Magnetically separable iron-based heterogeneous catalysts for dehydrogenation of alcohols and amines

Abstract

The present invention discloses an iron-based nitrogen doped graphene catalyst, process for preparation thereof and use of said catalyst in oxidant-free catalytic dehydrogenation of alcohols and amines to the corresponding carbonyl compounds, amines and N-heterocylic compounds with extraction of molecular hydrogen as the only by-product.

Claims

1. An iron based nitrogen doped graphene catalyst comprising magnetically separable iron nanoparticles supported on a nitrogen doped graphene catalyst, wherein the iron nanoparticles have a diameter in the range of 10 to 50 nm and iron is present as Iron (III) oxide (Fe.sub.2O.sub.3), Iron (II/III) oxide (Fe.sub.3O.sub.4), Iron nitride (Fe.sub.3N) and Iron carbide (Fe.sub.3C, Fe.sub.7C.sub.3).

2. A process for dehydrogenation of alcohol or amine comprising the steps of: i. refluxing a reaction mixture of alcohol or amine, potassium tert-butoxide and an iron based nitrogen doped graphene catalyst in a solvent at a temperature in the range of 150 to 160 C. for the period in the range of 30 to 40 hrs to afford the desired products; characterized in that the yield of said desired products is in the range of 50 to 100%, wherein the iron based nitrogen doped graphene catalyst includes magnetically separable iron nanoparticles supported on a nitrogen doped graphene catalyst, wherein the iron nanoparticles have a diameter in the range of 10 to 50 nm and iron is present as Iron (III) oxide (Fe.sub.2O.sub.3), Iron (II/III) oxide (Fe.sub.3O.sub.4), Iron nitride (Fe.sub.3N) and Iron carbide (Fe.sub.3C Fe.sub.7C.sub.3).

3. The process as claimed in claim 2, wherein said solvent is selected from the group consisting of octane, mesitylene, xylene, toluene, decane, and dodecane.

4. The process as claimed in claim 2, wherein said alcohol is selected from the group consisting of: ##STR00086## wherein R represents mono, di, tri, tetra or penta substituents, wherein each such substituent is independently selected from the group consisting of H, linear or branched alkyl, (un)substituted or substituted cycloalkyl, (un) substituted or substituted aryl, (un)substituted or substituted heteroaryl,aIkoxy, phenoxy, (un)substituted or substituted amino, thio, halides, trifluromethyl, nitro, cyano or ester; Ri represents linear or branched alkyl, (un)substiluted or substituted cycloalkyl, (un)substituled or substituted aryl, (un)substituted or substituted heterocyclyl or (un)substituted or substituted heteroaryl; R.sub.2 represents H, linear or branched alkyl,(un)substituted or substituted cycloalkyl, (un)substituted or substituted aryl or (un)substituted or substituted heteroaryl, R.sub.3 represents hydrogen, (un)substituted or substituted alkyl, (un)substituted or substituted aryl, (un)substituted or substituted cycloalkyl or (un)substituted or substituted heteroaryl or R.sub.4 is selected independently from hydrogen, (un)substituted or substituted alkyl, (un)substituted or substituted aryl, (un)substituted or substituted cycloalkyl or (un)substituted or substituted heteroaryl; or R.sub.3 and R.sub.4 represent together (un)substdtuted or substituted cyclic compound; n=1 and 2, which may be further substituted by halides, alkyl (linear and branched), aryl which may be further substituted.

5. The process as claimed in claim 2, wherein said amine is selected from the group consisting of: ##STR00087## wherein R represents mono, di, tri, tetra or penta substituents, wherein each such substituent is independently selected from the group consisting of H, alkyl (linear and branched), cycloalkyl, aryl and heteroaryl (further substituted), alkoxy, phenoxy, amino (NH.sub.2, mono- or di-substituted), thio, halides, trifluromethyl, nitro, cyano, ester, R.sub.1 represents alkyl (linear and branched), cycloalkyl, aryl (which may be further substituted), heterocyclyl, heteroaryl; R.sub.2 represents an aryl fusion with substituents or aryl substituted (which may be further substituted), The substitution may be mono, di, tri or tetra substituents, wherein each such substituent is independently selected from the group consisting of H, alkyl (linear and branched), cycloalkyl, aryl and heteroaryl (further substituted), alkoxy, phenoxy, amino (NH.sub.2, mono- or di-substituted), thio, halides, trifluromelyl, nitro, cyano, ester; n=1 and 2, which may be further substituted by halides, alkyl (linear and branched), aryl which may have further substituents, X is selected from CH.sub.2 or NH.

6. The process as claimed in claim 2, wherein said desired product is carbonyl compound when alcohol used as reactant.

7. The process as claimed in claim 2, wherein said desired product is imine when said amine is of formula 1.

8. The process as claimed in claim 2, wherein said desired product is N-hetcrocyclic compound when said amine is cyclic amine of formula 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: X-ray Powder Diffraction (XRD) pattern of FeNG material with indices of peaks pattern of Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Fe.sub.7C.sub.3, Fe.sub.3N, Fe.sub.3C, and graphene.

(2) FIG. 2: (a) Transmission electron microscopy (TEM) image of FeNG; Scale bar, 50 nm. (b) Field Emission Scanning Electron Microscope (FESEM) image of FeNG; scale bar, 1 m.

(3) FIG. 3: Deconvoluted X-ray photoelectron spectroscopy (XPS) spectra of FeNG sample: (a) C1s region, (b) N1s region.

(4) FIG. 4: Energy-dispersive X-ray spectroscopy (EDX), analysis of FeNG.

(5) FIG. 5: Thermogravimetric Analysis (TGA) of graphene oxide (black) and FeNG(red).

(6) FIG. 6: Raman Spectra of RG (black) and FeNGR (red).

(7) FIG. 7: Qualitative analysis of H.sub.2 evolved.

(8) FIG. 8: Separation of the catalyst under strong magnetic field (left: reaction mixture; right: under magnetic field).

DETAILED DESCRIPTION OF THE INVENTION

(9) Present invention provides a magnetically separable and reusable iron nanoparticles supported on nitrogen doped graphene catalyst, wherein the magnetisable particles has diameter in the range of 10 to 50 nm.

(10) Iron is present as Iron (III) oxide (Fe.sub.2O.sub.3), Iron (II, III) oxide (Fe.sub.3O.sub.4), Iron nitride (Fe.sub.3N) and Iron carbide (Fe.sub.3C, Fe.sub.7C.sub.3).

(11) The present invention provides a cost effective, simple process for synthesis of magnetically separable iron nanoparticles supported nitrogen doped graphene catalyst comprising the steps of: a) sonicating the mixture of Iron(III) acetyl acetone and 1-10-phenanthroline in solvent for the period in the range of 1 to 2 h; b) sonicating exfoliated graphene oxide in solvent for the period in the range of 1 to 2 h; c) mixing the solutions of step (i) and (ii) and further sonicating the mixture for the period in the range of 1 to 2 h; d) refluxing the reaction mixture of step (c) at temperature in the range of 80 to 90 C. for the period in the range of 3 to 5 hrs followed by calcination to afford iron based nitrogen doped graphene catalyst.

(12) Solvent is selected from methanol, ethanol, isopropanol, and t-butanol.

(13) The catalysts may be used in general at upto 250 C. and the reactions may be carried out at any pressure. The novel catalysts can be separated from the reaction mixtures by applying magnetic field.

(14) As prepared graphene (not carbonized in Ar at 800 C. but has been thermally exfoliated at 160 C.)=EGO (Stands for Exfoliated Graphene Oxide).

(15) Graphene+1,10-Phenonthroline ligand carbonized at 800 C. in Ar (without Fe)=NG (Stands for N-doped graphene).

(16) As prepared Fe catalyst after the decomposition of Fe-1,10-Phenonthroline complex in Ar at 800 C.=FeNG (stands for Fe on N-doped graphene).

(17) RG (stands for EGO heat treated in Ar at 800 C.).

(18) The XRD pattern of FeNG sample is presented in FIG. 1, shows diffraction peaks confirming the presence of Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Fe.sub.3N and Fe.sub.7C.sub.3. A peak at 2=26.5 degrees corresponding to (002) lattice plane of graphite is observed. The peak is broad suggesting the carbon support is composed of a few layers of graphene sheets. Formation of Fe.sub.3N is due to the decomposition of Fe-phenonthroline complex on EGO. Formation of Fe.sub.3O.sub.4 and Fe.sub.2O.sub.3 is usually expected under the reaction conditions in argon atmosphere, where carbon in graphite can act as a reducing agent.

(19) In FIG. 2, the morphology of the as prepared FeNG catalyst is shown. In FIG. 2a, TEM image of FeNG sample is shown. In the bright field image, one can observe the wrinkles of the thin layers of graphene support as dark lines and Fe-rich nanoparticles as dark spots. It is observed that the nanoparticles are located only on the graphene sheets suggesting a strong chemical interaction between the nanoparticles and the support. The nanoparticles distributed throughout the graphene sheets varied in size from 8 to 50 nm.

(20) In FIG. 2b, the SEM image clearly shows graphene layers with supported Fe-rich nanoparticles. In the dark field FESEM image of FeNG sample, the secondary electrons captured made Fe-rich nanoparticles appear brighter than graphene due to higher electron density of the metal. It is observed that Fe-rich particles are distributed spatially apart and are well supported on the graphene layers.

(21) The FIG. 3a describes the C1s region of the spectra and FIG. 3b describes the N1s region of the spectra. C1s region of the XPS spectra of the catalyst show four different peaks at 283.5, 284.5, 285.8 and 287.3 eV. The peaks at 283.5 and 284.5 correspond to interstitial carbon in Fe.sub.7C.sub.3, and sp.sup.2 carbon (CC) groups respectively. The peak at 285.8 eV is ascribed to sp.sup.3 carbon such as CC or COH groups. The peak at 287.3 eV is due to carbonyl functional group.

(22) In FIG. 3b, XPS spectra of N1s region of the catalyst has been deconvoluted by fitting the spectra with four sub peaks at 397.5 (N of Fe.sub.3N), 399.1 (pyridinic-N/N.sub.Pyri.), 400.1 (pyrrolic-N/N.sub.pyrr.), 401.4 eV (quaternary-N/NR.sub.4.sup.+) and 403.6 eV (NO). The results are as shown in table 1 below.

(23) TABLE-US-00001 TABLE 1 XPS peaks of C1s and N1s in the FeNG Peak Position (eV) Inference C1s Spectra (FIG. 3a) 284.5 sp.sup.2 carbon (CC) 285.8 sp.sup.3 carbon such as CC or COH groups 287.3 Carbonyl functional group (CO). N1s Spectra (FIG. 3b) 397.5 N of Fe.sub.3N 399.1 pyridinic-N/N.sub.Pyri 400.1 pyrrolic-N/N.sub.Pyrr 401.4 quaternary-N/NR.sub.4.sup.+ 403.6 NO

(24) The EDAX analysis of the catalyst is depicted in FIG. 4. The results of weight percent of different elements in the FeNG is as shown in table 2.

(25) TABLE-US-00002 TABLE 2 Weight percent of different elements in the FeNG Element Weight % Atomic % Uncert. % Correction k-Factor C(K) 76.36 83.29 0.41 0.26 3.940 N(K) 9.23 8.64 0.17 0.26 3.826 O(K) 8.02 6.56 0.09 0.49 1.974 Fe(K) 6.37 1.49 0.06 0.99 1.403

(26) In FIG. 5 Trace (i) shows TGA curve of fresh graphitic oxide prepared by Hummers method that is used as the starting material to prepare our catalyst. A weight loss at 150 C. is due to loss of physisorbed moisture. The weight loss at 350 C. is characteristic of the loss of oxygen functional groups that are present on the surface of graphitic oxide in the form of epoxide, alcohol and carbonyl groups. In comparison to trace (i), trace (ii) did not show any weight loss at 150 and 350 C. Trace (ii) is graphitic oxide loaded with Fe-phenonthroline complex. The percentage weight loss due to loss of functional groups is not seen due to the presence of relatively heavier Fe element. In addition, Fe is also oxidized to Fe.sub.2O.sub.3 and Fe.sub.3O.sub.4. (FIG. 4)

(27) FIG. 6 shows Raman spectra for FeNG and reduced graphene. It mainly shows two peaks. The D band of FeNG located at 1327 cm.sup.1 and 1330 for EGRO. D band is due to the graphitic lattice vibration mode of A1 g symmetry of the sp.sup.2 carbon lattice and characterizes structural defects or edges that can break the symmetry and selection rule. G band was found at 1595 cm.sup.1 for FeNGR while at 1586 cm.sup.1 for EFGO. G band is due to first-order scattering of the E2 g mode observed for sp.sup.2 carbon domains, characterizes the highly ordered graphite carbon materials. The relative intensity ratio of D- and G-band (I.sub.D/I.sub.G) is a measure of disorder degree. Increased I.sub.D/I.sub.G ratio for FeNGR (I.sub.D/I.sub.G=1.36) as compared to EXGO (I.sub.D/I.sub.G=1.13) indicating increase in the disorder of graphene after doping of iron nanoparticle on graphene. Peak position G band represents interaction of nanoparticles with graphene. FeNGR shows 9 cm.sup.1 blue shift of G band as compared to EFGO is mainly due to charge transfer from graphene to Iron nanoparticles. However, the electronic role of other phases such as Fe.sub.3O.sub.4, Fe.sub.7C.sub.3 and Fe.sub.3N are difficult to rule ascertain.

(28) The present invention provides a process for dehydrogenation of alcohol or amine comprises refluxing the reaction mixture of alcohol or amine, potassium tert-butoxide and iron based nitrogen doped graphene catalyst in a solvent at temperature in the range of 150 to 160 C. for the period in the range of 30 to 40 hrs to afford the desired products; characterized in that the yield of said desired products is in the range of 50 to 100%.

(29) Said solvent is selected from octane, mesitylene, xylene, toluene, decane, and dodecane

(30) Said process is carried out under inert atmosphere.

(31) Said desired product is carbonyl compound when alcohol used as reactant.

(32) Said alcohol is represented by structure A, B, C, D or E;

(33) ##STR00003##
wherein

(34) R represents mono, di, tri, tetra or penta substituents, wherein each such substituent is independently selected from the group consisting of H, linear or branched alkyl, (un)substituted or substituted cycloalkyl, (un)substituted or substituted aryl, (un)substituted or substituted heteroaryl,alkoxy, phenoxy, (un)substituted or substituted amino, thio, halides, trifluromethyl, nitro, cyano or ester.

(35) R.sub.1 represents linear or branched alkyl, (un)substituted or substituted cycloalkyl, (un)substituted or substituted aryl, (un)substituted or substituted heterocyclyl or (un)substituted or substituted heteroaryl;

(36) n=1 and 2, which may be further substituted by halides, alkyl (linear and branched), aryl which may be further substituted.

(37) R.sub.2 represents H, linear or branched alkyl,(un)substituted or substituted cycloalkyl, (un)substituted or substituted aryl or (un)substituted or substituted heteroaryl.

(38) Wherein R.sub.3 is selected independently from hydrogen, (un)substituted or substituted alkyl, (un)substituted or substituted aryl, (un)substituted or substituted cycloalkyl or (un)substituted or substituted heteroaryl or R.sub.4 is selected independently from hydrogen, (un)substituted or substituted alkyl, (un)substituted or substituted aryl, (un)substituted or substituted cycloalkyl or (un)substituted or substituted heteroaryl;

(39) or

(40) R.sub.3 and R.sub.4 represent together (un)substituted or substituted cyclic compound.

(41) Said amine is represented by formula 1, 2, 3, 4 or 5;

(42) ##STR00004##

(43) Wherein, R represents mono, di, tri, tetra or penta substituents, wherein each such substituent is independently selected from the group consisting of H, alkyl (linear and branched), cycloalkyl, aryl and heteroaryl (further substituted), alkoxy, phenoxy, amino (NH.sub.2, mono- or di-substituted), thio, halides, trifluromethyl, nitro, cyano, ester.

(44) R.sub.1 represents alkyl (linear and branched), cycloalkyl, aryl (which may be further substituted), heterocyclyl, heteroaryl.

(45) Wherein, R.sub.2 represents an aryl fusion with substituents or aryl substituted (which may be further substituted). The substitution may be mono, di, tri or tetra substituents, wherein each such substituent is independently selected from the group consisting of H, alkyl (linear and branched), cycloalkyl, aryl and heteroaryl (further substituted), alkoxy, phenoxy, amino (NH.sub.2, mono- or di-substituted), thio, halides, triflurometyl, nitro, cyano, ester;

(46) n=1 and 2, which may be further substituted by halides, alkyl (linear and branched), aryl which may have further substituents.

(47) X is selected from CH.sub.2 or NH.

(48) Said desired product is imine when said amine is of formula 1.

(49) Said imine compound is selected from the following:

(50) ##STR00005##

(51) Said desired product is N-heterocycle compound when said amine is cyclic amine of formula 5.

(52) The process for the conversion of cyclic amines to N-heterocycle is shown below in Scheme 1:

(53) ##STR00006##

(54) In another preferred embodiment, said N-heterocycle compound is selected from the following:

(55) ##STR00007## ##STR00008## ##STR00009##

(56) The significant advantage of heterogeneous catalysts over soluble homogeneous catalysts is its capability for easy separation and recycling. The iron catalyst is easily separated from the reaction medium under the strong magnetic field, as shown in FIG. 8. The recovered heterogeneous Fe-catalyst was reused for alcohol dehydrogenation, at least, five cycles without considerable loss of the selectivity, although the activity has a slight decay after 5th cycle. The hot filtration test is carried out, and it is observed that no further aldehyde formation took place after the catalyst is filtered off at the conversion of alcohol in 67%. Inductively coupled plasma (ICP) analyzes confirmed that the iron concentration in the filtrate is less than 0.22 ppm. Notably, no aldehyde formation is observed in reaction under complete homogeneous condition.

EXAMPLES

(57) The following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

Example 1

Catalyst Preparation

(58) Iron catalyst on nitrogen doped graphene were prepared by mixing Iron(III) acetyl acetone 176 mg (0.5 mmol) and 1-10-phenanthroline 90 mg (0.5 mmol) in 30 mL of ethanol. The mixture was sonicated for 2 hr. In another beaker 560 mg of exfoliated graphene oxide (prepared by hummers method) in 70 mL of ethanol was taken and sonicated for 2 hr. Both the mixtures were mixed together and further sonicated for 2 hr and subsequently refluxed for another 4 hr and the solvent was evaporated using rotary evaporator. Black coloured powder was obtained. It was calcined at 800 C. in argon atmosphere for 4 hr with heating rate of 25 C./min.

Example 2A

Dehydrogenation of Primary Alcohols to Aldehydes

(59) A freshly prepared heterogeneous iron catalyst (10 mol %), .sup.tBuOK (8 mol %), primary alcohol (0.5 mmol) and 2 mL of mesitylene were added to a 15 mL Schlenk flask under an atmosphere of argon. The flask was equipped with a reflux condenser and the solution was heated at 155 C. (oil bath temperature) with stirring in an open system under argon for 36 hr (Table 3). The reaction products were analyzed by GC-MS. After cooling to room temperature, m-xylene was added as internal standard to the reaction mixture and the products were quantitatively analyzed by GC.

(60) TABLE-US-00003 TABLE 3 Catalytic dehydrogenation of alcohols to aldehyde and molecular hydrogen 0 Entry Reactant Product Conversion.sup.b Selectivity.sup.b 1 98 85 (71).sup.c 2 95 80 (67).sup.c 3 55 100 4 99 95 (88).sup.c 5 0 60 80 6 81 90 7 99 100 (92).sup.c 8 60 100 9 52 100 10 0 71 100 (59).sup.c 11 67 90 12 50 99 .sup.bConversion and selectivity based on GC of crude reaction mixture using m-xylene as an internal standard. .sup.cYields in parenthesis represent isolated yields.

Example 2B

Dehydrogenation of Sec. Alcohols to Ketones

(61) A freshly prepared heterogeneous iron catalyst (10 mol %), .sup.tBuOk (8 mol %), sec.alcohol (0.5 mmol) and 2 mL of mesitylene were added to a 15 mL Schlenk flask under an atmosphere of argon. The flask was equipped with a reflux condenser and the solution was heated at 155 C. with stirring in an open system under argon for 36 hr (Table 4). The reaction products were analyzed by GC-MS. After cooling to room temperature, m-xylene was added as internal standard to the reaction mixture and the products were quantitatively analyzed by GC.

(62) TABLE-US-00004 TABLE 4 Catalytic dehydrogenation of sec.alcohols to ketones with liberation of H.sub.2 Entry Reactant Product Conversion.sup.a Selectivity.sup.a 1 99 99 (92).sup.b 2 99 99 (89).sup.b 3 0 90 99 (81).sup.b 4 75 93 5 79 99 (68).sup.b 6 75 89 7 70 99 8 0 75 99 9 40 60 10 52 99 11 32 99 12 45 85 13 0 22 63 .sup.aConversion and selectivity based on GC of crude reaction mixture using m-xylene as an internal standard. .sup.bYields in parenthesis represent isolated yields.

Example 3

Dehydrogenation of Diol to Lactone

(63) A freshly prepared heterogeneous iron catalyst (10 mol %), .sup.tBuOk (8 mol %), diol (0.5 mmol) and 2 mL of mesitylenewere added to a 15 mL Schlenk flask under an atmosphere of argon. The flask was equipped with a reflux condenser and the solution was heated at 155 C. with stirring in an open system under argon for 36 hr. The reaction products were analyzed by GC-MS. After cooling to room temperature, m-xylene was added as internal standard to the reaction mixture and the products were quantitatively analyzed by GC.

(64) ##STR00062##

Example 4

Dehydrogenation of Amines to Imines

(65) ##STR00063##

(66) A freshly prepared heterogeneous iron catalyst (8 mol %), .sup.tBuOK (10 mol %), amines 1 (0.5 mmol) and 2 mL of octane were added to a 15 mL Schlenk flask under an atmosphere of argon. The flask was equipped with a reflux condenser and the solution was heated at 145 C. (oil bath temperature) with stirring in an open system under argon for 36 hrs. The reaction products were analyzed by GC and GC-MS. After cooling to room temperature, the reaction mixture was kept under magnetic field and the liquid portion was pipette out. To the solid catalysts ethyl acetate (32 mL) was added and repeated the same procedure. Finally the collected organic layer was concentrated under reduced vacuum and the compound was purified through deactivated silica gel chromatography.

Example 5

Dehydrogenation of Cyclic Amines to N-heterocycles

(67) ##STR00064##

(68) A freshly prepared heterogeneous iron catalyst (8 mol %), .sup.tBuOK (10 mol %), cyclic amines 4 (0.5 mmol) and 2 mL of octane were added to a 15 mL Schlenk flask under an atmosphere of argon. The flask was equipped with a reflux condenser and the solution was heated at 145 C. (oil bath temperature) with stirring in an open system under argon for 36 hrs. After cooling to room temperature, the reaction mixture was kept under magnetic field and the liquid portion was pipette out. To the solid catalysts ethyl acetate (32 mL) was added and repeated the same procedure. Finally the collected organic layer was concentrated under reduced vacuum and the compound was purified through deactivated silica gel chromatography.

(69) a) (Z)-N-benzvlideneaniline

(70) ##STR00065##

(71) .sup.1H NMR (500 MHz,CDCl.sub.3) 4.90 (s, 2H), 7.33-7.35 (m,1H), 7.43-7.44 (m, 4H), 7.48- 7.49 (d, J=4.8 Hz, 3H), 7.87-7.88 (m, 2H), 8.45 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 64.9, 126.9, 127.0, 128.2, 128.4, 128.5, 130.6, 136.0, 139.2, 161.8.

(72) b) (Z)-4-methyl-N-(4-methvlbenzylidene)aniline

(73) ##STR00066##

(74) .sup.1H NMR (500 MHz, CDCl.sub.3) 2.35 (s, 3H), 2.39 (s, 3H), 4.78 (s, 2H), 7.15-7.17 (d, J=7.9 Hz, 2H), 7.22-7.28 (d, J=6.4 Hz, 4H), 7.67-7.68 (d, J=7.9 Hz, 2H), 8.35 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 21.08, 21.4, 64.7, 127.9, 128.2, 129.1, 129.3, 133.6, 136.3, 136.5, 140.9, 161.7

(75) c) (Z)-4-chloro-N-(4-chlorobenzylidene)aniline

(76) ##STR00067##

(77) .sup.1H NMR (200 MHz, CDCl.sub.3) 4.66 (s, 2H), 7.11-7.28 (m, 6H), 7.49-7.53 (dt, J=6.9 Hz, 1H), 7.69-7.70 (s, 1H), 8.20 (s, 1H); .sup.13C NMR (25 MHz, CDCl.sub.3) 64.1, 125.9, 126.6, 127.2, 127.8, 129.9, 129.7, 129.8, 130.8, 134.3, 134.8, 137.6, 141.0, 160.8.

(78) d) (Z)-4-fluoro-N-(4-fluorobenzylidene)aniline

(79) ##STR00068##

(80) .sup.1H NMR (500 MHz, CDCl.sub.3) 4.78 (s, 2H), 7.04-7.07 (t, J=8.5 Hz, 2H), 7.10-7.14 (t, J=8.5 Hz, 2H), 7.30-7.33 (q, J=5.4 Hz, 2H), 7.78-7.81 (q, J=5.4 Hz, 2H), 8.35 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 64.0, 115.1, 115.6, 115.7, 129.3, 129.4, 130.0, 130.1, 132.2, 132.3, 134.8, 134.9, 160.4, 160.9, 162.9, 163.3, 165.3

(81) e) (E)-N-benzylideneaniline

(82) ##STR00069##

(83) .sup.1H NMR (500 MHz, CDCl.sub.3) 7.25-7.29 (m, 3H), 7.42-7.45 (t, J=7.6Hz, 2H), 7.50-7.51 (m, 3H), 7.93-7.95 (dd, J=3.6Hz, 2H), 8.49 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 120.8, 125.9, 128.7, 128.8, 129.1, 131.3, 136.1, 152.0, 160.4

(84) f) 1H-indole

(85) ##STR00070##

(86) .sup.1H NMR (200 MHz, CDCl.sub.3) 6.62-6.65 (m, 1H), 7.15-7.32 (m, 3H),7.44-7.49 (d, J=8.2 Hz, 1H), 7.70-7.75 (d, J=7.5 Hz, 1H), 8.19 (s, 1H); .sup.13C NMR (25 MHz, CDCl.sub.3) 102.6, 110.9, 119.8, 121.9, 124.1, 127.8, 135.7.

(87) g) 2-methyl-1H-indole

(88) ##STR00071##

(89) .sup.1H NMR (500 MHz, CDCl.sub.3) 2.46 (s, 3H), 6.29 (s, 1H), 7.15-7.21 (m, 2H), 7.30-7.31(d, J=7.6 Hz, 1H), 7.60-7.11(d, J=7.6 Hz, 1H), 7.75 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 13.6, 100.2, 110.2, 119.5, 120.8, 128.9, 135.1, 135.9.

(90) h) 5-bromo-1H-indole

(91) ##STR00072##

(92) .sup.1H NMR (500 MHz, CDCl.sub.3) 6.52-6.53 (s, 1H), 7.27-7.30 (m, 3H), 7.29 (s, 1H), 8.22 (bs, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 120.3, 112.4, 113.0, 123.2, 124.8, 125.3, 129.6, 134.4.

(93) i) 1H-indole-2-carboxylic acid

(94) ##STR00073##

(95) .sup.1H NMR (500 MHz, CDCl.sub.3) 7.18-7.21 (t, J=7.6 Hz, 1H), 7.36-7.40 (m, 2H), 7.46-7.47 (d, J=8.2 Hz, 1H), 7.73-7.75 (d, J=8.2 Hz, 1H), 8.97 (bs, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 110.8, 111.9, 121.1, 122.9, 126.1, 127.4, 137.3, 166.1.

(96) j) 1H-indole-5-carbaldehyde

(97) ##STR00074##

(98) .sup.1H NMR (500 MHz, CDCl.sub.3) 6.72-6.73 (s, 1H), 7.33-7.34 (t, J=3.0 Hz, 1H), 7.49-7.50 (d, J=8.2 Hz, 1H), 7.78-7.80 (dd, J=8.5 Hz, 1H), 8.20 (s, 1H), 8.95 (bs, 1H), 10.06 (s, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 104.3, 111.8, 122.2, 126.3, 127.7, 129.6, 139.4, 192.8.

(99) k) 1H-pyrrolo [2.3-b]pyridine

(100) ##STR00075##

(101) .sup.1H NMR (500 MHz, CDCl.sub.3) 2.97 (bs, 1H), 6.54-6.54 (d, J=3.0 Hz, 1H), 7.11-7.14 (q, J=4.8 Hz, 1H), 7.41-7.41 (q, J=3.3 Hz, 1H), 8.00-8.02 (d, J=7.6Hz, 1H), 8.35-8.35 (d, J=4.5 Hz, 1H), .sup.13C NMR (125 MHz, CDCl.sub.3) 110.8, 115.8, 120.7, 125.4, 129.4, 141.9, 148.2.

(102) l) Isoquinoline

(103) ##STR00076##

(104) .sup.1H NMR (200 MHz, CDCl.sub.3) 7.34-7.79 (m, 4H), 8.09-8.13 (d, J=7.9 Hz, 2H), 8.90 (s, 1H); .sup.13C NMR (25 MHz, CDCl.sub.3) 120.9, 126.4, 127.6, 128.1, 129.2, 129.3, 135.9, 148.0, 150.1.

(105) m) Quinoline

(106) ##STR00077##

(107) .sup.1H NMR (200 MHz, CDCl.sub.3) 7.63-7.95 (m, 5H), 8.50-8.52 (d, J=5.1Hz, 1H), 9.24 (s, 1H); .sup.13C NMR (25 MHz, CDCl.sub.3) 120.4, 126.3, 127.1, 127.5, 128.5, 130.2, 135.6, 142.7, 152.3.

(108) n) 8-methylquinoline

(109) ##STR00078##

(110) .sup.1H NMR (50 MHz, CDCl.sub.3) 7.33-7.45 (m, 2H), 7.53-7.57 (d, J=6.8Hz, 1H), 7.62-7.66 (d, J=8.0Hz, 2H), 8.08-8.12 (d, J=8.3Hz, 1H), 8.93-8.96 (d, J=1.7Hz, 2H); .sup.13C NMR (125 MHz, CDCl.sub.3) 18.0, 120.6, 125.7, 126.1, 128.0, 129.4, 136.1, 136.8, 147.1, 149.0, 149.0

(111) o) 3-methylquinoline

(112) ##STR00079##

(113) .sup.1H NMR (200 MHz, CDCl.sub.3) 2.37 (s, 3H), 7.37-7.44 (t, J=7.0 Hz, 1H), 7.51-7.64 (m, 2H), 7.51 (s, 1H), 8.01-8.05 (d, J=8.4 Hz, 1H), 8.69 (s, 1H); .sup.13C NMR (25 MHz, CDCl.sub.3) 18.6, 126.4, 127.1, 128.3, 129.1, 134.6, 152.3.

(114) p) 6-methylouinoline

(115) ##STR00080##

(116) .sup.1H NMR (500 MHz, CDCl.sub.3) 2.47 (s, 3H), 7.26-7.29 (d, J=4.2 Hz, 1H), 7.48-7.49 (m, 2H), 7.97-8.00 (t, J=8.5 Hz, 2H), 7.80-8.81 (dd, J=3.9 Hz, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 21.3, 120.8, 126.4, 128.1, 128.8, 131.5, 135.1, 136.1, 146.6, 149.2.

(117) q) 6-methoxyquinoline

(118) ##STR00081##

(119) .sup.1H NMR (500 MHz, CDCl.sub.3) 3.92 (s, 3H), 7.05-7.06(d, J=2.7 Hz, 1H), 7.32-7.34 (q, J=4.2 Hz, 1H), 7.35-7.38 (dd, J=9.1 Hz, 1H), 7.99-8.01 (d, J=9.1 Hz, 1H), 8.02-8.04 (d, J=8.2 Hz, 1H), 8.75-8.76 (d, J=4.2 Hz, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 55.4, 105.1, 121.3, 122.2, 129.3, 130.8, 134.7, 144.4, 147.9, 157.7.

(120) r) 2-methylquinoline

(121) ##STR00082##

(122) .sup.1H NMR (500 MHz, CDCl.sub.3) 2.70 (s, 1H), 7.18-7.20 (t, J=8.2Hz, 1H), 7.40-7.43 (t, J=7.9Hz, 1H), 7.61-7.64 (t, J=8.5Hz, 1H), 7.68-7.70 (d, J=7.9Hz, 1H), 7.94-7.95 (d, J=8.5Hz, 1H), 7.99-8.01 (d, J=8.5Hz, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 25.2, 121.8, 124.4, 126.3, 127.3, 128.4, 129.2, 135.9, 147.7, 158.8.

(123) s) benzo[h]quinoline

(124) ##STR00083##

(125) .sup.1H NMR (500 MHz, CDCl.sub.3) 7.49-7.51 (q, J=4.2 Hz, 1H), 7.65-7.67 (d, J=8.8 Hz, 1H), 7.70-7.73 (td, J=6.7 Hz, 1H), 7.75-7.81 (m, 2H), 7.91-7.92 (d, J=8.2 Hz, 1H), 8.13-8.15 (dd, J=7.9 Hz, 1H), 9.02-9.03 (dd, J=4.5 Hz, 1H), 9.34-9.36 (d, J=7.6 Hz, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 121.6, 124.3, 125.2, 126.3, 126.9, 127.7, 128.1, 131.4, 133.5, 135.6, 146.5, 146.5, 148.7.

(126) t) Acridine

(127) ##STR00084##

(128) .sup.1H NMR (500 MHz, CDCl.sub.3) 7.49-7.51 (q, J=5.4 Hz, 2H), 7.74-7.78 (m, 2H), 7.94-7.97 (t, J=8.2 Hz, 2H), 8.24-8.25 (t, J=8.8 Hz, 2H), 8.69-8.71 (d, J=9.7 Hz, 1H); .sup.13C NMR (125 MHz, CDCl.sub.3) 125.6, 126.5, 128.1, 129.3, 130.1, 149.0.

(129) u) Ouinoxaline

(130) ##STR00085##

(131) .sup.1H NMR (500 MHz, CDCl.sub.3) 7.41(s, 2H), 7.78-7.81 (m, 2H), 8.51-8.54 (m, 2H); .sup.13C NMR (125 MHz, CDCl.sub.3) 128.8, 129.3, 142.2, 144.3.

Example 6

Reusability and Heterogeneity

(132) The significant advantage of heterogeneous catalysts over soluble homogeneous catalysts is its capability for easy separation and recycling. The iron catalyst was easily separated from the reaction medium under the strong magnetic field, as shown in FIG. 8. The recovered heterogeneous Fe-catalyst was reused for alcohol dehydrogenation, at least, five cycles without considerable loss of the. The hot filtration test was carried out, and it was observed that no further aldehyde formation took place after the catalyst was filtered at the conversion of alcohol in 67%. Inductively coupled plasma (ICP) analyzes confirmed that the iron concentration in the filtrate was less than 0.22 ppm. Notably, no aldehyde formation was observed in reaction under complete homogeneous condition All these results clearly demonstrate that the present Fe-catalysis is truly heterogeneous in nature.

ADVANTAGES OF THE INVENTION

(133) Novel catalyst FeNG heterogeneous catalyst which uses commercially inexpensive, earth-abundant elements such as carbon and Iron unlike several organometallic complexes containing precious metals such as Ru, Ir, and Rh. Employs a simpler method of preparation of catalyst. The catalyst does not require any hydrogen acceptor unlike its heterogeneous counterparts based on Ru, Ag, Au and Re. The catalyst is magnetically separable. The process is carried out under inert atmosphere.