Using decalin and tetralin as hydrogen source for transfer hydrogenation of renewable lignin-derived phenolics over activated carbon supported Pd and Pt catalysts

Selective heterogeneous hydrodeoxygenation of acetophenone over monometallic and bimetallic Pt-Co catalyst

The hydrodeoxygenation (HDO) of acetophenone was evaluated in liquid phase and gas phase over monometallic Pt/SiO₂, Co/SiO₂ and bimetallic Pt-Co/SiO₂ catalysts. The influence of reaction time and loading of the catalyst were analysed by following the conversion and products selectivity. Phenylethanol, cyclohexylethanone and cyclohexylethanol are the main products of reaction using the Pt/SiO₂ catalyst. By contrast, ethylbenzene and phenylethanol are the only products formed on the Co/SiO₂ and Pt-Co/SiO₂ catalysts. The bimetallic catalyst is more stable as a function of time and more active towards the HDO process than the monometallic systems. The presence of an organic solvent showed only minor changes in product yields with no effect on the product speciation. Periodic density functional theory analysis indicates a stronger interaction between the carbonyl group of acetophenone with Co than with Pt sites of the mono and bimetallic systems, indicating a key activity of oxophilic sites towards improved selectivity to deoxygenated products. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Downstream processing of lignin derived feedstock into end products

This review provides critical analysis on various downstream processes to convert lignin derived feedstock into fuels, chemicals and materials.

Kinetic modelling of hydrogen transfer deoxygenation of a prototypical fatty acid over a bimetallic Pd60Cu40 catalyst: an investigation of the surface reaction mechanism and rate limiting step

Application of tetralin as a source of hydrogen for catalytic conversion of oleic acid to diesel-like hydrocarbons using a bimetallic Pd–Cu catalyst.

Heterogeneous Catalyzed Thermochemical Conversion of Lignin Model Compounds: An Overview

Thermochemical lignin conversion processes can be described as complex reaction networks involving not only de-polymerization and re-polymerization reactions, but also chemical transformations of the depolymerized mono-, di-, and oligomeric compounds. They typically result in a product mixture consisting of a gaseous, liquid (i.e., mono-, di-, and oligomeric products), and solid phase. Consequently, researchers have developed a common strategy to simplify this issue by replacing lignin with simpler, but still representative, lignin model compounds. This strategy is typically applied to the elucidation of reaction mechanisms and the exploration of novel lignin conversion approaches. In this review, we present a general overview of the latest advances in the principal thermochemical processes applied for the conversion of lignin model compounds using heterogeneous catalysts. This review focuses on the most representative lignin conversion methods, i.e., reductive, oxidative, pyrolytic, and hydrolytic processes. An additional subchapter on the reforming of pyrolysis oil model compounds has also been included. Special attention will be given to those research papers using "green" reactants (i.e., H₂ or renewable hydrogen donor molecules in reductive processes or air/O₂ in oxidative processes) and solvents, although less environmentally friendly chemicals will be also considered. Moreover, the scope of the review is limited to those most representative lignin model compounds and to those reaction products that are typically targeted in lignin valorization.

An overview of biomass thermochemical conversion technologies in Malaysia

The rising pressure on both cleaner production and sustainable development have been the main driving force that pushes mankind to seek for alternative greener and sustainable feedstocks for chemical and energy production. The biomass 'waste-to-wealth' concept which convert low value biomass into value-added products which contain high economic potential, have attracted the attentions from both academicians and industry players. With a tropical climate, Malaysia has a rich agricultural sector and dense tropical rainforest, giving rise to abundance of biomass which most of them are underutilized. Hence, the biomass 'waste-to-wealth' conversion through various thermochemical conversion technologies and the prospective challenges towards commercialization in Malaysia are reviewed in this paper. In this paper, a critical review about the maturity status of the four most promising thermochemical conversion routes in Malaysia (i.e. gasification, pyrolysis, liquefaction and hydroprocessing) is given. The current development of thermochemical conversion technologies for biomass conversion in Malaysia is also reviewed and benchmarked against global progress. Besides, the core technical challenges in commercializing these green technologies are highlighted as well. Lastly, the future outlook for successful commercialization of these technologies in Malaysia is included.

Conversion of Stearic Acid into Bio-Gasoline over Pd/ZSM-5 Catalysts with Enhanced Accessibility

Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5 (h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid under nitrogen atmosphere (6 bar). The incorporation of Pd into ZSM-5 zeolite increased significantly the share of gasoline in the reaction products due to the promotion by this metal of both decarboxylation and hydrogen transfer reactions. Likewise, the Pd nanoparticles dispersed over the zeolitic support favored the conversion of light olefins formed by end-chain cracking reactions into gasoline-range hydrocarbons according to an oligomerization/cyclization/aromatization pathway. Additionally, Pd/h-ZSM-5 gave rise to higher conversion and selectivity towards gasoline than Pd/n-ZSM-5, due mainly to the enhanced accessibility and improved Pd dispersion achieved when using the hierarchical zeolite. The decrease in the Si/Al atomic ratio in Pd/h-ZSM-5 samples resulted in a rise in the stearic acid conversion, although it was lower than expected. This finding denotes that, for supports with high acid sites concentration, the Pd availability became the limiting factor as the metal was loaded in similar amounts in all catalysts. Finally, the increase of the reaction temperature with the Pd/h-ZSM-5 (122) catalyst augmented both stearic acid conversion and gasoline selectivity, since it enhanced the conversion of the light olefins, formed as primary cracking products, into liquid hydrocarbons. Therefore, it can be concluded that Pd supported on hierarchical ZSM-5 zeolite is a convenient catalyst for obtaining bio-gasoline from oleaginous feedstock.

Catalytic Transfer Hydrogenation of Biomass-Derived Substrates to Value-Added Chemicals on Dual-Function Catalysts: Opportunities and Challenges

Aqueous-phase hydrodeoxygenation (APH) of bioderived feedstocks into useful chemical building blocks is one the most important processes for biomass conversion. However, several technological challenges, such as elevated reaction temperature (220-280 °C), high H₂ pressure (4-10 MPa), uncontrollable side reactions, and intensive capital investment, have resulted in a bottleneck for the further development of existing APH processes. Catalytic transfer hydrogenation (CTH) under much milder conditions with non-fossil-based H₂ has attracted extensive interest as a result of several advantageous features, including high atom efficiency (≈100 %), low energy intensity, and green H₂ obtained from renewable sources. Typically, CTH can be categorized as internal H₂ transfer (sacrificing small amounts of feedstocks for H₂ generation) and external H₂ transfer from H₂ donors (e.g., alcohols, formic acid). Although the last decade has witnessed a few successful applications of conventional APH technologies, CTH is still relatively new for biomass conversion. Very limited attempts have been made in both academia and industry. Understanding the fundamentals for precise control of catalyst structures is key for tunable dual functionality to combine simultaneous H₂ generation and hydrogenation. Therefore, this Review focuses on the rational design of dual-functionalized catalysts for synchronous H₂ generation and hydrogenation of bio-feedstocks into value-added chemicals through CTH technologies. Most recent studies, published from 2015 to 2018, on the transformation of selected model compounds, including glycerol, xylitol, sorbitol, levulinic acid, hydroxymethylfurfural, furfural, cresol, phenol, and guaiacol, are critically reviewed herein. The relationship between the nanostructures of heterogeneous catalysts and the catalytic activity and selectivity for C-O, C-H, C-C, and O-H bond cleavage are discussed to provide insights into future designs for the atom-economical conversion of biomass into fuels and chemicals.