Ethylene from Renewable Resources

This chapter aims to provide information concerning ethylene from renewable resources. The intention is to give the reader an insight into the present development and the possibilities when using renewable resources. 

Ethylene is the most important intermediate in the chemical industry. The production volume was about 120 metric tonnes/year in 2007 and is expected to increase to approximately 180 metric tonnes/year by 2020 [1]. The main outlet for ethylene, roughly 60%, is used for polyethylene, followed by ethylene oxide, vinyl chloride and styrene. Ethylene oxide is a key material in the production of surfactants and detergents. It is mainly converted to ethylene glycol which ends up in, for example, polyethylene tereph-thalate and glycol ether solvents. Vinyl chloride and styrene are almost exclusively used to produce polyvinyl chloride and polystyrene, respectively. Ethylene is an intermediate for more than 50% of the polymer production volume. 

Today the feedstock for ethylene is different fossil fuel streams such as ethane, propane, butane and naphtha. They are obtained as products from natural gas processing and petroleum refining. However, the total production of chemicals based on fossil fuel streams only consumes a small fraction compared to energy and transportation. On a global basis approximately 3% of the oil and gas market is used for chemical production. This corresponds to approximately 1% of the global energy consumption. Over the years 

Surfactants from Renewable Resources Edited by Mikael KjeUin and Ingeg d Johansson (c) 2010 John Wiley Sons, Ltd 

It is obvious that we will see changes in the petrochemical industry in the coming 20-30 years. There are a number of different factors that will influence this development. First of all there are the normal considerations such as the cost of raw material and its availability, process development, capital requirement, and so on. In addition there will be a number of other factors that may be more difficult to predict, such as political decisions concerning a CO2 tmc and directives concerning renewable feedstock and public opinion, which may influence the behaviour of the consumer. 

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The pressure on companies producing products from chemicals to use renewable feedstock will most certainly increase. From an economical point of view this may influence both material and production costs. Products made of ethylene from renewable resources, whether it is plastics or surfactants, will have the same properties as if they were produced from fossil feedstock. This means that there will be no need to invest in new production equipment. 

Looking at the announcements made concerning commercial production of ethylene from renewable resources, more or less all of them are based on the ethanol-to-ethylene route. 

Polyester chemistry is the same as studied by Carothers long ago, but polyester synthesis is still a very active field. New polymers have been very recently or will be soon commercially introduced PTT for fiber applications poly(ethylene naph-thalate) (PEN) for packaging and fiber applications and poly(lactic acid) (PLA), a biopolymer synthesized from renewable resources (corn syrup) introduced by Dow-Cargill for large-scale applications in textile industry and solid-state molding resins. Polyesters with unusual hyperbranched architecture also recently appeared and are claimed to find applications as crosstinkers, surfactants, or processing additives. 

It should be pointed out that the raw materials for VAM and its related polymers (i.e. ethylene and acetic acid) are produced from fossil resources, mainly crude oil. It is possible to completely substitute the feedstock for these raw materials and switch to ethanol, which can be produced from renewable resources like sugar cane, com, or preferably straw and other non-food parts of plants. Having that in mind, the whole production of PVAc, that nowadays is based on traditional fossil resources, could be switched to a renewable, sustainable and C02-neutral production process based on bioethanol, as shown in Fig. 3. If the vinyl acetate circle can be closed by the important steps of biodegradation or hydrolysis and biodegradation of vinyl ester-based polymers back to carbon dioxide, then a tmly sustainable material circle can be established. 

Biopolymers and sustainable growth have been recently discussed by Singh (2). "Biopolymers" are defined as polymers made from "renewable" resources. However, not all biopolymers are biodegradable (2). For example, Dow and a Brazilian company called "Crystalsev" announced a joint venture in 2007 to manufacture LLDPE using ethylene produced from ethanol derived from sugarcane (22, 23). Though such LLDPE may be considered a biopolymer, it will not be any more biodegradable than LLDPE from petroleum-based ethylene. 

By chemical recovery of polyester [poly(ethylene terephthalate) (PET)] (Chapter 16) and PU wastes, by alcoholysis or by aminolysis (Chapter 20), new polyols are obtained that can be used in rigid PU foam fabrication. The vegetable oil polyols, obtained by chemical transformation of the double bonds in vegetable oils in various hydroxyl groups are a very attractive route to obtain polyols from renewable resources (Chapter 17). 

The L- isomer is produced in humans and other mammals, whereas both the D- and L-enantiomers are produced in bacterial systems. Lactic acid can also be derived chemically from renewable resources such as ethanol or acetaldehyde or from chemicals coming from coal (e.g. acetylene) or oil (e.g. ethylene)... 

Blends of starch with polar polymers containing hydroxyl groups, such as poly(vinyl alcohol), copolymers of ethylene and partially hydrolyzed vinyl acetate have been prepared since the 1970s, as described by Otey et al. [61, 68-72]. Since starch and other natural polymers are hydrophilic, water has been commonly used as a plasticizer for these materials. The possibility of using water as plasticizer makes it possible to add the polymer to be blended as an aqueous emulsion, as for example, in the case of natural rubber latex [112], poly(vinyl acetate) and other synthetic polymer lateces [71,113,114]. Blends of starch and biodegradable polymers and polymers from renewable resources have been reviewed recently due to their growing importance [82, 110, 111, 115, 116]. Table 15.3 gives some polymers commonly used in blends with starch. 

Poly(lactic acid) (PL A) is a renewable resource-based bioplastic with many advantages, compared to other synthetic polymers. PL A is eco-friendly, because, apart from being derived from renewable resources such as corn, wheat, or rice, it is recyclable and compostable [1, 2]. PLA is biocompatible, as it has been approved by the Food and Drug Administration (FDA) for direct contact with biological fluids [3] and has better thermal processability compared to other biopolymers such as poly(hydroxy alkanoate)s (PHAs), poly(ethylene glycol) (PEG), or poly(e-caprolactone) (PCL) [4]. Moreover, PLA requires 25-55% less energy to be produced than petroleum-based polymers, and estimations show that this can be further reduced by 10% [5]. 

However, not many people realize that polyethylene, another product that Commoner was very worried about, was originally produced in Britain by the fermentation of grain to produce alcohol and dehydration of alcohol to produce ethylene. It and many other common plastics including styrene and polyester can be produced by known chemical processes from renewable resources such as wheat, cellulose, starch, biomass, etc. through the following chemical reactions. 

The polyalcohols normally used in the alkyd synthesis include (di)pentaerythritol, glycerol, ethylene glycol, trimethylolpropane and neopentylglycol. Whereas the fatty acid or oil component is derived from renewable resources, the majority of the aforementioned polyacids and polyalcohols are alkyd building blocks derived from petrochemical resources. 

PET is produced by the polymerization of mono-ethylene glycol with terephthalic acid, which is usually utilized for the production of plastic bottles and textile fibers. The manufacturing of mono-ethylene glycol from renewable resources permitted several companies to use bio-based PET in product packaging. 

Most polymers can be made from renewable resources at a cost. For example polyethylene, the major commodity polymer used in packaging, was one of the earliest biopolymers. For some years ethylene was manufactured from sugar by fermentation to alcohol, followed by dehydration to ethene and, if and when the economics of alcohol manufacture justify its use as a biofuel, the polyolefins will again become biopolymers. So far as resource depletion is concerned, if fossil carbon resources were used only for the manufacture of polymers and not for energy production, the former would last for approximately 300 years based on present estimates. By that time, polyolefins will in any case probably be manufactured from renewable resources anyway for purely economic reasons. At... 

The increasing amounts of plastic products from petrochemical-based polymers in a landfill have led to serious environmental concerns over the past decade. In recent years, various biodegradable plasties have been developed as a sustainable alternative to replace commodity synthetic plastics. Polylactic add is typical biodegradable polyester produced from renewable resources and a versatile polymer that has been used for many applications in the biomedical industry [1] as well as the packaging industry [2,3]. PLA has been blended with other biodegradable and synthetic polymers for the development of improved properties, such as poly (e-caprolactone)[4], poly (vinyl butyral)[5], poly(3-hydroxy butyrate)[6], poly (ethylene oxide)[7], and poly(p-vinyl phenol) [8]. 

Because oil and gas ate not renewable resources, at some point in time alternative feedstocks will become attractive however, this point appears to be fat in the future. Of the alternatives, only biomass is a renewable resource (see Fuels frombiomass). The only chemical produced from biomass in commercial quantities at the present time is ethanol by fermentation. The cost of ethanol from biomass is not yet competitive with synthetically produced ethanol from ethylene. Ethanol (qv) can be converted into a number of petrochemical derivatives and could become a significant source. 

Ethylene. Where ethylene is ia short supply and fermentation ethanol is made economically feasible, such as ia India and Bra2il, ethylene is manufactured by the vapor-phase dehydration of ethanol. The production of ethylene [74-85-1] from ethanol usiag naturally renewable resources is an active and useful alternative to the pyrolysis process based on nonrenewable petroleum. This route may make ethanol a significant raw material source for produciag other chemicals. 

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