Green Technology Subject Code – PCE7J004 Chemical Engineering Department 7th Semester
Mrs. Laxmi Sethi IGIT Sarang Email ID: - [email protected]
PCE7J004 Green Technology 3-0-0
Module I: Principles of green technology and engineering, Principles of atom and mass economy, E-factor.
Module II: Design of greener and safer chemicals, Solvent-free methods: Microwave, Ultraviolet, and Solar. Green catalysts: ionic liquids, zeolites, photocatalyst, PEG, nanocatalyst, and biocatalyst. Green solvents: Supercritical fluids, fluorous phase, and non-aqueous solvents.
Module III: Scale-up effect, reactors, separators, Process intensification. Bio-conversion of renewables.
Reference Books: 1. Handbook of Green Chemistry, Vol. 1 to 9 by P T Anastas, Wiley VCH. 2. Green Chemistry and Engineering: A Practical Design Approach by C J González and D J C Constable, Wiley. 3. Green Chemistry and Engineering: A Pathway to Sustainability by A E Marteel- Parrish and M A Abraham, Wiley. 4. Green Chemistry for Environmental Sustainability by S K Sharma and AMudhoo, CRC Press. 5. Green Engineering: Environmentally Conscious Design of Chemical Processes by D T Allen and D R Shonnard, PHI.
Module I Contents Introduction Principles of Green Chemistry Green Metrices – Percentage Yield Atom Economy Reaction Mass Efficiency Effective Mass Yield E – Factor
Introduction Chemical industries play important role in our day to day life as well in supporting the nation’s economy. Chemical Engineering deals with the conversion of raw materials into commercially important products. This conversion is done in a number of steps starting from raw material beneficiation followed by the chemical reactions for the conversion of raw materials into product and finally recovery of product. After the product recovery, some waste effluents or gases may be discharged from the system. During the reactions also some waste and toxic materials or gases may be discharged. These wastes and toxic materials may be detrimental for the reaction vessel as well as the environment, human being and animals. Chemical industries also result into running out of petrochemical feedstocks. The total cost will also be higher if a significant amount of waste is released. So, it is desirable to introduce some novel methods to reduce waste and design an ideal process or ideal product.
Green Chemistry Definition Green Chemistry is the reduction or elimination of the use of or generation of hazardous substances in a chemical process. It also deals with replacing the traditional chemical processes with environmentally friendly alternate synthesis pathways for the reduction of wastes generated during chemical processes.
The U.S. Presidential Green Chemistry Challenge, March 1995 defines Green Chemistry as, the use of chemistry for source reduction or pollution prevention. [3]
One more aspect which is to be taken care of is sustainable development. It means fulfilling the needs of present generation without compromising with the needs of the future generation. It can only be achieved by applying green chemistry wherever possible.
For designing an ideal process or ideal product some guidelines should be followed or the efficiency of the reaction should be evaluated and shortcomings should be noted to take proper actions. The set of guidelines were given by Paul Anastas and John Warner which are called 12 Principles of Green Chemistry. For the evaluation of the reactions, Green Metrices were introduced.
THE TWELVE PRINCIPLES OF GREEN CHEMISTRY [4] Paul Anastas and John Warner gave a set of guidelines for the design of environmentally benign process as “The Twelve Principles of Green Chemistry”.
The Twelve Principles are:
1. Prevention. It is better to prevent waste than to treat or clean it up after it has been generated in a process. This is based on the concept of “stop the pollutant at the source.” Explanation: According to this principle the synthesis process should be designed in such a way that the waste generation will be minimum or nil as waste generation results in less efficient chemical processes which may increase the cost of production. This can be carried out by adopting grinding chemistry i.e. the reactants can be mixed by grinding without using any solvent. Some other methods for waste reduction may be use of microwave or solvent less chemistry.
2. Atom Economy. Synthetic steps or reactions should be designed to maximize the incorporation of all raw materials used in the process into the final product, instead of generating unwanted side or wasteful products. Explanation: According to this principle all the atoms present in the reactants should be converted into products as those atoms that are not used end up as waste. Atom economy is the efficiency of a reaction to convert reactant into desired product.
3. Less hazardous chemical use. Synthetic methods should be designed to use and generate substance that possess little or no toxicity to the environment and public at large. Explanation: This principle aims to use less hazardous reactants or use less hazardous synthesis pathways. Example: Styrene is traditionally produced from benzene which is carcinogenic in nature. This traditional route can be replaced by greener route i.e. instead of benzene, xylene can be used as the starting material.
4. Design for safer chemicals. Chemical products should be designed so that they not only perform their designed function but are less toxic in the short and long terms. Explanation: This principle is focussed on designing less hazardous chemicals. The molecules can be designed large enough such that they will not penetrate inside lungs. Example: Detergents are sodium salt of alkyl benzene sulphonic acids with branched alkyl groups. These are not degraded naturally. So, now these compounds are replaced by sodium salts of linear alkyl benzene sulphonic acid which are readily degraded.
5. Safer solvents and auxiliaries. The use of auxiliary substances such as solvents or separation agents should not be used whenever possible. If their use cannot be avoided, they should be used as mildly or innocuously as possible. Explanation: Traditionally organic solvents are used in chemical synthesis, which are highly dangerous. This principle aims to replace the organic solvents with greener solvents such as water, supercritical carbon dioxide etc. which are less hazardous.
6. Design for energy efficiency. Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, all reactions should be conducted at mild temperature and pressure. Explanation: This principle can be fulfilled by using catalysts in the chemical reactions.
7. Use of renewable of feedstock. A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable. Explanation: This principle basically deals with shifting our dependence on petroleum to renewable feedstocks. Examples: Biodiesel obtained from biomass and polylactic acid (Biodiesel plastic) made from renewable feedstocks such as corn and potato waste.
8. Reduction of derivatives. Use of blocking groups, protection/deprotection, and temporary modification of physical/chemical processes is known as derivatization. Unnecessary derivatization should be avoided or minimized. Such steps require additional reagents and energy and can generate waste.
9. Catalysis. Catalytic reagents are superior to stoichiometric reagents. Explanation: Catalysts are used to decrease energy requirements and to make reaction take place more efficiently. Green Technology deals with using green catalysts instead of traditional chemical catalysts.
10. Design for degradation. Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment. Explanation: Chemicals such as pharmaceutical drugs, plastics etc. should be designed in such a way that they will breakdown once their useful life is over. Example: Polythene and polypropylene can be replaced by biodegradable polymers which can be degraded by enzymatic action.
11. Real time Analysis for Pollution Prevention. Analytical methodologies need to be improved to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances. Explanation: If in-process monitoring can be done than it will be easier to control the reaction as per the desired requirement. Example: Micro fabricated micro fluidic analytical devices have been developed which are referred as lab-on-chip devices. All the steps in a chemical reaction can be carried out on a single microchip platform.
12. Inherently safer chemistry for accident prevention. Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, storage of toxic chemicals, explosions and fires. Explanation: This principle aims on the safety of workers and surrounding community of the industry. According to this principle chemical reactions, substances or materials having least potential for chemical accidents should be used in the industry.
Green Metrices
Green metrices quantify the efficiency or environmental performance of chemical processes and allow changes in performance to be measured. A single metric cannot be used to explain the greenness of a complete chemical process. So, it is very important to choose an appropriate metric to identify and describe all features of a chemical process. [4]
Percentage Yield
Percentage Yield is traditional way of comparing reactions and compares the expected mass of product with the actual mass of product.
퐴푐푡푢푎푙 푚푎푠푠 표푓 푝푟표푑푢푐푡 푃푒푟푐푒푛푡푎푔푒 푌𝑖푒푙푑 = × 100% 푇ℎ푒표푟푒푡𝑖푐푎푙 푚푎푠푠 표푓 푝푟표푑푢푐푡 Or 퐴푐푡푢푎푙 푌𝑖푒푙푑 푃푒푟푐푒푛푡푎푔푒 푌𝑖푒푙푑 = × 100% 푇ℎ푒표푟푒푡𝑖푐푎푙 푌𝑖푒푙푑
푇ℎ푒표푟푒푡𝑖푐푎푙 푌𝑖푒푙푑 = (푀표푙푒푠 표푓 푙𝑖푚𝑖푡𝑖푛푔 푟푒푎푔푒푛푡)(푆푡표𝑖푐ℎ𝑖표푚푒푡푟𝑖푐 푅푎푡𝑖표)(푀푊 표푓 푑푒푠𝑖푟푒푑 푝푟표푑푢푐푡) Where, MW = Molecular Weight 퐷푒푠𝑖푟푒푑 푃푟표푑푢푐푡 푆푡표𝑖푐ℎ𝑖표푚푒푡푟𝑖푐 푅푎푡𝑖표 = 퐿𝑖푚𝑖푡𝑖푛푔 푅푒푎푔푒푛푡
Atom Economy Atom Economy is the measure of amount of the reactant which completely converts into desired product without producing any side product or waste. Reactions having higher atom economy are more efficient. So, it is desirable to have a higher atom economy.
퐺푀푊 표푓 푑푒푠𝑖푟푒푑 푝푟표푑푢푐푡푠 퐴푡표푚 퐸푐표푛표푚푦 = × 100% 푇표푡푎푙 퐺푀푊 표푓 푎푙푙 푟푒푎푐푡푎푛푡푠
GMW = Gram Molecular Weight 푅푒푎푔푒푛푡푠 퐴 + 퐵 → 퐶 + 퐷 퐶푎푡푎푙푦푠푡푠 퐺푀푊 (퐶) % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 % 퐺푀푊 (퐴 + 퐵)
For Multi – Step Reaction: A+B H+I ↓ ↓ C+D K+J ↓ ↓ E+F → G+L → N
퐺푀푊 (퐺) % 퐴푡표푚 퐸푐표푛표푚푦 표푓 퐺 = × 100% 퐺푀푊 (퐴 + 퐵 + 퐷 + 퐹)
퐺푀푊 (푁) % 퐴푡표푚 퐸푐표푛표푚푦 표푓 푁 = × 100% 퐺푀푊 (퐴 + 퐵 + 퐷 + 퐹 + 퐻 + 퐼 + 퐾)
*Intermediates which are formed in one reaction and decomposed in the next reaction are not included in the atom economy calculation.
Atom Economy and Types of Reaction
(a) Substitution Reaction
Substitution reaction have poor atom economy.
Example:
퐶퐻3퐶퐻2퐶퐻2퐶퐻2푂퐻 + 푁푎퐵푟 + 퐻2푆푂4 → 퐶퐻3퐶퐻2퐶퐻2퐶퐻2퐵푟 + 푁푎2푆푂4 + 퐻2O
In the above reaction Sodium Sulphate and Water are undesired product or waste.
Therefore,
퐺푀푊 표푓 푑푒푠𝑖푟푒푑 푝푟표푑푢푐푡푠 퐴푡표푚 퐸푐표푛표푚푦 = × 100% 푇표푡푎푙 퐺푀푊 표푓 푎푙푙 푟푒푎푐푡푎푛푡푠 = 135 × 100% = 50% 275
Thus, only half of the mass of the reactants get converted into desired product.
(b) Elimination Reaction Elimination reaction results into loss of atoms (no gain of atoms). Thus, these types of reactions have very poor atom economy. Example: Base promoted dehydro-halogenation of alkyl halide.
CH3 CH3
H2C− C – CH3 + CH3CH2ONa → H2C = C – CH3 H Br -HBr 2- methyl propene 2- bromo, 2- methyl propane
(c) Addition Reactions Addition Reactions incorporates all the atoms of the reactants to form the product. That means all the reactants are converted into desired product. So, no waste formation occurs in case of addition reactions. Thus, atom economy of addition reactions is 100%. Example: Mercury (III) catalysed hydration of alkyne is an 100% atom efficient reaction.
+ H2O →
82.15 18.01 H2SO4/HgSO4 100.16
(d) Rearrangement Reactions
These are environmentally preferable reactions as these reactions involve organisations of atoms of a molecule. So, there is no loss of atoms in these types of reactions and hence, these reactions have 100% atom economy.
Example: CH3 CH3 CH3 ׀ ׀ ׀ CH3 – C – CH = CH2 → CH3 – C = C − CH3 ׀ CH3 Isomerisation Catalysis and Atom Economy Catalysts enhances the rate of reaction and reduces the energy requirement. Catalysts are omitted from the formal calculation of atom economy as they are not consumed in the reaction. So, it is desirable to use catalysts instead of stoichiometric reagents in reactions to increase the atom economy.
Example: Production of Ethylene Oxide
Traditional Route:
퐶2퐻4 + 퐶푙2 + 퐶푎 (푂퐻)2 → 퐶2퐻4푂 + 퐶푎퐶푙2 + 퐻2푂 Ethylene Oxide
44 % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 = 25.5% 28 + 70 + 74
Greener Route: Catalyst 퐶퐻2 = 퐶퐻2 + 1/2푂2 → 퐶2퐻4푂
44 % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 = 100% 28 + 16
Heterogenous Catalysis Heterogenous Catalysis is the process where a catalyst in one phase interacts with reactants in a different phase.
Example: Reduction of nitrobenzene to aniline
Traditional Route:
퐹푒퐶푙3 4퐶6퐻5푁푂2 + 9퐹푒 + 4퐻2푂 → 4퐶6퐻5푁퐻2 + 3퐹푒3푂4 퐻퐶푙
4 × 93 % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 = 35% 4 × 123 + 9 × 55 + 4 × 18
Greener Route: 푁𝑖(퐶푎푡)
퐶6퐻5푁푂2 + 3퐻2 → 퐶6퐻5푁퐻2 3000퐶 5 푝푠𝑖
93 % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 = 72% 123 + 3 × 2
(b) Homogenous Catalysis
Reactants and products are in same phase usually liquids. It is classified into two categories: (i) Organometallic Catalysis involve metallic complexes (ii) Acid/Base Catalysis or Organo Catalysis without metal.
Example: Preparation of Adiponitrile by hydrocyanation of butadiene
Figure 1: Preparation of Adiponitrile by hydrocyanation of butadiene [1]
108 % 퐴푡표푚 퐸푐표푛표푚푦 = = 100 = 100% 54 + 2 × 27
(c) Bio catalysis
Biocatalysts or enzymes are biodegradable, safe and highly selective.
Example: Synthesis of 6 – Amino - penicillanic Acid from Penicillin – G
The traditional four step of synthesis of 6- APA has Atom Economy of 28%. This traditional rout is replaced by greener route i.e. synthesis of 6-APA from Penicillin by using biocatalyst Penicillin acylase.
Figure 2: Synthesis of 6 – Amino - penicillanic Acid from Penicillin – G [2]
216 % 퐴푡표푚 퐸푐표푛표푚푦 = × 100 = 58% 372
Drawbacks of Atom Economy:
(i) Atom Economy does not give any information about reaction yield, selectivity or the nature of the waste. (ii) It does not account for catalysts and reagents. (iii) It also does not give any idea about energy of the reaction.
Reaction Mass Efficiency (RME)
Reaction Mass Efficiency is a realistic metric for describing the greenness of a process. It accounts for yield, stoichiometry and atom economy.
퐴 + 퐵 → 퐶
Mass: m1 m2 m3 Moles: X Y Z
GMW: MW1 MW2 MW3
푍(푀푊 ) 푅푀퐸 = 3 푋(푀푊1) + 푌(푀푊2)
Curzons Reaction Mass Efficiency
Curzons introduced an expression relating Reaction Mass Efficiency with Atom Economy, Yield and the reciprocal a stoichiometric factor. The stoichiometric factor was derived ny Androas which explains reactant excess.
푚 푍(푀푊 ) 푅푀퐸 = 3 = 3 푚1 + 푚2 푋(푀푊1) + 푌(푀푊2)
푍(푀푊 ) = 3 푋(푀푊1) + (푌 − 푋 + 푋)(푀푊2)
푍(푀푊 ) = 3 푋(푀푊1) + 푋(푀푊2) + (푌 − 푋)(푀푊3)
−1 푍 푀푊3 (푀푊1 + 푀푊2) = . −1 . −1 푋 푀푊1 + 푀푊2 + 푋 (푌 − 푋)푀푊2 (푀푊1 + 푀푊2)
푍 푀푊 1 = . 3 . 푋 푀푊 + 푀푊 (푌 − 푋)푀푊 1 2 1 + 2 푋(푀푊1 + 푀푊2)
1 = 푌𝑖푒푙푑 × 퐴푡표푚 퐸푐표푛표푚푦 × 푆푡표𝑖푐ℎ𝑖표푚푒푡푟𝑖푐 퐹푎푐푡표푟
Curzons, from the above expression found that atom economy influences the manufacture cost of pharmaceuticals much less than yield and stoichiometry. [2]
Androas Reaction Mass Efficiency (Generalised RME)
According to Androas definition, Reaction Mass Efficiency should include all the materials involved in the reaction i.e. mass of catalysts, solvents, auxiliary compounds and work- up/purification materials.
푀푎푠푠 표푓 푑푒푠𝑖푟푒푑 푃푟표푑푢푐푡 퐺푒푛푒푟푎푙𝑖푠푒푑 푅푀퐸 = 푇표푡푎푙 푀푎푠푠 표푓 푎푙푙 𝑖푛푝푢푡 푚푎푡푒푟𝑖푎푙푠
Kernel RME or Maximum RME
Kernel or Maximum 푅푀퐸 = 푌𝑖푒푙푑 × 퐴푡표푚 퐸푐표푛표푚푦
Drawbacks of RME
(i) RME value is influenced by the treatment of solvents and auxiliaries used in the reaction. (ii) Proper identification of all by products is difficult.
Effective Mass Yield (EMY)
EMY measures the environmental acceptability of a process. It is defined as the percentage of the mass of the desired product relative to mass of all non-benign materials used in its synthesis.
푚푎푠푠 표푓 푑푒푠𝑖푟푒푑 푝푟표푑푢푐푡 퐸푀푌 (%) = × 100% 푚푎푠푠 표푓 푛표푛 − 푏푒푛𝑖푔푛 푟푒푎푔푒푛푡푠
Example: Esterification of n – Butanol with acetic acid
퐶퐻3퐶퐻2퐶퐻2퐶퐻2푂퐻 + 퐶퐻3퐶푂푂퐻 → 퐶퐻3퐶퐻2퐶퐻2퐶퐻2퐶푂푂퐶퐻3 + 퐻2푂 n – butanol Acetic Acid n – butyl acetate 40 퐸푀푌 (%) = × 100 = 108% 37 This metric defines yield in terms of the product made from non – toxic materials.
Drawback of EMY: (i) Routine information of human toxicity and ecotoxicity is required to make use of the metric.
Environmental Factor (E - Factor)
E – factor is a simple and fast metric for the evaluation of environmental impact of industrial processes. E – factor is calculated as a total weight of all waste generated in technological or industrial process (in kilograms) per kilogram of product.
푘푔푠 표푓 푤푎푠푡푒 푝푟표푑푢푐푒푑 퐸 − 푓푎푐푡표푟 = 푘푔푠 표푓 푑푒푠𝑖푟푒푑 푝푟표푑푢푐푡
Higher the E – factor, more the waste generated. Ideal E – factor is 0. E – factor takes chemical yield into account and includes reagents; solvent loses and all process aids. E – factor can be calculated including or excluding water. E – factor ignores recyclable factors.
Environmental Quotient (EQ)
퐸푄 = 퐸푛푣𝑖푟표푛푚푒푛푡푎푙 퐹푎푐푡표푟 × 푄
Q = Environmental Hazard Quotient, it is related to ecotoxicity of waste generated during an industrial process or organic synthesis.
The Eco Scale
The Eco Scale is a semi-quantitative tool to evaluate the quantity of the organic preparation on a laboratory scale. It focuses on yield, cost, safety, conditions and ease of workup/purification. The Eco Scale has highest rank 100, which means ideal reaction. The Eco – Scale is classified into six categories – product yield, price of reaction components, safety, technical set-up, temperature/time and work-up/purification. It allows to select different preparations. If the above six parameters differ from the ideal value then penalty points will be awarded. The areas that need further attention are clearly indicated.
Disadvantage (i) It does not give any information about the types of hazard.
Mass Intensity (MI)
푇표푡푎푙 푚푎푠푠 푢푠푒푑 𝑖푛 푝푟표푐푒푠푠 & 푝푟표푐푒푠푠 푠푡푒푝 (퐾푔) 푀퐼 = 푀푎푠푠 표푓 푝푟표푑푢푐푡 (퐾푔)
퐸 − 푓푎푐푡표푟 = 푀퐼 − 1
It takes into account the yield, stoichiometry, the solvent and the reagent used in the reaction.
In the ideal situation Mass Intensity should approach (i) Total mass includes everything that is used in the process or process step with the exception of water i.e. reactants, reagents, solvents, catalysts etc. (ii) Total mass also includes all masses used in acid, base, salt and organic solvent washes and organic solvent used in crystallization or for solvent switching.
Summary:
Green Technology is novel approach for the reduction of wastes and increase efficiency of chemical reactions. For designing green chemicals and alternative pathways, guidelines have been given by Paul Anastas and John Warner, these guidelines are called 12 principles of green chemistry. Based upon the 12 principles of green chemistry, green metrices have been given, for the evaluation of the existing/traditional chemical reactions. After studying the above aspects, it can be summarised that the major sources of wastes in the chemical reactions are stoichiometric reagents and solvents.
Problems:
Q. No.1) 1 – bromobutane Production: 1.33 g of Sodium Bromide is dissolved in 1.5 ml of water. To this solution 0.80 ml of 1- Butanol and 1.1 ml of concentrated sulfuric acid are added. Calculate the percentage yield of 1 – bromobutane. (Theoretical yield = 1.20 g)
C4H9OH + NaBr + H2SO4 → C4H9Br + NaHSO4 + H2O
Q. No. 2) Calculate the Atom Economy of the following reactions.
3 eq. CH3I
(a)
1 - Butanamine Ag2O, H2O 1 - Pentene
Ether
(b) PBr3 2–Hydroxy–1,2–diphenylethanone 2–Bromo-1,2-diphenylethanone
SOCl2
(c) Pyridine 2–Hydroxy–1,2–diphenylethanone 2–Chloro-1,2-diphenylethanone
+ H3O
(d) + H2O NaOH Hydration of Benzillic Acid
Q. No. 3) Benzyl alcohol reacts with p – toluenesulfonylchloride to form sulfonate ester
triethylamin e + toluene
Mass: 10.81 g 21.9 g 23.6 g Moles: 0.10 0.115 0.09 GMW: 108.14 190.64 262.32
Calculate the following: (i) Atom Economy (ii) Yield (iii) RME (iv) Curzons RME
Q. No.4) Suzuki Reaction: Phenylboronic acid reacts with 4 iodophenol to from Phenylphenol
3K2CO3
Mass: 0.220 g 0.122 g 0.415 g 0.115 g Moles: 1.00 mmol 1.00 mmol 3.00 mmol 0.675 g GMW: 220.01 121.93 414.6 g 170.21 g
Catalyst mass: 0.003 g Reaction Solvent mass: 11g Workup/Purification Material mass: 38.1 g
Calculate the following: (i) Atom Economy (ii) Yield (iii) Kernel RME (iv) Curzons RME (v) Generalized RME
Q.No.5) Esterification of n- butanol with acetic acid to form butyl acetate.
퐶퐻3퐶퐻2퐶퐻2퐶퐻2푂퐻 + 퐶퐻3퐶푂푂퐻 → 퐶퐻3퐶퐻2퐶퐻3퐶푂푂퐶퐻3 + 퐻2푂 n- butanol Acetic Acid Butyl Acetate Water 37 g 40 g 60 g
Calculate the following: (i) Atom Economy (ii) E – factor (iii) Effective Mass Yield
References:
(1) Bini, L., Christian, M., Dieter, V. (2010). Ligand development in the Ni-catalyzed hydrocyanation of alkenes. Chem Commun, 46, 8325 – 8334.
(2) Dicks, A.P., Hent, A. (2015). Green Chemistry Metrics A Guide to Determining and Evaluating Process Greenness. Toronto, Springer.
(3) Doble, M., Kruthiventi, A.K. (2007). Green Chemistry & Engineering. Madras, Elsevier Science & Technology Books.
(4) Gurtu, A., Gurtu, J.N. (2017). Green Chemistry. Meerut, Pragati Prakashan.