Influence of Catalyst Acidity on Dealkylation, Isomerization and Alkylation in MTA Process

Jin-Gui, ZHANG; Qian, Weizhong; Tang, Xiaoping; Kui, SHEN; Wang, Tong; Huang, Xin; Wei, Fei

doi:10.3866/pku.whxb201304101

Cited by 9 publications

(5 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…ZSM-5 is mainly used as catalyst in acid-catalyzed reactions. And thus besides the porosity, the type, strength and the relative amount of the acid sits played an important role during the catalytic reactions, which might influence the conversion, selectivity 30,31 . The acid properties of the prepared samples were characterized using NH3-TPD and pyridine-adsorbed FTIR (Fig.…”

Section: Resultsmentioning

confidence: 99%

Green and Cost-Effective Preparation of Small-Sized ZSM-5

薛腾¹,

董黎路²,

Ying³

et al. 2018

Acta Physico-Chimica Sinica

View full text Add to dashboard Cite

Small-sized zeolite ZSM-5 for a wide SiO2/Al2O3 ratio range was prepared using a small amount of colloidal silicalite-1 as the active seeds. The thus-prepared small-sized ZSM-5 samples have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption analysis, temperature-programmed ammonium desorption (NH3-TPD) analysis, and adsorbed pyridine infrared spectroscopy (Py-IR). The use of the active silicalite-1 seeds was effective in directing the reaction towards the formation of the MFI phase, avoiding the impure phases and reducing the crystal sizes. The prepared sample exhibited aggregated morphologies when a lower ratio of starting batch SiO2/Al2O3 (SiO2/Al2O3 ratio = 30) was used. The aggregates, with the size of ~500 nm, were formed with nano-sized primary crystals 50 nm in size, possessing large external surface area (84.9 m 2 •g −1 ) and secondary pore volume (0.22 cm 3 •g −1 ) and relatively regular mesopores. Different morphologies could be observed when the SiO2/Al2O3 ratio was increased (SiO2/Al2O3 ratio = 60-120). ZSM-5 with the size of 200 nm could be prepared, with the external surface area and the secondary pore volume being ~60 m 2 •g −1 and 0.10 cm 3 •g −1 , respectively. It should be highlighted that all the prepared samples could be directly ion-exchanged to obtain the acidic H-form samples without complete blocking of the micropores due to the low dose of the organic structure-directing agent. The obtained acidic H-form samples exhibited acidic properties similar to the samples ion-exchanged after calcination and the conventional ZSM-5 possessing similar SiO2/Al2O3 ratio, showing catalytic performance comparative to the catalytic conversion of methanol to olefins. Compared with conventional methods, this method largely reduced the use of organic templates and avoided the subsequent combustion before ion-exchange. The method is green and cost-effective, possessing wide potentials in the industrial processes.

show abstract

Section: Resultsmentioning

confidence: 99%

Green and Cost-Effective Preparation of Small-Sized ZSM-5

薛腾¹,

董黎路²,

Ying³

et al. 2018

Acta Physico-Chimica Sinica

View full text Add to dashboard Cite

show abstract

“…In brief, the acid strength that is required to catalyze the main reaction and the side reactions follows the order methylation < isomerization < dealkylation < disproportionation. 60,61 The alkylation process of NA belongs to a shape-selective catalytic reaction, for which the molecular sizes of the reaction products are β,β-DMN < α,β-DMN < α,α-DMN. So the increase of the weak acid sites and proper shrinkage of the pore size caused by Al doping are beneficial to improving the selectivity of β,β-DMN (Table 4).…”

Section: Catalytic Activity Evaluationmentioning

confidence: 99%

Methylation of Naphthalene with Methanol over the Al-Modified SiO₂ Zeolite Catalysts

Zhong,

Xu,

et al. 2024

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

2,6-Dimethylnaphthalene (2,6-DMN) is a crucial intermediate in the synthesis of poly(ethylene naphthalate), a heatresistant insulating material. The key to synthesizing 2,6-DMN is the development of highly active catalysts, which still remains challenging. Herein, bare SiO 2 and a series of Al-modified SiO 2 catalysts (denoted as Al-SiO 2 ) were successfully synthesized through a hydrothermal method using sodium metaaluminate as the Al source. The prepared catalysts were used for catalytic alkylation of naphthalene, and it was found that the Al-doped SiO 2 exhibited better catalytic activity than bare SiO 2 . The main reason is ascribed to the increased acid sites for Bronsted and Lewis acids with the incorporation of Al. Among the Al-modified SiO 2 samples, the amount of weak and total acidities was the highest for the 30Al-SiO 2 sample. In addition, the reaction conditions over this prepared catalyst were studied and optimized. The results showed that it exhibited the highest activity when the temperature was 300 °C and the weight hourly space velocity was 1 h −1 . Furthermore, density functional theory calculations showed that the doping of Al into SiO 2 enhanced the adsorption of methanol, resulting in a faster rate of formation of methoxylated material in the first step. Besides, methylation at the 6 position was slightly preferred compared to that at the 7 position, in line with the experimental results.

show abstract

“…63 Correspondingly, due to the inhibition of methanol self-reaction, the formation of the byproduct ethylene was reduced, and the selectivity of ethylbenzene formed by benzene alkylation with ethylene decreased from 18% to 15%. Furthermore, the weakly acidic sites not only allowed more methoxy groups to participate in the alkylation of toluene but also weakened the dealkylation of polymethylbenzene species, 64 which together resulted in a selectivity of trimethylbenzene of up to 8%. Based on the above results, a brief schematic summarizes the various reactions in Figure 8d and the effect of water on the alkylation of methanol with benzene.…”

Section: Catalytic Effect Of Al 2 O 3 On Co 2 Hydrogenationmentioning

confidence: 99%

Boosting Benzene Alkylation Conversion with CO₂/H₂ via a Triple Composite Catalyst

Cao,

Fu,

Liu

et al. 2024

ACS Catal.

View full text Add to dashboard Cite

The alkylation of benzene with CO 2 /H 2 to synthesize toluene and xylene is of great significance for alleviating carbon emissions and upgrading light aromatics toward value-added chemicals. However, the alkylation reagent from CO 2 hydrogenation showed relatively weak alkylation activity and severe self-reaction, leading to a low alkylation efficiency. Here, a high-performance triple composite catalytic system was constructed by using ZnZrO x oxide, Al 2 O 3 oxide, and H-ZSM-5 zeolite as catalyst components for the alkylation of benzene with CO 2 /H 2 to toluene and xylene. According to the results, CO 2 is hydrogenated to methanol on oxygen vacancies, methanol is dehydrated to dimethyl ether (DME) on Lewis acid sites, and benzene is then alkylated with the formed DME to toluene and xylene over the acidic sites of the zeolite. The combined selectivity of toluene and xylene among all hydrocarbons reached 97% at a benzene conversion of 9.7%, surpassing that of most reported traditional catalysts. The methanol dehydration to DME is responsible for the high alkylation activity, providing more alkylation reagents with high activity and suppressing the self-reaction of methanol to light hydrocarbons (C1−C5). More importantly, water is formed by methanol dehydration before the alkylation step and outside the zeolite, thus reducing the competitive adsorption of benzene and water on the acidic sites in the zeolite channel, consequently increasing the conversion of benzene and improving the catalytic stability. The establishment of the triple composite catalytic system in this work opens valuable horizons for enhancing the alkylation of benzene by coupling with CO 2 hydrogenation.

show abstract

Influence of Catalyst Acidity on Dealkylation, Isomerization and Alkylation in MTA Process

Cited by 9 publications

References 4 publications

Green and Cost-Effective Preparation of Small-Sized ZSM-5

Green and Cost-Effective Preparation of Small-Sized ZSM-5

Methylation of Naphthalene with Methanol over the Al-Modified SiO₂ Zeolite Catalysts

Boosting Benzene Alkylation Conversion with CO₂/H₂ via a Triple Composite Catalyst

Contact Info

Product

Resources

About

Influence of Catalyst Acidity on Dealkylation, Isomerization and Alkylation in MTA Process

Cited by 9 publications

References 4 publications

Green and Cost-Effective Preparation of Small-Sized ZSM-5

Green and Cost-Effective Preparation of Small-Sized ZSM-5

Methylation of Naphthalene with Methanol over the Al-Modified SiO2 Zeolite Catalysts

Boosting Benzene Alkylation Conversion with CO2/H2 via a Triple Composite Catalyst

Contact Info

Product

Resources

About

Methylation of Naphthalene with Methanol over the Al-Modified SiO₂ Zeolite Catalysts

Boosting Benzene Alkylation Conversion with CO₂/H₂ via a Triple Composite Catalyst