Study on pyrolysis characteristics of lignocellulosic biomass impregnated with ammonia source

Biomass directional pyrolysis based on element economy to produce high-quality fuels, chemicals, carbon materials - A review

Biomass is regarded as the only carbon-containing renewable energy source and has performed an increasingly important role in the gradual substitution of conventional fossil energy, which also contributes to the goals of carbon neutrality. In the past decade, the academic field has paid much greater attention to the development of biomass pyrolysis technologies. However, most biomass conversion technologies mainly derive from the fossil fuel industry, and it must be noticed that the large element component difference between biomass and traditional fossil fuels. Thus, it's necessary to develop biomass directional pyrolysis technology based on the unique element distribution of biomass for realizing enrichment target element (i.e., element economy). This article provides a broad review of biomass directional pyrolysis to produce high-quality fuels, chemicals, and carbon materials based on element economy. The C (carbon) element economy of biomass pyrolysis is realized by the production of high-performance carbon materials from different carbon sources. For efficient H (hydrogen) element utilization, high-value hydrocarbons could be obtained by the co-pyrolysis or catalytic pyrolysis of biomass and cheap hydrogen source. For improving the O (oxygen) element economy, different from the traditional hydrodeoxygenation (HDO) process, the high content of O in biomass would also become an advantage because biomass is an appropriate raw material for producing oxygenated liquid additives. Based on the N (nitrogen) element economy, the recent studies on preparing N-containing chemicals (or N-rich carbon materials) are reviewed. Moreover, the feasibility of the biomass poly-generation industrialization and the suitable process for different types of target products are also mentioned. Moreover, the enviro-economic assessment of representative biomass pyrolysis technologies is analyzed. Finally, the brief challenges and perspectives of biomass pyrolysis are provided.

Comparative Assessment of Proportions of Urea in Blend for Nitrogen-Rich Pyrolysis: Characteristics and Distribution of Bio-Oil and Biochar

This study aimed to investigate the effect of the urea content on the characteristics and distribution of nitrogen-rich bio-oil and nitrogen-doped biochar. Cellulose, cellobiose, and glucose were used as feedstock. Urea was used as the exogenous nitrogen source in nitrogen-rich pyrolysis at 500 °C. The order of the nitrogen increase in the nitrogen-doped biochar was cellulose < cellobiose < glucose. Nitrogen-doped biochar consisted of abundant nitrogen and nitrogenous functional groups, and the stability of biochar was optimal. The nitrogen-doped biochar obtained from cellulose showed the optimal adsorption performance for diethyl phthalate with 50% urea addition. When the proportion of urea was 20%, the content of anhydro-sugars in bio-oil reached the maximum value (61.86%). Furans and other small-molecule oxygenates were intermediates to produce nitrogenous heterocyclic compounds (NHCs) from cellulose. When the proportion of urea was 40%, the bio-oil had the highest selectivity (91.63%) of NHCs. The NHCs in the obtained bio-oil mainly consisted of pyrroles, pyrimidines, pyridines, imidazoles, and pyrazines. Therefore, the excellent proportion of urea in the blend could promote the generation of high-value NHCs and nitrogen-doped biochar from the nitrogen-rich pyrolysis of cellulose (and its model compounds).

One-Step Pyrolysis of Nitrogen-Containing Chemicals and Biochar Derived from Walnut Shells to Absorb Polycyclic Aromatic Hydrocarbons (PAHs)

The pyrolysis of biomass is an efficient means of utilizing biomass resources. Biomass can be converted into various high-performance chemicals and functional materials through pyrolysis. However, current pyrolysis technologies suffer from low conversion rates and single products, so the preparation of nitrogen compounds with high economic value remains a challenge. The walnut shell was soaked in three nitrogen-containing compound solutions before carbonization to produce high-value-added nitrogen-containing chemicals (with a nitrogen content of 59.09%) and biochar for the adsorption of polycyclic aromatic hydrocarbons (PAHs). According to biochar analysis, biochar has a porous structure with a specific surface area of 1161.30 m²/g and a high level of rocky desertification. The surface forms a dense pyrrole structure, and the structure produces π-π interactions with naphthalene molecules, exhibiting excellent naphthalene adsorption with a maximum capacity of 214.98 mg/g. This study provides an efficient, rapid, and environmentally friendly method for producing nitrogen-containing chemicals with high-added value and biochar.

A comparative life cycle assessment of different pyrolysis-pretreatment pathways of wood biomass for levoglucosan production

In order to identify the most environmental-friendly pretreatment for pyrolsis of wood residue to levoglucosan (LG), for the first time a comparative life cycle assessment (LCA) was carried out for hot water treatment (HWT), torrefaction, acid pretreatment (AP) and salt pretreatment (SP) pathways. Since LG production can facilitate both resource recovery (RR) and wood residue handling (WRH), two different functional units (FUs), i.e., 1 kg LG production and 1 kg wood residue handling were considered. AP was found to generate the least global warming potential of 134.60 kg CO₂-eq and human carcinogenic toxicity of 0.59 kg 1,4-dichlorobenzene-eq. for RR perspective. However, for WRH perspective, HWT was found to be the best pretreatment (6.39 kg CO₂-eq; 0.03 kg 1,4-dichlorobenzene-eq.). Sensitivity analysis revealed that a reduction in electricity consumption by 15% could reduce the overall impacts by 14.00-14.82 %. This study also highlights the impact of goal and FU selection on LCA.

Production of aromatic amines via catalytic co-pyrolysis of lignin and phenol-formaldehyde resins with ammonia over commercial HZSM-5 zeolites

Aromatic amines could be produced from organic wastes via catalytic pyrolysis with ammonia that served not only as a carrier gas but also as a reactant. Aromatic amines of 14.2 C% with selectivity of 57.6% were obtained from phenol-formaldehyde resins via pyrolysis over commercial HZSM-5-3 zeolite (Si/Al ratio of 80) catalyst at 650 °C. Significant synergetic effects have been observed when lignin was added, which improved aromatic amines yield by 32.2% to 11.8 C% at the mixing weight ratio of lignin to PF resins of 1:1. HZSM-5-3 was slightly deactivated after 3 cycles with acid sites loss. Catalytic co-pyrolysis of plastics and biomass wastes is a fast and effective method to produce aromatic amines.

Pyrolysis of Biomass Impregnated With Ammonium Dihydrogen Phosphate for Polygeneration of Phenol and Supercapacitor Electrode Material

A new method was proposed for polygeneration of phenol and supercapacitor electrode material from pyrolysis of biomass impregnated with ammonium dihydrogen phosphate (NH₄H₂PO₄). The pyrolysis experiments were executed to demonstrate the product distributions under different NH₄H₂PO₄-to-poplar (PA-to-PL) ratios and pyrolysis temperatures in a lab-scale device. The results revealed that the phenol yield attained its optimal value of 4.57 wt% with a satisfactory selectivity of 20.09% at 500°C under PA-to-PL ratio of 0.6. The pyrolytic solid product obtained at this condition was then subjected to high temperature activation directly without additional activators to prepare N and P co-doped activated carbon (NPAC) as supercapacitor. The physicochemical analysis of NPAC showed that the N and P contents in NPAC reached 3.75 and 3.65 wt%, respectively. The electrochemical experiments executed in a three-electrode system indicated that the NPAC exhibited promising electrochemical performance with a satisfactory capacitance of 181.3 F g^-1 at 1 A g^-1.

Hydrothermal liquefaction of cellulose in ammonia/water

In order to obtain the N-containing organics from cellulose under mild conditions, hydrothermal liquefaction of cellulose in the presence of ammonia was conducted in this study. The results showed that the increasing reaction temperature and prolonging time facilitated the conversion of cellulose in hydrothermal liquefaction (HTL) with NH₃·H₂O and decreased the amount of solid residue. Reaction temperature showed more influence than reaction time on solid residue formation. The components of bio-oil were significantly affected by reaction temperature and reaction time. Electrospray ionization-Fourier transform-ion cyclotron resonance-mass spectrometry (ESI FT-ICR MS) provided an insight for understanding the distribution of the different kinds of N-heterocycle compounds in the bio-oil. The possible reaction pathway of N-heterocycle compounds formation from cellulose during hydrothermal liquefaction with NH₃·H₂O was proposed.

Two-step pyrolysis of corncob for value-added chemicals and high-quality bio-oil: Effects of alkali and alkaline earth metals

Two-step pyrolysis (TSP) of corncob(CC) coupled with water and acid washing pretreatment was conducted to investigate the effects of alkali and alkaline earth metals (AAEMs) on TSP by Py-GC/MS. TG-FTIR was used to analyze the pyrolysis characteristics of the samples. The results showed that the removal of AAEMs postponed the pyrolysis process and significantly influenced the distribution of the pyrolysis products. As the content of AAEMs decreased, the bio-oil yield increased and the biochar yield decreased. TSP of CC achieved high selectivities for phenols and ketones in the first step and for hydrocarbons in the second step. TSP of acid-washed corncob (ACC) achieved high selectivities for furans in the first step and for sugars in the second step. Additionally, some value-added chemicals such as furfural (11.54%, ACC), 4-vinylphenol (23.57%, CC) and levoglucosan (43.05%, ACC) were also enriched in TSP. Therefore, a promising polygeneration scheme of TSP for the efficient utilization of biomass was proposed.

Experimental study on fluidization behaviors of walnut shell in a fluidized bed assisted by sand particles

The fluidization behaviors and their differences for walnut shell (WS) assisted by different-sized sands at various blending proportions were investigated experimentally in a cold visual fluidized bed at ambient temperature and pressure. Through analyzing the fluidization characteristic curves, it was found that the WS/sand mixtures were clearly characterized by stratified fluidization during the fluidization process, presenting a velocity interval rather than a threshold for transition from fixed to fluidized bed. Sand-3, as the fluidizing medium, showed better performance for WS fluidization in terms of the relative difference between initial (U _mf,i) and final fluidization velocity (U _mf,f) as well as the average fluidization rate (R _f). Furthermore, the regularity and mechanism of mixing and segregation of WS/sand mixtures in two fluidized regions (semi and completed) are discussed in detail based on the flow pattern diagram, the axial and radial distribution of the components, as well as the mixing index.

Investigation on biomass nitrogen-enriched pyrolysis: Influence of temperature

Biomass (bamboo waste) nitrogen-enriched pyrolysis was carried out in a fixed bed with NH₃ atmosphere at 400-800 °C, and formation mechanism of N-containing species was explored in depth. Results showed that N-enriched pyrolysis greatly increased bio-oil and gas yields. H₂ yield increased sharply to 130 mL/g (32.93 vol%) and became the main composition at higher temperature, while CH₄ and CO yields deceased, and the lower heating value of gas reached ∼14 MJ/Nm³. For bio-oil, the content of phenols (main compositions) and N-containing species increased significantly, and the maximums reached 61.33% and 11.47%, respectively. While that of acetic acid (disappeared), O-containing species (aldehydes/ketones/furans/esters) and aromatics decreased largely accordingly. For biochar, Nitrogen content increased, and it contained abundant pyridininc-N, pyrrolic-N, quaternary-N, and pyridone-N-oxide. Possible reaction pathways of biomass N-enriched pyrolysis was proposed based on products evolution. In conclusion, biomass N-enriched pyrolysis could obtain high-valued N-containing chemical species and functional biochar.

Comparative study on pyrolysis of lignocellulosic and algal biomass using pyrolysis-gas chromatography/mass spectrometry

The cornstalk and chlorella were selected as the representative of lignocelulosic and algal biomass, and the pyrolysis experiments of them were carried out using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The physicochemical properties of samples and the pyrolytic product distribution were presented. And then the compositional differences between the two kinds of pyrolytic products were studied, the relevant pyrolysis mechanisms were analyzed systematically. Pyrolytic vapor from lignocellulosic biomass contained more phenolic and carbonyl compounds while that from algal biomass contained more long-chain fatty acids, nitrogen-containing compounds and fewer carbonyl compounds. Maillard reaction is conducive to the conversion of carbonyl compounds to nitrogenous heterocyclic compounds with better thermal stability.

A study on pyrolysis of Canada thistle (Cirsium arvense) with titania based catalysts for bio-fuel production

The catalytic pyrolysis of Cirsium arvense was performed with titania supported catalysts under the operating conditions of 500°C, 40°C/min heating rate, 100mL/min N2 flow rate in a fixed bed reactor for biofuel production. The effect of catalysts on product yields was investigated. The amount of pyrolysis products (bio-char, bio-oil, gas) and the composition of the produced bio-oils were determined by proton nuclear magnetic resonance ((1)H NMR), Fourier transform infrared spectroscopy (FT-IR), gas chromatography/mass spectrometry (GC-MS) and elemental analysis (EA) techniques. Thistle bio-oils had lower O/C and H/C molar ratios compared to feedstock. The highest bio-char and bio-oil yields of 29.32wt% and 36.71wt% were obtained in the presence of Ce/TiO2 and Ni/TiO2 catalysts respectively. GC-MS identified 97 different compounds in the bio-oils obtained from thistle pyrolysis. (1)H NMR analysis showed that the bio-oils contained ∼55-77% aliphatic and ∼6-19% aromatic structural units.

Effects of torrefaction on hemicellulose structural characteristics and pyrolysis behaviors

The effects of torrefaction on hemicellulose characteristics and its pyrolysis behaviors were studied in detail. The oxygen content decreased significantly after torrefaction, leading to the increase of high heating value. Two-dimensional perturbation correlation analysis based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was performed to characterize the structural evolutions. It was found the dehydration of hydroxyls and the dissociation of branches were the main reactions at low torrefaction temperature. When the temperature further increased, the depolymerization of hemicellulose and the fragmentation of monosaccharide residues occurred. The distributed activation energy model with double Gaussian functions based on reaction-order model was used to investigate the pyrolysis kinetics. The results showed that torrefaction enhanced the activation energy for degradation reactions while lowered that for condensation reactions, and increased the devolatilization contribution of condensation reactions. Besides, torrefaction decreased the yields of typical pyrolytic products, such as acids, furans, alicyclic ketones and so on.

Investigation of free radicals and carbon structures in chars generated from pyrolysis of antibiotic fermentation residue

The aromatization level of AFR was enhanced sharply with the increase of pyrolysis temperature, and the free radicals in raw AFR samples gradually transformed into carbon free radicals on the aromatic structures in chars.