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The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using Pd/C and Rh/C as catalysts. The catalytic tests were performed in batch reactors under different reaction conditions (various: amine concentration (0.1–0.4 mol/L), hydrogen pressure (0–2.5 bar), temperature (80–160 °C), and substituted phenols (phenol, o-cresol, p-cresol, and methoxyphenol)) and using tert-amyl alcohol as a solvent. The experimental observations were consistent with a multi-step mechanism, where hydrogenation of phenol to cyclohexanone is followed by condensation of the ketone with cyclohexylamine to form an imine, which is finally hydrogenated to produce secondary amines. In addition, there was evidence of parallel self-condensation of the cyclohexylamine. The study also supported a limited dehydrogenation capacity of Rh/C, unlike Pd/C, which increases this capacity at higher temperatures generating a higher yield of cyclohexylaniline (up to 15%). The study of the alkylated phenols demonstrated that the nature and propensity of hydrogenation of the phenolic controls their amination. Kinetic analysis revealed reaction orders between 0.4 and 0.7 for H2, indicating its dissociative adsorption. Meanwhile, phenol’s order (between 1–1.8) suggests a single participation of this compound in the hydrogenation step. The order of 0.4 for cyclohexylamine suggests its participation as a surface-abundant species. The apparent activation energies derived from a power law approximation were of 37 kJ/mol and 10 kJ/mol on Pd/C and Rh/C, respectively.

Iron-catalyzed tar decomposition is studied by inspecting changes in catalytic activity and its correlation to the metal oxidation numbers. A carbon-aerogel-supported iron (Fe/CAG) catalyst was used herein to decompose toluene (model tar) at between 500 °C and 700 °C. The catalytic decomposition was studied in a conventional reaction system, and the catalyst was characterized prior to and after the reaction to understand the effect of the structural changes in the catalytic activity. The results demonstrated that the iron oxidation state and coke deposition strongly depend on the reaction temperature. The X-ray diffraction patterns confirmed that at T

Tar removal from gasification gases is a determinant step to guarantee the operational feasibility of gasification-to-chemicals/energy systems. However, this is a very complex process requiring catalytic materials to proceed under reasonably low temperatures and to convert the tars into fuel gases (i.e., CHx). The use of Fe-based catalysts for application has been reported before, however, there are still unsolved questions related to its stability and interaction with some species of gasification gases. Therefore, we evaluated carbon-supported Fe for the decomposition of tar using simulated gasification gases, and toluene, naphthalene, and benzene as models for tar. The effects of temperature (565 < T < 665 °C) and co-feeding CO on the catalytic activity and stability were inspected at laboratory and bench scales. The activity of catalysts for decomposing tars was in the following order: benzene > toluene e > naphthalene. Moreover, there was evidence validating a reversible elemental step toluene⇔benzene over the Fe surface. The characterization of the spent catalysts evidenced the oxidation of the active phase and the carbon deposition on the surface. The formation of FexOy caused a marked loss of activity. Conversely, the carbides were stable and still active for tar decomposition.

The hydrogenation of CO2 to methanol is a viable alternative for reducing greenhouse gases net emissions as well as a route for hydrogen storage and transportation. In this context, the synthesis of active and selective catalysts is a relevant objective. In this work, we study the promotion of Pd with Ga and Zn in the hydrogenation of CO2 to methanol at 800 kPa and 220–280 °C. Mono and intermetallic catalysts (Pd/SiO2, Pd Ga/SiO2 and Pd Zn/SiO2) were synthesized by incipient wetness impregnation with the aid of triethanolamine as an organic additive, obtaining similar average metal particle sizes (between 9 and 12 nm). Kinetic analysis reveals that the addition of Ga and Zn increases the turnover frequency for methanol formation by an order of magnitude without significant changes in the reaction rate of the reverse water-gas shift (r-WGS) which is a parallel undesired reaction. The selectivity to methanol (at 220 °C) thus increases from 3% for Pd/SiO2 to 12% for Pd Ga/SiO2 and 30% for Pd Zn/SiO2. XPS studies, Infrared analysis of CO adsorption, and XRD analyses show the presence of intermetallic phases Pd2Ga and PdZn on the surface. The results suggest that Ga and Zn promote Pd, increasing its activity towards the synthesis of methanol, by creating more active sites for this reaction. These sites are likely formed by intermetallic compounds such as Pd2Ga and PdZn.

The present study reports on the technical, economic and environmental analysis of small-scale gasification-ICE systems integrated into sawmills in Chile. Two scenarios were considered, (i) a 100 kWe system for self-consumption in a sawmill and (ii) a 1000 kWe system for using residues from different sawmills. The gasification system was technically assessed by a comprehensive mathematical model implemented on Aspen One 10.0, while economics were studied by the Levelized cost of electricity (LCOE) and environmental impacts were quantified by a Life cycle assessment of forestry, sawmills and power plant processes. Results demonstrate that heat recovery is critical for the process economy, which exhibits an LCOE between 0.15 and 0.32 USD/kWh, and a return on investment of 6.4 years. Nevertheless, the gasification system is far for being an economically-feasible alternative for Chile, where electricity price is 0.08–0.10 USD/kWh. In contrast to economic assessment, the implementation of the gasification-ICE power plant would be a promising alternative for decarbonization of the Chilean energy matrix, showing a reduction of 93% of carbon emissions versus actual practices (viz. co-firing process). From the environmental point of view, biomass harvesting and transport are the critical stages during the whole life cycle of energy production, regardless of the scenario.

The CO hydrogenation reaction was studied under methanation conditions (H2/CO >3, 250–300 °C) on Co/SiO2 catalysts with different mean Co nanoparticle size (dp = 4 nm, 13 nm and 33 nm). The catalysts were prepared by incipient wetness impregnation; the cobalt loading and reduction conditions were suitably selected in order to produce catalysts with different dp. Operando FTIR and kinetic measurements provided consistent data for the heat of CO adsorption at low and full coverage. The results confirm the structural sensitivity of the CO hydrogenation reaction on supported cobalt catalysts and demonstrate the energetic heterogeneity of the cobalt surface. A model derived from the Temkin formalism accurately fits the kinetic data and renders the heterogeneity of the cobalt surface by capturing the change in the heat of CO adsorption with the CO coverage. This change is normalized by the heat of CO adsorption at high coverage (ΔQCO/Q1) in order to quantify and compare the heterogeneity of cobalt surfaces. The CO hydrogenation turnover rates are lower on the catalyst with smaller nanoparticles. This surface shows higher heterogeneity and lower apparent activation energy, which is attributed to a larger amount of the more active B5-B sites in this catalyst.

The size of copper nanoparticles affects the intrinsic rate of methanol and CO formation in the hydrogenation of CO2 at 230–270 °C and total pressure 8 bar. Cu/SiO2 catalysts with different mean Cu particle sizes were prepared by water-in-oil microemulsions and suitably pretreated to obtain samples with mean particle size between 4 and 36 nm. The intrinsic rates of methanol and CO formation are 3-fold higher for large particles (>10 nm) than for smaller ones (ca. 4 nm). The reaction path was studied by means of kinetic experiments, H/D isotopic substitution, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). Results demonstrate that the hydrogenation of formic acid is the rate-determining step (rds) for methanol synthesis, whereas for CO formation the reaction proceeds with the assistance of H atoms and the dissociation of the carboxyl intermediate is the rds. This reaction scheme implies that the ratio of CO to methanol formation rates is inversely proportional to H2 partial pressure, which is also consistent with results for similar catalysts reported in earlier studies. The similar kinetic parameters and H/D kinetic isotope effect observed for catalysts with significantly different Cu mean particle sizes suggests that active surface sites have similar topology regardless of Cu particle size. Step-edge sites whose relative abundance increases with particle size in a way similar to activity are suggested as the active sites for methanol and CO formation reactions.

A comprehensive study of carbon aerogel-supported nickel (Ni/CAG) in the catalytic fast pyrolysis (CFP) of torrefied Eucalyptus globulus was performed in a micropyrolysis unit (Py-GCMS). Effects of pyrolysis temperatures (450–600 °C), catalyst-to-biomass ratio (1:1 pi 2 adsorption-desorption at 77 K, X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Regardless the use of catalysts, the pyrolysis vapors produced from torrefied biomass were depleted in carboxylic acids (selectivity 2 -depleted atmosphere, presumably by a synergistic effect between water gas shift and reforming reactions with transalkylation and decarbonylation of phenolics and furanics. It was demonstrated that metal cluster sizes influenced the reaction routes by favoring hydrogenation on metal facets and deoxygenation on step/corners sites.

Nickel and iron supported on thermostable cellulose-derived carbon aerogels (CAG), were used for the catalytic fast pyrolysis (CFP) of crude and torrefied Eucalyptus globulus . Pyrolysis vapors produced from torrefied biomass under non-catalytic conditions were reduced by 70% in carboxylic acids with respect to vapors originating from crude biomass, but also were richer in ketones and aromatics. In the case of CFP of both crude and torrefied E.globulus on CAG-supported iron and nickel (Fe/CAG and Ni/CAG), the metallic clusters were activated for ketonization, while Ni 0 provided additional hydrogenation sites, increasing the production of monoaromatics (c.a.18% selectivity), leading to a high acids-to-ketone (ξ A-K = 1.3) and heavy-to-light (ξ H-L = 1.0) ratios. Accordingly, Ni/CAG and Fe/CAG were more effective than HZSM-5 –a traditional cracking catalysts– for upgrading CFP vapors to light compounds. The combination of zeolite acid sites with the oxophilic Ni 0 and Fe 0 allows the deoxygenation of vapors while the ratio of polyaromatics to light aromatics (ξ PAHs ) was reduced by nearly 50%.

The effects of using (NH4)2SO4 as a carbonization promoter for producing cellulose-derived carbon aerogels (CAG) was studied. The effects of pretreatment on the textural, morphological, and chemical properties of pristine cellulose nanofibers (CNF) were analyzed through N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the thermal behaviors of raw CNF and those impregnated with (NH4)2SO4 were investigated by coupling thermogravimetric analysis with mass spectrometry (TGA-MS). The results suggested that the pretreatment did not cause any morphological/structural changes in the nanofibers. However, the presence of (NH4)2SO4 affected their pyrolysis by favoring intermolecular dehydration, thereby reducing the formation of levoglucosan and increasing the carbon yield during pyrolysis. Interestingly, above certain impregnation level, the concentration of sulfate-derived species in the gas phase increased. This phenomenon was attributed to an excess of salt within the fiber structure and on their surfaces. Consequently, the levoglucosan-to-carbon route was inhibited, and the mechanisms of intra- and inter-molecular dehydration, chain scission, and crosslinking reactions were affected, leading to a reduced char yield. The chemical effects of ammonia-based salts is elucidated supported on the interpretation of MS signals and kinetic modeling results.

Rapidly growing research on biomass reactivity has not benefited enough from the very abundant knowledge acquired on coal-derived materials. Literature comparisons using similar methods are scant and inconclusive. To clarify differences (or similarities) between coal- and biomass-derived chars, we performed a systematic study using three different carbon-based solids at different stages of coalification. Two biomass materials and a low-rank coal were demineralized and heat-treated between 550 and 1450 °C. Even after heat treatment, biomass-derived chars remained less structurally ordered, more microporous, and more reactive towards oxygen than their coal-derived counterparts. Through computational chemistry, we compared the thermodynamic driving forces and kinetic barriers for biomass-like and coal-like representative graphene clusters. The oxidation pathway to CO was the same for both clusters, but different for CO2 formation. We predict that the energy barrier of CO desorption is higher for coal-derived chars, whereas that of CO2 desorption is higher for biomass-derived chars; this is consistent with the dominant formation of CO2 at the relatively low reaction temperatures used in our study. We demonstrate also that in a kinetically controlled reaction regime, in the absence of catalytically active minerals, the reactivity differences can be explained on the basis of differences in char surface chemistry.

The influence of lanthanum stoichiometry in Ag-doped (La 1-x Ag x Mn 0.9 Co 0.1 O 3 ) and A-site deficient (La 1-x Mn 0.9 Co 0.1 O 3-δ ) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O 2 -TPD and TPR. The formation of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag 2 O segregated phases and the redox pair Mn 4+ /Mn 3+ . A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn 4+ /Mn 3+ , which is attributed to the cubic crystalline structure.

Reduction of Fe-phases in a slag from the copper smelting process is studied for its use as a catalyst in methanation of carbon oxide (CO). This material contains 36.4 wt% Fe and the main Fe-phases in its fresh and reduced forms were identified and quantified. Chemical analysis and X-ray diffraction (XRD) for crystalline phase detection and determination of Fe dispersion were carried out. Reducibility of Fe-oxides was studied by thermal programmed reduction (TPR) under H2 at 650 and 800 °C using 0.5 and 2 h soak time. In the fresh slag, iron was found to be in the form of Fe3O4 (17.4 wt%) and fayalite, Fe2SiO4 (43.4 wt%). The composition was experimentally determined and verified by stoichiometric balances and thermogravimetric analysis (TGA). Upon reduction at 800 °C and 2 h soak time, 87 % of the Fe-phases were reduced, leaving an activated catalyst with a 35.2 % Fe0, which is the active phase for CO hydrogenation to methane. An expression was derived to determine the Fe0 concentration in the reduced slag based on the composition of the fresh slag and its reduction degree. The catalytic activity of the reduced slag during CO hydrogenation was evaluated in a fixed bed differential reactor. The selectivity to methane, at 300 °C, was 87 %, thus confirming its catalytic activity for the selected reaction.

Biomass gasification is a promising way to obtain &ldquo, green energy&rdquo, but the gas composition makes it unsuitable for use in traditional technologies (i.e., IC engine). Gas purification over nickel and/or iron catalysts is an attractive alternative. Cellulose-based carbon aerogels (CAGs) have shown suitable physical chemical properties for use as catalyst supports. In this work, nickel and iron catalysts are supported on CAG made from cellulose microfibers. Microfibers were impregnated with (NH4)2SO4 to increase the mass yield. Carbonization was evaluated at different heating rates, maximum temperatures, and dwell times to generate CAGs. Resulting chars were characterized by N2 adsorption, X-ray diffraction (XRD), and Raman spectroscopy. The CAG with better properties (specific surface, pore size, thermal resistance) was impregnated with the metal precursor salt via incipient wetness and treated with H2. Catalysts were characterized by transmission electron microscopy (TEM), XRD, N2 adsorption, and inductively coupled plasma optical emission spectrometry (ICP-OES). Ammonia adsorption was studied over CAG and catalysts to estimate the thermodynamic parameters. The impregnation with ((NH4)2SO4 improves thermal resistance of the char obtained from carbonization. The catalysts exhibit higher adsorption capacity than CAG (without metal), indicating chemical interaction between ammonia and metals. The metal-ammonia interaction is stronger on Fe than on Ni catalyst, which is consistent with reported theoretical calculations.

Torrefaction is a thermal pretreatment leading to the improvement of most of the fuel properties of biomass, namely energy density, HHV (higher heating value), grindability and hydrophobicity. The aim of this study is to identify the most feasible temperature to carry out torrefaction of Eucalyptus globulus and nitens , based on chemical evidences associated to the release of volatiles during thermal treatment of biomass. With that end: (i) Devolatilization kinetics, (ii) Effects of temperature and residence time and (iii) volatiles composition during torrefaction of both wood and bark were analyzed. In all cases DTG (derivative thermogravimetric curves) exhibited the typical shape of lignocellulosic materials, with three decomposition phases and two reaction zones. Values of activation energies for hemicellulose decomposition, were in agreement with those reported in the literature (121–170 kJ/mol). Carboxylic acids, water and phenolic compounds showed two peaks, which were associated to torrefaction (below 310 °C) and pyrolysis (310–410 °C) respectively. The most feasible temperatures for torrefaction were estimated as a function of these peaks, and it ranged between 295 °C and 310 °C for all samples. Main volatile species at the torrefaction peaks were distributed as Water > Acetic Acid > CO 2 > Others, while Levoglucosan formation was marginal, due to the catalytic effect of inorganics.

The use of wood as feedstock for the production of energy and chemicals is a strategy used by both developing and developed countries because it increases the sustainability of their energy infrastructure. Torrefaction of forest resources for co-firing and densification of biomass energy is among the most prominent alternatives. This study is focused on technical aspects of torrefaction technology by analyzing both energy and exergy changes through a comprehensive physico-chemical model (Aspen One v8.6 software) of a plant operating in mild (250 °C) and severe (280 °C) regimes. The main wood species in Chilean plantations, Eucalyptus globulus and Pinus radiata , were processed in a lab-scale apparatus to obtain the data for model calibration. We found that xylan composition in hemicelluloses has a considerable effect on global thermal efficiency, volatiles energy content, energy density, and exergy yield of torrefied product. The highest efficiency (96%) is obtained for Eucalyptus at 250 °C when moisture in the feedstock is ≤ 20%. Combustion of volatile products (torgas) for drying does not result in substantial technical benefits for the overall process; however, their post-combustion does lead to lower exergy losses.

Kinetic and isotopic data on Pt clusters and activation free energy barriers from density functional theory (DFT) on Pt(1 1 1) are used to assess the elementary steps involved in NO–H2 reactions. Pt clusters 1–10 nm in diameter gave similar turnover rates, indicating that these elementary steps are insensitive to surface-atom coordination. N–O cleavage occurs after sequential addition of two chemisorbed H-atoms (H * )t o NO * which are quasi-equilibrated with H2 and NO co-reactants. The first step is equilibrated and forms HNO * , while the second addition is irreversible and forms * HNOH * ; this latter step limits NO–H2 rates and forms OH * and NH * intermediates that undergo fast reactions to give H2O, N2O, NH3, and N2. These conclusions are consistent with (i) measured normal H/D kinetic isotope effects; (ii) rates proportional to H2 pressure, but reaching constant values at higher pressures; (iii) fast H2–D2 equilibration during catalysis; and (iv) DFT-derived activation barriers. These data and calculations, taken together, rule out N–O cleavage via NO * reactions with another NO * (forming O * and N2O) or with vicinal vacancies (forming N * and O * ), which have much higher barriers than H * -assisted routes. The cleavage of

This work shows that loading Fe into the K/MgO catalyst for soot combustion can reduce K volatilization due to the formation of potassium-iron oxide compounds. K/MgO and K–Fe/MgO catalysts were prepared by the impregnation of potassium and iron precursors on MgO, and their activity for soot combustion was assessed by thermogravimetric analysis. Catalysts were characterized by atomic absorption spectroscopy, BET surface area, X-ray diffraction and X-ray photoelectron spectroscopy. Fe addition on K/MgO catalyst enhanced its catalytic activity, which is ascribed to a larger K retention into the catalysts either as potassium oxides or as K–Fe–O compounds. The non-stoichiometric potassium oxide (KXOY) is considered as the active phase of this kind of catalysts; it tends to migrate to the surface and to coat the Fe and K–Fe oxides compounds, increasing the surface concentration of active sites for soot combustion. Thus, molecular oxygen from the gas phase is activated over these potassium oxides to generate highly active oxygen species that finally oxidize the carbonaceous matter through an oxygen-transfer mechanism.

The effect of the preparation method and calcination temperature on the stability and activity of KNbO3 as catalysts for soot oxidation is reported. The solids were prepared by three different procedures: (i) by a citrate method using NbCl5 as niobium precursor; (ii) by a citrate method using NbF5 as niobium precursor; and (iii) by an autocombustion method using Nb2O5 as niobium precursor. The powders were calcined at 600 °C and 700 °C and characterized by N2 physisorption, oxygen desorption profiles, XRD and SEM. The catalytic activity is discussed in terms of both the Tm value, the temperature at which combustion of carbon black occurs at the maximum rate, and the apparent activation energy. It is found that KNbO3 calcined at 600 °C shows the higher catalytic activity. Also, a strong dependence on the preparation method is observed. The solids prepared by the citrate method show the higher catalytic activities, being the most active the one that use NbCl5 as niobium precursor. This highest catalytic activity is discussed in terms of nanosized perovskite structure and rough interfaces associated to the oxygen's vacancies. Moreover, lower apparent activation energies were obtained for the solids prepared by the citrate method. In addition, it is observed that no deactivation by metal loss after consecutive soot combustion cycles because of the stabilization of the alkaline metal inside the perovskite structure.

Alumina supported catalytic systems K–Me (Me = Cu, Co and V) for the simultaneous removal of soot and NO x , were prepared by impregnation of a powder particle size alumina, using nitrate solutions of the corresponding metals. Physico-chemical characterization of the prepared catalysts was performed by means of XRD, SEM-EDX, ICP, N 2 -adsorption and TPR. The activity of the catalysts was assayed both, by thermogravimetric analysis and in a laboratory-scale fixed bed reactor. The effect of catalyst composition was examined. The catalysts showed high activity on the simultaneous removal of soot and nitrogen oxides at temperatures between 350 and 550 °C. Full selective conversion of NO x and total oxidation of the soot was attained; observing higher reaction rates in the case of the catalysts prepared using Cu as the active metal.

Tar removal from gasification gases is a determinant step to guarantee the operational feasibility of gasification-to-chemicals/energy systems. This study aimed to develop novel carbon-supported catalysts for the elimination of tarry aromatics (toluene, naphthalene and benzene) from gasification gases. Effects of reaction temperature (700 < T < 900 °C) and catalyst nature (Fe0 and Ni0) on the activity were assessed by considering thermo-catalytic conversion and steam reforming, under a simulated gasification gas. The catalysts (Ni and Fe) and support (AC) were characterized by X-ray diffraction (XRD), N2 physisorption, thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and compositional analyses. Both catalysts and support, presented a mesoporous-like texture with a considerable high surface area (690 < SBET < 743 m2/g). Furthermore, dispersion of the metal nanoparticles (active phase) was uniform as confirmed by TEM images. Results from activity tests suggest that Ni/AC has higher effectivity for converting tars than Fe/AC, as confirmed by the low apparent activation energies (34 < Eapp < 98 kJ/mol) for naphthalene and benzene conversion between 700 and 900 °C. The conversion was 100% above 850 °C; nevertheless; below 750 °C, a sharp reduction in benzene conversion was observed, which was attributed to reversible carbon deposition.

The thermal degradation of metal complexes formed by chitosan with Cu(II), Ni(II), Co(II), and Hg(II), at different metal concentrations, was studied by thermogravi- metric analysis in a nitrogen atmosphere over the tempera- ture range 25-800 � C. The results indicate that thermal degradation of chitosan and chitosan-metal ion complexes could be of one or two-stage reaction. In the thermal degra- dation of chitosan with metal complexes, the temperature of initial weight loss and the temperature of maximum weight loss rate decrease. Fourier transform infrared spectroscopy was used to probe the interaction of chitosan with metal ions. The bands of ANAH, AC¼ ¼O, ACAOACA groups of chitosan are shifted or change their intensity in the presence of metal. These changes in the characteristic bands are taken as evidence of the influence of metal ions on the thermal stability of chitosan. Broido's method was employed to evaluate the activation energies as a function of the degree of degradation. The presence of metal ions provoked a decrease in the thermal stability of chitosan, which became more marked when the concentration of metal was increased. The dynamic study showed that the apparent activation energy values of the main stage of the thermal degradation of chitosan-metal complexes decrease as the strength of the polymer-metal interaction increases. V C 2009