Synthesis and characterization of heterogeneous catalysts via silica obtained from Iraqi rice Husks

العناوين الأخرى

تحضير و تشخيص محفزات غير متجانسة عن طريق السليكا المستحصلة من قشور الرز العراقي

مقدم أطروحة جامعية

al-Hamidawi, Haydar Hamid Muhsin

مشرف أطروحة جامعية

al-Husni, Thana Jafar Muhammad

أعضاء اللجنة

Suhyl, Falah Sharif Abd
Mahdi, Bassim I.
Sarhan, Basimah Muhsin
Amin, Siham Tawfiq

الجامعة

جامعة بغداد

الكلية

كلية العلوم

القسم الأكاديمي

قسم الكيمياء

دولة الجامعة

العراق

الدرجة العلمية

دكتوراه

تاريخ الدرجة العلمية

2012

الملخص الإنجليزي

Rice husks (RH) are the hard protecting coverings of grains of rice.

The main function of rice husk is protecting rice during the growing season.

These (RH) pose as a waste in large quantities by plants producing rice.

In Iraq have not given any attention to this material, on the contrary, burn to get ride of it leading to a significant pollution.

It has been observed through the literature that rice husk ash (RHA) usually containing around 95% silica with small amounts of inorganic salts after complete combustion at 800 °C for 6 h.

It is used by the steel industry and concrete manufacturing, as an excellent insulator and as a catalyst support and heterogeneous catalyst for several catalytic reactions.

Sodium silicate from RHA was transformed to functionalized with 3- (chloropropyl)triethoxysilane (CPTES) and 3–(mercaptopropyl)triethoxysilane (MPTES) via a simple sol–gel technique in a one-pot synthesis to yield silica with chloro and thio groups on its surface.

The products were labeled as RHACCl and RHACSH.

Dithiooxamide, bis (dithiooxamide) palladium(II) chloride, pphenylenediamine and dichlorodiaquabis(p-phenylenediamine)copper(II) were immobilized onto RHACCl via nucleophilic substitution reaction to yield heterogeneous catalyst; These catalysts were labelled as RHAC-DTO, RHACPd( DTO)2, RHAC-p-PDA, and RHAC-Cu(p-PDA)2, respectively.

While chloroacetic acid and ethyl chloroacetate were immobilized onto the RHACSH to yield RHACS-ACOH and RHACS-ACOEt.

The BET surface area of RHACCl and RHACSH were found to be 633 and 331.61 m2 g-1, while the specific surface of RHAC-DTO, RHAC-p-PDA, RHAC-Pd(DTO)2, RHACCu( p-PDA)2, RHACS-ACOH and RHACS-ACOEt were found to be 9.75, 145, 70.83, 60.15, 66.13 and 269.35 m2 g-1, respectively.

Thermogravimetric analyses (TGA-DTA) for the RHACCl, RHACSH, RHAC-DTO, RHAC-p-PDA, RHACPd( DTO)2 , RHACS-ACOH and RHACS-ACOEt indication that the physical adsorb water was lost between 30-160 °, while the residual parts of material decomposed up to 300 °C.

The 29Si MAS NMR of RHACCl showed the presence of T2, T3, Q3 and Q4 silicon centres, while the T1, T2, T3, Q2, Q3 and Q4 silicon centres was present in RHACSH.

The 13C MAS NMR showed that the RHACCl had three chemical shifts at 10.37, 26.70 and 47.69 ppm, which was attributed to the three carbon atoms of the CPTES moiety.

RHACSH had two signals at 43.29 and 59.49 ppm instead of the expected three signals.

This was due to the superimpose of the two signals on each other.

According to these results and other results obtained by using CHNS analysis and FT-IR spectra, the structures of RHAC-DTO, RHAC-Pd(DTO)2, RHAC-p-PDA, RHAC-Cu(p- PDA)2, RHACS-ACOH and RHACS-ACOEt were suggested.

X-ray diffraction technique showed that the catalysts have amorphous face, while the scanning electron microscopy (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) techniques were proved that the catalysts have spherical nano particles.

Catalytic activity for RHAC-DTO and RHAC-p-PDA were investigated in the esterification reaction of acetic acid with ethyl alcohol to produce ethylacetate.

The optimum conditions of the esterification over RAHC-DTO and RHAC-p-PDA were found to be 6h reaction time, 1:1 mole ratio, 0.2 g the catalyst mass and 85 °C as reaction temperature.

The conversion of ethyl alcohol over RHAC-DTO is higher than that the RHAC-p-PDA, while the homogenous DTO and p-PDA gave a lower conversion than the heterogeneous RHAC-DTO and RHAC-p-PDA.

التخصصات الرئيسية

الكيمياء

الموضوعات

• الأكاسيد

عدد الصفحات

153

قائمة المحتويات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-600531