用于合成气制低碳醇的钼基催化剂研究进展

综述了用于合成气制纸碳醇的钼基催化剂的制备方法、反应条件和表面结构的变化规律,并总结了对活性中心的研究结果。     

由合成气制备低碳混合醇钼基催化剂的研究

钼基催化剂是由合成气制备低碳混合醇的具有工业化价值的催化剂体系。本文根据文献归纳分析了国外对该类催化剂体系的特点、催化剂的性能、钴等其他金属的协同作用、载体和碱金属的助催化作用等方面研究的发展状况及观点。在钼催化剂中加入钴可稳定催化剂的电导率而使其成醇活性和选择牲不易受反应温度及原料气中杂质 H_2S 的影响。用活性炭作载体时,催化剂的成醇活牲和选择性都要优于其它载体;碱金属是使钼基催化剂具有较高成醇选择性的关键。     

合成气制混合醇催化剂研究进展

将我国丰富的煤炭资源经合成气转化为混合醇,作为合成气化学重要的研究领域,该技术的突破对于提高煤化工产品品味、实现煤炭清洁利用、降低醇类化学品石油依赖度具有重要意义,受到了国内外工业界和学术界的广泛关注.制约合成气制混合醇发展的瓶颈在于高效能催化剂的开发,合成气制混合醇催化剂包括贵金属催化剂、改性甲醇合成催化剂、改性费托...     

合成气直接制低碳烯烃铁基催化剂助剂研究进展

综述了合成气直接制低碳烯烃铁基催化剂助剂的研究进展,主要分析了电子助剂和结构助剂对催化剂结构与性能的影响,认为碱金属、碱土金属、过渡金属、稀土金属及非金属等电子助剂在调变催化剂酸碱性与氧化还原性上各自表现出不同的正作用,抑制了链增长反应,增加低碳烯烃选择性,结构助剂的表面性质与孔道结构可控,方便低碳烯烃从催化剂中扩散,可以减少低碳烯烃的二次加氢副反应。最后指出了催化剂存在的问题并对以后的研究工作进行了展望。     

甲烷部分氧化制合成气镍基催化剂的研究进展

镍基催化剂是甲烷部分氧化制合成气研究最多、最有前途的催化剂.相对其他催化剂它具有较好的抗积碳性、稳定性且价格低廉.如何提高甲烷在部分氧化反应中的转化率是当前备受关注的重要研究课题.从镍基催化剂的载体、助剂、制备方法等方面的研究进行了综述.     

费托合成钴基催化剂助剂研究进展

针对助剂对钴基催化剂的促进作用,介绍了近年来钴基催化剂助剂的研究进展。综述了助剂添加方式、助剂功能和助剂作用、详细分析了助剂对钴基催化剂的还原度、分散度、稳定性和费托反应性能的影响、重点讨论了助剂的结构作用、电子作用和协同作用,并对今后催化剂的研究提出了一些建议。     

合成气制低碳醇用催化剂的研究进展

合成气选择催化合成低碳混合醇等清洁燃料是能源化工领域的研究热点,高选择性、高活性并具有优良稳定性的催化剂的设计与开发是低碳醇合成技术的关键。本文对目前研究相对集中的改性甲醇合成催化剂、Cu-Co基以及MoS₂基低碳醇合成催化剂进行了综合评述,系统总结了不同催化剂体系的研究现状,分析了当前合成低碳醇用催化剂领域的热点和难点问题,并指出了低碳醇合成催化剂在今后一段时间内的发展方向。     

费托合成制低碳烯烃钴基催化剂研究进展

概述了费托合成制低碳烯烃的背景和发展趋势,综述了费托合成制低碳烯烃反应机理和钴基催化剂的研究进展,重点评述了钴基催化剂活性相、助剂和载体等关键因素,探讨了活性相、助剂和载体对合成气制低碳烯烃的影响,并对费托合成制烯烃的研究提出了展望和建议。     

Development of cobalt–copper nanoparticles as catalysts for higher alcohol synthesis from syngas

The synthesis of higher alcohols from syngas has been studied over different types of Cu-based catalysts. In order to provide control over the catalyst composition at the scale of a few nanometers, we have synthesized two sets of Co–Cu nanoparticles with novel structures by wet chemical methods, namely, (a) cobalt core–copper shell (Co@Cu) and (b) cobalt–copper mixed (synthesized by simultaneous reduction of metal precursors) nanoparticles. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The catalysts were tested for CO hydrogenation at temperatures ranging from 230 °C to 300 °C, 20 bar and 18,000 scc/(hr.gcat). It was observed that the Co–Cu mixed nanoparticles with higher Cu concentration exhibit a greater selectivity towards ethanol and C₂₊ oxygenates. The highest ethanol selectivity achieved was 11.4% with corresponding methane selectivity of 17.2% at 270 °C and 20 bar.     

Higher alcohol synthesis from syngas over KCoMoP catalysts

Carbon modified K_xCo_0.75MoP (0 ≤ x ≤ 1.5) catalysts were prepared from a sol–gel method using citric acid as a complexant. The catalysts were evaluated with CO hydrogenation and characterized by XRD, XPS and CO₂-TPD techniques. Results show that the addition of cobalt accelerates the dispersion of catalytic components in phosphide catalysts while the participation of potassium in phosphide catalysts enhances the interaction between MoP and CoMoP and facilitates the rearrangement of electron density in different Mo species. In K₁Co_0.75MoP, a large number of Mo^4 + species resulted in high selectivity to C_2 + higher alcohol.     

Kinetic study of higher alcohol synthesis directly from syngas over CoCu/SiO2 catalysts

Higher alcohol synthesis (HAS) directly from syngas is one of the most promising approaches for utilizing nonoil resources cleanly and efficiently. A series of bimetallic CoCu catalysts with different Co/Cu ratios were prepared using a SiO₂ support. The structure of Cu modified Co catalysts was characterized using HRTEM, in/ex situ X‐ray diffraction, and temperature‐programmed reduction. It was evidenced that nanoscale metal particles were formed and the reduction of Co oxide at above 673 K. Meanwhile, the interaction between Co and Cu on the surface was assumed to be responsible for the enhanced selectivity to HAS. The intrinsic kinetics for this reaction was performed over a CoCu/SiO₂ catalyst under realistic conditions. The kinetic parameters, including apparent activation energies and reaction orders, were calculated through power‐law models. With the combination of chain growth probability and kinetics, the effect of temperatures on the reaction mechanism and the Cu promotional effects on Co catalysts were elaborated. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1797–1809, 2014     

铑基催化剂用于低碳醇合成反应研究进展

分别从反应机理、活性位点、助剂和载体4个方面对合成气制低碳醇铑基催化剂体系进行了文献综述,同时对理想催化剂的研究方向做出了预测.通过对不同学者的研究成果的对比,发现对于铑基催化剂催化的反应机理和活性中心等方面的研究仍存在较多争议,更为深入仔细的研究工作仍然需要.应用前景方面,虽然铑基催化剂对该反应具有较高的低碳醇选择性(尤其是乙醇)和较好的稳定性,但较低的反应活性及铑金属自身昂贵的价格很大程度上限制了其应用,具有工业应用价值的高效铑基催化剂仍有待开发.     

钾改性铁钼碳化物催化剂及其CO加氢性能

制备了碳化铁和钾掺杂碳化钼催化剂并对其CO加氢合成低碳混合醇性能进行了考察.结果表明当只有β-碳化钼存在时,产物主要是烃类以及微量的醇.经过钾改性后,β-碳化钼催化剂上产物低碳醇含鼍增加;而同时被碳化铁和钾改性后,低碳醇的含量进一步增加,并且高级醇(C_(2+)OH)收率町达到0.14 g/(mL·h).β-碳化钼催化剂上醇烃产物均符合线性Anderson-Schuhz-Mory(A-S-F)分布曲线,而钾改性β-碳化钼以及钾和碳化铁改性的催化剂上醇产物为独特的甲醇负偏离A-SF分布.这表明钾和碳化铁的加入有效促进了C_1OH到C_2OH的链增长步骤.从而有利于C_(2+)OH高级醇的生成.     

Selective synthesis of light olefins from syngas over potassium-promoted molybdenum carbide catalysts

In the hydrogenation of CO at atmospheric pressure, unsupported molybdenum carbide catalyst produced mostly C₁-C₅ paraffins. Promotion of the catalyst with K₂CO₃ yielded C₂-C₅ hydrocarbons consisting of 80–100% olefins and reduced the methane selectivity. The selectivity of C₂-C₅ olefins among all hydrocarbon products was 50–70 wt% at CO conversions up to 70%.This work has been supported by Korean Science and Engineering Foundation through a contract 88-03-1302.     

Chain growth mechanism on bimetallic surfaces for higher alcohol synthesis from syngas

Density function theory calculations are performed to investigate the chain growth mechanism on bimetallic surfaces during the syngas conversion. The weighted d-band center correlates well with the adsorption energy of two reactants on bimetallic surface. The boundary between Cu and Co domains facilitates the association reaction of chain growth. Particularly, the reduction of barrier for CO insertion step accelerates the formation of acyl intermediate and thus provides paths to higher alcohol synthesis. The present work demonstrates the synergistic effect in the bimetallic surface from the microscopic view.     

Effect of methanol addition on higher alcohol synthesis over modified molybdenum sulfide catalysts

One of the main problems in higher alcohol synthesis is the poor product distribution. Cofeeding of methanol, together with the synthesis gas, has been suggested in order to increase the yield of ethanol and higher alcohols. In this work, the effect of methanol addition on K–MoS₂ and K–Ni–MoS₂ catalysts was studied at 71 bar, 340 °C and GHSV = 6000 N mL/h · g_catalyst. Under these conditions methanol recycle is not a viable option for boosting higher alcohol production. The main result was an increase in methane yield, while the effect in higher alcohols was negative or not significant.     

Unsupported CuFe bimetallic nanoparticles for higher alcohol synthesis via syngas

CuFe bimetallic nanoparticles were synthesized by co-reduction method as model catalysts for HAS. Cu contacted with Fe component in the form of Cu–Fe alloy, CuFe₂O₄ and Cu(Fe)–CuFe₂O₄ interface in the fresh CuFe sample. However, Cu/Fe₃O₄ and Cu/FeC_x composites formed after activation. Cu–FeC_x center benefited alcohol formation which led to higher selectivity to total alcohol for CuFe than that for Fe and physical mixture of Fe and Cu nanoparticles. In addition, CuFe showed very high C_6 +OH selectivity in alcohol distribution and 33 wt.%–74 wt.% was achieved, demonstrating the potential for direct synthesis of C_6 +OH from syngas.     

Ga改性对Cu-Co低碳醇催化剂性能的影响

采用共沉淀法制备CuCoGaAl催化剂,考察Ga含量对催化剂织构及低碳醇合成性能的影响。结果表明,加入Ga可提高催化剂的比表面积,改变催化剂的表面性质。Ga改性促进CO的线式吸附能力,同时降低CO的桥式吸附能力,从而提高产物醇选择性,但过量Ga会大幅降低CO加氢反应活性。Ga含量对总醇收率的影响呈火山型变化规律,最佳Ga与Co物质的量比为0.3。