Hatem M. Altass

Enhancing surface reactivity with a noble metal

Gold, the archetypal noble metal, is usually associated with an inhibition of surface reactivity by site blocking. In this paper however, we show that on Cu(100) surfaces a gold adlayer can actually increase the extent of reaction with the substrate.

Kinetics and Mechanistic Approach to Palladium (II)-Catalyzed OxidativeDeamination and Decarboxylation of Leucine and Isoleucine byAnticancer Platinum (IV) Complex in Perchlorate Solutions

Oxidations of two aliphatic α-amino acids (AA), namely, leucine and isoleucine by hexachloroplatinate (IV) as an anticancer platinum (IV) complex has been studied using a spectrophotometric technique in perchlorate solutions in the presence of palladium (II) catalyst at a constant ionic strength of 1.0 mol dm-3 and at 25°C. The reactions did not proceed in the absence of the catalyst. The reactions of both amino acids showed a first order dependence on both [PtIV] and [PdII], and less than unit order dependences with respect to both [AA] and [H+]. Increasing ionic strength and dielectric constant of the reactions medium increased the rates of the reactions. A probable oxidations mechanism has been suggested and the rate law expression has been derived. Both spectral and kinetic evidences revealed formation of 1:1 intermediate complexes between AA and PdII before the rate-controlling step. The oxidation products of the investigated amino acids were identified as the corresponding aldehyde, ammonium ion and carbon dioxide. The activation parameters of the second order rate constants were evaluated and discussed

Competent, selective and high yield of 7-hydroxy-4-methyl coumarin over sulfonated mesoporous silica as solid acid catalysts

Highly ordered mesoporous MCM-41 and SBA-15 have been synthesized and functionalized with different amounts of propyl sulfonic acid groups using 3-mercaptopropyltrimethoxysilane as sulfur source. The synthesized catalysts have been well-characterized by different techniques such as XRD, FTIR and BET surface area and pore size distribution by BJH method. FTIR spectra of chemisorbed pyridine and temperature programmed desorption of NH3 techniques have been successfully used to characterize the acidic sites. The results showed that, both surface area, mean pore diameter and pore volume decrease as the extent of sulfonation increase. XRD results and TEM images confirm the stability of mesoporous long range order even after sulfonation process done. In addition, the study also showed that, sulfonation enhances the surface acidity and new moderate and strong acid sites were created. All the sulfonated catalysts under investigations have been found to be highly active and selective for the Pechmann condensation reaction of resorcinol with ethyl acetoacetate. More than 98% yield of 7-hydroxy-4-methyl coumarin was obtained with 100% selectivity. Presence of high number of moderate and strong Brönsted acid sites in sulfonated catalysts help in achieving high yields. Furthermore, the MCM-41 sulfonated catalysts showed higher catalytic performance due to their higher surface acidities.

Catalytic oxidation of carbon monoxide over of gold-supported iron oxide catalyst

Abstract In this work, a series of gold nanoparticles deposited on α-FeOOH nanorods were studied in relation to their performance in the low-temperature oxidation of CO. The catalysts were characterised by different techniques such as, Fourier transform infrared (FTIR), X-ray diffraction (XRD), N2 adsorption/desorption, hydrogen temperature programmed reduction (H2-TPR) and transmission electron microscope (TEM) images. The XRD proved the formation of α-FeOOH crystalline structure and also showed small diffraction peaks for Au-agglomerated particles on the surface. While TEM images revealed the formation of α-FeOOH with nanorod structure with different dimensions, TEM also showed some agglomerations of Au particles on the support surface. The H2-TPR experiments the enhancement of Au/α-FeOOH reducibility. The performance of Au/α-FeOOH in the CO oxidation was greatly affected by Au content and α-FeOOH preparation method.

Some natural aqueous extracts of plants as green inhibitor for carbon steel corrosion in 0.5 M sulfuric acid

ABSTRACT The inhibiting impact of natural aqueous extracts of some plants such as curcumin, parsley and cassia bark extracts for the corrosion of carbon steel (C-steel) in 0.5 M H2SO4 solution was inspected utilizing some techniques such as galvanostatic and potentiodynamic anodic polarization and weight loss measurements. Outcomes indicated that the percentage inhibition efficiency increases with increasing the concentration of the extract due to its horizontal adsorption on the C-steel surface. The process of adsorption is followed by the Temkin isotherm. These natural extracts acted as pitting corrosion inhibitors by shifting the pitting potential to more noble values. The sequence of inhibition efficiency of the natural extracts decreases in the following order: cassia bark extract > parsley extract > curcumin extract. This arrangement is related to the molecular size of the major components of the three natural extracts used. GRAPHICAL ABSTRACT

Competent inhibitor for the corrosion of zinc in hydrochloric acid based on 2,6-bis-[1-(2-phenylhydrazono)ethyl]pyridine

Abstract A novel compound, 2,6-bis-[1-(2-phenylhydrazono)ethyl]pyridine (BPEP), was synthesized and confirmed by NMR and IR spectroscopy. BPEP was examined as an inhibitor for the corrosion of zinc electrode in 1.0 M HCl. The inhibition efficiency of BPEP was assessed through various techniques such as hydrogen evolution, galvanostatic polarization, potentiodynamic anodic polarization, and electrochemical impedance spectroscopy. The inhibiting action of BPEP was explained in terms of the formation of a stable complex between zinc ions and BPEP and then adsorbed onto the zinc surface. The formation of the complex was established by FT-IR spectroscopy. A conductometric titration indicated that the stoichiometry of Zn+2:BPEP (metal:ligand) is 1:1. The adsorption follows the Langmuir isotherm. The Galvanostatic polarization measurements have shown that the BPEP molecule acts as a mixed-type inhibitor. The pitting potential shifted in the noble direction, indicating that the inhibition of pitting corrosion of zinc in the presence of BPEP.The activation energy and themodyanamic parameters of the adsorption process were calculated and have been explained.