Energy storage in residential and commercial buildings via Liquid Organic Hydrogen Carriers (LOHC)

This contribution proposes the usage of Liquid Organic Hydrogen Carriers (LOHC) for the establishment of a decentralised energy storage network. Due to the continually increasing amount of renewable energy within the power grid, in particular in countries of the European Union, a huge demand for storage capacities develops that can hardly be met by large-scale systems alone. Because of their high storage density and good manageability LOHC substances permit the local storage of excess energy in residential and commercial buildings. Following the approach of a CHP system ('combined heat and power' or more precisely a `combined heat and storage' system), thermal losses from the storage processes can be used for heating (and cooling) purposes in order to increase the overall efficiency. An evaluation of the economic feasibility identifies possible approaches to generate income from storage operation. The usage of exhaust heat for heating proves to significantly support the business case by providing a considerable financial contribution that is usually not exploitable for centralised storage units

Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m2/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process

On the recyclability of liquid organic hydrides: hydrogenation of 9-ethylcarbazole and other heterocyclic compounds for application in hydrogen storage

The main focus of the present work is the recovery process for spent fuels based on catalytic hydrogenation of liquid organic hydrides (LOH). To gain the knowledge about the possible hurdles of hydrogen loading process, the hydrogenation of 9-ethylcarbazole as a model compound was elected to be studied in more detail. The structures of the intermediates and products of this reaction were characterized for the first time using combined GC-MS and NMR analysis with reference to DFT calculations. The fully saturated product was found to be a mixture of stereoisomers. A reaction model was developed which agreed well with the experimental results. The combined theoretical and experimental approaches were also undertaken to identify catalytic sites on the metal surface and their role in the hydrogenation of 9-ethylcarbazole. Kinetically stable intermediate (Plus 8 [H]) containing a central unsaturated “pyrrole” ring was found to be accumulated in the solution over a ruthenium black catalyst. Its further hydrogenation was found to involve its unusual shuttling from terraced sites to higher indexed sites. The stability of Plus 8 [H] was found to be influenced by the type of active sites present on the surface of the catalyst, as well as by the electronic structure of the metal. In addition, the kinetics of the hydrogenation was analyzed experimentally and the activation energies were obtained for all of the intermediate steps. Further understanding of how the molecules interact with the catalyst surface was provided by examining the hydrogenation activity and selectivity of a series of LOH. The general factors involved in LOH structure- catalyst –activity trend were outlined. Overall, due to a number of defined challenges in the LOH spent fuel recharging, it is believed that this complex H2 storage strategy is not likely to meet the targets for wide scale applications

Structure-reactivity relationship in catalytic hydrogenation of heterocyclic compounds over ruthenium black; Part B: Effect of carbon substitution by heteroatom

The effect of the type of heteroatom in the structure on the recyclability of possible candidate compounds for application as LOC (liquid organic carriers) was studied by comparing the rate and selectivity obtained in hydrogenation of carbazole, dibenzothiophene, dibenzofuran and fluorene. The effect of a partial saturation of the compound on its hydrogenation yield and reaction pathway was also considered by studying hydrogenation of 1,2,3,4-tetrahydrocarbazole. Using Ru black catalyst, the rate of hydrogenation was found to decrease in order; dibenzofuran. >. 1,2,3,4-tetrahydrocarbazole. >. carbazole. >>. fluorene. No reaction was observed in the hydrogenation of dibenzothiophene under the conditions studied which was attributed to the immediate poisoning of ruthenium metal by sulphur compounds. The rate of hydrogenation of fluorene was around 3 times lower as compared to carbazole and over 8 times lower as compared to that of dibenzofuran under the same reaction conditions. With the exeption of S containing dibenzothiophene, the presence of the heteroatom in the structure was found to be beneficial in terms of increasing the rate of hydrogen loading step. Additionally, a higher reaction rate was obtained in the hydrogenation of the partially saturated 1,2,3,4-tetrahydrocarbazole as compared to the substrate carbazole. The structure and stability of intermediates was found to be significantly influenced by the type and presence of a heteroatom in the structure. A stable octahydro-intermediate was observed only with N-heterocycles, whereas a stable hexahydro-intermediate was produced in the polyaromatic hydrocarbon-fluorene. Additionally, the theoretically obtained lowest total enthalpies using DFT calculations agreed well with the stable intermediates observed experimentally in the hydrogenation of fluorene. Theoretical DFT differences in enthalpies also indicated the products of hydrogenolysis of perhydro-dibenzofuran to be the most favourable products of its hydrogenation, which agreed well with the experimental observations. Overall, taking into account the recyclability of LOC, substitution of carbon with a N heteroatom was demonstrated to be one of the promising approaches to improve the kinetics of the hydrogen loading step

RuSe Electrocatalysts and Single Wall Carbon Nanohorns Supports for the Oxygen Reduction Reaction

Selenium modified ruthenium electrocatalysts supported on carbon black were synthesized using NaBH4 reduction of the metal precursor. Prepared Ru/C electrocatalysts showed high dispersion and very small averaged particle size. These Ru/C electrocatalysts were subsequently modified with Se following two procedures: (a) preformed Ru/carbon catalyst was mixed with SeO2 in xylene and reduced in H2 and (b) Ru metal precursor was mixed with SeO2 followed by reduction with NaBH4. The XRD patterns indicate that a pyrite-type structure was obtained at higher annealing temperatures, regardless of the Ru:Se molar ratio used in the preparation step. A pyrite-type structure also emerged in samples that were not calcined; however, in this case, the pyrite-type structure was only prominent for samples with higher Ru:Se ratios. The characterization of the RuSe/C electrocatalysts suggested that the Se in noncalcined samples was present mainly as an amorphous skin. Preliminary study of activity toward oxygen reduction reaction (ORR) using electrocatalysts with a Ru:Se ratio of 1:0.7 indicated that annealing after modification with Se had a detrimental effect on their activity. This result could be related to the increased particle size of crystalline RuSe2 in heat-treated samples. Higher activity of not annealed RuSe/C catalysts could also be a result of the structure containing amorphous Se skin on the Ru crystal. The electrode obtained using not calcined RuSe showed a very promising performance with a slightly lower activity and higher overpotential in comparison with a commercial Pt/C electrode. Single wall carbon nanohorns (SWNH) were considered for application as ORR electrocatalysts' supports. The characterization of SWNH was carried out regarding their tolerance toward strong catalyzed corrosion conditions. Tests indicated that SWNH have a three times higher electrochemical surface area (ESA) loss than carbon black or Pt commercial electrodes

Analysis of Styrene-Butadiene Based Thermoplastic Magnetorheological Elastomers with Surface-Treated Iron Particles

Magnetorheological elastomers (MRE) are increasing in popularity in many applications because of their ability to change stiffness by applying a magnetic field. Instead of liquid-based 1 K and 2 K silicone, thermoplastic elastomers (TPE), based on styrene-butadiene-styrene block copolymers, have been investigated as matrix material. Three different carbonyl iron particles (CIPs) with different surface treatments were used as magneto active filler material. For the sample fabrication, the thermoplastic pressing method was used, and the MR effect under static and dynamic load was investigated. We show that for filler contents above 40 vol.-%, the linear relationship between powder content and the magnetorheological effect is no longer valid. We showed how the SiO2 and phosphate coating of the CIPs affects the saturation magnetization and the shear modulus of MRE composites. A combined silica phosphate coating resulted in a higher shear modulus, and therefore, the MR effect decreased, while coating with SiO2 only improved the MR effect. The highest performance was achieved at low deformations; a static MR effect of 73% and a dynamic MR effect of 126% were recorded. It was also shown that a lower melting viscosity of the TPE matrix helps to increase the static MR effect of anisotropic MREs, while low shear modulus is crucial for achieving high dynamic MR. The knowledge from TPE-based magnetic composites will open up new opportunities for processing such as injection molding, extrusion, and fused deposition modeling (FDM)

Comparison of catalytic performance of supported ruthenium and rhodium for hydrogenation of 9-ethylcarbazole for hydrogen storage applications

The stepwise hydrogenation of 9-ethylcarbazole to 9-ethyl-perhydrocarbazole (Pl 12[H]) via partially hydrogenated intermediate(s) was studied over a number of supported ruthenium and rhodium catalysts. The reaction pathways were modelled and the rate constants for individual hydrogenation steps were compared. It was found that the selectivities to the reaction intermediates and products were highly dependent on the electronic structure of the particular metal and the nature of the support used. Ruthenium was found to be the most active metal for this reaction but it suffered from a poor selectivity to the desired product due to the formation of a kinetically stable intermediate, 9-ethyl-octahydrocarbazole (Pl 8[H]) in short reaction time. On the other hand, rhodium catalysts with moderate activity gave a higher selectivity to the fully hydrogenated product under comparable conditions. It was also found that the presence of a hydrophilic support such as alumina or rutile can give kinetically favoured cis-isomers of the 9-ethyl-perhydrocarbazole. Regarding application of the reversible hydrogen storage concept, the storage material should be able to switch between fully hydrogen loaded and unloaded forms during hydrogenation (material regeneration) and dehydrogenation (delivery of hydrogen gas) in short times. Formation of any stable intermediates and stereo-non-favoured isomers with a particular type of catalyst can result in significant implications to the overall storage capacity as well as operation times for hydrogen gas delivery and regeneration. Thus, this study yields valuable information on the suitability of various metal catalysts for use in hydrogen storage systems based on the liquid organic hydride (LOH) concept. © 2012 The Royal Society of Chemistry