CHAPTER 1. INTRODUCTION
Chemical industry have no doubt brought development but has also left with the environmental problems also. Traditionally, waste is viewed as an unnecessary element arising from the activities of any industry. In reality, waste is a misplaced resource, existing at a wrong place at a wrong time. Waste is also the inefficient use of utilities such as electricity, water, and fuel, which are often considered unavoidable overheads. The costs of these wastes are generally underestimated by managers. It is important to realize that the cost of waste is not only the cost of waste disposal, but also other costs such as:
Disposal cost Inefficient energy use cost
Purchase cost of wasted raw material
Production cost for the waste material Management time spent on waste material ‘ Lost revenue for what could have been a product instead of waste ‘ Potential liabilities due to waste.
1.1 Waste Minimization
Waste minimization can be defined as “systematically reducing waste at source”. It means:
- Prevention and/or reduction of waste generated
- Efficient use of raw materials and packaging
- Efficient use of fuel, electricity and water Improving the quality of waste generated to facilitate recycling and/or reduce hazard
- Encouraging re-use, recycling and recovery.
Waste minimization is also known by other terms such as waste reduction, pollution prevention, source reduction and cleaner technology. It makes use of managerial and/or technical interventions to make industrial operations inherently pollution free
It should be also clearly understood that waste minimization, however attractive, is not a panacea for all environmental problems and may have to be supported by conventional treatment/disposal solutions.
Waste minimization is best practiced by reducing the generation of waste at the source itself. After exhausting the source reduction opportunities, attempts should be made to recycle the waste within the unit. Finally, modification or reformulation of products so as to manufacture it with least waste generation should be considered.
1.2 Classification of Waste Minimization (WM) Techniques
The waste minimization is based on different techniques. These techniques are classified as hereunder.
Figure: 1 Waste Minimization Techniques
CHAPTER:2. GREEN CHEMISTRY
Green chemistry is the utilization of a set of principles that will help reduce the use and generation of hazardous sub- stances during the manufacture and application of chemical products. Green chemistry aims to protect the environment not by cleaning up, but by inventing new chemical processes that do not pollute. It is a rapidly developing and an important area in the chemical sciences. Principles of green chemistry, developments in this field and some industrial applications.
Chemistry has provided valuable materials in the form of medicines, food products, cosmetics, dyes, paints, agrochemicals, biomolecules, high-tech substances like polymers, liquid crystals and nanoparticles. Chemists have used their knowledge and skill to prepare a large number of new materials which are far better and more useful than the natural products, such as high-tech polymers, liquid crystals, tough ceramics, nonlinear optical substances, novel electronics, designer drugs, genetic materials and new energy sources.
The processes on industrial scale involve many chemical reactions using huge quantities and wider varieties of smaller molecules, reagents, solvents, acids, alkali, etc. These chemical processes not only produce the required products but also large quantities of undesired and harmful substances in the form of solids, liquids and gases and have become the biggest challenge that chemistry has to face. So, the pressing need for the synthetic chemists is to minimize chemical pollution. During the last two decades much work has been going on in this direction. The term Green Chemistry was coined in 1991 by Anastas. The purpose is to design chemicals and chemical processes that will be less harmful to human health and environment
The terms ‘Environmental Chemistry’ and ‘Green Chemistry’ are two different aspects of environmental pollution studies. The former is the study of chemical pollutants in natural environment while the latter is an attempt to design chemical products and processes to reduce the harm they cause to the environment. Green chemistry seeks to reduce pollution at source, whereas environmental chemistry focuses on the study of pollutant chemicals and their effect on nature. Commercial applications of green chemistry have led to novel academic research to examine alternatives to the existing synthetic methods. The fundamental idea of green chemistry is that, the designer of a chemical is responsible for considering what will happen to the world after the chemical agent is put in place.
2.1 Basic Principles of Green Chemistry
1. Prevention
It is to prevent waste than to treat or clean up waste after it has been created.
2. Atom Economy
Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. Less Hazardous Chemical Synthesis
Whenever practicable synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. Designing Safer Chemicals
Chemical products should be designed to affect their desired function while minimizing toxicity.
5. Safer Solvents and Auxiliary
The use of auxiliary substances should be made unnecessary wherever possible.
6. Design for Energy Efficiency
Energy requirements of chemical processes should be recognized for their environmental and at low temperature and pressure.
7. Use of Renewable Feed stocks
A raw material or feedstock should be renewable rather than depleting whenever technically and practicable.
8. Reduce Derivatives
Unnecessary derivatization (use of blocking groups, protection, deprotection) should be avoided whenever possible.
9. Catalysis
Catalytic reagents (as selective as possible) are superior stoichiometric reagents.
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.
11. Real-time analysis for pollution prevention
Analytical methodologies need to be further developed to allow for real-time, in process monitoring and control prior to the formation of hazardous substances
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, explosions and fires. These principles can motivate chemistry at all levels: research, education and public perception. The first principle describes the basic idea of green chemistry in protecting the environment from pollution. The remaining principles are focused on atom economy, toxicity, solvent and other media using consumption of energy, application of raw materials from renewable sources and degradation of chemical products to simple, nontoxic substances that are friendly for the environment.
2.2 Metrics Used In Green Chemistry
Effective Mass Yield
Effective mass yield is defined as the percentage of the mass of the desired product relative to the mass of all non-benign materials used in its synthesis.
Effective mass yield (%) = mass of products ” 100 / mass of non-benign reagents
Carbon efficiency
Carbon efficiency is a simplified formula developed at GlaxoSmithKline (GSK).iv The mathematical representation is shown below:
Carbon efficiency (%) = amount of carbon in product ” 100 / total carbon present in reactants
Atom economy
Atom economy was designed in a different way to all the other metrics; most of these were designed to measure the improvement that had been made.The simple definition of atom economy is a calculation of how much of the reactants remain in the final product. This is shown below:
For a generic multi-stage reaction: A + B ‘ C C + D ‘ E E + F ‘ G
Atom economy = m.w. of G ” 100 / ” (m.w. A,B,D,F)
Reaction mass efficiency
The reaction mass efficiency takes into account atom economy, chemical yield and stoichiometry. The formula can take one of the two forms shown below:
From a generic reaction where A + B ‘ C
Reaction mass efficiency = molecular weight of product C ” yield / m.w. A + (m.w. B ” molar ratio B/A)
Or more simply Reaction mass efficiency = mass of product C ” 100 / mass of A + mass of B
Environmental (E) factor
The first general metric for green chemistry remains one of the best. Assumptions on solvent and other factors can be made or a total analysis can be performed.The E-factor calculation is defined by the ratio of the mass of waste per unit of product: E-factor = total waste (kg) / product
Chapter 3: H-Acid A Dye Intermediate
H-acid is a dye intermediate. In India, it is mainly manufactured by small and medium-sized enter- prises (SMEs) with a production capacity of between ten to hundred tonnes per month. The promotion of various types of employment-generating SM’s in India has resulted in multi-media pollution problems. Through the implementation of simple pollution prevention measures, substantial cost savings can be obtained in an H-acid manufacturing unit. For example, process modification can increase product yield as well as reducing the COD load to wastewater treatment systems.
The dyestuff industry in India made remarkable progress during the 1960sand 1970s.There are at present over 1000 units in the small-scale sector engaged in the manufacture of dyes and intermediates. Most of these units are located in the western part of India, i.e. the States of Gujarat and Maharashtra. H-acid (I-Amino, &Naphthol, 3-6 disulphonic acid) is one of the dye intermediates used in the manufacture of acid, reactive and direct dyes. Due to the usage of high-strength acids and alkalies in the manufacture of H-acid, the combined wastewater stream was contaminated with high chloride and sulphate content. In addition, the presence of toxic naphthalene-based dye intermediates in the wastewater made it non biodegradable. In order to meet the existing terminal standards, these industries have to install capiralintensive and more sophisticated treatment systems, with heavy recurring costs. Therefore, the feasible alternative was to implement various pollution prevention measures using a ‘methods approach’, with the objective of not only optimizing chemical usage but also reducing the pollution load to the subsequent wastewater
treatment system.
3.1 Manufacturing Process And Waste Generation
H-acid production was a batch process. On average, 30-33 batches were carried out in a month. Naphthalene was the starting material for H-acid synthesis. It was subjected to a series of chemical reactions like sulphonation,nitration followed by neutralization, reduction, fusion and isolation. The H-acid slurry after isolation with sulphuric acid was filtered in a Neutch filter, centrifuged, dried and packed. A schematic production process indicating the sources of pollution.
Figure: 3.1 Production process and source of pollution
All the above mentioned discharges were batch wise. I n order to simulate the characteristics of combined factory discharge which would serve as a design basis for the subsequent wastewater treatment system, a volume-proportion sample designated as ‘factory composite’ was prepared in NPC’s laboratory. Based on the above data, and by studying the various unit processes and operations involved in the H-acid production, the following in-plant pollution prevention measures were recommended.
3.2 In-plant pollution prevention measures
3.2.1 Process modification
Yield improvisation by the installation of an, additional autoclave: around 700 kg of amino solution was produced per batch. Out of this, only 550 kg amino solution per batch was processed in the autoclave (2000 litre capacity). Since the unit had only one autoclave, the remaining 150kg of amino solution per batch was accumulated for five batches and collected in a wooden vat (7000 litre capacity) and processed in Koch acid route. The frequency of amino solution processed in the Koch acid route was five batches per month.
This clearly indicated that about 3750 kg of amino solution was processed in the Koch acid route in a month. The Koch acid route involved the loss of (around 160 kg/Koch acid batch) intermediate in the neutch filter filtrate cum washing and centrifuge filtrate cum cloth washing. Moreover, in the Koch acid route the specific consumption of caustic (0.25 kg of Koch acid/kg of amino solution processed in the Koch acid route) was 7.7 per cent more than that in the amino route. This problem was overcome by installing an additional autoclave of 2000 litre capacity. The installation fan additional autoclave not only produced annual savings of around Rs. 10.8 lakhs (US$36,000), but also eliminated the generation of toxic wastewater streams from second stage Neutch filter and first-stage centrifuge. The above economic calculation amply demonstrates the payback period for the installation of an additional autoclave to be less than a year.
3.2.2 Recycling
3.2.2.1 Neutch filtration- stage I (after neutralization)
Washing of the Neutch filter contributed (0.35- 0.5 m3/batch) around 1.5 per cent to the combined wastewater discharge. This was collected in a drum of 500 litre capacity and reused in the neutralization vessel as a make-up for fresh water (around 1500 litres of fresh water was used) in the neutralization vessel.
3.2.2.2 Filtration in plate and frame filter press
Filter press washing constituted around (3.7m3/batch) 15per cent of the total combined wastewater discharge. On average, about 50 kg of amino solution per batch was lost in the filter press leakages, initial bed scouring and wash water streams. Around 70 per cent of the total amino loss was recovered by the implementation of the following measures: A collection tray below the P/F filter press was provided to collect leakages from the P/F interface, which were recycled to reduction vessel. + The wastewater from initial bed loosening (around 0.7 m3/batch) was filtered over a wooden vat (7 m3 capacity) in order to filter out the ferric oxide particles, and the clear filtrate was reused as a make-up to the water added in the reduction vessel. This recycling operation produced a monthly savings of about Rs 60,000/- (US$ 2000) as against the investment required for the installation of a wooden vat and a recycle pump.
3.2.2.3 Segregation of toxic concentrated streams
In view of the toxic and non-biodegradable nature of the (low volume and high COD & TDS streams) concentrated streams from the Neutch filter filtrate and centrifuge mother liquor, it was recommended to collect these streams separately at their respective sources and send them to a solar evaporation pond. However Research and Development (R&D) efforts are needed to find out the possibilities of producing cheap quality dyes from these concentrated streams. Due to this simple segregation, the COD load in the residual wastewater treatment stream was reduced by 92 per cent. The impact of these pollution prevention measures on the production process is depicted in the process block diagram in Figure 3.2. The impact of the pollution prevention measures described above on the combined wastewater flow rate and COD load.
Figure 3.2 Cleaner production process
3.3 Areas for further investigation Process control
The soluble losses of H-acid from Neutch filter filtrate and centrifuge mother liquor are analysed to be around 115 kg/batch. The reasons for this amount of loss are attributed to: inherent limitation in the kinetics of various reaction stages which ultimately lead to the formation of isomers; improper control of reaction parameters like temperature, pressure, etc; the excessive usage of acids and alkalies starting from sulphonation to isolation step. Due to this, sodium salts (NaCI and Na2SO2) get accumulated in the H-acid slurry, further inhibiting the precipitation rate of H-acid in the acidic medium; no closer pH control. By using a digital pH meter (at the time of study, the unit was using pH articles) at each and every reaction stage, excessive addition of acid and alkalies could be brought down. Through closer control of the pH, especially at the isolation step, the H-acid loss in the concentrated streams could also be brought down to a considerable extent. However, this measure requires closer supervision by experts during implementation.
3.3 Elimination of gypsum sludge generation
In order to separate the nitro naphthalene sulphonic acid from sulphuric acid, lime and soda ash were used to precipitate the sulphuric acid as calcium and sodium sulphate respectively. This resulted in 11-12 tonnes of gypsum sludge generation per tonne of H-acid manufactured. Gypsum sludge contained 0.5-1 per cent nitro naphthalene compounds. Through solvent extraction of organic acid from the inorganic acid, followed by distillation system, pure nitro naphthalene sulphonic acid could be produced and the gypsum sludge generation could be eliminated. By means of this technology’s adoption, the purity of the H-acid produced will also be high. However, a detailed techno-economic feasibility study has to be conducted to ascertain the application of this technology, to allow the scale of operation prevailing in this unit.
3.5 Catalytic Reduction
Iron powder and HCl were used for the reduction of nitro to amino group, resulting in the generation of3-3.5 tonnes of iron sludge (Fe20, sludge) per tonne of H-acid. The concentration of amino compound in iron sludge was analysed to be about 3-5 per cent. The amino naphthalene compounds are toxic and carcinogenic in nature. By a catalytic reduction using gaseous hydrogen on the active surface of a metallic catalyst, iron sludge generation could be eliminated. However, R&D efforts are required in this direction in order to arrive at a cost-effective catalytic reduction system catering to the small scale of operation prevailing in these industries. These efforts will not only increase the present yield and quality of H-acid production, but also eliminate the pollution problem due to high chloride and sulphate contaminate wastewater streams generated from these reaction steps.
3.6 Waste exchange opportunities
3.6.1 Reuse of scrubber wash waters
The SO gas generated from isolation step was scrubbed with caustic solution (2 per cent). The concentration of sodium bisulphite in the scrubber water was analysed to be around 8-10 per cent. This stream could be used for the reduction of Cr to Cr in metal finishing waste treatment. This salt solution could be concentrated and utilized as a reducing agent in the amination step of gamma acid manufacture. The NO, gas generated during nitration reaction was scrubbed with water, resulting in a dilute nitric acid solution. This waste could be transferred to a cold steel rolling mill where it could be used as a make-up for the pickling bath. However, these areas are to be further studied as there is no organized method of waste marketing prevailing in India.
3.6.2 Economics of recycling: filtration in plate and frame filter press
Amino loss in the filter press waste Recoverable amino loss due to 35 kg batch recycling of bed washing 50 kg/batch No. of batches 30 camed out one month Amount of amino 1050 kg solution that will be recovered in month Conversion factor for 0 5 processing H-acid from I amino solution Price of 1 Kg of H-acid Rs 120i- (US$ 3)
(Exclusive of excise I I duty & freight charges) Estimated monthly savings Rs 60,0001- I (US$2000) I utlized as a reducing agent in the amination step of gamma acid manufacture. The NO, gas generated during nitration reaction was scrubbed with water, resulting in a dilute nitric acid solution. This waste could be transferred to a cold steel rolling mill where it could be used as a make-up for the pickling bath. However, these areas are to be further studied as there is no organized method of waste marketing prevailing in India.
3.6.3Waste processing
Their the (ferricoxide) sludge generated from the reduction step could be used for the production of yellow or red iron oxide pigments. One large scale dye intermediate manufacturing unit in Gujarat is engaged in the production of iron oxide pigments from iron sludge generated within the plant. However, the economically ability of this process in small-scale industries is still under exploration. The concentrated streams from the Neutch filter filtrate and centrifuge were recommended to be used as a raw material in the coupling reaction for cheap quality dye manufacturing.
Chapter : 4 Experimental Analysis
Apparatus used: Conical flask, Beaker. Thermometer. Condenser, pipes
Chemicals used: naphthalene. Nitric acid, yetteberium(III) catalyst, hexane, methanol, distilled water
Procedure
Take a round bottom flask in it add 15ml of hexane, 1gm naphthalene, 0.489ml of nitric acid, and 0.4839gm of yetteberium catalyst.
Connect it with a condenser and seal pack the whole system.
Heat it for 4 hours at 40- 50oC with continuous stirring.
Cool the solution
Then add 10-15ml distilled water in it and pour it in to separating funnel allow it settle down for some time.
Separate the two layers formed in it.
The upper layer would be the solvent layer in which our product should be present and in the second layer catalyst should be present in the water.
Heat both the solution at 60oC till the hexane and water does not purely evaporates.
Figure: 5.1 Experimental setup
Figure:5.2 Separation of the two layer
Observations
Yellow coloured powder was been obtained on evaporation of hexane.
White colour powder where obtained after the evaporation of water
4.1 Thin Layer Chromatography
To see how much percentage the conversion has taken place TLC was been carried out
The solvent system was selected was
Hexane : Methanol
Hexane : ethylacetate
Hexane : ethylacetate : Methanol
Hexane : Ethylacetate : Acetic Acid
Out of all these Hexane : Ethyl Acetate : Methanol was found to be the best one.
Future Work To be Done
Analyse the activity of the catalyst.
Analyse the Activity of Nitro Napthalene
Optimisation of the process condition.
REFERENCES
https://en.wikipedia.org/wiki/Microwave_chemistry
file:///I:/concept%20of%20green%20chemistry.pdf
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For a range of reactions catalysed by Ln(OTf)3 see: (a) Marshmann, R. W. Aldrichimica Acta 1995, 28, (b) Kobayashi, S. Synlett 1993, 689. (c) Engberts, J. B. N. F.; Feringa, B. L.; Keller,E.; Otto, S. Recl. Trav. Chim. Pays Bas 1996, 115, 357.
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Silica Su;furic Acid as a novel heterogeneous system for the nitration of the phenols under mild conditions by M. A.Zolfiog, E.Madrakain, E. Gaemi. Department of chemistry. College of Science. University of Bu-Ali Sina.
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