苯与合成气在ZnAlCrO x &HZSM-5双功能催化剂上一步法制甲苯/二甲苯

与传统的甲醇和苯烷基化反应相比,合成气和苯一步法制甲苯/二甲苯具有苯转化率高,催化剂稳定性好,经济性高等优点。本研究将系列Zn基的金属氧化物与H-ZSM-5分子筛组成双功能催化剂,实现了合成气与苯高效转化为甲苯/二甲苯,并筛选出最优的双功能催化剂为ZnAlCrO _x &H-ZSM-5。原位红外实验发现,单独的合成气在催化剂上的转化较弱,但加入苯之后,苯与甲氧基等中间体的烷基化反应可以有效拉动合成气的转化。这表明,双功能催化剂中金属组分和分子筛组分间的协同作用拉动了该反应的高效进行。通过Zn、Mg、Ga等元素改性H-ZSM-5分子筛,使得分子筛B酸酸量与L酸酸量的比值降低,发现比值的降低有助于苯的转化。其中Zn改性后B酸与L酸的比值降低最为显著,苯转化率增加的也最多。调变反应温度、原料空速、合成气氢碳比可以控制苯的烷基化程度,调节苯烷基化各产物的选择性。ZnAlCrO _x &H-ZSM-5双功能催化剂在压力3MPa、温度400℃的反应条件下,兼具高的苯转化率（90.6%）和甲苯/二甲苯选择性（74.3%）,同时CO有效利用率为33.7%。     

复合分子筛催化剂上C9芳烃脱烷基的研究

将Ni负载在H-ZSM-5和H-MOR分子筛催化剂上，以异丙苯为模型化合物对分子筛催化剂加氢脱烷基性能进行评价。考察了分子筛复配比例、金属含量和酸浓度对催化剂活性的影响。结果表明，酸处理后的分子筛催化剂，异丙苯转化率和苯、甲苯、二甲苯(BTX)的收率有明显提高。当反应温度为340 ℃、压力0.8 MP和空速1 h^-1时，其转化率为81.5％，BTX收率为72.8％，选择性可达89.2％。     

Alkylation of benzene with carbon dioxide to low-carbon aromatic hydrocarbons over bifunctional Zn-Ti/HZSM-5 catalyst

Alkylation of benzene to value-added,high octane number and low toxic toluene and xylenes provides a way to lower benzene content in gasoline pool,and is hence a method to promote fuel quality.On the other hand,CO₂ accumulation in the atmosphere causes global warming and requires effective route for its valorization.Utilization of CO₂ as a carbon source for benzene alkylation could achieve both goals.Herein,alkylation of benzene with CO₂ and H2 was realized by a series of low-cost bifunctional catalysts containing zinc/titanium oxides(Zn/Ti oxides)and HZSM-5 molecular sieves in a fixed-bed reactor.By regulating and controlling oxygen vacancies of Zn/Ti oxides and the acidities of HZSM-5,benzene conversion and CO₂ conversion reached 28.7%and 29.9%respectively,along with a total selectivity of toluene and xylene higher than 90%.In this process,more than 25%CO₂ was effectively utilized and incorporated into the target products.Moreover,the mechanism of the reaction was analyzed and the course was simultaneously traced.CO₂ was transformed into methanol firstly,and then methanol reacted with benzene generating toluene and xylene.The innovation provides a new method for upgrading of fuels and upcycling the emissions of CO₂,which is of great environmental and economic benefits.     

乙烷与苯经接力催化路线制备乙苯

设计乙烷经氯氧化制备乙烯再与苯烷基化一步法制备乙苯的接力催化路线。研制铈基氧化物作为活化乙烷生成中间产物乙烯的催化剂,并耦合H-ZSM-5沸石分子筛与苯进一步烷基化生成乙苯。在Mn/CeO₂氧化物与H-ZSM-5沸石分子筛以研磨混合形成的双功能催化剂上,实现了乙烷与苯催化制备乙苯的可控接力催化。考察了氧化物的组成、氧化物与沸石分子筛的耦合方式与最适质量配比、沸石分子筛的硅铝比对接力催化反应的影响,并进行了催化剂稳定性研究。结合X射线衍射（XRD）、NH₃程序升温脱附（NH₃-TPD）、透射电子显微镜（TEM）、X射线荧光光谱分析（XRF）等表征手段分析了催化剂结构及其与催化性能的构效关系。提出后续催化剂研究的关键在于分子筛烷基化能力以及抗流失能力的提高。     

Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and s...     

ZnZr/HZSM-5双功能催化剂在合成气与苯烷基化反应中的催化性能

将系列锌锆金属氧化物与HZSM-5分子筛耦合制备成双功能复合催化剂,并将其应用于合成气与苯烷基化反应。研究结果表明,ZnO是合成甲醇的主要活性组分,ZrO₂的加入能够促进ZnO分散,同时其表面具有的氧空位可促进CO的活化,二者结合方式显著影响反应活性。SEM、XPS、CO-TPD等表征结果表明,ZnO与ZrO₂相结合不仅能够提高ZnO的分散度,而且能调控氧化物表面的氧空位浓度,当二者形成固溶体时,锌在氧化锆中的分散度最大,表面氧空位浓度最高,CO吸附量最大,催化活性最高。锌锆结合方式一定时,锌含量是影响催化活性的另一重要因素,n(Zr)/n(Zn)=2的锌锆固溶体与HZSM-5以质量比1∶2耦合表现出最高的催化活性,CO和苯的转化率为34.65%和35.82%时,甲苯和二甲苯的总选择性高达85.24%。     

On the role of gallium for the aromatization of lower paraffins with Ga-promoted ZSM-5 catalysts

Aromatization of butane or propane was conducted with a series of ZSM-5 catalysts. A small amount of oxygen in the feed promoted butane conversion to aromatic hydrocarbons on H-ZSM-5. It suggests that if hydrogen atoms on the zeolite surface are removed effectively, H-ZSM-5 exhibits a high selectivity for aromatic hydrocarbons. A hybrid catalyst composed of the physical mixture of Ga/SiO₂ and H-ZSM-5 showed comparable activity and aromatic selectivity to those of the Ga-supported ZSM-5 zeolite, whereas the Ga/SiO₂ itself exhibited little catalytic activity for the paraffin conversion and olefin aromatization. The excellent promotional effect of Ga/SiO₂for aromatics formation was observed only when it was intimately contacted with H-ZSM-5. These results suggest that the supported Ga promotes the zeolite-catalyzed aromatization of lower paraffins by promoting hydrogen desorption via the ‘reverse spillover’ effects.     

Transformation of ethylbenzene–m-xylene mixture on zeolites with different structures

Hierarchical zeolite ZSM-5 synthesized by applying amphiphilic organosilane as mesopore template, nanosized zeolite Beta and zeolite MCM-22 have been studied, for the first time in the conversion of mixed ethylbenzene–m-xylene feed. The effects of the channel structure, nanosizing and presence of mesopores in these zeolite materials with close Si/Al molar ratio on the catalytic activity and selectivity have been discussed. It was found that the diverse zeolites have different advantages and disadvantages in dependence on their structure and morphology. MCM-22 zeolite provides promising ethylbenzene conversion at low xylene loss with high production of the p-isomer among xylene.     

t-Butylation of 1,2-dihydroxybenzene over acidic zeolites

t-Butylation of 1,2-dihydroxybenzene (DHB) with isobutene as alkylating agent was carried out over various acidic zeolites such as USH-Y, H-beta, and H-ZSM-5. USH-Y zeolite exhibits the highest catalytic activity and considerable selectivity of 4-t-butylcatechol (4-TBC). The selectivity of 4-TBC is increased in the order of H-ZSM-5>USH-YH-beta. 3-t-Butylcatechol (3-TBC) is well produced over catalyst with high SiO₂/Al₂O₃ ratio and large pore aperture. 3,5-Di-t-butylcatechol (3,5-DTBC) selectivity is maximum in zeolite which contains strong acidity and large pore channel. The influences of various reaction parameters such as reaction temperature, space velocity, reactant molar ratio are discussed. In order to improve 4-TBC formation and decrease in 3,5-DTBC selectivity simultaneously, USH-Y zeolite was silylated by tetraethylorthosilicate (TEOS) resulting in the decrease of 3,5-DTBC selectivity over modified catalysts by about 25%. USH-Y zeolite shows high stability in the t-butylation for at least 350 h. The coke formed during the reaction was identified by FT-IR and the USH-Y zeolite could be regenerated through oxidative thermal treatment.     

超声浸渍无机盐改性Hβ分子筛催化合成乙基蒽醌

采用超声浸渍法将无机盐Al₂(SO₄)₃、(NH₄)₂SO₄、Ce(NH₄)₂(NO₃)₆和Fe(NO₃)₃负载于Hβ分子筛上,通过NH₃-TPD、XRD和吡啶-IR对分子筛进行表征,考察改性前后分子筛酸性能和晶相的变化。将改性的Hβ分子筛用于催化乙苯和苯酐合成乙基蒽醌。结果表明,不同无机盐超声浸渍改性分子筛的催化效果差别较大,其中,每克分子筛负载0.2 g的Al₂(SO₄)₃的Alβ分子筛催化效果最好,苯酐转化率为45.67%,乙基蒽醌选择性为50.12%。分子筛的酸性能（包括酸量、酸种类和酸强度）对催化性能影响较大。     

甲苯甲醇烷基化制对二甲苯催化剂中试反应性能研究

经过多步改性制备了负载二氧化硅（SiO₂）、氧化镁（MgO）、五氧化二磷（P₂O₅）、贵金属铂（Pt）的纳米ZSM-5分子筛催化剂,并在六段固定床反应器上分段装填该催化剂720 g进行甲苯、甲醇烷基化制对二甲苯反应活性评价。实验结果表明,通过调变甲醇和甲苯物质的量比可以使甲苯转化率在22%~30%可调,烷基化液相产物中二甲苯选择性保持在95%以上,二甲苯中对二甲苯选择性保持在95%以上;催化剂单程寿命达到1 300 h,随着反应时间延长催化剂的活性有所下降。通过X射线衍射（XRD）、热重分析（TG-DTG）和氮气吸附-脱附等手段对参加反应前后的催化剂进行了表征,结果表明反应中生成的积炭堵塞了分子筛的孔道或覆盖了催化剂的活性位;经过在反应器内原位再生,催化剂的反应活性基本恢复到新鲜催化剂水平。     

乙酰丙酸改性对HZSM-5甲醇芳构化催化剂性能的影响

利用葡萄糖水解原位产生的乙酰丙酸对HZSM-5分子筛进行改性,通过X射线衍射、X射线荧光分析、N2吸附-脱附、扫描电子显微镜、NH3-TPD、Py-Fourier透射红外光谱、热分析等手段对催化剂进行表征,在固定床微型反应器上评价催化性能.结果表明:改性后的HZSM-5在保留完整晶相结构的基础上产生了微孔-介孔结构,酸...     

Mesoporous zeolite single crystal catalysts: Diffusion and catalysis in hierarchical zeolites

During the last years, several new routes to produce zeolites with controlled mesoporosity have appeared. Moreover, an improved catalytic performance of the resulting mesoporous zeolites over conventional zeolites has been demonstrated in several reactions. In most cases, the mesoporous zeolites exhibit higher catalytic activity, but in some cases also improved selectivity and longer catalyst lifetime has been reported. The beneficial effects of introducing mesopores into the zeolites has in most instances been attributed to improved mass transport to and from the active sites located in the zeolite micropores. Here, we briefly discuss the most important ways of introducing mesopores into zeolites and, for the first time, we show experimentally that the presence of mesopores dramatically increases the rate of diffusion in zeolite catalysts. This is done by studying the elution of iso-butane from packed beds of conventional and mesoporous zeolite catalysts. Moreover, we discuss in detail the recent observation of improved activity and selectivity in the alkylation of benzene with ethene using mesoporous zeolite single crystal catalysts. For this reaction, we show by calculation of the Thiele modulus that this improved performance can be mainly attributed to a diffusional limitation of ethylbenzene in the zeolite pores. This is verified in new ethylbenzene dealkylation experiments where mesoporous zeolite catalysts show significantly improved activity over conventional zeolite catalysts.     

MgO/NaX zeolite as basic catalyst for oxidative methylation of toluene with methane

Oxidative methylation of toluene with methane was studied over a series of MgO/NaX zeolite catalysts. The effect of MgO on the zeolite was examined by X-ray diffraction (XRD) and temperature-programmed desorption (TPD) of CO₂. The results indicated that the conversion, selectivity and yield of C₈ hydrocarbons (ethylbenzene and styrene) are significantly improved by impregnation of maximum 13 wt.% MgO into the zeolite. The latter catalyst also displays a good stability. It is found that the amount of active sites but not their strength depends on the content of MgO in the zeolite. The catalysts possess well preserved crystal structure and low amount of MgO crystal phase.     

CO/CO2加氢高选择性合成化学品和液体燃料

一氧化碳/二氧化碳（CO/CO₂）转化利用是碳一化学与CO₂捕集利用中的重要环节,也是当今碳资源的非石油路线利用最具挑战性的方向之一。CO₂的高效活化与定向转化是CO₂利用过程中的关键问题,而CO加氢转化最大的瓶颈问题为如何有效控制C-O键的活化、C—C键的形成、碳链增长及终止。本文主要综述 CO/CO₂加氢高选择性合成重要化工原料低碳烯烃（C₂ ⁼～C₄ ⁼）以及一步高效合成汽油馏分（C₅～C₁₁）等方面取得的突破性进展。目前,CO/CO₂加氢主要经过费托合成与氧化物/分子筛双功能两条路线合成低碳烯烃与汽油燃料。针对费托合成C₂ ⁼～C₄ ⁼,分析表明棱柱状碳化钴得到的烃类产物分布可以显著突破Anderson-Schulz-Flory（ASF）分布的限制,而分子筛已被广泛用于构建双功能费托催化剂,由于酸性分子筛具有加氢裂化、低聚与异构化等功能,使得CO/CO₂还可以直接高选择性地转化为C₅～C₁₁烃类。另一方面,将可以活化CO或CO₂到甲醇的可还原型氧化物与具有C—C偶联功能的SAPO-34或HZSM-5分子筛进行耦合,也可以实现CO/CO₂加氢一步合成低碳烯烃或汽油且具有非常优异的选择性和高转化率。今后,借鉴纳米合成领域新方法,使产物分布打破经典ASF限制,最大限度地提高目标烃类化合物的选择性并显著减少甲烷的生成是研究关键。     

纳米Ga-ZSM-5分子筛的合成及其在苯和稀乙烯烷基化反应中的应用

采用晶种导向法合成了一系列不同硅镓比的纳米级Ga-ZSM-5分子筛,经过挤条成型、酸洗以及高温焙烧等处理后得到了纳米Ga-ZSM-5分子筛催化剂。利用多种表征技术对Ga-ZSM-5分子筛的结构和酸性质进行了表征,研究了其催化苯与稀乙烯烷基化反应性能。结果表明,水热合成的Ga-ZSM-5分子筛具有十字孪晶状形貌,晶粒尺寸均匀。与相同n（Si）/n（T）（T为金属原子）的Al-ZSM-5分子筛相比,Ga-ZSM-5分子筛的酸量和酸强度明显降低。在反应温度为360 ℃、压力为1.4 MPa、乙烯质量空速（WHSV）为1.5 h^-1、n（苯）∶n（乙烯）=1∶1,n（乙烯）∶n（氮气）=1∶5.67的反应条件下,Ga-ZSM-5分子筛催化剂表现出了较高的乙基选择性,副产物二甲苯比Al-ZSM-5减少了30%~50%,且在100 h内稳定运转,具有更好的抗积炭能力。     

Pt/ZSM-35催化长链正构生物烷烃加氢裂化/异构化制航空煤油

以生物质油加氢脱氧得到的长链正构生物烷烃为原料，考察了H-MCM-49、H-ZSM-5、H-ZSM-22和 H-ZSM-35这4种不同分子筛催化剂的物化性质及其加氢裂化/异构化制生物航空煤油的性能。在此基础上，以H-ZSM-35分子筛为载体，制备并表征了一系列低负载量（0.1%、0.2%和0.3%）的Pt/ZSM-35双功能催化剂，以长链正构生物烷烃转化率、C₉~C₁₆产物选择性、生物航空煤油收率和异正比为指标，对其加氢裂化/异构化制生物航空煤油反应性能进行了评价，并对反应工艺条件进行优化。结果表明：H-ZSM-35的强酸中心强度高、酸量大，其结构中较小的孔口和较大的球型笼使其具有一定的容烃量和较好的择形性能，0.1%~0.3% Pt负载后， Pt/ZSM-35双功能催化剂表现出很好的加氢裂化/异构化活性和选择性。采用0.1% Pt/ZSM-35双功能催化剂在反应条件为320℃、1MPa、0.7h^-1、氢油比840∶1时，长链正构生物烷烃的转化率为84.3%，生物航空煤油收率达41.1%，产物异正比为1.34。81h长运转测试结果表明，该催化剂具有很好的稳定性。     

Aromatization of methane in the absence of oxygen over Mo-based catalysts supported on different types of zeolites

The catalytic performance of Mo-based catalysts supported on various zeolites has been studied for methane aromatization in the absence of oxygen in a fixed-bed continuous-flow quartz reactor, and their catalytic properties are correlated with features of zeolite structure. It was found that H-type silica–alumina zeolites, such as ZSM-5, ZSM-8, ZSM-11 and β possessing two-dimensional structure and pore diameter equaling the dynamic diameter of a benzene molecule (about 6 Å) simultaneously, are fine supports for methane activation and aromatization catalysts. Among them, MoO₃/H-ZSM-11 has the best activity and stability; for instance, a methane conversion of 8.0% and selectivity higher than 90% was obtained at 973 K. The catalytic performance of MoO₃/H-ZSM-8 is somewhat lower than that of MoO₃/H-ZSM-5, while activity of MoO₃/H-β is lower than that of MoO₃/H-ZSM-8. Catalysts supported on H-MCM-41 and H-SAPO-34 exhibit low activity for methane aromatization and those supported on H-MOR, H-X and H-Y give only a little amount of ethylene. Over MoO₃/H-SAPO-5 and MoO₃/H-SAPO-11 no hydrocarbons were detected.     

H-beta分子筛催化苯与甲醇烷基化反应性能

采用两种促进剂协同作用改性制得了H-beta分子筛催化剂,通过XRD、BET及Py-IR对催化剂结构、比表面积及酸性变化进行表征,并将催化剂用于苯与甲醇烷基化测试其催化性能。结果表明,在反应压力为常压、反应温度400℃、空速2 h-1和苯与甲醇物质的量比为1∶1的最优条件下,苯转化率达到42. 5%、甲苯选择性为74. 6%,甲苯和二甲苯总选择性达到了94. 5%。基于结构及性能的研究,探讨了催化烷基化反应机理。     

In situ DRIFT study of the reactivity and reaction mechanism of catalysts based on iron–molybdenum oxides encapsulated in Boralite for the selective oxidation of alkylaromatics

An in situ DRIFT investigation of the behavior of iron–molybdenum oxides encapsulated in Boralite (FeMo/Bor) during the oxidation of toluene is reported. The study was carried out to obtain a better understanding of the differences between this catalytic material and (i) V–TiO₂ based catalysts and (ii) bulk Fe₂(MoO₄)₃. V–TiO₂ based catalysts show a severe decrease in the selectivity to benzaldehyde with increasing conversion of toluene, in contrast FeMo/Bor samples. The effect was attributed to the presence of stronger Lewis acid sites in vanadium-based catalysts which, activating the carbon atom of the carbonyl groups, facilitate its nucleophilic attack to form benzoate species which further degrade to carbon oxides. FeMo/Bor shows higher selectivity at low conversion than bulk Fe₂(MoO₄)₃, probably due to the presence of nanosized iron–molybdate particles inside the zeolite channels, and lower selectivity at high conversion. Due to back-diffusion limitations inside the zeolite pores, the aromatic ring of the alkylaromatic is oxidatively attacked to form maleic anhydride, precursor of the further oxidation to carbon oxides. In FeMo/Bor a different main pathway is responsible for the lowering of selectivity at high conversion with respect to V–TiO₂ based catalysts.