小晶粒ZSM-5分子筛的合成、改性与应用综述

沸石分子筛的粒径大小是影响其性能的一个重要参数。小晶粒ZSM-5分子筛因其具有更大的外表面积,更多的活性中心,高表面能,在提高催化剂利用率,增加大分子转化能力,减小深度反应,提高选择性以及降低结焦失活等方面均表现出优越性能,得到人们的广泛关注。本文综述了小晶粒ZSM一5分子筛的合成方法,改性手段与催化应用优势。     

含钛复合载体对长链烷烃脱氢催化剂性能的影响

采用浸渍法、沉淀法和共沉淀法制备了含钛复合载体,并制备Pt—sn双金属催化剂;分别采用XRD、TEM、Py-IR对所制得样品的晶相和表面酸性能进行了表征。结果表明,制备方法对含钛复合载体的存在形态有一定的影响;含钛复合载体表面只有L酸位,且共沉淀法制备的含钛复合载体的酸性最弱;共沉淀法所得含钛复合载体制得的催化剂表现出最好的催化剂活性稳定性和单烯烃选择性。     

ZSM-48分子筛的制备及其加氢异构催化性能研究

通过静态水热法合成了系列低硅铝比,且具有一维十元环孔道的酸性、孔径适中的ZSM-48分子筛,考察晶种加入量对晶化时间、结晶度和酸性的影响。选用结晶度较高的分子筛作为酸性组分与拟薄水铝石一起通过挤条成型、浸渍贵金属Pt,制得加氢异构裂化催化剂。选用正十六烷为模型化合物,在固定床微反装置上研究催化剂加氢异构性能,结果表明,加入晶种后合成的分子筛加氢异构活性大为提高。     

模板剂对SAPO-34分子筛性能的影响研究

采用XRD、SEM、NH3-TPD等方法深入研究了以三乙胺(TEA)、四乙基氢氧化铵(TEAOH)及二者的混合物为模板剂合成的产物的结构及物化性能。并以甲醇为探针分子,在固定床反应器上对合成产物在甲醇制取烯烃(MTO)反应中的催化性能进行了评价。结果表明,模板剂的种类及配比对所得产物的晶相结构、晶粒大小、酸强度、酸量以及催化性能有重要影响。双模板体系中,当TEAOH/ TEA=0.037～0.186时,可以得到纯SAPO-34分子筛;且当TEAOH/TEA=0.093时,得到的SAPO-34分子筛晶粒较小(1.0μm左右)且均匀,酸度适中,低碳烯烃(C2=～C4=)的选择性94.98%,催化寿命415min,较单独以TEA(TEA/Al2O3=2.15)或TEAOH(TEA/Al2O3=2.0)为模板剂合成的催化剂的低碳选择性 (88.22%和89.29%)和寿命(170min和165min)均有明显提高,且积炭速率(0.016%/min)明显降低。     

ZSM-5分子筛酸性和晶体大小对醛氨缩合合成吡啶碱的影响

针对Chichibabin醛氨缩合合成吡啶碱,用离子交换法制备具有相同酸性位类型,但Br?nsted(B)酸量不同的ZSM-5催化剂,并选择硅铝比接近但晶粒大小不同的H-ZSM-5分子筛,以及与ZSM-5具有相同MFI晶体结构的TS-1分子筛进行催化性能的比较。探讨了ZSM-5分子筛催化剂酸性、酸量和晶粒大小对反应活性、吡啶碱选择性和收率以及催化剂稳定性的影响。结果表明B酸位是进行醛氨缩合反应合成吡啶碱不可缺少的活性位,但酸强度较弱的末端硅羟基B酸位合成吡啶碱的活性较低;催化剂B酸含量越大,其进行醛氨缩合反应的初始活性和吡啶碱收率越高,催化剂失活越慢;小晶粒分子筛的初始活性、稳定性优于大晶粒分子筛,但合成吡啶碱的选择性和初始收率较低,这主要是因为与大晶粒分子筛相比,小晶粒分子筛具有更多的活性中心,特别是外表面活性中心,和相对较短的分子筛孔道。     

ZSM-5分子筛上轻烃裂解性能:晶粒尺寸的影响

设计合成了纳米、亚微米和微米级晶粒尺寸ZSM-5分子筛,并研究了其在两种反应温度下(510,650℃)对正庚烷催化制低碳烯烃反应行为。结果表明,在反应初始阶段,两种反应温度下晶粒尺寸对正庚烷转化率和产物选择性影响较小。但随着反应进行,纳米和亚微米ZSM-5在510℃下反应性能(低碳烯烃选择性及反应活性稳定性)相近且均高于微米ZSM-5;而650℃下,具有更短扩散路径和更大外表面积的纳米ZSM-5则体现出更高的反应性能。微米ZSM-5在两种温度下虽具有相对较高的低碳烯烃选择性,但其活性稳定性最低。进一步研究晶粒尺寸对费-托过程中石脑油催化裂解性能的影响发现,亚微米ZSM-5表现出最高的催化反应性能,这可能与反应原料的组成及相关反应途径变化有关。     

Influence of synthesis method on the properties and catalytic performance of MCM-49 zeolites

Highly crystalline and pure MCM-49 was hydrothermally synthesized by dynamic and static methods, respectively. The properties of the samples were studied by N₂ adsorption, XRD, TEM and FT-IR techniques. The results indicated that MCM-49 synthesized by dynamic method showed much smaller crystal and lower concentration of acid sites. The Pd-supported catalyst on MCM-49 synthesized by static method showed higher acetone conversion in one-step synthesis of methyl isobutyl ketone from acetone, which was attributed to higher concentration of acid sites. While the higher selectivity to methyl isobutyl ketone for Pd-supported on MCM-49 synthesized by dynamic method might be related with the lower acidity and higher BET surface area.     

Hydrogen adsorption on metal-organic framework (MOF-5) synthesized by DMF approach

Metal-organic frameworks (MOFs), especially MOF-5, are believed to be promising new porous materials for hydrogen adsorption. A comparative study of material synthesis, characterization and hydrogen adsorption was performed to examine the effects of different synthesis conditions on crystal structure, pore textural property and hydrogen adsorption performance of MOF-5 materials. Three MOF-5 samples synthesized with dimethyl formamide (DFM) as solvent and slightly different procedures have shown similar phase structure and chemical composition, diverse crystal structures, varying pore textural properties and different hydrogen adsorption performance. It was established from the experimental results that higher order of crystallinity in the MOF-5 materials generates better adsorbents with larger crystal size, higher specific surface area, uniform pore size distribution (PSD), larger hydrogen adsorption capacity and faster hydrogen diffusion rate in MOF-5 adsorbents. The best MOF-5 sample synthesized in this work (MOF-5(γ)) has a Langmuir specific surface area of 1157 m²/g; it can adsorb 0.5 wt.% of hydrogen at 77 K and 800 mmHg; and results in hydrogen diffusivity inside MOF-5 crystal of 2.3 × 10⁻⁹ cm²/s. The density functional theory reasonably predicts the presence of mesopores and macropores in all three MOF-5 samples synthesized in this work.     

The Crystal Size Effect of Nano-Sized ZSM-5 in the Catalytic Performance of Petrochemical Processes: A Review

The ZSM-5 catalyst has received significant attention in recent years due to its significant properties such as strong acidity and high surface area. Crystal size of the catalyst has been recognized as an important factor in its performance. This review investigates the effects of the crystal size of ZSM-5 on its catalytic performance—selectivity; conversion; lifetime, product distribution; and coke formation during methanol to hydrocarbons (MTH), methanol to dimethyl ether, ethanol to gasoline (ETG), ethylene to gasoline (ETG), acetone to gasoline (ATG), acetone to olefin (ATO), naphtha cracking, and and n-dodecane cracking processes. This study demonstrates that the reduction of crystal size leads to higher levels of activity, conversion, and stability in these various processes.     

复合模板剂诱导合成SAPO-34分子筛及其MTO性能研究

利用传统水热合成方法,分别采用单一模板剂、混合模板剂合成纯相SAPO-34分子筛,采用XRD、BET、SEM、NH3-TPD和FTIR对样品进行表征,考察其在甲醇制烯烃反应中的催化性能。结果表明,混合模板剂诱导合成的SAPO-34分子筛具有较小的颗粒尺寸,较大的比表面积和适宜的酸性,可以在MTO反应中表现出更优的催化性能。结果发现,MORTEAOH混合模板剂合成的SAPO-34分子筛的催化寿命达320 min,双烯选择性超过82%。     

PEG2000对MCM-22分子筛结构特性和催化性能的影响

以六亚甲基亚胺为模板剂,在动态水热合成MCM-22分子筛的过程中,加入有机辅助剂聚乙二醇2000(PEG2000),考察有机辅助剂PEG2000对MCM-22分子筛结构、酸性以及催化性能的影响。由X射线衍射谱图可以看出,合成时加入适量的PEG2000,可以得到结晶较好的MCM-22晶体,但结晶度稍微有些降低。由氮吸附脱附测试结果可以看出,适量助剂PEG2000的加入,改变了分子筛的最可几孔径分布,最可几孔径由0.556 nm提高至0.587 nm,孔容由0.35 m3/g增加到0.59 m3/g,BET比表面积由410 m2/g增加到456 m2/g。NH3-TPD方法测试样品的酸性结果显示,加入适量的PEG2000后,分子筛的强酸位得到加强。另外用合成的分子筛作为催化剂,以苯与丙烯烷基化为模型反应,考察了MCM-22分子筛的活性以及选择性,结果显示催化剂的活性有较大提高,然而对异丙苯的初始选择性降低,随着反应的进行,异丙苯的选择性却很快地增长。     

溶剂辅助超细二氧化锆纳米晶体的可控合成

在溶剂辅助作用下,通过蒸汽相水解一步合成了具有高比表面积的超细二氧化锆纳米晶体, 着重研究了前体浓度与溶剂种类等合成因素对二氧化锆纳米晶体结构的可控性。采用X射线衍射（XRD）、N₂吸附-脱附、扫描电镜（SEM）、透射电镜（TEM）、选区衍射（SAED）等手段对纳米晶体的结构进行了表征。结果表明,合成的样品具有高达237~450m²/g的比表面积和平均粒径小于5nm的超细纳米晶体颗粒。研究还发现,在较低的前体浓度和溶剂存在的条件下合成的样品显示了纯四方相结构和更高的比表面积,增加前体浓度或无溶剂条件下合成的样品则具有四方相和单斜相的混合相结构和更低的比表面积,表明通过调变前体浓度和溶剂可以实现对二氧化锆纳米晶体的晶相、比表面积和颗粒尺寸的有效调控。     

Toluene ethylation over metallosilicates of MFI structure. Effects of acidity and crystal size on para-selectivity

Toluene ethylation with ethanol over Al-MFI and B-, Fe-, Ga-isomorphously substituted zeolites of MFI structure was carried out. The acid properties of the metallosilicates increased in the order B < Fe < Ga < Al. This order is reflected in the activity of the zeolites in terms of toluene conversion. The separate effects of crystal size variation and acidity change by isomorphous substitution on para product selectivity have been established.     

制备方法对锆硅分子筛的催化性能影响

分别以水热法(DHT)、干胶法(DGC)和溶胶-凝胶法(Sol-Gel)合成了锆硅杂原子分子筛,采用XRD、TPD、SEM、TEM、FT-IR、N_2吸附-脱附等对分子筛样品的晶相结构、表面形貌、比表面积、孔径分布以及表面酸性进行表征。结果表明,水热法制备的锆硅杂原子分子筛特征峰明显,具有较高的结晶度,分子筛以微孔为主,并具有较多的酸中心和较大的比表面积,在α-蒎烯异构化反应中表现出较好活性和较高的柠檬烯选择性。     

模板剂对ZSM-5分子筛甲醛环化制三聚甲醛性能的影响

以四丙基氢氧化铵、四丙基溴化铵、正丁胺和季戊四醇为模板剂水热合成ZSM-5分子筛,采用XRF、XRD、SEM、NH₃-TPD、Py-FTIR和²⁷Al MAS NMR等进行了表征,研究了模板剂对ZSM-5分子筛性质及甲醛制三聚甲醛催化性能的影响。结果表明,通过改变模板剂可改变ZSM-5分子筛的酸中心分布、表面酸性质和粒径;较大空间的孔道交叉位置的酸性中心、小催化剂粒径和高表面B酸/L酸比值有利于提高三聚甲醛选择性。以四丙基氢氧化铵为模板剂合成的ZSM-5分子筛的颗粒尺寸为240nm×240nm×150nm,分布于直形孔道和S形孔道的孔道交叉处的Br?nsted酸中心较多,甲醛转化率和三聚甲醛的选择性分别为30.15%和88.35%。     

分子筛负载型加氢脱硫催化剂的制备及其性能

采用溶胶-凝胶法低温一步合成了2种纳米介孔分子筛,对合成的样品进行了表征,并将其分别负载30% Ni2P(Co2P),将该催化剂用于噻吩加氢脱硫实验,考察了其加氢脱硫性能及稳定性. 结果表明,样品具有介孔特性,晶粒粒径约30 nm,孔径集中在20 nm左右,比表面积为400 m2/g,有一定弱酸性,有较好的热稳定性. 4种催化剂的第一次加氢脱硫率以CTAC为模板剂的载体比以CTAB为模板剂的载体高,以Co2P为活性组分比Ni2P高,低温比高温高. 4种催化剂第二次加氢脱硫率都有较大程度的降低,以Ni2P为活性组分的催化剂减少比Co2P高,360℃比300℃高,以CTAB为模板剂所制催化剂减少比CTAC高.     

A high‐resolution solid‐state NMR study on nano‐structured HZSM‐5 zeolite

Variations in the structure and acidity properties of HZSM‐5 zeolites with reduction in crystal sizes down to nanoscale (less than 100 nm) have been investigated by XRD, TEM and solid‐state NMR with a system capable of in situ sample pretreatment. As evidenced by a combination of ²⁷Al MAS NMR, ²⁹Si MAS, CP/MAS NMR and ¹H MAS NMR techniques, the downsize of the zeolite crystal leads to an obvious line broadening of the ²⁷Al, ²⁹Si MAS NMR spectrum, an increasing of the silanol concentration on the external surface, and a pronounced alteration of the acidity distribution between the external and internal surfaces of the zeolite. In a HZSM‐5 zeolite with an average size at about 70 nm, the nonacidic hydroxyl groups (silanols) are about 14% with respect to the total amount of Si, while only 4% of such hydroxyl groups exist in the same kind of zeolite at 1000 nm crystal size. The result of ¹H MAS NMR obtained using Fluorinert^® FC‐43 (perfluorotributyl amine) as a probe molecule demonstrates that most of the silanols are located on the external surface of the zeolite. Moreover, the concentration of Brønsted acid sites on the external surface of the nano‐structured zeolite appears to be distinctly higher than that of the microsized zeolite.     

载体对Pd和Pt催化剂加氢脱硫反应性能的影响

以质量分数为0.8%的二苯并噻吩(DBT)的十氢萘溶液为模型化合物,考察了SiO_2,Si-MCM-41和Al-MCM-41负载的Pd和Pt催化剂加氢脱硫(HDs)反应性能,并与传统的γ-Al_2O_3负载的催化剂进行了对比.反应结果表明,负载型Pd和Pt催化剂在DBT的HDS反应中表现出不同的反应特点.Pd催化剂具有较高的加氢反应路径(HYD)选择性,而Pt催化剂则表现出较高的直接脱硫路径(DDS)选择性.载体结构和表面酸性显著影响其负载的Pd和Pt贵金属催化剂的HDS活性以及HYD选择性和稳定性.提高载体比表面积和酸性有利于提高负载型贵金属催化剂HYD选择性.Al-MCM-41具有规整的介孔结构、较高比表面积和较强酸性,其负载的Pd和Pt催化剂表现出较高的HYD选择性和稳定性.研究还发现,催化剂加氢裂化反应活性随载体酸性的提高而增加.     

模板剂对SAPO-34分子筛性能的影响

采用XRD、SEM、NH3-TPD等方法研究了以三乙胺(TEA)、四乙基氢氧化铵(TEAOH)及二者的混合物为模板剂合成的产物的结构及物化性能,并以甲醇为探针分子,在固定床反应器上对合成产物在甲醇制取烯烃(MTO)反应中的催化性能进行了评价。结果表明,模板剂的种类及配比对所得产物的晶相结构、晶粒大小、酸强度、酸量以及催化性能有重要影响。双模板体系中,当n(TEAOH)/n(TEA)=0.037～0.186时,得到纯相SAPO-34分子筛;且当n(TEAOH)/n(TEA)=0.093时,得到的SAPO-34分子筛晶粒较小(1.0μm左右)且均匀,酸度适中,低碳烯烃(C2=～C4=)的选择性94.98%,催化寿命415min,较单独以TEA〔n(TEA)/n(Al2O3)=2.15〕或TEAOH〔n(TEAOH)/n(Al2O3)=2.0〕为模板剂合成的催化剂的低碳选择性(88.22%和89.29%)和寿命(170min和165min)均有明显提高,且积炭速率(0.016%/min)明显降低。     

Synthesis of MgAPO-31 nanocrystals via different heating methods and their catalytic performance in the hydroisomerization of <Emphasis Type="Italic">n</Emphasis>-decane

MgAPO-31 molecular sieves substituted by different magnesium contents were synthesized using microwave irradiation (MW) and conventional electrical heating method, respectively. The bifunctional catalysts Pd/MgAPO-31 were prepared by the incipient wetness impregnation technique. The structure and acidity of MgAPO-31 were characterized by XRD, SEM, N₂ physical adsorption, FT-IR, and Py-IR. The catalytic performance of Pd/MgAPO-31 were tested in the hydroisomerization of n-decane, which was used as the probe-reaction, and the effect of heating method on acidity of MgAPO-31 and the catalytic performance of Pd/MgAPO-31 were investigated. The results showed that all of the MgAPO-31 samples with ATO topology structure were pure phase and high crystalline materials. The Mg(II) heteroatoms were confirmed to isomorphously substitute for the framework atoms of AlPO₄-31 molecular sieve. These Pd/MgAPO-31catalysts showed good catalytic performance for the hydroisomerization in the temperature range of 330–370 °C. The activity of Pd/MgAPO-31 in the hydroisomerization of n-decane and the selectivity for i-decanes were considered to depend on the crystal size and acidity of MgAPO-31.The highest selectivity for i-decanes was obtained over the catalyst Pd/0.05MgA31-MW prepared using the MW method.