H. Hermansyah*, R. Arbianti, D.A. Prameshwari
Abstract: Immobilized Candida rugosa lipase acts as a biocatalyst for interesterification of used cooking oil with methyl acetate in a packed bed reactor. Reactants and products are analyzed using HPLC, and the effect of residence time and operational stability are also investigated. The results indicate that this biocatalyst can convert 71.5% fatty acid from triglyceride in used palm oil for 5.5 h of residence time. Stability test results show that the immobilized biocatalyst retains good activity for 50 hours without appreciable loss in substrate conversion. The largest conversion obtained from this study was 87.09%, achieved during the stability testing under optimum operating conditions. Furthermore, the kinetic models based on the Ping Pong Bi Bi mechanism are applied to the experimental data to describe the reaction behavior. The fitted results show that the Model C gave the smallest error and fairly described the reaction behavior.
Keywords: Biodiesel, used cooking oil, candida rugosa lipase, interesterifcation, non-alcohol route, kinetics.
P.P.D.K. Wulan, W.W. Purwanto*, Y. Muharam, S. Shafa, E. Listiani
Abstract: Carbon nanotubes (CNTs) are tubular carbon molecules with superior mechanical, chemical, optical, and electrical properties. These unique properties make CNTs potentially valuable as hydrogen storage, superconductors, drug delivery and other end-use applications. Catalytic decomposition of methane is a promising method for producing hydrogen and CNTs simultaneously for several reasons: economic, high yield of products, and ease of control. Unfortunately, the presence of a metal catalyst in the CNTs product after reaction causes a negative impact on the quality of CNTs including reducing the electrical resistivity, density, tensile strength and structural properties of the nano tubes which can lead to the reduction of CNTs performance in many applications. Process optimization is needed to produce hydrogen and CNTs with the best quality by varying the reaction time to observe the influence of reaction time on the quality of the CNTs produced through the catalytic decomposition of methane. Production of CNTs was performed in a Gauze reactor at 700°C, 1 atm with methane as a feed was about 315 ml/min. A Stainless steel-wire mesh coated with a Ni-Cu-Al catalyst prepared by the dip-coating method as a spot for carbon deposition. The catalytic performance of the Ni-Cu-Al catalyst and the quality of carbons produced were discussed based on the X-ray diffraction (XRD) results and the Scanning Electron Micrograph (SEM) Image of the used catalysts. The diameter of CNTs produced by a longer reaction time were greater, and it can be concluded that the longer the time reaction, the worse the quality of the CNTs produced. The best of CNTs, which have a smaller diameter was given at 20 minutes reaction time. The crystal diameter of CNTs increased with increasing reaction time ranging from 5.93 nm for 20 minutes reaction to 7.33 nm for 240 minutes reaction.
Keywords: Carbon Nanotubes, Hydrogen, Purification, Quality, Reaction time.