Synergies in the production of olefins by combined cracking of n-butane and methanol on a HZSM-5 zeolite catalyst

Olefin production by cofeeding methanol and n‐butane: Kinetic modeling considering the deactivation of HZSM‐5 zeolite

“…À1 ; methanol/n-butane molar ratio in the feed, 3 (0.75 in CH 2 equivalent units) which corresponds to conditions of energy compensation (energy neutral reaction) for complete conversion of reactants, as determined in a previous work; 20 time on stream, 5 h. The compounds in the reaction medium have been quantified by considering the concentration of methanol (M) and dimethyl ether (D), n-butane (reactant and product) (B), methane (C) by-product formed by decomposition of methanol and product lumps, olefins (ethylene, propylene and butenes) (O), paraffins (ethane, propane and isobutane) (P), C 5þ aliphatics, which include all the olefins and paraffins with more than five carbon atoms and BTX aromatics (benzene, toluene, and xylenes). The formation of CO and CO 2 has not been considered, given that their maximum yield is lower than 0.5% (of C transformed) at the maximum temperature, 550 C, and for the minimum value of space time studied.…”

“…11,15,16 Catalyst hydrothermal stability has been improved by doping the HZSM-5 zeolite with Fe, 17 and agglomerating with bentonite and alumina. 18,19 The integration of both reactions schematized in Figure 1 is effective for increasing the yield of olefins over those corresponding to the two individual reactions, which is explained by the following findings based on synergies between the kinetic schemes of the two reactions: 20 (i) olefins formed at the initial section of the reactor in n-butane cracking activate the autocatalytic steps for methanol transformation, following the well-established ''hydrocarbon pool'' mechanism originally proposed for SAPO-34 catalyst, which establishes that methylbenzenes are the main reactive species; 12,[21][22][23][24][25] (ii) the incorporation of these olefins in the ''hydrocarbon pool'' maintains the reactivity of methylbenzenes released by the olefins, which delays the formation of polymethylbenzenes that are the precursors of polyaromatic coke; 26,27 (iii) water formation in methanol transformation inhibits the steps for n-butane cracking but also deactivation by coke, given that water adsorption on the active sites competes with coke precursor adsorption in the coke growing steps. 28,29 A further fact to be taken into account is that the heat released ''in situ'' in the dehydration of methanol on the same active sites avoids the presumable energy deficiency in the endothermic cracking step.…”

“…20 The reactor is made of 316 stainless steel with an internal diameter of 9 mm and 10 cm of effective length. It is located inside a ceramic covered stainless steel cylindrical chamber, which is heated by an electric resistance and can operate at up to 100 atm and 700 C with a catalyst mass of up to 5 g. The bed consists of a mixture of catalyst and inert solid (carborundum with an average particle diameter of 0.16 mm) to ensure bed isothermality and attain sufficient height under low-space-time conditions.…”

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

“…[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. [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.…”

Methanol-to-Olefin Conversion over UZM-9 Zeolite: Effect of Transition Metal Ion Exchange on its Deactivation

“…수 있어 효과적이다 [3][4][5]. MTO 공정 개발은 1980년대부터 시작되 었으나, 원유 가격이 오랫동안 낮게 유지되어서 2010년에 이르러 중 국에서 상업공장이 운전되고 있다 [6].…”