590-01-2Relevant academic research and scientific papers
Surface acidity and catalytic activity of aged SO24 /SnO2 catalyst supported with WO3
Alaya, M. Nasouh,Rabah, Marwa A.
, p. 285 - 291 (2013)
New solid acid was prepared by loading of aged 15 wt.% SO24 /SnO2 catalyst with 15 and 35 wt.% WO3. The catalysts were calcined at 400 and 650°C. The surface areas of the catalysts were determined by the data of N2 adsorption at -196°C. The surface acidity was measured potentiometricaly using n-butylamine solution in acetonitrile. The types of acidic sites were determined by FT-IR spectra of adsorbed pyridine. The catalytic activities of the catalysts were tested toward esterification of propionic acid (PA) with nbutanol (B). The SBET values of the ISS were decreased with an increase in the calcination temperature, whereas, the SBET of the loaded catalysts was maximum at 400°C. The results reveal that the used catalysts possess very strong acid sites and contain both Br?nsted and Lewis acidic sites. The acid strength, total surface acidity and the conversion of PA were maxima for 400°C products. The effect of the reaction parameters was also studied, and shows that the PA conversion was increased with an increase in the reaction temperature and the catalyst weight. The reactant molar ratio shows a maximum conversion at PA:B = 1:2. The kinetics study indicates that the catalytic esterification of PA with B obey first order kinetics equation.
Aluminum phosphate-based solid acid catalysts: Facile synthesis, characterization and their application in the esterification of propanoic acid with n-butanol
Liu, Boliang,Jiang, Pingping,Zhang, Pingbo,Zhao, Hui,Huang, Jie
, p. 540 - 548 (2017)
Novel solid acid catalysts synthesized from aluminum phosphate were prepared via a precipitation method and a subsequent sulfating treatment. Their catalytic performances for the esterification of propanoic acid with n-butanol were investigated. The as-prepared catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of ammonia (NH3-TPD), infrared spectroscopy of adsorbed pyridine, and other techniques. Experimental results of esterification reactions indicated that the calcination temperature can significantly affect the catalytic performances and the catalyst calcined at 500?°C (SO42?/AlPO4-500) exhibited the highest activity. The effects of different reaction conditions including reaction time, reaction temperature, catalyst amount and alcohol/acid molar ratio were studied in detail. The maximum propanoic acid conversion of 91% was achieved under optimum reaction conditions. Furthermore, the as-prepared SO42?/AlPO4-500 catalysts were tested for their reusability in repeated reaction cycles and could be effectively regenerated by a simple reactivation method.
Metallacarboranes in Catalysis. 7. Kinetics and Mechanism of Acrylate Ester Hydrogenation Catalyzed by closo-Rhodacarboranes
Behnken, Paul E.,Busby, David C.,Delaney, Mark S.,King III, Roswell E.,Kreimendahl, Charles W.,et. al.
, p. 7444 - 7450 (1984)
In a search for reactions catalyzed by rhodacarborane clusters, the species I, , II, , III, , and IV, , were examined as catalyst precursors in the hydrogenation of 1-butyl acrylate (C) in THF solution at 40.8 deg C.Only catalyst precursors I and III gave results that were free of complications and suitable for detailed kinetic analyses.Both I and III reversibly hydridometalate C to produce the chelated closo adducts VI and VII, respectively, and an equivalent quantity of PPh3.The slow attainment of equilibria in these hydrometalation reactions accounts for the appearance of a lengthy induction period at the outset of C hydrogenations which employed either I or III as catalyst precursor.The rate law for C hydrogenation using I or III was elucidated and found to be identical in form with that previously observed using closo- or exo-nido-rhodacarboranes in 3-metyl-3-phenylbutene-1 (A) hydrogenation.As in the case of A, it was shown by deuterium labeling that C hydrogenation did not involve the hydride ligand at the RhH vertex of either I of III.The BH vertices of these same species were similarly shown to not be involved.Reduction of C with D2 using I as the catalyst source gave a moderate amount of D scrambling into recovered C and produced 1-butyl propionate-d0-d4.The above results led to a proposed catalytic cycle that culminates in the slow, but probably not rate-limiting, elimination of 1-butyl propionate from a reversibly formed exo-nido alkyl hydride intermediate.These kinetic characteristics may have their origin in the weak electron donor properties of the chelated - ligands that are attached to Rh(1+) or Rh(3+) in exo-nido intermediates by a pair of B-H-Rh three-center bonds.
Immobilization of lipase in cage-type mesoporous organosilicas via covalent bonding and crosslinking
Zhou, Zhou,Piepenbreier, Frank,Marthala, V.R. Reddy,Karbacher, Karl,Hartmann, Martin
, p. 173 - 183 (2015)
Lipase from Thermomyces lanuginosus (TLL) was immobilized in cage-type mesoporous materials via two different protocols, viz. covalent bonding and cross-linking. The comparison between the biocatalysts generated by the two methods on both pure silica mesocellular siliceous foam (MCF) and cage-type large pore mesoporous organosilicas (PMOs) disclosed that cross-linking results in the immobilization of a larger amount of TLL and reduced diffusion problems compared to covalent bonding. Benzene-bridged PMOs positively influence the activity of immobilized lipase due to the hydrophobic properties of the surface. Furthermore, a transesterification reaction in organic solvent was carried out to verify the biocatalytic performance of differently immobilized lipase in both batch and fixed-bed reactors. The results further confirm the superiority of the PMO support compared to MCF and also reveal that the different immobilization protocols strongly influence the activity, stability and specificity of immobilized TLL. Moreover, two commercial available immobilize formed TLL were also used in a fixed-bed reactor under the same condition for comparison.
Membrane reactor for acceleration of esterification using a special ionic liquid with reaction and separation and microwave heating
Uragami, Tadashi,Kishimoto, Junji,Miyata, Takashi
, p. 57 - 63,7 (2012)
To improve conversion of n-butanol to the corresponding ester using acetic acid, the ionic liquid 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl) imide ([ABIM]TFSI), which does not dissolve in the water by-product, and poly(vinyl alcohol) (PVA) or PVA-TEOS (tetraethoxysilane) hybrid membranes were employed when using evapomeation (EV), along with microwave heating. The effect on the conversion of n-butanol of each individual process variable as well as that of all of the variables used in combination was investigated, and the characteristics of each approach are discussed.
Head-to-tail dimerization of acrylates catalyzed by iridium complexes
Nakagawa, Hideto,Sakaguchi, Satoshi,Ishii, Yasutaka
, p. 502 - 503 (2003)
Head-to-tail dimerizations of acrylates and vinyl ketone were successfully performed by the use of iridium complexes in good yields. An iridium hydride complex generated in situ from [IrCl(cod)]2 and alcohols in the presence of Na2CO
Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
supporting information, p. 18591 - 18598 (2021/06/28)
A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
Encapsulation of heteropolyacids within hollow microporous polymer nanospheres for sustainable esterification reaction
He, Zhiwei,Huang, Kun,Song, Chunmei,Wang, Huaqing,Yu, Haitao,Zhang, Li
, (2021/10/25)
Herein, the Keggin structural phosphotungstic acid (HPW) has been successfully encapsulated within hollow microporous polymer nanospheres (H-MPNs) by a “ship-in-bottle” approach. The H-MPNs are formed by self-assembly induced by hyper-crosslinking of polylactide-b-polystyrene (PLA-b-PS). The obtained catalysts (HPW@H-MPNs) exhibit more sustainable availability than the previously reported HPW-supported catalysts in esterification reaction. This excellent sustainability can be attributed to the stable microporous channels in H-MPNs which are smaller than the molecular size of HPW, thereby effectively preventing the HPW from leaking out. Moreover, such catalysts also perform well in terms of catalytic activity and universality because of the combination of a hollow structure in the interior and permeable pore channels in the shells. This type of polymer carrier and general encapsulation method may provide a new strategy for developing more sustainable catalysts for various chemical reactions.
Genome mining reveals new bacterial type I Baeyer-Villiger monooxygenases with (bio)synthetic potential
Bianchi, Dario A.,Carabajal, María Ayelén,Ceccoli, Romina D.,Rial, Daniela V.
, (2020/03/19)
Baeyer-Villiger monooxygenases (BVMOs) are oxidorreductases that catalyze the oxidation of ketones in a very selective manner. By genome mining we detected seven putative type I BVMOs in Bradyrhizobium diazoefficiens USDA 110. As we established the phylogenetic relationships among them and with other type I BVMOs, we found out that they belong to different clades of the phylogenetic tree. Thus, we decided to clone and heterologously express five of them. Three of them, each one from a divergent phylogenetic group, were obtained as soluble proteins, allowing us to proceed with their biocatalytic assessment and enzymatic characterization. As to substrate scope and selectivity, we observed a complementary behavior among the three BVMOs. BVMO2 was the more versatile biocatalyst in whole-cell systems while BVMO4 and BVMO5 showed a narrow substrate profile with preference for linear ketones and particular regioselectivity for (±)-cis-bicyclo[3.2.0]hept-2-en-6-one.
IrIII-Catalyzed direct syntheses of amides and esters using nitriles as acid equivalents: A photochemical pathway
Talukdar, Ranadeep
supporting information, p. 5303 - 5308 (2020/04/17)
An unprecedented IrIII[df(CF3)ppy]2(dtbbpy)PF6-catalyzed simple photochemical process for direct addition of amines and alcohols to the relatively less reactive nitrile triple bond is described herein. Various amides and esters are synthesized as the reaction products, with nitriles being the acid equivalents. A mini-library of different types of amides and esters is made using this mild and efficient process, which uses only 1 mol% of photocatalyst under visible light irradiation (λ = 445 nm). The reaction strategy is also efficient for gram-scale synthesis.
