Production of renewable phenolic resins by thermochemical conversion of biomass: A review

doi:10.1016/j.rser.2007.04.008

Renewable and Sustainable Energy Reviews

Volume 12, Issue 8, October 2008, Pages 2092-2116

https://doi.org/10.1016/j.rser.2007.04.008 Get rights and content

Abstract

This review covers the production and utilisation of liquids from the thermal processing of biomass and related materials to substitute for synthetic phenol and formaldehyde in phenol formaldehyde resins. These resins are primarily employed in the manufacture of wood panels such as plywood, MDF, particle-board and OSB. The most important thermal conversion methods for this purpose are fast pyrolysis and vacuum pyrolysis, pressure liquefaction and phenolysis. Many feedstocks have been tested for their suitability as sources of phenolics including hard and softwoods, bark and residual lignins. Resins have been prepared utilising either the whole liquid product, or a phenolics enriched fraction obtained after fractional condensation or further processing, such as solvent extraction. None of the phenolics production and fractionation techniques covered in this review are believed to allow substitution of 100% of the phenol content of the resin without impacting its effectiveness compared to commercial formulations based on petroleum derived phenol. This survey shows that considerable progress has been made towards reaching the goal of a price competitive renewable resin, but that further research is required to meet the twin challenges of low renewable resin cost and satisfactory quality requirements. Particular areas of concern are wood panel press times, variability of renewable resin properties, odour, lack of reactive sites compared to phenol and potential for increased emissions of volatile organic compounds.

Section snippets

Introduction and scope of review

Increasing petroleum prices, concerns over security of supply and concerns about climate change are major drivers in the search for alternative renewable energy sources. Biomass is a primary candidate because it is the only renewable source of fixed carbon, which is essential in the production of conventional hydrocarbon liquid transportation fuels and many consumer goods.

Lignocellulosic biomass is made up of three main components: hemicellulose, cellulose and lignin, of which the lignin

Biomass feedstocks for production of phenolics

Woody biomass primarily consists of hemicellulose, cellulose and lignin. It also contains small amounts of organic extractives and mineral matter. The amount of lignin in wood varies depending on a number of factors, including tree species, climate and soil conditions. Typically it makes up between 19% and 35% of the dry wood weight [7]. When heated, the lignin component depolymerises to form monomeric and oligomeric phenolic compounds. The most widely employed feedstocks to date for production

Phenolic compounds in bio-oils

Pyrolysis oils are a complex mixture of water, higher molecular weight lignin fragments and lower molecular weight organics. Considerable work has been done on analysing bio-oil from fast and vacuum pyrolysis [4], [5], [6], [7], [10], [11], [18], [19], [20]. Bio-oils contain up to 45% oxygen, and oxygen is a component of most of the more than 300 compounds that have been identified in pyrolysis oils [7]. Water is the most abundant compound, typically followed by hydroxyacetaldehyde (up to

Phenolic resins from fast pyrolysis liquids

Fast pyrolysis is a relatively recent thermochemical conversion technology. Its defining characteristics are: moderate reaction temperatures, usually between 400 and 600 °C, rapid heating rates and short vapour residence times before condensation of the liquid products, typically below 5 s. This combination of features gives very high liquid yields, up to roughly 75 wt% on a dry basis for clean, low ash content woody biomass. Attempts to use this liquid for the production of renewable phenolic

Phenolic resins from vacuum pyrolysis liquids

In addition to fast pyrolysis, vacuum pyrolysis has been investigated as a means of producing phenolic resin precursors from lingo-cellulosic materials. Compared to fast pyrolysis, longer residence times, of the order of 40 s, are employed in vacuum pyrolysis. The vacuum suppresses condensation reactions in the vapour, as the concentrations of reactants and therefore reaction rates are lower. This effect is, however, not capable of fully compensating for the longer residence times, as evidenced

Phenolic resins from pressure liquefaction liquids

Liquefaction of lingo-celullosic materials represents another route for obtaining phenolic resin precursors. It is generally performed under high pressure at temperatures of <350 °C and followed by a separation process. Russell et al. [42] liquefied a variety of lingo-cellulosic materials including sawdust, woodchips, agricultural residues and peat moss at 290–350 °C and 10–20 MPa in the presence of water and a Na₂CO₃ or CaCO₃ catalyst. A phenolic fraction was extracted as follows (see the diagram

Phenolic resins from phenolysis of lignins

Lignin from the pulp and paper industry is a low-cost waste product available in large amounts. Consequently, there has been considerable interest in converting it to phenolic precursors for phenol-based resins. Lignin can also be used directly, both as a filler and as a phenol substitute in PF resins. Because of its extremely low reactivity, however, direct use as a phenol substitute requires very long press times and temperatures and is therefore generally not commercially attractive [17]. To

Fractional condensation

During the slow heating required for conventional distillation, many bio-oil components, including in particular the reactive phenolics of interest for resin manufacture, will polymerise. Consequently, fractional condensation, sometimes under reduced pressure, has been investigated extensively as an alternative means of fractionating the oil.

Pyrolysis of pine sawdust combined with condensation of vapours at different temperatures followed by a coalescing filter has been used to obtain bio oils

Summary tables

Production and fractionation methods for fast and vacuum pyrolysis are summarised in Table 3. Key process conditions as well as phenolic and liquid yields are given.

A selection of renewable phenolic resins covered in this review are listed in Table 4. The table shows feedstocks used, processes employed, fractions applied in the resin and degrees of phenol substitution investigated. The properties of phenol-based resins prepared using renewable phenolics (and formaldehyde substitutes in some

Conclusions

Interest in renewable resins is motivated by the large availability of lignin-containing biomass feedstocks, particularly low-cost waste streams, the relatively high price commanded by phenol and more recently environmental considerations.

There are, however, significant hurdles that have so far prevented widespread commercialisation. The failure of the Pederson technology mentioned earlier is illustrative. In spite of good board properties, commercial use eventually ceased due to the

Acknowledgements

This work has been supported by the European Commission as part of the renewable adhesives for industrial wood-based panel production project, RenuResin, under contract number: QLK5-CT-2002-01596.

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Production of renewable phenolic resins by thermochemical conversion of biomass: A review

Abstract

Section snippets

Introduction and scope of review

Biomass feedstocks for production of phenolics

Phenolic compounds in bio-oils

Phenolic resins from fast pyrolysis liquids

Phenolic resins from vacuum pyrolysis liquids

Phenolic resins from pressure liquefaction liquids

Phenolic resins from phenolysis of lignins

Fractional condensation

Summary tables

Conclusions

Acknowledgements

Renew Energy

Sustainable Renew Energy Rev

Bioresource Technol

Bioresource Technol

J Anal Appl Pyrolysis

J Anal Appl Pyrolyis

Industrial Crops and Products

J Anal Appl Pyrolysis

J Anal Appl Pyrolysis

Biomass Bioenergy

Int J Adhes Adhes

Int J Adhes Adhes

Int J Adhes Adhes

Bioresource Technol

Overview of applications of biomass fast pyrolysis oil

Energy Fuels

Pyrolysis of wood/biomass for bio-oil: a critical review

Energy Fuels

Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering

Chem Rev

Growing markets for engineered products spurs

Wood Technol

State of the art report: adhesives from renewable resources

Holzforsch Holzverwert

Fast pyrolysis of forestry residue. 1. Effect of extractives on phase separation of pyrolysis liquids

Energy Fuels

Colloidal properties of bio-oils obtained by vacuum pyrolysis of softwood bark. characterization of water-soluble and water-insoluble fractions

Energy Fuels

Biomass pyrolysis for maximizing phenolic liquids