Double Metal Catalyst Based Efficient and Economical Production of Biodiesel
Dr Swati P Kolet
Assistant Professor of Applied Chemistry
International Institute of Information
Technology, Hinjawadi, Pune, India

Dr Prabhakar Ingle
Senior Principal Scientist and Head ,
Publication and Science Communication
CSIR-National Chemical Laboratory, Pune, India

For the enhanced production of biodiesel a solid catalyst is desired which can handle raw, non-edible vegetable oil as feedstock in transesterification reaction. Dr. D. Srinivas at CSIR-NCL synthesized a series of double metal cyanide (DMC) complexes of Fe2+ and other metals such as Zn2+, Cu 2+, Ni2+ and Co2+ using commercially available K3Fe(CN)6.3H2O complex and other metal chlorides. The Fe-Zn-1 DMC complex prepared in presence of t-butanol and tri-block copolymer poly(ethylene glycol)-block -poly(propylene glycol)-block-poly(ethylene glycol) was found to be highly efficient for the conversion of a range of vegetable oils to biodiesel. The yield of the transesterification reaction in presence of catalyst was always found more than 90%. DMC is a non-toxic solid catalyst insoluble in most of the solvents including aqua regia.

India's economy is improving at very high speed which demands for large amount of energy. In today's scenario, the energy requirement of India is about 400GW and 75% of it is fulfilled by non-renewable fossil fuels such as coal, crude oil (petroleum), natural gas. Specifically, 44% of India's total energy consumption comes from coal followed by petroleum which contributes 22% and natural gas at 7%. Presently with the meteoric developments in technologies the consumption of conventional fuels is increasing exponentially leading to rapid depletion of their stocks in nature. Also with the growth in transport sector which is one of the major end-user of fuels, the demand of petroleum is expanding over its production.

According to the ‘Petroleum Planning and Analysis Cell (PPAC), Government of India', India is the third largest importer of crude oil. Further, Industry and trade sources data reveal the increase in average demand for transportation fuel from 134 billion litres in CY 2015 to 145 billion litres in CY 2017 and estimated to rise up to 225 billion litres in CY 2026 which is major concern of economy. Beyond economy, the increased consumption of petroleum is associated with various environmental issues. Annual report on Bio-fuels demonstrates that India is the fourth largest global contributor of carbon emission in environment. Consequently, Indian Government is targeting towards development of new technologies to enhance the production of energy based on renewable sources and simultaneous reduction of carbon load on environment.

Under such circumstances, biofuels is considered as one of the most promising alternatives to conventional fuels. Bioethanol and biodiesel collectively called as biofuels are environment friendly, relatively cheap and can supplement conventional energy sources thereby help in reducing the dependency of India on imported fuels. The PPAC report for FY 2017 estimated that diesel alone fulfills 46% demand of the transportation fuel followed by gasoline/petrol at 24%. Therefore production of biodiesel and blending it with petroleum diesel for direct use in diesel engine can be a linchpin in alter native energy source.

To accelerate the production of biodiesel, Government of India (GOI) started Biodiesel mission in 2003 and announced the National Biodiesel Policy on 11th Sep 2008. The ministry of New and Renewable Energy(MNRE) has prepared the Policy and has set a target of 20% blending of biodiesel with petroleum diesel by 2017, however the current average blending rate is only 0.1 %. The policy is also focused on maintaining low cost of biodiesel so that it will get easily accepted by public. There are two main factors which affect the cost of biodiesel production, the cost of raw material and the cost of process. Therefore the policy is emphasized on use of non-edible oil obtained from waste and degraded land for the production of biodiesel. This objective is also failed due to unavailability of standard manufacturing process. Now the Ministry for Road Transport and Highway is emphasizing on replacement of vehicles running on petrol and diesel with electronic vehicles and vehicles using biofuels such as ethanol, biodiesel to control environment pollution and curb the oil import. Consequently, to accomplish the policy targets there is great necessity for developing an economical and environment friendly technology for production of biodiesel.

Biodiesel comprises mixture of methyl or ethyl esters of fatty acid which can be prepared by either transesterification of triglycerides(TG) or esterification of free fatty acids. Previously known method for production of biodiesel utilizes mineral acid or base as a catalyst and refined vegetable oil as feedstock for biodiesel production. However, use of these inorganic homogeneous catalysts is associated with corrosion and environment hazards. Also, these catalysts require high cost feedstock restricting their implementation on large scale production. Several heterogeneous solid acid and base catalysts have also been developed to carry out the transesterification of low quality, nonedible vegetable oils. But the known solid catalyst usually show low reaction rate or lead to side reactions such as saponification. Therefore various institutes in India viz, IICT Hyderabad , CSMCRI Bhavnagar, IIP Dehra Dun, NCL Pune, Department of Bioenergy Tamil Nadu Agricultural University, R & D Center of IOCL, Delhi College of Engineering are involved in discovering efficient catalyst for transesterification of crude oils and standardization of biodiesel production on a commercial scale.

Dr. Darbha Srinivas and team at CSIRNational Chemical Laboratory (CSIRNCL), Pune accepted the challenge and developed highly efficient and novel solid double metal cyanide (DMC) complexes as catalyst for production of biodiesel . The team demonstrated one-step DMC catalyzed transesterification of crude non-edible oils obtained from Jatropha, Karanja plants and unrefined rubber seed oil which can help to accomplish one of the targets of National Biodiesel Policy. Additionally, with DMC catalyst TG can be converted into esters of higher alcohols i.e. biolubricants which are very good additives in diesel. The catalyst developed at CSIR-NCL is reusable and active even in presence of significant amount of water. According to Dr.D.Srinivas high efficiency of DMC is due to hydrophobicity and Lewis acidic nature of the catalyst. In 2011, Dr. D. Srinivas has received Vasvik Research Award for his imperative contribution to the field of biofuels.

Technology Developed at CSIR-NCL
For the enhanced production of biodiesel, it is desirable to discover a solid catalyst which can handle raw, non-edible vegetable oil as feedstock in transesterification reaction. Based on this requirement Dr.D.Srinivas at CSIR-NCL synthesized a series of double metal cyanide (DMC) complexes of Fe2+ and other metals such as Zn2+, Cu2+, Ni2+and Co2+using commercially available K3Fe(CN)6.3H2O complex and other metal chlorides. The synthesized DMC complexes were then simultaneously used for the transesterification of vegetable oils under identical conditions. Transesterification was carried out using variety of vegetable oils in presence of excess alcohol and 3-5 wt% of catalyst at 353-443 K for 1-5 hrs. Out of the synthesized complexes Fe-Zn-1 DMC complex prepared in presence of t-butanol and tri-block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-blockpoly( ethylene glycol) was found to be highly efficient for the conversion of a range of vegetable oils to biodiesel. Structural identification revealed the structure of highly active Fe-Zn-1 as K4Zn[Fe(CN)6]2.xH2O where X = 6-12. The general formula of DMC for other metal complexes is K2M3[Fe(CN)6]2.x’H2O where M = Cu2+, Ni2+ and Co2+ and X' = 8-19. The yield of the transesterification reaction in presence of catalyst was always found more than 90%. DMC is a non-toxic solid catalyst insoluble in most of the solvents including aqua regia.

One of the targets of National Biodiesel Policy is to use crude, non-edible vegetable oil for the production of biodiesel to maintain low cost which mainly depends on feedstock use for transesterification reaction. The problem associated with low cost crude oil is the presence of considerable amount of free fatty acid which interfere in transesterification reaction catalyzed by previously known homogeneous and some solid catalyst. To overcome the fact, Dr. Srinivas had tried transesterifcation of various crude, nonedible oils such as Jatropha, Rubber seed, Pinnai, Karanja oil in addition to few edible oils in presence of newly developed DMC catalyst. It was observed that the reported catalyst can catalyze the reaction with 85% conversion even in presence of 35% of free fatty acids in feedstock in single operation. Additionally, activity of most of the previously reported catalyst is sensitive to water content of feedstock making them inadequate for crude oils, however when transesterification of sunflower oil was carried in presence of added water over Fe-Zn DMC catalyst 90% conversion of oil into biodiesel was obtained even in presence of 20% of added water in feedstock.

Usually transesterification reaction involving long chain alcohols lead to lower conversion of oil into fatty acid esters. The testing of Fe-Zn-1 catalyst activity for transesterification with higher alcohol from C1 to C8 showed that there is very small variation in reaction yield with the length of alcohol chain. The fatty acid esters obtained with lower alcohols(C1-C4) are compatible with diesel properties and those with hexanol to octanol suitable for biolubricant application. According to Dr.Srinivas the small decrease in conversion is due to decrease in diffusion of higher alcohols. Study also revealed about the reusability of alcohol. According to Dr. Srinivas the porosity, surface hydrophobicity and Lewis acid properties are responsible for the activity of discovered catalyst. CSIR-NCL has patented the developed solid catalyst for transesterification of oils.

The solid catalyst based large scale production of biodiesel and biolubricant is known as ENSEL process. The process is highly efficient, uses cheaper feedstock such as non-edible oils, animal fats and hence facilitates biodiesel production at lower cost than the conventional processes. In this process no pre-treatment of feedstock or washing of product is required. Additionally, in the reaction high quality glycerin (95 -97% pure) is obtained as a co-product which has various pharmaceutical applications. Considering these virtues, the ENSEL process has been validated at Matsuyamo in Japan and Eulees in the US in pilot plants in collaboration with CSIR-NCL. Sud-Chemie India Pvt. an Indian company which manufactures and supplies the solid catalyst developed at CSIR-NCL. Benefuel Inc. in association with Flint Hill Resources, USA formed a joint venture "Dionix" and commercialized the ENSEL® process in a 160,000 TPA plant commercialized at Beatrice, Nebraska, USA.

Various companies in government and private sectors are involved in the production of biodiesel. At present, oil marketing companies (OMCs) are purchasing biodiesel from manufacturing companies, blending it with diesel and selling in West Bengal, Orissa, Andhra Pradesh, Chennai and Gujarat. The oil ministry aims the current less than 1 percent blending of biodiesel to increase it up to 5% by 2022 which can expand the biofuel market to ` 50,000 crore from about 6,500 crore. For this, India would need 6.75 billion litres of biodiesel. This illustrates the great demand of processes for large scale biodiesel production. Presently known various processes for biodiesel production are setup only on small-scale and need to be standardized on commercial level. Commercialization of any process is regulated mainly by four factors: availability of feedstock, profit of owner, safety of employees and effect on environment.

In our country major hurdle for large scale production of biodiesel is availability of feedstock. As discussed Jatropha seeds are non-edible, cheap and very good source of oil which can be transesterified into biodiesel. Even the National biodiesel policy focuses on use of Jatropha seeds as feedstock for biodiesel production. However, currently Jatropha occupies only around 0.5 million hectares of low-quality wastelands across the country. Consequently, various corporations, private companies along with state governments are promoting plantation of Jatropha on government owned lands by contract farming. Further, proper channels for distribution of biodiesel do not exist and its major use for transportation is still on trial basis. Conclusively, the lack of assured supply of feedstock and insecure returns from the business has restricted the efforts of government as well as private sector to set up biodiesel plants in India.

We suggest to put these above two paragraphs in two separate boxes.

Acknowledgements: The authors thankfully acknowledge Dr. Darbha Srinivas, Chair, Catalysis and Inorganic Chemistry Division, CSIR-NCL for his inputs and suggestions.

Dr. Swati P. Kolet is Assistant Professor of Applied Chemistry at International Institute of Information Technology, Hinjawadi, Pune, India. Dr. Prabhakar Ingle is Senior Principal Scientist and Head, Publication and Science Communication at CSIR-NCL, Pune, India.