Online analysis of initial volatile products of Shenhua coal and its macerals with pyrolysis vacuum ultraviolet photoionization mass spectrometry

Initial volatile products from pyrolysis of Shenhua coal and its macerals were investigated by using online pyrolysis-vacuum ultraviolet photoionization mass spectrometry (Py-VUVPI-MS). The fragment-free spectra of initial volatile products were measured during the temperature-programmed pyrolysis of the samples, and the intensity profiles of the initial volatile products as the function of temperature were detected. Mononuclear aromatics and phenols are the primary constituents of initial volatile products along with alkenes, n-alkyl naphthalene, n-alkyl naphthol, etc. The relative content of phenols evolved from coal macerals shows the order of vitrinite > raw coal > inertinite and that of polycyclic aromatic hydrocarbons (PAHs) exhibits the opposite trends. The different relative content in initial volatile products can be attributed to the different structures of coal macerals. The main source of phenols is the thermal decomposition of the oxygen-containing functional groups. PAHs come from two parts: thermal decomposition of coal macromolecular and free PAHs in mobile phase. This work provides a method for online analysis of initial pyrolytic products from coal by Py-VUVPI-MS.