M. Mercedes Maroto-Valer

Solid state13C NMR investigation of lipid ligands in V-amylose inclusion complexes

The characteristics of the ligands in inclusion complexes formed from stearic, palmitic, oleic, linoleic, linolenic and docosahexaenoic acids, glycerol monooleate (GMO), glycerol monopalmitate (GMP) and lysophosphatidylcholine (LPC) have been studied by13C NMR in dry and hydrated forms of the complexes, with13C labels being used for the car☐yl and C-1(3) glycerol carbons in stearic acid and GMO, respectively.13C NMR provides definitive proof that V-amylose inclusion complexes have been formed with the mono-car☐ylic fatty acids of varying degrees of unsaturation, GMO, GMP and LPC. The chemical shift of the mid-chain methylenes in stearic acid moves about 1.5 ppm upfield upon complexation with the1H rotating frame relaxation times becoming identical for the lipid and amylose. With the exception of docosahexaenoic acid, the mid-chain methylenes inside the V-helical segments have essentially the same chemical shift for all the other unsaturated fatty acids and lipids investigated. The cross-polarisation dynamics for the car☐yl and glycerol groups in stearic acid and GMO, respectively, have indicated that these bulky polar groups occupy highly mobile conformations in the hydrated complexes which must lie outside the V-helical segments adjacent to the amorphous domains.

Photocatalytic CO2 reduction using an internally illuminated monolith photoreactor

One of the promising solutions to both global climate warming and increasing energy demands is artificial photosynthesis, which can be implemented via the photoreduction of CO2 to produce fuel. A monolith photoreactor was used to increase the amount of catalyst loading due to its multiple channels. The photocatalyst was dip coated using NiO/InTaO4 sol and then calcined at 1100 °C. A uniform NiO/InTaO4 layer was obtained on the top of pre-coated SiO2 sublayer on the internal channels of the monolith. The polymethylmethacrylate (PMMA) optical fibers, after being carved on their surface, could transmit and scatter light to effectively illuminate the catalyst inside the channels of the monolith. Vapor-phase CO2 with H2O was photocatalytically reduced to hydrocarbons by UV or visible-light in a steady-state flow mode. The maximum methanol conversion rate achieved was 0.16 µmol g−1 h−1 with visible-light of 290 klx at 25 °C. The highest rate of acetaldehyde was 0.3 µmol g−1 h−1 which was obtained with a loading of 2.6% NiO by simulated sunlight AM1.5G at 70 °C. More importantly, the quantum efficiency was significantly improved indicating that photon energy was effectively utilized in the monolith reactor, compared with previous optical-fiber reactor.

Integration of CO2 Capture and Mineral Carbonation by Using Recyclable Ammonium Salts

A new approach to capture and store CO2 by mineral carbonation using recyclable ammonium salts was studied. This process integrates CO2 capture with mineral carbonation by employing NH3, NH4HSO4, and NH4HCO3 in the capture, mineral dissolution, and carbonation steps, respectively. NH4HSO4 and NH3 can then be regenerated by thermal decomposition of (NH4)2SO4. The use of NH4HCO3 as the source of CO2 can avoid desorption and compression of CO2. The mass ratio of Mg/NH4HCO3/NH3 is the key factor controlling carbonation and the optimum ratio of 1:4:2 gives a conversion of Mg ions to hydromagnesite of 95.5 %. Thermogravimetric analysis studies indicated that the regeneration efficiency of NH4HSO4 and NH3 in this process is 95 %. The mass balance of the process shows that about 2.63 tonnes of serpentine, 0.12 tonnes of NH4HSO4, 7.48 tonnes of NH4HCO3, and 0.04 tonnes of NH3 are required to sequester 1 tonne of CO2 as hydromagnesite.

Post-processing pathways in carbon capture and storage by mineral carbonation (CCSM) towards the introduction of carbon neutral materials

Carbon dioxide capture and storage by mineral carbonation (CCSM) is a technology that can potentially sequester billions of tonnes of carbon dioxide (CO2) per year. Despite this large potential, the costs of CCSM are currently too high for a large deployment of the technology and new systems are being investigated to attempt to overcome these limitations. To improve this situation, the successful development of post-processing routes creating marketable carbon neutral products could help the deployment of mineral carbonation. This work investigates the current market for CCSM products and the role they can play in decreasing the overall cost of CCSM technology. The current global market for the raw commodities, primarily cement additives, fillers and iron ore feedstock which could be produced by rock and/or industrial waste/by-product mineralisation, is about 27.5 Gt and can be easily flooded assuming 10% of the global CO2 emissions sequestered by CCSM. The CCSM technology chosen will play a very important role in the products created, available post-processing routes and accessible markets if the resultant materials are of high purity. Low-value applications such as fill for land reclamation may represent the only viable opportunity at the current state of the technology, bearing in mind that these materials are competing with low-cost materials (i.e. crushed rock) and that the size distribution of the carbonated materials may need significant alteration to make them potentially useful. However, there is a lack of information available on the quality of the CCSM products towards access to high-value markets such as micro-silica and PCC. In summary, CCSM post-processing might be viable only in niche high-value markets, while low-value applications such as land/mine reclamation are potentially more feasible and could be able to absorb Gts of CCSM products.

Mercury policy and regulations for coal-fired power plants

IntroductionMercury is a high-priority regulatory concern because of its persistence and bioaccumulation in the environment and evidence of its having serious adverse effects on the neurological development of children.DiscussionMercury is released into the atmosphere from both natural and anthropogenic sources. Coal-fired utilities are considered to be one of the largest anthropogenic mercury emission sources. The period since the late 1990s has been marked by increasing concern over mercury emissions from combustion systems to the extent that a number of national governments have either already implemented or are in the process of implementing, legislation aimed at enforcing tighter control over mercury emissions and a reduction in mercury consumption.ConclusionThis review examines the most important national and international policies and agreements for controlling mercury emissions from coal-fired combustion systems. To provide a global perspective, this study lists the countries with the largest estimated mercury emissions and regulatory efforts to reduce them.

Quantitative solid-state 13C n.m.r. measurements on cokes, chars and coal tar pitch fractions

Bloch decay or single pulse excitation (SPE) 13C n.m.r., generally recognized as the best approach to obtain quantitatively reliable aromaticity values and other skeletal parameters for coals, was applied to partly carbonized coal samples, a biomass char and the toluene-insolubles from a coal tar and a corresponding pitch. As found previously for coals, the aromaticities and non-protonated carbon concentrations were generally higher than those estimated by cross-polarization (CP). Furthermore, in terms of accumulation times, the shorter 13C T1s of low-temperature chars makes SPE a more efficient technique than for coals. The higher concentrations of paramagnetic centres responsible for the shorter 13C T1s still result in observability of 75% of the carbon in the chars by the SPE technique. The HC ratios derived from the SPE measurements agree well with those obtained from elemental analysis.

Quantitative 13C NMR study of structural variations within the vitrinite and inertinite maceral groups for a semifusinite-rich bituminous coal

Abstract To determine the structural variation within vitrinite and inertinite maceral groups, fractions with purities over 90% in vitrinite and semifusinite were obtained by density gradient centrifugation from a medium volatile Australian bituminous coal and the bulk structural compositions of the maceral concentrates were determined by the quantitatively reliable single pulse excitation (SPE) solid state 13C NMR technique. As previously reported for coals and chars, the aromaticities determined by cross polarisation are often lower than those by SPE, due to the unfavourable spin dynamics. As expected, the aromaticities of the vitrinite fractions are significantly lower than those of the semifusinite ones, but the aromaticity, the fraction of non-protonated aromatic carbon and the number of rings per cluster all increase with density within both the maceral groups. The vitrinite and semifusinite fractions contain 3–6 and 9 to over 15 aromatic rings, respectively. Methyl groups account for greater proportions of the aliphatic carbon with increasing density. These structural trends are consistent with the variations evident in random reflectance.

Study of mercury in by-products from a Dutch co-combustion power station.

Fly ashes and gypsum are one of the main wastes produced in coal-fired power stations which may be sent to landfills for their disposal. In this work, leaching and speciation of mercury in fly ashes and gypsum from a modern co-combustion power plant equipped with a selective catalytic reduction (SCR) unit in the Netherlands were studied. The mercury leachable contents were checked against different regulations, including Dutch, German and the Council Directive 2003/33/EC. The speciation of mercury in coal combustion products is essential not only to determine the risk when the wastes are finally disposed but also to understand the behaviour of mercury during combustion and therefore to select the appropriate mercury removal technology. A temperature-programmed decomposition technique was used in order to identify and quantify which mercury species are associated with coal combustion products. The main mercury species identified in fly ash samples was mercury sulphate, whereas in the gypsum sample the mercury present was mercury chloride. The quantitative mercury results carried out using the thermal desorption method may be considered accurate. The results obtained show that fly ash and gypsum samples from this power plant can be acceptable at landfills as a non-hazardous waste.

Relationship between carbon aromaticities and HC ratios for bituminous coals

Carbon aromaticities for a selection of 19 bituminous coals and vitrinite concentrates have been obtained by solid-state 13C n.m.r. using the inherently quantitative single pulse excitation technique. Within experimental error, the aromaticity values in the range 0.75–0.90 correlate extremely well with the HC ratios (A2 = 0.93); the 11 samples investigated with HC ratios between 0.74 and 0.77 all have aromaticities in the range 0.75–0.81. Furthermore, the correlation holds for the coals investigated with high inertinite contents.

Copper based TiO2 honeycomb monoliths for CO2 photoreduction

The direct photoreduction of CO2via catalytic conversion of copper supported on TiO2 based monolithic structures is a means by which solar fuels can be produced. Copper based monolithic structures with varying loadings were synthesized through a sol–gel dip coating procedure and tested for CO2 reduction with H2O as a reductant in the gaseous phase. Results established that increased copper concentration can decrease crystalline size and promote anatase to rutile phase transformation. The coated monolithic structures were dominated by mainly Cu1+ species, as confirmed by XPS while bulk characterization suggests that these species are present in the crystal lattice via substitution of Ti4+ ions with Cu1+ ions. The catalytic performance of the Cu doped TiO2 monoliths for hydrocarbon formation was found to be considerably higher when compared to pure TiO2 under UVA or visible light irradiation.