PH12013000098A1

PH12013000098A1 - Process for producing carbon from poly-alcohols and the products therefor

Info

Publication number: PH12013000098A1
Application number: PH12013000098A
Authority: PH
Inventors: Erwin P Enriquez Phd; Jerick A Imbao; Geoffrey Matthew C Tan
Original assignee: Geoffrey Matthew C Tan; Erwin P Enriquez Phd; Jerick A Imbao
Priority date: 2013-03-27
Filing date: 2013-03-27
Publication date: 2014-10-13
Also published as: WO2014158037A1

Abstract

The present invention relates in general to the production of carbon from low molecular weight poly-alcohols. Specifically, it relates to the carbonization of volatile poly-alcohols having 2-6 carbons, such as glycol and glycerol. More specifically, it is directed to a process of producing carbon from poly-alcohols having 2-6 carbons comprising the steps of adding acid or base to the poly-alcohol at a 0.5 - 10 mol pcnt concentration in the final mixture, and heating the mixture to a temperature within the range of 200�C - 1000�C in a chamber of controlled inert atmosphere.

Description

PROCESS FOR PRODUCING CARBON FROM POLY-ALCOHOLS AND THE* ~~

PRODUCTS THEREFOR

N30 M2903

SPECIFICATION / l Technical Field of the Utility Invention / ]

The present invention relates in general to the production of carbon from low molecular weight poly-alcohols. Specifically, it relates to the carbonization of volatile poly-alcohols having 2-6 carbons, such as glycol and glycerol, which easily vaporize upon heating and are not readily carbonized or charred by heat. 1 il. Background of the Invention

Crude glycerol is a low molecular weight by-product of the biodiesel industry with a myriad of impurities that dramatically reduces its value (Bozell, J.

Biorefinery Product Opportunities from Glycerol. Integration of Agricultural and

Energy Systems. 2008: 41-48). The carbonization of glycerol could prove to be beneficial; as carbon materials like coke, carbon fibers, activated carbon, and the different allotropes of carbon, such as nanotubes and graphene, have various applications, such as in supercapacitors, catalyst support, and in the future, electronics devices (Wang, C., Y. Wang, Z Shi, Y. Huang, Y. Ma,

M.Chen, and Y. Chen. Supercapacitor devices based on grapheme materials. J. i

Phys. Chem. C 113 (2009): 13103-13107).

Recent studies show that direct utilization of crude glycerol is difficult.

These studies have greatly concentrated on the conversion of glycerol into high- valued products and alternative fuel like syngas. In US 2009/0151254 A1, the invention proposed to solve the problems arising from the direct use by gasification of glycerol-containing feedstock or crude glycerol due to the high proportion of contaminants present therein. In this invention, a liquid fraction of a glycerol-containing feedstock is subjected to thermal drying wherein volatile ; components, such as glycerol, are evaporated and form a gas fraction. At sufficiently high temperatures, glycerol is thermally decomposed or pyrolysed into agas containing hydrogen. 2 oma 3 a9 1 3 IN E

None of these previous studies or documents, however, shows that high- grade carbon can be obtained directly from crude glycerol-containing feedstock.

In the present invention, we show for the first time that glycerol can be converted to high-grade carbon, including activated carbon, with high yields.

Activated carbon is usually produced from biomass at high temperatures, usually above 600°C. However, using low molecular precursors are not amenable to direct pyrolysis because they volatilize at low temperatures.

Low molecular weight poly-alcohols, particularly those having 2-6 carbons, are known for their volatility. Hence, previous attempts to carbonize poly-alcohols produced very low carbon yields or otherwise have failed. For example, in the study of Loable (Loable, C.M., CARBONIZATION OF

GLYCEROL BY PYROLYSIS. Thesis report Ateneo de Manila University. May, 2009), attempts to carbonize technical grade glycerol using metal catalysts or carbon support produced very low carbon yields, i.e, 2.7% - 4.8% fractional conversion or 1.1% to 1.9% mass yield. In the present invention, high-grade carbon is produced with high yields from poly-alcohols, such as glycol and glycerol, preferably from glycerol, either reagent or technical grade, or crude glycerol obtained from transesterification reaction in the saponification of fats and oils or biodiesel production.

I. Summary and Objects of the Invention

The present invention relates in general to the production of carbon from low molecular weight poly-alcohols. Specifically, it relates to the carbonization of volatile poly-alcohols having 2-6 carbons, such as glycol and glycerol, which i easily vaporize upon heating and are not readily carbonized or charred by heat. i 30 .

The primary object of this invention is to provide a high-grade carbon in ! high yields obtained from the conversion of low molecular weight poly-alcohols, such as glycol and glycerol, at temperatures significantly higher than the known i temperatures at which poly-alcohols volatilize.

Another object of this invention is to produce activated carbon from low molecular weight poly-alcohols, such as glycol and glycerol, at temperatures which are generally lower than the decomposition temperatures used in the carbonization of biomass, preferably within the range of 200°C to 600°C.

It is also an object of this invention to provide a means for utilizing crude glycerol, a poly-alcohol by-product of the transesterification reaction in the saponification of fats and oils or biodiesel production. With the expansion of biodiesel production associated with the increasing demand and need for renewable fuel source to supersede petrochemical sources, more glycerol! is produced; resulting in the oversupply of glycerol, and consequently, dramatic decrease in its value. ;

The refinement and purification of crude glycerol proves to be expensive for small and medium biodiesel producers. Thus, another object of this invention is to provide an economical and inexpensive process for utilizing crude glycerol.

These and other objects will become apparent upon reading the following detailed description taken in conjunction with the accompanying drawing.

IV. Brief Description of the Drawings

Figure 1 is the FTIR spectra of samples of carbonized products produced according to the first and second embodiments of the present invention.

Figure 2 consists of the NMR and FTIR spectra of technical grade glycerol and polyglycerol obtained after the first and second heating of the glycerol-acid mixture according to the third embodiment of the present invention.

Figure 3 consists of thermograms of oligomerized glycerol obtained after the first and second heating of the glycerol-acid mixture according to the third embodiment of the present invention.

Figures 4-8 show sample products after the final heating according to the ] third embodiment of the present invention. ;

Known activating agents, such as ZnCl, or KOH, may be added during heating to the final temperature of 900°C -1000°C. ;

In another embodiment, heating may be through a temperature- programmed ramp wherein the poly-alcohol-acid/base mixture, preferably glycerol-acid mixture, is heated at a rate of 10°C — 20°C per minute up to a temperature within the range of 200°C -250°C and kept at this temperature for a prescribed time, preferably from 30 minutes to two (2) hours, and then heated again at a rate of 10°C — 20°C per minute up to 350°C -1000°C. Final heating temperatures exceeding 350°C produce higher carbon-to-oxygen ratio and leads to activation at the same time.

In still another embodiment, the poly-alcohol-acid/base mixture is first heated without use of a chamber of controlled inert atmosphere at a rate of 20°C per minute up to a temperature within the range of 200°C - 300°C. Thereafter, the heating of the mixture at 200°C - 300°C is continued for up to 2 hours. The temperature is then decreased to room temperature. Finally, the mixture is heated again in a chamber of controlled inert atmosphere at a rate of 20°C per minute up to a temperature within the range of 300°C - 1000°C. Known activating agents, such as ZnCl, or KOH, may be added during heating to the final temperature.

Example 1:

Carbon products were obtained according to the first embodiment of the present invention as follows. Crude glycerol (25 g) was mixed with 5% mol of

NaOH. Concentration of the sodium hydroxide was adjusted so that the total volume delivered was 2 ml. After transferring to a crucible, the mixture was placed into a box furnace under a flowing N, atmosphere. The temperature was raised to 280°C from room temperature at a rate of 20°C/min to 500°C. After which, the temperature was then held constant for 1 hour before allowing the 1 furnace to cool down.

Example 2:

Carbon products were obtained according to the second embodiment of the present invention as follows. Crude glycerol (25 g) was mixed with 5% mol of

H,S0, from concentrated sulfuric acid. Concentration of the sulfuric acid was adjusted so that the total volume delivered is 2 mL. After transferring to a crucible, the mixture is placed into a box furnace under a flowing N, atmosphere.

The temperature was raised to 280°C from room temperature at a rate of 20°C/min and kept there for two (2) hours before the temperature was raised further to 600°C at 20°C/min. After which, the temperature was then held constant for one (1) hour before allowing the furnace to cool down.

For pyrolysis of crude glycerol at 500°C and 600°C according to the first and second embodiments of the present invention, mass yields were 10.08% and 6.37%, respectively.

As shown in Figure 1, the FTIR spectra for all the samples pyrolysed 1 according to the first and second embodiments at 500°C and 600°C, washed and unwashed, did not show C-H stretch vibrations (~2820 cm™), signifying that the carbonized product was fully decomposed to carbon. The unwashed products j pyrolysed at 500°C and 600°C showed a peak at 1100 cm™; while the products that were washed with 1.0 M HCI did not have this band. This peak may correspond to SiO, as possible impurity present in the crude glycerol. Nonetheless, the FTIR is featureless, except for the rotational-vibrational band of moisture in the air during scan. A featureless spectrum and absence of bands around 2820 cm™ is typical for carbon. !

Example 3: i

Carbon products were also obtained according to the third embodiment of the present invention as follows. Technical grade glycerol (272 mmol), H,SO, (2.72 mmol) and deionized water (2.5 mL) were mixed in a round bottom flask connected to a reflux condenser. The system was heated by means of a sand bath at 20°C min” up to 280°C, then maintained at this temperature for two ! (2) hours and thereafter subjected to an ice bath until the temperature decreased to room temperature. ]

Figure 9 consists of FTIR and Raman spectra of carbonized products obtained after the final heating of polyglycerol at 300°C, 350°C, 400°C, 500°C and 600°C according to the third embodiment of the present invention.

V. Detailed Description

The present invention relates in general to the production of carbon from low molecular weight poly-alcohols. Specifically, it relates to the carbonization of 1 volatile poly-alcohols having 2-6 carbons, such as glycol and glycerol, which easily vaporize upon heating and are not readily carbonized or charred by heat.

In the present invention, for the first time, low molecular weight poly- ; alcohols, such as glycol and glycerol, can be converted to high-grade carbon with ] high yields at temperatures significantly higher than the known temperatures at which poly-alcohols volatilize. In addition, activated carbon is produced from these low molecular weight poly-alcohols at temperatures which are generally ; lower than the decomposition temperatures used in the carbonization of biomass, preferably within the range 200°C to 600°C.

Poly-alcohols having 2 to 6 carbons, preferably glycol or glycerol, most preferably, glycerol, either reagent or technical grade, or crude glycerol obtained from saponification of fats and oils or the biodiesel industry, can be carbonized by addition of acid or base followed by pyrolysis in a chamber of controlled inert or oxygen-free atmosphere. Known acids or bases may be used. The acids may be : selected from the group consisting of sulfuric acid or other mineral or organic acids. The base may consist of NaOH. These are then prepared into a poly- alcohol — acid/base mixture with an acid or base concentration of 0.5 — 10 mol % in the final mixture, or higher concentration depending on the acid or base ] strength. The inert atmosphere may be a nitrogen atmosphere.

In one embodiment of the present invention, pyrolysis is done by straight heating of the poly-alcohol-acid/base mixture at a prescribed rate, from 10°C to 1 20°C per min, up to 350°C or up to 900°C -1000°C, for the carbonization to occur. 1

To monitor and confirm the results, after heating the system as mentioned above, aliquots were obtained at 30-min intervals and were labeled PG1 to

PG4, respectively. The oligomerization process, which occurred during the initial heating, was terminated by subjecting each aliquot to an ice bath until the temperature decreased to room temperature. Formation of the condensation products were confirmed by nuclear magnetic spectroscopy (NMR) and

Fourier transform infrared (FTIR) analysis (Figure 2, top and bottom graphs, respectively).

Thermogravimetric analysis of the products (Figure 3, left graph) show three major decomposition regions evident in all the oligomerized samples. The thermograms of all the samples demonstrate a sudden mass loss converging at around 110°C, which corresponds to the release of moisture. As shown in the dTGA curve in Figure 3 (right graph), the second region of j decomposition of the four samples converge at around 225°C. This may correspond to the decomposition of diglycerol; since it is in close proximity to its boiling point, which is 205°C (Martin A., & M.Richter. Oligomerization of

Glycerol—a Critical Review. Eur. J. Lipid Sci. Technol. 2011, 113, 100-117). The third region of decomposition is broader which ranges from 350°C to 370°C, : signifying that it accounts for the degradation of more than one compound.

PG4 was subjected to pyrolysis; as it has been observed that glycerol conversion to compounds with higher molecular weight is observed to be at its highest after two hours of oligomerization (Martin A., & M.Richter, Supra). This is confirmed by the increase in viscosity from pure glycerol (1121 cP) to PG4 (4195 i cP). A high molecular weight corresponds to the presence of oligomers and other co-products with longer chains. Carbonization would then be more favored; since oligomers would not easily volatilize, unlike glycerol.

Based on the thermogravimetric analysis, PG4 was pyrolysed at 300°C, 350°C, 400°C, 500°C and 600°C in nitrogen atmosphere at 20°C/min for one (1) hour. The products of the pyrolysis of PG4 are shown in Figures 4-8. Figure 4 1 shows that the carbon product of polyglycerol pyrolysed at 300°C, has a charred appearance with wet caramel-like deposits on the walls. Figure 5 shows pyrolysis ] at 350°C also produced a charred product but there was no liquid ] ;

produced. Figures 6, 7 and 8, show that pyrolysis at 400°C, 500°C and 600°C, respectively, produced porous carbon without any wet deposits on the walls.

FTIR spectroscopy was employed to characterize the functionalities present on the pyrolysed samples. As shown in Figure 9 (top spectrum), the FTIR spectra of the samples reveal that the pyrolysed PG4 at 300°C exhibits peaks at 2855 cm” and 2980 cm™ which correspond to C-H stretching indicating that it was not fully decomposed to carbon. However, the disappearance of the bands associated with the C-H bonds in the pyrolysed

PG4 at 350°C, 400°C, 500°C and 600°C shows that PG4 was completely carbonized in the process. This is in accordance with the SEM-EDS analysis, { which reveals that the pyrolysed products at 350°C, 400°C, 500°C and 600°C consisted of mainly carbon and oxygen (Table 2). The FTIR spectra of the samples also demonstrate peaks associated with the expected polar { functionalities typical of activated and pyrolytic carbon: C=O stretching vibrations at 1640 cm™ and C-O stretching at 1200 cm™. The broad band at 3400 cm” corresponds to O-H vibrations attributed to adsorbed water. Nevertheless, the

FTIR spectra of the pyrolysed samples are nearly similar to the results published for activated and pyrolytic carbon produced from varied precursors like biomasses (Oliveira, L., E. Pereira, |. Guimaraes, A. Vallone, M.

Pereira, J. Mesquita & K. Sapag. Preparation of activated carbons from coffee husks utilizing FeCl; and ZnCl, as activating agents. Journal of hazardous

Materials 165 (2009): 87-94; He, X., Y. Geng, J. Qiu, M. Zheng, S. Long & X.

Zhang. Effect of Activation Time on the properties of activated carbon by microwave-assisted activation for electric double layer capacitance. Carbon 48 (2010): 1662-1669). As the temperature of pyrolysis increased, the % mass yield decreased (shown in table 2). The 40.07% yield of PG4 at 300°C cannot be 1 completely attributed to carbon alone; since its FTIR spectrum revealed that it was not fully decomposed in the process. On the other hand, pyrolysis at 350°C ] exhibits 26.71% mass yield, which is relatively high considering the fact that subjecting pure glycerol to similar pyrolysis parameters would result in ! complete volatilization. Moreover, the FTIR spectrum of the pyrolysed PG4 at 350°C indicates that it completely carbonized so the yield can be mainly accounted to carbon.

Table 2. Elemental composition of pyrolyzed PGE by

Table 1. “Mass vield of pyrolyzed SEM-EDS | Re eS

EE (°C) Carbon “Oxygen 500 DER 500 72.10 $27.90

The pyrolysed samples were also characterized by means of Raman spectroscopy to determine the type of carbon present in the products. Raman spectroscopy is widely utilized to characterize different allotropes of carbon including graphite, graphene, amorphous carbon and carbon nanotubes (CNTs) ! (McEvoy, N., N. Peltekis, S. Kumar, E. Rezvani, H. Nolan, G. Keeley, W. Blau &

G. Duesberg. Synthesis and Analysis of Thin Conducting Pyrolytic Carbon Films. J

Carbon 30 (2012): 1216-1226). Raman spectra of the products pyrolysed at different temperatures are shown in Figure 9 (bottom spectrum). The product pyrolysed at 300°C did not show any significant peak in its Raman spectrum while those pyrolysed at 350°C, 400°C, 500°C and 600°C exhibit similar peaks with different intensities and broadness at 1360 cm™ (D band) and 1580 ; cm™ (G band). The G band is associated with Eq in-plane vibrations observed in all sp? carbon systems, which suggests the formation of graphitic structures in the pyrolysed product. On the other hand, the D band at 1360 cm™ is caused by structural defects. Nevertheless, the Raman spectra of the samples pyrolysed at temperatures 350°C, 400°C, 500°C and 600°C are in conjunction with results from published works that characterized activated carbon from different sources (He, X., Y. Geng, J. Qiu, M. Zheng, S. Long & X. Zhang, Supra). The results of characterization thus show that starting at 350°C, pyrolysis of glycerol produces high-grade carbon.

Example 4: | Carbon products were obtained according to the second embodiment of the present invention as follows. Glycerol (25 g) was mixed with 10% mol of

H,SO, from concentrated sulfuric acid. Concentration of the sulfuric acid was adjusted so that the total volume delivered is 2 mL. The mixture was then mixed. !

After transferring to a crucible, the mixture was placed into a box furnace under a flowing N, atmosphere. The temperature was raised to 280°C from room temperature at a rate of 20°C/min and kept there for 2 hours before the : temperature was raised further to 1000°C at 20°C/min. After which, the temperature was then held constant for one (1) hour before allowing the furnace to cool down.

Example 5:

Activated carbon products were obtained according to the second embodiment of the present invention as follows. Crude glycerol (25 g) was mixed with 10% mol of H,SO,4 from concentrated sulfuric acid. Concentration of the sulfuric acid was adjusted so that the total volume delivered is 2 mL. The mixture i was then mixed. After transferring to a crucible, the mixture was placed into a box furnace under a flowing N, atmosphere. The temperature was raised to 280°C from room temperature at a rate of 20°C/min and kept there for 2 hours before the temperature was raised further to 350°C at 20°C/min. After which, the temperature was then held constant for one (1) hour before allowing the furnace to cool down. The product was washed with water and dried in the oven at 110°C ] for 2 hours. To 10 g of the product, 0.10 g ZnCl, dissolved in 10 mL water was added as activating agent and the mixture allowed to stand for 3 hours and then dried in the oven at 180°C for one (1) hour. The dried mixture was then heated in a furnace with flowing nitrogen up to 1000°C at 20°C/min. After which, the temperature was then held constant for one (1) hour before allowing the furnace to cool down.

Example 6:

Carbon products were obtained according to the second embodiment of the present invention as follows. Ethylene glycol (25 g) was mixed with 5% mol of

H,SO, from concentrated sulfuric acid. Concentration of the sulfuric acid was adjusted so that the total volume delivered is 2 mL. The mixture was then mixed. ]

After transferring to a crucible, the mixture was placed into a box furnace under a i flowing N, atmosphere. The temperature was raised to 280°C from room ] temperature at a rate of 20°C/min and kept there for 2 hours before the 1 temperature was raised further to 600°C at 20°C/min. After which, the temperature was then held constant for one (1) hour before allowing the furnace to cool down.

Table 3 below shows a summary of % Mass Yields from acid-catalyzed carbonization of glycerol and glycol according to the second and third : embodiments of the present invention.

Table 3

Pyrolysis Third Embodiment Second Embodiment (°C) % Mass Estimated % % Mass Estimated % i

Yield Mass Yield Yield Mass Yield

Glycerol Ethylene Glycerol Ethylene

Glycol Glycol ew |e | 3 ee | ®

For pyrolysis of crude glycerol at 500°C and 600°C according to the first and second embodiments of the present invention, mass yields were 10.08% and 6.37%, respectively. These yields were typically higher than those obtained according to the third embodiment. (Mass yields according to the first and second embodiments were computed using the original weight of crude glycerol.

For the third embodiment, the yield was based on the starting mass of polyglycerol obtained after the first and/or second heating prior to the final heating - the pyrolysis step). ft should be noted that the foregoing description and examples are made for illustrative purposes only and not in any way intended to limit the scope of this invention, the spirit and breadth of which are defined by the appended claims. 3 g go 1d

Claims

WE CLAIM:Son omg

1. A process of producing carbon from poly-alcohols having 2-6 carbons Td comprising the steps of adding acid or base to the poly-alcohol at a 0.5 - mol % concentration in the final mixture, and heating the mixture ¢ a’. —_ temperature within the range of 200°C — 1000°C in a champger of controlled inert atmosphere. ,

2. The process according to claim 1, wherein the poly-alcohol is ethylene 10 glycol or glycerol.

3. The process according to claim 1 or 2, wherein the heating is straight heating at a rate of 10°C- 20°C per minute up to a temperature of 350°C.

4. The process according to claim 1 or 2, wherein the heating is straight heating at a rate of 10°C-20°C per minute up to a temperature of 900°C - ] 1000°C.

5. The process according to claim 1 or 2, wherein the heating comprises heating the mixture at a rate of 10°C ~ 20°C per minute up to a temperature within the range of 200°C - 250°C, heating the mixture at 200°C - 250°C for 30 minutes to 2 hours, and thereafter heating the mixture at a rate of 10°C — 20°C per minute up to a temperature of 350°C - 1000°C. {

6. The process according to claim 1 or 2, wherein the acid is a mineral acid ] or an organic acid.

7. The process according to claim 6, wherein the acid is sulfuric acid.

8. The process according to claim 2, wherein glycerol is crude glycerol obtainable from the saponification of fats and oils or biodiesel production.

9. The process according to claim 2 wherein glycerol is reagent or technical ] grade glycerol. ] 13 2 = a= ] ohne Fem =o E

10. The process according to claim 1 or 2, wherein the inert atmosphere is nitrogen atmosphere.

11. The process according to claim 1, wherein the heating comprises heating the mixture without use of a chamber of controlled inert atmosphere at a rate of 20°C per minute up to a temperature within the range of 200°C - ] 300°C, heating the mixture at 200°C - 300°C for up to 2 hours, decreasing the temperature to room temperature, and thereafter heating the mixture in a chamber of controlled inert atmosphere at a rate of 20°C per minute up to a temperature within the range of 300°C - 1000°C.

12. The process according to claim 11, wherein the first heating is up to a temperature of 280°C and the final heating is up to 350°C. 1

13. The process according to claim 11, wherein the first heating is up to a temperature of 280°C and the final heating is up to 900°C- 1000°C.

14. The process according to claim 11, wherein the first heating is done by means of a sand bath.

15. The process according to claim 1 or 11, wherein the chamber of controlled inert atmosphere is a furnace.

16. The process according to claim 11, wherein the final temperature is 400°C.

17. The process according to claim 11, wherein the final temperature is 500°C. ]

18. The process according to claim 11, wherein the final temperature is ] 600°C.

19. The process according to claim 4, wherein the heating is done with the addition of activating agents selected from the group consisting of ZnCl, or KOH.

20. The process according to claim 13, wherein the heating is done with the : addition of activating agents selected from the group consisting of ZnCl, or KOH.

21. The product obtained by the process according to claim 1. 1

22. The product obtained by the process according to claim 5.

23. The product obtained by the process according to claim 11. ERWIN P. ENRIQUEZ, PhD JERICK A. IMBAO GEOFFREY MATTHEW C. TAN Inventors is