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2017年  第45卷  第6期

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研究论文
摘要:
The Ni-W/SBA-15 catalysts prepared by incipient-wetness impregnation method and controlled by the pH value were developed. Potassium hydroxide and citric acid regarded as the pH value regulators were added to the solution before impregnation to provide an acidic or basic condition at different pH values (0.83, 1.00, 3.09, 5.00, 7.03, 8.97 and 11.0). The 74.5% yield of total low carbon (C2, 3) polyols including ethylene glycol (EG), 1, 2-propylene glycol (1, 2-PG) and glycerol (Gly) was obtained over 10%Ni-20%W/SBA-15 catalyst prepared at pH value of 1.00 and 518 K under H2 pressure of 5.0 MPa. Furthermore, the physical properties of this series of nickel-tungsten catalysts were characterized by BET and SEM. The results demonstrated that the catalysts showed excellent thermal stability and the surface area was mainly in range of 330-450 m2/g. The particles had a good dispersion on the surface of SBA-15 but some aggregations were existed which could be characterized by TEM and SEM-EDX. However, the reduction of metallic oxides especially for NiO was obviously influenced by pH value control and some metallic species characterized by XRD. According to XRD results, the impregnation pH value influenced the reduction of NiO and the phase states of nickel and tungsten species.
摘要:
Dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) is one of the pivotal reactions in conversion of biomass towards valuable platform compounds. In this work, Nb/SBA-15 was prepared via incipient wetness impregnation with self-made SBA-15 as support; Nb/SBA-15 was further treated with phosphoric acid and calcined at 450℃, to obtain the Nb-P/SBA-15 catalyst. The Nb-P/SBA-15 catalyst was characterized by SEM, TEM, BET, XRD and NH3-TPD; its performance in the dehydration of fructose to 5-HMF was then investigated. The results indicate that the microscopic structure of SBA-15 is well preserved in Nb/SBA-15 with an internal channel diameter of about 10 nm and the niobic species are highly dispersed on the surface of the channels; the wall of channels became thinner after impregnation of Nb and treatment with phosphoric acid. After the treatment with phosphoric acid, the weak acid sites are increased, moreover, the medium and strong acidic sites are generated in Nb-P/SBA-15; as a result, for the dehydration of fructose in a water/MIBK biphasic system, Nb-P/SBA-15 exhibits higher catalytic activity and selectivity to 5-HMF. By reaction at 160℃ for 1.5 h, with a water/MIBK volume ratio of 1/2, the conversion of fructose and the yield of 5-HMF reach 96.1% and 92.6%, respectively. Moreover, the Nb-P/SBA-15 catalyst also exhibits excellent stability in view of water tolerance; it still demonstrates high catalytic activity and selectivity to 5-HMF even after successive recycling for four times.
摘要:
在反应温度240-320 ℃、甲醇用量0-200 mL、反应时间0-200 min的条件下,采用间歇式高温高压反应釜对玉米秸秆纤维素在亚/超临界甲醇中进行液化实验,结合GC-MS分析,研究不同液化反应条件下,生物油中轻油、重油产率及液化产物中烃类、醇类、酯类、酸类等主要化合物的组分分布及其变化规律。结果表明,反应温度和甲醇用量对化合物的分布与含量影响较大,反应温度和甲醇用量增加,促进纤维素向烃类、醇类、酯类转化,各化合物含量随之增加,并使轻油、重油产率升高,当反应条件为:甲醇用量160 mL,温度320 ℃,反应时间30 min时,生物油产率达到最高25.1%。生物油中组分含量顺序为:烃类>醇类>酯类>酸类,各化合物最高相对含量分别为77.2%、19.0%、30.9%、20.8%。初步分析发现,随着温度的升高和甲醇量的增加,自由基活性逐渐增强,当甲醇用量超过160 mL、温度超过300 ℃时,醇类以及酯类等化合物进一步发生氧化、缩合等反应形成酸类等化合物,造成化合物产率减小,进而使生物油产率降低。
摘要:
采用“沉淀-浸渍”法制备一系列不同硫酸负载量的SO42-/ZrO2-Al2O3催化剂,利用N2吸附-脱附、Py-FTIR、XRD等手段对催化剂进行表征。在常压、200 ℃、H2:C4=2:3和质量空速为3 h-1的反应条件下,在固定床微型反应评价装置上考察了硫酸负载量对SO42-/ZrO2-Al2O3催化正丁烷异构化反应性能的影响。Py-FTIR结果表明,硫酸化处理为催化剂表面提供了丰富的Brønsted酸性位,其中,强Brønsted酸性位在正丁烷异构化反应中起重要作用,因此,硫酸化处理可显著提高正丁烷异构化活性,而Lewis酸性位与之没有直接关系。
摘要:
以碱处理的MOR浆液为部分硅铝源、十六烷基三甲基溴化铵(CTAB)为模板剂,采用水热法合成了微孔-介孔复合分子筛MCM-41/MOR,并通过XRD、HRTEM、BET、Py-FTIR以及水热处理等方法对合成的复合分子筛进行了表征。结果表明,合成的复合分子筛具有微孔和介孔双重孔结构,比表面积高达567 m2/g,孔容为0.60 mL/g,平均孔径为3.26 nm,且具有较高的水热稳定性。正己烷在微反装置上的非临氢异构化反应结果表明,适宜的B酸和L酸协同构成了烷烃异构化的活性中心,催化剂表面的Ni离子在活化烷烃的同时还具有较好的酸性调变作用;与Ni-MOR、Ni-MCM-41以及HMCM-41/MOR相比,复合分子筛Ni-MCM-41/MOR由于其适宜的表面酸性和孔道结构,具有更好的异构化催化性能,正已烷转化率为34.40%,i-C60选择性提高到40.38%。
摘要:
采用浸渍法制备了Mn和Zr改性的介孔碳负载钴基催化剂,采用X射线衍射(XRD)、比表面积测定、H2程序升温还原(H2-TPR)、H2/CO程序升温脱附(TPD)及X射线光电子能谱(XPS)等手段对催化剂的物化性质进行了表征,采用固定床反应器对其F-T反应性能进行了研究。结果表明,Mn或Zr助剂的添加均降低了CH4的选择性。其中,Mn助剂的添加提高了C2-4的选择性,提高了烯烷比,而Zr的添加提高了钴物种的分散度,增加了反应活性位点,显著提高了钴基催化剂的F-T反应活性和C5+选择性。
摘要:
在反应温度550 ℃、空速5 500 h-1、H2S体积分数1.2%下对所研制的钼基催化剂进行了耐硫甲烷化活性评价,考察了反应气中添加H2O对Mo基催化剂耐硫甲烷化活性的影响。结果表明,反应气中添加水对Al2O3负载的Mo基催化剂可造成不可逆失活,而添加Co助剂及采用铈铝复合载体的催化剂其稳定性、活性得到了改善和提高。Co的添加能保护Mo基催化剂上的活性组分MoS2,抑制添加水导致的不可逆失活。当反应气中加入水时,催化剂上主要发生水汽变换反应,且随着水含量升高,水汽变换反应速率增大,会严重影响甲烷化反应的进行。此外,随着水含量的增加,其对催化剂的耐硫甲烷化活性和稳定性的影响程度变大。
摘要:
利用水热法制备了一种具有花朵状形貌的铈钛复合氧化物,该复合氧化物主要暴露CeO2{100}晶面。SEM、XRD表征结果表明,花朵状铈钛复合氧化物的形成主要分为两个阶段,即无定型的快速生长及缓慢结晶两个过程;在制备过程中,铈钛比例、KOH浓度、晶化时间和焙烧温度是该形貌形成的主要影响因素。其负载Au催化剂后常温即能实现CO的完全转化;TEM和H2-TPR结果表明,暴露的CeO2{100}晶面以及Au和载体的强相互作用是该催化剂具有高活性的主要原因。
摘要:
采用水热合成法制备了一系列不同金属掺杂的Ce-MM=Fe、Ni和Cu)复合氧化物,运用低温N2吸附-脱附、XRD、H2-TPR、拉曼光谱和XPS等表征技术对Ce-M复合氧化物的结构与其CO低温氧化反应性能之间的关系进行了关联。结果表明,将Fe、Ni和Cu掺入CeO2明显提高了其氧空位的含量,提升了晶格氧的流动性,从而使Ce-M催化剂的还原能力和催化活性高于纯CeO2。其中,CeCu催化剂氧空位最多、还原能力最好,催化活性最高,130 ℃下即可将CO完全氧化;其次是CeNi催化剂,180 ℃时实现CO完全氧化;与之相比,CeFe催化剂的活性最差,200 ℃时的CO转化率仅为92%。
摘要:
A Pt/HZSM-5 catalyst was prepared by atomic layer deposition (ALD) for aqueous-phase hydrogenation of levulinic acid (LA) to valeric acid (VA). 5Pt/HZSM-5 produced with 5 cycles of Pt ALD was identified as a highly active and stable bifunctional catalyst, and a high yield of VA (91.4%) was achieved in aqueous solution. A close interaction between Pt and acid sites of HZSM-5 is favor for the selective generation of VA. The microporous structure and the acid sites of HZSM-5 were not changed after Pt ALD, and some Pt nanoparticles were located in the micropore channel of HZSM-5. This reveals that the Pt ALD has the advantage to protect the structure of zeolite. The average particle size of Pt nanoparticles, electric state of surface Pt, and surface acid sites are nearly not changed with the increase of Pt ALD cycle number. However, the ratio of Pt in the pore channel to that out of the pore decreases with the increase of ALD cycle numbers, resulting in a decrease of TOF of VA yield. For comparison, Pt nanoparticles supported on HZSM-5 were also produced by impregnation. But the pore structure of HZSM-5 was damaged, and more micropore were formed by impregnation method for Pt loading. Moreover, it exhibited very low catalytic activity, selectivity of VA, and stability.
摘要:
A series of Ce-La/MgAl2O4-x catalysts were prepared by the incipient wetness impregnation method and characterized by BET, XRD, H2-TPR, CO-TPR and in situ FT-IR. The results demonstrate that the catalyst with a Mg/Al molar ratio of 0.5 yields the most uniform dispersion of CeO2 and greatly enhances formation of Ce-O-La solid solution, resulting in the increase of oxygen vacancy and surface Ce3+ content. Thereby, the synergistic effect between surface Ce3+ and oxygen vacancy gives rise to the best catalytic performance of NO reduction. Moreover, introduction of Mg species suppresses tranformation of CeO2 to Ce(SO4)2/Ce2(SO4)3 and then improves the SO2 resistance performance of Ce-La/MgAl2O4-0.5.
摘要:
先用十二烷基硫酸钠(SDS)对聚苯硫醚(PPS)滤料进行表面改性,随后通过氧化还原沉淀法制得不同质量比的Mn-Ce-Co-Ox/PPS复合滤料。考察了复合滤料在低温选择性催化还原(SCR)反应过程中的催化活性,并通过XRD、FESEM、TEM和XPS等表征手段对复合滤料的结构及性能进行表征分析。结果表明,Mn-Ce-Co-Ox/PPS复合滤料在120-160 ℃时的脱硝效率达到86%-100%,明显优于超声法制备的Mn-Ce-Co-Ox/PPS-UM复合滤料的低温SCR活性,且1.2Mn-Ce-Co-Ox/PPS复合滤料的活性最优。1.2Mn-Ce-Co-Ox/PPS复合滤料中MnO2、Ce2O3、CeO2、CoO、Co3O4以蜂窝状形式均匀分散在PPS纤维表面,且呈弱结晶性结构;其较高的Ce3+/(Ce3++Ce4+)比值和Co元素浓度是该1.2Mn-Ce-Co-Ox/PPS复合滤料具有优异低温SCR活性的主要原因。此外,与Mn-Ce-Co-Ox/PPS-UM复合滤料相比,1.2Mn-Ce-Co-Ox/PPS复合滤料也具有良好的抗H2O和抗SO2性能。
摘要:
用浸渍法制备Sb-V2O5-TiO2催化剂,在质量分数3%V2O5-TiO2催化剂基础上,研究锑的负载量、焙烧温度对催化剂活性的影响。结果表明,锑的负载量为11%(质量分数),500 ℃焙烧的催化剂具有最佳的SCR活性,在进口浓度为0.07% NOx、O2体积分数5%、空速27 000 h-1的条件下,170 ℃时脱硝活性可达92%。对催化剂进行H2-TPR表征,发现锑修饰后的催化剂氧化能力增强,使催化剂效率上升。通过XPS和NH3-TPD表征测试,催化剂表面的锑主要以五价的形式存在且随着锑负载量的增加催化剂表面酸性增强。考察SO2和H2O对催化剂的影响发现,加锑催化剂具有一定的抗硫抗水性能。通过FT-IR、TG、孔隙结构测试表明,锑的加入可以有效地抑制硫酸铵盐在催化剂表面的聚集,从而延长催化剂的寿命。
摘要:
研究了富氧环境中生物质基活性炭负载钾催化剂选择性还原氮氧化物的性能。结果表明,与煤基(褐煤)活性炭负载钾催化剂相比,生物质基(木屑)活性炭负载钾催化剂表现出高选择性还原NO能力,在2 h恒温稳态实验过程中能够保持80%的NO还原效率,而C-O2反应活性仅为18%。X射线衍射、比表面积、X射线光电子能谱以及程序升温脱附实验表征结果显示,生物质基活性炭负载钾催化剂优异的选择性还原NO性能应归因于炭表面钾物种的高度分散性,这与催化剂的高比表面积以及大量的表面氧基团有关。另外,生物质基炭材料还原NO反应产物中具有较高的CO2选择性。
摘要:
针对燃煤电厂湿法脱硫浆液中Hg2+易被还原的特性,研究Hg2+在模拟湿法脱硫系统中的迁移机制,考察了浆液温度、pH值以及SO32-、Cl-、Ca2+、Mg2+浓度等因素对Hg2+还原性能的影响。结果表明,Hg2+还原率随着浆液中SO32-浓度的增大而降低;pH值对Hg2+的还原呈先增加后降低的趋势,在pH值为5.5时还原率最高;温度的升高不利于浆液中稳定的二价汞盐络合物存在,导致Hg2+还原率增加;Ca2+、Mg2+以及Cl-浓度的增加有利于形成稳定化合物,从而抑制Hg2+的还原。
摘要:
以空气为气化剂、并通过GC-MS分析,研究了污水污泥流化床气化时气化温度(650、750和850 ℃)和污泥性质对污泥气化焦油产率及其化学组成的影响。结果表明,污泥气化焦油产率随气化温度的升高而降低,且厌氧消化污泥气化焦油的产率比未消化污泥的低。污泥气化焦油中的化学组成可分为五类:脂肪族化合物、脂环化合物、芳香烃、芳香烃衍生物和杂环化合物。随气化温度的升高,A2/O工艺的未消化污泥气化生成的焦油中脂肪族化合物和脂环化合物的产率均明显降低,芳香烃衍生物的产率则有显著地提高,而芳香烃和杂环化合物的产率均先增加后减少。气化温度为650 ℃时,活性污泥法消化污泥气化焦油中五类有机物的产率均低于未消化污泥的,而A2/O工艺消化污泥气化焦油中芳香烃产率高于未消化污泥的,其他四种有机物的产率则均低于未消化污泥的。