The conversion of butanes in HZSM-5

Chemical kinetic modeling of i‐butane and n‐butane catalytic cracking reactions over HZSM‐5 zeolite

“…This latter findings of Haag and co-workers are also emphasized in Figures 4 and 8 of the present work for n-butane and i-butane; respectively. [8][9][10][11][13][14][15][16][17] Similar to n-butane, the catalyst deactivation rate for i-butane cracking occurred slowly, even at low GHSV values and high temperatures. These results all are indicative of the consistency between the present investigation and that of Haag and co-workers as well as other researchers following their paths.…”

“…[1][2][3][4] Differences in market prices between light paraffins and olefins, coupled with the high-energy requirements of noncatalytic steam cracking reactions with low propylene yields (which currently supply 67% of total propylene production), have made catalytic processes for the production of light olefins more attractive. [7][8][9][10][11][12][13][14][15][16][17] The protolytic mechanism is favored at high reaction temperatures, low partial pressures of paraffin, and low conversions. Transformation of paraffins over ZSM-5 catalysts proceeds via two well-known mechanisms: (1) the protolytic (monomolecular) mechanism, which results in the formation of smaller olefins and paraffins through protolytic cracking reactions and (2) the classical bimolecular carbenium ion mechanism, which transforms paraffins into their corresponding olefin via hydrogen transfer reactions.…”

“…Moreover, with decreasing aluminum content in the zeolite structure, the relative contribution of the protolytic mechanism increases vs. the bimolecular mechanism. [13][14][15][16][17][18][19][20] Kinetic modeling is a very useful tool to develop a better understanding of catalytic cracking reactions. 7,8,14 This type of zeolite also enhances protolytic cracking reactions over secondary reactions because of its special shape selectivity, moderate acidic strength, and low capacity for hydrogen transfer.…”

“…Transformation of paraffins over ZSM-5 catalysts proceeds via two well-known mechanisms: (1) the protolytic (monomolecular) mechanism, which results in the formation of smaller olefins and paraffins through protolytic cracking reactions and (2) the classical bimolecular carbenium ion mechanism, which transforms paraffins into their corresponding olefin via hydrogen transfer reactions. [7][8][9][10][11][12][13][14][15][16][17] The protolytic mechanism is favored at high reaction temperatures, low partial pressures of paraffin, and low conversions. Moreover, with decreasing aluminum content in the zeolite structure, the relative contribution of the protolytic mechanism increases vs. the bimolecular mechanism.…”

“…Hence, many authors have investigated the mechanism and kinetics behind the catalytic cracking of butanes. [13][14][15][16][17][18][19][20] Kinetic modeling is a very useful tool to develop a better understanding of catalytic cracking reactions. Several authors have investigated the kinetics of paraffin catalytic cracking over HZSM-5 zeolite catalysts, using microkinetic modeling.…”