Particle Size and Crystal Phase Effects in Fischer-Tropsch Catalysts

Fischer-Tropsch synthesis (FTS) is an increasingly important approach for producing liquid fuels and chemicals via syngas—that is, synthesis gas, a mixture of carbon monoxide and hydrogen—generated from coal, natural gas, or biomass. In FTS, dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles, which depend on the particle size, morphology, and crystallographic phase of the nanoparticles. In this article, we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active, selective, and stable FTS catalysts.     

New Trends in Olefin Production

Most olefins (e.g., ethylene and propylene) will continue to be produced through steam cracking (SC) of hydrocarbons in the coming decade. In an uncertain commodity market, the chemical industry is investing very little in alternative technologies and feedstocks because of their current lack of economic viability, despite decreasing crude oil reserves and the recognition of global warming. In this perspective, some of the most promising alternatives are compared with the conventional SC process, and the major bottlenecks of each of the competing processes are highlighted. These technologies emerge especially from the abundance of cheap propane, ethane, and methane from shale gas and stranded gas. From an economic point of view, methane is an interesting starting material, if chemicals can be produced from it. The huge availability of crude oil and the expected substantial decline in the demand for fuels imply that the future for proven technologies such as Fischer-Tropsch synthesis (FTS) or methanol to gasoline is not bright. The abundance of cheap ethane and the large availability of crude oil, on the other hand, have caused the SC industry to shift to these two extremes, making room for the on-purpose production of light olefins, such as by the catalytic dehydrogenation of propane.     

Cleaner energy production with integrated gasification combined cycle systems and use of metal oxide sorbents for H2S cleanup from coal gas

 World primary energy demand increases with increases in population and economic development. Within the last 25 years, total energy consumption has almost doubled. In order to meet this demand, research into new sources of energy as well as improving the efficiency of energy production technologies is being carried out. In both cases, the production of clean energy is very important because of environmental concerns and regulations. Integrated gasification combined cycle (IGCC) technology seems to be one of the most promising technologies for production of energy by using fossil fuels, especially coal. Hot gas desulfurization is a crucial issue in the development of the IGCC system. This paper reviews the importance of clean energy production, the IGCC technology and focuses on the development of several metal oxide-based sorbents used for desulfurization of the hot coal gas in the IGCC system.     

Supercritical water synthesis of nano-particle catalyst on TiO2 and its application in supercritical water gasification of biomass

ABSTRACT

Hydrogen production by catalytic gasification in supercritical water (SCW) is a promising way to utilise biomass resource. Supercritical water not only provides homogeneous and rapid reaction environment for the biomass gasification but also causes catalyst agglomeration problems. In order to prepare activity and stable catalyst for biomass gasification in supercritical water, supercritical water synthesis method was utilised and the preparation method was investigated. Ni, Co, Zn and Cu metal elements were loaded on TiO₂ particles which was proved to be hythothermally steady in supercritical water. And nano-particles were successfully made. Based on gas chromatography/mass spectrometer (GC/MS), scanning electron microscopy, energy dispersive spectrometer (EDS) and X-ray diffraction analysis methods, it turned out that metal catalysts have a uniform spherical structure with diameter around 30 nm. Metal catalysts synthesised with supercritical hydrothermal method showed certain catalytic effects. Ni catalyst had the best performance in stability while Zn catalyst possessed highest hydrogen yield.     

In Situ TEM observation of the gasification and growth of carbon nanotubes using iron catalysts

We report the in situ transmission electron microscope (TEM) observation of the catalytic gasification and growth of carbon nanotubes (CNTs). It was found that iron catalysts can consume the CNTs when pumping out the precursor gas, acetylene, at the growth temperature, and reinitiate the growth when acetylene is re-introduced. The switching between gasification and growth of CNTs can be repeated many times with the same catalyst. To understand the phenomenon, thermogravimetric analysis (TGA) coupled with mass spectroscopy was used to study the mechanism involved. It was shown that the residual water molecules in the growth chamber of the TEM react with and remove carbon atoms of CNTs as carbon monoxide vapor under the action of the catalyst, when the precursor gas is pumped out. This result contributes to a better understanding of the water-assisted and oxygen-assisted synthesis of CNT arrays, and provides useful clues on how to extend the lifetime and improve the activity of the catalysts.      

锰基催化剂低温选择催化还原处理NOx的研究现状与展望

锰基催化剂具有较高的催化活性,且成本低,在选择性催化还原(SCR)尾气中的NO_x领域具有广阔应用前景。介绍了锰基低温SCR催化剂处理NO_x的最新进展。锰基催化剂可分为两类:锰氧化物催化剂和锰基掺杂过渡金属氧化物催化剂。针对锰氧化物催化剂,主要分析了锰的氧化价态、结晶形态、比表面积以及形态学对催化效果的影响;对于锰基掺杂过渡金属氧化物催化剂,重点分析了掺杂物对催化剂的催化能力、催化温度范围、N_2的选择性和抗SO_2、H_2O毒化能力的影响。最后在总结全文的基础上,展望了锰基催化剂的应用前景。     

The necessity for coatings in fossil energy conversion systems

The necessity for the development of coal-derived fuels and increased direct utilization of coal is identified, and the available data on corrosion and erosion of structural alloys in these applications are discussed. The data presented show that coatings may be required for the achievement of acceptable plant operability. Internal components of high Btu coal gasification pressure vessels and turbines combusting coal-derived fuels are the primary areas identified as requiring coatings to ensure reliable operation.     

Prospect of China’s synthetic natural gas from coal gasification technology under consideration of economic,environmental, and security factors

Clean Technologies and Environmental Policy - Synthetic natural gas (SNG) from coal gasification technology has become an alternative method to alleviate China’s natural gas shortage....     

Characteristics of porous carbon nano-fibers synthesized by selective catalytic gasification

Carbon nanofibers (CNFs) with uniquely oriented channels were prepared via selective catalytic gasification in air at 450 and 500 degrees C, using Pt or Ru nano particles as catalysts. Catalytic gasification was chosen because it can selectively generate channels in the vicinity of the catalyst particles at relatively low temperatures, where thermal oxidation does not intensively occur. The structures and surface properties of the CNFs were examined via X-ray diffraction, analysis of the nitrogen adsorption-desorption isotherms, and high-resolution transmission electron microscopy. The effects of the catalyst species and loading amount on the formation of pores (channels) were investigated. The gasification mechanism, especially the channeling direction, throught the selection of the gasification catalysts, is discussed based on the results. This process can be effectively utilized for preparation of porous carbons, which have a well-aligned graphitic structure, and also channel-type pores can be designed by selection of gasification catalysts and conditions. The present porous CNF can be applied for catalyst support in fuel cells, without further treatment (e.g., acid treatment for the removal of metallic components).     

Low temperature technology utilization in the solution of energy problems

Low temperature technology offers diverse solutions for conserving dwindling energy supplies, upgrading previously discarded low value energy resources and developing replacements for conventional fuels. Subjects discussed include enhanced oil recovery, upgrading of low energy content gases, nitrogen removal from LNG, coal gasification, recovery of light hydrocarbon liquids, hydrogen and benzene recovery and energy conservation (particularly the refrigeration potential of LNG).     

用于烯烃复分解反应的钌茚基催化剂的合成研究进展

基于钌金属的烯烃复分解反应现今已成为一种至关重要且快速有效的催化反应类型,在聚合领域以及现代有机合成的应用方面起着改革性的推进作用。作为烯烃复分解反应催化剂的一种,钌茚基催化剂在该领域得到成功应用。结合近年来钌茚基催化剂在烯烃复分解反应中的合成研究进展,简述了其发展过程,介绍了该领域创新性的研究成果,重点论述了一些新型钌茚基催化剂的合成方法,并且探讨了辅助配体的结构对催化剂稳定性和活性的影响,最后对其发展方向以及应用前景进行了展望。     

Nanostructured Metal‐Free Electrochemical Catalysts for Highly Efficient Oxygen Reduction

Replacing precious and nondurable Pt catalysts with cheap and commercially available materials to facilitate sluggish cathodic oxygen reduction reaction (ORR) is a key issue in the development of fuel cell technology. The recently developed cost effective and highly stable metal‐free catalysts reveal comparable catalytic activity and significantly better fuel tolerance than that of current Pt‐based catalysts; therefore, they can serve as feasible Pt alternatives for the next generation of ORR electrocatalysts. Their promising electrocatalytic properties and acceptable costs greatly promote the R&D of fuel cell technology. This review provides an overview of recent advances in state‐of‐the‐art nanostructured metal‐free electrocatalysts including nitrogen‐doped carbons, graphitic‐carbon nitride (g‐C₃N₄)‐based hybrids, and 2D graphene‐based materials. A special emphasis is placed on the molecular design of these electrocatalysts, origin of their electrochemical reactivity, and ORR pathways. Finally, some perspectives are highlighted on the development of more efficient ORR electrocatalysts featuring high stability, low cost, and enhanced performance, which are the key factors to accelerate the commercialization of fuel cell technology.     

Nb-Re-W/Ti无毒催化剂的脱硝性能研究

为满足大气污染治理的严格要求,改进商用V_2O_5-WO_3/TiO_2脱硝催化剂有毒的弊端,提高催化剂的脱硝效率,本文采用挤出成型法制备蜂窝状Nb-Re-W/Ti(Re=Pr,Nd)无毒催化剂,在模拟烟气脱硝试验装置上进行脱硝活性测试,利用XPS和H2-TPR等表征手段对催化剂进行分析,就Nb和稀土元素的负载量对催化剂脱硝性能的影响进行探讨.研究结果表明:Nb-W/Ti催化剂中Nb最佳负载量为2.8%,最佳反应温度为350℃,NOx转化率最高可以达到95%;当Nb负载量为1.1%时,分别加入1.5%Pr和2.0%Nd后,催化剂的脱硝效率均能达到98%以上.     

Benchmarking, insights, and potential for improvement of Fischer–Tropsch-based biomass-to-liquid technology

Biomass is one of the renewable energy sources which can play an important role in reducing dependency on crude oil specifically transportation fuels while maintaining the current infrastructure. This study investigates the potential that biomass could offer in supporting the production of ultra-clean liquid transportation fuels via biomass gasification and Fischer–Tropsch synthesis. Various biomass-to-liquid (BTL) processes may be developed; however, prior to the detailed analysis, it is important to understand the overarching insights of the system and to determine performance benchmarks. The major focus of this study is to develop a process-integration approach to determine the “big-picture” targets and to evaluate the role of certain variables (e.g., biomass source, composition, and processing) on potential liquid fuel yield. This assessment takes into consideration the major challenges facing BTL technology, and identifies areas for potential improvement. Several routes are synthesized and compared.     

催化剂研究应用的新成果

统计表明,在石油化工、环保、医药、食品等行业的产品或原料生产中,大约有1/3以上与催化剂有关.随着各行业的发展,催化剂的应用领域不断扩展,在工农业生产中显示出越来越重要的地位.报道和分析了催化剂研究应用的最新成果,探讨了催化剂研究应用的趋势.     

Synthesis of an integrated biorefinery via the C–H–O ternary diagram

An integrated biorefinery is designed to handle a wide variety of feedstocks (mainly biomass) and can produce a broad range of products (e.g., biofuel, biochemicals, etc.) via multiple conversion pathways and technologies. Gasification is recognized as one of the most promising technologies for initial processing of biomass. It uses thermal energy to convert the biomass feedstock into a gaseous mixture, which is also known as syngas, consisting mainly of carbon dioxide (CO₂), steam (H₂O), methane (CH₄), carbon monoxide (CO) and hydrogen (H₂). It is noted that the composition of syngas, especially the ratio of H₂ to CO, is crucial when the syngas is further converted to liquid fuels and chemicals. In this work, a graphical targeting approach for the evaluation of gas phase equilibrium composition of biomass gasification is proposed. Based on the targeted composition, a conceptual design of an integrated biorefinery can be systematically developed.     

The Efficiency of Different Technologies for the Preparation and Use of Wet Fuel in Power Engineering

We consider the possible technical solutions for the treatment moisture fuel from the standpoint of such general problems as a reduction in greenhouse gas emissions and lowering fuel costs with increased energy generation. The use of the biofuels, which is almost always highly wet, does solve these problems in perspective, but it results in an urgent problem regarding an increase of the energy efficiency of the suitable technologies. The practice shows that a reduction in the costs of fuel and energy production currently takes place with generation based on the cheap brown coal (lignite); however, it is necessary to increase qualitatively the efficiency of power plants in order to reduce fuel consumption, as well as atmospheric emissions. We consider the use of complex technologies of moisture fuel preparation for its efficient application via intensive drying with subsequent gasification in order to pass to the combined cycles with the gas turbines. A new technology for intensive energy-saving drying using superheated pressurized steam is presented. We present an analysis and comparison of the means of such approach to implementation and substantiate the selection of the optimal solutions, which are applicable not only to power engineering but also elsewhere in the utilization of moisture combustible materials and waste products.     

Decarbonised coal energy system advancement through CO2 utilisation and polygeneration

Development of clean coal technology is highly envisaged to mitigate the CO₂ emission level whilst meeting the rising global energy demands which require highly efficient and economically compelling technology. Integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) system is highly efficient and cleaner compared to the conventional coal-fired power plant. In this study, an alternative process scheme for IGCC system has been proposed, which encompasses the reuse of CO₂ from the flue gas of gas turbine into syngas generation, followed by methanol synthesis. The thermodynamic efficiency and economic potential are evaluated and compared for these two systems. The performances of the systems have been enhanced through systematic energy integration strategies. It has been found that the thermodynamic and economic feasibilities have attained significant improvement through the realisation of a suitably balanced polygeneration scheme. The economic potential can be enhanced from negative impact to 317?M€/y (3.6?€/GJ). The results have demonstrated promising prospects of employing CO₂ reuse technology into IGCC system, as an alternative to CCS system.     

Hydrogen production through catalytic low-temperature bio-ethanol steam reforming

As a provider of our energy requirements, hydrogen seems to be one of most promising fuels, in particular when used to feed PEM fuel cells. When produced from a renewable source, it has got the potential to reduce the dependence on non-renewable fossil fuels and lower the amount of harmful emissions. Ethanol steam-reforming (ESR) reaction is an interesting option to obtain a H₂- and CH₄-rich stream with a low content of CO, combining the deep knowledge of the technology with the advantage of the biomass-derived feedstock. Thermodynamic analysis has indicated that the most interesting operating range to enhance the H₂ production and minimize CO and coke formation requires low pressure, high temperature, and high water-to-ethanol molar ratio. On the other hand, despite its endothermic nature, ESR could be carried out at low temperature, to increase overall thermal efficiency, even if at these conditions the catalyst's deactivation, due to coking and sintering phenomena, is not negligible. The main objective of this study is to investigate on the activity, stability, and durability of bimetallic Pt–Ni and Pt–Co catalysts supported on CeO₂ for low-temperature bio-ESR reaction. The catalysts have been prepared through different methods and with an optimized metal's content. They have also been characterized with various physico-chemical characterization tests, and the catalytic studies have been carried out in a lab-scale apparatus. While evaluating the effects on the catalysts' performances of preparation method, reaction temperature, space time, and water-to-ethanol molar ratio, the selected catalysts were found effective for the production of H₂ by steam reforming at low temperature. In particular, the Pt/Ni/CeO₂ catalyst shows a perfect agreement with equilibrium calculations yet at low contact times, although some carbon deposition occurs. Also the cobalt-based catalysts appear attractive. The relative rates of carbon growth versus gasification have been studied, and ascending water contents were used to study the effect of steam addition in the feed stream. An in-depth investigation of the reaction mechanism and the evaluation of the kinetic parameters will be crucial to complete the study of the proposed process.     

Biomass-based gasifiers for internal combustion (IC) engines—A review

The world is facing severe problems of energy crisis and environmental problem. This situation makes people to focus their attention on sustainable energy resources for their survival. Biomass is recognized to be the major potential source for energy production. There are ranges of biomass utilization technologies that produce useful energy from biomass. Gasification is one of the important techniques out of direct combustion, anaerobic digestion – Biogas, ethanol production. Gasification enables conversion of these materials into combustible gas (producer gas), mechanical and electrical power, synthetic fuels, and chemical. The gasification of biomass into useful fuel enhances its potential as a renewable energy resource. This paper gives a comprehensive review of the techniques used for utilizing biomass, experimental investigation on biomass fuels, characterization, merits, demerits and challenges faced by biomass fuels.