SAPO-35分子篩的合成及其甲醇制烯烴反應性能

Chinese Journal of Catalysis 34 (2013) 798-807催化學(xué)報2013年第34卷第4期I www.chxb.cn值化管抓available at www. sciencedirect.comarabpolsScienceDirectEL SEVIERjournal homepage: www. elsevier.com/locate/chnjcArticleSynthesis of SAPO-35 molecular sieve and its catalytic properties inthe methanol-to-olefins reactionLI Bing, TIAN Peng, LI ]inzhe a, CHEN Jingrunab, YUAN Yangyang ab, SU Xiongab, FAN Dongab,WEI Yingxua, QI Yuea, LIU Zhongmina.*●Dalian National Laboratory for Clean Energy, National Engineering Laboratory for Methanol-to-Olefins, Dalian Institute of Chemical Physics, ChineseAcademy of Sciences, Dalian 116023, Liaoning, Chinab University of Chinese Academy of Sciences, Bejing 10049, ChinaARTICLEINFOABSTRACTArticle history:SAP0-35 molecular sieve samples with different Si contents were hydrothermally synthesized usingReceived 30 December 2012hexamethyleneimine as the template and characterized by XRD, XRF, SEM, MAS NMR, XPS and NzAccepted 30 lanuary 2013physisorption. Three SAP0-35 samples were tested as methanol-to-olefins catalysts. After the reac-Published 20 April2013tion, the evolution of coke species was investigated over SAPO-35 and SAPO 34 catalysts with simi-lar Si concentrations. A correlation between the cage size of the molecular sieves and the coke spe-cies was obtained.Keywords:SAPO-35o 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.Published by Elsevier B.V. All rights reserved.Methanol to olefnsSAP0-34Coke speciesDeactivation1. Introductionaminomethylation [4- _7]. Moreover, SAP0-35 is also exploredas an adsorbent for CO2/CH4 separation [8,9].Silicoaluminophosphate molecular sieves (SAPO-n) wereThe methanol-to-olefins (MTO) process is the key process tofirst synthesized and reported by Union Carbide Corporationproduce light olefins from coal or natural gas. The molecular(UCC) in 1984 [1]. Due to their mild acidity and special poresieves ZSM-5 and SAP0-34 with eight membered ring and CHAstructures, SAPO molecular sieves have widespread applica-cages exhibit excellent catalytic performance in the reactiontions in the chemical industry [2]. SAP0-35, as a member of the[6,7,10-12]. Other small pore molecular sieves with thefamily with the levyne-like crystal structure (LEV), is a small .eight-membered pore size such as SAP0-17, SAP0-18, andpore molecular sieve with a pore diameter of 3.6 nm x 4.8 nm.SAP0-35 have also been explored as catalysts for the MTO re-The framework of SAP0-35 comprises levyne cages connectedaction [7,13,14]. The SAPO-35 molecular sieve showed a fasterby single six- membered rings and double six-membered rings. coking deactivation rate compared with SAPO-34 [4.6]. At pre-There are two distinct T sites in the framework: one is in thesent, the correlations between the deactivation process (de-double six membered ring and the other is in the singleposited coke species) and the reaction conditions (such as timesix-membered ring The distribution of these two sites is in thend temperature) during the MTO reaction over the SAPO-34ratio of 2:1 [3]. Due to the special structure of SAP0-35, it hascatalyst are relatively clear [15,16]. However, there is no reportbeen employed as the catalyst in methanol conversion andso far on the deactivation process during methanol conversion*Corresponding author. Tel/Fax: +86-41 1-84379335; E-mail: liuzm@dicp.ac.cnDOI: 10.1016/S1872-2067(12)60557-9 I ht://www.sciencedirect.com/science/journal/18722067 I Chin.」. Catal,Vol.34. No. 4, April 2013LI Bing et al. / Chinese lournal of Catalysis 34 (2013) 798 -807799catalyzed by SAPO-35. It is speculated that the activity differ-resonance frequency of 600.13 MHz by using a 4 mm probeences between SAP0-34 and SAPO-35 are due to their differenthead. One pulse program was used and the π/2 pulse lengthstructures. Research on the deactivation during the MTO reac-was 4.4 us. The recycle delay time is 10 s. The spin rate was 12tion over SAPO-35 will help understand the effect of the cagekHz with 32 times sampling frequency. Before the H MAS NMRstructures of the molecular sieves and the deposited coke spic-experiments, all samples underwent vacuum dehydration ates400 oC and < 10-3 Pa for 20 h to remove water and impurities inIn this work, SAPO-35 molecular sieves with different Sithe molecular sieve. The samples were transferred in a nitro-contents were hydrothermally synthesized by using hexameth-gen-flled glove box to the NMR rotator for testing. The quanti-yleneimine as the template. The effect of Si content on thetative processing of the 1H MAS NMR data was as follows. Aphysical and chemical properties of the molecular sieves wascalibration curve for the correlation between peak areas andstudied in detail. In addition, three SAP0-35 molecular sievesmass of sample were first made by using adamantine as thewith different Si contents were chosen as MTO catalysts to in-external standard. Then the 1H MAS NMR spectra of the samplevestigate the effects of the acidity on the reaction. The evolutionwith known mass were acquired under identical acquisitionof the coke species in the reaction was investigated over bothconditions. The peak areas of Bronsted acid sites was calculat-SAPO-35 and SAP0-34 catalysts with similar Si concentrations.ed by Gauss-Lowrance linear ftting to get the density ofThe correlation between the cage size of the molecular sievesBronsted acid sites of the samples from the calibration curve.and deactivation due to the coke species is discussed.2.3. Reaction evaluation2. ExperimentalThe catalytic properties of the molecular sieves were evalu-2.1. Synthesis of molecular sievesated using an atmospheric fixed bed equipment. 1.2 g calcinedsample (40-60 mesh) was packed in the reactor, which wasThe SAP0-35 molecular sieves were synthesized as report-then purged with nitrogen at 520 oC for 30 min. After purging,ed elsewhere [17] Pseudoboehmite powder (w([Al2O3) = 70methanol solution (40 wt%) was injected into the reactor byawt%), sol (w(SiO2) = 31.1 wt%) and phosphoric acid (w(H3PO4}pump. The products were analyzed online using an Agilent= 85 wt%] were the aluminum source, silicon source, and7890A gas chromatograph (CC) with PoraPLOT Q-HT capillaryphosphorus source, respectively. Hexamethyleneimine (HMI,column and FID detector.chemical pure) was used as the template agent The molar ratioof reactants was 0.96P20s:1.0Al20x:nSiO2:1.51HMT:55.47H2O2.4. Collections of coke deposits and analysis of coke species(n= 0.1, 0.2, 0.3, 0.5, 0.8, 1.0). The detailed procedure was asfollows. Into a beaker, deionized water, aluminum source, sili-The deposited coke species were collected by stopping thecon source, phosphorus source, and HMI were sequentiallyfeed after a pre-determined reaction time, unloading the cata-added with vigorous strring to make the initial gel homogene-lysts quickly and then quenching in liquid nitrogen.ous. This was then transferred into a 100 ml stainless steelThe Guisnet method was used for the qualitative analysis ofreactor, which was then sealed and heated at 2000C for 24 h.the coke species [18,19]. In a Teflon bottle, 50 mg of catalystAfter crystallization, the product was collected by centrifugalwas added to 1 ml HF water solution (20 wt%}. After the mix.separation, rinsed with water until the pH level was neutral,and then dried at 120C. The samples with different Si contentschloromethane was added into the solution. 5 min later, NaOHwere denoted as 0.1Si, 0.2Si, 0.3Si, 0.5Si, 0.8Si, and 1.0Si.was added and mixed well. The mixture was then transferredto a separatory funnel and shaken vigorously. The lower layer2.2. Characterizationliquid was collected into a sample vial for GC testing by an Ag.ilent 7890-5975C MSD gas chromatograph-mass spectrometerX-ray powder diffraction (XRD) measurements were per-with a HP-5 capillary column. Each compound was identifiedformed using a PANalytical X'Pert PRO X-ray diffractometerusing the NIST 08 library.with Cu anode, Ka radiation [ = 0.15418 nm), voltage of 40 kVand current of 40 mA. The elemental analysis was carried out3. Results and discussionusing a Phillips Magix 2424X X-ray Fluorescence Spectrometer[XRF). Morphology images were acquired on a Hitachi S-3400N3.1. Synthesis and characterization ofSAP0-35 with different Siscanning electron microscopy (SEM]. X-ray photoelectroncontentsspectroscopy (XPS) was determined employing a ThermoESCALAB 250Xi X-ray photoelectron spectrometer with Al KaThe XRD results of the samples are shown in Fig. 1. All theradiation. The peak of Al 2p at 74.7 eV from Al203 on the sur-SAPO-35 molecular sieves with different Si contents had theface of the samples was used as the internal standard. N2 ad-LEV framework structure, as shown by comparing to thesorption measurement was performed on a Micromeriticsstandard pattern [7,20]. The relative crystallinit, relative yield,ASAP 2010 volumetric adsorption analyzer.and chemical composition of the SAP0-35 samples with differ-1H MAS NMR experiments were performed on a Brukerent Si contents are listed in Table 1. The solid yield of the sam-Avance 1600 solid phase NMR spectrometer with a protonples increased with increasing amount of SiO2 in the initial gels.800LI Bing et al. / Chinese Journal of Catalysis 34 (2013) 798-807Table 1Relative crystallinity and chemical composition of the SAPO-35 sampleswith different Si contents.1.0SiRelativeSSampleerysallinity (%) yield (%) composition incorporation*_ wlltum L0.8Si0.1Si8462 SiolooPas1.820.2Si974 SogAlok49yP-420.5Si0.3Si10036 Sg2Alo485Pa4231.0194Sio. I2Alo 487Po391)195Sio.69Al0.465Pa3670.803500Sio175A0457P0.3680.70*Defined as the molar ratio of [/5(i++P)]oux/[S/(Si+Al+P)]silicon incorporation in the framework of SAPO-5 molecular02(405(sieves and found that highly dispersed and singly substituted20(°)silicon was the most stable, fllowed 5Si and 8Si islands. TheseFig. 1. XRD ptterns of the SAPO-35 samples with diferent Si contents.results suggested that the energy of Si incorporation in theframework increased with increasing content of subtitutedHowever, the crstallinity exhibited first an increase then asilicon, leading to the decreasing ability for silicon incorpora-decrease trend. 0.3Si sample showed the highest crystallinity.tion in the framework. Their conclusion is consistent with ourIn our previous research on the synthesis of SAP0-34, we alsoexperimental results.found that samples with 0.2-0.3 Si contents had the highestThe SEM images of the samples with different Si contentscrystallinity [21]. This suggestedthat the Si content in the ini-are shown in Fig 2. The SAP0-35 grains presented the typicaltial gel not only afected the chemical composition of the sam-rhombohedral morphology, but the change of silicon contentples but also the crytallinity. In addition, the XRF elementalhad a significant effect on the surface roughness of the molecu-analysis results indicated that the Si content of SAP0-35 in-lar sieve crystals. With a low silicon content, the molecularcreased with the increase of Si content in the initial gel. To bet-ter correlate the Si contents of the starting materials and prod-rough and irregular small holes appeared when the siliconucts, we introduce a concept of "silicon incorporation" definedcontent was increased to 0.8. When the silicon content was 1.0,as [Si/Si+A)P]produa/[Si/(Si+AI+P)]el (shown in Table 1). Athe surface of the crystal was wrapped by small particles and itdescending tendency was found for silicon incorporation inshowed a 'core-shell' structure, which presumably resultedSAP0-35 with the increase of Si content in the starting materi-from a secondary crystal growth on the rough surface of theals. The 0.1Si sample exhibited the highest silicon incorporationcrystal or the enrichment of excessive amorphous silica in theof 1.82. The silicon incorporation decreased to less than 1.0gel on the crystal surface. The surface compositions of the 0.5Siwhen the Si content of the initial gel was more than 0.3. Siliconand 1.0Si samples were analyzed by XPS (Table 2). It was foundincorporation was only 0.7 when the Si content of the initial gelthat the crystal surface of these two samples comprised silica,was 1.0. Therefore, we believed that it is the high silicon incor-phosphorus oxide, and alumina. The relative silion content ofporation associated with the samples with low Si contents thatthe surface was higher than that of the bulk phase, and the en-resulted in their relatively low solid yields. Catlow et al. [22].richment of silicon on the high silicon content sample surfaceemployed lattice simulation to calculate the energy changes ofwas higher. It was thus speculated that the shell of the 1.0SiL.OSFFig. 2. SEM images of the SAPO-35 samples with diferent Si contents.LI Bing et al. / Chinese Journal of Cataysis 34 (2013) 798 -807801Table 23.2. Methanol conversion by SAP0-35 molecular sieve withBulk and surface compositions of the SAP0-35 samples with diferent Sidifferent Si contentscontents.Composition0.1Si, 0.3Si, and 0.5Si samples were selected for the study ofSampleBulkSurfaceSirface/Sibukmethanol conversion. The results are shown in Fig. 4 and Table0.5SiSio.122Alo.487Po.391Sio,178Alo.478Po.3351.464. The results of the MTO reaction on SAP0-34 (elemental1.0SiSio.15sA0o457P036Sioz275Alo.405P03201.58composition is Sio.o86Alo.493Po.421) are also listed in Table 4 forcomparison. During an initial period, the conversion of metha-sample grains was formed by a secondary crystal growth onnol on SAP0-35 with different Si contents was maintained atthe rough surface of the crystal. Meanwhile, from the siliconabove 99%. The conversion decreased as the reaction timeenrichment on the SAPO-35 crystal surface revealed by XPS, weincreased and the higher the Si content, the faster the conver-can suppose that the distribution of silicon in the SAP0-35sion of methanol dropped. The selectivity for ethylene of thesecrystals was non-uniform and there was a gradual increase ofmolecular sieves gradually rose as the reaction time increased,the silicon content from the inside outwards. We also found awhile the selectivity for propylene decreased. Compared withsimilar situation in the crsallization of SAP0-34 with di-SAP0-34, SAP0-35 exhibited the characteristic of fast deactiva-ethylamine as a template agent [23]. The main reason would beion.the gradual increase of the gel pH during the synthesis of SAPOThe MTO reaction is a typical acid catalyzed reaction, andmolecular sieves. The increase of pH promoted depolymeriza-the acidity of the molecular sieve plays an important role on thetion of the silicon source in the gel system, thus the ability forlifetime and the selectivity to light olefins. We determined thesilicon incorporation into the molecular sieve framework wasamount of Bronsted acid of the three SAP0-35 samples usingenhanced (the pH value of the gel in our synthesis system be-1H MAS NMR (shown in Table 5]. Generally, the density offore and after the crysallization of 0.5Si sample were 5.56 andBronsted acid sites increased in the samples with the increase8.20, respectively).of the Si contents. Both are almost in a linear relationship. TheFigure 3 and Table 3 show the N2 adsorption-desorptionhigher acid density in the samples with higher Si contentisotherms, specific surface areas, and pore volumes of the sam-caused serious side reactions, such as coke deposition and theples with different Si contents. All three samples displayed ahydrogen transfer reaction, which shortened the life time of thehigh micropore surface area and micropore volume. Moreover,catalyst and generated more methane and propane. Moreover,the outer specific surface area and mesopore volume of thethe deposited coke species gradually formed during the reac-samples increased with the increase of silicon contents, whichtion will decrease the cage size of the molecular sieves, reducewould be due to the rough grain surface of the samples withthe generation and diffusion rates of molecules with largerhigh silicon contents, as revealed by the SEM images.diameters, and consequently increase the selectivity for eth-ylene and decrease the selectivity for propylene.200-105 n180-160 f90- (a4)|75 t買(mǎi)12050 t(1)-0.8Si3)\宣80F45 F? 60-0一0.2Si30 t40F85 F2)、20(b)(2)0.00.2 0.4 0.60.81.0Relative pressure (p/po)75 taFig.3. N2 adsorption-desorption isotherms of the SAP0-35 samples70 twith dfferent Si contents.Table3要65Pore structure parameters of the SAP0-35 samples with diferent Si50。0 20406080100120140160180Surface area (m2/g)Pore volume (cm/g)Time on stream (min)Micropore External Total Micropore Mesopore TotalFig, 4. CH:0H conversion (a) and CzH+C3H6 selectivity (b) in the MTO0.2Si443.526.3469.7 0.220.01 0.21reaction over SAPO-35 and SAPO-34. (1) 0.1Si; (2) 0.3Si; (3) 0.5Si; (4]0.8Si497441.0 538.4 0.230.05 0.28SAPO-34. Reaction condition: 450 °C, 40% CH3OH solution (SAPO-35,45.80.220.070.29WHSV = 2 h-+; SAPO-34, WHSV=4h-).02u Bing et al./Chinese Journal ofCatalysis 34 (2013) 798-807Table 4MTO results over SAPO0-35 and SAP0-34 molecular sieves.TOSSelectivity (wt%)SampleCH4CzH4CzH6_C3HCaHaC4CcsCz+Gx0.1Si2.3737.800.2736.11.0510.4211.8773.96722.6643.851.0232.301.419.249.4376.160.3Si42.7133.940.340.551.3112.468.6974.505541.385 381 489.138.1076.750.5Si29.0434.482.9413.1316.0763.53。009.1675.0542.0932.958.904.0874. 0SAPO-34b0.9633.61.6540.384.6315.6418212131a43.320.6238.801.5411.03Reaction condition: WHSV= 2h-.450 oC, 40% CH:OH solution..The catalyst lfetime, which is defined as the reation duration with >99% CHzOH conversion.b Reaction condition: WHSV =4 h-t, 450 °C, 40% CH:OH solution (elemental composition of SAPO-34: SoAe.04Por4).3. Analysis of the deposited coke species formed in the MTOreaction over SAP0-35 and SAPO-34tives became the major coke species. By comparing the evolu-tion of the organic species in SAPO-35 and SAPO-34, a commonThe fast deactivation of SAP0-35 molecular sieve in thecharacteristic is that the main organic species generated in themethanol conversion reaction indicated that the deposited cokeinitial stage were methylated benzene compounds whichspeies and their evolution with reaction time on SAPO-35 isgradually changed to bulky aromatic hydrocarbons. The fnaldifferent from those on SAP0-34. We selected 0.3Si SAPO-35 tocoke molecules in SAPO-34 were significanty larger than thosestudy the deposited coke species fllowing the reaction timein SAPO-35.and compared these with those generated on SAPO-34. TheThe hydrocarbon pool mechanism is a widely recognizedorganic species extracted from the catalysts were analyzed byMTO reaction mechanism. Much experimental results indicatedGC-MS (Fig.5}.that the multiply methylated benzene (methyi substituents> 3)The organic species initally produced on SAP0-35 (15 min)were mostly toluene, xylene and trimethylbenzene. As the re-a)|creased to 32 min, the methanol conversion de-00 9creased from 98.49% to 76.37%, and organic species with alarger molecular size, such as naphthalene and methyl naph-thalene, started to appear in the deposited coke species, Whenthe reaction time was 83 min, the methanol conversion further會(huì )|decreased to 10.88%. Among the deposited coke species, thesignals of naphthalene and methyl naphthalene obviously in-=33.46%creased, and a smallX= 98.57%72 minlene and anthracene dihydride appeared in addition to toluene,xylene and trimethylbenzene. The organic species during the :X= 96% 21 minearly stage (21 min) of methanol conversion over SAPO-34molecular sieve were mainly trimethylbenzene, tetra-0152025303540 45 50methylbenzene, naphthalene, methyl naphthalene and dime-Retention time (min)thyl naphthalene. When the reaction time was 72 min, themethanol conversion was still maintained at a high levelOCoub)|(98.57%}. Coke species such as tetramethylbenzene, naphtha-lene, methylnaphthalene and dimethylnaphthalene were en-hanced, and new signals corresponding to trimethyinaphtha-L X= 10.88% 83 minlene, phenanthrene and pyrene appeared. At the stage of nearlycomplete deactivation of SAP0-34 (447 min, 33.46% methanol00[0conversion), methyl benzene compounds disappeared. A sig-nificant change in the relative amounts of the other organicMIL」__X= 38.60%，49 minspecies occurred, and the polycyclic aromatic hydrocarbonX= 76.37%。32 minTable5X- 98.49%，15 minConcentration of Bronsted acid sites in SAP0-35 molecular sieves cal-101520253035404550culated from 1H MAS NMR.B acid sites (mmol/g)0.54Fig 5. Coke species in SAPO-34 (間and SAPO-35 (b) in the MTO reac-0.97tion. Reaction condition: WHSV = 4 h-, 400 °C, 40% CHzOH solution; X1.20refers to the CH3OH conversion in the reaction.LI Bing et al. / Chinese lournal ofCatalysis 34 (2013) 798-807803Graphical AbstractChin. J. Catal, 2013, 34: 798-807 do: 10.1016/S1872-2067(12)60557-9Synthesis of SAP0-35 molecular sieve and its catalytic properties inSAPO-3Sthe methanol-to-olefns reaction00o CLI Bing, TIAN Peng, LI Jinzhe, CHEN jingrun, YUAN Yangyang su Xiong,FAN Dong, WEI Yingxu, QlYue, LIU Zhongmin*Dalian Instute ofChemical Physics, Chinese Academy of Sciences;University of Chinese Academy of Sciences出c91588SAPO4ICHA)SAP0-35 was hydrothermally synthesized using hexamethyleneimine asthe template. The coke species in the MTO reaction over both SAP0-35 andSAP0-34 were investigated and correlated with their cage size.is a hydrocarbon pool active center, on which the methylationhydrothermally synthesized. The yield of solid sample in-of methanol/diethyl ether occurred to form ethylene and pro-creased with the increase of Si content in the synthesis gel. Thepylene, while the resulting less methylated benzene iscrytallinity of the sample increased first and then decreased asre-methylated to start a new catalytic cycle [15,16,24-27]. Inthe Si content increased. 0.3Si sample exhibited the highestthe present experiments, in the initial stage of reaction the ex-crstallinity. The Si incorporation degree showed a droppingistence of some hydrocarbon pool active species (multiplytrend when the silica content rose. The surface of SAP0-35methylated benzenes) were observed in SAP0-34, whereas thecrystals with a high silica content was rough. In particular, 1.0Sicoke species was dominated by less methylated benzenes inshowed the characteristic of a core-shell structure, which couldSAPO-35. With increased reaction time, at the stage of nearlybe due to secondary crytallization on the rough surface.complete deactivation, the main coke species in SAP0-34 wereSAPO-35 showed fast deactivation than SAPO-34 in the MTObulky aromatic hydrocarbons such as phenanthrene and py-reaction, and a higher silica content will cause faster deactiva-rene (generated from ring condensation by hydrogen transfertion. The main reason is that the higher Bronsted acid concen-from methylbenzene and methylnaphthalene), while the coketration in the sample with higher silica content led to more sidespecies in SAP0-35 were methylbenzene, naphthalene andreactions such as coke deposition and hydrogen transfer. Bymethylnaphthalene. The difference in the coke species ofcomparing and analyzing the deposited coke species formed inSAP0-35 and SAP0-34 is probably related to their structures.SAP0-35 and SAP0-34 during the MTO reaction, we concludedThe CHA cage of SAPO-34 (0.67 nm x 0.67 nm x 1.0 nm) isthat the smaller cage of SAP0-35 limited the generation of hy-larger than the LEV cage of SAP0-35 (0.63 nm x 0.63 nm x 0.73drocarbon pool active species (polymethylbenzens) and mac-nm). The smaller cage of SAP0-35 restricted the formation ofromolecular coke species (polyaromatic hydrocarbons). More-the hydrocarbon pool active species (multiply methylated ben-over, the smaller cage of SAPO-35 had a lower capacity to ac-zene) and deactivated coke species (macromolecular fused-ringcommodate deposited coke species. These two reasons result-aromatic hydrocarbon). Also, it has a smaller accommodationed in the faster deactivation of SAP0-35.capacity for deactivated coke species, which thus resulted inthe rapid deactivation. The lack of hydrocarbon pool activeReferencesspecies also led to the relatively low ethylene and propyleneselectivity with SAP0-35. Moreover, it is worth noting that[1] Lok B M, Messina C A, Patton R L, Gajek R T, Cannan T R, Flanigenduring the reaction, the organic compounds deposited inEM. uS Patent 4 440 871.1984SAPO-35 always contained a small amount of saturated cyclo-[2]FuY,WangLF,TanYx,JiHB.ChemReactEngTechnol(付曄,王alkane adamantane compounds. In our recent research on the樂(lè )夫,譚宇新，紀紅兵化學(xué)反應工程與工藝)，2000, 16(1): 55coke species in SAPO-34 in the MTO reaction [28], we reported[3] ht://ww.iza-structure.org/databases/that adamantane compounds are the coke species in the low[4] Zhu Zh D, Hartmann M, Kevan L. Chem Mater, 2000, 12: 2781temperature reaction (≤350 oC), which were gradually trans-[5] Jeon H Y, Shin C H, Jung H I, Hong S B. Appl CatalA, 2006, 305: 70formed into naphthalene and substituted naphthalene species[6] Djieugoue M A, Prakash A M, Kevan L / Phys Chem B, 2000, 104:at elevated temperatures. In this experiment, the reaction6452temperature was 400 C, so the existence of adamantane com-[7] Venkatathri N, Yoo I w. Appl CatalA, 2008, 340: 265pounds in SAP0-35 once again demonstrated that the different[8] Cheung 0, Liu Q L, Bacsik z, Hedin N. Microporous Mesoporouscage size of the molecular sieve has a large influence on theMater, 2012, 156: 90generation and stability of the coke species.9] FalconerIL, Li Sh G, Noble R D. us Patent 20050204916A1.2005[10] Liu GY, Tian P, Liu zh M. Progr Chem(劉廣宇田鵬，劉中民化學(xué)4. Conclusions進(jìn)展), 2010, 22: 1531[11]ZhangICh,ZhangHB,YangXy,HuangZh,CaoWL.JNatGasSAP0-35 molecular sieves with different Si contents wereChem, 2011, 20: 266804L1 Bing et al / Chinese Jourmal ofCatalysis 34 (2013) 798- 807[12] Liu G Y, Tian P, Xia Q H, Liu Zh M.] Nat Gas Chem, 2012,21: 431[20] Prakash A M, Hartmann M, Kevan L Chem Mater, 1998, 10: 932[13) Nawaz s, Kolboe s, Sticker M. stud SurfSci Catal, 1994, 81: 393[21] Zhang D zh. [PhD Diseraion]. Dalian: Dalian Institute of Chemi-[14] Chen I Sh, Wright P A, Thomas I M, Natarajan s, Marchese L, :cal Physics, CAS (張大治。[博士學(xué)位論文]大連:中國科學(xué)院大連Bradley S M, Sankar G, Catlow C R A. Gai-Boyes P LJ Phys Chem,化學(xué)物理研究所),20071994, 98 10216[22 Sastre G, Lewis D w, CatlowC RA/ Phys Chem, 1996, 100: 6722[15] Yuan cY, Wei Yx, lij Zh, Xu Sh T, Chen I R, Zhou Y, Wang QY,Xu[23] LiuGY, Tian P, ZhangY,Li] zh, Xu L, Meng Sh H, Liu Zh M.L, Liu zh M. ChinJ Catol (袁翠峪魏迎旭，李金哲,徐舒濤,陳景Microporous Mesoporous Mater, 2008, 114: 416潤，周游,王全義，許磊,劉中民催化學(xué)報), 2012, 33: 367[24] Wang I D, YuX B, Liu Y, Yang Y R Progr Chem (王靖岱，虞賢波,劉[16] Hereigers BP C, Bleken F, Nilsen M H, Svelle S, Lllrud K P,燁,陽(yáng)永榮化學(xué)進(jìn)展), 2009,21: 1757Bjprgen M, Weckhuysen B M, Olsbye U.JCatal, 2009, 264: 77[25] Arstad B, Kolboe S.JAm Chem Soc, 2001, 123: 8137[17] ZhangF M, Kuang X H, uiL sh, ShuXT, Wang W D, QinF M (張鳳[26] Arstad B, Kolboe s. Catal Lett, 2001,71: 209美，匡曉輝,李黎聲,舒興田，王衛東，秦鳳明), CN Patent[27] Lesthaeghe D, De Sterck B, Van Speybroeck V, Marin G B,101 397 143. 2009Waroquier M. Angew Chem, Int Ed, 2007, 46: 1311[18] Guisnet M.J Mol Catal A, 2002, 182-183: 367[28]WeiYX,LiJZh,YuanCY,XuShT,ZhouY,ChenIR,WangQY,[19] Guisnet M, Costa L, Ribeiro F R.J Mol Catal A, 2009, 305: 69Zhang Q Liu Zh M. Chem Commun, 2012, 48: 3082SAPO- 35分子篩的合成及其甲醇制烯烴反應性能李冰，田鵬"，李金哲"，陳景潤“，袁揚揚叨，蘇雄叻，樊棟”,魏迎旭"，齊越"， 劉中民”“中國科學(xué)院大連化學(xué)物理研究所潔凈能源國家實(shí)驗室(籌),甲醇制烯烴國家工程實(shí)驗室,遼寧大連116023中國科學(xué)院大學(xué),北京100909摘要:以六亞甲基亞胺為模板劑,采用水熱法合成了不同硅含量的磷酸硅鋁分子篩SAPO-35,并利用X射線(xiàn)衍射、X射線(xiàn)熒光光譜、掃描電鏡、固體核磁、X射線(xiàn)光電子能譜和N:吸附脫附等方法對樣品進(jìn)行了表征.研究了不同硅含量的SAPO-35分子篩在甲醇轉化制烯烴反應中的催化行為,同時(shí)對比分析了具有相近硅含量的SAPO-35和SAPO-34分子篩在甲醇轉化反應過(guò)程中積炭物種隨反應時(shí)間的演變特征，嘗試將分子篩結構和其積炭失活行為進(jìn)行了關(guān)聯(lián)關(guān)鍵詞: SAPO0-35;甲醇制烯烴; SAPO-34;積炭物種;失活收稿日期: 2012-12-30.接受日期: 2013-01-30.出版日期: 2013-04-20.*通訊聯(lián)系人.電話(huà)/傳真: (0411)84379335;電子信箱: liuzm@dicp.ac.cn本文的英文電子版由Elsevier出版社在ScienceDirect上出(tp://w siedre.com/scicnce/joual18722067.0篩，如SAPO-17, SAPO-18和SAPO-35也被嘗試用作MTO1.前言反應的催化劑713.4.研究表明,與SAPO-34相比，磷酸硅鋁系列分子篩(SAPO-n)由美國聯(lián)合碳化物SAPO-35分子篩在MTO反應中表現出較快的積炭失公司(UCC)于1984年合成并報道"由于SAPO分子篩具活14.6].目前, SAPO-34分子篩上甲醇轉化失活過(guò)程(積炭有溫和可調的酸性和不同的孔道結構，在多個(gè)化工行業(yè)物種)隨反應時(shí)間和反應溫度等條件變化的規律和特點(diǎn)展現出廣闊的應用前景(21. SAPO-35作為其中的一員,晶已經(jīng)相對清楚I5.16,但是到目前為止,還未見(jiàn)到SAPO0-35體結構為插晶菱沸石型(LEV),孔徑0.36 nm x 0.48 nm,分子篩上甲醇轉化失活過(guò)程的研究.兩者催化性能的差屬小孔分子篩. SAPO-35的骨架結構可看作是LEV籠通別推測與自身結構的差異有關(guān).對SAPO-35積炭失活過(guò)過(guò)單六元環(huán)和雙六元環(huán)連接而成,它含有兩種不同的T程的研究分析將有助于深入理解分子篩籠結構變化對原子位置,分別在雙六元環(huán)和單六元環(huán)中,兩者的分布比反應過(guò)程和積炭物種的影響.例為2:13).依據SAPO-35分子篩獨特的結構特點(diǎn)研究者本文以六亞甲基亞胺為模板劑，采用水熱法合成出嘗試將其用作甲醇轉化反應和氨甲基化反應的催化不同硅含量的SAPO-35分子篩,詳細研究了硅含量變化劑14-7以及用于CO/CH吸附分離8.1.對最終產(chǎn)品物理化學(xué)性質(zhì)的影響，并選取了3個(gè)具有不甲醇轉化制烯烴(MTO)是以煤或天然氣為原料制同硅含量的SAPO-35分子篩作為MTO反應的催化劑,考取低碳烯烴的關(guān)鍵過(guò)程. ZSM-5分子篩及具有八元環(huán)孔察了酸性質(zhì)變化對反應結果的影響.另外,還對比研究道和cha籠的SAPO-34分子篩在MTO反應中表現出優(yōu)異了具有相近硅含量的SAPO-35和SAPO-34在MTO反應的催化性能710121.1此外，其它八元環(huán)孔道的小孔分子過(guò)程中積炭物種隨反應時(shí)間的變化，嘗試將分子篩結構LI Bing et al. / Chinese Journal ofCatalysis 34 (2013) 798- 807805和其積炭失活行為進(jìn)行關(guān)聯(lián).反應溫度,然后停止通載氣,并采用微量泵泵進(jìn)甲醇溶液(w= 40%).產(chǎn)物采用氣相色譜儀(Agilent7890A型)進(jìn)行2.實(shí)驗部分在線(xiàn)分析, PoraPLOT Q_HT毛細管色譜柱, FID檢測器.2.1.分子篩的合成2.4.積炭樣 品的收集及積炭物種分析SAPO-35分子篩的合成參照文獻[17].以擬薄水鋁反應過(guò)程同2.3節,在反應--定時(shí)間后停止進(jìn)料,快石粉(w(Al2O3) = 70%，質(zhì)量分數,下同)、硅溶膠(w(SiO2)=速卸出催化劑至液氮中急冷后保存，得到相應反應時(shí)間31.1%)和磷酸(w(H;PO4) = 85%)分別為鋁源、硅源和磷的積炭樣品.源,以六亞甲基亞胺(HMI,化學(xué)純)為模板劑.各組分摩積炭物種的定性分析采用Guisnet法18.191.分別稱(chēng)取爾配比為0.96P2Os:1.0Al203;:nSiO2:1.51HMT:55.47H2O 50 mg催化劑裝入聚四氟乙烯瓶中,加入1 ml的HF水溶(n= 0.1,0.2,0.3,0.5,0.8, 1.0).具體配料過(guò)程如下:依次向液(20%),搖勻后靜置1 h,樣品溶解后,再加入0.5 ml二氯燒杯中加入去離子水、鋁源、磷源、硅源和有機胺,攪甲浣,靜置5min后,加入NaOH溶液并搖勻,將混合物轉移拌均勻后，將初始凝膠移至100 ml不銹鋼合成釜中,密封到分液漏斗中振蕩靜置,將下層萃取液取出滴入微量進(jìn)后加熱至200 °C恒溫晶化24 h.晶化完成后將產(chǎn)物離心，樣 瓶中備分析用，采用安捷倫色質(zhì)譜(Agilent固體樣品用水洗至中性后120。C烘干備用.不同Si含量7890-5975C MSD)進(jìn)行分析, HP-5毛細管色譜柱.積炭物的樣品記為nSi (n= 0.1,0.2,0.3,05,0.8, 1.0).種定性采用Nist08數據庫.2.2.分子篩的表征X射線(xiàn)粉末衍射(XRD)物相分析在PANalytical3.結果與討論X'Pert PRO型X射線(xiàn)衍射儀上進(jìn)行，Cu靶K&輻射源(2=3.1.不同硅含量 SAPO-35分子篩的合成與表征結果0.15418 nm),電壓40 kV,電流40 mA.采用Philips公司的合成SAPO-35樣品的XRD譜見(jiàn)圖1.由圖可知,所制Magix 2424X型射線(xiàn)熒光(XRF)光譜儀對樣品進(jìn)行元素系列不同硅含量的樣品均為具有LEV結構的SAPO-35分析.樣品形貌在Hitachi S-3400N型掃描電子顯微鏡分子篩[.20.表1列出了它們的相對結晶度、相對收率和(SEM)上觀(guān)察.X射線(xiàn)光電子能譜(XPS)采用Thermo元素組成.可以看出,隨著(zhù)初始凝膠中SiO2用量的增加,ESCALAB 250Xi型X射線(xiàn)光電子能譜儀進(jìn)行測定(以單所得樣品的固體收率逐漸上升;而樣品的相對結晶度則色化AlKa為激發(fā)源),以樣品表面Al2O3的A12p=74.7先升高后降低，其中以0.3Si樣品的最高，我們在eV為內標來(lái)校正樣品表面的荷電.N2吸附_脫附實(shí)驗在SAPO-34的合成研究中也發(fā)現,初始凝膠中硅含量在0.2美國麥克ASAP2010型物理吸附儀上進(jìn)行.到0.3時(shí)所得樣品的相對結晶度最高121.這說(shuō)明凝膠中'H固體核磁共振(H MAS NMR)譜在Bruker Avance的硅 含量不僅影響產(chǎn)品的組成,同時(shí)對分子篩的結晶度II-600型固體核磁共振譜儀上測定，使用4 mm探頭. 'H也有影響.另外，XRF結果顯示，SAPO-35中硅含量隨著(zhù)的共振頻率為600.13 MHz,采用單脈沖(one pulse)程序,初始凝膠中硅含量的增加而上升.為了進(jìn)-步關(guān)聯(lián)投料π/2脈寬為4.4 us,弛豫延遲為10s,轉速為12 kHz,采樣次硅含量與所得樣品中硅含量的關(guān)系,這里提出硅進(jìn)入率數為32次.實(shí)驗前,所有樣品在400 °C,低于10-3 Pa真空的概念,將其定義為[Si/(Si+Al+P)]=*/[Si/(Si+Al+P)]初始凝權脫水20 h以上，以脫除吸附在分子篩中的水和雜質(zhì).樣品(見(jiàn)表1).可以看出，隨著(zhù)投料硅含量的增加，所得在N2手套箱中轉移到核磁轉子中待測.'HMASNMR譜SAPO-35樣品中的硅進(jìn)入率逐漸下降.其中0.1Si樣品的的定量分析方法如下:以金剛烷為外標物，首先獲得標硅進(jìn)入率最高為1.82;當初始凝膠中硅含量大于0.3時(shí),樣峰面積與質(zhì)量關(guān)系的標準曲線(xiàn).在相同的采譜條件下硅進(jìn)入率開(kāi)始小于1;至1.0時(shí)僅為0.7.因此,可以認為正獲得已知質(zhì)量樣品的'HMASNMR譜，根據是由于低硅樣品中高的硅進(jìn)入率導致了其較低的固體Gauss-Lowrance線(xiàn)型擬合獲得B酸峰面積，再根據標準收率.文獻[22]運用晶格模擬技術(shù)Lttce simulation曲線(xiàn)獲得樣品的B酸密度.techniques)計算了SAPO-5分子篩中硅進(jìn)入骨架能量的2.3.催化性能評價(jià)變化,發(fā)現分散度高的單取代硅是最穩定的，其次是5Si采用常壓固定床裝置評價(jià)分子篩樣品上甲醇轉化和8Si島,即隨著(zhù)硅取代量的增加,硅進(jìn)入骨架所需能量反應性能.將1.2 g焙燒后的催化劑樣品(40- 60目)裝填在也相應增大,從而導致硅進(jìn)入骨架的能力降低.這與本反應器中,于N2氣氛下升溫至520 °C吹掃30 min后降至文結果- -致.u Bing etal. /Chinese /ourmal ofCatays 34 (2013)798 807807通過(guò)氫轉移產(chǎn)生的環(huán)縮合反應), SAPO-35上則主要是4.結論甲基苯、蔡和甲基恭.這可能與它們自身的結構有關(guān).SAPO0-34分 子篩中的CHA籠(0.67 nm x 0.67 nmx1.0利用水熱法合成了不同硅含量的SAPO-35分子篩，m)要大于SAPO-35中的LEV籠(0.63 nmx 0.63 nmx發(fā)現隨著(zhù)合成凝膠中硅含量的增加,樣品的固體收率逐0.73 nm). SAPO-35中較小的籠體積限制了烴池活性物漸上升;樣品的結晶度則先升高后降低,其中0.3Si樣品種多甲基苯和大分子積炭失活物種稠環(huán)芳烴的生成，同具有最高的相對結晶度;硅進(jìn)入骨架的能力隨硅含量的時(shí)它對積炭失活物種也具有較弱的容納能力,因而失活增加而下降.高硅SAPO-35的晶體表面比較粗糙,尤其是較快，烴池活性物種的缺乏也使得乙烯、丙烯選擇性相1.0Si樣品的晶體形貌呈核殼結構，推測為粗糙晶體表面對較低.另外,值得注意的是,反應過(guò)程中SAPO-35催化的二次晶體生長(cháng)所致.不同硅含量的SAPO-35樣品在劑上沉積的有機物中始終含有少量飽和環(huán)烷烴結構的MTO反應中都呈現較快速失活的特征,且硅含量越高，金剛烷類(lèi)化合物.我們近期對SAP0-34在MTO反應的積失活速度越快.這主要是由于高硅樣品中較高的B酸中炭物種研究中，首次發(fā)現報道了金剛烷類(lèi)化合物是低溫心密度導致了嚴重的積炭和氫轉移反應等副反應.對比反應(≤350 °C)的積炭物種,升高溫度后其逐漸轉變?yōu)榉治鯯AP0-35與SAPO-34在MTO反應過(guò)程所產(chǎn)生的積蔡和取代萘類(lèi)物種2號本文實(shí)驗的反應溫度為400。C,金炭物種,發(fā)現SAPO-35中較小的籠體積限制了烴池活性剛烷類(lèi)化合物在SAPO-35中的穩定存在再次說(shuō)明分子物種多甲基苯和大分子積炭失活物種多苯環(huán)化合物的篩籠尺寸的變化對積炭物種的生成和穩定具有重要的生成，同時(shí)其對積炭失活物種也具有較弱的容納能力,從影響.而導致了較快速的失活.