Process for producing furan and its derivatives

Abstract

An efficient, hydrogen gas-free, high yielding, moderate temperature and safe-to-handle process for producing furan and its derivatives from furfural, which comprises contacting furfural and water-isopropanol mixture with a supported Pd or Pt catalyst at a temperature in the range of 200-250 C., is reported.

Claims

1. An improved process for the preparation of a compound of formula I from furfural ##STR00004## wherein R.sub.1 is independently hydrogen or CH.sub.3 comprising contacting furfural and water-isopropanol mixture with a supported metal catalyst in a reactor in the presence of a co-feed inert gas at a temperature in the range of 200-250 C., wherein the inert gas is at pressure in the range 1 to 10 bar so as to obtain the compound of formula I, and wherein the supported metal catalyst is a supported Pd or Pt catalyst.

2. The process as claimed in claim 1, wherein the ratio by weight of furfural to the water-isopropanol is in the 1:5 to 1:25.

3. The process as claimed in claim 1, wherein weight ratio of catalyst to furfural ranges between 2 and 5 wt %.

4. The process as claimed in claim 1, wherein the Pd or Pt catalyst content on the support ranges from 2-10 wt %.

5. The process as claimed in claim 4, wherein a support to the metal catalyst is selected from the group consisting of alumina, ceria, zirconia, ceria-zirconia, sulphated zirconia, silica, carbon, clay, hydrotalcite, MgOAl.sub.2O.sub.3 and mixtures thereof.

6. The process as claimed in claim 1, wherein the reaction is carried out in a semi-batch, continuous stirred tank or a fixed-bed reactor.

7. The process as claimed in claim 1, wherein the inert gas is nitrogen gas, argon gas, helium gas or a mixtures of two or more of such gases.

8. The process as claimed in claim 1, wherein the water-iso-propanol ratio by weight in the mixture is between 1:1 and 1:5.

9. The process as claimed in claim 1, wherein the catalyst is a recyclable catalyst.

10. The process as claimed in claim 1, wherein the wt % furfural converted to the compound is in the range of 29-99.7 wt %.

11. The process as claimed in claim 1, wherein the yield of the compound of formula 1 is in the range of 68-90 wt %.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention provides an improved process for preparation of furan and its derivatives from furfural. The present invention provides improved, hydrogen gas-free, high yielding, moderate temperature and safe-to-handle, green process for producing furan and its derivatives from furfural comprising contacting furfural and water-iso-propanol mixture with a supported Pd or Pt catalyst in the presence of an inert gas co-feed.

(2) Furfural used in this process is obtained either from the conventional sources or from the pentosan sugars of lignocellulosic biomass by the methods known in art (ChemSusChem, Year 2012, Vol. 5, pp. 751-761 and Sugar Technology, Year 2011, Vol. 13, issue 2, pp. 166-169).

(3) Moreover, the hydrogen-free, moderate temperature, high yielding, safe-to-handle process of the present invention leads to production of furan and its derivative at the site of its raw material production itself and thereby, enabling value addition to biomass and employment/economic opportunities to rural sector.

(4) The method of the present invention uses a supported Pd or Pt catalyst. It is a surprising discovery that the supported Pd or Pt catalyst of the present invention exhibits high activity and furan selectivity even without the use of hydrogen in the process. No side reactions are observed. More particularly, the catalyst is reusable. In the experiments leading to the present invention, it was found that the catalyst-supported Pd or Pt of the present invention is highly active yielding furfural conversion of 100 mol % and furan selectivity in the range of 75-90 mol %. Facile adsorption of furfural on active metal sites is the key factor responsible for the high catalytic activity of the catalyst of the present invention. While iso-propanol improves the stability, water enhances the activity and selectivity of the catalyst. Combination of both these solvents i.e., water and iso-propanol is essential for high activity and long time catalyst stability. Appropriate ratio of water and iso-propanol is critical for getting high conversion and furan yields. As this process is operated at moderate conditions, no waste streams are generated. Hence, the process of the present invention is safe and commercially easily adoptable.

(5) The present invention discloses safe, efficient, hydrogen-free catalytic process for preparation of compound of formula I from furfural in high yield

(6) ##STR00003##
wherein R1 is selected independently from hydrogen or CH.sub.3;
which comprises the steps of: a) contacting furfural and water-isopropanol mixture with a supported Pd or Pt catalyst taken in the reactor in the presence of an inert gas as co-feed at a temperature in the range of 200-250 C., wherein furfural to water-isopropanol mixture weight ratio is in the range 1:5 and 1:25, inert gas is at a pressure in the range 1-10 bar, ratio of catalyst to furfural ranges between 2 and 5 wt %, and Pd or Pt content on the support ranges from 2-10 wt %, and b) conducting the reaction at said temperature and pressure conditions, venting out the inert gas for recycle and separating the liquid product from catalyst by filtration followed by, distillation to obtain compound of formula (I).

(7) The water to isopropanol mixture is in the ratio ranging between 1:1 to 1:5.

(8) The catalyst of the present invention is Pd or Pt impregnated on a support selected from the group of alumina, ceria, zirconia, ceria-zirconia, sulphated zirconia, silica, carbon, clay, hydrotalcite, MgOAl.sub.2O.sub.3 or the compositions containing these oxides and their mixtures.

(9) In a feature of the present invention, the reaction is carried out either in a semi-batch or continuous batch/fixed-bed operation.

(10) In another feature of the present invention, the process is carried out in the absence of alkali metal.

(11) In yet another feature of the present invention, the inert gas is nitrogen, argon, helium or their mixture.

(12) It is a feature of the present invention that the conversion of furfural is 100 mol % and furan selectivity is between 75 and 90 mol %.

(13) It is another feature of the present invention that the catalyst in recyclable and reusable.

(14) It is still another feature of the present invention that no waste streams are generated.

(15) The supported Pd or Pt catalyst is prepared by wet impregnation method known in the art (Catalysis Letters, Year 2010, Vol. 140, pp. 55-64 and Journal of Catalysis, Year 2012, Vol. 285, pp. 31-40).

EXAMPLES

(16) Following are the examples given to further illustrate the invention and should not be construed to limit the scope of the present invention.

Example 1

(17) This example illustrates the preparation of the catalyst: 5 wt % Pd supported on alumina. To 1.484 g of 10 wt % aqueous tetraammine palladium (II) nitrate solution, 10 ml of distilled water was added. It was then added to 1 g of -Al.sub.2O.sub.3 taken in a glass round bottom flask. The suspension was mixed thoroughly and dried at 80 C. using a rotary evaporator. The solid obtained was recovered and dried at 100 C. for 6 h in an oven. Then, the material was calcined at 400 C. for 2 h. Prior to the reaction, catalyst was reduced under a flow of hydrogen (30 ml/min) at 250 C. for 2 h. Without exposing to atmosphere the catalyst was used in the reaction.

(18) 2 and 10 wt % Al.sub.2O.sub.3-supported Pd catalysts were prepared in the same manner taking 0.5749 g (for 2 wt % Pd/Al.sub.2O.sub.3) and 2.817 g (for 10 wt % Pd/Al.sub.2O.sub.3) of 10 wt % aqueous tetraammine palladium(II) nitrate solution, respectively.

Example 2

(19) This example illustrates the preparation of 5 wt % Pt supported on alumina. 0.1052 g of tetraammine platinum(II) nitrate was dissolved in 10 ml of distilled water. This was then added to 1 g of -Al.sub.2O.sub.3 taken in a glass round bottom flask. It was mixed thoroughly and dried at 80 C. using a rotary evaporator. The solid obtained was recovered and dried at 100 C. for 6 h in an electric oven. Then, the material was calcined at 400 C. for 2 h. Prior to the reaction, catalyst was reduced under a flow of hydrogen (30 ml/min) at 350 C. for 2.5 h. Without exposing to atmosphere the catalyst was used in the reaction.

(20) 2 and 10 wt % Al.sub.2O.sub.3-supported Pt catalysts were prepared in the same manner taking 0.0816, and 0.222 g of tetraamineplatinum(II) nitrate, respectively.

(21) The other supported Pt catalysts were prepared in the same manner taking appropriate support oxides and Pt precursor. Prior to deposition of the Pt, the commercial sulphated-ZrO.sub.2, MgO and SiO.sub.2 were activated at 120 C. for 2 h while -Al.sub.2O.sub.3 was activated at 150 C.

Example 3

(22) This example illustrates the conversion of furfural to furan over Pd(5 wt %)/Al.sub.2O.sub.3 catalyst. 1 g of furfural (Aldrich Co.), 20 g of water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas (5 bar). Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gas was vented out for recycle purpose and the liquid product was separated from the catalyst by filtration. It was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=35.1 wt % and furan selectivity=100 wt %. Finally, furan was separated from the liquid product by distillation.

Example 4

(23) This example illustrates the conversion of furfural to furan and 2-methyl furan over Pt(5 wt %)/Al.sub.2O.sub.3 catalyst. 1 g of furfural, 20 g of de-ionized water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pt(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas to a pressure of 5 bar. Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gaseous product was vented out for further recycling purpose. Liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=29.2%, furan selectivity=43.1% and others including 2-methyl furan selectivity=56.8%. Furan and 2-methyl furan were separated from the liquid product by distillation.

Example 5

(24) This example illustrates the conversion of furfural to furan over Pd(5 wt %)/Al.sub.2O.sub.3 catalyst in the presence of water-isopropanol (1:4) medium. 1 g of furfural, 20 g of isopropanol and 5 g of water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas (5 bar). Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gas was vented out for recycle purpose and the liquid product was separated from the catalyst by filtration. It was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=99.7 wt % and furan selectivity=82.5 wt %. Finally, furan was separated from the liquid product by distillation.

Example 6

(25) This example illustrates the conversion of furfural to furan and 2-methyl furan over Pd(5 wt %)/Al.sub.2O.sub.3 catalyst in the presence of water-isopropanol (1:1) medium. 1 g of furfural, 10 g of isopropanol and 10 g of water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas (5 bar). Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gas was vented out for recycle purpose and the liquid product was separated from the catalyst by filtration. It was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=30.0 wt %, furan selectivity=83.3 wt % and others including 2-methyl furan selectivity=13.2 wt %. Finally, furan and 2-methyl furan were separated from the liquid product by distillation.

Example 7

(26) This example illustrates the conversion of furfural to furan and 2-methyl furan over Pt(5 wt %)/Al.sub.2O.sub.3 catalyst. 1 g of furfural, 20 g of iso-propanol and 5 g of de-ionized water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pt(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas to a pressure of 5 bar. Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=93.5%, furan selectivity=76.5% and others including 2-methyl furan selectivity=23.5 wt %. Finally, furan and 2-methyl furan were separated from the liquid product by distillation.

Example 8

(27) This example illustrates the conversion of furfural to furan and 2-methyl furan over Pt(5 wt %)/Al.sub.2O.sub.3 catalyst in the presence of hydrogen and water-isopropanol (1:4) solvent medium. 1 g of furfural, 20 g of iso-propanol and 5 g of de-ionized water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pt(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with hydrogen gas to a pressure of 20 bar. Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=100 wt %, furan selectivity=53.0 wt % and 2-methyl furan selectivity=15.6 wt %. Finally, furan and 2-methyl furan were separated from the liquid product by distillation.

Example 9

(28) This example illustrates the conversion of furfural to furan and 2-methyl furan over Pt(5 wt %)/SO.sub.4ZrO.sub.2 catalyst in the presence of hydrogen and isopropanol medium. 1 g of furfural, 20 g of iso-propanol and 5 g of water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pt(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with hydrogen gas to a pressure of 20 bar. Temperature of the reactor was raised to 240 C. and the reaction was conducted for 8 h. Then the reactor was cooled to 25 C., liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=100 wt %, furan selectivity=33.3 wt % and 2-methyl furan selectivity=47.2 wt %. Finally, furan and 2-methyl furan were separated from the liquid product by distillation.

Example 10

(29) This example illustrates the conversion of furfural to furan over Pd(5 wt %)/Al.sub.2O.sub.3 catalyst without out using any inert gas. 1 g of furfural, 20 g of iso-propanol and 5 g of de-ionized water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. Temperature of the reactor was raised to 225 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=92 wt %, furan selectivity=75 wt %.

Example 11

(30) This example illustrates the conversion of furfural to furan derived from the pentosan sugars of lignocellulosic biomass over Pd(5 wt %)/Al.sub.2O.sub.3 catalyst in the presence of water-isopropanol (4:1) medium. 1 g of biomass-derived furfural, 20 g of isopropanol and 5 g of water were taken in a 100 ml stainless-steel reactor (Parr 4875 power controller and 4871 process controller). To that 0.05 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas (5 bar). Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gas was vented out for recycle purpose and the liquid product was separated from the catalyst by filtration. It was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=99 wt % and furan selectivity=84 wt %. Finally, furan was separated from the liquid product by distillation.

Example 12

(31) This example illustrates the conversion of furfural to furan in a fixed-bed reactor. 20 g of Pd(5 wt %)/Al.sub.2O.sub.3 extrudates ( 1/16 inch diameter) were placed in between inert alumina extrudates which work as pre and post heaters in a fixed-bed reactor. The reactor was maintained at 240 C. and pressurized with nitrogen to 5 bar at those conditions. Reactant mixture in the weight ratio of 1:20 containing furfural and isopropanol: water (4:1) were fed to the reactor at weight hourly space velocity of 0.8 h.sup.1. The liquid product after passing the effluent through condenser and gas-liquid separator was collected and subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). Furfural conversion=98 wt % and furan selectivity=83 wt %.

Example 13

(32) This example illustrates the reusability and catalyst stability in long term studies of Pd(5 wt %)/Al.sub.2O.sub.3 catalyst. 5 g of furfural, 100 g of iso-propanol and 25 g of de-ionized water were taken in a 300 ml stainless-steel Parr reactor. To that 0.25 g of the reduced Pd(5 wt %)/Al.sub.2O.sub.3 catalyst was added. The reactor was pressurized with nitrogen gas to a pressure of 5 bar. Temperature of the reactor was raised to 240 C. and the reaction was conducted for 2 h. Then the reactor was cooled to 25 C., gases were vented out for recycle, liquid product was separated from the catalyst by filtration and it was then subjected to analysis by gas chromatography (GC; Varian 3400; CP-SIL5CB column; 60 m-long and 0.25 mm-i.d.). The products were identified by GC-MS (Shimadzu GCMS-QP5050A; HP-5 column; 30 m-long0.25 mm i.d.0.25 m thickness). The catalyst separated was dried in at 100-110 C. for half-an-hour and reused in a subsequent recycle experiment conducted in the same as described above in this example. Six such catalyst recycling experiments were done. Furfural conversion on all the recycling experiments=99.7%, furan selectivity=82.7% (0.sup.th recycle), 82% (1.sup.st recycle), 83 (2.sup.nd recycle), 85% (3 recycle), 88% (4.sup.th recycle), and 90% (5.sup.th and 6.sup.th recycle).

Advantages of the Invention

(33) Advantages of instant invention are as following: i. Hydrogen-free process for producing furan from furfural; ii. Reusable catalyst process; iii. Sustainable process producing furan and 2-methyl furan from renewable, biomass-derived feedstock; iv. Eco-friendly process with zero waste stream generation; v. Furfural conversion of 100 mol % and furan selectivity of 75-90 mol %