Peigao Duan

Bio: Peigao Duan is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Catalysis & Hydrothermal liquefaction. The author has an hindex of 31, co-authored 108 publications receiving 3639 citations. Previous affiliations of Peigao Duan include East China Normal University & University of Michigan.

Hydrothermal liquefaction and gasification of Nannochloropsis sp.

Abstract: We converted the marine microalga Nannochloropsis sp. into a crude bio-oil product and a gaseous product via hydrothermal processing from 200 to 500 °C and a batch holding time of 60 min. A moderate temperature of 350 °C led to the highest bio-oil yield of 43 wt %. We estimate the heating value of the bio-oil to be about 39 MJ kg−1, which is comparable to that of a petroleum crude oil. The H/C and O/C ratios for the bio-oil decreased from 1.73 and 0.12, respectively, for the 200 °C product to 1.04 and 0.05, respectively, for the 500 °C product. Major bio-oil constituents include phenol and its alkylated derivatives, heterocyclic N-containing compounds, long-chain fatty acids, alkanes and alkenes, and derivatives of phytol and cholesterol. CO2 was always the most abundant gas product. H2 was the second most abundant gas at all temperatures other than 500 °C, where its yield was surpassed by that of CH4. The activation energies for gas formation suggest the presence of gas-forming reactions other than steam...

Hydrothermal Liquefaction of a Microalga with Heterogeneous Catalysts

Abstract: We produced crude bio-oils from the microalga Nannochloropsis sp. via reactions in liquid water at 350 °C in the presence of six different heterogeneous catalysts (Pd/C, Pt/C, Ru/C, Ni/SiO2−Al2O3, CoMo/γ-Al2O3 (sulfided), and zeolite) under inert (helium) and high-pressure reducing (hydrogen) conditions. To our knowledge, this is the first application of common hydrocarbon processing catalysts to microalgae liquefaction in water. In the absence of added H2, all of the catalysts tested produced higher yields of crude bio-oil from the liquefaction of Nannochloropsis sp., but the elemental compositions and heating values of the crude oil (about 38 MJ/kg) were largely insensitive to the catalyst used. The gaseous products were mainly H2, CO2, and CH4, with lesser amounts of C2H4 and C2H6. The Ru and Ni catalysts produced the highest methane yields. Only the zeolite catalyst produced significant amounts of N2. Typical H/C and O/C atomic ratios for the crude bio-oil are 1.7 and 0.09, respectively. In the presen...

Catalytic treatment of crude algal bio-oil in supercritical water: optimization studies

Abstract: We have investigated the catalytic treatment of a crude algal liquefaction bio-oil in supercritical water to discover how the properties of the treated oil depend on the experimental conditions. An L9 (34) orthogonal array design (OAD) with four factors at three levels was employed. The four factors were temperature (varied from 430–530 °C), time (varied from 2–6 h), catalyst type (Pt/C, Mo2C, HZSM-5), and catalyst loading (varied from 5–20 wt%). We used a direct analysis to determine the relationship between experimental conditions and properties of treated oils. The oil properties we examined were elemental composition, atomic ratios, chemical composition, and higher heating value. Of the four factors, the 100 °C variation in temperature was always the most influential for each of the oil properties examined. Of the remaining three factors, catalyst type had the greatest influence on the fatty acid content of the treated oil and the fraction of N- and O-containing compounds in the oil. Catalyst loading had the greatest effect on the higher heating value and O/C ratio in the treated oil. Reaction time had the greatest effect on the H/C and N/C ratios. The results demonstrated that treatment in supercritical water at 430 °C led to roughly a halving of the N and O content of the oil, a reduction in S to below detection limits, and about a 10% improvement in the higher heating value of the bio-oil. Within the parameter space investigated, the conditions leading to the highest content of saturated compounds in the treated oil are 430 °C, 6 h, with a 10 wt% loading of Mo2C as the catalyst. Around 76 wt% of the carbon in the feedstock was retained in the treated oil at these conditions.

Catalytic hydrotreatment of crude algal bio-oil in supercritical water

Abstract: We report herein on the catalytic hydrotreatment of crude bio-oil, produced from the hydrothermal liquefaction of a microalga ( Nannochloropsis sp.) over palladium on carbon (5% Pd/C) in supercritical water (SCW) at 400 °C and 3.4 MPa high-pressure H 2 . Influences of wide ranges of reaction time (varied from 1 to 8 h) and catalyst loading (varied from 5 to 80 wt%) on treated oil composition and yield, gas products composition and yield, and hydrogen consumption were explored. The C, H and energy recoveries were determined. The results demonstrated that longer reaction times and higher catalyst loadings did not favor the treated oil yield due to the increasing amount of gas and coke products formation but did lead to treated bio-oil with higher higher-heating-value (HHV) (41–44 MJ/kg) than that of the crude feed. Highest HHV of treated oil (∼44 MJ/kg) was obtained after 4 h using an 80 wt% intake of catalyst on crude bio-oil. The product oil produced at longer reaction times and higher catalyst loadings, which was a freely flowing liquid as opposed to being the viscous, sticky, tar-like crude bio-oil material, was higher in H and lower in O and N than the crude feed, and it was essentially free of sulfur (below detection limits). Typical H/C and O/C molar ratios ranges for the bio-oils treated at different reaction times and catalyst loadings were 1.65–1.79 and 0.028–0.067, respectively. The main gas-phase products were unreacted H 2 , CH 4 , CO 2 , C 2 H 6, C 3 H 8 and C 4 H 10 . Overall, many of the properties of the treated oil obtained from catalytic hydrotreatment in SCW in the presence of Pd/C are very similar to those of hydrocarbon fuels derived from fossil fuel resources.

An overview of advances in biomass gasification

Abstract: Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

A review on hydrothermal liquefaction of biomass

Abstract: The rapid depletion of conventional fossil fuels and day-by-day growth of environmental pollution due to use of extensive use of fossil fuels have raised concerns over the use of the fossil fuels; and thus search for alternate renewable and sustainable sources for fuels has started in the last few decades. In this context biomass derived fuels seems to be the promising path; and various routes are available for the biomass processing such as pyrolysis, transesterification, hydrothermal liquefaction, steam reforming, etc.; and the hydrothermal liquefaction (HTL) of wet biomass seems to be the promising route. Therefore, this article briefly enlightened a few concepts of HTL such as the elemental composition of bio-crude obtained by HTL, different types of feedstock adopted for HTL, mechanism of HTL processes, possible process flow diagrams for HTL of both wet and dry biomass and energy efficiency of the process. In addition, this article also enlisted possible future research scope for concerned researchers and a few of them are setting up HTL plant suitable for both wet and dry biomass feedstock; analysing influence of parameters such as temperature, pressure, residence time, catalytic effects, etc.; deriving optimized pathways for better conversion; and development of theoretical models representing the process to the best possible accuracy depending on nature of feedstock.