Co-MCM-41催化剂上临CO2-乙烷脱氢反应的研究

合成了不同Co掺杂量的Co-MCM-41分子筛.用XRD,FTIR和TG-DTA等技术对所制样品进行表征.在常压连续流动固定床反应器上考察了它们对临CO₂-乙烷脱氢制乙烯反应的性能,结果表明,3%Co-MCM-41在973K可使乙烷的转化率达到39.54%,乙烯的选择性达到98.59%,收率达到38.98%.Co的掺杂量和反应温度等条件对该反应均有一定影响.Co-MCM-41对乙烷催化脱氢制乙烯同样也有很高的活性.引入CO₂可消除积炭对催化剂活性的影响,更有利于催化反应的进行.     

制备方法对Cr/Si-2催化剂在CO2氧化乙烷脱氢制乙烯反应中的催化性能的影响

采用直接水热合成法和浸渍法制备了相同Cr含量的Cr/Si-2催化剂,并在常压固定床微反应器上,考察了它们在CO2或者N2气氛下的乙烷脱氢制乙烯反应中的催化性能及稳定性.由于存在逆水煤气反应和Boudouard反应,CO2能显著促进乙烷的脱氢反应.不论是在CO2还是在N2气氛下,直接水热法制备的催化剂均比浸渍法制备的催化剂显示出更好的催化性能.高价态的Cr物种被认为是催化剂具有高活性的关键.在CO2气氛下的乙烷脱氢制乙烯反应中,浸渍法制备的催化剂比水热法制备的催化剂失活更快,催化剂失活速率的差异可能与它们的氧化还原性质有关.然而在N2气氛下的乙烷脱氢制乙烯反应中,这两种方法制备的催化剂失活速率差异不大.     

溶胶-凝胶法制备Cr-基催化剂及其CO2氧化乙烷制乙烯

以硝酸铬为Cr源,正硅酸乙酯为Si源,采用溶胶-凝胶法制备了Cr质量分数为2.5%~10%的Cr-基催化剂;采用XRD、BET、SEM、H₂ TPR等分析测试技术对催化剂的结构进行了表征;在微型固定床反应器中对催化剂乙烷二氧化碳氧化脱氢制乙烯的催化性能进行了评价,并考察了反应条件对催化性能的影响。结果表明,催化剂中Cr的质量分数大于5%时,Cr的物相为Cr₂O₃,但Cr质量分数较低时,检测不到Cr的物相;Cr质量分数为5%的催化剂具有较大的比表面积,Cr质量分数变大或变小,催化剂的比表面积都会减小;催化剂的孔径在2nm左右,并与Cr的质量分数关系不大;Cr质量分数为5%的催化剂具有最好的催化活性,在750℃的反应条件下,乙烷和二氧化碳的转化率可达79.29%和23.74%,乙烯的收率可达67.91%;Cr质量分数为5%的催化剂具有适宜的氧化还原性能,这有利于乙烷和二氧化碳的转化。     

乙烷与CO2制乙烯反应的热力学和动力学研究

乙烷与ＣＯ２的主要反应及其热力学研究表明，乙烷与ＣＯ２反应很复杂，提高ＣＯ２氧化乙烷脱氢生成乙烯的选择，关键在一催化剂的开发；ＣＯ２不但可提高乙灶脱氢制乙烯的热力学平衡转化率，而且可与催化剂表面的积碳发生反应，延长催化剂的使用寿命。研究了催化剂上乙烷与ＣＯ２制乙烯反应的动力学，确定了ＣＯ２氧化乙烷脱氢反应的动力学方程及参数，表明乙烷与ＣＯ２制乙烯的反应速度比乙烷热裂解制乙烯的反应速度要大得多。     

羟基化氮化硼催化乙烷氧化脱氢制乙烯

乙烯是最为重要的化工原料之一,目前其工业来源主要来自于烃类的水蒸汽裂解过程.该过程本质上是一个高温均相裂解过程,温度(>800?℃)高,能耗大,碳排放严重.乙烷氧化脱氢制乙烯属于放热反应,反应温度低,速率快,无积碳等限制,是一条更富有竞争力的工艺路线.然而,常用的金属或金属氧化物催化剂容易导致乙烯深度氧化,从而降低了乙烯选择性.纳米碳材料在烃类氧化脱氢反应中展现出一定的催化活性,但容易被氧化,难以用于反应温度高的乙烷氧化脱氢反应.本文报道了羟基化的氮化硼(BNOH)可高效催化乙烷氧化脱氢制乙烯.氮化硼边沿羟基官能团脱氢生成了动态活性位,从而引发了乙烷的脱氢反应.BNOH对乙烷氧化脱氢制乙烯显示出高选择性.当乙烷转化率在11%,乙烯选择性可高达95%;当乙烷转化率增加到40%,乙烯选择性保持在90%.重要的是,当乙烷转化率超过60%时,BNOH仍然可保持80%的乙烯选择性以及50%的乙烯收率.这些性能指标与现有工业乙烷水蒸气裂解过程运行性能相当.进一步优化反应条件,BNOH催化剂能够实现高达9.1 gC2H4 gcat-1 h-1的时空收率.经过200 h的氧化脱氢反应测试,BNOH催化剂活性和选择性基本恒定,表明其具有非常好的稳定性.X射线粉末衍射结果显示,反应前后BNOH催化剂的物相没有发生变化.透射电子显微镜测试证实,反应后BNOH催化剂的形貌和微观结构也没有明显改变.X射线光电子能谱结果显示,反应200 h后BNOH催化剂表面的氧含量仅从反应前的6.9 atom%微增到8.3 atom%.1H固体核磁共振谱测试显示,反应200 h后,BNOH催化剂上羟基含量无明显改变.结合原位透射红外光谱和同位素示踪实验,初步确定了BNOH催化剂上引发乙烷氧化脱氢反应的活性中心.氮化硼边沿的氧官能团并不能引发乙烷的氧化脱氢反应,而羟基官能团才是氧化脱氢反应发生的活性位.在乙烷氧化脱氢条件下,分子氧脱除羟基官能团上的氢原子动态生成BNO·?和HO2·?活性位.密度泛函理论计算表明,乙烷首先在BNO·?或HO2·?位活化生成乙基自由基,这些中间物进一步与气相氧物种发生反应脱氢生成乙烯.动力学测试结果也验证了上述实验和理论结果.     

羟基化氮化硼催化乙烷氧化脱氢制乙烯（英文）

乙烯是最为重要的化工原料之一,目前其工业来源主要来自于烃类的水蒸汽裂解过程.该过程本质上是一个高温均相裂解过程,温度(800℃)高,能耗大,碳排放严重.乙烷氧化脱氢制乙烯属于放热反应,反应温度低,速率快,无积碳等限制,是一条更富有竞争力的工艺路线.然而,常用的金属或金属氧化物催化剂容易导致乙烯深度氧化,从而降低了乙烯选择性.纳米碳材料在烃类氧化脱氢反应中展现出一定的催化活性,但容易被氧化,难以用于反应温度高的乙烷氧化脱氢反应.本文报道了羟基化的氮化硼(BNOH)可高效催化乙烷氧化脱氢制乙烯.氮化硼边沿羟基官能团脱氢生成了动态活性位,从而引发了乙烷的脱氢反应.BNOH对乙烷氧化脱氢制乙烯显示出高选择性.当乙烷转化率在11%,乙烯选择性可高达95%;当乙烷转化率增加到40%,乙烯选择性保持在90%.重要的是,当乙烷转化率超过60%时,BNOH仍然可保持80%的乙烯选择性以及50%的乙烯收率.这些性能指标与现有工业乙烷水蒸气裂解过程运行性能相当.进一步优化反应条件,BNOH催化剂能够实现高达9.1g_(C2H4)g_(cat)~(-1)h~(-1)的时空收率.经过200 h的氧化脱氢反应测试,BNOH催化剂活性和选择性基本恒定,表明其具有非常好的稳定性.X射线粉末衍射结果显示,反应前后BNOH催化剂的物相没有发生变化.透射电子显微镜测试证实,反应后BNOH催化剂的形貌和微观结构也没有明显改变.X射线光电子能谱结果显示,反应200 h后BNOH催化剂表面的氧含量仅从反应前的6.9 atom%微增到8.3 atom%.~1H固体核磁共振谱测试显示,反应200 h后,BNOH催化剂上羟基含量无明显改变.结合原位透射红外光谱和同位素示踪实验,初步确定了BNOH催化剂上引发乙烷氧化脱氢反应的活性中心.氮化硼边沿的氧官能团并不能引发乙烷的氧化脱氢反应,而羟基官能团才是氧化脱氢反应发生的活性位.在乙烷氧化脱氢条件下,分子氧脱除羟基官能团上的氢原子动态生成BNO~·和HO_2~·活性位.密度泛函理论计算表明,乙烷首先在BNO~·或HO_2~·位活化生成乙基自由基,这些中间物进一步与气相氧物种发生反应脱氢生成乙烯.动力学测试结果也验证了上述实验和理论结果.     

甲烷在Li-Ln-MgO氧化物上催化氧化偶联

近年来,对天然气的综合利用已逐渐为人们所重视。甲烷氧化偶联制乙烯、乙烷这一新课题受到催化工作者愈来愈多的关注^[1~5]。本工作初步探讨了Li-Ln-MgO三元氧化物催化剂对甲烷氧化偶联反应的催化性能。添加稀土元素可使C₂的选择性、单收明显提高。本催化剂体系制备简单、原料便宜,值得进一步开发研究。     

负载型Co-Cr氧化物催化剂上CO2氧化乙烷脱氢制乙烯反应的研究

制备了一系列不同Co／Cr比例的Co-Cr／SiO2和Co-Cr／γ-Al2O3催化剂，并应用XRD等技术对所制样品进行了表征．在常压连续流动固定床石英反应器中考察了它们对CO2乙烷氧化脱氢反应的催化性能．实验结果表明，Co-Cr／SiO2和Co-Cr／γ-Al2O对CO2乙烷脱氢制乙烯都有较高的催化活性，其活性都明显高于负载单一组分的催化剂．以γ-Al2O为载体的催化剂活性明显比以SiO2为载体的催化剂活性高．1％Co-5％Cr／γ-Al2O活性最高，973K乙烷的转化率达25．57％，乙烯的选择性和收率分别达94．28％、24．10％．     

浆态法制备的MoVTeNbO催化剂上的乙烷氧化脱氢

 采用浆态法在N2气氛下焙烧制得了MoV0.3Te0.23Nb0.1Ox催化剂. 在以该催化剂催化的乙烷氧化脱氢制乙烯的反应中,440 ℃下乙烷的转化率和乙烯的选择性均在90%左右,乙烯产率达80.9%. 但在空气气氛下焙烧得到的催化剂几乎没有催化活性. 用XRD和SEM等方法考察了催化剂的结构.     

在Fe-Zn-Mg催化剂上丁烯-1氧化脱氢制丁二烯动力学

用玻璃流动外循环反应器研究了Fe_4.9Zn_0.9Mg_0.1(原子比)催化剂上丁烯-1氧化脱氢动力学,丁烯-1氧化脱氢制丁二烯、丁烯-1及丁二烯深度氧化生成CO₂的动力学用双反应分子强吸附的L-H(LangmuirHinshelwood)机理方程描述。速度方程的参数用非线性最小二乘法估计,得丁二烯生成速度r_D和CO₂生成速度r_co2的动力学方程式。     

纳米Cr2O3系列催化剂上CO2氧化乙烷脱氢制乙烯反应

 采用溶胶－凝胶法和共沸蒸馏法耦合技术制备了纳米Cr2O3催化剂，并采用共沉淀法和共沸蒸馏法耦合技术制备了纳米Cr2O3／Al2O3，Cr2O3／ZrO2和Cr2O3／MgO复合催化剂．应用BET，XRD，XPS，TPR和TEM等物理化学方法对催化剂的结构和物化性质进行了表征，并考察了该系列催化剂上CO2氧化乙烷脱氢制乙烯的反应性能．结果表明，纳米Cr2O3催化剂上乙烷和CO2的转化率均明显高于常规Cr2O3催化剂，但乙烯的选择性低于常规Cr2O3催化剂；纳米复合催化剂中的复合成分显著影响催化剂的催化性能．其中，10％Cr2O3／MgO纳米复合催化剂在温度为973K时，乙烷转化率和乙烯选择性分别可达到61．54％和94．79％．纳米催化剂表面Cr的还原性以及Cr6＋／Cr3＋比值是影响乙烷转化率和乙烯选择性的重要因素．     

Oxidative dehydrogenation of ethane with carbon dioxide over sulfated zirconia supported metal oxides catalysts

Several metal oxides supported on sulfated zirconia catalysts were tested for the oxidative dehydrogenation of ethane into ethylene by carbon dioxide. It is found that the catalytic behavior of supported oxide catalysts differ depending on the nature of metal oxides. Chromium oxide-sulfated zirconia exhibits the highest ethane conversion and medium level of ethylene selectivity, producing 38% ethylene yield at 50% ethane conversion at 650°C.     

Effect of methane co-feeding on the selectivity of ethylene produced from oxidative dehydrogenation of ethane with CO2 over a Ni-La/SiO2 catalyst

A Ni-La/SiO₂ catalyst was prepared through the incipient wetness impregnation method and tested in the oxidative dehydrogenation of ethane (ODHE) with CO₂. The fresh and used catalysts were characterized by XRD and SEM techniques. The Ni-La/SiO₂ catalyst exhibited catalytic activity for the oxidative dehydrogenation of ethane, but with low ethylene selectivity in the absence of methane. The selectivity to ethylene increased with increasing molar ratio of methane in the feed. The carbon deposited on the catalyst surface in the sole ODHE with CO₂ was mainly inert carbon, while much more filamentous carbon was formed in the presence of methane. The filamentous carbon was easy to be removed by CO₂, which might play a role in improving the conversion of ethane to ethylene. The introduction of methane might affect the equilibrium of the CO₂ reforming of ethane and the ODHE with CO₂. As a consequence, the synthesis gas produced from CO₂ reforming of methane partly inhibited the reaction of ethane and promoted the ODHE with CO₂, thus increasing the selectivity of ethylene.     

CO2 emission free co-generation of energy and ethylene in hydrocarbon SOFC reactors with a dehydrogenation anode

A dehydrogenation anode is reported for hydrocarbon proton conducting solid oxide fuel cells (SOFCs). A Cu-Cr(2)O(3) nanocomposite is obtained from CuCrO(2) nanoparticles as an inexpensive, efficient, carbon deposition and sintering tolerant anode catalyst. A SOFC reactor is fabricated using a Cu-Cr(2)O(3) composite as a dehydrogenation anode and a doped barium cerate as a proton conducting electrolyte. The protonic membrane SOFC reactor can selectively convert ethane to valuable ethylene, and electricity is simultaneously generated in the electrochemical oxidative dehydrogenation process. While there are no CO(2) emissions, traces of CO are present in the anode exhaust when the SOFC reactor is operated at over 700 °C. A mechanism is proposed for ethane electro-catalytic dehydrogenation over the Cu-Cr(2)O(3) catalyst. The SOFC reactor also has good stability for co-generation of electricity and ethylene at 700 °C.     

Copper-containing catalysts for the oxidative dehydrogenation of organic compounds

A method of doping magnesium aluminum hydrotalcites, which are precursors for oxidative dehydrogenation oxide catalysts of various compositions, with copper(II) was developed, and copper(II)-containing oxide catalyst samples were synthesized. The catalytic properties of these catalysts were studied in the oxidative dehydrogenation of ethane, propane, and hexane. The conversion of ethane into ethylene on the copper-containing catalysts was established to proceed with high selectivities (90?C97%) and at low temperatures (400?C450°C).     

低碳烷烃与二氧化碳催化转化研究进展

页岩气革命为低碳经济发展提供了重要契机.在低碳烷烃(甲烷和乙烷)催化转化过程中,以二氧化碳作为氧化剂参与反应,通过C–H键的选择性活化可将页岩气转化为优质化工原料——合成气和乙烯,是一种低碳烷烃转化与二氧化碳资源化利用的工艺路线.本文总结了近年来甲烷干重整与乙烷和二氧化碳反应中与C–H键活化相关的研究进展,分析了甲烷干重整中镍基催化剂积碳及乙烷和二氧化碳反应中产物选择性的主要影响因素,并对该研究未来的发展方向进行了展望.     

Effect of pressure on the oxidative conversion of ethane on VMoTeNbO catalyst

Study of the catalytic properties of the VMoTeNbO catalyst in the oxidative conversion of ethane to ethylene at pressures of 0.1 to 2.1 MPa demonstrated that the pressure positively affects the conversion of ethane and favors formation of oxygen -containing products of deep and partial oxidation: carbon oxides and acetic acid, respectively. With increasing pressure, the yield of the product of oxidative dehydrogenation of ethane, i.e., ethylene, decreases.     

Formation of active phases of Fe/C,Cr/C and Fe–Cr/C catalysts in oxidative dehydrogenation of ethane

The oxidative dehydrogenation of ethane into ethylene using CO₂ as an oxidant at temperatures of 650–750 °C was carried out over Fe/C, Cr/C and Fe–Cr/C catalysts deposited on a carbon support. Before and after the reaction the catalysts were investigated by X-ray powder diffraction (XRD), in situ magnetometry and transmission electron microscopy methods. The correlation between activity of Fe/C, Cr/C and Fe–Cr/C catalytic systems and their phase composition was established.     

Effect of group VIII elements on the behavior of Li/CaO catalyst in the oxidative dehydrogenation of ethane

The effect of addition of group VIII elements to Li/CaO on the oxidative dehydrogenation of ethane has been investigated in the range of 550–650°c. Iron, cobalt and nickel promote the reaction. The experiments show that iron and cobalt additives in Li/CaO catalysts mainly increase the catalytic activity. Li/Ni/CaO catalyst gives a high ethane conversion and excellent ethylene selectivity. The results on the catalyst are probably due to coordinative interaction between lithium and nickel. The characteristics of the catalysts revealed by XRD also give evidence that the promotion for both catalytic activity and ethylene selectivity is directly related to the formation of favorable crystal phases.