Methylation of 2-Methylnaphthalene with Methanol over NH_4 F and Pt Modified HZSM-5 Catalysts

Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH 4 F and Pt modified HZSM-5 (SiO 2 /Al 2 O 3 = 83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,3,5-trimethylbenzene (1,3,5-TMB) as a solvent. Pt promoted HZSM-5 catalysts showed low concentration of coke-like polycondensed aromatics, NH 4 F modification decreased non-shape-selective acid sites. After Pt and NH 4 F co-modification, both conversion of 2-MN and selectivity to 2,6-DMN were improved. 6%NH 4 F/0.5%Pt/HZSM-5 catalyst exhibited 13.8% of 2-MN conversion with 6.2% of 2,6-DMN yield after 7 h time on stream (TOS), and 2,6-/2,7-DMN ratio of 1.7 after 10 h of TOS.

Secondary Crystallization of Na_2CO_3-Modified HZSM-5 Zeolites with Tetrapropylammonium Hydroxide and Their Catalytic Performance in Thiophene Alkylation Reaction

The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting samples were characterized by a complementary combination of X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, X-ray fluorescence spectroscopy, XPS, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, BET and temperature-programmed desorption techniques. The results showed that the secondary crystallization of the HZSM-5 zeolite could result in migration of non-framework species from the internal channels to the zeolite surface and their transformation into framework species. The catalytic activity of these modified samples for thiophene alkylation was evaluated. Both the activity and stability of the catalysts were improved after secondary crystallization.

Fe-modified HZSM-5 catalysts for ethanol conversion into light olefins

A series of Fe/HZSM-5 catalysts with different iron loadings were prepared by impregnation method.Characterization was performed by N2 adsorption-desorption,X-ray diffraction（XRD）,NH3 temperature-programmed desorption（NH3-TPD）,temperature-programmed reduction （TPR）,temperature-programmed oxidation（TPO）and thermogravimetry（TG）analysis.Iron content in the synthesized samples varied from 1.1 wt%to 20 wt%.The obtained samples have been used for ethanol conversion into light olefins.It was found that the amount of strong acidity at 300 -5 50-C on Fe-modified samples was decreased,going with another new acid site appearance at 550- 600-C and that Fe/HZSM-5 catalysts were highly selective towards light olefins,especially the 9FZ sample.In addition,Fe-modified catalysts suppressed the conversion of ethanol to aromatics and paraffins and enhanced their anti-carbon deposit ability.

Catalytic performance of imidazole modified HZSM-5 for methanol to aromatics reaction

A facile approach was developed for the preparation of nano-sized HZSM-5 with a hierarchical mesoporous structure by adding imidazole into conventional zeolite synthesis precursor solution. The physicochemical properties of modified HZSM-5 were characterized by X-ray diffraction（XRD）, N;adsorption–desorption isotherms, scanning electron microscopy（SEM）, NH;-temperature-programmed desorption（NH;-TPD） and pyridine adsorption infrared spectroscopy（Py-IR）. The coke in spent catalysts was characterized by thermogravimetry（TG）. The results showed that hierarchical HZSM-5 zeolites with excellent textural properties, such as abundant porous structure, uniform particle size and suitable acidity, could be synthesized by the recipe of one-pot synthesis routes. Moreover, the obtained HZSM-5 exhibited higher selectivity of total aromatics as well as longer lifetime in the catalytic conversion of methanol to aromatics, comparing with conventional HZSM-5. It is expected that the synthesis approach demonstrated here will be applicable to other zeolites with particular textural properties and controllable particle sizes, facilitating the emergence of new-type porous materials and their related applications in catalysis and separation.

Catalytic conversion of asphaltenes to BTXN using metal-loaded modified HZSM-5

HZSM-5 zeolites with Si/Al ratios of 20,35,50 and 65 were prepared by the directing crystallization process of silicalite-1 seeds.The influence of Si/Al ratios on the production of benzene,toluene,xylene and naphthalene(BTXN)originated from asphaltenes catalytic pyrolysis was explored by adopting Py-GC/MS.Modified Z5-50 zeolites were prepared by various metal ions(Ni^(2+),Mo^(6+),Fe^(3+),and Co^(2+))with different loading rates(3%(mass),5%(mass),7%(mass),and 9%(mass))and the physical and chemical properties of these zeolites were characterized by XRD,SEM,ICP-OES,XPS,NH_(3)-TPD,FTIR,Py-IR and N_(2)adsorption-desorption isotherm.In addition,they were employed to catalyze the conversion of asphaltenes pyrolysis production to BTXN using Py-GC/MS.Results show that the highest relative content of aromatics has been obtained over HZSM-5 with Si/Al ratio of 50(Z5-50),reaching 61.87%.Besides,the loading of Ni,Mo,Fe,and Co on Z5-50 leads to an increase of acid strength and provides new active sites.The relative content of BTXN increases by 3.17%over 3Ni-Z5,which may be ascribed to that Ni promoted the conversion of polycyclic aromatic hydrocarbons(PAHs)to monocyclic aromatics due to the cracking of aliphatic side chains of PAHs and the decrease of phenolic activation energy.While under the catalysis of 5Mo-Z5,the relative content of aromatics and BTXN augmented by 5.75%and 4.02%,respectively.In addition,the highest relative content of aromatics reaches 70.09%when the loading rate of Fe was 7%(mass),and the relative content of BTXN increases from 25.87%to 29.42%.The results demonstrate that the active sites provided by different metal species expressed diverse effects on BTXN.Although the Bronsted/Lewis acid ratios of HZSM-5 modified by metal decreased,the acid strength and the relative content of BTXN both increased,which illustrated that there is a synergistic catalysis with the Bronsted acid sites and Lewis acid sites provided by metal species.In general,the performance of the catalyst is affected by the pore structure,acidity and metal active sites.Moreover,the possible formation mechanism of BTXN derived from asphaltenes catalytic pyrolysis was proposed on the basis of structural features and catalytic performances of a series of zeolites.

Properties and Characterization of Modified HZSM-5 Zeolites

Physicochemical and catalytic properties of phosphorus and boron modified HZSM-5 zeolites treated with 100% steam at 673 K were investigated. The acidity and distribution of acidic sites were studied by infrared spectroscopy using pyridine as probe molecule and temperature programmed desorption (TPD) of ammonia. The structure of the samples was characterized by XRD, and the textural properties of the catalysts were determined by nitrogen isothermal adsorption-desorption measurements and scanning electron microscopy (SEM). The XRD results show that the modified samples have no novel crystalline phase, indicating a high dispersion of phosphorus and boron species. After treatment, the microporous volume and surface area of the samples markedly decrease, implying the blockage of the channel. The nitrogen adsorption-desorption measurements suggest that the isothermal type of all samples is a combination of isothermal type I and IV, and all hysteresis loops resemble the H4-type in the IUPAC classification. The total acidity of the modified samples, determined by pyridine adsorption IR and TPD of ammonia, decreases in contrast to that of the parent HZSM-5. The conversion of n-heptane over P and B steam-modified HZSM-5 is higher than that of P and B-modified HZSM-5 zeolites but lower than that of the parent HZSM-5.

Catalytic activity of phosphorus and steam modified HZSM-5 and the theoretical selection of phosphorus grafting model

The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.

Catalytic cracking of 1-butene to propylene by Ag modified HZSM-5

Silver modified HZSM-5 （AgHZ） zeolite catalysts were prepared by ion exchange method and their catalytic properties in the l-butene cracking reaction were measured. The catalysts were characterized by infrared spec- troscopy with pyridine adsorption （Py-IR）, N2 adsorption and X-ray diffraction （XRD）. The effects of Ag loading and steaming treatment on catalytic performances were studied. It is found that the activity ofHT_SM-5 （HZ） catalyst significantly decreases with the steaming time, whereas AgHZ catalysts show stable activity in the steaming time of 24-48 h and their activities increase with the Ag loading. When the steaming time is 24-48 h, the yield of propylene over HZ catalyst significantly decreases, whereas it is stable over AgHZ catalysts. The AgHZ catalysts with Ag loadings of 0.28%-0.43% （by mass） show similar propylene yields （-30%）, which are higher than that over the AgHZ catalyst with a Ag loading of 0.55% （by mass）. These results indicate that the steam-treated AgHZ catalysts with optimum Ag loadings have higher yield of propylene and are more stable than the steam- treated HZ catalyst. The regeneration stability measurement in butene cracking also shows that the AgHZ catalyst steam-treated under a suitable condition has better stability than the HZ catalyst.

果糖酸处理HZSM-5己烯芳构化催化剂的结构及性能

为提高HZSM-5己烯芳构化催化剂的BTX(苯、甲苯、二甲苯)选择性和寿命,利用果糖酸对HZSM-5进行处理(F-HZS),并与磷酸和硝酸处理的HZSM-5(P-HZS和N-HZS)进行对比,采用XRD、XRF、N_(2)吸附-脱附、NH_(3)-TPD、Py-FTIR等方法对催化剂结构进行表征,考察了催化剂己烯芳构化的催化性能。实验结果表明,酸处理后催化剂的MFI结构保留完整,且出现了介孔结构。催化剂的孔体积、硅铝比及B酸量和L酸量比值(B/L)增加,但酸量及酸强度下降,F-HZS的B/L最高,BTX选择性和寿命也明显高于P-HZS和N-HZS。在0.2 MPa、405℃,质量空速2 h-1条件下,F-HZS的BTX选择性为61.34%,寿命为60 h。

花生秸秆热解挥发分在HZSM-5负载Ga催化剂上的裂解特性

生物质热解能够将木质纤维素类生物质转化为生物油,但粗油含氧量高、热值低。利用负载Ga的HZSM-5催化剂对生物质热解挥发分进行催化裂解,可以促进生物油的选择性脱氧和芳构化,实现生物油提质。分别采用离子交换法和水热法制备了两种负载Ga的HZSM-5催化剂(Ga-H5-E和Ga-H5-H),采用两段式固定床反应器进行了花生秸秆热解在线联合热解挥发分催化裂解实验。花生秸秆在反应器下段以10℃/min的加热速率从室温升温至700℃,其间逸出的挥发分通过保持在600℃的上段催化剂层进行催化裂解。结果表明,相比无负载的HZSM-5,Ga-H5-E和Ga-H5-H使BTX(苯、甲苯和二甲苯)产率分别提高了77%和93%,其中甲苯和二甲苯的增加尤为明显。采用热重分析仪、电感耦合等离子发射光谱仪、X射线衍射仪、扫描电子显微镜、能量色散X射线光谱仪、比表面积分析仪和化学吸附仪等对催化剂进行了表征分析。结果表明,两种Ga负载催化剂的积炭产率显著低于原催化剂(HZSM-5);Ga负载使催化剂强酸位显著增多,有利于增加脱氧反应的催化活性中心;相比于Ga-H5-E,Ga-H5-H含有容积较大的介孔和较小的平均孔径,而且更多Ga浸入了颗粒内部,这些差异可能促进乙烯和丙烯在介孔内发生芳香化反应,从而提高了单环芳香烃产量。

Ce改性HZSM-5分子筛催化甲醇与丁烯耦合转化制丙烯性能研究

为了进一步提高HZSM-5分子筛在甲醇与丁烯耦合转化制丙烯反应中的催化性能,采用浸渍法对HZSM-5分子筛进行Ce改性,得到了一系列具有不同Ce负载量的x Ce/HZSM-5催化剂。考察了Ce负载量和反应条件(甲醇与丁烯物质的量之比、反应温度和空时)对催化性能的影响,并结合催化剂表征结果,分析了Ce改性对催化性能和物化性质的影响,探讨了x Ce/HZSM-5催化剂的构效关系。结果表明,在温度550℃、压力0.1 MPa、甲醇与丁烯物质的量之比0.8、空时2.3(g cat·h)mol CH_(2)的最佳反应条件下,Ce负载量(w)为2.5%的2.5Ce HZSM-5催化剂具有最高的丙烯收率,为41.9%。Ce与HZSM-5分子筛上羟基官能团(OH)发生相互作用,降低了B酸酸量,同时生成新的L酸中心Ce(OH)^(2+),调变了催化剂表面酸中心密度和酸类型分布,提高了丙烯选择性和收率。

水热预处理Zn/HZSM-5催化剂对其催化乙烯芳构化反应性能的影响

针对用于低碳烯烃芳构化的Zn/HZSM-5催化剂存在易于结焦失活的问题,采用高温水热的方法对催化剂进行预处理,通过XRD、N2物理吸附-脱附、NH3-TPD、Py-FTIR、XPS和TG等技术对样品进行表征,并以乙烯芳构化为探针反应考察了高温水热预处理对催化剂反应性能和稳定性的影响。结果表明,Zn/HZSM-5催化剂经高温水热预处理48 h后表现出优异的催化性能,虽然乙烯转化率略微降低,但是催化剂寿命显著延长,由72 h延长至216 h,同时芳烃选择性保持在60%以上;水热处理促进了ZnO物种与B酸中心的相互作用及ZnOH+物种的生成,在抑制氢转移反应的同时显著促进了催化剂的脱氢性能,提高了氢气选择性;此外,水热处理后催化剂容碳量明显增加、积炭速率降低,表现出优异的抗结焦积炭特性。

纳米片状HZSM-5在联苯甲基化中的应用

采用晶种导向的方法合成了一系列具有不同硅/铝比、不同b轴厚度的纳米片状HZSM-5催化剂。利用XRD、SEM、NH 3-TPD、N_(2)吸附-脱附等手段对催化剂的物理和化学性质进行表征,并在反应温度为380℃、反应压力为0.1 MPa和进料速率为MHSV=1.0 h-1的反应条件下考察了硅/铝比和纳米片状HZSM-5 b轴厚度对于联苯甲基化反应性能的影响。研究结果表明,随着纳米片状HZSM-5硅/铝比降低,联苯转化率提高,同时4-甲基联苯(4-MBP)的选择性也小幅上升,4-MBP收率大幅提高;但催化剂失活严重,稳定性下降。在硅/铝摩尔比为20的条件下,通过提高晶种加入量,可将纳米片状HZSM-5的b轴厚度从100 nm降至20 nm。纳米片状HZSM-5的直孔道促进了反应物与产物分子在沸石微孔内的扩散,减缓了副反应的发生以及积炭的形成,提高了催化剂的稳定性;催化剂单程寿命从8 h延长到30 h。

Fe/HZSM-5催化剂类芬顿体系去除罗丹明B

本文以HZSM-5为载体、Fe(NO_(3))_(3)·9H_(2)O为铁源,采用过量浸渍法制备了不同负载量的Fe/HZSM-5催化剂,并将其与H_(2)O_(3)组成类芬顿体系用于降解罗丹明B。对所制备的材料进行了XRD、FT-IR、N_(2)吸附-脱附、NH,-TPD等表征分析。结果表明:Fe以Fe_(2)O_(3)的形式存在于HZSM-5中,负载铁后对HZSM-5的结构未产生明显的影响,但使其酸量略有降低。以5%-Fe/HZSM-5为催化剂的类芬顿体系处理50mL浓度为10mg·L^(-1)的罗丹明B溶液,在反应温度55℃、过氧化氢用量0.12mL、催化剂投加量0.03g的条件下,在较宽的pH范围(1~5)反应30min后,罗丹明B去除率均可达93%以上。

飞灰基HZSM-5催化松木热解选择性制备芳烃

以飞灰为原料,采用酸洗与碱熔联合预处理耦合水热法制备了飞灰基HZSM-5(FA-HZSM-5)催化剂,并应用于松木催化热解制备芳烃的研究。系统考察了FA-HZSM-5制备过程中盐酸溶液浓度、碱灰比等预处理参数对FA-HZSM-5理化特性的影响,揭示了催化剂制备条件和热解过程参数对芳烃选择性生成的调控机制。结果表明,与商业HZSM-5相比,FA-HZSM-5具有较大的孔结构以及温和的酸强度,有利于单环芳烃(MAHs)的生成,并大幅降低多环芳烃(PAHs)的产率。当盐酸浓度为10%、碱灰比为1.5、热解温度为650℃、催化剂/松木比为20时,芳烃产率达到最大值10.82%。其中,MAHs产率为7.65%,PAHs产率为3.17%,相较于商业HZSM-5,PAHs产率降低了26.11%。

Comparative study on pyrolysis of bamboo in microwave pyrolysis-reforming reaction by binary compound impregnation and chemical liquid deposition modified HZSM-5

The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis(CFP)process.To reduce the coke formation,binary compound impregnation(BCI)and chemical liquid deposition(CLD)were used to modify HZSM-5 catalysts.At the same time,the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor,which made the catalytic effect more thorough.Experimental results indicated that CLD used TiO 2 deposition to cover external acid sites,while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways.Within the scope of the loaded amount studied,the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased,while the coke formation reduced continuously.BTX(benzene,toluene and xylene),the most valuable product in bio-oil,drastically increased by 39.1%and 22.6%respectively over the CLD and BCI modified catalysts.Considering the catalytic performance as well as cost,CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.

HZSM-5 的低温水热改性及其己烯芳构化性能

对HZSM-5在70,100和150℃下进行低温水热改性,分别制得催化剂T 70-HZ-5,T 100-HZ-5和T 150-HZ-5,利用X射线衍射仪、X射线荧光光谱仪、物理吸附仪、化学吸附分析仪和红外光谱仪等对上述催化剂进行表征,并对其己烯芳构化催化性能进行了评价。结果表明:低温水热改性保持了HZSM-5的完整晶相结构,提高了其硅铝比[n(Si)/n(Al)],B酸和L酸酸量比(B/L)及平均孔径;酸量的降低和孔径的增大有利于HZSM-5寿命的延长,B/L值的增大有利于选择性的提高;在反应温度405℃,反应压力0.2 MPa,质量空速2 h-1的条件下,T 100-HZ-5的催化寿命可达44 h,比改性前延长了36 h;当反应8 h时,HZSM-5的苯、甲苯和二甲苯混合物(BTX)选择性已迅速降到35%左右,而T 100-HZ-5的仍接近55%。

Ni-MgO复合改性对HZSM-5分子筛催化性能的影响

采用等体积浸渍法制备了Ni和MgO改性的HZSM-5催化剂,考察Ni和MgO含量对甲醇制备丙烯的影响,并利用XRD、SEM、BET、NH 3-TPD等方法考察了Ni和MgO对HZSM-5分子筛的酸强度和结构的影响,结果表明,少量的Ni-Mg复合改性的HZSM-5分子筛MFI结构没有改变,但有效改变了催化剂的酸强度和孔径结构,显著降低催化剂中强酸含量,微孔孔径由0.5105 nm降为0.5016 nm,0.5%Ni-0.5%Mg/HZSM-5分子筛表现出较佳的丙烯选择性,丙烯的选择性提高了11.5%。

HZSM-5 zeolites undergoing the high-temperature process for boosting the bimolecular reaction in n-heptane catalytic cracking

High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.