Hydrolysis depolymerisation

Amoco generally takes a hydrolysis depolymerisation approach, the inventive nature of the intellectual property being confined to the means by which components are recovered. This may be done by recovering TA only and oxidising other components with oxygen and... 

PETP flakes produced from used soft drinks bottles were subjected to alkaline hydrolysis in aqueous sodium hydroxide. A phase transfer catalyst (trioctylmethylammonium bromide) was used to enable the depolymerisation reaction to take place at room temperature and under mild conditions. The effects of temperature, alkali concentration, PETP particle size, PETP concentration and catalyst to PETP ratio on the reaction kinetics were studied. The disodium terephthalate produced was treated with sulphuric to give terephthalic acid of high purity. A simple theoretical model was developed to describe the hydrolysis rate. 17 refs. 

The hydrolytic depolymerisation of PETP in stirred potassium hydroxide solution was investigated. It was found that the depolymerisation reaction rate in a KOH solution was much more rapid than that in a neutral water solution. The correlation between the yield of product and the conversion of PETP showed that the main alkaline hydrolysis of PETP linkages was through a mechanism of chain-end scission. The result of kinetic analysis showed that the reaction rate was first order with respect to the concentration of KOH and to the concentration of PETP solids, respectively. This indicated that the ester linkages in PETP were hydrolysed sequentially. The activation energy for the depolymerisation of solid PETP in a KOH solution was 69 kJ/mol and the Arrhenius constant was 419 L/min/sq cm. 21 refs. 

Polyamide 6 depolymerisation was performed using microwaves as the energy souree for the acid catalysed hydrolysis, with phosphorie aeid as the catalyst. The product mixture was analysed by ehromatographie and spectroscopic methods. 19 refs. 

The technical advantages of the chemical recycling of PETP bottles are discussed, and some developments in depolymerisation processes are examined. Particular attention is paid to glycolysis, hydrolysis and solvolysis processes respectively developed by TBl, Tredi and Eastman Chemical. 

Dicarboxylic acids or esters thereof are recovered from solid phase polyester materials, such as post-consumer products and factory scrap, by subjecting the polyester to at least two hydrolysis stages in at least the first of which the amount of water used is substantially less than needed to effect total conversion of the polyester to the dicarboxylic acid. Also the diol content is controlled in the course of carrying out the hydrolysis. The hydrolysis reactions may be preceded by reaction of the polyester with a diol, the resulting depolymerisation products then being hydrolysed. 

For the purpose of the identification and quantification of additives (broadly defined) in polymeric materials extraction and dissolution methods are favoured (Sections 3.3-3.7). However, additives are also made accessible analytically by digestion of the sample matrix (cf. Section 8.2). Such wet chemical techniques, that remove the sample matrix first, are often limited to mg amounts because of pressure build-up in destruction vessels. Another reactive extraction approach to facilitate additive analysis is depolymerisation by acid hydrolysis or saponification, sometimes under pressure. This is then frequently followed by chemical methods such as titrimetry or photometry for final identification and quantification. 

Although polymers in-service are required to be resistant toward hydrolysis and solar degradation, for polymer deformulation purposes hydrolysis is an asset. Highly crystalline materials such as compounded polyamides are difficult to extract. For such materials hydrolysis or other forms of chemolysis render additives accessible for analysis. Polymers, which may profitably be depolymerised into their monomers by hydrolysis include PET, PBT, PC, PU, PES, POM, PA and others. Hydrolysis occurs when moisture causes chain scissions to occur within the molecule. In polyesters, chain scissions take place at the ester linkages (R-CO-O-R ), which causes a reduction in molecular weight as well as in mechanical properties. Polyesters show their susceptibility to hydrolysis with dramatic shifts in molecular weight distribution. Apart from access to the additives fraction, hydrolysis also facilitates molecular characterisation of the polymer. In this context, it is noticed that condensation polymers (polyesters, -amides, -ethers, -carbonates, -urethanes) have also been studied much... 

Phosphate in combination with NaCl has a beneficial effect on the waterbinding capacity of processed meat products for a detailed description, see Schmidt.227 The effect of phosphates is suggested to be alterations in pH or ionic strength, sequestration of metal ions, dissociation of actomyosin and depolymerisation of myosin.103,104,228,229 However, before action, added phosphates must be hydrolysed by muscle phosphatases or non-enzymatically. Belton et al.230 studied the hydrolysis of pyrophosphate and tripolyphosphate in comminuted chicken meat using 31P NMR spectroscopy, and found that the rate of hydrolysis was dependent on the length of ageing period of the muscle as well as the presence of NaCl. Li et al.231 studied the hydrolysis of various types of phosphates in intact chicken muscle with a similar approach by 31P NMR spectroscopy and thereby demonstrated differences in rate of hydrolysis of various phosphates. The findings of these studies... 

Hydrolysis is the process by which a compound is broken down by reaction with water, thus it can be thought of as the opposite reaction of dehydration, where water is of course removed. Hydrolysis is a key reaction type in biomass chemistry, for it is central in the depolymerisation of polysaccharides to simpler monosaccharide building blocks, such as fructose, glucose, and xylose. 

The cyclopent-2-enone required for the photodimerisation is prepared by the hydrolysis and oxidation of 3-chlorocyclopentene, which is obtained by the low temperature addition of hydrogen chloride to cyclopentadiene. The latter is obtained by heating dicyclopentadiene. This depolymerisation is an example of a reverse (or retro) Diels-Alder cycloaddition reaction the diene readily reforms the dicyclopentadiene on standing at room temperature. 

The oldest method of using biomass to create energy is direct combustion, which has been used for thousands of years. Other thermochemical techniques which can be used for the production of chemicals from biomass usually involve depolymerisation at elevated temperatures and pressures. Among these are gasification, pyrolysis, liquefaction and acid hydrolysis. 

Depolymerisation of cellulose to glucose for fermentation has traditionally been achieved via dilute acid hydrolysis using sulfuric acid, with commercial plants... 

Therefore, TPAOH plays several roles it is the catalyst of alkoxide reactions (e.g. hydrolysis, alcoholysis and polymerisation/depolymerisation) and the gelling agent. 

The first reaction [Kl] is governed by the hydrolysis of the ester bonds, generally catalysed by extracellular enzymes, into oligomers and monomers [i.e., depolymerisation]. However, polymers with ester bonds may undergo hydrolysis at room temperature and neutral pH in the presence of moisture, even in the absence of enzymes of MOs. This primary depolymerisation is an erosion process, leading to water-soluble intermediates. If in the next step... 

Microtubules are not static constructs. They exist in an equilibrium, by which heterodimers add permanently to one end (the plus-end ) and are shed from the other (the minus-end ). In the heterodimer, the a-tubuUn bonded GTP at the interface of the dimer is enclosed by a loop of )5-tubulin and thus protected from hydrolysis. The GTP attached to )5-tubulin is however hydrolysed to GDP shortly after the addition of another heterodimer. This destabilises the microtubules, and causes a more facile depolymerisation of the microtubules from the minus-end in the direction of the plus-end. Both processes (polymerisation and depolymerisation) occur in the cell simultaneously, and... 

Puszaszeri depolymerised PET via acid-catalysed hydrolysis, and claimed to recover 98% of available TA [217], GE created macrocyclic polyester oligomers via tin or titanium salt catalysed hydrolysis [218]. Shell used base-catalysed hydrolysis, followed by oxidation of impurities to insoluble products which could then be filtered off prior to isolation of final products [219]. Sirek and Jirousek proposed a process in which PET is crystallised and crushed to a fine powder, hydrolysed with steam, then ammonium hydroxide added. The TA is recovered by acid treatment of the diammonium salt, and EG recovered by distillation of the liquid component of the reaction mix [220]. 

Traces of oxygen-containing materials such as water initiate cross-linking by providing bridging atoms, but poly-dichlorophosphazene (phosphonitrilic chloride polymer) decomposes slowly in contact with atmospheric moisture, and hydrolysis occurs rapidly and completely in water at 100°C. The tetramer polymerises more slowly than the trimer when heated, but eventually gives the same products. When the rubbery products are heated above about 350°C, depolymerisation begins (12.230). 

Due to the hydrolytic instability, most biodegradable polyesters undergo depolymerisation in aqueous mediums. Their degradability by simple hydrolysis of the ester backbone in aqueous environments such as body fluids is obviously a great advantage for them to be used in some biomedical applications (Eubeler et al., 2009 2010 Gijpferich, 1996). The degradation products are ultimately metabolised to carbon dioxide and water or are excreted via the kidney. 

---