共查询到16条相似文献,搜索用时 156 毫秒
1.
采用柠檬酸作络合剂的溶胶凝胶法制备了一系列的钼基催化剂,并应用到从生物质气化合成气有效合成低碳混合醇的实际过程中. 在钼基催化剂中,Cu1Co1Fe1Mo1Zn0.5-6%K催化剂具有相对较高的混合醇时空产率. 通过实验发现, 反应温度在340 oC以下时,碳转化率随着反应温度的增加而不断上升,总醇的选择性却逐渐下降. 在试验测试的条件内,从生物质气化合成气合成的混合醇最大产率为494.8 g/(kgcatal·h),其中C2+醇(C2-C6高碳醇)占总醇含量的80.4%. 在不同的钼基催化剂上合成的混合醇,其醇分布除甲醇以外均符合Schulz-Flory方程. 在醇类产物中,C2以上的高级醇含量占总醇重量的百分比为70%-85%. 同时,利用X射线衍射和BET等表征手段对钼基催化剂的形态和结构进行了表征. 从生物质合成气生产的洁净生物质燃料混合醇具有较高的辛烷值,可以用作运输燃料或汽油的添加剂. 相似文献
2.
Anis Hamza Fakeeh Muhammad Awais Naeem Wasim UllahKhan Ahmed Elhag Abasaee Ahmed Sadeq Al-Fatesh 《化学物理学报》2014,27(2):214-220
用浸渍法制备γ-Al2O3负载的Ni-Mn双金属催化剂.在500~700 oC按照17:17:2的CO2/CH4/N2比例,以36 mL/min的载气流速进行甲烷二氧化碳重整反应, 利用甲烷二氧化碳的转化率、生成的合成气H2/CO比例以及长期稳定性等指标评价了催化剂的催化性能. 实验表明, 添加Mn提高催化性能并使双金属催化剂的稳定性更高, 比单金属催化剂更好地抑制焦炭生成,Mn最合适的添加量0.5wt% .通过BET、CO2-TPD、TGA、XRD、SEM、EDX和FTIR各种技术对催化剂进行了表征. 相似文献
3.
本文基于第一性原理的微观动力学模拟方法,对Cu(221)和CuZn(221)上一氧化碳和二氧化碳加氢到甲醇进行了系统的理论计算研究.研究发现,碳转化率在两个表面上均表现出相同的活性顺序:CO加氢活性 > CO/CO2混合加氢活性 > CO2加氢活性.CO的高转化活性源于其基元反应能垒低于CO2甲醇合成的基元反应能垒.相比于Cu(221)表面,Zn的掺杂显著降低了甲醇合成活性,尤其是CO加氢的活性.对于CO和CO2共存的情况,研究发现CO是Cu(221)甲醇合成的主要碳源,而CuZn(221)上的碳源则由CO和CO2共同提供.反应速控度分析表明,CO/CO2混合气甲醇合成的速控步在Cu(221)表面是HCO、HCOO的加氢,而在CuZn(221)表面速控步则是HCOOH的加氢.这些研究结果表明铜基催化剂上Zn的表面合金效应、以及合成气组分对甲醇合成的活性和反应通道具有重要的影响. 相似文献
4.
制备出NiSAPO-34及NiSAPO-34/HZSM-5催化剂,考察了其对二甲醚催化转化制备低碳烯烃的性能.利用Cu/Zn/Al/HZSM-5和筛选出的2%NiSAPO-34/HZSM-5催化剂进行生物质气经由二甲醚两步法制备低碳烯烃的实验, 结果表明在SAPO-34上添加2%的Ni不改变其结构, 但降低了酸中心数量, 并生成了较强的酸中心. 添加少量具有稳定酸中心的HZSM-5, 该催化剂的活性提高到3 h以上, 反应进行2 h获得了最高的低碳烯烃选择性为90.8%. 当把该催化剂应用到两步催化转化过程的第二个反应器中, 其高催化活性可达5 h以上. 当以低氢碳比生物质气(H2/CO/CO2/N2/CH4=41.5/26.9/14.2/14.6/2.89)作为原料时,经两步转化,低碳烯烃的收率达到84.6 g/m3syngas. 相似文献
5.
Cr2O3是双功能催化合成气转化的重要氧化物组分,其可将合成气转化为重要的中间物种甲醇. 结合密度泛函理论计算和微观动力学模拟,本文系统研究了干净Cr2O3(001)和(012)表面,以及氢覆盖或含有氧空位的还原(012)表面的结构及催化合成气转化至甲醇的活性. 本文探讨了合成气转化为甲醇的分步或协同反应路径,并确定CO或CHO氢化是决速步骤. 微观动力学分析表明,Cr2O3(001)表面难以催化合成气转化为甲醇,在673 K 时,两个还原性(012)表面的反应速率(25∽28 s-1)比干净的(012)表面(4.3 s-1)高出约五倍. 计算结果表明了Cr2O3表面还原性对催化活性的重要性,或许可以为双功能催化体系中氧化物组分的设计提供参考. 相似文献
6.
7.
8.
利用微分电化学质谱和电化学原位衰减全反射红外光谱技术探究了Cu和CuPd催化剂上CO2和CO的电化学还原行为. 红外光谱观察到了生成甲醇、甲烷与乙烯的CHx中间物种. 在CuPd电极CO2还原过程中,红外光谱的CO吸附峰起始电位比Cu正移大约300 mV,说明CuPd能够有效促进CO2还原;CO饱和溶液中,Cu和CuPd电极CO起始吸附电位基本相同;两电极上CO谱带出现的电位与CO32-的谱带降低的电位基本相同,说明CO的吸附需要CO32-的脱附. 利用电化学在线质谱发现在CuPd电极上CO还原产生CH4和CH3OH的起始电位比Cu电极正移约200 mV. 推测催化活性的提升可能是由于Pd的引入改变了Cu的d能带,且Pd吸附更多的H,从而促进CO2还原,使CO能够与H结合并被深度还原. 相似文献
9.
选用四种不同的分子筛(SAPO-34, ZSM-5, Y, MCM-41)与CuCoMn(高醇合成组元)构成双功能催化剂,利用N2吸脱附、H2-TPR、XRD、NH3-TPD等表征了催化剂的结构性质. 研究了催化剂在生物质基合成气一段法制取液态烃燃料的应用. 相比于CuCoMn催化剂,加入分子筛的双功能催化剂均不同程度地提高了液体烃燃料的选择性及收率,且收率按顺序递减呈CCM-ZSM-5>CCM-SAPO-34>CCM-Y>CCM-MCM-41. 同时,共沉淀法制备的CuCoMn-ZSM-5 (20wt%, Si/Al=100) 具有最佳的CO转化率(76%)及液体产物收率(30%). 相比于CuCoMn氧化物,双功能催化剂的比表面及孔容均得到提高. CCM-ZSM-5具有适中的微孔尺寸和中等强度的酸性,增加CCM-ZSM-5中ZSM-5含量或降低ZSM-5中的Si/Al比,均有利于提高酸性位的数量,主要是较弱的酸性位. 而共沉淀法制备的CCM-ZSM-5具有更好的金属分散性及还原性能. 相似文献
10.
利用脉冲激光溅射-超声分子束载带方法制备了气相Ti+(CO2)2Ar和Ti+(CO2)n(n=3-7)络合物离子.采用红外光解离光谱研究了这些选定的质量离子的振动光谱. 对于每一种络合物离子, 在CO伸缩振动频率范围都观察到了振动峰,表明这些离子具有插入的OTi+CO(CO2)n-1结构. 对于n≦5的OTi+CO(CO2)n-1离子,其CO振动和CO2的反对称伸缩振动频率都比自由的CO和CO2的频率要高,表明CO和CO2配体与中心金属离子之间主要是静电相互作用.实验结果还表明TiO+可以直接络合五个配体(1个CO和4个CO2分子).对于n=2络合物体系,除了插入的OTi+CO(CO2)结构以外,还观察到了具有弯曲结构的OCO-Ti+-OCO异构体的存在 相似文献
11.
Steam reforming of methanol into a hydrogen-containing gas under activated methanol conversion on annular microchannel walls
was experimentally investigated. The methanol conversion was carried out on a copper-zinc catalyst deposited on the channel
internal wall. The concentrations of the chemical conversion products in the output gas mixture were determined at different
reactor temperatures and residence times. The channel wall temperature range within which the methanol steam reforming is
intensified was also determined. It was shown that the CO content in the reaction products is determined by the CO2 partial pressure rather than by the reactor temperature. A kinetic model of methanol steam reforming on a copper-zinc catalyst
was developed. 相似文献
12.
Mohammad Haghighi Zhi-qiang Sun Jin-hu Wu John Bromly Hui Ling Wee Esther Ng Yang Wang Dong-ke Zhang 《Proceedings of the Combustion Institute》2007,31(2):1983-1990
CO2 reforming of methane was studied over a bed of coal char in a fixed bed reactor at temperatures between 1073 and 1223 K and atmospheric pressure with a feed composition of CH4/CO2/N2 in the ratio of 1:1:8. Experimental results showed that the char was an effective catalyst for the production of syngas with a maximum H2/CO ratio of one. It was also found that high H2/CO ratios were favoured by low pressures and moderate to high temperatures. These results are supported by thermodynamic calculations. A mechanism of seven overall reactions was studied and three catalytic reactions of CH4 decomposition, char gasification and the Boudouard reaction was identified as being of major importance. The first reaction produces carbon and H2, the second consumes carbon, and the third (the Boudouard reaction) converts CO2 to CO while consuming carbon. Equilibrium calculations and experimental results showed that any water present reacts to form H2 and carbon oxides in the range of temperatures and pressures studied. Carbon deposition over the char bed is the major cause of deactivation. The rate of carbon formation depends on the kinetic balance between the surface reaction of the adsorbed hydrocarbons with oxygen containing species and the further dissociation of the hydrocarbon. 相似文献
13.
Luiz Clio S. Rocha Mariana S. Rocha Paulo Rotella Junior Giancarlo Aquila Rogrio S. Peruchi Karel Janda Rmulo O. Azevêdo 《Entropy (Basel, Switzerland)》2021,23(2)
The high proportion of CO2/CH4 in low aggregated value natural gas compositions can be used strategically and intelligently to produce more hydrocarbons through oxidative methane coupling (OCM). The main goal of this study was to optimize direct low-value natural gas conversion via CO2-OCM on metal oxide catalysts using robust multi-objective optimization based on an entropic measure to choose the most preferred Pareto optimal point as the problem’s final solution. The responses of CH4 conversion, C2 selectivity, and C2 yield are modeled using the response surface methodology. In this methodology, decision variables, e.g., the CO2/CH4 ratio, reactor temperature, wt.% CaO and wt.% MnO in ceria catalyst, are all employed. The Pareto optimal solution was obtained via the following combination of process parameters: CO2/CH4 ratio = 2.50, reactor temperature = 1179.5 K, wt.% CaO in ceria catalyst = 17.2%, wt.% MnO in ceria catalyst = 6.0%. By using the optimal weighting strategy w1 = 0.2602, w2 = 0.3203, w3 = 0.4295, the simultaneous optimal values for the objective functions were: CH4 conversion = 8.806%, C2 selectivity = 51.468%, C2 yield = 3.275%. Finally, an entropic measure used as a decision-making criterion was found to be useful in mapping the regions of minimal variation among the Pareto optimal responses and the results obtained, and this demonstrates that the optimization weights exert influence on the forecast variation of the obtained response. 相似文献
14.
采用廉价的无机锆源(无水硝酸锆)通过一步法合成表面含强Lewis酸位的SO42-/Zr-SBA-15,该催化剂材料在废弃食用油和甲醇酯交换制生物柴油过程中表现出良好的催化活性和选择性. 实验考察了酯交换反应的最佳条件为:反应温度160 oC、反应时间12 h、催化剂Zr:Si为0.11、催化剂用量为10%、醇油比30:1. SO42-/Zr-SBA-15在最佳反应条件下可使甘油三酯的转化率达到92.3%,脂肪酸甲酯的产率为91.7%. SO42-/Zr-SBA-15具有高比表面积的介孔结构和表面酸性,且具有良好的反应稳定性和重复性,反应7次后的脂肪酸甲酯的产率仍稳定保持在74 ±1%. 相似文献
15.
16.
Jinchen Ma Jinxing Wang Xin Tian Haibo Zhao 《Proceedings of the Combustion Institute》2019,37(4):4389-4397
Conventional air incineration of plastic waste has been considered as one of important sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) through de novo synthesis and precursor conversion. Chemical looping combustion (CLC) is an attractive technology for the conversion of plastic wastes to energy with the potential to drastically suppress the formation of PCDD/Fs. In this paper, the iG-CLC (in-situ gasification CLC) experiments of plastic waste were implemented in a semi-continuously operated fluidized bed reactor, which actually simulates the fuel reactor of a continuously-operated interconnected fluidized bed reactor. A kind of low-cost material, natural iron ore without/with 5 wt% CaO adsorbent through the ultrasonic impregnation method, was used as oxygen carrier (OC). Firstly, some key performances of the reactor system, such as the relevance of the bed inventory to the flow rate of fluidizing agent as well as the relationship between the feeding rate and overflow rate of OC, were calibrated. Then, 90 min of single experiment was conducted for each experimental case and an accumulative operation of more than 10 h was attained. Typically, the combustion efficiency can reach at about 98%, and both the carbon conversion and CO2 yield can approach to 95% at 900 °C and input thermal power of 150 W with a mixture of 5 vol% H2O and 95 vol% N2 as the fluidizing agent (UFR/Umf = 3). Moreover, the results obtained in the semi-continuously operated fluidized bed reactor demonstrated that CaO decoration to iron ore is conductive to suppressing the formation of chlorobenzene (as a toxic matter and precursor/intermediate of PCDD/Fs) and does not obviously deteriorate the OC performance. 相似文献