Cascade Conversion Research Articles

The influence of the surface chemistry of phosphorylated carbon xerogel catalysts on the production of HMF from fructose in water

Dehydration of fructose to 5-hydroxymethylfurfural (HMF) is a critical step in the cost-effective cascade conversion of biomass-feedstocks to advanced biofuels, fuel additives, biopolymers, and biochemicals. In this work, the surface chemistry of phosphorus-doped carbon xerogels (CX_P) was studied to identify the ways to boost their catalytic performance in the eco-friendly production of HMF. An excellent HMF yield of 73.3% from dehydration of fructose was obtained in just 2 h in the H2O-CO2 reaction system, using CX_P thermally treated in air. This was achieved by controlling the amount and type of active sites on the catalyst surface and by modifying of the reaction atmosphere. The best-performing catalyst exhibited Brønsted acids in the form of P-OH in proximity to high amounts of thermally stable oxygen functionalities such as phenol, carbonyl, and lactone, which were vital for obtaining a high yield of HMF. A positive correlation was obtained between the selectivity towards HMF and the total amount of oxygen present in the bulk of the catalysts. The oxygen groups improved selectivity towards HMF by hindering its further adsorption and degradation. In addition, the selectivity to HMF was dependnt on the ratio between O-functionalities and PO phosphates together with COP species. We finally demonstrated a superior green catalytic system to promote fructose dehydration to HMF under green conditions using pure water under a CO2 atmosphere.

Theoretical and technical analysis of the photo-thermal energy cascade conversion for fuel with high-temperature combustion

This study theoretically reveals the advantages of the photo-thermal energy cascading conversion over single thermal energy or a radiative energy conversion. It also analyzes the potential of the photo-thermal energy cascading conversion relying on typical power generation units with different parameters and considers the research outlook. The results demonstrate that the cascade conversion is more critical for high-temperature conditions since there are limitations for single radiation energy; thus, oxy-fuel combustion at a high temperature is more suitable. In consideration of technology conditions, the cascade system based on ultra-supercritical units can theoretically increase efficiency by more than 20% points under oxy-fuel combustion, whereas the efficiency of the cascade system based on combined cycle units can be theoretically increased by 15% points. The efficiency of the cascade system based on the small-parameter organic Rankine cycle unit can be increased by over 30% points according to the actual technology, and the small-scale unit could be applied in distributed energy systems. It is also pointed out that the further improvement of the system lies in the design of staged thermo-photovoltaic and complex thermal cycles to realize the cascade utilization of photo energy or thermal energy.

Improving the performance of steam power cycle through thermo-photovoltaic device: A novel combined system and thermodynamic analysis

In this study, a new system consisting of a thermophotovoltaic device and steam Rankine cycle system is proposed to prevent the mismatch between the combustion temperature and the steam maximum temperature to achieve photo-thermal energy cascade utilization and improve the fuel conversion efficiency. The energy balance model of the proposed system is established, and the influence of parameters such as emitter area and heat exchange coefficients on the system’s performance is investigated. Exergy analysis of the system is performed based on the second law of thermodynamics. The results show that the proposed system has 11–13% higher efficiency than the steam Rankine cycle system. The addition of a thermophotovoltaic device mainly reduces the exergy loss of the boiler due to the temperature difference between the combustion flue gas and the steam. Increasing the emitter area improves the system efficiency, and a system with Si cells is more efficient than a system with GaSb cells. Increasing the heat transfer coefficient of the air heat exchanger and the outlet flue gas temperature to generate a higher flame temperature is crucial to improving the performance of the combined system. The addition of a thermophotovoltaic device does not reduce the exergy loss during combustion. Thus, further energy cascade utilization should consider the efficient conversion of high-order chemical energy of a fuel. This study contributes to the theory of photo-thermal energy cascade conversion and provides new insights into improving the performance of the steam Rankine cycle.

Parametrical analysis of a novel solar cascade photovoltaic system via full-spectrum splitting and residual-spectrum reshaping

In this study, a novel cascade photovoltaic power generation system via full-spectrum splitting and residual-spectrum reshaping is proposed to realize the cascade conversion of solar energy. A cavity-structured absorber and outer-wall emitter combined device is designed for reshaping the residual infrared spectrum, and the corresponding physical model is also established. The parametric analysis of the whole system is conducted to investigate the effect of cavity structure, second-stage cell, spectrum-split frequency, selective emitter and concentration ratio on the system performance. The results indicate that the system efficiency can reach 34.32%, which is higher than that of solar photovoltaic (27.6%) by 6.72 percentage points. It is founded that the solar thermophotovoltaic conversion system equipped with the cavity-structured absorber, whose absorption efficiency can reach more than 99.06%, can efficiently absorb and utilize the infrared residual spectrum. The cavity structure can avoid the manufacture of complex micro/nano structured materials and the high design cost of selective absorber. When Si is selected as second-stage photovoltaic cell and the selective emitter is used, the system efficiency is higher than that using GaSb cell by about 2–3 percent points. Besides, the lower cost of Si cell also provides certain application advantages. The result of this study paves a theoretical guiding for the development and application of solar photovoltaic technology.

Performance analysis of biomass driven thermophotovoltaic system from energy and exergy perspectives

• Propose a thermo-physical model of biomass-TPV and conduct a parametric analysis. • Present biomass-TPV/T concept for photo-thermal energy cascade conversion. • Effect of fuel and combustion design is analyzed from energy and exergy perspectives. • Increasing the TPV area and the regenerator design improves efficiency by more than 10%. • Provide reference for the design of TPV power device driven by fuel combustion. The new thermophotovoltaic (TPV) technology driven by biomass fuel is an important way of solar indirect use, it can directly convert thermal energy into electrical energy through thermal radiation; and it is more suitable for the cascade utilization of energy when compared to direct solar-TPV. Therefore, to identify the principles of energy conversion within the biomass-TPV, this study conducted a thermodynamic analysis of a biomass-TPV power device from energy and exergy perspectives. A thermo-physical model of TPV verified by experimental data was established. The concept of biomass-thermophotovoltaic/thermal (TPV/T) combined conversion was summarized to achieve cascade utilization. Particular consideration is given to the effects of biomass fuels, combustion chamber designs and selective filters on the thermodynamic performance of biomass-TPV device and biomass-TPV/T conversion. The results show that the largest exergy loss of biomass combustion accounts for 40%. The biomass fuel moisture increases the exergy losses in combustion and flue gas and thus reduces TPV efficiency by more than 3 percent points. Increasing the TPV area and the regenerator design are beneficial for reducing the exergy loss of flue gas and improving TPV efficiency by more than 10 percent points. Narrow-band filters decrease the exergy losses of TPV emitter and cell, while increasing the loss in flue gas. The narrow-band filter is more suitable for TPV/T combined conversion. This study provides a reference for the design and optimization of biomass-driven TPV conversion system.

Facile Synthesis of Sugar Nucleotides from Common Sugars by the Cascade Conversion Strategy.

Sugar nucleotides are essential glycosylation donors in the carbohydrate metabolism. Naturally, most sugar nucleotides are derived from a limited number of common sugar nucleotides by de novo biosynthetic pathways, undergoing single or multiple reactions such as dehydration, epimerization, isomerization, oxidation, reduction, amination, and acetylation reactions. However, it is widely believed that such complex bioconversions are not practical for synthetic use due to the high preparation cost and great difficulties in product isolation. Therefore, most of the discovered sugar nucleotides are not readily available. Here, based on de novo biosynthesis mainly, 13 difficult-to-access sugar nucleotides were successfully prepared from two common sugars D-Man and sucrose in high yields, at a multigram scale, and without the need for tedious purification manipulations. This work demonstrated that de novo biosynthesis, although undergoing complex reactions, is also practical and cost-effective for synthetic use by employing a cascade conversion strategy.

One-pot, cascade conversion of cellulose to γ-valerolactone over a multifunctional Ru–Cu/zeolite-Y catalyst in supercritical methanol

A one-pot cascade conversion of cellulose to GVL was investigated over bimetallic Ru–Cu deposited on a zeolite Y (Ru–Cu/Z) catalyst. Under supercritical methanol conditions, high-yield (49.8%) cascade conversion of cellulose to GVL was achieved at 250 °C, with an initial H2 pressure of 3.0 MPa and reaction time of 5 h. The Ru–Cu/Z catalyst was synthesized using activated reductive deposition (ARD), which resulted in the selective deposition of Cu nanodomains on Ru nanoparticles, thereby facilitating the dissociative adsorption of H2. In addition, Lewis and Brønsted acid sites of Cu-doped zeolite Y effectively proceeded to cascade conversion reactions, including alcoholysis, isomerization, dehydration, and acetalization reactions, suppressing humin formation. The bimetallic Ru–Cu/Z catalyst was used in six consecutive runs, with a marginal loss of activity. The structure–performance relationships of the Ru–Cu/Z catalysts synthesized using ARD, incipient wet impregnation, and reduction deposition methods were compared.

Enhanced chemical looping gasification of biomass coupled with CO2 splitting based on carbon negative emission

Under the background of fossil fuel consumption and global climate change, an enhanced chemical looping gasification of biomass coupled with CO2 splitting (CLGCS) was proposed in this work to produce high-quality syngas from biomass and split CO2 into CO by using Fe-based mixed oxygen carriers (OCs) without extra catalyst and excessive energy consumption, which provided a carbon negative emission technology for the cascade conversion of biomass and resource utilization of greenhouse gas. The reaction equilibrium and regulation mechanism of CLGCS were analyzed in Ellingham diagrams via theoretical calculation. Variable conditions were designed and performed to investigate the reaction performance of OCs. The intermetallic synergy was analyzed, and the improvement order of heterologous metal on lattice oxygen transfer of OCs was Co2O3 > NiO > CeO2 > CaO. The NiO modified sample exhibited excellent reaction behavior in CLGCS, which provided active sites for catalytic cracking of tar in CLG stage and activating CO2 molecules in splitting stage. Syngas with heating value 13.32 MJ/m3 and carbon conversion 74.18% were achieved in CLG stage, corresponding to CO2 conversion 64.09% and CO yield 23.59 mmol/g in splitting stage. High temperature enhanced the endothermic reactions in CLGCS process, and the biomass occurrence ratio indicated a positive correlation with CO2 splitting. Although some OC particles agglomerated in reaction process, the pore structure and reactivity remained stable. After 20 cyclic reaction tests, the carbon conversion in CLG stage and CO2 conversion in splitting stage were kept at 67.52% and 73.5%, respectively. The reaction path of CLGCS with NiO modified OC was summarized as: Fe2O3/NiFe2O4 → Fe/FeO/Ni → Fe3O4/Ni → Fe2O3/NiFe2O4.

Cofactor-Driven Cascade Reactions Enable the Efficient Preparation of Sugar Nucleotides.

Glycosylation is catalyzed by glycosyltransferases using sugar nucleotides or occasionally lipid-linked phosphosugars as donors. However, only very few common sugar nucleotides that occur in humans can be obtained readily, while the majority of sugar nucleotides that exist in bacteria, plants, archaea, or viruses cannot be synthesized in sufficient quantities by either enzymatic or chemical synthesis. The limited availability of such rare sugar nucleotides is one of the major obstacles that has greatly hampered progress in glycoscience. Herein we describe a general cofactor-driven cascade conversion strategy for the efficient synthesis of sugar nucleotides. The described strategy allows the large-scale preparation of rare sugar nucleotides from common sugars in high yields and without the need for tedious purification processes.

Cofactor‐Driven Cascade Reactions Enable the Efficient Preparation of Sugar Nucleotides

Glycosylation is catalyzed by glycosyltransferases using sugar nucleotides or occasionally lipid-linked phosphosugars as donors. However, only very few common sugar nucleotides that occur in humans can be obtained readily, while the majority of sugar nucleotides that exist in bacteria, plants, archaea, or viruses cannot be synthesized in sufficient quantities by either enzymatic or chemical synthesis. The limited availability of such rare sugar nucleotides is one of the major obstacles that has greatly hampered progress in glycoscience. Herein we describe a general cofactor-driven cascade conversion strategy for the efficient synthesis of sugar nucleotides. The described strategy allows the large-scale preparation of rare sugar nucleotides from common sugars in high yields and without the need for tedious purification processes.

Total chemocatalytic cascade conversion of lignocellulosic biomass into biochemicals

Because of its complexity, selective conversion of lignocellulosic biomass into platform chemicals presents significant challenges. Herein, we converted birch wood into high-yield lignin-derived phenolic monomers and dimers and holocellulose-derived polyols and monocarboxylic acids via a two-step cascade reaction using 0.1 wt% Pd on N-doped carbon (Pd0.1/CNx) and passivated alumina-coated Ni on activated carbon (Ni2 @Al2O3/AC) catalysts. The catalytic fractionation of birch sawdust using Pd0.1/CNx produced 11.1 wt% monomers, 5.6% dimers, and 63.4 wt% pulp-rich solid (PRS) based on feed weight. The subsequent conversion of PRS over passivated Ni2 @Al2O3/AC produced 21.6 wt% C2–C6 polyols and 7.9 wt% monocarboxylic acids. After the whole biomass conversion reaction, the Pd0.1/CNx and Ni2 @Al2O3/AC catalysts were separated using their different magnetic responses and reused three times without activity loss. The structure–performance relationships of the Pd0.1/CNx catalysts synthesized using different methods and effect of passivation on the performance of the Ni2 @Al2O3/AC catalyst were analyzed.

Cascade Transformation of Carbon Dioxide and Alkyne-1,n-diols into Densely Substituted Cyclic Carbonates

A silver-catalyzed cascade conversion of modular alkyne-1,n-diols and carbon dioxide has been developed allowing for the selective formation of keto-functionalized cyclic carbonates. The protocol is characterized by its operational simplicity, excellent scope of carbonate-based heterocycles, and mild reaction conditions. In situ IR studies, control experiments, and detailed computational analysis of these manifolds reveal the intermediacy of an α-alkylidene carbonate that is intercepted by an intramolecular alcohol nucleophile. The synthetic potential of this conceptually attractive CO2 transformation is demonstrated in the preparation of larger ring carbonates and their thermal rearrangement to sterically crowded, five-membered fused carbonate products.

Comparison between spectrum-split conversion and thermophotovoltaic for solar energy utilization: Thermodynamic limitation and parametric analysis

The mismatch between solar radiation spectrum and photovoltaic cells is the main obstacle on photovoltaic efficiency. Solar spectrum-split conversion (SSSC) and solar thermophotovoltaic (STPV) are two important technologies to solve this problem. In this study, the basic characteristics of the two technologies are considered and compared from the perspectives of thermodynamic evaluation and parameter analysis. Based on the radiative thermodynamics, a theoretical model is established to analyze the thermodynamic limitation of the solar spectrum-split photo-thermal cascade conversion, which is in the range of 84.96%–93.10% and higher than that of STPV (84.96%). Furthermore, a parameter model is established for the three-band solar spectrum-split photovoltaic-heat engine combined system. Parameter optimization analysis indicates that the theoretical efficiency of the three-band SSSC system can reach 64%, which is higher than the two-band spectrum-split by 5–20 percent points and is also higher than the theoretical maximum efficiency of STPV by approximately 25 percent points. The study points out that the high-temperature emission loss of STPV absorber for concentrating solar energy is as high as 70%, which is the loss of high-quality energy and directly reduces the working capability of solar energy. Future development of STPV should pay more attention to the selective absorbers. The study provides guidance for the integrated utilization of solar energy.

Conversion of butanol to propene in flow: A triple dehydration, isomerisation and metathesis cascade

A combined three-step flow cascade conversion of n-butanol to propene is demonstrated. Zeolite H-ZSM-5 gives high conversion in the initial n-butanol dehydration step (98%). Subsequent isomerisation of terminal butenes to internal butenes over zeolite H-Fer takes place with good conversion (87%). Finally, cross-metathesis with ethene over a tungsten on acid-washed SiO2/Al2O3 catalyst affords propene with good selectivity (65%). Coupling these three steps into a single flow sheet gives an overall yield of 64% propene from n-BuOH. Ethene cross-metathesis catalyst performance was probed using 2-pentene as a model co-substrate giving good conversion (~90%) and moderate selectivity to butenes (67%).

Conversion of xylose to bioproducts on bifunctional supported platinum-group metals catalysts

Nb2O5-supported platinum-group metals catalysts were investigated in the one-pot aqueous-phase isomerization-dehydration-hydrogenation cascade conversion of xylose. The interplay between Nb2O5 acid sites and noble metal particles was discussed with a particular focus on catalyst stability. Pt/Nb2O5 was the best-performing catalyst for xylose upgrading regarding xylose consumption rates and high selectivity to furfuryl alcohol. It was chemically stable as no metal leaching to the aqueous phase was observed. Deposition of carbonaceous materials was identified as the main cause of deactivation and it disturbed the Brønsted acid sites in a more significant way. The impact of choosing an organic co-solvent was also demonstrated. Catalytic activity and distribution of bioproducts were determined by the organic solvent:water mixture. While polarity influenced activity, intermolecular interactions were suggested to tune selectivity.

One-step catalytic upgrading of bio-based furfural to γ-valerolactone actuated by coordination organophosphate–Hf polymers

A novel coordination organophosphate–Hf polymer with spherical porous structure, large surface area, and high Lewis/Brønsted acid density exhibits superior activity for one-pot cascade conversion of furfural to γ-valerolactone (81% yield).

Environmentally proved methods of cascade conversion of organic waste using a microbial complex with filamentous fungi

The article deals with the problem of microbial bioconversion as an effective way to utilize organic waste in relation to the industrial poultry industry. At modern poultry farms, with the implementation of an intensive technology for growing poultry, the main type of waste that could limit the scale of production is significant scale of waste litter. The cellulose and lignin components that make up the waste material and litter mass are hardly decomposable substrates. The article contains information on the results of examining the parameters of microbial processes that ensure the degradation of organic matter, including, in addition to the actual poultry litter, a significant proportion of natural components. The advantages and dynamics of the qualitative and quantitative composition of the aboriginal microflora of waste have been defined. The methods of the developed recycling technology, which is a cascade process of destruction of the waste material components, are described. Destructive processes are provided by the work of a kind of biological conveyor where various systematic and ecological-trophic groups of microorganisms have been applied. Consecutively realized fermentation provides the most efficient conversion of the substance by analogy with natural reduction and soil-forming processes. The efficiency of the use of ammonifying and nitrifying bacteria, as well as the cellulolytic and lignolytic potential of actinomycetes and filamentous fungi variates at the stage of decomposition that is optimal for each destructor has been examined. Bioconversion allows to ensure a waste mass loss of up to 30-33% of the original, to reduce emissions into the atmosphere of significant amounts of ammonia and amines, which have a characteristic pungent odor, thereby reducing social tension in the areas located closely to the storage sites. The final product of the cascade biodegradation is biocompost, which corresponds to the physicochemical parameters of organomineral fertilizer.

Selective oxidation of cellulose into formic acid over heteropolyacid-based temperature responsive catalysts

Formic acid (FA) is one of the most promising vectors for sustainable hydrogen energy and it can be synthesized from renewable biomass resources. In this work, a range of heteropolyacid derived temperature-responsive catalysts (ChnH4-nPMo11VO40, n=1–3) were prepared by modifying H3PMo12O40 heteropolyacid with an oxidation site V5+ and temperature-responsive monomer choline chloride (Ch+), and used for the cascade conversion of biomass derived cellulose into FA via hydrolysis-oxidation in water. The ChH3PMo11VO40 with a Ch/H ratio of 1/3 exhibited an outstanding catalytic performance to give a 49.5% yield of FA at 165 °C after 3 h reaction time. Catalytic activity of ChnH4-nPMo11VO40 was found to be related to its amount of H+ and V5+, while the recyclable ability of ChnH4-nPMo11VO40 was found to be related to its amount of Ch+. The as-prepared catalyst could be perfectly recycled with a single decrease the temperature of reaction systems, and be reused four times with limit loss in catalytic activity. The developed temperature-responsive catalysts have both advantages of homogeneous catalyst and heterogeneous catalyst, which should have potential application in other reactions of lignocellulosic biomass valorization.

Continuous aqueous-phase cascade conversion of trioses to lactic acid over Nb2O5 catalysts

Continuous aqueous-phase cascade conversion of trioses to lactic acid over Nb2O5 catalysts

A hybrid nanobiocatalyst with in situ encapsulated enzyme and exsolved Co nanoclusters for complete chemoenzymatic conversion of methyl parathion to 4-aminophenol

Combination of enzymatic and chemical reactions provides tremendous possibilities for chemoenzymatic cascade processes. However, constructing efficient hybrid catalysts still faces great challenges. Herein, we develop a hybrid catalyst by in situ encapsulating organophosphorus hydrolase (OPH) into a Zn-doped Co-based ZIF (0.8CoZIF) via biomimetic mineralization for the chemoenzymatic cascade conversion of methyl parathion to 4-nitrophenol and then 4-aminophenol. The exsolved Co nanoclusters in Zn/Co-ZIF are found to catalyze 4-nitrophenol reduction into 4-aminophenol in the presence of sodium borohydride (NaBH4). The as-synthesized OPH@0.8CoZIF catalyzes the complete conversion of 95 μM methyl parathion at nearly 100% 4-aminophenol production in the presence of 50 mM NaBH4 within 15 min, which is 1/4 that of the physical mixture of OPH and 0.8CoZIF, benefiting from the MP accumulation and substrate channeling in the hybrid catalyst. The maximum cascade conversion rate of MP to 4-AP reaches 8.07 μmol·min-1·g-catalyst-1, which is higher than most of the reported chemoenzymatic cascade catalysts. Therefore, the hybrid nanocatalyst containing Co-ZIF-based catalyst and OPH is successfully fabricated and enables to catalyze the complete conversion of a toxic pollutant like methyl parathion into a non-toxic resource like 4-aminophenol for recycling in useful chemical synthesis through efficient one-pot cascade reactions.