Toth, C; Baladincz, P; Kovacs, S; Hancsok, J
During the investigation our goal was the production of partially bio derived fuels in the gas oil boiling point range. In the last few years, to eliminate the unfavourable properties of biodiesels (FAME) intensive research has begun to convert the triglycerides (e. g. vegetable oils, fats, etc.) to products with other chemical structure. One of the examined different thermal and catalytic possibilities can be the positive solution the quality improvement of vegetable oils and gas oils together (co-processing). The aim of our experimental work was to produce product mixtures with high yield, and with maximum 10 mg/kg sulphur content from mixtures of high-sulphur gas oil (about 1.0%) and vegetable oil raw materials. In the co-hydrogenation experiments we applied mixtures of gas oil with different vegetable oil content (0 %, 5 %, 15 %, 25 %, 100 %). NiMo/Al(2)O(3) catalyst with targeted composition was used as a catalyst. In case of all feedstocks the same process parameter combinations were used (T= 300-380 degrees C, P= 60-80 bar, LHSV=1.0 h(-1), H(2)/HC= 600 Nm(3)/m(3)), which were selected on basis of the results of our pre-experiments. We investigated the effect of the process parameters and the vegetable oil content of the feedstocks on the yield, the physical-, chemical-and application properties of the main product.
On the basis of the results we obtained that both the vegetable oil conversion reactions (saturation of olefinic double bonds, deoxigenation) and gas oil quality improvement reactions (heteroatom-, mainly sulphur removal, aromatic content reduction) took place. Under the favourable operational conditions (360-380 degrees C, P= 80 bar, LHSV=1.0 h(-1), H(2)/HC=600 Nm(3)/m(3) and 15% vegetable oil content of feed) the main properties of the high-yield products except for the CFPP value satisfied the requirements of standard EN 590:2009. The amount of vegetable oil higher than 15% reduced the desulphurisation efficiency, whereas the removal of heteroatoms took place on the same active centres of the catalyst, so the deoxigenation reactions forced back the desulphurisation reactions because of the intake of large quantities of oxygen with the triglyceride molecule. Based on the results we concluded that an existing hydrogenation plant may be suitable for the co-processing of vegetable oil and gas oil mixtures. In a single step the quality improvement of gas oil (sulphur, nitrogen, aromatic content reduction) and the vegetable oil conversion to n-and i-paraffins can be achieved. The products - depending on the vegetable oil content of the feedstocks - have an increased n-and i-paraffin content, so their cetane numbers must be high, too.