Structural Defects and Acidic and Basic Sites in Sol−Gel MgO

Wang, Jinan; Novaro, O.; Bokhimi, X.; López, Tomás; Gómez, R.; Navarrete, Juan T. López; Llanos, M. E.; López-Salinas, E.

doi:10.1021/jp970233l

Cited by 65 publications

(53 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 shows the combined XRD patterns of the three sol-gel catalysts (SG-1, SG-2 and SG-3). The XRD pattern clearly shows the five well-resolved characteristic peaks of the MgO rock-salt lattice in all three samples [21]. We were not able to detect any separate phase for Fe 2 O 3 or MoO x from SG-2 and SG-3 catalysts (Figs.…”

Section: Characterization Of Fe-mo/mgo Catalystsmentioning

confidence: 77%

Synthesis of thin-multiwalled carbon nanotubes by Fe-Mo/MgO catalyst using sol-gel method

Dubey¹,

Choi²,

Kim³

et al. 2012

Carbon letters

View full text Add to dashboard Cite

The sol-gel technique has been studied to fabricate a homogeneous Fe-Mo/MgO catalyst. Ambient effects (air, Ar, and H 2 ) on thermal decomposition of the citrate precursor have been systematically investigated to fabricate an Fe-Mo/MgO catalyst. Severe agglomeration of metal catalyst was observed under thermal decomposition of citrate precursor in air atmosphere. Ar/H 2 atmosphere effectively restricted agglomeration of bimetallic catalyst and formation of highly-dispersed Fe-Mo/MgO catalyst with high specific surface-area due to the formation of Fe-Mo nanoclusters within MgO support. High-quality thin-multiwalled carbon nanotubes (t-MWCNTs) with uniform diameters were achieved on a large scale by catalytic decomposition of methane over Fe-Mo/MgO catalyst prepared under Ar-atmosphere. The produced t-MWCNTs had outer diameters in the range of 4-8 nm (average diameter ~6.6 nm) and wall numbers in the range of 4-7 graphenes. The as-synthesized t-MWCNTs showed product yields over 450% relative to the utilized Fe-Mo/MgO catalyst, and indicated a purity of about 85%.

show abstract

Section: Characterization Of Fe-mo/mgo Catalystsmentioning

confidence: 77%

Synthesis of thin-multiwalled carbon nanotubes by Fe-Mo/MgO catalyst using sol-gel method

Dubey¹,

Choi²,

Kim³

et al. 2012

Carbon letters

View full text Add to dashboard Cite

show abstract

“…IR spectrum of the precursor obtained after exposure of magnesium methoxide to air showed residual OH peak in the MgO lattice, whose intensity decreased in subsequent calcination. Apparently, similar to the sol-gel derived magnesium oxide [25], during calcination, dehydroxylation takes place and causes anion vacancies to form, and finally, aggregation of magnesium ions around them produce locally accumulated positive charge [21]. Those locally accumulated positive charges act as acidic sites that are needed for adsorption of ketone.…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

“…Those locally accumulated positive charges act as acidic sites that are needed for adsorption of ketone. As mentioned earlier, in addition to the acidic sites for the MPV reaction, basic sites are also needed, and a comprehensive study shows that the magnesium oxide prepared by the solgel method fulfills this requirement [21]. Apparently, the metal oxides derived from metal alkoxides, in general, and magnesium oxide in particular, are endowed with hydroxyl groups, in which some of the hydroxyl groups are embedded in the crystalline structure and generate defects [26].…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

“…Notably, the MgO-3 calcined at 400°C was the most active, followed by those calcined at 500 and 600°C. Considering the fact that the number of basic sites of magnesium oxide, their strength, and also the number of Mg vacancies decrease with the increase in calcination temperature [21], decrease in cyclohexanol yield is logical. This was in accordance with the decrease in the total amount of adsorbed carbon dioxide molecules for magnesium oxide that was calcined at higher temperature.…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

“…The MgO prepared by conventional methods, based on the decomposition of various magnesium salts, resulted in the formation of a coarse powder with small surface area. On the contrary, MgO prepared by the sol-gel route exhibits a smaller particle size, a larger surface area, and a large number of defects in crystalline structure [21]. Klabunde and co-workers [20] reported that defects on the nanocrystal surface promote the formation of basic and acidic sites; therefore, it is expected that nanocrystalline MgO prepared by various techniques should act as a suitable catalyst for the MPV reaction.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nanocrystalline Magnesium Oxide as a Versatile Heterogeneous Catalyst for the Meerwein–Ponndorf–Verley Reduction of Cyclohexanone into Cyclohexanol: Effect of Preparation Method of Magnesium Oxide on Yield

et al. 2009

View full text Add to dashboard Cite

The Meerwein-Ponndorf-Verley (MPV) reaction of cyclohexanone with 2-propanol in the liquid phase in the presence of two different nanocrystalline magnesium oxides, prepared by different methods, was investigated. The catalyst consisting of nanocrystalline magnesium oxide, which was prepared by calcination of magnesium methoxide in air at 400°C, showed the highest activity in the conversion of cyclohexanone to cyclohexanol with 97% yield. The effect of calcination temperature of magnesium oxide on the cyclohexanol yield and reusability of the catalyst has been studied.

show abstract

Catalytic Dehydration of 1,4‐Butanediol over Mg−Yb Binary Oxides and the Mechanism Study

et al. 2020

ChemCatChem

View full text Add to dashboard Cite

In this study, MgÀ Yb binary oxides were synthesized using different MgO concentrations and investigated for the catalytic dehydration of 1,4-butanediol (BDO) into 3-buten-1-ol (BTO). The physicochemical properties of the catalysts were characterized by N 2 physisorption, X-ray diffraction, Raman spectroscopy, temperature-programmed techniques, and diffuse reflectance infrared Fourier transform spectroscopy. The MgÀ Yb binary oxides exhibited superior catalytic activity and better BTO selectivity compared with the pristine Yb 2 O 3 or MgO. Structures of MgÀ OÀ Yb were generated in the binary oxides via the interchange of Yb or Mg in the MgO or Yb 2 O 3 crystalline phases. Extra basic and acidic sites were formed over the MgÀ Yb binary oxides because of the formation of surface defects and the presence of MgÀ OÀ Yb structures, respectively. The acidic as well as basic sites were observed to influence the catalytic performance: BDO reactivity was enhanced by the more acidic sites, while BTO selectivity was favored by the basic sites. The highest BTO yield of 71.1 % was achieved over the Mg7Yb3 catalyst with 90.4 % BDO conversion and 78.6 % BTO selectivity at 350°C. The in situ DRIFTS results indicated that BDO was first adsorbed on the catalyst and then reacted with the acidic sites to generate butoxides. The β-H of the surface butoxides was abstracted by the basic oxygen anions to produce aldehyde species, which dissociated to form BTO.[a] R.

show abstract

Structural Defects and Acidic and Basic Sites in Sol−Gel MgO

Cited by 65 publications

References 39 publications

Synthesis of thin-multiwalled carbon nanotubes by Fe-Mo/MgO catalyst using sol-gel method

Synthesis of thin-multiwalled carbon nanotubes by Fe-Mo/MgO catalyst using sol-gel method

Nanocrystalline Magnesium Oxide as a Versatile Heterogeneous Catalyst for the Meerwein–Ponndorf–Verley Reduction of Cyclohexanone into Cyclohexanol: Effect of Preparation Method of Magnesium Oxide on Yield

Catalytic Dehydration of 1,4‐Butanediol over Mg−Yb Binary Oxides and the Mechanism Study

Contact Info

Product

Resources

About