Michael Jerry Antal

Biomass Pyrolysis: A Review of the Literature Part 1—Carbohydrate Pyrolysis

A normative review of the literature describing the products, mechanisms and rates of carbohydrate pyrolysis is presented. The role of a complex sequence of competing solid and vapor phase pyrolysis pathways is elucidated.

Acid-catalysed dehydration of alcohols in supercritical water

At pressures exceeding its critical pressure water retains its ionic properties to temperatures of 400 °C or more. In water under these conditions trace amounts of Arrhenius acids dissociate and selectively catalyse the dehydration of alcohols, diols, and polyols. High yields of the desired dehydration product (ethene from ethanol, propene from propanol, acetaldehyde from ethylene glycol, and acrolein from glycerol) can be obtained with a residence time of less than one minute. However, for ethanol the equilibrium conversion appears to be less than predicted by ideal solution thermochemical calculations. This may be due to catalyst deactivation, or it may be an effect of hydrogen bonding between the water and the reactant alcohol. The dehydration of n-propanol proceeds by a first order reversible reaction whose equilibrium is close to that predicted by thermodynamics. Because these dehydration reactions proceed rapidly with a high degree of specificity, they appear to be good candidates for industrial exploitation.

A study of the gas-phase pyrolysis of glycerol

Abstract Pyrolysis of glycerol in steam was studied in a luminar flow reactor in the 650 °C region. The initial products of decomposition were carbon monoxide, acetaldehyde and acrolein. Acetaldehyde and acrolein further decomposed to produce primarily carbon monoxide, ethylene, methane and hydrogen. With residence times of μl the products from glycerol pyrolysis in decreasing order of importance were carbon monoxide, acetaldehyde, acrolein, hydrogen, ethylene, methane, ethane, carbon dioxide, propylene and 1,.3-butadiene. The overall reaction governing the disappearance of glycerol was found to be consistent with a first order rate law, with rate constant x = (1.52 ± 0.15 1023 exp -55.6±5.5, 103RT).

Pyrolytic sources of hydrocarbons from biomass

Abstract This paper reports progress of the Renewable Resources Research Laboratory on the conversion of biomass to olefins. Research on the depolymerization of cellulose supports the initiation/competitive reaction scheme first proposed independently by Arsenau and Broido, but indicates rate laws characterized by somewhat higher apparent activation energies than those reported by Bradbury et al. Research on the decomposition of the model compound glycerol in supercritical water evidences two major pathways. At lower temperatures, a heterolytic acid catalyzed, carbonium ion mechanism results in the formation of acrolein by the elimination of water from glycerol. At higher temperatures, homolytic cleavage of Cue5f8C bonds results in the preferential formation of acetaldehyde.

Charcoal ash and volatile matter effects on soil properties and plant growth in an acid ultisol.

There is a growing interest in converting organic wastes to charcoal for use as a sustainable soil amendment with a potential to improve soil productivity and sequester C. Three consecutive greenhouse experiments were conducted to investigate the effects of charcoal with different ash and volatile matter (VM) contents on soil properties and maize (Zea mays) growth and to evaluate the effect of time on charcoal performance. Five charcoal amendments (high-VM corncob, low-VM corncob, Kiawe, Binchotan, and a gasification charcoal of Leucaena leucocephala) applied at a 2.5% (wt/wt) rate were compared with a zero-charcoal control with and without fertilization. Only the gasification charcoal significantly increased maize growth without fertilization. The low-VM corncob charcoal with fertilization significantly increased maize growth by 164% compared with the fertilized control in the first planting cycle. Maize growth in the high-VM corncob charcoal supplemented with fertilizer treatment was significantly lower than that of the fertilizer-alone treatment in the first planting cycle. The negative effect of the high-VM charcoal on the fertilizer was caused by bioavailable carbon in the charcoal, which increased soil microbial activity and could have caused N immobilization. Both the beneficial and detrimental effects of charcoal did not persist beyond the first planting cycle, suggesting that charcoal impacts are temporary. Whereas charcoal ash and VM content seem to be important parameters for predicting charcoal behavior in the short-term, more research is needed to examine a broader spectrum of feedstocks exposed to varying thermal treatments.

Design and operation of a solar fired biomass flash pyrolysis reactor

Abstract The results of continuing research on the radiant flash pyrolysis of biomass as a source of fluid fuels, industrial feedstocks and chemicals are described in this paper. Windowed free fall reactors have been developed, which act as cavity receivers for the focused radiant energy and provide a means for direct use of the radiation to rapidly pyrolyze the entering biomass. Detailed results of experiments using the 400 kWth DOE Advanced Components Test Facility at Georgia Tech. are presented. These results suggest the use of concentrated solar energy as a selective means for the production of either a hydrocarbon rich synthesis gas or sugar related sirups from biomass by flash pyrolysis.

The flash pyrolysis of cellulosic materials using concentrated visible light

Abstract The radiant flash pyrolysis of Avicel cellulose and kraft paper particles using concentrated visible light is described. The particles circulate in a clear quartz spouted bed reactor while undergoing pyrolysis in an incident radiant flux of up to 200 W/cm2. This flux is supplied by an arc image furnace which uses a 5 kW Xenon bulb as its light source. The volatile pyrolysis products are quenched by the steam flow used to spout the bed and are entrained out of the reactor before secondary reactions can occur, ensuring a high sirup yield (63 per cent from cellulose). The major sirup component is levoglucosan.

Numerical studies of the flash pyrolysis of cellulose

Abstract Numerical simulations reveal that the time required for rapid pyrolysis of cellulosic biopolymer particles (diameter ⩽ 0.5 mm) is composed of a heatup time t h and a devolatilization time t d . Approximations of t h and t d are given by the time required for radiative and convective heat transfer to raise the particles temperature to a pyrolysis temperature T p (‘sensible’ heat requirement) and to provide the endothermic heat of reaction ΔH (‘latent’ heat requirement). The value of T p is specified by the chemical rate law governing pyrolysis. Recently reported rate laws place a practical upper limit on T p of ≈ 500 °C and provide for the complete vaporization of cellulose at high heating rates. Strong analogies exist between the time required for a given power input to provide both the sensible and latent heat requirements of a solid undergoing a phase change and the time required for heat transfer to effect cellulose pyrolysis. Correction factors reported here permit an accurate estimate of the time required for cellulose pyrolysis, based on the times required for the rate of heat transfer (power input) to provide the ‘sensible’ and ‘latent’ heats of pyrolysis at the (‘melting point’) temperature T p .

A Review of the Vapor Phase Pyrolysis of Biomass Derived Volatile Matter

Upon heating, biomass materials undergo solid phase pyrolysis at relatively low temperatures (> 300 oC), forming reactive volatile matter, a few permanent gas species and solid char. Unlike the various coals and peats, biomass materials typically lose 70% or more of their weight by the solid phase pyrolysis reactions. This transformation of the bulk of the biomass material from the solid to the vapor phase suggests the important role of vapor phase chemistry in the pyrolysis of biomass materials. Recognizing the highly reactive nature of the major constituents of the volatile matter, the significance of the vapor phase chemistry becomes even more apparent.

Numerical simulations of the performance of solar fired flash pyrolysis reactors

Abstract Numerical simulations of free falling and entrained flow, solar fired, biomass flash pyrolysis reactors are described. Good agreement with experimental results was obtained. Magnification factors exceeding 5 were predicted for some experimental conditions.