La-modified mesoporous Mg–Al mixed oxides: effective and stable base catalysts for the synthesis of dimethyl carbonate from methyl carbamate and methanol

Wang, Dengfeng; Zhang, Xuelan; Ma, Jie; Yu, Haiwen; Shen, Jingzhu; Wei, Wei

doi:10.1039/c5cy01712b

Cited by 42 publications

(22 citation statements)

References 61 publications

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“…Parameter 'a' (a= 2d110) depends mainly on the average radius of the metal cation and reflected the density of metal ions in 110 plane. [35]The observed results may be due to the isomorphous substitution of Fe by Ce having larger ionic radii [39]. Thus more Ce insertion leads to an increase in average radius of cations in the layers and this leads to increase in 'a' parameter.…”

Section: Nd: Not Detectedmentioning

confidence: 98%

“…Nevertheless, with increase in Ce concentration for LDH-4 to LDH-6 decrease in crystallinity (better ordering of brucite sheets) which is directly proportional to the peak intensity and sharpness of (003) and (006) planes; was observed. This is due to the substitution of Fe (0.65˚A) by larger ionic radii of Ce (1.01˚A), which inhibits the intercalation of Ce in LDH structure and also leads to significant distortion in the layers [35]. At higher Ce concentration (LDH-6, Fe:Ce=0:1) the layered structure collapsed completely and formation of phases like Mg(OH)2 (PCPDF-86-0441), Ce(OH)4 [36,37] and Ce2(CO3)2.…”

Section: Powder X-ray Diffractionmentioning

confidence: 99%

“…With further increase in Ce content from LDH-4 to LDH-6; slight decrease in surface area and pore volume was observed. This may be due to 1) distortion in layer structure because of incorporation of excess amount of Ce, 2) Deposition of the agglomerated particles formed during precipitation conditions or their incorporation into the pore system of LDH respectively[45].…”

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confidence: 99%

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MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

2017

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A series of Mg3:Fex+Ce1-x LDHs (3:1) were synthesized by co-precipitation method by varying molar ratio of Fe:Ce between 1:0 to 0:1 (LDH-1 to LDH-6). All synthesized LDHs were characterized by XRD, FT-IR, TEM, N2 sorption, benzoic acid titration and XPS in detail and evaluated for selective synthesis of dimethyl carbonate by transesterification of ethylene carbonate with methanol. It was demonstrated that the structural and basic properties of synthesized LDHs were strongly dependent on the Fe:Ce molar ratio (Ce concentration). The correlation between their physicochemical properties and catalytic performance was studied in detail. Among all synthesized LDHs the best result was obtained with LDH-3 (Fe:Ce=0.85:0.15) where LDH structure remained intact, and showed high number of strong basic sites on LDH surface. LDH-3 was recycled 7 times while maintaining high catalyst activity and selectivity towards DMC. The obtained results elucidate the important role of Ce in modifying the basic properties of LDH in enhancing the catalytic activity for DMC synthesis.

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Section: Nd: Not Detectedmentioning

confidence: 98%

Section: Powder X-ray Diffractionmentioning

confidence: 99%

mentioning

confidence: 99%

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MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

2017

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“…39 However, higher temperatures also favor MC decomposition. 40 In comparison with the FR, therefore, the MR allows not only NH 3 removal but also lower reaction temperatures with higher conversion, limiting undesired byproducts. Figure 3d shows the corresponding X DMC in the MR and FR.…”

Section: Results and Discussionmentioning

confidence: 99%

Dual-Role Membrane as NH₃ Permselective Reactor and Azeotrope Separator in Urea Alcoholysis

et al. 2019

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Urea methanolysis is a green alternative to synthesize dimethyl carbonate (UM-to-DMC). However, it is strongly challenged by the generated NH3 induced thermodynamic equilibrium limitation and the azeotropic products’ separation. Herein, these predicaments are well-relieved by introducing membranes in both reaction and product separation. An NH3 permselective membrane reactor (MR) based on modified SAPO-34 membrane is successfully realized for UM-to-DMC. The permselectivity and acidity of the SAPO-34 membrane are significantly adjusted to cater the strict molecular sieving of NH3/methanol and chemical inertness upon the reaction. The MR exhibits excellent reactant conversion and DMC selectivity, resulting in >139% higher DMC yield than that of the nonmembrane reactor, due to in situ removal of NH3 by the membrane. The MR also demonstrates reliable chemical, thermal, and mechanical stability during >2000 h. Moreover, the regular SAPO-34 membrane with controlled thickness presents remarkable separation performance for the methanol–DMC azeotrope, in which the methanol–DMC separation factors and the methanol permeance are 1–2 orders of magnitude higher than those of the polymeric membranes. This study suggests the great potential that integration of such membranes offers for process intensification, energy savings, and efficiency improvement in a series of urea alcoholysis and even other NH3 releasing reactions.

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“…FT-IR spectroscopy measurements were a strategy successfully employed by Zhank et al to elucidate the adsorption mechanism of the reactants on dimethyl carbonate synthesis from urea methanolysis [29]. Additionally, we measured these spectra in absence of b-citronellol (Fig.…”

Section: Mechanistic Insightsmentioning

confidence: 99%

Tin-Catalyzed Urea Alcoholysis With β-Citronellol: A Simple and Selective Synthesis of Carbamates

Chaves

Silva

2016

Catal Lett

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Tin(II) chloride is a stable and water tolerant Lewis acid, commercially available and less corrosive than Brønsted acid catalysts. Our proposal was demonstrated that SnCl 2 was an efficient catalyst on the urea alcoholysis with b-citronellol. We investigated the effects of main reaction parameters such as concentration and tin(II) catalyst nature, reagents stoichiometry and reaction temperature. In homogenous conditions with DMSO as solvent, the SnCl 2 -catalyzed urea alcoholysis reactions under air flux achieved high conversion and selectivity for b-citronellyl carbamate (ca. 90 and 95 %, respectively). Among tin(II) catalysts assessed, SnCl 2 was more active due to its total solubility. Possible intermediates of active Sn(II) species were discussed based on the results of catalytic runs and FT-IR spectroscopy measurements of the liquid phase after the reaction. FT-IR spectroscopy data showed that the active species could be a complex of a Sn(II) atom coordinated with N=C=O. This novel and phosgene-free selective process provide an inexpensive and attractive route to synthesize terpenic carbamates through inexpensive and renewable reactant (i.e. urea). Moreover, SnCl 2 was also an efficient catalyst on synthesis of b-citronellyl carbonate. Graphical AbstractOH -citronellol H 2 N NH 2 O Urea + SnCl 2 DMSO Air flow O NH 2 O -citronellyl Carbamate NH 3 + Ammonia β 0 3 0 6 0 9 0 0 20 40 60 80 100 (%) Time (min) β -Citronellol Conversion Selectivity β-Citronellyl Carbamate β

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La-modified mesoporous Mg–Al mixed oxides: effective and stable base catalysts for the synthesis of dimethyl carbonate from methyl carbamate and methanol

Abstract: The incorporation of a suitable amount of La into Mg–Al mixed oxide catalysts was beneficial for the production of dimethyl carbonate.

Cited by 42 publications

References 61 publications

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

Dual-Role Membrane as NH₃ Permselective Reactor and Azeotrope Separator in Urea Alcoholysis

Tin-Catalyzed Urea Alcoholysis With β-Citronellol: A Simple and Selective Synthesis of Carbamates

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La-modified mesoporous Mg–Al mixed oxides: effective and stable base catalysts for the synthesis of dimethyl carbonate from methyl carbamate and methanol

Abstract: The incorporation of a suitable amount of La into Mg–Al mixed oxide catalysts was beneficial for the production of dimethyl carbonate.

Cited by 42 publications

References 61 publications

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

Dual-Role Membrane as NH3 Permselective Reactor and Azeotrope Separator in Urea Alcoholysis

Tin-Catalyzed Urea Alcoholysis With β-Citronellol: A Simple and Selective Synthesis of Carbamates

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Dual-Role Membrane as NH₃ Permselective Reactor and Azeotrope Separator in Urea Alcoholysis