Papers by Keyword: Dehydrogenation

Abstract: In this work, in-situ TiC reinforced Ti matrix composites (TMCs) have been fabricated via blending TiH₂ powder and multi-walled carbon nanotubes (CNTs) followed by thermomechanical consolidation of the TiH₂/CNTs powder mixture. The dehydrogenation, in situ reaction and consolidation occurred simultaneously and took less than 15 minutes in total. The effect of CNTs content (1 and 3 vol.% (0.56 and 1.69 wt.%)) on the evolution of microstructures and mechanical performances of the extruded samples has been investigated. The results showed that the extruded TMCs had a duplex microstructure consisting of coarse alpha titanium grains and ultrafine grained (UFG) regions, and the in-situ formed TiC particles had a near-spherical shape. The extruded sample with 1 vol.% (0.56 wt.%) CNTs reinforced exhibited a yield strength of 807.3 MPa, ultimate tensile strength of 1085.9 MPa and elongation to fracture of 3.3% at room temperature. The mechanism of microstructural evolution and material failure are discussed.e are discussed.

Abstract: In the paper we study a method of increasing the yield of dehydrogenation products of methylbutenes by virtue of intermediate removal of the hydrogen formed during the dehydrogenation and partial compensation of heat losses. In the example of dehydrogenation of methylbutenes into the isoprene, the oxidation of hydrogen on the platinum catalyst [charged inside the layer of ferric potassium catalyst] for the dehydrogenation of olefins is considered.

Abstract: Ammonia borane (NH3BH3, AB) is an excellent source of hydrogen(19.6 wt %) for fuel cell applications. In this paper, pure ammonia borane is successfully prepared by using amino complex for ammonia complex Ag(NH3)2Cl as new ammonia source, and sodium borohydride (NaBH4) as boron source. The composition and constitution of the products are measured by XRD and FT-IR. The thermolysis of ammonia borane is significant for its practical application. Boric acid plays a role in improving ammonia borane hydrogen performance. The effects of different mass ratio of boric acid and ammonia borane on dehydrogenation are tested by XRD, TG/DTA and TPD-MS. The results show that boric acid can decrease the first level dehydrogenation temperature of ammonia borane decrease to about 85°C (working temperature of PEMFC). What’s more, the onset temperature of AB’s thermolysis can decrease to about 60°C when the mass ratio of ammonia borane and boric acid is equal to 3:1. This makes ammonia borane be more suitable for the application in on-board hydrogen storage system.

Abstract: The paper shows the effect of butylenes concentration in feedstock on the process of dehydrogenation of butane into butylenes using chromia-alumina-potassium catalyst. Butylenes as contained 1 to 7 % wt. in butane slip completely without hindering the process of converting of butane.

Abstract: Cyclohexane dehydrogenation is an important process in the petrochemical industry, chemical raw material such as cyclohexanol, cyclohexanone,benzene and cyclohexene can be produced from which.Divided cyclohexane dehydrogenation into catalytic dehydrogenation or oxidative dehydrogenation, homogeneous or heterogeneous reaction. Summarized vary catalysts, active constituent and process conditions in dehydrogenation process.

Abstract: A series of varying Cu/Zn ratio Cu-ZnO catalysts prepared by coprecipitation were evaluated for the vapor-phase dehydrogenation of sec-butanol (SBA) to methyl ethyl ketone (MEK) and characterized to investigate the roles of ZnO by X-ray diffraction (XRD), H₂ temperature programmed reduction (H₂-TPR), N₂O chemisorption decomposition. When Cu/Zn was 1:1, Cu-ZnO catalyst exhibited excellent reactivity. The catalytic properties of Cu-ZnO did not completely depend on Cu content and Cu⁰ surface area, revealing SBA dehydrogenation is a structure-sensitive reaction.

Abstract: The Ni-Pt bimetallic catalyst supported on nanofilm alumina was prepared by coprecipitation method under the assistance of ultrasonic vibration. The characterization result revealed that the prepared catalyst had a good dispersion with an average particle size around 7nm. The activities of supported catalyst of Ni, Pt and Ni-Pt were compared through using the dehydrogenation of methylcyclohexane (MCH) to produce toluene in Microreactor-Gas Chromatography System (MGCS). The conversion and the selectivity of the Ni-Pt catalyst at 350°C for the dehydrogenation of MCH was 97.0% and 100%, respectively. It was found that the bimetallic synergistic effect between Ni and Pt particles would affect the catalyst performance. The addition of Ni into Pt/γ-Al₂O₃ catalyst was beneficial to decrease the use of Pt in the dehydrogenation.

Abstract: The main results of thermodynamic analysis and mathematical simulation of the deactivation of a platinum dehydrogenation catalyst by coke-generating compounds are presented. Developed model allows calculating the optimal flow rate of water fed to the reactor to maintain the conditions of thermodynamic equilibrium of the coke formation reaction and oxidation of intermediate condensation products with water. A comparative evaluation of different raw cycles of platinum-dehydrogenation catalysts is presented and shown to cause reduced production of the desired product was the change the composition of the feedstock.

Abstract: In this study, 9 wt% V and 1 wt% Al were co-milled with MgH₂ at different milling times to produce nanostructured composite powders. The effect of milling time and additives on the hydrogen desorption properties of obtained powders was evaluated by thermal analyzer method and compared with pure MgH₂. The phase constituents and grain size of powders were characterized by X-ray diffractometry method. As the milling time was increased, both the grain size and hydrogen desorption temperature were decreased. An improved dehydrogenation temperature was achieved by alloying of MgH₂ with V and Al. The effect of the V and Al addition on improvement of the dehydrogenation properties was discussed.

Abstract: Sodium borohydride (NaBH₄) is considered to be a secure metal hydride for hydrogen storage and supply. In this study, the two-phase pressure drop in the dehydrogenation of aqueous NaBH₄ solution in a microchannel with a hydraulic diameter of 300 μm is investigated for the purpose of designing a dehydrogenation chemical reactor. Because hydrogen gas was generated by the hydrolysis of NaBH₄ in the presence of a ruthenium catalyst, two different phases of flow (aqueous NaBH₄ solution and hydrogen gas) exist in the microchannel reactor. For experimental studies, a microchannel was fabricated on a silicon wafer substrate with a 100 nm ruthenium catalyst deposited on three sides of the channel surface. Based on the experimental result, it is found that the two-phase multiplier linearly increases with the void fraction, which depends on the initial NaBH₄ concentration, the NaBH₄ reaction rate, and the flow residential time.