scholarly journals Solvent-Free Synthesis of Jasminaldehyde in a Fixed-Bed Flow Reactor over Mg-Al Mixed Oxide

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1033
Author(s):  
Zahra Gholami ◽  
Zdeněk Tišler ◽  
Pavla Vondrová ◽  
Romana Velvarská ◽  
Kamil Štěpánek

In spite of the rapid developments in synthesis methodologies in different fields, the traditional methods are still used for the synthesis of organic compounds, and regardless of the type of chemistry, these reactions are typically performed in standardized glassware. The high-throughput chemical synthesis of organic compounds such as fragrant molecules, with more economic benefits, is of interest to investigate and develop a process that is more economical and industrially favorable. In this research, the catalytic activity of Mg-Al catalyst derived from hydrotalcite-like precursors with the Mg/Al molar ratio of 3 was investigated for the solvent-free synthesis of jasminaldehyde via aldol condensation of benzaldehyde and heptanal. The reaction was carried out in a fixed-bed flow reactor, at 1 MPa, and at different temperatures. Both Brønsted and Lewis (O2− anions) base sites, and Lewis acid sites exist on the surface of the Mg-Al catalyst, which can improve the catalytic performance. Increasing the reaction temperature from 100 °C to 140 °C enhanced both heptanal conversion and selectivity to jasminaldehyde. After 78 h of reaction at 140 °C, the selectivity to jasminaldehyde reached 41% at the heptanal conversion 36%. Self-condensation of heptanal also resulted in the formation of 2-n-pentyl-2-n-nonenal. The presence of weak Lewis acid sites creates a positive charge on the carbonyl group of benzaldehyde, and makes it more prone to attack by the carbanion of heptanal. Heptanal, is an aliphatic aldehyde, with higher activity than benzaldehyde. Therefore, the possibility of activated heptanal reacting with other heptanal molecules is higher than its reaction with the positively charged benzaldehyde molecule, especially at a low molar ratio of benzaldehyde to heptanal.

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 835
Author(s):  
Xia Xiao ◽  
Zhongliang Xu ◽  
Peng Wang ◽  
Xinfei Liu ◽  
Xiaoqiang Fan ◽  
...  

Solvent-free synthesis methodology is a promising technique for the green and sustainable preparation of zeolites materials. In this work, a solvent-free route was developed to synthesize SAPO-34 zeolite. The characterization results indicated that the crystal size, texture properties, acidity and Si coordination environment of the resulting SAPO-34 were tuned by adjusting the SiO2/Al2O3 molar ratio in the starting mixture. Moreover, the acidity of SAPO-34 zeolite was found to depend on the Si coordination environment, which was consistent with that of SAPO-34 zeolite synthesized by the hydrothermal method. At an SiO2/Al2O3 ratio of 0.6, the SP-0.6 sample exhibited the highest conversion of 1-butene (82.8%) and a satisfactory yield of light olefins (51.6%) in the catalytic cracking of 1-butene, which was attributed to the synergistic effect of the large SBET (425 m2/g) and the abundant acid sites (1.82 mmol/g). This work provides a new opportunity for the design of efficient zeolite catalysts for industrially important reactions.


2016 ◽  
Vol 78 (6) ◽  
Author(s):  
Djoko Hartanto ◽  
Lai Sin Yuan ◽  
Sestriana Mutia Sari ◽  
Djarot Sugiarso ◽  
Irmina Kris Murwarni ◽  
...  

Lewis and Brönsted acidity were studied on ZSM-5 with combination of pyridine adsorption and FTIR vibration, ZSM-5 synthesized using kaolin Bangka Indonesia with an increase in the molar ratio of Si/Al 30-60 without pre-treatment and without organic templates and with seeds silicalite. Interestingly, the intensity of the infrared showed an increase of band vibration pyridine as absorbed Brönsted and Lewis acid sites in a molar ratio increase of Si/Al in ZSM-5, indicating an increase in the number of silanol (Brönsted acid) and deformed silica (Lewis acid) because the amount of Aluminum in ZSM-5 decrease with increase Si/Al but amount acidity increase. 29Si and 27Al MAS NMR analysis was supported by the results of infrared to indicate that all of the aluminum atom is coordinated with their neighbors are the same in ordering the ZSM-5 framework and 27Al MAS NMR showed a sharp peak of all the variations of Si/Al except the Si/Al 30 shows a low peak area. XRD analysis supported that the ZSM-5 structure formed is pure and crystal and a decrease in crystallinity proven for more than Si/Al 50, that defects silica occurs in ZSM-5, this corresponds to the growing number of Lewis acid sites caused by defects silica described the infrared results.


Author(s):  
Ehsan Kianfar ◽  
Mahmoud Salimi ◽  
Saeed Hajimirzaee ◽  
Behnam Koohestani

Abstract In this research, the catalytic conversion of methanol to gasoline range hydrocarbons has been studied over CuO (5 %)/ZSM-5 and CuO (7 %)/ZSM-5 catalysts prepared via sonochemistry methods. Conversion of methanol to gasoline (MTG) has been carried out in a fixed bed reactor under atmospheric pressure and 400˚C temperature, over copper oxide on the synthesized ZSM-5 catalyst. The samples were characterized by XRD, SEM, TEM, BET, and FTIR techniques; in which good crystallinity and high specific surface area of synthesized zeolite were proved after impregnation of zeolite with copper. The present investigation suggests that the CuO/ZSM-5 catalyst made by sonochemistry method can increase the yield toward hydrocarbon production. It was concluded that impregnation of zeolite with copper oxide can alter the Brønsted/Lewis acid sites ratio and provide new Lewis acid sites over the surface of the ZSM-5. The main products of methanol to gasoline reaction over the catalyst that prepared via sonochemistry method were toluene, xylene, ethylbenzene, ethyl toluene, tetra methylbenzene, diethyl benzene and butylbenzene. The total amount of aromatics in the products was 80 % by using this catalyst. Our results suggest that catalyst synthesized by using sonochemistry shows better production yield toward hydrocarbons by affecting the distribution of active sites on the surface of the ZSM-5.


Author(s):  
Emre Kilic ◽  
Selahattin Yilmaz

H-ZSM5 and H-Ferrierite acidities were modified by chemical liquid deposition using tetraethylorthosilicate (TEOS), silicontetratchloride (SiCl4) and triaminopropyltriethoxysilane (3-APTES). All depositions were carried out at room temperature for deposition times of 0.5 and 1 h. Reaction tests were performed in a tubular quartz fixed bed reactor at 375°C for weight hour space velocities of 22 h-1. Surface area and pore volume of the catalysts were decreased upon modifications. The least modification of acidity was achieved by TEOS. However, SiCl4 and 3-APTES deposition modification strongly decreased the number of Bronsted and Lewis acid sites. As the effect of the modification increased, total acidity of the SiCl4 modified catalyst decreased. The catalysts were tested in isomerization of n-butene. Modification decreased the activity of the catalysts, but improvement in selectivity was observed with TEOS deposition. TEOS deposition increased the selectivity of the catalysts; for synthesized H-ZSM5 from 57.95 to 63.74 percent, for commercial H-ZSM5-C from 26.78 to 32.52 percent, and for H-FER from 63.06 to 81.23 percent. However, modification with SiCl4 and 3-APTES decreased both conversion and selectivity of the parent catalysts.


Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.


Zeolites ◽  
1997 ◽  
Vol 19 (4) ◽  
pp. 288-296 ◽  
Author(s):  
G.L. Woolery ◽  
G.H. Kuehl ◽  
H.C. Timken ◽  
A.W. Chester ◽  
J.C. Vartuli

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