Modifying the acidity of H-MOR and its catalytic carbonylation of dimethyl ether

Among the reactions catalyzed by zeolites there are some that exhibit high selectivity due to the spatial confinement effect of the zeolite framework.Tailoring the acidity,particularly the distribution and location of the Bronsted acid sites in the zeolite is effective for making it a better catalyst for these reactions.We prepared a series of H-mordenite（H-MOR） samples by varying the composition of the sol-gel,using different structure directing agents and post-treatment.NH3-TPD and IR characterization of adsorbed pyridine were employed to determine the amount of Bronsted acid sites in the 8-membered ring and 12-membered ring channels.It was shown that controlled synthesis was a promising approach to improve the concentration of Bronsted acid sites in MOR,even with a low Al content.Using an appropriate composition of Si and Al in the sol-gel favored a higher proportion of Bronsted acid sites in the 8-membered ring channels.HMI as a structure-direct agent gave an obvious enrichment of Bronsted acid sites in the 8-membered ring.Carbonylation of dimethyl ether was used as a probe reaction to examine the modification of the acid properties,especially the Bronsted acid sites in the 8-membered ring channels.There was a linear relationship between methyl acetate formation and the number of Bronsted acid sites in the 8-membered ring channels,demonstrating the successful modification of acid properties.Our results provide information for the rational design and modification of zeolites with spatial constraints.

Organic‐free synthesis of MOR nanoassemblies with excellent DME carbonylation performance

Seed‐assisted low alkalinity gel system was developed to explore the organic‐free synthesis of MORzeolite.MOR nanoassemblies with Si/Al ratio(SAR)up to 9.4 and high solid yield(84–94%)weresuccessfully obtained under controlled low alkalinity conditions.Characterization results demonstratethat the acid strength increases in parallel with the SAR,while the total acid amount and theproton distribution in the main channels and the side pockets are similar for the samples.The protondistribution in the H‐MOR is not straightforwardly related to the Na+distribution in theas‐synthesized MOR,implying the transfer of the protons among the oxygen sites of framework Tatom.Relative to low‐silica samples I‐5.3 and I‐7.4,sample I‐9.4 displays the best mass transferperformance and accessibility of the acid sites by pyridine due to its relatively low Al density andmild dealumination degree.Correspondingly,sample I‐9.4(pyridine‐modified catalyst)shows thebest activity with ca.100%selectivity of methyl acetate(MAc)in the DME carbonylation reaction.The high steady MAc yield(6.8 mmol/g/h)over sample I‐9.4 suggests the promising application ofMOR nanoassemblies synthesized by this economical organic‐free strategy.

Synthesis of ZSM-5 with the silica source from industrial hexafluorosilicic acid as transalkylation catalyst

A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can be used to hydrothermal synthesize ZSM-5 zeolite without impurity phase contamination, which was confirmed by XRD, TG, SEM, BET and EDS characteristic techniques. It was found that with the increase of SiO_2/Al_2O_3 ratio and the extension of reaction time, the crystal type transform from the orthorhombic to the monoclinic phase. The impurity fluorine content of the recovered SiO_2 from H_2SiF_6 has great influence on the hydrothermal process for ZSM-5 crystal structure formation.Moreover, the increase of fluorine ions content in the hydrothermal process can control the crystal morphology and size of synthesized ZSM-5. Catalytic properties of synthesized HZSM-5 with different SiO_2/Al_2O_3 ratio in transalkylation of toluene and 1,2,4-trimethylbenzene show good and stable catalytic performance. The ZSM-5 synthesized with recovered silica source exhibits similar catalyst life as the performance of small particle size HZSM-5, because the ZSM-5 synthesized with the silica source from industrial hexafluorosilicic acid prefers a thin disk crystal along the b axis direction, which shortens the diffusion distance of generated products.

Comparative study of microwave-assisted versus conventional heated reactions of biomass conversion into levulinic acid over hierarchical Mn_(3)O_(4)/ZSM-5 zeolite catalysts

Conversion of delignified cellulose from rice husk biomass,and model compounds of cellobiose and glucose to levulinic acid(LA)over hierarchical Mn_(3)O_(4)/ZSM-5 catalyst was carried out using a household microwave method,and then compared to the established conventional thermos-reaction method.The hierarchical ZSM-5 was prepared using a double template method,aiming for micro and mesoporous systems developed in the structure.The as-prepared ZSM-5 were modified with Mn3O4 through incipient wetness impregnation with Mn2+solution followed by calcination at 550℃.The catalysts were characterized using various techniques such as powder XRD,SEM,BET,AAS,and FT-IR which indicated the hierarchical structure of MFI zeolite(Si/Al of 30-34)with Mn loading of 2.14 wt%.The conversion products were analyzed using HPLC,1H NMR,and 13C NMR instruments.The microwave-assisted reaction using 600 W for 180 s using delignified cellulose,cellobiose,and glucose gave conversion of 37.27%,46.35%,and 54.29%,respectively which is close to the conversion given by the conventional reaction carried out at 130◦C for 4 h(36.75%,55.62%,and 60.9%,respectively).Interestingly,the LA yield from the microwave-assisted reaction(4.33%,6.12%,and 9.57%)is higher than the yield from the conventional reaction,which only produced 5.2%,4.88%,and 6.93%respectively.The microwaveassisted method is also shown to give less by-products compared to the thermochemical reaction.Therefore,it could be considered an alternative method for converting cellulose to LA.

中孔沸石新材料MCM－41──Ⅰ．合成、酸性及稳定性

中孔沸石新材料ＭＣＭ－４１──Ⅰ．合成、酸性及稳定性赵修松，王清遐，徐龙伢，谢紊娟（中国科学院大连化学物理研究所，大连１１６０２３）李新生（中国科学院大连化学物理研究所催化基础国家重点实验室，大连１１６０２３）关键词ＭＣＭ－４１沸石，合成，酸性，稳定...

硼-β沸石的合成和酸性

研究了在Na_2O-B_2O-3-SiO_2-TEAOH-H_2O体系中合成B-β沸石的规律,根据晶化动力学曲线测得表观成核活化能和晶化活化能分别为152kJ·mol^(-1)和40kJ·mol^(-1),用核磁共振、红外光谱、X射线衍射等方法证明了硼进入分子筛骨架,用红外光谱和TPD研究了HB-β沸石的酸性并用正己烷和异丙苯裂解反应考察了其酸催化活性。

磷改性Y型分子筛的合成与表征

采用母液合成法制备了含磷的Y型分子筛PY。利用X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、固体魔角自旋核磁共振波谱(MAS-NMR)、吡啶吸附红外光谱等方法对PY分子筛进行表征。结果表明,制备过程中有部分磷原子进入了Y型分子筛的骨架中,磷的引入使PY分子筛的强B酸中心与总酸中心数量均下降。

纳米级MCM-49分子筛催化苯与1-十二烯烷基化反应的性能

在低碱度下合成了纳米级MCM 4 9分子筛 ,采用XRD ,TEM ,NH3 TPD ,吸附吡啶的红外光谱和异丙苯裂解等技术对分子筛进行了表征 .催化剂评价结果表明 ,纳米级MCM 4 9分子筛在 30～ 16 0℃下对苯与 1 十二烯的烷基化反应具有良好的催化性能 ,烯烃的转化率高于 99 6 % ,直链烷基苯的选择性大于 97% ,2 和 3 位直链烷基苯的选择性大于 6 7 5 % .常规的微米级MCM 4 9分子筛在低温下的催化活性低于纳米级MCM 4 9分子筛 .ZSM 5 ,M型分子筛和MCM 4 1分子筛催化烷基化反应的活性较低 ,Y型分子筛虽具有较高的催化活性 ,但生成 2 和 3 位直链烷基苯的选择性明显低于MCM 4 9.MCM 4 9的骨架结构与MCM 2 2相似 ,晶体外表面上含有大量的 12元环孔穴 ,该结构有利于烷基化反应的进行 .

ZSM-5沸石酸性对合成甲基叔丁基醚的影响

采用磺酸 +丙酮溶剂浸渍法对一组不同硅铝比 (2 8 0～ 6 8 0 )的ZSM 5沸石改质 ,得到不同酸性的ZSM 5沸石。利用NH3 TPD和Py IR法分别考察改质前后的两种ZSM 5沸石的酸性 ,并对两种沸石制成的催化剂进行了合成MTBE反应的活性评价 ,反应条件为 :T =92℃、P =1 6MPa、LHSV =1 2h-1、n(MeOH) /n(i C4 H8) =1 2。结果表明 ,改质后的ZSM 5沸石B酸量较改质前有所增加 ,ZSM 5沸石的活性同沸石的n(SiO) /n(Al2 O3 )呈现一致的变化规律。

加入柠檬酸微波合成超微分子筛

采用微波加热法进行分子筛的合成晶化,同时在制备过程中加入柠檬酸作为助剂,使得分子筛晶体粒径更小,形成的晶粒更加均匀。结果表明,将微波法与添加剂合用可以明显改善反应条件,晶化时间10 min,晶化温度100℃,合成分子筛粒径约为300 nm。

SO_4^(2-)-Fe_2O_3/Hβ增强酸催化剂上合成乙酸丁酯

将超强酸中心引入Ｈβ沸石表面，制备出具有增强酸性的ＳＯ２－４－Ｆｅ２Ｏ３／Ｈβ催化剂，并用于乙酸与正丁醇的酯化反应。采用数学模拟方法定量表征该催化剂的酸强度分布。建立了合成乙酸丁酯反应动力学模型。讨论不同类型沸石、氧化物改性对酯化反应性能的影响及表面酸性与酯化性能的关系。

微波辅助沸石-淀粉系高吸水复合材料的制备及性能

利用微波辅助合成了沸石-淀粉系高吸水复合材料,采用红外光谱表征了复合材料的微观特征,研究了淀粉与单体的配比、交联剂用量、引发剂用量、沸石添加量及中和度对吸水倍率的影响,探讨了复合材料的保水性。结果表明:沸石在聚合物中能较好分散,当沸石质量分数为10%、淀粉为5%、引发剂为0.4%、交联剂为0.04%、中和度为70%时,复合材料吸自来水倍率达459g/g,对生理盐水溶液的吸水倍率达85 g/g。其保水性能良好。

以微孔β沸石为硅铝源合成强酸性介孔分子筛

以微孔β沸石为硅铝源,通过碱处理和以十六烷基三甲基溴化铵为模板剂,合成了具有较强酸性的六方结构介孔分子筛材料B-MCM-41,并采用XRD、N2吸附脱附、FT-IR、27Al MAS NMR、HRTEM和水热处理等手段对其进行了结构表征,采用NH3-TPD对其进行了酸性表征。实验结果表明,B-MCM-41具有明显强于常规介孔分子筛的酸性,且在C1+0混合芳烃加氢脱烷基化反应中表现出了良好的催化性能。这主要是由于碱溶液将β沸石降解为沸石结构单元,在表面活性剂作用下五元环次级结构单元被引入了介孔铝硅酸盐B-MCM-41的结构。

以酸解正硅酸乙酯为硅源合成ZSM-5分子筛的过程调控

正硅酸乙酯(TEOS)作为合成ZSM-5分子筛的常用硅源,其在不同酸碱介质中水解的前驱体聚合状态对ZSM-5分子筛的粒径和孔径分布具有调控作用。以酸性介质TEOS水解缩合的前驱体为硅源,在水热条件下合成ZSM-5分子筛,并利用XRD、SEM、BET、FI-IR等方法对反应不同阶段的样品进行表征分析。主要考察了水解程度、水解时间、合成过程的pH、晶化温度、晶化时间及模板剂用量对ZSM-5分子筛合成过程的调控,结果表明:以乙醇为共溶剂,以TEOS在硫酸介质pH=2.0时水解20 h的前驱体为硅源,水热合成过程中加入模板剂四丙基氢氧化铵(TPAOH),铝源为氢氧化铝,180℃晶化30 h合成了粒径约为200 nm的ZSM-5分子筛,其比表面积提高了35.6%,平均孔径降低了48.6%。

HY分子筛催化合成油酸乙酯

采用NaY分子筛催化剂,经离子交换和高温焙烧制得HY分子筛,以油酸和乙醇为原料,在间歇反应釜进行酯化反应研究。考察反应温度、原料配比、催化剂用量和反应时间等条件对酯化反应的影响。结果表明,在反应温度180℃、n(油酸):n(乙醇)=1:2.5、催化剂用量为原料总质量的1.0%和反应时间4 h条件下,油酸转化率可达81.18%。实验中的HY分子筛表现出较高的活性和良好的稳定性。

二次合成FeY分子筛的表面酸性

二次合成ＦｅＹ分子筛的表面酸性＊张爱民鲍书林须沁华＊＊（南京大学化学化工学院化学系，南京２１００９３）关键词ＦｅＹ分子筛，二次合成，表面酸性二次合成含杂原子沸石的过程中，Ｆｅ的引入显示出其特有的性能，例如在甲醇转化反应中能提高烯烃的选择性，在甲苯烷基...

CoAPSO-5分子筛的合成与性能

用水热晶化法合成了ＣｏＡＰＳＯ５分子筛，用Ｘ射线衍射、电子探针、红外光谱以及吸附吡啶的红外光谱等方法对其结构和表面性质进行了研究，并用甲苯甲醇烷基化反应考察了其催化性能。结果表明，ＣｏＡＰＳＯ５为中强酸性分子筛，具有较高的甲苯甲醇烷基化活性和对二甲苯选择性，对二甲苯收率高于２０％，且烷基化活性和对二甲苯选择性出现了“同向效应”

Y-β复合分子筛负载磷钨酸催化合成乙酸仲丁酯

以乙酸酐与仲丁醇为原料,Y-β复合分子筛负载磷钨酸(H3PWl2O40/Y-β)为催化剂,使其发生酰化反应合成乙酸仲丁酯,考察了催化剂用量、反应时间、酐醇摩尔比对乙酸仲丁酯产率的影响。结果表明,Y-β复合分子筛负载磷钨酸催化活性良好,当乙酸酐的加入量为0.1 mol,醇酐摩尔比为1.2时,使用0.75 g催化剂,反应30 min后,乙酸仲丁酯收率可达到94.5%,且催化剂重复使用5次仍保持活性良好。产品经折光率和红外光谱进行了表征。

Y-β复合分子筛负载磷钨酸催化合成乙酸环己酯

以乙酸酐与环己醇为原料,Y-β复合分子筛负载磷钨酸(H3PW12O40/Y-β)为催化剂,使其发生酰化反应合成乙酸环己酯,考察了催化剂质量、反应时间、醇酐物质的量比对乙酸环己酯产率的影响。实验结果表明:Y-β复合分子筛负载磷钨酸催化活性良好,当乙酸酐的加入量为0.1mol、醇酐物质的量比为1.1:1、催化剂质量为0.60g,反应45min时,乙酸环己酯产率可达到93.4%,且催化剂重复使用5次仍保持活性良好。对产品进行了折光率和红外光谱的表征。

HF/USY分子筛催化合成2-叔丁基对甲酚

以USY负载HF为催化剂、甲基叔丁基醚(MTBE)和对甲酚为原料,在小型固定床反应器上进行合成2-叔丁基对甲酚的研究,考察了HF负载量、反应温度、空速及原料配比对反应转化率和选择性的影响以及催化剂的稳定性。结果表明,HF改性后,USY的L酸中心增加,B酸中心减少,对甲酚转化率增大。L酸中心是烷基化反应的主要活性中心。最佳反应条件为:反应温度160℃,HF负载质量分数1%,空速1.2h-1,n(MTBE):n(对甲酚)=1.5∶1。最佳条件下,对甲酚的转化率84.4%,2-叔丁基对甲酚的选择性98.6%。催化剂使用110h,仍保持较好的催化活性。