乙烷和二氧化碳催化转化的研究进展

CO₂与乙烷反应是实现碳减排目标、利用非常规能源的重要手段,符合国家重大需求和国际学术前沿。其中,二氧化碳通过“活性氧”机理、“晶格氧”机理以及“反应耦合”机理促进乙烷的活化。通过催化剂设计选择性地断裂C—H/C—C键,可以实现反应定向地按照两条路径进行——乙烷干重整反应（DRE）和乙烷氧化脱氢（ODH）。综述了DRE和ODH两类反应的热力学、反应物活化机制和催化剂研究进展,分析了催化剂均存在产物选择性低、易烧结、积炭问题的主要影响因素以及催化剂设计和改进策略,并对该研究未来的发展方向进行展望。     

Ni—Pd／C双金属催化剂羰基化反应合成丙酸的研究

考察了Ni—Pd／C双金属催化剂上催化乙醇气相羰基化合成丙酸的反应。实验结果表明,负载活性炭Ni—Pd双金属催化剂相比普通非贵金属催化剂具有很高的活性及选择性,最佳反应工艺条件为,在少量碘代乙烷存在下,压力0．15MPa,温度220℃,n（CO）：n（C2H5OH）=2．0：1,乙醇液体空速1．5h^-1此时乙醇羰基化反应产物中丙酸及丙酸酯的选择性可高达96．7％,通过GC—MS对反应产物分析,分析了反应过程的机理。     

Ni—Pd／C双金属催化剂上乙醇羰基化合成丙酸的研究

考察了Ni—Pd／C双金属催化剂上乙醇气相羰基化合成丙酸的反应。实验结果表明,活性炭负载Ni—Pd双金属催化剂相比普通非贵金属催化剂具有更高的活性及选择性,优化的反应工艺条件为压力0．15MPa,温度220℃,nCO：nEtOH,n：2．0：1,乙醇液体空速1．5h^-1。在上述条件和少量碘乙烷存在下,乙醇羰基化反应产物中丙酸及丙酸酯的选择性可高达96．7％,通过GC—MS对反应产物分析,分析了反应过程的机理。     

当归内酯和2-甲基呋喃合成可再生生物柴油前驱体

以生物质衍生的当归内酯与2-甲基呋喃为原料,杂多酸为催化剂,经羟烷基化或烷基化反应生成4,4-二（5-甲基呋喃-2-基）戊酸,然后加氢制得可再生生物柴油前驱体4,4-二（5-甲基四氢呋喃-2-基）-1-戊醇和双（5-甲基四氢呋喃-2-基）乙烷。首先,考察了硅钨酸、磷钼酸和硅钼酸催化剂对羟烷基化/烷基化反应的影响,并对催化剂用量、反应温度和时间进行了优化,结果表明,硅钨酸的催化性最高,在反应温度为60 ℃、硅钨酸的用量为0.05 g、反应时间为60 min条件下4,4-二（5-甲基呋喃-2-基）戊酸产率达到70.5%。然后,考察了Pd/C、Ru/C和Pt/C催化剂对当归内酯与2-甲基呋喃羟烷基化/烷基化产物的加氢反应,Ru/C催化剂表现出最好的活性和选择性,4,4-二（5-甲基四氢呋喃-2-基）-1-戊醇和双（5-甲基四氢呋喃-2-基）乙烷产率分别为60.5%和24.6%。最后对Ru/C催化剂的稳定性进行了考察,在24 h的反应时间内催化剂表现出良好的稳定性,活性没有明显下降。获得的4,4-二（5-甲基四氢呋喃-2-基）-1-戊醇和双（5-甲基四氢呋喃-2-基）乙烷混合物可作为柴油前驱体。     

乙烷溴氧化制溴乙烷的研究

主要利用廉价的乙烷、氧气、氢溴酸(40wt%)在催化剂Rh/SiO2氧化生成溴乙烷.通过对催化剂的BET和XRD的表征,以及影响反应结果的最佳反应温度、催化剂最佳焙烧温度、最佳金属组分负载量因素的研究考察,从中发现在乙烷与氧气的体积流量分别为10mL/min和5mL/min时,氢溴酸流量为3mL/h一定的条件下,反应温度为400℃,催化剂焙烧温度为900℃,铑的负载量为0.2%时,乙烷的转化率有49.2%,溴乙烷的选择性有57.3%,溴乙烷的收率为28.2%.     

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。     

铜系低温选择性催化还原脱硝催化剂的研究进展

选择性催化还原（SCR）技术已广泛应用在燃煤电站烟气脱硝技术中,开发低温高活性、高抗中毒性能的催化剂体系已经成为国内外学者的研究重点。Cu系催化剂由于具有良好的脱硝性能及水热稳定性,得到了广泛的研究和关注。本文综述了近年来活性组分Cu负载在TiO₂、Al₂O₃、碳基材料和分子筛等材料上的研究进展;重点分析了Cu系催化剂低温SCR反应机理,主要包括Eley-Rideal （E-R）机理和Langmuir-Hinshelwood （L-H）机理,同时分析了SCR反应的两个必然过程：吸附（NH₃吸附和NO_x吸附）和反应;简要地介绍了Cu系催化剂的抗水抗硫中毒性能研究现状以及反应机理,同时介绍了碱金属中毒、飞灰和催化剂烧结对催化剂失活的影响,结合生命周期分析SCR脱硝系统还原剂氨和尿素对NO排放的影响。在此基础上展望了未来铜系催化剂的研究方向：采用新型方式对催化剂进行改性、进一步采用表征和模拟技术研究催化体系的反应机理、优化锅炉和催化剂设计减轻催化剂失活以及研究适用于其他还原剂条件的高选择性催化剂。     

乙炔选择性加氢反应催化机理的分子模拟研究

以Pd-Ag合金为活性组分、Al₂O₃为载体的催化剂作为研究对象,运用量子力学理论和Monte Carlo方法对乙炔选择性加氢反应的催化机理进行探索性研究,得到Pd-Ag的分散状况与催化剂活性和选择性之间的关系。结果表明,助催化剂Ag的增加,使乙烯在催化剂表面的脱附能力增强,降低乙烯形成乙烷的可能性,从而增强乙炔加氢的选择性;计算得到在催化剂表面H2解离过程、乙炔以及乙烯加氢反应过程的活化能;乙炔选择性加氢最佳条件为：温度（70～80） ℃,氢气分压（0.03~0.04） MPa     

Ru-Na/C催化剂对4-（4＇-正丙基）环己基苯酚的催化反应

用NaOH处理Ru/C,制备了Ru-Na/C复合催化剂。评价结果表明：用Ru-Na/C催化剂,反应6小时后,4-（4＇-丙基）环己基苯酚（3PCO）苯环加氢的转化率为99.9%;4-（4＇-丙基）环己基环己基酮（3HHK）的选择性为80.4%,4-（4＇-丙基）环己基环己基醇（3HHE）的选择性为19.6%,较Ru/C催化剂的活性、转化率（82.0%）和选择性[分别的4-（4＇-丙基）环己基环己基酮64.1%、4-（4＇-丙基）环己基环己基醇18.0%有显著提高。Ru-Na/C复合催化剂的良好催化活性和选择性是由于NaOH的添加及烘培过程改变了Ru/C催化剂的表面组成和结构并提高了Ru的还原能力。     

Ru-Na/C催化剂对4-（4＇-正丙基）环己基苯酚的催化反应

用NaOH处理Ru/C,制备了Ru-Na/C复合催化剂。评价结果表明：用Ru-Na/C催化剂,反应6小时后,4-（4＇-丙基）环己基苯酚（3PCO）苯环加氢的转化率为99.9%;4-（4＇-丙基）环己基环己基酮（3HHK）的选择性为80.4%,4-（4＇-丙基）环己基环己基醇（3HHE）的选择性为19.6%,较Ru/C催化剂的活性、转化率（82.0%）和选择性[分别的4-（4＇-丙基）环己基环己基酮64.1%、4-（4＇-丙基）环己基环己基醇18.0%有显著提高。Ru-Na/C复合催化剂的良好催化活性和选择性是由于NaOH的添加及烘培过程改变了Ru/C催化剂的表面组成和结构并提高了Ru的还原能力。     

Kinetics of catalytic ethane hydrogenolysis: Stirred reactor study of commercial nickel catalyst

The kinetics of ethane hydrogenolysis catalyzed by a commercial 58% nickel-on-kieselguhr catalyst were studied at 1 atm. and from 220° to 250°C. The kinetic data could be fit by a simple power rate equation that is a limiting case of a more general equation. The reaction rate of ethane was first order with respect to ethane and —2 order with respect to hydrogen. A possible reaction mechanism is discussed. The apparent activation energy was 46.4 kcal. Ethane/hydrogen ratios as high as 1:1 were studied without catalyst deactivation. Kinetic data were obtained in a novel stirred-tank catalytic reactor.     

乙烯环氧化反应机理述评

本文就多年来人们对乙烯在银催化剂表面发生环氧化反应的机理研究结果进行了综述,指出银表面的吸附态原子氧物种是乙烯环氧化反应的关键物种,对环氧乙烷的选择性不存在85.7%的上限;依据吸附态原子氧与银之间相互作用的强弱,可将其分为“强吸附氧”和“弱吸附氧”。“弱吸附氧”利于乙烯环氧化,“强吸附氧”易导致乙烯完全氧化。凡有利于“弱吸附氧”生成的化学环境均利于催化剂选择性的提高。并对次表面氧（Ｏsub）及氯抑制剂、Cs和Re助剂的作用机理进行了概括。     

Kinetic and mass transfer studies in the catalytic oxidation of thiophenol in a gas—liquid reactor

A study has been made of the absorption of gaseous oxygen in a thiophenol solution. The chemical reaction which occurred in solution was promoted by a copper chloride—pyridine catalyst. There were two reaction products, diphenyldisulphide and diphenylthiolsulphinate. In some experiments the liquid was unstirred, in other experiments the liquid was either stirred with a rotating bar or vigorously agitated with a vibrating disc.The reaction process was apparently zero order with respect to the thiophenol. The concentration of the catalyst affected both the reaction rate and the product ratio. The relationship between the absorption rate and catalyst concentration depended markedly on the mixing conditions within the reactor. The course of the absorption cannot be described simply in terms of the “classical” regimes of mass transfer with chemical reaction. However, it is probable that the absorption is in the transition region between the “diffusion” and “fast” regimes at low catalyst concentration and approaches the “instantaneous” regime at high catalyst concentrations. The relative yield of disulphide increases as the catalyst concentration increases and as the temperature increases. Improvements in the agitation of the liquid can lower the proportion of disulphide in the reaction product.These results have important implications for the processes which use this catalyst in the “selective” manufacture of disulphides and polydisulphides.     

环己烷绿色氧化合成环己醇/环己酮(KA油)催化剂及机理研究进展

环己烷绿色氧化合成环己醇/酮(KA油)一直是饱和C—H氧化领域的研究热点。本文综述了近十年来过氧化氢环己烷氧化和分子氧液相环己烷氧化的催化研究情况,指出过氧化氢环己烷氧化反应虽然条件温和、环己烷转化率和KA油选择性高,但活性较高的反应体系一般为包含昂贵配合物、酸、溶剂和氧化剂的复杂均相体系,不利于产物和催化剂分离,同时过氧化氢利用率较低,氧化剂成本高。液相分子氧环己烷氧化采用多相催化剂,操作简单,其中金和纳米氧化物有望成为潜在的工业催化剂。对环己烷氧化机理成果进行分析,指出除了金属卟啉的氧异裂非自由基机理,环己烷氧化按自由基机理进行,为自催化反应,但催化剂可促进活性自由基产生,活化C—H键,提高反应速率。最后指出开发有潜力的环己烷氧化多相催化剂和探索反应机理是今后的研究方向。     

The investigation of individual reaction steps in the oxidative coupling of methane over lithium doped magnesium oxide

To elucidate the importance of various reaction steps in the oxidative conversion of methane, experiments were carried out with three reaction products: ethane, ethylene and carbon monoxide. These products were studied separately in oxidation experiments with and without a catalyst. Moreover, the effect of admixing them to a methane/oxygen feed was investigated. All experiments were carried out in a micro flow tubular quartz reactor which was either empty or filled with catalyst at a temperature of 800 °C. The ethane and ethylene experiments showed that the conversion of ethane to ethylene is much more rapid than ethane combustion, irrespective of the presence of a catalyst. The main combustion path goes via ethylene. Ethane is converted much more rapidly than methane and this imposes serious constraints on the maximum attainable yields. The principal combustion product in the absence of a catalyst is CO but with a catalyst, CO₂ dominates, in agreement with rapid catalytic oxidation observed with CO/O₂ feeds.

The conclusions are summarized in a simplified overall reaction scheme.     

Performance of combined cobalt—nickel—zirconia and HZSM-5 catalyst systems for carbon monoxide hydrogenation

The synthesis of hydrocarbons via hydrogenation of carbon monoxide was investigated over cobalt—nickel—zirconia catalysts of various compositions in combination with zeolite HZSM-5 in “mixed bed” and “follow bed” arrangements. These combinations resulted in the formation of aromatics in amounts as high as 30-35 wt% under relatively mild operating conditions (1 atm, 250–280°C). Although the olefinicity of C₂ and C₃ fractions in the product stream was higher in the mixed bed compared to the follow bed arrangement, the selectivities to aromatics were comparable in the two bed arrangements. The aromatic selectivity was found to be sensitive to operating conditions. The formation of aromatics was favored at high HZSM-5/metal catalyst ratios, low space velocities and high reaction temperatures. The product distributions obtained using various metal/zeolite bifunctional catalysts have been discussed.     

甲烷氧化偶联制C2烃催化剂及催化反应机理研究进展

综述了甲烧氧化偶联制乙烷、乙烯催化剂及催化机理研究概况。重点介绍1989年以来对碱及碱土金属化合物、烯土氧化物、复合氧化物等各类催化剂的研究进展。对目前催化剂上甲烷活化途径、甲基自由基在反应过程中的作用机理、不同氧化物种及表面酸、碱位与催化性能的关系等方面的研究抉况及不同观点也作了简介。     

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO_x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO_x with metal Ru particles can form “MoO_x-Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.     

Kinetics of vapour phase oxidation of furfural on vanadium catalyst

Vapour phase oxidation of furfural over vanadium pentoxide catalyst was studied using an isothermal flow reactor in the temperature range of 220–280°C. Maleic anhydride and carbon dioxide are found to be formed from furfural by a parallel reaction scheme. The following rate equation based on the two-stage redox mechanism—the substance to be oxidized reduces the catalyst which in turn is reoxidized by oxygen from the feed—is found to explain the data satisfactorily.

The reoxidation of the reduced catalyst was found to be the rate controlling step.