Production process of alkylene oxides from alkylene carbonates

Abstract

Catalytic process for producing alkylene epoxide, selected between ethylene oxide or propylene oxide, from the corresponding alkylene carbonate, selected between ethylene carbonate or propylene carbonate, comprising the decomposition reaction of alkylene carbonate, in the presence of sodium bromide as catalyst,

in which: the reaction temperature is between 207 and 245° C., and the catalyst is in amounts comprised between 5×10.sup.−4 and 8×10.sup.−3 moles per mole of alkylene carbonate.

This process can be carried out continuously. A further object of the invention is the modular plant which allows carrying out such a process.

Claims

1. Catalytic process for producing alkylene epoxide, selected between ethylene oxide or propylene oxide, from the corresponding alkylene carbonate, selected between ethylene carbonate or propylene carbonate, comprising the decomposition reaction of alkylene carbonate, in the presence of sodium bromide as catalyst, according to the following scheme: ##STR00003## with R═H, methyl and wherein: the reaction temperature ranges between 207 and 245° C., the catalyst is in amounts comprised between 5×10.sup.−4 and 8×10.sup.−3 moles per mole of alkylene carbonate.

2. The process of claim 1 wherein, when the reagent is ethylene carbonate, the reaction temperature ranges between 221 and 235° C. and said catalyst is present in amounts comprised between 7×10.sup.−4 and 5×10.sup.−3 moles of catalyst/moles of ethylene carbonate.

3. The catalytic process of claim 1, wherein when the reagent is propylene carbonate the reaction temperature ranges between 237 and 243° C., the mole ratio of catalyst/propylene carbonate ranges between 8×10.sup.−4 and 7×10.sup.−3.

4. The catalytic process according to [[any one of claims from]] claim 1 wherein the pressure ranges between 1 and 50 bar, preferably between 1 and 10 bar.

5. The catalytic process according to claim 1, conducted in a modular plant comprising a module (A) in turn comprising the reactor in which said catalytic demolition of the alkylene carbonate occurs, and associated with: a module (B) comprising a CO.sub.2 blast chiller, or a module (C), comprising a further reactor in which the alkylene oxide from the module (A) is subjected to a further reaction to give an industrial product.

6. The catalytic process according to claim 1, conducted in a modular plant comprising a module (A) in turn comprising the reactor in which said catalytic demolition of the alkylene carbonate occurs, and associated with: a module (B) comprising a CO.sub.2 blast chiller and a module (C), comprising a further reactor in which the alkylene epoxide from the module (A) is subjected to a further reaction to give an industrial product.

7. The catalytic process according to claim, wherein the module (A) comprises at least one batch reactor of cylindrical shape (A1), possibly provided with a stirrer, externally thermostated through electrical resistors, through a contact fluid or through irradiation.

8. The process according to claim 1, conducted continuously or discontinuously, preferably continuously.

9. The catalytic process according to claim 8, wherein when said process is conducted continuously, the module (A) comprises a single CSTR reactor (A1), or multiple CSTR reactors (A1), said multiple reactors being arranged in series or in parallel with each other.

10. The catalytic process according to claim 5, wherein the module (A) is tubular in shape (A2) and is thermostated by immersion in a heating fluid bath or is inserted inside a sleeve arranged for the entire length of the reactor in which a heating fluid passes.

11. The catalytic process according to claim 5, wherein the module (A) comprises downstream of the reactor a condenser or an exchanger which allows the separation of the unreacted alkylene carbonate from the reaction products in gaseous form, the CO.sub.2 and the alkylene epoxide, said unreacted alkylene carbonate being recycled in the reactor of the module (A), while the aforementioned reaction products in gaseous form, CO.sub.2 and alkylene epoxide, are conveyed to the module (B) or (C).

12. The catalytic process according to claim 5, wherein the module (B) comprises a filler or perforated-plate adsorption column.

13. The catalytic process according to claim 5, wherein the alkylene epoxide and CO.sub.2 formed in the reactor (A) are sent to the module (C) where they are subjected, in the presence of a specific reagent, to a further reaction, the CO.sub.2 has the function of inert gas and said reactor is adapted to gas-liquid or gas-solid reactions.

14. The catalytic process according to claim 13, wherein said reactor of the module (C) is adapted to gas-liquid reactions and is selected from flat or filler columns, coiled tubular reactors, heat exchangers.

15. The catalytic process according to claim 14, wherein said reactor of the module (C) is adapted to gas-solid reactions and is selected from a fluid bed reactor, extruder, powder compactor, granulator.

16. The process according to claim 13, wherein said further reaction of the alkylene epoxide occurring in the reactor of the module (C) is selected from: alkyleneoxylation reaction of fatty alcohols, such as lauryl alcohol, coconut or palm alcohol, linear or branched petrochemical-derived alcohols; alkyleneoxylation reaction of acrylate compounds selected from: acrylic acid or methacrylic acid; alkyleneoxylation reaction of diols; reaction with hydrochloric acid or hydrogen sulfide for the production of 2-chloroethanol, 2-chloropropanol, 2 hydroxychloropropane, hydroxythioethane, 2-hydroxythiopropane, 2-thiopropanol, reactions catalysed by magnesium chloride or other alkali or alkaline earth metals salts alkyleneoxylation reaction of polysaccharides or celluloses in flour or powder such as hemicellulose, carboxymethylcellulose, carboxyethylcellulose, guar gum, xanthan gum, alginates, amides.

Description

DESCRIPTION OF THE FIGURES

[0026] FIG. 1 depicts preferred embodiments of the modular plant in which the alkylene epoxide is produced according to the process of the invention.

[0027] FIG. 2 shows the embodiments of the reactor of the module of the modular plant in which the alkylene epoxide is produced according to the process of the invention.

[0028] FIG. 3 shows the temperature variation as a function of the reaction time observed for tests 1-6 of example 1 using specific catalyst/ethylene carbonate ratios.

[0029] FIG. 4 shows the temperature variation as a function of the reaction time observed for tests 7-13 of example 1 using specific catalyst/propylene carbonate ratios.

[0030] FIG. 5 graphically depicts the values given in table 2 of example 1 of the decomposition time as a function of the different molar ratios of sodium bromide/ethylene carbonate used in tests 1-6 of the same example.

[0031] FIG. 6 graphically depicts the values given in table 2 of example 1 of the decomposition time as a function of the different molar ratios of sodium bromide/propylene carbonate used in tests 7-13 of the same example.

[0032] FIG. 7 shows the .sup.1H-NMR spectrum of the pentanol solvent/reagent before coming into contact with ethylene oxide

[0033] FIG. 8 shows the .sup.1H-NMR spectrum of the reaction product between ethylene oxide with pentanol to give pentanol ethoxylate.

DETAILED DESCRIPTION OF THE INVENTION

[0034] For the purposes of the present invention, the verb “comprising” is intended to define a set of elements, expressly indicating some, without excluding the presence of others not expressly indicated; while the term “constituting” or “constituted” is intended to define a set of elements, expressly indicating them all, and thus excluding the presence of components not expressly listed.

[0035] In the process of the invention when the reagent is ethylene carbonate, the reaction temperature is preferably comprised between 221 and 235° C. and said catalyst is present in amounts preferably comprised between 7×10.sup.−4 and 5×10.sup.−3 moles of catalyst/ moles of ethylene carbonate.

[0036] In the process of the invention, when the reagent is propylene carbonate the reaction temperature is preferably comprised between 237 and 243° C., the mole ratio of catalyst/propylene carbonate is preferably comprised between 8×10.sup.−4 and 7×10.sup.−3.

[0037] As noted above, the process according to the present invention operates at pressures close to atmospheric pressure; therefore, it is not necessary to operate at pressures lower than atmospheric pressure as is the case with EP0047473.

[0038] In particular, the decomposition reaction of the alkylene carbonate of the catalytic process preferably occurs at a reaction pressure comprised between 1 and 50 bar, more preferably at a pressure comprised between 1 and 10 bar.

[0039] As illustrated above, a further object of the invention is the modular plant of relatively limited size which allows the catalytic process to be carried out in accordance with the present invention.

[0040] This modular plant can consist of a single module (A) comprising the reactor in which the formation of the alkylene oxide occurs according to the process of the invention, i.e., the alternative I) shown in FIG. 1.

[0041] This module can possibly be associated with a module (B) comprising a CO.sub.2 blast chiller, or alternative II) shown in FIG. 1, or can be associated with a module (C) according to alternative III) shown in FIG. 1, comprising a reactor in which the alkylene epoxide, which exits from the module (A), is subjected to a further reaction in the presence of a suitable reagent to give a product for industrial use.

[0042] According to a further alternative not shown in the figure, the plant according to the present invention contains all three modules (A), (B) and (C),

[0043] The module (A) is associated or connected with the module (B) or (C) by means of hydraulic/mechanical connection means, such as valve/flange/valve.

[0044] The reactor of module (A) preferably consists of material capable of (or suitable for) resisting the pressures of the gases formed at the process temperature and pressure. Preferably, the catalytic reactor (A) is made of steel, more preferably it is made of stainless steel 316—but it can also be made of glass or ceramic material, in the latter two cases it can be further enclosed in a metal or plastic protection. A specific system of pressure regulating valves ensures the set point pressure (or preset pressure) and the possible vent in the case of overpressure.

[0045] According to a preferred embodiment of the invention, the module (A) can comprise at least one batch reactor indicated as (A1) in FIG. 2 of cylindrical shape possibly provided with a stirrer, externally thermostated through electrical resistors or through a contact fluid (oil or steam) or through irradiation (IR lamps).

[0046] The process can be conducted continuously or discontinuously, preferably it is conducted continuously.

[0047] When the process of the invention is conducted continuously, the module (A) can comprise a single batch reactor (A1) also defined as CSTR (Continuous Stirred Tank Reactor) or multiple CSTRs (A1) arranged in series or in parallel with each other. This solution is preferred in the case where alkylene epoxide is to be produced in mass quantities.

[0048] The size of the batch reactor for the discontinuous process or for the CSTR is preferably comprised between 1 cm.sup.3 and 10 m.sup.3, more preferably between 1 dm.sup.3 and 1 m.sup.3.

[0049] According to another preferred embodiment, to conduct the process continuously the reactor of the module (A) has a tubular shape (A2) of the PFR (Plug Flow Reactor) type as shown in FIG. 2, where it specifically has a coiled shape and is immersed in a heating fluid bath, indicated in the figure with the rectangle.

[0050] According to another preferred embodiment, the tubular reactor is inserted inside a tubular sleeve arranged for the entire length of the reactor and in which a heating fluid passes.

[0051] The module (A), in addition to the reactor, will comprise support units such as steam supply units for heating, units for cooling the exhaust gases, units for melting the alkylene carbonate, pumping and reagent supply units in the reactor.

[0052] The module (A) can further comprise devices for feeding inert gases in liquids to facilitate the removal of gaseous products (alkylene oxides and CO.sub.2). Preferably, said inert gases are selected between: nitrogen, and helium.

[0053] The module (A) will comprise different forms of reactor instrumentation and control such as meters and specifically pressure, temperature, conductivity, heat, viscosity, infrared spectrum sensors at both medium and low frequencies. In the plant in which the process of the invention is carried out continuously, particular care will be taken to control the flow rate of the input liquid, while in any case, it will be important to measure the total output gaseous flow rate. Thus the module (A) will comprise mass or volume flow meters.

[0054] All this instrumentation will be coordinated according to the usual control techniques, by means of one or more central units or the so-called programmable logic controllers (PLC) attached to the module or relocated to a remote location (distributed control systems, DCS).

[0055] The reactor of module (A) advantageously allows to reduce or even cancel the amount of inert gas necessary to ensure a continuous flow and thus allow the passage of the gaseous products to the other operating units.

[0056] The module (A) preferably comprises, downstream of the reactor, a condenser or a heat exchanger which allows the separation of the unreacted alkylene carbonate, which is separated and recycled from the reaction products in gaseous form, such as CO.sub.2 and alkylene epoxide, which are conveyed to module (B) or (C). The condenser or heat exchanger is a tube bundle with mains water inside for cooling. The condenser or heat exchanger can comprise instrumentation units for measuring, controlling and stabilizing the internal temperature and pressure. The temperature and pressure conditions of the condenser (or heat exchanger) are such that the unreacted alkylene carbonate in condensed form can return to the reaction mixture to undergo decomposition; at the same time, the reaction products, CO.sub.2 and alkylene epoxide undergo cooling but remain in the form of non-condensable gases, and can be conveyed to the module (B) comprising the CO.sub.2 abatement unit to separate the alkylene epoxide from the CO.sub.2, to be used as a disinfectant.

[0057] The CO.sub.2 blast chiller of module (B) is preferably a filler or perforated-plate adsorption column.

[0058] As noted above, the reaction mixture output from the module (A) is preferably conveyed to the module (C).

[0059] In this case, the alkylene epoxide and the CO.sub.2, after having undergone a cooling process by means of the condenser, are sent to the module reactor (C) in which the alkylene epoxide undergoes a further reaction and the CO.sub.2 used as an inert gas.

[0060] The reactions which can occur in the reactor of module (C) are for example: [0061] fatty alcohol alkyleneoxylation reaction, such as lauryl alcohol, coconut or palm alcohol, linear or branched petrochemical-derived alcohols; [0062] alkyleneoxylation reaction of acrylate compounds selected from: acrylic acid or methacrylic acid; [0063] alkyleneoxylation reaction of diols; [0064] reaction with hydrochloric acid or hydrogen sulfide for the production of 2-chloroethanol, 2-chloropropanol, 2 hydroxychloropropane, hydroxythioethane, 2-hydroxythiopropane, 2-thiopropanol, reactions catalysed by magnesium chloride or other alkali metal or alkali earth salts [0065] alkyleneoxylation reaction of polysaccharides or celluloses in flour or powder such as hemicellulose, carboxymethylcellulose, carboxyethylcellulose, guar gum, xanthan gum, alginates, amides.

[0066] The alkyleneoxylation reaction of acrylate compounds, selected between acrylic acid or methacrylic acid, allows to obtain ethoxylated monomers which can then be used in acrylate polymerization reactions.

[0067] Likewise, the alkyleneoxylation reaction of diols allows to obtain ethoxylated monomers which can then be used in urethane polymerization reactions.

[0068] Module (C) preferably comprises a reactor which is suitable for gas-liquid or gas-solid reactions.

[0069] The reactor of module (C) is suitable for conducting gas-liquid reactions and is preferably selected from flat or filler columns, coiled tubular reactors, heat exchangers.

[0070] When module (C) comprises a reactor suitable for gas-solid reactions, the reactor is preferably selected between a fluid bed reactor, extruder, powder compactor, granulator.

[0071] The Applicant gives examples merely for illustrative and non-limiting purposes of the invention below.

Example 1— Experimental Tests of Ethylene Carbonate and Propylene Carbonate Decomposition

[0072] The decomposition reaction was studied by conducting the reaction in batches. The experimentation was carried out considering EC ethylene carbonate and PC propylene carbonate.

[0073] The decomposition reactions of both ethylene carbonate and propylene carbonate of the catalytic process are endothermic reactions with a measured value of reaction enthalpy (ΔH.sub.R in kJ/mol), as measured by the enthalpy of reactant and product formation, equal to 219.09 kJ/mol for EC ethylene carbonate and equal to 124.81 kJ/mol for PC propylene carbonate. The Applicant carried out a series of experimental tests shown in table 2 for both ethylene carbonate and propylene carbonate, proceeding as follows: [0074] (a) initial heating step of the reactor of module (A) where the thermal power supplied is between 90 and 100 W (sleeve of module (A) set to an instrument value of 6.8); [0075] (b) secondary decomposition/production and heating step from the maximum temperature reached in the initial step (a) and for the following 15 minutes with a value of deliverable thermal power between 120 and 125 W (sleeve of module (A) set at an instrument value of 10.0).

[0076] Each test, for both EC ethylene carbonate and PC propylene carbonate, was performed with the same molar amount of alkylene carbonate (50 g and 100 g for EC; 58 g and 116 g for PC). The tests therefore differ only for the amount of catalyst (NaBr) added. Below are the results obtained in the same format as the previous series, for ease of reading.

[0077] 6 tests were performed using ethylene carbonate and 7 tests using propylene carbonate.

[0078] The alkylene oxide obtained as a product was measured by titration; specifically, the alkylene oxide product was adsorbed with a catalysed acid (HCl) bath (MgCl.sub.2) (measurement by titration of the amount of alkylene epoxide formed by reaction with MgCl.sub.2 catalysed hydrochloric acid by the method proposed by F. W. Kerckow in Analytische Bestimmung von Äthylenoxydthylenoxyd, Analytical and Bioanalytical Chemistry, volume 108, issue 7-8, 1937). The hardware (glass fittings, etc.) of all the tests is identical.

[0079] During the decomposition reaction, a lively formation of gas and a progressive reduction in the volume of the liquid phase is observed.

[0080] The graphs in FIGS. 4 and 5 show the change in temperature as a function of time for tests 1-6 wherein the reagent is ethylene carbonate and for tests 7-13 where the reagent is propylene carbonate, respectively.

[0081] The Applicant reports below, in the aforesaid table 2 the decomposition time as a function of the ratio of catalyst moles/starting alkylene carbonate moles. The results obtained are also depicted in the graphs of FIGS. 5 and 6.

TABLE-US-00002 TABLE 2 Formation time Formation time Moles of 0.50 mol of Moles of 0.50 mol of NaBr/ ethylene oxide NaBr/ propylene oxide EC from 100 g of PC from 116 g of Test moles EC (minutes) Test moles PC (minutes) 1 0.00000 310 7 0.00000 2350 2 0.00086 19 8 0.00104 122 3 0.00137 24 9 0.00139 80 4 0.00188 29 10 0.00207 55 5 0.00248 32 11 0.00285 42 6 0.00376 36 12 0.00380 82 13 0.00647 56

[0082] The formation time of 0.50 mol of ethylene oxide from the initial 100 g of ethylene carbonate occurs in a minimum time of 19 minutes using 0.00086 moles of NaBr per mole of ethylene carbonate and under the experimental conditions described in terms of pressure and temperature. The decomposition reaction of ethylene carbonate in the absence of sodium bromide catalyst does not occur.

[0083] The formation time of 0.50 mol of propylene oxide from the initial 116 g of propylene carbonate occurs in a minimum time of 42 minutes using 0.00285 mol NaBr per mole of propylene carbonate and under the experimental conditions described in terms of pressure and temperature. In this case, the propylene carbonate decomposition reaction in the absence of sodium bromide catalyst is very slow.

Example 2— Ethoxylation Reaction

[0084] The ethylene oxide generated in module (A) and conveyed after module (C) as described above can immediately react with an alcohol, ethoxylating it. The NMR analysis of the initial solvent/reagent (pentanol) is shown in the .sup.1H-NMR spectrum in FIG. 8; while FIG. 9 shows the transformation thereof into ethoxylated alcohol (left peaks increased in number and intensity), obtained by bubbling ethylene oxide at a temperature comprised between 180 and 200° C. and using sodium methylate in pentanol as catalyst.