Ghazala Yasmeen

Surface modification of alumina by metal doping

Abstract A series of metal impregnated alumina samples were prepared by incipient wetness impregnation technique. Pore structure and surface area for metal doped alumina (Cr, Mn, Fe and Co) containing different concentration of metals was assessed by mercury penetration and low temperature nitrogen adsorption. It was observed that mercury intrusion and extrusion curves are irreversible giving the evidence of ‘ink bottle’ pores in the alumina samples. From comparison of results of mercury porosimeter, it was also noted that total pore area values decreased with increasing metal concentration. Nitrogen adsorption data revealed that surface area decreased with increasing metal fraction (due to dispersion of metal residues on the surface of alumina samples). On the other hand, metal concentration per unit area increased with increasing the amount of metal used in doping.

Temperature-programmed reduction of metal-exchanged zeolite-A catalysts

The reduction of metal (Co, Ni, and Cu)-exchangedzeolite-A was studied by a temperature programmed reduction (TPR) technique. The TPR profiles indicate that the metals are in a dispersed form. The hydrogen consumption in the reduction process demonstrates that the metals are present in monovalent and divalent forms. High-temperature reduction peaks are also observed in the cases of CoA and NiA. Nitrogen adsorption reveals that, on heating at high temperature, the pore capacity of zeolite-A increases when exchanged with transition metals because more space is occupied by water molecules. This is confirmed by thermal analysis. After dehydration, the cations are in changed positions; they are often located in hidden sites (hexagonal prism and sodalite cages). The activation energy for the reduction process is calculated.

TG and DTA Study of the Thermal Dehydration of Metal-exchanged Zeolite-4A Samples

Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.

Synergistic effect of interfacial phenomenon on enhancing catalytic performance of Pd loaded MnOx–CeO2–C hetero-nanostructure for hydrogenation and electrochemical reactions

Hetero-nanostructures have proven to be impressive materials due to their multi-functionalities in various catalytic applications. Here, the basic focus has been devoted to interface chemistry among different domains in the field of catalysis to develop an outstanding composite material with exceptional redox and catalytic properties in hydrogenation and as well in electrochemical reactions. The unique nano-hybrid material is synthesized by the loading of Pd nanoparticles onto MnOx–CeO2 mixed oxides. The heterogeneous catalytic ability for hydrogenation reactions were studied such as the reduction of organic pollutant 4-nitrophenol into 4-aminophenol and the hydrogenation of styrene into ethylbenzene. However, for electrochemical reactions, a comprehensive investigation as anode and cathode materials in direct formic acid fuel cells was performed. The strong reducing property of Pd enhanced the catalytic performance of mixed oxides and the synergistic effect of mixed oxides through interfacial phenomenon improved the performance of the hetero-nanostructured catalyst. The as-designed nanocomposite depicts high catalytic efficiency with low-cost economical standards.

Comparative study of the adsorption of n-aliphatic alcohols on metal-doped alumina samples

A study has been made of the adsorption isotherms of n-aliphatic alcohols (methanol, ethanol, 1-propanol, and n-butanol designated C1, C2, C3, and C4, respectively) on parent and metal-doped γ-alumina samples in the temperature range 273–313K as a function of temperature and coverage, using CAHN 1000 electrobalance. It is noted from the data that at a given relative pressure, the adsorbed amount for the sample treated at the same temperature decreases in the order From the adsorption data, thermodynamic parameters such as isosteric heat of adsorption (q st), free energy (ΔG 0), differential enthalpy (ΔH), and molar entropy (ΔS 0) of adsorption have been calculated as a function of temperature and coverage. The values of q st are found to be higher for metal-doped alumina which may be due to the coordination of n-aliphatic alcohols to metal vacancies present on the surface of alumina. It has been observed that at a given relative pressure, the enthalpy of adsorption for n-aliphatic alcohols (C1–C4) treated at the same temperature decreases in the order The values of ΔH are higher for metal-doped alumina than parent alumina, which indicate that strong adsorbate–adsorbent interaction is found after impregnation. It has also been noted that the values of ΔG 0 for (C1–C4) are negative showing that the adsorption processes are spontaneous. These values decrease with increase in temperature indicating that alumina samples have higher adsorption affinity for (C1–C4) at low temperature. The low values of entropy (ΔS 0) indicate more constraint on the mobility of adsorbate molecules.

Adsorption of n-Aliphatic Alcohols in the Determination of Surface Areas of Metal-Doped Alumina Samples

A series of metal-impregnated alumina samples were prepared by the incipient wetness impregnation technique. The surface areas of the powdered samples (AL and ABET) were determined by the two most common methods, i.e. the Langmuir method and the BET method. The adsorbates used were methanol, ethanol, l-propanol and n-butanol (n-aliphatic alcohols) which were designated C1, C2, C3 and C4, respectively. It was observed that AL and ABET of the adsorbent occupied by the adsorbate molecules decreased from C1 to C4. It was also noted that the variation of AL and ABET with temperature followed exactly the same trend.

Photoenhanced degradation of methylene blue on polyaniline engineered multiferroics (BiAl0.3Mn0.3Fe0.4O3) nanocomposite systems: a comprehensive study

aGovernment Sadiq College Women University, Bahawalpur, Pakistan, email: farzanawajid67@gmail.com bInstitute of Chemical Sciences, Bahauddin Zakariya University, Multan 60800, Pakistan, Tel/Fax: +86551-3600246; emails: suryyia.manzoor@bzu.edu.pk, suryyia878@gmail.com (S. Manzoor), aamirmirza321@yahoo.com (M. Aamir), naeembzu@bzu.edu.pk (M. NaeemAshiq), ghazalayasmmin@bzu.edu.pk (G. Yasmeen), sana.ijaz@live.com (S. Ijaz), drtariq2000@gmail.com (T.M. Ansari), sajidmalikchem@gmail.com (S. Abbas) cCenter for Advanced Materials, Qatar University, Doha 2713, Qatar, emails: ammar@mail.ustc.edu.cn, ammar.chemist18@gmail.com (A.B. Yousaf)