Ethylene Oxide Formation in a Microreactor From Qualitative Kinetics to Detailed Modeling
Ethylene Oxide Formation in a Microreactor:From Qualitative Kinetics to Detailed Modeling
Jose′R.Herna′ndez Carucci,*,?Ville Halonen,?Kari Era¨nen,?Johan Wa¨rn?,?Satu Ojala,?
Mika Huuhtanen,?Riitta Keiski,?and Tapio Salmi?
Laboratory of Industrial Chemistry and Reaction Engineering,Process Chemistry Centre,?bo Akademi
Uni V ersity,Biskopsgatan8,FI-20500,Turku/?bo,Finland,and Department of Process and En V ironmental
Engineering,Uni V ersity of Oulu,FI-90014,Oulu,Finland
Silver/R-alumina catalysts were wash-coated in stainless steel microchannels.The microchannels were used
for the epoxidation of ethylene.Pure silver microplates were also investigated giving the highest activities
and selectivities toward the ethylene oxide formation.Pretreatment conditions with oxygen and ethylene for
the pure silver catalyst were studied and optimized.The experiments were carried out under atmospheric
pressure,varying the temperature from220to300°C and the total gas?ow from5.4to10.5cm3/min.A
precise kinetic model for the ethylene oxide formation in pure silver microchannels was developed at260°C.
The model was based on the competitive adsorption of ethylene and molecular oxygen over the silver surface.
The concentrations of the reactants(oxygen and ethylene)in the gas?ow were systematically varied from5
to25vol%using helium gas as balance.The model was confronted with experimental data obtained in the
microchannels,resulting in a very high degree of explanation(97%).
Introduction
The production of intermediates for the chemical industry is a crucially important issue.Reactive intermediates are needed not only in manufacturing of bulk chemicals but also in the production of?ne and specialty chemicals,ingredients in cosmetic products,and pharmaceuticals.A characteristic feature of chemical intermediates is its very high reactivity and selectivity.One major drawback,however,is their toxicity,even though the?nal product is completely nontoxic.Ethylene oxide (EO)is one of the most important organic intermediates with an annual global production of roughly19million metric tons, and it is expected to grow4.5%/year from2007to2012.1 Ethylene oxide is produced industrially on the basis of the direct oxidation of ethylene by using either air or pure oxygen.Silver is the state-of-the-art catalyst with different promoters,for enhancing activity and selectivity toward the desired product (ethylene oxide).Commercially available R-Al2O3-supported catalysts have been reported to achieve conversions from7to 65%and selectivities up to80%.2Current industrial catalysts consist of silver particles deposited on ultrapure(over99%) aluminum oxide support with a well-de?ned pore structure(pore diameter0.5-50μm)and low speci?c surface area(<2m2/g). EO can,in principle,be produced on site with the aid of suitable,selective heterogeneous catalysts.This requires,how-ever,advanced reactor technology,in which the classical problems of scale-up and operability are avoided.Such a technology is provided by microstructured devices,particularly gas-phase microreactors,which are inherently safe and have very good operability properties.3,4
Microreactors are still a relatively novel technology in chemistry,but already many advantages over conventional reactor design have been identi?ed.5Many of these advantages are related to the issue,that even though the chemistry itself is scale-independent,transport phenomena are not.In microengi-neered systems,mass and heat transfer are intensi?ed,because the heat exchange gradients become higher making the local concentration gradients smaller due to the decrease of the characteristic lengths of the system.The decrease of the characteristic dimensions lead to the increase of the surface-to-volume ratio enhancing the mass and heat transfer between the surfaces and the?uid.The high surface-to-volume ratio is the main feature of microreactors;typically it is in the range of 10000-50000m2/m3,much higher than conventional reactors, which usually have a surface to volume ratio of around100 m2/m3and seldom exceeds1000m2/m3.6
The intrinsic safety provided by microreactors allows the operation under explosive regime,e.g.,ethylene in pure oxygen, conditions not possible to obtain in conventional laboratory vessels.
Microreactors have been used for the investigation of highly exothermic reactions and with reagents working in the explosive region.7-11Earlier studies in microreactors have shown the versatility of these devices in reaction engineering.The highly exothermic oxidation of hydrogen has successfully been carried out in microreactors.7Propylene epoxidation has also attracted attention and experiments have been performed taking advantage of the microchannels.8Rebrov et al.9have studied the kinetics of ammonia oxidation in the explosive region using Pt-coated microreactors under a wide range of conditions.Kinetic parameters of the oxidation of organic components(n-butane and alcohols)have also been obtained in microdevices by applying kinetic modeling.10More recently,highly explosive mixtures of H2and O2have been investigated in microreactors for the direct synthesis of hydrogen peroxide and the determi-nation of the overall reaction kinetics,even considering mass-transfer effects,11demonstrating the usefulness of microdevices for experimentation and kinetic modeling studies.
Ethylene oxide(C2H4O)is produced by partial oxidation of ethylene(C2H4)over a silver catalyst as shown in Scheme1. Also,the two competing combustion reactions are present in the reaction scheme.12,13
The oxidation rate of ethylene oxide(r3)is much smaller compared to the rates of partial oxidation(r1)and total oxidation
*To whom correspondence should be addressed.E-mail:johernan@
abo.?.
??bo Akademi University.
?University of Oulu.
Ind.Eng.Chem.Res.2010,49,10897–1090710897
10.1021/ie100521j 2010American Chemical Society
Published on Web09/15/2010
(r 2)of ethylene;hence,the reaction scheme is generally considered to be parallel.All the reactions are highly exothermic:?H )-105kJ/mol for r 1,-1323kJ/mol for r 2and -1218kJ/mol for r 3.14The heat generated from the total oxidation reactions is much higher than the heat produced by the partial oxidation reaction.Thus,the chemical equilibrium strongly favors the formation of the total oxidation products,and the reason why ethylene oxide is not oxidized further is purely kinetic.15
The total heat of reaction in a conventional industrial reactor reaches -350to -550kJ/mol,causing “hot spots”and heat removal problems.16The involved reactions in the ethylene oxidation range from mildly exothermal (partial oxidation)to strongly exothermal (complete oxidation).In that sense,it is required to quench the reactor as fast as possible to avoid problems with selectivity.Microreactors,because of their very high surface-to-volume ratio,permit an ef?cient removal of the produced heat,avoiding unwanted temperature gradients inside the microchannels.
The mechanism of the ethylene oxidation over silver catalysts has been studied by many researchers,and there is extensive open literature available on the subject.17Several different reactor systems,operation conditions,and various catalysts with varying concentrations of silver and additives have been used.However,despite extensive studies by both experimental and
theoretical methods the reaction mechanism remains contro-versial.15Furthermore,although a lot of research has been done on catalytic gas-phase processes in microdevices,kinetic model-ing is often missing.In this work,we present a systematic approach to a very precise kinetic modeling of ethylene oxide production data obtained from a stainless steel microreactor.Experimental Section
Equipment.A stainless steel microreactor purchased from Institut fu ¨r Mikrotechnik Mainz GmbH (IMM)was used for the synthesis of EO.The reactor consists of two parts:the top and the housing.Figure 1,left,shows the top part where 10catalyst and 10mixer plates are stacked.
The lower part of the chamber has two recesses,each ?lled with a stack of 10stainless steel or silver microstructured plates,which are connected by a diffusion tunnel,with a 1mm length and an approximate volume of 52.8mm 3,where the gases from the two reactor inlets mix before entering into the catalytic area (Figure 1,right).The ?rst stack contains a total of 10mixing plates with nine semicircular channels of different radii but with a common center.They are arranged in the stack in such a way that they meet the two inlets in alternation.The second stack,the catalytic zone of the reactor consists of 10rectangular plates with nine parallel shallow microchannels each (total of 90microchannels:i.d.)460μm,length )9.5mm,and depth )75μm)coated with an Ag/Al 2O 3catalyst or made by pure silver.Figure 2shows a scheme of the plates’con?guration inside the microreactor.The reactor housing is made of Inconel 600(2.4816)and 1.4571for the mixing and catalytic plates.The reactor is sealed with graphite gaskets and tightened with six screws.
The inlet gas concentrations were regulated by using four mass ?ow controllers (MFC):0-3cm 3/min Brooks 5850S for ethylene,0-3cm 3/min Brooks 5850E for oxygen,and two 0-20cm 3/min Brooks 5850S for helium.The mass ?ow controllers were previously calibrated to each gas by using a
Scheme 1.Reaction Stoichiometry of Partial and Total
Oxidation of Ethylene and Total Oxidation of Ethylene Oxide over Silver Catalyst
13
Figure 1.Top part of the microreactor with one catalytic and one mixing plate (left)and microreactor housing
(right).
Figure 2.Scheme of the reactor con?guration (10stacked microplates,catalytic zone).
10898Ind.Eng.Chem.Res.,Vol.49,No.21,2010
Humonics 520digital ?owmeter.The scheme of the system used for the catalytic experiments with the stainless steel microreactor (MR)is presented in Figure 3.
The temperature of the microreactor was regulated by external heating cartridges controlled by a CAL9500temperature controller.K-type thermocouples (chromel -alumel)were used for temperature measurements/control.The temperature was measured in the top part of the microreactor (Figure 1,left)behind the catalytic zone.Due to the small dimensions of the device,and given its high heat-transfer capabilities,this tem-perature was assumed to be identical as the temperature in the microchannels.After the microreactor,the ef?uent gases were analyzed by Agilent 3000A Micro GC with four independent columns (PLOT U for identifying carbon dioxide,OV-1for ethylene oxide,alumina for ethylene,and Molsieve 5A for measuring oxygen concentrations)and TC detectors.The gases used in the preparation of ethylene oxide were scienti?c ethylene (99.95%,Linde Gas)and instrument oxygen (99.999%,AGA).Helium (99.996%)was used as carrier gas.For the kinetic experiments,the temperature was kept at 260°C and the total ?ow was set to 6cm 3/min with concentrations of oxygen and ethylene varying from 5to 25vol %.Different channel widths are assumed to provide a constant volume ?ow through all channels,regardless of their length.18The kinetic measurements were done 18min after both ethylene and oxygen were fed to the microreactor.
Catalyst Preparation.A silver/R -alumina catalyst was prepared by thermally decomposing ground γ-alumina (A300LaRoche Industries Inc.)for 12.5h at 1500°C.The incipient wetness method was used for further impregnating the obtained R -alumina powder.A 3.786g amount of silver nitrate (99.8%,Merck)was dissolved in 5g of deionized (DI)water.A 13.354g amount of R -alumina was further mixed slowly into the solution.The obtained suspension was thoroughly mixed for 30min and placed to dry overnight at 60°C.The powder was further dried at 100°C for 2h and then calcined at 650°C for 3h.
Before the deposition of the wash coat,the catalyst plates of the microreactor were cleaned from impurities by using the method described by Howell and Hatalis.19First,the plates were immersed in acetone for 5min and rinsed with deionized water.They were further immersed in a solution of 5:1:1DI water,hydrogen peroxide (29-32%,Merck),and ammonium hydrox-ide (32%,Sigma-Aldrich)for 5min and rinsed with DI water.Finally,the plates were immersed in a solution of 5:1:1:1DI
water,hydrogen peroxide (29-32%,Merck),phosphoric acid (85%,FF-Chemicals),and acetic acid (99%glacial,J.T.Baker)in an ultrasonic bath for 5min,rinsed with DI water,and then dried.
The catalyst was then wash-coated in the microplates as described in Stefanescu et al.20A suspension of 77wt %of DI water,5wt %of acrylic acid (99%,Fluka Chemika),2wt %of acetic acid,and 16wt %of catalyst powder was prepared.Water and acids were mixed at ?rst,followed by the powder.The suspension was kept under stirring for 24h at room temperature,before deposition.The microplates were calcined in air at 800°C for 2h prior to the wash-coating procedure.The suspension was applied to the microchannels of the plates by a syringe,and the excess suspension was wiped off.The plates were dried at 100°C for 2h and calcined at 650°C for 3h.
Pure silver plates obtained from IMM were also evaluated for the chemical synthesis.The plates were made from pure polycrystalline silver,having the same dimensions as the catalyst plates made from stainless steel described above.
Catalyst Characterization Methods.The surface areas of the alumina supports and impregnated catalyst powders were measured with a sorptometer (Carlo Erba Instruments Sorp-tomatic 1900),by nitrogen physisorption.The total surface area was obtained by using the Brunauer -Emmett -Teller (BET)equation.Additionally,scanning electron microscope images were taken from the plates,and the elemental composition was analyzed by energy dispersive X-ray spectroscopy (EDS).The SEM device used was Leo Gemini 1530manufactured by Zeiss with an energy dispersive X-ray detector (ThermoNONAN Vantage,120kV).Results and Discussion
Catalyst Characterization Results.Speci?c surface area measurements,SEM images,and elemental composition from SEM-EDS analysis were used to characterize the synthesized catalysts.Speci?c surface area measurements were taken from the resulting R -Al 2O 3supports,obtaining a value of 3.7m 2/g.After impregnation with silver,the surface area remained unchanged.
The elemental composition of the prepared catalyst was analyzed by SEM-EDS.The silver loading with respect to alumina was found to be 15wt %,while the nominal loading was aimed to 18wt %.A SEM image of the
catalyst
Figure 3.Scheme of the system used.
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(magni?cation,1000×)is shown in Figure 4,where the brighter silver clusters can be clearly seen on the alumina support.The thickness of the catalyst layer was also estimated from the SEM micrographs.According to Stefanescu et al.,20the thickness of the coatings should be in the range of 20-25μm.Figure 5shows the pro?le of the microplate at 35×magni?ca-tion.The coating of the catalyst in the microchannels resulted in a uniform distribution,as shown by SEM imaging (Figure 6).The catalytic layer thickness was determined to be between 15and 20μm,results that are in agreement with previous ?ndings.20Activity Evaluation.Ag/r -Al 2O 3.The ?rst set of experiments was conducted with the 15wt %Ag/R -Al 2O 3catalyst.The reactor was assumed to operate at constant temperatures.The high surface-to-volume ratio present in the microreactor permits an ef?cient heat transfer,allowing the operation at isothermal conditions even with highly exothermic reactions.Furthermore,due to the low conversion levels obtained in this work,the reaction heat produced would not effectively raise the temper-ature of the reactor.Low ethylene conversion and selectivity toward ethylene oxide was observed without previous catalytic treatment (0.28and 14%at 300°C,respectively).Only
at
Figure 4.SEM image of the prepared Ag/Al 2O 3catalysts.The bright spots were identi?ed as silver by SEM-EDS analysis,magni?cation 1000×
.
Figure 5.Pro?le of one Ag/Al 2O 3coated plate.
10900Ind.Eng.Chem.Res.,Vol.49,No.21,2010
temperatures higher than 280°C,ethylene oxide could be analytically detected when high concentrations of ethylene were fed (20vol %).Additionally,to check the reproducibility of the experiments,every ?fth experiment was conducted in the following conditions:20vol %ethylene and 10vol %oxygen with a total ?ow of 6cm 3/min and a temperature of 280°C.Nault et al.21tried pretreating the catalyst with oxygen,ethylene,hydrogen,and ethylene oxide in order to improve the stability and activity of the catalyst.A similar approach of different pretreatments with oxygen and ethylene was tested in this study,in order to ?nd good stability and activity windows for the catalyst.
For the oxidation/reduction pretreatment the catalyst was ?rst exposed to 20vol %oxygen for 15min at 300°C and a total ?ow of 5.4cm 3/min,followed by a helium ?ow for 10min.The microplates were further treated with 20vol %ethylene for 15min at 300°C,with a total ?ow of 5.4cm 3/min.Prior to the experiment,the microreactor was purged with helium for 10min.This procedure was inverted for the reduction/oxidation pretreatment.
The oxygen/ethylene pretreatment gave better initial conver-sion and selectivity toward ethylene oxide formation.According to Nault et al.,21this behavior could be explained by the extra ethylene adsorbed on the catalyst.The activity decreased rapidly at the beginning (conversion of ethylene from 0.67to 0.43%).After 18min of reaction,the activity continued to decrease steadily.With the reduction/oxidation pretreatment,the catalyst kept a stable activity (conversion of ethylene,0.31-0.33%),but the conversion was lower than with the oxidation/reduction pretreatment.The selectivity toward ethylene oxide had a similar trend:for oxygen/ethylene pretreatment the selectivity decreased from 15.5to 12.5%over 27min,while for ethylene/oxygen pretreatment it ?uctuated between 10.6and 11.1%(Figure 7).Additionally,experiments with longer times-on-stream were performed over the studied catalysts.The experiments showed a very stable behavior after 24h of operation where both conversion and selectivities remained very much constant (results not shown).
The conversion levels obtained in this work were clearly lower than conventional reactors,although selectivity levels were comparable.In the absence of any promoter,the reaction of ethylene and oxygen over silver catalysts produces ethylene oxide at about 50%selectivity while,with Cl and Cs promoters,levels of 80%in selectivity have been found.22,23However,the experiments carried out in this study were performed at atmospheric pressure,whereas,conventionally,the pressures can go up to 30bar.Higher conversions might still be achieved by
obvious approaches,i.e.,increasing the pressure,increasing the residence time inside the microchannels,and increasing the thickness of the wash coats.Nonetheless,for a pure kinetic study,low conversions are required in order to neglect the concentration gradient over the axial reactor coordinate.
Moreover,the conversion issue could be resolved by scaling-out (numbering-up)the microreactors to build a network as suggested in the literature.24The microreactor network should be constructed in a way that allows the macrosystem to operate under conditions similar to each elementary microchannel.However,numbering-up or scaling-out of the microstructure reactor is not straightforward and could present problems when operating at macroscopic ?ow rates.Numbering-up of microre-actors might result in a large ?ow maldistribution broadening and shifting the reactants residence time curve.25Additionally,higher conversions might also increase the risk of explosion in the downstream equipment and a need of puri?cation and separation would be needed.
The catalytic activity seemed to be diminished by the oxidation,probably due to adsorbed molecular oxygen on the catalytic surface and not reacting with ethylene.Nonetheless,it occupies catalytic sites diminishing the space available on the surface.Figure 7shows that conversion,as well as selectivity with oxygen/ethylene pretreatment would eventually reach the same level as the one obtained with the ethylene/oxygen pretreatment (conversion of ethylene ca.0.33%and
selectivity
Figure 6.SEM images of an Ag/Al 2O 3-coated
microplate.
Figure 7.Effect of pretreatment with oxygen and ethylene on conversion (?lled symbols)and selectivity (open symbols)on Ag/alumina wash-coated microchannels.Oxygen/ethylene pretreatment:20vol %O 2for 15min plus 20vol %C 2H 4for 15min at 300°C;total ?ow of 6cm 3/min (-b -).Ethylene/oxygen pretreatment,inverse order (-9-).Reaction conditions:20vol %ethylene,10vol %oxygen,and a total ?ow of 6cm 3/min at 300°C.
Ind.Eng.Chem.Res.,Vol.49,No.21,201010901
toward ethylene oxide ca.11%).It was determined that only the last component used for pretreatment (either ethylene or oxygen alone)was suf?cient for determining the catalytic activity.It was concluded from these experiments that pretreat-ment with ethylene would be bene?cial for achieving better conversions and selectivities toward ethylene oxide.Basically,the second step of the pretreatment (oxidation in the reduction/oxidation or reduction in the oxidation/reduction)was the one affecting the reaction.In that sense,an experiment with only oxidizing pretreatment gave the same results as the reduction/oxidation pretreatment.The same was true for the case of only reducing of the oxidation/reduction pretreatment.It seems that either oxygen or ethylene was able to rapidly desorb from the silver surface when the microplates were further treated with helium.
Figure 8illustrates the in?uence of the total ?ow on the conversion of ethylene and selectivity to ethylene oxide.As the total ?ow increased from 6to 10.5cm 3/min,the residence time decreased from 0.101to 0.058s inside the microreactor,causing a conversion reduction from 0.15to 0.07%.The selectivity toward ethylene oxide remained more or less stable,varying slightly from 19.5to 22%.The yield of ethylene oxide decreased vaguely from 0.03to 0.02%,while the total ?ow increases from 6to 10.5cm 3/min.
The effect of temperature on conversion and selectivity is shown in Figure 9.The measurements were taken 18min after introducing both reactant gases (ethylene and oxygen).The conversion of ethylene to ethylene oxide increased rapidly from
0.03to 0.28%,as the temperature increased from 220to 300°C.The yield of ethylene oxide showed a similar behavior.The selectivity toward ethylene oxide decreased linearly from 29to 14%at the same temperature range.As expected,the total oxidation reaction became more dominant at higher temperature.Pure Silver Plates.For the case of pure silver plates,similar pretreatment conditions were used.Figure 10shows the effect of pretreatment over the pure silver microplates.When pre-treating with ethylene,a 20vol %?ow was kept for 20min at 260°C with a total ?ow of 5.4cm 3/min.As oxygen was used as pretreatment gas,the parameters were kept identical.Before starting the experiment,the microreactor was purged with helium for 20min in both cases.
A peak of ethylene oxide formation was observed after 6min after beginning the reaction,together with a slight decrease in the selectivity (Figure 10)when the silver plates were treated with ethylene.
Because oxygen was used as a pretreatment gas,the conver-sion was gradually increasing from 0.05to 0.08%after 18min of reaction,while the selectivity toward ethylene oxide changed from 25.9to 38.7%.
An important difference between the pretreatments was noticed since the conversion for ethylene-treated catalyst resulted in almost twice the conversion of oxygen-treated microplates.Similar trends of catalytic behavior were observed by Nault et al.in their study.21They treated ?rst the catalyst overnight with pure oxygen at 200°C and followed it with an ethylene treatment.They noticed that,after an initial activity peak,the catalyst slowly decreased its activity,stabilizing only after 2h.Additionally,the treatment of the catalyst with hydrogen and consecutively with ethylene resulted in a further enhancement of the activity.21They presented the possibility that the catalytic sites are,at least,partially reduced and the pretreatment with ethylene oxide increased the activity of the existing catalytic sites or produced entirely new ones.
Figure 11shows the results from different residence times inside the microreactors.The trend was analogous to that obtained with the Ag/alumina-wash-coated microplates (Figure 8).As the total ?ow increases from 6to 10.5cm 3/min,the conversion of ethylene decreases from 0.10to 0.06%.Still,the selectivity toward ethylene oxide increases from 36to 38%.The effect of temperature on conversion and selectivity is presented in Figure 12.The conversion of ethylene increased rapidly from 0.03to 0.21%,while the temperature
increased
Figure 8.Effect of total ?ow on conversion (-b -),yield (-2-),and selectivity (-0-)on the production of ethylene oxide over Ag/alumina wash-coated microchannels.Reaction conditions:20vol %ethylene and 10vol %at 280°
C.
Figure 9.Effect of temperature on conversion (-b -),yield (-2-),and selectivity (-0-)on the production of ethylene oxide over Ag/alumina wash-coated microchannels.Reaction conditions:20vol %ethylene,10vol %oxygen,and a total ?ow of 6cm 3
/min.
Figure 10.Effect of pretreatment with oxygen and ethylene on conversion (?lled symbols)and selectivity (open symbols)on pure silver microchannels.Oxygen pretreatment (-9-):20vol %O 2for 20min at 260°C and total ?ow of 5.4cm 3/min.Ethylene pretreatment (-b -):20vol %C 2H 4for 20min at 260°C and total ?ow of 5.4cm 3/min.Reaction conditions:20vol %ethylene,10vol %oxygen,and a total ?ow of 6cm 3/min at 260°C.
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from 220to 300°C.The selectivity toward ethylene oxide decreased linearly from 51to 24%in the same temperature range.
van Santen and Kuipers 26account for the uniqueness of silver as an ethylene epoxidation catalyst to two factors:?rst,the bond strength and chemical nature of the adsorbed oxygen;and second the inability to activate the C -H bond.The latter factor is supposed to limit the catalysts to elements or components not containing transition metals,because these transition metals activate C -H bonds.Oxygen has to dissociate,but the resulting metal -oxygen bond strength should not be high that epoxidation could be excluded because of thermodynamic reasons.Silver is unique,since oxygen can dissociatively adsorb on its surface and at high oxygen coverage it contains weakly bound oxygen.The relatively weak bond strength of oxygen to silver thermo-dynamically allows formation of ethylene oxide upon reaction with ethylene.26
According to van Santen and Kuipers,26clean silver surfaces have an initial selectivity to EO of approximately 40%,which is relatively low.It can be,however,explained by the low surface oxygen concentration,which enhances the fraction of strongly adsorbed oxygen.The studies by Campbell 27showed a clean Ag(111)surface had a selectivity of 36-48%,while clean Ag(110)surface has a selectivity of 36-39%toward ethylene oxide formation depending on the reaction temperature.Kestenbaum et al.,14while synthesizing ethylene oxide in a catalytic microreactor,used polycrystalline catalytic plates similar to the plates used in this study.Additionally,no
promoters were used for enhancing the catalytic reaction.They found that the selectivities of ethylene oxide on polycrystalline silver were about 50%,which does not differ too much from the values reported in the literature for conventional reactors.It was also found that,in the microreactor,the selectivity toward EO increased as more oxygen was fed to the reactor.
Lee et al.28studied the effects of various support materials on silver catalysts.The conclusion was that catalysts with several carriers including γ-Al 2O 3exhibited a signi?cant activity in ethylene oxide isomerization and oxidation,and thus they gave only a very poor selectivity toward the ethylene oxide formation or formed only carbon dioxide and water.This was attributed to the surface acidity of the catalysts.
Kinetic Analysis:Qualitative.Traditionally,silver-supported catalysts have been investigated for ethylene oxide production in both laboratory and industrial scale.Nonetheless,studies over pure silver are not rare,since they help in understanding the role of the metal in this important reaction.14,29,30Furthermore,with the introduction of microreactors,the possibility of using pure silver microplates becomes economically feasible and likely to be exploited at laboratory scale.14,30
The in?uence of the oxygen concentration on the conversion of ethylene and selectivity toward ethylene oxide is shown in Figure 13.It was found that both conversion and selectivity were enhanced by higher oxygen concentrations in the feed.The conversion of ethylene increased from 0.12to 0.22%at oxygen concentrations of 20vol %,as the selectivity toward ethylene oxide increased almost linearly from 32to 45%.This positive effect of oxygen concentration has also been reported by Kestenbaum et al.30As industrial reactors operate at an oxygen concentration of 4-9vol %and ethylene concentrations up to 40vol %in order to avoid dangerous gas mixtures in explosive regime,it is an advantage of the microreactor system to safely operate in an excess of oxygen and gas compositions within the explosive regime.However,as soon as an explosive mixture leaves the microreactor,it could represent a potential hazard for the ethylene oxide production system as mentioned earlier.Furthermore,in microreactors,in order to achieve the desired conversion,instead of the conven-tional approaches (scaling-up and reactants recycling),number-ing-up of the devices is suggested.In this sense,the same conditions studied in a laboratory-scale device could be attained in pilot and even industrial scales without changing the reaction environment.This could lead to signi?cant process improvement as the bene?t of excess oxygen is evident for the studied reactions.
30
Figure 11.Effect of total ?ow on conversion (-b -),yield (-2-),and selectivity (-0-)on the production of ethylene oxide over pure silver microplates.Reaction conditions:20vol %ethylene and 10vol %oxygen at 260°
C.
Figure 12.Effect of temperature on conversion (-b -),yield (-2-),and selectivity (-0-)on the production of ethylene oxide over pure silver microplates.Reaction conditions:20vol %ethylene,10vol %oxygen,and a total ?ow of 6cm 3
/min.
Figure 13.Effect of oxygen on conversion (-b -)and selectivity (-0-)on the production of ethylene oxide over pure silver microplates.Reaction conditions:10vol %ethylene and total ?ow of 6cm 3/min at 260°C.
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For the case when ethylene was varied,keeping an oxygen concentration constant,the opposite effect was observed.The conversion decreased rapidly at the beginning of the reaction from 0.29to 0.10%and started to stabilize as ethylene concentration reached twice the amount of oxygen (Figure 14).The ethylene oxide selectivity remained almost constant at 36%.Previous studies 30showed similar trends in a similar microre-actor system.
Kinetic Analysis:Quantitative.The kinetics of the ethylene epoxidation and combustion have been studied extensively by a number of authors.However,no single kinetic expression that reproduces the kinetics for both ethylene-rich and oxygen-rich feeds exists.Instead,different kinetic expressions are used for different reaction conditions.This indicates a very complicated kinetics for this process.The most favored kinetic expressions in the literature seem to be of competitive Langmuir -Hinshelwood type.15
For the kinetic runs,the catalyst was ?rst treated with ethylene in order to remove most of the adsorbed oxygen from the catalyst after the previous experiment and further outgassed with oxygen in order to achieve stability,even if the conversions were lower.Overall,a good stability and activity of the catalyst were achieved and a set of kinetic runs were completed with pure silver plates.
Since the characteristic lengths in microreactors and the high surface-to-volume ratio,heat-and mass-transfer effects tend to be very high;hence,kinetic regime is easily achievable.The temperature for the experiments was kept constant at 260°C,and the total ?ow was set to 6cm 3/min for all of the experiments (the residence time was 0.138s).A total of 25experiments were conducted with varying the ethylene and oxygen concen-tration from 5to 25vol %.
Petrov et al.31investigated steady-state kinetics of ethylene epoxidation over Ag/R -Al 2O 3catalyst promoted by Ca additive in a circulation ?ow system.Their empirical kinetic model corresponds to a single-site Eley -Rideal mechanism,where adsorbed molecular oxygen produces ethylene oxide and the atomic oxygen is responsible for the complete oxidation reaction.Both reactions proceed on the same catalytic site.Rate expres-sions were given to partial and complete oxidation reactions.Nonetheless,in later studies 13,32the Eley -Rideal type expres-sions were rejected,as they contradicted their experimental observations.
Borman and Westerterp 32studied oxidation of ethane with industrial Ag/R -Al 2O 3catalyst in an internal recycle reactor.It was found that all reactants and reaction products in?uence the reaction rates.The reaction rate expression was based on a
Langmuir -Hinshelwood mechanism in which adsorbed ethylene and dissociatively adsorbed oxygen react to yield ethene oxide,carbon dioxide,and water.The two reactions are assumed to proceed over different catalytic sites,and the surface reactions are rate-limiting.Other studies have also pointed out the importance of the products in the rate expressions.33On the other hand,by using a differential reactor and an Ag/Cs/R -Al 2O 3catalyst,Lafarga et al.13studied kinetics of the ethylene epoxidation network.In their experimental conditions (temper-ature range,210-270°C;total pressure,1bar),both ethylene and oxygen in?uenced the reaction rates.The in?uence of the products was found to be negligible due to their low partial pressure in the reactor.In this work,due to the low concentration of products (from 0.03to 0.30vol %)compared to the concentration of reactants (from 5to 25vol %),the in?uence of products in the model was assumed to be minimal and thus the product inhibition is not accounted for in the kinetic model.The total oxidation reaction of ethylene oxide to carbon dioxide and water was also neglected.The results with kinetic experi-ments indicated the presence of adsorption terms for both ethylene and oxygen;thus,a Langmuir -Hinshelwood mecha-nism can be assumed for the reaction.The rate-limiting step was assumed to be the surface reaction between adsorbed ethylene and adsorbed oxygen as suggested by many of the recent studies.13,32,33
A plug-?ow reactor model was used to describe the microre-actor.The conversions were low (<0.30%for kinetic experi-ments),and hence the concentration and temperature gradients were small.Under the ?ow conditions,a steady-state plug-?ow was approximated.The catalyst was pure silver catalyst;thus,the effect of internal diffusion can be assumed to be negligible.While many studies agree that the reaction is based on the Langmuir -Hinshelwood mechanism,a controversy exists be-tween whether oxygen adsorbs dissociatively or molecularly on the catalytic site.Both models were proposed:the ?rst one assumed competitive adsorption of ethylene and oxygen on the catalyst surface.The oxygen adsorbs dissociatively being the surface reaction rate-limiting step as presented in
where r 1)rate for conversion of ethylene to ethylene oxide,k ′)kK E (K O )1/2,c i )concentration of compound i ,K i )adsorption constant of compound i ,and k )rate constant for ethylene oxide formation.
The second model (eq 2)assumed competitive adsorption of ethylene and molecular oxygen on the surface,while the surface reaction was considered to be the rate-limiting step.
where r 1)rate for conversion of ethylene to ethylene oxide,k ′)kK E K O ,c i )concentration of compound i ,K i )adsorption constant of compound i ,and k )rate constant for ethylene oxide formation.Even if the ?rst model resulted in a good ?tting (degree of explanation,93%),the second model ?tted the experimental data best,obtaining a degree of explanation of 96.7%.
The kinetic modeling and parameter estimation performed in this work are based on the experimental data obtained in the activity experiments.The kinetic data were simultaneously ?tted by nonlinear regression to the rate equations as a function
of
Figure 14.Effect of ethylene on conversion (-b -)and selectivity (-0-)on the production of ethylene oxide over pure silver microplates.Reaction conditions:10vol %oxygen and a total ?ow of 6cm 3/min at 260°C.
r 1)
k ′c E √c O
(1+K E c E +√K O c O )
2
(1)
r 1)
k ′c E c O
(1+K E c E +K O c O )2
(2)
10904Ind.Eng.Chem.Res.,Vol.49,No.21,2010
the independent variables:concentrations of C 2H 4and O 2that were measured at the inlet and outlet of the microreactor.The model predictions and kinetic parameters were obtained by using the parameter estimation software ModEst 6.0.34A stiff ODE-solver (Odessa)with the Simplex -Levenberg -Marquardt al-gorithm implemented in the software was used to solve the system.The sum of residual squares was minimized using the following objective function:
The degree of explanation that represented the accuracy of the ?t was given by
where c j exp represents the mean value of all the data points.In the model,the temperature dependences of the rate constants were expressed as a typical Arrhenius dependence.The esti-mated parameters (from model 2)are presented in Table 1.The comparisons between estimated and experimental values of the rate of ethylene oxide formation are shown in Figures 15and 16,while a parity plot is presented in Figure 17.
The increasing oxygen concentration had a positive in?uence on the formation of ethylene oxide as shown in Figure 15.For example,at 10vol %ethylene in feed,the rate of formation increased from 2.8×10-8to 7.2×10-8mol/s,while oxygen concentration in the feed increased from 5to 25vol %.The rate of formation increases more rapidly ?rst and starts to moderate as higher oxygen concentrations are reached.Similar results of the in?uence of oxygen concentration were observed by Kestenbaum et al.30and Lafarga et al.13in their studies.It was also observed that,at higher concentrations of reactants,the rates of formation of ethylene oxide as well as carbon dioxide were enhanced in similar ways.Nonetheless,when increasing the oxygen concentration,the rate of ethylene oxide formation increased more than the rate of formation of carbon dioxide,which leads to a selectivity increase in the reaction.
As the ethylene concentration was increased in the feed,the rates of formation of ethylene oxide followed the same trend.However,as high ethylene concentrations were reached (above 15vol %),the rates of formation began to stabilize indicating a possible saturation of catalytic sites (Figure 16).
In the ethylene epoxidation reaction over silver catalyst,the adsorption of oxygen is arguably the most important aspect of the reaction mechanism.The special selectivity of the silver catalyst in the partial oxidation of ethylene has been attributed to its adsorption characteristics for the oxygen.Three species of oxygen,i.e.,the molecular,the atomic,and the subsurface oxygen,are generally accepted in literature.35
The mechanism of oxygen adsorption (molecular vs dissocia-tive)still remains controversial.Even if it is true that model 2,which assumes molecular adsorption of oxygen,gave a better experimental data ?t,a good estimation was also achieved with model 1that assumed dissociative adsorption of oxygen.Further studies might be required in order to develop a more precise kinetic model for the partial oxidation of ethylene.
There is a general agreement that the atomic oxygen is the active oxygen species both for ethylene epoxidation and total oxidation,while molecularly adsorbed oxygen is rather inactive.15,36,37Subsurface oxygen is believed to play an important role,as it is necessary for obtaining high selectivity to ethylene oxide,although it does not directly participate in catalytic events.The selectivity to ethylene oxide is governed by the binding state of atomic oxygen,which can exist on the catalyst surface in two extreme conformations.Weakly bound,
Table 1.Kinetic Parameters Obtained from Model 2parameter value parameter
value
K E 132(40.1k ′(9.75(4.42)×10-3K O
77.4(13.4
k
(9.54(5.33)×10-7
Q )|c exp -c est |2)
∑t
∑i
(c
exp,it
-c est,it )2
(3)
R 2
)100×(
1-|c exp -c est |2|c exp
-c j exp |2
)
(4)
Figure 15.Experimental (symbols)and predicted (lines)rates of ethylene oxide formation at different ethylene oxide concentrations over pure silver microchannels (where 1.2E-07,for example,represents 1.2×10-7).Reaction conditions:5vol %ethylene (-9-),10vol %ethylene (-b -),15vol %ethylene (-2-),and 25vol %ethylene (-(-).Total ?ow of
6cm 3/min at 260°C.
Figure 16.Experimental (symbols)and predicted (lines)rates of ethylene
oxide formation at different oxygen concentrations over pure silver microchannels (where 1.2E-07,for example,represents 1.2×10-7).Reaction conditions:5vol %oxygen (-9-),10vol %oxygen (-b -),15vol %oxygen (-2-),20vol %oxygen (-(-),and 25vol %oxygen (--).Total ?ow
of 6cm 3/min at 260°C.
Figure 17.Parity plot of the ?t of the model.Experimental vs calculated rate of formation of ethylene oxide.Degree of explanation is 96.7%(where 1.2E-07,for example,represents 1.2×10-7).
Ind.Eng.Chem.Res.,Vol.49,No.21,2010
10905
electrophilic adsorbed oxygen reacts preferentially with the C d C bond of the adsorbed ethylene thus producing ethylene oxide,while the strongly bound ionic oxygen reacts with the hydrogen atoms of the adsorbed ethylene breaking the C -H bond and forming carbon dioxide.This explains the role of subsurface oxygen,the presence of which causes a weakening in the bond strength of adsorbed atomic oxygen via withdrawal of electrons from the silver sites,thus favoring the formation of the electrophilic oxygen atoms.38
The comparison between experimental data and calculated values is given in Figure 17.The proposed model was ?tting the data with a very good degree of accuracy (97%degree of explanation).Sometimes,in these types of systems,problems of overparametrization could occur.To discard this possibility,sensitivity analysis was applied.Sensitivity plots of two parameters k ′(Figure 18,left)and k O (Figure 18,right)were also obtained.There is a clear minimum indicating convergence to reasonable values.The behavior of the other estimated parameters was similar,obtaining a minimum of the objective function close to the estimated value.Conclusions
Microplates were successfully wash-coated with a silver/R -alumina catalyst showing activity and good selectivity in the oxidation of ethylene.The selectivity toward ethylene oxide for silver -alumina catalysts remained low (<29%).Pure silver microplates were alternatively investigated,obtaining selectivi-ties up to 51%,comparable to values found in the literature.The pure silver plates resulted in the highest catalytic activity and selectivity toward EO formation and were further used for kinetic studies in the microreactor.The catalyst behavior was sensitive to changes in the feed concentrations;especially high oxygen concentrations,that were found to decrease the catalyst activity over time.
A good stability of the catalyst was achieved by a two-step pretreatment,where the catalyst was initially treated under an ethylene ?ow in helium,followed by a ?ow of oxygen in helium before each kinetic experiment as the long time-on-stream experiments showed.Increasing reaction temperature was found to linearly decrease the selectivity toward ethylene oxide,while increasing the conversion of ethylene.Increasing the total ?ow decreased the conversion of ethylene,while the selectivity toward ethylene oxide remained almost constant.
It was found that both increasing ethylene and oxygen concentration had a positive effect on the rates of formation of the reaction products (ethylene oxide and carbon dioxide).Two models of competitive Langmuir -Hinshelwood type were developed for the partial oxidation of ethylene.The surface reaction between adsorbed ethylene and either molecular or
dissociatively adsorbed oxygen was considered the rate-limiting step.The in?uence of the reaction products and internal diffusion limitations were negligible,and a model based on the competi-tive adsorption of ethylene and molecular oxygen on the surface ?tted the experimental data best.A steady-state plug-?ow reactor model was used for the ?tting.The model was veri?ed against the obtained experimental data,obtaining a very good agreement (explanation degree of 97%).The work shows that microreactors are useful tools for the determination of gas-phase kinetics,and they can be used for a safe production of chemical intermediates.Acknowledgment
This work is part of the activities at the ?bo Akademi Process Chemistry Centre within the Finnish Centre of Excellence Programme (2006-2011)appointed by the Academy of Finland.Literature Cited
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10906Ind.Eng.Chem.Res.,Vol.49,No.21,2010
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Accepted August30,2010
IE100521J Ind.Eng.Chem.Res.,Vol.49,No.21,201010907
聚醋酸乙烯酯胶粘剂
本科生毕业设计(论文） 摘要 随着人们环境保护意识的不断增强，开发绿色环保型产品已成为各行各业发展的主流方向。聚醋酸乙烯酯乳液俗称白乳胶，是应用最广的胶粘剂之一，由于它为水基胶粘剂，具有其他胶粘剂不可比拟的无毒、无腐蚀和优良的环保性能，并且原料来源广泛，成本较低，在胶粘剂中所占比例也越来越大，但白乳胶也存在一些性能上的不足，如耐水性，耐热性，抗蠕变性，耐寒性及耐机械稳定性等均较差。因此，需要对聚醋酸乙烯酯乳液的合成工艺进行研究，确定最佳工艺条件，或对聚醋酸乙烯酯乳液进行改性，以提高其各方面的性能，也扩大其应用领域。 本文重点阐述了聚醋酸乙烯酯乳液合成原理，最佳合成工艺及改性研究。在其应用上，除普遍适用于木材的粘合以外，聚醋酸乙烯酯类胶粘剂正渐渐的被应用于建筑等很多行业，并且，本文针对目前研究较少的胶类降解的研究给予简单的分析。 关键字：聚醋酸乙烯酯；合成；改性；应用
Abstract Along with the enhancement of people’s environment protection consciousness, the green environment protection product has become the mainstream. The polyvinyl acetate emulsion is named the white emulsion, which is one of the most widely used adhesives. Because it is water base adhesive, comparing with other adhesives it is non-toxic, non-corrosion and fine environment protection performance. The raw material of polyvinyl acetate emulsion is widespread, costs lower, so its proportion in the adhesive is more and more.But the white emulsion also has the insufficiency in some performance, like the water resistance, the thermal stability, the anticreep, the resistance to cold and bears mechanical stability are all infirmness. Therefore, we need to conduct the research to the polyvinyl acetate emulsion synthesis craft, and find the best craft condition, or carry on the modification to the polyvinyl acetate emulsion. We can enhance its various performance through the craft improvement and the modification of the performance, also expand its application. This article elaborates the polyvinyl acetate emulsion synthesis principle, best synthesis craft and modified research. In its application, besides it is generally used for the lumber agglutination, the polyvinyl acetate adhesive is gradually applied to the construction and so on. In this article, some simple analysis of degradation is also mentioned . Key word：polyvinyl acetate; synthesis; application; modification
CPVC专用PVC树脂标准的制定分析
万方数据
CPVC专用PVC树脂标准的制定分析 作者：魏镇 作者单位：河北盛华化工有限公司 刊名： 中小企业管理与科技 英文刊名：MANAGEMENT & TECHNOLOGY OF SME 年，卷(期)：2010(24) 参考文献(2条) 1.王敏氯化聚氯乙烯 2001 2.邓福平合成树脂生产工艺及标准全书 2006 本文读者也读过(10条) 1.陈斌武.CHEN Binwu氯化聚氯乙烯的发展前景[期刊论文]-聚氯乙烯2010,38(10) 2.马玫.胡行俊.MA Mei.HU Xing-jun CPVC与Ca/Zn热稳定剂体系的研究[期刊论文]-合成材料老化与应用 2009,38(3) 3.刘浩.张学明.LIU Hao.ZHANG Xue-ming氯化聚氯乙烯树脂综述[期刊论文]-聚氯乙烯2008,36(11) 4.李玉芳.李明.LI Yu-fang.LI Ming氯化聚氯乙烯树脂的生产及应用前景[期刊论文]-中国氯碱2009(6) 5.刘岭梅水相法CPVC市场应用及生产技术要点[会议论文]-2009 6.马玫.胡行俊.麦伟宗.雷祖碧.MA Mei.HU Xing-jun.MAI Wei-zong.LEI Zhu-bi CPVC加工稳定性研究-复合铅体系[期刊论文]-合成材料老化与应用2008,37(1) 7.鲍洁.宋宏宇.袁向前.Bao Jie.Song Hongyu.Yuan Xiangqian水相法制备氯化聚氯乙烯树脂工艺[期刊论文]-上海化工2007,32(5) 8.朱兰瑾.莫晨杰空心微珠在塑料管材中的应用研究[期刊论文]-国外塑料2009,27(6) 9.庄力滑石粉改性CPVC高压电力电缆用护套管研究[期刊论文]-现代商贸工业2008,20(5) 10.徐超.赵志强.张兆刚.赵季若.冯莺.Xu Chao.Zhao Zhiqiang.Zhang Zhaogang.Zhao Jiruo.Feng Ying高强度高软化点CPVC的制备与性能[期刊论文]-现代塑料加工应用2010,22(6) 引证文献(1条) 1.靖志国.熊新阳气固相法氯化聚氯乙烯的研究进展[期刊论文]-中国氯碱 2013(9) 引用本文格式：魏镇CPVC专用PVC树脂标准的制定分析[期刊论文]-中小企业管理与科技 2010(24)
甲基苯乙烯
甲基苯乙烯 一、标识 化学品名称：甲基苯乙烯 别名：2-苯基丙烯 分子式：C9H10 危险性类别：第3.3类高闪点易燃液体 二、理化性质 外观与性状：无色液体, 具有刺激性臭味。 Ph值：熔点(℃)：-23 相对密度(水=1)：0.90(25℃) 沸点(℃)：165-169 相对密度(空气=1)： 4.1 饱和蒸汽压(kPa)：0.27(20℃) 燃烧热(Kj/mol)：无资料临界温度(℃)：无资料 临界压力(MPa)：无资料辛醇／水分配系数：无资料 闪点(℃)：54 引燃温度(℃)：494 爆炸下限[%(V/V)]： 1.9 爆炸上限[%(V/V)]： 6.1 最小点火能(mJ)：无资料最大爆炸压力(MPa)：无资料 溶解性：不溶于水。 主要用途：用于ABS树脂、聚酯树脂、醇酸树脂改性。 三、危险性 侵入途径：吸入、食入、经皮吸收。 健康危害：对皮肤、眼睛、粘膜和上呼吸道有刺激作用。接触后可引起烧灼感、咳嗽、眩晕、喉炎、气短、头痛、恶心和呕吐。严重时引起肝、肾损害。 环境危害：对环境有危害，对大气可造成污染。 燃爆危险：本品易燃，具刺激性。 四、急救措施 皮肤接触：脱去污染的衣着，用流动清水冲洗。 眼睛接触：提起眼睑，用流动清水或生理盐水冲洗。就医。 吸入：脱离现场至空气新鲜处。如呼吸困难，给输氧。就医。 食入：饮足量温水，催吐。就医。 五、消防措施
危险特征：其蒸气与空气可形成爆炸性混合物，遇明火、高热能引起燃烧爆炸。与氧化剂可发生反应。受热或储存过久能聚合，并放热。流速过快，容易产生和积聚静电。容易自聚，聚合反应随着温度的上升而急骤加剧。其蒸气比空气重，能在较低处扩散到相当远的地方，遇火源会着火回燃。若遇高热，容器内压增大，有开裂和爆炸的危险。 有害燃烧产物：一氧化碳、二氧化碳。 灭火方法：消防人员须佩戴防毒面具、穿全身消防服，在上风向灭火。尽可能将容器从火场移至空旷处。喷水保持火场容器冷却，直至灭火结束。处在火场中的容器若已变色或从安全泄压装置中产生声音，必须马上撤离。灭火剂：雾状水、泡沫、干粉、二氧化碳、砂土。 六、泄漏应急处理 应急行动：迅速撤离泄漏污染区人员至安全区，并进行隔离，严格限制出入。切断火源。建议应急处理人员戴自给正压式呼吸器，穿防毒服。尽可能切断泄漏源。防止流入下水道、排洪沟等限制性空间。小量泄漏：用砂土、干燥石灰或苏打灰混合。也可以用不燃性分散剂制成的乳液刷洗，洗液稀释后放入废水系统。大量泄漏：构筑围堤或挖坑收容。用泵转移至槽车或专用收集器内，回收或运至废物处理场所处置。 七、操作处置与储存 操作处置注意事项：密闭操作，注意通风。操作人员必须经过专门培训，严格遵守操作规程。建议操作人员佩戴自吸过滤式防毒面具（半面罩），戴化学安全防护眼镜，穿防毒物渗透工作服，戴橡胶耐油手套。远离火种、热源，工作场所严禁吸烟。使用防爆型的通风系统和设备。防止蒸气泄漏到工作场所空气中。避免与氧化剂接触。充装要控制流速，防止静电积聚。搬运时要轻装轻卸，防止包装及容器损坏。配备相应品种和数量的消防器材及泄漏应急处理设备。倒空的容器可能残留有害物。 储存注意事项：通常商品加有阻聚剂。储存于阴凉、通风的库房。远离火种、热源。包装要求密封，不可与空气接触。应与氧化剂分开存放，切忌混储。不宜大量储存或久存。采用防爆型照明、通风设施。禁止使用易产生火花的机械设备和工具。储区应备有泄漏应急处理设备和合适的收容材料。 八、防护措施
sPS间规聚苯乙烯改性
间规聚苯乙烯改性研究进展 一、选题的依据及意义： 按照苯乙烯聚合物分子中侧链苯对链骨架空间取向的不同，聚苯乙烯分子有3种不同立体构型，相应地形成了三种聚合物，即无规聚苯乙烯(aPS)、等规聚苯乙烯(iPS)和间规聚苯乙烯(sPS)。自从Ishihara[1]等用TiCl4/MA CpTiCl3/MAO(Cp为茂环)合成高结晶度的sPS以来，苯乙烯间规聚合研究受到了重视。 sPS的主要特征是熔点高(270℃)，比Ips[2]高40℃，相当于aPS的3倍，与工程塑料尼龙-66相近。sPS具有结晶性，结晶速度较快，有时被称为高结晶聚苯乙烯。这种结晶型sPS构成了全新的PS工程塑料系列，它具有优良的耐热、耐化学腐蚀、耐水、耐蒸汽和耐溶剂性，某些性能能与尼龙-66聚苯硫醚(PPS)[3]等工程塑料相匹敌。并且材料流动性能较好，适合于常规方法加工，如注塑、挤塑，成型产品尺寸稳定性好，目前已有片级、膜级、纤维级和挤管级制品用于汽车保险杠、机械制品、集成电路及印刷电路板等。新的特殊应用领域还在不断的开拓中，因此具有广泛的应用前景，被看作是复兴苯乙烯行业的希望。同时，其单体苯乙烯便宜易得，sPS产品的利润可观，目前sPS的价格在~万元/吨左右。价格相比昂贵的氟塑料具有很大的优势。然而，sPS分子链刚性较大，导致材料较脆，抗弯、抗冲击强度低，加工流变性较差，因而限制了其广泛应用。经玻纤增强后的SPS复合材料[4]，其综合物性可与其它工程塑料如PET、PBT、PAG6、PPS相媲美。故此，SPS在汽车工业、膜材料、照相基材、食品容器、电子/电器等方面有广泛应用。由于sPS分子链的侧链上存在空间位阻较大的苯环，与其它工程塑料相比，韧性相对较差，如何进一步提高sPS的综合力学性能，对sPS应用领域的拓展具有重要意义。一般纯的sPS主要用作膜材料、纤维等，而要作其他用途必须经过改性。本文主要详细描述了，近几年来国内外对sPS的改性研究进展，并对其各个方面做了写详细的汇总，并且加以总结概述。 二、国内外研究概况及发展趋势： 20世纪80年代初，德国汉堡大学[5]Kaminsky等发现，金属茂Cp2MCl2(M=Ti、Zr、Hf)与三甲基铝的部分水解产物-三甲基铝氧烷(MAO)作用，可以得到高活性间规聚合催化剂-金属茂催化剂，sPS[4]也引起人们高度重视。在这以前，sPS是用苯乙烯α-甲基苯乙烯[6]和其它苯乙烯衍生物在实验室中用阳离子催化剂如(Et)2、TiCl4、AlCl3、SnCl4和各种金属的三甲基苯盐或阴离子引发剂如n-C4H9Li、萘基钠、萘基钾和萘基铯制备的。但因为聚合条件苛刻，且sPS产率低、聚合速度慢、大多数品种不可能工业化。1985年日本出光兴产公司(IdemitsuKosan .)Ishihara[1]合成了间规聚苯乙烯[7]后，立即引起企业和研究机构的广泛兴趣。1988年日本出光兴产公司与美国DOW公司联合开发sPS生产工艺，并获得成功[8]。日本出光兴
聚乙酸乙烯酯
聚乙酸乙烯酯乳液的中温合成 ( 摘要：介绍了一种用氧化-还原体系引发醋酸乙烯酯中温合成的工艺。实验比较了氧化还原引发体系与单一的水溶性引发剂所合成的乳液的性能，探讨了最佳工艺条件，讨论了单体、乳化剂、引发剂、反应温度、聚乙烯醇对乳液粘度和固含量的影响，以及搅拌速度对聚合速率的影响。确定了适宜的用量，并且从实验中得到了由中温50℃合成的生产成本低而性能优良的聚乙酸乙烯酯乳液胶粘剂。 关键词：中温氧化-还原体系聚乙酸乙烯酯乳液
THE MIDDLE TEMPERATURE GATHERING ACETIC ACID THENE ESTER EMULSION IS COMPOSED （Changzhou Institute of Technology Engineering Department of Chemical Engineering 213164） ABSTRACT The system having introduced that one kind uses oxide- to restore initiates the handicraft that the temperature composes in acetic acid ethene ester. Parallel experiment oxide deoxidation initiates system and unitary water-solubility initiates two kind type emulsion function of agent, have discussed the best technological conditions, viscosity and the effect strengthening contents having discussed that the monomer , the emulsifier, initiate the agent , the reaction temperature and poval to emulsion, in having ascertained proper dosages, and having got a reason from experiment middle 50℃ warm composite cost of production is low but the function is good gather acetic acid ethene ester emulsion adhesive. Keywords：middle temperature oxide-deoxidation system gathers acetic acid ethene ester emulsion
氯化聚氯乙烯(CPVC)塑料及其制备方法和应用
前言 氯化聚氯乙烯（CPVC）塑料具有耐热、耐候、耐化学介质腐蚀、阻燃、阻烟及无色无味无嗅等优越的理化性能，是近几年来应用领域发展速度较快的新颖塑料材料。由于美国、欧洲及日本等先进国家和地区对CPVC材料的研制和开发已经日趋成熟，所以CPVC塑料制品已具有一定的市场潜力，尤其是在中国这一庞大的塑料市场中，CPVC塑料尚属新产品、新材料，其利润空间和市场发展空间均有很大的吸引力。本文通过对CPVC树脂及CPVC塑料制品的简要分析，帮助人们提高对这种新材料的认识。 1．CPVC树脂 CPVC树脂是PVC树脂氯化改性的产物，其性能取决于PVC树脂本身及对PVC树脂进行氯化的氯化工艺。 1．1．PVC树脂 PVC是氯乙烯聚合的产物，而目前氯乙烯的生成方法主要有电石法和石油（天然气）乙炔法等。我国工业化生产PVC树脂的方法主要有石油（天然气）乙炔法、电石法及采购VCM单体进行聚合三种。由于VCM的生产方法不同，相同聚合度的PVC树脂其分子构型及性能也略有不同，不容忽视的关键事实是：PVC树脂的结构与性能直接影响了对其氯化的工艺及氯化后的CPVC树脂的分子构型及性能。相同氯含量的CPVC树脂由于PVC树脂的结构不同或氯化工艺不同，其性能上的差别是非常明显的。具体表现在理化性能上的差别及加工性能上的差别。 图1至图4为PVC树脂颗粒的外部和内部形貌的电子照片。它们的K 值和聚合度相似，但分别为中国宜宾天源（本体聚合法）、中国齐鲁石化、日本信越、及中国北二化的产品。
图为PVC树脂颗粒的电子照片，其为中国北二化的产品 1．2．CPVC树脂 由于PVC树脂是工业化生产CPVC树脂的主要原料，所以对PVC树脂的选用显得尤为重要。其结构必须是疏松状，且孔隙应适度。目前CPVC树脂的生产主要采用水相悬浮法，在这一过程中，因为氯气在PVC 树脂中扩散速率对PVC的氯化速率有很大影响，这又要求PVC树脂的皮膜尽可能簿，且表面积要大，结构规整度要好。因此，CPVC树脂的生产最好由具有一定规模且科研能力较强的PVC树脂生产厂来承担。国外生产CPVC的著名厂商例如美国的B.F.Goodrich公司、德国的BASF公司、法国的ATOFINA公司、日本的Kaneka公司等均是生产PVC树脂的国际性大公司。这些公司首先研制生产CPVC树脂的专用PVC树脂，它在采用悬浮法聚合的过程中添加了特殊助剂，然后将这一专用PVC树脂再经过水相悬浮法生产CPVC树脂。 由于不同的氯化条件，相同氯含量的CPVC树脂的分子构型并不一样，其性能也不一样。所以氯化工艺是生产CPVC树脂的关键技术。 中国山东旭业公司在参阅了国际上CPVC生产的文献资料的基础上，利用自己的科研力量所生产的氯含量在64～68%的CPVC树脂，其加工性能优越，已在中国市场上显示了较强的竞争力。该公司采用水相悬浮法进行氯化反应生产氯化聚氯乙烯，其主要特点是分段氯化，利用可控制的分段反应温度和压力使其获得氯化均匀的CPVC树脂。为了尽量减少在氯化过程中所产生的断链和支化反应现象，宜在氯化反应前进行脱氧处理。应
α-甲基苯乙烯
化学品安全技术说明书（三氯化铝） 第一部分化学品及企业标识 化学品中文名称：α-甲基苯乙烯 化学品英文名称：α-methylstyrene 企业名称： 地址： 邮编： 电子邮件地址： 传真号码： 企业应急电话： 技术说明书编码： 生效日期：2010年12月1日 第二部分危险性概述 危险性类别：第3.3类高闪点液体 侵入途径：吸入、食入、经皮吸收。 健康危害：对皮肤、眼睛、粘膜和上呼吸道有刺激作用。接触后可引起烧灼感、咳嗽、眩晕、喉炎、气短、头痛、恶心和呕吐。严重时引起肝、肾损 害。 环境危害：对环境有害。 燃爆危险：易燃，其蒸气与空气混合，能形成爆炸性混合物。容易自聚。 第三部分成分/组成信息 纯品 混合物CAS 甲基苯乙烯98-83-9 第四部分急救措施
皮肤接触：脱去污染的衣着，用流动清水冲洗。如有不适感，就医。 眼睛接触：提起眼睑，用流动清水或生理盐水冲洗。如有不适感，就医。 吸入：脱离现场至空气新鲜处。如呼吸困难，给输氧，就医。 食入：饮足量温水，催吐。就医。 第五部分消防措施 危险特性：其蒸气与空气可形成爆炸性混合物，遇明火、高热能引起燃烧爆炸。 与氧化剂可发生反应。受热或储存过久能聚合，并放热。流速过快， 容易产生和积聚静电。容易自聚，聚合反应随着温度的上升而急骤加 剧。蒸气比空气重，沿地面扩散并易积存于低洼处，遇火源会着火回 燃。若遇高热，容器内压增大，有开裂和爆炸的危险。 有害燃烧产物：一氧化碳。 灭火方法：用雾状水、泡沫、干粉、二氧化碳、砂土灭火。 灭火注意事项及措施：消防人员须佩戴防毒面具、穿全身消防服，在上风向灭火。 尽可能将容器从火场移至空旷处。喷水保持火场容器冷却，直至灭火 结束。处在火场中的容器若已变色或从安全泄压装置中产生声音，必 须马上撤离。 第六部分泄漏应急处理 应急行动：消除所有点火源。根据液体流动和蒸气扩散的影响区域划定警戒区，无关人员从侧风、上风向撤离至安全区。建议应急处理人员戴正压自 给式呼吸器，穿防静电服。作业时所用的所有设备应接地。禁止接触 或跨越泄漏物。尽可能切断泄漏源。防止泄漏物进入水体、下水道、 地下室或密闭性空间。小量泄漏：用砂土或其它不燃材料吸收。使用 洁净的无火花工具收集吸收材料。大量泄漏：构筑围堤或挖坑收容。 用泡沫覆盖，减少蒸发。喷水雾能减少蒸发，但不能降低泄漏物在受 限制空间内的易燃性。用防爆泵转移至槽车或专用收集器内。 第七部分操作处置与储存 操作注意事项：密闭操作，注意通风。操作人员必须经过专门培训，严格遵守操
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氯化聚氯乙烯塑料管材的生产技术问题解答
氯化聚氯乙烯塑料管材 的生产技术问题解答 肖祥骅 ( 上海高聚物实用产品研究所，上海2 0 0 0 6 2 ) 摘要：氮化聚氯乙烯塑料( P V C - ( 、) 管材是当前发展比较迅速的一种新颖管材，其配方工艺、加工设备、模具等均与原P V C塑料管材有相同之处，也有许多不相一致的地方。为使该管材健康发展，对读者提出的有关配方、 工艺等方面的问题作了详细解答。 关键词：氯化聚氯乙烯乙塑料( P V C —C) 管枝术问题解答 中图分类号：T Q 3 2 5．3 文献标识码：A文章编号：1 0 0 9 — 5 9 9 3 ( 2 0 0 3 ) 03 一0 l 9 一04 自从《上海塑料》刊登了笔者关于氯化聚氯乙烯( P V C — C ) 管材生产技术方面的文章后，笔者收到函电、传真等1 4 3次之多。经与《上海塑料》编辑部联系，觉得该管材是当前国内重点发展的产品，笔者认为有必要就读者提出的几个重要问题简要解答如下，供参考。1 有关配方方面的问题与解答 问题1：为什么制作氯化聚氯乙烯塑料( P V C — C ) 热水管和电力、电缆埋管所加入的氯化聚氯乙烯( C P V C ) 份数不同? 解答：这是因为氯化聚氯乙烯( c P v c ) 的理化指标有一定的标准，其中对加工来讲，含氯量( 6 7 ．0 ±0 ．1 ) ％是至关重要的。日本的C P V C 含水率( 即挥发物) ≤0 ．i ％我国只能把含水率定为≤0 ．2 ％，且只能维持三个月不变。因此，用纯的C P V C 作样板，测试其维卡耐热指标时，日本产的C P V C 可以达到131℃，国内的仅能达到126℃。在方中加入除增塑剂以外的添加剂及其它高聚物，均可使维卡温度下降。再加上设备、模具、工艺条件等因素变化均会有所影响。笔者2001 2～3月在日本钟渊化工株式会社研究所作现试验，产品抽样检测为维卡温度≤116℃，因而，对于国际和国内标准要求PVC—C热水管耐热指标≥110℃的指标，只是稍有余地一不小心就会达不到。也就是说，用100份CPVC和各种添加剂来配合，在一定的工艺条件及设备、模具等条件支撑下，只有认真操作才能过关至于管件耐热温度≥1 0 3 ℃的要求，则可通过适当添10份PVC或增10 .2 份的润滑剂和稳定剂来达到.对于电力电缆埋管，建议主要原料配比以 5 5 份C P V C 对4 5 份P V C 为好。笔者曾请化工部北京化工研究院中心试验室做了5 0 份C P V C 对5 0 份P V C的配方试验，结果性能不但没有提高，反而下降。故向读者推荐的5 5 份C P V C 对4 5 份P V C 的配方完全可以比较可靠地达到维卡温度≥9 3 ℃的日本和国内行业标准要求，当然其它添加剂也要注意。另外，对于壁厚3 m m的薄壁管其维卡温度应在( 9 0±4 ) ℃范围内。 问题2 ：为什么加入M B S 后还要加C P E? 解答：加入M B S目的是提高配方系统的冲击强度。但鉴于其双键过多，在紫外线照射下会产生双键断裂现象，强度反而下降，表现在管材到工地后如不及时埋设，5～7 d强度将下降一半，因此，配方中加入6 ～8 份M B S ( 它使维 卡温度下降不多，这是M B S 的又一特点) 后，再加入3 份C P E ，可提高材料的耐寒和耐候性。笔者曾先后设计出在西北寒冷季节和西南潮湿紫外线强烈照射地区使用的材料配方，满足了这些地区电力系统的高压和超高压电缆保护管材
a-甲基苯乙烯二聚体的应用
α-甲基苯乙烯线性二聚体的应用 α-甲基苯乙烯线性二聚体，作为低味绿色产品，已成功地替代了进口的十二硫醇(等摩尔替代)用于丙烯酸类树脂的聚合和共聚反应，同时应用于PS、AS、ABS、氯丁胶、丙苯胶乳、丁苯胶乳，EPS、加工助剂 ACR等聚合反应。例如: (1) 在丙烯酸类树脂聚合(如锤纹漆)生产中, 本品可有效调节树脂分子量分布,使树脂流平性好, 粘度均匀, 漆膜表面明亮； (2) 在粉末涂料流平剂(聚丙烯酸酯类高分子化合物)制备中, 本品作为功能性助剂而大量添加以增强成品的流平作用； (3)在塑料加工助剂ACR(甲基丙烯酸酯类聚合物)生产中, 本品可有效控制产品的特性粘度,使甲基丙烯酸酯类按工艺要求完成聚合； (4) 生产可发性聚苯乙烯(EPS)，添加线性二聚体，用作链转移剂，得到的聚台物颗粒具有窄的粒径分布和良好的表面性能；线性二聚体与PE蜡配合作用，用于苯乙烯的悬浮聚台，得到的EPS含水率低，将回收的EPS废料谘解于苯乙烯中，掭加精制分离的PE蜡和线性二聚体．进行悬浮水溶液聚台反应，可回收利用EPS； (5) 生产橡胶改性的苯乙烯聚合物时，添加线性二聚体后进行聚合反应，当苯乙烯的聚合速率在2％～1O％之间时，再添加硫醇，则得到无味的聚合物，具有极好的熔体流动性及平衡的物理性能； (6) 丙烯腈一丁二烯共聚，以线性二聚体作分子量控制剂得到分子量为6500的低分子量液态聚合物，可用作聚合物改性剂和增塑剂； (7) 丁二烯一苯乙烯一甲基丙烯酸甲酯共聚合反应时，添加线性二聚体作分子量调节剂，并添加减味剂松香，可以生产低气味的聚合胶乳；线性二聚体预乳化后加入，利于稳定聚台反应，并减少精制丁二烯的量；线性二聚体也可以在聚台反应时连续地加入，至单体转化率达到指定值，得到的乳胶具有良好的性能，可用作地毯背村胶；线性二聚体作该聚合反应的链转移剂，还可以生产具有良好抗起泡性的胶乳；。 (8) 生产光固化的丙烯酸酯树脂，以线性二聚体作分子量调节剂，可以得到透明的聚合物； (9) 制造可发性甲基丙烯酸甲酯树脂颗粒时，在聚台反应中以线性二聚体替代叔丁基硫醇．可以得到具有良好外观的泡沫材料，消除发泡成型时的熔融现象； (10) 生产打印纸涂料用乳胶粘台剂时，以线性二聚体作分子链转移剂，得到的涂料具有良好的粘接性、抗起泡性、光洁度、表面强度和易印刷性。 上述高聚物的大量生产, 为α-甲基苯乙烯线性二聚体提供广阔市场。 2. 本产品新用途不断开发, 市场潜力无限 α-甲基苯乙烯线性二聚体的其他用途如下:
聚醋酸乙烯酯的调研报告..
聚醋酸乙烯酯的调研报告 一、引言 聚醋酸乙烯酯是1912年由F.克拉特发现，1925年加拿大沙维尼根化学公司投入工业化生产。可用乳液聚合、悬浮聚合、本体聚合和溶液聚合四种方法生产。乳液法产物直接用作涂料和胶粘剂等，俗称乳胶或白胶；溶液法产物用于制造聚乙烯醇和聚乙烯醇纤维。聚醋酸乙烯酯 聚醋酸乙烯酯玻璃化温度较低，仅28℃，因而在室温下有较大的冷流性，不能用作塑料制品，但它具有能与多种材料，尤其是与纤维素物质（如木材、纸等）粘接的优良性能，被广泛用作涂料、胶粘剂、纸和织物整理剂等（见造纸用化学品、染整助剂），如粘合木料的白胶水、粘接砖瓦的胶粘剂，透明胶纸带，砖石表面涂料，以及预先涂有聚醋酸乙烯酯的标签和信封、邮票等。醋酸乙烯酯和丙烯酸酯或乙烯的共聚物应用于粘结不易粘结的材料（见乙烯－醋酸乙烯酯树脂），如聚氯乙烯塑料等。此外，也作无纺布的胶粘剂。 二、聚醋酸乙烯酯性质 物理性质：无色黏稠液或淡黄色透明玻璃状颗粒，无臭，无味，有韧性和塑性。折射率1.45～1.47，软化点约为38℃，熔点(600C)，密度(1.191g/ml) ,软化点约为38℃;不能与脂肪和水互溶，可与乙醇、醋酸、丙酮、乙酸乙酯互溶;溶于芳烃、酮、醇、酯和三氯甲烷;黏着力强，耐稀酸、稀碱;在阳光及125℃温度下稳定。 化学性质:可燃，燃烧(分解)产物有一氧化碳等，与硝酸盐、硝酸、硫酸等发生反应。遇浓碱和浓酸分解。由醋酸乙烯以自由基引发剂引发。[4]可燃;加热分解释放刺激烟雾。加热到250℃以上分解出醋酸。 三、聚醋酸乙烯酯应用 1、作胶姆糖基料，中国规定可用于乳化香精和胶姆糖，最大使用量为 60g/kg；
常用塑料名称中英文对照
英文缩写中文详细名称 AAS 丙烯腈-丙烯酸酯-苯乙烯共物 ABS 丙烯腈-丁二烯-苯乙烯共聚物 acrylonltrile-butadiene-styrenecopolymer ACS 丙烯腈-氯化乙烯-苯乙烯共聚物 A/MMA 丙烯腈-甲基丙烯酸甲酯共聚物 acrylonitrile-methyl meth acrylat copolymer AN 丙烯腈 AC 偶氯二甲酰胺（发泡剂） ACR 丙烯酸酯（聚氯乙烯加工助剂） ALSt 梗脂酸铝（稳定剂） A/S 丙烯腈-苯乙烯共聚物 acrylonltrile-styrene-copolymer A/S/A 丙烯腈-苯乙烯-丙烯酸酯共聚物 acrylonitrile-styrene-acrylate copolymer BBP 邻苯二甲酸丁酯（增塑剂） BMC 预制整体模塑料 BPO 过氧化苯甲酰（交联剂） BS 硬脂酸正丁酯（增塑剂） BaSt 硬脂酸钡（稳定剂） BPBG 丁基邻苯二甲酰基甘醇酸丁脂增塑剂 BR 丁二烯橡胶 CA 乙酸纤维素 cellulose acetate CAB 乙酸-丁酸纤维素 cellulose acetate butyrate CaCO3 碳酸钙（填料） CAP 乙酸-丙酸纤维素 cellulose acetate propionate CaSt 硬脂酸钙（稳定剂） CdSt 硬脂酸镉（稳定剂） CF 甲酚-甲醛树脂 cresol-formaleehyde resin CMC 甲羧基纤维素 carboxymethyl cellulose CN 硝酸纤维素 cellulose nitrate CPCB 四醇已二酯（增塑剂） CPE 氯化聚乙烯 CPP 氯化聚丙烯Colorinated Polypropylene CPVC 氯化聚氯乙烯 CR 氯丁橡胶 CS 酪素塑料 casein plastics CTA 三乙酸纤维素 cellulose triacetate DAP 邻苯二甲酸二戊酯（增塑剂） DBP 邻苯二甲酸二丁酯*（增塑剂） DBS 癸二酸二丁酯（增塑剂） DBTL 月桂酸二丁基铜（稳定剂） DCP 邻苯二甲酸二促辛酯（增塑剂） DCP 过氧化二异丙苯（交联剂） DEP 邻苯二甲酸二乙酯（增塑剂） DHP 邻苯二甲酸二庚酯（增塑剂） DIBA 已二酸二异丁酯（增塑剂） DIBS 癸二酸二异丁酯（增聚剂） DIDP 邻苯二甲酸二异癸酯（增塑剂） DIHP 邻苯二甲酸二酯（增塑剂） DINP 邻苯二甲酸二异壬酯（增塑剂） DIOA 已二酸二异辛酯（增塑剂） DIOP 邻苯二甲酸二异辛酯（增塑剂） DIOS 癸二酸二异辛酯（增塑剂） DIOZ 壬二酸二异辛酯（增塑剂） DLTP 硫代二丙酸二月桂酯（助抗氧剂） DMA 二甲基乙酰胺 DMC 团状模塑料