Effect of pre-dealumination by (NH4)2SiF6 on the properties of ZSM-5 with steam aging treatment

Huang, Limin; Li, Quanzhi; Xue, Zhixin; Ding, Guangya; Niu, Guoxing; Li, Zaiting; Zhicheng, Shi

doi:10.1016/s0167-2991(97)80666-0

Cited by 3 publications

(2 citation statements)

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“…This would force the proximity of nickel with a Brønsted acid site, either terminal or pseudo‐bridged one, and enhance electrodeficiency of the nickel atom to increase its activity . Inspired by the action of ammonium hexafluorosilicate, (NH 4 ) 2 SiF 6 , to dealuminate zeolites by substituting aluminum atoms with silicon atoms under the action of SiF 6 2− , we used commercial nickel hexafluorosilicate, NiSiF 6 , as a nickel precursor for incipient wetness impregnation on alumina. Its high water solubility allows for a single‐step impregnation by the pore saturation technique.…”

Section: Resultsmentioning

confidence: 99%

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

2017

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Only a few catalytic transformations can be efficiently catalyzed by both homogeneous or heterogeneous technologies, with short olefin oligomerization promoted by a nickel‐based catalysts among them. Homogeneous and heterogeneous catalysis are often opposed in terms of activity, active‐site description or recyclability, traditionally mentioned as “homogeneous versus. heterogeneous”. Unlike previous studies, we propose to emphasize the similarities between both catalysis by comparing industrially representative results obtained in continuous flow‐mode under similar mild conditions. A detailed analysis of both primary products of olefins oligomerization, and a set of secondary products obtained in experimental assays completed with recently published results of DFT calculations prompted us to postulate a common mechanistic pathway for nickel‐catalyzed ethylene oligomerization. Heterogeneous metallic ethylene oligomerization, for which nickel active sites identification has indeed long been under debate, seems to follow the Cossee–Arlman mechanism, well accepted as major mechanism in the homogeneous counterpart. This analysis allowed us to design an unprecedented heterogeneous catalyst active for ethylene and butene oligomerization.

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Section: Resultsmentioning

confidence: 99%

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

2017

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“…These results indicated that silylation took place on the surface and caused pore narrowing and blockage. Hibino et al [20] and Weber et al [13] reported pore narrowing and increase in the external surface area of ZSM-5 upon silicon alkoxides deposition [13,15,[18][19][20].…”

Section: Resultsmentioning

confidence: 99%

Effect of different acidity modifications on the activity and selectivity on H-ZSM5 zeolites in n-butene isomerization

Kılıç

2014

Reac Kinet Mech Cat

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H-ZSM-5 was modified by silylation [tetraethylorthosilicate (TEOS) and triaminopropyltriethoxysilane], alkali (NaOH), acid (HCl) and ammoniumhexafluorosilicate (AHFS) treatments. The parent and modified zeolite forms were tested in n-butene isomerization. Modifications affected total acidities, the strength of the acid sites, pore sizes and surface areas of the H-ZSM-5 differently. The modifications decreased the conversion obtained by the parent catalyst. TEOS and alkali modifications did not promote formation of isobutene. Pre-alkali treatment before acid treatment increased selectivity to isobutene from 56.0 to 66.7 %, while conversion changed a little, it dropped from 52 to 50 %. AHFS modification provided the highest enhancement in selectivity to isobutene (87.5 %) for which n-butene conversion was dropped by about 10 % compared to H-ZSM-5. This was attributed to a slight modification of the pore size and to the reduction in strong and weak acid sites and generation of new Lewis acid sites.

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Catalytic Upgrading of Lignite Pyrolysis Volatiles over AlF₃-Modified HZSM-5 to Light Aromatics: Synergistic Effects of One-Step Dealumination and Realumination

Zhao

Cao

et al. 2021

Energy Fuels

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Aluminum fluoride (AlF3)-modified HZSM-5 obtained by simple mechanical mixing and calcination was used to enhance the conversion of the lignite pyrolysis volatiles to light aromatics. The results revealed that the appropriate amount of AlF3 modification can simultaneously dealuminize and aluminize to enhance the catalytic performance, in which dealumination considerably enlarged the pores while realumination generated more midstrength acid sites to compensate for the loss of acid sites caused by dealumination. HZ-2 (HZSM-5 mixed with 2 wt % AlF3) obtained the maximum light aromatics yield of 31.0 mg/g as a result of its abundant mesopores and suitable midstrength acid sites, especially the yield of benzene increased by 6.3 mg/g in comparison with that of the original HZSM-5. However, mixing with only a small amount of AlF3 generated the most serious carbon depositions because of the acidity enhancement by the critical role of alumination. Moreover, excessive AlF3 etched more framework Al that dramatically reduced the midstrength acid sites, inhibiting the formation of light aromatics, although the enlargement of pore size facilitated mass transfer. This one-step modification combining the expansion of the pore size and the optimization of acid sites provides a promising strategy for upgrading the lignite pyrolysis volatiles.

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Effect of pre-dealumination by (NH4)2SiF6 on the properties of ZSM-5 with steam aging treatment

Cited by 3 publications

References 2 publications

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

Effect of different acidity modifications on the activity and selectivity on H-ZSM5 zeolites in n-butene isomerization

Catalytic Upgrading of Lignite Pyrolysis Volatiles over AlF₃-Modified HZSM-5 to Light Aromatics: Synergistic Effects of One-Step Dealumination and Realumination

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Effect of pre-dealumination by (NH4)2SiF6 on the properties of ZSM-5 with steam aging treatment

Cited by 3 publications

References 2 publications

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

Homogeneous and Heterogeneous Nickel‐Catalyzed Olefin Oligomerization: Experimental Investigation for a Common Mechanistic Proposition and Catalyst Optimization

Effect of different acidity modifications on the activity and selectivity on H-ZSM5 zeolites in n-butene isomerization

Catalytic Upgrading of Lignite Pyrolysis Volatiles over AlF3-Modified HZSM-5 to Light Aromatics: Synergistic Effects of One-Step Dealumination and Realumination

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Catalytic Upgrading of Lignite Pyrolysis Volatiles over AlF₃-Modified HZSM-5 to Light Aromatics: Synergistic Effects of One-Step Dealumination and Realumination