Direct production of speciality chemicals by concurrent catalytic processing with pyrolysis has also attracted some attention. There has been scattered research on the effects of adding various catalysts to biomass prior to pyrolysis. Addition of sodium chloride increased yields of char and of certain chemicals such as glycolaldehyde (hydroxyacetaldehyde), and suppressed levoglucosan production (41). Similar effects were found with zinc chloride, except that higher yields of furfural were obtained (50), and also with cobalt chloride additions to almond kernels which gave higher yields of 2-fura! dehyde (29).

Pyrolysis in molten salts gave significant yields of acetone and hydrocarbon gases (51) and under different conditions, gave high yields of relatively pure hydrogen (above 90% vol. with the balance methane) (52, 53, 54). It was postulated that careful temperature control and temperature variation such as ramping or pre-

dissolution at low temperature could lead to higher yields of potentially valuable speciality chemicals. It was not clear if there were any catalytic effects present, or if the results were derived from physical absorption of carbon dioxide in the alkaline melt with possible effects on the equilibrium through the shift reaction as demonstrated by Hallen (55). The economic and energetic consequences of melt regeneration have not been evaluated, but are recognised as significant (51).

Hydrogen has been used as a reactive gas in a catalyticaily modified atmospheric fluid bed flash pyrolysis using nickel process to give 70-75% conversion to a gas containing 85-90% methane (48, 56, 57), and olefins have also been produced in interesting yields (57). Although this is referred to as hydropyrolysis, this term is more usually employed for high pressure systems. This route has not yet been used to derive liquids although there are many interesting possibilities based on pressure processing which may be viable at the lower temperatures that are optimal for liquids production as well as atmospheric pressure catalytic pyrolysis using, for example, modified zeolites which are described below.

Integrated catalysis and flash pyrolysis has been carried out on lignins for improved cracking to fuels and chemicals over a temperature range of 500 — 800°C (58).

A review of recent developments in thermal and thermo-catalytic biomass conversion has been published (3) and the opportunities for chemicals production reviewed (59).

In ail cases of chemicals recovery, there is little evidence that the higher yields of specific chemicals will be economically viable or that there are markets for the products. Addition of environmentally sensitive materials such as chloride may cause treatment and disposal problems for wastes and by-products. For char production, addition of chloride can only be deleterious and expensive in most applications for the charcoal.