Judul: Study on mixing process using static-mixer method to increase transesterification efficiency of refined palm oil into biodiesel
Abstrak: One of the difficulties faced in the current technology for biodiesel production is the requirement for rigorous mixing of methanol with the feedstock oil in the reactor. Utilization of blade mixer has limitation due to the immiscible state of those substances. This research was devoted to assess of static-mixer utilization in a transesterification reactor for biodiesel production in terms of kinetics reaction (reaction rate coefficient k, activation energy Ea, and collision factor or coefficient factor A). The experiments were conducted by reacting refined bleached deodorized palm olein (triglyceride or TG) with methanol (MeOH) at 50, 55, 60, 65, and 70o C, using potassium hydroxide (KOH) as a catalyst at atmospheric pressure. Molar ratio of TG and MeOH was 1 : 11.5 and KOH used was 1% of palm oil weight. Transesterification process using blade agitator with the same reaction condition was performed as base of comparison to those of static-mixer. Energy consumption was measured for heater during oil heating, transesterification, boiling water and biodiesel drying by kWh meter. It was also conducted for pump for distribution, reactant mixing, and impeller of blade agitator. The experiments showed that static-mixer has significant effect in reducing reaction time to reach required fatty acid methyl ester content (FAME) i.e. 96.5% than those of blade agitator. Transesterification reaction time with static-mixer were shorter than with blade agitator for all temperature levels. Reaction temperature of 65o C with 5 minutes of reaction time demonstrated the best condition for running the static-mixer reactor.
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Judul: Analisis Metode Response Surface pada Produksi Biodiesel secara Katalitik dengan Static Mixing Reactor
Abstrak: Transesterification process of palm olein with static mixing reactor is influenced by temperature, time and percentage of KOH catalyst. This study aims to determine optimum operating condition of a static mixing reactor for biodiesel production in batch system using Response Surface Methodology ( RSM ) box - Behnken. Catalytic biodiesel production process was carried out using a static mixing reactor, where palm olein, methanol, and catalyst were flown to the static mixer with reaction temperature of 30oC, 45oC, 60oC . Catalyst concentration given in this study were 0.3 % , 0.4 %, 0.5 %, while time for sampling was 20, 30, and 40 minutes. Laboratory analysis was conducted to obtained acid number, saponification number and total glycerol numbers, and by calculation that methyl esters content was 97.41 % w / w. This figure has met the SNI standard of methyl ester content which is 96.5%. Optimum operating condition was found at temperature of 300C, operating time is 45 minutes and 0.4 % of KOH catalyst.
Keyword: response surface, methyl esther, biodiesel

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