In situ and Ex situ Catalytic Pyrolysis of Microalgae and Integration With Pyrolytic Fractionation

Abstract

Microalgae are attractive feedstocks for biofuel production and are especially suitable for thermochemical conversion due to the presence of thermally labile constituents—lipids, starch and protein. However, the thermal degradation of starch and proteins produces water as well as other O- and N-compounds that are mixed-in with energy-dense lipid pyrolysis products. To produce hydrocarbon-rich products from microalgae biomass, we assessed in situ and ex situ catalytic pyrolysis of a lipid-rich Chlorella sp. in the presence of the HZSM-5 zeolite catalyst over a temperature range of 450–550°C. Results show that product yields and compositions were similar under both in situ and ex situ conditions with benzene, toluene and xylene produced as the primary aromatic products. Yields of aromatics increased with increasing temperature and the highest aromatic yield (36.4% g aromatics/g ash-free microalgae) and selectivity (87% g aromatics/g bio-oil) was obtained at 550°C. Also, at this temperature, oxygenates and nitrogenous compounds were not detected among the liquid products during ex situ catalytic pyrolysis. We also assessed the feasibility of a two-step fractional pyrolysis approach integrated with vapor phase catalytic upgrading. In these experiments, the biomass was first pyrolyzed at 320°C to degrade and volatilize starch, protein and free fatty acids. Then, the residual biomass was pyrolyzed again at 450°C to recover products from triglyceride decomposition. The volatiles from each fraction were passed through an ex situ catalyst bed. Results showed that net product yields from the 2-step process were similar to the single step ex situ catalytic pyrolysis at 450°C indicating that tailored vapor phase upgrading can be applied to allow separate recovery of products from the chemically distinct biomass components—(1) lower calorific value starch and proteins and (2) energy-dense lipids.

Marine waste upcycling—recovery of nylon monomers from fishing net waste using seashell waste-derived catalysts in a CO2-mediated thermocatalytic process

“…This may be attributed to the intimate contact of the catalyst with high molecular weight volatile species generated via thermal depolymerization. 37,38 The high diffusion efficiency of polymer-derived (e.g., FNW-derived) heavy volatiles enables their diffusion into catalyst pores; this facilitates direct contact between volatiles and catalytic sites using in situ conguration. 39,40 This may amplify the catalytic effect for promoting the thermal depolymerization of FNW, which may potentially contribute to higher caprolactam yields than those derived from using ex situ conguration.…”

Comprehensive Kinetic Study of Pyrolysis of Sunan Candlenut: The Effect of Using Iron Oxide, Zeolite and ZSM-5 as Bed Materials

“…The pyrolysis test was carried out using a thermogravimetric analyzer TGA-701 Leco (temperature measurement precision of ± 2℃, and microbalance sensitivity of 0.0001 g), under a continuous Nitrogen gas flow at 10 mL/min. The test sample consisted of SCO without a mixture of bed material, and was mixed with the composition of SCO versus bed material set at 1:5 similar ratios used in previous studies [20,[26][27][28]. Furthermore, the sample mixture was stirred evenly to obtain a homogeneous composition.…”

“…The use of a catalyst in pyrolysis is carried out through the following methods (1) the catalyst is mixed into the raw material; (2) the catalyst is placed in the pyrolysis reactor and allows direct contact between vapor with the catalyst; (3) the catalyst is placed in a secondary reactor located downstream of the primary reactor (pyrolizer). The first two methods are called in-situ, while the last one is ex-situ, and each has a different effect [20][21][22]. The effect of catalysts will be distinct for different biomass because pyrolysis products depend on the suitability of the catalyst.…”

Biorefinery via Catalytic Upgraded Fast Pyrolysis of Biomass

“…"In-situ fast catalytic pyrolysis" (called also catalytic fast pyrolysis) is the liquefaction of woody biomass by pyrolysis and its catalytic upgrading from oxygenates compounds to aromatics in the same reactor. The bio-oil obtained by "In situ catalytic fast pyrolysis" (in -situ CFP) is better of that one obtained by simple fast pyrolysis (FP) in terms of heating value, oxygen content, viscosity and stability [19][20][21][22][23]. The evolved vapours obtained with "in situ CFP" are converted in lesser reactive compounds than those produced by noncatalytic fast pyrolysis and char and coke and catalyst are separated by cyclone present after the reactor and the char and coke after separation from catalyst are send to the combustion to produce energy and the catalyst is recycled.…”

“…"Ex situ catalytic fast pyrolysis" (ex-situ CFP) or "Two stages catalytic fast pyrolysis" is constituted by a fast pyrolysis reactor and a down-stream catalytic reactor for upgrading the bio-oil [19][20][21][22][23]. In ex-situ CFP the two reactions of transformation of biomass are separated and the optimization of the pyrolysis conditions and of the catalyst performance occurs separately [24][25][26][27].…”