The catalytic performance of a series of imidazole derivatives in the β-hydroxyethylation reaction of hydroquinone(HQ)with ethylene carbonate(EC)to prepare hydroquinone bis(β-hydroxyethyl)ether(HQEE)was investigated.The results showed that the hydroxyethylation reaction occurs first on the imidazole ring to generate 1-(2-hydroxyethyl)imidazole derivative when the nitrogen atom at position 1 of the imidazole ring has a hydrogen atom.There are no significant differences for the catalytic performance of 1-substituted,2-substituted,and multi-substituted imidazoles.Imidazole catalysts activate EC through a nucleophilic catalysis mechanism rather than activating HQ via a basic mechanism.The nitrogen atom at position 3 of the imidazole ring is the active site for activating EC ring-opening.The results of hectogram-scale synthesis show that the substituent effect of 1-substituted alkyl imidazoles was not significant,the by-product CO2 gas could remove reaction heat from the system in a timely manner,and the recrystallized HQEE product yield could reach approximately 94％.
Dry reforming of methane(DRM)can simultaneously convert two greenhouse gases into syngas,offering both environmental and resource utilization benefits.However,this reaction still faces key challenges such as high energy consumption and catalyst deactivation due to carbon deposition and sintering.In this study,NiCuMgAl hydrotalcite precursors were prepared via the urea hydrothermal method,and cerium nitrate solutions of different concentrations were introduced by impregnation.After calcination and reduction,a series of NiCuMgAl catalysts with CeO2 loadings of 5％,10％,15％,and 20％were obtained.The effects of CeO2 content on the catalyst structure,surface properties,and DRM performance were systematically investigated.The catalysts were characterized by XRD,BET,SEM,TEM,XPS,CO2-TPD,NH3-TPD,FTIR,and TG.The results indicate that the formation of Ni-Cu alloy effectively suppresses carbon deposition,while the introduction of CeO2 generates abundant oxygen vacancies.Among all catalysts,NiCuMgAl-15％Ce exhibits the highest oxygen vacancy concentration(33.80％),together with the strongest medium-strong basic sites(250.4 ℃)and medium-strong acid sites(240.7 ℃),forming an ideal acid-base synergy.Under the conditions of 600 ℃ and a mass space velocity of 36000 mL·g-1·h-1,this catalyst achieves CH4 and CO2 conversions of 36.2％and 53.1％,respectively,operates stably for 32 h,and shows a coke deposition of only 6.2％.Its performance is significantly superior to that of the unmodified catalyst and those with either too low or too high CeO2 contents.
Monometallic metal-organic framework(MOF)catalysts(Cu-MOFs and Ni-MOFs)and bimetallic Cu/Ni-MOFs catalyst were fabricated via a solvothermal method.The as-prepared three catalysts were systematically characterized by XRD,XPS,HADDF-STEM-EDS,FT-IR,and other analytical techniques.Meanwhile,the catalytic performances of the three catalysts were investigated in the cycloaddition reaction of styrene oxide with CO2.The results revealed that bimetallic Cu/Ni-MOFs exhibited outstanding catalytic performance with a conversion of 93％and selectivity of 99％,which was remarkably superior to those of monometallic Cu-MOFs(58％conversion,99％selectivity)and Ni-MOFs(69％conversion,99％selectivity).The enhanced catalytic activity was mainly attributed to the synergistic effect between Cu2+and Ni2+bimetallic ions,which effectively regulated the electronic structure of the catalyst and improved the catalytic activity and stability of active sites.Furthermore,substrate scope experiments verified that the Cu/Ni-MOFs catalyst possessed excellent catalytic activity and selectivity toward the cycloaddition of various styrene oxide derivatives with carbon dioxide,demonstrating great application potential.
Olefin hydroformylation is an important C1 chemical transformation that has been widely applied in the production of fine chemicals and chemical feedstocks.Although traditional homogeneous catalytic systems exhibit excellent catalytic activity and selectivity,they still suffer from severe problems such as difficult catalyst separation and metal loss.Therefore,the development of efficient and stable heterogeneous catalytic systems has become an important research direction in this field.Metal-organic frameworks(MOFs),owing to their high surface area,regular porous structures,and tunable framework compositions,have demonstrated unique advantages in heterogeneous catalysis.In recent years,MOFs and their derived catalytic materials have attracted much attention in hydroformylation reactions,especially the introduction of phosphine ligands into MOFs based on their framework characteristics to construct stable metal-phosphine active centers,providing a new approach to the heterogenization of homogeneous catalytic systems.This article reviews the series of research progress of MOFs catalysts in hydroformylation reactions,focusing on the preparation strategies,structural features,and reaction performance of phosphine-functionalized MOFs catalytic materials,and summarizes the main factors affecting activity and selectivity.On this basis,the challenges and future development directions of MOFs-based hydroformylation catalytic systems are prospected.
Acetophenone is a significant organic compound with extensive applications across various industries owing to its unique chemical properties.The direct catalytic oxidation of ethylbenzene to acetophenone is highly attractive due to its high atom economy and low raw material cost,highlighting the environmental friendliness of this route.However,it faces the dual challenges of difficult that C-H bond is activated on the aromatic side chain and the susceptibility of the product to over-oxidation.This review systematically evaluates and compares the principles and limitations of traditional processes,such as Friedel-Crafts acylation and stoichiometric oxidation,as well as modern technologies including heterogeneous catalytic oxidation and photocatalytic oxidation.Further-more,it focuses on homogeneous and heterogeneous catalyst systems,with heterogeneous catalysts encompassing zeolites,nanomaterials,and novel multifunctional materials.Finally,the review concludes that developing highly stable non-noble metal catalysts,achieving efficient low-temperature activation of molecular oxygen,and constructing coupled reaction-separation processes are the key steps toward realizing the green and economic production of acetophenone via this route.
Isosorbide is an important bio-based green chemical with a backbone containing two tetrahydrofuran rings in a V-shape,which can be added to polymers to enhance mechanical strength and high-temperature performance.As a chemical intermediate,isosorbide is commonly used in food additives,solvents for cosmetics,and as a reactant in medicine.The acid catalysts are the key to the dehydration of sorbitol to isosorbide,and therefore,developing efficient,high-stability,and reusable heterogeneous catalysts has attracted more attention recently.The research summarizes the progress on metal oxide catalysts for the dehydration of sorbitol to isosorbitol,including the catalytic reaction mechanism,classification,and application of metal oxides,catalyst deactivation,regulatory strategies,and future development.It provides theoretical guidance and technical support for the theoretical design and process optimization of high-performance solid acid catalysts.
Carbon materials exhibit promising metal-free catalytic properties in various catalytic processes due to their adjustable physical and chemical characteristics.In this study,we developed a highly active carbon nanotube(CNT)by adjusting the surficial oxygen functionality as a metal-free electrode to mediate the electrooxidation of 5-hydr-oxymethylfurfural(HMF)to 2,5-furandicarboxylic acid(FDCA),utilizing TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl)as a co-catalyst.The oxygen-functionalized carbon nanotube(CNT)exhibited good HMF oxidation activity with an onset potential of 1.09 V and good stability of recycling 5 times.A systematic study of the CNT surface was conducted to reveal the mechanism of the HMF oxidation process on the CNT during the reaction.Phenolic groups on the CNT surface were confirmed to be active sites for the reaction;carbonyl groups also contributed to the activity by converting into phenolic groups during the reaction.Carbon shows no valence change during the catalysis process,allowing it to maintain structural stability compared to different metal catalysts.Therefore,carbon materials are promising electrode material for scalable and sustainable applications in the HMF electrochemical oxidation process.
