Amino-acids in humic,nitrohumic and nitrofuvic acids from coal

The humic acids, HA, extracted from a Spanish lignite and the nitrohumic acids, NHA, and nitrofulvic acids, NFA, extracted from the same lignite after its nitration, are hydrolysed with 6N HCI under reflux. The α-amino acids present in the hydrolysates are determined and thirteen α-amino acids are identified. The amounts of nitrogen in the amino-acids released by the hydrolysis increase according to the sequence: NFA > NHA > HA.     

NH3-SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths: Effect of H2O and SO2 traces in the gas feed

The objective of this research is to asses the impact of the addition of H₂O, SO₂, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N₂ in the low temperature range, i.e. 473–500 K, when either H₂O or SO₂ is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H₂O and SO₂ are added simultaneously because H₂O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components.     

Influence of support’s oxygen functionalization on the activity of Pt/carbon xerogels catalysts for methanol electro-oxidation

Highly mesoporous carbon xerogels (CXs) were synthesized using two different resorcinol to catalyst, R/C, molar ratios and functionalized with different oxidation treatments. The synthesized carbon materials were used as supports for Pt particles, deposited by impregnation and reduction in formic acid. Both carbon supports and the catalysts prepared were characterized by means of N₂ physisorption, scanning and transmission electron microscopy, temperature programmed desorption and X-ray diffraction. The electrochemical activity of the catalysts towards the oxidation of carbon monoxide and methanol was assayed by means of cyclic voltammetry and chronoamperometry. Textural characterization of the materials prepared evidenced more developed and mesopore-enriched porous structure for the carbon xerogel prepared using the highest R/C molar ratio. Enhanced textural properties of this material led to the preparation of highly active Pt-catalysts, which showed increased tolerance to CO and higher activity in methanol electro-oxidation, in comparison to Pt-E-TEK and the catalysts prepared in an analogous way using Vulcan XC-72R carbon black as support. Functionalization treatments resulted in enhanced dispersion, lower Pt crystal size and improved catalytic performance in the case of the catalysts prepared using the carbon xerogel possessing a less developed porous structure. Pt agglomeration was found to strongly determine the activity of the catalysts prepared. At high potentials, i.e. 1 V vs. RHE, the catalyst prepared using the carbon xerogel submitted to the most stringent oxidation treatment showed the highest specific peak activity towards methanol electro-oxidation, probably due to the positive influence of the presence of oxygen surface groups in Pt-carbon interaction, in spite of the higher agglomeration extent confirmed by TEM. On the other hand, at 0.60 V vs. RHE, highest activity towards methanol electro-oxidation was determined for the catalysts prepared using the non-functionalized carbon xerogel which can be explained in terms of enhanced reactant/product diffusion together with intrinsic higher catalytic activity due to lower Pt crystal size. In any case, the activity of this catalyst prepared using a carbon xerogel as support was found to be more than 2 times higher than the one determined for Pt/E-TEK, confirming the considerable improvement of the electrocatalytic system by means of optimization of the carbon support employed.     

Carbon based catalytic briquettes for the reduction of NO: Catalyst scale-up

Exhaust gasses from small and medium stationary sources contain NO_x that will be regulated by new European legislation in the coming years. Among all the processes the SCR-NH₃ seems to be the more promising one. However, the application of commercial catalysts to these new facilities presents some drawbacks such as the high and narrow operation temperature, its low withdraw to SO₂ or its high cost production.In order to improve this technology, in previous works, carbon-supported catalytic briquettes have shown a good kinetic performance under the above commented conditions. In this study, other aspects such as thermal stability, long-term performance, spatial velocity influence and mechanical resistance were evaluated. Finally, a simple economic assessment was carried out providing a three times lower cost production than commercial catalysts. From all the data collected, there are some evidences that these catalyst briquettes will have a good performance in small and medium facilities, being an interesting alternative to commercial ones.     

Carbon supports for the catalytic dehydrogenation of liquid organic hydrides as hydrogen storage and delivery system

The use of liquid organic hydrides as hydrogen carriers is a promising storage and delivery system due to the advantages of using liquid-based infrastructures and its economic feasibility compared to other conventional systems. The reversible dehydrogenation/hydrogenation of liquid organic hydrides is a key point for the development of highly performance reactors. In this study different carbon materials have been investigated as platinum supports, including carbon nanofibers, carbon black, carbon xerogel, activated carbon and ordered mesoporous carbon. To individuate the effect of the carbon support on the catalytic activity, platinum particles were synthesized by a microemulsion procedure. The analysis of the hydrogen evolution curves indicate that the support BET surface area plays a very important role on the initial catalytic activity, obtaining a maximum rate of 220 mmol g_Pt⁻¹ min⁻¹ when using an ordered mesoporous carbon with a surface area of 930 m² g⁻¹. Nevertheless, the analysis of catalytic activity at prolonged duration indicates a better behavior toward deactivation for supports characterized by wide pores and low graphitization degree like carbon black or carbon xerogel, despite their lower initial dehydrogenation rate (100–140 mmol g_Pt⁻¹ min⁻¹). The ultimate use in the dehydrogenation reactor as well as the operation conditions will define the best catalyst structure from the point of view of the carbon support.     

Catalytic decomposition of methane for the simultaneous co-production of CO2-free hydrogen and carbon nanofibre based polymers

Through the catalytic decomposition of methane (CDM) it is possible to obtain in a single step both CO₂-free hydrogen and carbon nanostructures with a wide range of applications such as nanocomposite reinforcements. In this work, a Ni-based catalyst has been used to carry out the catalytic decomposition, obtaining an hydrogen concentration up to 47% (vol.) in the flue gas and carbon nanofibres (CNF). These structures have been inserted into two epoxy resins with different viscosity in order to study the influence of the CNF load in the electrical resistivity of the new materials prepared. As a result, the resistivity of these materials decreases up to 10⁶ Ω cm, values which avoid the electrostatic discharge and allow the electrostatic painting.     

Relationships Between Organizational Justice and Burnout at the Work-Unit Level.

Relationships between organizational justice and well-being are traditionally investigated at the individual level. This article extends previous efforts by testing such relationships at the work-unit level. Three corridors of influence were examined. First, the level (work units' average scores) of justice is related to the level of burnout. Second, justice climate strength (level of agreement among work-unit members) moderates the predictability of the level of burnout. Third, justice strength is related to burnout strength. The authors interviewed 324 contact employees from 108 work units in 59 service organizations. Findings showed the predominance of interactional justice over distributive and procedural justice in all 3 corridors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gel permeation chromatography applied to the study of the nitrohumic acids from coal

Gel permeation chromatography on Sephadex (G-types) was applied to nitrohumic acids (NHA) from lignites. Deionized water and TRIS (Tris-hydroxymethylaminomethane) buffer were tested as eluents. Deionized water provided the same number of fractions and better resolution than TRIS. In both cases, interactions between the gel matrix and the NHA occurred. Five NHA fractions were obtained and characterized by elemental and spectral analysis, which showed significant differences between them. Molecular weights of the fractions, calculated from Cameron's calibration for soil humic acids, are < 9000 or > 100 000 with no significant fractions having molecular weights in the range 9000–100 000.     

Copper removal from effluents using a sulphonated lignite Bath and fixed-bed studies

Copper(ll) retention by a sulphonated lignite has been studied under equilibrium (adsorption isotherms) and dynamic (fixed-bed) conditions. Adsorption isotherms were fitted to the Langmuir equation from which saturation capacity and distribution coefficient for the sulpholignite were calculated. Breakthrough curves were determined and the overall mass transfer coefficients and exchange zone height were calculated from them. A model for the exchange mechanism is proposed.