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CHAPTER 12 FEEDSTOCKS: MAXIMUM UTILIZATION OF RENEWABLE AND BIOLOGICAL MATERIALS From Green Chemistry and the Ten Commandments of Sustainability, Stanley.

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Presentation on theme: "CHAPTER 12 FEEDSTOCKS: MAXIMUM UTILIZATION OF RENEWABLE AND BIOLOGICAL MATERIALS From Green Chemistry and the Ten Commandments of Sustainability, Stanley."— Presentation transcript:

1 CHAPTER 12 FEEDSTOCKS: MAXIMUM UTILIZATION OF RENEWABLE AND BIOLOGICAL MATERIALS From Green Chemistry and the Ten Commandments of Sustainability, Stanley E. Manahan, ChemChar Research, Inc., 2006

2 12.1. SOURCES OF FEEDSTOCKS Feedstocks are the main ingredients that go into the production of chemical products Reagents act upon feedstocks and often the two are not readily distinguished Feedstock selection largely dictates the reactions and conditions that will be employed in a chemical synthesis Feedstocks should come from renewable sources rather than depletable resources, if possible Biomass is renewable Petroleum is depleting

3 Feedstocks (Cont.) Most feedstocks now from petroleum Petroleum hydrocarbon molecules are in a highly reduced chemical state and often must be oxidized for feedstocks Oxidation of petroleum hydrocarbons Consumes energy Often severe and hazardous reagents Challenge and potential environmental harm in separating feedstock from other materials Cellulose from wood Hydrocarbon mixture in petroleum Consider the whole life cycle of materials in evaluating feedstocks

4 12.2. UTILIZATION OF FEEDSTOCKS Ideal feedstock Renewable Poses no hazards Converted to the desired product using few steps 100% yield 100% atom economy

5 Three Major Categories of Reaction Processes by Which Feedstocks are Acted upon by Reagents to Yield Products

6 12.3. BIOLOGICAL FEEDSTOCKS Organisms have provided a huge share of the materials used by humans throughout their existence. Biomass: Plant material generated by photosynthesis Leading candidate to replace petroleum as a feedstock for the organic chemicals industry Partially oxidized biomass material avoids expensive, sometimes difficult oxidation steps in oxidizing petroleum

7 Major Categories of Biomass That Can Be Used for Feedstock 1.Carbohydrate, general formula of approximately CH 2 O Glucose sugar from photosynthesis In cellulose 2. Lignin, a complex biological polymer in wood having few uses 3.Lipid oils extracted from seeds, including soybeans, sunflowers, and corn. 4.Hydrocarbon terpenes produced by rubber trees, pine trees, and some other kinds of plants. 5.Proteins, produced in relatively small quantities, but potentially valuable as nutrients and other uses.

8 Obtaining Feedstocks from Biomass Pathways by which feedstocks can be obtained from biomass Simple physical separation of biological materials, such as tapping latex from rubber trees Extraction of oils by organic solvents Physical and chemical processes such as separation of cellulose bound together by lignin “ glue ” in making paper

9 Carbohydrate Feedstocks Carbohydrates as feedstocks for chemical processes Carbohydrates in several forms Sucrose sugar, C 12 H 22 O 11, squeezed from sugar cane as sap and extracted from sugar beets and sugar cane with water Starch, a polymer of glucose readily isolated from grains, such as corn, or from potatoes and readily broken down adding water to give glucose Huge amounts of cellulose, which occurs in woody parts of plants and broken down to glucose with cellulase enzymes

10 Lipid Oils and Terpenes Lipid oils are extracted from the seeds of some plants Volatile solvent n-hexane, C 6 H 14, is used to extract oils Solvents are distilled off from the extract and recirculated through the process. Hydrocarbon terpenes can be tapped from rubber trees as a latex suspension in tree sap Steam treatment and distillation to extract terpenes from sources such as pine or citrus tree biomass

11 Proteins Grain seeds as sources of protein Generally used for food Potentially useful as chemical feedstocks for specialty applications Transgenic plants to make specialty proteins, such as medicinal agents

12 12.4. FERMENTATION AND PLANT SOURCES OF CHEMICALS Two main biological sources of materials to provide specialty and commodity chemicals and feedstocks Plants Microorganisms, especially bacteria and yeasts Fermentation refers to the action of microorganisms on nutrients under controlled conditions to produce desired products Anaerobic (anoxic, absence of air) Aerobic (oxic, presence of air) Fermentation used for thousands of years to produce alcoholic beverages, sauerkraut, vinegar, pickles, cheese, yogurt, other foods and ethanol Lactic acid from fermentation More recently production by fermentation of organic acids, antibiotics, enzymes, and vitamins

13 Penicillin Starting in the 1940s, Later, Other Antibiotics from Fermentation Penicillin Fermentation Process

14 Fermentation Processes (Cont.) Requirements for successful fermentation production processes The right microorganisms Proper nutrients Sterile conditions Temperature regulation Oxygen levels pH Transgenic microorganisms in fermentation Most commonly to make proteins and polypeptides that are used as pharmaceuticals Human insulin Largest scale production of chemicals by fermentation is ethanol Other large-scale chemicals may be possible in the future

15 Production of Materials by Plants Plants generate their own biomass and are very efficient producers of materials Distinct advantages in plant production and harvesting No contamination problems such as those in fermentation Grown by relatively untrained personnel using well known agricultural practices Easily harvested in the form of grains, stalks, and leaves Now transgenic plants can be bred to produce a variety of more pure materials directed by genes transplanted from other kinds of organisms Example of almost pure cellulose in cotton Hybrid plants may generate large amounts of biomass by photosynthesis Hybrid corn is one of the most productive field crops Hybrid poplar tree

16 Advantages of glucose Produced in abundance by plants Partially oxidized 12.5. GLUCOSE AS FEEDSTOCK Contains hydroxyl groups (-OH) around the molecule, which act as sites for the attachment of various functionalities Metabolized by essentially all organisms, so it serves as an excellent starting point for biosynthesis reactions using enzymes Glucose and many of its products are biodegradable, adding to their environmental acceptability Glucose from several sources Enzyme-catalyzed processes from other sugars including sucrose and fructose Most glucose from enzymatic hydrolysis of cornstarch Enzymatic hydrolysis of cellulose

17 Ethanol from Glucose The greatest use of glucose for synthesis is by fermentation with yeasts to produce ethanol, Gasoline additive Solvent Chemical feedstock A byproduct of fermentation to make ethanol is carbon dioxide Green chemical applications such as for supercritical fluid solvent Glucose as a feedstock for the biological synthesis of a number of different biochemical compounds Ascorbic acid Citric acid Lactic acid Amino acids used as nutritional supplements, including lysine, phenylalanine, threonine, and tryptophan The vitamins folic acid, ubiquinone, and enterochelin

18 Glucose in Chemical Manufacture Glucose feedstock for chemical manufacture Genetically engineered microorganisms that can be made to express genes for the biosynthesis of a number of products Example of synthesis from glucose of adipic acid required for nylon The muconic acid is then treated under relatively mild conditions with H 2 under 3 atm pressure over a platinum catalyst to give adipic acid. Conventional synthesis of adipic acid is not green Severe conditions Dangerous chemicals Wastes N 2 O Biological synthesis using genetically modified Escherichia coli bacteria

19 Catechol from Glucose Flavors Pharmaceuticals Carbofuran pesticide Other About 20 million kilograms catechol per year worldwide Catechol May be made by E. coli bacteria of a genetically modified strain designated AB2834/pKD136/pKD9/069A acting on glucose Antioxidant 3-Dehydroshikimic acid may be synthesized by action of E. coli on glucose

20 12.6. CELLULOSE Segment of the cellulose molecule in which from 1500 to several thousand anhydroglucose units (glucose molecules less H 2 O) are bonded together: Cellulose is the most abundant natural material produced by organisms Annual world production around 500 billion metric tons

21 Preparation of Cellulose from Plant Sources Preparation of cellulose Separation from matrix of lignocellulose (hemicellulose and lignin) Harsh chemical processing required Cellulose product may require bleaching with potentially hazardous chemicals Microcrystalline cellulose used in foods, pharmaceuticals, and cosmetics

22 Cellulose Products Cellulose acetate, an ester in which most of the -OH groups on cellulose are replaced by acetate groups by reaction with acetic anhydride Chemically modified cellulose Chemical modification aided by abundance of -OH groups to which various other groups can be bonded to impart a variety of properties Rayon made by treating cellulose with base and carbon disulfide, CS 2, then extruding the product through fine holes to make thread Similar process extruding through a long narrow slot to make cellophane

23 Cellulose Nitrate Cellulose nitrate in which the -OH groups on cellulose are replaced by - ONO 2 groups by treating cellulose with a mixture of nitric acid (HNO 3 ) and sulfuric acid (H 2 SO 4 ) Used as explosive Transparent film used in the early days of moving pictures for movie film resulting in some disastrous fires giving off highly toxic fumes of NO 2 gas

24 12.7. FEEDSTOCKS FROM CELLULOSE WASTES Large quantities of cellulose-rich waste biomass as byproducts of crop production Straw remaining from grain harvest Bagasse residue from the extraction of sucrose from sugar cane Other plant residues Rumen bacteria acting on cellulose wastes treated with lime in large fermentors from which oxygen is excluded Produce calcium acetate, calcium propionate, and calcium butyrate that can be acidified to produce corresponding acids

25 Feedstocks from Cellulose Wastes (Cont.) Hydrogenation to convert organic acids to alcohols: Heat treatment of the organic acids at 450˚C to produce ketones

26 12.8. LIGNIN Lignin is a chemically complex biopolymer that is associated with cellulose in plants Serves to bind cellulose in the plant structure Ranks second in abundance only to cellulose as a biomass material produced by plants Lignin is difficult to use because of its inconsistent, widely variable molecular structure, a typical segment of which is shown below:

27 Lignin (Cont.) Lignin ’ s resistance to biological attack makes it a difficult substrate to use for the enzyme-catalyzed reactions favored in the practice of green chemistry Some current uses of lignin: Burned for fuel Binders to hold materials together in coherent masses, fillers, resin extenders, and dispersants Some potential as a degradation-resistant structural material, such as in circuit boards

28 12.9. DIRECT BIOSYNTHESIS OF POLYMERS Cellulose in wood and cotton Protein polymers in wool and silk Environmental advantage in that polymers made biologically are also the ones that are most likely to be biodegradable From the standpoint of green chemistry, it is ideal to have polymers that are made by organisms in a form that is essentially ready to use Recent interest has focused on poly(hydroxyalkanoate) compounds, of which the most common are polymers of 3- hydroxybutyric acid: Can be engineered to have a variety of properties ranging from rubber-like to hard solid materials Biodegradable Thermoplastic properties, meaning that they melt when heated and resolidify when cooled

29 Biosynthesis of Polymers (Cont.) Biological synthesis of a polymer in which 3-hydroxybutyrate groups alternate with 3-hydroxyvalerate groups, where valeric acid has a 5-carbon atom chain using a genetically engineered bacterium called Ralstonia eutropia fed glucose and the sodium salt of propionic acid to make the polymer in fermentation vats Poly(hydroxyalkanoate) polymers produced by transgenic plants may eventually be possible

30 12.10. BIOCONVERSION PROCESSES FOR SYNTHETIC CHEMICALS Advantages of enzymatic processes to make synthetic chemicals Work well on natural products Mild conditions Safe reagents such as molecular O 2 High specificity p-Hydroxybenzoic Acid from Toluene This compound is an important intermediate used in the synthesis of pharmaceuticals, pesticides, dyes, preservatives, and liquid crystal polymers Currently p-hydroxybenzoic acid is made by reacting potassium phenolate with carbon dioxide under high pressure at 220˚C:

31 Synthesis of p-Hydroxybenzoic Acid (Cont.) Process for making p-hydroxybenzoic acid from potassium phenolate Dates back to the early 1860s Converts slightly less than half of the potassium phenolate Produces substantial impurities Requires severe conditions Produces metal and phenol wastes Reactive alumina powder (Al 2 O 3 ) used to catalyze the process has caused explosions

32 Biosynthesis of p-Hydroxybenzoic Acid from Toluene Biosynthetic alternative synthesis of p-hydroxybenzoic acid from toluene with genetically engineered Pseudomonas putida bacteria 1.Attachment at the para position on toluene of a hydroxyl group by the action of toluene-4-monooxygenase (T4MO) enzyme system transferred to Pseudomonas putida from Pseudomonas mendocina: 2.p-Cresol methylhydroxylase (PCMH) enzyme from a strain of Pseudomonas putida to give p-hydroxybenzyl alcohol followed by conversion to p-hydroxybenzaldehyde: p-Hydroxybenzaldehyde p-Hydroxybenzyl alcohol

33 Biosynthesis of p-Hydroxybenzoic Acid (Cont.) 3.Aromatic aldehyde dehydrogenase enzyme designated PHBZ also obtained from a strain of Pseudomonas putida to convert the aldehyde to the p-hydroxybenzoic acid product:

34 Biosynthesis of 5-Cyanovaleramide Production of 5-Cyanovaleramide Currently performed chemically with a stoichiometric mixture of adiponitrile with water and a manganese dioxide catalyst under pressure at 130˚C: Isolation of the 5-cyanovaleramide product entails dissolving the hot reaction mixture in toluene solvent, which is then cooled to precipitate the product For each kilogram of 5-cyanovaleramide product isolated, approximately 1.25 kg of waste MnO 2 requires disposal

35 Biosynthesis of 5-Cyanovaleramide (Cont.) Biochemical synthesis of 5-cyanovaleramide with microoorganisms that had nitrile hydratase enzymes to convert the C  N functional group to the amide group using Pseudomonas chloroaphis B23 Run at 5˚C over cells immobilized in beads of calcium alginate, the salt of alginic acid isolated from the cell walls of kelp with 97% conversion Water-based reaction mixture simply separated mechanically from the calcium alginate beads containing the microorganisms, which are then recycled for the next batch of reactant Water then distilled off of the product to leave an oil, from which the 5-cyanovaleramide product was dissolved in methanol, leaving adipamide and other byproducts behind with only 0.006 kg of water-based catalyst waste residue produced per kg of product

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