Hydrogenolysis-Isomerization of Waste Polyolefin Plastics to Multibranched Liquid Alkanes.

Upcycling of waste polyolefin plastics still meets with economic and technological challenges in practice. In this work, the catalytic hydrogenolysis-isomerization of nondegradable polyolefin plastic waste to high-value gasoline, diesel, and light lubricants with highly branched chain is achieved over a bifunctional Rh/Nb2 O5 catalyst under relatively mild conditions. Owing to the high efficiency of metallic Rh active sites, the dehydrogenation/hydrogenation of long carbon chains of polyolefins is enhanced. With the assistance of strong Brønsted acidity of Nb2 O5 , the cleavage of C-C bonds, skeletal rearrangements, as well as the ß-scission of alkylcarbenium ions occurs, which boosts the one-step solvent-free catalytic hydrogenolysis and isomerization of polyolefins. In addition, the preliminary economic analysis shows that this technology is economical, feasible, and has great potential in accelerating the transition to a circular plastics economy for sustainable development.

Insights into a Low-Rank Naomaohu Coal Structural Information by Multistage Fractions Coupled with LIAD-VUVPI-TOFMS.

In-depth insights into the chemical composition and structural information of coal are an effective way to improve the efficiency of coal utilization. Laser-induced acoustic desorption coupling with vacuum ultraviolet photoionization time-of-flight mass spectrometry (LIAD-VUVPI-TOFMS) was applied to structural characterization of cyclohexane extracts of low-rank Naomaohu coal. The characterization of four types (12 model compounds) of mixed coal model compounds (three compounds per category)-saturated hydrocarbons, substitute aromatic hydrocarbons, aromatic hydrocarbons, and aromatic heteroatom rings-demonstrated that the approach can provide intact molecular weight information. The cyclohexanone extract (E CYC) was obtained by microwave-assisted extraction and separated into four group components (F1-4) by column chromatography to achieve component classification and simplify analysis. The molecular weight and structure were obtained by LIAD-VUVPI-TOFMS and synchronous fluorescence spectroscopy, combined with microwave-assisted extraction and column chromatography to separate product characteristics. Chemical components of a total of 248 species were observed, of which 46 are derived from aliphatic hydrocarbons embedded in the coal skeleton structure, 132 species are derived from aromatic hydrocarbons embedded in the coal skeleton structure, 61 are derived from possible coal skeleton units (compounds have obvious stacking and bonding effects), and 9 could not be determined (aromatic hydrocarbons or a possible coal skeleton structure unit).

Pyrolysis behavior of low-density polyethylene over HZSM-5 via rapid infrared heating.

Catalytic fast pyrolysis experiments of low-density polyethylene (LDPE) over HZSM-5 were carried out by using infrared heating technology. The effects of heating rate (1-30 °C/s), pyrolysis temperature (450-650 °C), and mass ratio of catalyst to LDPE (0:100 to 50:100) on product distribution and oil composition in LDPE pyrolysis were investigated, and the fast pyrolysis mechanism was explored. The results indicated that a higher heating rate, namely 20 °C/s, can remarkably enhance the liquid oil yield (93.42%), but the oil is heavy due to about 90% high­carbon n-aliphatics. The addition of HZSM-5 performed an excellent effect on obtaining high-quality liquid oils, among which the total content of monocyclic aromatic hydrocarbons (MAHs) and iso-aliphatics obviously increase from 0.68% to 70.26%. The optimal HZSM-5/LDPE ratio of 10:100 was identified by considering the cost-effective factor. Furthermore, the lower catalytic temperature is favorable to the generation of light oil components, especially MAHs. The feasible generation paths were proposed, which mainly derived from the secondary reaction of the intermediate formed by initial chain cleavage including cyclization, aromatization, Diels-Alder reaction, as well as isomerization.

Transparent and ultra-wideband metamaterial absorber using coupled hexagonal combined elements.

Optically transparent microwave absorbers have been widely reported for electromagnetic stealth applications over the past few years, but developing ultra-wideband absorbers with high angular stability remains challenging. In this work, an absorber comprising a double-layer polymethylpentene (TPX) block and indium tin oxide (ITO) films has been designed, fabricated, and measured, respectively. Firstly, an impedance layer with novel coupled hexagonal combined elements is exploited to achieve ultra-wideband absorption. Secondly, to provide the optimal reflection response for high angular incidences, the TPX block with the lower permittivity is initially employed in the compensation and substrate layers. Finally, the experimental results agreed with simulation ones illustrate the excellent performance is concurrently achieved, including a 90% absorption bandwidth within 2.53-8.94 (111.8%), high angular stability (60°), and the high light transmittance (70.7%).

Effects of Vitrinite in Low-Rank Coal on the Structure and Combustion Reactivity of Pyrolysis Chars.

Pyrolysis is a highly promising technology for the efficient utilization of low-rank coal. The structure of coal plays an important role in its utilization. In this paper, the evolution of the char structure during heat treatment (200-800 °C) of Naomaohu coal and its different vitrinite-rich fractions was studied. The functional group structure, aromatic ring structure, and crystallite size of chars were determined by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) spectroscopy, respectively. The results indicated that minerals inhibit the condensation reaction of aromatic rings during pyrolysis. The high vitrinite content in coal is conducive to the formation of larger char crystallite average sizes (L a). The relationship between L a (1.69-3.10 nm) and the Raman band area ratio A (GR+VL+VR)/A D or A D/A all was established. In addition, the combustion performance and kinetics of chars were also investigated. The results showed that the char from high contents of the liptinite fraction has lower combustion reactivity, and demineralization treatment has significantly reduced the combustion reactivity of char.

Novel insight into pyrolysis behaviors of lignin using in-situ pyrolysis-double ionization time-of-flight mass spectrometry combined with electron paramagnetic resonance spectroscopy.

In-situ detection on primary volatiles and stable radicals is of great importance for better understanding of lignin pyrolysis mechanisms and utilization. In this study, a novel in-situ pyrolysis time-of-flight mass spectrometry with double ionization sources was taken to in-situ detect primary volatiles and gas products, and the evolution of stable radicals in lignin pyrolysis residues was explored by EPR spectroscopy. The results show that the cleavage of ß-O-4 linkage is mainly responsible for lignin depolymerization at 100-300 °C, releasing the G-type compounds. And these G-type compounds can further undergo O-CH3, Car-OCH3 and Car-OH bonds cleavage to form biphenolic hydroxyl compounds, phenols and aromatic hydrocarbons. According to the EPR analysis, the radical concentration increased from 1017 to 1019 spins/g with the temperature, and stable free-radical species are mainly composed of the o-methoxy and hydroxyl substituted phenoxy radicals and carbon-centered aromatic radicals, which can well interpret the demethylation, demethoxylation and dehydroxylation mechanisms.

A review on high catalytic efficiency of solid acid catalysts for lignin valorization.

It is imminent to develop renewable resources to replace fossil-derived energies as fossil resources are on the brink of exhaustion. Lignin is one of the major components of lignocellulosic biomass, which is a natural amorphous three-dimensional polymer with abundant C-O bonds and aromatic structure. Hence, valorization of lignin into high value-added liquid fuels and chemicals is regarded as a promising strategy to mitigate fossil resource shortages. Solid acid catalysts are extensively studied due to environmentally friendly in terms of the ease of separation, recovery and reduced amount of wastes. Hence, this review focuses on summarizing the recent progress of catalytic valorization of lignin over different kinds of solid acid catalysts including zeolites, heteropolyacids, metal oxides, amorphous SiO2-Al2O3, metal phosphates, and Lewis acid. Based on reviewing of current progress of lignin conversion, the challenges and future prospects are emphasized.

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs < Pt/5HNbWO6/CNTs < Pt/20HNbMoO6/CNTs < Pt/20HNbWO6/CNTs < Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

Fast pyrolysis behaviors of cedar in an infrared-heated fixed-bed reactor.

To explore fast pyrolysis behaviors of cedar biomass, the infrared heating technique with quick heating rate was taken in a fixed-bed reactor. The effects of heating rates (5-30 °C/s) and pyrolysis temperatures (400-600 °C) on pyrolysis products distribution and compositions were discussed, and the reaction mechanism was proposed. The results show that high heating rate can significantly suppress secondary reaction of primary volatiles. GC/FID and GC/MS analyses indicate that higher heating rate is favorable to the generation of glucose derivatives such as acids and furans. However, higher temperature can obviously promote further conversion of guaiacyl-contained structure following demethylation, demethoxylation and H/CH3 assisted demethoxylation routes, which were proposed to interpret the formation of biphenolic hydroxyl and monophenolic hydroxyl compounds such as phenol, 2-methyl-phenol and 2,4-dimethyl-phenol, respectively. Moreover, the demethylation route exhibits obvious conversion advantage at higher temperature due to lower energy barrier.

An ordered mesoporous aluminosilicate with completely crystalline zeolite wall structure.

An ordered mesoporous aluminosilicate with completely crystalline zeolite pore wall structure, denoted as OMZ-1, was successfully synthesized by recrystallization of SBA-15 using in situ formed CMK-5 as the hard template. The role of carbon material not only serves as a hard template to preserve ordered mesoporous structure but also kinetically controls the crystallization process to form large crystals.

Preparation and evaluation of a large-volume radial flow monolithic column.

In this study, a 38 mL monolith with homogeneous porous structure was produced by a single polymerization from glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) in the presence of porogens and an initiator. The uniform temperature distribution within the reaction system was achieved by adding reactant mixture continuously and enhancing the heat transfer ability of the polymerization system. Homogeneous porous structure in the monolith was proved by SEM and the pore size distribution profiles measured by mercury intrusion porosimetry. Experimental results from proteins separation indicated that the dynamic capacity and resolution of radial flow monolithic column were independent of flow rates. Furthermore, the pressure drop on the column was linearly dependent on the flow rate and did not exceed 1.7 MPa even at a flow rate of 50 mL/min, which proved that the prepared monolith could be used in the quick separation and preparation of biopolymers.