Search results for "Exothermic reaction"

Mechanisms of covalent dimerization on a bulk insulating surface

2017

Combining density functional theory and high resolution NC-AFM experiments, we have studied the on surface reaction mechanisms' responsible for the covalent dimerization of 4-iodobenzoic acid (IBA) organic molecules on the calcite (10.4), insulating surface. When annealed at 580 K, the Molecules assemble in one-dimensional chains of covalently bound dimers: The chains have a unique orientation and result from a complex set of processes, including a nominally rather. costly double dehalogenation reaction followed by dimerization. First, focusing on the latter two processes and using the nudged elastic band method, we analyze a number of possible mechanisms involving one and two molecules, an…

Microflow Technology in Polymer Synthesis

2012

Microflow technology, i.e., the use of microfluidic devices for continuous flow synthesis, represents a highly useful and increasingly popular method in organic chemistry. Recently, also an increasing number of polymer synthesis protocols attain benefit from this technique. In particular, the control of highly exothermic, fast polymerization reactions can be improved due to the excellent heat and mass transfer within the small dimensions of the microreactors. Continuous flow setups with different micromixer geometries and flow patterns are currently used for the preparation of a variety of macromolecular architectures by ionic and (controlled) radical polymerization techniques. This Perspec…

Heat and Helium Production during Exothermic Reactions between Gases through Palladium Geometrical Elements Loaded with Hydrogen

2000

In this research, the effect of the shape of hydrogen-loaded palladium elements on exothermic reactions between gases is shown. It was found that an element with parts of its surface next to each o...

Study of the MAu6(M = Cr, Mo, W) molecular species: A transition from halogenlike to hydrogenlike chemical behavior for gold

2004

Quantum chemical calculations suggest that a series of molecules with the general formula MAu6 are stable, where M is a a group 6 atom, Cr, Mo, W, respectively. These species have a structure analogous to the corresponding MH6 compounds, while they differ from the MX6, where X is a halogen. The further reaction MAu6 + 3Au2 → MAu12 is strongly exothermic.

Synthesis of Hyperbranched Polyglycerol in a Continuous Flow Microreactor

2007

Hyperbranched polymers have been synthesized in a microreactor for the first time, employing the known ring-opening multibranching polymerization of glycidol. Microreactors are well-known to be beneficial for highly exothermic reactions because of their capability to enhance mass and heat transfer due to short diffusion pathways and large interfacial areas per volume. The characteristics of the microstructured reaction system were utilized to engineer a continuous flow process for the preparation of well-defined hyperbranched polyglycerols with molecular weights up to 1,000 g/mol. Increased flow rates, as well as the use of highly polar solvents, led to the partial formation of very narrowl…

1984

Provided a polymer is soluble, i. e., molecularly dispersed in another polymer irrespective of the molecular weight of the components, the solution is exothermic. By increasing the temperature two effects, both unfavourable to mixing become larger: (i) the excess entropy of mixing caused by contact interaction and (ii) the total effect from the difference of the free volumes of the pure components. So, an upper miscibility gap occurs. The thermodynamic properties of the mixture cannot be derived from the properties of the pure components. They can be described by the corresponding states theory of Prigogine, Flory, and Patterson with suitable values for the contact energy and contact entrop…

Influence of torrefaction pretreatment on the pyrolysis of Eucalyptus clone: A study on kinetics, reaction mechanism and heat flow

2016

Abstract The adverse nature of biomass requires specific pretreatment processes to better utilize it in bioenergy applications, and torrefaction is one of the most recognized thermal pretreatment methods. In this regard, we studied the effect of torrefaction pretreatment on kinetics, reaction mechanism and heat flow during the pyrolysis of biomass by making a comparative analysis between the pyrolysis of dried and torrefied Eucalyptus wood. Torrefied biomass was produced at three temperatures, namely 250, 275 and 300 °C. Pyrolysis was performed at 700 °C. The char yield during pyrolysis increased from 22.39 percent to 36.34 percent when the torrefaction temperature was increased from 250 to…