Formaldehyde: History and Importance

methanal annals and Importance1.0INTRODUCTION methanal is the first member of the aldehyde family (C urine) and is the most important aldehyde in the environment.3 It is a natur exclusivelyy occurring chemical and a by- convergence of most organisms, including human, industrial and natural litigatees. methanal random variables from the un dispatch combustion of blow copy-containing materials smoke from forest fires, in automobile exhaust, and in tobacco smoke. Atmospheric methanal is formed by the action of sunlight and oxygen on methane and both(prenominal) different hydro snows.2 Due to its open temperament, metabolic playes break methanal into carbon dioxide. methanal does not store up in the environment or within plants, animals or people, as it promptly breaks down in the body and the atmosphere.1 It has a pungent odour and is an sticker and is an prickle to eyes, nose and throat, even at mild concentrations. The recommended odour spying limit is between 0.05 1ppm.3 methanal is an important industrial chemical and is engaged in the manufacture of many industrial carrefours and consumer articles. More than 50 branches of assiduity now recitation methanal, mainly in the form of aqueous solutions and methanal-containing resins. In 1995, the demand for methanal in the three major markets Northern America, westerly Europe, Japan was 4.1-106 t/a Chem. Systems Inc. methanal (April 1996)..History of methanalenquiry in the early 1800s by Liebig discoered the chemical composition and nature of various aldehydes excluding methanal repayable to the ease with which wood spirit was oxidized to formic acid and further synthesized to carbon dioxide and weewee.5In 1859, Alexandra Mikhailovich Butlerov inadvertently discovered formaldehyde as a result of his proposed synthesis of methylene glycol CH2 (OH)2. During his science laboratory experiment, Butlerov observed the distinctive odour of the formaldehyde solution while hydrolysing me thylene acetate, which decomposed to form formaldehyde and water. 5He as wellhead as germinated formaldehyde in other forms which led him to publish a detailed report of formaldehyde solution, its gas and polymer. He gave additional evidence of its structure and described the chemical reactions together with the creation of hexamethylenetetramine, (CH2)6N4 on reacting with ammonia, (NH3). The main way by which formaldehyde is still being produced till date was discovered by A.W. Hofmann entirely with other accelerator pedals. In 1868, Hofmann made a successive break with by passing a alloy of methyl alcohol and air over a horninessed platinum spiral. This handle is currently industrialised by use up of a metal accelerator. Over two decades later, the isolation and purification of formaldehyde was achieved by Friedrich Von Stradonitz (1892). 41882 marked two signifi fagt improvements in formaldehyde investigate. Kekule then described the preparation of pure formaldehyde and Tollens discovered a method of regulating the wood alcohol vapour air ratio, thereby affecting the award of the reaction.6The spiral platinum catalyst was replaced with much(prenominal) efficient blur gauze in 1886 by Leow. Commercial manufacture of formaldehyde was initiated by a German firm, Mercklin and Losekann in 1889 with the first use of silver catalyst patented by Hugo Blank, another German troupe in 1910. 6Industrial festering continued from 1900 to 1905, when plant sizes, f hapless lays, yields, and efficiency were increased. In 1905, Badische AnilinSoda-Fabrik (BASF) started to manufacture formaldehyde by a continuous passage employing a crystalline silver catalyst. formaldehyde out compose was 30 kg/d in the form of an aqueous 30 wt% solution. The methanol required for the payoff of formaldehyde was initially play alonged from the timber assiduity by carbonizing wood. The education of the aggressive synthesis of methanol by BASF in 1925 allowed the pr oduceion of formaldehyde on a true industrial scale. 6Importance of FormaldehydeFor some(prenominal) decades, formaldehyde has been utilise consistently in a wide extend of products, ranging from personal hygiene, to medicine, to building products and much more. Many different resins argon created from formaldehyde, which atomic number 18 in turn utilize to create other materials having different decentties. Formaldehyde derivatives are utilise as preservatives in personal hygiene products because they garbage down bacteria or they are utilize to make other products more effective in terms of foaming action such as soaps and detergents. Its versatile chemistry and unique properties behave created applications for use of formaldehyde in all kinds of every day products such as plastics, carpeting, clothing, resins, glues, medicines, vaccines and the film used in x-rays.One of the first benefits you derive from formaldehyde chemistry is as a child, when you received your va ccinations for childhood diseases. These include diphtheria, polio and in good lucknza, to name a few. Since it also acts as a preservative, formaldehyde plays a critical design in our medical schools, preserving cadavers used in teaching human anatomy. It has been used for tissue and organ preservation for more than a century and has greatly assisted the advance of biological science.1Importance of parkland surgical procedureesThe concept of honey oil Chemistry attend tos reduce or eliminate the use or coevals of hazardous substances in the design, manufacture and application of chemical products. This helpers in dealing with the ever growing increase to protect the environment and the concept of sustainability. A lot of emphasis is buttocksd on the research and development phase angle of each chemical or product, to curtail issues affecting human wellness and environmental pollution. For every chemical or given product, the following guidelines should rate the choice of track7* Choice of feed-stock ( addresss are relevant of course, only also total re root words, nix, waste, etc. in the manufacture of the given feed-stock are important factors) * Choice of reaction path (minimise energy requirements by use of selective catalysts) * Choice of catalyst (efficiency, separation from product, recycling of catalyst) * Down-stream processing/ building block operations (minimising the number of stages necessary to obtain the product in the solid ground desired by the customer) * Minimising not only the amount pollutants, but also the volume of waste streams (effluent/ off-gases and solid waste) * Recycling of auxiliary, side-, and intermediate products into the process. This report focuses on physical and chemical properties of formaldehyde (CH2O), its production processes and evolution through term as it tries to conform to some of the principles of green chemistry. 2.0PROPERTIES OF VARIOUS FORMS OF methanalFormaldehyde is more complicated than many simple carbon compounds because it adopts different forms. Formaldehyde is a gas at room temperature, but the gas right away converts to a variety of derivatives. These derivatives generally behave similarly to gaseous formaldehyde and are used in industry.4Physical PropertiesI. Monomeric formaldehyde This form of formaldehyde 50-00-0, CH2O is a colorless gas that has a foul, overpowering odour and is an irritant to eyes, nose, throat and skin. Monomeric formaldehyde liquefies at -19C, and solidifies at -80C to give a white paste. The liquid and gas phases polymerise promptly at low and normal temperatures up to 80C. Pure formaldehyde gas, on the other hand, does not polymerise between 80 100C and behaves as an ideal gas. Though it is not commercially available in this form, it earth-closet be prepared in the laboratory by the Spencer and Wilde method.6, 3The jettyeecular(a) formula of gaseous formaldehyde in ambient air is shown below. II. Trioxane 1, 3, 5- Trioxane is a sta ble cyclic trimer of formaldehyde, C3H6O3. It appears as a white solid with a chloroform-like odour but does not cause any form of lovesomeness to living things. The pure form of trioxane melts at 61 62C boils at 115C and has a flash point of 45C. Trioxane is used as a feedstock for some plastics, solid fuel tablet formulas and as a stable source of formaldehyde in laboratories.8, 3III. Paraformaldehyde this is a colourless, granular solid with a pungent and irritating smell. It is prepared by condensation of methylene glycol (HOCH2 OH), and its composition is best expressed by the formula HO- (HCHO) Q-H. Paraformaldehyde melts over a wide temperature range (120-170C), which depends on the full stop of polymerization. It has similar uses to formaldehyde it is commonly used as a source of formaldehyde for disinfecting large areas.3IV. Formalin The ancient market for formaldehyde is in aqueous form, Formalin. It is a clear solution with the characteristic odour of formaldehyde. methyl alcohol is normally present, 6-15%, to suppress polymerisation. In aqueous phase, the dominant form of formaldehyde is methylene glycol and polyoxymethlene glycol for concentrated solutions.3 Chemical replys of FormaldehydeI. annihilation In thermal decomposition, formaldehyde is copulationly stable. At 150C, formaldehyde belowgoes complex decomposition to form methanol and carbon dioxide. Above 350C, the reaction decomposes to form carbon dioxide hydrogen. Catalysts such as platinum, slob, chromium and aluminum are gnarly in this decomposition reaction to form methanol, methyl formate, formic acid, carbon dioxide and methane.6 2HCHO CH3OH+COHCHO CO+ H2II. Polymerisation At room temperatures and very low pressures, formaldehyde monomer vapours tend to polymerise while at higher(prenominal) temperatures, monomeric HCHO can be maintained readily for several hours without polymerisation at an equilibrium vapour pressure. In the aqueous phase, formaldehyde is oxidized read ily by even mild oxidizing agents, such as Ag(NH3)2+, and this property has been exploited in the development of several wet-chemical analytical methods for formaldehyde.3III. Reduction and Oxidation Reactions Formaldehyde is readily reduced to methanol with hydrogen over a atomic number 28 catalyst and is oxidized by nitric acid, potassium permanganate, potassium dichromate or oxygen to form formic acid or carbon dioxide, and water.6, 3 A Cannizzaro reaction occurs when formaldehyde reacts with a strong basis or heated acid to form methanol and formic acid. HCHOaq+ NaOH HCO2Na+ H2H2+ HCHOaq CH3OHIn the presence of aluminum or magnesium methylate, paraformaldehydes react to form methyl formate. This is known as the Tischenko Reaction.2HCHO polymerHCO2CH3IV. Addition ReactionsV. Condensation Reactions Formaldehyde is a base product in many synthetic resin product.9 Formaldehyde condenses with urea, melamine, urethanes, cyanamide, redolent sulfonamides and amines, and phenols to g ive a wide range of resins Amino, Phenolic and Synthetic Resins.63.0METHODS OF PRODUCING FORMALDEHYDEOver the geezerhood, the starting feedstock for the commercial production of formaldehyde is Methanol. This feedstock has been produced by reacting carbon monoxide and hydrogen, both usually from natural gas or petroleum fractions, under high pressures in the presence of a catalyst.3 confused patents have been published for the production of formaldehyde but most with no commercial importance. Of all these, the procedure to be discussed is the decrement of carbon monoxide.3.1Reduction of Carbon OxidesThis process has been put through a lot of research due to its low cost of raw materials and potential simplicity. The end-product of this reaction is usually methanol with formaldehyde as an intermediate in the reaction. This process is a two-step reaction sort out of the reaction is a simple hydrogenation process and the other, by the Cannizzaro reaction of formaldehyde with itsel f. The reaction with strapper-alumina catalyst forms formaldehyde at temperatures of 282 487C and pressures of 117 410 atmospheres.10 CO+ H2 CH2OThis reduction reaction is highly unfavorable as a promoter of formaldehyde synthesis due to the following reasons. * Unreasonable high pressures required to obtain high yields* To obtain equilibrium at a reasonable rate and avoid hydrogenation, an extremely active and selective catalyst would be required. 3.2Methanol and FormaldehydeFormaldehyde is industrially manufactured with methanol through three main processes.6 1. fond(p) oxidation and dehydrogenation with air in the presence of silver crystals, steam, and dissipation methanol at 680 720C (BASF process, 97 98 % methanol innovation).2. overtone oxidation and dehydrogenation with air in the presence of crystalline silver or silver gauze, steam, and excess methanol at 600 650C (77 87 % primary conversion of methanol). The conversion is completed by distilling the product an d recycling the unreacted methanol3. Oxidation only with excess air in the presence of a modified iron molybdenum vanadium oxide catalyst at 250 four hundredC (98 99% methanol conversion).Process 3, also known as the FORMOX process, a highly exothermic process, occurs at temperatures of about 350C. Though this process uses land temperatures and a cheaper catalyst, the dehydrogenation process is still prevalent in the industry because of its lower operating cost.2, 3Production of formaldehyde via conversion of propane, ethylene, propylene, butylene, ethers and butane are not economic therefore have microscopical or no industrial relevance. In addition, the partial hydrogenation of CO and methane oxidation results in lower yields as compared to the former processes.63.3Development of the Methanol Process The initial method for the development of formaldehyde was originated from by Hofmann, which is the passing of a mixture of air and methanol over a heated platinum spiral and di ssolution of this product to form aqueous formaldehyde, formalin.10 This process was replaced due to difficulties with explosions in completing the product recollecty. Subsequent development involved the replacement of the platinum catalyst with platinised asbestos in a heated tube by Volhard. Further research by Tollens introduced the direct relationship between the methanol-air vapour ratio and the formaldehyde yield which is still a main principle in todays industries. 10 Leow full-strength the two later processes by replacing the platinum catalyst with copper gauze. This initiated the first continuous process for formaldehyde production. The first stage of this process yielded about 15 20% formaldehyde, with an additional 30% conversion due to further heating of the reaction gases. 10 Though not alert at the time of the concept of green chemistry, research was carried out covert the preparation of catalysts, reaction times and temperatures, and product absorption during the early years of commercial development of formaldehyde. This led to technological development for the use of a silver catalyst by O. Blank in 1910. Thorough probe with the use of this catalyst proved that higher yields were obtainable as to that of the copper catalyst. 10 Large scale manufacturing welcomed improvements in the method for vapourising alcohol, the scrubbing systems and in the control of the heat of reaction. The copper gauze was observed to disintegrate or fuse together with high air-methanol ratios. To tackle this issue, low ratios were introduced to help keep the catalyst active but this resulted in excess methanol distilled from the formaldehyde. 10 The progress made throughout the years has been achieved by the following* cost-efficient catalysts* amend methods of control* Implicit engineering economies3.3.1 smooth-spoken Catalyst ProcessThis route is the classic method for the industrial production of formaldehyde. The two main reactions governed by this proces s are dehydrogenation and partial oxidation. The dehydrogenation of methanol is a highly endothermic, 650C, and heat of reaction is usually obtained from the burning of the hydrogen enclosed in the flue gas. These processes are usually carried out by reacting methanol and air over a heated stationary catalyst and scrubbing the off gases with water to obtain aqueous formaldehyde. 6 Addition of inert substances, water or nitrogen, aids conversion by using higher methanol concentrations relative to the oxygen supplied without reaching the explosive phase. A few key reactions chance upon place during methanol conversion to formaldehyde. 3 CH3OH CH2O+ H2 H= +84kJ/mol H2 +12O2 H2O H= -243kJ/molCH3OH+12O2 CH2O+ H2O H= -159kJ/molMethyl formate, methane and formic acid are important by products of the above reactions. Below are a few undesirable reactions that must be avoided by proper control of temperature and other factors to obtain high yields. CH2O CO+ H2 H= +12.5kJ/molCH3OH +32O2 CO2+ 2H2O H= -674kJ/molCH2O +O2 CO2+ H2O H= -519kJ/molThe usual process for the commercial production of formaldehyde is through the incomplete oxidation of the methanol. So far, this has been proven to be the most optimal process because the distilled methanol is recovered and recycled in the process. This results in higher yield, higher conversion and a high atom economy. 6, 10 The BASF ProcessThis process involves the complete conversion of methanol to formaldehyde (Reaction 1). This process indirectly applied some of the principles of green chemistry. 6, 10 1. Few reaction steps2. Recycling of materials within the production system to optimise product recovery resulting in a very high atom economy. 3. Environmental awareness with combusted off-gases having no unfortunate effect on the environment4. The use of water as a solvent 5. Incorporation of all materials in the process, maximizing final product with extremely low weight percent of by-products formed6. Optimum summon re action with arrangement of catalyst7. Process conditions adjusted to ensure that in retrieving of the final product, the mixture is easily stripped without scare of an explosion. Incomplete metempsychosis and Distillative Recovery of MethanolIn this process, methanol is partially oxidised and distilled to recover formaldehyde. This is the most widely used method of production. It should be noted that an economically feasible process is not necessarily a green process. Partial oxidation of methanol has similar characteristics but differ with the following with appraise to green chemistry. 61. Two-stage reaction2. Lower reaction temperatures adopted in the first stage to help suppress the formation of unwanted by-products.3. warming of reaction generated from cooling the off gases, recycled in the system reducing energy requirements.4. Larger amount of methanol is recovered in this process with little presence of the b-products5. Similar off-gases as produced in the BASF process6. It also has an substitute route that recycles the tail gas from the top of the absorber. This reduces the amount of feedstock, methanol, required in the process. This produces a more concentrated solution and saves up cost for the distillation process and the yield is relatively high (91-92%).Factors affecting the yield in methanol oxidation processes* The higher the temperature in a dehydrogenation reaction, the higher methanol is converted in the process system. 10,6 * Process air controls the desired reaction temperature and the extent to which the endothermic reactions occur. 10,6* Besides catalyst temperature, the inert materials added as say earlier also affect the yield. 10,6Some of the advantages of the silver catalyst process are listed below11 * Most cost effective means of manufacturing formaldehyde* Increased formaldehyde yield, methanol conversion and catalyst lifespan* Reduced silver requirements* Greater resistance to plant upsets and poisoning* Improved formaldeh yde product quality* Technology demonstrated worldwide3.2.2FORMOX ProcessThe FORMOX process is the direct oxidation of methanol with metal oxide catalysts (iron, molybdenum or vanadium oxide) to produce formaldehyde. Normally, the catalyst used for this process is a mixture of molybdenum and iron in a ratio of 1.52.0. Due to the development of this catalyst, a few advantages have been attributed to this process over the silver catalyst processes. This will be discussed in the later part of this report. The FORMOX process can be characterised as follows 1. Two stage oxidation reaction in gaseous state. This prevents waste that would have been generated by use of a solvent.62. Reaction carried out under atmospherical pressure and at lower temperatures (270 four hundredC), results in an almost complete reaction. 63. Careful adjustments of process conditions help prevent the formation of unwanted by-products. These side reactions occur at temperatures surpassing 470C. 64. The conversi on rate for this process is relatively high with a high optimization process. 5. One short-coming of this process is with the tail gas that has very much of impurities and flammable components. The alternative route used instead of combustion is in the addition of fuel to the system which burns the tail gas as a supplement for energy in other start-up processes. 6 In summary, the green advantages of the three commercial processes can be summarised as follows 71. Few unit operations2. Waste is minimised by a highly selective reaction3. Use of catalysts to optimise process reactions4. Water used as the only solvent5. Reaction carried out at atmospheric pressure 6. Gas-phase reaction for the FORMOX process means that catalyst does not have to be recovered from solution 7. Recovery of energy from exothermic reactions to help reduce environmental and economic impacts.8. High conversion rates achieved through efficient use of equipment, energy and material9. Use of air as oxidant instead of chemical oxidising agents reducing the toxicity and by-products formed. 3.3Development of New ProcessesVarious research works have been carried out for developing new formaldehyde synthesis. Unfortunately, there has been no existence of commercial units of the techniques discussed below 1. Partial oxidation of methane to produce formaldehyde which has an advantage of reducing raw material costs of producing the methanol from methane. The inducement for such a process is reduction of raw material costs by avoiding the capital and expense of producing the methanol from methane. 122. Production of anhydrous or highly concentrated formaldehyde solutions via dehydrogenation of methanol. In some instances, energy costs are reduced as well as effluent generation, and losses, providing a more favorable condition. 12 3. Formaldehyde production from methylal (produced from methanol and formaldehyde) which is in two phases. Firstly, methylal oxidation which yields up to 70% of the concentr ated formaldehyde product as compared to methanol oxidation with 55%. After this, methylal is produced by reacting formaldehyde obtained in aqueous recycle streams from other units with methanol as opposed to recovery by other more costly means, e.g. distillation and evaporation. Development of this process is complete. 12Further research is still being carried out in the use of bacteria to produce formaldehyde. This will not be discussed in this report. 4.0ENVIRONMENTAL ISSUES ASSOCIATED WITH FORMALDEHYDEREFERENCES1. Formaldehyde Council, I. (2007, November). Formaldehyde Facts and Background Information. Retrieved May 10, 2010, from http//www.formaldehyde.org/_base/pdf/fact_sheets/11_01_07-FormadehydeFactsandBackgroundInformation.pdf2. Daily, C. (2004, April 01). The Chemistry Encyclopedia. Retrieved May 07, 2010, from http//www.chemistrydaily.com/chemistry/Formaldehyde3. Council, N. R. (1981). Formaldehyde and other Aldehydes. Washington, D.C, USA.4. Wikimedia. (2010, May 02). Fo rmaldehyde. Retrieved May 07, 2010, from http//en.wikipedia.org/wiki/Formaldehyde5. Harrison, K. (1998, July). Formaldehyde. Retrieved May 07, 2010, from 3d Chem http//www.3dchem.com/molecules.asp?ID= one hundred one6. Wiley, I. (2006). Formaldehyde. Retrieved May 07, 2010, from Ullmans Encyclopedia of IndustrialChemistry http//mrw.interscience.wiley.com.resourceproxy.manchester.ac.uk/emrw/9783527306732/ueic/article/a11_619/current/pdf7. Chuck, R. (n.d.). A Catalytic Green Process for the Production of Niacin. Retrieved May 07, 2010, from Lonza Group http//www.lonza.com/group/en/company/news/publications_of_lonza.-ParSys-0002-ParSysdownloadlist-0026-DownloadFile.pdf/25_A%20Catalytic%20Green%20Process%20for%20the%20Production%20of%20Niacin.pdf8. Wikimedia. (2010, April 15). Trioxane. Retrieved May 07, 2010, from http//en.wikipedia.org/wiki/1,3,5-Trioxane9. Smith, S. (2010). What is formaldehyde resin? Retrieved May 07, 2010, from Wisegeek http//www.wisegeek.com/what-is-formaldehyde-r esin.htm10. Walker, J. F. (1967). Formaldehyde. Wilmington, Delaware Reinhold Publishing Corporation.11. GFRT. (Updated 2010). Silver Catalysts. Retrieved May 07, 2010, from Global Formaldehyde and Resin Technologies http//www.globalformaldehyde.com/silver.htm12. Kirk-Othmer Encyclopedia of Chemical Technology. Formaldehyde, Vol12. derriere Wiley Sons.