Chemicals, biomass phenolic resins

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

Currently, existing pilot plants in Canada, Netherlands, UK utilize mainly well defined non contaminated biomass fractions such as wood particles, saw dust, and bark. The performed investigations in this work should broaden the knowledge of the pyrolytic behaviour of various industrial biomass waste. This wilt facilitate the introduction of flash pyrolysis processes into existing industrial processes. Therefore, a new way of biomass exploitation will be demonstrated. In cooperation with several companies different biomass waste such as cocoa shell, wood waste, fibre sludge and panel boards with a high content of phenol-foimaldehyde resin were decomposed by flash pyrolysis into smaller molecules to use them for the production of energy and/or chemicals. 

Fast pyrolysis of biomass produces a phenol-rich oil suitable for incorporation into phenol-formaldehyde (PF) resins. To evaluate the reactivity and network formation characteristics of the compounds typically found in these oils, a series of phenolic model compounds was reacted with formaldehyde under conditions typically used to prepare PF resins. This study indicates that the substituted phenolics commonly found in pyrolysis oils are more reactive than phenol. It also showed that the network formation process for tiiese complex phenolic mixtures follows the predictions of the simple statistical approaches developed by Flory (23) and Stockmayer (24). These results show that the substituted phenolics commonly found in pyrolysis oils will be chemically bonded into the polymer network and that under the proper reaction conditions a highly stable network will be formed. 

Fast pyrolysis of biomass can produce phenolic-rich oils in high yields, 40%-50% based on the weight of the dry feed (5). These oils can be used to replace some of the petroleum-derived phenol used to prepare PF resins. However, to effectively replace the monomeric phenol, the phenolic oils must be chemically incorporated into the PF resin network under typical resin synthesis conditions they cannot simply act as fillers or extenders. 

To better understand how the complex phenolics produced by biomass pyrolysis can be chemically incorporated into the PF resin network, we used a series of phenolic model compounds to study the reaction rate and the gelation processes under conditions typically used to synthesize PF resins. The model compounds (Figure 1) include 2-methoxy-4-methylphenol, 4-methylcatechol, 2-methylphenol (o-cresol), 4-methylphenol (p-cresol), phenol, 4,4 -isopropylidenediphenol (Bisphenol A), and trisphenol. Figure 1 also shows the number of reactive sites (f) on each model compound. 

In the case of biomass pyrolysis oils, all three chemical features defined in equation 2 are important. To some extent the resin chemist can control the ratio of reactive sites (r). But in the case of phenolic-rich pyrolysis oils, determining the actual number of reactive phenolic sites is veiy difficult. The number of reactive phenolic sites can be estimated statistically by measuring the total number of phenolic hydroxyls and the methoxyl content of the pyrolysis oil. Analytically the number can be estimated by reacting pyrolysis oils with an aldehyde and then measuring the amount of unreacted aldehyde. 

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