Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

Method for the cooling of solid residues of gasification

Abstract: The present specification describes and claims a method and apparatus for use in cooling the solid residue of gasification of a reactor operated at a pressure above atmospheric for the gasification of carbonaceous materials The residue of gasification is conducted out of the reactor into a cooling apparatus located therebelow and flows through the cooling apparatus from the top to the bottom thereof A cooling liquid is introduced into the solid residue in the upper region of the cooling apparatus and is metered such that the greater portion of the heat contained in the residue is eliminated in the form of heat of vaporization, sensible heat and chemical binding energy with the resultant steam and reaction products produced The remaining residual heat which corresponds to the difference between the desired final temperature and the temperature after cooling by the liquid, is eliminated by a gas blown into the bottom region of the cooling apparatus and/or by indirect heat exchange

First-principles study of the interaction between NO and large carbonaceous clusters modeling the soot surface.

Abstract: First-principles calculations are performed to characterize the NO adsorption on large carbonaceous clusters modeling the surface of soot. Adsorption on the face and on the edges of perfect and defective clusters is considered in the calculations. It is shown that the first situation corresponds to physisorption and requires taking into account long-range dispersion interactions in the calculations. In contrast, interaction of NO with the unsaturated edge of a defective cluster leads preferentially to a C–N rather than to a C–O chemical binding. This indicates that soot may be an efficient sink for NO in the troposphere only if it contains a high number of unsaturated carbon atoms. From a more fundamental point of view, this study also clearly evidences that quantum calculations have to be carefully conducted when considering the interaction between radical species and carbonaceous surfaces. Problems encountered with the choice of the functional used in density functional theory approaches as well as with...

The Selective Formation of Di-σ N−Si Linkages in Pyrazine Binding on Si(111)-7 × 7

Abstract: The highly selective covalent binding of pyrazine on Si(111)-7 x 7 has been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. HREELS results clearly suggest that covalently attached pyrazine retains the sp 2 electronic configuration for all four carbon atoms, indicating that the carbon atoms of the ring are not directly involved in the chemical binding with the surface. The vibrational results further reveal that the aromatic ring of pyrazine is transformed to an unconjugated cyclodiene structure, implying the participation of N atoms in surface binding. This is further confirmed by the binding energy of N Is shifting to 399.0 eV in chemically bonded pyrazine compared to the value of 400.6 eV for physisorbed molecules. These experimental results coupled with our theoretical DFT calculations strongly suggest the di-σ binding of the two para nitrogen atoms of pyrazine with an adjacent adatom-rest-atom pair on Si (111)-7 x 7, forming a 1,4-N,N-dihydropyrazine-like structure.

Speciation and Availability of Cr, Ni and Co IN Serpentine Soils of Ranau, Sabah

Abstract: Problem statement: Serpentine soils are known as a geogenic source of heavy metal pollution because they are anomalously rich in chromium, nickel and cobalt. Approach: However, only that portion of these metals which is available in the ecosystem and incorporates in the bio-transformation processes, is dangerous for the environment. Availability of Cr, Ni and Co depends on their speciation into the different fractions of a soil and corresponds with their chemical binding forms. Soil is a combination of several reactive fractions which have the ability to interact physically and chemically with heavy metals and changes their existence form in the soil. Results: Thus, understanding the geochemical form and distribution of metals in different fractions of soil is fundamental for predicting the availability and potential toxicity of them under natural condition. Conclusion: This study set out with the aim of fractionation of Cr, Ni and Co in serpentine soils of Ranau in Sabah state of Malaysia. Selective Sequential Extraction analysis (SSE) was combined with X-ray diffraction of soil powders to find the mineralogical source and mobility of Cr, Ni and Co in serpentine soils.