PREPARASI DAN KARAKTERISASI KATALIS NaOH/γ-ALUMINA DAN Na2CO3/γ-ALUMINA UNTUK TRANSESTERIFIKASI MINYAK JARAK (Ricinus communis) MENJADI BIODIESEL

Farida Noor Arifah, Prof. Dra. Wega Trisunaryanti, M.S., Ph.D.Eng.

2014 | Tesis | S2 Ilmu Kimia

Telah dilakukan preparasi dan karakterisasi katalis NaOH/ɤ-alumina dan Na2CO3/ɤ-alumina untuk reaksi transesterifikasi minyak jarak (Ricinus communis) menjadi biodiesel. Katalis NaOH/ɤ-alumina dan Na2CO3/ɤ-alumina dibuat melalui metode impregnasi basah dengan perbandingan berat senyawa yang diembankan:pengemban sebesar 1:5. Karakterisasi katalis meliputi penentuan struktur kristal dan spesies pada sampel katalis menggunakan XRD, gugus fungsi dengan FT-IR, nilai kebasaan dengan metode titrasi Hammett, dan luas permukaan spesifik dan volume total pori dan rerata jejari pori menggunakan adsorpsi-desorpsi isotherm gas nitrogen. Uji aktivitas katalis untuk proses transesterifikasi minyak jarak dilakukan dalam reaktor sistem batch pada temperatur 60 °C selama 120 menit. Konversi dihitung dari hasil perkalian antara berat produk dan persentase luas area metil ester hasil analisis GC-MS dibagi berat minyak. Katalis yang menghasilkan konversi yang lebih tinggi dipilih untuk selanjutnya divariasi jumlah katalis (1, 2, 3, 4, dan 5% b/b berdasarkan berat minyak) dan waktu reaksi (60, 90, 120, 150 dan 180 menit) untuk memperoleh kondisi optimum produksi biodiesel. Produk biodiesel yang diperoleh pada kondisi optimum dianalisis dengan ASTM (American Standart of Testing Materials). Hasil karakterisasi menunjukkan bahwa pengembanan NaOH maupun Na2CO3 membentuk fase kristal baru, meningkatkan kebasaan dan rerata jejari pori namun menurunkan luas permukaan spesifik dan volume total pori ɤ-alumina. Katalis yang menghasilkan konversi lebih tinggi pada temperatur 60 °C, jumlah katalis 3% selama 120 menit. adalah NaOH/ɤ-alumina, yaitu sebesar 86,12% b/b. Berdasarkan analisis GC-MS, biodiesel didominasi oleh metil risinoleat. Konversi biodiesel tertinggi, sebesar 90,88% b/b, dicapai oleh katalis NaOH/ɤ-alumina pada reaksi yang menggunakan jumlah katalis 3% b/b dengan waktu reaksi 150 menit. Berdasarkan data ASTM, biodiesel minyak jarak belum dapat digunakan sebagai bahan bakar mesin diesel secara langsung.

Preparation and characterization of NaOH/γ-alumina and Na2CO3/γ-alumina catalysts for transesterification of castor oil (Ricinus communis) into biodiesel have been studied. The NaOH/γ-alumina and Na2CO3/γ-alumina catalysts were prepared by wet impregnation with weight ratio of loaded compound:support about 1:5. The characterization of catalysts consisted of determination of crystal structure and spesies on the catalyst by using XRD, functional group with FT-IR, basicity with Hammett titration method and specific surface area, total pore volume and average pore radius by nitrogen adsorption-desorption isotherm. The catalyst activity test for transesterification of castor oil was carried out in a batch system of reactor at a temperature of 60 °C for 120 min. The conversion was calculated from multiplication of weight product and percentage of methyl ester peak area, resulted from GC-MS analysis, divided to weight of oil. The catalyst with higher conversion was choosen for further variation of catalyst amount (1, 2, 3, 4, and 5 wt% based on oil) and reaction time (60, 90, 120, 150, and 180 min) to obtain the optimal condition for biodiesel production. The yield that was produced from the optimum condition was analyzed using ASTM (American Standard of Testing Materials) The result of characterization showed that the impregnation of NaOH and Na2CO3 have formed a new crystal phase, increased the basicity and average pore radius but decreased specific surface area and total pore volume of γ-alumina. The catalyst that produced higher conversion of biodiesel at a temperature of 60 °C, catalyst amount of 3 wt % for 120 min (86.12 wt%) was NaOH/γ-alumina. Based on GC-MS analysis, known that the biodiesel has been dominated by methyl ricinoleate. The highest conversion of biodiesel as high as 90.88 wt% was produced by NaOH/γ-alumina catalyst under the reaction with catalyst amount of 3 wt % and reaction time 150 min. Based on the ASTM data, the biodiesel wasn’t qualified yet as a automotive diesel fuel.

Kata Kunci : NaOH/ɤ-alumina, Na2CO3/ɤ-alumina, metil risinoleat, transesterifikasi, minyak jarak (Ricinus communis), biodiesel