Fluoride-treated H-ZSM-5 as a highly selective and stable catalyst for the production of propylene from methyl halides

Xu, Ting; Zhang, Qinghong; Song, Hang; Wang, Ye

doi:10.1016/j.jcat.2012.08.014

Cited by 69 publications

(56 citation statements)

References 61 publications

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“…determined that the kinetic constant of light olefins formation is greater for DME than for methanol and that of deactivation is greater too . Xu et al . and Fickel et al .…”

Section: Introductionmentioning

confidence: 99%

“…Pérez-Uriarte et al determined that the kinetic constant of light olefins formation is greater for DME than for methanol [38] and that of deactivation is greater too. [39] Xu et al [40] and Fickel et al [16] ratified that chloromethane suffer a similar sequence of transformations than methanol or DME, while Gamero et al [15] have identified that the entire reaction network of chloromethane is similar than the oxygenate counterparts. However, the observed reactivity of chloromethane is slower due the thermodynamically harder formation of methoxy species from this reactant.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

et al. 2019

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The conversions into hydrocarbons of methanol, dimethyl ether and chloromethane (MTH, DTH and CTH, respectively) on a H‐ZSM‐5 zeolite catalyst were compared trough ab‐initio calculations and experiments, using a fixed‐bed reactor and in‐situ FTIR spectroscopy. The molecular modelling of the reaction was performed using force field calculations. The nature and location of retained species were assessed by a combination of techniques. The experimental results of activity, product distribution and deactivation match these of the molecular modelling as the three reactions proceed through the dual‐cycle mechanism. However, the initiation, evolution and degradation of hydrocarbon pool species are kinetically different depending on the reactant. The reactions are faster in the order DTH>MTH≫CTH whereas the rate at which coke forms and grows (linked with the rate of deactivation) is in the order CTH≫DTH>MTH.

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“…determined that the kinetic constant of light olefins formation is greater for DME than for methanol and that of deactivation is greater too . Xu et al . and Fickel et al .…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

et al. 2019

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“…9,10 The lower reactivity of chloromethane with respect to methanol is related to its lower adsorption rate on Brønsted acid sites. 11 The chloromethaneto-hydrocarbons mechanism has been analyzed by FT-IR spectroscopy 12 and is believed to involve the following steps: (i) dissociation of chloromethane; (ii) formation of methoxy species on the acid sites; (iii) formation of poly-alkylbenzenes as active intermediates; (iv) olefins release, while parallel (v) hydrogen transfer and condensation reactions occur to form paraffins and aromatics. Other authors 13,14 observed that the steps (i) and (ii) are limiting the overall reaction and account for the longer induction period compared to the catalytic transformation of methanol in the MTH and MTO processes.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous coking and dealumination of zeolite H-ZSM-5 during the transformation of chloromethane into olefins

Ibáñez

Gamero

Ruiz‐Martínez

et al. 2016

Catal. Sci. Technol.

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ARTICLE This journal isThe deactivation pathways of a zeolite H-ZSM-5 catalyst, containing bentonite and α-Al2O3 as binder material, have been studied during the transformation of chloromethane into light olefins, which is considered as a possible step to valorize methane from natural gas. The reactions have been carried out in a fixed bed reactor, feeding pure chloromethane at 400, 425 and 450 °C; 1.5 bar and with a space-time of 5.4 (gcatalyst) h (molCH2) -1 during 255 min. The properties of the fresh and spent catalysts have been assessed by several techniques, such as N2 physisorption, adsorption/desorption of NH3, XPS and 29 Si NMR. Additional measurements of the spent catalysts have been performed to study the nature of the deactivating coke species: TG-TPO, SEM, FT-IR and UV-vis spectroscopies. With the results in hand, two deactivation mechanisms were proposed: irreversible dealumination at temperatures higher than 450 °C by HCl and reversible coke fouling, while coke formation results from the condensation of poly-alkylbenzenes, which are also intermediates for olefin production. The coke deposits grow in size with the addition of Cl to the carbonaceous structure.

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“…The most widely studied catalysts in the transformation of chloromethane are SAPO-34 10-16 (used in the MTO process) and HZSM-5 zeolite (used in the DTO process), with different modifications, mainly by means of metal incorporation. [17][18][19][20][21][22] Furthermore, spectroscopic studies show that the reaction mechanism on both catalysts proceeds, as in the MTO and DTO processes, through the formation of The SAPO-18 has been synthesized following the method by Chen et al, 28 from a source of aluminum (Al 2 O 3 3H 2 O) and N,N-diisopropylethylamine (iPr 2 EN) as organic template. The preparation method of SAPO-34 has been the proposed by Wendelbo et al, 29 using aluminum isopropoxide (Al(OC 3 H 7 ) 3 ) as aluminum source, tetraethylammonium hydroxide (TEAOH, 20 wt%) as organic template and HCl (35 wt%) for pH control.…”

Section: Introductionmentioning

confidence: 99%

Role of Shape Selectivity and Catalyst Acidity in the Transformation of Chloromethane into Light Olefins

Gamero

Aguayo

Ateka

et al. 2015

Ind. Eng. Chem. Res.

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The transformation of chloromethane into light olefins (C 2 -C 4 ) has been studied both on HZSM-5 catalysts with different SiO 2 /Al 2 O 3 ratios (30, 80 and 280) and on SAPO-n catalysts in order to analyze the role of shape selectivity and acidity in the kinetic behavior. The catalysts have been prepared by agglomerating these acid functions with bentonite and -Al 2 O 3 , and the kinetic runs have been performed in a fixed bed reactor under the following operating conditions: 350 and 450 ºC; space time, 2.35, 5.89 and 14.99 g cat h (mol CH2 ) -1 ; and time on stream, 255 min. A comparison of the reaction indices (conversion of chloromethane, selectivity to light olefins and propylene fraction) at zero time and throughout time on stream using the different catalysts has allowed establishing, on the one hand, the significance of the shape selectivity and acidity of these catalysts (which are more influential in this reaction than in the transformation of methanol), and on the other, the need for a compromise between these properties. A HZSM-5 zeolite catalyst with moderate acidity (SiO 2 /Al 2 O 3 = 80) has a good kinetic behavior at 350 °C, and recovers its activity by coke combustion with air. However, all the catalysts studied undergo irreversible deactivation at 450 °C by dealumination of the acid function to form AlCl 3 . Highlights-Shape selectivity and acidity are essential for stability and olefin selectivity -The significance of these factors is greater than in the transformation of methanol -The acidity and severity of shape selectivity favor deactivation -A SiO 2 /Al 2 O 3 ratio of 80 for the HZSM-5 zeolite is suitable -Deactivation occurs by coke deposition at 350 ºC and also by dealumination at 450 ºC Abstract Chloromethane SAPO-n HZSM-5 zeolite 0 5 10 15 20 25 30 35 40 45 CZ-30 CZ-80 CZ-280 CS-18 CS-34 Yield, % M O C5+ P BTX Methane C2-C4 olefins HC5+ C2-C4 paraffins Aromatics (BTX) SAPO-18 SAPO-34 HZSM-5 zeolite 280 30 SiO2/Al2O3 = 80 methoxy ions as active species for the formation of polymethylbenzenes as intermediate compounds. These intermediates release light olefins, being also the precursors of the coke that blocks the catalyst micropores. 22,23 Although the aforementioned studies reveal many similarities in the kinetic behavior of SAPO-34 and HZSM-5 zeolite in the MTO and DTO processes, the lower activity in the transformation of chloromethane and the faster deactivation should be highlighted. The deactivation of HZSM-5 zeolite catalyst in the transformation of chloromethane has been studied in a previous work, showing similarities with the transformation of methanol according to the mechanisms involving reaction steps and coke formation and growth throughout time on stream. 24 This work explores the role that the key properties of the catalysts acidity and shape selectivity play in the transformation of chloromethane into olefins, i.e., the effect these properties have on activity, selectivity to light olefins and stability. Therefore, two different families of catalysts with different...

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Fluoride-treated H-ZSM-5 as a highly selective and stable catalyst for the production of propylene from methyl halides

Cited by 69 publications

References 61 publications

Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

Simultaneous coking and dealumination of zeolite H-ZSM-5 during the transformation of chloromethane into olefins

Role of Shape Selectivity and Catalyst Acidity in the Transformation of Chloromethane into Light Olefins

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