Recent advances in one-stage conversion of lipid-based biomass-derived oils into fuel components - aromatics and isomerized alkanes

Chemicals and fuels from lipid-containing biomass: A comprehensive exploration

In response to address the climate crisis, there has been a growing focus on substituting conventional refinery-derived products with those derived from biorefineries. The utilization of lipids as primary materials or intermediates for the synthesis of chemicals and fuels, which are integral to the existing chemical and petrochemical industries, is a key step in this transition. This review provides a comprehensive overview of the production of sustainable chemicals (acids and alcohols), biopolymers, and fuels (including gasoline, kerosene, biodiesel, and heavy fuel oil) from lipids derived from terrestrial and algal biomass. The production of chemicals from lipids involves diverse methods, including polymerization, epoxidation, and separation/purification. Additionally, the transformation of lipids into biofuels can be achieved through processes such as catalytic cracking, hydroprocessing, and transesterification. This review also suggests future research directions that further advance the lipid valorization processes, including enhancement of catalyst durability at harsh conditions, development of deoxygenation process with low H2 consumption, investigation of precise separation of target compounds, increase in lipid accumulation in algal biomass, and development of methods that utilize residues and byproducts generated during lipid extraction and conversion.

Bifunctional MoS2/Al2O3-Zeolite Catalysts in the Hydroprocessing of Methyl Palmitate

A series of bifunctional catalysts, MoS2/Al2O3 (70 wt.%), zeolite (30 wt.%) (zeolite-ZSM-5, ZSM-12, and ZSM-22), and silica aluminophosphate SAPO-11, were synthesized for hydroconversion of methyl palmitate (10 wt.% in dodecane) in a trickle-bed reactor. Mo loading was about 7 wt.%. Catalysts and supports were characterized by different physical-chemical methods (HRTEM-EDX, SEM-EDX, XRD, N2 physisorption, and FTIR spectroscopy). Hydroprocessing was performed at a temperature of 250-350 °C, hydrogen pressure of 3.0-5.0 MPa, liquid hourly space velocity (LHSV) of 36 h-1, and an H2/feed ratio of 600 Nm3/m3. Complete conversion of oxygen-containing compounds was achieved at 310 °C in the presence of MoS2/Al2O3-zeolite catalysts; the selectivity for the conversion of methyl palmitate via the 'direct' hydrodeoxygenation (HDO) route was over 85%. The yield of iso-alkanes gradually increases in order: MoS2/Al2O3 < MoS2/Al2O3-ZSM-12 < MoS2/Al2O3-ZSM-5 < MoS2/Al2O3-SAPO-11 < MoS2/Al2O3-ZSM-22. The sample MoS2/Al2O3-ZSM-22 demonstrated the highest yield of iso-alkanes (40%). The hydroisomerization activity of the catalysts was in good correlation with the concentration of Brønsted acid sites in the synthesized supports.

Hydrodeoxygenation–Isomerization of Methyl Palmitate over SAPO-11-Supported Ni-Phosphide Catalysts

Ni-phosphide catalysts on SAPO-11 were studied in the hydrodeoxygenation–isomerization of methyl palmitate (C15H31COOCH3—MP). The catalysts were synthesized using temperature-programmed reduction (TPR) of a phosphate precursor ((NH4)2HPO4 and Ni(CH3CH2COO)2), TPR of a phosphite precursor (H3PO3 and Ni(OH)2), and using phosphidation of Ni/SAPO-11 by PPh3 in the liquid phase. The samples were characterized by ICP-AES chemical analysis, N2 physisorption, NH3-TPD, XRD, and TEM. First, the screening of the catalysts prepared by the TPR method was carried out in a semi-batch autoclave to determine the influence of the preparation method and conditions on one-pot HDO–isomerization (290–380 °C, 2–3 MPa). The precursor’s nature and the amount of phosphorus strongly influenced the activity of the catalysts and their surface area and acidity. Isomerization occurred only at a low P content (Ni/P = 2/1) and blocking of the SAPO-11 channels by unreduced phosphates at higher P contents did not allow us to obtain iso-alkanes. Experiments with liquid phosphidation samples in a continuous-flow reactor also showed the strong dependence of activity on phosphidation duration as well as on Ni content. The highest yield of isomerized products (66% iso-C15–16 hydrocarbons, at complete conversion of O-containing compounds, 340 °C, 2 MPa, and LHSV = 5.3 h−1) was obtained over 7% Ni2P/SAPO-11 prepared by the liquid phosphidation method.

Green Chemistry, Biocatalysis, and the Chemical Industry of the Future

In the movement to decarbonize our economy and move away from fossil fuels we will need to harness the waste products of our activities, such as waste lignocellulose, methane, and carbon dioxide. Our wastes need to be integrated into a circular economy where used products are recycled into a manufacturing carbon cycle. Key to this will be the recycling of plastics at the resin and monomer levels. Biotechnology is well suited to a future chemical industry that must adapt to widely distributed and diverse biological chemical feedstocks. Our increasing mastery of biotechnology is allowing us to develop enzymes and organisms that can synthesize a widening selection of desirable bulk chemicals, including plastics, at commercially viable productivities. Integration of bioreactors with electrochemical systems will permit new production opportunities with enhanced productivities and the advantage of using a low-carbon electricity from renewable and sustainable sources.

Current progress in lipid-based biofuels: Feedstocks and production technologies

The expanding use of fossil fuels has caused concern in terms of both energy security and environmental issues. Therefore, attempts have been made worldwide to promote the development of renewable energy sources, among which biofuel is especially attractive. Compared to other biofuels, lipid-derived biofuels have a higher energy density and better compatibility with existing infrastructure, and their performance can be readily improved by adjusting the chemical composition of lipid feedstocks. This review thus addresses the intrinsic interactions between lipid feedstocks and lipid-based biofuels, including biodiesel, and renewable equivalents to conventional gasoline, diesel, and jet fuel. Advancements in lipid-associated biofuel technology, as well as the properties and applicability of various lipid sources in terms of biofuel production, are also discussed. Furthermore, current progress in lipid production and profile optimization in the context of plant lipids, microbial lipids, and animal fats are presented to provide a wider context of lipid-based biofuel technology.

Production of Gasolines and Monocyclic Aromatic Hydrocarbons: From Fossil Raw Materials to Green Processes

The properties and the applications of the main monocyclic aromatic hydrocarbons (benzene, toluene, ethylbenzene, styrene, and the three xylene isomers) and the industrial processes for their manufacture from fossil raw materials are summarized. Potential ways for their production from renewable sources with thermo-catalytic processes are described and discussed in detail. The perspectives of the future industrial organic chemistry in relation to the production of high-octane bio-gasolines and monocyclic aromatic hydrocarbons as renewable chemical intermediates are discussed.

Effects of Zn Addition into ZSM-5 Zeolite on Dehydrocyclization-Cracking of Soybean Oil Using Hierarchical Zeolite-Al2O3 Composite-Supported Pt/NiMo Sulfided Catalysts

Zn-exchanged ZSM-5-Al₂O₃ (ZA) composite-supported Pt/NiMo (NM) sulfided catalysts were prepared using the conventional kneading method and were tested for dehydrocyclization-cracking of soybean oil. The effects of Zn addition on the activity and selectivity of products were investigated under moderate-pressure conditions of 0.5 and 1.0 MPa H₂ in the temperature range of 420-580 °C. At the temperature 500 °C and higher, most of the sample soybean oil was converted at both the pressures of 0.5 and 1.0 MPa. At 1.0 MPa and 500 °C, the effects of Zn addition appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. Further, at 0.5 MPa and 580 °C, the gas formation was inhibited in comparison to the cases of 1.0 MPa and the effects of the Zn addition also appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. The Pt/NM/Zn(122)ZA test catalyst produced more than 63% of liquid fuels in the range C5-C18, and the yield of aromatics was 13%, the maximum value in the present study. The following reaction routes were proposed. The structure of triglyceride is converted by hydrocracking to three molecules of aliphatic acids and propane on the surface PtNiMo sulfide on Al₂O₃ support. The converted aliphatic acids are decomposed through decarboxylation to hydrocarbon fragments, which are further decomposed by cracking on the acid sites of the catalyst, the surface of NiMo sulfide, Al₂O₃, or ZSM-5. Finally, the formed C3 and C4 olefins are transformed to aromatics through the Diels-Alder reaction on the Zn species of ZnZSM-5. On the other hand, although gases were relatively small in amount, aromatic compounds were formed significantly, suggesting that cyclization might directly occur without conversion to gaseous hydrocarbons to some extent.

Effect of Water and Glycerol in Deoxygenation of Coconut Oil over Bimetallic NiCo/SAPO-11 Nanocatalyst under N2 Atmosphere

The catalytic deoxygenation of coconut oil was performed in a continuous-flow reactor over bimetallic NiCo/silicoaluminophosphate-11 (SAPO-11) nanocatalysts for hydrocarbon fuel production. The conversion and product distribution were investigated over NiCo/SAPO-11 with different applied co-reactants, i.e., water (H₂O) or glycerol solution, performed under nitrogen (N₂) atmosphere. The hydrogen-containing co-reactants were proposed here as in-situ hydrogen sources for the deoxygenation, while the reaction tests under hydrogen (H₂) atmosphere were also applied as a reference set of experiments. The results showed that applying co-reactants to the reaction enhanced the oil conversion as the following order: N₂ (no co-reactant) < N₂ (H₂O) < N₂ (aqueous glycerol) < H₂ (reference). The main products formed under the existence of H₂O or glycerol solution were free fatty acids (FFAs) and their corresponding C_n−1 alkanes. The addition of H₂O aids the triglyceride breakdown into FFAs, whereas the glycerol acts as hydrogen donor which is favourable to initiate hydrogenolysis of triglycerides, causing higher amount of FFAs than the former case. Consequently, those FFAs can be deoxygenated via decarbonylation/decarboxylation to their corresponding C_n−1 alkanes, showing the promising capability of the NiCo/SAPO-11 to produce hydrocarbon fuels even in the absence of external H₂ source.

Green Diesel Production over Nickel-Alumina Nanostructured Catalysts Promoted by Copper

A series of nickel–alumina catalysts promoted by copper containing 1, 2, and 5 wt. % Cu and 59, 58, and 55 wt. % Ni, respectively, (symbols: 59Ni1CuAl, 58Ni2CuAl, 55Ni5CuAl) and a non-promoted catalyst containing 60 wt. % Ni (symbol: 60NiAl) were prepared following a one-step co-precipitation method. They were characterized using various techniques (N2 sorption isotherms, XRD, SEM-EDX, XPS, H2-TPR, NH3-TPD) and evaluated in the selective deoxygenation of sunflower oil using a semi-batch reactor (310 °C, 40 bar of hydrogen, 96 mL/min hydrogen flow rate, and 100 mL/1 g reactant to catalyst ratio). The severe control of the co-precipitation procedure and the direct reduction (without previous calcination) of precursor samples resulted in mesoporous nano-structured catalysts (most of the pores in the range 3–5 nm) exhibiting a high surface area (192–285 m2 g−1). The promoting action of copper is demonstrated for the first time for catalysts with a very small Cu/Ni weight ratio (0.02–0.09). The effect is more pronounced in the catalyst with the medium copper content (58Ni2CuAl) where a 17.2% increase of green diesel content in the liquid products has been achieved with respect to the non-promoted catalyst. The copper promoting action was attributed to the increase in the nickel dispersion as well as to the formation of a Ni-Cu alloy being very rich in nickel. A portion of the Ni-Cu alloy nanoparticles is covered by Ni0 and Cu0 nanoparticles in the 59Ni1CuAl and 55Ni5CuAl catalysts, respectively. The maximum promoting action observed in the 58Ni2CuAl catalyst was attributed to the finding that, in this catalyst, there is no considerable masking of the Ni-Cu alloy by Ni0 or Cu0. The relatively low performance of the 55Ni5CuAl catalyst with respect to the other promoted catalysts was attributed, in addition to the partial coverage of Ni-Cu alloy by Cu0, to the remarkably low weak/moderate acidity and relatively high strong acidity exhibited by this catalyst. The former favors selective deoxygenation whereas the latter favors coke formation. Copper addition does not affect the selective-deoxygenation reactions network, which proceeds predominantly via the dehydration-decarbonylation route over all the catalysts studied.