Renaissance of Nuclear Energy in the USA Opportunities Challenges and Future Research Needs

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Masahiro Kawaji and Sanjoy Banerjee

Abstract The future of nuclear energy is an important issue for many countries intending to reduce their dependence on fossil fuels and achieve the reduction targets for green house gas (GHG) emissions. As of June, 2008, there were 439 operating nuclear reactors with a total generating capacity of 372 GWe and 42 power reactors under construction in 15 countries. In the USA, a total of 104 nuclear reactors currently produce 20% of the electricity and account for at least 70% of all GHG-free electricity generation. Their performance has been improving steadily over the past 20 years and has now reached 90% capacity factor. The Energy Policy Act of 2005 authorized future nuclear R&D and provided incentives for construction of new nuclear plants. As a result, there are now 17 COL applications for construction of as many as 26 new reactors in the USA. This paper summarizes some of the opportunities, challenges and future research needs for achieving and sustaining nuclear renaissance in the USA.

Keywords Nuclear energy • Nuclear reactors • Nuclear power • LWR • PWR • BWR

1 Introduction

The future of nuclear energy is an important issue for many countries in the world aiming to reduce both their dependence on fossil fuels and green house gas (GHG) emissions. As of June, 2008, there were 439 operating nuclear reactors with a total generating capacity of 372 GWe and 42 power reactors were under construction in 15 countries. Today, the nuclear power accounts for approximately 17% of worldwide electricity generation. In 2004, the United States, France and Japan together accounted for ~56% of the nuclear electricity generation capacity as shown in Fig. 1, and their share is expected to decrease slightly to ~50% in 2020 as other countries, especially

The Energy Institute, City University of New York, New York, USA e-mail: [email protected]

g 26

1 10

ra 8

OO3.6 India (7) Canada (7) Ukraine (7) 2,0 South Africa (8)

2004 2020

Source: Based on annual nuclear power generation, TWh Share of world nuclear electricity generation [1]

OO3.6 India (7) Canada (7) Ukraine (7) 2,0 South Africa (8)

2004 2020

Source: Based on annual nuclear power generation, TWh Share of world nuclear electricity generation [1]

United Kingdom (12)

China, Russia and India plan to expand their nuclear energy generation [1]. European countries, on the other hand, have reduced their use of nuclear power in recent years but countries such as United Kingdom and Italy have decided to deploy more nuclear power in the future.

In the USA, 85% of all the energy consumed comes from fossil fuels: oil, natural gas, and coal [2]. The rest is provided by nuclear and hydro. The renewable energy sources such as solar, wind and biomass contribute very little at the present time. In electricity generation, the fuels used in US power plants are coal (48.5%), natural gas (21.3%), nuclear (19.6%), hydro (5.9%), wind (1.3%), petroleum (1.1%), wood (0.4%), waste (0.4%), geothermal (0.4%) and solar/PV (<0.1%).

As developing countries increase their electricity use and plug-in hybrid and electric vehicles are commercialized in the near future, the global consumption of electricity is expected to keep growing at a rapid pace. If GHG emission is to be significantly reduced in the next 20-40 years, the role of nuclear energy in the global energy supply needs to be expanded significantly since the renewable energy sources could take many years to become a significant source of nonfossil energy.

2 Opportunities and Challenges for Nuclear Energy in the USA

Nuclear and hydroelectric power accounts for most of non-CO2 emitting source of electricity in the USA as shown in Fig. 2a. The nuclear share has been steady at about 20% over the past 20 years, and now accounts for at least 70% of all GHG-free electricity generation (Nuclear Energy Institute website: http://www.nei.org/ resourcesandstats/documentlibrary/reliableandaffordableenergy/graphicsand-charts/uselectricitygenerationfuelshares/) (Fig. 2b).

A total of 104 nuclear reactors are currently operating in the USA and produce 800 billion kilowatt hours of electricity per year. Some nuclear power plants have increased their power output so that additional electricity equivalent to 16 new units has been added to the grid through power uprates. The existing nuclear power plants have also improved their operating performance significantly in the past 20 years as evident from their capacity factor data [3], reaching 90% as shown in Fig. 3.

In 2009, the USA officially entered the license renewal era, as two reactors passed the 40-year mark and are continuing to operate. Many of the reactors that soon enter their license renewal periods have been slightly less productive. Thus, as more reactors move into their fourth decade of operation and beyond, the challenge now is to continue achieving capacity factors at the current level.

In spite of their excellent performance record in the past 20 years, no nuclear power plants have been built and nuclear R&D was severely curtailed after the last of the Gen-II reactors went online in the early 1990s. A decade later, the Energy Policy Act of 2005 authorized future nuclear R&D and provided incentives for construction of new nuclear plants. As of June, 2009, 17 Construction and Operating License (COL) applications for as many as 26 new reactors have been docketed by the US Nuclear Regulatory Commission [4]. The planned sites and reactor types to be built are shown in Fig. 4. The first COL licenses are expected to be granted in July 2011 as shown in Table 1.

Fig. 2 Power plant fuels used (a) and emission-free electricity generation (b) in the USA (2008)

1GG-

iPWRs dlBWRs

CS O

Q c ra iPWRs dlBWRs

CS O

Fig. 3 Nuclear reactor capacity factors in the USA

G 1976- 1979-1982- 1985- 1988- 1991-1994-1997- 2cGG- 2GG3-2GG6-1978 1981 1984 1987 199G 1993 1996 1999 2GG2 2GG5 2GG8

Fig. 3 Nuclear reactor capacity factors in the USA

Fig. 4 COL applications announced for new nuclear reactors in the USA as of January, 2009 [4]

There are five new designs of advanced reactors which will be built in the future. Some designs have already been certified by the US Nuclear Regulatory Commission (NRC), and others are currently under review as summarized in Table 2.

Table 1 Expected dates for COL issuance and design certification [4]

NRC target dates for COL

issuance and design certification

Project

Date

North Anna-3

July 13, 2011

Vogtle-3, -4

August 24, 2011

Lee-1, -2

Seplemher27, 2011

Harris-2, -3

November 22, 2011

Summer-2, -3

December 13, 2011

Grand Gulf-3

February 1, 2012

Calvert Cliffs-3

March 16, 2012

US EPR

February 5, 2012

US-APWR

June 25, 2012

These new reactors possess the following advanced features and improvements over the existing reactors: standardized designs; easier to operate; faster and cheaper to build, operate and maintain; simpler and safer; latest technology; less equipment and components; passive safety systems (AP1000 and ESBWR); simplified operations and maintenance. Their power output ranges from 1,100 to 1,700 MWe, and some are already operating (ABWR in Japan) or under construction (US-EPR in Europe, AP1000 in China).

2.1 Financial Challenges

Although many COL applications have been submitted to NRC and are undergoing review, recent economic downturn and credit crisis has created financial obstacles for the construction of new nuclear power plants in the near future. The loan guarantees recently requested by the prospective owners of new reactors amount to $122 billion which is far above the original DOE offer of $18.5 billion. However, under the current economic conditions, financing is difficult to obtain and it would be more realistic to expect four to eight new reactors entering service in the 2018 time frame [5].

Additional financial incentives for construction of new nuclear power plants can be provided by local governments in the form of rate recovery during the construction phase. For example, in 2007, the Florida Public Service Commission adopted new rules that will let investor-owned utility companies recover some of the costs of the new plants before they begin operation (http://www.floridapsc.com/home/ news/?id=459). The partial recovery of the planning and construction costs of a new nuclear plant before it begins operation would allow the companies to recoup those costs earlier and will encourage more investment in the facilities while lessening the chance for "rate shock" that could occur if the company waited to recoup all its construction costs when the plant began operation.

Table 2 Advanced reactor designs

Reactor power Electric output

Reactor type Vendor Design certification (MWt) (MWe) Design life (years)

Table 2 Advanced reactor designs

Reactor power Electric output

Reactor type Vendor Design certification (MWt) (MWe) Design life (years)

API 000

Advanced pressurized water reactor (passive design)

Toshiba-

Westinghouse

Certified by NRC - 2005 Revision under review - expected in 2011

3,400

1,117

60

ESBWR

Boiling water reactor (passive design)

GE-Hitachi

Under review - expected in 2010

4,500

1,560

60

ABWR

Advanced boiling water reactor

Hitachi, GE-Hitachi, Toshiba

Certified by NRC - 1997

3,926

1,350

60

US-EPR

Pressurized water reactor

AREVA

Under review - expected in 2012

4,300

1,600

60

US-APWR

Advanced pressurized water reactor

Mitsubishi

Under review - expected in 2012

4,451

1,700

In the next quarter century, aggressive investments in new plants will be needed along with an ongoing effort to up-rate existing plants; extend operating licenses from 40 to 60 years; and license and construct Gen-III nuclear plants. At the same time, the US government needs to control nuclear materials, assure nuclear nonpro-liferation abroad, and conduct ultimate management of used nuclear fuel.

Nuclear R&D requirements identified by the US Department of Energy (DOE) include understanding how materials age in a harsh reactor environment over many decades of service; developing a sustainable fuel cycle consisting of fuel recycling, advanced reactors, robust waste forms, and a geologic repository; and developing very high-temperature gas reactors (VHTRs) for process industry applications as one of the main Gen-IV reactor designs to be developed by the USA [6].

From a licensing perspective, the thermal-hydraulic performance of nuclear systems during normal operation and accident conditions continues to be central to reactor safety evaluation [7]. This is because many of the current generation of light water reactors have either been granted or are seeking increases in power outputs, requiring better estimates of safety margins. As well, several reactor designs with new, and sometimes passive, safety features require improved understanding for design certification and construction. Generic safety issues have also arisen, e.g., with regard to potential blockage of screens or strainers by debris generated, during blowdown in postulated loss-of-coolant accidents, which may impact long term coolant recirculation and core cooling. An overview of Light Water Reactor Thermalhydraulics and Safety issues is summarized in Table 3.

3.1 Nuclear Engineering Education

To perform the required research, development, and deployment of new reactor technologies in the future, renewed investments into the human capital and infrastructure capabilities as well as expansion of international collaboration will be required [6]. The expansion of nuclear power for electricity generation would lead to an increased demand for skilled labor at all levels. It is expected that each new reactor will require between 1,400 and 1,800 workers for construction with peak employment of up to 2,300 workers. Once built, these potential power plants would require tens of thousands of permanent, full-time workers to operate the plants and additional supplemental labor for maintenance and outages.

American industry faces increased competition for skilled talent and the nuclear industry is not an exception. In addition, the nuclear industry is also challenged by an aging work force, with nearly 50% of workers aged 47 or older who will be eligible to retire during the next 10 years. Along with plans for industry growth, the expected attrition of a large portion of the industry's total work force has prompted an unprecedented recruitment effort throughout the industry. Still, recruitment of skilled workers remains a significant challenge for the nuclear industry.

Table 3 LWR thermalhydraulics/safety issues overview [7]

Current

Next generation

Issues

BWRs EPU PWRs EPU Generic areas API000

ESBWR

USAPWR

CHF (new fuel X

designs, experiments & correlations) Neutronic- X

thermalhydraulic instability/ATWS (coupling analysis tools) LOCA (best estimate & uncertainties modeling) CCFL/reflux condensation (experiments & models) Sump screen/strainer ?

blockage Containment X

overpressure credit (model accuracy) Steam dryer failure X

(experiments & models) Specific safety features (behavior)

Gas in safety Gas in safety Gas in safety Refluxing injection injection injection lines lines lines

Refluxing

ADS systems

Containment noncondensable distribution

Accumulator, delayed injection secondary depressurization

Secondary depressurization safety injection

Table 4 Numbers of nuclear engineering and health physics degrees granted in the USA

Table 4 Numbers of nuclear engineering and health physics degrees granted in the USA

Year

Nuclear engineering degrees8 B.S. M.S. Ph.D.

Health physics degreesb Year B.S. M.S.

Ph.D.

2008

454

260

127

2008

73

108

8

2007

413

227

89

2007

79

91

28

2006

346

214

70

2006

71

90

12

2005

268

171

74

2005

78

77

14

2004

219

154

75

2004

54

64

14

2003

166

132

78

2003

56

73

25

2002

195

130

67

2002

41

76

20

2001

120

145

80

2001

37

71

23

2000

159

133

74

2000

33

79

24

1999

55

115

22

aSurvey of 31 universities with nuclear engineering programs bSurvey of 26 universities granting health physics degrees aSurvey of 31 universities with nuclear engineering programs bSurvey of 26 universities granting health physics degrees

The US NRC has estimated that the nuclear industry as a whole will need an influx of 90,000 new workers within 10 years. Fortunately, increasing public recognition of the value of nuclear energy as a clean, reliable electricity source is leading more young people to identify nuclear energy as a career path. The number of nuclear engineering programs at US institutions dropped from about 50 programs in 1990 to fewer than 30 in the late 1990s, but bounced back to more than 30 programs currently. A recent Department of Energy study also found that enrollments in undergraduate nuclear energy programs have grown to more than 1,900 in the 2006-2007 academic year, compared to fewer than 500 eight years ago. Graduate enrollments also have jumped to more than 1,100 in the 2006-2007 year vs. just 220 in 1998-1999. The numbers of undergraduate and graduate degrees awarded in nuclear engineering and health physics programs between 2000 and 2008 are shown in Table 4 [8].

4 Summary

Nuclear power is an important source of emission-free electricity that can contribute to reduced dependence on fossil fuels and mitigation of global warming effects around the world. In the USA, aggressive investments in new plants will be needed in the next quarter century, along with an ongoing effort to uprate existing plants, extend operating licenses from 40 to 60 years, and license and construct Gen-III nuclear plants. To date, a total of 17 Construction and Operating License (COL) applications have been submitted for construction of five types of advanced reactors, reflective of the opportunities for nuclear renaissance in the USA. At the same time, there are challenges to be faced in controlling nuclear materials, assuring nuclear nonproliferation abroad, and conducting ultimate management of used nuclear fuel. To perform the required R&D and new reactor deployment, renewed investments into the human capital and infrastructure capabilities will be required.

References

1. Nuclear News (2009) American Nuclear Society, January, 2009, p. 44

2. Nuclear Energy Agency (2008) Nuclear energy outlook 2008. OECD, Washington, DC, ISBN: 9789264054103

3. Nuclear News (2009) American Nuclear Society, May, 2009, p. 33

4. Nuclear News (2009) American Nuclear Society, January, 2009, pp. 35-36

5. Nuclear News (2009) American Nuclear Society, June, 2009, p. 28

6. US Department of Energy (2008) Required assets for a nuclear energy applied R&D program. Draft Report by Idaho National Laboratory (September, 2008)

7. Banerjee S, Abdullahi Z (2009) Thermal and hydraulic issues related to light water reactors. A Keynote paper to be presented at the 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13), Sept. 27 - Oct. 2, 2009, Kanazawa, Japan

8. Nuclear News (2009) American Nuclear Society, July, 2009, pp. 93-94

Eco-Friendly Production of Biodiesel by Utilizing Solid Base Catalysis of Calcium Oxide for Reaction to Convert Vegetable Oil into Its Methyl Esters

Masato Kouzu

Abstract Since biodiesel is commonly produced by converting vegetable oil into its methyl esters with the help of catalysis of alkali-hydroxide dissolved in methanol, it is necessary to eliminate the homogeneous catalyst from the crude biodiesel by washing with a large amount of water. With a view of studying the eco-friendly production without discharging wastewater, we investigated the solid base catalysis of calcium oxide. Primarily, transesterification of soybean oil at reflux methanol under atmospheric pressure was carried out on a glass batch reactor, for testing calcium oxide as compared with the other solid base such as calcium hydroxide magnesium oxide, and alumina supported potassium. Calcium oxide was superior in the catalytic activity and the reusability to the other solid bases. Additionally, the interesting facts on the solid base catalysis were found through the primary test. Based on these results, the practical catalyst was manufactured as an experiment. For testing the practical catalyst, rapeseed oil was transesterified on the laboratory scale pilot plant.

Keywords Biodiesel • Solid base catalyst • Calcium oxide • Lime stone

1 Introduction

Biodiesel is an eco-friendly alternative to fossil diesel fuel, because the raw material is vegetable oil that is one of the renewable energy resources. Additionally, diesel engine fueled by biodiesel is sure to reduce toxic emissions like SOx, unburned hydrocarbons, and soot particles [1]. In 2008, the total of biodiesel produced globally seems to reach ten-million tons.

Commonly, biodiesel is produced by converting vegetable oil into its methyl esters with the help of catalysis of alkali-hydroxide dissolved in methanol. The homogeneous catalyst brings about the very fast conversion of vegetable oil:

Research Center of Fine Particle Science and Technology, Doshisha University, Kyoto, Japan e-mail: [email protected]

soybean oil was turned into biodiesel after 1 h of the base-catalyzed reaction carried out at 333 K under atmospheric pressure in the presence of sodium hydroxide dissolved in methanol [2]. However, a massive amount of wastewater is discharged from the production process, because it is necessary to wash the homogeneous catalyst off the crude biodiesel. Also, emulsification of biodiesel occurs in the washing step with the result that it is very difficult to operate the production process.

For the problems mentioned above, various solutions have been proposed by many researchers. Saka et al. has investigated the non-catalytic reaction in supercritical methanol [3]. The reaction was performed at 623 K under 30 MPa as a result and rapeseed oil was converted into biodiesel after only 4 min. In their recent study, the non catalytic reaction was modified by pre-treating the feedstock oil with subcritical water [4]. On the other hand, the enzymatic reaction can convert vegetable oil into its methyl esters at room temperature [5]. In order to improve the cost efficiency of the biodiesel production, lipase-producing microbial cells immobilized within porous support material was used as the whole-cell biocatalyst [6]. Also, the heterogeneous catalytic reaction is useful in producing biodiesel without discharging wastewater. There was a research paper stressing that anion-exchange resin is a candidate for the solid base catalyst [7]. From the economical point of view, our interests were taken in utilizing the solid base catalysis of calcium oxide [8].

Calcium oxide is one of typical solid bases that can catalyze reactions making carbon-carbon bond, such as aldol addition, Michael addition, and Tishchenko reaction [9-11]. For these reactions, as well as the reaction to produce biodiesel, the solid base catalysis is effective in generating nucleophile [12]. Due to the molecular structure formed out of ionic crystal, oxygen anion functions as the basic active site. However, the catalytic activity was seriously reduced by contacting with CO2 and H2O contained in air.

In this paper, we investigated solid base catalysis of calcium oxide for the reaction to produce biodiesel, with a view of studying the eco-friendly production. Primarily, on a batch glass reactor, soybean oil was transesterified with refluxing methanol under atmospheric pressure, in order to test calcium oxide as compared with calcium hydroxide, magnesium oxide, strontium oxide, anion-exchange resin, and alumina supported potassium. Mechanism on the heterogeneous catalytic reaction was discussed with relating to properties of the catalyst collected after the reaction. Furthermore, based on results of the primary test, the practical catalyst was manufactured as an experiment. In order to test the practical catalyst, the rapeseed oil transesterification was performed on the laboratory scale pilot plant.

2 Materials and Methods

Calcium oxide (CaO) was prepared by calcining lime stone powder at 1,173 K for 1.5 h in helium gas flow of 100 ml min-1. Purity of the lime stone powder was 99.5%. Properties of CaO were shown in Table 1, in comparison with those

Table 1

Properties of solid base catalysts tested

in the present study

Surface area (m2 g-1)a

Basic strengthb

CaO

13

15.0 < H_ < 18.4

Ca(OH)2

16

9.3 < H_ < 15.0

MgO

198

15.0 < H_ < 18.4

SrO

2

15.0 < H_ < 18.4

K/Al2O3

102

15.0 < H_ < 18.4

Resinc

-

-

a Calculated by BET method using data on nitrogen adsorption at 77 K b Determined by indicator method cAnion-exchange resin, a commercially available product a Calculated by BET method using data on nitrogen adsorption at 77 K b Determined by indicator method cAnion-exchange resin, a commercially available product of the other solid bases tested in the present study. Calcium hydroxide (Ca(OH)2) was made of CaO, by storing in humid nitrogen. For obtaining magnesium oxide (MgO) and strontium oxide (SrO), their carbonates were calcined at the prescribed temperature: 773 K for MgO and 1,323 K for SrO. For alumina supported potassium (K/Al2O3), its precursor was prepared by impregnating potassium nitrate onto alumina support. Then, calcination of the precursor was conducted at 773 K for transforming into the solid base catalyst. Anion-exchange resin was the commercially available product. Prior to the test, the resin was washed with methanol on a glass column and a tubular pump.

For the practical catalyst manufactured as an experiment, uneven form of the roughly crushed lime stone was the raw material. Size distribution of the raw material was regulated within the range of 1.0-1.7 mm by sieving.

Primarily, on a glass batch reactor, soybean oil was transesterified at reflux of methanol in the presence of the solid base tested. Soybean oil was of edible grade: Acid value <0.1 mg-KOH g-1 and water content <0.01%. For methanol, water content was below 0.1%. After 100 ml of soybean oil was mixed with 50 ml of methanol in the glass batch reactor, 14 mmol of the catalyst was stirred into mixture of the reactants. Then, the glass batch reactor was heated on a mantle heater, and reflux of methanol was continued for 2 h. At the interval of 0.5 h, a small amount of the transesterified oil was withdrawn for analysis to determine the yield of fatty acid methyl esters (FAME). The analysis was carried out on Agilent 6890 gas chromatograph which was equipped with a cool-on column reactor, a stainless steel capillary column and a flame ionization detector.

Following the transesterifying operation, whole of the product containing the catalyst was collected. The catalyst was separated from the product by filtration, in order to examine the properties by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In advance of these instrumental analyses, the separated catalyst was washed several times with methanol.

The practical catalyst, prepared on the basis of results of the primary test, was employed for the rapeseed oil transesterification on a laboratory scale pilot plant. As shown in Fig. 1, the laboratory scale pilot plant was characterized by the batch unit consisting of a circulating stream passing through a column reactor. Into the column reactor, 20 ml of the practical catalyst was packed. First, 270 ml of rapeseed

Fig. 1 Schematic flow diagram of a laboratory scale pilot plant to test practical catalyst manufactured as an experiment

oil was emulsified with 210 ml of methanol in the glass vessel at the temperature of 333 K under atmospheric pressure. Then, the emulsified reactants were pumped into the column reactor at the feeding rate of 50 ml min-1. The circulation was continued with keeping temperatures of the column reactor and the glass vessel at 333 K till rapeseed oil was converted into biodiesel.

3 Results and Discussion 3.1 Catalytic Activity

Figure 2 shows the yields of FAME produced by transestrifying soybean oil for 1 h in the presence of the solid base tested. CaO was employed for the reaction as a result and the yield of FAME reached 93%. For Ca(OH)2, MgO, and anion-exchange resin, the FAME yield was 13%, 4%, and 14%, respectively. Therefore, it was evident that CaO was very active in the reaction as compared to the other solid bases mentioned above. However, relationship between the catalytic activity and the basic strength among these solid bases was not appreciable.

As shown in Fig. 3, there were the solid bases matching CaO for the catalytic activity: SrO and K/Al2O3. But, SrO could not reused for the reaction successively repeated, due to the serious leaching of the catalyst. Although K/Al2O3 could be collected after the reaction, the yield of FAME produced in the presence of the reused catalyst seriously decreased. The deactivation of the catalyst was caused by leaching of the active phase from the catalyst. On the other hand, CaO seemed to be reused without deactivating. From these results, we concluded that calcium

NaOH CaO Ca(OH)2 MgO Resin

Fig. 2 Yield of FAME produced by transesterifying soybean oil with methanol for 1 h in the presence of the solid base tested

NaOH CaO Ca(OH)2 MgO Resin

Fig. 2 Yield of FAME produced by transesterifying soybean oil with methanol for 1 h in the presence of the solid base tested

CiO SrO K A1203

Fig. 3 Variation in yield of FAME with successive repetition of reaction, with reusing the solid base catalyst oxide is the solid base catalyst useful in producing biodiesel. Also, we were very interested in the good reusability of CaO, because researchers in the field of solid base catalyst know that calcium oxide is deactivated by contacting with a slight CO2 and moisture contained in air [12]. Since it was difficult to guard the catalyst perfectly from air-exposure during the test to evaluate the reusability, it was expected that the reused CaO was deactivated to some extent. Accordingly, it was very important to understand the mechanism on the reaction catalyzed by CaO.

3.2 Mechanism on the Catalytic Reaction

From our interest in the reusability of CaO, a mechanism on the catalytic reaction was investigated by appreciating change in properties of the catalyst during the soybean oil transesterification. Figure 4 show change in shape of the catalyst

Fig. 4 SEM images of catalyst â

White Queen Quotes
Reused CaO

particles, observed by SEM. Fresh CaO, obtained after calcination of the raw material, was formed into particles of sub-micron size. After the reaction, the catalyst consisted of particles of two types. One was shaped a large angular rock, and the other looked like a cluster of thin plates. The drastic change of the shape was likely to reflect the chemical conversion of the catalyst.

Figure 5 compares fresh CaO and reused one using their XRD patterns. Only a diffraction pattern of calcium oxide was drawn for fresh CaO, while the diffraction pattern of reused CaO differed obviously from that of fresh one. From the diffraction pattern, it was evident that calcium oxide was turned into calcium diglycerox-ide, Ca(C3H7O3)2. Also, Fig. 5 show that the chemical conversion of CaO was not obvious at 15 min. of the reaction time. When the FAME yield reached 70% at 30 min. of the reaction time, the major compound of the catalyst was calcium dig-lyceroxide. These results indicated calcium oxide was combined with glycerol, and not methanol, under the transesterifying condition.

Since calcium diglyceroxide seemed to be the catalytically active phase of the reused CaO, the reference sample of calcium diglyceroxide (Ca-Gly) was prepared by immersing CaO in glycerol blended with methanol. The soybean oil transesteri-fication was carried out in the presence of Ca-Gly as a result and the catalyst was as active as the reused CaO: The yield of FAME produced after 2 h was close to 90% for Ca-Gly. Furthermore, data from the reaction indicated that Ca-Gly was the tolerant catalyst to air-exposure.

(a)FreshCaO

1

(b) At 1 Smin. of reaction i i

(c) At 3 Omm. of reaction

IJ

(d) Reused CaO

Fig. 5 XRD patterns of catalyst

Fig. 6 Mechanism on conversion of methanol into nucleophile by solid base catalysis of calcium diglyceroxide

A mechanism on the reaction catalyzed by calcium diglyceroxide was illustrated with Fig. 6, assuming that oxygen neighboring calcium cation functioned as the basic active site [13]. When methanol got access to the basic active sites, an attractive intermolecular force causing hydrogen bond was possibly generated between OH groups in the glyceroxide anion and oxygen in methanol. The accessibility was enhanced by the attractive intermolecular force with the result that abstraction of proton for converting methanol into the nucleophile was promoted. Also, the basic site was weaker for Ca-Gly (9.3 < H_ < 15.0) than for CaO (15.0 < H_ < 18.4).

Probably, this was the reason why Ca-Gly was not deactivated in air. Although the catalyst adsorbed CO2 and moisture, they were possibly desorbed from the catalyst under the reacting condition due to weakness of the basic property.

3.3 Performance of the Practical Catalyst

Since data from test on the glass batch reactor indicated that the solid base catalysis of calcium oxide was appropriate to the reaction producing biodiesel, we manufactured the practical catalyst as an experiment. For the practical use, the proper shape matching with the column reactor and the sufficient mechanical strength are required. In order to meet the requirement, the roughly crushed lime stone was selected as the raw material. The manufactured practical catalyst was tested by employing it for the rapeseed oil transesterification performed on the laboratory scale pilot plant.

Figure 7 shows variation in the reaction efficiency with successive repetition of the operation to transesterify rapeseed oil. The transesterifying operation was repeated 17 times with reusing the catalyst. Also, the FAME yield measured after 2 h of the reaction reached 96.5% successively till the number of the repetition times was over 10. Thereafter, the reaction efficiency gradually deceased. In our future work, it is necessary to elucidate the reason that the practical catalyst was deactivated with repetition of the transesterifying operation.

4 Conclusion

In order to study the eco-friendly production of biodiesel, solid base catalysis of calcium oxide for a chemical reaction to convert vegetable oil into its methyl esters was investigated. Data from the test carried out on a batch glass reactor indicated

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Thenumberofsuccessive repetition times

Fig. 7 Variation in reaction efficiency with successive repetition of operation transesterifying rapeseed oil on a laboratory scale pilot plant

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Thenumberofsuccessive repetition times

Fig. 7 Variation in reaction efficiency with successive repetition of operation transesterifying rapeseed oil on a laboratory scale pilot plant that calcium oxide was superior in the catalytic activity and the reusability to the other solid bases: calcium hydroxide, magnesium oxide, strontium oxide, anion-exchange resin and alumina supported potassium. Interestingly, calcium oxide was converted into calcium diglyceroxide during the reaction. Thereafter, calcium dig-lyceroxide functioned as the solid base catalyst. Furthermore, the transformation of the active phase made the catalyst tolerant to air-exposure. When the practical catalyst prepared on the basis of the results mentioned above was tested on the laboratory scale pilot plant, the operation to transesterify rapeseed oil was successively repeated 17 times. However, the reaction efficiency gradually decreased on and after the 11th operation.

References

1. Ma F, Hanna MA (1999) Biodiesel production: a review. Bioresour Technol 70:1-15

2. Freedman B, Pryde EH, Mounts TL (1984) Variables affecting the yield of fatty esters from transesterified vegetable oil. J Am Oil Chem Soc 61:1638-1643

3. Saka S, Kusdiana D (2001) Biodiesel fuel from rapeseed oil as prepared in supercritical methanol. Fuel 80:225-231

4. Saka S (2005) Biodiesel fuel production by supercritical methanol technology. J Jpn Inst Energy 84:413-419

5. Shimada Y, Watanabe Y, Samukawa T, Sugihara A, Noda H, Fukuda H, Tominaga Y (1999) Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase. J Am Oil Chem Soc 76:789-793

6. Oda M, Kaieda M, Hama S, Yamaji H, Kondo A, Izumoto E, Fukuda H (2005) Facilitatory effect of immobilized lipase-producing Rhizopus oryzae cells on acryl migration in biodiesel-fuel production. Biochem Eng J 23:45-51

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8. Kouzu M, Umemoto M, Kasuno T, Tajika M, Aihara Y, Sugimoto Y, Hidaka J (2006) Biodiesel production from soybean oil using calcium oxide as a heterogeneous catalyst. J Jpn Inst Energy 85:135-141

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Part II

Contributed Papers

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