Effect of Metal Doping on the Initial Pyrolysis Chemistry of Cellulose Chars

Abstract

Laser pyrolysis (LP) using a CO2 laser was used to rapidly heat Avicel cellulose char with and without doping by Na, K, Ca, Mg, Co, Ni, Cu, Pd, and Zn as their respective acetates in the uncharred cellulose. LP−molecular beam mass spectrometry (LP−MBMS) was used to probe the chemistry of the pyrolysis of the chars and to characterize the initial volatilized reacting plume of pyrolyzate. The mass spectra were deconvoluted by multivariant factor analysis (MVA). MVA revealed that, at the 1 wt % doping level, Cu did little to change the pyrolysis chemistry of cellulose char, among the other metals, Na, K, Ca, Mg, Co, Ni, and Zn did effect the pyrolysis chemistry, and Co and to a lesser extent Pd acted by a differing mechanism. A liquid N2 cold trap coated with diphenyldisulfide was used to understand the chemistry of the evolving pyrolyzate plume. The washings from this trap were analyzed by gas chromatography−mass spectrometry (GC−MS) allowing for speciation of both the chemically trapped radicals and the nonradical volatiles. It was clear that the species trapped had a much greater degree of methyl substitution than observed in the LP−MBMS. Radicals trapped included hydrogen, methyl, and phenyl but did not include cyclopentadienyl or benzyl. Zn, which was volatilzed by the LP, had the highest yield of radicals. In general, the cold-trapped 1 and 2 aromatics had a higher level of methyl substitution. Cu and Pd increase the formation of aromatic species during the pyrolysis of cellulose char and have a variable effect on radical production. Na, K, Mg, Ca, Co, and Ni suppress the formation of aromatic species and have a variable effect on radical production.

Physical and chemical characteristics of aging pyrolysis oils produced from hardwood and softwood feedstocks

“…The work in this study continues investigations from this laboratory involving the thermochemical conversions of biomass and its constituents [27]. There were three particular objectives in the current study.…”

Carbothermal synthesis of metal-functionalized nanostructures for energy and environmental applications

“…High catalytic efficiency is typically expected with metal or metal oxides nanoparticles. 727 A great deal of fundamental work has been carried out on the addition of metal species to biomass by impregnation with metal salts solutions, which can explain the role of minerals during pyrolysis of biomass, 728-732 modify primary pyrolysis and increase selectivity towards one or more specic products, [729][730][731][732][733][734][735][736][737] or study the effect of re retardants. 737 It is well known that the presence of inorganic species dispersed in biomass can inuence the behavior of pyrolysis and thereby the distribution of pyrolysis products.…”

Effect of slight chemical modification on the pyrolysis behavior of cellulose fibers

“…Kawamoto et al [33] observed that levoglucosan undergoes secondary reactions in the presence of cellulose-derived pyrolysis vapors. Recently, catalytic pyrolysis of cellulose [34][35][36] has widely been investigated with the goal of preparation of a specific product from cellulose. Dobele et al [20][21][22] studied the dehydration reactions of cellulose in the presence of phosphoric acid and high levoglucosenone yield was achieved, while levoglucosan formation was hindered.…”