Heather Trajano

Associate Professor

Research Classification

Biomass (Energy)
Wood
Pulp and Paper

Research Interests

Biorefining
Biochemicals
Biomass extractives recovery and utilization
catalysis
Hemicellulose
Pretreatment
Kinetics

Relevant Degree Programs

 

Research Methodology

Reactors for biomass fractionation, enable time-dependent studies
Gel permeation chromatography: analysis of molecular weight
High pressure liquid chromatography for analysis of sugars
Accelerated solvent extraction system for recovery of biomass extractives
Total organic carbon analyzer for solid and liquid samples. Equipped with high salt combustion kit.

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Master's students
2019
I am open to hosting Visiting International Research Students (non-degree, up to 12 months).

Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2019)
Economic feasibility of lignocellulosic ethanol production with enzyme recycling (2014)

Ethanol produced from lignocellulose is one of the most promising biofuels. However, the technology to produce lignocellulosic ethanol is still under development and needs to be improved to become economically viable. Enzymatic hydrolysis is one of the most expensive process stages, primarily due to high enzyme costs. Consequently, two cost reduction strategies were studied: optimization of hydrolysis conditions and enzyme recycle by adsorption. To optimize enzymatic hydrolysis, the changes in concentration of cellulases during the reaction must be determined. Protein concentration changes under hydrolysis conditions for Celluclast 1.5L and Novozyme 188, were studied in the absence of substrate. Novozyme 188 protein concentration decreased by 55 to 64% at 50°C after 92 h. A model describing Novozyme 188 protein concentration changes was developed and used to determine free and adsorbed cellulases concentrations. Glucose and xylose yields (58 to 89% conversion) during enzymatic hydrolysis were modeled as a function of enzyme loading, time, lignin content and solids concentration. The proposed model successfully describes hydrolysis of substrates with different lignin contents, linking pretreatment and hydrolysis. The effect of lignin content, enzyme loading and hydrolysis time on enzyme recovery was evaluated, achieving 0 to 35% cellulases recycled. A mass balance of the enzyme recovery process was built and used to achieve a uniform production of sugar. Based on experimental data and the proposed models, the production of ethanol with and without enzyme recycling was simulated in AspenPlus. The ethanol production process at different operating conditions was economically evaluated. The economic analysis showed that raw material expenses determine production costs, where biomass, caustic and enzyme expenses are the major contributors to the operating cost. The lowest production costs ($1.86 and $2.13/ kg ethanol) were obtained at low enzyme loadings and mild pretreatment conditions. Sugar losses at severe pretreatment conditions have a significant negative effect on production costs: severe conditions increased production cost by 18 to 23%. Therefore, optimal hydrolysis conditions must be determined considering the entire process. The implementation of the enzyme recycling process decreased production costs up to 14% depending on operating conditions, demonstrating the potential benefits of the enzyme recycling technology.

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Master's Student Supervision (2010 - 2018)
Fractionation of pulp mill waste to produce hemicellulose oligomers for adsorption onto NBSK pulp (2018)

Non-renewable fossil fuels and the dangers of climate change have drawn significant research into the forest biorefinery. The pulp and paper industry is positioned to lead the implementation of new technologies from such research.Northern Bleached Softwood Kraft (NBSK) pulp is one of the chief products of the pulp and paper industry in British Columbia (B.C). It is primarily used as reinforcing pulp. Hemicellulose present in mill waste streams such as hog fuel, primary sludge, and chip fines, can be separated and utilized as a strength additive to improve physical strength properties of NBSK pulp, and reduce refining energy.This study investigated the influence of operating variables on the separation of hemicellulose oligomers from these lignocellulosic waste streams, and the adsorption of these oligomers onto NBSK pulp. Reaction temperature and residence time were studied for the separation of hemicellulose, while adsorption temperature, time, fibre consistency, oligomer-to-pulp percentage, and weight average molar mass Mw, were studied for the adsorption of hemicellulose onto NBSK pulp. Hog fuel and primary sludge were found to contain 58.98% and 67.90% polysaccharides respectively. Hemicellulose oligomer yields greater than 90% were obtained from hog fuel via liquid hot water treatment, and from primary sludge via dilute acid hydrolysis. A maximum total oligomer mass of 3.25g was obtained from 25g oven-dry hog fuel. Oligomer-to-pulp percentage and fibre consistency showed a linear effect on the adsorption yield, while adsorption temperature showed a nonlinear effect. The results are encouraging, and suggest the potential of these waste streams to produce a green hemicellulose-based paper strength additive.

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Partial oxidation of pyrolysis oil by model compounds (2017)

The challenges of upgrading pyrolysis oil to transportation fuel limit the economic viability of biomass pyrolysis. Therefore, this dissertation investigated partial oxidation of pyrolysis oil to produce value-added chemicals. Two model compounds, acetic acid (AcOH) and acetaldehyde (AcH) were selected for gas phase oxidation trials. Thermal oxidation of AcOH emphasized AcOH’s refractory nature as the maximum conversion of AcOH was less than 6% at 350 ⁰C at 1 atm with GHSV of 2000 h-¹. AcH was more reactive; conversion of AcH was approximately 40% under identical conditions. Thermal oxidation of both compounds produced only carbon dioxide (CO₂). Although the true reaction mechanism of AcH thermal oxidation could not be determined, the activation energy was calculated to be between 47.1±0.55 kJ/mol and 55.2±0.6 kJ/mol. Catalytic partial oxidation (CPO) of AcOH and AcH was examined using vanadium pentoxide supported by titanium oxide (V₂O₅/TiO₂). Conversion of CPO of AcOH was slightly higher than thermal oxidation but produced only CO₂. CPO of AcH generated AcOH, a desirable product, as well as formic acid (FA), carbon monoxide (CO) and CO₂, suggesting that multiple reactions occurred. However, the selectivity to AcOH was relatively low (43% at 175 ⁰C, GHSV=20000 h-¹, 2.4V/TiO₂). The selectivity of AcH to AcOH was improved by adjusting temperature, adopting higher vanadium (V) loading catalysts, and increasing oxygen (O₂) concentration. At 200 ⁰C, GHSV=20000 h-¹, and using 6.9V/TiO₂, the selectivity to AcOH increased to 70%. Constant selectivity of all products with respect to residence time indicates the reactions are likely parallel. The rate constant for AcH CPO was calculated assuming an overall 1st order reaction. The linearized Arrhenius law yielded an activation energy of 43.9 kJ/mol for the overall AcH CPO reaction. Simultaneous CPO of AcH and AcOH was also examined. The conversion of AcH in the mixture was similar to the conversion of CPO of AcH alone. This study demonstrated the feasibility of producing AcOH via CPO of AcH. The viability of partial oxidation of pyrolysis oil must be confirmed using model compounds with more complex functional groups and pyrolysis oil.

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