This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references).

Conversion of biomass to selected chemical products

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Lignocellulosic biomass pyrolysis mechanism: A state-of-the-art review

Mechanical and chemical recycling of solid plastic waste.

Mechanisms of metal sorption by biochars: Biochar characteristics and modifications

Citation: James, M., Yuan, W., Boyette, M. D., Wang, D., & Kumar, A. (2016). Characterization of biochar from rice hulls and wood chips produced in a top-lit updraft biomass gasifier. Transactions of the Asabe, 59(3), 749-756. doi:10.13031/trans.59.11631

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Characterization of Biochar from Rice Hulls and Wood Chips Produced in a Top-Lit Updraft Biomass Gasifier

The objective of this study was to evaluate the performance of an in-chamber tar cracking and syngas reforming unit. This unit was composed of a two-stage tubular reactor placed within the combustion zone of an updraft biomass gasifier. Heat generated in the exothermic combustion reactions of biomass gasification drove tar cracking and syngas reforming in the tubes, eliminating the need of external heating. The performance of the unit was evaluated using char-supported NiO catalysts and was found to be very effective in tar removal and syngas composition enhancement. A tar removal rate of 95% was achieved at 0.3 s residence time and 10% nickel loading. This condition also gave syngas high-heating value increment of 36% (to 7.3 MJ/m3). The effect of gas residence time and Ni loading on tar removal and syngas composition of the unit was also studied. Gas residence of 0.2-0.3 s and Ni loading of 5%-10% were found appropriate to produce clean syngas with tar content appropriate for industrial applications (smaller than 0.6 g/m3) in an updraft biomass gasifier without external heating.
Keywords: biomass gasification, tar cracking, syngas reforming, nickel catalyst, char catalyst
DOI: 10.3965/j.ijabe.20140706.011

Citation: James A, Yuan W, Boyette M D, Wang D, Kumar A. In-chamber thermocatalytic tar cracking and syngas reforming using char-supported NiO catalyst in an updraft biomass gasifier. Int J Agric & Biol Eng, 2014; 7(6): 91－97.

In-chamber thermocatalytic tar cracking and syngas reforming using char-supported NiO catalyst in an updraft biomass gasifier

Thermochemical conversion of biomass results in producer gas as a raw material for the production of power, many fuels, and chemicals. It is important to clean producer gas of its tars before its intended use. Three different commercial catalysts, one platinum based (cerium zirconium platinum) and two nickel based (Hifuel R110 and Reformax 250), were investigated for their ability to convert toluene (model tar). Studies were carried out in a fixed bed reactor using a gas mixture comparable to the producer gas composition produced from switchgrass gasification. The operating parameters tested were space time (6.86 × 10-4 to 1.262 × 10-3 kg h m-3) corresponding to different catalyst loadings and catalyst particle sizes (pellets and powder). Decreasing the particle size resulted in better toluene conversion for all three catalysts. Additionally, an increase in space time resulted in an increase in toluene conversion. Furthermore, an overall increase in H2 and CO2 concentrations and an overall decrease in CH4 and CO concentrations were observed during toluene conversion. Rate constants were calculated for all three catalysts.

Conversion of Toluene (Model Tar) Using Selected Steam Reforming Catalysts

Prediction of biomass-generated syngas using extents of major reactions in a continuous stirred-tank reactor

. Pretreatment of switchgrass by torrefaction or densification can improve its physical and chemical characteristics by making it hydrophobic, increasing the bulk density and energy content, and improving ability to store and transport. The goal of this study was to investigate the effects of four pretreatments (torrefaction at 230°C, torrefaction at 270°C, densification, and combined torrefaction and densification) and heating rates on the thermal devolatilization characteristics of switchgrass in both inert and oxidizing atmospheres. The thermal devolatilization characteristics of biomass were determined using a thermogravimetric analyzer. Torrefaction of switchgrass increased its carbon content and higher heating value but decreased hydrogen and oxygen contents. These effects increased with increase in torrefaction temperature from 230°C to 270°C. However, the rate of devolatilization of switchgrass torrefied at 230°C was higher than that of switchgrass torrefied at 270°C in both inert and oxidizing atmospheres. The weight loss of switchgrass occurred in three stages in both inert and oxidizing atmospheres. In both atmospheres at a heating rate of 50°C min-1, switchgrass pretreated with combined torrefaction and densification showed the highest rate of weight loss peak (34 and 44 mg min-1 in inert and oxidizing atmospheres, respectively) and the lowest start and end temperatures of the rate of weight loss peak. Overall, in both inert and oxidizing atmospheres, switchgrass pretreated with combined torrefaction and densification had the highest rate of devolatilization, followed by switchgrass pretreated with densification, switchgrass pretreated with torrefaction at 230°C, switchgrass pretreated with torrefaction at 270°C, and raw switchgrass. Heating rate also had significant effects on the weight loss and rate of weight loss of switchgrass but did not have significant effects on the start and end temperatures of the rate of weight loss peaks.

Ajay Kumar

Papers

Characterization of Biochar from Rice Hulls and Wood Chips Produced in a Top-Lit Updraft Biomass Gasifier

In-chamber thermocatalytic tar cracking and syngas reforming using char-supported NiO catalyst in an updraft biomass gasifier

Conversion of Toluene (Model Tar) Using Selected Steam Reforming Catalysts

Prediction of biomass-generated syngas using extents of major reactions in a continuous stirred-tank reactor

Thermal Devolatilization Kinetics of Switchgrass Pretreated with Torrefaction and Densification