METHOD OF PRODUCING C2-C4 CARBONYL COMPOUNDS

Abstract

The invention relates to a method of producing carbonyl compounds, more particularly C.sub.2-C.sub.4 ketones and aldehydes. The method is based on the gas-phase oxidation by nitrous oxide of C.sub.2-C.sub.4 alkane-olefin mixtures, such as a butane-butylene fraction or a propane-propylene fraction, obtained by thermal and/or catalytic cracking, to produce C.sub.2-C.sub.4 ketones and aldehydes. The process is carried out under continuous flow conditions at a temperature of 300-550° C. and pressure of 1-100 atm, without prior isolation of individual olefins from the fractionation products and in the absence of a catalyst. The process provides for high productivity, high overall selectivity for ketones and aldehydes, and explosion-safe operation.

Claims

1. A process for producing C.sub.2-C.sub.4 carbonyl compounds from C.sub.2-C.sub.4 olefins, characterized in that said process for producing C.sub.2-C.sub.4 carbonyl compounds, in particular C.sub.2-C.sub.4 aldehydes and ketones, is carried out in a gas phase by reacting nitrous oxide with a mixture of aliphatic C.sub.2-C.sub.4 olefins and alkanes at a temperature of 300-550° C. and pressure of 1-100 atm.

2. The process of claim 1, wherein gaseous fractionation products of thermal and/or catalytic cracking process are used as a starting alkane-olefin mixture with no preliminary isolation of the individual olefins from the fractionation products.

3. The process of claim 1, herein a butane-butylene fraction of thermal and/or catalytic cracking process is used as the starting alkane-olefin mixture.

4. The process of claim 1, wherein a propane-propylene fraction of thermal and/or catalytic cracking process is used as the starting alkane-olefin mixture.

5. The process of claim 1, wherein a fraction of thermal and/or catalytic cracking process enriched in ethylene is used as the starting alkane-olefin mixture.

6. The process of claim 1, wherein a butane-butene mixture enriched in butene-2 is used as the starting alkane-olefin mixture.

7. The process of claim 1, wherein a mixture comprising C.sub.2 and/or C.sub.3 and/or C.sub.4 olefins with C.sub.1 and/or C.sub.2 and/or C.sub.3 and/or C.sub.4 alkanes in any ratios is used as the starting alkane-olefin mixture.

8. The process of claim 1, wherein the starting alkane-olefin mixture may comprise other hydrocarbons as impurities caused by the method of preparation of said mixture.

9. The process of claim 1, wherein the nitrous oxide may comprise other gases, the presence of which is associated with the method for its preparation.

10. The process of claim 1, wherein the oxidation process of the alkane-olefin mixture is carried out in a single flow-type reactor, without recycling the reaction mixture, with nitrous oxide conversion being at least 90%, preferably 99%, even more preferably with complete nitrous oxide conversion.

11. The process of claim 1, wherein in order to achieve an olefin conversion of at least 90%, the oxidation of the alkane-olefin mixture is carried out in several stages using several oxidation reactors with independent feeding of nitrous oxide at each stage, and the reaction products are isolated from the reaction mixture after each oxidation reactor.

12. The process of claim 1, wherein in order to achieve an olefin conversion of at least 90%, the oxidation process of the alkane-olefin mixture is carried out in several stages using several oxidation reactors with independent feeding of nitrous oxide at each stage, and with intermediate partial cooling of the reaction mixture, but with no isolation of the reaction products from the reaction mixture after the intermediate oxidation reactors.

Description

EXAMPLE 1

[0039] Butane-butene fraction of catalytic cracking process having butenes content of 87.4% by volume and butanes content of 12.1% (Table 1, Mixture 1) is mixed with nitrous oxide in a ratio of 9:1. The reaction mixture at a pressure of 1 atm. is passed through a stainless steel reactor having a volume of 2.5 cm.sup.3, in which temperature of 400° C. is maintained. The feed rate of the mixture is 25 cm.sup.3/min (at normal conditions). The results of the experiment are given in Table 2. Here, the reaction temperature (T), nitrous oxide conversion (X.sub.N2O), total olefin conversion (X.sub.R,), total ketone and aldehyde performance (Pr) and total selectivity for carbonyl products (S.sub.Σ) are provided. One can see that the total selectivity for carbonyl compounds, considering the accuracy of the selectivity determination, approaches 100%. The main product of the reaction is methyl ethyl ketone (MEK), which is formed with a selectivity of 44.8%. Along with MEK, acetone (A) with a selectivity of 17.5%, propanal (PA) with a selectivity of 17.5%, acetaldehyde (AA) with a selectivity of 11.3%, isobutanal (i-BA) with a selectivity of 4.6%, and butyraldehyde (BA) with a selectivity of 4.3% are formed. The main by-products are C.sub.5 hydrocarbons: dimethyl- and ethyl-cyclopropanes.

EXAMPLES 2-4

[0040] The reaction is carried out similarly to Example 1, with the main difference being that the reaction temperature is adjusted at 450° C. (Table 2, Example 2), 500° C. (Table 2, Example 3) and 550° C. (Table 2, Example 4). These experiments show that an increase in the temperature leads to a significant acceleration of the reaction: the performance of the volume unit of the reactor increases by more than 40 times. The total selectivity for carbonyl compounds remains above 94% with an increase in temperature from 450° C. to 500° C., and only the increase in temperature to 550° C. leads to a decrease in the total selectivity for carbonyl compounds to 77%.

EXAMPLE 5

[0041] The experiments are carried out in the same manner as in Example 1, with the difference being that the temperature in the reactor is maintained at 350° C., and the pressure of the reaction mixture is set at 5 atm. One can see from Table 2 that, despite the temperature decrease, in comparison with Example 1, an increase in pressure in the reactor results in an increase in the reactor performance, in what concerns the carbonyl compounds. At the same time, there is an increase in the selectivity for MEK by almost 10% (from 45 to 54%).

EXAMPLES 6-8

[0042] The test is carried out similarly to Example 5, with the difference being that the reaction temperature is set at 400° C. (Table 2, Example 6), 450° C. (Table 2, Example 7) and 500° C. (Table 2, Example 8). With an increase in temperature from 400° C. to 500° C., the performance per unit volume of the reactor increases by more than 7 times. In this case, the selectivity for the MEC formation essentially does not change with the increase in the temperature. With increasing temperature, the total selectivity for carbonyl compounds decreases from 100 to 89% due to the formation of cyclopropanes (C5) and other products. At 500° C., complete conversion of nitrous oxide is observed.

EXAMPLE 9-12

[0043] The experiment is carried out similarly to Example 5, with the difference being that the pressure of the reaction mixture in the reactor is set at 10 atm (Table 2, Example 9), 20 atm (Table 2, Example 10), 50 atm (Table 2, Example 11) and 70 atm (Table 2, Example 12). Increasing the pressure of the reaction mixture from 10 to 70 atm is accompanied by an increase in the performance of the reactor volume unit by more than 100 times, from 7.4 g/l h to 770 g/l h, reaching the level of the most effective industrial petrochemical processes. As the pressure increases, the conversion of nitrous oxide increases from 43 to 99%, with a decrease in the total selectivity for carbonyl compounds from 94 to 76%, while the selectivity for MEC decreases insignificantly from 46 to 40%.

EXAMPLE 13

[0044] The test is carried out similarly to Example 5, with the difference being that the butane-butene fraction of catalytic cracking process (composition 1) with butenes content of 87.4% by volume and butanes content 12.1% is mixed with nitrous oxide in a ratio of 7:3. An increase in the content of nitrous oxide in the reaction mixture from 10 mol. % to 30 mol. % is accompanied by an increase in the performance of the reaction volume unit by more than 2 times with an insignificant decrease in the total selectivity for carbonyl compounds (less than 2%).

EXAMPLE 14

[0045] The test is carried out in a manner similar to that of Example 13, with the difference being that the temperature of the reaction mixture is maintained at 450° C., Table 2 shows that the increase in temperature leads to an increase in the performance of the reactor volume unit by more than 2 times from 7.4 g/l h to 16.4 g/l h. At the same time, the conversion of nitrous oxide increases by 2.5 times, approaching 80%, while maintaining the total selectivity for carbonyl compounds at 90%.

EXAMPLES 15-20

[0046] Examples 15-20 describe the effect of the composition of the alkane-olefin mixture on the production of C.sub.2-C.sub.4 aldehydes and ketones. The composition of the products of thermal and/or catalytic cracking is highly dependent on the petrochemical feedstock, the process conditions, the nature of the catalyst, and can vary widely. In the stepwise oxidation of alkane-olefin mixtures, with the partial conversion of the olefin, the composition of the reaction mixture will change as the transition from the previous to the subsequent reactor takes place. Table 1 shows the composition of C.sub.2-C.sub.4 butane-butene mixtures used to prepare carbonyl compounds.

[0047] Mixture 1 corresponds to harsh catalytic cracking conditions. The results of its oxidation are provided above (Examples 1-15). Mixture 2 corresponds to mixture 1, partially converted according to the embodiment 2 of the process, with the recovery of the reaction products from the reaction mixture. Mixture 3 corresponds to mixture 1, partially converted according to the embodiment 2 of the process, with the recovery of the reaction products from the reaction mixture, where the conversion of the olefins is higher than in mixture 2.

[0048] Mixture 4 corresponds to milder cracking conditions. Mixture 5 is enriched in butene-2, and Mixture 6 corresponds to butane-butene fraction of thermal cracking, Mixture 7 corresponds to butane-butene fraction of catalytic cracking, from which isobutene has been recovered by means of esterification thereof, with methanol. A description of the experimental conditions and the obtained results is provided in Table 3 (Examples 15-20). One can see that varying the process conditions makes it possible to efficiently perform the oxidation of butane-butene with low olefin content in the mixture. With a relatively high performance in what concerns the carbonyl compounds, the total selectivity for aldehydes and ketones exceeds 80%.

EXAMPLES 21-30

[0049] Examples 21-30 describe the oxidation of the propane-propylene fraction of catalytic cracking process. The experimental conditions and results are provided in Table 4. The main products of the oxidation are carbonyl compounds: acetone (A), acetaldehyde (AA), and propanal (PA). The total selectivity for carbonyl compounds varies from 71 to 95% depending on the reaction conditions. The maximum performance reaches 10 g/l h with the conversion of nitrous oxide being 75%.

[0050] The disclosed process provides high productivity, high total selectivity for ketones and aldehydes, and explosion safety.

TABLE-US-00001 TABLE 1 Composition of the starting butane-butylene mixtures Mixture composition, % by volume Component Mixture 1 Mixture 2 Mixture 3 Mixture 4 Mixture 5 Mixture 6 Mixture 7 Methane — — — — 0.21 Ethane — — — — 0.07 Ethylene — — — — — — 0.05 Propane — — — 0.4 1.3 Propylene — — — 4.3 0.1 Isobutane 1.6 3.8 6.4 0.6 1.57 1.1 50.3 Butane 10.5 71.0 80.3 41.5 45.3 55.9 9.92 Butene-1 32.9 9.5 5.0 25.6 5.6 13 14.34 Butadiene 0.5 0.1 0.1 0.3 0.486 0.3 0.23 t-Butene-2 24.9 7.2 3.8 15.3 24.9 11.6 12.8 Isobutene 15.1 4.3 2.3 3.2 7.7 5.3 2.9 c-Butene-2 14.5 4.2 2.2 13.5 14.45 8.1 7.8 Sum of olefins, % 87.4 25.1 13.2 57.6 52.7 42.3 37.95

TABLE-US-00002 TABLE 2 Gas phase oxidation of butane butylene mixture (BBM) with a butene content of 87.4% by volume and a butane content of 12.1% (Mixture 1 in Table 1) by nitrous oxide. Reaction conditions: flow-type reactor 25 cm.sup.3, temperature 300-550° C., pressure 1-20 atm; feedstock mixture: 10-30 mol % N.sub.2O, 90 mol % BBM; the volume flow rate of the mixture is 25 cm.sup.3/min (for normal conditions) P, T, X.sub.N2O, Pr, Selectivity, S, % S.sub.Σ.sup.b), No atm. ° C. % X.sub.R, % g/l h C5 AA PA i-BA A BA MEK Other products %  1 1 400 0.7 0.1 0.1 0.0 11.3 17.5 4.6 17.5 4.3 44.8 0.0 100  2 450 2.9 0.4 0.5 0.0 5.1 17.4 6.2 14.6 5.3 51.4 0.0 100  3 500 10.6 1.4 1.8 0.0 7.9 16.0 5.8 13.3 2.3 48.5 6.2 93.8  4 550 33.5 4.2 4.4 0.0 6.0 13.2 4.6 12.4 1.3 39.5 23.0 77.1  5 5 350 3.0 0.4 0.52 0.0 11.0 15.0 4.2 13.2 3.1 53.5 0.0 100  6 400 14.0 1.7 2.3 0.0 12.5 16.3 4.8 12.4 3.2 50.8 0.0 100  7 450 47.7 6.1 7.8 4.3 12.1 14.9 5.0 12.8 2.6 47.7 0.7 95.1  8 500 100.0 13.6 16.8 8.7 6.9 10.4 3.9 14.3 2.1 50.9 2.8 88.5  9 10 400 42.5 5.9 7.4 3.2 15.1 14.0 4.3 11.7 3.1 45.6 3.0 93.8 10 20 400 87.1 11.9 14.3 5.5 14.0 13.0 3.3 11.4 3.0 44.7 5.1 89.4 11 50 400 98.2 13.7 147.6 5.7 16.7 8.5 2.7 9.3 2.7 42.6 11.9 82.4 12 70 400 98.3 13.7 770.1 5.5 16.3 7.1 2.4 7.8 2.4 39.9 18.5 76.0  13.sup.a) 10 400 31.0 17.1 16.4 5.6 15.2 14.1 3.9 12.1 2.9 43.9 2.3 92.1  14.sup.a) 450 78.0 40.5 37.5 5.9 17.1 10.0 3.2 13.4 2.5 43.6 4.3 89.8 .sup.a)feedstock mixture composition 30% N.sub.2O + 70% BBM; C.sub.5cyclopropane derivatives; AA—acetaldehyde; PA—propanal; i-BA—isobutanal; A—acetone; BA—butanal; MEK—methyl ethyl ketone; .sup.b)total selectivity for carbonyl products (S.sub.Σ).

TABLE-US-00003 TABLE 3 Gas phase oxidation of butane butylene mixtures (BBM) with different olefin contents using nitrous oxide. Reaction conditions: flow-type reactor 25 cm.sup.3, temperature 400° C., pressure 10-50 atm; feedstock mixture; 10-20 mol % N.sub.2O, 90 mol % BBM; the volume flow rate of the mixture is 25 cm.sup.3/min (for normal conditions) Pr, Selectivity, S, % P, T, X.sub.N2O, μmol/cm.sup.3 Pr, Other S.sub.Σ.sup.a), No atm. ° C. % X.sub.R, % min g/l h C5 AA PA i-BA A BA MEK products % Mixture 2 (olefin content 25.1 mol. %) 19* 50 400 96.7 99.7 7.2 27.3 5.4 16.5 6.5 2.9 8.7 2.8 42.8 14.3 80.2 Mixture 3 (olefin come a 13.2 mol. %) 20** 50 400 99.9 93.7 0.8 3.0 5.4 17.5 7.1 2.8 8.3 2.8 42.3 13.7 80.8 Mixture 4 (olefin content 57.6 mol. %) 15 10 400 36.2 7.4 1.6 6.1 5.1 14.3 11.1 2.1 2.7 5.4 55.6 3.7 91.2 Mixture 5 (olefin content 52.7 mol. %) 16 10 400 33.2 7.8 1.5 6.0 5.2 11.2 2.9 3.1 6.9 4.5 62.1 4.2 90.7 Mixture 6 (olefin content 42.3 mol. %) 17 10 400 27.3 7.7 1.2 4.5 4.4 18.2 9.1 1.9 8.4 3.5 48.3 6.2 89.4 Mixture 7 (olefin content 37.9 mol. %) 18 10 400 26.2 8.8 1.2 4.4 5.5 21.2 10.2 1.5 8.3 3.3 43.3 6.7 87.8 *the content of nitrous oxide in the reaction mixture is 20 mol. %; **the volume of the reactor is 125 cm.sup.3; C5—cyclopropane derivatives; AA—acetaldehyde; PA is propanal; i-BA is isobutanal; A is acetone; BA is butanal; MEK—methyl ethyl ketone; .sup.a)the total selectivity for carbonyl products (S.sub.Σ).

TABLE-US-00004 TABLE 4 Gas-phase oxidation of propane-propylene mixtures (PPM) with nitrous oxide. Reaction conditions: flow-type reactor 25 cm.sup.3, temperature 350-550° C., pressure 1-7 atm; feedstock mixture: N.sub.2O 10 mol %, PPM 90 mol %; the volume flow rate of the mixture is 25 cm.sup.3/min (for normal conditions) Pr, Selectivity, % P, T, X.sub.N2O, μmol/cm.sup.3 Pr, Other S.sub.Σ.sup.a), No atm. ° C. % X.sub.R, % min g/l h MCP AA PA A products % 21 1 400 0.8 0.1 0.0 0.1 0.0 28.0 26.4 40.3 5.3 94.7 22 450 3.9 0.6 0.2 0.6 2.0 26.7 24.7 38.3 8.4 89.7 23 500 13.9 2.2 0.6 2.0 4.7 24.0 22.6 36.4 12.5 83 24 550 42.1 5.9 1.4 4.5 2.0 24.1 14.0 32.5 27.4 70.6 25 4 350 2.4 4 0.1 0.3 3.3 37.2 16.8 32.7 10.0 86.7 26 400 14.8 2.3 0.7 2.1 5.3 28.9 18.6 35.2 12.0 82.7 27 450 46.4 7.9 2.0 6.4 5.0 21.9 18.3 33.1 21.7 73.3 28 7 350 8.8 1.3 0.4 1.2 4.8 35.2 15.3 32.5 12.1 83 29 400 28.4 4.7 1.3 4.0 6.0 27.2 17.4 33.9 15.5 78.5 30 450 74.5 12.5 3.2 10.3 6.1 21.3 16.5 36.8 19.2 74.6 MCP—methylcyclopropane; AA—acetaldehyde; PA—propanal; A—acetone; .sup.a)total selectivity for carbonyl products (S.sub.Σ).