醋酸锌自催化剂表面上的流失机理和流失速度(英文)

乙炔和醋酸合成醋酸乙烯的反应过程中 ,催化剂的失活 ,是由催化剂中的醋酸锌Zn (OAc) 2 从活性炭表面上升华到气相中以及被凝聚物堵在微孔内部而引起的 .升华机理是反应产物与Zn (OAc) 2作用生成挥发性络合物再升华到气相中去 .总流失速度可用LR =1-exp (-kvt)来描述 ,这是升华速度方程式的应用推广 .式中v为气流速度 ,t为反应时间 。

不对称自催化反应

评论了在手性氨基醇催化下 ,二烃基锌同醛基的对映选择性加成反应和不对称自催化反应 ,参考文献 2

随机3变量自催化模型的长时行为

研究了一个受白噪声干扰的随机化学3变量自催化剂反应模型的动力学行为.证明了随机系统的解是正的且全局存在的,并在白噪声强度值满足一定的条件下,得出随机自催化剂反应系统具有遍历性且是平稳分布的.

双功能CuX_(2)参与的芳基-7-氮杂吲哚邻位C-H键的卤化反应

开发了一种双功能铜参与催化芳基-7-氮杂吲哚的芳基卤化反应,该方法以N-苯基-7-氮杂吲哚类化合物为底物,CuX_(2)既为卤素源,又可以作为C-H键活化试剂,在无外加催化剂下,通过7-氮杂吲哚的导向作用选择性地发生芳环的亲电卤代反应。经过一系列条件筛选之后得到最佳反应条件为:CuCl_(2)(0.65eq)为催化剂,DMAP(0.25 eq)为配体,苯甲酸(1.2 eq)为添加剂,氯苯为溶剂,于120℃下反应24小时,产率最高达到95%。除7-氮杂吲哚导向基团外,还成功兼容了吡啶、喹啉等导向基团,该反应可应用于较多的底物范围。

基于超循环理论的高校“三风”建设研究

超循环理论具有重要的社会科学意义,它为各种系统组织的发展、优化提供了坚实的理论基础。高校的校风、学风、教风是一个有机整体,体现了超循环的结构特征。超循环理论对于高校的"三风"建设具有重要的启示意义。基于超循环理论,高校的"三风"建设在目标定位上应体现功能和效率的统一,即"三风"的良性循环;在实现途径上应注重整体效应,强化"三风"间的功能耦合,充分发挥"三风"载体的作用。

Proton-gradient-transfer acid complexes and their catalytic performance for the synthesis of geranyl acetate

Special proton-gradient-transfer acid complexes （PGTACs） in which the bonded protons are not equivalent and have gradients in transfer ability, acidity, and reactivity were reported. The acidity gradient of the protons gave the PGTACs excellent catalytic activity and selectivity in the esterifica- tion of terpenols. These PGTACs are ＂reaction-induced self-separation catalysts＂ and can be easily reused. The kinetics with PGTACs as catalyst in the esterification of geraniol were also studied for use in engineering design.

Maximum Hydrogen Production by Autothermal Steam Reforming of Bio-oil With NiCuZnAI Catalyst

Autothermal steam reforming （ATR） of bio-oil, which couples the endothermic steam reform- ing reaction with the exothermic partial oxidation, offers many advantages from a technical and economic point of view. Effective production of hydrogen through ATR of bio-oil was performed at lower temperature with NiCuZnAl catalyst. The highest hydrogen yield from bio-oil reached 64.3% with a nearly complete bio-oil conversion at 600℃, the ratio of steam to carbon fed （S/C） of 3 and the oxygen to carbon ratio （O/C） of 0.34. The reaction conditions in ATR including temperature, O/C, S/C and weight hourly space velocity can be used to control both hydrogen yield and products distribution. The comparison between the ATR and common steam reforming of bio-oil was studied. The mechanism of the ATR of bio-oil was also discussed.

Ti_(3)C_(2) MXene co-catalyst assembled with mesoporous TiO_(2) for boosting photocatalytic activity of methyl orange degradation and hydrogen production

Photocatalytic degradation and hydrogen production using solar energy through semiconductor photocatalysts are deemed to be a powerful approach for solving environmental and energy crisis.However,the biggest challenge in photocatalysis is the efficient separation of photo-induced carriers.To this end,we report that the mesoporous TiO_(2)nanoparticles are anchored on highly conductive Ti_(3)C_(2)MXene co-catalyst by electrostatic self-assembly strategy.The constructed mesoporous TiO_(2)/Ti_(3)C_(2)composites display that the mesoporous TiO_(2)nanoparticles are uniformly distributed on the surface of layer structured Ti_(3)C_(2)nanosheets.More importantly,the as-obtained mesoporous TiO_(2)/Ti_(3)C_(2)composites reveal the significantly enhanced light absorption performance,photo-induced carriers separation and transfer ability,thus boosting the photocatalytic activity.The photocatalytic methyl orange degradation efficiency of mesoporous TiO_(2)/Ti_(3)C_(2)composite with an optimized Ti_(3)C_(2)content(3 wt%)can reach 99.6%within 40 min.The capture experiments of active species confirm that the·O_(2)-and·OH play major role in photocatalytic degradation process.Furthermore,the optimized mesoporous TiO_(2)/Ti_(3)C_(2)composite also shows an excellent photocatalytic H2 production rate of 218.85μmol g^(-1)h^(-1),resulting in a 5.6 times activity as compared with the pristine mesoporous TiO_(2)nanoparticles.This study demonstrates that the MXene family materials can be applied as highly efficient noble-metal-free co-catalysts in the field of photocatalysis.

Catalyst-free and solvent-free oxidation of cycloalkanes(C5-C8) with molecular oxygen:Determination of autoxidation temperature and product distribution

Autoxidation of cycloalkanes （C5-C8） with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distribution. The autoxidation of cyclopentane, cyclohexane, cycloheptane and cyclooctane occurs at 120 ℃, 130 ℃, 120 ℃, and 105 ℃ respectively, with obvious oxidized products formation. At 140 ℃, 145 ℃, 130 ℃ and 125 ℃, acceptable yields of the oxidized products could be obtained for them, and the oxidized product distributions were investigated in detail. The autoxidation of cycloalkanes follows the pseudo-first-order kinetic model and the apparent activation energies （Ea） for the autoxidation of cyclopentane and cyclohexane are 159.76 kJ. tool-1 and 86.75 kJ. mol-1 respectively. This study can act as an important reference in screen of suitable reaction temperature and comparison of the performance of various catalysts in the catalytic oxidation of cycloalkanes in the attempt to enhance the oxidized product selectivity.

Mechanism of Photo-Fenton Degradation of Ethanol and PVA

Contrast degradation experiments between ethanol and polyvinyl alcohol (PVA) were conducted during H2O2, UV/H2O2, Fenton, and Photo-Fenton processes in this study. UV/VIS spectra showed' that complexes between Fe(Ⅲ) and organics were easily formed and degraded within reaction time. Compared with ,the degradation of complex, hydroxyl radicals acted weakly in Fenton or Photo-Fenton process. Hydroxyl radi'cals involved in Photo-Fenton process were deemed to be generated from the split decomposition of H2O2, photolysis of Fe_aq^3+, and degradation of hydrated Fe(Ⅳ)-complex but not traditional Fenton reaction. Experimental evidence to support this point was presented in this paper.

Effect of catalyst on formation of poly(methyl methacrylate) brushes by surface initiated atom transfer radical polymerization

Poly （methyl methacrylate） （PMMA） brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization （SI-ATRP）. Energy disperse spectroscopy （EDS） and atomic force microscopy （AFM） confirmed that PMMA brushes were successfully prepared on the silicon wafers, and the surface became more hydrophobic according to the contact angle of 69~. It is found that CuCI/1, 1, 4, 7, 10, 10-hexamethyl triethylenetetramine （HMTETA） system is more suitable than CuBr/N, N, N′, N″, N′″-pentamethyl diethylenetriamine （PMDETA） system to control the free radical polymerization of MMA in solution. Nevertheless, better control on the thickness of PMMA brushes was achieved in CuBr/PMDETA than in CuC1/HMTETA due to higher activity and better reversibility of the former system.

Surfactant effect of antimony addition to the morphology of self-catalyzed InAS1-xSbx nanowires

The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires （NWs） has been systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony （Sb） flux. It is demonstrated that trace amounts of Sb flux are capable of tuning the geometry of NWs, i.e., enhancing lateral growth and suppressing axial growth. We attribute this behavior to the surfactant effect of Sb which results in modifications to the kinetic and thermodynamic processes. A thermodynamic mechanism that accounts for Sb segregation in InAsSb NWs is also elucidated. This study opens a new route towards precisely controlled NW geometries by means of Sb addition.

Self-assembly of anthraquinone covalent organic frameworks as 1D superstructures for highly efficient CO_(2) electroreduction to CH_(4)

The design of selective and efficient covalent organic frameworks(COFs)based electrocatalysts with tunable morphology for efficient CO_(2) reduction reaction(CO_(2)RR)to CH_(4) is highly desirable.Here,two kinds of anthraquinone-based COFs(i.e.,AAn-COF and OH-AAn-COF)with tunable 1D superstructures(e.g.,nanofibers(NF)and hollow tubes(HT))have been produced via Schiff-base condensation reaction.Interestingly,a rarely reported nanosheet-based self-template mechanism and a nanosheet-crimping mechanism have been demonstrated for the production of COF-based nanofibers and hollow tubes,respectively.Besides,the obtained COF-based superstructures can be post-modified with transition metals for efficient CO_(2)RR.Specifically,AAn-COF-Cu(NF)and OH-AAn-COF-Cu(HT)exhibit superior faradaic-efficiency with CH_(4)(FECH_(4))of 77%(-128.1 mA cm^(-2),-0.9 V)and 61%(-99.5 mA cm^(-2),-1.0 V)in a flow-cell,respectively.Noteworthy,the achieved FECH_(4) of AAn-COF-Cu(NF)(77%)is the highest one among reported crystalline COFs.This work provides a general methodology in exploring morphology-controlled COFs for electrocatalytic CO_(2)RR.

Construction and evaluation of nitric oxide generating vascular graft material loaded with organoselenium catalyst via layer-by-layer self-assembly

A new biomimetic material for artificial blood vessel with in situ catalytic generation of nitric oxide(NO) was prepared in this study. Organoselenium immobilized polyethyleneimine as NO donor catalyst and sodium alginate were alternately loaded onto the surface of electrospun polycaprolactone matrix via electrostatic layer-by-layer self-assembly. This material revealed significant NO generation when contacting NO donor S-nitrosoglutathione(GSNO). Adhesion and spreading of smooth muscle cells were inhibited on this material in the presence of GSNO, while proliferation of endothelial cells was promoted. In vitro platelet adhesion and arteriovenous shunt experiments demonstrated good antithrombotic properties of this material, with inhibited platelet activation and aggregation, and prevention of acute thrombosis. This study may provide a new method of improving cellular function and antithrombotic property of vascular grafts.

TiO_2-doped Fe_3O_4 nanoparticles as high-performance Fenton-like catalyst for dye decoloration

Fenton reaction based on Fe2+-H2O2 system has been widely applied in water remediation, but the obvious drawbacks largely hinder its practical uses. Alternatively, heterogeneous nanomaterials with proper surface modification could be used as Fenton-like catalysts. Surface doping of Ti O2 could concentrate the pollutants surrounding the Fe3O4 catalyst, which might benefit the catalytic performance of Fe3O4. Herein, we reported that Ti O2-doped Fe3O4 nanoparticles(NPs) could be used as high-performance Fenton-like catalyst for dye decoloration in near neutral environment, where the doping of Ti O2 on Fe3O4 surface dramatically improved the catalytic activity of Fe3O4 in Fenton-like reaction. Ti O2-doped Fe3O4 NPs catalyzed the decomposition of H2O2 to oxidize methylene blue without external energy supply, resulting in effective decoloration. Ti O2-doped Fe3O4 NPs showed high catalytic activity under various p H values and even in the presence of radical scavenger. More catalysts and H2O2 would facilitate the decoloration. At higher temperature, the decoloration became faster and more effective. The implication to the environmental applications of Ti O2-doped Fe3O4 NPs is discussed.

Efficient and ligand free palladium catalyst for Suzuki and Heck cross-coupling reactions

A simple and efficient system for Suzuki cross-coupling reactions was developed using a ligandless catalyst of Pd nanoclusters generated in situ from Pd(acac)2. The cross-coupling reactions proceeded under mild reaction conditions with a high reaction rate(5 min) to give various biaryls in high yields. The system also exhibited catalytic potential for Heck reaction between aryl bromides and styrene.