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AZ9RBAYCAN KIMYA JURNALI № 3 2016
193
UDC 544.4; 17.544.47:544.344
GAS PHASE HETEROGENEOUS CATALYTIC OXIDATION OF CHLOROHYDROCARBONS
A.C.Efendi, E.M.Babayev, I.G.Malikova, B.A.Ismayilova, F.A.Yunisova, N.R.Aykan,
A.M.Aliyeva
M.Nagiev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
iradam@rambler.ru Received 18.05.2016
Oxidation reactions of chloroalphatic hydrocarbons studied in the presence of vanadium based oxide catalysts at the temperature range 400-6000C. Showed that their reactivity increase by the growth of the amount of carbon atoms in the content and the order of catalytic activity have also been identified. Moerever, the oxidation of chlorinated C4 olefin hydrocarbons to maleic and chloromaleic anhydrides in the precense of V-P-O/Al2O3 and V-P-O/SiO2 has been studied. Possibility of forecasting the orientation of the oxidation reaction depending on the amount and position of chlorine atoms contained in olefins, and a double communication is shown. Selective oxidation directions and also the reactivity of chlorinated butadienes determinated. The effect of an initial oxidation reaction to the intermediate and final products' oxidation reaction rate determined and explored that the main products of the reaction does not effect inhibiting to the reaction rate. The oxidation mechanism of chlorinated C4 hydrocarbons to maleic anhydride has been identified to occur by the passage intermediate chlorfuranone type compounds. The oxidation of clorbenzenes to maleic anhydride has to go parallel-sequential oxidation-reduction mechanism.
Keywords: chlorohydrocarbons, chlorbutenes, chlorofuranons, chlorobenzenes, chlorotoluenes, maleic, chloromaleic anhydrides, CO2, Cl2, oxide solid catalytic systems.
Introduction
Rapid development of oil refining and petrochemical industries suggest researches widely applicability fields different type of hydrocarbons and their chlorinated analogues. At the same time, the multifunctional compounds; car-boxylic acids, anhydrides and their chlorinated analogues obtained from the process are widely used as additives in the synthesis of biologically active substances, medicines, dyes, polyesters, polymer materials, as well as to receive a variety of intermediate products in the organic synthesis. From this point it's important to emphasize the conversion of Ci-C4, aromatic hydrocarbons and their chlorinated derivations to organic compounds and their chlorinated analogues, particularly carboxylic acid derivatives. On the other hand, during wide range production on an industrial scale due to the impossibility of their complete separation and waste segregation some portion of these compounds thrown into environment aggravate environmental condition even more gruelling which is the already heavy. Catalytic disposal methods of these compounds are considered to be the most important conversion way. Scientific basis of catalytic oxidation reaction of Ci-C4 aliphatic hydrocarbons, and their
reactivity determined and developed by us. Reactivity of Ci-C4 alkanes in the catalytic oxidation reaction was studied.The ranks of an activity and selectivity of catalytic oxidation systems established for various chlorinated hydrocarbons (CH). It is shown that the reactivity of the saturated chlorohydrocarbons in oxidation reactions enhanced in the order by the increase of carbon chain: tetra-chloromethane (CC14)<1,2-dichlo-roethane (1,2-DCE)<1-chloropropane (1-CP)< 1-chlorobutane (1-CB)<tetra-chlorobutane (TeCB) <penta-chlorobutane (PCB)<hexa-chlorobutane (HCB), and selectivity in the order: CCU<1,2-DCE< 1 -CB<1 -CP<TCB<PCB<HC. The activity of studied catalytic system in the oxidation reaction of saturated CH changed in the order: CoMo < V-P-O/S1O2 < V-P-0/Si02+Mg < V-M0-O/AI2O3 < V-P-O/AI2O3, and selectivity in the order: V-P-O/AI2O3 < V-M0-O/AI2O3 < Co-Mo<V-P-O/SiO2 < V-P-O/SiO2+Mg. Some correlations revealed between the amount of chlorine atoms in the molecule of CB and the optimum technological parameters, conversion rate, as well as selectivity of the process.
But it's difficult to say the same about aromatic hydrocarbons (AHC). The most attractive processes among the AHC are the heterogeneous
catalytic oxidation of benzene and its chloro-derivatives to maleic anhydride and its chlorinated derivatives. The most significant points are selection of active and selective catalysts, the study of kinetic regularities and mechanism of the oxidation reactions for carrying out these processes.
The surplus of petrochemical industry, especially derivation and conversion processes of hydrocarbons and their chloric analogues causes to increasing the quantity of ecological pollutions. It's known that, polychlorinated bi-phenyls take distinctive place among the CH and they are included steady organic wastes. These chemicals are classified as similar as dioxins. They are very harmful, immiscible in water, incombustible, thermo-, acid-, alkali stable and "not readily biodegradable". According to their noteworthy fuse behaviours in fats, lipids and organic solvents they are able to be bio accumulated. Even small quantity of them effect to organism toxic, cancerous. Their stability for chemical and biological changes gives them widespread ability. Due to these facts the production of these chemicals declared prohibited with International Global Convention at Stockholm on 23 may 2002. Although this argument it had manufactured approximately 2 million tons of polychlorinated biphenyls. In this order it can be shown, dibenzo-p-dioxin, alderin, dialderin, DDT (dichlorodiphenyltrichloroethane), hexa-chlorobenzene, toksafen, chlorbutadienes and etc. Notwithstanding, most of them under different names in USA (Aerochlors), Japan (Ke-nachlor), Germany (Chlorofan), France (Pheno-chlor), Russia (Sovol, Sovtol), Italy (Phenchlor) beside agricultural purpose are widely used as an industrial substances, such as condenser oil, dielectric liquids in transformer, plastificators, elastomers in the production of hydraulic liquids, lubricating oils, varnishes, glues [1-5].
Protecting environment from the polluting with these compounds and their harm to human organism is ecological important issue. Nowadays, variety of methods are utilised for their disposal. As well chlorinated benzenes and toluenes received during their decomposition are also toxic and harmful compounds. There are several methods for the derivation and conver-
sion of chlorobenzenes and chlorotoluenes. They are also use as pesticide, herbicide, industrial solvents, dielectric liquids, antimicrobial substance. It should be noted, infinitesimal mole
1 2
concentration of them (10-1-10-2 mol/l) make their counteraction more difficult, it is nearly impossible to effectuate the disposal with available methods. It will be purposeful both neutralization of them and also using of rewarding raw materials in chemical industry.
In this regard, to attain new catalytic systems for catalytic conversion of chloro-, polychlo-robenzene and toluenes to useful substances is intended as a pressing problem. Considering that polychloro compounds are thermally steady even at 700-800°C are not the subject of conversion, then their exposition at 400-500°C in the presence of catalyst is important in terms of energy.
So many different directions are known for the oxidation reactions of hydrocarbons. These processes are considered one of the most remarkable fields receiving oxygenated compounds- mainly, aldehyde, acid, anhydride, alcohols and etc. that have wide range applicability. In this case, the inclusion of different element atoms to the structure of the organic compounds leads them other positive qualities. Especially, inclusion of halogen atoms in organic acid, anhydride, aldehyde, and etc. provides them with the thermostable, fireproof, and incombustible. In this respect the compounds obtained from the oxidation processes of hydrocarbons make halogenated derivates by the being exposed to halogenations. In this case the application of this process happens very gradual, and separation, cleaning of received substances costs as a result of some difficulties. At the same time leads to the loss of many raw materials and products. According to recent studies began to turn towards obtain chlorinated organic compounds from direct oxidization of chlorinated hydrocarbons. In this regard, certain advantages given to heterogeneous catalytic processes in gas phase, so as a result of the reactions directed to be received of organic compounds with high selectivity and yields. On the other hand, as mentioned organic chlorine chemical industry, massive quantities of items
АЗЕРБАЙДЖАНСКИЙ ХИМИЧЕСКИЙ ЖУРНАЛ № 3 2016
are thrown into the environment. The majority of these toxic compounds there isn't still application areas, their deep oxidation process of trying to implement the disposal by burned exposure, although it is believed to be a difficult process in itself. Therefore, synthesize and structure of active and selective catalysts for disposal of chlorinated hydrocarbons, such as chlorinated C1-C4 hydrocarbons (alkanes) (CAH), chlorofuranones (CF), chlorobenzenes (CB), chlorotoluene (CT) and etc. chlorinated pesticides will be a very pressing problem of the researchers for a long time which is not still available to be explored. Recently, catalytic oxidation processes of CAH derivatives to chlo-ro-analogues of maleic anhydrides are studied [6-9] in a wide range but an oxidation processes of aromatic hydrocarbons,especially CT and CB remains very little studied.
Maleic anhydride and its chlorinated derivatives are widely used in petrochemical, organic and chloro-organic industry. The production capacity of maleic acid and its anhydrides are justover than million tons. Polyfunctional compounds that are widely used in different fields obtain based on chloro analogues of ma-leic anhydride; monochloromaleic anhydride (MCMA) and dichloromaleic anhydride (DCMA) due to their comprising reactive functional groups and double bond on isstructure. Inclusion of both active chlorine atom, carbonyl group, collar oxygen atom and double bound creates opportunities to get into the mergers of their various double communication, substitution, diene synthesis, copolymerization, esterifi-cation, amination, oxidation, decarboxylation, isomerization reactions. Furthermore, inclusion of chlorine atoms to desired products leads to form cold, heat resistant, fireproof, firmness against destructiveconditions. Texture of MCMA and DCMA have been investigated by the modern physical-chemical methods; IR spectroscopy, NMR, UV spectroscopy. Maleic, chlormaleic, diclormaleic acids and anhydrides obtained from catalytic oxidation reactionsof corresponding C4-C6 hydrocarbons and their chlorinated derivatives. In particular, purchas-ingprocesses of maleic acid and anhydrides from butane, butane, butadiene, furans, benzene
and etc. hydrocarbons in the presence of variety oxides of vanadium, molybdenum, phosphorus, cobalt, bismuth, antimony catalyst have thoroughly been investigated; their kinetic regularities and the catalytic oxidation processes of butenes, as well as benzene to maleic anhydride have been carried out on an industrial scale. We can see the importance of their production processes taking into account wide usage of ma-leicanhydride and its chlorinated derivatives in the manufacture of drugs and biologically ac-tivesubstances and petrochemical synthesis, additives to polymer substances. The kinetic regularities, mechanisms should be studied extensively, kinetic and mathematical models have to be developed and optimization of processes should be implemented and presented to designers for carrying outindustrial production processes. It should also be noted, although receiving maleic anhydride from the catalytic oxidation processes of C4 hydrocarbons and benzene have been carried out on an industrial scale, but the researches in the processes of synthesizing MCMA and DCMA are still ongoing level. Investigation of modern state and development prospects of synthesizing CH shows that the demand for chlorinated anhydride, acid and aldehydes are going to increase. The growth of researches in recent years carried out toward to obtain of these compounds once again confirms above mentioned opinions [8, 9]. On the other hand, except desired products tons of chlorinated hydrocarbons while theproduction of CH. Sometimes it is difficult to separate them due to very low concentrations or not in terms of economic efficiency. In many cases they are thrown into environment and cause pollution.
Experimental part
Conducting heterogeneous catalytic oxidation of CH in the fluid bed V-P-O/SiO2-catalyst is characterized by several of ad-vantages:high heat emission, low resistance internal diffusion due to the usage of small grains (0.4-0.8 mm) of the catalyst, simplicity of the reactor design, convenient input and output of products and the particles, an ease of regeneration and etc. A series of special experiments established appropriate fluid velocity, catalyst pellets is made certain range of sizes and the linear
velocity of the gas stream was determined.The other series of experiments demonstrated to precede the oxidation reaction in the kinetic mode [7]. The effect of the size of a catalyst pellets on the conversion CH at temperatures 653-773 K by means of variation catalyst particle sizes from 0.25-0.5 to 0.6-0.8 mm was studied.
Conversion rate of CH, as well as selectivity of the process at the same temperature practically unchanged due to the absence of diffusion complications. Although changes in flow rate of feed gas does not affect process parameters, but indicate the absence of external diffusion inhibition, i.e. oxidation reaction proceeds in the kinetic mode. The data obtained during the studies in fixed-circulation-flow-bed and flow-bed facilities are in agreement between themselves and with the results of research [9, 10].
The effect of various parameters in a wide range of their changes have been studied in order to reveal kinetic regularities of oxidation reactions chlorinated C4 hydrocarbons and setting up kinetic models, enabling to control
the oxidation process: T=673-793 K, C0 = 110-20-10, Cch=1-10-20-10 mol/L, T=0.1-1.0 s examples of oxidation reactions 1-chlorobutane (1-CB), 1,3-dichlorobutene-2 (1,3-DCB-2), 1,2,4-trichlorobutene-2 (1,2,4-TCB-2), 2,3,3-trichloro-butene-1 (2,3,3-TCB-1).
Apart from the presence of chlorine atoms in a molecule, the ratio of chlorine and hydrogen atoms was also taken into account during studying kinetic regularities of oxidation reactions of chlorinated hydrocarbons [6]. In this paper oxidation of 2-monochlorobutadien (2-MCBD), 2,3-dichlorobutadien (2,3-DCBD), and hexachloro-butadien (HCBD) has been investigated. The study of kinetics of 2-MCBD, 2,3-DCBD carried out in flow bed type of reactor in the presence of V-P-0/Si02 at following condition: T=213-763 K, t=0.2-0.9 s, Ccb: C0j =1:30 mol.%.
As it is seen on kinetic curves (Figure 1.), the oxidation rate of 2-MCBD exceeds the rate of MCMA formation, however the formation rate of CO + CO2 is very high.
a? ^
i : 3 4 i * A,a
Î 4 S 6 ^.a
Fig. 1. Correlation between the amount of chlorine atoms (A) in the molecule and the optimum parameters of chlorobutadien (CBD) oxidation reactions: yield of products B. Selectivity s (a), temperature T, contact time x (b). Deactivation dynamics of V-P-O/SiO2-catalyst from its continuous operation length of oxidation reactions CBD (c) 1 - 2,3-DCBD, 2 - 2-MCBD, 3 - 1,1,2-TCBD, 4 - 1,2.3-TCBD, 5 - 1,1,2-TeCBD, 6 -1,1,2.2,4-PCBD, 7 - HCBD.
Between both the number of chlorine atoms in the molecule CBD and a conversion, and the yield of desired products and selectivity of reactions observed correlation (Fig.la). It is revealed that the optimum temperature and contact time of the oxidation reaction enhances by the increasing number of chlorine atoms in the molecule (Figure 1b).
According to the yields and selectivity of desired products chlorobutadiene are arranged as follows in the oxidation reaction: MCBD<DCBD<TCBD<TeCBD<PCBD<HCBD.
Thus, the study of the kinetics of the heterogeneous catalytic oxidation of C4 chlorbuta-dienes lead to the conclusion that they have a common pattern in implementing kinetic reactions in the fluidized bed V-P-O/SiO2 catalyst. Established the presence of series-parallel reactions in the oxidation of CBD with the formation of organochlorines and deep oxidation products, which is of great importance at an establishment mechanism of the oxidation reactions.
Effects of water additives and MCMA on 1,3-dichlorobutene-2 (1,3-DCB-2) oxidation reactions are shown in Figure 1 a, b. As seen from the results shown in Figure 1 a by increasing the water concentration in the reaction zone from 0.5-10-4 to 2.0-10-4 mol/L expenditure initial speed 1,3-DCB-2 (curve 1) is slightly reduced.It also significantly reduced the rate of accumulation MCMA and COX (curves 2, 3, respectively). Consumption rate of 1.3-DCB-2 does not almost change when in an amount 0.75-3.8-10-3 mol/L MCMA added to the reaction zone. The same applies to the accumulation rate of MCMA. However, the accumulation rate of COx decreases slightly.
Similar studies carried out in the oxidation 1,2,4-TCB-2. Although in the course of this reaction, the additive H2O and MCMA affected to a lesser degree which occurs still a tendency rate Wtcb-2, Wco2, Wmcma from CO and Cmcma (Figure 2 c, q).
Fig. 2. Reaction yields concentration influence to the reaction rate of chlorobutenes oxidation reaction;
1 — Wgeneral, 2 — Wanhydrides, 3 — WCO2 •
As seen, the oxidation of 1.3-DCB-2 and 1,2,4-TCB-2 subordinated to the general regularities. This behaviour is related to the structure in which the double bond is located at position "two", and the chlorine atoms in scatter from it; this apparently promotes the formation of such a surface compounds that influence the formation of H2O and MCMA. Therefore, in the oxidation of chlorohydrocarbons appears the dominant role of deep reaction rather than partial oxidation. We have also studied the influence of changes in water concentration and DCMA on kinetics of the oxidation reaction 2,3,3-TCB-2. This clorohydro-carbons (CH) is interesting because of its structure wherein the positions of 2,3 hydrogen atoms are changed. CH 0 and CDCMA concentrations remained in the same range; results are shown in Figure 2 d,e. As seen from Figure 1d increase of water concentration to a value of 2.5-10-4mol/L at the surface of V-P-O/SiO2-catalyst has little effect on the rate of consumption of 2.3.3-TCB-2. A curve-rate of expenditure 2,3,3-TCB-2 significantly reduced at values of CH 0 =2.5 10-4 mol/L. At the same time up to the indicated concentrations CH 0 rate of accumulation DCMA practically unchanged. In the future, decrease in Wdcma occurs with decreasing consumption rate 2,3,3-TCB-2.
It's interesting to observe the C02 accumulation rate.At the initial stage by the adding water it is reduced, and subsequently remains constant.This behaviour is accumulation rate of COx at specified concentrations of water because the water inhibits the reaction of deep oxidation, i.e. it modifies the active catalyst sites. Hence, the shape of initial chlorohydrocarbon (CHC) adsorption varies with the presence of other substances in the centres, for example, water, oxygen, etc. This is in agreement with the results obtained in the oxidation of DCMA (Figure 2). The effect of the water at high concentrations explained by the fact that it covers the surface of the catalyst and inhibits the oxidation reac-tion.This is noticeable in the sharp decrease of mode parameters. The constancy of accumulation rate decreases DCMA W2,3,3-tcb-2 and Wco2 can be explained, pushing the hypothesis of modification of active sites with water, promoting selective oxidation 2,3,3-TCB-2.
TCB consumption rate decreases simultaneously by the reduction of CDCMA at the reaction zone which at the beginning occur even sharp reduction CO2 accumulation rate (Figure 2 q). However, this increases the rate of accumulation of DCMA exceeding WDCMA without additives. This means that with an increase of the desired product concentration at the surface of the V-P-O/SiO2 catalyst reaction is strongly inhibited the oxidation of deep initial 2.3.3 TCB-2, respectively, and increased its selective oxidation to DCMA. Taking into consideration previously obtained results on the kinetics of the oxidation 2,3,3-TCB-2 [68] where indicated the presence of serial-parallel paths of COx may be assumed that the oxidation of the deep initial 2,3,3-TCB-2 and desired DCMA occurs onnon-oxidizedcentres of the catalyst surface. Then with increasing CDCMA begins competition for such centres on the surface. However, considering the effect of water addition it can also be assumed that increasing the concentration DCMA leads to modification of active sites.
Changes in parameters at wide range of temperature 653-753 K, contact time (t) 0.21.2 s, furan-oxygen mole ratio 2-22, the concentration
of furans 0.3-2.1-10-3 mol/L; over the active and selective V-P-O/SiO2+Mg system chosen for the oxidation reactions of furans [furan (F), furfural (FF), tetrahydrofuran (THF)] and chlorofurans [dichlorofuran (DCF), trichlorofuran (TCF), tetra chlorofuran (TeCF)] were studied. It should be noted, the main yields of oxidation reaction MA, MCMA, DCMA and side yields were CO2, Cl2, HCl some organic and chloroorganic compounds, chlorpropionic and chloroacetic acid etc. (Figure 3). The impact of a temperature to the F, THF, DXF, TXF, TeXF oxidation reaction the conversion of the initial furans is constantly increasing and while other furans are reached to 100% at 713-733 K, almost for F and TeCF its 693 K. Meantime, the selectivity of maleic and chloromaleic anhyidride changes different. Thus, the conversion of initial furans increase to its maximum by the temperature growth, then decreases. Further decline of selectivity after its maximum, almost is due to the oxidation of reaction products.
Fig. 3. The effect of temperature to the furan' s oxidation reaction on the fluid bed layer of V-Mo-O/SiO2 +Mg: a - TeHF, b - FF, c - DCF, d - TCF; 1 - conversion of furans, 2 - selectivity of anhydrides (MA, MCMA, DCMA), 3 - selectivity of CO2, 4 - yield of COx.
The yields of organic and organic chlorine compounds are always decreases by the increasing temperature, and this amount mainly is not more than 10-15% and gradually declining. The effect of temperature growth effect to deep oxidation in the catalytic oxidation reactions of furans and chlorofurans is too interesting. Thus, although the yield of CO2 are high at comparatively low temperature its quantity decreases by the temperature increasing and this reduction this reduction begins to grow after passing through its minimum. The minimum value of CO2 is compatible with the maximum value of anhydrides selectivity.
The basic technological parameters for implementation each of the furan's catalytic oxidation reaction have been determined and the optimum reaction condition structured to attain desired products with high yields and selectivity. The values of optimum parameters and selectivity for every individual furan are generalized and given on the Table.
Optimum condition of the oxidation and its derivations
reactions of furans
Furans Tempe- Con- F:O2, Con- Selecti- Yields of
rature, tact mol version, vity, products.
K time, s mol. % mol.% mol.%
F 693 0.6 1:8 91 66 60.0
THF 733 0.8 1:14 94 56 52.6
FF 693 0.7 1:6 92 70 64.4
DCF 673 0.7 1:10 96 82 78.2
TCF 693 0.8 1:12 95 90 85.5
TeCF 713 0.7 1:15 100 98 98.0
The study of oxidation reaction of chlorobenzene and chlorotoluene on fixed bed and fluid bed layer of catalyst
Purpose of selection highly active and selective catalytic systems in the oxidation reaction of CB the systems was explored both on fixed bed and fluid bed layer of catalyst. First of all the influence of temperature on the activity of catalyst was investigated at 653-753 K temperature range. According to figure 1 it should be mentioned that both on fixed bed and fluid bed layer the V-Mo-O/Al2O3+P2O5 system performance highest results
while V-P-O/SiO2+Co2O3 system showed the lowest result. But on fluid bed layer at 713-733 K V-P-O/A12O3+MoO3 showed best result and provided 100% conversion of CB.
As regards the influence of temperature (Figure 4) on the selectivity of oxidation of mono-CB to MCMA both on fixed bed layer and fluid bed layer of catalyst the highest performance has shown by V-P-O/Al2O3+MoO3 catalytic systems (Figure 4 curve 4). But while the selectivity of MCMA at 733 K temperature on the fixed bed layer was 32%, it enhanced 38-40% on fluid bed layer (Figure 4 curve 5). The similar results have shown by the V-Mo-O/AhO3+P2O5 (Figure 4 curve 5) and V-P-O/SiO2+MoO3 (Figure 4 curve 6).
Fig. 4. Activity dependence different type of catalytic systems in oxidation reaction of CB on temperature over the fixed bed layer: 1 - V-P-O/SiO2, 2 - V-P-O/Al2O3, 3 - V-P-O/SiO2+ MoO3, 4 - V-P-O/Al2O3+MoO3, 5 - V-Mo-O/AI2O3+P2O5, 6 - V-P-O/SiO2 + Co2Os.
Then influence the contact time (t) to the activity and selectivity of these synthesized systems have been studied on 0.1-1.1 s range and the results are given in Figure 5. As it is seen from results the catalytic activity of continually rising by the increasing contact time 0.1-0.9 s at fixed bed layer of catalyst. The V-Mo-O/Al2O3+ P2O5 and V-P-O/SiO2+MoO3 systems sowed high performance at the low value of contact time 0.1-0.5 s and V-P-O/A12O3+ MoO3 system appropriated its maximum value at 0.5-0.9 s contact time.
Approximately the same was repeated at the fluid bed layer. The situation is chanced a little during the selective oxidation of MCT to
MCMA in these systems (Figure 5). Thus, the highest have shown in the presence of V-P-O/SiO2+MoO3 (Figure 5 curve 3) and V-P-O/Al2O3+MoO3 (Figure 5 curve 4) catalysts on fixed bed layer of catalyst and 0.5-0.7 s contact time. The selectivity of MCMA (curve 3) and catalytic system (curve 4) arranged 32 and 30% respectively at 0.5 s contact time.
As seen in the results shown in Figures 5 and 6 CT:O2=1:5-1:15 ratios the rate of oxidation reaction increases, then at 1:15-1:25 values are almost remains unchanged. Analysis of the results shows that the fixed-bed layer catalyst at the ratio of CT:O2=l:5 CT conversion consists 40-80% due to lack of oxygen for the oxidation reaction.
Fig. 5. Dependence of selectivity on the temperature at fixed bed catalytic systems in the oxidation reaction of chlorotoluene under fluid bad layer catalyst: 1 - V-P-O/SiO2, 2 - V-P-
O/Al2O3, 3 - V-P-O/SiO2+MoO3, 4 - V-P-O/Al2O3+MoO3, 5 - V-Mo-O/Al2O3+P2O5,
6 - V-P-O/SiO2+Co2O3.
Fig. 6. The selectivity dependence on the contact time at fixed bed catalytic systems in the oxidation reaction of chlorotoluene: 1 - V-P-O/SiO2, 2 - V-P-O/Al2O3, 3 - V-P-O/SiO2+MoO3, 4 -
V-P-O/Al2O3+MoO3, 5 - V-Mo-O/Al2O3+P2O5,
6 - V-P-O/SiO2+Co2O3.
АЗЕРБАЙДЖАНСКИЙ ХИМИЧЕСКИЙ ЖУРНАЛ № 3 2016
Although the amount of oxygen was more than stoichiometry at the ratio CT:O2= 1:10-1:15 the selectivity of the oxidation process continues to enhance, and in some cases (at fluid bad layer on 1:15 ratio) reaches a maximum. A further increase in this ratio does not significantly affect the occurrence of the reaction, either conversion of CT or, the selectivity of the catalyst is almost remains constant. Although the activity of V—P—O/A^O3+MoO3 system at CT-O2= l: 5—l: 10 rates has low values, but it performances high values at the ratio 1:15—1:20. According to these results, it's possible to say that the consumption of oxygen during the reaction of oxidation of MCT plays an
Fig. 7. Dependence of CT:O2 molar ratio on the activity (a) at fixed bed catalytic systems in the oxidation reaction of chlorotoluene: l — V—P-O/SiO2, 2 — V—P—O/M2O3, 3 — V—P—O/SiO2+MoOs, 4 — V—P—O/Al2O3+ MoO3, 5 — V—Mo— O/Al2O3+P2O5, 6 — V—P—O/SiO2 + Co2O3.
important role in the phase formation. V—P— O/Al2O3+MoO3 (Figure 6 curve 4) catalytic system showed high performance. Activity and selectivity dependence of CT:O2 on molar ratio at fluid and fixed bed layer of catalysts is shown in Figures 7, 8.
Relying on the basis of their previous research on these systems MoO3, P2O5 added over them and their activity and selectivity was studied in the catalytic oxidation of 2,3-DCT. The effect of temperature range 653—753 K, contact time x=0.3—l.l s, mole ratio of l,2-DCT:O2=l:5—1:20 in the presence of V—P—O/SiO2+MoO3, V—P— O/Al2O3+MoO3, V—Mo—O/Al2O3+P2O5 catalytic systems on the oxidation of 1,2-DCT was studied.
Fig. 8. Dependence of 1,2-DCT:O2 molar ratio on the selectivity (s) at fluid bed catalytic systems in the oxidation reaction of chlorotoluene: 1 — V—P— O/SiO2, 2 — V—P—O/Al2O3, 3 — V—P—O/SiO2+MoO3, 4 — V—P—O/A12O3+MoO3, 5 — V—Mo— O/Al2O3+P2O5, 6 — V—P—O/SiO2+Co2O3.
The study of electronacceptor centers on a surface oxide catalysts in the oxidation reactions chlorobenzenes
Oxide catalysts based on vanadium, stibium, molybdenum, phosphorous precipitated over the Al2O3 and SiO2 synthesized for the catalytic oxidation reactions of chloro-, dichloro-, and tri-chlorobenzenes to the mono-, dichloromaleic anhydrides. These catalysts generally show high activity at 623—753 K during 0.2—1.2 s contact time (Figure 9). In order to clarify the mechanism of catalytic oxidation reactions we tried to learn the nature of active centres on the surface of the both new synthesized and used catalysts for the catalytic oxidation reaction chlorobenzenes and
chlorobutenes. This study has been dedicated to the investigation of nature, quantity and power of electron-accepting centres acetone adsorbed new synthesized system by the derivatographic methods [10—13].
The derivatogram of the new synthesized V—P—O-catalysts after acetone adsorbed is shown on the Figure 10. It is clear that DTG curve characterized with endothermic effects which 90, 300,480, 580 C temperature observed on it. Nevertheless DTA curve of the same sample characterized with endothermic and ec-tothermic affects which are 480 and 5200C temperature respectively. It is clear from TG curve weight loss reaches to 1 mmol/g.
Fig. 9. Effect of temperature (a), contact time (b, c) molar ratio of 1,2-CB:O2 (d) on activity (a, b) and selectivity (c, d) of 1,2-CB oxidation reaction. 1 - V-P-O/SiO2+MoO3, 2 - V-P-O/Al2O3+MoO3, 3 - V-Mo-O/Al2O3+P2O5.
Fig. 10. The derivatogram of the new synthesized V-P-O-catalysts after acetone adsorbed.
Fig. 11. The derivatogram of the new synthesized V-P-O-catalysts promoted with Co after acetone adsorbed.
U3EPEAHflKCAHCKHH XHMHHECKHH KKY PHAJI № 3 2016
It is clear from the derivatogram of the new synthesized V—P—O-catalysts promoted with Co after acetone adsorbed shown on the Figure 11 the DTG curve characterized with endothermic effects which 60, 340, 470,580C temperature observed on it, but DTA curve of the same sample characterized with endothermic and ectothermic affects which are 100, 360 and 4800C temperature respectively. It should be noticed that electron avidity enhanced and quantity of adsorption reached to 1.5 mmol/g after the catalyst was trimmed with Co salt.
Consequently, there are several electron-accepting centres on the catalyst which both the concentration and powers are increasing when it is trimmed with Co. Endothermic effects observed up to 1250C on DTA and DTG curves acetone molecule adsorption to the surface explains by means of physical forces, but endo-thermic effects observed above 1200C the surface of the catalysts says there are interaction effects among acetone electron-accepting centers and it also shows that the chemical bonds. The investigation of the surface of catalytic systems explored that there are weak, middle and strong electron-accepting as well as oxidizing centers on the surface.
Conclusion
In conclusion, It is shown that the reactivity of the saturated chlorohydrocarbons in oxidation reactions enhanced in the order by the increase of carbon chain: tetra-chloromethane (CC 14)< 1,2-di-chloroethane (1,2-DCE)< 1 -chloro-propane (1-CP)<1-chlorobutane (1-CB) <tetra-chlorobutane (TCB) < penta-chlorobutane (PCB) <hexa-chlorobutane (HCB), and selectivity in the order: CC14<1,2-DCE< 1 -CB< 1 -CP<TCB<PCB<HC. The activity of studied catalytic system in the oxidation reaction of saturated CH changed in the order: Co—Mo<V—P—0/Si02<V—P—0/Si02+ Mg < V—M0—O/AI2O3 < V—P—O/AI2O3, and selectivity in the order: V-Р-0/Al203< V—Mo— 0/Al2Oз<Cо-Mо<V-Р-O/SiO2<V-Р-O/SiO2 +Mg.
In this paper oxidation of 2-monochlo-robutadien (2-MCBD), 2,3-dichlorobutadien (2,3-DCBD), and hexachlorobutadien (HCBD) has been investigated. The study of kinetics of 2-MCBD, 2,3-DCBD carried out in flow bed type of reactor in the presence of V—P—0/Si02 at fol-
lowing condition: 7=213—763 K, 1=0.2—0.9 s, Ccb: Cn =1:30 mol.%.
Between both the number of chlorine atoms in the molecule CBD and a conversion, and the yield of desired products and selectivity of reactions observed correlation. It is revealed that the optimum temperature and contact time of the oxidation reaction enhances by the increasing number of chlorine atoms in the molecule.
According to the yields and selectivity of desired products chlorobutadiene are arranged as follows in the oxidation reaction: MCBD<DCBD<TCBD<TeCBD<PCBD<HCBD.
Similar studies carried out in the oxidation 1,2,4-TCB-2. Although in the course of this reaction, the additive H2O and MCMA affected to a lesser degree which occurs still a tendency rate Wtcb-2, Wco2, Wmcma from Co2 and Cmcma . As seen, the oxidation of 1.3-DCB-2 and 1,2,4-TCB-2 subordinated to the general regularities. This behaviour is related to the structure in which the double bond is located at position "two", and the chlorine atoms in scatter from it; this apparently promotes the formation of such a surface compounds that influence the formation of H2O and MCMA. Therefore, in the oxidation of chlorohydrocarbons appears the dominant role of deep reaction rather than partial oxidation.
Summarizing all of the obtained results it's considered that based on the obtained results, it is considered that the presence of catalytic oxidation of chlorinated C4 hydrocarbons to maleic anhydrides occurs passing through an intermediate chlorofurans type product. This provision approved by the direct oxidation of chlorofurans to chloromaleic anhydride and the increase of the reaction rate by the addition of them into reaction.
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XLORKARBOHIDROGENLORIN QAZ FAZADA HETEROGEN KATALITIK OKSIDLO§MOSI
A.C.Ofandi, E.G.Babayev, LQ.Malikova, B.A.ismayilova, F.A.Yunisova, N.R.Aykan, A.M.0liyeva
Xloralifatik karbohidrogenlarin vanadium asasli oksid katalizatorlanmn i§tirakinda 400-6000C temperatur intervalinda oksidla§ma reaksiyalari tadqiq edilmi§dir. Tarkibinda olan karbon atomlannin artmasi ila onlann reaksiya qabilliyinin artmasi göstarilmiij, katalitik sistemlarin aktivlik sirasi müayyan edilmi§dir. Eyni zamanda xlorlu C4 olefin karbohidrogenlarinin V-P-O/AI2O3 va V-P-O/SiO2 katalizatorlanmn i§tiraki ila malein va xlor malein anhidridlarina oksidla§masi öyrsnilmi§dir. Olefinlarin tarkibindaki xlor atomlarinin miqdarindan, yerindan va ikiqat rabitanin mövqeyindan asili olaraq oksidla§ma reaksiyasinin istiqamatini proqnozla§dirmagin mümkünlüyü göstarilmi§dir. Xlorlu butadienlarin da selektiv oksidla§ma istiqamatlari va onlarin reaksiya qabilliyi müayyan edilmi§dir. ilkin oksidla§ma reaksiyasinin araliq va son mahsullarinin oksidla§ma reaksiyasinin süratina tasiri müayyanla§dirilarak göstarilmi§dir ki, reaksiyanin asas mahsullan reaksiyanin süratina tormozla§dirici tasir göstarmir. Xlorlu C4 karbohidrogenlarinin xlormalein anhidridlarina oksidla§masinin araliq xlorfuranon tipli birla§malardan kegmasi ila ba§ verma mexanizmi müayyan edilmi§dir. Xlorbenzollarin xlormalein anhidridlarina oksidla§masinin paralel-ardicil oksidla§ma reduksiya mexanizmi ila getmasi göstarilmi§dir.
Agar sözlzr: xlorkarbohidrogenbr, xlorbutenbr, xlorfuranonlar, xlorbenzollar, xlortoluollar, malein, xlormalein anhidridi, CO2, Cl2, oksid heterogen katalitik sistemhr.
ГАЗОФАЗНОЕ ГЕТЕРОГЕННОЕ КАТАЛИТИЧЕСКОЕ ОКИСИЛЕНИЕ ХЛОРУГЛЕВОДОРОДОВ
А.Дж.Эфенди, Э.М.Бабаев, И.Г.Меликова, Б.А.Исмаилова, Ф.Ф.Юнисова, Н.Р.Айкан, А.М.Алиева
Исследована реакция окисления хлоралифатических углеводородов при температурах 400-6000С с участием вана-дийоксидных катализаторов. Показано, что с увеличением количества атомов хлора в молекулах увеличивается их реакционная способность. Установлен также ряд активностей каталитических систем. Одновременно изучено газофазное окисление С4-хлоролефинов на поверхностях V-P-O/Al2O3-, V-P-O/SiO2-катализаторов до малеин- и хлор-малеиновых ангидридов. Установлено, что в зависимости от количества атомов хлора и их месторасположения а также месторасположения двойной связи в молекуле можно прогнозировать направление реакции окисления. Также показано направление селективного газофазного каталитического окисления хлорбутадиенов и установлена их реакционная способность. Изучением виляния исходных, промежуточных и конечных продуктов реакции на скорость окисления установлено, что основные продукты реакции не оказывают тормозящее действие на скорость реакции. Установлено, что каталитическое окисление С4-хлоруглеводородов происходит по механизму через образование промежуточных хлорфуранонов. Установлено также, что, каталитическое газофазное окисление хлорбензолов до хлормалеиновых ангидридов происходит параллельно-последовательно по окислительно-восстановительному механизму.
Ключевые слова: хлоруглеводороды, хлорбутены, хлорфураноны, хлорбензолы, хлортолуолы, малеин-леиновые ангидриды, CO2, Cl2, гетерогенно-каталитические оксидные системы.
хлорма-
АЗЕРБАЙДЖАНСКИЙ ХИМИЧЕСКИЙ ЖУРНАЛ № 3 2016
