Mars-van Krevelen-like Mechanism of CO Hydrogenation on an Iron Carbide Surface

Computational chemistry is used to explore a mechanism for CO hydrogenation to methane on iron carbides. As CO dissociation is endothermic on carbon terminated Fe₅C₂ (100) cuts, we explore a path starting with the hydrogenation of the surface, which liberates iron 4-fold sites for adsorption and dissociation of CO. The reaction cycle to methane resembles the Mars-van Krevelen mechanism for oxidation reactions.     

Catalysis of Selective Hydrogen/Deuterium Exchange at Allylic Positions Using Deuterium Oxide

Deuterated organic compounds can be prepared efficiently and cost effectively by the direct exchange of a hydrogen atom by a deuterium atom on a carbon center rather than classical synthetic procedures. H/D exchange is achieved at allylic positions of alkenes catalyzed by alkene isomerization catalyst 1. An outstanding degree of deuteration is achieved at positions accessible by isomerization in homogeneous and biphasic reaction settings.     

Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer?CTropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H₂ and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.     

超声处理对活性炭表面形态及负载催化剂活性的影响

采用超声预处理活性炭,并用N_2物理吸附、X射线能谱仪(EDS)、透射电镜(TEM)、和场发射扫描电镜(FE-SEM)等表征手段,研究了超声预处理条件对活性炭表面结构、化学成分及表面形貌以及所负载钌基氨合成催化剂性能的影响。研究结果表明,超声预处理活性炭,可有效降低活性炭表面灰分和不稳定含氧基团的含量,从而提高所负载催化剂的活性。在实验范围内,当超声频率为39.0 kHz,功率为100w时,在10 000 h~(-1),10.0 MPa和400℃的反应条件下,钌基催化剂的反应速率达到了97.6 mmol/(g·h)。     

合成2,3,5-三甲酚催化剂的研究

采用等体积浸渍法制备负载型催化剂用于3,5-二甲酚甲基化反应,在固定床反应器中考察了载体的焙烧温度、助剂、催化剂的焙烧温度和焙烧时间等因素对催化剂活性影响分析。结果表明:Fe2O3-Cr2O3/Al2O3催化剂在反应中具有较高的反应活性和选择性。     

饱和活性炭催化双氧水氧化处理染料废水生化出水

分别采用Fe~(2+)/H_2O_2、活性炭(AC)/H_2O_2、AC/H_2O_2/Fe~(2+)和再生AC四种体系对染料废水生化出水进行处理,分别考察了不同体系中,H_2O_2的投加浓度、n(H_2O_2)/n(Fe~(2+))、pH和反应时间及再生炭对废水处理效果的影响,并对处理效果进行对比。结果表明AC/H_2O_2/Fe~(2+)体系对废水COD的去除效果最好,去除率为64%,再生AC对废水色度去除率最高为94%。     

Effect of Hydrogen Treatment on the Catalytic Activity of Iron Oxide Based Materials Dispersed Over Activated Carbon: Investigations Toward Hydrogen Peroxide Decomposition

The effect of hydrogen treatment (400 °C/1 h) on the catalytic properties toward H₂O₂ decomposition of iron oxide based materials dispersed over activated carbon were investigated. Two different supports were evaluated: a commercial activated carbon (ACM) and an activated carbon produced from spent coffee grounds (ACR). The catalysts were characterized using XRD, SEM, N₂-sorption, XPS and TPR analysis. The main results suggest the formation of composites with high surface area (>800 m² g^?1) and the hydrogen treatment resulted in a great increase in the catalytic activity, probably as a function of the reduced iron species (Fe²⁺ and Fe⁰) formed with the treatment. Moreover, the catalyst prepared with ACR showed to be more active than that prepared from ACM.     

Low-Temperature Adsorption of Hydrogen on Activated Carbon

Abstract

The adsorption isotherm of pure hydrogen on activated carbon (coconut shell) was determined at — 186[ddot]C over a pressure range of 1 to 772 mm Hg. A McBain balance apparatus with a modified refrigerant thermostat was used.     

负载型钌炭加氢催化剂的工艺研究

通过对负载型钌炭催化剂的制备工艺的研究,分析讨论了载体种类、制备工艺中的负载和还原操作对钌炭催化剂性能的影响。研究结果表明:在催化剂的制备过程中,活性炭载体、负载方式和还原操作对表面活性金属的分散度有影响,从而造成催化剂的性能差异。选择椰壳炭为载体、沉淀法进行活性金属的负载,经过液相法硼氢化钠还原得到的催化剂表面活性金属的分散度高,催化剂在苯部分加氢反应中具有高活性和高选择性,环己烯的收率达到55%。     

功能化活性炭固载离子液体催化剂

制备了活性炭固载溴化1-（2-胺乙基氢溴酸）-3-甲基咪唑翁盐离子液体催化剂,并用TG和XPS对催化剂进行了表征。将该催化剂首次用于Knoevenagel缩合反应,结果表明活性炭固载离子液体催化剂具有良好的催化活性和稳定性,同时克服了均相催化剂难以分离的不足。     

Characterization of the N370S Mutant of Glucocerebrosidase by Hydrogen/Deuterium Exchange Mass Spectrometry

An asparagine‐to‐serine substitution at residue 370 (N370S) in glucocerebrosidase (GCase) is the most prevalent mutation leading to Gaucher's disease, the most common lysosomal storage disorder. Two types of hydrogen/deuterium exchange experiment coupled with proteolysis and liquid chromatography–mass spectrometry (HDX–MS) were used to investigate the dynamic properties and unfolding stability of wt, R495H, and N370S GCases in the presence and absence of ligands. R495H GCase is used for enzyme replacement therapy and is considered to be a wt surrogate, whereas N370S is the most prevalent mutation leading to Gaucher's disease. Time‐course HDX experiments of the GCases were performed under near‐physiological conditions to detect the protein's local unfolding motions at a submolecular level. In guanidine‐titration experiments, HDX reactions were performed with various concentrations of a chemical denaturant to provide the global stability of the proteins. The two types of experiment showed that all three purified GCases, wt, R495H, and N370S, have virtually identical local unfolding motions and global stabilities in solution. Combined with previous X‐ray crystallographic studies, which showed indistinguishable backbone conformations for N370S and R495H GCase mutants and very similar melting temperatures for the wt, R495H, and N370S mutants, all three GCases are likely to have virtually identical structural and dynamic properties in solution. The guanidine‐titration experiments revealed that the pharmacological chaperone, isofagomine (IFG), interacts more weakly with the N370S mutant than with the R495H GCase; this is consistent with the higher IC₅₀ value of IFG against N370S than against R495H. The time‐course experiments showed that IFG restricts the local unfolding motions of N370S in the same way as those of R495H when the ligand saturates the proteins.     

高温氢气处理对活性炭及钯炭催化剂性能的影响

采用高温氢气对不同活性炭进行处理,并分别采用比表面分析仪(BET)、红外光谱(IR)、氩气-程序升温脱附实验(Ar-TPD)和热重分析(TGA)对高温氢气处理前后的活性炭进行表征.结果表明,高温氢气处理对活性炭的孔结构和比表面影响较小,高温氢气处理后活性炭表面含氧官能团含量降低.以高温氢气处理后的活性炭为载体制备钯炭催化剂,催化剂上的钯的分散度降低,在粗对苯二甲酸精制反应中的初活性下降.     

载体处理对Pt/C催化剂的选择性加氢性能影响

研究了活性炭处理方式对以其为载体制备的铂炭催化剂性能的影响,以对氯硝基苯催化加氢制备对氯苯胺反应为模型反应对催化剂的性能进行评价。结果表明,经过处理的活性炭制备的铂炭在对氯硝基苯加氢反应中表现出的催化性能更高,5%NaOH在80℃下处理2 h的活性炭可以达到最佳效果,所制备的Pt/C催化剂重复使用4次,对氯苯胺收率在99%以上,脱氯率在0.3%以下。     

原料气氢氮分压变化对熔铁催化剂氨合成率的影响

通过理论分析和实验,提出了在工业条件下原料气中氢氮分压变化（包括氢氮比、惰性气体含量、合成压力变化）与熔铁催化剂氨合成率变化之间的关系式。利用该式所得的计算值与实验值十分吻合。     

过氧化氢溶液改性活性炭催化微波照射降解结晶紫的研究

在过氧化氢改性活性炭（AC）存在下,微波照射能使结晶紫溶液快速降解。本文采用UV-vis光谱、离子色谱和液相色谱（HPLC）探讨了过氧化氢浓度、浸泡时间、微波照射时间、催化剂用量以及结晶紫溶液初始浓度和酸度等因素对结晶紫降解率的影响。结果表明,提高微波照射时间或增加改性AC加入量可提高降解率。改性AC作为微波降解结晶紫...     

化肥催化剂活性检测的危险性因素分析

化肥催化剂活性检验试验室安全问题往往被企业所忽视。根据化肥催化剂活性检测的特点,对检测过程中所使用的原料气、操作条件、火源等方面进行危险性分析。指出了化肥催化剂活性检测过程中存在燃烧、爆炸、中毒和灼伤等不可忽视的安全隐患,应引起企业安全部门的重视。提出了化肥催化剂活性检测和装置建设必须符合安全规范要求,采取必要的安全预防措施,防患于未然。     

将碳化硅用于催化剂载体的研究进展

碳化硅陶瓷材料由于具有耐磨、耐蚀、高温强度高、高热导、宽禁带等优良特性,被广泛应用于航空航天、石油化工、机械电子等领域。如果能攻克其比表面积低的缺陷,还将是一种催化剂载体的理想候选材料,它可被应用于一些高温、强腐蚀等苛刻反应条件中。而目前国内在这方面的研究尚未见公开的报道。本文将对近年来高比表面碳化硅材料的研究工作进行小结,阐述其制备原理、方法及应用,同时阐述了本研究小组下一步的研究方向。     

对苯二甲酸精制钯炭催化剂载体活性炭的研究

分析了不同厂家生产的对苯二甲酸精制用钯炭催化剂载体活性炭的各种物性指标。实验结果表明,各种活性炭比表面相同时,其吸附量基本相近,但孔结构有较大差异,尤其是中孔孔容相差较大。中孔孔容增大,有利于钯炭催化剂分散度的提高和热稳定性增强.活性炭的表面基团对催化剂分散度也有影响,表面酸性基团含量增加,值化剂分散度提高.     

表面分散剂对Ru/AC氨合成催化剂的影响

采用表面分散剂处理Ru／Ac氨合成催化剂的钌盐浸渍液,研究了表面分散剂对钌催化剂活性、分散度及耐热性的影响,结果表明合适的表面分散剂能有效提高钌催化剂的Ru金属分散度从而提高催化性能。     

Isotopic Study of N2O Decomposition on an Ion-Exchanged Fe-Zeolite Catalyst: Mechanism of O2 Formation

N₂O decomposition on an ion-exchanged Fe-MFI catalyst has been studied using an ¹⁸O-tracer technique in order to reveal the reaction mechanism. N₂ ¹⁶O was pulsed onto an ¹⁸O₂-treated Fe-MFI catalyst at 693 K, and the O₂ molecules produced were monitored by means of mass spectrometry. The ¹⁸O fraction in the produced oxygen had almost half the value of that on the surface oxygen, and ¹⁸O¹⁸O was not detected. The result shows that O₂ formation proceeds via the Eley–Rideal mechanism (N₂ ¹⁶O + ¹⁸O(a) N₂ + ¹⁶O¹⁸O).