Supercritical water gasification of lignocellulosic biomass materials for hydrogen production

The primary aim of this research is to optimize supercritical water gasification process operating conditions and develop a cost effective heterogeneous catalyst to reduce reaction temperature and improve H2 yield. Furthermore, a detailed techno- economic feasibility study was performed to evaluate the economic feasibility of SCWG process. The work plan is divided into five phases. In the phase one, model lignocellulosic biomass comprising of cellulose, hemicellulose and lignin were selected as the feedstock for SCWG process optimization. The objective of the study was to optimize the process conditions, propose a detailed reaction pathway for model compounds and understand how each intermediate product behaves under subcritical and supercritical conditions. The response surface methodology using the Box-Behnken design was applied for the first time to optimize the process parameters during subcritical and supercritical water gasification of cellulose. The process parameters investigated include temperature (300-500 °C), reaction time (30-60 min) and feedstock concentration (10-30 wt%). Temperature was found to be the most significant factor that influenced the yields of hydrogen and total gas yield. Among the three model compounds, hydrogen yields increased in the order of lignin (0.73 mmol/g) < cellulose (1.95 mmol/g) < xylose (2.26 mmol/g). Based on the gas yields from these model compounds, a reaction pathway of model lignocellulosic biomass decomposition in supercritical water was proposed. The results from the first phase raised several research questions, for example, does biomass heterogeneity have an effect on product yield? How far are the batch experimental results from equilibrium values when considering a real feedstock? Lignocellulosic biomass is heterogeneous in nature and it comprises of several molecules of different compounds including cellulose, hemicellulose, and lignin along with extractives. Lignocellulosic biomass (soybean straw and flax straw) were gasified under similar conditions as those of the model compounds in Phase two. Soybean straw exhibited superior H2 yield (6.62 mmol/g) and total gas yield (14.91 mmol/g). Similarly, the gaseous products from soybean straw showed improved lower heating value (1592 kJ/Nm3). The experimental results showed slight deviations from the thermodynamic models which could be as a result of temperature gradient and absence of agitation in the batch reactor. In the third phase, several Ni-based catalysts were screened and tested for SCWG of soybean straw. The aim is to develop a cost-effective heterogeneous catalyst that could improve the gas yields towards equilibrium values and lower the reaction temperature. All experiments were performed at the desired operating conditions identified in Phase 2. A comprehensive screening of different support materials ranging from activated carbon (AC), carbon nanotubes (CNT), ZrO2, Al2O3, SiO2 and Al2O3-SiO2 was performed at 10 wt% Ni loading. The effectiveness of each support in improving H2 yield and selectivity was in the order: ZrO2 > Al2O3 > AC > CNT > SiO2 > Al2O3-SiO2. The effect of three promoters (i.e. Na, K and Ce) added to the supported Ni/ZrO2 catalysts was evaluated. Ce promoter was found to be the best for ZrO2 supported Ni catalysts. The performance of Ce was attributed to its high capacity for storing oxygen species which have the ability to react with the carbon deposits on the surface of the catalysts thereby preventing carbon deposition. The objective of the fourth phase was to study the kinetics of Ni - Ce/ZrO2 catalyzed SCWG of soybean straw. The lumped parameter kinetics method was employed with several reactions resulting from the experimental results in Phase three and the proposed reaction pathway in Phase one. The pathways were used to develop the kinetic equations. Kinetic model results were found to correlate with experimental results. Furthermore, the kinetic model was used to predict experimental yields for long residence time. The kinetics results are also in agreement with thermodynamic predictions. In the last phase, a detailed techno-economic evaluation and sensitivity analysis was performed for a conceptual design for hydrogen production from soybean straw gasification in SCW. The economic feasibility of hydrogen production was evaluated based on a discounted cash flow analysis. Economic analysis suggested a minimum selling price of U.S. $1.94/kg for hydrogen. The cost is relatively low when compared with that of hydrogen produced from other biomass conversion processes. Besides, the net rate of return (NRR) estimated was 37.1%. A positive NRR value indicates that the project is profitable from an economic perspective. Sensitivity analysis indicates that the minimum selling price of hydrogen is affected by the feedstock price, utility cost, tax rate and labor cost

Modelling of sorption-enhanced steam reforming (SE-SR) process in fluidised bed reactors for low-carbon hydrogen production: A review

Sorption-enhanced steam reforming (SE-SR) offers lower capital costs than conventional steam reforming with carbon capture, which arises from the compact makeup that allows reforming and CO2 capture to occur in a single reactor. However, the technology readiness level (TRL) of SE-SR technology is currently low and large-scale deployment can be expedited by ramping up activities in reactor modelling and validation at pilot scale. This work first explores the concept of SE-SR technology, then the experimental activities and pilot tests performed for this technology, followed by the review of progress made on SE-SR modelling. It was found that the Eulerian-Eulerian two-fluid model is the most popular approach widely adopted for modelling SE-SR in fluidised bed reactors. However, the averaging method used to close equations ignores flow details at particle level and simplifies the particle system. Moreover, while hydrogen purity and yield have been predicted within an acceptable error, larger errors for CO2 gas output relative to experimental data have been reported for this model type. Limitations and future perspectives for reactor designs and the various models and modelling approaches are also analysed, to provide guidance and advance research, modelling and scaleup of SE-SR technology

Catalytic Conversion of Biomass-Derived Polyols to Value-Added Chemicals: Catalysis and Kinetics

Replacing fossil-based feedstocks with biomass to produce renewable fuels and chemicals is one of the major sustainability challenges facing human society. In this context, catalytic upgrading of non-food bio-derived polyols, including glycerol, erythritol, xylitol, sorbitol and mannitol, on heterogeneous catalysts attracts increasing attentions, because it will provide alternative routes for the production of fuels and chemicals. However, several issues are plaguing current technologies: (a) high oxygen contents in these C3~6 polyols demand several difficult steps of deoxygenation, which require elevated reaction temperature (T = 220~300 oC) and high operating pressure of hydrogen; (b) conversion under such harsh conditions involving multi-phase, multi-step and multi-component reactions results in low selectivity towards desired products, loss of large quantities of carbon to less valuable wastes and (c) fast deactivation of catalysts due to poor intrinsic activity and stability. The present work successfully demonstrates that, by rational design of multi-functional metal-based catalytic systems, conversion of various biopolyols to valuable megaton everyday chemicals, such as 1,2-propanediol, ethylene glycol, lactic acid and alcohols, can occur in one pot process under significantly milder reaction conditions with improved efficiency. Detailed investigation on C-C/C-O cleavage revealed possible reaction pathways and mechanism of polyols on metal based catalysts. Therefore design of multi-functional metal catalysts was achieved. It was for the first time to demonstrate that Cu catalysts exhibited an excellent C-C and C-O cleavage activity by immobilizing active sites for retro-aldol, dehydration and hydrogenolysis on one single catalyst, leading to 98% yield towards liquid products. Studies on reaction parameters and surface characterization enabled the establishment of activity-performance correlation for polyol conversion. Further, by rational combining hydrogen generation and hydrogenolysis functionality to one metal catalyst, conversion of biopolyols occurred at only 115~160 oC even without adding external hydrogen, with 95%+ overall atom efficiency. Detailed kinetic modeling revealed that the reaction potential for hydrogen generation and hydrogenolysis is much lower on Pt/C catalyst. This is a significant advancement compared with conventional technologies. In collaboration with material scientists, mono and bimetallic Cu-based catalysts with predominant active [111] surface plane were also designed via lattice match engineering. The Cu nanocatalysts exhibited more than five-fold enhancement in activity compared to traditional ones and selectivity promoted dehydrogenation thus lactic acid was favorably formed in our system. The methodologies and achieved results in this work will provide insights on the further studies on rational design of biomass conversion as well as other chemical processes

Production of Biofuels and Numerical Modeling of Chemical Combustion Systems

Biofuels have recently attracted a lot of attention, mainly as alternative fuels for applications in energy generation and transportation. The utilization of biofuels in such controlled combustion processes has the great advantage of not depleting the limited resources of fossil fuels while leading to emissions of greenhouse gases and smoke particles similar to those of fossil fuels. On the other hand, a vast amount of biofuels are subjected to combustion in small-scale processes, such as for heating and cooking in residential dwellings, as well as in agricultural operations, such as crop residue removal and land clearing. In addition, large amounts of biomass are consumed annually during forest and savanna fires in many parts of the world. These types of burning processes are typically uncontrolled and unregulated. Consequently, the emissions from these processes may be larger compared to industrial-type operations. Aside from direct effects on human health, especially due to a sizeable fraction of the smoke emissions remaining inside residential homes, the smoke particles and gases released from uncontrolled biofuel combustion impose significant effects on the regional and global climate. Estimates have shown the majority of carbonaceous airborne particulate matter to be derived from the combustion of biofuels and biomass. “Production of Biofuels and Numerical Modelling of Chemical Combustion Systems” comprehensively overviews and includes in-depth technical research papers addressing recent progress in biofuel production and combustion processes. To be specific, this book contains sixteen high-quality studies (fifteen research papers and one review paper) addressing techniques and methods for bioenergy and biofuel production as well as challenges in the broad area of process modelling and control in combustion processes

Book of abstracts of the 10th International Chemical and Biological Engineering Conference: CHEMPOR 2008

This book contains the extended abstracts presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, over 3 days, from the 4th to the 6th of September, 2008. Previous editions took place in Lisboa (1975, 1889, 1998), Braga (1978), Póvoa de Varzim (1981), Coimbra (1985, 2005), Porto (1993), and Aveiro (2001). The conference was jointly organized by the University of Minho, “Ordem dos Engenheiros”, and the IBB - Institute for Biotechnology and Bioengineering with the usual support of the “Sociedade Portuguesa de Química” and, by the first time, of the “Sociedade Portuguesa de Biotecnologia”. Thirty years elapsed since CHEMPOR was held at the University of Minho, organized by T.R. Bott, D. Allen, A. Bridgwater, J.J.B. Romero, L.J.S. Soares and J.D.R.S. Pinheiro. We are fortunate to have Profs. Bott, Soares and Pinheiro in the Honor Committee of this 10th edition, under the high Patronage of his Excellency the President of the Portuguese Republic, Prof. Aníbal Cavaco Silva. The opening ceremony will confer Prof. Bott with a “Long Term Achievement” award acknowledging the important contribution Prof. Bott brought along more than 30 years to the development of the Chemical Engineering science, to the launch of CHEMPOR series and specially to the University of Minho. Prof. Bott’s inaugural lecture will address the importance of effective energy management in processing operations, particularly in the effectiveness of heat recovery and the associated reduction in greenhouse gas emission from combustion processes. The CHEMPOR series traditionally brings together both young and established researchers and end users to discuss recent developments in different areas of Chemical Engineering. The scope of this edition is broadening out by including the Biological Engineering research. One of the major core areas of the conference program is life quality, due to the importance that Chemical and Biological Engineering plays in this area. “Integration of Life Sciences & Engineering” and “Sustainable Process-Product Development through Green Chemistry” are two of the leading themes with papers addressing such important issues. This is complemented with additional leading themes including “Advancing the Chemical and Biological Engineering Fundamentals”, “Multi-Scale and/or Multi-Disciplinary Approach to Process-Product Innovation”, “Systematic Methods and Tools for Managing the Complexity”, and “Educating Chemical and Biological Engineers for Coming Challenges” which define the extended abstracts arrangements along this book. A total of 516 extended abstracts are included in the book, consisting of 7 invited lecturers, 15 keynote, 105 short oral presentations given in 5 parallel sessions, along with 6 slots for viewing 389 poster presentations. Full papers are jointly included in the companion Proceedings in CD-ROM. All papers have been reviewed and we are grateful to the members of scientific and organizing committees for their evaluations. It was an intensive task since 610 submitted abstracts from 45 countries were received. It has been an honor for us to contribute to setting up CHEMPOR 2008 during almost two years. We wish to thank the authors who have contributed to yield a high scientific standard to the program. We are thankful to the sponsors who have contributed decisively to this event. We also extend our gratefulness to all those who, through their dedicated efforts, have assisted us in this task. On behalf of the Scientific and Organizing Committees we wish you that together with an interesting reading, the scientific program and the social moments organized will be memorable for all.Fundação para a Ciência e a Tecnologia (FCT

Production of oxygenated fuel additive from glycerol

Glycerol ethers have the potential to be used as additives with biodiesel as it can be easily blended and can improve fuel performance. It also facilitates easier passing of fuel through injector. Addition of glycerol ether increases the cetane number and improves the antiknocking property. Glycerol ethers are produced by reacting glycerol with tert-butanol (TBA). To initiate the etherification reaction between two alcohols (glycerol and tert-butanol) on solid acid catalyst, acidity of catalyst is one of the primary requirement since the production of protonated molecules in the reaction mixture is crucial. In this work, acidic solid catalysts were developed by the impregnation of heteropolyacids (HPA, H3PW12O40) on SBA-15 support. The SBA – 15 was prepared by hydrothermal method using P123 polymer, HCl, water and tetra ethyl ortho silicate (TEOS). Textural properties of the support were determined using N2 – physisorption method and it was found that the surface area, pore volume and average pore diameters were 819 m2/g, 1.14 cc/g and 5.02 nm, respectively. The pore volume can accommodate higher amount of HPA. HPA is acidic in nature and impregnation of HPA on support can develop the acidic functional groups. Generally, HPA is highly soluble in alcohol and addition of Cesium (Cs) can exchange the proton from HPA and inhibit the solubility by the formation of CsxH3-xPW12O40. Three different catalyst samples were prepared by changing the Cesium (x) wt% (for x = 1.5, 2.2 and 2.9) on SBA-15 using incipient wetness method. These samples were dried at 120 ˚C for 2 hours and then calcined at 300 ˚C for 3 hours. The catalysts were characterized by N2 physisorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), elemental analysis (inductively coupled plasma mass spectroscopy, ICP-MS), thermogravimetric/differential thermal analyzer (TG/DTA), scanning electron microscopy (SEM), and temperature programmed desorption of ammonia (NH3-TPD). The progressive reduction in textural properties of the support with HPA loading is identified in BET-Surface area. The enhancement of functional groups is indicated in FTIR. And also the change in crystalline nature is identified in XRD. The screened catalyst was used for etherification of glycerol. Etherification of glycerol with TBA was performed in 100 ml autoclave and the product consists of mono, di and tri-tert butyl glycerol ethers along with some unreacted glycerol. The effects of various reaction parameters such as temperature, catalyst loading and molar ratio (glycerol/TBA) were studied to obtain an optimized condition for etherification of glycerol. Maximum conversion 76% of glycerol was achieved at the conditions of 120 °C, 1 MPa, 1:5 molar ratio (glycerol/TBA), 3% (w/v) catalyst loading and 800 rpm for 5 hours. The kinetic studies were performed and a mathematical model was developed using Langmuir-Hinshelwood mechanism. The reaction rate followed second order kinetics and the activation energy of 78 kJ/mol for the reaction signifies that the reaction was kinetically controlled

Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration

In this book, we propose a collection of scientific and review articles on the production of hydrogen. The articles focus on the controlled storage and release of hydrogen; on the production of hydrogen from reforming from renewable sources, water splitting, and biological and photonic methods; on the intensification of the water gas shift process; and on the integration with purification methods such as pressure swing adsorption

Catalytic Processes for The Valorisation of Biomass Derived Molecules

In the last decades, inedible lignocellulosic biomasses have attracted significant attention for being abundant resources that are not in competition with agricultural land or food production and, therefore, can be used as starting renewable material for the production of a wide variety of platform chemicals. The three main components of lignocellulosic biomasses are cellulose, hemicellulose and lignin, complex biopolymers that can be converted into a pool of platform molecules including sugars, polyols, alchols, ketons, ethers, acids and aromatics. Various technologies have been explored for their one-pot conversion into chemicals, fuels and materials. However, in order to develop new catalytic processes for the selective production of desired products, a complete understanding of the molecular aspects of the basic chemistry and reactivity of biomass derived molecules is still crucial. This Special Issue reports on recent progress and advances in the catalytic valorization of cellulose, hemicellulose and lignin model molecules promoted by novel heterogeneous systems for the production of energy, fuels and chemicals