FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13) A PROCESS FOR PREPARING FURFURAL
GALAXY LABORATORIES PVT LTD.
an Indian Company
of Plot No. B-22, MIDC, Aurangabad Industrial Area,
Gut No. 34, Grampanchayat Satara Parisar,
Beed By-pass, Aurangabad,
Maharashtra 431005
Inventors:
1. DESHMUKH SHRIKANT RAMCHANDRA
2. WALIMBENAGESHSAYAJIRAO
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE DISCLOSURE:
The present disclosure relates to a process for preparing Furfural. The present disclosure particularly relates to a process for preparing Furfural from agricultural or agro-industry waste.
BACKGROUND:

The pentose thus obtained is converted to Furfural in a dehydration reaction as
Furfural is an important raw material in the pharmaceutical industry. Furfural is produced on an industrial scale from agricultural wastes such as corn cobs, bagasse, rice husk, oat hulls, saw dust, wood residues and straw. All of these materials contain pentosan which is initially hydrolyzed to pentose as;

In the prior art processes, dilute sulfuric acid is used as a catalyst. For example, the process disclosed in W0199817727 employs 0.10 % to 0.35 % by weight of sulfuric acid or sulfur dioxide along with steam for converting hemicellulose and/or cellulose into products comprising furfural.
US Patent Application 20040068147 discloses a method for manufacturing furfural using gaseous acid catalysis. Another, US Patent Application 20120083611 also discloses a process for producing furfural from solid biomass in the presence of superheated steam and hydrochloric acid as an acid catalyst.
These prior art processes suffer from several limitations. Firstly, dilute/catalytic sulfuric acid or catalytic sulfur dioxide fails to seep into a majority of the particles of the agriculture waste used resulting into incomplete hydrolysis which in turn generates acidic effluents leading to pollution. Secondly, due to incomplete hydrolysis the yield

of the intended product is low. Further, these processes employ sulfur compounds which are toxic gas with a pungent and irritating smell. Still further, some of the processes employ corrosive hydrochloric acid for producing furfural.
Furthermore, the mass obtained after isolating Furfural is acidic in nature. Acidic nature of the mass corrodes the boiler. The calorific value of the corroded boiler decreases leading to inefficient fuel energy and generation of hazardous waste. Further, it also increases the overall maintenance cost of the equipment.
Therefore, there exists a need for improved process for preparing Furfural that overcomes the above limitations associated with the prior art.
OBJECTS:
Some of the non-limiting objects which at least one embodiment of this disclosure may achieve are:
It is an object of the present disclosure to provide a process for preparing Furfural.
It is another object of the present disclosure to provide a process for preparing
Furfural with improved yield.
It is yet another object of the present disclosure to provide a process for preparing
Furfural which is economic and environment friendly.
It is still another object of the present disclosure to provide a process for preparing
Furfural which facilitates removal of the by-products.
It is further object of the present disclosure to provide a process for preparing Furfural
which obviates the use of corrosive reagents.
It is still further object of the present disclosure to provide a process for preparing
Furfural with the reduced generation of toxic effluents.
SUMMARY:
In one aspect of the present disclosure there is provided a process for preparing furfural, said process comprising the following steps:

a. charging an agricultural waste produce having a particle size ranging
between 2 mm and 10 mm and pentosan from 2% to 35 % with respect
to the total mass of the agricultural waste produce into a pressure vessel
having a top man hole and a bottom valve;
b. impregnating sulphur trioxide gas into said agricultural waste produce
by supplying said gas;
c. pressurizing the contents of said pressure vessel by injecting a steam at a
pressure ranging between 8.0 kg/cm2 and 12 kg/cm2;
d. maintaining the temperature of the contents of said pressure vessel at
120 °C to 160 °C for a time period ranging between 4 hours and 10
hours at a pH ranging between 1 and 5; and
e. subjecting generated vapors comprising furfural, acetic acid, acetone.
methanol and steam.
The process of the present disclosure further comprises neutralizing a mass left in said pressure vessel after step (e) using at least one base selected from the group consisting of ammonium hydroxide and at a pressure ranging between 0.5 kg/cm2 and 1.0 kg/cm2 for a time period of 0.5 hours to 1.0 hours at a temperature ranging between 60 °C and 80 °C.
Typically, the agricultural waste produce is at least one selected from the group consisting of corn cobs, bagasse, rice husk, cotton seed, oat hulls, saw dust, wood residues, straw, bamboo, wood chips, and olive press-cake.
Typically, the method step of supplying said gas is carried out through the operative top of said pressure vessel.
Typically, the method step of subjecting is carried out through the operative bottom of said pressure vessel.
Typically, the proportion of said sulphur trioxide gas to said agricultural waste produce ranges between 1:50 and 1 : 100.

Typically, the proportion of said steam to said agricultural waste produce ranges between 1:15 and 1:20.
Typically, the proportion of said base to said mass ranges between 1:50 and 1 : 100.
Typically, the pH of the neutralized mass ranges between 6.5 and 7.5.
DETAILED DESCRIPTION:
In accordance with one aspect of the present disclosure there is provided a process for preparing Furfural from agricultural waste. The agricultural waste produce used for producing Furfural is a pentosan containing agricultural or agro-industry waste. Reaction scheme for preparation of Furfural:

In a first step, an agriculture waste produce having a particle size ranging between 2 mm2 and 10 mm2 and comprising pentosan in an amount ranging between 2 and 35 % with respect to the total mass of the agriculture waste produce is placed on a grating present at the operative bottom of a pressure vessel. The vessel is provided with a top man hole which is made air tight.
The agriculture waste produce used includes but is not limited to corn cobs, bagasse, rice husk, cotton seed, oat hulls, saw dust, wood residues, straw, bamboo, wood chips and olive press-cake.
In a second step, the agricultural waste produce is impregnated with sulphur trioxide gas by supplying sulphur trioxide gas through the operative top part of the pressure vessel. The supply of sulphur trioxide gas is continued till the pressure vessel is saturated with the vapors of sulphur trioxide. The saturation of the pressure vessel is indicated by the escape of the gas from the bottom valve. At this point of time the bottom valve is closed and steam is passed into the pressure vessel to pressurize the

contents of the pressure vessel. The pressure in the vessel is maintained between 8.0 kg/cm2 and 12.0 kg/cm2 and the temperature is maintained in the range of 120 °C to 160 °C for a time period of 4 hours to 10 hours. The combination of sulphur trioxide gas and steam under high pressure and pH of 1 to 5 ensures complete hydrolysis on account of thorough and intimate exposure of the particles of the agricultural waste produce to the gas and the steam. The sulphur trioxide gas comes into contact with most of the pentosan present in the agricultural waste produce and hydrolyzes it into furfural and by-products such as acetic acid, acetone and methanol.
For effective hydrolysis of pentosan present in the agricultural waste produce the proportion of sulphur trioxide gas to the agricultural waste produce ranges between 1:50 and I: 100 whereas; the proportion of steam to the agricultural waste produce ranges between 1:15 and 1:20.
After completion of the reaction the bottom valve of the pressure vessel is opened and steam along with vapors containing Furfural, acetic acid, acetone and methanol are allowed to pass to a heat exchanger. In the heat exchanger the vapors are condensed to obtain a condensate containing Furfural, acetic acid, acetone and methanol.
The condensate is then fractionated in a stripping column to recover Furfural and other by-products. Other by-products include but are not limited to acetic acid, acetone and methanol.
However, to completely neutralize the mass (pH 6.5 to 7.5) left in the vessel after passing off the vapors containing Furfural, acetic acid, acetone and methanol to the heat exchanger at least one base selected from the group consisting of ammonium hydroxide is charged in the vessel. The amount of the base used to neutralize the mass is such that the proportion of the base to the mass ranges between 1:50 and 1:100. The mass neutralization reaction is carried out at a pressure ranging between 0.5 kg/cm2 and 1.0 kg/cm2 for a time period ranging between 0.5 hours and 1.0 hours and at a temperature ranging between 60 °C and 80 °C.

The present disclosure is further described with the help of the following non-limiting examples which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure.
Example:
In all the trials, the following equipment and utilities were used:
1. SS316L Cylindrical Pressure Vessel with grating at the bottom and bottom valve. Capacity 700 liters, working Pressure min. 10 kg/cm2 with insulation,
2. SS 316 Heat Exchangers (3 units) of 6 m capacity each,
3. collection Tank SS 316 for storing steam distillate, capacity 600 liters,
4. fractional distillation Column DD 316 with 1000 liters still capacity, Height 18 mtrs,
5. diameter 300 mm packed with structured packing (250 Y TYPE ) equipped with
vacuum and receivers collecting fore run, main run & Furfural fraction.
6. boiler,
7. cooling Tower,
8. chilling Plant (0 to 5 °C), and
9. vacuum generator.
Example 1:
210 kg of corn cobs having a particle size ranging between 2 mm2 and 10 mm2 was charged on the grating provided at the bottom of a 700 liter SS316L Cylindrical Pressure Vessel having a top man hole and a bottom valve. The top man hole was tightened but the bottom valve was left open after charging corn cobs. Then 8.2 kg of sulphur trioxide gas was slowly charged from the top into the vessel to fully impregnate corn cobs (this is indicated by the escape of sulphur trioxide gas from the bottom valve). The bottom valve was closed at this point. The impregnation was followed by slowly injecting steam into the vessel to pressurize up to 9 to 9.5 kg /cm2. The steam pressure in the vessel was maintained for 6 hours at 145°C. Then the bottom valve of the vessel was opened to allow the passage of vapors containing Furfural, acetic acid, acetone, methanol along with steam to a heat exchanger system

leaving behind a mass in the vessel. The pH of the mass was found to be 3.5. The vapors were then condensed. The condensate so obtained was analyzed and fractionated in stripping column to recover 23 kg of Furfural. 12.65 kg of acetic acid, 6.5 kg of acetone & 6.55 kg of methanol. 3.4 kg of ammonia gas was introduced in the vessel at 0.5 kg/cm pressure for a time period of 0.5 hours at 60 °C to neutralize the mass to pH 7.0.
Analysis:
Table 1: GC analysis of the condensate:

Sr.
No. Composition of the condensate %
1. Water 87.0
2. Furfural 6.0
3. Acetic Acid 3.0
4. Acetone 1.7
5. Methanol 1.7
Table 2: Analysis of individual fractions after recovery

Sr. No. Test Furfural Acetic acid Acetone Methanol
1. Appearance Light yellow liquid Clear Colorless liquid with pungent odor Clear water white liquid Clear colorless liquid with characteristic odor
2. % Moisture by KF 0.4 0,4 0.4 0.5
3. Boiling Range (°C) 161-163 116-117 56-57 64.5-65.5
4. Specific Gravity @ 20
°C (g/ml) 1.16 1.035 0.792 0.78- 0.80
5. % Purity by GC 99.2 99.3 99.5 99.5

Example 2:
210 kg of bagasse having a particle size ranging between 2 mm and 10 mm was charged on the grating provided at the bottom of a 700 liter SS316L Cylindrical Pressure Vessel having a top man hole and a bottom valve. The top man hole was tightened but the bottom valve was left open after charging bagasse. Then 8.2 kg of sulphur trioxide gas was slowly charged from the top into the vessel to fully impregnate bagasse (this is indicated by the escape of sulphur trioxide gas from the bottom valve). The bottom valve was closed at this point. The impregnation was followed by slowly injecting steam into the vessel to pressurize up to 9.5 kg /cm2. The steam pressure in the vessel was maintained for 7.5 hours at 158°C. Then the bottom valve of the vessel was opened to allow the passage of vapors containing Furfural, acetic acid, acetone, methanol along with steam to a heat exchanger system leaving behind a mass in the vessel. The pH of the mass was found to be 3.5. The vapors were then condensed. The condensate so obtained was analyzed and fractionated in stripping column to recover 22.5 kg of Furfural, 11.2 kg of acetic acid, 6.5 kg of acetone & 6.7 kg of methanol. 3.4 kg of ammonia gas was introduced in the vessel at 0.5 kg/cm pressure for a time period of 0.5 hours at 60 °C to neutralize the mass to pH 7.0.
The analysis of the condensate and the individual fractions after recovery is tabulated in Table 3 and Table 4.
Analysis:
Table 3: GC analysis of the condensate:

Sr.
No. Composition of the condensate %
1. Water 87.5
2. Furfural 5.9
3. Acetic Acid 3.2
4. Acetone 1.4
5. Methanol 1.4

Table 4: Analysis of individual fractions after recovery

Sr.
No. Test Furfural Acetic acid Acetone Methanol
1. Appearance Light yellow liquid Clear Colorless liquid with pungent odor Clear water white liquid Clear colorless liquid with characteristic odor
2. % Moisture by KF 0.3 0.4 0.4 0.6
3. Boiling Range
(°C) 161-163 116-117 56-57 64.5-65.5
4. Specific-Gravity @ 20 °C (g/ml) 1.17 1.04 0.79 0.79
5. % Purity by GC 99.3 99.3 99.6 99.4
Example 3:
210 kg of cotton seeds having a particle size ranging between 2 mm and 10 mm was charged on the grating provided at the bottom of a 700 liter SS316L Cylindrical Pressure Vessel having a top man hole and a bottom valve. The top man hole was tightened but the bottom valve was left open after charging cotton seeds. Then 8.2 kg of sulphur trioxide gas was slowly charged from the top into the vessel to fully impregnate cotton seeds (this is indicated by the escape of sulphur trioxide gas from the bottom valve). The bottom valve was closed at this point. The impregnation was followed by slowly injecting steam into the vessel to pressurize up to 9.9 kg /cm2. The steam pressure in the vessel was maintained for 5 hours at 160°C. Then the bottom valve of the vessel was opened to allow the passage of vapors containing Furfural. acetic acid, acetone, methanol along with steam to heat exchanger system leaving behind mass in the vessel. The pH of the mass was 3.1. The vapors are then condensed. The condensate so obtained was analyzed and fractionated in stripping column to recover 24 kg of Furfural. 13.1 kg of acetic acid, 7.7 kg of acetone & 7.8 kg of methanol. 3.4 kg of ammonia gas was introduced in the vessel at 0.5 kg/cm2 pressure for a time period of 0.5 hours at 60 °C to neutralize the mass to pH 7.0. The analysis of the condensate and the individual fractions after recovery is tabulated in Table 5 and Table 6.

Analysis:
Table 5: GC analysis of the condensate:

Sr.
No. Composition of the condensate %
1. Water 87.3
2. Furfural 6.2
3. Acetic Acid 3.4
4. Acetone 1.2
5. Methanol 1.3
Table 6: Analysis of individual fractions after recovery

Sr. Test Furfural Acetic acid Acetone Methanol
No.
1. Appearance Light yellow Clear Colorless Clear water Clear colorless
liquid liquid with pungent odor white liquid liquid with
characteristic
odor
2. % Moisture by KF 0.5 0.3 0.5 0.4
3. Boiling Range
(°C) 161-163 116-117 56-57 64.5-65.5
4. Specific Gravity @ 20 °C (g/ml) 1.162 1.042 0.793 0.8
5. % Purity by GC 99.1 99.4 99.5 99.3
ADVANTAGES:
The process for preparation of Furfural in accordance with the present disclosure has the following advantages:
- it is simple, economic and environmental friendly,
- by-products formed during the reaction can be isolated,
- provide higher yield,
- mass left after completion of the reaction is comparatively non-acidic and non-corrosive,
- requires less water compared to prior art processes, and
- the process is amenable to larger scale.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention and the claims unless there is a statement in the specification to the contrary.
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications in the process or compound or formulation or combination of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.

We Claim:
1. A process for preparing furfural, said process comprising the following steps:
a. charging an agricultural waste produce having a particle size ranging
between 2 mm and 10 mm and pentosan from 2% to 35 % with respect
to the total mass of the agricultural waste produce into a pressure vessel
having a top man hole and a bottom valve;
b. impregnating sulphur trioxide gas into said agricultural waste produce
by supplying said gas;
c. pressurizing the contents of said pressure vessel by injecting a steam at a
pressure ranging between 8.0 kg/cm and 12 kg/cm ;
d. maintaining the temperature of the contents of said pressure vessel at
120 °C to 160 °C for a time period ranging between 4 hours and 10
hours at a pH ranging between 1 and 5; and
e. subjecting generated vapors comprising furfural, acetic acid, acetone,
methanol and steam to condensation followed by fractionation to obtain
furfural.
2. The process as claimed in claim 1. further comprises neutralizing a mass left in said pressure vessel after step (e) using at least one base selected from the group consisting of ammonium hydroxide and at a pressure ranging between 0.5 kg/cm2 and 1.0 kg/cm2 for a time period of 0.5 hours to 1.0 hours at a temperature ranging between 60 °C and 80 °C.
3. The process as claimed in claim 1, wherein said agricultural waste produce is at least one selected from the group consisting of corn cobs, bagasse, rice husk, cotton seed, oat hulls, saw dust, wood residues, straw, bamboo, wood chips, and olive press-cake.
4. The process as claimed in claim 1, wherein the method step of supplying said gas is carried out through the operative top of said pressure vessel.

5. The process as claimed in claim 1, wherein the method step of subjecting vapors to condensation is carried out through the operative bottom of said pressure vessel.
6. The process as claimed in claim 1, wherein the proportion of said sulphur trioxide gas to said agricultural waste produce ranges between 1:50 and 1:100.
7. The process as claimed in claim 1, wherein the proportion of said steam to said agricultural waste produce ranges between 1:15 and 1:20.
8. The process as claimed in claim 1, wherein the proportion of said base to said mass ranges between 1:50 and 1:100.
9. The process as claimed in claim 1, wherein the pH of the neutralized mass ranges between 6.5 and 7.5.