Lefu Wang

Simultaneous delignification and selective catalytic transformation of agricultural lignocellulose in cooperative ionic liquid pairs

Catalytic transformation of readily available widely distributed and renewable non-food lignocelluloses to value-added chemicals has been recognized as an efficient approach for the alleviation of the increasing energy crisis and climate change. An efficient catalytic transformation process for agricultural residual lignocelluloses in cooperative ionic liquid pairs was achieved. The promotion of the dissolution equilibrium, combined with rapid, in situ acid-catalyzed degradation of cellulose and hemicellulose, resulted in significantly greater conversion of the biomass to biochemicals and selective delignification through further comparative analyses of the raw materials, products and residues by GC-MS, GPC, FT-IR, SEM and elemental characterization.

One step catalytic conversion of cellulose to sustainable chemicals utilizing cooperative ionic liquid pairs

A 100% conversion of cellulose to industrially useful chemicals is, for the first time, achieved in a single pot reaction by the use of cooperative ionic liquid pairs for combined dissolution and catalytic degradation of cellulose, which overcomes the long intrinsic phase problem in the conversion of biomass to chemicals.

Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations

A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl-, Br-, BF4- and PF6- counter-anions at a concentration of 2.5 mM can be degraded at 50 degrees C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C-N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.

Ship-in-a-bottle synthesis of amine-functionalized ionic liquids in NaY zeolite for CO2 capture

CO2 capture on solid materials possesses significant advantages on the operation cost, process for large-scale CO2 capture and storage (CCS) that stimulates great interest in exploring high-performance solid CO2 adsorbents. A ship-in-a-bottle strategy was successfully developed to prepare the [APMIM]Br@NaY host–guest system in which an amine-functionalized ionic liquid (IL), 1-aminopropyl-3-methylimidazolium bromide ([APMIM]Br), was in-situ encapsulated in the NaY supercages. The genuine host-guest systems were thoroughly characterized and tested in CO2 capture from simulated flue gas. It was evidenced the encapsulated ILs are more stable than the bulk ILs. These host–guest systems exhibited superb overall CO2 capture capacity up to 4.94 mmol g−1 and the chemically adsorbed CO2 achieved 1.85 mmol g−1 depending on the [APMIM]Br loading amount. The chemisorbed CO2 can be desorbed rapidly by flushing with N2 gas at 50°C. The optimized [APMIM]Br@NaY system remains its original CO2 capture capacity in multiple cycling tests under prolonged harsh adsorption-desorption conditions. The excellent physicochemical properties and the CO2 capture performance of the host-guest systems offer them great promise for the future practice in the industrial CO2 capture.

Synthesis of multicarboxylic acid appended imidazolium ionic liquids and their application in palladium-catalyzed selective oxidation of styrene

A series of multicarboxylic acid appended imidazolium ionic liquids (McaILs) with chloride [Cl]– or bromide [Br]– as anions have been synthesized and characterized. Deprotonation of these ionic acids gives the corresponding zwitterions. Re-protonation of the zwitterions with strong Bronsted acids gives a series of new ionic acid-adducts, many of which remained as room-temperature ionic liquids. A new catalytic system, McaIL/PdCl2 for the selective catalytic oxidation of styrene to acetophenone with hydrogen peroxide as an oxidant has been attempted. In the presence of McaILs, it is found that the quantity of palladium chloride PdCl2 used can be greatly reduced while the activity (TOF) and selectivity towards acetophenone are enhanced sharply. It is also shown that the catalytic properties of this system could be finely tuned through the molecular design of the McaILs. The best TOF value obtained so far is 146 h–1 with 100% conversion of styrene at 93% selectivity to acetophenone. In addition, the catalytic activity has been maintained for at least ten catalytic cycles.

Cumene Liquid Oxidation to Cumene Hydroperoxide over CuO Nanoparticle with Molecular Oxygen under Mild Condition

Abstract CuO nanoparticle was synthesized via wet chemical method and was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and scanning electron microscopy (SEM). Catalytic oxidation of cumene with molecular oxygen was studied over CuO nanoparticle. The catalysts showed markedly higher activities as compared to CuO prepared by conventional method, CuO/Al2O3,orhomogeneous copper catalyst under comparable reaction conditions. The cumene conversion, cumene hydroperoxide (CHP) yield, and selectivity using 0.25 g CuO nanoparticle catalyst and 0.1 mol cumene at 358 K for 7 h were 44.2%, 41.2% and 93.2%, respectively. The catalyst can be recycled. After 6 recycled experiments, no loss of catalytic activity was observed.

Deep oxidation in propane oxidative dehydrogenation to propene over V2O5/γ-Al2O3 studied by in-situ DRIFTS

Abstract In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150∼250 °C with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.

Selective Catalytic Reduction of NOx with NH3 on a Cr-Mn Mixed Oxide at Low Temperature

Abstract A series of Cr-Mn mixed oxide catalysts were prepared by the citric acid method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. The effect of Cr/(Cr + Mn) molar ratio on activity for the selective catalytic reduction (SCR) of NO x by ammonia in the presence of excess oxygen at low temperature (80–220 °C) was studied. A 98.5% NO x conversion with 100% selectivity for N 2 was obtained with Cr(0.4)-MnO x mixed oxide (Cr/(Cr + Mn) molar ratio = 0.4) at 120 °C and a space velocity of 30000 h −1 . XRD results showed that the addition of chromium to MnO x produced a CrMn 1.5 O 4 crystal phase, which played an important role in low-temperature SCR.

Preparation of palladium nanoparticle catalyst in ionic liquid and its catalytic properties for Heck-Mizoroki reaction

Abstract A palladium nanoparticle (PdNPs) catalyst was synthesized in halogen-free anion ionic liquid (1-buthyl-3-methylimidazolium lactate, [Bmim]Lac) by a simple chemical approach. The transmission electron microscopy analysis confirmed the presence of highly dispersed PdNPs in [Bmim]Lac with small average particle size distribution from 2.2 to 3.1 nm. The size of the PdNPs increases with decreasing molar ratio of [Bmim]Lac to Pd(OAc) 2 and increasing temperature. The activity of PdNPs@[Bmim]Lac catalyst was tested by the Heck-Mizoroki reaction, and the conditions were optimized. The catalyst can efficiently catalyze couplings of various aryl bromides and iodides with different olefins, giving good yields of products under the optimal conditions and be recycled up to six consecutive times.

Stable narrowband red emission in fluorotellurate KTeF5:Mn4+via Mn4+ noncentral-site occupation

Unlike conventional central-site doping, herein, abnormally equivalent Mn4+ accommodation in a five-fold coordinated distorted octahedron in the vertical occupation site is reported in fluorotellurate KTeF5:Mn4+. This very unique substitution results in thermally stable (remaining emission of 86.7% at 423 K) and highly purified red emission in KTeF5:Mn4+. Refined contrasts of the coordination environment, crystal field, nephelauxetic effect, temperature-dependent static and dynamic luminescence behavior, and defect mechanism between fluorides with different Mn4+ accommodation models (K2SiF6:Mn4+, K2NaAlF6:Mn4+, KTeF5:Mn4+, K3ZrF7:Mn4+, K2TaF7:Mn4+ and Na3TaF8:Mn4+) are conducted to investigate the local environment dependence of the Mn4+ emission properties. It is found that the emission of KTeF5:Mn4+ might be stabilized by equivalent octahedral Mn4+ accommodation with interstitial defects. These findings reveal the possible effects of special accommodation models on the Mn4+ emission properties, which further enlighten us to explore stable fluoride red phosphors with suitable Mn4+ accommodation for white light-emitting diode applications.