CHA/AEI intergrowth materials as catalysts for the Methanol-to-Olefins process

Smith, R. L.; Svelle, Stian; Campo, Pablo del; Fuglerud, Terje; Arstad, Bjørnar; Lind, Anna; Chavan, Sachin; Attfield, Martin P.; Akporiaye, Duncan; Anderson, Michael W.

doi:10.1016/j.apcata.2015.06.027

Cited by 51 publications

(41 citation statements)

References 39 publications

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“…[silicon islands] environments, respectively (see SAPO-18_1 in Figure 5). This 29 Si MAS NMR spectrum indicates that the synthesis of the Si-rich SAPO-18 material using DIPEA as OSDA results in a SAPO catalyst, where almost 50% of the Si species are agglomerated under different Si environments. Similar Si distributions have been described in the literature for the SAPO-18 materials synthesized using DIPEA as OSDA.…”

Section: 1-zeolite Synthesis and Characterizationmentioning

confidence: 99%

“…[17] However, if the Si content is decreased for the preparation of the SAPO-18 using DIPEA, it can observed that the amount of Si species forming agglomerated Si environments are notoriously reduced (see 29 Si MAS NMR spectrum of SAPO-18_2 in Figure 5), improving the overall Si distribution as isolated species. On the other hand, the 29 Si MAS NMR spectra of the two SAPO-18 materials synthesized using DMDMP as OSDA, exhibit the presence of a single peak centered at -93 ppm (see SAPO-18_3 and _4 in Figure 5). This result indicates that all silicon atoms are selectively replacing phosphorous atoms within the SAPO-18 framework when DMDMP is used as OSDA, regardless the Si content introduced in the samples.…”

Section: 1-zeolite Synthesis and Characterizationmentioning

confidence: 99%

“…ICP analysis gives a Si/TO 2 molar ratio for SAPO-34 of 0.10 (see Table 3), and the 29 Si MAS NMR spectrum indicates the presence of a mixture of silicon environments, most of them as isolated silicon species (see signal centered at ~ -93 ppm, see Figure 5). Finally, NH 3 -TPD shows that SAPO-34 presents medium and strong Brønsted acid sites, with similar measured values to those obtained for the SAPO-18_4 (see Table 3).…”

Section: 1-zeolite Synthesis and Characterizationmentioning

confidence: 99%

“…The silicon distribution within the different SAPO-18 materials has been studied by solid 29 Si MAS NMR spectroscopy (see Figure 5). [silicon islands] environments, respectively (see SAPO-18_1 in Figure 5).…”

Section: 1-zeolite Synthesis and Characterizationmentioning

confidence: 99%

“…7 The 29 Si MAS NMR spectra were recorded at room temperature using a Bruker AV 400 spectrometer MAS, with a spinning rate of 5 kHz at 79.459 MHz a 55˚ pulse length of 3.5 µs and repetition time of 180 s. 29 Si chemical shift was referred to tetramethylsilane.…”

Section: 2-characterizationmentioning

confidence: 99%

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Improving the catalytic performance of SAPO-18 for the methanol-to-olefins (MTO) reaction by controlling the Si distribution and crystal size

Martínez-Franco

Martínez‐Triguero

et al. 2016

Catal. Sci. Technol.

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The physico-chemical properties of the small pore SAPO-18 zeotype have been controlled by properly selecting the organic molecules acting as organic structure directing agents (OSDAs). The two organic molecules selected to attempt the synthesis of the SAPO-18 materials were N,N-diisopropylethylamine (DIPEA) and N,N-dimethyl-3,5-dimethylpiperidinium (DMDMP). On one hand, DIPEA allows achieving small crystal sizes (0.1-0.3 µm) with limited silicon distributions when the silicon content in the synthesis gel is high (Si/TO 2 ~ 0.8). On the other hand, the use of DMDMP directs the formation of larger crystallites (0.9-1.0 µm) with excellent silicon distributions, even when the silicon content in the synthesis media is high (Si/TO 2 ~ 0.8). It is worth noting that this is the first description of the use of DMDMP as OSDA for the synthesis of the SAPO-18 material, revealing not only the excellent directing role of this OSDA to stabilize the large cavities present in the SAPO-18 structure, but also to selectively place the silicon atoms in isolated framework positions. The synthesized SAPO-18 materials have been characterized by different techniques, such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), N 2 adsorption, solid NMR, or ammonia temperature programmed desorption (NH 3 -TPD). Finally, their catalytic activity has been evaluated for the Methanol-to-Olefin (MTO) process at different reaction temperatures (350 and 400ºC), revealing that the SAPO-18 catalysts with optimized silicon distributions and crystal sizes show excellent catalytic properties for the MTO reaction. These optimized SAPO-18 materials present improved catalyst lifetimes compared to standard SAPO-34 and SSZ-39 catalysts, even when tested at low reaction temperatures (i.e. 350ºC). 3 1.-IntroductionThe Methanol-to-Olefins (MTO) process has received a significant attention in the last years since it has been considered as an alternative route for the production of light olefins, such as ethylene and propylene, which are currently mainly achieved from fluid catalytic cracking or steam cracking of hydrocarbons. [1,2] Small pore silicoaluminophosphate (SAPO) materials containing large cavities in their structures, have been described as the most efficient catalysts for the MTO reaction. [2,3] Indeed, SAPO-34 material, which is the silicoaluminophosphate form of the crystalline structure of CHA, [4] is being applied as commercial catalyst for this process. [3,5] It is claimed that the unique crystalline structure of CHA, combining the presence of large cavities (~ 6.7x10.9 Å) and small pores (~ 3.8 Å), allows the formation of the required bulky aromatic intermediate states, known as "hydrocarbon pool", and permits the preferential diffusion of the desired light olefins, respectively. [6,7,8,9,10] In addition to the SAPO-34 catalyst, other small pore SAPO materials presenting large cavities in their structure have also been studied as catalysts for the MTO process. [11,12] From the different SAPO materials, SAPO-18 has sho...

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Section: 1-zeolite Synthesis and Characterizationmentioning

confidence: 99%