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Tham khảo tài liệu 'phân tích eclectron trong hóa phân tích phần 2', kỹ thuật - công nghệ, hoá học - dầu khí phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | made as both a stability test and a process variable study. In the first part of the run conditions were held constant at 250 C 1.48 MPa 2.0 NỈ g-caX-h Hj CO 0.67 for 5 mass balances about 340 h on stream . Catalyst activity was stable during this period with the H2 CO conversions measured in the range 42.6-46.4 . Following the stability test process conditions were varied to determine their effect on catalyst activity and selectivity. The conditions ranged from 235265 C 1.48-2.96 MPa 1.0-4.0 ĩĩlỊg-ta h H2 CO 0.67-1.0 and 8 mass balances including a repeat of the initial conditions were completed. Changing of process conditions increased the rate of catalyst deactivation and during the repeat of conditions at 619 h the H2 CO conversion was 35.9 . Three precipitated iron catalyst compositions were selected for resynthesis on the basis of overall catalytic performance for the Fischer-Tropsch reaction. Approximately 100 g batches of each of the following compostions were prepared using the controIled-pH continuous preripltatlon technique that has been detailed previously and employed for all prior catalyst syntheses 100 Fe 1 Cu 0.2 K 100 Fe 3 Cu 0.2 K 100 Fe 5 CU 4.2K 8 S1O2 Elemental analyses were performed by atomic absorption spectroscopy for each material and were found to be within acceptable limits. - Metal exposures dispersions are an indication of the fraction of total reduced metal that Is available for adsorption or reaction at the surface of precipitate crystallites. Exposures were determined for 12 representative catalyst compositions by temperature-programmed desorption of adsorbed Ha following calcination at 300 C and subsequent reduction in either H2 or co at the same temperature. A affirming dissociative adsorption of Họ fractional metal exposures were calculated from the total amount of desorbed H2 in each case. The observed values showed relatively little variation. Most were within the range H Fe 0.02 to 0.05 and appeared to be 6 largely independent
