Gas-Phase Beckmann Rearrangement of Cyclohexanone Oxime over B-ZSM-5 Derived Titanosilicalite

TSINGHUA SCIENCE AND TECHNOLOGYISSN 1007-0214 03/21pp11 - 14Volume 7，Number 1，February 2002Gas-Phase Beckmann Rearrangement of CyclohexanoneOxime over B-ZSM-5 Derived Titanosilicalite .YIN Shuangfeng (尹双凤)**，ZHANG Fazhi ( 张法智)，XU Boqing (徐柏庆)State Key Laboratory of C, Chemical Technology, Department of Chemistry .Tsinghua University, Beijing 100084, ChinaAbstract: Four different ZSM-5 zeolites are tested for the gas- phase Beckmann rearrangement ofcyclohexanone oxime (CHO) into lactam. B ZSM-5 derived titanosilicalite (Ti-ZSM-5) exhibits catalyticperformances comparable to hydrothermally synthesized titanosilicalite (TS- 1)，much better than B ZSM-5 andAl-ZSM-5. The effect of reaction conditions (solvent， feed space velocity， and water) on the catalyticperformance of Ti-ZSM-5 is studied. It is found that a quantitative relationship exists among the feed spacevelocity, the reaction time, and the CHO constant conversion. Ethanol or methanol as solvent shows higheractivity，lactam selectivity， and stability than benzene and n _hexanol. The addition of water to therearrangement with a maximum amount of 1. 0 mole per mole CHO results in the increase of CHO conversionwhile no meaningful changes in lactam selectivity and stability are observed.Key words :titanosilicalite; gas _phase Beckmann rearrangement; cyclohexanone oxime ; lactam; B. ZSM-5zeolitetitanosilicalite by allowing TiCl4 gas to react withIntroductionB- ZSM-5 zeolite is reported here， and theDue to its remarkable catalysis, titanosilicalite hasrearrangement reaction over the titanosilicalite isattractedconsiderableattentionTitano-investigated.silicalite-1prepared by hydrot hermal synthesis[4exhibits much better catalytic performance for the1 Experimentalgas- phaseBeckmannrearrangementofA sample of Ti-ZSM-5 (molar ratio of Si/Ti= 97)cyclohexanone oxime ( CHO ) into lactam thanwas prepared by allowing TiCl4 gas to react with B-other solid catalysts, such as silicalite-1[4], B2O3/ZSM-5 zeolite. Standard titanosilicalite designatedZrO2[5]，Ta2O./SiO.0]， HZSM-57， Hβ[8]， andas TS-1 with the same molar Si/Ti ratio as Ti-HMCM-41[9. However, it is surprising that only .ZSM-5 washydrothermally synthesized usingtwo papers have been published on the researchtetrapropylammonium hydroxide as a templatingaboutthereactionusingagent. The detailed preparation was described intitanosilicalites as catalysts. In addition，it is veryRef. [10]. Fourier- transform-infrared (FT-IR )，expensive to synthesize titanosilicalite usingultra-violet-visible ( UV-Vis )，andX-raydiffraction ( XRD ) techniques confirmed thelocation of Ti of Ti-ZSM-5 or TS-1 in theagent.A cheap and simple method for the synthesis of7SM5 rorlite. For facilitating theinv中国煤化工ionof Ti，Al-ZSM-5(rMYHCNM H G) and B ZSM-5 (molarReceived: 2001-04-04, revised: 2001-05-28ratio of Si/B = 10 ) zeolites were prepared by* Supported by the Foundations for Basic Research ofhydrot hermalsynt hesis.Tsinghua University and of China Petrochemicalrearrangement of CHO was carried out at 380CCompanyunder atmospheric pressure in a downflow，vertical* * Towhr*数雅pondence should be addressed. E mailtubular Pyrex reactor. The catalyst loading wasaddress: 4402@ 263. net.0.125 g. A mixture of CHO, solvent and nitrogen12Tsinghua Science and Technology, February 2002，7(1): 11- 14at a molar ratio of 1 : 26 : 28 was passed throughcyanopentane，and cyanopentene. In addition, ththe reactor. The product collected by an ice/waterproduct distribution over all the catalysts seemstrap was analyzed by GC- 8A gas chromatographyaffected little by the time on stream (TOS).equipped with a 20% PEG20 M (2 m) column and2.2 Influence of feed space velocityFID detector. The mass balance before and afterthe catalyst bed was always higher than 97%. TheResults of the studies on the effect of feed spacemethod for treating the experimental data wasvelocity over Ti- ZSM-5 are presented in Fig. 2.described in Ref. [11].The solvent is ethanol. It is evident that with theincrease of space velocity， Ti-ZSM-5 deactivates2Results .more quickly. In contrast to the CHO conversion ，1o meaningful change in the lactam selectivity2. 1Comparison of rearrangement reactionoccurs when the space velocity of the feed is variedon different ZSM-5 zeolites(not shown in Fig. 2). In addition, although theTi-ZSM-5，TS-1，Al-ZSM-5，and B ZSM-5 arelactam yield decreases with increasing feed spacetested for the gas-phase Beckmann rearrangementvelocity，the actual lactam production， (i. e.using ethanol as solvent.‘ The space velocitylactam selectivity X CHO conversion X space(WHSV) of feed is 4.5 h'. Figure 1 presents thevelocity) is increased.time course of these catalysts. TS-1 and Ti-ZSM-5100with CHO conversion no less than 82. 0% can lastfor 33 h while Al-ZSM-5 and B- ZSM-5 zeolites8Ideactivate very rapidly. After the reaction proceedsfor about 3 h, CHO conversions of both Al -ZSM-56Mand B ZSM-5 zeolites reduce to 30%. During thewhole reaction， Ti- ZSM-5 shows CHO conversionand stability similar to TS-1, better than Al-ZSM-5 and B -ZSM-5. In the case of lactam selectivity0 10015X 250Time on streamn h( presented in Table 1 )，TS-1 shows lactamselectivity of about 98% similar to Ti-ZSM-5,higher than that of Al-ZSM-5 (94. 0%) and B-Fig. 2Effect of space velocity ( WHSV，h-1) onZSM-5( 92. 0%). The by-products of thecatalytic performance of Ti ZSM-5rearrangement over different ZSM-5 zeolites aredominated by cyclohexanone， cyclohexenone ,2.3 Effect of solventCyclohexanone oxime exists in the solid state atroom temperature andatmosphericpressure. .Therefore, it should be dissolved in solvent beforebeing delivered into the reactor. Here， polar40Ti-ZSM-5methanol，ethanol， n-hexanol， and non-polarTS-Ibenzene are selected as solvents for the reaction onAl ZSM-5B-ZSM-5Ti-ZSM-5 zeolite. The space velocity of CHO is 10121826h-'. Figure 3 presents the effect of solvent onTime on stream (h)CHO conversions， lactam selectivity and stabilityof Ti-ZSM-5. When polar n- hexanol and non- polarbenzene are used for dissolving CHO, the averageFig. 1 Rearrangement reaction on different zeolitesCHO conversions within the initial 30 min areTable1 Product distribution of Beckmann rearrangement53.中国煤化工1verHowever, usingover different ZSM-5 zeolites'me>lvent shows high CHOconYHC N M H G4. 7%, respectively. InSamplesCyclohexanone+ Cyanopentane +the case of lactam selectivity， when methanol andLactamcyclohexenonecyanopenteneOthersethanol are fed with CHO， both of lactamTi- ZSM-598. 00. 60.398.2selectivities are above 97. 0%; while using benzeneB-ZSM-5 92. 04.52. 80.7and n-hexanol as solvent， the selectivities areAl-ZSM-53.4_2.10.5reduced to 52. 8% and 82. 5%，respectively.* Data are averaged for TOS≤6 h.Moreover，the desired lactam selectivity tends toYIN Shuangfeng (尹双凤) et al: Gas- Phase Beckmann Rearrangement of ....13decline with reaction time when using n-hexanol asDiscussionsolvent. The by-products are still dominated bycyclohexanone，cyclohexenone， cyanopentane andIn recent decades, many attempts have been madecyanopentene. During the whole reaction， CHOto use zeolites for the gas-phase Beckmannconversion is kept at ca 66. 0% with methanol asrearrangement of cyclohexanone oxime.solvent while Ti-ZSM-5 can not activate CHO withpresent results show that the incoporation of Ti inbenzene as solvent after only 8 h of TOS. Inthe ZSM-5 framework leads to the simultaneousaddition，Ti-ZSM-5 deactivates from CHOincrease of activity, lactam selectivity and stabilityconversion of 74. 7% to 44. 0% with ethanol asof ZSM-5，which is in agreement with the resultssolvent more slowly than using n-hexanol asy ThangarajJ41. In general， the isomorphoussolvent.substitution of B or Al by Ti in the ZSM-5framework results in the decrease of its acidity and100名名8a 10hydrophilicity simultaneously. The decrease in0。。hydrophilicity is beneficial for the adsorption ofCHO molecules on AI-ZSM-5 zeolites，which leads5060to the increase of CHO conversion. Since the40strong acidic sites on zeolites are responsible for20the catalyst deactivation[13]， the lifetime of Al-ZSM-5 is improved with the decrease in acidity. In12Time on stream (h)addition，Ti-ZSM-5 shows the same catalysis asTS-1 with the same Si/Al ratio， which implies aFig.3Effect of solvent on the performances ofpotential cheap route for the synthesis ofTi- ZSM-5titanosilicalitewhich isattractive for the， ethanol;， methanol: 一一，benzene:pet rochemical industry.，hexanol; solid. conversion: hollow selectivityThe excellent catalytic performance of Ti ZSM-5for the rearrangement stimulates our research onthe process parameters. In general， with the2.4 Influence of waterincrement of space velocity of CHO, the retentionThe addition of water to the rearrangement .time on the catalyst is shortened, which results inreaction over B-MFI zeolite has been reported-12].the decline of CHO conversion and the quickIn contrast to the previous results， Fig. 4 showsdeactivation. However, the effect of space velocitythat the addition of 0. 5 mole water per mole CHOon the lactam selectivity is still being debated. Forgives the maximum increase in CHO conversion ofexample，Singh et al.L14] reported that the lactam7.4%. In the range of water amount up to 1. 0selectivity for SAPO-11 was enhancedoymole per mole CHO, the addition of water leads toincreasing the space velocity while no meaningfulthe increment of CHO conversion while ncchange in lactam selectivity was observed on B2O:/remarkable changes in the stability and lactamZrO, catalystI1. It can be seen from Fig. 2 that’selectivity are observed. When the water additionZSM-5 catalyst almost deactivates linearly withreaches 1. 5 mole per mole CHO, the stabilty isTOS when the feed space velocity is greater thanimproved at the expense of the CHO conversion.2.5 h-', and the increase in space velocity leads tothe quick deactivation. According to the slopes of90 |lines corresponding to the space velocities of 2. 5，5，and 10 h-1 in Fig. 2，a linear relationshipbetween the space velocity and the deactivationfactor can be formulated bv an equation:0.0中国煤化工- 0. 0973.5,0w.YHCN M H Gation factor and V。isspace velocity. When CHU conversion is less thanTime on strearm (h)100% at the initial reaction， a deactivationfunction is assumed by the following equation:x= x。十btFig.4 Effect of molar ratio of water on conversion andst2石流数据ri- ZSM-5.where x represents the instant CHO conversion,is the initial CHO conversion, b is the deactivation14Tsinghua Science and Technology, February 2002，7(1): 11- 14factor，and t is the time on stream ( hour ).Competitiveadsorptionoccursamong theTherefore, we can get,reactants，products， solvent and water. Strongx= xo+ (0.2921V,- 0.0973) X t (3)adsorption of water on the active sites of catalystsEquation (3) can be used to extrapolate thewill lead to the decline of CHO conversion andcatalyst deactivation at certain space velocity. .lactam selectivity， while weak adsorption wilWhen the space velocity is very low， theaccelerate the adsorption of high molecules relatedtheoretical xo is equal or close to 100%. Thus,to the catalyst deactivation. On the other hand .even after the rearrangement proceeds for longthe addition of water gives rise to the inhibition oftime，the available active sites on Ti ZSM-5 areby-product of cyanopentene while the side- reactionenougho activate CHOcompletely.Theof hydrolysis is strengthened. Therefore ，whetherrelationship between CHO instant conversion ，to add water to CHO or not is correlated with thespace velocity, and reaction time may be revised byproperties of the catalyst.a staged function. However， when the reaction4 Conclusionswith low space velocity proceeds till the CHOconversion is less than 100%， the catalystB- ZSM-5 derived titanosilicalite ( Ti-ZSM-5) isdeactivation behavior also follows Eq. (3).studied for the gas- phase Beckmann rearrangementStudies of the effect of solvent on the catalyticof cyclohexanone oxime into lactam. TS-1， B-behavior of zeolite are very significant. In ourZSM-5，and Al-ZSM-5 are used as references forprevious work， B2O3/ZrO2 catalyst was found t(Ti- ZSM-5 to investigate the effect of Ti in ZSM-5show better catalysis for the gas-phase Beckmannframework on the rearrangement reaction. It isrearrangement using non- polar benzene as solventshown that the incorporation of Ti in the ZSM-5than that using polar alcohols or acidsl. Dai etframework leads to the remarkable improvemental.[8] reported that Hβ zeolite exhibited highon the catalysis of rearrangement over ZSM-5activity and selectivity for lactam formation whencatalyst. The Beckmann rearrangement over Tn-hexanol was fed with CHO instead of benzene orZSM-5 is closely correlated with the polarity of thelow-alcohol like methanol and ethanol. Detailedsolvent. Using ethanol and methanol as solvents iskinetic investigation of the effect of solvent on themore suitable for the reaction than benzene and n-gas -phase rearrangement on silicalite-lwashexanol. The addition of water to the feed affectsreported by Komatsu[1s]. He tried to explain thethe solvent polarity and the adsorption of reactants“solvent effect ”according to the solvent polarityand products on the catalyst surface. The optimaland the competitive adsorption of solvent, reactantaddition is 0.5 mole water per mole CHO.and product on the catalyst surface. He found thatInvestigation on the effect of CHO space velocityethanol with medium polarity is more effective inon the catalyst stability results in a quantitativethe formation of lactam than other solvents. Irrelationship between the CHO instant conversion,general，metal oxide catalysts with solid acidspace velocity， and time on stream, which suppliesproperties exhibit promising catalysis for thea convenient method to infer the catalyst stability.Beckmann rearrangement reaction when polarReferencessolvent is used, while the non-polar solvents arefavorable for the rearrangement reaction on theSynthesis of a titaniumsilicoaluminate isomorphouszeolite catalysts，which is further confirmed by ourTi zeolite beta and its application as a catalyst for theexperimental results on Ti-ZSM-5 zeolite. Theselective oxidation of large organic molecules. J.improvement of lactam selectivity with ethanol O1Chem. Soc. Chem. Commu.，1992, 8: 589 - 599.methanol as solvent is attributed to their polarity.[2] Inagaki S，Fukushima Y，Kuroda K. Synthesis ofThe polar OH groups are prone to be adsorbed onhighly ordered mesoporous materials from a layeredTi-ZSM-5 catalyst surface， which accelerates th_nolvsilicate. 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