Controlled decrease of acid strength by orthophosphoric acid on ZSM5

Lercher, Johannes A.; Rumplmayr, Gerd

doi:10.1016/s0166-9834(00)81239-7

Cited by 126 publications

(83 citation statements)

References 17 publications

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“…Similar results were reported in the literature (Hodala et al, 2014;Takahashi et al, 2012;Lu and Liu, 2011;Song et al, 2010;Vu et al, 2010;Li et al, 2010;Ramesh et al, 2009;Zhao et al, 2007;Lercher and Rumplmayr, 1986). The addition of P up to 1.2 wt.…”

Section: Catalyst Characterizationsupporting

confidence: 91%

“…Phosphorus addition to HZSM-5 caused a decrease in the total acid site density. It also appears that the decrease in strong acid sites density was greater than that observed for weak acid sites, as reported previously (Takahashi et al, 2012;Lu and Liu, 2011;Ramesh et al, 2009;Song et al, 2010;Vu et al, 2010;Li et al, 2010;Zhao et al, 2007;Lercher and Rumplmayr, 1986).…”

Section: Catalyst Characterizationsupporting

confidence: 85%

“…However, the addition of phosphorus resulted in a minor modification in the density of Brönsted acid sites. Lercher and Rumplmayr (1986) showed that adding H3PO4 to HZSM-5 might convert strong Brönsted acid sites to weak ones, without altering the acid-base properties in general. However, Lischke et al (1991) reported a decrease in the density of Brönsted acid sites as a result of interaction of H3PO4 with the framework hydroxyl groups of HZSM-5.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

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Synthesis of Propylene From Ethanol Using Phosphorus-Modified HZSM-5

Costa

Silva

2016

Braz. J. Chem. Eng.

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-Effects of phosphorus addition to HZSM-5 on ethanol conversion to propylene were evaluated. Catalysts were characterized by XRF, XRD, nitrogen adsorption, 27Al and 31 P MAS NMR, n-propylamine and ammonia TPD. Increasing P content decreased the strength and density of acid total sites. Ethanol dehydration was carried out in a fixed bed reactor operating at atmospheric pressure. Conversion was around 100% for all catalysts. 1.2 wt% of P catalyst showed the highest propylene yield, and was used to evaluate temperature and ethanol partial pressure effects on the product distribution. The highest propylene accumulated productivity was obtained for an ethanol partial pressure of 0.4 atm. Propylene formation was favored in the temperature range 475-500 °C. Significant changes in the product distribution as a function of time on stream were observed at higher temperatures, suggesting stronger catalyst deactivation. The ethylene yield decreased up to 500 °C, rising significantly at 550 °C, possibly due to heavier product cracking reactions.

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Section: Catalyst Characterizationsupporting

confidence: 91%

Section: Catalyst Characterizationsupporting

confidence: 85%

Section: Catalyst Characterizationmentioning

confidence: 99%

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Synthesis of Propylene From Ethanol Using Phosphorus-Modified HZSM-5

Costa

Silva

2016

Braz. J. Chem. Eng.

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“…9a and c which is in accordance to literature. 7,12,14,17,18 STXM data presented in Fig. 8 reveal both inter-, and intraparticle heterogeneities in the distribution of phosphorus.…”

Section: Effect Of Thermal Treatment On Phosphated Samplesmentioning

confidence: 89%

“…[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. [6][7][8][9][10][11][12] Even though there is still some debate on the effect of acid site strength on the MTO product distribution, the promoting effect of phosphorus on the hydrothermal stability of H-ZSM-5 is undisputed. 4,9,[13][14][15][16][17][18][19][20][21][22][23][24][25] Zeolite H-ZSM-5 catalysts that contain phosphorus are more stable under hydrothermal conditions i.e.…”

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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