Promotion of the performance of La, Ce and Ca impregnated HZSM-5 nanoparticles in the MTO reaction

Abstract

Effects of calcium, cerium and lanthanum on the catalytic performance of HZSM-5 nanoparticles in the methanol to olefin, MTO, conversion were investigated. Each samples with the target Si/Al = 400 was synthesized producing nanoparticles about 300 nm. The reactor MTO performance of catalysts at methanol WHSV = 8 g/(g · h) was evaluated at the temperatures of 390, 440, and 490 °C. Based on the yield of ethylene and propylene, Ce-Ca-HZSM-5 showed the best catalytic performance. The metal modification of HZSM-5 resulted in the improved yield of ethylene and propylene, which the effect on the yield of ethylene was stronger. Another advantageous feature of metal modified catalyst was the reduction of sensitivity of the yield of propylene to temperature. With decreasing temperature from 490 to 390 °C, the yield of propylene decreased from 0.16 to 0.13 over Ce-Ca-HZSM-5 which is significantly more narrow than HZSM-5 (0.15 to 0.10). The main improved characteristic in the performance of the modified catalyst was substantial decrease of coke precipitation as determined by TG analysis. Ce-Ca-HZSM-5 was found to be more stable than parent HZSM-5 over 100 h time on stream, although its initial conversion was lower at the conditions of experiment.