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.
The imbalance between the growing demand for isoprene and the surplus of isobutene has stimulated research interest in the production of isoprene from isobutene,wherein the Prins condensation of isobutene with poly-oxymethylene serves as a crucial step.In this study,a series of metal-doped ceria(CeO2)solid acid catalysts were systematically investigated for the catalytic performance,with a focus on how the dopant metal,preparation method,doping amount,and calcination temperature regulate the acidic properties.XPS,Py-FTIR,and NH3-TPD characterization revealed that Al doping effectively induces the generation of oxygen vacancies in CeO2,which in turn promotes the formation of Brønsted acid sites and introduces medium-strength acid sites.This leads to a synergistic optimization of the Brønsted/Lewis acid ratio and acid strength distribution.Among the catalysts evaluated,Al-CeO2 prepared by co-precipitation with a Ce/Al molar ratio of 8 and calcined at 600 ℃ exhibited the most favorable Brønsted/Lewis acid ratio and medium-strength acid site density.Under optimized reaction conditions at 140 ℃ for 4 h,this catalyst achieved 51.75％polyoxymethylene conversion with 83％selectivity to the target product,3-methyl-1,3-butanediol(MBD).This enhanced catalytic performance is attributed to the cooperative interplay between Lewis acid sites that activate polyoxymethylene and Brønsted acid sites that facilitate the hydrolysis of the 4,4-dimethyl-1,3-dioxane intermediate.Furthermore,the catalyst exhibited good reusability,maintaining its catalytic activity over six consecutive cycles without significant deactivation and demonstrating stable performance in this reaction system.
Using a simple two-step calcination method,an iron molybdate catalyst rich in oxygen vacancies was successfully prepared for the photo-Fenton degradation of tetracycline hydrochloride.The composition,morphology and optical properties of the catalyst were characterized using XRD,SEM,EDS mapping,XPS,UV-Vis DRS,EPR and BET analyses.The results indicate that grinding and mixing iron molybdate with tartaric acid,followed by a second calcination,significantly enhances the specific surface area of the iron molybdate,creates a wealth of oxygen vacancy defects,and improves its light absorption capacity and photocatalytic activity.Under conditions of pH=4,5 mg of catalyst,and 30 μL of 30％H2O2,the oxygen-vacancy-containing iron molybdate catalyst achieved a degradation efficiency of 82.2％for hydrochloride tetracycline within 30 min,representing a 36.6％improvement over the pure iron molybdate system,and maintained a high degradation efficiency even after five cycles.Radical trapping experiments and EPR spectroscopy indicated that·OH,·O-2and h+all participate in the degradation process.This study provides a reference for enhancing the efficiency of photocatalytic Fenton degradation of tetracycline hydrochloride through oxygen vacancy engineering.
Carbonylation reactions are important transition metal-catalyzed reactions that used extensively in chemical industry.Transition metal complexes bearing NHC ligands have attracted widespread attention in the field of homogeneous catalysis in recent years due to its great coordination ability and versatile structure,these give NHC unique characteristic to control the chemical properties of complex and have been applied in carbonylation reactions.This review summarizes carbonylation reactions employing NHC as ligands,briefly introduces the structure and characters of NHC ligands,and focuses on hydroformylation reactions using styrene and aliphatic olefins as substrates.The latest advances in transition metal-NHC complexes for carbonylation reactions are also discussed.Considering existing experimental results,current challenges in the application of NHCs in carbonylation reactions are outlined,and the future development prospects are proposed based on the distinctive features of NHCs.
Acrylic acid,as an important organic chemical raw material,is widely used in plastics,coatings,textiles,and other fields.In recent years,the international demand for acrylic acid has shown a growing trend.The catalytic selective oxidation of C3(propane,propylene)represents an important route for the production of acrylic acid,with the advantages of abundant raw material sources,low cost and simple process.This paper reviews the recent research progress in the catalytic selective oxidation of C3 to acrylic acid,focusing on the structural characteristics,preparation methods,modification strategies and catalytic performance of MoVTeNbOx catalysts.Combined with the latest advances in in-situ characterization techniques,the reaction mechanism and structure-activity relationship are thoroughly analyzed,and the future development directions in this field are prospected.
甲烷热裂解制氢并生成高附加值的纳米碳材料,被认为是极具发展前景的氢气生产途径,但高性能催化剂的研发仍存在诸多挑战.我们选择多种载体(TS-1、IM-5、Y、介孔SiO2、γ-Al2O3、CNTs),采用浸渍法制备Ni-Cu负载催化剂,通过低温N2吸附-脱附、XRD、SEM和H2-TPR等系列表征方法对样品进行分析,考察不同载体对催化剂甲烷裂解制氢和纳米碳材料的影响.实验结果发现,分子筛载体独特的孔道结构有利于金属颗粒的分散,能有效避免反应中界面效应导致的催化剂失活,可提高催化剂反应活性并延长反应寿命,也显著提高了其碳产率.其中以IM-5分子筛为载体的催化剂表现最佳,在反应温度为700℃时,NiCu/IM-5催化剂甲烷转化率高达80％,氢气选择性达100％,反应400 min后活性未见明显降低.NiCu/IM-5催化剂碳产率高达1 446 gc/gcat,是NiCu/SiO2催化剂的5.7倍,NiCu/y-Al2O3催化剂的7.1倍.
通过计算和实验研究相结合的方法研究丙烷甲醇共进料制烯烃反应热力学及动力学过程.热力学过程采用Gibbs最小自由能法模拟丙烷甲醇制烯烃反应体系的平衡组成,同时结合响应面分析法建立了温度、压力、丙烷甲醇进料摩尔比对产物中丙烯的摩尔分数的函数关系,通过回归方程分析最佳工艺范围.热力学分析了反应条件对平衡产物的影响,随着反应温度升高,平衡产物丙烯的质量分数先增高后降低;平衡产物中丙烯的质量分数随着丙烷甲醇进料中丙烷摩尔比增高而增高,但是实际的反应状态和催化剂也是相关的,因此研究了存在催化剂情况下,丙烷脱氢和丙烷甲醇共进料反应的活化能.反应活化能动力学实验表明,通过添加少量甲醇可以降低耦合过程中丙烷脱氢表观活化能.
半导体光催化制氢是一种可实现持续制备和储存氢气的绿色技术.石墨相氮化碳(g-C3N4)是研究广泛的光催化剂,但其仍存在光利用率低、光生电子和空穴易复合等问题,制约着光催化产氢的性能.利用给电子卟啉修饰g-C3N4,构建了四(4-羧基)苯基卟啉(TCPP)以共价/非共价方式修饰g-C3N4的催化剂.卟啉共价修饰g-C3N4(g-C3N4-TCPP0.1)及非共价复合结构(TCPP0.1/g-C3N4)光催化产氢速率分别为6 997和5 399 μmol·g-1·h-1,较g-C3N4分别提高了 53％和18％.TCPPx/g-C3N4异质结加强了界面接触,促进了电荷转移,增强了可见光吸收能力,进而提高了光催化制氢性能.g-C3N4-TCPPx中,TCPP的接枝拓展了共轭结构,优化了电子结构,增大了分子偶极,促进了电荷分离,共价桥键为电荷传输提供了通道.
通过表相、体相硫组分的表征分析,结合不同温度下含硫气氛下的活性演变及原位红外研究,获得了 V-Ce(0.1)/TiO2催化剂在180、240和300 ℃下含硫氛围的NH3-SCR反应中毒机理.180 ℃下催化剂上沉积了大量的硫酸氢铵和少量的金属硫酸盐,共同导致在8 h内活性从77.8％降至51.2％,热再生后的活性测试结果表明硫酸氢铵的沉积导致了催化剂活性降低8.3％,金属硫酸盐的沉积导致了催化剂活性降低18.3％.原位红外结果表明中毒后催化剂在180℃下的NH3-SCR反应遵循L-H反应路径.随着温度升高至240、300 ℃,催化剂上沉积的硫酸氢铵逐渐减少,金属硫酸盐含量增加.不同温度下的抗硫活性结果表明,低温NH3-SCR反应需要较高的氧化还原性能,中高温NH3-SCR反应则需要较高的酸性,金属硫酸盐的生成导致了氧化还原性能降低、酸性增加,因此低温NH3-SCR活性大幅降低,中高温活性则能保持在100％.
利用Zn2+和2-甲基咪唑自组装形成的ZIF-8,800 ℃ N2氮气气氛下焙烧得到Zn/C-N载体.采用NaBH4还原法将不同含量Pd负载于Zn/C-N上焙烧后得到Pd/Zn/C-N催化剂,ICP测得Pd实际负载量为0.02％、0.05％、0.1％、0.3％.负载Pd后,由于Pd氢溢流作用,ZnO表面还原温度降低,氧空穴增加,更有利于CO2解离吸附,因此Pd负载量越高,催化剂CO2转化率越高.甲醇选择性受Pd纳米颗粒大小显著影响,小颗粒Pd与ZnO相互作用更强,更有利于甲醇生成,其中0.02％Pd/Zn/C-N催化剂在275 ℃,2 MPa反应条件下,Pd/g上甲醇时空收率最高,STYMeOH值为 11.0mol/(gPd·h).
基于密度泛函理论计算,研究了H2和CO2在氮掺杂石墨烯负载单原子Zr催化剂(ZrNx-Gr)上的吸附和CO2催化加氢反应.H2和CO2在ZrN3-Gr上单独吸附的吸附能分别为-0.49和-2.17 eV,在H2和CO2共吸附状态下,吸附能为-2.24 eV,均高于在ZrN4-Gr表面的吸附能,表明ZrN3-Gr表面更利于CO2加氢反应的发生.在ZrN3-Gr表面,CO2在共吸附后保持了其单独吸附时的特性,削弱了 H2分子的吸附.CO2在ZrNx-Gr表面催化加氢反应起始于H2和CO2的共吸附构型,沿反式HCOOH路径形成甲酸盐(HCOO*)中间体,然后HCOO*基团吸附H原子形成反式甲酸,在ZrN3-Gr和ZrN4-Gr表面该路径的反应能垒分别为1.85和2.48 eV.另一路径为产生CO与H2O的反应,在ZrN3-Gr和ZrN4-Gr表面的反应能垒分别为1.86和1.73 eV,表明ZrN3-Gr更利于CO2加氢生成甲酸反应的发生,而ZrN4-Gr表面更利于CO的产生.
利用活性炭模板剂制备了氧化还原催化剂LaMnO3,采用X射线衍射、透射电子显微镜和比表面积分析仪(BET)等分析手段对催化剂进行了表征,通过循环伏安、线性扫描、蓝电测试等测试方法对LaMnO3电化学性能进行了测试分析.实验结果表明:利用活性炭模板法所制备出的LaMnO3-AC比表面积(20.561 m2·g-1)远大于共沉淀法制备的LaMnO3-G(8.486 m2·g-1),并且所制备出的LaMnO3具有良好ORR催化活性.这为相关催化剂材料的设计和研究提供了实验依据和理论基础.
2-甲基四氢呋喃(2-MTHF)是极具市场潜力的生物燃料、绿色溶剂和化学中间体.采用浸渍法制备Ni/γ-Al2O3催化剂,在固定床反应器评价其2-甲基呋喃(2-MF)气相加氢合成2-甲基四氢呋喃(2-MTHF)反应性能.通过XRD、N2等温吸附-脱附、H2-TPR、NH3-TPD、TEM、H2吸附和XPS对催化剂结构和表面性质进行表征,研究Ni负载量、焙烧温度和反应条件对催化剂性能的影响规律.结果表明:Ni/γ-Al2O3催化剂的Ni金属面积、晶粒尺寸、反应温度和压力都会影响2-MF的转化率;孔结构、酸量和反应温度是影响2-MTHF选择性的主要原因,平均孔径大、酸量大和适宜的反应温度有利于提高2-MTHF选择性.400 ℃焙烧的负载量为15％的Ni/γ-Al2O3催化剂,Ni金属面积大、晶粒尺寸小、总酸量多,催化剂表面的金属活性中心与酸性中心协同作用促进了 2-MF呋喃环上C=C加氢生成2-MTHF,性能较优.在2 MPa、100 ℃、WHSV=2.7 h-1、H2/2-MF=6.4的条件下,该催化剂上2-MF转化率为99.8％,2-MTHF选择性为98.0％,催化剂可以稳定运行40 h.
