PROCESS FOR THE PRODUCTION OF MIXTURES USABLE AS JET FUEL OR JET FUEL PRECURSORS STARTING FROM C2-C4 ALCOHOLS AND RELATED PLANT

Abstract

A process for the production of mixtures including compounds having a number of carbon atoms 6, usable as jet fuel or as jet fuel precursors starting from one or more alcohols having from 2 (C2) to 4 (C4) carbon atoms, wherein the one or more alcohols are introduced into a continuously operating fixed bed catalytic reactor, in an amount from 1 to 100 mol %, in the vapour phase and at a temperature ranging from 200 to 450 C., the catalyst includes metallic copper on a zirconia-based support, the metallic copper is in a percentage by weight ranging from 0.5% to 25% of the total weight of the catalyst. A plant for the production of a mixture including compounds having a number of carbon atoms 6, usable as a jet fuel or jet fuel precursor, starting from one or more alcohols having from 2 to 4 carbon atoms.

Claims

1. A process for production of a mixture comprising compounds having a number of carbon atoms 6, usable as jet fuel or as a jet fuel precursor, starting from one or more alcohols having from 2 to 4 carbon atoms, preferably ethanol, wherein said one or more alcohols are introduced into a continuously operated fixed bed catalyst reactor, in an amount from 1 to 40 mol %, in a vapour phase, at a temperature ranging from 200 C. to 450 C. and wherein said one or more alcohols are placed in contact with a catalyst for a contact time , wherein =catalyst volume (mL)/total volumetric flow (mL/s), said contact time ranges from 1.5 to 5 seconds, wherein said catalyst comprises metallic copper on a zirconia-based support, said metallic copper is in a percentage by weight ranging from 0.5% to 25% of total weight of the catalyst.

2. The process according to claim 1, wherein said contact time t ranges from 1.5 to 3 seconds.

3. The process according to claim 1, wherein said contact time ranges from 1.85 to 2.53 seconds.

4. The process according to claim 1, wherein said contact time is 2 seconds.

5. The process according to claim 1, wherein said process is carried out at a pressure ranging from atmospheric pressure to 10 bar.

6. The process according to claim 1, wherein said process is carried out at a pressure ranging from atmospheric pressure to 5 bar.

7. The process according to claim 5, wherein said process is carried out at a pressure ranging from atmospheric pressure to 2 bar.

8. The process according to claim 5, wherein said process is carried out at atmospheric pressure.

9. The process according to claim 1, wherein said one or more alcohols are introduced into said reactor in an amount from 1 to 25 mol %.

10. The process according to claim 1, wherein said one or more alcohols are introduced into said reactor in an amount of 10 mol %.

11. The process according to claim 1, wherein said temperature ranges from 250 to 340 C.

12. The process according to claim 1, wherein said temperature is 300 C.

13. The process according to claim 1, wherein said metallic copper is in a percentage by weight from 1% to 10%.

14. The process according to claim 1, wherein said metallic copper is in a percentage by weight of 5%.

15. The process according to claim 1, wherein said one or more alcohols are introduced into said reactor in an inert gas flow, in particular consisting of helium, nitrogen, argon and/or other gaseous component inert to reaction conditions, in particular water vapour or CO.sub.2.

16. The process according to claim 1, wherein said zirconia is tetragonal zirconia or monoclinic zirconia.

17. The process according to claim 1, wherein said zirconia-based support comprises a lanthanide included in structure of said zirconia.

18. The process according to claim 1, wherein the Zr:lanthanide atomic ratio ranges from 50:1 to 1:1, preferably from 20:1 to 2:1, more preferably being 5:1.

19. The process according to claim 1, wherein said catalyst is selected from a catalyst comprising metallic copper on a tetragonal zirconia-based support, wherein the metallic copper is present in an amount of 5% by weight of the total weight of the catalyst; a catalyst comprising metallic copper on a tetragonal zirconia-based support, wherein the metallic copper is present in an amount of 1% by weight of the total weight of the catalyst; a catalyst comprising metallic copper on a tetragonal zirconia-based support, wherein the metallic copper is present in an amount of 10% by weight of the total weight of the catalyst; a catalyst comprising metallic copper on a monoclinic zirconia-based support, wherein the metallic copper is present in an amount of 5% by weight of the total weight of the catalyst; a catalyst comprising metallic copper on a zirconia-based support comprising lanthanum included in a structure of said zirconia, wherein the metallic copper is present in an amount of 5% by weight of the total weight of the catalyst.

20. The process according to claim 1, wherein hydrogen is fed together with said one or more alcohols or, when said one or more alcohols are introduced into the reactor in an inert gas flow, together with said inert gas flow.

21. The process according to claim 1, wherein the inert gas:H.sub.2 ratio ranges from 1:10 to 10:1.

22. The process according to claim 1, wherein said catalyst is in the form of powder or pellet.

23. The process according to claim 1, wherein said mixture comprises esters, in particular linear and branched esters, alcohols, in particular branched and linear alcohols, ketones, in particular branched, linear and cyclic ketones, aldehydes, aliphatic hydrocarbons, such as for example alkanes and olefins, and aromatic compounds, in particular phenolic compounds.

24. The process according to claim 1, further comprising a hydrogenation of aldehydes and unsaturated compounds and, optionally, a dehydration.

Description

[0053] The present invention will now be described, for illustrative but not limiting purposes, according to a preferred embodiment thereof, with particular reference to the examples and figures of the attached drawings, wherein:

[0054] FIG. 1 shows a simplified reaction scheme of upgrading reactions of ethanol to jet fuel blends according to the process of the present invention;

[0055] FIG. 2 shows the catalytic test results under the following reaction conditions: t-ZrO.sub.2, 10 mol % EtOH in He, contact time 2 s, 300 C., in the absence of copper;

[0056] FIG. 3 shows the catalytic test results under the following reaction conditions: m-ZrO.sub.2, 10 mol % EtOH in He, contact time 2 s, 300 C., in the absence of copper;

[0057] FIG. 4 shows the catalytic test results under the following reaction conditions: LaZrO, 10 mol % EtOH in He, contact time 2 s, 300 C., in the absence of copper;

[0058] FIG. 5 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He, contact time 1 s, 300 C.;

[0059] FIG. 6 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0060] FIG. 7 shows the C.sub.6 fraction composition expressed as a molar fraction in percentage of the total C.sub.6 fraction; reaction conditions: Cu/t-ZrO.sub.2 catalyst with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0061] FIG. 8 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He, contact time 3 s, 300 C.;

[0062] FIG. 9 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 1% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0063] FIG. 10 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 10% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0064] FIG. 11 shows the catalytic test results under the following reaction conditions: Cu/m-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0065] FIG. 12 shows the C.sub.6 fraction composition expressed as a molar fraction in percentage of the total C.sub.6 fraction; reaction conditions: Cu/m-ZrO.sub.2 catalyst with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0066] FIG. 13 shows the catalytic test results under the following reaction conditions: Cu/LaZrO with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0067] FIG. 14 shows the C.sub.6 fraction composition expressed as a molar fraction in percentage of the total C.sub.6 fraction; reaction conditions: Cu/LaZrO catalyst with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C.;

[0068] FIG. 15 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He:H.sub.2 mixture in a 1:1 ratio, contact time 2 s, 300 C.;

[0069] FIG. 16 shows the C.sub.6 fraction composition expressed as a molar fraction in percentage of the total C.sub.6 fraction; reaction conditions: Cu/t-ZrO.sub.2 catalyst with 5% by weight of Cu, 10 mol % EtOH in He:H.sub.2 mixture in a 1:1 ratio, contact time 2 s, 300 C.;

[0070] FIG. 17 shows the catalytic test results under the following reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % 1-butanol in He, contact time 2 s, 300 C.;

[0071] FIG. 18 shows the C.sub.6 fraction composition expressed as a molar fraction in percentage of the total C.sub.6 fraction; reaction conditions: Cu/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % 1-butanol in He, contact time 2 s, 300 C.

[0072] With particular reference to the scheme shown in FIG. 1, without wanting to be limited by theory, it is believed that the reaction of the process according to the present invention comprises the following steps: [0073] dehydrogenation of ethanol to acetaldehyde; [0074] aldol condensation of acetaldehyde to C.sub.4 aldol; [0075] direct dehydrogenative coupling of alcohols with corresponding esters (aldehydes as reactive intermediates); [0076] ketonisation of esters to ketones characterised by a number of carbon atoms equal to the sum of the carbon atoms of the acid part of the two esters minus one (CO.sub.2 co-production); [0077] consecutive aldol condensations of acetone and acetaldehyde to make cyclic ketones and/or alcohols; [0078] dehydrogenation of cyclic to aromatic compounds; [0079] possible dehydration or decarboxylation of compounds containing oxygen and aliphatic hydrocarbons (alkanes and olefins).

[0080] The process according to the present invention exploits the ability of the Cu/ZrO.sub.2-based catalyst to develop large quantities of acetaldehyde and to simultaneously promote the dehydrogenative coupling reaction of alcohols to give esters. These, thanks to the high reactivity of zirconia for the ketonisation reaction, are effectively converted to (symmetrical and not symmetrical) ketones.

[0081] In particular, the mixture obtained according to the process of the invention consists of (linear and branched) esters, (branched and linear) alcohols, (branched, linear and cyclic) ketones, aldehydes, aliphatic hydrocarbons (alkanes and olefins) and aromatic compounds (especially phenolic compounds).

[0082] By way of example, a mixture obtained, according to the process of the invention, from one of the preliminary tests has proved to be promising for applications such as Jet fuel A and A1. In this regard, some information obtained by comparing the properties of the mixture obtained according to the process of the invention with the specific ASTM D1655 mixture are shown below: [0083] Aromatics: 36% against a maximum of 25% for A and A-1; [0084] Olefins: not specified in ASTM Std; [0085] Density: 865 against 775-840 for A and A-1; [0086] Gross Heat of Combustion: 37.7 MJ/kg against a minimum of 42.8 MJ/kg for A and A-1;

[0087] Naphthalene: 0.93% against a maximum of 3% for A and A-1; [0088] Flash point: 34 C. against a minimum of 38 C. for A and A1; [0089] Sulfur: 0% (not analysed) against a maximum of 0.3%; [0090] Freezing point: 36.5 C. against a maximum of 40 C. for A and a maximum of 47 C. for A1.

EXAMPLES

Reference Examples: Catalytic Tests on Zirconia-Based Supports in the Absence of Copper

[0091] As mentioned above, the process according to the invention operates under conditions such that the catalyst is surprisingly capable of promoting all the one-pot reactions in an extremely efficient manner, showing a synergistic and not easily predictable effect. In order to show the improving and inventive effect of the method according to the present invention, the ethanol decomposition tests, carried out on the various supports used in examples 1-14 in the absence of copper, are hereby proposed as reference examples. In particular, in the reference examples it is shown the catalytic activity of the individual supports in the ethanol upgrading reaction under the same reaction conditions used for the copper-containing catalysts shown in the following examples. By observing the results obtained in the reference example (shown in FIGS. 2-4) it is possible to notice how, regardless of the support taken into consideration, the conversion of ethanol is around 20% with preferential formation of compounds bound in acid catalysis (ethylene, diethyl ether) and products from the Guerbet and Lebedev reactions (acetaldehyde, butadiene and butanol). Heavy compounds (>C6) are formed in trace amounts only on the monoclinic zirconia support.

[0092] By comparing the results obtained in the reference example with the results obtained in examples 1-14, it is possible to notice how the addition of copper as active metal on these catalytically active supports produces both an unpredictable increase in the conversion of ethanol and a radical change of the distribution of the obtainable products, making it possible to obtain complex mixtures usable as jet fuel.

Reference 01: Catalytic Test Results Under Conditions: t-ZrO.sub.2, 300 C., =2 s

[0093] The tetragonal ZrO.sub.2 support (t-ZrO.sub.2) was synthesised by precipitation at controlled temperature and pH starting from an aqueous solution of ZrO(NO.sub.3).sub.2. In particular, the solution of the metal precursor (0.3 mol/l) was dripped, under vigorous stirring, into an ammonia aqueous solution (5 mol/l at 25 C.) promoting the precipitation of a white solid (hydroxide derivative of the precursor). Subsequently, the solution containing the solid was subjected to a digestion process lasting 24 h at 100 C., maintaining the pH between 9 and 11 by progressively and continuously adding a concentrated ammonia aqueous solution (28% w/w). The sample was then filtered, dried and calcined at 500 C. for 12 h at a ramp rate of 5 C./min. This procedure allows the synthesis of a ZrO.sub.2 characterised by a tetragonal crystalline phase.

[0094] The catalytic test was carried out as shown in example 2, modifying the overall volumetric flow and the amount of loaded catalyst so as to obtain tau=2 s. The results are shown in FIG. 2.

Reference 02: Catalytic Test Results Under Conditions: m-ZrO.sub.2, 300 C., =2 s

[0095] The ZrO.sub.2 support was obtained by hydrothermal synthesis in an autoclave at 140 C. for 20 h at autogenous pressure starting from an aqueous solution of ZrO(NO.sub.3).sub.2 and urea. The product is washed several times with ethanol, then it is dried and calcined at 450 C. for 3 h, at a ramp rate of 5 C./min. In this way zirconia in the monoclinic crystalline phase is obtained. The catalytic test was carried out as shown in example 2, modifying the overall volumetric flow and the amount of loaded catalyst so as to obtain tau=2 s. The results are shown in FIG. 3.

Reference 03: Catalytic Test Results Under Conditions: LaZrO, 300 C., =2 s

[0096] The LaZrO support was synthesised by precipitation in a basic environment at 25 C. starting from an aqueous solution of ZrO(NO.sub.3).sub.2*2H.sub.2O and La(NO.sub.3).sub.3*6H.sub.2O such that the atomic ratio La:Zr in the final material was 0.19 and the total cation concentration was 0.3 mol/l. The suspension was subjected to a digestion of 72 h at 100 C. and at controlled pH 10-12 by continuously adding a concentrated ammonia aqueous solution (28% w/w). The sample was then filtered, dried and calcined at 450 C. for 12 h at a ramp rate of 5 C./min. The catalytic test was carried out as shown in example 2, modifying the overall volumetric flow and the amount of loaded catalyst so as to obtain tau=2 s. The results are shown in FIG. 4.

Example 1: Synthesis of the Cu/t-ZrO.SUB.2 .Catalyst with 5% by Weight of Cu

[0097] The tetragonal ZrO.sub.2 support (t-ZrO.sub.2) was synthesised by precipitation at controlled temperature and pH starting from an aqueous solution of ZrO(NO.sub.3).sub.2. In particular, the solution of the metal precursor (0.3 mol/l) was dripped, under vigorous stirring, into an aqueous solution of ammonia (5 mol/l at 25 C.) promoting the precipitation of a white solid (hydroxide derivative of the precursor). Subsequently, the solution containing the solid was subjected to a digestion process lasting 24 h at 100 C., maintaining the pH between 9 and 11 by progressively and continuously adding a concentrated ammonia aqueous solution (28% w/w). The sample was then filtered, dried and calcined at 500 C. for 12 h at a ramp rate of 5 C./min. This procedure allows the synthesis of a ZrO.sub.2 characterised by a tetragonal crystalline phase. The Cu was deposited on the support using the incipient wetness impregnation (IWI) method, by dissolving the amount of precursor (Cu(NO.sub.3).sub.2) necessary to obtain a copper load of 5% by weight of the final catalyst in a volume of distilled water equal to the volume of the pores of the support. This solution is added drop by drop and evenly distributed on the support until it reaches the slurry point (filling of the pores). After which the sample is dried in a furnace and calcined at 500 C. for 5 h at a ramp rate of 2 C./min.

[0098] The powder thus obtained is subjected to a pelletising process so as to obtain particles of a defined size (20-40 mesh).

[0099] A suitable amount of material is loaded into the plant operating continuously in the vapour phase as described in example 2 and subjected to a reduction process in a hydrogen flow at 350 C. for 3 hours so as to obtain the desired catalyst.

Example 2: Standard Catalytic Test Procedure and Results Under the Conditions: Cu/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =1 s

[0100] The catalytic tests were carried out in a tubular quartz reactor, operating continuously, in the vapour phase and at atmospheric pressure. In particular, the catalyst, obtained as described in example 1, is loaded into the reactor in the form of pellets (20-40 mesh), so as to be inserted into the isothermal area of the reactor supported by a suitable porous quartz septum. The reactor operates in down-flow mode. The organic reagent, ethanol (EtOH), is fed as a liquid through a high precision infusion pump (KPS 100 Syringe Pump) into a vaporisation section consisting of a stainless-steel line maintained at a temperature of 135 C. in order to favour an instantaneous vaporisation of the reagent and an adequate mixing with the inert current (He) entering the plant. The vaporisation zone is in fact connected to the quartz reactor (length 600 mm, internal diameter 11 mm) in such a way as to guarantee the tightness of the whole system. The reactor, containing the catalyst, is placed inside a tube furnace. The volume of loaded catalyst, the flows of the syringe for feeding EtOH and the flow of He, controlled by a dedicated Mass Flow meter, are suitably selected so as to have a contact time (=Catalyst volume/total volumetric flow) on the catalyst equal to 1 second at the chosen reaction temperature (300 C.) with a percentage of ethanol being fed equal to 10 mol % (90 mol % He).

[0101] Even the lines of the plant downstream the reactor are insulated and, through the use of electric resistances controlled by thermocouples, heated at a temperature of 250 C. The mixture leaving the reactor is passed through suitable traps maintained at 25 C. so as to favour the condensation of only the heavier products. The light products and the non-condensables are analysed using an online Agilent 6890A GC equipped with two different chromatographic columns and two TCD detectors (carrier: He). In particular: a PLOT-Q column (30 m0.32 mm20 m) for the analysis of compounds such as CO.sub.2, ethylene and butadiene; a DB-1701 column (30 m0.53 mm1 m) for the analysis of alcohols, aldehydes, esters, ketones and other non-condensed products into the trap.

[0102] The traps are changed approximately every hour and the condensed products contained inside are recovered, diluted in methanol and added with octane as an internal standard for the analyses. The solutions thus obtained are analysed by gas chromatograph coupled with a mass spectrometer (GC-MS, Agilent 6890N coupled with mass spectrometer Agilent Technologies 5973 Inert) equipped with an HP-5 ms capillary column (30 m250 m0.25 m). The details of the analysis method are as follows: injected volume 0.5 L, injector T: 280 C., split ratio: 50:1, carrier: He 1 ml/min, temperature ramp: isotherm at 40 C. for 7 minutes then ramp rate at 5 C./min up to 100 C. and ramp rate at 10 C./min up to 250 C., temperature then maintained for 2 minutes.

[0103] Conversions (X), yields (Y), selectivity(S) and carbon balance were calculated as follows:

[00001]$\%=\frac{n_{EtOH}^{in}-n_{EtOH}^{out}}{n_{EtOH}^{in}}100$$Y_p\%=\frac{C_{atom}^p.Math.n_p^{out}}{C_{atom}^{EtOH}.Math.n_{EtOH}^{in}}100$$S_p\%=\frac{Y_p}{}100$$\mathrm{Carbon}\mathrm{balance}=\frac{{.Math.}_i{Y}_{p_i}}{}100$ [0104] n being equal to the number of moles of the particular product p (or of the ethanol, EtOH) and C being the number of carbon atoms contained in the particular product p (or in the ethanol, EtOH).

[0105] In particular, the 40 most abundant and recurring chemical compounds in the mixtures exiting the reactor were selected and calibrated (by means of calibration straight lines with suitable commercial standards, where available, or with suitable isomers) in order to quantify their yields with a suitable response factor. Unless otherwise specified in the figures, the calibrated compounds and the remaining obtained products were grouped into three groups: [0106] Light others (C.sub.3-C.sub.5): GC-MS retention times from 0 to 6 minutes; [0107] Mid others (C.sub.6-C.sub.8): from 6 to 16.5 minutes; [0108] Heavy others (>C.sub.8): from 16.5 minutes to the end of the analysis.

[0109] The response factor of these compounds was estimated on the basis of the known response factors for the most similar molecules exiting in the same range of retention times and by averaging the number of carbon atoms of the molecules in the same range. The yields of these compounds were then calculated as follows:

[00002]$Y_{\mathrm{LIGHT}\mathrm{OTHERS}}\%=\frac{4.Math.{\mathrm{mol}}_p^{out}}{C_{atom}^{EtOH}.Math.{\mathrm{mol}}_{EtOH}^{in}}100$$Y_{\mathrm{MID}\mathrm{OTHERS}}\%=\frac{7.Math.{\mathrm{mol}}_p^{out}}{C_{atom}^{EtOH}.Math.{\mathrm{mol}}_{EtOH}^{in}}100$$Y_{\mathrm{HEAVY}\mathrm{OTHERS}}\%=\frac{10.Math.{\mathrm{mol}}_p^{out}}{C_{atom}^{EtOH}.Math.{\mathrm{mol}}_{EtOH}^{in}}100$

[0110] The results of the catalytic test are shown in FIG. 5.

[0111] It can be observed how the conversion of ethanol undergoes a more sudden drop as a function of the reaction time in the flow and the selectivity in the >C6 fraction generally remains lower than in FIG. 6, example 3 (same conditions but tau=2). This leads to a yield in the >C6 fraction equal to 5% under conditions of tau=1 s after 12 hours of reaction, while this yield is equal to 11% (more than double) under conditions of tau=2 s.

Example 3: Catalytic Test Under the Conditions: Cu/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =2 s

[0112] The catalyst used, Cu/t-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 1. The catalytic test was carried out as shown in example 2, modifying the overall volumetric flow and the amount of loaded catalyst so as to obtain tau=2 s. The results are shown in FIG. 6. The C6 fraction composition is shown in FIG. 7.

[0113] Under the above optimised conditions, the use of the Cu/t-ZrO.sub.2 catalyst with 5% by weight of Cu (5% by weight of metallic copper supported on tetragonal zirconia) made it possible to obtain ethanol conversions equal to 90% during the first two hours, with the product distribution shown in the following tables, which summarise the results shown in FIGS. 6 and 7. The percentages correspond to the Sp selectivities expressed as the ratio between product yield Y.sub.P and ethanol conversion X.sub.EtOH; SP=Y.sub.P/X.sub.EtOH. The yields are normalised on the carbon atoms of the various products. The <C.sub.6 others fraction brings together light minority components, of which n-butanol is the main one.

[0114] In particular, Table 1 shows the mixture composition exiting the plant after two hours of reaction, comparing it with that averaged over the first six hours of reaction.

TABLE-US-00001 TABLE 1 reaction mixture composition exiting the plant. Reaction conditions: 300 C., contact time: 2 s, 10 mol % EtOH in He, Cu/t-ZrO.sub.2 with 5% by weight of Cu. Ethanol conversion: 90% after 2 h, 83% averaged over the first 6 h. Selectivity Compound Selectivity after 2 h averaged over 6 h Acetaldehyde 27% 28% Acetone 2% 1% Ethyl acetate 4% 5% Butyraldehyde 7% 5% Crotonaldehyde 2% 3% 2-pentanone 5% 3% Butadiene 3% 6% CO.sub.2 2% 1% <C.sub.6 others 6% 6% C.sub.6 fraction 31% 26%

[0115] The C.sub.6 fraction is further divided into the following classes of compounds (Table 2). The composition is expressed as a molar fraction in percentage of the total C.sub.6 fraction (T.sub.eb>120 C.) obtained by removing the <C.sub.6 fraction with T.sub.eb<120 C. The C.sub.6 others fraction consists mainly of higher alcohols and aldehydes, together with other minority compounds.

TABLE-US-00002 TABLE 2 details about the C6 fraction composition. Reaction conditions: 300 C., contact time: 2 s, 10 mol % EtOH in He, Cu/t-ZrO.sub.2 with 5% by weight of Cu. Molar fraction % Molar fraction % Compound after 2 h averaged over 6 h Ethyl butyrate 11% 9% C.sub.8 esters 11% 12% Linear ketones 25% 11% Cyclic ketones 25% 27% Aliphatic hydrocarbons 8% 4% Aromatics 8% 16% C.sub.6 others 12% 21%

Example 4: Catalytic Test Under the Conditions: Cu/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =3 s

[0116] The catalyst employed, Cu/t-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 1. The catalytic test was carried out as shown in example 2, modifying the overall volumetric flow and the amount of loaded catalyst so as to obtain tau=3 s. The results are shown in FIG. 8.

Example 5: Catalytic Test Under the Conditions: Cu/t-ZrO.SUB.2 .with 1% by Weight of Cu, 300 C., =2 s

[0117] The catalyst employed, Cu/ZrO.sub.2 with 1% by weight of Cu, was synthesised as in example 1, modifying the amount of copper precursor used in the IWI in order to obtain a total copper load of 1% by weight of the final material. The catalytic test was carried out as shown in example 3 (tau=2 s). The results are shown in FIG. 9.

Example 6: Catalytic Test Under the Conditions: Cu/t-ZrO.SUB.2 .with 10% by Weight of Cu, 300 C., =2 s

[0118] The catalyst employed, Cu/ZrO.sub.2 with 10% by weight of Cu, was synthesised as in example 1, modifying the amount of copper precursor used in the IWI in order to obtain a total copper load of 10 wt % of the final material. The catalytic test was carried out as shown in example 3 (tau=2 s). The results are shown in FIG. 10.

Example 7: Catalytic Test Under the Conditions: CuO/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =2 s

[0119] The catalyst employed, CuO/t-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 1, with the exclusion of the last reduction step which was not carried out. Therefore, a suitable amount of material is loaded into the plant operating continuously in the vapour phase as described in example 2 and used directly, keeping the active phase in the form of cupric oxide. The catalytic test was carried out as shown in example 3 (tau=2 s). The ethanol conversion averaged over the first 6 h of reaction is 62% and the distribution of the products is shown in Table 3

TABLE-US-00003 TABLE 3 Results of the catalytic test under the conditions: CuO/t-ZrO.sub.2 with 5% by weight of Cu, 10 mol % EtOH in He, contact time 2 s, 300 C. Selectivity averaged Compound over 6 h Acetaldehyde 46% Ethyl acetate 5% Butyraldehyde 4% Crotonaldehyde 5% 2-pentanone 5% <C.sub.6 others 3% C.sub.6 fraction 18%

Example 8: Synthesis of Cu/m-ZrO.SUB.2 .with 5% by Weight of Cu

[0120] The ZrO.sub.2 support was obtained by hydrothermal synthesis in an autoclave at 140 C. for 20 h at autogenous pressure starting from an aqueous solution of ZrO(NO.sub.3).sub.2 and urea. The product is washed several times with ethanol, then it is dried and calcined at 450 C. for 3 hours, at a ramp rate of 5 C./min. In this way it is obtained zirconia in the monoclinic crystalline phase. The Cu was deposited on the support with the incipient wetness impregnation (IWI) method, by dissolving the amount of precursor (Cu(NO.sub.3).sub.2) necessary to obtain a copper load of 5% by weight of the final catalyst in a volume of water equal to the volume of the pores of the support. This solution is added drop by drop and evenly distributed on the support until it reaches the slurry point (filling of the pores). After which the sample is dried in a furnace and calcined at 450 C. for 5 hours, at a ramp rate of 2 C./min.

[0121] The powder thus obtained is subjected to a pelletising process so as to obtain particles of a defined size (20-40 mesh). A suitable amount of material is loaded into the plant operating continuously in the vapour phase as described in example 2 and subjected to a reduction process in a hydrogen flow at 350 C. for 3 hours so as to obtain the desired catalyst.

Example 9: Catalytic Test Under the Conditions: Cu/m-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =2 s

[0122] The catalyst employed, Cu/m-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 8. The catalytic test was carried out as shown in example 3 (tau=2 s) and the results are shown in FIG. 11. The >C.sub.6 fraction composition is shown in FIG. 12.

[0123] Under the same reaction conditions shown above, the use of the Cu/m-ZrO.sub.2 catalyst with 5% by weight of Cu (5% by weight of metallic copper supported on monoclinic zirconia) makes it possible to obtain a different distribution of products and a greater stability of the catalyst. During the first 6 hours of reaction the conversion stands at 96% with the following selectivity in the products.

[0124] Tables 4 and 5 summarise the results shown in FIGS. 11 and 12.

TABLE-US-00004 TABLE 4 reaction mixture composition exiting the plant. Reaction conditions: 300 C., contact time: 2 s, 10 mol % EtOH in He, Cu/m-ZrO.sub.2 with 5% by weight of Cu. Ethanol conversion: 98% after 2 h, 97% averaged over the first 6 h. Selectivity Compound Selectivity after 2 h averaged over 6 h Acetaldehyde 13% 17% Acetone 10% 9% Ethyl acetate 1% 2% Butyraldehyde 5% 7% 2-pentanone 23% 21% CO.sub.2 9% 8% <C.sub.6 others 4% 4% C.sub.6 fraction 35% 32%

[0125] The C6 fraction is further divided into the following classes of compounds (Table 5). The composition is expressed as a molar fraction in percentage of the total C.sub.6 fraction (T.sub.eb>120 C.) obtained by removing the <C.sub.6 fraction with T.sub.eb<120 C. The C6 others fraction consists mainly of higher alcohols and aldehydes, together with other minority compounds.

TABLE-US-00005 TABLE 5 details about the C6 fraction composition. Reaction conditions: 300 C., contact time: 2 s, 10 mol % EtOH in He, Cu/m-ZrO.sub.2 with 5% by weight of Cu. Molar fraction % Molar fraction % Compound after 2 h averaged over 6 h Ethyl butyrate 2% 5% C.sub.8 esters 8% 15% Linear ketones 80% 67% Cyclic ketones / 1% Aliphatic hydrocarbons 1% 1% Aromatics 2% 2% C.sub.6 others 7% 9%

Example 10: Synthesis of Cu/LaZrO with 5% by Weight of Cu

[0126] The LaZrO support was synthesised by precipitation in a basic environment at 25 C. starting from an aqueous solution of ZrO(NO.sub.3).sub.2*2H.sub.2O and La(NO.sub.3).sub.3*6H.sub.2O such that the atomic ratio La:Zr in the final material was 0.19 and the total cation concentration was 0.3 mol/l. The suspension was subjected to a digestion of 72 h at 100 C. and at controlled pH 10-12 by continuously adding a concentrated ammonia aqueous solution (28% w/w). The sample was then filtered, dried and calcined at 450 C. for 12 h at a ramp rate of 5 C./min. The Cu was deposited on the support using the incipient wetness impregnation (IWI) method, by dissolving the amount of precursor (Cu(NO.sub.3).sub.2) necessary to obtain a copper load of 5 wt % on the final catalyst in a water volume equal to the pore volume of the support. This solution is added drop by drop and evenly distributed on the support until it reaches the slurry point (filling of the pores). After which the sample is dried in a furnace and calcined at 450 C. for 5 h, at a ramp rate of 2 C./min.

[0127] The powder thus obtained is subjected to a pelletising process so as to obtain particles of a defined size (20-40 mesh). A suitable amount of material is loaded into the plant operating continuously in the vapour phase as described in example 2 and subjected to a reduction process in a hydrogen flow at 350 C. for 3 hours so as to obtain the desired catalyst.

Example 11: Catalytic Test with Cu/LaZrO with 5% by Weight of Cu, 300 C., =2 s

[0128] The catalyst was synthesised as in example 9. The catalytic test was carried out as shown in example 3 (tau=2 s) and the results are shown in FIG. 13. The C6 fraction composition is shown in FIG. 14.

Example 12: Catalytic Test with Cu/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =2 s, EtOH in He:H.SUB.2 .Flow in a 1:1 Ratio

[0129] The catalyst employed, Cu/t-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 1. The catalytic test was carried out as shown in example 3 (tau=2 s), but the carrier gas was modified from 100% He (as per example 3) to a mixture of He and H.sub.2 in a 1:1 ratio. The molar percent of EtOH was maintained at 10 mol % of the total fed moles. The results of the catalytic test are shown in FIG. 15. The C6 fraction composition is shown in FIG. 16.

Example 13: Catalytic Test with Cu/t-ZrO.SUB.2 .with 5% by Weight of Cu, 300 C., =2 s, 1-Butanol (10 Mol %) in He Flow

[0130] The catalyst employed, Cu/t-ZrO.sub.2 with 5% by weight of Cu, was synthesised as in example 1. The catalytic test was carried out as shown in example 3, modifying the reactant alcohol, i.e. feeding 1-butanol instead of ethanol. The results are shown in FIG. 17. The C6 fraction composition is shown in FIG. 18.

[0131] The present invention has been described for illustrative, but non-limiting purposes, according to its preferred embodiments, but it is to be understood that variations and/or modifications can be made by those skilled in the art without thereby departing from its scope of protection, as defined by the attached claims.

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