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The catalytic reduction of nitrites over Pt-In catalysts supported on activated carbon has been studied in a semi-batch reactor, at room temperature and atmospheric pressure, and using hydrogen as the reducing agent. The influence of the indium content on the activity and selectivity was evaluated. Monometallic Pt catalysts are very active for nitrite reduction, but the addition of up to 1 wt% of indium significantly increases the nitrogen selectivity from 0 to 96%. The decrease in the accessible noble metal surface area reduces the amount of hydrogen available at the catalyst surface, this favoring the combination of nitrogen-containing intermediate molecules to promote the formation of N2 instead of being deeply hydrogenated into NH4+. Several activated carbon-supported Pt-In catalysts, activated under different calcination and reduction temperatures, have been also evaluated in nitrite reduction. The catalyst calcined and reduced at 400°C showed the best performance considering both the activity and the selectivity to nitrogen. This enhanced selectivity is ascribed to the formation of Pt-In alloy. The electronic properties of Pt change upon alloy formation, as it is demonstrated by XPS.

The hydrogenation of nitroarenes to produce the corresponding amines using dihydrogen as reducing agent has an important industrial role, since it allows to obtain important added-value products. This reaction needs the help of a catalyst to proceed. Many catalysts have been already tested and studied. Most of them are based on noble metals supported on metal oxides. These catalysts perform well, but they are expensive and thus, alternative systems are needed. In this context, cobalt-based catalysts have emerged as adequate alternatives, despite cobalt nanoparticles per se are not very active for this reaction. A way to improve the catalytic activity of cobalt nanoparticles is by supporting them on a support with functional groups that are able to change their intrinsic properties and to enhance their catalytic properties. In this sense, N-containing carbons are promising candidates to be used as support, since nitrogen functionalities may modify the catalytic properties of cobalt. In this work, cobalt nanoparticles supported on N-doped activated carbons have been prepared and studied as catalysts for the hydrogenation of 1-chloro-4-nitrobencene to the corresponding chloro-aniline. It is demonstrated that the catalytic activity is enhanced by the presence of nitrogen species in the support. When the temperature of the catalyst activation treatment (reduction under flowing hydrogen) is increased, the catalytic activity increases drastically in the presence of nitrogen functionalities on the support. The catalysts have been characterised by transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray diffraction, X-ray photoelectron spectroscopi (XPS) and N2 adsorption at 77 K. It has been found that the enhanced catalytic activity was due to two different factors, namely the interaction of the cobalt particles with the nitrogen functional groups (forming Co4N), and the development of mesopores in the support during the activation process that increases the accessibility of reactants to the active sites. Authors acknowledge financial support by MINECO (Spain) through the projects MAT2017-86992-R and MAT2016-80285-P and the European Union for the project “eForFuel”, grant agreement 763911. J. C. S. R. would like to thank the Spanish Ministry of Science and Innovation for financial support through the Ramón y Cajal Program, Grant: RYC-2015-19230 J. C. S. R. would also like to thank Junta de Andalucía for financial support through the projects PY18-RE-0012 and IE18_0047_FUNDACIÓN LOYOLA.

In-situ hydrodeoxygenation of guaiacol over Ni-based nitrogen-doped activated carbon supported catalysts is presented in this paper as an economically viable route for bio-resources upgrading. The overriding concept of this paper is to use water as hydrogen donor for the HDO reaction suppressing the input of external high-pressure hydrogen. The effect of nitrogen sources, including polyporrole (PPy), polyaniline (PANI) and melamine (Mel) on the structural, electronic and ultimately of catalytic features of the design materials have been addressed. Nitrogen-doped samples, are more active than the undoped counterparts in the “H2-free” HDO process. For instance, the conversion of guaiacol increased by 8% for Ni/PANI-AC compared to that of Ni/AC catalysts. The superior performance of Ni/NC can be attributed to the acid-base properties and modified electronic properties which favours the C-O cleavage and water activation as well as enhances dispersion of Ni particles on the catalysts’ surface

A mechanism for the reduction of aqueous nitrate with metal-free polypyrrole (PPy) is proposed. The activity and selectivity of the polymer has been compared to those of metal catalysts supported on polypyrrole, activated carbon or titania (TiO2). The role of formic acid (FA) and hydrogen (H2) as reductants, and carbon dioxide (CO2) as buffer of the aqueous nitrate solution is discussed and compared to the performance of PPy by itself. The ion-exchange and the redox properties of PPy are strongly affected by the oxidation state of the nitrogen moieties in the polymeric chain. This is determined by the oxidant/dopant used in the polymer synthesis (FeCl3 or K2S2O8). The degree of oxidation of PPy can also be modified by a plasma treatment of the polymer, which determines the ability of PPy to carry out the reduction of nitrate by the electrons provided by the polymeric chain and also affects the selectivity of the nitrate reduction. Financial support from Generalitat Valenciana, Spain (PROMETEOII/2014/004) and Ministry of Economy and Competitiveness (MAT2016-80285-P) is gratefully acknowledged.

Bio-hydrogenated diesel (BHD), derived from vegetable oil via hydrotreating technology, is a promising alternative transportation fuel to replace nonsustainable petroleum diesel. In this work, a novel Pt-based catalyst supported on N-doped activated carbon prepared from polypyrrole as the nitrogen source (Pt/N-AC) was developed and applied in the palm oil deoxygenation process to produce BHD in a fixed bed reactor system. High conversion rates of triglycerides (conversion of TG > 90%) and high deoxygenation percentage (DeCOx% = 76% and HDO% = 7%) were obtained for the palm oil deoxygenation over Pt/N-AC catalyst at optimised reaction conditions: T = 300 °C, 30 bar of H2, and LHSV = 1.5 h−1. In addition to the excellent performance, the Pt/N-AC catalyst is highly stable in the deoxygenation reaction, as confirmed by the XRD and TEM analyses of the spent sample. The incorporation of N atoms in the carbon structure alters the electronic density of the catalyst, favouring the interaction with electrophilic groups such as carbonyls, and thus boosting the DeCOx route over the HDO pathway. Overall, this work showcases a promising route to produce added value bio-fuels from bio-compounds using advanced N-doped catalysts. This research was funded by the Department of Chemical and Process Engineering of the University of Surrey and the EPSRC grants EP/J020184/2 and EP/R512904/1 as well as the Royal Society Research Grant RSGR1180353. Authors would also like to acknowledge the Ministerio de Economía, Industrial Competitividad of Spain (Project MAT2016-80285-P) and the Chinese Scholarship Council (CSC). L.P.-P. also thanks Comunitat Valenciana for her postdoctoral fellow APOSTD2017. K.P. is grateful for the support of the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT), under the HFRI PhD Fellowship grant (GA. No. 359). The APC was funded by University of Surrey.

Microporous activated carbons were prepared from date pits using thermal activation with CO2 or steam. The adsorbents were characterized by N2 and CO2 adsorption at 77 K and 273K, respectively. The H2 adsorption was measured at 298K and 100 bar using a volumetric equipment. To increase the hydrogen storage, activated carbons are doped by metals. The results show that the H 2 adsorption capacity is influenced by the size and volume of micropores in the activated carbon adsorbent. A relationship between hydrogen adsorption capacity calculated using Langmuir isotherm and the volume of narrow micropores deduced from the CO2 adsorption isotherm at 273 K was found. A correlation was also found between both micropore volumes and the amount of hydrogen adsorbed at 298 K and 100 bar. Additionally, vanadium doping of activated carbons could positively influence hydrogen adsorption.

In this work, the WGS performance of a conventional Ni/CeO2 bulk catalyst is compared to that of a carbon-supported Ni-CeO2 catalyst. The carbon-supported sample resulted to be much more active than the bulk one. The higher activity of the Ni-CeO2/C catalyst is associated to its oxygen storage capacity, a parameter that strongly influences the WGS behavior. The stability of the carbon-supported catalyst under realistic operation conditions is also a subject of this paper. In summary, our study represents an approach towards a new generation of Ni-ceria based catalyst for the pure hydrogen production via WGS. The dispersion of ceria nanoparticles on an activated carbon support drives to improved catalytic skills with a considerable reduction of the amount of ceria in the catalyst formulation., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)., Financial support of Ministerio de Ciencia e Innovacion of Spain (Project MAT2010-21147) is gratefully acknowledged. L.P.P. acknowledges her grant BES-2011-0406508. The Spanish Ministerio de Economía y Competitividad (MINECO) is also acknowledged for the funding linked to the projects ENE2012-374301-C03-01 and ENE2013-47880-C3-2-R.

Catalysts consisting in platinum supported on cerium oxide highly dispersed on activated carbon, with a Pt loading of 1 wt.% and ceria loadings of 5, 10 and 20 wt.% have been prepared by impregnation method and characterized by several techniques (N2 adsorption at 77 K, ICP, XRD, H2-TPR and XPS). Their catalytic behavior has been evaluated in the total oxidation of ethanol and toluene after reduction at 473 K. The obtained results show that the prepared catalysts have better performances than platinum supported on bulk CeO2. The best catalytic performance was obtained for 10 wt.% ceria loading, likely due to an optimum synergistic interaction between highly dispersed cerium oxide and platinum particles. Pt-10Ce/C achieves total conversion of ethanol and toluene to CO2 at 433 K and 453 K, respectively, and shows no deactivation during a test for 100 h. Under humid conditions (relative humidity, RH, of 40 and 80%), the activity was only slightly influenced due to the hydrophobic character of the activated carbon support, which prevents the adsorption of water. Financial support from Generalitat Valenciana (Spain, PROMETEO/2009/002-FEDER and PROMETEOII/2014/004) is gratefully acknowledged.

The low temperature water–gas shift (WGS) reaction has been studied over carbon-supported nickel catalysts promoted by ceria. To this end, cerium oxide has been dispersed (at different loadings: 10, 20, 30 and 40 wt.%) on the activated carbon surface with the aim of obtaining small ceria particles and a highly available surface area. Furthermore, carbon- and ceria-supported nickel catalysts have also been studied as references. A combination of N2 adsorption analysis, powder X-ray diffraction, temperature-programmed reduction with H2, X-ray photoelectron spectroscopy and TEM analysis were used to characterize the Ni–CeO2 interactions and the CeO2 dispersion over the activated carbon support. Catalysts were tested in the low temperature WGS reaction with two different feed gas mixtures: the idealized one (with only CO and H2O) and a slightly harder one (with CO, CO2, H2, and H2O). The obtained results show that there is a clear effect of the ceria loading on the catalytic activity. In both cases, catalysts with 20 and 10 wt.% CeO2 were the most active materials at low temperature. On the other hand, Ni/C shows a lower activity, this assessing the determinant role of ceria in this reaction. Methane, a product of side reactions, was observed in very low amounts, when CO2 and H2 were included in the WGS feed. Nevertheless, our data indicate that the methanation process is mainly due to CO2, and no CO consumption via methanation takes place at the relevant WGS temperatures. Finally, a stability test was carried out, obtaining CO conversions greater than 40% after 150 h of reaction. Financial support of Ministerio de Ciencia e Innovación of Spain (Project MAT2010-21147) is gratefully acknowledged. L.P.P. acknowledges her grant BES-2011-0406508.

In this work, the low-temperature hydrogen production via glycerol steam reforming over activated carbon-supported Ni and Ni-Sn catalysts promoted by ceria was studied. A combination of N2 adsorption, powder X-ray diffraction, temperature-programmed reduction with H2, X-ray photoelectron spectroscopy and TEM analysis were used to characterise the Ni-Sn-CeO2 interactions and the CeO2 dispersion over the activated carbon support. The catalytic activity results show that the presence of ceria enhances the water-gas shift reaction, thus promoting the selectivity towards hydrogen. The inclusion of Sn stresses the influence of ceria in the displayed performance. Moreover, the formation of a Ni-Sn alloy seems to be an efficient way to mitigate Ni sintering and therefore to improve the overall catalyst’s stability. This work has been supported by Ministerio de Economía y Competitividad (Spain, project MAT2013-45008-P). L. P-P. acknowledges her grant BES-2011-0406508.

The effect of the support (activated carbon or titanium dioxide) on the catalytic activity and selectivity to nitrogen of Pt-Sn catalysts in nitrate reduction was studied. The effects of the preparation conditions and the Pt:Sn atomic ratio were also evaluated. It was observed that the support plays an important role in nitrate reduction and that different preparation conditions lead to different catalytic activities and selectivities. Generally, the catalysts supported on activated carbon were less active but more selective to nitrogen than those supported on titanium dioxide. The monometallic Pt catalyst is active for nitrate reduction only when supported on titanium dioxide, which is explained by the involvement of the support in the reaction mechanism. The catalysts were characterized by different techniques, and significant changes on metal chemical states were observed for the different preparation conditions used. Only metallic Pt and oxidized Sn were observed at low calcination and reduction temperatures, but some metallic Sn was also present when high temperatures were used, being also possible the formation of Pt-Sn alloys.

Several catalysts of cerium oxide highly dispersed on activated carbon were prepared varying the cerium precursor, the solvent and the chemical surface properties of the support, and characterized by several techniques. Afterwards, these materials were investigated as ozonation catalysts for the mineralization of two organic compounds (oxalic acid and aniline). The ozonation results were compared with those obtained in the absence of catalyst and in the presence of the parent activated carbons used for the preparation of these materials. The prepared catalysts have better performances than the parent activated carbons, denoting a clear synergic effect between activated carbon and cerium oxide. The efficiency of the catalysts is mainly affected by the amount of Ce 3+ species on the surface. However, in the ozonation of oxalic acid, the specific surface area and metal oxide particle diameter also played an important role. The use of activated carbon as support favors the removal of both organic compounds studied. Highly dispersed cerium oxide on activated carbon shows better catalytic performance than a composite with the same composition.

The low temperature water gas shift reaction has been studied over carbon-supported platinum catalysts promoted by ceria. To this end, CeO2 has been dispersed over an activated carbon support at different loadings (20, 30 and 40 wt.%) in order to obtain a high ceria surface area. Then, platinum has been incorporated by impregnation with an acetone solution of [Pt(NH3)4](NO3)2. Two more catalysts have been prepared with aqueous and ethanolic solutions, respectively, to assess the effect of the solvent in the final catalysts. Pt/CeO2 and Pt/C catalysts have been used as references. Catalysts have been characterized (N2 adsorption at 77 K, TEM, H2-TPR) and tested in reaction after reduction with H2 at 473 K. The obtained results show that CO conversion increases with the amount of ceria loaded, from 20 to 40 wt.%. At this temperature, platinum supported on bulk CeO2 is less active than its carbon-based counterparts. The best results are obtained for the catalysts with 40 wt.% CeO2 prepared by aqueous impregnation of the platinum precursor, which achieves conversions higher than 70% at 573 K, and shows no deactivation under reaction at this temperature for 120 h. On the other hand, Pt/C shows a very low activity, this certifying the determinant role of ceria in this reaction. These results indicate that dispersion of ceria on activated carbon allows to obtain catalysts with superior performance than using bulk CeO2 as support, and with a lesser amount of ceria.

A parent activated carbon (C-0) was subjected to four different treatments: (i) heat treatment at 1273 K in Ar (C-1); (ii) heat treatment at 473 K in air (C-2); (iii) oxidation with H 2 O 2 (C-3) and, (iv) oxidation with HNO 3 (C-4). These materials were evaluated as supports of CuBr–[1,1,4,7,10,10-hexamethyltriethylenetetramine] (Cu I Br–HMTETA), a catalyst for the Atom Transfer Radical Polymerization (ATRP) of methyl methacrylate (MMA) using methyl-α-bromophenylacetate (MBP) as radical initiator. The supported catalysts showed an adequate control of polymerization, evidenced by polydispersity indexes (PDI) falling in the range 1.13–1.55. The best performance was achieved when activated carbon was treated with nitric acid (C-4) and with air at 473 K (C-2). Some copper leaching was always detected. The catalysts were reused and an adequate polymerization control was obtained in subsequent runs.

The influence of calcination and reduction temperatures on the catalytic properties of Pd–Cu and Pt–Cu bimetallic catalysts supported on activated carbon for the reduction of nitrates was studied. The catalysts were prepared using different calcination and reduction temperatures, and the respective activities and selectivities for the reduction of nitrates in water with hydrogen were assessed. It was found that the different preparation conditions lead to different catalytic performances. For both catalysts, the activity decreases by increasing calcination and reduction temperatures, whereas the effect on the selectivity is not uniform. For the 1%Pd–0.3%Cu (wt.%) catalyst, the nitrate conversion after 5 h of reaction varies from 93% (sample calcined at 200 °C and not reduced) to 25% (sample calcined and reduced at 400 °C). The formation of alloys during the preparation of the catalysts is prejudicial for nitrate reduction. In all the preparation conditions tested the Pd–Cu pair is more selective for the transformation of nitrate into nitrogen. All the samples have been characterized by nitrogen adsorption at −196 °C, CO adsorption microcalorimetry, TPR, XRD, XPS and TEM.

A series of binderless activated carbon monoliths (ACMs) have been prepared from petroleum pitch and using KOH as activating agent. Characterization shows that these activated carbons combine a large “apparent” surface area (up to S BET ∼ 3000 m 2 /g) together with a well-developed narrow micropore size distribution. Dynamic column adsorption experiments using different volatile organic compounds (VOCs), ethanol and benzene, show that these activated carbons prepared from mesophase-based materials exhibit a superior saturation capacity compared to conventional carbon materials. The total amount adsorbed reaches values as high as 18 g/100 g AC and 40 g/100 g AC, for ethanol and benzene, respectively. These are the best results reported in the literature. The total amount adsorbed for both molecules correlates with the total volume of narrow micropores, thus confirming the pore size specificity required for the adsorption of VOC molecules. Regeneration studies show that ethanol can be easily desorbed at room temperature by flowing clean air through the adsorbent whereas benzene requires a further heating for complete desorption/regeneration.

Two series of activated carbons have been prepared from date pits; series C, using carbon dioxide as activating agent, and series S, prepared by activation with steam under the same experimental conditions. The obtained samples were oxidized with nitric acid in order to introduce more oxygen surface groups. The surface area and porosity of the parent and oxidized activated carbons were studied by N2 adsorption at 77 K and CO2 adsorption at 273 K. The oxygen surface complexes were characterized by temperature-programmed decomposition (TPD). The results show that carbon dioxide and steam activations produce microporous carbons with an increasing amount of CO evolving groups when increasing the burn-off. On the other hand, oxidation with nitric acid increases the amount of CO and CO2 evolved by the decomposition of surface oxygen groups, this increase being related to the development of porosity in the carbon with the degree of activation and to the activating agent used (CO2 versus steam).

Activated carbons with increasing porosity have been prepared by chemical activation of olive stones using ZnCl2 followed by physical activation with CO2. The development of porosity and surface area with burn-off favours the adsorption capacity for ethanol. However, the total amount adsorbed (g/100 g AC) achieves a maximum for the sample with 30% burn-off, this amount decreasing thereafter. Apparently, for a low boiling point alcohol such as ethanol there is a critical pore size which allows an optimum packing of the adsorbed ethanol molecules. A further broadening of the porosity becomes detrimental due to the decreased overlapping adsorption potential inside the micropores. Incorporation of surface functionalities (oxygen surface groups) on the activated carbon enhances the adsorption capacity through the development of specific interactions between the ethanol molecule and the oxygen surface groups.

Catalytic adsorption of SO2 on activated carbon materials provides an appropriate alternative for the control of low concentration emissions of this air pollutant. The surface complexes formed upon SO2 adsorption at 30 °C were studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The effect of the addition of O2 and the presence of copper as catalyst were studied. Copper assisted the oxygen transfer to the carbon matrix. For the Cu-impregnated carbon sample, the presence of O2 favored SO2 adsorption by increasing the breakthrough time, the adsorption capacity and the formation of sulfur and oxygen complexes of higher thermal stabilities, which mainly desorb as SO2 and CO2.

A new material constituted by cerium dioxide highly dispersed on activated carbon (CeO 2 /AC) was prepared by an impregnation method using cerium(III) nitrate as CeO 2 precursor. In order to evaluate the degree of ceria dispersion on the carbon support, CeO 2 /AC was characterized by a number of techniques: thermogravimetry coupled with a mass spectrometer (TG-MS), N 2 adsorption at 77 K, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR) and transmission electron microscopy (TEM). The analysis of the decomposition process under inert atmosphere indicated that cerium nitrate decomposes at 440–460 K, with the evolution of NO. Furthermore, this process produces an additional oxidation of the carbon surface (with evolution of N 2 O) and the subsequent onset of new oxygen surface groups, detected by means of temperature-programmed desorption. The ceria deposition process takes place with a decrease in the N 2 adsorption capacity of the starting carbon support, and the analysis of the pore size distribution showed that the majority of ceria particles are situated at the most internal part of the carbon porosity. The temperature-programmed reduction profile of CeO 2 /AC was very different to that shown by unsupported CeO 2 , with only one continuous reduction process at low temperatures (800–900 K). Finally, TEM pictures gave direct evidence that ceria is highly dispersed on the carbon surface, with a narrow CeO 2 particle distribution centred around 3 nm.

Activated carbon-supported cerium dioxide (CeO2/C) was prepared by impregnation of a commercial support (Norit R2030) with aqueous solutions of two different cerium precursors, [(NH4)2Ce(NO3)6] and Ce(NO3)3·6H2O. The effect of carbon surface chemistry on the dispersion of ceria was studied by using two different carbon supports, the R2030 and the same material after an oxidation treatment with H2O2. Thus, four samples were obtained by combining the precursors and the supports. The prepared materials were characterized by thermogravimetry, nitrogen adsorption isotherms (77 K), X-ray diffraction, temperature-programmed desorption, temperature-programmed reduction and transmission electron microscopy, in order to study the degree of ceria dispersion over the supports. It was found that the best results in terms of ceria dispersion were obtained for the material prepared with the oxidized carbon and ammonium cerium nitrate as cerium precursor.

The removal of propanethiol from liquid phase (1-hexene as solvent) at room temperature has been investigated using different activated carbons. The experimental results show that both the porous structure and surface chemistry of the activated carbon influence the kinetics of propanethiol removal and the total removal capacity (adsorption plus oxidation to dipropyl disulfide). In this sense, while the microporous structure of the carbon is the main parameter defining the removal kinetics, the presence of oxygen functionalities on the carbon surface affects the extent of propanethiol oxidation to dipropyl disulfide and, consequently, the total removal capacity. An oxidation treatment with HNO 3 of selected carbons confirms the promoting effect of the oxygen surface groups in this oxidation process. However, this study shows that the oxidation capacity of the activated carbons is not defined by the amount but mainly by the nature of the oxygen surface groups. The high stability of these groups after a heat treatment at 973 K in a He flow indicates that the conjugated ketone groups (quinone groups) may be responsible of the oxidation of propanethiol to dipropyl disulfide.

The influence of metal loading and support surface functional groups (SFG) on methane dry reforming (MDR) over Ni catalysts supported on pine-sawdust derived activated carbon were studied. Using pine sawdust as the catalyst support precursor, the smallest variety and lowest concentration of SFG led to best Ni dispersion and highest catalytic activity, which increased with Ni loading up to 3 Ni atoms nm-2. At higher Ni loading, the formation of large metal aggregates was observed, consistent with a lower "apparen" surface area and a decrease in catalytic activity. The H2/CO ratio rose with increasing reaction temperature, indicating that increasingly important side reactions were taking place in addition to MDR. Financial support was provided by CONICYT PFB-27 project (UDT-University of Concepción) and FONDECYT 1100884 grant.

Simultaneous adsorption of NO and SO2 on activated carbon provides an adequate alternative to control the low concentration emissions of these air pollutants. The surface complexes formed during the NO and SO2 adsorptions at 30 °C were studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). The effects of the addition of copper supported on the carbon and O2 on the gas stream were studied. The presence of copper enhanced the chemical adsorption of both NO and SO2. In the simultaneous adsorption of NO and SO2, SO2 inhibited the adsorption of NO, while SO2 adsorption was notably improved. The reaction carried out under a NO/SO2/O2 gas mixture showed a synergic effect increasing the formation of surface complexes. The addition of copper assisted the oxygen transfer to the carbon matrix.

The effect of different preparation parameters (pyrolysis temperature, process time, benzene concentration and residence time) on the properties of carbon molecular sieves obtained by pyrolytic carbon deposition from benzene on a microporous activated carbon, has been studied. For a fixed process time of 2 h, the increase of the pyrolysis temperature from 525 to 700∘C produced a strong increase of the CO2/CH4 selectivity, reaching a maximum value of 13 for pyrolysis at 700∘C. Selectivity also increased with process time (up to 5 h, with the pyrolysis temperature fixed at 650 and 675∘C), yielding values as high as 28. The obtained results have allowed to find the optimal preparation parameters for the preparation of CMS with high selectivity.

Two series of ceria-promoted carbon-supported platinum catalysts have been prepared and evaluated in total oxidation of ethanol, as a model volatile organic compound (VOC), in order to study the effect of the metal precursor (H2PtCl6 or Pt(NH3)4(NO3)2) on their physico-chemical properties and catalytic behavior. Catalysts with Pt loading of 1 wt.% and ceria loading of 5, 10 and 20 wt.% have been prepared by the impregnation method, and characterized by several techniques (N2 adsorption at 77 K, ICP, XRD, H2-TPR and XPS). Toluene hydrogenation has been used to obtain an estimation of the platinum dispersion on the investigated catalysts. On the other hand, their catalytic behavior has been evaluated in the total oxidation of ethanol, selected as a VOCs probe molecule. A much higher catalytic activity and selectivity to CO2 was achieved with chlorinated catalysts. This behavior has been correlated with a high platinum dispersion and a strong metal–CeO2 interaction in these catalysts which promotes their redox properties. Financial support from Generalitat Valenciana (Spain, PROMETEO/2009/002-FEDER and PROMETEOII/2014/004) is gratefully acknowledged.

Carbons were prepared from resins synthesised using the phenolic precursors phenol, para methylphenol, para ethylphenol, para n -propylphenol, para isopropylphenol and 3,5-dimethylphenol. Loss of phenolic OH from these materials was followed using solid-state nuclear magnetic resonance. The surface areas of the carbons were determined using N 2 and CO 2 adsorption. No significant differences in the loss of phenolic OH were observed. Under the same carbonisation conditions, the para alkyl phenols gave carbons with wide micropores, while the phenol and 3,5-dimethylphenol gave carbons with narrow micropores. Grinding the cured resins prior to carbonisation was found to significantly increase the surface area of the carbons obtained, with the microporous surface area increasing rapidly with a fall in particle size, without a significant increase in burn-off. Higher carbonisation temperatures widened the micropore size distribution, as shown by fitting the CO 2 adsorption isotherm with the Dubinin–Astakhov equation. The ability to change the carbon micropore structure obtained from a simple, well defined precursor, has many potential applications in carbon molecular sieves, catalyst supports and the investigation of adsorption processes.

The catalytic oxidation of Fe(II) species in aqueous solution by activated carbons with different degrees of surface oxidation is described. The parent activated carbon was oxidized with aqueous solutions of nitric acid or hydrogen peroxide, and submitted to thermal treatment at 373, 523 and 773 K. The activated carbons prepared were characterized by N2 adsorption and temperature-programmed desorption, and their catalytic behavior was determined by measuring the oxidation rate of Fe(II) to Fe(III) and the generation of hydrogen peroxide. Catalytic activity is a function of the nature of oxygen surface groups generated by oxidation.

This paper reviews the fundamentals and main applications of immersion calorimetry in the study of microporous adsorbents such as activated carbons, including carbon molecular sieves, and microporous zeolites. In the former case, it will be shown that immersion calorimetry into liquids of different molecular sizes easily allows for the assessment of the micropore size distribution. Furthermore, the use of liquids with different polarity permits the study of the evolution of the surface chemistry of these materials after different treatments. On the other hand, the study of zeolites with this technique is not as straightforward as in the case of carbonaceous materials, given the higher complexity of these systems. It will be shown that this technique can be used to analyze the evolution of the surface properties of zeolites A and X after thermal treatments at different temperatures and after ion-exchange.

Nonylphenol is a compound with estrogenic activity that is found in aquatic environments as a consequence of the biodegradation of nonylphenyl polyethoxylates discharged by many industries. The adsorption capacity for nonylphenol from aqueous solutions has been studied for four commercial microporous carbons. The texture and properties of the activated carbons were studied by means of N2 adsorption at 77 K and CO2 adsorption at 273 K, X-ray diffraction, immersion calorimetry and chemical analyses. Two-step isotherms have been determined for all carbons. The first isotherm plateau of the adsorbed nonylphenol is related to the mean pore width of the activated carbons. The second plateau seems to be related to the presence of inorganic impurities (carbonates and SiO2). Depending on the type of inorganic carbonate impurity, different behaviour was found for the nonylphenol adsorption. These differences are attributed to the type of inorganic components present in the carbon, as well as their particle sizes and locations in the porous framework. Finally, the introduction of acidic oxygen surface groups on the activated carbon surface enhances nonylphenol adsorption.

The effects of treatment of an activated carbon with Sulphur precursors on its textural properties and on the ability of the complex synthesized for mercury removal in aqueous solutions are studied. To this end, a commercial activated carbon has been modified by treatments with aqueous solutions of Na2S and H2SO4 at two temperatures (25 and 140 °C) to introduce sulphur species on its surface. The prepared adsorbents have been characterized by N2 (-196 °C) and CO2 (0 °C) adsorption, thermogravimetric analysis, temperature-programmed decomposition and X-ray photoelectron spectroscopy, and their adsorption capacities to remove Hg(II) ions in aqueous solutions have been determined. It has been shown that the impregnation treatments slightly modified the textural properties of the samples, with a small increase in the textural parameters (BET surface area and mesopore volumes). By contrast, surface oxygen content was increased when impregnation was carried out with Na2S, but it decreased when H2SO4 was used. However, the main effect of the impregnation treatments was the formation of surface sulphur complexes of thiol type, which was only achieved when the impregnation treatments were carried out at low temperature (25 °C). The presence of surface sulphur enhances the adsorption behaviour of these samples in the removal of Hg(II) cations in aqueous solutions at pH 2. In fact, complete Hg(II) removal is only obtained with the sulphur-containing activated carbons. The financial support by Generalitat Valenciana, Spain (PROMETEO/2009/002) is gratefully acknowledged.

This work presents the different effects of steam and carbon dioxide activation of a char in both the development of microporosity and the micropore size distribution using immersion microcalorimetry of liquids with different molecular size (benzene, 2,2 dimethylbutane, iso-octane and α-pinene). The study has been carried out with three series of carbons, two of them prepared by steam activation and the third one by carbon dioxide activation, covering a wide range of burn-off (8–70%). The experimental results show that carbon dioxide activation mainly causes the creation of microporosity. However, steam activation widens the microporosity as from the early stages of the activation process, the resulting activated carbons exhibiting a lower micropore volume. The different porous structures produced by both activating agents is related to the oxygen surface groups in the carbon, as measured by temperature programmed desorption (TPD). Activation by carbon dioxide creates not only a larger number of groups evolving as CO but also these groups are thermally more stable than those produced by steam activation.

Pt/activated carbon catalysts were prepared by using [Pt(NH3)4]Cl2 as the metal precursor, and characterized by a number of techniques. The selectivity of these catalysts towards crotyl alcohol in the gas-phase hydrogenation of crotonaldehyde was considerably increased when the activated carbon support was slightly oxidized before the metal incorporation.

The reforming of CH4 with CO2 over activated carbon- or silica-supported cobalt catalysts with and without added MgO as promoter has been studied over a range of temperatures (500–700°C). A significant effect of the MgO on catalyst efficiency was observed. The presence of MgO markedly reduces the carbon deposition on the surface of the catalyst and therefore, contributes to the stability of the catalyst. Based on temperature-programmed surface reaction experiments of chemisorbed CO2, the role of MgO may be ascribed to the formation of strongly adsorbed CO2 species over its surface. These CO2 species can easily react with the surface carbon deposits under CO2-reforming reaction conditions, preventing in this way catalyst deactivation.

Iron and molybdenum mono- and bimetallic catalysts supported on activated carbon have been prepared using iron pentacarbonyl and molybdenum hexacarbonyl as metal precursors. They have been characterized by temperature programmed reduction (TPR) and carbon monoxide chemisorption at 195 K and 298 K, and their catalytic activity for carbon monoxide hydrogenation at atmospheric pressure was studied under differential conditions, after reduction in hydrogen at several temperatures. Carbon monoxide chemisorption on the monometallic molybdenum catalyst was found to be strongly temperature dependent. On the other hand, the irreversible carbon monoxide chemisorption was largely decreased in the bimetallic catalyst in relation to the monometallic iron sample. The effect of molybdenum on the catalytic activity of FeMo/C is very important, producing an increase in catalytic activity which is very dependent on the reduction temperature. The selectivity of the monometallic iron catalyst is strongly modified by molybdenum addition, which produces a great increase in the yield to methane and a decrease in the alkenes to alkanes (C2 + C3) ratio.

Pt/activated carbon catalysts were prepared by using [Pt(NH3)4]Cl2 as the metal precursor, and characterized by a number of techniques. The selectivity of these catalysts towards crotyl alcohol in the gas-phase hydrogenation of crotonaldehyde was considerably increased when the activated carbon support was slightly oxidized before the metal incorporation.

6 pages, 6 figures, 1 table.-- Available online Oct 2, 2008., Activated carbon binderless monoliths with high consistency and large porosity, synthesised from a mesophase pitch, are studied as electrodes for supercapacitors. The electrochemical cells prepared provided high capacitance values in sulphuric acid media (334 F g−1) and very low electrical resistivity, which results in a very efficient energy storage device (12 Wh Kg−1 maximum energy density and 12,000 W Kg−1 maximum power density). Long-term cycling experiments showed excellent stability with a reduction of the initial capacitance values of 19% after performing 23,000 galvanostatic cycles at ~300 mA g−1., This work has been performed with financial support from MEC (projects MAT2007-61467 and MAT2007-61734). V. Ruiz acknowledges a predoctoral research grant from FICYT.

To study the effect of chromium addition to iron/active carbon catalysts in the carbon monoxide hydrogenation reaction at atmospheric pressure, five FeCr/C catalysts were prepared with a range of Cr/Fe atomic ratii. Three samples were prepared by coadsorption of the respective nitrates and the other two by successive adsorption. Catalysts were characterized by carbon monoxide chemisorption at 298 K and their catalytic activity was studied in differential conditions after reduction in hydrogen at 673 K. Both the irreversible carbon monoxide chemisorption and the catalytic activity of the samples decrease with increasing chromium content, this decrease being more important in the catalyst prepared by successive adsorption, with the chromium precursor added after adsorption of iron. Chromium favors methane production without modifying the selectivity towards alkenes. These results are interpreted on the basis of a diluent effect of chromium, which results in a decrease in the amount of surface-reduced iron sites.

5 pages, 4 figures, 1 table. -- Available online 27 June 2007., Various microporous carbon molecular sieves are studied as active electrode material for supercapacitors in order to clarify the controversy about the accessibility of the electrolyte to the micropores. Cyclic voltammetry experiments were performed in electrolytes with different ion size. The results showed a clear ion sieving effect when the porosity of the carbon was similar to that of the ions of the electrolyte. Impedance spectroscopy was also useful to evidence diffusion restrictions of the ions into the pores. The results obtained in this study clearly demonstrate that in aqueous media very narrow micropores (0.5 nm) are still capable of forming the electrical double layer. Therefore, the majority of microporous carbons, with wider porosity, are perfectly suitable as active electrode materials for supercapacitors when aqueous electrolytes are used., This work has been performed with financial support from MICYT (project MAT2004-03480-C02) and FICYT (project IB05-086-C1). V. Ruiz acknowledges a predoctoral research grant from FICYT.

The effect of the tin content and the reduction temperature on the ability of bimetallic platinum-tin catalysts supported on activated carbon cloth (ACC) to retain hydrogen after the reduction treatments has been analysed by temperature-programmed desorption of hydrogen (H2-TPD). A series of Sn/ACC samples with different tin contents has been prepared by impregnation of ACC with a solution of tin (II) oxalate in diluted HNO3 and subsequent heat-treatment at 623 K under flowing helium. Platinum (1 wt.%) was then introduced by impregnation of the Sn/ACC samples with aqueous solutions of H2PtCl6. Catalysts have been characterised by temperature-programmed reduction under diluted hydrogen and X-Ray Photoelectron Spectroscopy (XPS). The extent of hydrogen spillover from the metallic particles to the support has been determined by H2-TPD, the products being analysed by online mass spectrometry. The presence of tin oxide provides anchoring sites for hydrogen atoms spilt-over from platinum, although the ability of the latter to dissociate H2 molecules seems to be influenced by the presence of tin, both in an oxidised state after reduction at low temperature (523 K) and in the metallic state (possibility of alloy formation) after reduction at higher temperatures (623 and 723 K).

This chapter deals with the porous carbons in adsorption and catalysis. Carbonaceous materials with different structures, properties, and shapes are currently used in industry for a number of diverse applications such as adsorbents, catalysts and catalyst supports, structural materials, and electrical devices. The main application of activated carbon is the removal of impurities from gases and liquids. It is used in the form of carbonized wood. Porous carbons constitute a fascinating group of materials. Different types and physical forms find a wide range of industrial applications in adsorption and catalysis. The chapter describes the surface chemistry characteristics. Both types of parameters can be easily tailored to fulfill the requirements of a given application, and thus porous carbons can be used for the removal of pollutants, as well as to separate gas mixtures and for gas storage. On the other hand, the use of porous carbons in catalytic processes depends, besides the same factors as for adsorption, on the relative inertness of their surface.