Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves

Zhang, Aihua; Sun, Shouli; Komon, Zachary J. A.; Osterwalder, Neil; Gadewar, Sagar B.; Stoimenov, Peter K.; Auerbach, Daniel J.; Stucky, Galen D.; McFarland, Eric W.

doi:10.1039/c0cp01985b

Cited by 35 publications

(30 citation statements)

References 35 publications

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“…In general, the hydrothermal conditions of the regeneration may cause a redistribution of silicon atoms into aggregates termed “silicon islands” 9, 10. This will lead to the formation of silanol groups that can be detected with IR spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

2016

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Operando UV/Vis spectroscopy with on‐line mass spectrometry was used to study the effect of different types of impurities on the hydrocarbon pool species and the activity of H‐SAPO‐34 as a methanol‐to‐olefins (MTO) catalyst. Successive reaction cycles with different purity feedstocks were studied, with an intermittent regeneration step. The combined study of two distinct impurity types (i.e., feed and internal impurities) leads to new insights into MTO catalyst activation and deactivation mechanisms. In the presence of low amounts of feed impurities, the induction and active periods of the process are prolonged. Feed impurities are thus beneficial in the formation of the initial hydrocarbon pool, but also aid in the unwanted formation of deactivating coke species by a separate, competing mechanism favoring coke species over olefins. Further, feedstock impurities strongly influence the location of coke deposits, and thus influence the deactivation mechanism, whereas a study of the organic impurities retained after calcination reveals that these species are less relevant for catalyst activity and function as “seeds” for coke formation only.

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Section: Resultsmentioning

confidence: 99%

“…Over time, great efforts have been made towards decreasing deactivation rates and increasing catalyst activity. Critical improvements have been made by modification of the catalyst crystal size and acidity; and an increased catalyst lifetime is reported for smaller crystal size and lower acidity 5, 6, 7, 8, 9, 10, 11…”

Section: Introductionmentioning

confidence: 99%

Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

2016

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“…Many contributions involving the conversion of chloromethane or bromomethane to olefins over various zeolite catalysts have been made in recent years [36][37][38][39][40][41][42][43]. Su and co-workers comparatively investigated the transformation of chloromethane to hydrocarbons over different zeolite catalysts and proposed the reaction mechanism over SAPO-34 molecular sieve [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…Olsbye et al studied the methyl halide to hydrocarbon reaction over HSAPO-34 in experimental and computational methods [41,42]. McFarland et al reported an improved light olefins yield from bromomethane over metal modified SAPO-34 catalyst [43]. In summary, SAPO-34 could be the most promising catalyst in the reaction of methyl halide to give olefins until now, like in the MTO process.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of SAPO-34 with the presence of additives and their catalytic performance in the transformation of chloromethane to olefins

Kong

Shen

Jiang

et al. 2014

Reac Kinet Mech Cat

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SAPO-34 molecular sieves were synthesized in the presence of soluble starch, sodium dodecyl sulfate and cetyltrimethylammonium bromide as the additives under hydrothermal conditions, and the differences stemmed from the additives among all obtained SAPO-34 samples were characterized by XRD, SEM, BET, NH 3 -TPD and TG. Compared with the conventional SAPO-34 sample, the SAPO-34 samples modified by sodium dodecyl sulfate and cetyltrimethylammonium bromide showed less crystalline order, enlarged mesopore volume and external surface area and a reduction in total acidity amounts. Meanwhile, the SAPO-34 modified by soluble starch exhibited more total acidity amounts than the conventional SAPO-34 samples. The SAPO-34 samples modified by sodium dodecyl sulfate and cetyltrimethylammonium bromide showed better catalytic stability and less carbon deposition than the conventional SAPO-34 catalyst in the conversion of chloromethane to olefins due to the reduction in total acid sites and the increasing mesopore volume. The overall results of this study demonstrate that it is an effective way to modify the SAPO-34 molecular sieve with sodium dodecyl sulfate and cetyltrimethylammonium bromide as the additives for improving the SAPO-34 catalyst stability in the transformation of chloromethane to olefins.Keywosrds SAPO-34 Á Soluble starch Á Sodium dodecyl sulfate Á Cetyltrimethylammonium bromide Á Chloromethane Á Light olefins Electronic supplementary material The online version of this article (

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“…An alternative pathway for methane partial oxidation using bromine, rather than oxygen, has been demonstrated and piloted [5][6][7][8][9]. Bromine can be generated from the reaction of oxygen with hydrogen bromide (HBr), or from many solid metal bromides (MBr 2 ), (reaction 1).…”

Section: Introductionmentioning

confidence: 99%

Molten salt chemical looping for reactive separation of HBr in a halogen-based natural gas conversion process

Upham

Snodgrass

Zavareh

et al. 2017

Chemical Engineering Science

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Hydrogen bromide (HBr) oxidation to molecular bromine (Br 2 ) is demonstrated in a chemical looping process using a molten bromide salt. The two-step process is operated at 500 °C and first contacts oxygen with molten KBr-LiBr-NiBr 2 to form Br 2 gas and a suspension of nickel oxide (NiO) particles in one reactor. The oxide suspension is then contacted with HBr to regenerate the bromide salt and produce steam. Sixty-eight metal oxides/bromides were considered. The cyclic interconversion between oxide and bromide, by alternating exposure to HBr and oxygen, at a single temperature was only possible with nickel. In contrast to solidbased chemical looping systems, the liquid bromide salt (NiBr 2 dissolved in KBr-LiBr eutectic) was found to be cycleable without attrition or deactivation. Further, when mixtures of olefins and hydrogen bromide were reacted with the oxide suspension, selective oxidation of HBr was observed without hydrocarbon oxidation. High selectivity for HBr oxidation is due to the solubility of HBr in the molten salt, which allows contact with NiO, whereas, the insoluble hydrocarbons do not contact the reactive oxide. A process model that makes use of reactive separation of HBr from hydrocarbons and process intensification using molten salt-based chemical looping is presented as a potentially lower cost alternative to a process model using conventional separations in bromine-based methane conversion. The total heat exchanged in a corrosive environment in the molten salt based process is 205 MW, and the heat exchanged in a corrosive environment in the conventional process is 581 MW.

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Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves

Cited by 35 publications

References 35 publications

Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

Synthesis of SAPO-34 with the presence of additives and their catalytic performance in the transformation of chloromethane to olefins

Molten salt chemical looping for reactive separation of HBr in a halogen-based natural gas conversion process

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