Liquid discharge plasma for fast biomass liquefaction at mild conditions: The effects of homogeneous catalysts

Non-thermal plasma exhibits unique advan-tages in biomass conversion for the sustainable production of higher-value energy carriers.Different homogeneous catalysts are usually required for plasma-enabled biomass liquefaction to achieve time-and energy-efficient conver-sions.However,the effects of such catalysts on the plasma-assisted liquefaction process and of the plasma on those catalysts have not been thoroughly studied.In this study,an electrical discharge plasma is employed to promote the direct liquefaction of sawdust in a mixture of polyethylene glycol 200 and glycerol.Three commonly used chemicals,sulfuric acid,nitric acid and sodium p-toluene sulfate,were selected as catalysts.The effects of the type of catalyst and concentration on the liquefaction yield were examined;further,the roles of the catalysts in the plasma liquefaction process have been discussed.The results showed that the liquefaction yield attains a value of 90%within 5 min when 1%sulfuric acid was employed as the catalyst.Compared with the other catalysts,sulfuric acid presents the highest efficiency for the liquefaction of sawdust.It was observed that hydrogen ions from the catalyst were primarily responsible for the significant thermal effects on the liquefaction system and the generation of large quantities of active species;these effects directly con-tributed to a higher efficacy of the plasma-enabled liquefaction process.

POLYMERIZATION MECHANISM OF DIENES WITH HOMOGENEOUS RARE EARTH CATALYSTS

The reaction mechanisms of diene polymerization with homogeneous rare earth catalyst are studied by means of the spectra of ~1H-NMR, one-and two-dimensions ^(13)C-NMR. Based on the data of above NMR spectra, it is proposed that the polymerization reaction proceeds according to the following mechanism: η~4-diene (cis-trans-)and η~3-allyl (syn-anti-).

Homogeneous Oxidative Coupling Catalysts： Reactivity of [（Pyr）nCuX]4O2 with Carbon Dioxide to Generate New Active Initiators [（Pyr）nCuX]4（CO3）2 （n = 1 or 2, X = Cl, Br or I, Pyr = Pyrrolidine）

This paper represents the interaction of well characterized Lewis base [（Pyr）nCuX]4O2, n = 1 or 2, X = Cl, Br or I, Pyr = pyrrolidine with CO2 as a Lewis acid to produce new series of oxidative coupling and catechol oxidase initiators [（Pyr）nCuX]4（CO3）2. These carbonato derivatives are isolated as stable solids. They are easily soluble in aprotic solvents as CH2Cl2 or PhNO2. Cryoscopic measurements support tetranuclear core structure for all of them. Infrared spectra show differences from their oxo analogous in the carbonato domains but those differences did not distinguish between tridentate bridging carbonato and bidentate one. Rate of oxidation of 2,6-dimethylphenol （DMP） by [（Pyr）CuCl]4（CO3）2, supports coordination number six for Cu（Ⅱ） centers in [（Pyr）CuCl]4（CO3）2. In order to fulfill coordination number six, for n = 1, carbonate will act as tridentate while for n = 2, it will act as bidentate, as shown in Scheme 4. Near infrared spectra indicate a [（3 halo） Cu（Ⅱ） charge transfer] for [（Pyr）nCuX]4（CO3）2, n = 1 or 2, X = Cl or Br. Low molecular absorptivities of the maxima at 825 nm and 730 nm for [（Pyr）nCuI]4（CO3）2, n = 1 or 2 with a minimum of high molecular absorptivities at 600 nm, comparing to X= CI or Br analogous, support a step structure for [（Pyr）,Cul]4（CO3）2, as shown in Scheme 5. Cyclic voltammograms for [（Pyr）nCuX]4（CO3）2; n = 1 or 2, X = CI or Br, are irreversible in characters.

Catalytic effect in lithium metal batteries: From heterogeneous catalyst to homogenous catalyst

Lithium metal batteries are regarded as prominent contenders to address the pressing needs owing to the high theoretical capacity.Toward the broader implementation,the primary obstacle lies in the intricate multi-electron,multi-step redox reaction associated with sluggish conversion kinetics,subsequently giving rise to a cascade of parasitic issues.In order to smooth reaction kinetics,catalysts are widely introduced to accelerate reaction rate via modulating the energy barrier.Over past decades,a large amount of research has been devoted to the catalyst design and catalytic mechanism exploration,and thus the great progress in electrochemical performance has been realized.Therefore,it is necessary to make a comprehensive review toward key progress in catalyst design and future development pathway.In this review,the basic mechanism of lithium metal batteries is provided along with corresponding advantages and existing challenges detailly described.The main catalysts employed to accelerate cathode reaction with emphasis on their catalytic mechanism are summarized as well.Finally,the rational design and innovative direction toward efficient catalysts are suggested for future application in metal-sulfur/gas battery and beyond.This review is expected to drive and benefit future research on rational catalyst design with multi-parameter synergistic impacts on the activity and stability of next-generation metal battery,thus opening new avenue for sustainable solution to climate change,energy and environmental issues,and the potential industrial economy.

NONBRIDGED HALF-TITANOCENES CONTAINING ANIONIC ANCILLARY DONOR LIGANDS:PROMISING NEW CATALYSTS FOR PRECISE SYNTHESIS OF CYCLIC OLEFIN COPOLYMERS(COCs)

Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp TiCl_2(L)(Cp =cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp TiCl_2(X)(X=N=C Bu_2,O-2,6- Pr_2C_6H_3; Cp =Cp,C_5Me_5,indenyl)was related to the calculated coordination ene...

Kinetics of esterification of methanol and acetic acid with mineral homogeneous acid catalyst

In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L-1to 0.3268 mol·L-1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot.The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.

A simple hydroxypyridine ionic liquids for conversion of CO_(2)into quinazoline-2,4(1H,3H)-diones under atmospheric conditions

The transformation of CO_(2)into high value-added product is a promising pathway for utilizing CO_(2).However,the process tends to require harsh reaction conditions owing to CO_(2)chemical inertness.Designing a high efficiency catalytic system with environmentally benign characteristic are important determinants.In this work,protic ionic liquids[TMG][2-OPy]were prepared via one-step neutralization between 1,1,3,3-tetramethylguanidine and 2-hydroxypyridine,applying to the domain of synthesizing quinzoline-2,4(1 H,3H)-diones from CO_(2)and 2-aminobenzontiles without any solvent or metal,achieving the yield of 97%at 90℃for 8 h under atmospheric.A series of substrates with good to acceptable yield were detected,revealing the generality and universality of the catalyst.Furthermore,the system could be facilely reused for at least six runs,retaining the yield of 94%.A preliminary kinetic equation is calculated with the activation energy of 68 kJ·mol^(-1),and a plausible reaction mechanism was put forward.This study highlights that the[TMG][2-OPy]enables to activate CO_(2)carboxylation efficiently.

Single-atom catalysis: Bridging the homo-and heterogeneous catalysis

Single-atom catalysis,the catalysis by single-atom catalysts(SACs),has attracted considerable attention in recent years as a new frontier in the heterogeneous catalysis field.SACs have the advantages of both homogeneous catalysts(isolated active sites)and heterogeneous catalysts(stable and easy to separate),and are thus predicted to be able to bridge the homo-and heterogeneous catalysis.This prediction was first experimentally demonstrated in 2016.In this mini-review,we summarize the few homogeneous catalysis progresses reported recently where SACs have exhibited promising application:a)Rh/ZnO and Rh/CoO SAC have been used successfully in hydroformylation of olefin of which the activity are comparable to the homogeneous Wilkinson’s catalyst;b)a Pt/Al2O3 SAC has shown excellent performance in hydrosilylation reaction;and c)M-N-C SACs(M=Fe,Co etc.)have been applied in the activation of C–H bonds.All of these examples suggest that fabrication of suitable SACs could provide a new avenue for the heterogenization of homogeneous catalysts.These pioneering works shed new light on the recognition of single-atom catalysis in bridging the homo-and heterogeneous catalysis.

Efficient and recyclable Rh-catalytic system with involvement of phosphine-functionalized phosphonium-based ionic liquids for tandem hydroformylation—acetalization

The phosphine-functionalized phosphonium-based ionic liquids(dppm-Q, dppe-Q, dppp-Q and dppb-Q) as the bi-functional ligands enable the efficient one-pot tandem hydroformylationeacetalization. It was found that, in dppm-Q, dppe-Q, dppp-Q and dppb-Q, the incorporated phosphino-fragments were responsible for Rh-catalyzed hydroformylation and the phosphoniums were in charge of the subsequent acetalization as the Lewis acid catalysts. Moreover, the diphosphonium-based ionic liquid of dppb-DQ could be applied as a co-solvent to immobilize the Rh/dppb-Q catalytic system with the advantages of the improved catalytic performance, the available catalyst recyclability, and the wide generality for the substrates.

Engineering Coordination Environment of Cobalt Center in Molecular Catalysts for Improved Photocatalytic CO_(2) Reduction

The creation of effective and inexpensive catalysts is essential for photocatalytic CO_(2) reduction.Homogeneous molecular catalysts,possessing definite crystal structures,are desirable to study the relationship between catalytic performance and coordination microenvironment around catalytic center.In this report,we elaborately developed three Co(II)-based molecular catalysts with different coordination microenvironments for CO_(2) reduction,named[CoN_(3)O]ClO_(4),[CoN_(4)]ClO_(4),and[CoN_(3)S]ClO_(4),respectively.The optimal[CoN_(3)O]ClO_(4) photocatalyst has a maximum TON of 5652 in photocatalytic reduced CO_(2) reduction,which is 1.28 and 1.65 times greater than that of[CoN_(4)]ClO_(4) and[CoN_(3)S]ClO_(4),respectively.The high electronegativity of oxygen in L1(N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine)provides the Co(II)catalytic centers with low reduction potentials and a more stable*COOH intermediate,which facilitates the CO_(2)-to-CO conversion and accounts for the high photocatalytic activity of[CoN_(3)O]ClO_(4).This work provides researchers new insights in development of catalysts for photocatalytic CO_(2) reduction.

A series of 1,8-dioxooctahydroxanthenes are prepared using trichloroisocyanuric acid

A series of aromatic aldehydes are turned in to 3,3,6,6-tetramethy1-9-aryl-1,8-dioxooctahydroxanthene derivatives using trich/oroisocyanuric acid （TCCA） as the catalyst.

Homogeneous Electrocatalytic Water Oxidation by a Rigid Macrocyclic Copper（Ⅱ） Complex

A copper（Ⅱ） complex with a rigid macrocyclic ligand has been synthesized and utilized as a homogeneous electrocatalyst for water oxidation in sodium phosphate buffer at pH 12,0.By using a glassy carbon electrode in a 3 h electrolysis,a high current density of 1.3-1.4 mA/cm2 and a turn-over number of 4 can be obtained with 1.0 mmol·L-1 of the copper catalyst at an overpotential of 750 mV.Kinetic studies revealed that the electrocatalysis with this complex is a single-site catalysis with proton-coupled electron transfers.Finally,its possible catalytic mechanism was tentatively proposed.

Catalytic alkane dehydrogenations

Olefins find widespread applications in the synthesis of polyolefins and fine chemicals. With an increasing demand for olefins, the technologies for alkane dehydrogenation have drawn much attention. Several types of heterogeneous catalysts have found applications in industry for the dehydrogenation of light alkanes, mainly ethane, propane, and butane. In the past three decades, a number of transition-metal complexes,particularly pincer-ligated iridium complexes, have been developed as the homogeneous catalysts for alkane dehydrogenations. The homogeneous catalyst systems operate under much milder conditions compared with the heterogeneous systems, and some systems exhibit good activity and high regioselectivity in dehydrogenation of alkanes longer than butane.

Hydrogen generation from methanol reforming under unprecedented mild conditions

A homogeneous catalyst [Cp＊Rh（NH3）（H2O）2]-（3＋） has been found for the clean conversion of methanol and water to hydrogen and carbon dioxide. The simple and easily available reaction steps can circumvent the formation of CO, therefore, making it possible to avoid inactivating catalysts and contaminating the hydrogen fuel. Different from conventional reforming method for hydrogen production, no additional alkaline or organic substances are required in this method. Valuable hydrogen can be obtained under ambient pressure at 70 C, corresponding TOF is 83.2 h 1. This is an unprecedented success in reforming methanol to hydrogen. Effects of reaction conditions, such as reaction temperature, initial methanol concentration and the initial p H value of buffer solution on the hydrogen evolution are all systematically investigated. In a certain range, higher reaction temperature will accelerate reaction rate. The slightly acidic condition is conducive to rapid hydrogen production. These findings are of great significance to the present establishment of the carbon-neutral methanol economy.

A Simple and Efficient Copper（Ⅱ） Complex as a Catalyst for N-Arylation of Imidazoles

Four inexpensive and air-/moisture-stable pyrrolecarbaldiminato-Cu complexes 1-4 were synthesized and evaluated to be a novel class of catalysts for the N-arylation of imidazoles with aryl halides. A variety of aryl iodides, bromides and activated aryl chlorides underwent the coupling with imidazoles, promoted by the catalyst 4, in moderate to good yields without the protection by an inert gas.

A green multicomponent synthesis of bioactive pyrimido[4,5-b]quinoline derivatives as antibacterial agents in water catalyzed by RuCl_3·xH_2O

An efficient, convenient and environmentally benign one-pot multicomponent reaction for the preparation of pyrimido[4,5-b]quinoline derivatives as biologically, pharmacologically and antibacte- rially active products has been developed using RuC13.xH20 as a reusable homogenous catalyst. Use of water as a green solvent, purification of products by non-chromatographic methods, reusability of transition metal homogenous catalyst, saving energy by employing multicomponent reactions, short reaction times and high yields, are some of the advantages of this process.

One-pot five-component synthesis of highly functionalized piperidines using oxalic acid dihydrate as a homogenous catalyst

An efficient green protocol is described for the preparation of highly functionalized piperidines via a one-pot five-component reaction between aromatic aldehydes,anilines andβ-ketoesters in the presence of oxalic acid dihydrate as catalyst in ethanol at ambient temperature.The structure as well as the relative stereochemistry of these compounds was confirmed by single X-ray crystallographic analysis.

Catalytic effect of lucunary heteropolyanion containing molybdenum and tungsten atoms on decolorization of direct blue 71

In this research,a lucunary Keggin structure,[PMo_2W_9O_（39）]^（7-） was selected as an efficient homogenous catalyst for degradation of an azo dye（direct blue 71） and a simple method was developed for degradation of DB71.The method is based on the oxidation of azo dye in the presence of a lucunary Keggin form of polyoxometalates,K_7[PMo_2W_9O_（39）]？ 19H_2O,as a homogenous catalyst at room temperature.The reaction is monitored spectrophotometrically by measuring the absorbance of dye atλ=585 nm.Some parameters including concentration of catalyst,concentration of H_2O_2,pH and reaction time were investigated and optimized. Results show that K_7[PMo_2W_9O_（39）]？ 19H_2O is more efficient in the presence of hydrogen peroxide.Degradation of dye in the presence of the catalyst and H_2O_2 could lead to the disappearance approximately 65%of dye after 60 min.But degradation for the same experiment performed in the absence of catalyst or in the absence of H_2O_2 was 22%or 5%respectively.Approximately 87% azo dyes has been eliminated after 90 min in the presence of catalyst,H_2O_2 and optimize conditions（0.6 g/L of K_7[PMo_（2-） W_9O_（39）H_9H_2O,0.08 mol/L hydrogen peroxide and room temperature）.

Propane-1,2,3-triyl tris(hydrogen sulfate): A mild and efficient recyclable catalyst for the synthesis of biscoumarin derivatives in water and solvent-free conditions

A simple, efficient, and ecofriendly procedure has been developed using propane-l,2,3-triyl tris（hydrogen sulfate） as a catalyst for the synthesis of biscoumarin derivatives in water and solvent-free conditions. The significant features of the present protocol are simplicity, environmentally benign, high yields, no chromatographic separation, and recyclability of the catalyst.

Highly active iridium catalyst for hydrogen production from formic acid

Formic acid（FA） dehydrogenation has attracted a lot of attentions since it is a convenient method for H_2 production. In this work, we designed a self-supporting fuel cell system, in which H_2 from FA is supplied into the fuel cell, and the exhaust heat from the fuel cell supported the FA dehydrogenation. In order to realize the system, we synthesized a highly active and selective homogeneous catalyst Ir Cp＊Cl_2 bpym for FA dehydrogenation. The turnover frequency（TOF） of the catalyst for FA dehydrogenation is as high as7150 h^（-1）at 50°C, and is up to 144,000 h^（-1）at 90°C. The catalyst also shows excellent catalytic stability for FA dehydrogenation after several cycles of test. The conversion ratio of FA can achieve 93.2%, and no carbon monoxide is detected in the evolved gas. Therefore, the evolved gas could be applied in the proton exchange membrane fuel cell（PEMFC） directly. This is a potential technology for hydrogen storage and generation. The power density of the PEMFC driven by the evolved gas could approximate to that using pure hydrogen.