Renewable Hydrocarbon Research Articles

Conversion of glycerol into renewable hydrocarbons employing platinum and iron catalysts supported on mixed zirconium and aluminum oxides

Conversion of glycerol into renewable hydrocarbons employing platinum and iron catalysts supported on mixed zirconium and aluminum oxides

Pathway elucidation and heterologous reconstitution of the long‐chain alkane pentadecane biosynthesis from Pogostemon cablin

SummaryVery‐long‐chain (VLC) alkanes are major components of hydrophobic cuticular waxes that cover the aerial epidermis of land plants, serving as a waterproofing barrier to protect the plant against environmental stresses. The mechanism of VLC‐alkane biosynthesis has been extensively elucidated in plants. However, little is known about the biosynthesis of long‐chain alkanes (LC, C13 ~ C19) such as pentadecane in plants. Alkanes with different chain lengths are also major constituents of fossil fuels and thus the discovery of the alkane biosynthetic machinery in plants would provide a toolbox of enzymes for the production of renewable hydrocarbon sources and next generations of biofuels. The top leaves of Pogostemon cablin at young stage accumulate large amounts of LC‐alkane pentadecane, making this plant an excellent system for the elucidation of LC‐alkane biosynthetic machinery in plant. We show here that LC‐alkane pentadecane biosynthesis in P. cablin involves an endoplasmic reticulum (ER)‐localized complex made of PcCER1‐LIKE3 and PcCER3, homologues of Arabidopsis ECERIFERUM1 (AtCER1) and AtCER3 proteins that are involved in Arabidopsis VLC‐alkane biosynthesis. We reconstitute the biosynthesis of pentadecane in Nicotiana benthamiana by co‐expression of PcCER1‐LIKE3 and PcCER3 and further improve its production by silencing multifunctional acetyl‐CoA carboxylases involved in fatty acid elongation pathway. Taken together, we uncovered the key biosynthetic machinery of LC‐alkane pentadecane in P. cablin and demonstrated that using these newly identified enzymes to engineer this LC‐alkane for liquid biofuel production in a heterologous plant host is possible.

Production of renewable hydrocarbons through hydrodeoxygenation of crude oil from microalgae Scenedesmus sp. with “in-situ” hydrogen production

Production of renewable hydrocarbons through hydrodeoxygenation of crude oil from microalgae Scenedesmus sp. with “in-situ” hydrogen production

3D Printable Materials Based on Renewable Polymers from Terpene Alcohols and Calcium Carbide

AbstractThe transition to a sustainable future requires the use of waste‐free technologies for production. Potentially, additive technologies can be a promising approach for accessing circular economy due to the precise amount of feeding materials and the absence of molds. However, the initial feeding materials for additive approaches are often based on non–renewable hydrocarbon sources. This work focused on the use of polymers derived from terpene alcohols to develop a filament suitable for 3D printing. Initially, the vinylation of menthol using calcium carbide was optimized and scaled up, then a series of terpenyl–based vinyl ethers were obtained under optimal conditions. The cationic polymerization of vinyl ethers was also scaled up and resulted in 99 % yield of the polymers, which was subsequently subjected to hot extrusion. The initial terpenol was used as an additive to increase polymer flexibility. The addition of menthol (30 wt %) to polyvinyl menthol led to the suitable filament. Using the filament, a series of objects were 3D printed at 125 °C. The material demonstrated good sinterability and adhesion to glass and shrinkage comparable to that of commercial 3D printing filaments. Furthermore, the polymers obtained were used as additives to enhance the adhesion of commercially available filaments.

Catalytic pyrolysis of apricot kernel shell over metal supported MCM-41 catalysts obtained by synthesizing sonochemical method

In this study, it is targeted to examine the efficiency of metal supported MCM-41 catalysts on the liquid product yield from pyrolysis process of apricot kernel shell selected as a biomass and to characterize the pyrolysis liquids. In the non-catalytic pyrolysis experiments, the maximum liquid yield is obtained as 21.41 % at 500 °C. At the determined optimum condition, catalytic pyrolysis process of the biomass sample is performed with metal supported MCM-41 catalysts synthesized by sonochemical method (metal: aluminium, cobalt, iron) at different ratios to biomass (1 and 2 wt %). The pyrolysis procedures of apricot kernel shell are carried out in a tubular fixed-bed reactor at different pyrolysis temperatures. The use of catalysts improved both the liquid product (tar) yield and tar quality in respect to the calorific value, the distribution of hydrocarbons and the elimination of oxygenated groups. The results revealed that all metal-supported MCM-41 catalysts, especially the Fe-MCM-41 catalyst ratio of 2, showed an excellent catalytic ability for thermal conversion of biomass. In the catalytic pyrolysis experiments carried out at 500 °C, 75.84 % conversion to liquid and gaseous products was obtained using 2 % Fe-MCM-41 catalyst, and the calorific value of the liquid product obtained was determined as 40.96 MJ/kg. The functional group analyses in the structure of the liquid products are characterized using FT-IR spectroscopy, and the distributions of the aliphatic/aromatic fractions of the liquid products are characterized using GC-MS technique. The H/C ratio of the liquid product obtained from catalytic pyrolysis is between light and heavy petroleum products and also has lower oxygen content and higher calorific value, indicating the potential of metal-supported MCM-41 catalyst for renewable hydrocarbon production from apricot kernel shell.

Conversion of microalgae into renewable hydrocarbons through catalytic pyrolysis: A bibliometric analysis

The imperative in transitioning to a low-carbon economy involves capturing and utilizing CO2 emissions from industrial sources. Within this framework, microalgae are widely acknowledged for their capacity to sequester CO2 and biologically convert it into high-energy-content biomass. This biomass subsequently finds applications in the production of biofuels and chemical compounds. Within the biorefinery framework, microalgae biomass undergoes pyrolysis with appropriate catalysts, producing renewable hydrocarbons. This process is significant for developing biofuels intended for aviation and maritime transport. To bolster the technological advancement of microalgae biomass conversion into renewable hydrocarbons, a bibliometric analysis of articles on catalytic pyrolysis of microalgae published in the Scopus search platform was conducted. This analysis identified the first article published in 1990, with publications continuing to the present. Utilizing bibliometric and content analyses, this study emphasized key topics in research and development, evaluating the current state of research on the catalytic pyrolysis of microalgae. A total of 178 articles were identified on the Scopus search platform, with 68 % of these scientific contributions published in the last 5 years. This underscores a recent surge in interest and acknowledgment of emerging technologies centered around decarbonization and biofuel generation directly tied to the catalytic pyrolysis of microalgae. As per bibliometric analysis, the leading three countries in terms of scientific contributions in this field were, sequentially, China, the United States, and Brazil. The journal Bioresource Technology offered the most extensive coverage of catalytic pyrolysis of microalgae. The principal challenges impeding the advancement of catalytic pyrolysis of microalgae from laboratory to industrial scale encompass the substantial energy consumption for thorough microalgae biomass drying, a limited comprehension of kinetic reactions and associated mechanisms, and a need for more results from pilot-scale experiments. Future research directions encompass the development of cost-effective and efficient catalysts for application in pyrolysis.

Reaction Mechanisms of Fe‐Dependent Fatty Acid Decarboxylases

AbstractThe escalating demand for fossil fuels has raised environmental concerns, urging the exploration of biosynthetic pathways for renewable hydrocarbon fuels. Terminal alkenes (α‐alkenes) emerge as “drop‐in” compatible fuels and chemicals, holding the potential to replace traditional fossil fuels. Fatty acid decarboxylases present a promising route for converting fatty acids into α‐alkenes, underscoring the imperative need for comprehending the catalytic mechanisms governing these enzymes in the quest for renewable biofuel production. The reported fatty acid decarboxylases entail the involvement of heme and non‐heme iron cofactors in the redox process. In this review, we summarize the reaction mechanisms of four iron‐dependent fatty acid decarboxylases (OleTJE, OleTPRN, UndA, and UndB), providing a critical analysis of the factors influencing chemical selectivity and catalytic performance.

Production of Renewable Hydrocarbon Biofuels with Lignocellulose and Its Derivatives over Heterogeneous Catalysts.

In recent years, the issues of global warming and CO2 emission reduction have garnered increasing global attention. In the 21st Conference of the Parties (convened in Paris in 2015), 179 nations and the European Union signed a pivotal agreement to limit the global temperature increase of this century to well below 2 K above preindustrial levels. To fulfill this objective, extensive research has been conducted to use renewable energy sources as potential replacements for traditional fossil fuels. Among them, the production of hydrocarbon transportation fuels from CO2-neutral and renewable biomass has proven to be a particularly promising solution due to its compatibility with existing infrastructure. This review systematically summarizes research progress in the synthesis of liquid hydrocarbon biofuels from lignocellulose during the past two decades. Based on the chemical structure (including n-paraffins, iso-paraffins, aromatics, and cycloalkanes) of hydrocarbon transportation fuels, the synthesis pathways of these biofuels are discussed in four separate sections. Furthermore, this review proposes three guiding principles for the design of practical hydrocarbon biofuels, providing insights into future directions for the development of viable biomass-derived liquid fuels.

Catalytic Upgrading of Pyrolysis Vapors from Scenedesmus sp. Microalgae towards Renewable Hydrocarbons using a Low-Cost Zeolite Synthesized from Rice Husk Ash and Diatomite Residue

Catalytic Upgrading of Pyrolysis Vapors from Scenedesmus sp. Microalgae towards Renewable Hydrocarbons using a Low-Cost Zeolite Synthesized from Rice Husk Ash and Diatomite Residue

Recent Advances in Diverse MXenes‐Based Structures for Photocatalytic CO2 Reduction into Renewable Hydrocarbon Fuels

AbstractPhotocatalytic CO2 reduction into renewable hydrocarbon fuels is a green solution to address CO2 emission and energy issues simultaneously. However, the fast recombination of photogenerated charge carriers and the sluggish surface reaction kinetics restrict the efficiency of photocatalytic CO2 reduction. The emergence of 2D MXenes has potential in improving the efficiency of photocatalytic CO2 reduction, owing to their high electrical conductivity, flexible structural properties, and abundant active sites. Hence, this review will concisely summarize and highlight recent advances of MXenes‐based photocatalysts used in photocatalytic CO2 reduction. First, the synthesis and properties of MXenes is briefly introduced. Second, the mechanism of CO2 photoreduction along with the roles of MXenes in photocatalytic CO2 reduction are summarized, including promoting the adsorption of CO2, enhancing the separation of photo‐induced charge carriers, acting as a robust support, and photothermal effect. Third, different kinds of MXenes‐based photocatalysts such as MXenes/metal oxides, MXenes/nitrides, MXenes/LDH, MXenes/perovskite, and MXene‐derived photocatalysts for CO2 reduction are classified via the type of semiconductors. Finally, the challenges and perspectives are also presented, including exploring suitable MXenes via machine learning, uncovering the structure‐activity relationship by in situ, time‐ and space‐resolved characterization techniques, improving anti‐oxidization ability, and scale‐up applications.

Photocatalyzed hydrodecarboxylation of fatty acids: a prospective method to produce drop-in biofuels.

A direct and practical method for photocatalyzed hydrodecarboxylation of fatty acids is reported herein. The catalytic system consists of a commercially available acridinium salt as the photocatalyst and thiophenol as the Hydrogen Atom Transfer (HAT) co-catalyst. Results evidenced that Cn-1 alkanes were obtained in yields up to 77%. Furthermore, the protocol was employed for a complex mixture of fatty acids bio-derived from a real sample of licuri oil to obtain hydrocarbons in the range of C9-C17 with high selectivity and excellent conversion (>90%). This work provides a powerful strategy for producing drop-in biofuels under mild conditions. Finally, an energetic assessment of our proposed protocol (∼22.9 kW h) reveals the benefit of a sustainable production of renewable hydrocarbons.

Photocarrier tunneling triggering CO2 photocatalysis.

Solar CO2 reduction to renewable hydrocarbon fuels offers a promising pathway to carbon neutrality, but it is retarded by tough CO2 activation, complicated mechanisms, sluggish charge transport kinetics, and a scarcity of strategies for precise tuning of charge transport pathways. Herein, we first conceptually design a novel insulating polymer-mediated electron-tunneling artificial photosystem via progressive interface configuration regulation, wherein tailor-made Ag@citrate nanocrystals (NCs) are controllably self-assembled on transition metal chalcogenides (TMCs) assisted by an ultrathin insulating polymer interim layer, i.e., poly(allylamine hydrochloride) (PAH). In this multilayered nano-architecture, a solid ultra-thin insulating PAH interim layer serves as an unexpected charge tunneling mediator to stimulate smooth electron transfer from the TMC substrate to the terminal electron reservoirs of Ag@citrate NCs, engendering the tandem charge transfer route and significantly boosting the visible-light-driven photocatalytic CO2-to-syngas conversion performances. Furthermore, we have ascertained that such TMC-insulating polymer-metal NC tunneling photosystems are universal. This study would spark new inspiration for unleashing the long-term neglected charge tunneling capability of insulating polymers and diversifying non-conjugated polymer-based artificial photosystems for solar-to-fuel energy conversion.

Upgrading of fast pyrolysis bio-oils to renewable hydrocarbons using slurry- and fixed bed hydroprocessing

Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.

Exploration of bio-hydrocarbon gases production via pyrolysis of fresh natural rubber: Experimental and volatile state kinetic modeling studies

The investigation of natural rubber pyrolysis holds substantial significance for the advancement of renewable hydrocarbon chemical production. Given its composition of almost 100% volatile matter and nearly zero fixed carbon content, natural rubber as a renewable chemical source offers a promising route for bio-hydrocarbon producers. Remarkably, natural rubber pyrolysis behavior and kinetic mechanism still have received limited attention. This study, hence, aims to characterize and model natural rubber pyrolysis, which offers a better understanding of the pyrolysis phenomenon. The modeling employs a novel methodology, the volatile state approach, as the basis for kinetic investigation to comprehensively predict the mass composition and yield, as well as determine kinetic parameters. The pyrolysis was investigated under variations of temperature conditions in laboratory-scale of semi-batch thermogravimetry apparatus. The kinetic parameters were obtained from the combination of Arrhenius equation and volatile state Kissinger-Akahira-Sunose (KAS) method. The result reports that the pyrolysis of natural rubber presents excellent potential for producing a range of valuable products, including both liquid and gas products as bio-hydrocarbon (CH4, C2H4, C2H6, C3H6, C3H8, C4H10, and C5H12) and non-hydrocarbon (CO2, CO, and H2). Moreover, the activation energy of each gas component is obtained as temperature dependence while still adhering to the mass conservation principle. Notably, the volatile state kinetic modeling is valuable for enhancing the understanding of natural rubber pyrolysis, providing kinetic parameters for pyrolysis optimization and prediction of the composition and yield of each gas product, closely aligned to the experimental data.

Multivariate combined optimization strategy and comparative life-cycle assessment of biomass and plastic residues via microwave co-pyrolysis approach towards a sustainable synthesis of renewable hydrocarbon fuel

The present study revealed the optimum co-pyrolysis process condition and simultaneously evaluated the environmental impact potential during co-valorisation of electronic plastic waste (WEEP) with Hydnocarpus de-oiled seed cake (HDSC) to produce renewable hydrocarbon fuel. In this work, the primary co-pyrolysis process parameters such as operating temperature, mixture ratio, and catalyst loading were modeled and optimized using a combined approach of both Response Surface Methodology (RSM) and Artificial Neural Network (ANN). In the optimized condition, a maximum pyrolysis oil yield of 30.79 wt% was achieved at an operating temperature of 530 °C, a mixture ratio of 0.49, and catalyst loading of 20 wt%. The obtained co-pyrolysis products were characterized to evaluate their physiochemical properties. Finally, a detailed life cycle assessment (LCA) of the scaled-up microwave-assisted co-pyrolysis plant has been modeled, and the result revealed that the emission levels of 771.95 kg CO2 eq, 3.11 kg SO2 eq, 1.69 kg PO4 eq, 338.59 DCB eq, and 0.11 kg C2H4 eq were projected for processing 1 tonne of feedstock. Further, sensitivity analysis revealed that a decrease of 15% in electricity consumption results in a reduction of the overall environmental impact by 13.69%. Above results demonstrate that microwave co-pyrolysis of biomass with plastic waste holds great potential for positive energy production and negative emission technology when compared to other waste management methods. Hence, this investigation paves the way for the sustainable conversion of e-waste plastic and biomass residue into renewable fuel and helps to achieve the sustainability goal of reducing GWP emissions.

(Invited) Reach for the Sky: Solid Oxide Fuel Cell Hybrid Systems Enable Carbon-Neutral Flight in ARPA-E’s REEACH Program

The carbon-neutral economy of 2050 may rely on several sustainable fuels, including hydrogen, ammonia, and renewable hydrocarbons. Solid Oxide Fuel Cells (SOFCs) deliver value for each candidate carbon-neutral fuel thanks to their inherent fuel flexibility and high efficiency. This talk examines the additional benefits that can be realized in hybrid systems comprised of an SOFC with an engine bottoming cycle. Developments in ARPA-E’s REEACH program involving SOFC-turbogenerator hybrids for electrified flight will be discussed. The interplays between design and operation of system components can significantly impact the energy storage and power generation (ESPG) system metrics. Modeling work has been performed to inform hybrid system design and will be presented. Finally, next steps for hybrid system deployment at commercial scale will be discussed.

Progress of non-destructive hydrocarbon extraction technology of Botryococcus braunii

Coal, petroleum and natural gas have remained the premium energy sources driving the economy and sustaining population growth for years. Global human population has shown a 7-fold increase in the last two centuries and, consequently, an astronomical increase in the global economy and energy demand. Interestingly, rising global warming, climate change and destruction of the natural environment are trends parallel with the world population profile and continual dependence on fossil fuels. Actions to mitigate these challenges have ignited interest in autotrophic production of hydrocarbons from microalgae as an alternative to fossil-based fuels. The microalgal strain, Botryococcus braunii, offers an excellent platform for renewable hydrocarbons production. B. braunii has unusual and fascinating attributes, and by producing liquid hydrocarbons extracellularly, a classical non-invasive, non-destructive extraction technique known as milking can be applied. In the milking process, hydrocarbons in the extracellular matrix of the algae are repetitively extracted without the need for cell harvesting, dewatering, disruption, and purification of the metabolites, thereby reducing downstream processing costs. In this way, the algae do not need to grow for cellular biomass production but can act only as light-driven catalysts to convert CO2 into hydrocarbons that accumulate externally in the medium. In this work, the different lipid extraction techniques from B. braunii are discussed in depth, taking critical analysis of the effect of each process on hydrocarbon recovery and purity as well as their economic viability. Moreover, hydrocarbon composition of B. braunii and the factors influencing the hydrocarbon production is comprehensively reviewed. The milking process is critically discussed, and the cultivation protocols suitable for milking as well as strategies to improve this process are highlighted. We indicate that switchable solvent-based milking has exceptional potential and biofilm-based cultivation holds great promise to reduce downstream costs. However, more research is needed to improve their large-scale implementation and feasibility.

Dimer-assisted mechanism of (un)saturated fatty acid decarboxylation for alkene production

The enzymatic decarboxylation of fatty acids (FAs) represents an advance toward the development of biological routes to produce drop-in hydrocarbons. The current mechanism for the P450-catalyzed decarboxylation has been largely established from the bacterial cytochrome P450 OleTJE. Herein, we describe OleTPRN, a poly-unsaturated alkene-producing decarboxylase that outrivals the functional properties of the model enzyme and exploits a distinct molecular mechanism for substrate binding and chemoselectivity. In addition to the high conversion rates into alkenes from a broad range of saturated FAs without dependence on high salt concentrations, OleTPRN can also efficiently produce alkenes from unsaturated (oleic and linoleic) acids, the most abundant FAs found in nature. OleTPRN performs carbon-carbon cleavage by a catalytic itinerary that involves hydrogen-atom transfer by the heme-ferryl intermediate Compound I and features a hydrophobic cradle at the distal region of the substrate-binding pocket, not found in OleTJE, which is proposed to play a role in the productive binding of long-chain FAs and favors the rapid release of products from the metabolism of short-chain FAs. Moreover, it is shown that the dimeric configuration of OleTPRN is involved in the stabilization of the A-A' helical motif, a second-coordination sphere of the substrate, which contributes to the proper accommodation of the aliphatic tail in the distal and medial active-site pocket. These findings provide an alternative molecular mechanism for alkene production by P450 peroxygenases, creating new opportunities for biological production of renewable hydrocarbons.

Synergistic recovery of renewable hydrocarbon resources via microwave co-pyrolysis of biomass residue and plastic waste over spent toner catalyst towards sustainable solid waste management

The present study unveiled the effect of operating temperature, blending ratio and catalyst addition on the product distribution during microwave co-pyrolysis of Hydnocarpus de-oiled seed cake (HDSC) and Waste electrical and electronic plastic (WEEP). In this work, a new approach of “treatment of wastes with waste” was proposed by converting spent toner powder into a low-cost catalyst. Initially, co-pyrolysis process was conducted in which the operating temperature were changed to 450, 500, and 550 °C corresponding to HDSC:WEEP mixture ratios of 100:0, 75:25, 50:50, 25:75, 0:100. The result shows that oil phase yield was significantly higher for 50:50 mixture ratio and this condition further selected for addition of catalyst. The catalytic co-pyrolysis result shows that produced oil have a density of 0.862 g/mL, high calorific value of 39.51 MJ/kg and viscosity 2.71 cSt which is comparable to commercial diesel fuel. The GC-MS study discovered that addition of catalyst could significantly suppress the oxygen and nitrogen compounds while promote the formation of aromatic hydrocarbons through Diels-Alder reaction mechanism. Finally, techno economic analysis revealed that 1000 kg/h plant demonstrated to be economically viable, with minimal production cost (USD 0.53/L compared to USD 1.15/L of commercial diesel fuel price in India).

The effects of supported Pd, Pt, Re, Rh, Ru, Ir, Au, and Ni catalysts on renewable hydrocarbon production from alternative feedstock

Screening tests of supported commercial and prepared Pd, Pt, Re, Rh, Ru, Ir, Au (5%), and Ni (5–65%) metal catalysts were conducted under one-pot solvent-free hydrotreating (HT) conditions to evaluate their activity, selectivity, and potential for renewable hydrocarbon (RH) production from rapeseed oil (RO). Catalysts were characterized by XRF, XRD, FE-SEM, TEM, and N2 sorption analysis. Composition of RO, liquid, and gaseous products were analyzed by GC-FID, GC-MS, C, H, N, S elemental analysis, FT-IR, and GC-TCD. Full conversion of RO with RH yield up to 85% were achieved over most active supported commercial Ni (65%) and Re, Rh, Ru (5%) catalysts in short residence time (up to 10 min) under relatively mild reaction temperature 340 °C and initial H2 pressure 10 MPa. Noticeable effect of Ru catalysts on cleavage of -C-C- bond reactions make them promising for practical application in RH synthesis. Multi-function SiO2–Al2O3 supported Ru (5%) catalyst (Ru5SAp) prepared by developed simple method is perspective for wide molecular weight hydrocarbon production by –CC- hydrogenation, oxygen removal and cleavage of -C-C- bonds including ring opening reactions for structure modification of different raw materials – fats, oils, phenols, and fossil based feedstocks. Benzene, toluene, tetralin, guaiacol, and n-nonadecane were used as model compounds for investigation of catalytic effects. Ru5SAp possesses similar performance as most active supported commercial noble metal catalysts in HT process of RO. It is reusable up to three HT reaction cycles although deactivation of catalyst causes significant changes in obtained hydrocarbon composition.