Judul: Pembuatan Biodiesel Karet dan Biodiesel Sawit dengan Instrumen Ultrasonik serta Karakteristik Campurannya
Abstrak: Biodiesel is one of known alternative fuel, obtained by oil processing, for example from rubberseed oil and palm oil. Conventionally, biodiesel obtained by reacted oil with methanol for 1 hour at temperature of 65 oC with mechanical stirring, using homogenous catalyst such as NaOH. Homogeneous catalysts dissolve fully in the glycerol layer and partially in the biodiesel layer during the triglyceride transesterification process. Heterogeneous (solid) catalysts, such as CaO, can prevent contamination, making product separation much easier. Moreover, the reaction time of conventional methods can be shortened by applying ultrasonic energy. This research consists of several stages, aimed to obtain biodiesel yield from transesterification using homogenous and heterogenous catalyst, to produce rubberseed biodiesel and palm biodiesel by applying ultrasonic energy, and then obtain the characteristics of palm biodiesel, rubberseed biodiesel, and mix of both. The result showed that the transesterification process using heterogenous catalyst need longer time and give the lower biodiesel yield than the transesterification using homogenous catalyst. Ultrasonic transesterification of palm oil gives a greater yield then the conventional stirring methods, which ultrasonic transesterification yield range between 96.52% to 98.03% and the acid number range from 0.50 mg KOH/g sample to 0.63 mg KOH/g sample. Ultrasonic esterification succeeded in reducing acid value of rubber seed oil in a shorter time, which is smaller than acid value by 30 minute conventional esterification. Ultrasonic transesterification only succeeded to form biodiesel from rubberseed oil that has gone through the 30 minutes ultrasonic esterification (78.84% yield) and through an 1 hour conventional esterification (91.55% yield). Rubberseed biodiesel, palm methyl ester, and a blended of both meets the SNI-04-7182-2006 on the characteristics of acid value, density, viscosity, and cloud point. The iodine number of rubberseed biodiesel was still above the standard, but blending palm methyl ester to rubberseed biodiesel can reduce the iodine number of blended biodiesel to meet the standards. Production cost analysis at biodiesel blended (25% palm methyl ester ini rubberseed biodiesel) resulted : ultrasonic methods still more expensive than conventional methods.
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Judul: Sintesis dan Karakterisasi Biodiesel dari Minyak Biji Karet (Hevea brasiliensis) Melalui Proses Estrans (Esterifikasi- Transesterifikasi)
Abstrak: Biodiesel is alkyl ester produced from of vegetable, animal or fat oil derivate which could be used in diesel machine. One of the materials that can be used in making biodiesel is rubber seed oil. In order to influence the effective and efficient of biodiesel production, the process held in two steps esterificationtransesterification with the appropriate catalyst. The process had to be held in two step because of the high concentration of free fatty acid in rubber seed oil. The general purpose of this research was to add the utilization of rubber seed oil. The particular purposes of this research were to obtain the opted esterification-transesterification process from rubber seed oil and to know the characteristic of biodiesel produced from rubber seed oil esterificationtransesterification process and compare it with the obtained biodiesel standard. The result of proximate analysis of rubber seed showed that fat concentration in rubber seed was high enough about 38.65 % (dry basis) and the mean of rubber seed oil yield after extraction was 15.69 %. The characteristics of rubber seed oil after degumming were; cinematic viscosity at 40 oC was 23.31 cSt, the oil density at 25 oC was 0.896 g/ml and fatty acid value was 22.22 mg KOH/g of sample. Moreover, the oil could not be used directly as biodiesel because of three parameter values were higher than the standard. Therefore, the Esterification-Transesterification process must be carried out, so biodiesel that produced could fulfill the standard and could be used as fuel. Based on biodiesel production of rubber seed oil through Esterification- Transesterification could be known that the opted condition of esterification process was at A1B2C3 (HCl 1 %, reaction time 120 minutes, and mole ratio of methanol: oil = 20:1), fatty acid value was 0.32 mg KOH/g sample. The opted condition of transesterification was at A1B2 (reaction time 30 minutes and mole ratio of methanol:oil = 6:1), cinematic viscosity at 40 oC was 4.77 cSt, yield of biodiesel was about 74.51 %, and fatty acid value was 0.22 mg KOH/g of sample. Based on biodiesel characterization, the biodiesel quality produced in this research was appropriate with the standard of biodiesel for cinematic viscosity, density, fatty acid number, and flash point.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf