Selective production of propylene from methanol: Mesoporosity development in high silica HZSM-5

Mei, Changsong; Wen, Ping; Liu, Zhicheng; Liu, Hongxing; Wang, Yangdong; Yang, Weimin; Xie, Zaiku; Hua, Weiming; Gao, Zi

doi:10.1016/j.jcat.2008.06.019

Cited by 356 publications

(251 citation statements)

References 33 publications

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“…However, improved olefin and especially propylene selectivity can be achieved using highly siliceous H-ZSM-5. 5,6 The selectivity towards propylene is increased even more with the introduction of phosphorus. [6][7][8][9][10] Usually, the improved selectivity towards propylene is attributed to the decrease in the acid site strength that is so often observed in phosphated H-ZSM-5, although steric factors have also been suggested to be responsible.…”

Section: Introductionmentioning

confidence: 99%

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

127

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In order to elucidate phosphorus-zeolite H-ZSM-5 interactions, a variety of phosphorus-modified zeolite H-ZSM-5 materials were studied in a multi-spectroscopic manner. By deploying single pulse 27 Al, 31 P MAS NMR, 2D heteronuclear 27 Al-31 P correlation (HETCOR), 27 Al MQ MAS NMR spectroscopy, TPD of pyridine monitored by FT-IR spectroscopy, and Scanning Transmission X-ray Microscopy (STXM) the interplay and influence of acidity, thermal treatment and phosphorus on the structure and acidity of H-ZSM-5 were established. It was found that while acid treatment did not affect the zeolite structure, thermal treatment leads to the breaking of Si-OH-Al bonds, a decrease in the strong acid site number and the formation of terminal Al-OH groups. No extra-framework aluminium species was observed. Phosphorus precursors interact with the zeolitic framework through hydrogen bonds and physical coordination, as phosphorus species can be simply washed out with hot water. After phosphatation and thermal treatment two effects occur simultaneously, namely (i) phosphorus species transform into water insoluble condensed poly-phosphoric acid and (ii) phosphoric acid binds irreversibly to the terminal Al-OH groups of partially dislodged four-coordinated framework aluminium, forming local silico-aluminophosphate interfaces.These interfaces are potentially the promoters of hydrothermal stability in phosphated zeolite H-ZSM-5.

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Section: Introductionmentioning

confidence: 99%

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

127

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“…Light olefins are important basic raw materials for the petrochemical industry, and demand for light olefins such as ethylene and propylene is increasing every year [1,2]. Light olefins have been mainly produced by thermal cracking of naphtha, which gives yields of ethylene and propylene of approximately 25% and 13%, respectively [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Kinetics of n-hexane cracking over ZSM-5 zeolites – Effect of crystal size on effectiveness factor and catalyst lifetime

Konno

Okamura

Kawahara

et al. 2012

Chemical Engineering Journal

168

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The catalytic cracking of n-hexane over ZSM-5 zeolite (MFI-type zeolite, Si/Al = 150 and 240) catalysts was examined at reaction temperatures ranging from 823 to 923 K under atmospheric pressure. The reaction rate constants and activation energies of n-hexane cracking over ZSM-5 zeolites with various crystal sizes and Si/Al ratios were evaluated. The catalytic cracking of n-hexane was first order with respect to the n-hexane concentration, and the activation energies of n-hexane cracking over ZSM-5 zeolites were found to be approximately 123-128 kJmol -1 . Compared with the macro-sized zeolite, the nano-sized zeolites exhibited high n-hexane conversion with stable activity for 50 h. This is because the cracking reaction with nano-sized zeolite proceeded under reaction-limiting conditions, whereas the reaction with macro-sized zeolite proceeded under transition conditions between reaction-and diffusion-limiting conditions. As a result, the application of nano-zeolite to the catalytic cracking of n-hexane was effective and gave light olefins with high yield and excellent stable activity.

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“…The corresponding yield to major liquid aromatics obtained after 5 h reaction, including benzene, toluene, and xylenes (BTX) as well as tri-methyl benzene was calculated from methanol consumption of selected products and total methanol injected. The definitions below are based on previous researches and modified to this research [19,20].…”

Section: Methodsmentioning

confidence: 99%

A research into the thermodynamics of methanol to hydrocarbon (MTH): conflictions between simulated product distribution and experimental results

et al. 2017

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Thermodynamic calculations and analysis were carried out for a rational understanding of the results from selected laboratory MTH reactions. Simulations without solid carbons (coke), CO, CO 2 and light alkanes target on the yield of olefin and aromatic products, which has been found better referenced to the real experimental observations that occur in time-on-stream (TOS). The confliction between simulated data and real experimental results is presumably ascribed to the limited dwelling time of products in the reaction system. Hydrocarbon pool based reactions donate olefins and methyl-benzenes as primary products in a continuous-flow MTH reaction; when the dwelling time of product extends intra-conversions (H 2 transfers) between products would further adjust the composition of MTH yield, in which case alkanes and aromatic products (cokes precursors) increase. In the case of intraconversions are ignored due to limited product dwelling time, thermodynamic calculation on Gibbs free energy change of selected sub reactions shows fairly close results to the real experimental data, which well supports the above explanations. This work highlights the importance of proper choosing target products and/or sub reactions for a rational thermodynamic prediction of MTH product distribution obtained in time-on-stream.Keywords Methanol to hydrocarbon Á Hydrocarbon pool mechanism Á Thermodynamic Á Intra-conversion Á Dwelling time IntroductionAt present, the pathways of methanol to hydrocarbon reaction especially the formation of first C-C bond are still in debate. The most acceptable hypothesis by far relies on the mechanism based on a 'hydrocarbon pool' [1]. In this theory, limited trace amount of hydrocarbons introduced as impurities in the methanol feedstock formed the initial aromatics (some benzene ring structures), which play a key role as the 'scaffold' in later process [2]. Methyl groups are added onto the hydrocarbon pool molecules in alkylation steps and light olefins are subsequently formed by the corresponding de-alkylation steps. The initial olefins can be converted into alkanes by occupying H 2 , whereas continuous loss of H 2 , followed by the cyclization steps forms more aromatics [3][4][5]. In a mature MTH system, series of the above reactions proceed in a parallel way and, therefore, bring in a complexity to the products and orders of their formation; however, thermodynamics always say coke (extremely dehydrogenated products, or solid carbons) is the dominating product in MTH and most other hydrocarbon transformations [6]. Before the reaction reaches a final format of solid carbons [C (s) ], Electronic supplementary material The online version of this article

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Selective production of propylene from methanol: Mesoporosity development in high silica HZSM-5

Cited by 356 publications

References 33 publications

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Kinetics of n-hexane cracking over ZSM-5 zeolites – Effect of crystal size on effectiveness factor and catalyst lifetime

A research into the thermodynamics of methanol to hydrocarbon (MTH): conflictions between simulated product distribution and experimental results

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