In-situ Synthesis of ZSM-5 Zeolite from Metakaolin/Spinel and Its Catalytic Performance on Methanol

China Petroleum Processing and Petrochemical Technologv2010. Vol.12. No.1.Dp 23-28In-situ Synthesis of ZSM-5 Zeolite from Metakaolin/Spineland Its Catalytic Performance on Methanol ConversionLiu Ye; Yu Xianbo; Qin Lei; w ang Jingdai; Yang Yongrong(Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027)Abstract: ZSM-5 zeolite was in-situ syntbesized from metakaolin or spinel by incorporating additional silica andalumina sources, respectively. The ZSM-5 zeolite was characterized by X-ray diffractometry (XRD), scanningelctron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and N2 adsorption measurement.This supported zeolite was tested on the methanol to propylene (MTP) processes. Experimental results showed thatthe ZSM-s5 zeolite exhibited high sletivity for propylene. The yield of propylene on ZSM-5 zeolite made fommetakaolin was increased by 17.73%, while that on ZSM-5 zeolite made from spinel was raised by 9.90%, com-pared to that achieved with the commercial ZSM-5 zeolite. The significant increase in propylene production isprobably due to the distinctive morphology of the ZSM-5 zeolite, which possessed a rough extermal surface Cov-ered with sphere-like particles and distribution of small crystals sized at around 400- -500 nm. This morphologycould help to generate more crystal defects so that more active centers could be exposed to the reaction mixture. Inadition, the zeolite product had a gradient pore distribution and many medium Broinsted acid sites, both of whichmight also contribute to the increased propylene production.Key words: metakaolin; spinel; in-situ synthesis of ZSM-S; methanol to propylene (MTP)1 Introductionsilica and alumina ability in kaolin composite, i. e:ther-mal activation of the kaolin; and hydrothermal reactionThe demand for propylene used as a basic organic rawwith aqueous alkali mediumlol. As for the first treatingmaterial in modern petrochemical industry has beenstep, Sun'] reported that metakaolin was obtained bygrowing steadily. Currently, propylene is mainly pro-calcining kaolin between 450 C and 750 C. When theduced as a by-product during production of ethylenecalcination temperature was increased to between 900through catalytic cracking of petroleum oilsl!I. However,C and 950 C, metakaolin would be transformed intodue to the shortage of oil resources in the world, greatspinel. Both metakaolin and spinel contain partially ac-interest has been focused on searching alternative manu-tivated silica and alumina, making themselves the mostfacture procedure with high yield of propylene insteadfavorite phases of kaolin being in use. It is useful to ex-of using the original petroleum route. Recently, metha-amine the difference in property of the zeolite made fromnol to olefins (MTP) process has been atracting lots ofmetakaolin and spinel respectively in order to provideattentions since methanol can be economically producedguidance on catalyst application.from natural gas and coal. The ZSM-5 zeolite has beenextensively used to increase the yield of propylenel231 In this paper, we focused on a method to synthesize thedue to its adaptable intrinsic acidity and well-defined ZSM-5 zeolite with metakaolin or spinel by incorporat-microporous structure. In addition to acid property anding silica and alumina additionally. Exact physicochemi-pore structure of the catalyst, its morphology is consid- cal properties of the zeolite products were examined. Theered as another critial factor in terms of catalytic per- zeolite products were for the first time involved in MTPformance of zeolitel. Frioozil5] reported that the ZSM-5 reaction and their catalytic activity was also studied.zeolite with smaller crystal size showed consistent higher2 Experimentalpropylene selectivity with time-on-stream compared tothat of ZSM-5 zeolite with larger crystal size.2.1 Sy中国煤化工Kaoin has been used as the binder or matrix for the pur- Raw IMHCNMHGfurnaceat700Cpose of diluting and stabilizing zeolite during catalyst Corresponding author: Professor Wang Jingdai,Telepbone:synthesis. Typically, there are two steps to activate the +86-571-87951227; E-mail:Wangjd@cmsce.zju.edu.cnLiu Ye, et aL In-situ Synthesis of ZSM-5 Zeolite from Metakaolin/Spinel and Its Catalytic Performance onMethanol Conversionand 950 C for 4 h, respctively, to obtain metakaolin detector (FID) coupled with a 30-m plot-Q capillaryand spinel. RK, MK and SK are used hereinafter to stand column.for raw kaolin, metakaolin and spinel, respectively. Dur-3 Results and Discussioning the synthesis process, water glass, ethylenediamine(EDA) and MK or SK were frst added into dstlld water. Kaolinite [AlSiO;(OH)4] is the main mineral phase inA mixture of sulfuric acid and aluminum sulfate was in- kaolin. It is composed of two interlayer surfaces com-silled dropwise to the solution to obtain the following bined by hydrogen bonding interaction, with one sur-molar ratio: 40MK (SK): 80SiO: 10EDA: 1Al2O;: 3100 face of slion atoms in tetrahedral positins and anotherH2O. Aluminum sulfate and water glass were used as surface of aluminum atoms in octahedral positions8-9.supplementary alumina and silica sources. After contin- After calcination treatment, aluminum atoms in one ka-ued stiring at room temperature for 2 h, the slurry was olin surface would transform from octabedral positionsremoved into an autoclave and the mixture was hydro- to tetrahedral positions with higher activity. The envi-thermally treated at 180 C for 40 h. Then the product ronment of silicon atoms becomes distorted and finallywas washed with distilled water three times, driedat 110 amorphous silica is liberatedlI01 along with a dehydroxylationC overmight and calcined at 550 C to remove the template. process. Amounts of these activated silica and aluminaThe ZSM-5 sample obtained thereby is referred to as species in kaolin are altered with an increasing calcina-ZSM-5 zeolite made from metakaolin (MZ) or ZSM-5 tion temperature. Sun et al.7] reported that the amount ofzeolite made from spinel (SZ). The commercial ZSM-5 activated alumina was higher than that of activated silicazeolite (RZ) was used as the reference for comparison in metakaolin, while the amount of activated aluminaof catalytic performance.was lower than that of activated silica in spinel.2.2 Characterization3.1 FT-IR studyX-ray dffaction (XRD) patterns were recorded on a Figure Ia shows the IR spectra of dferent phases in .Rigaku D/max 2500 powder dffractometer equipped kaolin. The peak at 540 cm' crresponding to the stetch-with Cu Ka radiation (40 kV, 80 mA). The relative crys- ing vibraion of octahedral Al(O,OH)6 in RK disappears,tllinity of the sample was defined by comparing the sum and is replaced by a peak at 815 cm-' which belongs toof the itensitis of dffaction peaks at 20- 23.19, 23.39，Al-O bonds in Al2O3. This indicates that after calcination,23.7°, 23.9 and 24.4, respectively, with that of the com-activated alumina was generated in MK and SK. Themercial ZSM-5 zeolite. The SEM images of productspeaks around 815 cm:1 become relatively weaker in SZ,were acquired on a JEOL JSM-6301F instrument. The whereas the peaks around 1090 cml asigned to theFT-IR spectra were obtained on a Nicolet 560 spec-stretching Si- 0 bonds in SiO2 become stronger. Thistrograph with infrared optical bench in the range fromresult is consistent with the study of Sun et al.I7.400 cm-! to 4000 cm:' waveband. N2 adsorption/desorp-Meanwhile, peaks at 3620 cm-l and 3692 cm-' assignedtion tests were conducted on an automatic Micromerticsto inner-hydroxyl groups and inner-surface 0- H groups,respectively, cannot be observed in either MK or SKASAP 2400 apparatus.spectra.2.3 Catalytic activity testsThe IR spectra of MZ, SZ and RZ are presented in FigureThe MTP reaction was arried out at 450 c ina fixed- 1b. The sructure sensitive infrared band of ZSM-5 zeo-bed stainless-steel reactor under atmospheric pressure. lite at 1222 cm.", and the five- membered rings vibra-The weight hourly space velocity (WHSV)was setat 1h". tions at 545 cm1"121 appear in MZ and SZ. This confirmnsThe catalyst powder was preformed, ground and sieved the formation of ZSM-5 zeolite in both MZ and sz. Ac-to obtain particles in the range of 40- 60 mesh and was cordin中国煤化工absorbance at 545then loaded in the middle section of the reactor. The com- cm-! toYCNMHGlantitatively reflectpositions of gaseous products were analyzed on-line by the crystanmy uruc cuic. inc absorbance intensi-a gas chromatograph equipped with a flame ionization ties ratio of SZ is higher than that of MZ in Figure lb,24China Petroleum Proessinge and Petrochemical TechnologvRKSKyMKyrvRIMWh40003500 3000 2500 2000 1500 1000 500510152025303540Waveoumbers, cm'20.(°)RZMiMZmSZ4000 3500 3000 2500 2000 1S00 1000 5005120 3303540Wavenumbers, cm'20()Figure 1 FT-IR spectra of RK, MK, SK (a), RZ, MZ, andFigure 2 XRD patterns of RK, MK, SK (a), MZ, sz, andSZ (b)RZ (6) .which indicates that the crystallinity of SZ is higher thanTable 1 Crstallinity of MZ. sz and RZthat of MZ.SamplesCrysallity, %3.2 XRD study3243The XRD patterns of different phases of kaolin are pre-100sented in Figure 2a, in which the phase transformationbehavior of kaolin is revealed. The broad and smooth3.3 SEM studysignal of MK indicates that when RK transforms intoMK, the originally ordered crystal structure of RK hasFigure 3 displays the surface morphology of crysallizedturned into an amorphous phase, which confirms thesamples. Both samples of MZ and SZ exhibit typical hex-formation of activated silica and alumina species. Mul-agonal-shaped crystal rods of ZSM-5 zeolite. However,lite peaks, besides amorphous phase, also appear in thetheir appearances are quite different from that of com-XRD pattern of SK along with a further increase in themercial ZSM-5. The external surface of ZSM-5 zeoliteobtained with regular synthesis method is clear andcalcination temperature.smooth as shown in Figure 3c. After adding MK or SKThe XRD patterns of crystallization samples are shownduring the synthesis process, it was found that there werein Figure 2b. Peaks in the range of20=79- 99 and 239- many sphere-like particles randomly distributed on the25° identifed as rtflections of ZSM-5 zelitel are de- external surface of the crystals, which might be ascribedtected both in MZ and sZ without other unidentified to the residue of untransformed MK or SK. Furthermore,phases. Meanwhile, the intensities of the diffraction this untransformed portion of MK or SK might retardpeaks in MZ and Sz are lower than those of RZ, indicat- the growth of zeolite so that an incompletely formeding to a decrease in crystallinity of MZ and sZ after in- zeolite with defect cites mioht he oenerated. Besides,volving MK and SK in zeolite synthesis. The crytallin- accord中国煤化工re 3(a, b), cystality of samples is listed in Table 1. The crystallinity loss sizes 。YHC N M H Gtributed at aroundof MZ is calculated to be 11% compared with sz, which 400 - -500 nm, which are much smaller than that of RZ.is in accordance with the results of FT-IR measurement. Both rough surface and small crystal size are conducive25LIu Ye, et al. In-sius Synthesis of ZSM-5 Zecolite from Metakaolin/Spinel and Its Catalytic Performance onMethanol ConversionFigure 3 SEM images ofMZ (a), sZ (6) and RZ (e)to exposing more active sites, which could largely en- distribution shown in Figure 4b that a broad distribu-hance the accessibility of reactant molecules to active tion of pore diameter extends to a range larger than 20centers to significantly improve the catalytic activity. nm. The formation of mesopores and macropores can bepartially ascribed to the formation of the second-level3.4 Pore structurepores derived from agglomeration of MZ or SZ crystals.Adsorption and desorption isotherms of ZSM-5 zeolite andThe higher surface energy resulted from small crystalthe calculated BJH pore size distributions are presented sizes of MZ and SZ makes particles aggregate tightly asin Figure 4. Both MZ and Sz belong to the type IV sorp- ilustrated in SEM images.tion isotherms and the type Hs bhysteresis lopslsl, Evi-The specific surface area and pore volume data obtaineddent hysteresis loops appear when the relative pressurefrom pore size distribution are summarized in Table 2.p/po varies from 0.45 to 1.0, which indicates the exist-The average pore widths of MZ and SZ are significantlyence of large mesopores or macropores in the crystal-larger than that of RZ. MZ and SZ almost display theline products. This is in agreement with the pore sizesame pore properties. The gradient pore distribution in10zeolite can belp to decrease the limitations betweenmolcules and zeolite walls, which could facilitate the80removal of product molcules and reduce the undesir-70 Fable side reactions.60}Table 2 Pore properties of MZ, SsZ and RZBET surfaceTotal poreAverage pore40 fSamplearea, m2/gvolume, mLgwidth (A)30 5.,20.40.6.81169.960.12730.00Relative pressure, P/P。sz180.100.12628.030.30RZ243.120.10517.280.253.5 Acidity。0.20Typical pyridine adsorption experiments followed bys 0.15FT-IR measurements were carried out. In the infrared宣0.10-spectra, Bronsted and Lewis acidities have been quanti-0.05|fied according to the integrated areas of the peaks at001540 cm*' and 1450 cm', respectively. Pyridine wasPore diameter, AFigure 4 Adsorption and desorption isotherms (a) and Pore5 h.'中国煤化工as crried out bysize distribution of MZ andSZ (b)stepwiYHCNMHGto250,350,450C, respectively. The IR spectra taken at intervals from26China Petroleum Processing and Petrochemical Technologev250 C to 350 C and from 350 C to 450 C correspondpropylene was by 9.9% higher than that achieved by RZ.to medium acid sites and strong acid sites, respectively. Besides increasing propylene yield, MZ and SZ samplesTable 3 gives quantitative information about the mediummight also help to enhance ethylene production judgingBronsted acid properties of samples MZ, SZ and RZ. Asftom the data displayed in Table 4. Total yields of ethyl-shown in Table 3, SZ exhibits a bit higher content ofene and propylene achieved by the ZSM-5 zeolite mademedium Bronsted acid sites than RZ. However, thefrom MK were increased by 24.20%, while those ob-amount of medium Bronsted acid sites of MZ increasestained on the ZSM-5 zeolite made from SK were raisednotably by 50% as compared to RZ. Bronsted acid isby 11.95%, compared to those achieved by the commer-critical to MTP reaction since it favors deprotonation ofcial ZSM-5 zeolite.methoxy species. Also, Changl reported that the more The above-mentioned catalytic results can fully dem-the medium acidity of zeolite was, the more it was ben- onstrate that ZSM-5 zeolite made from MK or SK is ben-eficial to light olefin production. Hence MZ might beeficial for ethylene and propylene production, in par-more favorable to MTP reaction than SZ did.ticular propylene production. The better reactivity of thesaid ZSM-5 zeolite might be resulted from the combina-3.6 Catalytic activity evaluationstion contributions of its unique surface morphologies,The MTP reaction resuts are listed in Table 4. All crys- gradient pore structures and enhanced acidity properties.talline samples could achieve almost complete conver-4 Conclusionssion of methanol. Changl pointed out that the conver-sion rate of reactants could affect the product ZSM-5 zeolite was hydrothermally in-situ synthesizeddistribution. Since reactants in the experiments all on the basis of metakaolin and spinel, respectively, byachieved nearly 100% conversion, the influence of con-adding silica and alumina sources. The addition ofversion rate on product yield could be ignored. It can bemetakaolin or spinel rendered the supported ZSM-5 zeo-seen from Table 4 that the yield of propylene generated lite a distinctive morphology with rougher external sur-on MZ was by 17.73% higher than that obtained on RZface and smaller crystal size, and an enbanced pore struc-during the MTP reaction. As for sZ, the selectivity of ture with a gradient pore distribution. Besides, the ZSM-5Table 3 Acid properties of MZ, sZ and RZzeolite made from metakaolin has more mediumdetermined by pyridinemmol/gBronsted acid sites than conventional ZSM-5 zeolite. TheMediumStrongcatalytic activity evaluation shows that the ZSM-5 zeo-|CatalystsBronsted acidlite made from either metakaolin or spinel is a promis-MZ0.0450.021ing catalyst for conducting MTP reaction, while thesz0.033 .0.017ZSM-5 zeolite made from metakaolin demonstrates rela-0.0300.047tively better propylene selectivity than the ZSM-5 zeo-Table 4 MTP reaction results of sample MZ, sZ and RZlite made from spinel.ItemsSZRZAcknowledgments:The authors thank the Fushun Research In-Conversion, %98.69100.099.85stitute of Petroleum and Petrochemicals (FRIPP) for peformingYield, m%the XRD, SEM, FTIR, and BET analyses. The authors grate-2.811.561.48fully acknowledge the financial support from National Natural18.0113.5911.54Science Foundation of China (20776124 and 20736011).0.610.84 .0.5227.3119.489.58ReferencesC39.4813.9811.02[1] Mc中国煤化工elective productin ofC.r+C;"45.3221.12propyi|_development in high24.1331.6636.38silica:DHCNMHG.243-249Cs+I 7.6518.8929.48[2] Zhao T s, Tomokazu T, Noritatsu T. Direet synthesis of pro-2Liu Ye, et aL In-stu Synthesis of ZSM-5 Zeolite from Metakaolin/Spinel and Its Catalytic Perormance onMethanol Conversionpylene and light olefis from dimethyltber catalyzed by modi- olinite-NMF itercalate[J], Clays Clay Mine, 1993, 41(6): 707-fied H-ZSM-5[J]. Catal Commun, 2006, 7(9): 647-650[3] Abul-Hamayel M A, Aitani A M, Saced M R. Enhancement [10] Chandrasekhar s, Pramada P N. Investigation on the syn-of propylene production in a downer FCC operation using a thesis of zeolite NaX from kerala kaolin[J]. J Porous Mat, 1997,ZSM-5 aditive[J]. 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Ka- Catal, 1977, 47(2): 249-253Mechanical Completion of Three Units at Shenhua Coal-to-Olefin ProjectThree process units, i. e. the gasification unit, the syngas This project, which is a giant commercial demonstrationpurification unit and the methanol unit of the coal-to- coal-to-olefin project invested by the Shenbua Group,olefin project at the Shenhua Baotou Plant approved by is located in the Halinger Industry Base of Baotou city.the State Development Reform Commission have been The overall project covers an 1.8 Mt/a coal-to-methanolhanded over to the owner after mechanical completion unit, a 600 kt/a MTO (methanol-to-olefin) unit, a 310of construction, which symbolized major progress in the kt/a PP unit, a 300 kt/a PE unit and a 224000 Nm/h airproject construction to lay a good foundation for the pre~ separation unit. The investment in the said project totalscommissioning of chemical units slated for May 2010. more than 12 billion RMB.New Process for Increasing Propylene Output Developed by LPEC ;The SINOPEC Luoyang Petrochemical Engineering Com- mercial application tests conducted on the No. 1 FCCpany (LPEC) after analyzing the advanced FCC tech- unit of the SINOPEC Changling Branch Company havenologies both inside and outside of China has developed indicated that at a catalyst temperature of 630"C in thethe FDFCC-1II process for increasing propylene output bottom of resid riser and a catalys/oil ratio of 9.82, thecoupled with manufacture of clean gasoline. Pilot tests yield of LPG and propylene was 26.66% and 10.22%,have revealed that the FDFCC-III process can dramati- respectively, and the dry gas yield was only 4.33%. Thecally reduce thermal cracking reactions and enhance olefin中国煤化工17.7% by volumecatalytic cracking reactions to promote transfer of sul- with tYHCN MH Gaching only 0.032fur contained in the feedstock into FCC gas. The com- m%.28