Pyrolysis of saccharide tobacco ingredients: a TGA-FTIR investigation

摘要

Thirteen saccharide tobacco ingredients have been pyrolysed in a thermogravimetric analyser (TGA) under 10% oxygen in nitrogen. The saccharides comprised seven sugars, three cellulosic materials (a cellulose fibre, hydroxypropyl cellulose and carboxymethyl cellulose), starch and two gums (xanthan and acacia). The objective of the study was to measure the formation rates of low molecular weight products that were not detected in a mass spectrometry based system, in particular the formation rates of formaldehyde. A two-stage ramped temperature programme was used that simulated the burning conditions of a smouldering cigarette: an initial heating rate of 0.5℃ s~(-1) to 300℃ followed by 2.9℃ s~(-1) from 300 to 900℃. This was followed by further holding the temperature at 900℃ for 108 s to allow char combustion to occur. The yields of 10 products, selected for their relevance to cigarette smoke and their suitability to be detected by infrared spectrometry, were measured by a Fourier-transform infrared spectrometer (FTIR). The infrared spectra were deconvoluted off-line using a multivariate (target-factor) analysis, which tested the significance of individual hypothetical compounds in the presence of a host of other unknown analytes. The common degradation products monitored from the 13 saccharides were carbon dioxide, carbon monoxide, water and methane. In addition, acetic acid, formaldehyde, acrolein, acetaldehyde, ethanol and furfural were produced from some saccharides but not all. The formation rate for each compound identified was monitored as a function of temperature. Some products were generated in several distinct temperature regions, indicating that more than one mechanism of pyrolysis was operating in a given saccharide. The work has indicated that formaldehyde is generated from the pyrolysis of most of the saccharides in 10% oxygen in nitrogen.