Conversion of dimethyl ether into lower olefins on a La-Zr-HZSM-5/Al2O3 zeolite catalyst

Biryukova, E. N.; Goryainova, T. I.; Kulumbegov, R. V.; Колесниченко, Н. В.; Хаджиев, С. Н.

doi:10.1134/s0965544111010026

Cited by 19 publications

(5 citation statements)

References 2 publications

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“…Surely, the industrial implementation of the transformation of chloromethane into olefins will require the catalyst regeneration by coke combustion and the subsequent use of the regenerated catalyst in successive reaction–regeneration cycles, similarly to the MTO process (with SAPO-34 catalyst in a fluidized bed reactor and regeneration in another fluidized bed), and to the DTO process (with HZSM-5 zeolite catalyst, in a fixed bed reactor with in situ regeneration). , The stability of the catalysts has been studied by operating in successive reaction–regeneration cycles, under the following conditions: reaction step, 350 and 450 °C; space time, 2.35 and 5.89 g cat h (mol CH2 ) −1 ; time on stream, 75 min. The regeneration step involves two stages: (i) coke aging by sweeping the catalyst with He (20 min at the reaction temperature with a flow rate of 30 cm 3 min –1 ) in order to remove the volatile components and (ii) coke combustion in situ in the reactor with air (1 h at 550 °C with a flow rate of 30 cm 3 min –1 ).…”

Section: Resultsmentioning

confidence: 99%

“…This fact explains the essential role of shape selectivity by enhancing the blockage of SAPO-n crystals and, in the case of HZSM-5 zeolite, the flow of coke precursors towards the exterior of the crystals, thereby minimizing micropores blockage.3.3. Stability in reaction-regeneration cyclesSurely, the industrial implementation of the transformation of chloromethane into olefins will require the catalyst regeneration by coke combustion and the subsequent use of the regenerated catalyst in successive reaction-regeneration cycles, similarly to the MTO process (with SAPO-34 catalyst in a fluidized bed reactor and regeneration in another fluidized bed),50 and to the DTO process (with HZSM-5 zeolite catalyst, in a fixed bed reactor with in situ regeneration) 51,52. The stability of the catalysts has been studied by operating insuccessive reaction-regeneration cycles, under the following conditions: Reaction step: 350 and 450 ºC; space time, 2.35 and 5.89 g cat h (mol CH2 ) -1 ; time on stream, 75 min.…”

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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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Section: Resultsmentioning

confidence: 99%

mentioning

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 difference in its values for investigated samples is less than 0.3%. No distinct peaks for ZrO2 (2θ = [30][31][32][33][34][35][36][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] and MgO (2θ = 30-45, 62) were observed, possibly due to the low sensitivity of the applied method to samples with low metal concentrations. However, it may also be caused by fine dispersion of Zr and Mg particles [44] or the amorphous state of oxides [45].…”

Section: Catalysts 2018 8 X For Peer Review 3 Of 18mentioning

confidence: 99%

“…One of the main ways to influence activity and selectivity of zeolite-based catalysts of the oxygenate conversion is their modification. The HZSM-5 zeolite can be doped with elements-such as B [17,29], P [18,30], alkaline earth metals (Mg [31][32][33], Ca [15], Sr, and Ba [34]), and rare metals (La and Zr [16,35,36])-to increase the efficiency of the process. The chemical effect of modification for fresh samples consists of changing the acidity of the catalyst and the ratio of weak and strong Brönsted acid sites.…”

Section: Introductionmentioning

confidence: 99%

Dimethyl Ether to Olefins over Modified ZSM-5 Based Catalysts Stabilized by Hydrothermal Treatment

et al. 2019

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The reaction of dimethyl ether to olefin over HZSM-5/Al2O3 catalysts modified by Zr and Mg and stabilized by hydrothermal treatment has been studied. Regardless of the introduction method and the nature of the metal, the dependence of the key products selectivity on X(DME) over hydrothermally treated steady-state catalysts does not change, and the experimental points are described by the same curves. Metal introduction and the corresponding changes in the acid sites distribution do not change the ratio of main reaction rates, only the absolute values of the formation rate of the products are changed. Zr doping leads to the greatest activity in the DME conversion due to an equable decrease in the total acidity of the sample. On the other hand, the Mg-modified sample has a higher amount of weak acid sites, which reduces activity. At low DME conversion, methanol is one of the primary reaction products which formed from DME simultaneously with propylene in alkene cycle. At high DME conversion, the methanol acts as a main reagent which leads to ethylene formation in the arene cycle. Based on the results, the role of the metal in the reaction chemistry is considered and the mechanism of product formation from DME over steady-state catalyst is proposed, which describes both the participation of DME and the methanol produced.

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“…Metal doping is proven to help enhance the efficiency of the MTH process. Alkaline earth metal (e.g., Mg, Ca, Sr, and Ba), rare earth metals (e.g., La), transition metals (e.g., Co, Ni, Fe, and Zr), and other chemical elements, such B and P, are, among others, used to achieve higher selectivity to light olefins [20,[24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Impact of the Location of Magnesium in Zeolite-Based Shaped Catalyst Bodies on the Methanol-to-Hydrocarbons Process

et al. 2022

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Conversion of dimethyl ether into lower olefins on a La-Zr-HZSM-5/Al2O3 zeolite catalyst

Cited by 19 publications

References 2 publications

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

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

Dimethyl Ether to Olefins over Modified ZSM-5 Based Catalysts Stabilized by Hydrothermal Treatment

Impact of the Location of Magnesium in Zeolite-Based Shaped Catalyst Bodies on the Methanol-to-Hydrocarbons Process

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