90-05-1Relevant articles and documents
Deposition–precipitation approach for preparing core/shell SiO2@Ni-Rh nanoparticles as an advanced catalyst for the dehydrogenation of 2-methoxycyclohexanol to guaiacol
Feng, Junbo,Jiang, Wei,Yuan, Caicai,Shi, Xiancai,Zang, Kai,Zhang, Yadong
, p. 106 - 113 (2018)
A novel core/shell nano-bimetallic catalyst SiO2@Ni-Rh was successfully prepared by deposition–precipitation method, using liquid ammonia as a precipitating agent. SEM, TEM, XRD, XPS, H2-TPR, H2-TPD and adsorption/desorption of nitrogen were employed to systematically investigate the surface morphology, size, chemical composition, reducibility, Ni dispersion and structure of the as-synthesized nanoparticles. It is found that the nickel and rhodium are uniformly dispersed on the silica surface to form core/shell SiO2@Ni-Rh nanoparticles with Ni atoms and Rh atoms as the outer shell and SiO2 as the core, which possess high dispersion of Ni on the surface and high specific surface area (234.063 m2/g) of the catalyst with the mean particle size of ca. 130 nm. The dehydrogenation of 2-methoxycyclohexanol to guaiacol was used as the model reaction for evaluating the catalytic activity of the as-synthesized core/shell various Ni and Rh-containing bimetallic nanoparticles in a tubular stainless steel reactor. SiO2@15Ni-0.4Rh nanoparticles have exhibited remarkable catalytic performance, with 98.3% conversion and 93.6% selectivity of guaiacol, due to high dispersion of metal nanoparticles and synergistic effect of bimetallic Ni-Rh over the special core/shell SiO2@Ni-Rh by the addition of rhodium. Furthermore, turn over frequency value of SiO2@15Ni-0.4Rh nanoparticles achieves 0.47 s?1, showing high catalytic efficiency. In general, the dehydrogenation of 2-methoxycyclohexanol over the core-shell-like SiO2@Ni-Rh nanoparticles in a continuous fixed-bed reactor is a more promising, high atom economy, high efficient, easy separation, environmental friendliness, green synthetic pathway of guaiacol.
-
Pearl
, p. 2196,2199 (1949)
-
-
Bamberger,Vischner
, p. 564 (1900)
-
Catechol O-methylation with dimethyl carbonate over different acid-base catalysts
Luque, Rafael,Manuel Campelo, Juan,Conesa, Tomas David,Luna, Diego,Marinas, Jose Maria,Romero, Antonio Angel
, p. 1228 - 1234 (2006)
A series of meso and microporous materials, previously described and characterised, were tested in the catechol O-alkylation process using methanol (MeOH) and dimethyl carbonate (DMC) as alkylating reagents. In this regard, interesting results in terms of catalytic activity and selectivity to the desired monomethylated product (guaiacol) compared to the dimethylated one (veratrole) were found for the majority of the catalysts. Moreover, DMC is a better methylating agent than methanol with respect to the conversion ratio of catechol and guaiacol. The presence of n-type nucleophilic centres (oxygen from the OH groups) together with π-type ones (aromatic ring) in catechol led only to O-alkylated (guaiacol and veratrole), whereas no C-alkylated products were found under the reaction conditions. AlPO4 and, especially, AlPO 4-Al2O3 systems showed the best performance in this alkylation process in comparison with silicoaluminophosphates (SAPO) and some acidic commercial zeolites (H-Y, H-β and H-ZSM-5). the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
-
Eisenbraun,Purves
, p. 2127 (1961)
-
Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
Martos, Mario,Pastor, Isidro M.
, (2022/01/03)
Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
One-Pot Transformation of Lignin and Lignin Model Compounds into Benzimidazoles
Guo, Tao,He, Jianghua,Liu, Tianwei,Zhang, Yuetao
supporting information, (2022/02/07)
It is a challenging task to simultaneously achieve selective depolymerization and valorization of lignin due to their complex structure and relatively stable bonds. We herein report an efficient depolymerization strategy that employs 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as oxidant/catalyst to selectively convert different oxidized lignin models to a wide variety of 2-phenylbenzimidazole-based compounds in up to 94 % yields, by reacting with o-phenylenediamines with varied substituents. This method could take full advantage of both Cβ and/or Cγ atom in lignin structure to furnish the desirable products instead of forming byproducts, thus exhibiting high atom economy. Furthermore, this strategy can effectively transform both the oxidized hardwood (birch) and softwood (pine) lignin into the corresponding degradation products in up to 45 wt% and 30 wt%, respectively. Through a “one-pot” process, we have successfully realized the oxidation/depolymerization/valorization of natural birch lignin at the same time and produced the benzimidazole derivatives in up to 67 wt% total yields.
