Indian Journal of Chemistry Vol. 54A, February 2015, pp. 199-202 Hydroisomerization of long chain saturated hydrocarbon over Pt/SiO 2 -Al 2 O 3 catalysts J K Satyarthi, T Chiranjeevi*, Sudha Tyagi & DT Gokak Corporate R&D Centre, Bharat Petroleum Corporation Ltd., Greater Noida 201 301, UP, India Email: chiranjeevit@bharatpetroleum.in Received 11 August 2014; revised and accepted 2 February 2015 Hydroisomerization of hexadecane and the products obtained from hydroprocessing of jatropha oil has been carried out over different silica-alumina supported Platinum catalysts for the reduction of pour point. Amorphous silica-alumina support is found to be suitable for the required conversion and selectivity. Optimum reaction conditions such as platinum loading, silica- alumina ratio and various reaction conditions have been determined. Keywords: Isomerization, Hexadecane, Pour point, Platinum, Silica-alumina support Depleting petroleum reserves, their increasing prices and environmental concerns are the main driving forces pushing the search of alternative options of petroleum 1, 2 . One of the options is hydroprocessing of vegetable oils to renewable diesel or green diesel. It is a two step process, wherein in the first step the vegetable oils/fats are converted into straight chain saturated hydrocarbon by hydrodeoxygenation/hydrodecarboxylation 3-5 . In the second step, long-chain n-paraffins are isomerized to meet the cold flow properties of diesel specification. These hydrocarbons can also be selectively cracked and isomerized to obtain biojet fuel. This type of fuel provides an alternative renewable option to the conventional petroleum fuel. Hydroisomeriation is generally carried out over bifunctional catalysts which possess both hydrogenation and acidic properties. The metalllic sites are responsible for dehydrogenation of n-paraffins to corresponding olefins followed by hydrogenation of iso-olefins to corresponding isoparaffins, while acidic sites achieve skeletal isomerization of olefins via carbenium ion. High hydrogenation activity and a low acidity are needed for maximizing hydroisomerization versus hydrocracking. A balance is required between hydrogenation functionality and acidity to obtain high isomerization selectivity for long-chain paraffins 6–8 . The present study is aimed at obtaining low pour point renewable diesel by hydroisomerization of long straight chain saturated hydrocarbons obtained by hydroprocessing of Jatropha oil. Initial reaction optimization was arrived at with n-hexadecane which has chemical and physical properties similar to those of hydroprocessed Jatropha oil (HJO), especially the pour point. Experimental The catalysts were prepared with different supports such as HZSM-5, HY, SAPO-11, Al-MCM41 and SiO 2 -Al 2 O 3 . SiO 2 -Al 2 O 3 support with varying silica- alumina content were procured from Sasol, Germany and designated as SN(X), where N represents the silica content in the support and X indicates the surface area of the support. In the catalyst 0.5%Pt/(20HZSM5+Al 2 O 3 ), the support consisted 20% HZSM5 and rest was alumina while the 0.5%Pt/(20HY+Al 2 O 3 ) support consisted of 20% HY and rest was alumina. First the support was dried at 523 K for at least 2 h and pore volume was measured with water. The requisite amount of hexachloroplatinic acid (H 2 PtCl 6 .6H 2 O-99.9%, MW-517.91) was dissolved in calculated amount of water and added to the support slowly dropwise with constant mixing. Then the sample was left at room temperature for 2-3 h and dried at 363 K overnight. Finally, the sample was calcined at 773 K for 5 h. To optimize the platinum loading, SiO 2 -Al 2 O 3 support was loaded with 0.1%, 0.2%, 0.3%, 0.5%, 0.7% and 1% Pt. All the prepared catalysts were characterized by X-ray diffraction, nitrogen adsorption-desorption for surface area and pore size, SEM-EDX and chemisorptions studies. The activity of the catalysts was evaluated by high pressure and high temperature batch and continuous FBR studies. In batch reactor studies, the catalysts were first reduced in a separate continuous reactor at 350 °C under flow of H 2 (100 mL/min) for 3 h. After reduction, the reactor was cooled to room temperature and the catalyst was quickly transferred to a 500 mL Parr reactor, loaded with hexadecane/HJO feed. The reactor was flushed with H 2 until the unit was free