Recycling Method

Hydroperoxide Process. The hydroperoxide process to propylene oxide involves the basic steps of oxidation of an organic to its hydroperoxide, epoxidation of propylene with the hydroperoxide, purification of the propylene oxide, and conversion of the coproduct alcohol to a useful product for sale. Incorporated into the process are various purification, concentration, and recycle methods to maximize product yields and minimize operating expenses. Commercially, two processes are used. The coproducts are / fZ-butanol, which is converted to methyl tert-huty ether [1634-04-4] (MTBE), and 1-phenyl ethanol, converted to styrene [100-42-5]. The coproducts are produced in a weight ratio of 3—4 1 / fZ-butanol/propylene oxide and 2.4 1 styrene/propylene oxide, respectively. These processes use isobutane (see Hydrocarbons) and ethylbenzene (qv), respectively, to produce the hydroperoxide. Other processes have been proposed based on cyclohexane where aniline is the final coproduct, or on cumene (qv) where a-methyl styrene is the final coproduct. 

ICI Polyurethanes and du Vergier are evaluating a PU recycling method. The three-year project aims to use a pilot plant to demonstrate the practicality of the split-phase glycolysis process that ICI has developed. Work will initially focus on flexible foams based on MDI and specially made at Id s Rozenberg plant. In the second phase, the unit will use post-industrial waste. Assuming the trials are successful, a full-scale unit to handle at least 5000 t/y of scrap foam will be built. 

A significant amount of waste composites is generated each year and the need for a recycling method is becoming a necessity. Environmental Technical Services has developed, with the support of the University of Missouri-St.Louis, a method for recovering valuable constituents from composite materials. The process converts the polymer matrix to lower chain hydrocarbons and fuel gas leaving behind fibres. Mechanical tests of BMC panels, reinforced concrete and compression moulded panels made with recovered fibres were carried out. 10 refs. USA... 

Mechanical recycling, feedstock recycling and thermal energy recovery are all valid methods of recycling plastics. This is the conclusion reached by an ecobalance study coordinated by the TUV Rheinland. According to this study, a mixture of all three recycling methods provides... 

Methods for recycling used plastic materials are reviewed. Emphasis is placed on the research projects into chemical recycling methods for used plastics at the Leuna location. These include development of a process for the thermaL thermooxidative pretreatment of used plastic materials, utilisation of pretreated used plastic materials in the visbreaker by gasification and by hydrogenation and the production of wax oxidates from pretreated used plastics. The results are discussed. 

The direct release of toxic materials into the environment by the burning, burying, dumping, or discharge into waterways of the by-products of crude recycling methods will likely make zones where this work is done unsafe for habitation. Those living in such areas or working with the waste without protective equipment will risk the effects of exposure. 

These first examples illustrate the importance of a sufficient separation of products and byproducts, whereas membranes are one possibility in pharmaceutical production to obtain this aim. Therefore, they are one key tool to obtaining better quality products and environmentally friendly processes. For a more detailed article about the state of the art of membranes in biotechnology, see Rios et al. [27]. At the same time, it can be seen that stoichiometric cofactor need is no longer a limitation for industrial biotransformations, since they can be overcome with efficient recyclization methods. 

It is possible to use isolated, partially purified enzymes (dehydrogenases) for the reduction of ketones to optically active secondary alcohols. However, a different set of complications arises. The new C H bond is formed by delivery of the hydrogen atom from an enzyme cofactor, nicotinamide adenine dinucleotide (phosphate) NAD(P) in its reduced form. The cofactor is too expensive to be used in a stoichiometric quantity and must be recycled in situ. Recycling methods are relatively simple, using a sacrificial alcohol, or a second enzyme (formate dehydrogenase is popular) but the real and apparent complexity of the ensuing process (Scheme 8)[331 provides too much of a disincentive to investigation by non-experts. 

The main polymer recycling method for building and construction wastes is mechanical recycling, which accounts for around 10% of the collected wastes. Landfill and incineration are used far too much, representing 90% of the total wastes. 

If we make the assumption that the difficulties of collecting, sorting and cleaning are solved, some examples of mechanical recycling methods (shredding and grinding) are listed below ... 

HMW, (or MAP,) This high-molecular-weight protein remains associated with microtubule protein during isolation from brain by the recycling method (Borisy et al., 1975 Sloboda et aL, 1976 Weingarten et al., 1975). See text for additional comments on this protein... 

Regeneration by S02 Recycle Method. In this case, clearly, the two reactions, which need to be studied, are reactions of iron sulfide, FeSi i with O2 and with S02 The reaction of FeSi.i with O2 was found to be very fast and formed Fe2C>3 directly. No intermediates could be identified using Mossbauer spectroscopy. 

The basic idea in partitioning procedures is a successive identification and condensation of recycles into pseudonodes with the same inputs and outputs as the included recycles. Methods for identification of recycles for partitioning purposes can be divided into two main classes Powers of adjacency matrix (e.g. 

Improve the selectivity of the reaction step leading to the desired product by using a more selective catalyst. Make use primarily of heterogeneous solid catalysts, but consider pollution incurred by regeneration. If homogeneous catalysis is more efficient tben developing a recycle method is necessary. 

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