Initiated conversion of ethanol to divinyl by the Lebedev reaction

ISSN 0965�5441, Petroleum Chemistry, 2014, Vol. 54, No. 3, pp. 195–206. © Pleiades Publishing, Ltd., 2014.Original Russian Text © V.F. Tret’yakov, R.M. Talyshinskii, A.M. Ilolov, A.L. Maksimov, S.N. Khadzhiev, 2014, published in Neftekhimiya, 2014, Vol. 54, No. 3, pp. 195–206.

195

In the 1930s, divinyl (butadiene�1,3) was manufac�tured by combining the dehydrogenation and dehy�dration of ethanol in a single catalytic process accord�ing to the method proposed by S.V. Lebedev [1–3]. Asystematic study of the desired reaction was also car�ried out by Yu.A. Gorin [4]. The mechanism of theprocess was supposed to involve the followingsequence of transformations: the formation of acetal�dehyde on the dehydrogenating catalyst component,the condensation of acetaldehyde to crotonaldehyde,and the reduction of the latter with ethanol hydrogento crotyl alcohol followed by dehydration of the crotylalcohol with the accompanying rearrangement of thedouble bonds and the formation of divinyl. However,the reaction mixture contains about 30 various com�pounds and, thus, it is quite a demanding task toincrease the selectivity of the process for divinyl.

Bhattacharyya and Avasthi [5] reported data on theone�step catalytic conversion of ethanol into divinylwith a moving�bed catalyst. The maximum attainablevalues for the ethanol conversion and the yield of divi�nyl on a reacted ethanol basis over the Al2O3 /ZnO(60 : 40) catalyst were shown to be as high as 25.1 and72.8%, respectively. Note that Lebedev managed toget a 10–13% yield of divinyl on a fed ethanol basiswith its formation selectivity of at most 25% under lab�oratory conditions. Later on the industrial scale, thesequantities were improved to 18 and 44%, respectively.

Among the catalysts proposed for producing divi�nyl by the Lebedev process, individual aluminum, sil�icon, and iron oxides; Al2O3–ZnO, TiO2, ZrO3–ThO3, Al2O3–Cr2O3, Al2O3–MgO, and Al2O3–CaObinary oxides; and ternary aluminum–iron–chro�

mium compositions were reported in the literature[6, 7]. The conversion of ethanol on these catalysts wascarried out at temperatures of 350–450°С.

Niiyama et al. [6] revealed that the addition of ace�taldehyde increases the yield of divinyl. In this case,there was an induction period (1 h) in reaching asteady state, which is due to the unstable oscillatorymode of the reaction, according to the cited authors.Because of the lack of stability, the catalyst requiredperiodic regeneration.

A moving�bed TiO2–ZrO2 catalyst with various zir�conium contents was used to convert ethanol intodiethyl ether, ethylene, and divinyl in [7]. A maximumin activity was reached with a 50% ZrO2 content in thecatalyst.

An attempt to accomplish the ethanol conversionreaction in a helium atmosphere on aluminized sepio�lite having the approximate formulaMg4(Si6O15)(OH)2 ⋅ 6H2O at a reduced temperature(280°С) and a pressure of 50 torr (50 mmHg) also gavediscouraging results. The selectivity for divinyl at anethanol conversion of 60% did not exceed 10%, andthe major product of the reaction was diethyl ether [8].

Of the systems examined, the MgO–SiO2 catalyst(molar ratio 1 : 1) prepared from ethyl orthosilicate o�Si(C2H5)4 and magnesium nitrate and promoted with0.1% Na2O showed the highest activity and a highselectivity (87% of theory) in the formation of divinylat 350°C [9, 10]. However, the results of the study ofthis process have not found industrial application.

The activity and selectivity of the catalytic processon the ZnO/Al2O3 system substantially depends on thechoice of the form of ZnO/Al2O3. Thus, the properties

Initiated Conversion of Ethanol to Divinyl by the Lebedev Reaction

V. F. Tret’yakov, R. M. Talyshinskii, A. M. Ilolov, A. L. Maksimov, and S. N. KhadzhievTopchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia

e�mail: [email protected] March 3, 2013

Abstract—A synergistic effect has been revealed upon hydrogen peroxide initiation of the catalytic ethanol�to�divinyl conversion process, proposed by S.V. Lebedev, on the (K2O)ZnO/γ�Al2O3 catalyst. The efficiencyof the initiator has been examined, depending on the form of aluminum oxide, hydrogen peroxide concen�tration in the system, and the linear velocity of the feed stream. The behavior of the process characteristicshas been analyzed and a kinetic model of the process has been proposed on this basis, enabling the selectivityof the initiated reaction to be controlled.

Keywords: divinyl, ethanol, catalyst, kinetics, initiator, dehydrogenation, dehydration, compartmented reac�tor, hydrogen peroxide

DOI: 10.1134/S0965544114020133

196

PETROLEUM CHEMISTRY Vol. 54 No. 3 2014

TRET’YAKOV et al.

of the Al oxide forms used in the catalyst preparationshould be taken into account in the research.

Aluminum oxide obtained by calcining fine crys�talline boehmite (γ�Al2O3) at 450–600°C has a spe�cific surface area of 200–300 m2/g, whereas α�Al2O3has a low specific surface area of about 25 m2/g.

It is known that calcination in an air stream in therange of 350–750°C changes the specific surface areaand the acidity of Al oxides. At the same time, the spe�cific surface area of boehmite�based Al2O3 (commer�cial grade A�64) remains substantially unchanged. Amixture of bayerite with boehmite (A�75) givesγ�Al2O3 with a surface area of 500 m2/g, and this valueis relatively stable in the aforementioned temperaturerange.

By IR spectroscopy, it was shown that water mole�cules remaining in Al oxide react with Al2O3 with theincreasing temperature to form surface hydroxylgroups. As the temperature further increases, OH–

ions are gradually removed in the form of Н2О, but afew tenths percent of water remain in the oxide even at1000°C [5].

The OH– ions located on the surface of Al oxide,like hydroxyls of a colloidal Al hydroxide precipitate,are capable of exchange with cations and anions. It istherefore necessary to consider the possibility ofhydroxylation of the oxide surface by the action of thereaction medium, which greatly influences the cata�lyst properties.

An analysis of the relevant published data showsthat all studies on the mechanism of the reaction inquestion were limited to consideration of the targetroute only. The lack of kinetic data for the Lebedevreaction hampered the search and development of cat�alyst systems and their improvement from the stand�points of controlling the selectivity and optimizing thechemical composition and structure.

In the present study, we attempted for the first timeto assess the most characteristic stoichiometric routesby which a scientifically grounded kinetic model of thereaction can be created so that to enable controllingthe divinyl formation selectivity and the performanceof the catalytic process.

Thus, it follows that for the process of divinyl man�ufacturing from ethanol to be further improved, it isnecessary to study the physicochemical principles ofthe synthesis of pertinent catalyst compositions ensur�ing high selectivity and productivity of the systems, toinvestigate the characteristic features of the reactionwith the aim to create a kinetic model for scientificallysubstantiated controlling the selectivity of the multi�path reaction, and to develop new approaches tointensification of the process in order to increase theon�stream cycle time of the reaction.

EXPERIMENTAL

The materials used in the synthesis of the sampleswere γ�Al2O3, Al(NO3)3 ⋅ 9H2O, Zn(NO3)2 ⋅ 6H2O,KNO3, and α�Al2O3. The amount of Zn oxide intro�duced into the catalyst corresponded to Lebedev’s for�mulation (~25 wt %). Aluminum nitrate was used as abinder to adhere the initial Al oxide to the Zn oxideformed during the subsequent calcination of the pre�cursor.

Catalysts were prepared by mechanically mixingthe ingredients followed by preparing an aqueousslurry, air drying, and heat treatment or by impregnat�ing γ�Al2O3 with solutions of nitrates of the activecomponents (Zn, Al, and K).

The samples were impregnated with Zn and Alnitrate solutions at 40–80°C for 3 h followed by dryingat 120°C for 6 h and stepwise calcining in an air streamat 200, 300, and 450°C for 2 h in each step. The major�ity of nitrogen oxides were removed at 300–320°C,and the remaining oxides were removed in a stream ofhydrogen during catalyst activation directly in thereactor prior to testing at 420–450°C.

The phase composition of the samples was studiedby X�ray diffraction (XRD). Diffraction patterns weretaken on a Bruker D8 Advance powder X�ray diffrac�tometer using CuK

α radiation (λ = 0.15406 nm) by

points at 0.1 deg intervals and an exposure of 20 s. Thediffraction patterns were recorded in the angular rangeof 2θ 10°–100°. The results of the phase analysis wereobtained by matching with the STOE WinXPOWcomputer database.

The average size (D) of the coherent scatteringregion (CSR) was determined by the XRD techniquebased on the harmonic analysis of diffraction peakprofiles. The average CSR size was evaluated by the

Selyakov–Scherrer equation

The reaction was run in a differential gradientlessmicroreactor, made of glass (Pyrex or fused silica), inthe temperature interval of 380–420°C with a catalystcontact time of 2–5 s in the absence or presence of theinitiator H2O2. The ZnO/γ�Al2O3 catalyst charge ofthe reactor was 1 to 2 cm3. Long�term tests were per�formed in an integral stainless steel reactor with a cat�alyst charge of 50 cm3, with the temperature gradientalong the length of the catalyst bed being 10–15°C.

After exiting the reactor and cooling, contact gasand condensate were analyzed by chromatography onKristall�2000M (Chromatec, Russia) gas chromato�graphs using a packed column of 3 m length and 3 mminner diameter with the HayeSep DB phase, a carriergas (helium) flow rate of 30 cm3/min, temperatureprogramming in the 30–150°С range, and a thermalconductivity detector (TCD).

For accurate peak assignment, calibration withindividual components of the gas (butadiene, ethyl�ene, butylene) and the liquid organic phase (ethanol,acetaldehyde, butanal) and experiments with the

.cosKD λ

=β θ


INITIATED CONVERSION OF ETHANOL TO DIVINYL 197

simultaneous detection by FID and TCD were carriedout. The liquid fraction was analyzed on the same col�umn in the same mode with a sample volume of 1 μL.Components at the column outlet were identified withthe FID. The determinations were repeated severaltimes, and the data were averaged and compared withthe results of independent gas chromatography–massspectrometry analysis (Finnigan MAT 95 XL instru�ment).

The initiator used to induce the divinyl synthesisprocess was 30% hydrogen peroxide solution added tothe reactant mixture in an amount of 1 wt %.

RESULTS AND DISCUSSION

Testing the Synthesized Samples for Catalytic Activity

The initial activity of the catalyst, prepared on thebasis of Al2O3 available from a French manufacturer,in the absence of hydrogen peroxide reached the val�ues corresponding to the divinyl concentration of 70%in the gas phase. However, the catalyst activitydeclined and the yield of divinyl sharply dropped to10% during the first 10 minutes. In the presence ofН2О2, the catalyst activity remained unchanged for1 h. Note that the catalysts on the basis of French�made γ�Al2O3 tested in the presence and absence of theinitiator turned very fragile in preparation by bothmechanical mixing of the ingredients and impregnat�ing Al2O3 with zinc and aluminum nitrates. To make acatalyst with a higher mechanical strength, we devel�oped a special impregnation procedure (see Experi�mental) comprising the use as a binder of Al(NO3)3doped with 0.25% K2O, which ensured that catalystswould have an optimal composition and texture, alongwith improved strength properties, suitable for indus�trial application [10, 11].

It is on this impregnation catalyst prepared on thebasis of domestic γ�Al2O (manufactured at the Insti�

tute of Catalysis, Russian Academy of Sciences,Novosibirsk) that the further tests were focused. Thecatalyst turned out to be the most active (divinyl con�centration in the gas phase, up to 65–70%) and stableand did not lose activity in the presence of Н2О2 for120 h. The catalyst on�stream time in the absence ofН2О2 was 48 h, after which the activity began todecrease. The results obtained with the use of the ini�tiator give grounds to believe that it is feasible to designa continuous process [12].

As shown by the results of testing in a quartz flowreactor (10 cm3 charge), the activity of the catalystprepared by impregnation of Al oxide with a Zn nitratesolution was higher by 10% compared with the sampleprepared by mechanical mixing of zinc and aluminumoxides.

Table 1 collates data obtained in the laboratoryand industrial data and illustrates the influence of theinitiator PV�1 (H2O2). The addition of the initiator(PV�1) to ethanol produces a complex modifying, ini�tiating, and regenerating effect. The modifyingeffect can be regarded as the result of hydroxylationof the catalyst surface by the hydroxyl radicals gener�ated during the thermal decomposition of hydrogenperoxide.

Table 2 presents values for the yield of divinyl (onfed ethanol basis) and the selectivity of the process onan industrial catalyst sample and our synthetic samplesА (mechanical mixing of zinc oxide with γ�alumina),В (impregnation of γ�alumina with zinc and alumi�num nitrates), and С (mechanical mixing of zinc oxidewith α�alumina) at various temperatures and liquidhourly space velocities. The effect of initiation withhydrogen peroxide is achieved at space velocities of noless than 3 h–1, with the initiating effects being moresignificant with samples А and В on which the processruns at optimal space velocities of 3.0 and 4.4 h–1,respectively. Catalyst В appeared to be the most effec�tive.

Table 1. Development of the Lebedev process (main parameters)

No. ParameterIndustrial data by Efremov

synthetic rubber plant (1985) 420–430°C

Data by Topchiev Institute

without initiator 400–410°C

using initiator PV�1 390–400°C

1 Ethanol space velocity, L/(L cat h) 1.5 2.7 2.85

2 Selectivity, at least 44.15% 50% 52%

3 Ethanol conversion, at leas 42% 40% 42%

4 Yield of divinyl on reacted alcohol basis, percent of theoretical value, at least

75% 85% 88%

5 Yield of divinyl on fed alcohol basis, at least 18.5% 20% 21.8%

6 Alcohol consumption per 1 t of divinyl, at most

2.27 t 2.0 t 1.92 t

7 Process continuity With periodic regeneration

With periodic regeneration

Without catalyst regeneration

198


TRET’YAKOV et al.

Our analysis of the chemical composition of theindustrial sample by atomic absorption spectroscopyshowed the prevalence of magnesium and silicon; thepresence of aluminum and zinc; and traces of calcium,iron, and molybdenum (see Table 3). We also foundthat the ratio of Zn and Al oxides (their total amountin the catalyst is 1.5%) exactly coincides with that ofthe Lebedev catalyst formula. This indicates that thegiven industrial catalyst is a combination of magne�sia–silica and zinc–alumina catalysts.

Figure 1 presents a SEM (scanning electronmicroscopy) image of the industrial catalyst. It is seenthat the sample has a porous structure and is composed

of particles bonded by a substance having a uniformtexture, probably, a solid solution of magnesium andsilicon.

Energy�dispersive spectra (EDS) (Fig. 2) exhibitlines due to the basic elements Mg, S, and O in thesample and also show the presence of traces of Mo, Fe,Ca, C, Al, and Zn.

According to the XRD data, the commercial sam�ple is a disordered phase of MgO with SiO2 (Fig. 3)and the sample synthesized in the laboratory (Fig. 4) isa mixture of two phases, the main ordered ZnO phase(CSR size is D (ZnO) = 42 nm) and a concomitant dis�ordered Al2O3 phase. All the smeared diffuse peaks areattributed to γ�Al2O3. (The CSR size of γ�Al2O3 couldnot be calculated because of a strong overlap of lines).

Kinetic Features of the Process

The bulk of the experimental data on the kinetics ofthe process of divinyl production from ethanol is pre�sented below. Table 4 shows the effect of hydrogen per�oxide and Tables 5 and 6 present the experimentaldata used in the simulation of the ethanol conversionkinetics.

The mass balance and molar concentrations werecalculated with the use of the following basis of parallelroutes:

2C2H5OH = C4H6 + 2H2O + H2,

2C2H5OH= C4H8 + 2H2O,

C2H5OH = C2H4 + H2O,

C2H5OH = CH3CHO + H2,

2C2H5OH = C4H8O + H2O + H2,

C2H5OH → H2 + CH3−CHO,

By the amount of key substances in the reactionmixture, the rates of water and hydrogen formation are

Table 2. Influence of the type of catalyst depending on the form of aluminum oxide on the parameter of the ethanol�to�divinyl conversion process

Run no. Catalyst T, °C LHSV, h–1Divinyl, %

yield selectivity

1 Industrial (1985) 420 1.2 18.1 44.2

2 A 410 3 20.0 48.0

3 B 400 4.2 22.0 53.1

4 C 425 1.1 17.2 42.3

5 Industrial (1985) (+PV�1) 415 1.3 18.2 44.5

6* A(+PV�1) 400 3.2 22.3 54

7* B(+PV�1) 395 4.4 24.5 55

8 C(+PV�1) 420 1.2 17.5 43.2

* The process does not require regeneration (no drop in activity).

Table 3. Elemental composition of an industrial catalyst fordivinyl production from ethanol [13]

Element keV wt % Deviation, % Atomic %

C 0.277 4.16 0.37 7.04

O 0.525 33.29 0.24 42.35

Mg 1.253 53.89 0.14 45.12

Al 1.486 0.40 0.29 0.30

Si 1.739 6.35 0.24 4.60

Ca 3.690 0.19 0.24 0.10

Fe 6.398 0.25 0.52 0.09

Zn 8.630 0.80 1.38 0.25

Mo 2.293 0.68 0.53 0.14

Total: – 100.00 – 100.00



defined as: = 2(w1 + w2) + w3 + w5 +

[here, is the feed rate of water contained in

the initial feed stream and = w1 + w4 + w5].

Tables 5 and 6 list values for the ethanol conversionrate w and the rates of formation of divinyl, butylenes,ethylene, acetaldehyde, and butanal w1, w2, w3, w4, andw5, respectively. The flow rate of unreacted ethanol is(w0 – w).

The basis set of the overall stoichiometric routes isdefined by the following reaction scheme:

I C2H5OH → C2H4 + H2O,

II C2H5OH → CH3CHO + H2,

III CH3CHO + C2H4 → C4H6 + H2O,

IV CH3CHO + C2H4 → C4H8O,

V 2CH3CHO + H2 → C4H6 + 2Н2О,

wH2O wH2O( )0

wH2O( )0

wH2

VI 2C2H4 → C4H8,

VII C4H8 → C4H6 + H2.

To elucidate the idea of the mechanism of the reac�tion, the basis of stoichiometric routes is depicted as amultistep scheme (Table 7).

According to the multistep scheme, the number ofoverall routes (Horiuti number) is P = S – N + 3 =16 – 12 + 3 = 7, where S is the number of steps, N isthe number of intermediates, and 3 is the number oftypes of centers (Z, ZH, and ZO) corresponding to thenumber of additional stationarity conditions. Fromthe multistep scheme, the number of intermediates(transient compounds with the catalyst surface) wascalculated.

In the proposed scheme, three characteristic typesof centers classified by the degree of reduction withhydrogen and the reaction medium, Z, ZH, and ZO,are shown. Two of these (Z and ZH) responsible forthe desired conversion of ethanol include Al oxide andZn oxide in their composition, and the third, oxidizedcenter ZO mediates the formation of the byproductsaldehydes, ethers, and butanal. The catalyst surfacereleases divinyl from the centers of the normal (Z) andreduced (ZH) types at steps 6 and 16 (see staged dia�gram).

After the stoichiometric analysis of the overallequations and detailing the steps in which slow, fastreversible equilibrium, and irreversible reactions aredistinguished, kinetic equations relating the flow ratesof substances and their concentrations were sought for.In accordance with the adopted stoichiometric basis ofoverall kinetic routes, the observed rates pertaining tokey substances are expressed in terms of the rates viaroutes ri (system of equations (1)):

50 µm×400

Fig. 1. Electron micrograph of the industrial catalyst (at agrain section) after the reaction. Scale: micrometers (sam�ple texture).

72000

64000

48000

40000

32000

24000

16000

8000

0 211912963

56000

15

CK

aO

Ka

FeL

a Cu

La

Zn

La

AlK

a SiK

a Mo

Ll M

oL

aM

oL

bM

gKsu

m

CaK

a CaK

b

MgK

a

FeK

a

FeK

b

Cu

Ka

Zn

KbZ

nK

aC

uK

b

Mo

Ka

Mo

Kb

Co

un

ts

keV

Fig. 2. EDS spectrum of a sample of the industrial catalyst (distribution of elements) after the reaction.

200


TRET’YAKOV et al.

(1)

Under steady state conditions, the equilibriumstate of the system is reached; then, in accordancewith the principle of microscopic reversibility of steps,we have

[Z] + [C2H4Z] + [C4H8Z] + [C4H6Z] = 1,

[ZH] + [CH3CHOZH] + [C4H6ZH]

+ [CH3CHOHCH2CHOZH]

+ [CH3CH=CHCHOZH] = 1,

[ZO] + [C2H4ZO] + [C4H8OZO] =1;

w r1 r2––=

w1 r3 r4 r5+ +=

w2 r6 r7–=

w3 r1 r3 r4– 2r6––=

w4 r2 r3 r4 2r5–––=

w5 r4=

ethanol

divinyl

butylenes

ethylene

acetaldehyde

butanal

3

5 4 6 1

ZH]X[ZH CH CHOZH

X [ZH] C H ZH X [ZH]

3 4

4 6 6

[ ] [ ]

[ ] 0,

d k kd

k k k− −

= − + −

τ

− + − =

3

4 8 4

ZOX [ZO]

[C H OZO] X [ZO]

7

9 9

[ ]

0,

d kd

k k−

= − +

τ

+ − =

1 2 4

4 8 2 4 6

[Z]X [Z C H Z [ ]

C H Z X [Z] C H Z]

1 2 2 3

14 14 16

] [ ]

[ ] [ 0,

d k k k X Zdk k k

−

−

= − + − +

τ

+ − + =

4 64 8 4 6

C H Z][C H Z] C H Z15 16

[[ ] 0,

dk k

d= − =

τ

4 83 2 4

4 8 2

C H ZX [C H Z]

[C H Z X [Z

13

14 14

[ ]

] ] 0,

dk

dk k

−

=

τ

− + =

800

700

600

500

300

200

100

0

400Inte

nsi

ty

Fig. 3. XRD data for the industrial catalyst sample after the reaction.

1200

1000

800

600

400

200

010080604020

2θ, deg

Inte

nsi

ty

ZnOγ�Al2O3

Fig. 4. XRD data for the (K2O) ZnO/γ�Al2O3 sample, synthesized in the laboratory, after the reaction.



Table 4. Testing parameters for the catalyst based on Novosibirsk aluminum oxide, impregnated Al and Zn nitrate with anadmixture of K nitrate rate to have 0.25% K2O (75 wt % Al2O3 in the final sample)

Run no. T, °C w0, h–1 Yield, % Conversion, % Selectivity, %

1 410 3.5 15.5 65.8 23.6

2 417 2.9 21.9 69.0 31.7

3 400 2.9 13.0 65.2 19.9

4 400 2.9 9.5 52.8 18.0

5 387 1.2 12.8 87.2 14.7

6 416 6 20.7 53.4 38.8

7 416 6 22.5 49.5 45.6

8 416 6 9.8 31.9 30.5

9 416 6 22.0 59.1 37.3

Effect of hydrogen peroxide

0.8% H2O2 410 6 18.0 38.6 46.5

Without hydrogen peroxide 416 6 19.3 52.4 36.9

w0, h–1 is the liquid (water + ethanol + hydrogen peroxide) hourly space velocity.

Table 5. Flow rates of substances in the system in the presence of the initiator (1% H2O2)

T, °C w0, L/(L s)

w0–w, L/(L s)

wi, L/(L s)

C4H6 C4H8 C2H4 CH3CHO C4H8OH2O H2

overall, L/(L s)

1 2 3 4 5

380 0.203 0.140 0.0068 0.0076 0.027 0.0030 0.0009 0.068 0.011 0.264

390 0.203 0.131 0.0110 0.0084 0.028 0.0036 0.0008 0.078 0.015 0.276

400 0.203 0.109 0.0178 0.0098 0.031 0.0050 0.0008 0.098 0.024 0.295

410 0.203 0.095 0.0200 0.0095 0.034 0.0070 0.0008 0.105 0.028 0.299

420 0.203 0.093 0.0190 0.0090 0.041 0.0084 0.0011 0.102 0.029 0.303

380 0.305 0.200 0.0196 0.0079 0.034 0.0100 0.0020 0.107 0.032 0.413

390 0.305 0.193 0.0232 0.0085 0.033 0.0107 0.0028 0.117 0.037 0.425

400 0.305 0.177 0.0320 0.0090 0.029 0.0120 0.0028 0.132 0.043 0.437

410 0.305 0.160 0.0348 0.0100 0.033 0.0164 0.0024 0.141 0.053 0.451

420 0.305 0.155 0.0350 0.0102 0.039 0.0176 0.0015 0.151 0.053 0.462

380 0.508 0.372 0.0262 0.0090 0.044 0.0200 0.0008 0.142 0.047 0.661

390 0.508 0.361 0.0295 0.0101 0.044 0.0220 0.0005 0.151 0.052 0.670

400 0.508 0.340 0.0347 0.0118 0.044 0.0280 0.0009 0.165 0.064 0.688

410 0.508 0.313 0.0363 0.0160 0.044 0.0339 0.0011 0.177 0.071 0.692

420 0.508 0.288 0.0351 0.0180 0.050 0.0471 0.0012 0.184 0.083 0.706

202


TRET’YAKOV et al.

where X, X1, X2, X3, X4, and X5 are the molar concen�trations of ethanol, divinyl, butylenes, ethylene, ace�taldehyde, and butanal, respectively.

Slow (rate�determining) steps (see Tables 7, 8) aresteps 1, 3, 5, 8, 12, 13, and 15, since they involve C–Hbond breaking.

Aldol and crotyl alcohol as intermediates are con�sidered to be Bodenstein products, since their builduprate in the system is close to zero.

The problem of determining the constants in thefinal form was solved according to the system of equa�tions (2):

for center Z b1 = 500,

(2)

for center Z b2 = 100,

for center ZO b3 = 550.

The system of rate equations (2) in combinationwith the conditions expressed by the system of Eqs. (1)quite reliably describes relationships in the array ofexperimental data. A criterion for the accuracy of thekinetic description of the system is the optimization

function in which wcalc and

wexp are the calculated and observed values, respec�tively, for the rates of formation and consumption ofsubstances in all the experiments and all the selectedkey substances (ethanol, divinyl, butyl, ethylene, ace�taldehyde).

The involvement of ethylene and crotyl alcoholfragments in the divinyl formation mechanism wasnoted even by Lebedev himself [1–3]. It was he whofirst noted a high probability of a coupled mechanisminvolving the classical route through acetaldehydewith allowance for the second, slow step of ethyleneformation. Lebedev suggested that there are somesteps in which this coupling manifests itself:

Our experimental data show that the mechanismproposed by Lebedev holds in the case of the zinc–aluminum oxide system without the initiator. Theinfluence of ethylene and butylene on the selectivityfor divinyl can be judged from the relative contributionof the third, fifth, and seventh routes in its formation:

where r3, r5, and r7 are the rates of divinyl formation viaoverall routes III, V, and VII, respectively, and r1 and r2are the rates of ethylene conversion to ethanol andacetaldehyde via the first and second routes of the sto�ichiometric basis.

The chemical structure of active centers Z, ZH,and ZO in the multistep scheme (Table 7) in terms ofthe obtained data (Figs. 2–4) can be represented asfollows, depending on the nature of the catalyst:

2 42 4

3 3 2 4

[C H ZX[Z] C H Z

X [Z X [C H Z

1 2

2 13

][ ]

] ] 0,

dk k

dk k−

= −

τ

+ − =

4 63 3 4 6

1 3 2

C H ZHX [CH CHOZH [C H ZH

X [ZH] [CH CH CHCHOZH][H ]

5 6

6 12

[ ]] ]

0,

dk k

dk k−

= −

τ

+ + = =

33

5 3

4 3

CH CHOZHX[ZH CH CHOZH

X [ZH] X CH CHOZH

X [CH CHOZH

3 4

4 5 3

10

[ ]] [ ]

[ ]

] 0,

dk k

dk k

k−

= −

τ

+ −

− =

4 84 2 4

4 8 4

C H OZOX [C H ZO

C H OZO X [ZO

8

9 9

[ ]]

[ ] ] 0,

dk

dk k

−

=

τ

− + =

2 43 4 2 4

C H ZOX [ZO X [C H ZO7 8

[ ]] ] 0,

dk k

d= − =

τ

X

X1

11 4

;1

kr

b=

+

23X

X13

61 4

;1

kr

b=

+ 4X15 2

71

;1

k Xr

b=

+

4 4 4

5 5 5

X XX X X

X X X

3 5 3 122 3 5

2 2 2

; ; ;1 1 1

k k kr r r

b b b= = =

+ + +

X8

43 4

;1

kr

b=

+

−

= →

∑calc

calc

2exp

exp1

( )

0,

nw w

w wF

n

CH2 CH(OH) CH2 CH2

CH(OH) CH2 CH2 CH2CH2 CH(OH) CH2 CH2

CH2 CH CH CH2

+

+ H2O

3 5 71

1 2

2( )100%,

r r rS

r r

+ += ×

+



Table 6. Concentrations of substances in the system in the presence of the initiator (1% H2O2)

T, °C w, L/(L s)

Mole fractions of substances in the system, Xi

C2H5OH

X

C4H6 C4H8 C2H4 CH3CHO C4H8O H2O H2total

X1 X2 X3 X4 X5

380 0.063 0.530 0.0258 0.029 0.102 0.0114 0.0034 0.258 0.042 1.00

390 0.062 0.475 0.0400 0.030 0.101 0.0130 0.0029 0.283 0.054 1.00

400 0.094 0.369 0.0 603 0.033 0.105 0.0169 0.0027 0.332 0.081 1.00

410 0.108 0.31S 0.0669 0.032 0.114 0.0234 0.0027 0.351 0.094 1.00

420 0.110 0.307 0.0627 0.030 0.135 0.0277 0.0036 0.336 0.096 1.00

380 0.105 0.454 0.0475 0.019 0.0S2 0.0242 0.0043 0.259 0.077 1.00

390 0.112 0.454 0.0544 0.020 0.073 0.0252 0.0066 0.275 0.087 1.00

400 0.128 0.405 0.0732 0.021 0.066 0.0275 0.0064 0.302 0.098 1.00

410 0.145 0.35S 0.0770 0.022 0.073 0.0364 0.0053 0.313 0 118 1.00

420 0.150 0.335 0.0758 0.022 0.084 0.0381 0.0032 0.327 0.115 1.00

380 0.136 0.563 0.0396 0.014 0.067 0.0303 0.0012 0.215 0.071 1.00

390 0.147 0.539 0.0440 0.0151 0.066 0.0328 0.0007 0.225 0.078 1.00

400 0.168 0.494 0.0504 0.0172 0.064 0.0407 0.0013 0.240 0.093 1.00

410 0.195 0.452 0.0524 0.0231 0.064 0.0490 0.0016 0.256 0.103 1.00

420 0.220 0.408 0.0497 0.0255 0.071 0.0667 0.0017 0.261 0.118 1.00

XH2O XH2

Table 7. Staged scheme of the ethanol conversion process on the ZnO/γAl2O3 catalyst

StepStoichiometric numbers for step routes

I II III IV V VI VII

1* C2H5OH + Z → C2H4Z + H2O 1 0 0 0 0 0 0

2 C2H4Z ↔ C2H4 + Z 1 0 0 0 0 –1 0

3* C2H5OH + ZH ↔ CH3CHOZH + H2 0 1 0 0 0 0 0

4 CH3CHOZH ↔ CH3CHO + ZH 0 1 –1 0 –1 0 0

5* CH3CHOZH + C2H4 → C4H6ZH + H2O 0 0 1 0 0 0 0

6 C4H6ZH ↔ C4H6 + ZH 0 0 1 0 1 0 0

7 C2H4 + ZO → C2H4ZO 0 0 0 1 0 0 0

8* CH3CHO + C2H4ZO → C4H8OZO 0 0 0 1 0 0 0

9 C4H8OZO C4H8O + ZO 0 0 0 1 0 0 0

10 CH3CHOZH + CH3CHO → CH3CHOHCH2CHOZH 0 0 0 0 1 0 0

11 CH3CHOHCH2CHOZH → CH3CH=CHCHOZH + H2O 0 0 0 0 1 0 0

12* CH3CH=CHCHOZH + H2 ↔ C4H6 ZH + H2O 0 0 0 0 1 0 0

13* C2H4Z + C2H4 → C4H8Z 0 0 0 0 0 1 0

14 C4H8Z ↔ C4H8 + Z 0 0 0 0 0 1 –1

15* C4H8Z ↔ C4H6Z + H2 0 0 0 0 0 0 1

16 C4H6Z ↔ C4H6 + Z 0 0 0 0 0 0 1

* Slow steps.

204


TRET’YAKOV et al.

According to the experimental data, route V pro�ceeds with zero orders in ethylene and acetaldehyde.This fact is presumably due to the complex heteroge�neous–homogeneous interaction of intermediatesand the influence of the diffusion term on the reactionrate.

As is evident from the kinetic model (set ofEqs. (2)), the competitive adsorption of acetaldehydeand butanal has an effect on reaction selectivity at thecenter ZH.

In the case of the initiated process, center ZO ismodified by the action of the hydrogen peroxide mol�

ecule H2O2 → 2OH•, ZO + OH• → Z + Thereleased center Z responsible for the desired transfor�

MgO SiO2 ZnO/γ Al2O3

Si O

O

OMg

Si O

O

O

OMg

O Al

O

OHZn

O Al OHZn

OH

O Al OHZnO

O

Si O

OH

OMg

Z

ZH

ZO

HO2.i

mations accelerates them, and the species [14]initiates the divinyl formation process. As a result, theyield of butanal is reduced and the selectivity of theprocess for divinyl increases.

Thus, the initiation of the process with hydrogenperoxide reduces the proportion of surface ZO centersand, as a consequence, decreases the concentration ofbutanal competing for the place on the surface ofreduced ZH�type centers. The multistep schemeshows that steps 7 and 8 are blocked in this case,resulting in a decrease in the rate of the fourth route ofbutanal formation.

It should be emphasized that all types of the classi�cal mechanisms known since the 1930s are based onlyon the slow acetaldehyde formation step (Gorin andNiiyama [4–6]). However, our kinetic studies of thereaction mechanism showed that slow steps in the caseof using γ�Al2O3 are the formation of ethylene andbutylene along with acetaldehyde formation.

The analysis of the kinetics on the synthesized cat�alyst samples having different productivities made itpossible to explain the effect in terms of limiting thelinear velocity of the hydrogen peroxide�containingstream.

The initiator is effective only at high linear veloci�ties of stream for a catalyst containing the γ�form ofAl2O3. The initiator provides for continuity of the pro�cess on the synthesized samples А and В at high linear

flow velocities that preclude the decay of OH and radicals, generated in the evaporation zone of the

HO2i

HO2i

Table 8. Kinetic parameters of the Lebedev reaction in the presence of hydrogen peroxide

Route Slow step

Constants, ki, s

–1 Rates by routes, ri, s–1

Rate parameters for reaction routes, s–1

673 K 683 K 673 K 683 K

I 1 2.19 3.8 0.060 0.070k1 = (4.86 ± 1.2) × 1016

II 3 72.7 76.5 0.067 0.077k3 = (2.30 ± 0.7) × 103

III 5 11.0 11.40.0018 Lebedev

0.0049k5 = (1.26 ± 0.3) × 102

IV 8 23.0 23.8 0.0028 0.0029k8 = (2.29 ± 0.7) × 102

V 12 11.0 11.20.0255 Gorin

0.0268k12 = (3.76 ± 1.0) × 103

VI 13 46.4 47.7 0.0135 0.0150k12 = (3.06 ± 1.3) × 102

VII 15 0.71 2.610.0035 Topchiev Institute

0.0055k15 = (2.90 ± 1.0) × 1038

e

–210600 2100±

RT��

e

–19050 190±

RT��

e

–13650 136±

RT��

e

–13070 130±

RT��

e

6890– 70±

RT��

e

–10650 120±

RT��

e

–497500 4900 ±

RT��



reactor, before entering the catalyst bed. As a result,the suppression of coking is observed, as well as theinitiation of the process by the coupled radical reac�tions in the bulk of the homogeneous space and sur�face modification by its hydroxylation. At space veloc�ities above 2.5 h–1, all these effects, which ultimatelyincrease the productivity and selectivity of the processfor divinyl, are manifested. Since both the catalystbased on α�alumina and the magnesia–silica systemare limited in the space velocity (at most 1.5 h–1), itbecomes quite clear why hydrogen peroxide turnedout ineffective in both the quartz and metal reactorswith the commercial sample and the catalyst synthe�sized on the basis of α�alumina. Hydrogen peroxide is

converted into water and oxygen, not OH• and radicals, before reaching the surface of the catalyst bedin the evaporator zone.

The numerical values of the kinetic parameters ofthe reaction via the overall routes show that route Vfavors the formation of divinyl. Routes I and VII areimpeded, judging by the activation energy, and theiroccurrence requires a more effective number of colli�sions in slow steps 1 and 15. The mechanism of thereaction of interest is graphically represented by thediagram in which the dashed line shows the coupledinitiating effect of hydrogen peroxide:

Seven cyclic hinged edges of the graph reflect theoverall kinetic routes of the process. The graph verticesrepresent the three types of surface active sites respon�sible for the target directions (at Z and ZH centers)and the side route (at ZO center).

In this study we have developed a technology forpreparing an impregnation catalyst on the basis ofzinc, aluminum, and potassium oxides (K2O�ZnO/Al2O3) for the Lebedev process of divinyl pro�duction from ethanol and examined the catalyticactivity using samples with γ�Al2O3. It has been shownthat the optimal catalyst synthesis procedure is the oneusing aluminum nitrate as the binder during theimpregnation of alumina, wherein the impregnatingsolution contains Zn and Al nitrates with an admixture

of 0.25% potassium nitrate and impregnation is fol�lowed by thermal treatment.

Long�term testing (120 h) of the optimal sample Вshowed that the process in the presence of hydrogenperoxide proceeds continuously without regenerationto give the yield of divinyl in the gas phase 10% abovethat obtained in its absence.

The achieved yield and selectivity for divinyl in theprocess make 22.2 and 50% on a fed ethanol basis (ver�sus 18% and 44% under industrial conditions), respec�tively. The yield of divinyl is 80–90% of the theoreticalvalue.

The testing of the commercial and laboratory cata�lyst samples showed that the selectivity of the processfor divinyl in the metal reactor is lower by 2–3% thanin the quartz reactor under the same conditions,

HO2,i

Z

ZO

ZH

CH3CHO

C2H4

C2H5OH

I

II

IV

V

VI

VII

H2O2

C2H5OH

C4H8O

C2H4

C2H4

C4H8C4H6

C4H6

C4H6

III

2OH�

ZO� + OH� Z + HO2�

CH3CHO

Scheme. Graph of the mechanism of the initiated process of divinyl production from ethanol.

206


TRET’YAKOV et al.

results that essentially agree with the relevant pub�lished data [15].

A kinetic model of the process has been also pro�posed as a result of the study. It has been found that themechanism of initiation of the process by hydrogenperoxide is associated with the possibility of surfacemodification via the interaction of the oxidized centerZO with hydroxyl groups and the generation of the

reactive radical and the center Z responsible forthe formation of divinyl. Along with the regeneratingand modifying functions, hydrogen peroxide is a

source of radicals in the bulk, which radicalsinduce the formation of divinyl from butylenes. Themodel of the initiated process of ethanol conversionsatisfactorily describes the experimental resultsobtained in the temperature range of 390–410°C at aliquid ethanol space of 2.5–3.5 h–1.

ACKNOWLEDGMENTS

This work was partially carried out on the equip�ment of CCU “New petrochemical processes, poly�mer composites, and adhesives” under State contractno.16.552.11.7072.

REFERENCES

1. S. V. Lebedev, Zh. Org. Khim., No. 111, 698 (1931).2. N. I. Smirnov, Production of Synthetic Rubber from Ethyl

Alcohol, Ed. by V. P. Krauze (ONTI Khimteoret, Len�ingrad, 1936) [in Russian].

3. S. V. Lebedev, Life and Works (ONTI Khimteoret, Len�ingrad, 1938) [in Russian].

4. Yu. A. Gorin, Zh. Org. Khim., No. 16, 283 (1946).

5. S. K. Bhattacharyya and N. Avasthi, J. Appl. Chem. 2,45 (1963).

6. H. Niiyama, M. Saburo, and E. Echigoya, Bull. Chem.Soc. Jpn. 45, 655 (1972).

7. K. Arata and H. Sawamura, Bull. Chem. Soc. Jpn. 48,3377 (1975).

8. V. Gruver, A. Sun, and J. J. Fripiat, Catal. Lett. 34, 359(1995).

9. R. Ohnishi, T. Akimoto, and K. Tanaba, J. Chem. Soc.,Chem. Commun. 15, 1613 (1985).

10. E. V. Makshina, W. Janssens, B. F. Sels, andP. A. Jacobs, Catal. Today 198, 338 (2012).

11. (a) V. S. Aliev, R. G. Rizaev, V. S. Gadzhi�Kasumov,et al., US Patent No. 4198536 (1980); (b) L. P. Pilaeva,Zh. M. Seifullaeva, V. S. Aliev, et al., FR PatentNo. 2444019 (1980).

12. V. F. Tret’yakov, S. N. Khadzhiev, R. M Talyshinskii,et al., RU Patent Appl. No. 2010148026/04(069440)(favorable decision of 27 Jan 2012).

13. V. F. Tret’yakov, R. M. Talyshinskii, A. M. Ilolov, et al.,AvtoGazoZaprav. Kompl. + Al’tern. Topl., No. 8 (68),16 (2012).

14. T. M. Nagiev, Interplay of Synchronized Reactions inChemistry and Biology (ELM, Baku, 2001) [in Russian].

15. T. M. Nagiev, Chemical Conjugation (Nauka, Moscow,1989) [in Russian].

Translated by S. Zatonsky

HO2i

HO2,i

Documents

Initiated conversion of ethanol to divinyl by the Lebedev reaction