Process intensification of synthesis of magnetite using spinning disc reactor

An instantaneous co‐precipitation reaction for the synthesis of magnetite particles has been investigated in conventional mechanically agitated reactor and novel spinning disc reactor (SDR) with an objective of process intensification. Characteristics of the particles have been analysed using Coulter Counter particle analyser. It has been observed that the particle size distribution is more uniform with overall lower power consumption in the SDR as compared to the conventional reactors. With a viewpoint of improving the synthesis process in terms of the obtained conversion levels in the SDR, effect of different operating parameters viz. rotational speed, diameter and type of the disc, flow rate of the reactants and the operating temperature on the synthesis process has also been investigated. It has been observed that the flow rate of the reactants as well as disc characteristics have a significant influence on the extent of conversion. Overall, it has been established that the SDR gives excellent particle size distribution characteristics as compared to the conventional approaches and hence results in process improvement/intensification for magnetite synthesis process at comparatively lower energy inputs.     

多相反应体系的微界面强化简述

加氢、氧化等气液慢反应过程广泛存在于现代过程工业之中,这些反应过程一般受传质速率控制。因此,对这类多相反应体系的传质强化一直是研究热点之一。但总体而言,除外场和微通道（微流控）强化等一类强化反应器外,以往的研究大多集中于界面尺度为毫-厘米级的传统反应器的搅拌与混合方式、气泡分布状态、流体流型、构效关系等方面,而鲜有将研究视角投放到传统以米为直径计量单位的反应器平台上如何构建尺度为微米级的界面体系及其特殊效应方面。探讨了多相反应体系的微界面反应强化理念,并简述了微界面的涵义、微界面反应强化与构效调控方法、微界面反应器的结构与形成原理、微界面体系的微颗粒测试与相界面表征技术、微界面反应强化面临的问题与挑战等,以与本领域同行共同研讨。     

Review on the applications and developments of drag reducing polymer in turbulent pipe flow

Drag reduction phenomenon in pipelines has received lots of attention during the past decades due to its potential engineering applications, especially in fluid transporting industries. Various methods to enhance drag reduction have been developed throughout the years and divided into two categories;non-additives method and additives method. Both categories have different types of methods, with different formulations and applications which will generally be discussed in this review. Among all the methods discussed, drag reduction using polymer additive is as one of the most enticing and desirable methods. It has been the subject of research in this field and has been studied extensively for quite some time. It is due to its ability to reduce drag up to 80% when added in minute concentrations. Reducing drag in the pipe will require less pumping power thus offering economic relieves to the industries. So, this paper will be focusing more on the use of polymer additives as drag reducing agent, the general formulations of the additives, major issues involving the use of drag reducing polymers, and the potential applications of it. However, despite the extensive works of drag reduction polymer, there are still no models that accurately explain the mechanism of drag reduction. More studies needed to be done to have a better understanding of the phenomenon. Therefore, future research areas and potential approaches are proposed for future work.     

Design aspects of sonochemical reactors: Techniques for understanding cavitational activity distribution and effect of operating parameters

Cavitation is a phenomenon having enormous potential for intensification of physical and chemical processing applications such as chemical synthesis, industrial wastewater treatment, cell disruption for release of intracellular enzymes, crystallization, extraction and leaching. However, the dynamic behavior of cavitational activity, especially in sonochemical reactors based on the use of ultrasonic irradiations, creates problems in proposing reliable design and operating strategies. The present work presents an overview of different techniques to understand the cavitational activity distribution in the reactor, highlighting the basic aspects, its applicability and relative merits/demerits. A detailed analysis of the literature has also been made with an aim of explaining the dependency of the cavitational activity on the design of sonochemical reactors and also the operating parameters. Recommendations for optimum operating parameters and design of reactor based on the experimental as well as theoretical analysis have been reported. Some trends in the future reactor designs useful in large scale applications have also been discussed.     

The Behavior of α-Olefins Butyl Acrylate Copolymers as Viscosity Index Improvers and Pour Point Depressants for Lube Oil

A lubricant additive may be defined as a material that imparts a new and desirable property not originally present in the oil or reinforces a desirable property already possessed in some degree by the oil. These materials are normally more chemically reactive than the base oil. The additives are being used at various concentrations from a few parts per million to over 30%. A great deal of research is being done at present into the synthesis, technology, and applications of different lube oil additives. In the present work, polymeric additives were prepared by reaction of butyl acrylate with different α-olefins (octene, dodecene, tetradecene, and octadecene). The efficiency of the prepared copolymers as viscosity index improvers and pour point depressants for a base lube oil were studied. It was found that the efficiency as viscosity index improvers increases with increasing the concentration of the prepared copolymers and increasing the chain length of alkyl groups of the α-olefins, and the efficiency as pour point depressants increases with decreasing the concentration and decreasing the molecular weights of the prepared copolymers.     

Controlling the electrical resistivity of porous silicon carbide ceramics and their applications: A review

Porous silicon carbide (SiC)-based ceramics are widely used in numerous applications of technical importance owing to their exceptional structural (e.g., excellent chemical, mechanical, and thermal stability) and functional (e.g., controlled electrical resistivity) properties. Porous SiC with controlled electrical resistivity is required for various advanced applications, for example, power electronic devices, semiconductor processing parts, fusion reactors, thermoelectric energy conversion, electromagnetic shielding, and environmental applications such as heatable filters. The electrical properties of sintered porous SiC are significantly affected by its chemical composition, processing conditions, and microstructure. This article reviews the influence of certain critical factors, such as the polytype, doping conditions, porosity (%), additive composition (oxide additives, element additives, metal nitride/carbide additives, etc.), and processing conditions on the electrical resistivity of porous SiC. Novel applications of porous SiC with controlled electrical resistivity are also discussed in this review.     

氯代烷的合成及应用

通过试验确定了用盐酸和醇为原料合成氯代烷的较佳工艺条件,得到了合格的助剂产品,在此工艺条件下,助剂收率可达到68%～69%。同时还考察了不同助剂对重芳烃副产的烷基化反应的影响,用合成的精制助剂对重芳烃副产进行烷基化反应,可使甲乙苯的转化率达到95%～96%。     

Surface tension studies of additives in acrylic resin-based powder coatings using the Wilhelmy balance technique

A modified Wilhelmy balance technique using thin fibers as solid probes has been applied to study the effect of silicone additives in acrylic resin-based powder coatings on the surface tension of non-reactive binder systems. By measuring the temperature dependence of the surface tension in the temperature range between 140 and 180°C, it could be shown that the silicone additives investigated had a very different surface activity in the molten acrylic resin. Due to the high accuracy of the measuring technique and the good reproducibility of the experiments the influence of different additive concentrations on the surface tension was detectable even at very low concentrations (below 1 wt.%).

Compared to the pure powder coating binder which has a surface tension of about 30 mN/m the values decreased between 2–15 mN/m depending on the type of the silicone additive. In addition, the temperature coefficient −(dγ/dT) of the surface tension of the binder melt was changed. In the case of two additives, the surface tension of the powder coating and its temperature coefficient were lowered considerably. This effect of additives is desirable to reach good wetting and leveling of the powder coating.     

霍夫曼重排反应过程的研究进展

霍夫曼重排反应作为制备伯胺及其衍生物的一种重要手段,在药物合成和功能材料制备等领域有广泛的应用。传统霍夫曼重排反应工艺存在反应效率低、流程烦琐和安全性差等问题。针对以上问题,研究者们主要从反应条件优化和过程强化两方面入手。通过反应条件优化,发展了许多温和、高选择性的反应工艺条件,为不同酰胺底物的反应方案设计提供了更多选择;微波辅助、电化学合成以及微化工技术等新型反应过程强化技术的出现,为实现高效绿色的霍夫曼重排反应创造了有利的条件。本文重点阐述了霍夫曼重排反应在反应条件优化和过程强化方面的最新研究进展。在此基础上,对该反应未来的研究方向进行了展望。     

Influence of n-butanol and isomers on the combustion mechanisms of isooctane and coke formation based on ReaxFF simulation

Fuel additives play a significant role in enhancing the thermal stability of fuel combustion. The effect of additives on the combustion of hydrocarbon fuels and the combustion performances of isooctane with three different isomer additives, (n-butanol (1-BuOH), diethyl ether (DEE), and 2-butanol(2-BuOH)), and additive-free isooctane were explored by ReaxFF simulation in this work. The simulation system was heated to 3000 K at a heating rate of 10 K/ps and kept stable at 3000 K. A variety of combustion products (e.g., small gas molecules and C1-C8 hydrocarbon compounds) in each system were analyzed, and the reaction paths were speculated based on the computed trajectory. The simulation results showed that the C C bond scission reaction dominated the combustion process of the three additives. All three additives promote the formation of toxic carbonyl compounds such as formaldehyde, while the pure DEE additive has the best inhibition effect on the formation of the coke precursor, C₂H₂, C₃H₄, and C₃H₆. The pure 1-BuOH additive can shorten the initial reaction time of the reactants. The effects of DEE/1-BuOH additive on the combustion of isooctane were investigated to obtain a desirable additive mixture with good performance. The expansion of the DEE proportion (80%/20% DEF/1-BuOH) shows a slightly better coke (C₃H₄ and C₃H₆) reduction effect, while the inhibition effect is not as obvious as that of a pure DEE additive.     

2,6-萘二甲酸的合成研究

使用1,8-萘二甲酸酐为原料,采用亨克尔法,以碳酸锌做催化剂、萘和碘化钾为助剂,在二氧化碳气氛中进行反应,通过异构化反应制备2,6-萘二甲酸.探讨了反应温度、反应时间、催化剂用量、反应压力、搅拌速度、助催化剂和助剂用量对异构化转位反应的影响.结果表明:根据正交实验确定了1,8-萘二甲酸二钾盐异构化转位反应的较优工艺,各...     

Studies on the autoclave dehydration of gypsum

The effects of some additives on the autoclave dehydration of gypsum have been determined. It was possible to accelerate the reaction by the addition of calcium sulphate hemihydrate or orthorhombic calcium sulphate to the gypsum. Plasters prepared by the sodium succinate method in the presence of the latter additive had a high water requirement and poor mechanical properties.     

Effect of sodium iodide additive on the electrochemical performance of sodium/nickel chloride cells

The effect of sodium iodide and sulfur additives on the performance of Na/-alumina/NaAlCl₄/NiCl₂/Ni cells was investigated in quasi-sealed laboratory research cells (0.5–1.0 Ah capacity) and in sealed full-size cells (4 Ah capacity). It was found that sodium iodide additive especially in combination with sulfur in Na/NiCl₂ cells significantly increases the usable capacity and reduces the impedance of the Na/NiCl₂ cells. It is proposed that the use of sodium iodide enhances the energy and power performance of the NiCl₂ electrode by two different mechanisms. The first mechanism, iodide ion doping of the anodically formed solid NiCl₂, is dominant at potentials lower than that of iodine evolution. The doping effect of the iodide ions produces a higher-capacity, lower-impedance NiCl₂ layer on the positive electrode. The second mechanism, anodic formation of very reactive iodine species, is effective when the cell is cycled through the iodine evolution potential range (2.8–3.1 V vs Na). During this process, the dissolved iodine species improve electrode kinetics through liquid-phase mass transport. Use of the sodium iodide additive is safe in sealed cells, causing no over-pressurizing problems. A maximum pressure increase of only 10 kPa was detected by a pressure sensor during severe overcharge tests.     

Aluminium as anode in primary alkaline batteries. Influence of additives on the corrosion and anodic behaviour of 2S aluminium in alkaline citrate solution

The inhibitive effects of various additives on the corrosion of 2S aluminium in 4N NaOH containing calcium oxide and sodium citrate (base electrolyte) have been examined by studying the self corrosion, anodic polarization and anode efficiency of 2S aluminium in solutions containing different additives. It has been found that among the different additives investigated, those forming anions in solution act favourably.     

H2SO4-catalyzed isobutane alkylation under low temperatures promoted by long-alkyl-chain surfactant additives

To deeply understand the role of surfactants on the acid/C4 hydrocarbon miscibility, the catalytic activity and molecular-level interfacial properties of long-alkyl-chain cationic surfactants (hexadecyltrimethylammonium bromide, CATB and dihexadecyldimethylammoniumchloride, DDAB) and anionic one (sodium dodecyl benzene sulfonate, SDBS) were studied as additives for H₂SO₄ alkylation using experiments and molecular dynamics simulations. Surfactant additives are found to efficiently decrease by-products and promote higher selectivity of trimethylpentanes (TMPs) and higher research octane number (RON), which is attributed to the improvement of acid/hydrocarbons interface, including better interfacial dispersion, higher I/O ratio, and lower interfacial tension. Surfactant additives show an interfacial intensification, quite different from intrinsic reaction intensification by low temperature. Combination of SDBS additive and lower temperature contributes to significantly higher TMP selectivity and higher RON up to 84.20 wt% and 99.07 at 269.2 K from 60.21 wt% and 94.34 at 281.2 K, respectively. The information provides good reference for the industrial H₂SO₄ alkylation.     

A novel chemically amplified positive deep UV photoresist with significantly reduced sensitivity to environmental contamination

t-Boc protected Deep-UV transparent polymers with photoacid generators have been widely investigated as potential positive deep-UV resist systems. However, utility of these systems is seriously handicapped by environmental contaminants leading to an insoluble “surface skin” formation. Only with a specially controlled environment or by use of an “overcoat” material is the performance of these systems acceptable. We have investigated a series of t-Boc protected poly(styrene-maleimide) copolymers and poly(hydroxy styrene) polymers with onium-salts. Upon incorporation of a special class of organic additive, the surface effects inherent to these positive deep-UV systems are significantly reduced thereby avoiding any extraneous precaution of protecting the resist surface from a typical manufacturing environment. We evaluated these t-Boc polymer/onium-salt systems with different additives under a varied set of processing conditions. In addition, plausible structure-activity relationship of these additives in controlling the surface effects is presented.     

Large‐scale sonochemical reactors for process intensification: design and experimental validation

Acoustic cavitation results in substantial enhancement in the rates of various chemical reactions but the existing knowledge about the application of reactors based on acoustic cavitation is limited to very small capacities (of the order of few millilitres). In the present work, an overview of the application of acoustic cavitation for the intensification of chemical reactions has been presented briefly, discussing the causes for the observed enhancement and highlighting some of the typical examples. A novel reactor has been developed operating at a capacity of 7 dm³ and tested with two reactions, ie liberation of iodine from aqueous potassium iodide and degradation of formic acid. The energy efficiency of the reactor has been calculated and compared with the conventional sonochemical reactors. The effect of frequency of irradiation on the percentage conversion of the reactants has been studied. Due to quite low conversions in the case of formic acid degradation, further intensification was attempted using aeration, addition of hydrogen peroxide, and the presence of solid particles (TiO₂). Compared with conventional reactors the novel reactor gives excellent results and it can be said that the future of using acoustic cavitation for process intensification lies in the development of large‐scale multiple frequency multiple transducer reactors. Copyright © 2003 Society of Chemical Industry     

A high temperature stable electrolyte system for dye-sensitized solar cells

The effect of the addition of single and binary additives to a mixed solvent, ethylene carbonate + γ-butyrolactone, on the performance of dye-sensitized TiO₂ solar cells (DSSCs) has been investigated. The addition of a single additive, 2-(dimethylamino)-pyridine, to the electrolyte containing an ionic salt, 1,2-dimethyl-3-propylimidazolium iodide, in the mixed solvent results in an enhancement of the cell performance. The performance of the cell has been further enhanced by the addition of the second additive, 5-chloro-1-ethyl-2-methylimidazole. The resulting DSSC has performed better than the one based on the conventional electrolyte in acetonitrile. The dependence of the stability of the cells on the temperature has been evaluated over the range of 30-120 °C for outdoor applications.     

Examination of the effects of LiOH, LiCl, and LiNO3 on alkali-silica reaction

Lithium additives have been shown to reduce expansion associated with alkali-silica reaction (ASR), but the mechanism(s) by which they act have not been understood. The aim of this research is to assess the effectiveness of three lithium additives—LiOH, LiCl, and LiNO₃—at various dosages, with a broader goal of improving the understanding of the means by which lithium acts. The effect of lithium additives on ASR was assessed using mortar bar expansion testing and quantitative elemental analysis to measure changes in concentrations of solution phase species (Si, Na, Ca, and Li) in filtrates obtained at different times from slurries of silica gel and alkali solution. Results from mortar bar tests indicate that each of the lithium additives tested was effective in reducing expansion below an acceptable limit of 0.05% at 56 days. However, different lithium additive threshold dosages ([Li₂O]/[Na₂O_e]) were required to accomplish this reduction in expansion; these were found to be approximately 0.6 for LiOH, 0.8 for LiNO₃, and 0.9 for LiCl. Quantitative elemental analysis indicated that sodium and lithium were both bound in reaction products formed within the silica gel slurry. It is also believed that lithium may have been preferentially bound over sodium in at least one of the reaction products because a greater percent decrease in dissolved lithium than dissolved sodium was observed within the first 24 h. It appears that lithium additives either decreased silica dissolution, or promoted precipitation of silica-rich products (some of which may be nonexpansive), because the dissolved silica concentration decreased with increasing dosage of lithium nitrate or lithium chloride additive.     

Investigation of degradation of polypropylene in soil using an enzymatic additive

Polypropylene (PP) has been widely used industrially in several sectors, mainly in the use of packaging of different products. Thus, this has been accumulated in our environment due to the incorrect disposal and its high resistance toward degradation, causing an array of environmental impacts. With this, one alternative that has been explored to minimize the problems intensified by these residues is the use of pro-degrading additives. Therefore, the aim of this work is to evaluate the degradation process of PP blends in soil using enzymatic additive. The soil degradation experiment was done for 6 months; monthly collected samples were checked for alterations on the material properties during that time. The extent of PP degradation with enzymatic additive was compared to an organic additive by techniques of FTIR, TGA, DSC, carbonyl index (CI), and crystallinity. From the obtained results it was observed that the additives influenced the degradation of PP. In addition, the enzymatic additive caused more significant changes in the CI (increase of 3693%), crystallinity (variation of 18.7%), and structural characteristics, indicating a greater influence on the degradation process in relation to the organic additive. In this way, this work has had an important role in the research and development of biodegradable materials with the aim of minimizing the effects induced by plastic waste in the environment.