共查询到20条相似文献,搜索用时 328 毫秒
1.
氮氧化物是大气主要污染源之一,危害人体健康,并引发酸雨。随着环保法规的升级,氮氧化物排放浓度的限值要求越来越高。这要求脱硝工艺尤其是脱硝催化剂必须进一步提高脱硝性能。以ZSM-5分子筛为载体,以铜、铈为活性组分,制备脱硝催化剂活性组分;用铝胶将脱硝催化剂活性组分附着在蜂窝状陶瓷上,得到脱硝催化剂。与ZSM-5分子筛相比,脱硝催化剂活性组分增加了4.73%的铜(以CuO质量分数计)和5.40%的铈(以CeO2质量分数计),比表面积由287.04 m2/g降到275.05 m2/g,孔容、孔径未发生变化,酸性增强,晶型基本保持不变。脱硝催化剂最佳反应条件:反应时间≥60 min,反应温度≥250 ℃,空速≤10 200 h-1。脱硝催化剂在最佳反应条件下的脱硝效率约为85%。脱硝催化剂能适应较低的反应温度,并且具有较高的脱硝效率。 相似文献
2.
3.
4.
《中国石油和化工标准与质量》2016,(21)
本文采用浸渍法制备了PW1 2/S i O2催化剂,催化氧化二甲醚制取甲缩醛。采用XRD、IR两种分析手段表征催化剂样品。当PW1 2负载量为30%,反应温度为613 K时,催化剂的活性最佳且稳定性良好,二甲醚转化率为52.1%,甲缩醛选择性为10.3%。 相似文献
5.
6.
采用溶胶-凝胶法制备了用于甲醇气相脱水制二甲醚的新型催化剂全氟磺酸树脂/二氧化硅,应用X射线衍射、红外光谱、热重-差示扫描量热、低温氮物理吸附和氨程序升温脱附法对所得催化剂进行了表征。考察了反应温度、甲醇液空速、全氟磺酸树脂含量对甲醇气相催化脱水制二甲醚反应性能和催化剂稳定性的影响。结果表明,催化剂比表面积达820m2/g,在全氟磺酸树脂负载量10.0%、甲醇液空速1h?1、反应温度184℃时,甲醇转化率92.0%,二甲醚选择性99.9%,经350h实验测试,活性和稳定性没有明显变化。 相似文献
7.
8.
生物质合成气合成二甲醚的研究 总被引:1,自引:1,他引:0
在加压固定床反应装置上进行了生物质合成气合成二甲醚(DME)的研究.采用机械混合法制备二甲醚合成双功能催化剂.考察了组成为V(H_2):V(CO):V(CO_2):V(CH_4)=52:24:23:1的生物质合成气在不同反应温度、空速、压力下对合成二甲醚反应的影响.同时进行了102 h的催化剂的稳定性实验.结果表明,在260-300℃范围内,随反应温度的升高,CO转化率和二甲醚的选择性均先增大后减小;随反应压力的升高,CO转化率和二甲醚选择性都随之升高;原料气中高浓度的CO_2可导致铜基催化剂较快的失活. 相似文献
9.
二甲醚既是一种重要的有机化工原料,也可作为清洁燃料,应用前景十分广阔。通过用不同浓度的硫酸改性高岭土制备了酸改性高岭土催化剂,在自制的光催化反应器中进行活性测试。研究结果表明:高岭土经硫酸改性前后晶体结构没有明显变化,但随着硫酸浓度的增加催化剂出现了明显的B酸和L酸;硫酸改性高岭土催化剂在二氧化碳反应环境下光催化甲醇的主要产物是二甲醚和甲酸甲酯;当硫酸改性高岭土的酸浓度为50%、反应时间30 min时,甲醇转化率可达94%、二甲醚选择性为98%、二甲醚收率为92%。 相似文献
10.
含氮合成气直接合成二甲醚复合催化剂与混合催化剂性能及本征动力学 总被引:2,自引:0,他引:2
在直流流动等温积分反应器中,反应压力 3.0~7.0MPa、温度 220~260℃及空速 500~2000 mL?g?1?h?1下,研究了含氮合成气直接合成二甲醚双功能复合型催化剂和混合型催化剂的催化性能。实验结果表明在两种不同双功能催化剂上,240℃、7.0 MPa 及 1000 mL?g?1?h?1是较好的反应条件,复合型催化剂与混合催化剂反应性能相近,反应温度较高时复合催化剂二甲醚选择性基本保持不变,而混合型催化剂二甲醚选择性随温度升高降低。在复合催化剂上进行了含氮合成气合成二甲醚本征动力学研究,选用了双曲型动力学模型,采用遗传算法与单纯型算法相结合的方法对模型参数进行估值,获得了模型参数,比较了混合催化剂、复合催化剂上合成二甲醚的反应速率。 相似文献
11.
Sung-Hwan Ahn Song-Hyoung Kim Kwang-Bo Jung Hyun-Sik Hahm 《Korean Journal of Chemical Engineering》2008,25(3):466-470
The effect of pressure on the direct synthesis of dimethyl ether (DME) from syngas over metal (Cu, Zn) pillared ilerites and
metal (Cu, Zn) impregnated metal-pillared ilerites was explored. The prepared catalysts were characterized by XRD, BET, ICP-AES,
SEM and FT-IR. The direct DME synthesis reaction was carried out in a differential fixed bed reactor with the prepared catalysts
at various pressures (10, 20, 30 bar), 250°C and H2/CO ratio of 2. The Cu/Zn-pillared ilerite catalyst showed the highest catalytic activity among the prepared catalysts at
20 bar, in which CO conversion was about 62% and DME selectivity was about 89%. CO conversion increased with pressure, and
DME selectivity increased with pressure in the range of 10–20 bar, and above the pressure slightly decreased with pressure.
The optimum pressure for this reaction was 20 bar. 相似文献
12.
A series of iron (Fe) modified CuO-ZnO-ZrO2-Al2O3 (CZZA) catalysts,with various Fe loadings,were pre-pared using a co-precipitation method.A bifunctional catalyst,consisting of Fe-modified CZZA and HZSM-5,was studied for dimethyl ether (DME) synthesis via CO2 hydrogenation.The effects of Fe loading,reaction temperature,reaction pressure,space velocity,and concentrations of precursor for the synthesis of the Fe-modified CZZA catalyst on the catalytic activity of DME synthesis were investigated.Long-term stability tests showed that Fe modification of the CZZA catalyst improved the catalyst stability for DME synthesis via CO2 hydrogenation.The activity loss,in terms of DME yield,was significantly reduced from 4.2% to 1.4% in a 100 h run of reaction,when the Fe loading amount was 0.5 (molar ratio of Fe to Cu).An analysis of hydrogen temperature programmed reduction revealed that the introduction of Fe improved the reducibility of the catalysts,due to assisted adsorption of H2 on iron oxide.The good stability of Fe-modified CZZA catalysts in the DME formation was most likely attributed to oxygen spillover that was introduced by the addition of iron oxide.This could have inhibited the oxidation of the Cu surface and enhanced the thermal stability of copper during long-term reactions. 相似文献
13.
14.
Four CuZnAl slurry catalysts with different contents of Al were directly prepared from the solution of these metal salts to catalyst slurry by a complete liquid-phase method. The structure properties of the catalysts were characterized by XRD, BET, XPS, FTIR, and their catalytic performances for the single-step synthesis of Dimethyl ether (DME) from syngas were evaluated in a slurry reactor of 250 mL with a mechanical magnetic agitator. The results indicate the main phase existed in the catalysts are Cu, Cu2O, ZnO and boehmite (AlOOH) and the structures of pore and surface are comparable with those of the commercial methanol synthesis catalysts. Activity tests show that the slurry catalysts are quite effective for the single-step synthesis of DME from syngas. Among them, the catalyst with 2.09 mol% Al is best, whose DME selectivity reaches 93.08%. All of the catalysts prepared by the novel method exhibit good stability during the reaction time investigated for 18 days. 相似文献
15.
Liquid phase methanol and dimethyl ether synthesis from syngas 总被引:4,自引:0,他引:4
The Liquid Phase Methanol Synthesis (LPMeOHTM) process has been investigated in our laboratories since 1982The reaction chemistry of liquid phase methanol synthesis over commercial Cu/ZnO/Al2O3 catalysts, established for diverse feed gas conditions including H2-rich, CO-rich, CO2-rich, and CO-free environments, is predominantly based on the CO2 hydrogenation reaction and the forward water-gas shift reactionImportant aspects of the liquid phase methanol synthesis investigated in this in-depth study include global kinetic rate expressions, external mass transfer mechanisms and rates, correlation for the overall gas-to-liquid mass transfer rate coefficient, computation of the multicomponent phase equilibrium and prediction of the ultimate and isolated chemical equilibrium compositions, thermal stability analysis of the liquid phase methanol synthesis reactor, investigation of pore diffusion in the methanol catalyst, and elucidation of catalyst deactivation/regenerationThese studies were conducted in a mechanically agitated slurry reactor as well as in a liquid entrained reactorA novel liquid phase process for co-production of dimethyl ether (DME) and methanol has also been developedThe process is based on dual-catalytic synthesis in a single reactor stage, where the methanol synthesis and water gas shift reactions takes place over Cu/ZnO/Al2O3 catalysts and the in-situ methanol dehydration reaction takes place over -Al2O3 catalystCo-production of DME and methanol can increase the single-stage reactor productivity by as much as 80%. By varying the mass ratios of methanol synthesis catalyst to methanol dehydration catalyst, it is possible to co-produce DME and methanol in any fixed proportion, from 5% DME to 95% DMEAlso, dual catalysts exhibit higher activity, and more importantly these activities are sustained for a longer catalyst on-stream life by alleviating catalyst deactivation. 相似文献
16.
Xiao Fan Baitang Jin Shoujie Ren Shiguang Li Miao Yu Xinhua Liang 《American Institute of Chemical Engineers》2021,67(11):e17353
The roles of interaction between two catalyst components in CuO–ZnO–ZrO2–Al2O3 (CZZA)/HZSM-5 bifunctional catalyst for dimethyl ether (DME) synthesis via carbon dioxide hydrogenation were investigated. It was found that CZZA catalyst showed excellent stability during methanol (MeOH) synthesis for 100 h, while there was a severe loss of catalytic activity in the bifunctional catalyst for DME synthesis. Hence, the effects of different degrees of intimacy of two catalyst components were studied for DME synthesis, including mixed and separated modes. For the mixed mode, the particle size of catalysts and the amount of reaction intermediates were proven to influence the catalyst deactivation. For the separated mode, the catalysts showed rapid deactivation within a short time. Various characterizations indicated that the remarkable deactivation of separated mode was mainly caused by the decrease of copper active centers (e.g., sintering and oxidation) and blockage of acid sites via increased coke deposition on HZSM-5. 相似文献
17.
Miriam StiefelRuaa Ahmad Ulrich ArnoldManfred Döring 《Fuel Processing Technology》2011,92(8):1466-1474
Various dehydration catalysts were studied in the synthesis of dimethyl ether (DME) directly from carbon-monoxide-rich synthesis gas under a series of different reaction conditions. The investigated catalyst systems consisted of combinations of a methanol catalyst (CuO/ZnO system) with catalysts for methanol dehydration based on γ-Al2O3 or zeolites and γ-Al2O3 was identified as the most favorable dehydration catalyst. Various reaction parameters such as temperature, H2/CO ratio and space velocity were studied. The impact of water on Cu/ZnO/Al2O3-γ-Al2O3 catalysts was investigated and no deactivation could be observed at water contents below 10% during running times of several hours. A running time of several days and a water content of 10% led to a significant increase of CO conversion but the water gas shift reaction became dominating and CO2 was the main product. After termination of water feeding significant deactivation of the catalyst system was observed but the system returned to high DME selectivity. Catalyst stability and the influence of CO2 in the gas feed were studied in experiments lasting for about three weeks. The presence of 8% of CO2 caused an approximately 10% lower CO conversion and an about 5% lower DME selectivity compared to the reaction system without CO2. 相似文献
18.
Synthesis of AlOOH slurry catalyst and catalytic activity for methanol dehydration to dimethyl ether
Lei Liu Wei Huang Zhi-hua Gao Li-hua Yin 《Journal of Industrial and Engineering Chemistry》2012,18(1):123-127
AlOOH slurry catalysts were prepared by complete liquid-phase technology from aluminum iso-propoxide (AIP). Dehydration of methanol to dimethyl ether (DME) over these catalysts was investigated in slurry reactor. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, temperature-programmed desorption of ammonia (NH3–TPD). The results showed that the slurry catalysts had high specific surface area and pore volume, and the specific surface area and the strength of weak acidic sites were influenced considerably by the molar ratio of H2O/AIP and HNO3/AIP. Activity tests indicated that AlOOH slurry catalysts had excellent catalytic activity and stability in slurry reactor for the dehydration of methanol to dimethyl ether, and the activity correlated well with the strength of weak acidic sites of catalysts, which can be controlled by changing the H2O/AIP and HNO3/AIP molar ratios. The average methanol conversion at even stage reaches nearly 80% and DME selectivity almost 100% over CAT-P1 catalyst. No deactivation was found during the reaction of 500 h. It is also expected that CAT-P1 becomes a promising methanol dehydration catalyst for the STD process based on CuZuAl methanol synthesis catalyst. 相似文献
19.
完全液相法催化剂上甲醇脱水合成二甲醚的动力学及DFT研究 总被引:1,自引:1,他引:0
采用完全液相法制备AlOOH催化剂并进行了浆态床反应器中甲醇脱水制备二甲醚的反应动力学和DFT的研究。在3种甲醇脱水制备二甲醚的反应机理中,以表面反应即两个同时吸附的甲醇反应生成二甲醚作为速控步骤,所建立动力学模型的计算值和实验值吻合较好。采用DFT计算了液体石蜡环境中AlOOH(100)面的脱水反应,其反应过程和活化能结果与动力学模型结果基本一致,进一步表明采用该模型可以合理描述完全液相法制备的AlOOH催化剂表面甲醇脱水反应过程。 相似文献
20.
CO2加氢制二甲醚(DME)是有潜力实现CO2资源化利用的重要途径之一。与光、电催化相比,CO2的非均相催化转化具有转化效率高等优点,但目前CO2加氢一步制备DME催化剂的反应活性较低、稳定性较差。本文在简要介绍CO2加氢一步制DME的铜基双功能催化剂、复合氧化物和氮化镓催化剂的基础上,重点总结了活性中心结构和反应机理的研究进展。对于铜基双功能催化剂,CO2加氢经甲醇中间体合成DME,其中还原态铜(Cu0、Cu+及Cu δ+,0<δ<2)是其催化活性中心,且还原态铜的分散度及稳定性、固体酸的性质和酸性位分布以及两类活性中心的耦合效应是决定DME收率和催化剂稳定性的关键因素。与此相反,DME是氮化镓催化CO2加氢的初级产物。这与铜基双功能催化剂有着本质区别,属新催化剂体系。在此基础上,文章对CO2加氢制DME的可能研究方向进行了展望,认为“二甲醚经济”更具发展潜力。 相似文献