Indian Journal of Chemistry Vol. 51A, Sept-Oct 2012, pp. 1252-1262

Carbon dioxide utilisation

Carbon dioxide – A potential raw material for the production of , fuel additives and bio-derived chemicals

Sivashunmugam Sankaranarayanan & Kannan Srinivasan* Discipline of Inorganic Materials and Catalysis, CSIR-Central Salt and Marine Chemicals Research Institute, Gijibhai Bhadheka Marg, Bhavnagar 364 002, India Email: [email protected]/ [email protected]

Received 12 July 2012; revised and accepted 18 August 2012

Amongst the various greenhouse gases emitted into the atmosphere, carbon dioxide emission is the highest in terms of tonnage and has been identified as a predominant source contributing to climate change. Owing to its abundance through anthropogenic sources, it is highly desirable to utilize CO 2 to produce valuable products, in particular and large volume chemicals, and thereby mitigate significantly its environmental impact. This review aims to cover the attempts made in utilizing CO 2 for the production of fuels, fuel additives and bio-derived chemicals, in particular organic carbonates. Although this review does not intend to encompass the literature in the holistic manner, it does endeavor to provide recent approaches, difficulties, challenges and offer perspective in the years to come on this important area of research.

Keywords : Carbon dioxide utilization, Raw material for fuel production, Syngas, Methane, Dimethyl carbonate, Fatty cyclic carbonate, Glycerol carbonate

Carbon dioxide (CO 2) is a greenhouse gas and occupies International Energy Outlook 2011, world’s energy the top position (more than 80 % in terms of amount related CO 2 emission is estimated to increase from for USA) in the overall emissions amongst other gases 30.2 billion metric tons (BMT) in 2008 to 35.2 and 5 such as (CO), methane (CH 4), 43.2 BMT in 2020 and 2035 respectively. chlorofluorocarbons (CFC’s), etc. Increase in the In the current scenario, decreasing the CO 2 amount emission of greenhouse gases makes significant in the atmosphere is the biggest challenge and needs climate changes and will lead to consecutive effects new ideas and technologies. Possible ways to reduce such as increase in global temperature and changes in the CO 2 concentration in the atmosphere are using wind patterns. China occupies the top position in CO 2 renewable fuels instead of fossil fuels and by emissions with 24 % of world emissions, followed by converting the emitted CO 2 into useful products by United States (18 %), while India contributes around chemical transformations. Although sincere efforts 1 5 %. Longer estimated life time of CO 2 in are being made for replacing fossil fuels by renewable the atmosphere (50-200 years) and a profound surge energy, 6 there are several practical difficulties and in the human related emissions in recent decades limitations. Although a single solution is not going to cause serious concerns on its emission and impact on the environment. Sources of CO 2 emissions can be broadly classified into three categories, namely, stationary, mobile and natural sources. Generally, industrial emissions belong to stationary sources, emissions from vehicles are classified as mobile sources, and emission from volcano are natural sources. 2 Figure 1 shows the different anthropogenic sources of CO 2 and their sinks (based on 2010 data). 3 Burning of fossil resources such as petroleum and coal contributes significantly to CO 2 emission whose rate are estimated at 22.29 and 4 24.65 kg C/GJ, respectively. According to the Fig. 1 − Anthropogenic sources of CO 2 and their sinks. SIVASHUNMUGAM & KANNAN: CO 2 AS POTENTIAL RAW MATERIAL FOR FUEL PRODUCTION 1253

solve such a mega problem, an alternative approach to by its utilization as a source for fuel production. This reduce CO 2 emission is by its value addition to will be advantageous not in terms of value but also in produce large quantities of useful products. Such an significantly curbing its emission, which in turn will approach would also create new opportunities that are mitigate greenhouse effect. hitherto not realized or known. Utilization of biomass for energy and chemical High abundance and low cost are the production is an active research domain currently main advantages of CO 2 as a promising feedstock pursued all over the world because of its ecological 7,8 11 in organic synthesis. CO 2 is an interesting and economic gains. CO 2 is also gaining C1 building block and can be an apt replacement significance in the biorefining processes of biomass to for hazardous molecules like phosgene in many value-added bio-derived chemicals. Herein, recent industrial processes. Efforts have been made to attempts in the use of CO 2 as a raw material for fuel, utilize CO 2 in commercial applications such as food fuel additives and bio-derived chemicals, in particular processing and carbonated beverages. In recent organic carbonates is reviewed (Fig. 3). years, CO 2 has attracted the attention of chemical industries as it can be categorized as a sustainable raw CO 2 for the Production of Fuels material that can be used to produce diverse products Products obtained from CO 2 have applications as through a variety of chemical transformations. fuels and fuel additives. Figure 4 shows the schematic Despite such practices, currently in industries, only representation of production of fuel and fuel 110 million metric tons (MMT) of CO 2 are used for additives from CO 2. Carbon dioxide is in the highly chemical transformation which is less than 1 % of oxidized form, and hence reduction process is largely global emissions. 9 applicable to produce fuel and fuel additives. In redox Sakakura et al. 10 categorized a variety of reactions reactions, high energy substances or electro-reductive using CO 2 as a potential starting material resulting in processes are needed because of high thermodynamic 12 many products. Figure 2 summarizes the possible stability and lower reactivity of CO 2. Chemical reactions and some important chemicals derived using reduction routes are being explored for the reduction CO 2. Production of chemicals like urea and processes. Very recently, a research group carbonates using CO 2 is well-known and has been from University of California at Los Angeles commercialised. Besides chemicals, energy products reported a method wherein genetically engineered from CO 2 would make a considerable impact on its microorganism was deployed for the successful emission. The worldwide requirement of fuels is conversion of CO 2 into fuels such as iso -butanol and nearly two orders of magnitude higher than that of 3-methyl-1-butanol. 13 Carbon Sciences, a California- chemicals. CO 2 emission can be effectively reduced based company is developing a bio-catalytic

Fig. 3 − Overall scheme for the utilization of CO 2 for the Fig. 2 − Possible reactions and important chemicals from CO 2. production of fuel, fuel additives and bio-derived chemicals. 1254 INDIAN J CHEM, SEC A, SEPT-OCT 2012

Fig. 5 − Hydrogenation of CO 2. [Adapted from Ref. 15 with permission from Elsevier, Amsterdam, The Netherlands].

Carbon monoxide Conversion of CO 2 via reverse water gas shift (RWGS) reaction is the most lucrative route for the production of CO (Eq. 1) that can further be used in Fischer-Tropsch (FT) process to produce hydrocarbons.

Fig. 4 − Schematic representation of fuel and fuel additives …(1) production from CO 2. process for converting CO 2 into hydrocarbons such as The equilibrium can be shifted towards the right by methane, ethane and , which can be utilized (a) increasing the CO 2 concentration, (b) operating at 14 instead of and jet fuels. Generally, high H 2 concentration, and, (c) removing the product biocatalytic routes are more expensive and time (water) from the system. 17 Different metals such as Cu, consuming than other catalytic routes. Highly active Zn, Fe and Ce containing catalysts are well known for metal catalysts have been investigated for the the WGS reaction and these catalysts can effectively hydrogenation of CO 2 in homogenous or carry out RWGS reaction also. Apart from these, heterogeneous forms. Pt catalyst was also studied for RWGS reaction with 18,19 20 Hydrogenation of CO 2 results in various products different catalyst supports. Recently, Rosen et al. of C 1-type and higher chain length hydrocarbons reported electroreduction of CO 2 to CO below depending upon the reaction conditions. Hydrogen is overpotential using ionic liquid as electrolyte and generally obtained either from fossil sources or silver cathode as catalyst. through water splitting. Development of various The formation of CO in RWGS reaction is catalyst systems and surface science techniques has explained by two models, namely, redox mechanism created interest in the hydrogenation of CO 2 and formate decomposition mechanism. In the case of in recent years. Direct hydrogenation of CO 2 redox mechanism it was suggested that reduction of and hydrogenation of CO obtained from CO 2 are CO 2 and oxidation of H 2 that result in the formation of 21 among the two possible ways for producing CO and H 2O, occur due to the metal species. In the fuels. Some of the previous studies 15 have case of formate decomposition mechanism, it was suggested that CO 2 hydrogenation proceeds via the suggested that association of H 2 with CO 2 results in dissociative adsorption of CO 2 to form CO and O formate species as intermediate which decomposes to atoms on the surface, which on further give CO. 22 hydrogenation renders products as shown in Fig. 5. Even at 400 °C, due to the low equilibrium Several routes can be proposed for the use of CO 2 in constants, it requires hydrogen-rich or carbon dioxide- hydrogen reduction such as (i) conversion to rich reactant mixtures to yield acceptable results. products via synthesis gas, (ii) direct hydrogenation Otherwise the operating temperature needs to be into useful products, and, (iii) reactions to other increased to around 750 °C. It was identified that products via MeOH. 16 activity of the catalysts depends on the operating This section mainly covers the hydrogenation temperature 23 and both ZnO-Al and ZnO-Cr catalysts process of CO 2 for the production of fuels. show poor activity below 600 °C. Theoretical studies SIVASHUNMUGAM & KANNAN: CO 2 AS POTENTIAL RAW MATERIAL FOR FUEL PRODUCTION 1255

27 to determine the likely reaction mechanisms processes. CO 2 and CO follow different pathways augmented by instrumental techniques, is the during hydrogenation that largely depend on the requirement at this stage to design and develop nature of the catalyst. For example, Fe based catalysts improved catalysts that can work under energy promote hydrocarbons production via CO formation efficient conditions. whereas Co based catalysts convert CO 2 directly to methane due to its limited WGS reactivity. In Hydrocarbons addition, supports and promoters also play an Fischer-Tropsch synthesis is a well-known reaction important role in CO 2 hydrogenation. Although many wherein CO is hydrogenated to give hydrocarbons. In efforts are being made for the production of a modified FT process, hydrocarbons can be prepared hydrocarbon from CO 2, specific methodologies/ by hydrogenating syngas (CO + H 2) that contains a technologies to improve the selectivity of the desired considerable amount of CO 2 or by hydrogenating CO 2 products are required. via CO and CH 3OH formation (Eqs 2 & 3). The main criterion for this reaction is the additional functionality of the catalyst which predominantly Methanol (CH 3OH) is an important chemical that forms hydrocarbons. Even though catalytic FT finds application in various industrial processes. It process is well established, only a few studies are was identified that worldwide consumption of reported for catalytic hydrogenation of CO 2 for methanol increased by 1 % from 2003 to 2008 and is 28 hydrocarbons production. CO 2 emission from projected to increase by 2 % from 2008 to 2013. transportation fuels can be utilized with H 2, which Such robust growth obviously suggests high market may be obtained from solar power, etc. This is one of potential for methanol and efforts are continuously the possible effective ways to maintain carbon cycle. being made to increase its production and meet global Processes such as photochemical, electrochemical and demands. Methanol can be directly used as fuel or as thermochemical are applicable for the catalytic an additive to gasoline and can also be used as conversion of CO 2 of which the first two routes have platform chemical for the synthesis of various some drawbacks. Hence, thermochemical CO 2 chemicals. Currently, the focus is on methanol for the conversion is preferred for producing hydrocarbons production of biodiesel (fatty acid methyl esters) by with high conversions. 24 transesterification of vegetable oils. Generally, methanol can be produced from CO 2 /CO and hydrogen … (2) (Eqs 4 & 5). Methanol Holdings (Trinidad) Limited (MHTL), a USA based company, is one of the largest

methanol producers in the world with a total capacity 29 …(3) of over 4 MMT/year. It is well known that CO 2 is the preferred substrate for methanol production than CO Transition metal catalysts have been reported for because it forms active carbonates/formates on catalyst catalytic hydrogenation of CO 2 and/or syngas to surface which favour the reaction. Also it was hydrocarbons. In some studies, FT process was evidenced that feeding small amount of CO 2 facilitates checked with the feeding of CO 2 gas along with methanol production from syngas. syngas to produce the hydrocarbons. Fe based FT catalysts are promising for hydrocarbons synthesis …(4) and various efforts have been made to increase the …(5) 25 26 conversion of CO 2. Dorner et al. reported the hydrocarbons production using ceria modified iron Methanol production by the hydrogenation of CO 2 catalysts. They have reported that addition of ceria is possible using homogeneous as well as enhances the CO 2 conversion and selectivity for C 2-C5 heterogeneous catalysts. Generally, homogeneous hydrocarbons. Cobalt-based catalysts have also been catalysts work at lower temperature for methanol studied for the FT process and were not found production than heterogeneous catalysts. Designing of attractive for the production of long chain length homogeneous catalysts to improve the reactivity and hydrocarbons. Iron-based FT catalysts are reported selectivity is one of the main challenges being for high temperature processes whereas cobalt-based pursued for the reaction. 30 It was reported that FT catalysts are reported for low temperature hydrogenation of CO 2 occurs via RWGS reaction in 1256 INDIAN J CHEM, SEC A, SEPT-OCT 2012

which the water produced acts as an inhibitor for One-step synthesis using bifunctional catalysts for the further conversion into methanol. Hence, it is synthesis of methanol as well as dehydration necessary to design catalysts which show high activity of methanol to DME is plausible. Generally, at lower temperature and can tolerate the water metal oxides are used for the production of methanol formed during the reaction. Very recently, Leitner and and acidic catalysts are used for the co-workers 31 have reported the first molecularly dehydration reactions. defined ruthenium phosphine complex as homogeneous catalyst for efficient hydrogenation of ...(7) CO 2 (turnover number > 200) to methanol under mild reaction conditions. Cu based heterogeneous catalysts ...(8) are effectively studied for the methanol production 32,33 reactions. Precious metal supported catalysts are 34 ...(9) also reported for this reaction. The function of the catalyst towards the selectivity 37 and water tolerance are not yet clearly understood. According to 2011 data , Korea Gas Technology Economically cheap catalyst which can overcome the Corporation, Korea, received a contract from Unitel Technologies, Inc. to build a plant for the catalytic process drawbacks for the conversion of CO 2 to production of DME at the scale of 300,000 tons per CH 3OH is the necessity at this stage. Krossing and his team 35 from Freiburg Materials Research Center, year by single step method using tri-reformed syngas Germany, have developed a method for methanol obtained from natural gas as feedstock. They have successfully demonstrated this one-step model unit production using CO 2 and H 2. The obtained methanol 37 can be converted into gasoline through well-known with 10 tons/day capacity. MTG process. Methanol production was carried out CO 2 is thermodynamically more stable than H 2O and facilitates DME formation at higher temperature under high pressure by combining CO 2 and H 2. Their with 1:1 feed of CO /H . Generally, a two-step goal is to control CO 2 emission in large scale along 2 2 with the complete utilization for energy production process is in practice because of the thermodynamic and increasing the rate of chemical reaction by favorability of methanol which gives DME via designing new catalyst systems and methods. Metal dehydration reaction. Copper-based catalysts are oxides were used to carry out the reaction at low known for the selective production of methanol by temperature and they found that nanoparticles CO 2 hydrogenation, which can be converted to DME containing catalyst shows higher activity for methanol using acidic catalysts. Interestingly, Cu based core shell membrane catalysts showed direct synthesis of production. They have also attempted different 38 preparation techniques such as catalyst impregnation DME from CO 2. Designing highly active with ionic liquids and covering the catalyst with a thin bifunctional catalysts which can produce DME from CO under moderate reaction conditions, is the film of salt solutions that assist in fixing CO 2 and H 2 2 effectively on the catalyst and allow facile desorption targeted interest of this reaction. of products. 35 Methane Dimethyl ether (DME) Methane has application as synthetic fuel and is Dimethyl ether (CH 3OCH 3) is the first derivative of produced from the hydrogenation of CO 2 by the methanol effectively used as an alternative for Sabatier reaction. The challenges associated in the LPGs. 36 Traditionally, dehydration of methanol storage of hydrogen instrumental in the efforts to results in DME in presence of acid catalysts (Eq. 6). convert it into methane that can be stored and Care should be taken in the reaction conditions to get transported easily. Methane can be obtained by the DME from methanol because of the equilibrium hydrogenation of CO or CO 2; the latter process is less between the reactants and products. exothermic than the former. Hydrogenation of CO or CO 2 (Eqs 10 & 11), commonly reported as methanation, is also used in ammonia plants for the ...(6) purification of syngas, reducing the residual carbon Hydrogenation of CO 2 or syngas is an alternative oxides in hydrogen-rich reforming gases and polymer method for the production of DME (Eqs 7-9). electrolyte fuel cell anodes. 39 SIVASHUNMUGAM & KANNAN: CO 2 AS POTENTIAL RAW MATERIAL FOR FUEL PRODUCTION 1257

...(10) this reaction. Ni was effectively used due to its lower cost and easier availability than noble metals such as ...(11) Rh, Ru, Ir, Pd and Pt containing catalysts which are also active for this reaction. Formation of coke is the main drawback as it involves deactivation of the Selective methanation of CO in CO 2-rich gas catalysts. The support is reported to plays a crucial mixtures has gained interest in recent years because of role in this reaction. Ni containing catalysts were its advantage as a viable alternate to selective CO explored extensively with various supports and along oxidation. In this case, CO adsorbs strongly on the with promoters. 46-49 Recently, Labrecque and Lavoie 50 catalyst surface due to its higher adsorption energy studied the activity of Fe catalyst in the presence of than CO 2, resulting in surface blocking and thus electrical current and found that electron flow and inhibiting CO 2 adsorption, which in turn facilitates 40 addition of water vapour play a crucial role in methanation reaction. Easy availability and low cost methane conversion. Developing a technology that makes Ni based catalyst promising for industrial improves the resistance toward carbon deposition and methanation reactions. Overheating and sintering designing the catalyst with proper support and/or results in problems such as decrease in the surface promoter which can enable this reaction at lower area due to crystallite size growth of Ni and temperature are the key challenges to be addressed in deactivation of the catalyst. This may be overcome by the CO 2 reforming of methane. choosing proper supports that are mechanically and thermally stable. Different metals such as Co, Ru and Ethanol Rh containing catalysts were also studied for the Ethanol (C2H5OH) is the one of the largest methanation reactions. 41-44 Particle size, operating producing alternative fuel from renewables by temperature and supports play a major role in the fermentation process. Ethanol can be produced form methanation reaction. Developing a new technology CO 2/CO via hydrogenation process (Eqs 13 & 14). that selectively makes methane from CO/CO 2 is of Though direct hydrogenation of CO 2 to C2H5OH is considerable interest. Designing active catalyst and possible, indirect method via methanol homologation developing a protocol to disperse the catalyst on a is in use only for the production of ethanol. rationally selected support and deriving optimized reaction conditions for such systems are the hurdles ...(13) which have to be overcome. Methanogens (also called as Archea) produce one billion ton of methane from

CO 2 naturally every year. Hence, these microbes have ...(14) been suggested as one of the effective sources for the preparation of methane and Europe has already Hydrogenation of C2 oxygenates (such as initiated this process. 45 acetaldehyde and acetic acid from syngas which can Dry reforming of methane with CO 2 is the perfect be made from CO 2) to ethanol is the best possible way to make syngas (ratio of H 2/CO is 1) which is route. Catalysts with some active centres which can one of the main building blocks for the fuels (Eq. 12). reduce CO 2 to CO, promoting C-C bond formation The main advantage of dry reforming process is using and allowing –OH group insertion are the main two greenhouse gases (CO 2 & CH 4) and this makes it criteria for this reaction. Composite catalysts superior to steam reforming or partial oxidation of satisfying the above mentioned properties were methane. Fundamentally, dry reforming of methane is studied for this reaction due to their multifunctional an endothermic process and requires high temperature nature. 51,52 Potassium supported Cu based catalysts (> 700 °C) to get moderate conversions. have shown high activity for this reaction; herein, potassium acts as a promoter for C-C bond forming ...(12) reaction. 53 Rh based catalysts have also been studied and it was found that promoters play a crucial role for Methane dry reforming is a catalytic process and the selectivity of ethanol. 54 Modification of catalysts development of a suitable catalyst that can sustain was attempted to satisfy the requirement of the under high temperature without deactivation and reaction condition; Rh containing catalysts showed produce high yields of syngas is the key endeavor for the best results. Basically, catalysts which are active 1258 INDIAN J CHEM, SEC A, SEPT-OCT 2012

for ethanol production from syngas and RWGS are section discusses the non hydrogenation process of also active for methanol homologation reactions. CO 2 (or CO) for the production dimethyl carbonate. Ethanol has been undoubtedly proved to be the best Dimethyl carbonate (DMC; (CH 3O) 2CO) is a linear alternative for fuels and enzymatic production alkyl carbonate and has been reported as a potential predominates for its production. Designing the gasoline fuel additive. 58 Various methods are possible catalyst with highly efficient production of ethanol for the production of DMC from methanol. High from CO 2 is the challenging task in front of many toxicity of phosgene gas and formation of researchers. New technology developments are hydrochloric acid as by-product are the drawbacks of required to replace and/or augment the currently the ongoing phosgene-based process. Alternative practiced microbial process. routes are utilizing CO 2 or CO as reactant for the production of DMC from methanol. Lummus Formic acid Technology developed a process in which reaction Formic acid (HCOOH) is the simplest carboxylic between methanol, carbon monoxide and in acid and its worldwide production was estimated to be presence of Cu-based catalysts results in DMC and 55 around 720,000 tonnes/annum in 2009. It has water (Eq. 16). 59 A small amount of HCl is fed into application in various areas including fuel cells. the reactor to maintain the catalyst activity and the Commercially, formic acid is produced by four obtained byproduct CO 2 can be further used for different production processes, viz., methyl formate CO production. hydrolysis, oxidation of hydrocarbons, hydrolysis of formamide, and, preparation of free formic acid from formates. Direct hydrogenation of CO 2 is the best alternative + method for production of formic acid (Eq. 15). ...(16) ...(15) Production of DMC using CO 2 with methanol is a Mainly, homogeneous transition metal catalysts preferred route (Eq. 17). It was found that and zinc selenide/zinc telluride have been studied for thermodynamic limitation of the reaction, this reaction. 56 British Petroleum has developed a deactivation of the catalyst and hydrolysis of the multistep process using Ru complex as catalyst in DMC by the formed water results in low methanol presence of nitrogen-containing bases. 56 Even though conversion and low DMC yield. Selective synthesis of efforts have been made to produce formic acid using DMC is highly influenced by the presence of both homogeneous catalysts, recent reports suggest that acidic and basic sites on the catalyst surface. 60 formic acid can be produced from CO 2 hydrogenation Reaction temperature is an important parameter for with high selectivity using heterogeneous catalysts. 57 DMC synthesis. At higher temperatures, conversion Development of new catalytic technology to produce of methanol and selectivity of DMC are decreased formic acid in attractive yields in a safe manner is the due to decomposition of DMC and result in unwanted major task. products. 61

CO 2 for the Production of Fuel Additives Efforts have been made to produce fuel additives from CO 2 without using hydrogen source. Generally, this non-hydrogenation process results in carbonates + and carbamates; among these, carbonates were found to be effective fuel additives. Dimethyl carbonates are ...(17) prepared by reacting methanol with CO 2. Methanol, Various catalysts were reported for this reaction which is produced by the hydrogenation of CO 2, and many diverse efforts were made to improve the undergoes dehydration when treated with CO 2 selective synthesis of DMC such as catalyst resulting in dimethyl carbonates. Also, oxygenation of modification, addition of co-reagents and dehydrating 62-65 CO which is produced by the RWGS of CO 2, is agents. Improving the conversion of methanol another way to produce dimethyl carbonate. This along with selectivity of DMC is necessary for it to be SIVASHUNMUGAM & KANNAN: CO 2 AS POTENTIAL RAW MATERIAL FOR FUEL PRODUCTION 1259

commercially practicable. Designing the desired bio-reactors and for making bio-derived chemicals. 69,70 catalysts and developing a new or redeploying water The primary aim of this section is to highlight the role removal technology are the basic requirements of CO 2 in the synthesis of biomass derived chemicals, necessary to achieve this endeavour. in particular organic carbonates (Fig. 6).

CO 2 for the Production of Bio-derived Chemicals Fatty cyclic carbonate Biomass mainly constitutes of lignocelluloses and In recent years, fatty cyclic carbonates have gained related materials (70-75 % of biomass), oils and fatty interest in the area of renewable sources since they acids (15-20 % of biomass) and proteins (5 % of have been used in lubricants, fuel additives and biomass). It is estimated that around the world polymer precursors, as solvents, biomedical 71,72 approximately 170 BMT of biomass are being applications and in plasticizers. Traditionally, produced per annum. 66 Of this barely 4 % is used for these kinds of cyclic carbonates were prepared by food/feed and non-food purposes by the humans. 67 using hazardous phosgene gas and organic solvents. Hence, biomass is perceptibly a potential alternate CO 2 insertion reaction can play a profound role in the source for the production of fuels and chemicals. synthesis of cyclic carbonates. Generally, two step Using biomass for energy producing processes also processes are carried out for the preparation of fatty results in the emission of CO 2, but the amount cyclic carbonates such as sequential epoxidation of produced during this process is approximately the unsaturated centers and then carboxylation of the same as that consumed during biomass re-growth. epoxy fatty derivatives. The main advantage of this Hence, emission of CO 2 from biomass is considered as process is insertion of CO 2 without forming any 68 CO 2 neutral. The combination of biomass and CO 2 in byproducts (100 % atom economical). Direct energy conversion technologies has some similarities oxidative carboxylation of fatty derivatives can also with the combination of fossil sources and CO 2. CO 2, result in fatty cyclic carbonates (Scheme 1). 73 in the context of biomass value addition, is currently Doll and Erhan have reported the production of being explored as a solvent for pre-treatment of carbonated FAMEs using supercritical CO 2. They biomass for delignification, for the growth of algae in reported a two-step reaction for the production of fatty cyclic carbonates from methyl oleate and methyl linoleate. In the first step, the unsaturated centres present in these methyl esters were converted into epoxides and then CO 2 was direct inserted in the oxirane ring using tetrabutylammonium bromide as catalyst under supercritical CO 2. The same catalyst was studied for the carbonation of epoxidized soybean oil methyl esters at atmospheric pressure and at pressurized conditions. 74 Interestingly, Kenar and

Preparation of fatty cyclic carbonates from fatty derivatives Fig. 6 − Preparation of organic carbonates using CO2. Scheme 1 1260 INDIAN J CHEM, SEC A, SEPT-OCT 2012

Tevis 75 reported preparation of fatty cyclic carbonates using tetramethylammonium hydrogen carbonate as catalyst at low temperatures and in shorter reaction time by bubbling with CO 2. Due to the renewable nature, bio-derived products have gained interest in recent years. Fatty cyclic carbonates have wide applications and researchers are attempting to produce them in economically Preparation of glycerol carbonate from glycerol attractive and in large volumes to replace some of Scheme 2 the petro-derived polymeric derivatives. Further, were made for the direct insertion of CO 2 into glycerol most of the studies involve two-step processes for moiety to form glycerol carbonate using tin based the production of cyclic carbonates via epoxides catalysts. 78,79 Formation of water as byproduct formation and CO 2 insertion. Unfortunately, direct prevents further conversion of glycerol due to oxidative carboxylation to produce fatty cyclic solubility of glycerol in water and the reaction is carbonates is scarcely studied. Appropriate design thermodynamically limited (Scheme 2). It was of catalyst that offers macroporosity for further identified that addition of methanol can efficient diffusion (avoiding mass transport enhance the reaction. 79 limitation) of the long-chain molecules which can Direct carboxylation of glycerol to glycerol give high yield of fatty cyclic carbonates under near carbonate is an important reaction not only in being ambient or energetically favorable conditions is the industrially relevant but also in green chemistry challenge at present. Further, production of perspective. Technology development to increase the polycarbonates and polyether carbonates from fatty conversion of glycerol concomitantly with high derivatives/vegetable oils using CO 2 needs a more selectivity of glycerol carbonate is indispensable at focused approach. this time.

Glycerol carbonate Glycerol is the simplest triol which has various Conclusions & Perspectives applications due to its functionality. Glycerol can be The global atmospheric concentration of CO 2 is obtained from triglycerides via hydrolysis or increasing every year and has reached 391.3 parts per transesterification processes. The continuously million in 2011 according to the data from 80 expanding production of biodiesel from different Worldwatch Institute. Increasing CO 2 level in the sources results in enormous amounts of glycerol as atmosphere can be controlled by utilizing it in a useful byproduct. In order to reduce the disposal of glycerol and voluminous way, given its availability in giga as waste, value addition of glycerol for a variety of tons, through the production of fuels and large volume applications is being studied. Glycerol carbonate is chemicals. Decreasing fuel availability has created important as solvent and starting material for enormous interest in the search for alternatives from polymers etc., due to its peculiar properties. different sources and various attempts are being Industrially this compound is produced by the explored. Syngas, methanol and hydrocarbons, are transesterification of propylene carbonate with some of the important options for the production of glycerol. Basically these carbonate derivatives are fuels (or can be used as such) due to their properties. prepared by the CO 2 insertion reaction with the Also, possibilities of forming various products from corresponding oxides. CO 2 would be of great significance since the end- Earlier studies revealed that ethylene carbonate was products obtained after combustion of fossil fuel can needed as starting material for the preparation of be refurbished back into the fuel chain, thus closing glycerol carbonate from glycerol and supercritical the energy/material loop cycle. Needless to say, the 76 CO 2 as carbonate source. In this case ethylene energy penalty and balance are some of the key issues carbonate can enhance the CO 2 utilization for glycerol that need to be sharply addressed while exploring 77 carbonate synthesis. Very recently, Ma et al. such options. Utilizing CO 2 to develop large volume reported the synthesis of glycerol carbonate from chemicals, in particular those derived from biomass, glycerol and CO 2 in presence of propylene oxide as is one of the biggest opportunities in this area of the coupling agent using alkali catalysts. Some efforts research. Although not many profitable technological SIVASHUNMUGAM & KANNAN: CO 2 AS POTENTIAL RAW MATERIAL FOR FUEL PRODUCTION 1261

solutions are available at present, solutions that would 28 Davenport R E, Issues Facing Global Methanol Industry , (SRI not only limit the growth of CO in atmosphere but Consulting. Presented to Chemical Week Conference) 2004. 2 29 http://www.energy.gov.tt/energy_industry.php?mid=47 also create some sustainable options for the growing (Accessed on 27 th June 2012). population and energy/material demands of this world 30 Huff C A & Sanford M S, J Am Chem Soc , 133 (2011) are expected in this century. 18122. 31 Wesselbaum S, vom Stein T, Klankermayer J & Leitner W, Angew Chem Int Ed, 51 (2012) 7499. Acknowledgement 32 Zhang L, Zhang Y & Chen S, Appl Catal A: Gen , 415-416 The authors thank CSIR, New Delhi, India, for (2012) 118. financial support under Network Project, Clean Coal 33 Bonura G, Arena F, Mezzatesta G, Cannilla C, Spadaro L & Technology (NWP-021). Frusteri F, Catal Today , 171 (2011) 251. 34 Kong H, Li H, Lin G & Zhang H, Catal Lett , 141 (2011) 886. 35 http://www.pr.uni-freiburg.de/pm/2012/pm.2012-06-13.137- References en/ (Accessed on 31 st July 2012). 1 http://www.iea.org/co2highlights/co2highlights.pdf 36 Arcoumanis C, Bae C, Crookes R & Kinoshita E, Fuel , (Accessed on 26 th June 2012). 87 (2008) 1014. 2 Song C, Gaffney A F & Fujimoto K F, CO 2 Conversion and 37 http://www.businesswire.com/news/home/20110209005232/ Utilization , (ACS Symposium Series 809, American en/Korea-Gas-Build-300000-Tons-Year-Dimethyl (Accessed Chemical Society, Oxford University Press, Washington, on 27 th June 2012). D.C.) 2002, Chap. 1. 38 Zha F, Ding J, Chang Y, Ding J, Wang J & Ma J, Ind Eng 3 http://co2now.org/images/stories/graphics/carbon-budget/ 2010/ Chem Res , 51 (2012) 345. global-carbon-budget-2010-hi-rez.png (Accessed on 39 Gabrovska M, Edreva-Kardjieva R, Crisan D, Tzvetkov P, 29 th June 2012). Shopska M & Shtereva I, React Kinet Mech Catal , 105 4 Marland G & Turhollow A F, Energy , 16 (1991) 1307. (2012) 79. 5 http://205.254.135.7/forecasts/ieo/emissions.cfm (Accessed 40 Eckle S, Augustin M, Anfang H & Behm R J, Catal on 25 th June 2012). Today ,181 (2012) 40. 6 Wang M, Wu M & Huo H, Environ Res Lett , 2 (2007) 1. 41 Janlamool J, Praserthdam P & Jongsomjit B, J Nat Gas 7 Zevenhoven R, Eloneva S & Teir S, Catal Today , 115 Chem , 20 (2011) 558. (2006) 73. 42 Sharma S, Hu Z, Zhang P, McFarland E W & Metiu H, 8 Leitner W, Coord Chem Rev , 153 (1996) 257. J Catal , 278 (2011) 297. 9 Aresta M & Dibenedetto A, Dalton Trans , (2007) 2975. 43 Sarusi I, Fodor K, Baan K, Oszko A, Potari G & Erdohelyi 10 Sakakura T, Choi J & Yasuda H, Chem Rev , 107 (2007) 2365. A, Catal Today , 171 (2011) 132. 11 Eggersdorfer M, Meijer J & Eckes P, FEMS Microbiol Rev , 44 Beuls A, Swalus C, Jacquemin M, Heyen G, Karelovic A & 103 (1992) 355. Ruiz P, Appl Catal B: Environ , 113-114 (2012) 2. 12 Baiker A, Appl Organomet Chem, 14 (2000) 751. 45 http://www.science20.com/news_releases/methanogen_ 13 http://www.extremetech.com/extreme/124383-bacteria-converts- microbes_making_methane_from_co2_could_be_energys_ki carbon-dioxide-into-liquid-fuel (Accessed on 26 th June 2012). ller_app (Accessed on 27 th June 2012). 14 http://articles.cnn.com/2008-10-08/tech/co2.fuel_1_recycling 46 Sokolov S, Kondratenko E V, Pohl M, Barkschat A & -projects-fuel-co2?_s=PM:TECH (Accessed on 26 th June 2012). Rodemerck U, Appl Catal B: Environ , 113-114 (2012) 19. 15 Iizuka T, Tanaka Y& Tanabe K, J Catal , 76 (1982) 1. 47 Du X, Zhang D, Shi L, Gao R & Zhang J, J Phys Chem C , 16 Xiaoding X & Moulijn J A, Energy & Fuels , 10 (1996) 305. 116 (2012) 10009. 17 Centi G & Perathoner S, Catal Today , 148 (2009) 191. 48 Frontera P, Macario A, Aloise A, Crea F, Antonucci P L, 18 Kim S S, Lee H H & Hong S C, Appl Catal A: Gen , 423-424 Nagy J B, Frusteri F & Giordano G, Catal Today , 179 (2012) 100. (2012) 52. 19 Goguet A, Meunier F C, Tibiletti D, Breen J P & Burch R, 49 Al-Fatesh A S A, Fakeeha A H & Abasaeed A E, Chinese J J Phys Chem B , 108 (2004) 20240. Catal , 32 (2011) 1604. 20 Rosen B A, Salehi-Khojin A, Thorson M R, Zhu W, Whipple 50 Labrecque R & Lavoie J, Bioresour Technol , 102 (2011) 11244. D T, Kenis P J A & Masel R I, Science , 334 (2011) 643. 51 Inui T &Yamamoto T, Catal Today , 45 (1998) 209. 21 Fujita S I, Usui M & Takezawa N, J Catal , 134 (1992) 220. 52 Inui T, Yamamoto T, Inoue M, Hara H, Takeguchi T & 22 Shido T & Iwasawa Y, J Catal , 140 (1993) 575. Kim J B, Appl Catal A: Gen , 186 (1999) 395. 23 http://www.marspedia.org/index.php?title=Reverse_Water- 53 Arakawa H, Stud Surf Sci Catal , 114 (1998) 19. Gas_Shift_Reaction (Accessed on 27 th June 2012). 54 Kusama H, Okabe K, Sayama K & Arakawa H, Catal Today , 24 Dorner R W, Hardy D R, Williams F W & Willauer H D, 28 (1996) 261. Appl Catal A: Gen , 373 (2010) 112. 55 http://en.wikipedia.org/wiki/Formic_acid (Accessed on 25 Chun D H, Lee H, Yang J, Kim H, Yang J H, Park J C, Kim 30 th June 2012). B & Jung H, Catal Lett , 142 (2012) 452. 56 http://onlinelibrary.wiley.com/doi/10.1002/14356007.a12_ 26 Dorner R W, Hardy D R, Williams F W & Willauer H D, 013. pub2/full (Accessed on 30 th June 2012). Catal Commun , 15 (2011) 88. 57 Zhang Z, Xie Y, Li W, Hu S, Song J, Jiang T & Han B, 27 Gnanamani M K, Shafer W D, Sparks D E & Davis B H, Angew Chem Int Ed , 47 (2008) 1127. Catal Commun , 12 (2011) 936. 58 Pacheco M A & Marshall C L, Energy Fuels , 11 (1997) 2. 1262 INDIAN J CHEM, SEC A, SEPT-OCT 2012

59 http://www.cbi.com/images/uploads/tech_sheets/DMC.pdf 70 Putt R, Singh M, Chinnasamy S & Das K C, Bioresour (Accessed on 26 th June 2012). Technol , 102 (2011) 3240. 60 Tomishige K, Sakaihiro T, Ikeda Y & Fujimoto K, Catal 71 Kenar J A, Knothe G, Dunn R O, Ryan T W I & Matheaus A, Lett , 58(1999) 225. J Am Oil Chem Soc , 82 (2005) 201. 61 Aouissi A & Al-Deyab S S, J Nat Gas Chem , 21(2012) 189. 72 Tamami B, Sohn S, Wilkes G L & Tamami B, J Appl Polym 62 Lee H J, Park S, Song I K & Jung J C, Catal Lett , 141 Sci , 92 (2004) 883. (2011) 531. 73 Doll K M & Erhan S Z, J Agric Food Chem , 53 (2005) 9608. 63 Lee H J, Park S, Jung J C & Song I K, Korean J Chem Eng , 74 Holser R A, J Oleo Sci , 56 (2007) 629. 28 (2011) 1518. 75 Kenar J A & Tevis I D, Eur J Lipid Sci Technol , 107 (2005) 135. 64 Ballivet-Tkatchenko D, Bernard F, Demoisson F, Plasseraud 76 Vieville C, Yoo J W, Pelet S & Mouloungui Z, Catal Lett , L & Sanapureddy S R, ChemSusChem , 4 (2011) 1316. 56 (1998) 245. 65 Zhang Z, Liu Z, Lu J & Liu Z, Ind Eng Chem Res , 50 77 Ma J, Song J, Liu H, Liu J, Zhang Z, Jiang T, Fan H & Han B, (2011) 1981. Green Chem ,14 (2012) 1743. 66 Corma A, Iborra S & Velty A, Chem Rev , 107 (2007) 78 Aresta M, Dibenedetto A, Nocito F & Pastore C, J Mol Catal 2411. A: Chem , 257 (2006) 149. 67 Roper H, Starch/Starke , 54 (2002) 89. 79 George J, Patel Y, Pillai S M & Munshi P, J Mol Catal A: 68 Demirbas A, Prog Energy Combust Sci , 31 (2005) 171. Chem , 304 (2009) 1. 69 Zheng Y Z, Lin H M & Tsao G T, Biotechnol Prog , 80 http://www.worldwatch.org/economic-recovery-brings-return 14 (1998) 890. -growth-co2-emissions-0 (Accessed on 18 th June 2012).