Degradation of Alkaline Lignin in the Lactic Acid-Choline Chloride System under Mild Conditions

Lignin is a natural polymer,second only to cellulose in natural reserves.Degradation is one of the ways to achieve the high-value transformation of lignin.Deep eutectic solvent(DES)thermal degradation of lignin can be used as an excellent green degradation method.This paper introduces the degradation mechanism and effect of the lactic acid-choline chloride DES system in dissolving and degrading alkaline lignin,and the final solvent recovery.It can also be found from the scanning electron microscope(SEM)images that the surface of the degraded solid product is transformed from smooth to disordered.Fourier transform infrared(FTIR)spectroscopy and 1H-NMR spectroscopy were used to characterize the changes in lignin functional groups during DES treatment.The results showed that the content of phenolic hydroxyl groups increased after degradation,indicating that theβ-O-4 ether bond was broken.The molecular weight of the degraded lignin was observed by gel permeation chromatography(GPC),and the lignin residue with low molecular weight and narrow polydispersity index was obtained.The lowest average molecular weight(Mw)reached 2512 g/mol.The ratio of oxygen to carbon atoms in lignin increased substantially during degradation as measured by X-ray photoelectron spectroscopy(XPS),probably because DES treatment was accompanied by many oxidation reactions,which led to significant structural changes in lignin and a large number of ether bond breakage reactions during the reaction.The main final degradation products are aromatic monomers,vanillin,butyrovanillone,etc.

Insight into the oxidative desulfurization of high-sulfur petroleum coke under mild conditions:a journey of vanadium-substituted Dawson-type phosphotungstic acid

High-sulfur petroleum coke(HSPC),that is a by-product from slag oil in the coking process of refning,shows versatility values in practical applications and,however,concentrates the majority of organic sulfur.Herein,we design and construct a highly efective CTAB@HPA composites to be explored for the catalytic oxidative desulfurization of HSPC under mild conditions using hydrogen peroxide as the oxidant and 1-butyl-3-methylimidazole tetrafuoroborate ionic liquid as the extractant.The results demonstrate that the sulfur content of HSPC could be strikingly reduced from 4.46 wt%to 2.48 wt%under 60℃ and atmospheric pressure,and that the organic sulfur in HSPC is mainly oxidized to sulfoxide,sulfone and sulfate,which latter can be directly separated from petroleum coke.Moreover,the efect of reaction conditions on the desulfurization performance of HSPC as well as the catalytic oxidation reaction kinetic of HSPC desulfurization was systematically investigated.Furthermore,a mechanism for the oxidative desulfurization of HSPC over CTAB@HPA catalysts was proposed.Therefore,this work provides new insight into how to construct active catalysts for the desulfurization of HSPC under mild conditions.

Electrochemical Activation of CO_2 for the Synthesis of Ethyl Carbanilate under Mild Conditions

A novel electrochemical procedure for the synthesis of ethyl carbanilate from aniline and carbon dioxide was developed via the selective cathodic reduction of carbon dioxide in CO2-saturated DMF solution containing 0. 1 mol/L TEABr at room temperature, followed by the addition of Eft as an alkylating agent. The synthesis was carried outun der mild[p（CO2） = 1.0×10^5 Pa, t =20 ℃ ] and safe conditions. Influences of the nature of the electrodes, the current densities, the passed charges during electrolysis, temperatures, and supporting electrolytes on the yield of ethyl carbanilate were studied to optimize the electrolytic conditions. The selectivity of ethyl carbanilate is 100%.

Novel HBD-Containing Zn (dobdc) (datz) as efficiently heterogeneous catalyst for CO_(2) chemical conversion under mild conditions

A novel Zn-based metal–organic framework Zn(dobdc)(datz)[Zn_(2)(H2dobdc)(datz)2$1.5DMF]with plentiful hydrogen bond donors(HBD)groups was facilely synthesized from mixed ligands.The dual activation of metal Zn sites and HBD groups for epoxides by forming Zn–O adduct and hydrogen bonds facilitated the ring-opening of epoxide substrate,which is critical for the subsequent CO_(2) fixation.Also,the existence of micropores and N-rich units in Zn(dobdc)(datz)afforded affinity towards CO_(2),which is beneficial to further improvement on catalytic CO_(2) conversion performance.Satisfactorily,Zn(dobdc)(datz)/Bu4NBr system was proved efficient heterogeneous catalyst for the CO_(2) cycloaddition with epoxides,and 98%propylene carbonate yield was obtained under mild conditions(80C,1.5 MPa and solvent-free).In addition,Zn(dobdc)(datz)/Bu4NBr exhibited remarkable versatility to different epoxides and could be completely recycled over six runs with high catalytic activity.The highly stable,easily recycle and solvent-free Zn-based MOF reported here displays eco-friendly and efficient performance to CO_(2)conversion.

Recent advances on aerobic photocatalytic methane conversion under mild conditions

Photocatalytic methane conversion to high value-added chemicals under mild conditions acts as a promising approach to utilize natural gas and renewable energy.Specifically,aerobic photocatalytic methane conversion that uses molecular oxygen as oxidant has attracted much attention because it is thermodynamic favorable and could generate various reactive oxygen species,resulting in many value-added products like methanol,formaldehyde,ethane,and ethylene.In this review,we classify the aerobic photocatalytic methane conversion into aerobic photocatalytic partial oxidation of methane(APPOM)and aerobic photocatalytic coupling of methane(APCM).We particularly focus on the fundamentals of oxygen activation and methane reaction modes in these conversions.Finally,we provide a brief summary for current challenges and future prospects towards aerobic photocatalytic methane conversion.

Mesoporous titanium-aluminosilicate as an efficient catalyst for selective oxidation of cyclohexene at mild reaction conditions

Mesoporous titanium containing alumino-silicate materials with various titanium/silicon(Ti/Si) ratio(AlSi-Ti(n);n = Ti/Si mole ratio) have been successfully synthesized by a novel single-step sodium(Na)-free method, for the first time. The obtained characterization results of the prepared materials reveal that in-situ addition of Ti into AlSi shows ordered mesoporous structure along with uniformly dispersed Ti species in +4 and +3 oxidation states suitable for selective oxidation of allylic C—H bond. The prepared mesoporouse Ti-AlSi(n) samples exhibited excellent activity in the oxidation of cyclohexene with 100%conversion and 100% selectivity to ketone-alcohol(KA) oil(cyclohex-2-en-1-ol and 2-cyclohexen-1-one) at low temperature and reaction time(35℃ and 30 min reaction time). This study suggests that AlSi-Ti(0.05) material can be a promising catalyst for the selective oxidation of cyclohexene under mild reaction conditions.

Hydrodesulfurization of coal tar pitch using Pt/Al_(2)O_(3)and Pd/Al_(2)O_(3)catalysts under mild conditions

Hydrodesulfurization(HDS)of coal tar pitch(CTP)using Pt/Al_(2)O_(3)and Pd/Al_(2)O_(3)catalysts in tetrahydrofuran at 333 K and atmospheric pressure was investigated.The HDS of dibenzothiophene(DBT)proceeded over both the Pt and Pd catalysts under the mild conditions.The effects of polycyclic aromatic hydrocarbons on the HDS of DBT were examined:a naphthalene ring suppressed the HDS,while a benzene ring did not.CTP underwent HDS as well as partial hydrogenation under the mild conditions.The Pt catalyst was more active than the Pd catalyst in the HDS of CTP.The sulfur content in CTP was reduced by over 50%through the HDS process.

Defective NH_(2)-UiO-66(Zr) effectively converting CO_(2) into cyclic carbonate under ambient pressure,solvent-free and co-catalyst-free conditions

In this study,a series of metal-organic frameworks(MOFs)NH_(2)-UiO-66-x HAc catalysts were synthesized by solvothermal method using acetic acid(HAc)as a modulator,and were applied to the cycloaddition of CO_(2)and epichlorohydrin(EPIC)under ambient pressure.Influences of the modulation by HAc on morphologies and structures of the MOFs are demonstrated via PXRD,FESEM,FTIR,N_(2)adsorption-desorption,XPS and ^(1)H NMR characterizations.The results show that the MOFs containing mesoporous pores can be prepared by adjusting the concentration of HAc.By optimizing the amount of HAc added,the specific surface area of NH_(2)-UiO-66-8 HAc is as high as 879.17 m^(2)·g^(-1),which is 28.3%higher than that of the original MOFs.And the evaluation of catalytic performance showed that HAc modulation enhanced the activity of NH_(2)-UiO-66-x HAc under mild conditions.The exposure of Lewis acid sites,increased specific surface area and porosity via the modulation of HAc defective ligand can be supposed the key factors to determine the enhanced catalytic activities.In addition,considering the influence of gas concentration on the reaction,the concept of TOP(Turnover of Pressure,defined as the mass of conversions of a unit mass catalyst under unit pressure and unit time)was first proposed in this article.

Sub/supercritical carbon dioxide induced phase switching for the reaction and separation in ILs/methanol

Separation of products from ionic liquid(IL) solvents is one of the main challenges that hinder their utilizations. In this study, the production of γ-valerolactone(GVL) by selective hydrogenation of α-angelica lactone(AL) and separation of the products from the IL solvent were carried out by using subcritical CO_2 as a "switch" at room temperature. After the mixture was separated into two phases by subcritical CO_2, AL and nano Pd/C catalyst were only found in the lower IL-rich phase, GVL was produced with quantitative yield and enriched in the upper methanolrich phase. Pure GVL can be obtained by depressurizing to release CO_2 and evaporation to remove methanol of the upper phase, the lower phase containing IL, catalyst and methanol can be recycled for the next reaction. The strategy may provide a new approach to produce and separate products from IL solvents at mild conditions.

Mild and efficient recovery of lithium-ion battery cathode material by deep eutectic solvents with natural and cheap components

Dissolution of lithium cobalt oxide(LCO)is the key step for the recovery of valuable metals(e.g.,Co and Li)from spent LCO-based lithium-ion batteries(LIBs).However,the dissolution process of LCO either needs toxic solvents,and high temperature,or shows low efficiency.Deep eutectic solvents(DESs)are potential green solvents to dissolve LCO.Here,DESs with polyethylene glycol(PEG)as hydrogen bond acceptor and ascorbic acid(AA)as hydrogen bond donor are found to dissolve LCO with 84.2%Co leaching efficiency at 80℃ and 72 h,which is higher than that from the reported references by common DESs.Furthermore,both DESs components(i.e.,PEG and AA)are cheap,biodegradable,and biocompatible.AA could be easily and abundantly extracted from natural fruits or vegetables.It provides a new guide for the green,mild,and efficient dissolution of LCO aiming at sustainable recovery of spent LIBs.

[Bmim]OAc Catalyzed Michael Addition of Active Methylene to α,β-Unsaturated Carboxylic Esters and Nitriles

Michael addition of active methylene compounds to α,β-unsaturated carboxylic esters and nitriles was effectively catalyzed by a basic ionic liquid, 1-butyl-3-methylimidazolium acetate（[Bmim]OAc）. The his-addition products were selectively obtained in high yields under mild reaction conditions.

Visible-light-promoted tandem decarboxylation coupling/cyclization of N-aryl glycines with quinoxalinones: Easy access to tetrahydroimidazo [1,5-a]quinoxalin-4(5H)-ones

A visible-light-promoted formal[2+2+1]cyclization of N-aryl glycines with quinoxalin-2(1H)-ones to synthesize tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones have been developed.The protocol features operational simplicity,mild reaction conditions with blue LED light employing Ru(bpy)3Cl2.6H2O as a photoredox catalyst,a combination of O2 from air and Cu(OAc)2 as the oxidant and broad substrate applicability.

An efficient synthesis of bis(indolyl)methanes and N,N'-alkylidene bisamides by Silzic under solvent free conditions

An operationally simple and green method for the synthesis of a wide range of bis（indolyl）methanes,and N,N＇-alkylidene bisamides under mild conditions,with excellent yields using Silzic,has been developed.This improved method furnishes in good yields bis（indolyl）methanes derivatives starting from indole and aldehydes,or ketones,and N,N＇-alkylidene bisamides derivatives starting from acetamide and aldehydes.The catalytic system was reused up to three times with the same efficiency.

W/Mo-polyoxometalate-derived electrocatalyst for high-efficiency nitrogen fixation

Ammonia is the feedstock chemical for most fertilizers and the alternative of renewable energy carriers.Environmentally benign electrochemical nitrogen reduction reaction (NRR) under mild conditions has been recognized as one of the most attractive strategies for N_(2) fixation.Herein,inspired by Mobased nitrogenase,W/Mo-doping electrocatalysts were developed with mixed-metal polyoxometalate H_(3)PW_6Mo_6O_(40) as the precursor for high performance electrocatalytic NRR.Trace amount of Pt was transplanted on the surface of W/Mo@rGO via in situ electroplating treatment to further improve the NRR performance.The resulting Pt-W/Mo@rGO-6 achieves excellent performance for NRR with a high NH_(3)yield of 79.2μg h^(-1)mg_(cat)^(-1) due to the multicomponent synergistic effect in the composite catalyst.The Pt-W/Mo@rGO-6 represents the first example of highly efficient NRR electraocatalyst derived from mixed-metal polyoxometalate,which exhibits outstanding stability confirmed by the constant catalytic performance over 24 h chronoamperometric test.This finding opens a new avenue to construct highly efficient NRR electrocatalyst by employing mixed metal polyoxometalate as the precursor under ambient conditions.

Insight into rare-earth-incorporated catalysts:The chance for a more efficient ammonia synthesis

Recent studies have suggested that rare earth(RE)elements in catalysts significantly influence the performance of the ammonia synthesis.The REs appear in various forms in the ammonia synthesis catalysts including supports(oxides,hydrides,and nitrides),promotors,and intermetallic.Besides the conventional RE oxide-supporting catalysts(mainly Ru/REO),some new RE-containing catalyst systems,such as electrode and nitride systems,could drive the ammonia synthesis via a benign Mars-van Krevelen mechanism or multi-active-site mode,affording high ammonia synthesis performance under mild conditions.These works demonstrate the great potential of RE-containing catalysts for more efficient ammonia synthesis.This review summarizes the contributions of different kinds of RE-based catalysts and highlights the function mechanism of incorporated REs.Finally,an overview of this area and the challenges for further investigation are provided.

Recent advances in TiO_(2)-based catalysts for N2 reduction reaction

Nitrogen(N_(2))fixation under mild conditions is a promising approach for green production of ammonia(NH_(3)).In the past decades,various advanced catalysts have been fabricated to achieve this goal through electrocatalytic and photocat-alytic processes.Among them,the TiO_(2)-based catalysts have been recognized as promising candidates due to their high activity,low cost,chemical stabil-ity,and nontoxicity.In this review,recent advances in the fabrication of high-performance TiO_(2)-based materials for N_(2)reduction reaction(NRR)under mild conditions are summarized,including electrocatalytic and photocatalytic NRR.The design principles,synthetic strategies,and corresponding chemical/physical properties of TiO_(2)-based NRR catalysts are described in detail.Moreover,the key challenges and potential opportunities in this field are presented and discussed.

Cobalt-Catalyzed Intermolecular Hydroamination of Unactivated Alkenes Using NFSI as Nitrogen Source

Cheap metal(Fe,Mn,and Co)-catalyzed hydroamination of alkenes has been an attractive method for synthesis of amines because of biocompatibility of metal,excellent Markovnikov selectivity and chemoselectivity.However,most reports are limited to unsaturated nitrogen sources(nitric oxide,azos,azides,cyano,etc.),for which aminated products are very limited.Notably,while used widely for fluorinating reaction,N-fluorobenzenesulfonimide(NFsI)as amine source for hydroamination has seldom been reported.Here we developed a cobalt-catalyzed intermolecular hydroamination of unactivated alkenes using NFSl as nitrogen source under mild conditions.The reaction exhibits excellent chemo-and regio-selectivity with no hydrofluorination or linear-selectivity products.Notably,the reaction proceeded with excellent yield even though the amount of Co(salen)catalyst was reduced to 0.2 mol%.Recently,a similar work was also reported by Zhang and coworkers(ref.19).

Visible light induced cross-coupling synthesis of asymmetrical heterobiaryls using Pd/CeO_2 nanocomposite photocatalyst

A simple, mild and green approach has been developed for the synthesis of asymmetrical heterobiaryls under the irradiation of visible light without any oxidants and promoting reagents through using Pd/Ce O2 nanocomposite photocatalyst. This method can tolerate considerable functional groups such as electrondonating groups and electron-withdrawing groups through CààC cross-coupling. Moreover, we obtain the products with moderate yields in an efficient way. Finally, a plausible mechanism is proposed.