Yaning Zhang

Fast microwave-assisted catalytic co-pyrolysis of lignin and low-density polyethylene with HZSM-5 and MgO for improved bio-oil yield and quality

Fast microwave-assisted catalytic co-pyrolysis of lignin and low-density polyethylene (LDPE) with HZSM-5 and MgO was investigated. Effects of pyrolysis temperature, lignin to LDPE ratio, MgO to HZSM-5 ratio, and feedstock to catalyst ratio on the products yields and chemical profiles were examined. 500°C was the optimal co-pyrolysis temperature in terms of the maximum bio-oil yield. The proportion of aromatics increased with increasing LDPE content. In addition, with the addition of LDPE (lignin/LDPE=1/2), methoxyl group in the phenols was completely removed. A synergistic effect was found between lignin and LDPE. The proportion of aromatics increased and alkylated phenols decreased with increasing HZSM-5 to MgO ratio. The bio-oil yield increased with the addition of appropriate amount of catalyst and the proportion of alkylated phenols increased with increasing catalyst to feedstock ratio.

Effects of feedstock characteristics on microwave-assisted pyrolysis – A review

Microwave-assisted pyrolysis is an important approach to obtain bio-oil from biomass. Similar to conventional electrical heating pyrolysis, microwave-assisted pyrolysis is significantly affected by feedstock characteristics. However, microwave heating has its unique features which strongly depend on the physical and chemical properties of biomass feedstock. In this review, the relationships among heating, bio-oil yield, and feedstock particle size, moisture content, inorganics, and organics in microwave-assisted pyrolysis are discussed and compared with those in conventional electrical heating pyrolysis. The quantitative analysis of data reported in the literature showed a strong contrast between the conventional processes and microwave based processes. Microwave-assisted pyrolysis is a relatively new process with limited research compared with conventional electrical heating pyrolysis. The lack of understanding of some observed results warrant more and in-depth fundamental research.

Bio-oil from fast pyrolysis of lignin: Effects of process and upgrading parameters

Effects of process parameters on the yield and chemical profile of bio-oil from fast pyrolysis of lignin and the processes for lignin-derived bio-oil upgrading were reviewed. Various process parameters including pyrolysis temperature, reactor types, lignin characteristics, residence time, and feeding rate were discussed and the optimal parameter conditions for improved bio-oil yield and quality were concluded. In terms of lignin-derived bio-oil upgrading, three routes including pretreatment of lignin, catalytic upgrading, and co-pyrolysis of hydrogen-rich materials have been investigated. Zeolite cracking and hydrodeoxygenation (HDO) treatment are two main methods for catalytic upgrading of lignin-derived bio-oil. Factors affecting zeolite activity and the main zeolite catalytic mechanisms for lignin conversion were analyzed. Noble metal-based catalysts and metal sulfide catalysts are normally used as the HDO catalysts and the conversion mechanisms associated with a series of reactions have been proposed.

Determination of the intrinsic reactivities for carbon dioxide gasification of rice husk chars through using random pore model.

Rice husk is abundantly available and environmentally friendly, and char-CO2 gasification is of great importance for the biomass gasification process. The intrinsic reaction rates of carbon dioxide gasification with rice husk chars derived from different pyrolysis temperatures were investigated in this study by conducting thermogravimetric analysis (TGA) measurements. The effects of gasification temperature and reactant partial pressure on the char-CO2 gasification were investigated and the random pore model (RPM) was used to determine the intrinsic kinetic parameters based on the experimental data. The results obtained from this study show that the activation energy, reaction order and pre-exponential factor varied in the ranges of 226.65-232.28kJ/mol, 0.288-0.346 and 2.38×10(5)-2.82×10(5)1/sPa(n) for the rice husk chars pyrolyzed at 700-900°C, respectively. All the determination coefficients between the RPM predictions and experimental results were higher than 0.906, indicating the RPM is reliable for determining and evaluating the intrinsic reactivities of rice husk chars.

In-situ and ex-situ catalytic upgrading of vapors from microwave-assisted pyrolysis of lignin

In-situ and ex-situ catalytic upgrading with HZSM-5 of vapors from microwave-assisted pyrolysis of lignin were studied. The in-situ process produced higher bio-oil and less char than ex-situ process. The gas yield was similar for both processes. The ex-situ process had higher selectivity to aromatics and produced more syngas and less CO2 than the in-situ process. Additional experiments on ex-situ process found that the bio-oil yield and coke deposition decreased while the gas yield increased at higher catalyst-to-lignin ratios and catalytic upgrading temperatures. The increased catalyst-to-lignin ratio from 0 to 0.3 reduced the selectivity of methoxy phenols from 73.7% to 22.6% while increased that of aromatics from 1.1% to 41.4%. The highest selectivity of alkyl phenols (31.9%) was obtained at 0.2 of catalyst-to-lignin ratio. Higher catalytic temperatures favored greater conversion of methoxy phenols to alkyl phenols and aromatics. Appropriate catalyst-to-lignin ratio (0.3) together with higher catalytic temperatures favored syngas formation.

Development and application of a continuous fast microwave pyrolysis system for sewage sludge utilization

A continuous fast microwave-assisted pyrolysis system was designed, fabricated, and tested with sewage sludge. The system is equipped with continuous biomass feeding, mixing of biomass and microwave absorbent, and separated catalyst upgrading. The effect of the sludge pyrolysis temperature (450, 500, 550, and 600 °C) on the products yield, distribution and potentially energy recovery were investigated. The physical, chemical, and energetic properties of the raw sewage sludge and bio-oil, char and gas products obtained were analyzed using elemental analyzer, GC-MS, Micro-GC, SEM and ICP-OES. While the maximum bio-oil yield of 41.39 wt% was obtained at pyrolysis temperature of 550 °C, the optimal pyrolysis temperature for maximum overall energy recovery was 500 °C. The absence of carrier gas in the process may be responsible for the high HHV of gas products. This work could provide technical support for microwave-assisted system scale-up and sewage sludge utilization.

Exergy of Oat Straw

ABSTRACT The exergy values of three oat straws were investigated. The effects of moisture content, ash content, S content, correlation factor (C, O, H, and N), and lower heating value (LHV) were also studied. The results showed that the moisture-related exergy, ash-related exergy, and S-related exergy varied in the ranges of 283.630–337.502, 28.474–111.054, and 4.357–13.944 kJ/kg, respectively. They accounted for 1.346–1.661%, 0.164–0.538%, and 0.021–0.068% of the exergy of oat straw, respectively. The O/C, H/C, and N/C atomic ratios varied in the ranges of 0.7042–0.7780 (10.480%), 1.4713–1.6000 (8.747%), and 0.0024–0.0254 (958.333%), respectively, whereas the correlation factors varied between 1.131 and 1.142 (0.973%). The exergy values of the three oat straws were between 20.325 and 21.065 MJ/kg. They were mainly determined by the correlation factors and the LHVs. A positive linear relationship between the exergy and LHV was observed.

In situ plasma-assisted atmospheric nitrogen fixation using water and spray-type jet plasma

In this study, a sustainable nitrogen fixation process was presented under atmospheric conditions and without introducing hydrogen or any catalyst. The novel in situ synthesis in this study used an advanced spray-type jet plasma, which significantly improved the fixation rate of nitrite, nitrate, and ammonium. Furthermore, the mechanism focusing on the co-synthesis of the abovementioned three nitrogen compounds was proposed based on the synergistic interactions between the gas-phase plasma and liquid surface dissociation.

Microwave‐Assisted Pyrolysis of Biomass for Bio‐Oil Production

Microwave‐assisted pyrolysis (MAP) is a new thermochemical process that converts bio‐ mass to bio‐oil. Compared with the conventional electrical heating pyrolysis, MAP is more rapid, efficient, selective, controllable, and flexible. This chapter provides an up‐to‐ date knowledge of bio‐oil production from microwave‐assisted pyrolysis of biomass. The chemical, physical, and energy properties of bio‐oils obtained from microwave‐assisted pyrolysis of biomass are described in comparison with those from conventional pyroly‐ sis, the characteristics of microwave‐assisted pyrolysis as affected by biomass feedstock properties, microwave heating operations, use of exogenous microwave absorbents, and catalysts are discussed. With the advantages it offers and the further research and devel‐ opment recommended, microwave‐assisted pyrolysis has a bright future in production of bio‐oils that can effectively narrow the energy gap and reduce negative environmental impacts of our energy production and application practice.

Microwave-assisted Pyrolysis of Biomass for Bio-oil Production: A Review of the Operation Parameters

Microwave‐assisted pyrolysis (MAP) is a new thermochemical process that converts bio‐ mass to bio‐oil. Compared with the conventional electrical heating pyrolysis, MAP is more rapid, eicient, selective, controllable, and lexible. This chapter provides an up‐to‐ date knowledge of bio‐oil production from microwave‐assisted pyrolysis of biomass. The chemical, physical, and energy properties of bio‐oils obtained from microwave‐assisted pyrolysis of biomass are described in comparison with those from conventional pyroly‐ sis, the characteristics of microwave‐assisted pyrolysis as afected by biomass feedstock properties, microwave heating operations, use of exogenous microwave absorbents, and catalysts are discussed. With the advantages it ofers and the further research and devel‐ opment recommended, microwave‐assisted pyrolysis has a bright future in production of bio‐oils that can efectively narrow the energy gap and reduce negative environmental impacts of our energy production and application practice.