DIRECT SYNTHESIS OF LPG FROM SYNGAS OVER HYBRID CATALYST OF Cu/ZnO AND SILICA FIBER COATED WITH ZSM-5

Abstract

The LPG synthesis process was performed by using hybrid catalyst of Cu/ZnO-ZrO2-Al2O3 catalyst and ZSM-5/silica fibers. The methanol synthesis catalyst as Cu/ZnO-ZrO2-Al2O3 was prepared by co-precipitation method and ZSM–5/silica fibers were prepared by using sol-gel method assisted with electrospinning technique followed by hydrothermal process. Tetraethyl orthosilicate and aluminium nitrate were used as Si and Al sources, respectively, for ZSM-5 synthesis by using tetrapropylammonium hydroxide as an organic base. The ZSM-5 coated on silica fibers was synthesized with different crystallization times (24, 48, 72 and 120 h), solution pH (8, 9 and 10) and Si/Al ratios (20, 40 and 60). At the appropriate conditions (crystallization time of 48 h, at 180 ºC and pH 9), it achieved the ZSM-5/silica fibers with a surface area of 273 m2/g. The ZSM-5/silica fibers offers several advantages over other forms like powder and granule catalyst such as flexibility and self-adjusting shape to fit into the channel. The catalytic activity of ZSM-5/silica fiber was tested by mixing with Cu/ZnO-ZrO2-Al2O3 catalyst in fixed bed reactor for LPG synthesis from syngas and compared with conventional powder form catalyst. The highest CO conversion was achieved by using hybrid catalyst of Cu/ZnO-ZrO2-Al2O3 and ZSM-5/silica fibers at the condition of 2 MPa, 260 oC with W/F=40 g.h/mol. It provided the CO conversion and LPG selectivity of 59.3% and 79%, respectively.