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Steam iron process represents a technology for H2 production based on iron redox cycles. FexOy are reduced by syngas/carbon to iron, which is subsequently oxidized by steam to produce pure H2. However, the system shows low stability. In this work, the effect of promoters (Al2O3, MgO and CeO2) on FexOy stability is investigated (10 consecutive redox cycles). Bioethanol is used as a reducing agent. The particles are synthesized by coprecipitation method, analysed by BET, XRD, SEM and tested in a fixed bed reactor (675 °C, 1 bar). Pure H2 is obtained controlling the FexOy reduction degree feeding different amounts of ethanol (4.56–1.14 mmol) until no CO is detected in oxidation. The results show that the promoters not only improve the thermal stability of FexOy but also affect its redox activity and react with iron forming spinel structures. MgO led to the highest activity and cyclability (H2 = 0.15 NL; E = 35%).

Gasification converts biomass into syngas; however, severe cleaning processes are necessary due to the presence of tars, particulates and contaminants. The aim of this work is to propose a cleaning method system based on tar physical adsorption coupled with the production of pure H2 via a chemical looping process. Three fixed-bed reactors with a double-layer bed (NiO/Al2O3 and Fe-based particles) working in three different steps were used. First, NiO/Al2O3 is used to adsorb tar from syngas (300 °C); then, the adsorbed tar undergoes partial oxidization by NiO/Al2O3 to produce CO and H2 used for iron oxide reduction. In the third step, the reduced iron is oxidized with steam to produce pure H2 and to restore iron oxides. A double-layer fixed-bed reactor was fed alternatively by guaiacol and as tar model compounds, air and water were used. High-thermal-stability particles 60 wt% Fe2O3/40 wt% MgO synthetized by the coprecipitation method were used as Fe-based particles in six cycle tests. The adsorption efficiency of the NiO/Al2O3 bed is 98% and the gas phase formed is able to partially reduce iron, favoring the reduction kinetics. The efficiency of the process related to the H2 production after the first cycle is 35% and the amount of CO is less than 10 ppm.

Thermal plasma gasification has been demonstrated as one of the most effective and environmentally friendly methods for MSW treatment. In this study, experiments were carried out in a 30 kW direct current thermal plasma gasification system, specifically focusing on the influence of feedstock type, steam/carbon ratio, running power and continuous feed rate on the product characteristics. As the S/C ratio increased, the H2 yield increased firstly and then decreased and reached the maximum value of 36.42 mol/kg at the S/C ratio of 0.84 while the H2 content continued to grow from 59.87–61.04%. The H2 proportion in syngas and H2 yield both showed a steady rise trend with the increase of running power. Continuous feeding method was conductive to the promotion of syngas LHV. Compared with other conventional technologies, plasma gasification exhibits superior capacity of H2 production (H2 proportion of 60.34 vol.% and H2 yield of 39.77 mol/kg).

Catalytic hydrotreating of guaiacol as a model compound was investigated using bifunctional catalysts constituted of Ni supported on chemically modified zeolites with increased mesoporosity. In the reaction conditions, the hydrogen required for the process was generated in situ by the Zn–H2O redox system, which represents a promising green alternative to the use of gaseous hydrogen. The guaiacol hydrotreating conversion using as support zeolites with increased mesoporosity, is largely higher than that obtained with the original ones. The introduction of mesopores through desilication treatment with NaOH and TBAOH significantly increased the mass transfer of guaiacol and improved the accessibility of the active sites, accordingly enhancing the catalytic performance. The alkaline treatment notably increased the mesopore volume of Ni/HZSM-5 and Ni/HBeta by 5.6 and 3.8 times, respectively. Ni supported on desilicated HBeta zeolite displayed high hydrodeoxygenation and hydrodearomatization efficiencies with values of 69.37% and 62.82%, respectively. The reusability of this catalyst was investigated, showing a decrease in the performance after three consecutive runs due to the oxidation of Ni active site, coking and zinc oxide contamination. The main of guaiacol conversion products are cyclohexane, cyclohexanone, cyclohexanol, benzene and phenol. A reaction pathway of guaiacol hydrotreating using Ni-zeolites catalysts is proposed.

The current study focused on the heterogenous catalytic hydrothermal liquefaction (HTL) of Brachychiton populneus biomass seed, using Ni as hydrogenation catalyst and Fe as active hydrogen producer. The activity of Ni metal and of Ni/Al2O3 in the HTL of seed (BS) and of a mixture of seed and shell (BM) was studied. To establish the best operating process conditions, the influence of variation of temperature and reaction time on the product yields was also examined. The highest bio-crude yields of 57.18% and 48.23% for BS and BM, respectively, were obtained at 330 °C and 10 min of reaction time, in the presence of Ni/Al2O3 as catalyst and Fe as hydrogen donor. Elemental analysis results showed that at these operative conditions, an increase of the higher heating value (HHV) from 25.14 MJ/kg to 38.04 MJ/kg and from 17.71 MJ/kg to 31.72 MJ/kg was obtained for BS and BM biomass, respectively, when the combination of Fe and Ni/Al2O3 was used. Gas chromatography–mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FT-IR), used to determine the oils’ chemical compositions, showed that the combined presence of Fe and Ni/Al2O3 favored the hydrodeoxygenation of the fatty acids into hydrocarbons, indeed their amount increased to ≈20% for both biomasses used. These results demonstrate that the obtained bio-crude has the capacity to be a source of synthetic fuels and chemical feedstock.

Hydrothermal liquefaction (HTL) is a promising technology for the production of high quality bio- crude. Aim of this study is to investigate the effect of the addition of iron powder into the HTL process of oak wood biomass. Fe in HTL conditions should be oxidized by water into Fe3O4 producing H2 in situ which is responsible for the increase of bio-crude yield. Furthermore, the presence of Fe contributes to enhance bio-crude quality due to the presence of Fe3O4 which is recognized to have catalytic activity in hydrogenation reactions. Tests in presence of oxides containing Fe in higher oxidation number such as Fe3O4 and Fe2O3 were performed. The tests were conducted with water to biomass ratio of 5, in a range of temperature of 260–320 °C, the reaction time was set to 15 min and the catalysts were added in an amount of 10% with respect to the biomass weight. Highest bio-crude yields of about 40% were reached using zerovalent Fe. Tests performed in presence of Fe3O4 gave intermediate behaviour while no improvements were registered adding Fe2O3. These results confirmed the positive dual effect of Fe addition. In fact, the H/C ratio in the bio-oil increases of about 15% with respect to the reaction conducted without iron-based compounds and Gas Chromatography–Mass Spectrometry analyses showed that the presence of aliphatic compounds is improved.

Dry reforming could become an effective route to mitigate CO2 emission. The process required high temperatures due to its endothermicity and its accompanied by coke formation; therefore, the development of suitable catalysts is fundamental. In this work, ternary perovskites type oxides, AZrRuO3, were synthetized and used in the methane dry reforming. The influences of the preparation method, modified citrate and autocombustion method, and of substitution of the A cation within alkaline earth metals (Ba, Sr and Ca) on the texture, physiochemical characteristics, activity and stability of the catalysts were evaluated. Tests were conducted in a fixed bed bench scale reactor in a temperature range of 600–750 °C. Catalysts synthetized by autocombustion method showed higher reducibility and major surface area and thus better performance in the methane dry reforming. Between them, SrZrRUO3 gave the best results in terms of conversion and stability during long duration tests (66 h). Furthermore, these catalysts showed very good resistance to thermal stresses as demonstrated by XRD analysis performed on used catalysts.

Hydrothermal liquefaction is a promising process for the production of high quality bio-oil from biomass. Aim of this study is to investigate the effect of temperature and biomass composition on the yield and quality of bio-oils produced from three different biomass such as natural hay, oak wood and walnut shell. The hydrothermal liquefaction of cellulose was also investigated. The experimental tests, conducted in water sub-critical conditions, were carried out in a microreactor in a temperature range of 240–320 °C with a reaction time of 30 min. All the products of the process were analyzed and characterized by elemental analysis and GC–MS. It was observed an increase of the bio-oil yields with the lignin content of biomass, being the maximum bio-oil yield obtained for walnut shell and the minimum one for cellulose. This trend is representative of the obtained bio-oils composition, where the phenolic compounds are the major constituents, while the other identified compounds were mainly alcohols, ketones and aldehydes.

Ni-CeO2, Ni/Co-CeO2, and Ni-Ca12Al14O33 were synthesized by the auto-combustion method and tested as catalysts in the steam reforming of tar model compounds in a fixed bed reactor. Toluene, phenol, and n-heptane were chosen as representative of the different classes of organic compounds that can be found in tar. The catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). From XRD analysis it was observed in all the synthesized catalysts the presence of two phases, NiO and CeO2 or Ca12Al14O33. A stronger interaction of NiO with mayenite structure, compared to that of NiO with CeO2, was also shown by TPR analysis. The best performances in terms of conversion and stability were obtained when Ni supported on mayenite was used, confirming the higher redox properties of this support that confers to the catalyst a better resistance to deactivation by carbon deposition. The lower performances observed for Ni supported on CeO2 in terms of conversion and activity were substantially improved by partial substitution of Ni with Co, confirming its ability to increase the Ni catalytic activity and to enhance the reforming of oxygenated species. The apparent kinetic parameters calculated for all the catalysts and the model compounds confirm the obtained experimental results.

The biomass conversion into more valuable fuels represents one of the most viable routes for the exploitation of this material. Hydrothermal liquefaction is currently considered one of the most efficient processes to convert wet biomass into a bio-crude, which however requires expensive upgrading treatments to be used as biofuel. The use of catalysts able to directly improve bio-crude yield and quality during the reaction is of fundamental importance to increase the overall process efficiency. Homogeneous alkaline catalysts are the most studied, but they are not recoverable at the end of the process and so cannot be reused. The use of heterogeneous catalysts allows to overcome this issue making the recovery and reuse possible, maintaining anyway high activity and selectivity in the bio-crude production. The aim of this review is to critically summarize the effect of heterogenous catalyst addition on the hydrothermal liquefaction of lignocellulosic biomass, looking specifically at the improvement in bio-crude yield and quality. On the basis of literature data about the effect of heterogeneous catalyst addition on bio-crude yield and quality in the hydrothermal liquefaction of lignocellulosic biomass, a common catalytic action was identified allowing to group the several catalysts into four classes (alkaline metal oxides, transition metals, lanthanides oxides and zeolites). The hydrodeoxygenation activity of the catalysts, their effect on bio-crude yield and quality and the operating conditions used are highlighted. The highest bio-crude yields are reported using transition metals and lanthanide oxides which are able to guarantee, at the same time, a high-quality bio-crude.

The problem of the production of tar along with syngas in gasification processes limits the diffusion of this technology. In this work, the tar abatement capacity of four bed materials was investigated. The bed materials, namely, activated carbon, aluminum oxide, olive residue char, and pumice stone, listed in order of decreasing surface area, were chosen to investigate their effect on the abatement capacity. Furthermore, the deactivation of these materials with time on stream was measured, and the results were used to develop a kinetic model. The tar abatement capacities were highly influenced by the surface area. Activated carbon presents a removal capacity of about 97%, while pumice stone presents a removal capacity of 80%. A correlation between the surface area and tar abatement capacity was found.

The knowledge of cellulose behavior in hydrothermal conditions assisted by different transition metals, represents a necessary step towards a full comprehension of the more complex lignocellulosic biomass liquefaction mechanism and the consequent effect on the yield and quality of the bio-crude produced. Hydrothermal liquefaction (HTL) of cellulose was carried out with the addition of the metals Ni, Fe and Zn. Ni is a well-known hydrogenation catalyst while Fe and Zn are considered potential indirect hydrogenating agents, producing active hydrogen in situ through redox reaction with water. Among the tested metals Fe showed the best performances, by increasing the bio-crude yield from 17.4 % of the blank test to 26.5 % and by raising its higher heating value (HHV) from 27.0 MJ/kg to 29.7 MJ/kg. Using Zn an increase of the water-soluble products was obtained but only a slight increase in the bio-crude amount was observed. With all the tested transition metals the H/C ratio and HHV of the obtained bio-crude was significantly raised. Fe and Zn reduced furan derivatives and increased the 2-cyclopenten-1-ones and aromatic compounds in the bio-crude. The possible reaction pathway of cellulose HTL was also reported in this article.

In recent years dry reforming of methane has received considerable attention as a promising alternative to steam reforming for synthesis gas (H 2 and CO) production, yielding a syngas with a H 2 /CO ratio close to 1 and thus suitable for many chemical processes. The major drawback of the process is the endothermicity of the reaction that implies the use of a suitable catalyst to work at relatively low temperatures (923–1023 K). In this work methane dry reforming over three ternary perovskite type oxides BaZr (1-x) Me x O 3 using Rh, Ru and Pt as metal was studied at atmospheric pressure and in a temperature range 850–1150 K. Experimental tests at different temperatures were performed in order to analyze and compare the performances of the catalysts and to carry out a detailed kinetic study. Furthermore, long duration tests were conducted to evaluate the possible deactivation of the perovskites. Rhodium-perovskite catalyst shows the highest activity for dry methane reforming while the Pt one the lowest. No deactivation of the catalysts was observed meaning that the perovskite structure is very stable and allows to minimize the carbon deposition that is the main responsible of catalyst deactivation in this process.

The biological treatment of the aqueous residue produced during poplar wood pyrolysis was investigated. The biological treatment experiments were carried out at two different pH conditions (controlled at 7, uncontrolled) in batch mode at three different temperatures (15 &deg, C, 25 &deg, C and 30 &deg, C) and initial total organic carbon of the water ranging from 800 mg/L to 2800 mg/L. Results show that a substantial removal of organic carbon could be achieved in aerobic conditions after biomass acclimation. After 72 h of treatment, total organic carbon (TOC) removal mean values of 49.47% and 53.03% were observed at 30 &deg, C for solution at 1400 and 2000 mg/L initial TOC, respectively. In the case of 1400 mg/L, a further mineralization (61.80%) was achieved during 144 h of treatment, by using a two-step process. A kinetic study of the process was also made, showing that organics mineralization followed a first-order kinetic model.

A thermo-economic analysis of a combined heat and power (CHP) plant fed by syngas produced through the gasification of dry olive pomace is presented. The plant is composed by a 800 kWt downdraft gasifier, a gas clean-up system, a 200 kWe microturbine (MGT) and a heat recovery system to cogenerate hot water. Surplus heat is used to dry olive pomace from 50% to 17% wb moisture content. The plant is modeled in ASPEN Plus. Real data from experimental tests are used to calibrate the gasifier model, while the technical specification and performance of the CHP plant are collected from commercial plants in operation and data from manufacturers. Mass and energy balances are reported throughout the paper. The thermodynamic simulation of the biomass gasifier coupled to the MGT, the thermal and electrical conversion efficiency and temperature of cogenerated heat available are also presented. A thermo-economic assessment is then proposed, to investigate the economic profitability of this small scale CHP plant in the Italian energy policy scenario and considering the subsidies available for renewable electricity in the form of feed-in tariffs. For this purpose, the case study of base load CHP plant operation and heat supplied to different typologies of energy end user is assumed. The results allow quantifying the most influencing economic and technical factors that affect the performance and profitability of such investment and the bottlenecks that should be faced to facilitate a broader implementation of such CHP schemes for on site generation.

Understanding and modeling of coal and biomass pyrolysis assume particular importance being the first step occurring in both gasification and combustion processes. The complex chemical reaction network occurring in this step leads to a necessary effort in developing a suitable model framework capable of grasping the physics of the phenomenon and allowing a deeper comprehension of the sequence of events. The aim of this work is to show how the intrinsic flexibility of a model based on a double distribution of the activation energy is able to properly describe the two separate steps of primary and secondary pyrolysis, which characterize the thermochemical processing of most of the energetic materials. The model performance was tested by fitting the kinetic parameters from experimental data obtained by thermogravimetric analysis of two materials, which represent very different classes of energy source: a microalgae biomass and a sub-bituminous coal. The model reproduces with high accuracy the pyrolysis behavior of both the materials and adds important information about the relative occurring of the two pyrolysis steps.

Microalgae have been recognized as one of the most promising biomass sources of energy, in particular for bio-fuels production. In this paper the production of bio-oil from a fast growing microalgae species with low lipids content is proposed. The influence of both the cultural medium and the reaction conditions on bio-oil yields and quality is investigated performing fixed and fast pyrolysis tests on Chlorella vulgaris grown in complete and nitrogen starved medium. Nitrogen starvation leads to a higher lipids amount in the biomass, increasing its calorific value. Fast pyrolysis of nitrogen starved microalgae is proposed to achieve high bio-oil yield and quality. In this case, experiments have pointed out a maximum bio-oil yield of about 72% mass on dry basis at 400 °C. Bio-oil products were characterized on the basis of GC–MS, elemental analysis and calorific content. In particular, the GC–MS analysis accounts for an oily fraction of the bio-oil formed by several hydrocarbons as well as oxygenated and nitrogenous species, including indoles, fatty acids and alcohols. The bio-oil produced from nitrogen starved biomass exhibits higher amount of fatty acids and lower amount of nitrogenous species, resulting in an improved quality. Furthermore, the higher lipids amount of the nitrogen starved biomass leads to a major carbon content in the bio-oil and thus to a slight increase of its calorific value. For all the experimental tests the energy consumption ratio was calculated, and fast pyrolysis of nitrogen starved biomass has proved to be the most convenient process in the energetic valorization of microalgae.

Pyrolysis is a widely studied thermochemical process, however the disposal of the produced byproducts is an unexplored field. In particular, the acqueous phase, characterized by a high organic load (TOC), must be necessarily treated. Aims of this work is to study the potentiality of biochar as adsorbent material for the treatment of this wastewater. For this aim, pyrolysis wastewater and biochar produced in the same plant were used. Two biochars produced at different temperatures (550 and 750 °C) and an activated biochar produced by chemical activation with NaOH of the raw biomass were tested. The study shows that higher temperature in the biochar production leads to higher sorption capacity of the organic compounds due to an increase of the surface area. The activation process further increases the surface area of the biochar that becomes similar to that of a commercial activated carbon while the sorption capacity exceeds that of commercial activated carbon of 2.5 times.

Understanding and modeling of coal pyrolysis assume particular importance, since it is the first step of combustion and gasification processes. The complex reactions occurring during pyrolysis lead to difficulties in the process modeling. The aim of this work is to find a global kinetic model that well represents the pyrolysis of two different coals with opposite rank, a sub-bituminous and an anthracite coal, in order to carry out the kinetic parameters of the process. The Distributed Activation Energy Model (DAEM) was used to fit experimental data obtained with a thermogravimetric analysis. The model assumes that a series of first order parallel reactions occurs sharing the same pre-exponential factor, k0, and having a continuous distribution of the activation energy. One of the limits of the standard Gaussian DAEM is that with this model is not possible to distinguish the primary from the secondary pyrolysis. A two Gaussians DAEM was developed considering that two classes of reactions take place having ...

In this work the oxidation of benzo-, dibenzo-, 4-methyldibenzo-, and 4,6-dimethyildibenzothiophene in the presence of hydrogen peroxide and formic acid was studied over the temperature range of 20–65 °C. The experimental data were interpreted by means of a interfacial mass transfer and reaction model developed in the first part of this study. The parameters identification tool available in gPROMS environment allowed a regression of the Arrhenius constants of the rate determining step characterizing the considered oxidation reactions. The activation energies of the thiophenes oxidation reactions result in 34.6 kJ/mol and 29 ± 1 kJ/mol for BT and DBTs, respectively.

Peroxyformic acid has been recently assuming a growing importance due to the versatile oxidizing properties in several applications in the chemical industry. However, quite surprisingly, a lack of data exists about the kinetics of formation of this compound, an even more singular event considering that the acid, when used, is generally produced in situ via the reaction between formic acid and hydrogen peroxide. This paper is a contribution to fill this gap. A series of batch experiments were carried out to measure the conversion rate in the peroxyformic acid formation reaction in the temperature range 30−60 °C. The results from experiments were successfully interpreted through a kinetic mechanism consisting of the reversible formation of the peroxyformic acid and its irreversible decomposition to CO2 and H2O, both catalyzed by hydrogen ions. With the considered kinetic mechanism, a pre-exponential factor of 13065.1 L6 mol−2 s−1 and an activation energy of 43524.2 J mol−1 were calculated. This last value a...

This study presents the results of experimental Fenton-like treatments conducted on marine sediment slurries (2g sediment vs. 20 ml liquid). The sediment was collected in a harbor situated in a high density industrial area, characterized by a great hydrocarbon C12 and PAHs contamination. The investigated parameters were: the H(2)O(2) dose, the reagent's pH and the effect of a phosphate salt and ferrous iron addition. To evaluate sediment's characteristics COD, particle size, thermogravimetric and differential thermal analyses were performed under N(2) and O(2) atmosphere while dissolved organic carbon and COD analyses were performed on the filtrate. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the organic carbon (up to 78% decrease of the 200-400 degrees C labile organic matter), to lower the COD of the sediment (60% COD removal maximum) and to increase the cumulated distribution undersize. In addition as the treated sediment showed easier-to-handle characteristics, reduced caking and lower aggregation capacity, the modified Fenton treatment could also be considered a pre-treatment of a successive thermal treatment.

This paper examines the activity as a catalyst of sodium phosphate compounds to produce methyl esters of rapeseed oil. The research shows that the transesterification of rapeseed oil by methyl alcohol could be efficiently catalyzed by both anhydrous and hydrated trisodium phosphate, while polytrisodium phosphate has only a negligible catalytic activity. Trisodium phosphate catalysts are less active than sodium hydroxide due to the lower ability to form sodium methoxide. However, these catalysts can lead to decreasing the number of technological stages and the amount of unwanted waste products. The experimental data are interpreted by using a kinetic model showing that a first-order reaction with respect to glycerides concentration is adequate to describe the reaction. This paper also indicates that under the selected experimental conditions, the chemical reaction is the main factor affecting the rate-determining step.

The harvest of sugarcane in the 80 main producing countries is about 1.2 Gt with an amount of its residues potentially able to produce 300 TWh a −1 of electric power. However, in spite of its potential, the use of bagasse as a source of energy is not so common. Bagasse, in fact, is considered a difficult fuel due to its fibrous nature, low bulk density and high moisture content, and the use of conventional stoker-fired combustors does not clearly show the economic feasibility of the process. Moreover, the high efficiency fluidized-bed technology cannot be directly applied to bagasse due to the difficulties associated with its fluidization. In this work, a two-stage gasification reactor is proposed for bagasse gasification. Bench scale gasification tests indicate that this reactor allows a complete gasification of biomass avoiding the formation of carbon and tar. Moreover, the use of a nickel catalyst makes the composition of outgoing syngas close to that predicted at the equilibrium conditions.

The dry treatment of flue gas produced by incineration processes is discussed thermodynamically. The study investigates the theoretical limits achieved by sodium and calcium based sorbents in the removal of the pollutant species HCl, NOx and SO2. Calculations were performed varying the temperature and the molar ratio between the amount of the injected alkaline sorbent and the content of the pollutant gaseous species in the flue gas. Results show that sodium cation based sorbents are more efficient than calcium based ones in the whole investigated temperature range (100–600 C). The higher effectiveness of sodium based sorbents is particularly remarkable towards hydrogen chloride, whose concentration can always be reduced below the values set by the environmental regulations. Possible improvements in the treatment efficiency of combustion fumes obtainable with sodium based sorbents can be mainly summarised in a lower concentration of HCl in the treated gas and in a partial reduction of NOx concentration. 2003 Elsevier Ltd. All rights reserved.

This paper compares the syngas produced from methane with the syngas obtained from the gasification, in a two-stage reactor, of various waste feedstocks. The syngas composition and the gasification conditions were simulated using a simple thermodynamic model. The waste feedstocks considered are: landfill gas, waste oil, municipal solid waste (MSW) typical of a low-income country, the same MSW blended with landfill gas, refuse derived fuel (RDF) made from the same MSW, the same RDF blended with waste oil and a MSW typical of a high-income country. Energy content, the sum of H2 and CO gas percentages, and the ratio of H2 to CO are considered as measures of syngas quality. The simulation shows that landfill gas gives the best results in terms of both H2+CO and H2/CO, and that the MSW of low-income countries can be expected to provide inferior syngas on all three quality measures. Co-gasification of the MSW from low-income countries with landfill gas, and the mixture of waste oil with RDF from low-income MSW are considered as options to improve gas quality.

Sulfur oxidation appears a very promising route for obtaining ultralow-sulfur fuels requested worldwide by the new regulation mandates. In this work, the oxidizing system constituted by hydrogen pe...

Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a suitable kinetic model is an essential tool to predict the evolution of the resulting products of reaction. However, many difficulties arise in modeling this process step due to the very high number of the involved reactions. In this work, a new double-Gaussian distributed activation energy model was applied in fitting the experimental data of olive residue pyrolysis obtained by thermogravimetric analysis. 2-DAEM formulation considers two sets of parallel reactions occurring and sharing the same pre-exponential factor, but shows different distributions of the activation energy, described by two separate Gaussian distributions that, in turn, grasp the two pyrolysis steps with a high accuracy. Since it is well known that in fitting all the kinetic parameters the pre-exponential factor results highly correlated with the activation energy, the former parameter was separately estimated as a linear combination of the values obtained for the three main biomass components, cellulose, hemicellulose and lignin.

The use of peroxycarboxylic-acid-functionalized hexagonal mesoporous silica (HMS) as an oxidizing solid agent was investigated. The experimentation was performed on organic sulfur compounds that have been selected as representative of those contained in crude distillates. The results clearly show the potentiality of this oxidizing agent for the development of oxidative desulfurization (ODS) processes for the purpose of producing ultralow-sulfur fuels and sulfoxides and sulfones as secondary products.

Coal gasification and combustion are strongly dependent on devolatilization step. Aim of this work is to obtain the parameters of global kinetics of devolatilization of a sub-bituminous coal with high sulfur content. The kinetic parameters are obtained by means of TG experimental data, and applying different approaches to extrapolate the data to industrial relevant conditions. The simpler method is a model-free one which supposes a single step process whose Arrhenius kinetic parameters (A and E a) have to be determined. Another common approach is the distributed activation energy model (DAEM) which assumes a series of first order parallel reactions occurring and sharing the same pre-exponential factor, A, with a continuous distribution of the activation energy. For the fitting of the experimental data, a numerical solution to DAEM and two approximate methods have been evaluated. Moreover, the results of these kinetic methods based on empirical approaches were compared with simulated data obtained using a more complex model based on percolation theory with cross-linking mechanism and vapor-liquid equilibrium (chemical percolation devolatilization, CPD model), which allows to simulate the coal pyrolysis from volatile yield data. © 2014 Akadémiai Kiadó, Budapest, Hungary.

In this work the effects of nutrients starvations on Chlorella vulgaris were investigated in different trophic regimens. For all the tested conditions, the cellular response to nutrient starvation and trophic regimen was evaluated on specific growth rate, biomass and lipids productivity, lipids content and quality. These parameters are all crucial for microalgae biodiesel production, but in literature the lipids quality, in terms of polar and nonpolar lipids, is often neglected. Thus the typical high content of polar lipids, a class of molecules that negatively affects the biodiesel production process, of microalgae crude oil is generally not analyzed. In the tested conditions the triggering effect of nitrogen starvation on total lipids productivity is confirmed only in autotrophic regimen, while in mixotrophic and heterotrophic conditions the total lipids productivity is reduced, as a consequence of the lowered biomass productivity, but with an evident compositional shift towards nonpolar lipids production (from 0.5 mg/Ld to 41.6 mg/Ld in mixotrophic regimen). Nitrogen and phosphorus co-starvation induced the highest nonpolar lipids productivity in all trophic regimens. Maximum nonpolar lipids productivity was obtained in nitrogen limited and phosphorus deprived condition during mixotrophic growth, equal to 118.2 mg/Ld, representing the 80% of produced lipids. On the basis of the obtained results, the possibility of a short pre-harvesting cultural step to maximize the nonpolar lipids yield of the crop could be envisaged.

This paper investigates the gasification efficiency of a two stage gasifier, described in all detail in previous works, as a function of the heat loss across the reactor walls. The behaviour of the reactor was simulated using a simple mathematical model already reported in previous papers. The examined heat loss ranges from 0% of the heat produced by the exothermic reactions into the reactor, up to 20%. Calculations have been performed by keeping constant both the injected total oxygen and its partition between the two stages, while different feedstocks have been used, such as landfill gas, municipal solid waste (MWS), willow and rice straw. The results of calculation show that the gasification efficiency at fixed oxygen injection is greatly influenced by the feedstock. The elaboration of the obtained data indicates also that the trend of the gasification efficiency vs. heat loss is a function of the high heating value of the feedstock and of the ratio between the oxygen present into the reactor (injected + the one of the feedstock) and the stoichiometric oxygen necessary to transform the feeding into carbon dioxide and steam.