氮化硅陶瓷的制备及性能研究进展

氮化硅陶瓷是一种具有广阔发展前景的高温、高强度结构陶瓷,它具有强度高、抗热震稳定性好、疲劳韧性高、室温抗弯强度高、耐磨、抗氧化、耐腐蚀性能好等高性能,已被广泛应用于各行业。本文介绍了氮化硅陶瓷的基本性质．综述了氮化硅陶瓷的制备工艺和提高其高温性能的方法以及增韧的途径,并展望了氮化硅陶瓷的发展前景。     

硼基催化剂丙烷氧化脱氢制丙烯

自2016年Hermans课题组发现六方氮化硼（h-BN）在丙烷氧化脱氢制丙烯（ODHP）反应中优异的烯烃选择性,各类硼基材料引起了研究者强烈的研究兴趣并广泛地用于ODHP反应。与传统金属与金属氧化物基催化剂不同,非金属硼基催化体系能够有效抑制CO _x 等过度氧化产物,提高烯烃产率,具有较广阔的工业应用前景。本综述对硼基丙烷氧化脱氢催化剂从催化剂的设计、合成策略和反应性能等方面进行了系统地讨论,阐明了催化剂的构效关系;总结了反应路线、关键中间体、决速步以及催化动力学行为,加深了硼基催化剂催化丙烷氧化脱氢活性位点和机理的理解。指出三配位B—O/B—OH活性位点的有效构建及实现表面与气相自由基反应的协同催化是提高硼基催化剂丙烷脱氢性能的关键。基于目前的研究现状和存在的问题,对硼基催化剂体系研发前景和未来工业化应用进行了展望。     

凹凸棒石低温SCR脱硝催化剂的研究进展

选择性催化还原（SCR）脱硝技术是目前主流的氮氧化物脱除技术,其核心是催化剂。凹凸棒石成本低廉,性能优越,适合用作SCR催化剂的载体,而且以凹凸棒石为载体的催化剂显示出良好的低温选择性和稳定性,具有很好的应用前景。本文总结了凹凸棒石低温SCR脱硝催化剂的研究进展,阐述了活性组分、制备方法、前体物种、活性组分负载量、煅烧温度、元素掺杂等因素对催化剂脱硝活性的影响,同时简要介绍了导致此类催化剂失活的原因以及失活催化剂的再生方法,并指出在凹凸棒石负载型低温脱硝催化剂上进行的SCR脱硝反应遵循E-R机理,最后指出此类催化剂的未来研究方向主要是进一步提高现有催化剂的低温催化活性和抗中毒能力,实现工业化应用。     

低温甲醇水重整制氢催化剂研究进展

甲醇具有结构简单、含氢量高、产能大等优点,利用甲醇与水蒸气进行重整是一种节能高效的现场制氢方式。甲醇水蒸气重整(MSR)与燃料电池联用能够实现多场景应用,但由于反应温度较高(250~300℃),存在启动速度较慢、副产CO含量较高和热效率较低等问题。低温甲醇水重整(LT-Methanol Water Reforming, LT-MWR)包括低温甲醇水蒸气重整(LT-MSR)与液相甲醇水重整(Aqueous-phase Reforming of Methanol, APRM),反应通常在200℃以下进行,同时保持较高的反应活性,进而能够减少预热时间、减弱副反应发生,且能与燃料电池实现更强的热耦合。本工作首先介绍了商用催化剂优异的性能与存在的缺陷,然后对低温甲醇水重整制氢催化剂,诸如Cu基催化剂、贵金属催化剂与光协同催化剂的研究进展进行了回顾。归纳了低温铜基催化剂的改性策略,包括合成方法、结构设计与元素掺杂。对国内外商用CuZnAlOx催化剂结构与性能的测试表明,其转化率高和稳定性好,存在的缺陷是价格较贵且在低温区催化活性急剧下降。Cu基催化剂活性受温度影响较大,在低温区活性很低,但通过适当的改性能够实现其应用价值,其改性策略包括合成方法、结构设计与元素掺杂。贵金属催化剂低温下活性较高,但存在价格昂贵、合成复杂等缺点。光协同催化剂则是在光照条件下进行催化重整,尚处于研究阶段。对于Cu基催化剂,合成方法的改进能够大大改善催化剂的微观混合程度与可重现性。适当的结构设计可提升催化剂的比表面积与热稳定性。元素掺杂则能够提升活性组分的分散度,修饰催化剂表面结构。三种改性策略能够有效提升Cu基催化剂低温下甲醇重整制氢的性能,在保持较高活性的同时,降低CO副产物的含量。展望了低温甲醇水重整制氢催化剂的发展前景和挑战,对催化剂的开发与应用有指导意义。     

Fabrication of super flux and high thermal shock resistance ceramic membrane support

Ceramic membranes play an important role in high temperature gas-solid filtration. However, the thermal stability of the ceramic support at high temperatures has always been a problem. In this study, porous fused silica ceramic supports were fabricated with hexagonal boron nitride as a sintering aid. The results shown that hexagonal boron nitride could inhibit the crystallization of fused silica ceramic particles at high temperature and act as a sintering addictive to reduce firing temperature. The obtained supports have an average pore size of 72?µm, an open porosity of 42%, a bending strength of 16.5?MPa, a Weibull modulus of 8.67 and a gas permeability of 4.23?×?10⁵ m³/(m² h bar). The bending strength of the support remained 16?MPa after 30 cold-hot cycles, exhibiting high thermal shock resistance. After corrosion in 20?vol% H₂SO₄ solution for 8?h, the weight and the bending strength of the support were diminished by 0.6% and 24.32%, respectively. So, the ceramic support showed good acid corrosion resistance.     

Thermal imaging of catalyst surface during catalytic dehydrogenation of cyclohexane under spray-pulsed conditions

Infra-red thermographic imaging, a tool widely used for screening of active catalytic materials in the field of combinatorial chemistry, has been used during dehydrogenation of cyclohexane on Pt catalyst supported on active carbon cloth and alumite supports. A spray-pulsed reactor with injection of atomized cyclohexane and to create alternate wet and dry conditions on the catalyst surface was used in this study. Since the production rate of hydrogen via endothermic dehydrogenation reaction is greatly dependent on the temperature of the catalyst surface, the temperature profile of the catalyst is important to observe. The observed change in the temperature profile at wet and dry conditions with varying pulse injection frequency and corresponding product gas analysis reveals that the spray-pulse mode is useful in improving the catalyst activity. Further, the comparison between activated carbon support and a more conductive support such as alumite is reported using thermal imaging for more suitable support in this endothermic reaction.     

Fe2O3/β-SiC: A new high efficient catalyst for the selective oxidation of H2S into elemental sulfur

Over the last decades, sulfur recovery from the H₂S-containing acid gases (issued from oil refineries or natural gas plants) has become more and more important due to the ever increasing standards of efficiency required by environmental protection pressures. The H₂S-tail gas was directly oxidized by oxygen to yield elemental sulfur. A significant improvement of the H₂S conversion and selectivity has been developed, however, the support which is the core of the process still needs to be improved. Recently, β-SiC has been reported to be an efficient and selective catalyst support for the H₂S-to-S reaction. One expected reason for this superior yield should be due to the high thermal conductivity of the support. The high thermal conductivity of the silicon carbide plays an important role in the maintenance of the high selectivity by avoiding the formation of hot spots on the catalyst surface which could favor secondary reactions. On the other hand, insulator supports such as alumina exhibit a poor selectivity due to catalyst surface temperature runaway.     

氮化铝粉体工程的研究进展

电子技术微型化、轻型化、高集成和大功率的发展,对基板和封装材料提出更高要求。氮化铝陶瓷具有高导热性、绝缘性、热膨胀系数与半导体硅相近、机械强度高、化学稳定性好、无毒无害等优良特性,是理想的基板材料之一,具有很好的发展前景。高质量氮化铝粉体是制备高性能氮化铝陶瓷的关键。本文分别归纳介绍了微米/纳米氮化铝合成的新技术、新方法及其研究进展,并展望了氮化铝粉体合成的发展趋势。     

预硫化催化剂钝化研究

以硫化度和自放热温度为评价指标,确定了固定床气体钝化适宜工艺条件为:温度50℃,O2浓度1%,时间30min。利用XRD、DTA对催化剂进行了表征并总结出了预硫化催化剂机理。结果表明,钝化催化剂没有出现活性相聚集现象。钝化催化剂的放热峰比硫化态催化剂放热峰低得多,也比较平坦,TGA曲线表明,钝化催化剂在高温有SO2的生成。催化剂经过钝化后活性组分发生了变化,有新相生成,同时改善了硫化催化剂低温热稳定性。     

新型催化热分解脱酸催化剂研究

催化热分解脱酸是一种方便且成本低廉的脱酸方法，但脱酸率较低，限制了工业化。通过采用氧化镁、氧化锌、镁铝水滑石和H-ZSM-5作为催化剂活性组分进行脱酸实验，发现镁铝水滑石对催化热分解脱酸具有较高的活性，可作为催化剂的活性组分，从机理方面证明具有催化石油酸分解的作用。对不同制备工艺制备的催化剂进行评价，得出最佳的催化剂制备工艺为：采用机械混合制球法，镁铝水滑石用量为催化剂质量的30%，活性氧化铝为载体，焙烧温度500 ℃。将中海油减二线馏分油与脱酸后油品进行红外分析，表明脱酸后油品中的环烷酸消失，证明镁铝水滑石催化剂具有良好的脱酸效果。     

Selective catalytic reduction of NOx with NH3 over a V2O5/TiO2 on silica catalyst

The catalytic properties of various supported and unsupported vanadium oxide based catalysts for the Selective Catalytic Reduction of NO_x with NH₃ (SCR) are investigated. It is concluded, that in order to achieve good selectivity in the SCR, the number of active sites favouring SCR has to be increased at the cost of sites favouring ammonia oxidation. This can be achieved by the application of the active vanadium oxide onto a suitable support. A specific catalyst preparation procedure is described which enables the application of vanadium oxide onto TiO₂-adlayered silica. The thus prepared catalyst is shown to exhibit the desired properties, that is, a high selectivity and good activity in the Selective Catalytic Reduction of NO_x with NH₃.     

磷酸功能化聚丙烯腈纤维催化合成吡喃类杂环化合物

以廉价易得的聚丙烯腈纤维为载体，采用共价键接枝法合成了磷酸功能化纤维PAN_EAPF，用于催化吡喃类杂环化合物的合成。以芳香醛、丙二腈和α-萘酚的三组分反应以及4-羟基香豆素和芳香醛的Friedel-Crafts反应为模型评价磷酸纤维的催化活性，并考察了纤维的官能度、溶剂、温度、时间和催化剂用量（摩尔分数，下同）对反应的影响。PAN_EAPF水相催化合成吡喃类衍生物的反应显示出高的催化活性和广泛的底物范围。此外，该催化剂易于从反应体系中回收，并且在多次循环后仍然保持了良好的稳定性和催化活性，表明这种绿色、高效、可回收的纤维催化剂具有潜在的应用价值。     

氧化铝载体改性及其应用研究进展

氧化铝不仅价格低廉、易获取,且具有多孔性、大比表面积、高分散性、高热稳定性等优点,常用作催化剂载体,广泛应用于工业催化领域。氧化铝的孔结构对工业催化剂性能影响很大。为优化氧化铝载体的性能,对氧化铝的扩孔和添加助剂改性已进行了大量研究。扩孔改性可降低扩散阻力并改善传质、提高活性位点的有效利用率、增强抗结焦性能,进而提高加氢催化的产率;添加助剂改性可有效抑制氧化铝载体高温烧结和相变,防止孔结构被破坏,提高催化剂的寿命。本工作介绍了制备氧化铝的方法?拟薄水铝石脱水法和溶胶?凝胶法,综述了氧化铝的扩孔方法,总结了改性氧化铝载体的最新研究进展,包括自组装法、水热处理法、扩孔剂法;阐述了氧化铝添加助剂的改性方法,包括加入稀土金属氧化物、碱(土)金属氧化物、其它金属氧化物及非金属氧化物。最后,展望了氧化铝未来的研究和发展方向。     

A novel reverse flow reactor coupling endothermic and exothermic reactions: Part II: Sequential reactor configuration for reversible endothermic reactions

The new reactor concept for highly endothermic reactions at elevated temperatures with possible rapid catalyst deactivation based on the indirect coupling of endothermic and exothermic reactions in reverse flow, developed for irreversible reactions in Part I, has been extended to reversible endothermic reactions for the sequential reactor configuration. In the sequential reactor configuration, the endothermic and exothermic reactants are fed discontinuously and sequentially to the same catalyst bed, which acts as an energy repository delivering energy during the endothermic reaction phase and storing energy during the consecutive exothermic reaction phase. The periodic flow reversals to incorporate recuperative heat exchange result in low temperatures at both reactor ends, while high temperatures prevail in the centre of the reactor. For reversible endothermic reactions, these low exit temperatures can shift the equilibrium back towards the reactants side, causing ‘back-conversion’ at the reactor outlet.The extent of back-conversion is investigated for the propane dehydrogenation/methane combustion reaction system, considering a worst case scenario for the kinetics by assuming that the propylene hydrogenation reaction rate at low temperatures is only limited by mass transfer. It is shown for this reaction system that full equilibrium conversion of the endothermic reactants cannot be combined with recuperative heat exchange, if the reactor is filled entirely with active catalyst. Inactive sections installed at the reactor ends can reduce this back-conversion, but cannot completely prevent it. Furthermore, undesired high temperature peaks can be formed at the transition point between the inactive and active sections, exceeding the maximum allowable temperature (at least for the relatively fast combustion reactions).A new solution is introduced to achieve both full equilibrium conversion and recuperative heat exchange while simultaneously avoiding too high temperatures, even for the worst case scenario of very fast propylene hydrogenation and fuel combustion reaction rates. The proposed solution utilises the movement of the temperature fronts in the sequential reactor configuration and employs less active sections installed at either end of the active catalyst bed and completely inactive sections at the reactor ends, whereas propane combustion is used for energy supply. Finally, it is shown that the plateau temperature can be effectively controlled by simultaneous combustion of propane and methane during the exothermic reaction phase.     

耐高温催化材料研究进展

本文简述了高温催化燃烧的原理, 概括了燃烧速率与温度的关系, 并详述了高温催化燃烧用催化剂的基体、载体和活性组分材料科研与开发近况, 指出筛选和制备出一种以氧化铝或氧化镁或其它耐高温、比表面大的氧化物为基体, 在其上引入高温下具较强活性组分的复合型氧化物涂层, 使其获得较大的比表面积及较佳的热稳定性, 并具有一定活性的催化剂是高温催化燃烧催化剂发展趋势。     

Catalytic and thermal effects during hydrotreating of bitumen-derived heavy oils

The relative magnitude of catalytic and thermal reactions during the hydrotreating of PR Spring bitumen-derived heavy oil was evaluated in a fixed-bed reactor as a function of temperature, residence time and catalyst selection. The relative effects of thermal and catalytic reactions were evaluated by hydrotreating the PR Spring bitumen-derived heavy oil over three catalysts: sulfided Ni/Mo/alumina HDN catalyst, Mo/alumina HDM catalyst and sodium-impregnated alumina. Catalytic and thermal effects for each of the catalysts were evaluated under a range of temperature (625–685 K) and liquid hourly space velocity (0.14–0.81 h⁻¹). The reactor pressure, 13.7 MPa, and the hydrogen-to-oil ratio, 890 m³ m⁻³ (5000 scf H₂ per bbl), were fixed in all experiments.The catalysts' activities were ranked as follows: HDN catalyst>HDM catalyst>sodium-impregnated alumina, based on their activities for nitrogen, sulfur and nickel removal as well as for the conversion of Conradson carbon residue (CCR) and residuum. The catalyst activities were strongly dependent on the metal loading and were dependent, to a lesser extent, on the acidity of the alumina support. CCR and residuum conversion was closely linked relative to heteroatom and metal removal. This is attributed to a significant overlap between moieties which are classified as CCR precursors and moieties which are classified as residuum. Catalyst selection significantly affected residuum conversion. This is because the high catalyst densities employed in packed bed reactors accentuate catalytic reactions relative to thermal reactions. Although sulfur was generally more reactive than nitrogen, sulfur conversions in excess of 70% were difficult to achieve. It was presumed that 30–40% of the sulfur was asphaltic in nature and exhibited low reactivity. For this reason it was easy to achieve significant sulfur conversion as low severities, but difficult to achieve deep desulfurization at high severities. The deactivation rates of HDN and HDM catalysts were 0.06 and 0.2°API per day, respectively.     

改性铝土矿为载体的Ni-Mn-K一氧化碳高温变换催化剂工业侧流试验

采用等体积浸渍法,以改性天然铝土矿为载体,工业小试生产80 L一氧化碳高温变换催化剂。在福建永安智胜合成氨厂变换工段侧流装置上,进行催化剂工业在线侧流试验。结果表明,该催化剂活性好,机械强度高,热稳定性能良好,副反应不明显,能在低汽气体积比（约0.4）条件下运行,节能效果显著。     

Microspherical chromium oxide/alumina catalyst KDM for fluidized-bed isobutane dehydrogenation: Development and industrial application experience

A microspherical chromium oxide/alumina catalyst (KDM) has been developed for fluidized-bed isobutane dehydrogenation. This catalyst shows a high catalytic activity, selectivity, and thermal stability. The KDM preparation technology involves an alumina support produced by centrifugal thermal activation (CTA) of gibbsite-CEFLAR? technology. This technology makes it possible to regulate the phase composition of the CTA product in a wide range and to synthesize, from this product, supports with preset structural and textural properties. The support and catalyst production technologies have been commercialized by Altailyuminofor Co. Since 2008, the KDM catalyst has been employed by SIBUR Holding Co. and Ekooil Co. (Omsk). Industrial-scale application of the catalyst has demonstrated that isobutane dehydrogenation over an IM-2201 + KDM mixture reduces the catalyst consumption (kg/(t isobutylene)) from 22–23 for pure IM-2201 to 8-9.5 for the IM-2201 + KDM mixture. For further improvement of the KDM catalyst, fundamental studies of the nature of the active component of this catalyst have been carried out: the role of different states of supported chromium oxide species in dehydrogenation has been elucidated and approaches to controlling the proportion of active and selective chromium oxide species have been devised. These studies have culminated in the development of a catalyst modification whose activity and selectivity exceeds the same characteristics of the original KDM catalyst by 2–4 wt %.     

Fischer-Tropsch synthesis on ruthenium supported ETS-10 titanium silicate catalysts

Titanium silicate ETS-10 was found to be a suitable metal catalyst support, having high surface area, high ion exchange capacity and no acidic functions. In this work, ETS-10 was used as a support in preparing ruthenium supported catalyst for Fischer-Tropsch synthesis. Ru/METS-10 catalytic systems (M standing for Na or K) showed some important characteristics, as good metal dispersion and shape selectivity. Moreover, no side reactions due to acidic functions were evidenced; indeed readsorption of olefins on active metal centers was found to control the activity of the catalysts.In part presented at 10th IZC, Garmisch-Partenkirchen, July 1994.     

In-situ infrared thermographic analysis during dehydrogenationof cyclohexane over carbon-supported Pt catalysts using spray-pulsed reactor

Infrared thermography, a tool used for screening of active catalytic materials generally during the exothermic reactions has been used for thermal imaging during strong endothermic reaction of dehydrogenation of cyclohexane on Pt catalyst supported on active carbon cloth (CFF-1500s) sheets. A spray-pulsed mode was used for injection of atomized cyclohexane and to create alternate wet and dry condition on catalyst surface. The simultaneous product gas analysis and recording of the temperature profile of the catalyst surface using an IR camera was carried out. The production rate of hydrogen via endothermic dehydrogenation reaction is greatly dependent on the temperature of the catalyst surface. The observed change in the temperature profile at wet and dry conditions with varying pulse-injection frequency and corresponding product gas analysis reveals that the spray-pulse mode is useful in improving the catalyst activity. Further the reaction conditions were optimized using thermal profile data.Rajesh B. Biniwale-On deputation from NEERI, Nagpur India.