Judul: The Effect of Using Zeolite as Catalyst in Esterification process of Jatropha Curcas Oil to Yield and Biodiesel Qualities
Abstrak: This research is divided in three steps: raw material preparation, introductary research and main research. In the first step, the process of activation is done in natural zeolite by using heating method and degumming process to Jatropha curcas oil with heating and acidic method. The purpose of introductary research is to find type and concentration of zeolite which gives the best result in esterification process. In this step the randomize complete factorial experiment with two factor is used as experimental design th etype of zeolite (Z) as the first factor and the concentration of zeolite (A) as the second one. The Z factor consist of two level natural zeolite and activated zeolite, whereas factor A consist of three level: 1%, 2% and 3%(b/b) to oil. In the main research, zeolite as a catalyst in esterification process is used for several times and the effects of reusing it was evaluated to yield and biodeisesl qualities. Every reused, zeolite firstly washed with water and alkohol. Biodiesel qualities is decided by yield measurement and analyzing the acid number, saponification number, esters number, visitory and density.
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Judul: Transformation of jatropha seeds (Jatropha curcas L.)  into biodiesel by in situ transesterification
Abstrak: Biodiesel is defined as mono-alkyl esters from transesterification reaction of triglycerides with alkyl alcohol. In situ transesterification is a method to produce biodiesel from oil sources of material by eliminating process steps of oil extraction and refining. The purpose of this research is to study the transformation process of Jatropha seeds into biodiesel by in situ transesterification on the 10 liters scale by studying the influence of reaction time, stirring speed and ratio methanol/hexane/material on the yield and quality of biodiesel. In situ transesterification of Jatropha seeds was carried out under the following process condition: the moisture content of Jatropha seeds were less than 2%, the particles size were ± 20 mesh and KOH concentration was 0.075 mol/L methanol. Operating condition of in situ transesterification was varied at 4 and 6 hours reaction time, 200 and 600 rpm stirring speed and ratio methanol/hexane/material (v/v/w) were 3:3:1, 4:2:1 and 5:1:1. Analysis of variance showed that reaction time, stirring speed and ratio methanol/hexane/material did not significantly affected the yield, acid value, saponification value, ester value, viscosity and ash content of biodiesel. The biodiesel yield was produced between 82.54-87.57%. The best biodiesel yield on all of treatments was 87.57% with condition treatment were reaction time of 6 hours, stirring speed 600 rpm and ratio methanol/hexane/material (v/v/w) of 4:2:1. Acid value, saponification value and ester value of biodiesel were 0.20-0.26 mg KOH/g, 185.49-194.30 mg KOH/g and 185.29-194.10 mg KOH/g respectively. Viscosity of biodiesel was 3.49-6.36 cSt. The ash content of biodiesel was 0%, but the condition treatment, were reaction time of 4 hours, stirring speed of 600 rpm and ratio methanol/hexane/material (v/v/w) of 5:1:1, had ash content of 0.007%. Jatropha cakes had total volatile matter content 1.80-3.64% and extracted material content 3.94-11.42%.
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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