Catalyzed direct reactions of methanol with silicon powder and low-temperatures oxidation of carbon monoxide over supported gold using fixed-bed reactors

Other Title(s)

تفاعل الميثانول المباشر و المحفز مع مسحوق السليكون و أكسدة أول أوكسيد الكاربون بدرجات حرارة منخفضة على الذهب المسند باستخدام مفاعلات الفرشة الثابتة

Dissertant

al-Sadi, Fouad Abd al-Amir

Thesis advisor

Karim, Samir Hakim
Hikmat, Nuaymah Ahmad

University

University of Baghdad

Faculty

College of Science

Department

Chemistry Department

University Country

Iraq

Degree

Ph.D.

Degree Date

2008

English Abstract

The work in this thesis involves two important researches parts, the first part is "catalyzed reaction of silicon powder with methanol in fixed bed reactor", which was accomplished at the Baghdad University, college of science, department of chemistry, and the second part is "low temperatures CO oxidation", it was accomplished in the school of chemistry, Cardiff University.

Part One: Tetra alkoxysilanes are Silicon-containing compounds of the formula (RO)4Si where R is an alkyl group .They are very important in the production of ceramics, in the preparation of pure and ultra- pure SiO2 , and bonding agent for precision casting.

The present research involves the study of the direct reaction of methanol with elemental silicon in the presence of copper as a catalyst.

Catalyst used in the experiments was CuCl which was mixed with powder silicon to the extents of 5 or 10 and 15 weight percent as Cu of the total composition.

This was formed through the reduction of freshly prepared copper (I) chloride.

The mixture which was selected for studying the promotion or inhibition experiments was 10 % Si-CuCI with which 1 % (Al, Sn,CaCl2,ZnCl2) by weight of additive was mixed.

The extent of CH3OH adsorption on various powders was expressed in terms of θ, where: θ=VMe/Vm Where VMe was the volume of CH3OH adsorbed and Vm was the volume of nitrogen gas monolayer.

The adsorption increased, and such II behavior became extensive as the percentage of Cu in the mixture increased.

The products of the interaction were mainly TrMS (Trimethoxysilane) ,TMS (Tetramethoxysilane) in addition to non-silicon products HCOH, CO, and H2 .On increasing the content of the mixture as well as the reaction temperature ,the percentage of silane products TrMS and TMS and the non-silane products H2 increased ,while the free-silicon products HCOH and CO decreased .

The production of TrMS and TMS increased on mixtures which were promoted with each of Al and Sn ,but decreased in the presence each of ZnCl2 and CaCl2.

The rate of CH3OH reaction with silicon on CuCI directly depended on its pressure giving rise to an apparent reaction order of unity with respect to the CH3OH reactant.

The rate also depended on temperature in accordance with Arrhenius rate equation.

Activation energies (Ea), preexponential factors (A), and ΔS*of the reaction have been estimated.

A compensation effect operated in the kinetics of the CH3OH interaction with silicon as indicated by the linear relationships which existed between the values of Ea and the corresponding values of log A.

The manner in which the points corresponding to Ea and log A values which have been obtained on various Si-catalyst mixtures resulted in a sequence as: 15%CuCI > 10% CuCl > 5% CuCl The introduction of additives into the CuCI catalyst caused either promotion or inhibition.

Thus, the mixtures containing additives may be arranged in a sequence toward gaseous CH3OH as: Al > Sn > ZnCl2 > CaCl2 III Part Two: CO known as the "silent killer", carbon monoxide is a very poisonous gas.

It is especially dangerous to humans because it is not easily detected by our senses.

Breathing air that Contains even small amounts of CO; as little as 0.1 % carbon monoxide by volume, can prove fatal.

Concentration of only 1% is enough to cause death in only a few minutes.For this reason many catalysts were prepared (Gold is one of them) to oxidation it to CO2 .The catalyst was prepared by precipitation the HAuCl4 solution on TiO2 powder by Deposition Precipitation method, after filtration, washing and drying the catalyst was calcinated at different temperatures.

The catalyst capability was tested by CO conversion (from gas mixture contains CO,He,Air) over 50 mg of catalyst in U tube was immersed in the water bath and connected to the G.C equipment, from the retention times of the CO and CO2 the percentage CO conversion was determined.

Many parameters were discussed: 1- Surface area effect.

2- PH effect.

3- Gold loading percentage effect.

4- Aging effect.

The catalysts surface (in two parts) were characterized by using a number of surface analysis techniques, such as XRD (X-Ray Diffraction), SEM, (Scanning Electron Microscopy), and EDX (Energy Dispersive X-Ray) at school of chemistry - Cardiff University -U.K.

Main Subjects

Chemistry

Topics

• Alcoholic beverages
• Chemical processes
• Chemical reactions
• Silicon

No. of Pages

181

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-600311