Abstract:
A series of beta zeolites supported palladium catalysts were prepared by ion exchange (IE) or incipient wetness impregnation (IWI). The characterizations such as XRD,N2 adsorption and temperatureogrammed desorption(TPD)of ammonia were carried out. Hydrogenation of tetralin was conducted with a continuous-flow fixed bed micro-reactor under 4 MPa, 270 ℃,WHSV 16 h-1 and 100 mg/kg S (thiophene as S source). It is found that catalytic behaviours of the supported Pd catalysts depend both on the preparation methods and on the properties of supports. For Pd/Beta25,the catalytic activity of the sample prepared via ion exchange (IE for short) is superior to the initial wetness impregnated(IWI for short)one. Among three ion exchanged catalysts, Pd/Beta80(IE) is most active and sulphur tolerant during the whole time on stream. Pd/Beta25(IE) deactivates most rapidly because the conversion of tetralin decreases from the initial 77% to 10% after 8?h. With Pd/Beta60(IE), the corresponding conversion are 60% and 16% respectively. And with Pd/Bera80(IE) those are 75% and 55% respectively. The excellent activity of Pd/Beta80(IE) can be attributed to the carrier's higher strong acidity/weak acidity ratio, especially the presence of more medium strength acid sites and the mesopores structure. Besides,the addition of alumina to Pd/Beta25 is favourable to improving its catalytic activity.