Catalysts For Biomass Conversion Research Articles

N‐Heterocyclic Carbene–Based Catalysts for Glycerol Valorisation: Current State and Perspectives

ABSTRACTN‐Heterocyclic carbenes (NHCs) are molecules with exceptional catalytic properties in a wide range of reactions. Recently, there has been a growing interest in using them as catalysts for biomass conversion. In this review, we examine the current state of glycerol valorisation (GV) using several catalytic systems, including metallic complexes bearing NHCs as ligands, polymeric building blocks and organocatalysts. The study covers literature published in the last 15 years, detailing the catalyst scope, reaction conditions and products of GV. This analysis emphasises the importance of varying the steric and electronic properties of NHCs within the reviewed catalytic systems. Furthermore, a critical evaluation of the proposed mechanistic pathways complements these results. A comprehensive understanding of the challenges of using such catalytic systems will emerge by compiling literature on the use of NHCs for the studied reactions. Additionally, this will promote new opportunities for further research in both academic and industrial fields.

Catalytic hydrolysis of cellulose to glucose: On the influence of graphene oxide morphology under microwave radiation

Carbon nanostructures provide a unique platform for the synthesis of novel catalysts for biomass conversion. In this work, a set of graphene oxide (GO)-based materials (nanofibers (GONF), sheets of few-layers (FLGO), and quantum dots (GOQD)), differing structurally in morphology and size, was prepared from fishbone-carbon nanofibers (CNF) and their catalytic behavior was compared on the hydrolysis of amorphous cellulose under microwave (MW) radiation. First, the influence of the reaction temperature (135–180 ºC), holding time (0–120 min), catalyst morphology and cellulose/water ratio (0.25–2.0 wt%) was thoroughly screened and compared with conventional heating mode. The use of GO morphologies in concert with MW energy showed the potential to achieve similar kinetic profiles than previously reported sulfonated carbons (110 kJ/mol) but using considerably less amount of catalyst (cellulose-to-catalyst ratio 12-fold lower). Overall, the reactivity of the GO-catalyst was related to their degree of oxidation/exfoliation, decreasing as follows: GOQD > FLGO > GONF. Compared with conventional heating, MW-technology enabled higher loadings of cellulose (2.0 vs. 0.25 wt%) to be processed in a shorter time (20 min instead of 24 h), which is a landmark achievement toward process intensification.

Synthesis and performance of piperidinium-based ionic liquids as catalyst for biomass conversion into 3-acetamido-5-acetylfuran

Ionic liquids have shown good catalytic performance and been widely used in the biomass conversion process due to their unique properties, including environmentalfriendship, low toxicity, and simple preparation. In this work, a series of novel piperidinium-based ionic liquids were synthesized under mild conditions via a simple protonation reaction or nucleophilic substitution reaction. Among them, 4,4′-(propane-1,3-diyl)bis(1-(carboxymethyl)piperidin-1-ium) chloride ([PDCMPi]Cl) displayed the best catalytic performance. The highest yield (42.81 %) of 3A5AF from NAG was obtained after reacting in N-methyl-pyrrolidone (NMP) in the presence of piperidinium-based ionic liquids at 180 °C for 20 min under normal atmospheric conditions. Additionally, ionic liquid [PDCMPi]Cl showed good catalytic activity in six repeated catalytic runs. Meanwhile, a possible reaction pathway was also proposed on the basis of the results of NMR spectra.

Nanoarchitectonics of sulfonated biochar from pine needles as catalyst for conversion of biomass derived chemicals to value added products

Utilizing waste lignocellulosic biomass to synthesize biofuel precursors constructs an important way to solve the current energy crisis. In this work, we have prepared a sulfonated acid catalyst from pine needles derived biochar using chlorosulfonic acid for conversion of fructose to levulinic acid and levulinic acid to ethyl levulinate. In the best optimized conditions, sulfonated biochar as a catalyst exhibited excellent catalytic activity for the fructose conversion to levulinic acid and its esterification to ethyl levulinate with yield 33% and 97%.

Efficient Method for α-TiP Synthesis using Alkaline Decomposition Pretreatment of Ilmenite Natural Beach Sand

The layered, acidic compound; α-TiP is widely popularized as a sorbent material for heavy metal removal from wastewater, as catalysts for biomass conversion and as an intermediate to produce high purity titanium dioxide particles. One of the conventional route for its synthesis is to react ilmenite with orthophosphoric acid under reflux conditions. However, the major drawback of this method is that the titanium recovery is only 35 wt. % and about 10 wt. % of the initial ilmenite remain unreacted as the residue. The conversion of ilmenite into an easily acid digestible compound could be attained via alkaline roasting. The objective of this research was to increase the yield of α-TiP from ilmenite using an additional alkaline roasting pre-treatment step to the acid leaching. Potassium hydroxide was selected for the alkaline roasting step since it is regarded to be an environmentally benign chemical. The pre-treatment of ilmenite with a 1:4 molar ratio of KOH to ilmenite at 700 C generated potassium iron oxides and potassium titanium oxides as intermediate compounds which were then washed with distilled water, filtered and dried at 100 C for 24 hours. The solid compound was reacted with orthophosphoric acid with a solid to liquid ratio of 1/8 under reflux conditions for 4 hours. Then the remaining acid leachate was decanted and the white precipitate from the leach liquor was filtered, washed and dried at 100 C for 24 hours. The obtained powder was characterized using X-Ray Diffraction (XRD) analysis, X-Ray Fluorescence (XRF) spectroscopy, FTIR spectroscopy and Raman spectrophotometry and was confirmed to be α-TiP. The parameters; the effect of KOH/ilmenite ore molar ratio, calcination temperature, solid to liquid ratio in the acid leaching step, acid leaching reflux time on the titanium recovery were fine tuned. This research concluded the possibility of increasing the titanium extraction. Therefore the research concludes the increment of α-TiP yield after the pre-treatment step using KOH.
 Keywords: Ilmenite, Titanium phosphate, Alkaline roasting, Alkaline pretreatment

Spent lithium-ion battery materials recycling for catalytic pyrolysis or gasification of biomass

This research work studied the pyrolysis characteristics of main biomass components (i.e. cellulose, lignin) in the presence of the spent Li-ion battery cathode (BC) enriched in transition-metals (e.g., Ni, Co). The BC with a good thermostability even at > 700 °C could be used as a catalyst for biomass conversion. The addition methods of BC to biomass such as one-step (directly mixing) and two-step (impregnation-drying) were comparatively studied. The two-step method had a better catalytic effect in biomass pyrolysis, contributing to the reduction of decomposition temperature and activation energy. Significantly, the two-step method had a strong catalytic effect in reducing the content of cellulose-derived sugars and increasing the content of ketones via dehydration and decarboxylation. In addition, the BC used by the two-step method had a high potential for biomass pyrolysis or gasification in promoting the catalytic cracking (i.e. H-transfer) of lignin-derived phenols (tar surrogates) to hydrocarbons and aliphatics (e.g., ketones).

Review: cascade reactions for conversion of carbohydrates using heteropolyacids as the solid catalysts

Conversion of biomass into renewable chemicals and fuels has received significant attention as an approach to enhance global sustainability. Biomass conversion, especially carbohydrate conversion, commonly involves cascade reactions. During these cascade reactions, various activity sites on carbohydrates may have different reactivities that enable us to control the final products through adjusting these activity sites. Heteropolyacids (HPAs), one of the major solid acid catalysts, are extensively used in biomass conversion owing to their numerous excellent physicochemical properties, such as strong Bronsted acidity, oxidizability, structural versatility, and easy design. Accordingly, this review aims to outline recent breakthroughs in obtaining platform chemicals from carbohydrates by cascade reactions involving heteropolyacid catalysts. Moreover, the relationship between the final products and the structure of heteropolyacid catalysts is discussed and insights will help us to design more efficient solid acid catalysts for conversion of biomass to more sustainable chemical products.

Metal organic frameworks for biomass conversion.

Biomass is increasingly used as a source of fuels and chemicals as a renewable alternative to fossil feedstocks. Cellulose, hemicellulose and lignin are converted into platform chemicals from which a large range of compounds are derived with different structures. These biomass transformation processes require the use of efficient and durable catalysts that should drive the selectivity of the process. This review focuses on the use of metal-organic frameworks (MOFs) and derivatives as catalysts for biomass conversion. After an introduction setting up the importance of the field and the MOF features that justify their prevalence as heterogeneous catalysts for liquid phase reactions, the two main parts of the review are the description of MOF synthesis and adaptation and coverage of the catalytic reactions involving biomass substrates organized according to the type of MOF. The last section summarizes the current state of the art and our outlook for the future development of the field.

Hydrothermal stability of MTT zeolite in hot water: The role of La and Ce

Stability of catalysts under steam and hot water environment is a crucial issue in upgrading of water-containing feedstocks such as biomass and heavy oil. The hydrothermal stability of MTT zeolite in hot water under autogenous pressure was investigated at 473 K. The effect lanthanum (La) and cerium (Ce) on the hydrothermal behavior of MTT zeolite were also studied under the same condition. The parent MTT zeolite, as well Ce and La modified zeolites showed remarkable stability in hot water. Minimal losses in textural properties originated from the hydrolysis of Si–O–Si and Si–O–Al bonds in the zeolite framework. The study shows the potential of the MTT zeolite as a catalyst for biomass conversion and heavy oil upgrading.

A DFT study of Ni clusters deposition on titania and zirconia (101) surfaces

Density functional calculations are employed to simulate the deposition of an isolated Ni atom and a Ni10 particle on the stoichiometric and reduced anatase TiO2 (101) and tetragonal ZrO2 (101) surfaces. The main purpose of this work is to study the modification of the electronic structure of the oxide induced by the metal, aiming at the understanding of the physical properties of new catalysts for biomass conversion. When the adsorption of a Ni atom takes place on stoichiometric surfaces, no major charge transfer is observed. On reduced titania, and more pronouncedly on reduced zirconia, the Ni atom is negatively charged, provided that the vacancy is in direct contact with the adsorbed metal atom. For Ni10, on titania the bonding is dominated by the hybridization of the metal and the oxide states but we did not find evidence for a direct reduction of the oxide via formation of Ti3+ states. For Ni10 on zirconia, the metal particle is positively charged on the stoichiometric surface and negatively charged on the reduced one but, again, there is no indication of a direct reduction of the oxide. Finally, the reverse oxygen spillover is considered as a possible route to reduce the oxide support. The result is that Ni10 promotes oxygen spillover on titania almost spontaneously, while on zirconia this process is thermodynamically unfavourable.

ChemInform Abstract: Catalytic Materials that Improve Selectivity of Biomass Conversions

AbstractReview: 181 refs.

Catalytic materials that improve selectivity of biomass conversions

Lignocellulosic biomass is composed of cellulosic and hemicellulosic components. Degradation of these components leads to short-chain aqueous soluble glucan with β-1,4-glycosidic linkages and its further degradation produces hexose and pentose sugars. Dehydration of these sugar units result in building blocks (platform chemicals) which upon further chemical transformation produces fine chemicals and liquid fuels. Materials with considerable surface acidity and suitable microstructure play crucial roles as catalysts at different steps of the biomass transformation to chemicals and fuels. This review focuses on explaining the roles of the catalytic materials that are employed for improving selectivity of biomass conversions. The article also advances issues such as the morphology and preparation method of materials as a function of their performance. In attempt to keep the focus on materials aspects, mechanistic aspects of biomass conversion has also been discussed in relevant cases. Apart from conventional acidic materials, applications of recently introduced new materials with functionalized surfaces are highlighted with suitable examples. Factors which govern solid materials to perform as catalysts for biomass conversion have been expanded to inform readers with a possible correlation of the reactivity patterns of the materials for different substrates and their macro- and micro-structures.

Energy and nanotechnologies: Priority areas for Australia's future

This paper explores the possibilities offered by the use of nanotechnologies to contribute to new and improved approaches to energy conversion, storage and distribution in Australia in the short term (less than 5 years), medium term (5–15 years) and long term (greater than 15 years). In 2007 the Australian Academy of Technological Sciences and Engineering (ATSE) examined the potential for the application of nanotechnologies to future energy systems in Australia. Four workshops were held in major cities around Australia bringing ATSE Fellows and experts together for brainstorming sessions and a questionnaire was circulated more widely. These provided inputs on future energy needs in Australia and the critical areas to be considered in research and commercialisation of nanotechnologies in energy systems. Using a matrix approach a number of opportunities were identified as short term — energy conservation, environmental management, catalysts for combustion, photovoltaic cells; medium term — catalysts for conversion of biomass, gas and coal, fuel cells, advanced photovoltaics, capture and storage of carbon dioxide; and long term — hydrogen production, storage and use. These applications are discussed in the Australian context. The implications for government policy on support of the findings are discussed.

Catalysts for Emerging Energy Applications

AbstractCatalysis is the essential technology for chemical transformation, including production of fuels from the fossil resources petroleum, natural gas, and coal. Typical catalysts for these conversions are robust porous solids incorporating metals, metal oxides, and/or metal sulfides. As efforts are stepping up to replace fossil fuels with biomass, new catalysts for the conversion of the components of biomass will be needed. Although the catalysts for biomass conversion might be substantially different from those used in the conversion of fossil feedstocks, the latter catalysts are a starting point in today's research. Major challenges lie ahead in the discovery of efficient biomass conversion catalysts, as well as in the discovery of catalysts for conversion of CO2and possibly water into liquid fuels.

Synthesis of Nanophased Metal Oxides in Supercritical Water: Catalysts for Biomass Conversion

Nanoparticles of zinc oxide‐based materials (ZnO, ZnAl2O4) with various morphologies were synthesized in supercritical water (SCW) with a flow‐type apparatus and in sub‐ and supercritical water with a batch reactor. In the flow‐type apparatus, smaller particles were obtained. Depending on the precursors, the morphology of crystallites is rod, hexagonal, or rectangular shaped. ZnAl2O4 was synthesized with a high specific surface area (SBET) reaching 210 m2/g and nanocrystallite sizes ≤10 nm. The KOH concentration played a major role in the formation of ZnO and ZnAl2O4 phases. Then, the synthesized materials were used as catalysts for the biomass conversion by the oxidation process to produce hydrogen.