Search

This study systematically investigated the co-slagging characteristics of high-rank coal and biomass ashes considering entrained flow slagging gasifier. Despite favourable performance parameters, coal might not be feasible for entrained flow gasification because of not forming slag within the gasifier operating temperature (1200–1500 °C). To overcome this issue, co-gasification can be a potential solution, which simultaneously helps to reduce the carbon footprint and environmental impact. Hence, this study studied the feasibility of co-gasification of coal and biomass by testing co-slagging behaviour of bituminous coal and pine park biomass ashes. The slag viscosity is measured using a Brookfield DV-III Ultra rheometer coupled with a high-temperature furnace. Results show that pure coal ash does not form slag using the maximum furnace temperature of 1670 °C. However, co-slagging by 50/50 (wt./wt.) ratio of coal and biomass ash (PB50) significantly drops the slagging temperature due to the higher fluxing agents (i.e. CaO) in biomass ash. The temperature of critical viscosity was determined to be 1390 °C using PB50 ash, which maintained the maximum industrial viscosity limit of 25 Pa s up to the temperature of 1360 °C.

In this work, a marine microalga Tetraselmis suecica was pyrolyzed in a fixed-bed reactor in the presence of a series of zeolite (Si/Al = 30) supported Ni catalysts to increase the hydrocarbon composition of the pyrolysis oil by a two-step process - devolatilization followed by catalytic treatment. A 3 wt% Ni-loading on zeolite showed the highest hydrocarbon content of 55.38%, in which aliphatic hydrocarbons and aromatic hydrocarbons were 35.21% and 20.17%, respectively. Besides, the oxygen-containing compounds decreased from 42.88% to 9.55% while the nitrogen-containing compounds decreased from 40.68% to 35.07%. The activity of the Ni-loaded catalysts was found to increase up to 3 wt % Ni-loading and decrease at higher loadings in similar lines to catalyst acidity measurements. Besides, the catalytic activity decreased with an increase in crystallite size of Ni at higher Ni loadings. The results indicate that the Ni-loaded catalysts can deoxygenate pyrolysis oils, but it is necessary to address the removal of the nitrogenous compounds. Pyrolysis temperature and Ni-loading play an important role in the removal of oxygen and nitrogen from the bio-oil. The quality of the bio-oil can be affected by the presence of strong acid sites, nickel-loading and the pore size.

This paper presents an in-depth review of recent research on catalytic pyrolysis of microalgae and suitable approaches for bio-oil upgrading. The performance of three types of catalysts commonly used in pyrolysis, particularly focusing on microalgae pyrolysis are examined and compared. Also, two deoxygenation methods of catalytic pyrolysis and hydrodeoxygenation and two denitrogenation methods of adsorptive denitrogenation and hydrodenitrogenation for microalgae bio-oil upgrading are reviewed. It is evident that metal-loaded zeolites, particularly loaded with Ni and Pd, are the most favourable catalysts for the reduction of oxygen compounds and partial reduction of nitrogenous compounds from the microalgae bio-oil. Alternative methods for nitrogen removal are necessary for the application of microalgae pyrolysis bio-oils. Adsorptive denitrogenation is found to be the method of interest for dealing with the major nitrogen-containing compounds. The potential adsorbents used for denitrogenation include activated carbon, activated alumina and metal-exchanged zeolites; these all can effectively remove the nitrogen-containing compounds. Besides, all of them can be regenerated by solvent washing or thermal treatment up to five times. A multi-step process with the initial step of devolatilization and followed by catalysis and adsorption is necessary for the best removal of oxygeneous and nitrogenous compounds simultaneously from microalgae bio-oil. Though, there are some challenges in production of high-quality bio-oil from catalytic pyrolysis of microalgae, these processes are of interest for application on commercial scale. Further research and development are still required to maximize the yield and improve the quality of bio-oil from fast and catalytic pyrolysis of microalgae.

This study investigates the yield and quality of bio-oil produced from catalytic and non-catalytic pyrolysis of microalgae Chlorella vulgaris using Ni supported zeolite (Si/Al = 30) prepared by two different methods, ion exchange (IE) and wet impregnation (WI) to examine the effect of catalyst preparation methods on the bio-oil quality. The experiments were also conducted to investigate the effect of different temperatures (300–600 °C) and catalyst to algae ratio (1:5, 1:2, 1:1 and 2:1) on the yield and quality of bio-oil. The results showed that catalytic pyrolysis using Ni supported zeolites produced high hydrocarbon, less oxygenated and acid compounds compared to non-catalytic pyrolysis. The catalyst preparation method did not affect the yield but had an effect on the bio-oil composition. The results obtained from this study are useful in developing the catalytic pyrolysis process to refine bio-oils for commercial use.

Mechanism of CO2 adsorption on amine loaded SBA-15 sorbents with varying amine coverage has been assessed using thermogravimetric analysis (TGA) and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). TGA study showed that sorbent adsorption capacities increased by 122–153% with CO2 concentrations (5–80%) in the gas at 50/75 °C. The DRIFTS studies indicate that low amine loaded sorbents exhibit higher uptakes with an increase in CO2 concentrations which is attributed to the mode of CO2 adsorption i.e. 1:1 CO2 to amine forming carbamic acid. At higher amine loadings CO2 is adsorbed following the 1:2 CO2 to amine forming carbamate-ammonium ions pair resulting in lower adsorption capacities per amine site. The studies also showed an increase in carbamic acid formation with pressure from 100 to 500 kPa at low amine loadings and both carbamic acid and carbamates at higher amine loadings. The paper provides insights into the mechanistic understanding of CO2 adsorption behaviour of the varyingly covered amines on the SBA-15 support with a change in concentration and pressure of CO2. The current work presents the conditions to alter the CO2 adsorption mechanism on amine sites with potential application in CO2 conversion to chemicals.

A bench scale, two-stage, thermo-catalytic reactor equipped with a continuous feeding system was used to pyrolyse pure and waste plastics. Experiments using five zeolitic and clay-based catalysts of different forms (pellet and powders) and different plastic feedstocks – virgin HDPE, HDPE w1aste and mixed plastic waste (MPW) were compared to the control experiments – pyrolysis without catalyst. Results indicated that the two pelletized catalysts were the most promising for the conditions employed. Of these two, one with higher acidity and surface area was highly selective for the gasoline fraction (C 5 –C 11 ) giving 80% from the total medium distillate conversion using virgin HDPE as feedstock. It also produced the least amount of olefins (17% for virgin HDPE, 4% for HDPE waste and 2% for MPW) and coke ( 12 –C 25 ) giving 63% from the total medium distillate conversion using virgin HDPE as feedstock. The amount of coke deposited on the catalyst surface depended mainly on the mesopore volume, with less coke deposited as the mesopore volume increased. The variation in catalyst selectivity with acidity strength due to Lewis sites on the catalyst surface controls selectivity towards carbon chain length.

This two-part study firstly investigated Tetraselmis suecica grown in different CO2 (0.04–15% v/v) concentration through indoor and outdoor cultivation systems. A high CO2 concentration led to a high lipid content, and low nitrogen and oxygen content, which are desirable for transport fuel production. Pyrolysis characteristics were investigated by TG-IR and synchrotron IR microscopy. The results show Tetraselmis suecica grown in 10% CO2 had the highest decomposition rate corresponding to more volatile products produced during the main thermal cracking stage and derived from protein-and lipid-corresponding functional groups. Moreover, a high reaction temperature and CO2 concentration resulted in a low retention of surface functional groups. The nitrogen functional groups initially decomposed at a temperature range of 250–300 °C and still remained at 550 °C, while the lipid-corresponding functional groups completely disappeared at a temperature range of 400–500 °C. Besides, the decomposition of chemical components followed the order of carbohydrate, protein and lipid.

Electronic and electrical equipment has become a buzzword in the world of solid waste management and metal recovery due to large volumes of precious metals utilized in the making of these equipment. For the most of the studies nowadays revolve around recovering the metals from e-waste using large amounts of solvents that tend to be highly toxic with a specific limit on the recovery. Electrochemical techniques are vital to convert the metallic ions generated in the first few steps of hydrometallurgy, that is, performing the leaching operations followed by separation using solvent extraction to upgrade to metal ions. Electrochemical processes are utilized to recover the metallic ions to bare metals, which can be later utilized as secondary resources for the metal industries. This chapter focuses on the electrochemical processes to enhance the recovery of these different elements that are being accumulated from the e-waste and further details the solvent, electrode, conditions required for optimizing the migration of the target metals that either present in the electrolytes as leachate or as anode scrap.

Catalytic pyrolysis is a useful technique for the conversion of scrap tyres into liquid fuels. Zeolite catalysts were employed in the pyrolysis of scrap tyres for the production of aromatic rich fuel. Deactivation of zeolite catalysts during pyrolysis reaction was investigated which played an important role in the product quality and composition. Herein, the performance of microporous zeolite catalysts and mesoporous MCM-41 catalyst was evaluated in a two-stage fixed bed reactor for the pyrolysis of scrap tyres. Comparative studies showed the increase in the production of aromatic compounds up to 23.7% over zeolite catalyst as compared to 18.7% over MCM-41 catalyst. However, Zeolite Y catalyst exhibited higher coke formation led to the rapid deactivation. The stability of zeolite catalysts is addressed by the incorporation of Cerium metal within the framework of two zeolite catalysts namely Zeolite Y and ZSM-5 through the ion-exchange technique. Parent and spent catalysts were characterised using synchrotron FT-IR spectroscopy, temperature-programmed desorption of ammonia (NH3-TPD), N2 Physisorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and hydrogen temperature-programmed reduction (H2-TPD). A higher percentage of aromatics were produced over the large pore Zeolite Y. Cerium ion-exchange decreased the formation of coke from 8.1% to 5.7% over submicron and large pore Zeolite Y catalyst. Moreover, naphthalene production decreased over both Ce-Zeolite Y and Ce-ZSM-5.

In-situ synchrotron FTIR studies were conducted using four Victorian brown coals and one Thailand lignite to examine the evolution of functional groups from the surface of the sample during pyrolysis from room temperature to 550 °C. TGA data showed that the pyrolysis of all coals is comprised of a drying stage (30–200 °C) and devolatilization stage (200–900 °C). FTIR data showed that compared to Victorian brown coals, less surface functional groups were found in Thailand lignite. The loss of functional groups from Thailand lignite was observed during drying, and the devolatilization consisted of two stages. For Victorian brown coals, the concentration of oxygen contained hydroxyl and carboxyl groups decreased during the drying stage, due to the removal of water, and breakdown of weakly bonded alkene and alkyne. When temperature gradually increased during devolatilization stage, more functional groups were released. However, by 550 °C, the groups at the wavenumber of 1700–1340 cm−1 (carbonyl, carboxylate, aromatic ring, CH3 and CH2 groups) remained in the sample. Based on the spectra taken of two chars from the same brown coals, these groups were not completely removed until 1000 °C.

In this study, the direct and catalytic pyrolysis of microalgae Tetraselmis suecica was conducted to determine the composition of bio-oil obtained. Thermogravimetric analysis showed that at high heating rate, the decomposition temperature and volatile matter evolution increased. Direct pyrolysis results identified the optimum temperature for bio-oil production to be 400 °C. The bio-oil produced from catalytic pyrolysis showed a decrease in the oxygenated compounds which indicate that the addition of zeolite catalyst (Si/Al = 30, 60) can improve the bio-oil composition. However, zeolite catalyst (Si/Al = 30) showed a higher decrease in the oxygenated compounds compared to (Si/Al = 60). Furthermore, this study found that some functional groups are still present in the char of T . suecica biomass at 550 °C (5 °C/min heating rate), while most already disappeared at 350 °C (150 °C/min heating rate) when using in situ Synchrotron-based Infrared Microscopy.

In this study, the pyrolysis behavior of two lipid-extracted microalgal biomasses, specifically freshwater microalgae Chlorella sp. and marine microalgae Tetraselmis suecica , was examined using a thermogravimetric analyzer. The study assessed the effects of different heating rates (5, 10, and 15 °C/min) on the devolatilization stage and determined the kinetics using the Flyn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. The activation energy and pre-exponential factor values for T. suecica were slightly lower compared with Chlorella sp. and other types of microalgal and lignocellulose biomasses. The results obtained from this study provide useful information for designing a pyrolytic processing system using lipid-extracted microalgal biomass as a feedstock.

Enzymatic saccharification of biomass for reducing sugar production is one of the crucial processes in biofuel production through biochemical conversion. In this study, enzymatic saccharification of dilute potassium hydroxide (KOH) pre-treated Tetraselmis suecica biomass was carried out by using cellulase enzyme obtained from Trichoderma longibrachiatum. Initially, the pre-treatment conditions were optimised by changing alkali reagent concentration, retention time for reaction, and temperature. The T. suecica biomass after pre-treatment was also characterized using Fourier Transform Infrared Spectra and Scanning Electron Microscope. These analyses revealed that the functional group such as acetyl and hydroxyl groups, structure and surface of T. suecica biomass were changed through pre-treatment, which is favourable for enzymatic saccharification process. Comparison of enzymatic saccharification of untreated and pre-treated microalgal biomass indicated that higher level of reducing sugar can be obtained from pre-treated T. suecica. Enzymatic saccharification of pre-treated T. suecica biomass was optimised by changing temperature, pH, and enzyme concentration to solid ratio ([E]/[S]). Highest conversion of carbohydrate into reducing sugar of 95% amounted to reducing sugar yield of 20 (wt%) from pre-treated T. suecica was obtained from saccharification, at temperature: 40°C, pH: 4.5 and [E]/[S] of 0.1 after 72 h of incubation. Hydrolysate obtained from enzymatic saccharification of pretreated T. suecica biomass was further fermented into biobutanol using Clostridium saccharoperbutyliticum as biocatalyst. The results from this study demonstrate a positive prospect of application of dilute alkaline pre-treatment to enhance enzymatic saccharification and biobutanol production from microalgal biomass., {"references":["Naik, S.N., Goud, V.V., Rout, P.K., Dalai, A.K. (2010) Production of\nfirst and second generation biofuels: A comprehensive review. Renew\nSust Energ Rev 14: 578-597.","Dürre, P. (2007) Biobutanol: An attractive biofuel. Biotechnol J 2: 525-\n1534.","Jang, Y.S., Malaviya, A., Cho, C., Lee, J., Lee, S.Y. (2012) Butanol\nproduction from renewable biomass by Clostridia. Bioresource Technol\n123: 653-663.","Qureshi, N., Ezeji, T.C. (2008) Butanol, 'a superior biofuel' production\nfrom agricultural residues (renewable biomass): recent progress in\ntechnology. Biofuels, Bioprod Bior 2: 319-330.","Ellis, J.T., Hengge, N.N., Sims, R.C., Miller, C.D. (2012) Acetone,\nbutanol, and ethanol production from wastewater algae. Bioresource\nTechnol 111: 491-495.","Harun, R., Singh, M., Forde, G.M., Danquah, M.K. (2010) Bioprocess\nengineering of microalgae to produce a variety of consumer products.\nRenew Sust Energ Rev 14: 1037-1047.","Balat, M. (2011) Production of bioethanol from lignocellulosic materials\nvia the biochemical pathway: A review. Energ Convers Manage 52: 858-\n875.","Harun, R., Danquah, M.K. (2011) Enzymatic hydrolysis of microalgal\nbiomass for bioethanol production. Chem Eng J, 168: 1079-1084.","Zeng, X., Danquah, M.K., Halim, R., Yang, S., Chen, X.D., Lu, Y.\n(2013) Comparative physicochemical analysis of suspended and\nimmobilized cultivation of Chlorella sp. J Chem Technol Biotechnol 88:\n247-254.\n[10] Nielsen, S.S. (2010) Phenol-Sulfuric Acid Method for Total\nCarbohydrates, Food Analysis Laboratory Manual, Springer US2010,\npp. 47-53.\n[11] González López, C.V., García, M.D.C.C., Fernández, F.G.A., Bustos,\nC.S., Chisti, Y., Sevilla, J.M.F. (2010) Protein measurements of\nmicroalgal and cyanobacterial biomass. Bioresource Technol 101: 7587-\n7591.\n[12] McIntosh, S., Vancov, T. (2010) Enhanced enzyme saccharification of\nSorghum bicolor straw using dilute alkali pretreatment. Bioresource\nTechnol. 101: 6718-6727.\n[13] Saha, B.C., Cotta, M.A. (2008) Lime pretreatment, enzymatic\nsaccharification and fermentation of rice hulls to ethanol. Biomass\nBioenerg 32: 971-977.\n[14] Baadhe, R.R., Potumarthi, R., Mekala, N.K. (2014) Influence of dilute\nacid and alkali pretreatment on reducing sugar production from corncobs\nby crude enzymatic method: A comparative study. Bioresource Technol\n162: 213-217.\n[15] Rawat, R., Kumbhar, B.K., Tewari, L. (2013) Optimization of alkali\npretreatment for bioconversion of poplar (Populus deltoides) biomass\ninto fermentable sugars using response surface methodology. Ind Crop\nProd 44: 220-226.\n[16] Kim, S., Holtzapple, M.T. (2005) Lime pretreatment and enzymatic\nhydrolysis of corn stover. Bioresource Technol 96: 1994-2006.\n[17] Zhu, L., O'Dwyer, J.P., Chang, V.S., Granda, C.B., Holtzapple, M.T.\n(2008) Structural features affecting biomass enzymatic digestibility,\nBioresource Technol 99: 3817-3828.\n[18] Chen, Y., Stevens, M.A., Zhu, Y., Holmes, J., Xu, H. (2013)\nUnderstanding of alkaline pretreatment parameters for corn stover\nenzymatic saccharification. Biotechnol Biofuels 6: 1-10.\n[19] Lima, M.A., Lavorente, G.B., Silva, H.K.D., Bragatto, J., Rezende,\nC.A., Bernardinelli, O.D., deAzevedo, E.R., Gomez, L.D., McQueen-\nMason, S.J., Labate, C.A., Polikarpov, I. (2013) Effects of pretreatment\non morphology, chemical composition and enzymatic digestibility of\neucalyptus bark: a potentially valuable source of fermentable sugars for\nbiofuel production – part 1. Biotechnol Biofuels 6: 1-17.\n[20] Grierson, S., Strezov, V., Shah, P. (2011) Properties of oil and char\nderived from slow pyrolysis of Tetraselmis chui. Bioresource Technol\n102: 8232-8240.\n[21] Siengchum, T., Isenberg, M., Chuang, S.S.C. (2013) Fast pyrolysis of\ncoconut biomass – An FTIR study. Fuel 105: 559-565.\n[22] Kumar, L., Chandra, R., Saddler, J. (2011) Influence of steam\npretreatment severity on post-treatments used to enhance the enzymatic\nhydrolysis of pretreated softwoods at low enzyme loadings. Biotechnol\nBioeng 108: 2300-2311.\n[23] Sun, X.F., Xu, F., Sun, R.C., Fowler, P., Baird, M.S. (2005)\nCharacteristics of degraded cellulose obtained from steam-exploded\nwheat straw. Carbohyd Res 340: 97-106.\n[24] Laureano-Perez, L., Teymouri, F., Alizadeh, H., Dale, B. (2005)\nUnderstanding factors that limit enzymatic hydrolysis of biomass. Appl\nBiochem Biotechnol, 124: 1081-1099.\n[25] Gautam, S.P., Bundela, P.S., Pandey, A.K., Khan, J., Awasthi, M.K.,\nSarsaiya, S. (2011) Optimization for the production of cellulase enzyme\nfrom municipal solid waste residue by two novel cellulolytic fungi.\nBiotechnol Res Intern 1-8.\n[26] Andreaus, J., Azevedo, H., Cavaco-Paulo, A. (1999) Effects of\ntemperature on the cellulose binding ability of cellulase enzymes. J Mol\nCatal B: Enzym 7: 233-239.\n[27] Hamzah, F., Idris, A., Shuan, T.K. (2011) Preliminary study on\nenzymatic hydrolysis of treated oil palm (Elaeis) empty fruit bunches\nfibre (EFB) by using combination of cellulase and β 1-4 glucosidase.\nBiomass Bioenerg 35: 1055-1059.\n[28] Xu, Z., Wang, Q., Jiang, Z., Yang, X.X., Ji, Y. (2007) Enzymatic\nhydrolysis of pretreated soybean straw. Biomass Bioenerg 31: 162-167."]}