High-temperature Steam Treatment Research Articles

Synthesis of high hydrophobicity USY zeolite with excellent VOCs adsorption performance under humid condition: Combined strategy of high temperature steam and acid treatment

Y Zeolite and its ultra-stabilized hierarchical derivative (USY) as absorbents have low adsorption capacity for VOCs under humid conditions thus limits their industrial applications. It is well known that high SiO2/Al2O3 ratio (SAR) can improve the hydrophobicity of zeolite, and the increase of pore volume can enhance the adsorption performance. In the present work, SAR and the pore size of CY were enlarged by oxalic acid-high temperature steam-citric acid treatment, as the framework aluminum in the zeolite was removed and maintaining its structural integrity. The surface morphology and structure of samples were characterized by XRD, BET, TEM, SEM and TG. 27Al MAS NMR, XPS and Pyridine infrared analysis the mechanism of aluminum removal from the CY framework. The dynamic adsorption properties of the samples were systematically investigated with toluene selected as representative volatile organic compounds. The hydrophobicity of the samples was investigated by static water adsorption, and the adsorption kinetics model of the samples were plotted to study their adsorption characteristics. N2 adsorption-desorption results showed that the modified CY material has larger surface area, wider pore size and larger microporous volume than the raw material. On the other hand, with the improved SiO2/Al2O3 ratio and hydrophobicity, the modified USY also exhibited excellent adsorption performance under humid conditions, with 4.2 times more capacity to adsorb toluene. Therefore, this method can provide effective adsorption of VOCs in humid environments.

A Novel Gene Cluster Is Involved in the Degradation of Lignin-Derived Monoaromatics in Thermus oshimai JL-2.

A novel gene cluster involved in the degradation of lignin-derived monoaromatics such as p-hydroxybenzoate, vanillate, and ferulate has been identified in the thermophilic nitrate reducer Thermus oshimai JL-2. Based on conserved domain analyses and metabolic pathway mapping, the cluster was classified into upper- and peripheral-pathway operons. The upper-pathway genes, responsible for the degradation of p-hydroxybenzoate and vanillate, are located on a 0.27-Mb plasmid, whereas the peripheral-pathway genes, responsible for the transformation of ferulate, are spread throughout the plasmid and the chromosome. In addition, a lower-pathway operon was also identified in the plasmid that corresponds to the meta-cleavage pathway of catechol. Spectrophotometric and gene induction data suggest that the upper and lower operons are induced by p-hydroxybenzoate, which the strain can degrade completely within 4 days of incubation, whereas the peripheral genes are expressed constitutively. The upper degradation pathway follows a less common route, proceeding via the decarboxylation of protocatechuate to form catechol, and involves a novel thermostable γ-carboxymuconolactone decarboxylase homolog, identified as protocatechuate decarboxylase based on gene deletion experiments. This gene cluster is conserved in only a few members of the Thermales and shows traces of vertical expansion of catabolic pathways in these organisms toward lignoaromatics.IMPORTANCE High-temperature steam treatment of lignocellulosic biomass during the extraction of cellulose and hemicellulose fractions leads to the release of a wide array of lignin-derived aromatics into the natural ecosystem, some of which can have detrimental effects on the environment. Not only will identifying organisms capable of using such aromatics aid in environmental cleanup, but thermostable enzymes, if characterized, can also be used for efficient lignin valorization. However, no thermophilic lignin degraders have been reported thus far. The present study reports T. oshimai JL-2 as a thermophilic bacterium with the potential to use lignin-derived aromatics. The identification of a novel thermostable protocatechuate decarboxylase gene in the strain further adds to its significance, as such an enzyme can be efficiently used in the biosynthesis of cis,cis-muconate, an important intermediate in the commercial production of plastics.

Antioxidant activity of water extract from bamboo by high-temperature and high-pressure steam treatment

The antioxidant activity of water extract from bamboo by high-temperature and high-pressure steam treatment was analyzed. Bamboo was decomposed by high-temperature and high-pressure steam treatment, and more decomposition products were extracted with water extraction. The maximum antioxidant activity, i.e., EC50 = 0.127 mg/mL, and the maximum flavonoid content, i.e., 3.94 mg-quercetin equiv./g-dry weight bamboo, of water extract were obtained at a treatment pressure of 30 atm for a steaming time of 5 min. Compared with the untreated sample, they showed about 4.16 times higher of antioxidant activity and 6.02 times higher of flavonoid content. The maximum total polyphenol content, i.e., 35.7 mg-catechin equiv./g-dry weight bamboo, of water extract was obtained at 25 atm for 5 min. Compared with the untreated sample, it showed 6.69 times higher of total polyphenol content. The water extract from bamboo by high-temperature and high-pressure steam treatment was fractionated by high-performance liquid chromatography (HPLC). The structure of the fraction showing the highest antioxidant activity in the fractionated extract was determined. It had a structure having two highly reactive phenolic hydroxyl groups. The two phenolic hydroxyl groups reacted with reactive oxygen species (ROS) to cause a reduction reaction, thereby exhibiting antioxidant activity.

Effect of high-temperature saturated steam treatment on the physical, chemical, and mechanical properties of moso bamboo

Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens) was subjected to heat treatment with saturated steam at 140, 160, and 180 °C for 10–30 min to evaluate the effects of the treatment on the properties of bamboo. The changes in the physical, mechanical, and chemical properties as well as microscopic structures of moso bamboo were analyzed in this study. Results indicated that its equilibrium moisture content (EMC) decreased gradually after being treated by high-temperature saturated steam mostly due to the hemicelluloses’ degradation. Both the temperature and duration of treatment affect the mechanical properties of bamboo. The modulus of elasticity (MOE) of bamboo was prone to be affected by heat treatment with saturated steam as compared to the modulus of rupture (MOR). The MOR and MOE increased as compared to the control when the sample was treated at 140 °C. However, a severe treatment negatively affects the mechanical properties of bamboo. The MOR and MOE decreased by 47% and 20% as compared to the control when the sample was heated at 180 °C for 30 min.

Effect of magnesium on the catalytic properties of polymetallic zeolite catalysts for conversion of dimethyl ether to light olefins

Abstract The effects of magnesium modification of mono- and bimetallic zeolite catalysts (La-НZSM-5, Zr-НZSM-5, and La–Zr-НZSM-5) and high-temperature steam treatment of these catalysts on the conversion of dimethyl ether to light olefins were studied. The additional introduction of magnesium resulted in higher catalyst activity and selectivity to light olefins. The high-temperature steam treatment of the catalysts not only increased the catalyst activity, but also resulted in higher selectivity to propylene, which is most likely due to higher contribution of the alkene cycle. The developed magnesium-containing zeolite catalysts can be used for the synthesis of light olefins from dimethyl ether with dilution of dimethyl ether in the feed with steam or synthesis gas of different compositions.

Production of Eco-refinery Pulp from Moso Bamboo Using Steam Treatment Followed by Milling Treatment

In this study, we produced cellulose nanofiber (CNF) from moso bamboo using high-temperature and high-pressure steam treatment combined with the milling treatment. This pretreatment method can be considered as an environmentally friendly method because the treated product contains only wood-derived components and water that generally do not lead to significant corrosion problems and formation of neutralization sludge. The specific tensile strengths of CNF obtained in this work were almost the same values as that of a commercial CNF. Furthermore, an eco-refinery pulp was made of holocellulose and CNF those were obtained from moso bamboo by this pretreatment method and its mechanical strength was evaluated. By changing the steam treatment conditions, it is possible to produce eco-refinery pulp of various specific tensile strengths adapted to the application and purpose.

Production of cellulose nanofibers from Aspen and Bode chopsticks using a high temperature and high pressure steam treatment combined with milling

Holocellulose was generated from Aspen and Bode chopsticks by high temperature, high pressure steam treatment combined with milling. The steam treatment conditions were increased, the holocellulose component ratio in the treated sample as well as its molecular weight decreased. The treated holocellulose was subjected to grinder treatment to obtain cellulose nanofibers (CNF). Field-emission scanning electron micrographs indicated that CNF were successfully produced. The maximum tensile strength values of 86.9 and 109.9 MPa/(g/cm3) for Aspen and Bode, respectively, were obtained at a steam pressure of 15 atm and steaming time of 5 min. Furthermore, it was demonstrated that the optimal molecular weight of holocellulose to produce CNF with high tensile strength was around 1.2 × 105, while the optimal holocellulose recovery rate (HR; the degree of fibrillation was defined as HR in this study) was around 1.00.

Effects of high temperature steam treatment on microbial and phytochemical contents, antioxidant activities, chemical stability, and shelf life of oral liquid prepared from the leaves ofZanthoxylum bungeanumMaxim

The effects of high temperature steam (HTS) treatment on liquid prepared from the leaves of Zanthoxylum bungeanum Maxim (ZBOL) were studied with by comparing other three treatment methods. After HTS treatment, the microbial content met the standard requirements, the ratios of the phytochemical content were all higher than 84.5%, the antioxidant activities had decreased by <9.57%, no obvious changes were observed in the sensory characteristics, and the results were all better than other treatments. Furthermore, ZBOL showed excellent chemical stability in assays in terms of the use of high temperature (60 ± 2°C) and strong illumination (4,500 ± 500 lx), and prediction and verification tests determined the shelf life of ZBOL to be 12 months (25°C). In summary, HTS was demonstrated to be an efficient treatment method of ZBOL, and these results can be used for the utilization of Z. bungeanum leaves in an industrial setting. Practical application This work provides an efficient method for treatment of oral liquid prepared with flavonoids and antioxidants from the leaves of Zanthoxylum bungeanum Maxim (ZBOL). Herein, the quality information of ZBOL is provided, and a theoretical basis is established for the market promotion of ZBOL and the comprehensive utilization of the resources of Z. bungeanum leaves.

Optimization of High Temperature and Pressurized Steam Modified Wood Fibers for High-Density Polyethylene Matrix Composites Using the Orthogonal Design Method

The orthogonal design method was used to determine the optimum conditions for modifying poplar fibers through a high temperature and pressurized steam treatment for the subsequent preparation of wood fiber/high-density polyethylene (HDPE) composites. The extreme difference, variance, and significance analyses were performed to reveal the effect of the modification parameters on the mechanical properties of the prepared composites, and they yielded consistent results. The main findings indicated that the modification temperature most strongly affected the mechanical properties of the prepared composites, followed by the steam pressure. A temperature of 170 °C, a steam pressure of 0.8 MPa, and a processing time of 20 min were determined as the optimum parameters for fiber modification. Compared to the composites prepared from untreated fibers, the tensile, flexural, and impact strength of the composites prepared from modified fibers increased by 20.17%, 18.5%, and 19.3%, respectively. The effect on the properties of the composites was also investigated by scanning electron microscopy and dynamic mechanical analysis. When the temperature, steam pressure, and processing time reached the highest values, the composites exhibited the best mechanical properties, which were also well in agreement with the results of the extreme difference, variance, and significance analyses. Moreover, the crystallinity and thermal stability of the fibers and the storage modulus of the prepared composites improved; however, the hollocellulose content and the pH of the wood fibers decreased.

Steam-dealuminated, OSDA-free RHO and KFI-type zeolites as catalysts for the methanol-to-olefins reaction

RHO and KFI-type zeolites are synthesized in the absence of organic structure-directing agents (OSDAs), post-synthetically dealuminated via high temperature (600–800 °C) steam treatments, and evaluated as catalysts for converting methanol-to-light olefins (MTO). The proton forms of the as-made zeolites deactivate rapidly when tested for the MTO reaction (conducted at 400 °C and atmospheric pressure) due to their high aluminum content. Steam treatments lead to improvements in olefin selectivities and catalyst lifetimes with samples steamed at 600 °C giving the best combination of lifetime and olefin selectivity. Zeolite characterizations by 27Al NMR, 29Si NMR and argon physisorption indicate that the steam treatments extract framework aluminum, leading to reductions in the total number of Brønsted acid sites and the creation of mesopores that can facilitate transport of reactants. Poisoning of the acid sites external to the 8MR pores of the zeolites by treatments with trimethylphosphite results in longer catalyst lifetimes but do not affect the observed olefin selectivities, suggesting that olefins do not undergo secondary dimerization or methylation reactions at these sites.

Organic-Free Synthesis of CHA-Type Zeolite Catalysts for the Methanol-to-Olefins Reaction

Chabazite (CHA)-type zeolites are prepared from the hydrothermal conversion of faujasite (FAU)-type zeolites, dealuminated by high-temperature steam treatments (500–700 °C), and evaluated as catalysts for the methanol-to-olefins (MTO) reaction. The effects of temperature and partial pressure of water vapor during steaming are investigated. Powder X-ray diffraction (XRD) and Ar physisorption data show that the steam treatments cause partial structural collapse of the zeolite with the extent of degradation increasing with steaming temperature. 27Al MAS NMR spectra of the steamed materials reveal the presence of tetrahedral, pentacoordinate, and octahedral aluminum. NH3 and i-propylamine temperature-programmed desorption (TPD) demonstrate that steaming removes Bronsted acid sites, while simultaneously introducing larger pores into the CHA materials that make the remaining acid sites more accessible. Acid washing the steamed CHA-type zeolites removes a significant portion of the extra-framework aluminum, prod...

Chemical characteristics and enzymatic saccharification of lignocellulosic biomass treated using high-temperature saturated steam: Comparison of softwood and hardwood

This study investigated the effect of high-temperature saturated steam treatments on the chemical characteristics and enzymatic saccharification of softwood and hardwood. The weight loss and chemical modification of cedar and beech wood pieces treated at 25, 35, and 45atm for 5min were determined. Fourier transform infrared and X-ray diffraction analyses indicated that solubilization and removal of hemicellulose and lignin occurred by the steam treatment. The milling treatment of steam-treated wood enhanced its enzymatic saccharification. Maximum enzymatic saccharification (i.e., 94% saccharification rate of cellulose) was obtained using steam-treated beech at 35atm for 5min followed by milling treatment for 1min. However, the necessity of the milling treatment for efficient enzymatic saccharification is dependent on the wood species.

ИЗУЧЕНИЕ СВОЙСТВ АКТИВНЫХ УГЛЕЙ, ПОЛУЧЕННЫХ ИЗ СУХИХ ШИШЕК СОСНЫ ОБЫКНОВЕННОЙ

We have investigated the reception of activated carbons from waste softwood Pinus sylvestris by modifying the phosphoric acid followed by carbonization at 800 °C and high temperature steam treatment. The sorption properties of the material obtained with respect to copper ions (II). The structural features of the products obtained in the course of carbonization. It is shown that in the process of carbonization samples with additives H 3 PO 4 at 800 °C, a porous material with a specific surface of 870 m 2 /g. It is found that the sorption capacity for iodine sorbent carbonized at 800 °C, is 128.68%. Also shown is that the resulting active carbons can be used in the purification of water from a copper ion (II), the kinetics of this process model is described pseudo-first order precedes sorption diffusion.

Selective dealumination of mordenite for enhancing its stability in dimethyl ether carbonylation

Abstract Selective dealumination of mordenite by high-temperature steam treatment improved its stability in dimethyl ether carbonylation. Most of the framework Al species in the 12-membered ring channels of mordenite was removed while those in the 8-membered ring channels were retained. On the resulting mordenite catalyst, the formation rate of methyl acetate was only slightly decreased and maintained at 1.71 mol (mol H+)− 1 h− 1 at 15 h. Temperature-programmed oxidation analyses on the used sample evidenced that the deposition of hard coke was effectively suppressed in the selectively dealuminated catalyst because of the reduced number of acidic sites in the 12-membered ring channels.

Effect of high-temperature steam treatment on structural characteristics of Y-type zeolites with various sodium contents

The effect exerted by temperature of steam treatment and degree of exchange of Na+ for H+ on the lattice parameters and texture of Y zeolites with the initial SiO2/Al2O3 ratio 4.9 and 6.0 was determined.

Potential use of high-temperature and low-temperature steam treatment, sodium hydroxide and an enzyme mixture for improving the nutritional value of sugarcane pith

The effectiveness of different treatment methods to improve the nutritional value of the sugarcane byproducts (pith or bagasse) has been evaluated. The treatment methods included a high-pressure steam treatment (HPST; 19 bar, 3 min), treating the products with sodium hydroxide, sulphuric acid plus an enzyme mixture, or low-temperature steam treatment (LTST) under different conditions. Gas production (GP), two-step in vitro digestibility (IVD) and in situ degradability (ISD) techniques were used to monitor the effectiveness of the treatments. HPST resulted in a significant increased in the total soluble sugar (TSS) content of unsteamed pith (USP), 20 vs. 123.75 mg/100 mL. Except for the enzyme treatment, the other treatments led to a significant improvement in the nutritional value of sugarcane by-products, as measured by the IVD method. LTST resulted in an increase in potential GP (B) at higher temperature, reaction time and amount of acid. The highest potential GP (110.92 mL/300 mg DM) was achieved under the conditions, 134 °C, 18 g acid/kg DM, 120 min, and the lowest (72.4 mL/300 mg DM) under the conditions, 121 °C, no acid, 40 min. In situ dry matter degradability (ISDMD) was unaffected by LTST. Dry matter digestibility results indicated that the optimal treatments for treating pith were HPST and NaOH, but that enzymes were ineffective. Furthermore, considering treatment cost (creating high-pressure are more expensive than low temperature treatments), potential environmental health problems and the relative improvement in the nutritional value of pith achieved by the LTST + acid method, compared to the HPST method (as measured using GP), these results suggested that the methods based on the use of LTST and acid (especially under harsher conditions), have the best potential to improve the nutritive value of sugarcane by-products.

Hydrothermal Stability of Mesostructured Cellular Silica Foams

The hydrothermal stability of mesostructured cellular silica foams (MCFs) was studied in detail for the first time, using a variety of techniques including transmission electron microscopy, nitrogen sorption, small-angle X-ray scattering, 29Si solid-state nuclear magnetic resonance, and Fourier transform infrared spectroscopy. It was found that the high aging temperature, greater microporosity, and high calcination temperature contribute to the stability of MCFs in high-temperature steam. The frameworks of MCFs calcined at 550 °C are stable in 100% steam at 600 °C for 12 h, but cannot withstand more critical conditions of 800 °C steam and collapse completely. By elevating the calcination temperature of MCFs to 900 °C, the polymerization degree of the silica frameworks is further enhanced, and the obtained MCF materials exhibit high hydrothermal stability under steam at 800 °C for 12 h. The results indicate that increasing the calcination temperature is an effective method to improve the hydrothermal stability of MCFs. It is concluded that 3-D disordered MCFs show structural variations during the high-temperature steam treatments different from those of 2-D ordered hexagonal SBA-15 materials. The pore size, window size, and wall thickness were unaltered for the steam-treated MCFs, while the pore size decreased and the pore wall thickness became thicker for SBA-15.

Direct Synthesis of a Fluidizable SAPO-34 Catalyst for a Fluidized Dimethyl Ether-to-Olefins Process

The dimethyl ether to olefins process is very important for converting coal to chemicals. A SAPO-34 molecular sieve with a particle size up to 50 μm has been synthesized with morpholine as the template. The cold model fluidization experiment indicates that the SAPO-34 catalyst with average size of 45–50 μm is of good fluidization properties. After high temperature steam treatment at 1073 K for 8 h, this large fluidizable catalyst showed good reactivity and selectivity for the dimethyl ether to olefins (DTO) reaction in a micro-reactor. X-ray diffraction characterization showed that the structure of the catalyst was maintained well. A fluidized reactor of 50 mm inner diameter was used to carry out the DTO reaction, which showed that the fluidizable SAPO-34 is a selective catalyst for light olefin production.

Synthesis of ZSM-34 and Its Catalytic Properties in Methanol-to-Olefins Reaction

ZSM-34 (OFF/ERI intergrowth) was synthesized using choline chloride as the template in a shorter crystallization time under hydrothermal conditions. Many factors that may influence the synthesis were investigated. The ERI content in ZSM-34 could be adjusted by selecting different synthesis conditions. The synthesized products were characterized by X-ray diffraction, scanning electron micros-copy, and X-ray fluorescence spectroscopy. Adsorption experiments showed that ZSM-34 possessed high pore volume, and the adsorption amount of n-hexane reached 11.4%. In the methanol-to-olefins reaction, HZSM-34 exhibited high selectivity for ethylene. The maximum selectivity for total olefins (C2H4 + C3H6) over HZSM-34 was 86.0%, and it nearly did not change even when the methanol conversion decreased. High-temperature steam treatment caused the increase of the framework Si/Al ratio and thus decreased the acidity of HZSM-34, which led to the obvious decrease in propane selectivity and the increase in initial olefins selectivity.

Understanding Effect of Wall Structure on the Hydrothermal Stability of Mesostructured Silica SBA-15

Mesostructured silica SBA-15 materials with different structural parameters, such as pore size, pore volume, and wall thickness, etc., were prepared by varying the postsynthesis hydrothermal treatment temperature and adding inorganic salts. The hydrothermal stabilities of these materials in steam (100% water vapor) were systematically investigated using a variety of techniques including powder X-ray diffraction, transmission electron microscopy, nitrogen sorption, and (29)Si solid-state NMR. The effect of the pore size, microporosity or mesoporosity, and wall thickness on the stability was discussed. The results show that all of the SBA-15 materials have a good hydrothermal stability under steam of 600 degrees C for at least 24 h. N(2) sorption measurements show that the Brumauer-Emmett-Teller surface area of SBA-15 materials is decreased by about 62% after treatment under steam at 600 degrees C for 24 h. The materials with thicker walls and more micropores show relatively better hydrothermal stability in steam of 600 degrees C. Interestingly, we found that the microporosity of the mesostructured silica SBA-15 is a very important factor for the hydrothermal stability. To the materials with more micropores, the recombination of Si-O-Si bonds during the high-temperature steam treatment may not cause direct destruction to the wall structure. As a result, SBA-15 materials with more micropores show better stability in pure steam of 600 degrees C. Nevertheless, these materials are easily destroyed in steam of 800 degrees C for 6 h. Two methods to effectively improve the hydrothermal stability are introduced here: one is a high-temperature treatment, and another is a carbon-propping thermal treatment. Thermal treatment at 900 degrees C can enhance the polymerization degree of Si-O-Si bonds and effectively improve the hydrothermal stability of these SBA-15 materials in 800 degrees C steam for 12 h. But, this approach will cause very serious shrinkage of the mesopores, resulting in smaller pore diameter and low surface area. A carbon-propping thermal treating method was employed to enhance the polymerization of Si-O-Si bonds and minimize the serious shrinkage of mesopores at the same time. It was demonstrated to be an effective method that can greatly improve the hydrothermal stability of SBA-15 materials in 800 degrees C steam for 12 h. Furthermore, the SBA-15 materials obtained by using the carbon-propping method possess larger pores and higher surface area after the steam treatment at 800 degrees C compared to the materials from the direct thermal treatment method after the steam treatment.