Pyrolysis is one of the thermochemical technologies for converting biomass into energy and chemical products consisting of liquid bio-oil, solid biochar, and pyrolytic gas. Depending on the heating rate and residence time, biomass pyrolysis can be divided into three main categories slow (conventional), fast and flash pyrolysis mainly aiming at maximising either the bio-oil or biochar yields. Synthesis gas or hydrogen-rich gas can also be the target of biomass pyrolysis. Maximised gas rates can be achieved through the catalytic pyrolysis process, which is now increasingly being developed. Biomass pyrolysis generally follows a three-step mechanism comprising of dehydration, primary and secondary reactions. Dehydrogenation, depolymerisation, and fragmentation are the main competitive reactions during the primary decomposition of biomass. A number of parameters affect the biomass pyrolysis process, yields and properties of products. These include the biomass type, biomass pretreatment (physical, chemical, and biological), reaction atmosphere, temperature, heating rate and vapour residence time. This manuscript gives a general summary of the properties of the pyrolytic products and their analysis methods. Also provided are a review of the parameters that affect biomass pyrolysis and a summary of the state of industrial pyrolysis technologies.

Lignocellulosic biomass pyrolysis: A review of product properties and effects of pyrolysis parameters

Increasing energy demand, especially in the transportation sector, and soaring CO2 emissions necessitate the exploitation of renewable sources of energy. Despite the large variety of new energy carriers, liquid hydrocarbon still appears to be the most attractive and feasible form of transportation fuel taking into account the energy density, stability and existing infrastructure. Biomass is an abundant, renewable source of energy; however, utilizing it in a cost-effective way is still a substantial challenge. Lignocellulose is composed of three major biopolymers, namely cellulose, hemicellulose and lignin. Fast pyrolysis of biomass is recognized as an efficient and feasible process to selectively convert lignocellulose into a liquid fuel—bio-oil. However bio-oil from fast pyrolysis contains a large amount of oxygen, distributed in hundreds of oxygenates. These oxygenates are the cause of many negative properties, such as low heating value, high corrosiveness, high viscosity, and instability; they also greatly limit the application of bio-oil particularly as transportation fuel. Hydrocarbons derived from biomass are most attractive because of their high energy density and compatibility with the existing infrastructure. Thus, converting lignocellulose into transportation fuels via catalytic fast pyrolysis has attracted much attention. Many studies related to catalytic fast pyrolysis of biomass have been published. The main challenge of this process is the development of active and stable catalysts that can deal with a large variety of decomposition intermediates from lignocellulose. This review starts with the current understanding of the chemistry in fast pyrolysis of lignocellulose and focuses on the development of catalysts in catalytic fast pyrolysis. Recent progress in the experimental studies on catalytic fast pyrolysis of biomass is also summarized with the emphasis on bio-oil yields and quality.

Catalytic fast pyrolysis of lignocellulosic biomass

Due to increasing population and industrialization, the demand of energy is increasing day by day. Simultaneously, the worldwide bio-ethanol production is increasing constantly. The maize, sugarcane and sugar beets are major traditional agricultural crops used as bio-ethanol production but these crops are unable to meet the global demand of bio-ethanol production due to their primary value of food and feed. Hence, cellulosic materials such as agro-residues are attractive feedstock for bio-ethanol production. The cellulosic material is the most abundant biomass and agro-residues on the earth. Bio-ethanol from agro-residues could be a promising technology that involves four processes of pre-treatment, enzymatic hydrolysis, fermentation and distillation. These processes have several challenges and limitations such as biomass transport and handling, and efficient pre-treatment process for removing the lignin from the lignocellulosic agro-residues. Proper pre-treatment process may increase the concentrations of fermentable sugars after enzymatic hydrolysis, thereby improving the efficiency of the whole process. Others, efficient microbes and genetically modified microbes may also enhance the enzymatic hydrolysis. Conversion of cellulose to ethanol requires some new pre-treatment, enzymatic and fermentation technologies, to make the whole process cost effective. In this review, we have discussed about current technologies for sustainable bioethanol production from agro-residues.

Sustainable bio-ethanol production from agro-residues: A review

A review on co-pyrolysis of biomass: An optional technique to obtain a high-grade pyrolysis oil

As our high dependence on the supply of diminishing fossil fuel reserves raise great concerns in its environmental, political and economic consequences, utilization of renewable biomass as an alternative resource has become increasingly important. Along this background, furfural as a building block, offers a promising, rich platform for lignocellulosic biofuels and value-added chemicals. These include 2-methylfuran and 2-methyltetrahydrofuran, furfuryl alcohol, tetrahydrofurfuryl alcohol, furan, tetrahydrofuran as well as various cyclo-products (e.g., cyclopentanol, cyclopentanone). The various production routes started from furfural to various fuel additives and chemicals are critically reviewed, and the current technologies for efficient production are identified. Their potential applications as well as the fuel properties of these products are discussed. Challenges and areas that need improvement are also highlighted in the corresponding area. In short, we conduct a comprehensive review of the strategies to produce furfural, new approaches and numerous possibilities to utilize furfural in industrial and laboratory sector for the production of fuel additives and value-added chemicals.

Production, properties and catalytic hydrogenation of furfural to fuel additives and value-added chemicals

The paper provides an updated review on thermal conversion of biomass for the production of liquid products referred as bio-oil. This technology is described focusing on the characterization of feedstock, reactor design, products formation and upgrading. For feedstock characterization is covered in terms of several pretreatment methods. The reactor designs are illustrated number of design ranging from fixed bed to circulating fluidized bed. The properties of bio-oil composition have caused increasingly extensive research to be undertaken to address properties that need modification and this area is reviewed in terms of physical, catalytic and chemical upgrading. The mechanism of the products formation is also illustrated by several chemical routes. Reactor parameters such as heating rate, temperature of pyrolysis, catalysts etc are reviewed.

A review on bio-oil production from biomass by using pyrolysis method

By thermodynamics considerations, it was shown that the adsorption of CO 2 on CuO surfaces is favourable (Δ G  = +4.9 kJ mol −1 ) under standard conditions (1 atm and 298 K). Various analytical methods such as FTIR, BET, TPD-CO, TGA, XRD, XPS and FESEM were carried out to determine the properties of Cu 2 O and CuO and CO 2 adsorption performance. Surface analysis by XPS, it was noted that 52.4% of carbonates (CO 3 2− ) was formed and deposited on CuO surface. By BET-CO 2 method, typical amount of CO 2 was adsorbed (9 cm 3 per gram sample) at relative pressure of 0.78. It was relatively high compared to Cu 2 O with 2.1 cm 3 per gram sample. The sphere-flower structure of CuO gives a better adsorption and desorption behaviour. Copper carbonate (CuCO 3 ) formed after CO 2 adsorption was heated up until 573 K as a regeneration study of adsorbent materials. No significant loss was measured until three times regeneration. The desorption studies using TPD-CO 2 indicated that about 9.5 mmol of CO 2 was captured at room temperature.

Adsorption-desorption of CO2 on different type of copper oxides surfaces: Physical and chemical attractions studies

An efficient approach for capturing and utilising high concentrations of CO 2 from the atmosphere involves converting the CO 2 into stable and valuable products, such as a series of carbonates. First, we review the reactions and thermodynamic conditions for the carbonate formation using CO 2 and for the fast back reactions of pure CO 2 releasing from the carbonates. The related reactor and process design for CO 2 transformation into carbonates is also discussed. The metal carbonates that can decompose into metal oxides and CO 2 at low temperature is mentioned briefly. Thermodynamic approaches can be applied to determine whether the reaction is favourable or unfavourable. Several parameters, namely the role of surface structure, moisture, pressure and temperature, are major factors that can influence the CO 2 -adsorbent interactions. Theoretical data from molecular simulations, such as atomic charge and attraction energy, can aid in the understanding of CO 2 adsorption. Over the last six years, highly active catalysts for the synthesis of cyclic and polycyclic carbonates from epoxides and CO 2 have been developed. This reaction appears to be useful for CO 2 utilisation programmes. The mechanisms behind the formation of carbonates can help to elucidate the reaction of CO 2 and epoxides to form a series of cyclic carbonates.

The formation of a series of carbonates from carbon dioxide: Capturing and utilisation

Studies on reduction of chromium doped iron oxide catalyst using hydrogen and various concentration of carbon monoxide

This study was focused on carbon dioxide (CO{sub 2}) adsorption ability using Magnesium oxide (MgO) nanoparticles and MgO nanoparticles supported activated carbon based bamboo (BAC). The suitability of MgO as a good CO{sub 2} adsorbent was clarified using Thermodynamic considerations (Gibbs-Helmholtz relationship). The ΔH and ΔG of this reaction were − 117.5 kJ⋅mol{sup −1} and − 65.4 kJ⋅mol{sup −1}, respectively, at standard condition (298 K and 1 atm). The complete characterization of these adsorbent were conducted by using BET, XRD, FTIR, TEM and TPD−CO{sub 2}. The surface areas for MgO nanoparticles and MgO nanoparticles supported BAC were 297.1 m{sup 2}/g and 702.5 m{sup 2}/g, respectively. The MgO nanoparticles supported BAC shown better physical and chemical adsorption ability with 39.8 cm{sup 3}/g and 6.5 mmol/g, respectively. The combination of MgO nanoparticle and BAC which previously prepared by chemical method can reduce CO{sub 2} emissions as well as better CO{sub 2} adsorption behavior. Overall, our results indicate that nanoparticles of MgO on BAC posses unique surface chemistry and their high surface reactivity coupled with high surface area allowed them to approach the goal as an efficient CO{sub 2} adsorbent.

Mohamed Wahab Mohamed Hisham

Papers

A review on bio-oil production from biomass by using pyrolysis method

Adsorption-desorption of CO2 on different type of copper oxides surfaces: Physical and chemical attractions studies

The formation of a series of carbonates from carbon dioxide: Capturing and utilisation

Studies on reduction of chromium doped iron oxide catalyst using hydrogen and various concentration of carbon monoxide

Magnesium oxide nanoparticles on green activated carbon as efficient CO2 adsorbent