One-pot Aldol Condensation and Hydrodeoxygenation of Biomass-derived Carbonyl Compounds for Biodiesel Synthesis (original) (raw)

Thermo-catalytic process for conversion of lignocellulosic biomass to fuels and chemicals: a review

International Journal Of Petrochemical Science & Engineering

Fossil fuels, the dominant source of energy in today's modern civilization has significant negative impact on global climate change. The lignocellulosic biomass can be a more sustainable replacement of fossil fuel in the production of transportation fuels and petrochemical feedstock. However, high concentration of oxygen functionalized compounds in biomass presents a major challenge in the development of biomass technology. For a biomass conversion to be efficient, achieving faster heating rate >10°C/s of the solid biomass is the key to achieve higher liquid yield and lower coke make. In the fast pyrolysis, There are again two major approaches: i. Thermal pyrolysis of biomass and subsequent separate treatment of bio-oil ii. Combining catalytic fast pyrolysis within-situ upgrading of the generated bio oil in a single reactor system. The bio-oil produced by the first approach can be co-processed in an existing secondary conversion unit of a refinery, such as FCC or hydroprocessing. Fluidized bed has proven to be the best reactor for biomass pyrolysis in both the approaches i.e. thermal or catalytic, mainly due to the excellent heat/ mass transfer rate and high solid handling flexibility of fluidized system. However, the major challenges, following the second approach i.e. the catalytic fast pyrolysis is to achieve high degree of de-oxygenation, while retaining maximum C and H within the liquid. Good de-oxygenation >70% is essential to get a stable liquid product with acceptable corrosivity. The other challenge is the fast deactivation of catalyst due to the impurities present in biomass, specifically K > 5 ppm. Upgrading the bio oil quality to achieve the high standard of transportation fuel requires costly multi step high pressure hydroprocessing system. Thus the new advent is to directly produce olefins and aromatics from biomass which not only helps to enhance the product value but also greatly minimizes the need of too much hydrotreating Figure 1.

Recent research progress on bio-oil conversion into bio-fuels and raw chemicals: a review

Journal of Chemical Technology & Biotechnology, 2018

Recent advances in lignocellulosic biomass valorization for producing fuels and commodities (olefins and BTX aromatics) are gathered in this paper, with a focus on the conversion of bio-oil (produced by fast pyrolysis of biomass). The main valorization routes are: i) conditioning of bio-oil (by esterification, aldol condensation, ketonization, in situ cracking, and mild hydrodeoxygenation) for its use as a fuel or stable raw material for further catalytic processing; ii) production of fuels by deep hydrodeoxygenation; iii) ex situ catalytic cracking (in line) of the volatiles produced in biomass pyrolysis, aimed at the selective production of olefins and aromatics; iv) cracking of raw bio-oil in units designed with specific objectives concerning selectivity, and; v) processing in fluidized bed catalytic cracking (FCC) units. This review deals with the technological evolution of these routes, in terms of catalysts, reaction conditions, reactors, and product yields. A study has been carried out on the current state-of-knowledge of the technological capacity, advantages and disadvantages of the different routes, as well as on the prospects for the implementation of each route within the scope of the Sustainable Refinery.

Catalytic conversion of biomass to biofuels

Green Chemistry, 2010

Biomass has received considerable attention as a sustainable feedstock that can replace diminishing fossil fuels for the production of energy, especially for the transportation sector. The overall strategy in the production of hydrocarbon fuels from biomass is (i) to reduce the substantial oxygen content of the parent feedstock to improve energy density and (ii) to create CC bonds between biomass-derived intermediates to increase the molecular weight of the final hydrocarbon product. We begin this review with a brief overview of first-generation biofuels, specifically bioethanol and biodiesel. We consider the implications of utilizing starchy and triglyceride feedstocks from traditional food crops, and we provide an overview of second-generation technologies to process the major constituents of more abundant lignocellulosic biomass, such as thermochemical routes (gasification, pyrolysis, liquefaction) which directly process whole lignocellulose to upgradeable platforms (e.g., synthesis gas and bio-oil). The primary focus of this review is an overview of catalytic strategies to produce biofuels from aqueous solutions of carbohydrates, which are isolated through biomass pretreatment and hydrolysis. Although hydrolysis-based platforms are associated with higher upstream costs arising from pretreatment and hydrolysis, the aqueous solutions of biomass-derived compounds can be processed selectively to yield hydrocarbons with targeted molecular weights and structures. For example, sugars can be used as reforming feedstocks for the production of renewable hydrogen, or they can be dehydrated to yield furfurals or levulinic acid. For each of the platforms discussed, we have suggested relevant strategies for the formation of CC bonds, such as aldol condensation of ketones and oligomerization of alkenes, to enable the production of gasoline, jet, and Diesel fuel range hydrocarbons. Finally, we address the importance of hydrogen in biorefining and discuss strategies for managing its consumption to ensure independence from fossil fuels.

Biodiesel Production by Using Heterogeneous Catalysts

Alternative Fuel, 2011

While transesterification is an equilibrium reaction between esters and alcohols, the reaction may be under kinetic control before thermodynamic equilibrium is achieved, and this would favor the formation of monoalkyl esters (Meneghetti et al., 2006). The transesterification reaction produces two liquid phases: alkyl esters and crude glycerol (the heavier liquid). In a typical stirred tank reactor, glycerol is collected at the bottom after some time of settling. Phase separation can be observed within short time (approximate 10 minutes) and can be complete within 2 to 20 h, when the reaction is carried out at laboratory scale (Demirbas, 2005). In the case of alcohols, these can be primary or secondary monohydric aliphatic alcohols having from 1 to 8 carbon atoms. Among the alcohols that have been used to produce biodiesel, either homogeneously or heterogeneously, are methanol, ethanol, propanol, isopropanol, butanol, pentanol and amyl alcohol (Demirbas, 2005; Fukuda et al., 2001; Meneghetti et al., 2006). The use of methanol is advantageous as it can quickly react with triglycerides (polar and shortest chain alcohol) and is a relatively inexpensive alcohol, while the same reaction using ethanol has as drawback that the produced ethyl esters are less stable and a carbon residue is observed after reaction. The use of ethanol as solvent, however, is becoming more popular since this alcohol is a renewable resource and does not raise the same toxicity concerns than methanol (Demirbas, 2005; Geise, 2002; Meneghetti et al., 2006). Similar yields of biodiesel can be obtained using either methanol or ethanol. With the former, however, mild reaction temperature (approximately 60 °C) can be employed, whereas for the latter and other alcohols (butanol) at similar molar ratios higher temperatures (75 and 114 °C, respectively) are required for optimum conversion (Geise, 2002). Also, the reaction time is shorter in the methanolysis because of the physical and chemical properties of methanol: polar character and the short chain alcohol. For instance, Meneghetti et al. (2006) reported that the production of biodiesel from castor oil was faster with methanol compared with ethanol. In such a study, maximum yields of esters were obtained after 1h of reaction time with methanol or 5 h with ethanol. Biodiesel is usually prepared in the presence of homogeneous base or acid catalysts. With homogenous base catalysts (sodium and potassium hydroxides, carbonates, sodium and potassium alkoxides, principally) the reaction is faster than with acid catalysts (sulfuric acid, phosphoric acid, hydrochloric and sulfonic acid principally) (Fukuda et al., 2001; Ma & Hanna, 1999). However, the main disadvantage of the aforementioned homogeneous catalysts is the undesirable production of both, soap and glycerol. This fact increases the production costs. On the other hand, heterogeneous catalysts could improve the synthesis methods by eliminating the neutralization salts in the glycerol and therefore the number of separation steps can be reduced (MacLeod et al., 2008). Also, heterogeneous catalysts exhibit a less corrosive character and can be used in a fixed-bed reactor, leading to safer, cheaper and more environment-friendly operation (Dossin et al., 2006b). In addition to the type of catalyst, important parameters of the transesterification reaction are the molar ratio of a l c o h o l , t y p e o f a l c o h o l , t e m p e r a t u r e , r e a c t i o n t i m e a n d d e g r e e o f r e f i n e m e n t o f t h e vegetable oil (

Diesel production from lignocellulosic residues: trends, challenges and opportunities

Biofuels, Bioproducts and Biorefining (Biofpr) , 2024

This article aims to review the various techniques used to produce diesel from lignocellulosic biomass. Data were collected using the Web of Science database to identify trends, barriers, and prospects associated with the alternative methods used. The analysis reviewed 359 papers published between 2006 and 2021, focusing on three key areas: biomass pretreatment, biomass conversion, and biorefining. Pretreatment technologies require extensive research to reduce excessive energy and reagent consumption, thereby reducing overall costs. Fast pyrolysis and lipid-producing microorganisms have been shown to be the most promising conversion routes due to their versatility in utilizing different lignocellulosic residues and producing a wide range of marketable co-products. The most widely used method used for refining is hydroprocessing coupled with catalysts, with the objective of improving biooil quality. Two of the main challenges are the excessive cost of the overall process and the limitations imposed by the technology. These limitations require processing optimization to achieve sustainable production and valuable co-products. The growth of lignocellulosic diesel production will depend on the integration with other biodiesel and biofuel production processes by the optimization of new processes and the generation of new bioproducts to increase efficiency and reduce costs for commercial viability.

Catalytic Conversion of Lignocellulosic Biomass into Fuels and Value-Added Chemicals

Fuel Processing and Energy Utilization, 2019

Biomass as a renewable and abundantly available carbon source is a promising alternative to fossil resources for the production of chemicals and fuels. The development of biobased chemistry, along with catalyst design, has received much research attention over recent years. However, dedicated reactor concepts for the conversion of biomass and its derivatives are a relatively new research field. Continuous flow microreactors are a promising tool for process intensification, especially for reactions in multiphase systems. In this work, the potential of microreactors for the catalytic conversion of biomass derivatives to value-added chemicals and fuels is critically reviewed. Emphases are laid on the biphasic synthesis of furans from sugars, oxidation and hydrogenation of biomass derivatives. Microreactor processing has been shown capable of improving the efficiency of many biobased reactions, due to the transport intensification and a fine control over the process. Microreactors are expected to contribute in accelerating the technological development of biomass conversion and have a promising potential for industrial application in this area.