DESC:FIELD
The present disclosure relates to a process for hydrothermal conversion of a biomass to crude bio-oil.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Biomass refers to a material such as algal biomass, distillery spent wash, urban refuse, wood, agricultural crops or wastes, municipal wastes, distillery wastes, industrial wastes and the like, which can be used as a source of fuel or energy.
Crude bio-oil (CBO) refers to an oil or biofuel derived from a biomass and which can be used as an alternative to petroleum fuel.
Hydrothermal Liquefaction (HTL) refers to a thermal de-polymerization process which is used to convert wet biomass, into crude-like oil (also referred to as bio-oil or bio-crude oil), under moderate temperature and high pressure.
CBO Yield (%) refers to %volume of CBO obtained in the process.
BACKGROUND
Interest in alternative and renewable biological sources of fuels has increased in recent years because of the growing shortage of fossil fuels and the rising environmental pollution, which are the two urgent problems the world is facing today. Biomass, a renewable energy source, can either be used directly, via combustion to produce heat, or indirectly after converting it to various forms of biofuels. Biofuels are derived from biomass and are intended to provide an alternative to petroleum fuels. Conversion of biomass to biofuel can be achieved by different methods, which are broadly classified into thermal, chemical and biochemical methods. Biomass is a resource that shows promise for advanced biofuels because of their higher photosynthetic efficiency, faster growth rate and higher area-specific yield relative to terrestrial biomass.
Hydrothermal liquefaction (HTL) is a technology for converting high-moisture waste biomass into energy dense “crude bio-oil” that can be used for direct combustion or refined to obtain transportation grade fuels. HTL, also called as hydrous pyrolysis, is a process for the reduction of complex organic material such as bio - waste or biomass into crude bio-oil and other chemicals.
Hydrothermal Liquefaction (HTL) technique, which involves application of heat and pressure to the biomass medium, has an advantage that the lipids and other organic components can be efficiently converted while the biomass is in wet condition. During HTL, high moisture biomass is subjected to elevated temperature and pressure in order to break down and reform the chemical building blocks into crude bio-oil.
Lipids present in crude bio-oil can be extracted by solvent extraction or by physical extraction. However, such techniques may not be able to extract lipids completely. In order to make the biomass an economically viable alternative for bio crude oil production, the revenues from all their fractions (and not only the lipids) need to be maximized. A temperature and high pressure thermochemical conversion technique that processes the whole biomass in order to produce a liquid energy carrier, the crude bio-oil, is required.
There is, therefore, felt a need to develop a process for the conversion of biomass to crude bio-oil (CBO).
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the production of crude bio-oil.
Yet another object of the present disclosure is to provide a simple, energy efficient, time saving and high yielding process for the production of crude bio-oil.
Still another object of the present disclosure is to provide a process which is capable of producing crude bio-oil containing high carbon content.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for hydrothermal conversion of a biomass to crude bio-oil. The process steps include mixing the biomass with water with help of the mixer to form a biomass slurry. The concentration of the biomass in the biomass slurry is in the range of 5 wt% to 35 wt%. A predetermined amount of a quaternary ammonium catalyst is added to the biomass slurry to form a reaction mixture. The reaction mixture is hydrothermally liquefied, while stirring the reaction mixture at a speed in the range of 450 rpm to 550 rpm, in the presence of gas selected from nitrogen and hydrogen, at a temperature ranging from 250 °C to 400 °C and at a pressure ranging from 70 bar to 250 bar for a time period ranging from 10 minutes to 90 minutes, to obtain a resultant crude bio-oil. The resultant crude bio-oil is cooled to obtain cooled resultant crude bio-oil. The crude bio-oil is separated from the cooled resultant crude bio-oil to obtain crude bio-oil and a residue. The yield of the crude bio-oil can be in the range of 55 wt% to 78 wt%.
The process of the present disclosure further comprises an additional step of recovering and recycling the quaternary ammonium catalyst. The quaternary ammonium catalyst can be recovered from the residue by sieving, calcining or reducing the residue, followed by recycling the quaternary ammonium catalyst to the process step of forming the reaction mixture.
The biomass can be selected from the group consisting of algal biomass, distillery spent wash, urban refuse, wood, agricultural crops or wastes, municipal wastes, distillery wastes, industrial wastes.
The algal biomass can be selected from the group consisting of Rhodophyta, Chlorophyta, Phaeophyta, Chrysophyta, Cryptophyta, Dinophyta, Tribophyta, Glaucophyta, Spirulina, Nannochloropsis, Chlorella, cyanobacteria, Euglena, Microcystis, Anabaena, Dictyosphaerium, Nodularia, Oscillatoria, Spirogyra, Hydrodictyon, Chara, Nitella, Oedognium, Phormidium and filamentous algae.
The quaternary ammonium catalyst can be at least one of tetraethylammonium bromide, tetramethylammonium bromide and tetramethylammonium chloride.
The predetermined amount of the quaternary ammonium catalyst can be in the range of 5 wt% to 15 wt% with respect to the total weight of the biomass.
The crude bio-oil prepared by the process of the present disclosure has the carbon content in the range of 60 wt% to 85 wt%.
DETAILED DESCRIPTION
Increased market prices for energy and fuels are driven by a number of factors, including depletion of easily accessible petroleum and natural gas deposits, growth of emerging economies, political instabilities and mounting environmental concerns. Increasing energy prices will eventually require a significant restructuring or replacement of a portion of fossil fuels by renewable energy technologies such as biomass-based fuels. These renewable energy technologies are clean sources of energy that possess a much lower environmental impact than the existing conventional energy technologies.
The present disclosure, therefore, envisages a process for hydrothermal conversion of the biomass to crude bio-oil.
The process is described herein below.
The biomass is mixed with water with the help of mixer to form a biomass slurry. The concentration of the biomass in the biomass slurry is in the range of 5 wt% to 35 wt%. In accordance with the present disclosure, the biomass is selected from the group consisting of algal biomass, distillery spent wash, urban refuse, wood, agricultural crops or wastes, municipal wastes, distillery wastes, industrial wastes.
In accordance with the present disclosure, the algal biomass is selected from the group consisting of Rhodophyta, Chlorophyta, Phaeophyta, Chrysophyta, Cryptophyta, Dinophyta, Tribophyta, Glaucophyta, Spirulina, Nannochloropsis, Chlorella, cyanobacteria, Euglena, Microcystis, Anabaena, Dictyosphaerium, Nodularia, Oscillatoria, Spirogyra, Hydrodictyon, Chara, Nitella, Oedognium, Phormidium and filamentous algae.
A predetermined amount of a quaternary ammonium catalyst is added to the biomass slurry to form a reaction mixture. In accordance with embodiments of the present disclosure, the quaternary ammonium catalyst is at least one of tetraethylammonium bromide, tetramethylammonium bromide and tetramethylammonium chloride. In accordance with the present disclosure, the predetermined amount of the quaternary ammonium catalyst is in the range of 5 wt% to 15 wt% with respect to the total weight of the biomass.
The reaction mixture is hydrothermally liquefied, while stirring the reaction mixture at a speed in the range of 450 rpm to 550 rpm, in the presence of a gas selected from hydrogen and nitrogen, at a temperature ranging from 250 °C to 400 °C and at a pressure ranging from 70 bar to 250 bar for a time period ranging from 10 minutes to 90 minutes, to obtain a resultant crude bio-oil;
The resultant crude bio-oil is cooled to obtain cooled resultant crude bio-oil, followed by separating the crude bio-oil from the cooled resultant crude bio-oil to obtain crude bio-oil and a residue. Typically, the crude bio-oil is separated by at least one step selected from the group consisting of filtration, centrifugation, decantation, adsorption, chromatography, liquid-liquid extraction and solid-phase extraction.
The process of the present disclosure further comprises an additional step of recovering and recycling the quaternary ammonium catalyst. In accordance with the present disclosure, the quaternary ammonium catalyst is recovered from the residue by sieving, calcining or reducing said residue, followed by recycling the quaternary ammonium catalyst to the process step of forming the reaction mixture.
In case of the algal biomass (algae), the yield of the crude bio-oil is in the range of 55 wt% to 78 wt%. Further, in case of the distillery spent wash, the yield of the crude bio-oil is greater than 30 wt%.
In accordance with the present disclosure, the crude bio-oil prepared in accordance with the present disclosure has the carbon content in the range of 60 wt% to 85 wt%.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experiments 1 to 19: Conversion of biomass to crude bio-oil (CBO).
Conversion of algal biomass to crude bio-oil (CBO)
Initially, in a reaction vessel 23 g of algal biomass was mixed with water with the help of mixer to form a slurry until the concentration of algal biomass in the slurry was found to be 30 wt%. Further 2.3 g of a quaternary ammonium catalyst (at least one selected from the group consisting of tetraethylammonium bromide, tetramethylammonium bromide and tetramethylammonium chloride), was added to the biomass slurry to form a reaction mixture.
The reaction mixture was then subjected to hydrothermal liquefaction (HTL) under continuous stirring at a speed of 500 rpm in the presence of hydrogen gas, at a temperature of 400 °C, 25 wt% moisture and at a pressure of 200 bar for 60 minutes, in order to break down and reform the chemical building blocks of the distillery spent wash to obtain a resultant crude bio-oil.
Further, the resultant crude bio-oil was cooled to obtain cooled resultant crude bio-oil. The crude boil-was separated from the cooled resultant crude bio-oil by centrifuging the resultant crude bio-oil at 10000 rpm for 15 min to obtain crude bio-oil and a residue.
Different algae were used to carry out HTL process. The results are tabulated below in table 1.
Further, various other concentrations of algae in the slurry were tried and it was found that below 5 wt% of algae, the slurry was too dilute and above 30 wt% of algae, the slurry was too viscous to carry out the process.
Conversion of distillery spent wash to crude bio-oil (CBO)
Initially, in a reaction vessel 100 mL of distillery spent wash was mixed with 900 mL water with the help of mixer to form slurry. Further 10 mg of a quaternary ammonium chloride (TMAC) was added to the slurry to form a reaction mixture.
The reaction mixture was then subjected to hydrothermal liquefaction (HTL) under continuous stirring at a speed of 500 rpm in the presence of nitrogen gas, at a temperature of 400 °C, 25 wt% moisture and at a pressure of 200 bar for 60 minutes.
Further, the resultant crude bio-oil was cooled to obtain cooled resultant crude bio-oil.
The crude bio-oil was separated from the cooled resultant crude bio-oil by centrifuging the resultant crude bio-oil at 10000 rpm for 15 min to obtain crude bio-oil and a residue.
Table 1 summarizes the quaternary ammonium catalyst assisted HTL performance.
Experiments 1 to 4 were carried out in the absence of the catalyst, and experiments 5 to 14 were carried out in the presence of the quaternary ammonium catalyst. Experiments 15 to 19 illustrate the results when the recycled quaternary ammonium catalyst was used.

Experiment No. Biomass Quaternary ammonium catalyst CBO Yield, %

1 Spirulina No 43
2 Nannochloropsis No 54
3 Nannochloris No 45
4 Distillery spent wash No 28.4
5 Spirulina Tetramethylammonium chloride 55
6 Spirulina Tetramethylammonium bromide 57
7 Spirulina Tetraethylammonium bromide 56
8 Nannochloropsis Tetramethylammonium chloride 75
9 Nannochloropsis Tetramethylammonium bromide 76
10 Nannochloropsis Tetraethylammonium bromide 75
11 Nannochloris Tetramethylammonium chloride 56
12 Nannochloris Tetramethylammonium bromide 58
13 Nannochloris Tetraethylammonium bromide 58
14 Distillery spent wash Tetramethylammonium chloride 31.3
15 Spirulina Recycled catalyst from experiment no. 6 56
16 Spirulina Recycled catalyst from experiment no. 13 57
17 Spirulina Recycled catalyst from experiment no. 14 56
18 Spirulina Recycled catalyst from experiment no. 15 57
19 Spirulina Recycled catalyst from experiment no. 16 56

It was found that the carbon content of the crude bio-oil obtained from the experiments 4 to 18 ranges from 60 wt% to 85 wt%.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process:
• that is simple, energy efficient, time saving, and high yielding process for catalyst assisted production of crude bio-oil from biomass;
• that is capable of producing bio-oil containing high carbon content; and
• that reuses the quaternary ammonium catalyst in the next cycle of biomass conversion without affecting the yield of CBO.
The disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein.
The foregoing description of the specific embodiments so fully revealed the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We claim:
1. A process for hydrothermal conversion of a biomass to crude bio-oil, said process comprising:
a. mixing the biomass with water with the help of mixer to form a biomass slurry;
b. adding a predetermined amount of a quaternary ammonium catalyst to said biomass slurry to form a reaction mixture;
c. hydrothermally liquefying (HTL) said reaction mixture, while stirring said reaction mixture at a speed in the range of 450 rpm to 550 rpm, in the presence of a gas selected from nitrogen and hydrogen, at a temperature ranging from 250 °C to 400 °C and at a pressure ranging from 70 bar to 250 bar for a time period ranging from 10 minutes to 90 minutes, to obtain a resultant crude bio-oil;
d. cooling said resultant crude bio-oil to obtain cooled resultant crude bio-oil; and
e. separating said crude bio-oil from said cooled resultant crude bio-oil to obtain crude bio-oil and a residue.
2. The process as claimed in claim 1, wherein the concentration of said biomass in said biomass slurry is in the range of 5 wt% to 35 wt%.
3. The process as claimed in claim 1, further comprises an additional step of recovering and recycling said quaternary ammonium catalyst, wherein said quaternary ammonium catalyst is recovered from said residue by sieving, calcining or reducing said residue, followed by recycling said quaternary ammonium catalyst to the process step (c).
4. The process as claimed in claim 1, wherein said biomass is selected from the group consisting of algal biomass, distillery spent wash, urban refuse, wood, agricultural crops or wastes, municipal wastes, distillery wastes and industrial wastes.
5. The process as claimed in claim 4, wherein said algal biomass is selected from the group consisting of Rhodophyta, Chlorophyta, Phaeophyta, Chrysophyta, Cryptophyta, Dinophyta, Tribophyta, Glaucophyta, Spirulina, Nannochloropsis, Chlorella, cyanobacteria, Euglena, Microcystis, Anabaena, Dictyosphaerium, Nodularia, Oscillatoria, Spirogyra, Hydrodictyon, Chara, Nitella, Oedognium, Phormidium and filamentous algae.
6. The process as claimed in claim 1, wherein said quaternary ammonium catalyst is at least one selected from the group consisting of tetraethylammonium bromide, tetramethylammonium bromide and tetramethylammonium chloride.
7. The process as claimed in claim 1, wherein said predetermined amount of said quaternary ammonium catalyst is in the range of 5 wt% to 15 wt% with respect to the total weight of said biomass.
8. The crude bio-oil obtained by the process as claimed in claim 1, has the carbon content in the range of 60 wt% to 85 wt%.