VmTi和KnV0.04Ti担载氧化物催化剂的表征与催化燃烧柴油炭黑的性能

用FTIR和UV-Vis研究了2个系列不同V和K负载量的VOx/TiO2和K-VOx/TiO2催化剂结构的变化;并使用程序升温氧化反应技术对这两种催化剂催化柴油炭黑燃烧活性进行了考察.结果表明,当VOx/TiO2催化剂中n(V)∶n(Ti)=0.04时,催化剂活性最好(tm=389℃).添加K能显著改善VOx/TiO2催化剂活性,n(K)∶n(V)∶n(Ti)=0.04∶0.04∶1时,炭黑燃烧的反应温度最低(tm=343℃).FTIR和UV-Vis结果表明,当VOx/TiO2催化剂n(V)∶n(Ti)>0.04∶1时,催化剂表面有V2O5形成,由于V2O5氧化能力较弱,因而催化剂的活性反而降低.而当K-VOx/TiO2催化剂中n(K)∶n(V)达到1∶1时,由于形成的KVO3物种与TiO2载体有很好的协同作用,所以催化剂活性最好.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature

Commercially available copper(II) tetrafluoroborate hydrate was found to be a highly efficient catalyst for chemoselective N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions and at room temperature. Various aromatic amines were protected as their N-tert-butyl carbamates in high yields and in short times. No competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation was observed. Chemoselective N-tert-butoxycarbonylation was achieved with substrates bearing OH and SH groups. Chiral α-amino acid esters afforded the corresponding N-t-Boc derivatives in excellent yields.     

Osmium catalyzed asymmetric dihydroxylation of methyl trans-cinnamate in ionic liquids, followed by supercritical CO2 product recovery

In this work, osmium-catalyzed asymmetric dihydroxylation (AD) of methyl trans-cinnamate was studied. Osmium and chiral ligand catalysts were immobilized in ionic liquid only, without any other reaction solvents, while the recovery of the product was performed by extraction with supercritical CO₂, and compared with results obtained by extractions with organic solvents such as hexane and diethyl ether. In supercritical CO₂ extraction experiments, optimal extraction pressure was found and ionic liquid chosen, so that the highest reaction yields coupled with lowest osmium content in the crude product can be achieved. Finally, recycle experiments of the same (ionic liquid + catalytic system) mixture were successfully conducted. Application of ionic liquids and supercritical CO₂ in osmium catalyzed AD allows for the isolation of the diol basically without contamination with osmium, in high yield and enantiomeric excess, and it makes possible the efficient reuse of ionic liquid solvent and the catalytic system.     

Imine Derivatives of Fumaraldehyde From Oxidation of A β-Aziridinyl Alcohol

Oxidation of a β-aziridinyl alcohol with tetrapropylammonium perruthenate yields a pyrrole and two unusual imine derivatives of fumaraldehyde.     

Improving the Efficiency of Dehydrogenation Catalyst Resource while Reducing the H2 Gas Circulation Rate

In the research the various ways of increasing the selectivity of the dehydrogenation process and reducing the intensity of coke formation have been studied. All results were received by means of the mathematical model of the dehydrogenation process with the calculating technique of optimal water flow. The main conclusion consists in the fact that the decrease in molar ratio H2/feed leads to increasing the catalyst deactivation by coke. It can be partially compensated by increasing the supplied water flow to the reactor to 13-14 l/h instead of 9-10 l/h at the end of cycle. Reducing the life of the catalyst to 270-290 days even at an increased water flow is determined by the intensity of the coking reactions. However, the economic feasibility of operating in such condition causes a considerable increase in production of LAB to 181-186 t/day.     

Renewable Feedstocks: The Problem of Catalyst Deactivation and its Mitigation

Much research has been carried out in the last decade to convert bio‐based feedstock into fuels and chemicals. Most of the research focuses on developing active and selective catalysts, with much less attention devoted to their long‐term stability. This Review considers the main challenges in long‐term catalyst stability, discusses some fundamentals, and presents options for their mitigation. Three main challenges are discussed: catalyst fouling, catalyst poisoning, and catalyst destruction. Fouling is generally related to the deposition of insoluble components present in the feed or formed by degradation of the feed or intermediates. Poisoning is related to the deposition of electropositive contaminants (e.g. alkali and alkaline earth metals) on acid sites or of electronegative contaminants (e.g. N and S) at hydrogenation sites. Catalyst destruction results from the thermodynamic instability of most oxidic supports, solid acids/bases, and hydrogenation functions under hydrothermal conditions.     

1-Methylimidazolium tetrafluoroborate [Hmim][BF4]: an efficient acidic ionic liquid catalyst for insertion of α-diazo compounds into the N–H bonds of amines

The reusable acidic ionic liquid, 1-methylimidazolium tetrafluoroborate [Hmim][BF₄], was found to be an effective catalyst for the insertion of α-diazoacetate into the N–H bonds of amines. The corresponding products were obtained in good yields and short reaction times via a simple procedure. The catalyst could be recycled and reused without any noticeable decrease in its activity.     

Promoting the Phosphidation Process using an Oxygen Vacancy Precursor for Efficient Hydrogen Evolution Reaction

Based on previous works, most of the transition metal phosphides (TMPs) were directly prepared by decomposing NaH₂PO₂ with the precursors at high temperatures, which resulted in different degrees of phosphidation in the final product. Therefore, it is necessary to design an innovative approach to enhance the degree of phosphidation in the material using crystal defects. Here, oxygen-vacancy iron oxide/iron foam (Ov-Fe₂O₃/IF) was firstly prepared by generating oxygen vacancy in situ in an iron foam through heating in vacuum conditions. Subsequently, FeP/IF was formed by phosphating Ov-Fe₂O₃/IF. Under the effects of oxygen vacancies, oxygen-vacancy iron oxide could be completely phosphatized to produce more active sites on the surface of the material. This, in turn, could result in a catalyst with exceptional hydrogen evolution activity. Thus, the successful fabrication of FeP/IF demonstrated in this work provides an effective and feasible way for the preparation of other high-efficiency catalysts.     

Unveiling the importance of reactant mass transfer in environmental catalysis: Taking catalytic chlorobenzene oxidation as an example

To date, investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis. Herein, we demonstrated that by rationally designing the adsorption sites of multi-reactants, the pollutant destruction efficiency, product selectivity, reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation (CBCO). Experimental results revealed that the co-adsorption of chlorobenzene (CB) and gaseous O₂ at the oxygen vacancies of CeO₂ led to remarkably high CO₂ generation, owning to their short mass transfer distance on the catalyst surface, while their separated adsorptions at Brönsted HZSM-5 and CeO₂ vacancies resulted in a much lower CO₂ generation, and produced significant polychlorinated byproducts in the off-gas. However, this separated adsorption model yielded superior long-term stability for the CeO₂/HZSM-5 catalyst, owning to the protection of CeO₂ oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Brönsted acidic sites. This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer; investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.