Reaction chemistry and kinetics of corn stalk pyrolysis without and with Ga/HZSM-5

Abstract

The bifunctional Ga/HZSM-5 catalyst has been proven having the capabiliity to increase the selectivity of aromatics production during catalytic pyrolysis of furan and woody biomass. However, the reaction chemistry and kinetics of pyrolysis of herbaceous biomass promoted by Ga/HZSM-5 is rarely reported. Pyrolysisgas chromatography / mass spectrometry (Py-GC/MS) analysis and nonisothermal thermogravimetric (TG) analysis at four heating rates were carried out to investigate the decomposition behavior and pyrolysis kinetics of corn stalk without and with Ga/HZSM-5. The effective activation energies for corn stalk pyrolysis were calculated by using the Friedman isoconversional method. The Py-GC/MS analysis results indicated that the Ga/HZSM-5 catalyst had a high selectivity towards producing the aromatic chemicals of xylene, toluene and benzene, whereas the major products from noncatalytic pyrolysis of corn stalk were oxygenated compounds. The presence of Ga/HZSM-5 could significantly reduce the effective activation energies of corn stalk pyrolysis from 159.9-352.4 kJ mol-1 to 41.6-99.8 kJ mol-1 in the conversion range of 0.10-0.85.

Catalytic Copyrolysis of Sugarcane Leaves and Low-Density Polyethylene Waste to Produce Bio-Oil and Chemicals Using Copper-Doped HZSM-35

“…Then, the secondary cracking reaction enhances the cracking of small volatile vapor molecules, affecting the formation of noncondensable gases. , Subsequently, the bio-oil yield increases to its highest value (33.23 wt %) at a temperature of 550 °C. At 600 °C, the bio-oil yield dramatically decreases to 26.37 wt % and moderately changes to 26.96 wt % at 650 °C due to the influence of the high temperature accelerating the secondary reaction of volatile vapor and depolymerization; thus, these are not suitable conditions for producing a high yield of bio-oil. ,, The solid yield shows a monotonically decreasing trend because the chemical bonds in the char matrix are disintegrated, causing a moderate decrease in the solid yield, while a small amount of coke forms during the secondary reaction.…”

“…Moreover, both furan and furfural yields tend to decrease as the operating temperature increases, indicating that the presence of Cu on ZSM-35 contributed to the deoxygenation of furans and their derivatives into aldehydes and ketones and that further cracking affected hydrogen transfer, leading to enhanced formation of C 7 –C 12 hydrocarbons that manipulate the liquid yield of the aliphatic compounds. ,− ,, Furthermore, the synergistic effect of SCLs and LDPE at temperatures of 500–550 °C illustrated a positive effect on the bio-oil yield, and GC–MS analyses showed that the composition of the pyrolyzed bio-oil, which contained a proportion of aliphatic hydrocarbon compounds, resulted in the copyrolysis of SCLs and LDPE since the process conditions did not involve a higher temperature, which showed a positive synergistic effect. At low temperature, the thermal decomposition of LDPE to hydrocarbon radicals and anhydrosugar derivatives was enhanced from the thermal decomposition of lignocellulosics due to depolymerization into oligosaccharides, cleavage of its monomer, and deoxygenation. ,, Cleavage and rearrangement occur, and further cracking into low-molecular weight compounds, for example, furfural, noncondensable gases, and short alkane intermediates, occurs, while long alkanes might be produced by oligomerization or polymerization of short hydrocarbons. ,, …”

“…This result indicates that the thermal degradation of LDPE at low temperatures promotes the initial production of radicals and affects the scission of large hydrocarbon molecules, and then, the catalyst facilitates the catalytic reaction from deoxygenation, decarboxylation, decarbonylation, dehydration, and aromatization as the reaction temperature is increased. 28,29 Furthermore, the acidity of the copper-modified HZSM-35 catalyst during catalytic pyrolysis accelerates the decomposition of large-chain volatile vapors, which is followed by βscission, deoxygenation, dehydrogenation, and hydrotreating into smaller volatile vapors. Additionally, the surface pore structure facilitates the desired production of olefins and enhances aromatization to produce aromatic hydrocarbons.…”

Non-isothermal kinetics: best-fitting empirical models instead of model-free methods

“…They deal with the kinetics of organic samples with highly complex chemical composition. A few recent works on similarly complex samples are also listed from the Journal of Thermal Analysis and Calorimetry [7][8][9][10][11][12][13][14]. Many further references can be found in the work of Cai et al [6] which is an overview of the application of the isoconversional methods for biomass pyrolysis till 2017.…”

“…It assumes one pool of reactants for which the reactivity varies as the reaction proceeds. However, most of the samples of practical interest contains more than one sort of reacting species, as it was the case in the studies [4][5][6][7][8][9][10][11][12][13][14] as well as in the nearly 100 works reviewed by Cai et al [6]. Each species has its own reacted fraction, its own reactivity parameters, and its own concentration in the sample.…”