comparation glycerol degradation by microwave heating and by hydrothermal treatment

7/25/2019 Comparation Glycerol Degradation by Microwave Heating and by Hydrothermal Treatment

1/6

83

Vol. 10 No. 2 : 83-88INDUSTRI

ISSN 1693-0533

COMPARATION GLYCEROL DEGRADATION

BY MICROWAVE HEATING

AND BY HYDROTHERMAL TREATMENT

Lailatul Qadariyah1, Siti Machmudah1,2, Armando T.Quantain3,

Mitsuru Sasaki3, Motonobu Goto2, Sumarno1, Mahfud11)Departement of Chemical Engineering, Faculty of Industrial Technology

Institut Teknologi Sepuluh Nopember

Kampus ITS Sukolilo Surabaya 60111, Indonesia2)Bioelectrics Research Center, Kumamoto University, Japan

3)Graduate School of Science and Technology, Kumamoto University, Japan

Email : [email protected]

Abstract:Degradation of glycerol was carried out by microwave heating and hydrotermal process in temperature

range of 100-200oC, in power range of 200-500 Watt and in reaction time range of 2-60 minutes. The effect of

temperature, power, reaction time and using activated carbon as catalyst was investigated. As a result, the rate of

acetaldehyde formation using microwave heating with activated carbon was higher than the hydrothermal

treatment and microwave heating without a catalyst, but the rate of acrolein formation acrolein was lower than

hydrothermal treatment and microwave heating without a catalyst. The constant rate of glycerol degradation

were 0.012, 0.009, and 0.008 for microwave heating using activated carbon catalyst, hydrothermal, and

microwave heating without catalyst.

Keywords:Degradation, glycerol, microwave, hydrothermal, activated carbon

Abstrak:Degradasi gliserol dilakukan dengan pemanasan microwave dan proses hidrotermal dalam range suhu

100-200oC, range power 200-500 Watt dan waktu reaksi 2-60 menit. Pengamatan dilakukan terhadap pengaruh

suhu, power, waktu reaksi, dan penggunaan karbon aktif sebagai katalis. Sebagai hasilnya, kecepatan

pembentukan asetaldehid menggunakan pemanasan microwave dengan karbon aktif lebih tinggi daripada

proses hidrotermal dan pemanasan microwave tanpa katalis, tetapi kecepatan pembentukan acrolein lebih

rendah daripada proses hidrotermal dan pemanasan microwave tanpa katalis. Konstanta degradasi gliserol

adalah 0.012, 0.009, dan 0.008 masing-masing untuk pemanasan microwave dengan karbon aktif, proses

hidrotermal, dan pemanasan microwave tanpa katalis.

Kata kunci:Degradasi, gliserol, microwave, hidrotermal, karbon aktif

INTRODUCTION

Biodiesel production is expected to increase in

future with the depletion fossil fuels, leading to an

increase in by products of biodiesel production,

approximately 10% of which is glycerol. Glycerol

is widely used in various fields such as food,

pharmacy, and cosmetics. An excessive amount

of glycerol will put downward pressure on its price;

thus, its conversion into added value products is

interest. Decomposition of glycerol produce

varieties of added value products such as acrolein,

acetaldehyde, propionaldehyde, allyl alcohol,

methanol, ethanol, formaldehyde (Buhler et

al.2002), and gas products, such as syngas

(Adhikari et al. 2007; Bird et al. 2008; Slinn et al.

2008; Vallyapan et al. 2008).

Decomposition of glycerol has been widely

carried out with or without catalyst. Reactions ofglycerol decomposition have been studied with

various processes such as pyrolysis (Valliyappan

et al. 2008), steam reforming (Adhikari et al. 2007;

Bird et al. 2008; Slinn et al. 2008), catalytic

reaction (Lili et al. 2008; Tsukuda et al. 2007) and

subcritical or supercritical water (Antal et al. 1985;

Buhler et al. 2002; May et al. 2010; Ott et al.

2006; Rammaya et al. 1987; Watanabe et al.

2007). In addition to the above reaction, glycerol

decomposition can be performed using microwaves

to generate high temperatures required in glycerol

degradation (Fernandez et al. 2009).

Microwave is not only known as food heating

in the kitchen, but now also used in chemical

reactions. Microwaves are in the region between

infrared and radiowave wavelengths in the

electromagnetic spectrum. More specifically,

microwaves are defined as those waves with

wavelengths between 0.001 and 1 m, whichcorrespond to frequencies between 300 and 0.3


2/6

Lailatul et.al.

84

Comparation Glycerol Degradation

GHz. The microwave band is widely used in

telecommunications. In order to avoid interference

with these uses, the wavelengths of industrial,

research, medical and domestic equipment areregulated both at national and international levels.

Thus, the main operating frequency in the majority

of countries is 2.450 (+/-0.050) GHz (Menendez

et al. 2010).

Polar molecules, like water try to follow the field

and align themselves in phase with the field when

exposed to an oscillating electromagnetic field.

However, owing to inter-molecular forces, polar

molecules experience inertia and are unable to

follow the field. This results in the random motion

of particles, and this random interaction generatesheat (Taylor et al. 2005).

Microwave dielectric heating have many

advantages compared to conventional heating for

chemical conversions. The introduction of

microwave energy into a chemical reaction which

has at least one component which is capable of

coupling strongly with microwaves can lead to

much higher heating rates than those which are

achieved conventionally (Gabriel et al. 1998),

moreover microwave heating achieve rapid and

uniform heating of materials, because microwaves

can penetrate materials and deposit energy, heat

can be generated throughout the volume of the

material, besides that microwave heating is the

transfer of electromagnetic energy to thermal

energy and is energy conversion, rather than heat

transfer (Thoestenson and Chou, 1999).

Microwaves can be utilitized for selective

heating of materials. The molecular structure

affects the ability of the microwave to interact with

materials and transfer energy. Based on its

characteristic of microwave, activated carbon is

used not only as a catalyst, but also as an absorber

of microwave. In activated carbon, delocalized

-electrons are free to move in relatively broad

regions, an additional and very interesting

phenomenon may take place. The kinetic energy

of some electrons may increase enabling them to

jump out of the material, resulting in the ionization

of the surrounding atmosphere. At a macroscopic

level, this phenomenon is perceived as sparks or

electric arcs formation. But, at a microscopic level,

these hot spots are actually plasmas. Most of the

time these plasmas can be regarded as

microplasmas both from the point of view of space

and time, since they are confined to a tiny regionof the space and last for just a fraction of a

second. An intensive generation of such

microplasmas may have important implications for

the processes involved (Menendez et al. 2010).

There are few research related to glycerol

degradation using microwave heating. Fernandez

et al. (2009) conducted pyrolysis of glycerol over

carbonaceous catalyst to produce synthesis gas

using microwave. This study focuses on the

degradation of glycerol using microwave heating

and hydrothermal process and comparing both ofthem. The effect of reaction time, power and

temperature were observed.

The hydrotermal technologies are widely used

both in organic reactions and extraction. The

water properties are dependent on temperature

and pressure. In the subcritical region, water has

different properties from water at room

temperature: its ion product is higher than in

ambient conditions, meaning that it acts as an acid/

base catalyst precursor. In a hydrothermal

process, water may act not only as a solvent but

also as a reactant, catalyst or product (Kruse and

Dinjus, 2007).

Buhler et al. (2002) described glycerol pyrolysis

in near-critical and supercritical water through two

competing pathways, ionic and free radical. The

ionic reaction pathway was favored within the

subcritical region due to the waters high ion

product; the free radical pathway was favored for

supercritical water, where the ion product of water

and dielectric constant were low. Buhler et al.

(2002) conducted experiments in the temperature

range of 622-748 K, pressures of 25, 35 or 45

MPa, and reaction times of 32 to 165 s.

MATERIALS AND METHODS

Materials

Glycerol with 99% purity, acetaldehyde,

acetonitrile, HClO4and BTB were purchased from

Wako Pure Chemical Co., Japan. Acrolein was

obtained from Tokyo Chemical Industry Co., LTD,

Japan.


3/6

85


ISSN 1693-0533

Methods Microwave HeatingThe experiments were carried out in

temperature range of 100-200oC, power range of

200-500 Watt and reaction time range of 20-60minutes. The experiments were conducted in a

teflon reactor with a volume 100 cm3. The

glycerol solution 0.96 M was loaded to reactor.

Figure 1. Acetaldehyde yield vs reaction time at

200oC.

The sealed reactor was heated in microwave

(Shikoku Instrumentation Co., Ltd., Japan)

equiped with fiber optic termocouple. After a

certain time, the microwave was turned off, and

the reactor was immersed in a water bath. Prod-

uct liquid was analyzed by HPLC.

Hydrothermal TreatmentThe experiments were carried out in a SUS 304

reactor with an inner volume of 8.8 cm3(AKICO

Co., Ltd., Japan) in time reaction range of 20-60

minutes at 200oC. The reactor containing the

glycerol solution 0.96 M was purged by Argon

gases to eliminate air, sealed and heated in an

electric furnace (ISUZU Co., Ltd., model NMF-

13AD). Following the desired time, the reactorwas immersed in a water bath to stop the reaction.

Product Analysis

The liquid product was analyzed by HPLC

installed with an ODS-3 Inertsil column using

0.6 ml/min of 20% volume acetonitrile in water.

The column was maintained at 30oC and the

volume injected was 20 L. The analysis was

performed using a UV-Vis detector at 210 nm.

The Chromatograph peaks were identified by

comparison of retention time of sample with thoseof standard compounds. The concentration of

un-reacted glycerol was analyzed by HPLC with

a Sugar SH-1011 column using RI detector.

Mobile phase was HClO4(0.003 M) and BTB

(0.1 M) for coloring medium with flow rate of 1ml/min and 0.5 ml/min, respectively. Column

temperature was held on 60oC.

RESULTS AND DISCUSSION

Experiments were carried out under microwave

heating without and with activated carbon as

catalyst. Microwave heating was indicated as mw.

As a comparison, hydrotermal treatment was also

carried out on glycerol degradation. Product yield

was defined as concentration of product divided

by initial concentration of glycerol, while

conversion of glycerol was obtained based on

initial and residual concentration of glycerol. The

identified products were acetaldehyde and

acrolein.

The Effect of Reaction ConditionsThe effect of reaction time on acetaldehyde yield

at various method can be seen in Figure 1.

Acetaldehyde yield in microwave heating activated

carbon catalyst is higher than hydrothermal

treatment and microwave heating without catalyst.

Although measurements recorded same

temperature of 200oC, but in microwave heating

gives rise to hot spots, which can be considered

as microplasmas, inside the dielectric solid,

where the temperature is much higher than the

average temperature of the bed (Fernandez et al.,

2010). This affects the reaction and the results of

acetaldehyde is higher compared to microwave

heating without a catalyst or a hydrothermal

process, but at longer reaction time of 40 minutes,

hydrotermal treatment produced acetaldehyde yield

is higher than microwave heating using catalyst.

With increasing reaction time, acrolein

decreased. Acrolein yield obtained using

microwave heating without catalysts have the

differences 13-40% of acrolein yield in

hydrothermal treatment, whereas by microwave

heating using catalyst, acrolein yield is very low.

This indicates an activated carbon catalyst

selectively produces more acetaldehyde than

acrolein. In Figures 1 and 2, both acrolein andacetaldehyde decreased with increasing of


4/6

Lailatul et.al.

86


reaction time. In this research, there are many

un-identified products but Stein and Antal (1983)

have shown that acrolein and acetaldehyde

decomposed into CO, CO2, and other products.

The effect of temperature was conducted at

reaction time of 50 minutes without catalyst.

Acetaldehyde yield was higher than acrolein yield.

It can be seen in Figure 3, but both of them show

the same trend curve. The formation of acrolein

and acetaldehyde occur in a competitive reaction.

Antal et al. (1985) stated that acrolein can be

formed from glycerol via dehydration followed by

another dehydration. The intermediate

2-hydroxypropanal could also suffer homolytic

cleavage to form acetaldehyde and formaldehyde.

Buhler et al. (2002) explained acrolein and

acetaldehyde is formed by ionic and by radical

reaction. If glycerol is protonated at secondary

OH-group, only the formation of acrolein occurs,

but for primary carbenium ion, competitivereaction occur.

Figure 4 shows the effect of microwave power

at reaction time of 2 minutes using activated

carbon catalyst. In a short time, acrolein does not

appear as product, only acetaldehyde andun-identified peaks appear as product.

Experimentally, the reaction temperature was also

recorded at each power. The temperature

increased with the power of microwave as shown

by Table 1.

Figure 2. Acrolein yield versus reaction time at

200oC.

Figure 3. Acetaldehyde and acrolein yield vs

temperature at reaction time of 50 minuteswithout catalyst.

Figure 4. Acetaldehyde yield vs power at reaction

time of 2 minutes using catalyst of

activated carbon.

Table 1. The temperature of reaction at various

power

Power (Watt) T(oC)

200 70.5

300 97

400 117.1

500 181

600 215.7

At power of 500 Watt and reaction time of 2

minutes, fiber optic thermocouple recorded the

temperature of 181oC and acetaldehyde yield was

0.33 mol%, while in the hydrothermal treatment,

the temperature of 200oC and reaction time of 20

minutes, acetaldehyde yield was 0.24 mol%. This

indicated the microwave heating with activated

carbon catalyst is an efficient and effective heating

due to shorter heating produces higher

acetaldehyde yield.

Kinetic Analysis

The effect of reaction time on conversion ofglycerol can be seen in Figure 5. The conversion


5/6

87


ISSN 1693-0533

Kinetic analysis for glycerol degradation was

conducted based on data for a reaction time of

20-60 minutes at temperature of 200oC by

hydrothermal treatment, microwave heating

without and with catalyst.

The mechanism of glycerol degradation was

complicated by the many unidentified products, sosimplifications were made to determine the

kinetics equation. The kinetic equation was

calculated based on the initial and remaining

concentrations of glycerol. The overall rate

reaction was described by pseudo-first-order

kinetics due to the two reactants, but the amount

of water was excessive can be expressed in the

following forms:

Glycerol + Water ======> products

Reaction rate:

b

B

a

A1A CCk

dt

dC= (1)

1a,Ckdt

dCA

'

1A

== (2)

Here k1 is kinetic constants of glycerol

consumption and k1is k

1[C

B]b, respectively, and

CA

, CB

are the concentration of glycerol, water.

The rate constant, k1, was determined from

equation (2) can be seen in Table 2.

CONCLUSIONS

The microwave heating using activated carbonproduced acetaldehyde higher than the

hydrothermal treatment and microwave heating

without a catalyst, but produced acrolein lower

than hydrothermal treatment and microwave

heating without a catalyst.

Acetaldehyde and acrolein yield increased with

the temperature and acetaldehyde yield was higher

than acrolein yield.

At reaction time of 2 minutes, the reaction only

produced acetaldehyde and un-identified product.

The rate of glycerol degradation using

microwave heating with activated carbon was

higher than hydrothermal and microwave heating

processes without catalyst where k1 values were

0.012, 0.009, and 0.008 for microwave heating

using activated carbon catalyst, hydrothermal, and

microwave heating without a catalyst.

REFERENCES

Adhikari, S., Fernando, S., and Haryanto, A.

(2007),Production of hydrogen by steam

reforming of glycerin over alumina-supported

metal catalysts, Catalysis Today, Vol. 129, pp.

355-364.

Antal, Jr, M. J., Mok, W.S.L., Roy, J.C., and

T-Raissi, A. (1985),Pyrolytic sources of

hydrocarbons from biomass,J. Anal. Appl.

Pyrolysis, Vol. 8, pp. 291-303.

Bird, A.J., Pant, K.K., and Gupta, R.B. (2008),

Hydrogen production from glycerol by

reforming in supercritical water over Ru/Al2O

3

catalyst, Fuel, Vol. 87, pp. 2956-2960.

of glycerol in microwave heating using catalyst was

higher than in hydrothermal treatment and in mi-

crowave heating without catalyst. The highest of

glycerol conversion was 55% at reaction time of60 minutes by microwave heating using catalyst.

Figure 5. The conversion of glycerol vs reaction

time at 200oC.

Table 2. Reaction rate constant at certain

temperature.

k1

(min-1

)

Microwave heating with

catalyst0.012

Microwave heating

without catalyst0.008

Hydrothermal treatment 0.009

Method


6/6

Lailatul et.al.

88


Buhler, W., Dinjus, E., Ederer, H.J., Kruse, A.,

and Mas, C. (2002), Ionic reactions and

pyrolysis of glycerol as competing reaction

pathways in near- and supercritical water,J.Supercrit. Fluids, Vol. 22, pp.37-53.

Fernandez, Y., Arenillas, A., Dez, M.A., Pis, J.J.,

and Menendez, J. A., (2009), Pyrolysis of

glycerol over activated carbons for syngas

production,J. Anal. Appl. Pyrolysis 84, 145

150.

Gabriel, C., Sami Gabriel, S., Grant, E.H., a,b,

Ben S. J. Halstead, B.S.J., and Mingos, D.M.P.

(1998), Dielectric parameters relevant to

microwave dielectric heating, Chemical

Society Reviews, Vol. 27, pp.213-223.Kruse, A., and and Dinjus, E. (2007),Hot

compressed water as reaction medium and

reactant 2. Degradation reactions,J. Supercrit.

Fluids, Vol. 41, pp. 361379.

Lili, N., Yunjie, D., Weimiao, C., Leifeng,G.,

Ronghe, L., Yuan, L., and Qin, X. (2008),

Glycerol dehydration to acrolein over activated

carbon-supported silicotungstic acids,Chinese

J. Catalyst, Vol. 29 (3), pp.212214.

May, A., Salvada, J.,Torras, C., and

Montana, D. (2010),Catalytic gasification of

glycerol in supercritical water, Chem. Eng. J,

Vol. 160, pp. 751759.

Menndez, J.A., Arenillas, A., Fidalgo, B.,

Fernndez, Y., Zubizarreta, L., Calvo, E.G., and

Bermdez, J.M. (2010),Microwave heating

processes involving carbon materials, Fuel

Processing Technology, Vol.91, pp. 18.

Ott, L., Bicker, M., and Vogel, H. (2006),

Catalytic dehydration of glycerol in sub-and

supercritical water: a new chemical process for

acrolein production, Green Chem, Vol. 8, pp.

214220.

Ramayya, S., Brittain, A., DeAlmeida, C., Mok,

W., and Antal Jr, M.J. (1987),Acid-catalysed

dehydration of alcohols in supercritical water,

Fuel, Vol.66, pp. 13641371.Slinn, M., Kedall, K., Mallon, C.,and Andrews,

J. (2008), Steam reforming of biodiesel by-

product to make renewable hydrogen,

Bioresource Technol, Vol. 99, pp. 5851-5858.

Stein, Y.S., and Antal, Jr, M.J. (1983),A study of

the gas-phase pyrolysis of glycerol,Journal

of Analytical and Applied Pyrolysis, Vol 4,

pp.283-296.

Taylor, M., Atri, B.S., and Minhas, S. (2005),

Developments in microwave chemistry,

Evalueserve, pp.1-50.Thostenson, E.T., and Chou, T.-W. (1999),

Microwave processing: fundamentals and

applications, Composites: Part A, Vol.30, pp.

10551071.

Tsukuda, E., Sato, S., Takahashi, R., and

Sodesawa, T. (2007), Production of acrolein

from glycerol over silica-supported heteropoly

acids,Catalysis Communications, Vol. 8, pp.

13491353.

Valliyappan, T., Bakhshi, N.N., and Dalai, A.K.

(2008),Pyrolysis of glycerol for the production

of hydrogen or syngas,Bioresource Technol,

Vol. 99, pp. 44764483.

Watanabe, M., Iida, T., Aizawa, Y., Aida, T.M.,

and Inomata, H. (2007),Acrolein synthesis

from glycerol in hot-compressed water,

Bioresource Technol, Vol. 98, pp. 1285-1290

comparation glycerol degradation by microwave heating and by hydrothermal treatment

Documents