Characterization of Copper Foam as Catalytic Material in Ethanol Dehydrogenation

Copper foam was used as a catalyst in ethanol dehydrogenation to acetaldehyde. Catalyst pretreatment, reaction temperature, liquid feed composition, and catalyst loading all affect ethanol conversion. Copper foam pretreated by oxidation yielded the highest ethanol conversion but deactivated due to copper surface reconstruction. The foam catalyst can be repeatedly reactivated by a short time exposure to air under reaction conditions. Yet, copper foam performance for ethanol dehydrogenation has been inferior in terms of activity and stability to that of supported copper catalysts.     

乙醇催化脱氢合成乙醛的工艺研究

采用共沉淀法制备系列CuZnAl催化剂,在固定床反应器考查了催化剂对乙醇脱氢制备乙醛并副产氢气的催化性能。研究了CuZnAl组分比例对催化剂活性的影响,并对工艺条件进行优化。结果表明:Cu∶Zn∶Al=4∶4∶2时,乙醇脱氢反应催化活性达到最高;在温度为280℃,压力为1MPa,床层空速为0.8h-1,n(乙醇)∶n(水)=2,乙醇转化率达53.6%,乙醛选择性达92.2%,副产氢气纯度高达97.5%。200h连续实验,CuZnAl催化剂催化乙醇脱氢反应转化率稳定在50%以上。     

反应条件对环己醇低温脱氢过程的影响

在固定床反应器中,采用Cu系催化剂研究了环己醇低温脱氢合成环己酮的反应,考察了反应温度、反应压力、空速和原料组成对环己醇低温脱氢转化率和选择性的影响。确定较佳的反应条件为:反应温度264～272℃,反应压力为常压,空速0.6～0.8 h~(-1),还应控制原料中环己酮和杂质的含量。在264℃、常压、空速0.8 h~(-1)的条件下,环己醇转化率为65.6%,环己酮选择性为99.0%。     

Effect of Oxygen on the Reaction Between Copper and Sapphire

The effect of oxygen potential on the wetting behavior and interfacial energy between Cu and sapphire was studied using the sessile drop technique in a CO-CO₂ atmosphere. A linear relation was found between γ_SL and log p O₂ (atm) from 10⁻¹⁶ to 10⁻⁵. Beyond 10⁻⁵ atm γ_SL approached a constant value asymptotically. A barrier surface layer was proposed to explain this change. The Gibbs adsorption equation was used to evaluate the characteristics of the interfaces. Formation of a Cu₂O film at the liquid-vapor interface and a CuAlO₂ film at the solid-liquid interface is suggested. The work of adhesion reached a maximum at ∼ 0.01 at.% oxygen, corresponding to p O₂∼ 10⁻⁹atm. Measurements of the basal radius as a function of oxygen content were used to evaluate the role of oxygen in promoting spreading. Spreading on sapphire is directly proportional to the logarithm of oxygen present in the molten Cu drops.     

Effect of Transition Metals on Polysialic Acid Structure and Functions

Polysialic acid (PSA) is one of the most abundant glycopolymer present in embryonic brain, and it is known to be involved in key roles such as plasticity in the central nervous system, cell adhesion, migration and localization of neurotrophins. However, in adult brain, its expression is quite low. The exception to this is in Alzheimer′s disease (AD) brain, where significantly increased levels of polysilylated neural cell adhesion molecule (PSA‐NCAM) have been reported. Here, we confirm the role of PSA as a metal chelator, allowing it to decrease cytotoxicity caused by high levels of transition metals, commonly found in AD brain, and as a regulator of cell behavior. UV‐visible (UV‐vis) and circular dichroism (CD) spectroscopy, atomic force microscopy (AFM), and isothermal titration calorimetry (ITC) techniques were used to investigate the assembly of PSA–metals complexes. These PSA–metal complexes exhibited less toxicity compared to free metal ions, and in particular, the PSA–Cu²⁺ complex synergistically promoted neurite outgrowth in PC12 cells.     

Effect of Some Transition Metals on the Monolayer Oxidation of Methyl Linoleate

Methyl linoleate was deposited as a monolayer on a silica gel control and on silica gel supplemented with double or quadruple the control’s amount of the transition metal ions (TMI) iron, copper, vanadium or titanium. The treatments were oxidized at 25 °C, and periodically samples were examined for peroxide values (PV) and by gas chromatography for oxidation products (GC). Comparison of the treatments revealed that: Surface oxidation on silica gel owes its high rate to TMI, which may speed free radical initiation. Epoxidation is catalyzed by the presence of vanadium and titanium. Scission products (SP) and unrecovered mass increased with the extent of oxidation probably because of increased free radical life time.     

乙醇与氨脱氢法合成乙腈

介绍了乙腈的制造方法和国内主要厂家的产能情况及工业开发情况;重点介绍了乙醇与氨脱氢法合成乙腈的工艺过程、催化剂选择,并进行简单的经济性分析。     

二乙醇胺脱氢反应动力学研究

二乙醇胺脱氢制亚氨基二乙酸是草甘膦生产中的关键步骤之一。为了研究固体催化剂Raney-Cu催化下二乙醇胺脱氢反应动力学,设计了单因素多水平实验方案,考察二乙醇胺初始浓度、催化剂用量、反应温度、反应压力等因素对反应的影响,在5L高压反应釜中测定了脱氢反应动力学数据。依据脱氢反应的基本原理,提出了二乙醇胺脱氢反应机理,建立了动力学模型:-dCAdt=VcatKAkCA(1+KACA)·VL。利用数值计算方法对实验数据进行非线性拟合,求得动力学参数:k=4.914×1010exp(-7.364×104/RT)mol·(Lcat)-1·h-1,KA=3.308×106exp(-5.450×104/RT)L·mol-1,并且验证其可靠性。结果表明,二乙醇胺脱氢反应由二乙醇胺在催化剂表面的反应所控制,得到的动力学方程在实验范围内是可靠的。     

焙烧温度对乙醇脱氢制备乙酸乙酯Cu-Cr催化剂性能的影响

研究了制备过程中焙烧温度对乙醇脱氢制备乙酸乙酯Cu-Cr催化剂性能的影响。结果表明,焙烧过程中催化剂发生了晶型转变,释放出氧气。随着焙烧温度的提高,催化剂的比表面积先增加后减少,在400℃时焙烧的催化剂比表面积达到最大。在反应温度220℃,乙醇液体空速1h-1,反应压力常压的条件下,400℃时焙烧的催化剂具有最高的反应性能。     

Studies on Palladium Membrane Reactor for Dehydrogenation Reaction

Abstract

In current industrial practice dehydrogenation reactions require high temperatures and large amounts of inert (usually steam). Membrane reactors can be used to shift the equilibrium for these reversible reactions by removing products from the reaction zone. In this paper, experimental results will be presented for a palladium reactor system designed to investigate the feasibility of using palladium (Pd) alloy as the membrane material. Experiments have been conducted for isothermal and adiabatic conditions with air on the permeation side, wherein the oxygen reacts exothermically with the permeating hydrogen to decrease its partial pressure, thereby increasing its flux, and provide heat for the endothermic dehydrogenation reaction. Both theoretical and experimental results have been presented for dehydrogenation of 1-butene.     

Catalytic Dehydrogenation of Ethanol in Ru-Modified Alumina Membrane Reactor

Abstract

Ru-modified alumina composite membranes were prepared by the sol-gel method. The pore size distribution from nitrogen adsorption showed that average pore diameters were 3.1–4.5 nm, and the ideal separation factor was obviously higher than that of a pure γ-AI₂O₃ membrane. Ethanol dehydrogenation was carried out in the Ru-modified alumina membrane reactors. The effects of the reaction temperature, feed rate, and argon sweep flow rate on acetaldehyde yield were investigated. The results showed that the yield of acetaldehyde increased by 25–28% at the same conditions in a Ru-modified alumina membrane reactor. The reduced temperature of the Ru-modified alumina composite membrane was measured by temperature-programmed reduction, and the morphology of the membrane was characterized by SEM, TEM, and XRD.     

Effect of Reaction and Permeation Rates on the Performance of a Catalytic Membrane Reactor for Methylcyclohexane Dehydrogenation

Abstract

The effect of the relative rates of reaction and H₂ permeation through palladium-silver (Pd-Ag) membranes upon the performance of a catalytic membrane reactor (CMR) for methylcyclohexane dehydrogenation has been investigated. Mathematical models have been used to identify the conditions at which a membrane reactor gives yields of toluene (TOL) and H₂ significantly in excess of equilibrium values at throughputs of industrial interest. The simulation shows that a catalyst with no product TOL inhibition performs exceptionally well in a CMR, giving conversions considerably above the equilibrium values at favorable operating conditions. Using a membrane unit between two conventional packed-bed reactors to separate the H₂ ex-situ gives significant improvement in performance over the shell-and-tube type CMR, resulting in conversions substantially higher than equilibrium at 633 K, 1.5 MPa, and liquid hourly space velocities of 3–10 volume feed/h/catalyst volumes.

     

乙醇脱水反应的动力学研究

在管式固定床反应器中,采用改性的分子筛催化剂,在温度195～220℃、乙醇浓度30～70 wt%、乙醇液时空速0.08～0.17 mol/g-cat./h的范围内,对乙醇脱水反应的本征动力学进行了研究。动力学研究结果表明,在实验条件范围内,乙醇脱水生成乙烯和乙醚的反应属于平行反应,符合Langmuir-Hinshelwood机理模型,表面反应为速率控制步骤。     

Effect of Tetrachloromethane on Redox Behaviors of Copper(II) Oxide in the Oxidative Dehydrogenation of Propane

The oxidative dehydrogenation of propane on CuO has been investigated at 723 K in the presence and absence of tetrachloromethane (TCM). Under oxygen-limiting conditions, the conversion of propane and the selectivity to propylene were enhanced by the introduction of TCM. The catalyst converted to metallic Cu during the oxidation in the absence of TCM while no conversion of CuO was observed in the sample used in the presence of TCM. In contrast, the conversion of propane dramatically decreased upon addition of TCM into the feedstream for the oxidation of propane under the oxygen-excess conditions. The catalyst used under the oxygen-excess conditions was not reduced to metallic Cu, regardless of the addition of TCM. It is suggested that an abstraction of lattice oxygen from the catalyst is strongly influenced by the concentration of oxygen in the feed, resulting in the different effect of TCM on the oxidative dehydrogenation of propane.     

Theoretical Investigation of Ethanol Conversion to Ethylene over H–ZSM–5 and Transition Metals–Exchanged ZSM–5

Abstract  

Reaction mechanisms of ethanol conversion to ethylene over H–ZSM–5, Cu–ZSM–5, Ag–ZSM–5, and Au–ZSM–5 catalysts were investigated using density functional theory calculations. Energetics, thermodynamic quantities, rate and equilibrium constants of ethanol conversion to ethylene were obtained using the B3LYP/LanL2DZ method. The catalytic abilities of these catalysts on the reaction rates of ethanol conversion to ethylene are in order: Au–ZSM–5 > > Ag–ZSM–5 > H–ZSM–5 > > Cu–ZSM–5.     

Reaction Coupling of Ethylbenzene Dehydrogenation with Nitrobenzene Hydrogenation

The chemical equilibrium for the coupling of ethylbenzene dehydrogenation with nitrobenzene hydrogenation, to produce styrene and aniline simultaneously, has been calculated on the basis of the Soave–Redlich–Kwong equation of state. The dehydrogenation of ethylbenzene in the presence of nitrobenzene over the catalysts -Al₂O₃, ZSM-5, activated carbon and platinum supported on activated carbon has been carried out at 400 °C. The effects of Pt loading and the pretreatment of the catalysts have been investigated. It has been revealed that the conversion of ethylbenzene can be greatly improved by the reaction coupling due to the elimination of the hydrogen produced in the reaction by the hydrogenation of nitrobenzene. Platinum supported on the activated carbon has been suggested as a suitable catalyst. The best results with ethylbenzene conversion of 33.8% and styrene selectivity of 99.2% were obtained over Pt(0.02 wt%)/AC at 400 °C. Moreover, such process is also energetically favored since the necessary process heat to drive the ethylbenzene dehydrogenation can be provided by the coupling with the exothermic nitrobenzene hydrogenation reaction.     

多相态甲基环己烷催化脱氢反应过程的研究

从系统动态能量平衡的角度对以Raney-Ni为催化剂的甲基环己烷在"多相态"模式下的脱氢反应过程进行了研究,考察了反应温度(453～573 K)、反应液用量(0.2～4.0 mL)和催化剂用量(2～10 g)对甲基环己烷脱氢转化率的影响.反应过程中生成的气体通过冷凝回流装置不断地从反应体系中分离溢出,通过对Raney-Ni催化剂表面温度和冷凝回滴液量的控制,使整个反应体系始终介于"液-固"和"气-固"的中间状态,实现反应体系的"液(由反应物系的冷凝回滴实现)、气(通过催化剂表面高温气化反应物系实现)、固(即固体催化剂)"的三相共存.研究表明,在多相态的反应体系中存在一个最佳的能量平衡点,它所对应的反应物在催化剂表面的停留时间,既能保证反应液与催化剂充分有效地接触,又能使反应物在发生脱氢反应后立即被气化脱离催化剂,抑制逆反应的发生,从而有效地提高甲基环己烷的脱氢转化率.在523 K,0.5 mL甲基环己烷和8 g Raney-Ni的反应条件下,甲基环己烷的脱氢转化率达到65%.     

Catalytic Transfer Dehydrogenation of Geraniol to Geranial Over Palladium and Copper Supported Catalysts

Dehydrogenation of geraniol into geranial in the presence of a hydrogen acceptor (alkene) was studied. Supported palladium catalysts were not suitable for this transformation, but supported copper catalysts showed promising results at 150 °C; selectivity to the expected geranial was strongly dependent on the support and the calcinations/reduction procedure (>50 % in the presence of Mg–La hydrotalcite-supported copper).

     

助剂对乙醇脱氢制乙酸乙酯MoS2/C催化剂影响研究

通过X射线衍射、X光电子能谱和催化剂活性评价方法研究了助剂钾(K)、锆(Zr)的添加对乙醇一步法合成乙酸乙酯MoS2/C催化剂性能的影响。结果表明,K的加入有利于抑制乙醇脱水生成副产物乙烯,提高联合选择性,Zr的加入可以提高催化剂的乙醇转化率,Zr和K同时加入在提高乙醇转化率的同时,也可提高联合选择性。Zr及Zr、K的加入对催化剂中Mo的价态有比较明显的影响。     

Factors Affect on the Reaction Performance of the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene Over Zn-Ferrite Catalysts

Two types of zinc ferrite catalysts have been prepared by physical mixing or coprecipitation and applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. It is observed that the catalytic activity is significantly dependent upon not only the crystallinity but also the composition of a ferrite catalyst. If crystallinity of a catalyst is too high, the oxygen spillover through the lattice is severely suppressed and results in low catalytic activity. On the other hand, the presence of α-Fe₂O₃ in ferrite structure may lead to decrease of the reaction performance. Coprecipitation with strong base such as NaOH is found to be one of the efficient methods to form a catalytically active ferrite structure in that it is advantageous to obtain pure ferrite composition with appropriate crystallinity. During catalyst preparation, complete removal of sodium is essential because the residual sodium in catalyst considerably reduces the reaction performance. Although the use of mild base such as NH₄OH is advantageous to prevent the exhaustive washing, the formation of mixed phase both α-Fe₂O₃ and ZnFe₂O₄ may reduce n-butene conversion as well as 1,3-butadiene selectivity.