of tars produced in a small-scale drop-tube gasifier, dealcoholised marc of grape being used as biomass fuel. An analytical HPLC method has been used for the detection of polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethyl-benzene and xylenes (BTEX), phenol, and pyridine. Results show that an increase in the relative biomass/air ratio, a decrease in temperature, and higher steam content lead to a higher tar production. BTEX have been found as the main constituents of tars (60–70% wt.), whereas among PAHs, the most significant are the lighter ones (naphthalene, acenaphtylene, acenaphtene). Phenol production is favoured at lower temperatures or/and higher steam content (around 50% wt. of the tar mixture at 750 °C and steam gasification). A progressive aromatisation of tars has been observed when increasing the temperature, the effect of steam addition on tar composition being not significant at temperatures higher than ∼1000 °C.

Steam reforming of ethanol–phenol mixture on Ni/Al2O3: Effect of Ni loading and sulphur deactivation

The steam reforming of ethanol/phenol mixture (168gTOT/Nm3, ethanol:phenol 2:1mol, GHSV=54,000h−1) assumed as a model for tar mixtures, has been studied over Ni/Al2O3 catalysts. The effects of reaction temperature, Ni loading (from 0 to 39 (wt%/wt%)) and of the presence of sulphur has been investigated. If sufficiently charged with Nickel (e.g. 39% Ni with 107m2/g surface area), Ni/Al2O3 catalysts are effective in complete steam reforming of the tar model molecules at 873K, with CO2 as the main C-containing reaction product and H2 yield of 85%. The 5% Ni/Al2O3 can also produce the complete destruction of the molecules but at 973K. These catalysts do not deactivate significantly by coking in the timescale of some hours at 873–1023K. Starting with unreduced catalysts, a conditioning effect is evident on stream, supposed to be associated to the formation of “optimal” nickel metal particles. At lower temperatures the steam reforming activity towards phenol+ethanol mixture vanishes, with the appearance of reactions producing ethylene, acetaldehyde, and mono- and di-alkyl-phenols. Working at 973K, all Ni/Al2O3 catalysts are strongly deactivated by 210ppm of tetrahydrthiophene. However, catalytic activity is recovered by flowing with sulphur-free steam reforming feed, although the CO2/CO product ratio, and consequently also the final hydrogen yield, is permanently altered. It is proposed that the last reaction step, i.e. the oxidation of adsorbed CO to CO2 previous of its desorption, involves isolated cationic Ni centres that are irreversibly deactivated by sulphur or during the poisoning/regeneration cycle.

Compositional and pH Effects on the Interfacial Tension Between Complex Tar Mixtures and Aqueous Solutions

Tars at former manufactured gas plants (FMGPs) are a major environmental concern and present a number of challenges to remediators. This experimental study investigates the relationship between composition and tar-water interfacial tension (IFT), a property of primary importance in determining the transport of tar in porous media. Nine field-collected FMGP tars and a commercially available coal tar were characterized by means of fractionation, gas chromatography, Fourier transform infrared (FTIR) spectrometry, and vapor pressure osmometry. The tar-aqueous IFT of the tars, as well as resins and asphaltenes extracted therefrom, were measured over a range of pH. The IFTs were found to be strongly dependent on pH, with the lowest values obtained at high pH. The reduction of IFT at high pH was found to correlate well with the I(C═O) values from the FTIR analysis, which provide an indication of the relative amount of carbonyl groups present. Reductions of IFT at low pH were also observed and found to correlate well with the extractable base concentration. The aromaticity and asphaltene average molar mass are also correlated with IFT reductions at both low and high pH, suggestive of compositional patterns related to the tar source material.

Characterization of Za'tar (thyme) mixture

Introduction Five formulae of Za’tar mixtures were analysed to determine the characterization and identify the quality factors of this food product. Methods The formulae were based on differing mixtures of ingredients which affect the characteristics and qualities of the product. Results The averages of moisture, ash, oil, protein, crude fibre and available carbohydrate percentage for the tested mixtures were 4.21, 9.15, 6.86, 11, 8.5 and 60.2, respectively. The extracted essential oil content in Za’tar mixtures ranged from 2.7% in Jabali to 2.01% in Extra Za’tar. Salt, acidity, insoluble ash in hydrochloric acid, gross energy and density values were of higher formulae, containing less than 25% of thyme and 3% sumac. The overall acceptability of the Za’tar mixture showed Super and Jabali Za’tar mixtures which are high in thyme, sesame, sumac that are more preferred by the consumers. The overall acceptability as well as preference sensory tests correlated positively (P < 0.005) with both thyme and sumac which are the major ingredients in Za’tar mixtures. In contrast, all of the other components in the Za’tar mixture were negatively correlated (P < 0.005) with the overall panellist acceptability and preference. Conclusions Ingredients, proximate analysis, gross energy, insoluble acid ash, essential oil content, acidity, density, microscopic test and sensory properties can be used to measure the quality of this food product.

Dissolution and transport of coal tar compounds in fractured clay-rich residuum

We investigated the dissolution and transport of organic contaminants from a crude coal tar mixture in a monolith of fractured clay-rich residuum. An electrolyte solution was eluted through the residuum monolith containing a small emplaced source of coal tar under biologically inhibited and mildly acidic conditions. Concentrations of 10 coal tar compounds, representing mono-, poly-, and heterocyclic aromatic hydrocarbons that constitute crude coal tar were monitored in the effluent over a period of 377 days. Most compounds appeared in the effluent within the first 0.1 pore volume eluted indicating the importance of rapid dissolution and transport through the fracture networks. The concentrations continued to rise but did not reach the corresponding effective solubility limit in most cases. Compounds that were less soluble and those that were more susceptible to sorption or matrix diffusion eluted at a much slower rate. Analysis of contaminant concentrations in microcore residuum samples indicated that all 10 compounds had spread throughout the entire monolith and had diffused into the fine-grained matrix between fractures. These data suggest that the predominantly fine pore structure did not appear to inhibit coal tar dissolution and subsequent transport, even though only a small portion of tar was in direct contact with fractures and macropores that control most flow.

Study of PAH dissipation and phytoremediation in soils: Comparing freshly spiked with weathered soil from a former coking works

A comparison was made between the dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil freshly spiked with pure PAHs, soil spiked with a coal tar mixture and a contaminated soil from a former coking works where the PAHs had been present for more than a century. The potential of five selected plant species for phytoremediation was investigated. The levels of all 7 PAHs in chemically amended soil, both planted and unplanted, fell significantly (>80% reduction) over the 12 weeks of the growing trial. In the coal tar treated soils all PAHs were significantly reduced. In both the planted and unplanted soils the 2–3 ringed compounds demonstrated much greater loss (>77%) than the 4–6 ringed (16–39%). The 3–4 ringed compounds demonstrated strong evidence of phytoremediation but not the 5–6 ringed. The coking soil showed limited reduction (7–24%) of all 12 PAHs present. There was little difference in dissipation between the PAHs and little evidence of a phytoremediation effect in coking soil. The results demonstrated that the form in which PAHs were added to soil influenced their susceptibility to dissipation. Therefore, predictions of PAH dissipation from laboratory amended soil do not reflect the true situation in the field.

Coke quality on adding coking byproducts to the batch

Conditions for the granulation and heat treatment of coking byproducts—heavy coal tar, acid tars, and distillation residues—are developed so as to produce suitable additives for coking batch. It proves possible to improve poorly clinkering batch by adding a mixture of coal and acidic tar from the sulfate department.

Influence of carbon structure of the anode on the production of graphite in single-walled carbon nanotube soot synthesized by arc discharge using a Fe–Ni–S catalyst

We investigated the production of the graphite contained in the soot of single-walled carbon nanotubes (SWCNTs) synthesized using the arc discharge method with a poorly graphitized carbon (PGC) rod in comparison to a graphite rod. A PGC rod was produced using a mixture of coal tar and carbon black and was heat treated to 1000 °C. The rod was packed with a mixture of iron (Fe), nickel (Ni), sulfur (S), and PGC and used for the production of SWCNT soot using arc discharge. From the results of X-ray diffraction and electron microscopy, the amount of graphite in the SWCNT soot synthesized by PGC rod was lower than that by graphite rod. The production of graphite in the soot was found to be dependent on the carbon structure of the anode and the current density of arc discharge.

Activation of group IVC phospholipase A2 by polycyclic aromatic hydrocarbons induces apoptosis of human coronary artery endothelial cells

Exposure to environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs) found in coal tar mixtures and tobacco sources, is considered a significant risk factor for the development of heart disease in humans. The goal of this study was to determine the influence of PAHs present at a Superfund site on human coronary artery endothelial cell (HCAEC) phospholipase A(2) (PLA(2)) activity and apoptosis. Extremely high levels of 12 out of 15 EPA high-priority PAHs were present in both the streambed and floodplain sediments at a site where an urban creek and its adjacent floodplain were extensively contaminated by PAHs and other coal tar compounds. Nine of the 12 compounds and a coal tar mixture (SRM 1597A) activated group IVC PLA(2) in HCAECs, and activation of this enzyme was associated with histone fragmentation and poly (ADP) ribose polymerase (PARP) cleavage. Genetic silencing of group IVC PLA(2) inhibited both (3)H-fatty acid release and histone fragmentation by PAHs and SRM 1597A, indicating that individual PAHs and a coal tar mixture induce apoptosis of HCAECs via a mechanism that involves group IVC PLA(2). Western blot analysis of aortas isolated from feral mice (Peromyscus leucopus) inhabiting the Superfund site showed increased PARP and caspase-3 cleavage when compared to reference mice. These data suggest that PAHs induce apoptosis of HCAECs via activation of group IVC PLA(2).

Co-liquefaction of Makarwal coal and waste polystyrene by microwave–metal interaction pyrolysis in copper coil reactor

A novel method for the co-pyrolysis of waste polystyrene with coal was investigated. This method is based on high temperature obtained by microwave copper interaction. This pyrolysis is believed to be the combine action of the high temperature, microwaves interaction and the active species produced during the process. The metal antenna may also catalyze the pyrolysis process and affect the nature of products. This is a faster method of the co-pyrolysis and gives 66% oily liquid which was a mixture of tar and oil, 10% aqueous liquid mainly composed of sulfides, 6% gases and 18% residues. The liquid product was collected using cold traps and the amount of gas was obtained by taking difference. The oily liquid product was analyzed using GC–MS and found that it contains mainly aromatic compounds in a narrow range. The range of products and product formation is also discussed in this communication.

Application of the margin-of-exposure (MoE) approach to substances in food that are genotoxic and carcinogenic e.g.: Benzo[a]pyrene and polycyclic aromatic hydrocarbons

Benzo[a]pyrene (BaP) and a number of other polycyclic aromatic hydrocarbons (PAH) are mutagenic and are also carcinogenic in rodent bioassays. Oral carcinogenicity data are not available for individual PAH other than BaP, and so BaP has been used as a marker of the carcinogenicity of, and exposure to, PAHs. Carcinogenicity studies of coal tar mixtures, considered to be representative of the genotoxic and carcinogenic PAH in food, have been used for dose-response modelling. Modelling the number of tumour-bearing mice resulted in a BMDL 10 of 0.122 mg BaP/kg-bw/day, which was lower than that for any of the individual tumours and was considered to be most appropriate since the different PAH may have different mechanisms of carcinogenicity. An average dietary exposure estimates of 0.008 μg BaP/kg-bw/day was identified from the range of national estimates. The calculated MoE was 15,000.

Manipulation of the ash flow temperature and viscosity of a carbonaceous Sasol waste stream

In 2001 Sasol investigated the possibility to convert a Sasol-Lurgi MK III fixed bed dry bottom coal gasifier at the former Sasolburg coal-to-liquids plant to a slagging gasification process and selected the Lurgi Multi Purpose Gasification (MPG) process for this purpose. At the time the MPG process was considered as a possible technology option suitable for the gasification of feedstocks which are difficult to manage, for example solid–liquid mixtures which are unsuitable for conventional solids or liquids processes and furthermore tars with a large variety of properties and high solids content have been gasified successfully. The most obvious differences between the feedstocks previously gasified, compared to the Sasol dusty tar, were found to be the viscosity and melting point of the dusty tar. The viscosity of the Sasol dusty tar mixture (as received) was higher than a factor of 10 of the previously used feedstocks. Another important feedstock property is the ash melting point of the feed within the gasifier. Ash particles fed with the tar melt in the high temperature zone of the flame. Molten ash particles, which hit the gasifier wall, will solidify and stick to the wall, if the wall temperature is below the melting point of the ash. The melting point of the dusty tar ash is 1380 °C and a fluxing agent has to be added to the dusty in order to reduce the melting temperature below 1250 °C to limit excessive wear of the refractory lining. Two approaches were evaluated in order to lower the viscosity, i.e. milling of the dusty tar and addition of low viscosity feedstocks to the dusty tar. It was concluded from this study that the viscosity of dusty tar can be decreased with the addition of specific waste solvent streams. The ash fusion temperatures of dusty tar can be lowered with the addition of a fluxing agent. The addition of spent Fe-catalyst as fluxing agent was also investigated, but was found to be not as effective as limestone. In some cases the addition of Fe can cause the acid/base ratio to change in such a way that the ash fusion temperature increases. In conclusion it can be highlighted that the ash flow temperature and viscosity of the Sasol dusty tar stream, and possibly other carbonaceous sources as well, can be decreased to acceptable values for slagging gasification applications. The results clearly show in both oxidizing and reducing atmospheres the Fe-catalyst was transformed into the slag melt as either Fe 2O 3 under oxidizing conditions and FeO under reducing conditions. The slag showed no sign of metallic Fe and was very homogeneous under oxidizing and reducing conditions. Spent Fe-catalyst can be discarded in a safe and environmentally acceptable way during high temperature gasification.