The pyrolysis of a chromium-tanned waste (bovine split leather) under inert atmosphere has been carried out in a vertical lab scale reactor. The influence of process conditions, such as temperature, residence time, and heating rate on the pyrolytic product distribution has been studied, in order to optimize the liquid fraction obtained. Flash pyrolysis at three different temperatures (450, 500, and 550°C) and slow pyrolysis up to 750°C have been performed. Results indicate that, in the range of low temperatures, the product distribution is slightly dependent on temperature. In general, a reduction of the heating rate or residence time favors the presence of heavy gases (i.e., more than four carbon atoms hydrocarbons). The analysis of the pyrolytic liquid shows a wide spectrum of products (mainly nitrogenated and oxygenated compounds and phenols) which can be useful as a source of chemicals. A comparison between the results reached in the pyrolysis of tanned leather and a commercial collagen allows us to study the effect of the tanning process. According to the result obtained, the tanned leather produces more nitrogenated compounds and phenols and less ketones and linear hydrocarbons than pure collagen. A very good agreement between the evolution of pyrolytic gases produced in a slow pyrolysis and the weight loss of the solid measured by thermogravimetric analysis has been observed.

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The main objective of this paper is to study the thermal decomposition of waste products from leathers tanned with different tanning agents, from two different points of view: (i) thermogravimetric analysis and (ii) flash pyrolysis using a Pyroprobe device connected to a gas chromatograph with a mass spectrometer (Py/GC-MS). Both techniques allow us to characterize the samples by evaluating their potential differences regarding the decomposition process as well as by identifying the significant volatile compounds obtained depending on the tanning processes. The results have been treated using a multivariate statistical analysis method.

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