Yiqin Wan

Microwave-assisted pyrolysis of microalgae for biofuel production

The pyrolysis of Chlorella sp. was carried out in a microwave oven with char as microwave reception enhancer. The results indicated that the maximum bio-oil yield of 28.6% was achieved under the microwave power of 750 W. The bio-oil properties were characterized with elemental, GC-MS, GPC, FTIR, and thermogravimetric analysis. The algal bio-oil had a density of 0.98 kg/L, a viscosity of 61.2 cSt, and a higher heating value (HHV) of 30.7 MJ/kg. The GC-MS results showed that the bio-oils were mainly composed of aliphatic hydrocarbons, aromatic hydrocarbons, phenols, long chain fatty acids and nitrogenated compounds, among which aliphatic and aromatic hydrocarbons (account for 22.18% of the total GC-MS spectrum area) are highly desirable compounds as those in crude oil, gasoline and diesel. The results in this study indicate that fast growing algae are a promising source of feedstock for advanced renewable fuel production via microwave-assisted pyrolysis (MAP).

Physical and Chemical Properties of Bio-Oils From Microwave Pyrolysis of Corn Stover

This study was aimed to understand the physical and chemical properties of pyrolytic bio-oils produced from microwave pyrolysis of corn stover regarding their potential use as gas turbine and home heating fuels. The ash content, solids content, pH, heating value, minerals, elemental ratio, moisture content, and viscosity of the bio-oils were determined. The water content was approx 15.2 wt%, solids content 0.22 wt%, alkali metal content 12 parts per million, dynamic viscosity 185 mPa·s at 40°C, and gross high heating value 17.5 MJ/kg for a typical bio-oil produced. Our aging tests showed that the viscosity and water content increased and phase separation occurred during the storage at different temperatures. Adding methanol and/or ethanol to the bio-oils reduced the viscosity and slowed down the increase in viscosity and water content during the storage. Blending of methanol or ethanol with the bio-oils may be a simple and cost-effective approach to making the pyrolytic bio-oils into a stable gas turbine or home heating fuels.

Catalytic pyrolysis of microalgae and their three major components: Carbohydrates, proteins, and lipids

To better understand the pyrolysis of microalgae, the different roles of three major components (carbohydrates, proteins, and lipids) were investigated on a pyroprobe. Cellulose, egg whites, and canola oil were employed as the model compounds of the three components, respectively. Non-catalytic pyrolysis was used to identify and quantify some major products and several reaction pathways were proposed for the pyrolysis of each model compound. Catalytic pyrolysis was then carried out with HZSM-5 for the production of aromatic hydrocarbons at different temperatures and catalyst to feed ratios. The aromatic yields of all feedstocks were significantly improved when the catalyst to biomass ratio increased from 1:1 to 5:1. Egg whites had the lowest aromatic yield among the model compounds under all reaction conditions, which suggests that proteins can hardly be converted to aromatics with HZSM-5. Lipids, although only accounted for 12.33% of Chlorella, contributed about 40% of aromatic production from algal biomass.

Fast microwave assisted pyrolysis of biomass using microwave absorbent

A novel concept of fast microwave assisted pyrolysis (fMAP) in the presence of microwave absorbents was presented and examined. Wood sawdust and corn stover were pyrolyzed by means of microwave heating and silicon carbide (SiC) as microwave absorbent. The bio-oil was characterized, and the effects of temperature, feedstock loading, particle sizes, and vacuum degree were analyzed. For wood sawdust, a temperature of 480°C, 50 grit SiC, with 2g/min of biomass feeding, were the optimal conditions, with a maximum bio-oil yield of 65 wt.%. For corn stover, temperatures ranging from 490°C to 560°C, biomass particle sizes from 0.9mm to 1.9mm, and vacuum degree lower than 100mmHg obtained a maximum bio-oil yield of 64 wt.%. This study shows that the use of microwave absorbents for fMAP is feasible and a promising technology to improve the practical values and commercial application outlook of microwave based pyrolysis.

Fast microwave-assisted catalytic pyrolysis of sewage sludge for bio-oil production.

In this study, fast microwave-assisted catalytic pyrolysis of sewage sludge was investigated for bio-oil production, with HZSM-5 as the catalyst. Pyrolysis temperature and catalyst to feed ratio were examined for their effects on bio-oil yield and composition. Experimental results showed that microwave is an effective heating method for sewage sludge pyrolysis. Temperature has great influence on the pyrolysis process. The maximum bio-oil yield and the lowest proportions of oxygen- and nitrogen-containing compounds in the bio-oil were obtained at 550°C. The oil yield decreased when catalyst was used, but the proportions of oxygen- and nitrogen-containing compounds were significantly reduced when the catalyst to feed ratio increased from 1:1 to 2:1. Essential mineral elements were concentrated in the bio-char after pyrolysis, which could be used as a soil amendment in place of fertilizer. Results of XRD analyses demonstrated that HZSM-5 catalyst exhibited good stability during the microwave-assisted pyrolysis of sewage sludge.

Fast microwave-assisted catalytic gasification of biomass for syngas production and tar removal

In the present study, a microwave-assisted biomass gasification system was developed for syngas production. Three catalysts including Fe, Co and Ni with Al2O3 support were examined and compared for their effects on syngas production and tar removal. Experimental results showed that microwave is an effective heating method for biomass gasification. Ni/Al2O3 was found to be the most effective catalyst for syngas production and tar removal. The gas yield reached above 80% and the composition of tar was the simplest when Ni/Al2O3 catalyst was used. The optimal ratio of catalyst to biomass was determined to be 1:5-1:3. The addition of steam was found to be able to improve the gas production and syngas quality. Results of XRD analyses demonstrated that Ni/Al2O3 catalyst has good stability during gasification process. Finally, a new concept of microwave-assisted dual fluidized bed gasifier was put forward for the first time in this study.

Fractionation and characterization of hemicelluloses from young bamboo (Phyllostachys pubescens Mazel) leaves

Bamboo leaves are considered as an important source of bioactive molecules. In this work, leaves from young bamboo (Phyllostachys pubescens Mazel) aged 3 months were subjected to aqueous extraction and 2% NaOH solution extraction followed by precipitation in ethanol-water medium with different ethanol concentrations. The dissolved hemicellulosic polysaccharides presented a total recovery of 67.83% based on the total hemicellulose content in bamboo leaves. Chemical analysis of the fractions was performed by sugar composition analysis, Fourier-transform infrared spectrometry, and 1D nuclear magnetic resonance imaging. The results revealed that all polysaccharide fractions contained xylose, arabinose, glucose, galactose, ribose, and uronic acid. The polysaccharides from young bamboo leaves mainly consisted of arabinoxylans, arabinogalactans, and non-cellulosic β-D-glucans having (1→3)- and (1→4)-glucosidic linkages. The content of these polysaccharides was found to vary among the fractions depending on the separation method. Finally, the thermal behavior was also discussed.

Catalytic conversion of microwave-assisted pyrolysis vapors.

Abstract The effect of the following catalysts: MS (Molecular sieve) 4A, Fe2O3/MS 4A, CoO/MS 4A, NiO/MS 4A, MgO/MS 4A, PtO/MS 4A, Al2O3/MS 4A, La2O3/MS 4A, Cl−/MS 3A, SO2− 4/MS 3A, Na2O/MS 3A, CaO/MS 3A, K2O/MS 3A, CoO/ZrO2, NiO/ZrO2, La2O3/ZrO2, NiO/CaO-ZrO2, Cl−/ZrO2, SO2− 4/ZrO2, Na2O/ZrO2, CaO/ZrO2, and MgO/ZrO2, on chemical profile of the products from microwave-assisted pyrolysis of biomass was studied. A microwave oven with a frequency of about 2.4 gigahertz, and a power of about 1–1.3 kilowatt was used to pyrolyze aspen (Populus tremuloides). The steam that evolved was removed from the oven and passed to a catalyst column where the temperature was controlled at about 350–600°C, and the converted vapors were then condensed to bio-oils. The chemical profiles of the bio-oils were determined using gas chromatography-mass spectrometry. Solid acids were proved to be effective catalysts to decompose pyrolysis vapors, while solid alkaline and other catalysts do not seem to affect the composition of the liquid products from microwave-assisted pyrolysis. Increasing the temperature of the catalyst bed and the ratio of catalysts to biomass adversely affected the liquid yield.

Single-step synthesis of DME from syngas on CuZnAl–zeolite bifunctional catalysts: the influence of zeolite type

In this study, single-step synthesis of DME from syngas on bifunctional catalysts containing Cu–ZnO–Al2O3 and seven different zeolites was investigated. Various characterization techniques were used to determine the structure, reducibility, and surface acidity of the catalysts. The experimental results showed that the zeolite type had great influence on the activity, selectivity and stability of the bifunctional catalyst during the syngas-to-DME process. Zeolite properties including density of weak and strong acid sites, pore structure, and Si/Al distribution were found to affect the CO conversion and DME selectivity of the bifunctional catalyst. In addition, the deactivation of the bifunctional catalyst could be attributed to the sintering of metallic Cu and a loss of the zeolite dehydration activity.

Syntheses of 5-Hydroxymethylfurfural Through Glucose Dehydration in Diphasic Solvent System on ZrO2 and SO42−/TiO2-SiO2 Catalyst

Synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose in water-dimethyl sulfoxide diphasic system using solid base ZrO2 and SO42−/TiO2-SiO2 catalysts was studied. The effects of calcining temperature, Ti/Si ratio in SO42−/TiO2-SiO2, catalyst dosage, and mass ratio of ZrO2 and SO42−/TiO2-SiO2 mixture on 5-HMF yield were evaluated. Both the base and acid catalyst exhibited best performance when calcined at 450°C. The optimal Ti/Si ratio was found to be 4:1. ZrO2 and SO42−/TiO2-SiO2 mixture worked much better than ZrO2 or SO42−/TiO2-SiO2 alone. The optimal catalyst dosage was found to be 20% of the glucose amount (w). Instrumental characterization of the catalysts indicate that mild base and acid sites are suitable for conversion of glucose to 5-HMF, and the base and acid catalysts in the mixture do not interact chemically to a noticeable extend that influences the functionality. The water-organic diphasic system proved to be efficient in catalytic transformation of glucose to 5-HMF.