EFFECT OF STIRRING, EXTRUSION AND PELLETIZATION ON HIGH-PRESSURE PROPENE OLIGOMERIZATION AND XYLENE ISOMERIZATION OVER ZSM-5

The effect of stirring a ZSM-5 synthesis mixture was to decrease the crystal size. Mechanical stirring was more effective than magnetic stirring. Static synthesis conditions yielded a number average crystal size of 2.4-mu-m, and stirring decreased the crystal size to as low as 0.4-mu-m. The decrease in crystal size improved catalyst lifetime and activity for propene oligomerisation at 250-degrees-C, WHSV ca. 12 h-1 and 5 MPa, with the CUV (catalyst utilisation value in g liquid produced/g catalyst) increasing from 110 g/g for an unstirred sample to about 400 g/g for a mechanically stirred sample. Extrusion had no detrimental effect on lifetime and activity for propene oligomerisation, while activity and lifetime decreased with the wt.-% coke deposited in ZSM-5 by ca. 50%. Extrudates yielded heavier liquid products than powder during oligomerisation, probably due to better temperature control in extrudate catalyst beds. The cetane numbers computed for the hydrogenated liquid fractions obtained with powdered and extruded catalysts were similar to that obtained for a sample of commercial diesel. However, product obtained from pelletised catalysts yielded higher cetane numbers. For xylene isomerisation, powdered catalyst was more active than extrudates and pellets.