Sains Malaysiana 39(5)(2010): 765–768

Comparison Studies on Lauric Acid Ethoxylated Using Homogenous and Heterogenous Catalysts

(Kajian Perbandingan Terhadap Asid Laurik Teretoksi Menggunakan Mangkin Homogen dan Heterogen)

Zarina Edris*, Norhafipah Mohamad And Mohd Ambar Yarmo

School of Chemical Sciences and Food Technology

Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 Bangi, Selangor D.E., Malaysia

Received: 2 January 2009 / Accepted: 3 March 2009

ABSTRACT

The application of homogenous and heterogeneous catalysts for ethoxylation of lauric acid (LAc) with ethylene oxide (EO) was conducted in this study. Ethoxylation reaction of LAc with EO with the mole ratio 1:3 (LAc:EO) have been done at reaction temperature 130-135 ^oC under 1.8 bar pressure to produce Ethoxylated Lauric Acid (LAc:3EO), a type of nonionic surfactant. This experiment showed that potassium tert-butoxide (^tBuOK) as a base homogenous catalyst gave good selectivity and activity compared with potassium methoxide, potassium ethoxide and potassium butoxide. Studies on intercalation of hydrotalcite (HT) with tBuO- to form HTtBuO as solid base catalyst was conducted. Ethoxylation reaction using heterogenous catalyst based on intercalated of HT-tBuO gave lower activity compared with tBuOK as homogenous catalyst. This might be due to diffusion which occurred significantly in heterogenous catalyst compared with homogenous catalyst. Analysis of nonionic surfactant LAc:3EO using HTtBuO as a catalyst gave no undesired side product. Detail analysis of the reaction products using GC-Tof technique gave a mixture of ester of LAc:3EO and polyethylene glycol (PEG).

Keywords: Ethoxylated lauric acid; hydrotalcite; intercalation; nonionic surfactant tert-butoxide

ABSTRAK

Aplikasi mangkin homogen dan heterogen bagi tindak balas asid laurik (LAc) dengan etilena oksida (EO) telah dikaji. Tindak balas LAc dengan EO dengan nisbah molar 1:3 (LAc:EO) telah berjaya dilakukan pada suhu tindak balas 130-135 ^oC di bawah tekanan 1.8 bar bagi menghasilkan asid laurik teretoksilat (LAc:3EO), sejenis surfaktan bukan ion. Eksperimen ini menunjukkan bahawa penggunaan kalium tert-butoksida sebagai mangkin homogen memberikan selektiviti dan aktiviti yang lebih baik berbanding kalium metoksida, kalium etoksida dan kalium butoksida. Kajian seterusnya dilakukan dengan menyelit anion tBuO- pada HT bagi menghasilkan mangkin bes pepejal HTtBuO. Penggunaan mangkin heterogen HTtBuO dalam tindak balas pengetoksilan memberikan aktiviti yang lebih rendah berbanding tBuOK sebagai mangkin homogen. Keadaan ini kemungkinan besar disebabkan oleh fenomena penyerakkan yang berlaku secara signifikan dalam mangkin heterogen berbanding dengan mangkin homogen. Hasil analisis GC-Tof terhadap surfaktan nonionic AL:3EO yang menggunakan mangkin HT tBuO menunjukkan kehadiran campuran ester dan polietilena glikol (PEG).

Kata kunci: Asid laurik teretoksilat; hidrotalsit; penyelitan; surfaktan bukan ion tert-butoksida

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*Corresponding author; email: zarinaedris@yahoo.co.uk