Synthesis of functionalized carbon microspheres and their catalyst activity in C—O and C—N bond formation reactions

Abstract

Disclosed herein is a simple process for functionalization/grafting of carbon microspheres obtained from bagasse with various active functional groups onto it and use of the same as catalyst for various organic reactions, having very high selectivity and conversion rate.

Claims

1. A process for preparation of functionalized carbon microspheres by grafting catalytically active functional groups on to carbon microspheres obtained from bagasse to generate an acidic or basic surface wherein said process comprises the steps of: a) heating bagasse, water and oxalic acid at a temperature ranging between 150 to 180 C. for a time period ranging between 6 to 12 hours to obtain carbon microspheres; and b) refluxing of carbon microspheres as obtained in step (a) and an organic solvent selected from the group consisting of n-pentane, n-hexane, toluene, and lower alcohols in the presence of a functional group grafting agent at a temperature ranging between 80-120 C. for a time period in the range of 8 to 12 hours to obtain functionalized carbon microspheres, wherein a CO formation reaction is an epoxidation process which comprises mixing an olefin, an oxidant H.sub.2O.sub.2, an organic solvent acetonitrile and amine functionalized carbon microspheres to obtain a reaction mixture followed by immersing the reaction mixture in a thermostat oil bath at a temperature ranging between 60-80 C. for a time period ranging between 24 to 48 hours to obtain an epoxide with yield in the range of 45-90%.

2. The process as claimed in claim 1, wherein the olefin is selected from the group consisting of cyclic olefines selected from the group consisting of Cyclohexene, Cyclococetene, 1,3 cyclohexene, Pentene, and 1,5 cyclooctadiene.

3. The process as claimed in claim 1, wherein the epoxide is produced from cyclic epoxides selected from the group consisting of Cyclohexeneepoxide, Cycloocene epoxide, Penteneoxide-oxabicyclo[4.1.0]hept-2-ene 1, and Z)-9-oxabicyclo[6.1.0]non-4-ene.

4. The process as claimed in claim 1, wherein a CN bond formation reaction is a nitroaldol reaction which comprises mixing substituted benzaldehyde selected from the group consisting of benzaldehyde, and p-hydroxybenzaldehyde, nitromethane and amine functionalized carbon microspheres to obtain a reaction mixture followed by immersing the reaction mixture in a thermostat oil bath at a temperature in the range of 70-100 C. for a time period in the range of 0.5 to 35 hours to obtain nitroalcohol and nitrostyrene with yield in the range of 30 to 95% and conversion in the range of 10 to 98%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts the TEM of carbon microspheres.

(2) FIG. 2 depicts the .sup.13C NMR of carbon microspheres prepared at different conditions.

(3) FIG. 3 depicts the .sup.13C NMR of amine functionalized carbon microspheres.

(4) FIG. 4 depicts the .sup.29Si NMR of amine functionalized CMS.

(5) FIG. 5 depicts the P-XRD of amine functionalized CMS

(6) FIG. 6 depicts the thermo-gravimetric analysis (TGA) of prepared amines-CMS

(7) FIG. 7 depicts FTIR (Fourier transform infrared spectroscopy) of CMS and amine functionalized (NH.sub.2) CMS.

(8) FIG. 8 depicts the CHN (elemental) analysis of CMS and amine functionalized (NH.sub.2) CMS.

(9) FIGS. 9A and 9B depict the FTIR of CMS and OX-CMS (oxidized-CMS)

DETAILED DESCRIPTION OF THE INVENTION

(10) The present invention relates to a process for grafting catalytically active functional groups on to the functionalized carbon microsphere (CMS) obtained from bagasse to generate acidic or basic surface, wherein said grafted carbon microsphere is stable and can be used as a catalyst in various organic reactions comprising; a) heating a mixture of bio derived material and distilled water, optionally in the presence of an acid to a temperature in the range of 180-210 C. for 4 to 12 h, to obtain functionalized carbon microspheres as black solid, and b) dispersing the black solid obtained in step (a) in dry toluene and adding functional groups for post grafting followed by refluxing for 8 h to yield corresponding grafted/functionalized carbon microsphere.

(11) The bio derived material used in step (a) of the process is selected bagasse which mainly contain of cellulose, pentosan, and lignin as a carbon source.

(12) The organic solvent used in step (b) of the process is selected from aliphatic or aromatic hydrocarbons such as n-pentane, n-hexane, toluene or lower alcohols.

(13) The functionalized carbon microspheres obtained in step (a) are post grafted with functional groups selected from, but not limited to the group consisting of silylated acid, amine, SO.sub.3H groups to obtain acidic, basic or bi functional characteristics.

(14) The grafted/functionalized CMS prepared by the process of the instant invention can be used as metal free catalyst for various organic reactions that generate CN and CO bond formation, which generates no hazardous byproduct, and has very high conversion rate of substrate. Further, the grafted/functionalized CMS can also be used as support for dispersing various active components on them.

(15) The diameter or the particle size of grafted/functionalized CMS prepared by the process of the instant invention having active functional groups is in the range of 1-5 M.

(16) The present invention provides a grafted/functionalized carbon microsphere comprising active functional groups selected from, but not limited to the group consisting of silylated acid, amine, SO.sub.3H groups thereby having acidic or basic surface, wherein the said grafted carbon microsphere is stable and useful as catalyst in various organic reactions

(17) The grafted/functionalized CMS prepared by the process of the instant invention due to their further functionalized nature imparts structural stability to the said carbon microsphere when used as catalysts or active component and does not leach out during organic reactions, leading to an efficient recyclable catalyst.

(18) The present invention discloses a simple one step process for the synthesis of functionalized carbon microspheres (CMS) comprising mixing bio derived material with distilled water to obtain a mixture and heating to 180-210 C. for 4 to 12 h, in the presence of an acid, to afford the product as black solid.

(19) The surface of the CMS so obtained contain hydroxyl, carboxyl, esters, ethers, carbonyl groups, that provide ease in functionalization to create hydrophilic and hydrophobic surface using a short-chain diol, acid or a long-chain alkylamine.

(20) The biomass is selected from celluloses, sugars such as glucose, fructose, sucrose bagasse and such like.

(21) The acid is selected from the group consisting of oxalic acid, succinic acid, glutaric acid, adipic acid and such like. The carbon microsphere obtained are uniform microspheres of porous carbon and have diameter in the range of 1-10 m; preferably 4-5 m. Further, the synthesized CMS are characterized by SEM, TEM, FTIR and NMR. Transmission electron microscopy (TEM) measurements were performed on a Tecnai G2-20 FEI instrument operating at an accelerating voltage at 200 kV, refer FIG. 1. Samples were withdrawn periodically and analysed on Agilent 6890 Gas chromatograph equipped with a HP-5 dimethyl polysioxane column (60 m length, 0.25 mm diameter and 0.25 m film thicknesses with flame ionization detector. Products were confirmed by injecting the authentic on GC and GCMS.

(22) The present invention provides use of functionalized/grafted carbon microspheres (CMS) as catalyst for organic reactions which generates that generate CN and CO bond formation with high conversion rate of the substrate.

(23) The present invention provides an epoxidation process of 90% conversion and 96% selectivity catalyzed by the instant carboxyl functionalized carbon microspheres comprising:

(24) a. mixing Olefin, H.sub.2O.sub.2, Acetonitrile and carboxyl functionalized carbon microspheres as prepared above to obtain a reaction mixture and b. immersing the reaction mixture obtained in step (a) in thermostat oil bath at 80 C. for 48 h to obtain the desired epoxide.

(25) The present invention provides the nitroaldol reaction/Henry reaction catalyzed by the instant amine functionalized carbon microspheres comprising: a) mixing hydroaldehyde, nitromethane and amine functionalized carbon microspheres as prepared above to obtain a reaction mixture; and b) immersing the reaction mixture obtained in step (a) in thermostat oil bath at 90 C. for 2 h to obtain the desired product.
The process is shown in Scheme 1 below:

(26) ##STR00001##

(27) The % conversion obtained is 100% and % product selectivity is 90% of -nitrostyrene as the major product obtained in Henry reaction. Recyclability studies performed using the instant catalyst indicated 100% conversion and 100% selectivity.

(28) (Table 1)

(29) Thus the present invention provides an efficient tethering of the active organic acid and/or base functional groups onto a robust carbon support which will be metal free catalyst for various organic reactions which generates minimum hazardous byproduct, having very high conversion of substrate and yielding as the nitroaldol and epoxide as products.

EXAMPLES

(30) The following examples are given by way of illustration of working of the invention in actual practice and should not be constructed to limit the scope of the present invention in any way

Example 1

(31) Synthesis of Carbon Microspheres (CMS) from Cellulose:

(32) 100 mL stainless steel reactor was charged with 4 gm of cellulose, 50 mL distilled water and 0.25 gm of oxalic acid and reactor was closed and kept static at 180 C. for 8 h. Then reactor was cooled to room temperature (25 C.). The black solid was collected by and filtered under vacuum using whatman filter paper no 41 and washed with water (4100 mL) followed by ethanol (250 mL) and final product was dried at room temperature (25 C.). Product weight1.02 g

Example 2

(33) Synthesis of Carbon Microspheres (CMS) from Bagasse:

(34) 100 mL stainless steel reactor was charged with 4 gm of bagasse (sample of bagasse was taken from Vikas SSK limited, Vaishali Nagar, Nivali Taluka & DistLatur, Maharashtra), 50 mL distilled water and 1 gm of oxalic acid and reactor was closed and kept static at 180 C. for 12 h. Then reactor was cooled to room temperature (25 C.). The black solid was collected by and filtered under vacuum using whatmann filter paper no 41 and washed with water (4100 mL) followed by ethanol (250 mL) and final product was dried at room temperature (25 C.). Product weight1.09 g

Example 3

(35) Synthesis of Amine Functionalized Carbon Microspheres (CMS) in Toluene:

(36) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 1 g of carbon microspheres as obtained in example 2 and 200 mL dry toluene and 1 gm of 3-aminopropyltrimethoxysilane (APTMS). The reaction mixture was refluxed for 8 h 110 C. followed by cooling the reaction mixture to room temperature (25 C.) and filtering it by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.). Product weight0.512 g CHN analysis given in FIG. 8

Example 4

(37) Synthesis of Amine Functionalized Carbon Microspheres (CMS) in IPA:

(38) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 0.5 g of carbon microspheres as obtained in example 2 and 200 mL dry isopropyl alcohol and 0.5 gm of aminopropyltrimethoxysilane (APTMS). The reaction mixture was refluxed for 8 h at 80 C. then the reaction mixture was cooled to room temperature (25 C.) and filtered by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.). Product weight0.504 g

Example 5

(39) Synthesis of 2 Amine Functionalized Carbon Microspheres (CMS) in Toluene:

(40) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 1 g of carbon microspheres as obtained in example 2 and 200 mL dry toluene and 1 gm of (3-(2aminoethylamino) propyl)-trimethoxysilane. The reaction mixture was refluxed for 8 h 110 C. followed by cooling the reaction mixture to room temperature (25 C.) and filtering it by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.). Product weight0.512 g CHN analysis given in FIG. 8

Example 6

(41) Synthesis of 2 Amine Functionalized Carbon Microspheres (CMS) in IPA:

(42) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 1 g of carbon microspheres as obtained in example 2 and 200 mL dry isopropyl alcohol and 1 gm of (3-(2aminoethylamino) propyl)-trimethoxysilane. The reaction mixture was refluxed for 8 h 80 C. then the reaction mixture was cooled to room temperature (25 C.) and filtered by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.). Product weight0.504 g

Example 7

(43) Synthesis of SO.sub.3H Functionalized Carbon Microspheres (CMS) in Toluene:

(44) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 0.5 g of carbon microspheres as obtained in example 2 and 200 mL dry isopropyl alcohol and 0.5 gm of (3-(mecaptopropyl)-trimethoxy silane. The reaction mixture was refluxed for 8 h at 110 C. then the reaction mixture was cooled to room temperature (25 C.) and filtered by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.) named as SH-CMS Product weight0.510 g

(45) Then 0.5 gm SH-CMs was dispersed in 25 mL of toluene and added 5 mL of 30% H.sub.2O.sub.2 and stirred at room temperature for 24 hr. then filtered and washed with water and ethanol and dried at room temperature. Yield: 0.425 gm.

Example 8

(46) Synthesis of COOH Functionalized Carbon Microspheres (CMS) in Toluene:

(47) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 1 g of carbon microspheres as obtained in example 2 and 250 mL dry toluene and 1 mL gm of 3-cyanopropyltriethoxysilane. The reaction mixture was refluxed for 24 h at 110. then the reaction mixture was cooled to room temperature (25 C.) and filtered by vacuum and washed with toluene (325 mL) and dichloromethane (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.) named as CNCMs.

(48) Product weight1.110 g and product were characterized with FTIR.

(49) Then 0.5 gm CN-CMs was dispersed in 25 mL of toluene and added 5 mL of 70% H.sub.2SO.sub.4 and stirred at room temperature for 24 hr. then filtered and washed with water and ethanol and dried at room temperature. Yield: 0.425 gm.

Example 9

(50) Synthesis of COOH Functionalized Carbon Microspheres (CMS)

(51) The functionalization of CMS was carried out in a two necked round bottom flask fitted with water condenser charged with 1 g of carbon microspheres as obtained in example 2 and 4.5 ml of conc.HNO.sub.3. The reaction mixture was heated at 90 C. for 6 h. then the reaction mixture was cooled to room temperature (25 C.) and filtered by vacuum and washed with acetone (325 mL) and water (225 mL) and finally with ethanol (225 mL). Final reaction mixture was dried at room temperature (25 C.) named as COOHCMs Product weight0.350 g and product were characterized with FTIR See FIG. 9.

Example 10

(52) Nitroaldol Reaction

(53) The liquid phase Henry reaction was carried out in a two necked round bottom flask fitted with water condenser charged with substituted benzaldehyde (0.01 mol) and Nitromethane8 ml and 10 mg of amine functionalized carbon microspheres as prepared in example 4. The reaction was initiated by immersing in a thermostat oil bath at 90 C. and stirring at 600 pm. The reaction was carried out for till completion. The samples were withdrawn periodically and analysed on Agilent 6890 Gas chromatograph. Results are summarised in table 1.

(54) TABLE-US-00001 TABLE 1 % Conversion and % selectivity of catalyst Time % Selectivity (%) Sr. No. Sustrate Catalyst (H) Con alcohol Styrene 1 P-nitrobenzaldehyde CMS before 30 0 0 0 functionalization 2 P-nitrobenzaldehyde Functionalized 30 0 0 0 CMS obtained from glucose 3 P-nitrobenzaldehyde 1 NH.sub.2in T 8.30 28 100 28 78 100 4 P-nitrobenzaldehyde 1 NH.sub.2in IPA 10 20 100 35 100 29 71 5 P-nitrobenzaldehyde 2 NH.sub.2in T 9 78 100 22 79 100 6 P-nitrobenzaldehyde 2 NH.sub.2in IPA 35 69 100 7 Benzaldehyde CMS 0 0 0 0 8 Benzaldehyde 1 NH.sub.2 in T 6 40 59 41 9 Benzaldehyde 2 NH.sub.2 in T 4 98 43 57 10 p- CMS 0 0 0 0 hydroxybenzaldehyde 11 p- 1 NH.sub.2 in T 30 min 100 100 0 hydroxybenzaldehyde 12 p- 2 NH.sub.2 in T 30 min 100 6 94 hydroxybenzaldehyde

(55) Reaction Conditions:p-nitro benzaldehyde/Benzaldehyde/p-hydroxybenzaldehyde: 0.1 gm; nitro methane: 8 mL; Catalyst: 0.01 gm; Temp:90 C.T-toluene, IPA-Isopropyl alcohol

Example 11

(56) Oxidation of Olefines Reaction

(57) The liquid phase oxidation of olefines was carried out in a two necked round bottom flask fitted with water condenser charged with olefines (2.5 mmol) and oxidant (5 mmol)- and 10 wt % of catalyst to substrates acid functionalized carbon microspheres as prepared in example-14. The reaction was initiated by immersing in a thermostat oil bath at 80 C. and stirring at 600 pm. The reaction was carried out for 48 h. The samples were withdrawn periodically and analysed on Agilent 6890 Gas chromatograph. It gave 90% conversion and 96% selectivity to epoxide as major product.

(58) TABLE-US-00002 Selec- tivity (%) Sr. Oxi- Time Conver- Epox- No. Substrate dant Structure of product (hr) sion (%) ide 1 H.sub.2O.sub.2 48 90 96 2 H.sub.2O.sub.2 28 94 100 3 H.sub.2O.sub.2 48 78 80 4 H.sub.2O.sub.2 40 96 58.4 (mono) 5 0 H.sub.2O.sub.2 60 45 75
Advantages of Invention:
The major advantages of this process are as follows: 1. Simple, inexpensive synthetic procedure for functionalization of active groups onto surface of carbon and better catalyst 2. Use of simple source of bio-derived sugars 3. Grafting of various catalytically active functional groups onto the carbon microsphere such as NH.sub.2, COOH. 4. Formation of CN bond reaction 5. Formation of CO bond reaction 6. Very high selectivity towards epoxide 7. Use of green oxidant and hence environmentally benign process 8. Easily recyclable catalyst.