载体物化性质对锰铈催化剂NH3-SCR脱硝性能的影响

选取TiO₂、SAPO-34、Al₂O₃三种常用载体,通过浸渍法以Mn-Ce-O为活性组分制备了负载型MnCeO_x脱硝催化剂。采用XRD、BET、H₂-TPR、XPS、Py-FTIR等手段对催化剂的固相结构、比表面积、还原性能、表面元素及酸量进行表征分析。结果表明,MnCeO_x/SAPO-34催化剂具有最大的比表面积（439.87 m²/g）,酸量适中,还原性能最差;MnCeO_x/Al₂O₃催化剂中Mn⁴⁺、Ce³⁺所占比例较高,但酸性最弱;MnCeO_x/TiO₂催化剂还原性能最优,表面Mn、Ce元素浓度最高,并具有大量Lewis酸性位。通过气固相催化反应装置对催化剂性能进行了NH₃-SCR脱硝评价,结果表明,MnCeO_x/TiO₂催化剂具有较好的脱硝性能,反应温度为280 ℃时,NO转化率达100%（空速为42000 h^-1）;与催化剂物化性质对比分析,催化剂的氧化还原能力和Lewis酸性位对其脱硝性能至关重要。     

Cu/WO3-TiO2光催化剂上丙烯和二氧化碳合成MAA反应性能

研究了Cu/WO₃-TiO₂对CO₂和C₃H₆的吸附特性和光催化性能.结果表明,在Cu/WO₃-TiO₂催化剂表面存在金属位Cu,Lewis酸位W⁶⁺和Ti⁴⁺以及Lewis碱位W-O-Ti的桥氧和WO的端氧三类活性中心;在金属位Cu和Lewis酸位Ti⁴⁺(或W⁶⁺)的协同作用下,CO₂形成活性较高的卧式吸附态Cu-(CO)-O→Ti⁴⁺(或W⁶⁺),C₃H₆的β-H和β-C分别吸附在Lewis碱位WO与金属位Cu上,形成Cu-(CH₂)C(CH₃)-H→OW吸附态;Cu/WO₃-TiO₂催化剂吸收阈值蓝移和光吸收量的提高均有利于其催化活性的提高,担载质量分数为10%的WO₃光催化剂的催化活性优于其它含量的催化剂,光量子效率最高(19.7%);在383K,0.1MPa,空速200h^-1和125W紫外灯辐照下,C₃H₆转化率为7.4%,甲基丙烯酸(MAA)的选择性超过95%.根据实验结果提出了光促表面催化合成反应的机理.     

The effect of FER zeolite acid sites in methanol-to-dimethyl-ether catalytic dehydration

In this paper, the effect of acidity of zeolites with FER framework was studied in the methanol dehydration to dimethyl ether reaction, by comparing catalysts with different Si/Al ratios(namely 8, 30 and60). The aim of this work was to investigate how the acid sites concentration, strength, distribution and typology(Br?nsted and Lewis) affect methanol conversion, DME selectivity and coke formation. It was found that the aluminium content affects slightly acid sites strength whilst a relevant effect on acid sites concentration and distribution(Br?nsted/Lewis) was observed as 24% of Lewis sites were found on Alrichest samples, whilst less than 10% of Lewis acid sites were observed on FER at higher Si/Al ratio. All the investigated catalyst samples showed a selectivity toward DME always greater than 0.9 and samples with the lowest Si/Al ratio exhibit the best performances in terms of methanol conversion, approaching the theoretical equilibrium value(around 0.85) at temperatures below 200 °C. Turnover-frequency analysis suggests that this result seems to be related not only to the higher amount of acid sites but also that the presence of Lewis acid sites may play a significant role in converting methanol. On the other hand, the presence of Lewis acid sites, combined with a high acidity, promote the formation of by-products(mainly methane) and coke deposition during the reaction. As final evidence, all the investigated catalysts exhibit very high resistance to deactivation by coke deposition, over 60 h continuous test, and a GC–MS analysis of the coke deposited on the catalyst surface reveals tetra-methyl benzene as main component.     

微波辐射下稀土交换ZSM-5分子筛的制备及裂解反应研究

借助微波技术制备出一系列具有不同La³⁺交换度的LaHZSM-5样品。初步探讨了微波强度、微波作用时间及Si/Al比对交换度的影响。对其表面酸性的考察发现,样品均含有B酸和L酸中心,并且随La³⁺进入ZSM-5沸石的量的不同,强弱酸中心的强度与数量均有所改变。对样品催化性能的研究结果表明,催化活性与La³⁺含量及酸量呈顺变关系。     

催化裂化条件下噻吩与改性Y分子筛的作用机制

以HY、NiY和稀土离子改性的Y分子筛(REY)为研究对象,采用固定床装置评价噻吩模拟油催化裂化性能;运用气相色谱-氢火焰离子发光检测器(GC-FID)、气相色谱-硫化学发光检测器(GC-SCD)和原位红外光谱技术分析产物,关联分子筛的酸性,研究催化裂化条件下噻吩与改性Y分子筛的作用机制。实验结果表明,催化裂化条件下,噻吩与分子筛的作用机制差异主要取决于与B酸或L酸相关的非骨架铝物种或金属离子物种的存在形式。其中,NiY分子筛中,噻吩主要是吸附在与NiOH⁺物种相关的L酸中心,而Ni₄AlO₄³⁺等物种减弱B酸性中心从而降低其裂化性能。对HY来说,噻吩易在与AlO⁺等物种相邻的B酸中心上聚合形成三联噻吩,并发生一定的氢转移和裂化反应;而对REY而言,分子筛中与RE物种相关的L酸位会促进噻吩在与非骨架铝羟基等物种(如Al(OH)₂⁺、Al(OH)²⁺等)相邻的B酸中心形成的二联噻吩发生氢转移和裂化反应。     

Cu-SAPO-18催化剂氨选择性催化还原NOx钾中毒机理的研究

研究了不同水热老化温度对钾(K)中毒0.4K-Cu-SAPO-18样品的结构及其NH₃-SCR(NH₃作为还原剂的选择性还原技术)催化活性的影响. 结果表明, K中毒对样品结构影响较小, 但明显降低了其NH₃-SCR性能, 在350 ℃ 时, K中毒样品0.4K-Cu-SAPO-18的NO转化率为65.88%, 明显低于未中毒Cu-SAPO-18样品的90.85%. 水热老化温度明显影响催化剂的结构, 减少了活性位点, 降低了表面酸性. 随着水热老化温度升高, 催化剂的AEI结构被破坏, 活性物种数量降低, 催化活性明显下降. 氢气程序升温还原 (H₂-TPR)结果表明, 孤立的Cu²⁺和Cu⁺的总量分别从未中毒Cu-SAPO-18样品的66.61和1.32 μmol/g变化到K中毒0.4K-Cu-SAPO-18样品的39.52和101.96 μmol/g, 表明K中毒样品中孤立Cu²⁺ 容易转化为Cu₂O. K中毒后, 样品的弱酸、 中强酸、 强酸性位点的数量降低, 分别从未中毒Cu-SAPO-18样品的0.201, 0.103和0.302 mmol/g降低到中毒0.4K-Cu-SAPO-18样品的0.102, 0.086和0.071 mmol/g. 氨气程序升温脱附(NH₃-TPD)和原位红外结果表明, K竞争性地取代了催化剂中孤立的Cu²⁺和H⁺, 使K中毒0.4K-Cu-SAPO-18样品的活性位和酸性位减少, 导致催化活性下降. 在低温 NH₃-SCR反应中, K中毒和未中毒样品均以Eley-Rideal(E-R)和Langmuir-Hinshelwood(L-H)机理进行, 而L-H机理占主导地位, 但K中毒样品的反应速率明显降低.     

12-钨磷酸及其盐的酸性与催化性能的研究

红外法研究结果表明12-钨磷酸Fe³⁺、Mg²⁺和Na⁺盐都具有L酸点和B酸点。用Benesi法测得10种12-钨磷酸盐的酸强度顺序为(Al³⁺、Fe³⁺、La³⁺、Cu²⁺、Cd²⁺>Zn²⁺>(Ca²⁺、Mg²⁺>(Na⁺、Li⁺,其酸量与抗衡阳离子的离子势和电负性大体成线性关系。还看出酸量与所含结晶水量有关。催化剂的酸量与其对异丙醇脱水反应和丁烯-1异构化反应的催化活性的关系表现出不同的特征,这可用“体相型”和“表面型”催化作用的不同特点来解释。     

FTIR研究不同硅铝比HZSM-5沸石的酸性质

用IR和NH₃-TPD测定了硅铝比为31.4～137.1的HZSM-5沸石样品的酸中心数;由Lang-muir吸附模型推导出B、L酸的吸附热公式,并由此计算了B酸的吸附热。发现在Al/u.c.为3.64附近,酸中心数与Al/u.c的关系发生了转折,并发现B酸吸附符合Langmuir模型,L酸强度不均匀而不符合该模型,测定了HZSM-5分子筛的B、L酸消光系数8_B=7.52×10⁵cm·mol^-1、8_L=1.09×10⁶cm·mol^-1。     

无额外供氢体下负载型MoFeO_x催化剂催化甘油制丙烯醇

采用浸渍法制备MoFe/X(X=SnO_2,ZrO_2,CeO_2,TiO_2,CNTs,MgO)以及MoFe氧化物催化剂用于甘油气-固相催化转化制丙烯醇。通过XRD、BET、XPS、H_2-TPR和NH_3-TPD表征,MoFe主要由晶相Fe_2O_3和Fe_2(MoO_4)_3组成而MoFe/X主要为高分散态的Fe、Mo氧化物(Fe~(3+)、Mo~(6+)),其表面均只存在弱酸中心;所采用载体由于自身性质(比表面积和酸碱性)差异与Mo、Fe氧化物之间存在不同的相互作用,进而有效地调控了MoFe/X的表面弱酸强度、酸浓度和可还原性能。所制备催化剂对甘油制丙烯醇的催化性能(收率)依次为:MoFe/TiO_2MoFe/CeO_2MoFe/ZrO_2MoFe/CNTsMoFe/SnO_2MoFeMoFe/MgO。340°C时,MoFe/TiO_2上甘油的转化率达到83.4%,丙烯醇的选择性和收率分别达到26.7%和22.3%;同时其展现出优于MoFe/CeO_2、MoFe/ZrO_2和MoFe/CNTs的稳定性。甘油转化率与催化剂表面弱酸中心浓度呈正相关性,而丙烯醇的生成则与氧化中心(非酸中心)密切相关。甘油转化率和丙烯醇选择性在MoFe/X上随反应温度变化而呈现相悖的变化趋势。     

Flexible regulation of C3=/C2= ratio in methanol-to-hydrocarbons by delicate control of acidity of ZSM-5 catalyst

A very wide range of the C₃⁼/C₂⁼ ratio from 0.72 to 7.56 with high C₂⁼+C₃⁼ selectivity of around 66% in the methanol-to-hydrocarbons process can be realized over ZSM-5 catalyst in a fixed-bed reactor. We firstly conduct a single factor experiment of acidity, demonstrating that the acidity control of MTH catalyst is crucial to adjusting light olefins selectivity. Weak Brønsted acid sites favor to high C₃⁼ selectivity (59.0%) due to the suppression of the conversion reactions from the alkene-based to arene-based cycle, while Lewis acid sites conduce to high C₂⁼ selectivity (39.6%) due to the promotion of the conversion reactions for the aromatics formation and steric constraints of Lewis acid sites making the aromatics crack more efficiently to C₂⁼.     

Aromatization of methane by using propane as co-reactant over cobalt and zinc-impregnated HZSM-5 catalysts

The activities of the cobalt and zinc-impregnated HZSM-5 catalysts to the non-oxidative conversion of propane (C3) and methane (C1) into aromatic hydrocarbons were evaluated using a fixed-bed microreactor. C1 conversion reached 36.7% and the selectivity of aromatic products reached above 88.7% at atmospheric pressure, weight (hourly) space velocity (WHSV) 1.6 g h⁻¹/(g cat)⁻¹ and 873 K. The influence of the acidity and the ratio of cobalt in the catalyst on the conversion of methane and propane was evaluated. C1 incorporation was conclusively confirmed by the mass spectral analyses of aromatic products produced in a run with ¹³CH₄ which shows a significant ¹³C enrichment in the C₆H₆⁺, C₇H₈⁺ and C₈H₁₀⁺ fragments. The methane activation could result from its hydrogen-transfer reaction with alkenes. These catalysts were thoroughly characterized using XRD, N₂ adsorption measurements, TPD of NH₃, and FT-IR. The results showed that the activation of methane in low temperature was due to existence of propane. The acidic changes and micropore area of the catalyst severely affected aromatization, and resulted in drastic modifications in product distribution. From this work, we found that only a small fraction of tetrahedral framework aluminum, which corresponds to the Bronsted acid sites, is sufficient to accomplish the aromatization of the intermediates in methane and propane aromatic reaction, while the superfluous strong Bronsted acid sites, which can be decreased by adding Co and Zn, are showed to be related with the aromatic carbonaceous deposits on the catalysts. The density of acidic site and the strength of strong acid decreased when the concentration of Co and Zn in the catalyst increased. Therefore, a much higher benzene yield and a longer durability of the catalysts are obtained when compared with the conventional HZSM-5 catalysts.     

Cu改性Fe/Al-PILC催化剂的SCR-C3H6脱硝特性实验研究

为提高Fe/Al-PILC催化剂的SCR脱硝的低温活性,采用Cu对Fe/Al-PILC催化剂进行改性。采用超声浸渍法合成系列xCu-Fe/Al-PILC催化剂,通过XRD、N₂吸附-脱附、H₂-TPR、UV-vis、XPS、Py-FTIR等系列技术手段进行表征。在固定床微反应器上进行C₃H₆的选择性催化还原NO的实验。结果表明,经过铜改性后的xCu-Fe/Al-PILC催化剂有效解决了Fe/Al-PILC催化剂低温SCR活性不足的问题,同时提高了中高温活性。催化剂在200-500℃能够实现80%以上脱硝效率,其中,0.13Cu-Fe/Al-PILC在250-500℃实现了90%以上NO转化率,并在250℃达到最高脱硝效率93%。XRD、N₂吸附-脱附结果表明,经过铜改性的催化剂可以提供更多反应活性位,提高反应速率。H₂-TPR结果表明,掺杂铜使催化剂获得低温还原能力,同时增强了中高温还原能力。UV-vis、XPS结果表明,铜掺杂不仅使铁获得更高氧化态,同时产生了更多低温活性物质孤立Fe³⁺。Py-FTIR结果表明,催化剂表面同时存在Lewis酸和Brønsted酸,Lewis酸是SCR反应活性中心。     

Sn-Al-β分子筛酸性在葡萄糖转化反应中作用的固体NMR研究

制备了一系列具有不同酸性质的β分子筛催化剂, 通过固体核磁共振(NMR)探针分子技术对其酸性质进行了表征, 并考察了其催化葡萄糖转化为乙酰丙酸甲酯的性能. 吸附三甲基磷的³¹P NMR实验结果表明, 含有骨架Sn以及Al原子的Sn-Al-β催化剂同时具有Br?nsted与Lewis酸性. 通过2-¹³C-丙酮探针分子区分出 3种酸强度的Br?nsted酸位, 其中一种酸强度接近“超强酸”, 可能是由于空间邻近的Br?nsted酸位和Lewis酸位发生协同作用产生的. 葡萄糖转化为乙酰丙酸甲酯的催化反应结果表明, 相比于分别只含有Lewis酸位和Br?nsted酸位的Sn-β和Al-β样品以及两者的物理混合样品, Sn-Al-β分子筛催化剂具有高催化活性与产物选择性, 这主要是由于Br?nsted酸位和Lewis酸位的协同作用产生了强Br?nsted酸位, 这种强Br?nsted酸位进一步导致了更高的催化活性.     

Production and reactions of xylenes over H-ZSM5

Disproportion of toluene, isomerization of xylenes and alkylation of toluene with methanol were investigated over a series of H-ZSM5 zeolites varying in Si/Al ratio. The specific rates per unit cell of H-ZSM5 for disproportionation of toluene and isomerization of xylene were found to be directly proportional to the concentration of strong Brönsted acid sites for all temperatures investigated. For temperatures above 573 K, the corresponding specific rates for alkylation of toluene with methanol were found to be independent of the concentration of strong Brönsted acid sites. In contrast, at 473 K a significant dependence was observed. We explain this variation of the dependence of the specific rate upon the concentration of strong Brönsted acid sites by the contribution of two reaction pathways to the overall reaction rate.     

热处理时间对CuZnAl催化剂合成C2+OH性能的影响

采用完全液相法在不同热处理时间下制备了CuZnAl催化剂,利用X射线光电子能谱（XPS）、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、NH₃吸附-脱附（NH₃-TPD-MS）和N₂物理吸附-脱附等方法对其结构进行了表征分析,并在浆态床反应器上对其催化合成气制C₂₊OH的性能进行了研究。研究发现,延长热处理时间增强了催化剂中Cu和Al物种之间的相互作用力,改变了其中Cu⁺的量,从而影响Cu⁺-Cu⁰活性位的协同作用。同时,热处理时间的延长减少了催化剂的表面酸量,增大了孔容和孔径;催化剂表面较少的弱酸位及较大孔容和孔径均有利于C₂₊OH的生成。热处理时间为7 h时所制备的CuZnAl催化剂表现出了优良的低碳醇合成催化活性,CO转化率和总醇中C₂₊OH的质量分数分别达到了38.1%和65.9%。     

NaBH4处理LaCuZnX(X=Zr、Al、Zr+Al)(类)钙钛矿型催化剂及其CO2加氢合成甲醇性能的研究

采用共沉淀法分别制备了不同F-T组分(Fe、Co、Ni)改性的KCuZrO_2催化剂,并用于催化CO加氢合成异丁醇。通过BET、XRD、TEM、XPS、H_2-TPR、CO-TPD以及in-situ DRIFTS对催化剂进行了表征。结果显示,F-T组分的加入促进了乙醇和丙醇的形成,但是对异丁醇选择性影响不同。结果表明,Fe促进了催化剂中各组分的分散,活性组分Cu在催化剂表面发生了富集,提高了H_2/CO活化吸附;另外,KFeCuZrO_2的催化剂表面含有较多的C_1物种,有利于乙醇和丙醇进一步发生β-加成反应得到异丁醇,而Co和Ni改性的催化剂上缺少足够的C_1物种,因此,异丁醇的选择性并未明显增加。Co的引入对催化剂结构以及Cu的分散影响不大,但是Co改性后催化剂性能有所下降,其原因是催化剂发生了失活;Ni添加后催化剂比表面积有所减小,且催化剂表面Cu/Zr物质的量比也降低到0.19,催化剂粒径增大,Cu-Zr之间相互作用减弱,异丁醇选择性降低。     

计时电流法测定Fe3+在离子液体BPBF4中的扩散系数

室温离子液体(简称离子液体)作为新型的反应介质和功能材料受到学术界和产业界的高度关注,正在迅速成为多学科交叉的前沿研究领域和具有良好应用前景的“绿色”高新技术,过渡金属化合物是许多重要反应的催化剂,过渡金属离子在室温离子液体中的性质是工业界关心的课题,有关过渡金属的离子液体的研究,     

锰负载钛锆和钛锡复合氧化物催化剂烟气脱汞实验研究

采用共沉淀法制备了TiO_2、TiZr和TiSn载体,浸渍锰制备了10%MnO_2的MnTi、MnTiZr和MnTiSn催化剂。采用BET、XRD、H_2-TPR、FT-IR和XPS等对样品进行表征,并对三种催化剂进行固定床脱汞性能实验。结果表明,在100-300℃,MnTiZr和MnTiSn催化剂脱汞性能均优于MnTi催化剂,这归因于Sn和Zr的引入提升了催化剂比表面积和低温氧化还原性能增加了催化剂表面的酸性位点数量、高价态锰离子和O~*含量;在反应温度为150-300℃,MnTiSn催化剂脱汞效率均高于MnTiZr催化剂这是由于前者具有更好的氧化还原性能,表面具有更多含量的高价态锰离子、O~*含量和酸性位点数量;在Hg~0脱除过程中催化剂表面活性组分如高价态锰离子和O~*均消耗,参与了Hg~)氧化为Hg~(2+)的反应且MnTiSn催化剂表面活性组分的消耗量更多。     

添加Li+对MgO催化性能的影响

本文以IR、TPD、丁烯异构化及直接脱氢反应为手段,对不同Li⁺添加量的MgO催化剂进行了研究。结果表明,表面低配位氧集团是催化剂的主要活性物种,起碱中心作用;表面金属离子起L酸中心作用。酸、碱中心的数目、强度随Li⁺添加量不同而呈规律性变化。这种变化影响了酸、碱中心的协同作用,从而影响其催化活性。     

Synthesis of binaphthols over mesoporous molecular sieves

Mesoporous aluminosilicates (Al-containing NaMCM-41) were applied as catalyst supports for oxidative coupling of β-naphthol and substituted β-naphthols due to their remarkable features such as surface area, ordered mesopores and high thermal stability. The NaMCM-41 supported copper catalysts prepared by impregnation method, and Cu-NaMCM-41 was prepared by incorporating copper during synthesis. Oxidative coupling of β-naphthol reaction was studied using molecular oxygen as oxidant. The copper supported NaMCM-41 catalysts were prepared with different Si/Al ratios and calcined from 120 to 420 °C were observed to show varied product selectivity. The NaMCM-41 supported copper catalysts and Cu-NaMCM-41 were more active than the corresponding Cu/Fe supported on NaY zeolite. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), UV–DRS, ICPMS and BET surface area techniques and the reaction products were confirmed by ¹H-NMR, FTIR and HRMS. An attempt has been made to explain the product selectivity of the catalysts discussed with the above techniques. The high dispersion of Cu⁺² species observed in the catalysts having high Si/Al ratios in NaMCM-41 support and catalysts that are calcined at low temperatures, i.e. less than 420 °C, yielded an unexpected product perylene diol. A comparatively low dispersion of Cu⁺² species, noticed in catalysts having low Si/Al ratios and calcined at high temperatures, yielded binapthol as the coupled product. The effect of the variation of catalyst and the solvent are also studied.