Guanidinylated SBA-15/Fe3O4 mesoporous nanocomposite as an efficient catalyst for the synthesis of pyranopyrazole derivatives

In this study, a novel mesoporous nanocomposite was fabricated in several steps. In this regard, SBA-15 was prepared by the hydrothermal method, next it was magnetized by in-situ preparation of Fe3O4 MNPs. After that, the as-prepared SBA-15/Fe3O4 functionalized with 3-minopropyltriethoxysilane (APTES) via post-synthesis approach. Then, the guanidinylated SBA-15/Fe3O4 was obtained by nucleophilic addition of APTES@SBA-15/Fe3O4 to cyanimide. The prepared nanocomposite exhibited excellent catalytic activity in the synthesis of dihydropyrano[2,3-c]pyrazole derivatives which can be related to its physicochemical features such as strong basic sites (presented in guanidine group), Lewis acid site (presented in Fe3O4), high porous structure, and high surface area. The characterization of the prepared mesoporous nanocomposite was well accomplished by different techniques such as FT-IR, EDX, FESEM, TEM, VSM, TGA, XRD and BET. Furthermore, the magnetic catalyst was reused at least six consequent runs without considerable reduction in its catalytic activity.

Synthesis of Dimethyl Carbonate from CO2 and Methanol over Zr-Based Catalysts with Different Chemical Environments

The adsorption and activation of both CO2 and methanol are mainly affected by the distance of the Lewis acid site, Zr4+, and Lewis base, Zr4+/O2−, of the Zr-based catalysts. In this paper, Zr-incorporated SBA-15 (Zr-SBA-15) and Zr-grafted SBA-15 (Zr/SBA-15) catalysts were prepared with different Zr environments, and were analyzed with N2 adsorption–desorption isotherms, X-ray diffraction, UV-vis spectra, and XPS. It was proposed that Zr-SBA-15 catalyst with Si-O-Zr-OH and Zr-O-Si-OH structure exhibited non-adjacent sites between Zr4+ and Zr4+/O2−, while Zr/SBA-15 catalyst with Zr-O-Zr-OH structure showed neighboring sites between Zr4+ and Zr4+/O2−. Furthermore, the Zr/SBA-15 catalyst exhibited good catalytic activity, while no DMC was detected over the Zr-SBA-15 catalyst at the same reaction conditions. For combined in situ infrared and catalytic performance, it was indicated that the methanol and CO2 could be activated to form DMC, only when the Zr4+ and Zr4+/O2− sites existed and were adjacent to each other in the Zr-O-Zr-OH of Zr/SBA-15 catalyst.

The bifunctional Lewis acid site improved reactive oxygen species production: a detailed study of surface acid site modulation of TiO2 by ethanol and Br-

Modulation of surface acid sites (SAS) can effectively enhance the efficiency of reactive oxygen species (ROS) production in recent. However, the role of SAS has been neglected for photo-reduction reactions....

A DFT Study for Catalytic Deoxygenation of Methyl Butyrate on a Lewis Acid Site of ZSM-5 Zeolite

The catalytic deoxygenation mechanism of fatty acid esters on a Lewis acid site of ZSM-5 zeolite was elucidated via density functional theory (DFT) by using a methyl butyrate (MB) as the model compound for fatty acid esters. The configurations of the initial reactant, transition states, and products together with the activation barrier of each elementary reaction were determined. The activation barrier of different initial cracking reactions decreases in the order of α-C–C > β-C–C > α-C–O > β-C–O. The best reaction path for catalytic deoxygenation of methyl butyrate over Lewis acid site is CH3CH2CH2C(OCH3)=O⋯Lewis → CH3CH2⋯Lewis⋯C(=CH2)OCH3 → CH2=CH2 + CH3COOCH3 + Lewis. The oxygen of methyl butyrate is mainly removed as CO2, methyl acetate, formaldehyde, and butyraldehyde, while ethylene, propylene, and butane are the main hydrocarbon products. In addition, the group generated by cracking of methyl butyrate form a bond with the Lewis acid site, promoting the transformation between a Lewis acid and a Brønsted acid. The corresponding intermediates have a high single point energy, but the poor stability leads to further deoxygenation and cracking reactions. This work provides a theoretical basis for the modification in the number of Brønsted acid and Lewis acid sites in the ZSM-5 zeolite.

Sintesis Dan Karakterisasi H-Aluminosilikat Sebagai Katalis Sintesis Biogasoline Dari Asam Oleat

ABSTRACT Aluminosilicate can be used for cracking reaction. In this study, catalyst of H-aluminosilicate has been synthesized by hydrothermal method with ratio molar Si/Al is 20. The characterizations has been performed by XRD, FTIR and acidity test. Characterization by XRD showed that catalyst of H-aluminosilicate have structure amorphous, while FTIR showed Si-O-Al bond at 457 cm-1. The acidity test showed that catalyst of H-aluminosilicate have Brønsted acid site 0.0272 mmol/g and Lewis acid site 0.0005 mmol/g. Oleic acid was cracking at 340 oC for 3 and 5 hours. The product has been analyzed by GC-MS not showed compound forming biogasoline.Keywords: H-aluminosilicate, biogasoline, oleic acid ABSTRAK Aluminosilikat dapat digunakan sebagai katalis dalam reaksi prengkahan. Pada penelitian ini telah dilakukan sintesis katalis H-aluminosilikat melalui metode hidrotermal dengan rasio Si/Al sebesar 20. Karakterisasi yang telah dilakukan meliputi uji XRD, FTIR, dan keasaman.Hasil XRD menunjukkan katalis H-aluminosilikat berbentuk amorf, sedangkan pada FTIR menunjukkan ikatan Si-O-Al pada bilangan gelombang 457 cm-1. Uji situs asam menunjukkan katalis H-aluminosilikat memiliki jumlah asam Brønsted sebesar 0.0272 mmol/g dan jumlah sisi asam Lewis sebesar 0.0005 mmol/g. Proses perengkahan asam oleat telah dilakukan pada suhu 340oC selama 3 jam dan 5 jam. Produk cracking yang diuji dengan GC-MS tidak menunjukkan pembentukan senyawa biogasoline.Kata kunci: H-aluminosilikat, biogasoline, asam oleat

Catalytic valorization of hardwood for enhanced xylose-hydrolysate recovery and cellulose enzymatic efficiency via synergistic effect of Fe3+ and acetic acid

Background Poplars are considered suitable dedicated energy crops, with abundant cellulose and hemicellulose, and huge surplus biomass potential in China. Xylan, the major hemicellulosic component, contributes to the structural stability of wood and represents a tremendous quantity of biobased chemicals for fuel production. Monomeric xylose conversion to value-added chemicals such as furfural, xylitol, and xylonic acid could greatly improve the economics of pulp-paper industry and biorefinery. Acetic acid (HAc) is used as a friendly and recyclable selective catalyst amenable to xylan degradation and xylooligosaccharides production from lignocellulosic materials. However, HAc catalyst usually works much feebly at inert woods than agricultural straws. In this study, effects of different iron species in HAc media on poplar xylan degradation were systematically compared, and a preferable Fe3+-assisted HAc hydrolysis process was proposed for comparable xylose-hydrolysate recovery (XHR) and enzymatic saccharification of cellulose. Results In presence of 6.5% HAc with 0.17–0.25 wt% Fe3+, xylose yield ranged between 72.5 and 73.9%. Additionally, pretreatment was effective in poplar delignification, with a lignin yield falling between 38.6 and 42.5%. Under similar conditions, saccharification efficiency varied between 60.3 and 65.9%. Starting with 100 g poplar biomass, a total amount of 12.7–12.8 g of xylose and 18.8–22.8 g of glucose were harvested from liquid streams during the whole process of Fe3+-HAc hydrolysis coupled with enzymatic saccharification. Furthermore, the enhancement mechanism of Fe3+ coupled with HAc was investigated after proof-of-concept experiments. Beechwood xylan and xylose were treated under the same condition as poplar sawdust fractionation, giving understanding of the effect of catalysts on the hydrolysis pathway from wood xylan to xylose and furfural by Fe3+-HAc. Conclusions The Fe3+-assisted HAc hydrolysis process was demonstrated as an effective approach to the wood xylose and other monosaccharides production. Synergistic effect of Lewis acid site and aqueous acetic acid provided a promising strategy for catalytic valorization of poplar biomass.

Effect of Temperature, Pressure, and Reaction Time on Hydrogenation of Hexadecanoic Acid to 1-Hexadecanol Using a Ru-Sn(3.0)/C Catalyst

Effect of temperature, initial H2 pressure, and reaction time on the selective hydrogenation of hexadecanoate acid to 1-hexadecanol over bimetallic ruthenium-tin supported on carbon (denoted as Ru-Sn(3.0)/C; 3.0 is molar ratio Ru/Sn) has been systematically investigated. Ru-Sn(3.0)/C catalyst was synthesized using a simple hydrothermal method at temperature of 150oC for 24 h followed by reduction with hydrogen at at 400oC and 500°C for 1.5 h. The XRD patterns of reduced Ru-Sn(3.0)/C showed a series diffraction peaks of bimetallic alloy Ru3Sn7 at 2θ = 30.0°; 35.0°; and 41.3° which are recognized as (310), (321), and (411) reflection planes present. The N2-adsorpsion/desorption profiles confirmed that the catalyst structure was microporous and mesoporous sizes with specific surface area (SBET) of 207 m2/g, pore volume (VpBJH) 0.1015 cm3/g, and pore diameter (dpBJH) 1,21 nm. NH3-TPD profile shows that the desorption temperature of 157.1°C was a weak acidity (Bronsted acid site) with amount of acid sites was 0.117 mmol/g. Meanwhile, the desorption temperature of 660.3°C was a strong acidity (Lewis acid site) with amount of acid sites was 0.826 mmol/g. The highest conversion of hexadecanoic acid (86.24%) was achieved at reaction temperature180°C, initial H2 pressure of 5.0 MPa, a reaction time of 6 h in ethanol solvent and afforded yield of hexadecane (0.15%), 1-hexadecanol (4.27%), and ethyl hexadecanoate (81.82%). At reaction temperature of 150°C, H2 of 3.0 MPa, and a reaction time of 18 h, 73.27% of hexadecanoic acid was converted to 1-hexadecanol (0.24%) and ethyl hexadecanoate (73,03%).