Various ZSM-5 type zeolites containing alkaline earth metals (AE-ZSM-5) were synthesized and catalytic performances in the conversion of methanol to light olefins were investigated. The AE-ZSM-5 showed increased selectivity for light olefins at temperatures above 500 °C. High (C2H4 + C3H6) yields (>50 C%) were obtained over Mg-ZSM-5, Ca-ZSM-5, and Sr-ZSM-5 with SiO2/Al2O3 ratios of 200-800, 100-800, and 80-300, respectively. Maximum (C2H4 + C3H6) yield of ca. 65 C% was achieved over Ca-ZSM-5 with SiO2/Al2O3 ratios of 100-300. The strong acid sites of ZSM-5 became weakly acidic after incorporation of alkaline earth metals, which suppressed coking and dealumination, resulting in improved catalyst lifetime. However, part of the incorporated alkaline earth metals underwent leaching from the weak acid sites due to H2O and CO2 produced during the reaction, which resulted in the regeneration of the strong acid sites of the zeolite. These strong acid sites promote the formation of carbonaceous deposits that are ultimately responsible for the deactivation of the zeolite catalysts. Investigation of the stabilization of weak acid sites found that the zeolite catalyst lifespan could be greatly extended by modification with alkaline earth metal carbonates. SrCO3/Sr-ZSM-5 (SiO2/Al2O3 = 100) maintained a (C2H4 + C3H6) yield of more than 50 C% for 2000 h at 550 °C with only three regeneration cycles. The high catalytic performance of CaCO3/Ca-ZSM-5 was evaluated by a bench-scale test. Total C2H4 and C3H6 production was 11.52 kg from a methanol feed of 42.347 kg after 266 h. The conversion of ethanol to light olefins over various ZSM-5 zeolites with different acidity, especially zeolites with isomorphous framework-substitution, was also investigated. The highest propylene yield of ca. 29 C% was obtained over co-modified La/P/ZSM-5(Ga) with P/Ga and La/Ga ratios of 1 and 0.4, respectively. The introduced lanthanum reacts with the pre-introduced phosphorus to regenerate some of the Brønsted acid sites (Si(OH)Ga).
Selective production of light olefins over zeolite catalyst requires control of consecutive reactions because the objective products are intermediates. In catalytic reactions using zeolite, the diffusion resistance of both the raw material and products within the crystal, and acid site strength of the zeolite, strongly affect the catalyst activity and selectivity. This review describes the preparation of macro-, and nano-sized ferrisilicate and ferroaluminosilicate with MFI and MTW-type zeolite structures and their application to the production of light olefins from oxygenated organic compounds such as acetone and methanol. Nano-sized ferrisilicate with MFI-type zeolite structure showed more stable activity compared to macro-sized zeolite in the acetone to olefin and methanol to olefin reactions. Moreover, metallosilicates containing Fe atoms in the zeolite framework had higher selectivity for light olefins compared to aluminosilicate due to suppression of the consecutive reactions forming aromatics and coke. Ferroaluminosilicate containing two types of Brønsted acid sites, derived from both Fe and Al atoms in the framework, was the most effective catalyst for the production of light olefins from methanol.
Selective production of propylene was investigated with preparation routes to MSE-type zeolite catalysts, microporous aluminosilicates with a 12-10-10-ring micropore system. Some examples of catalytic application including the conversions of petroleum and non-petroleum resources are reviewed. Variation of the synthetic route provided characteristic aluminosilicate MSE-type materials that exhibited improved catalytic performances for hexane cracking. La-modification is effective for enhancing the catalytic performance in hexane cracking. To control the acid sites distribution in MCM-68 zeolite catalyst, phosphate-loaded MCM-68 catalyst was prepared by impregnation and subsequent calcination. Phosphate impregnation increased the selectivity to propylene and butenes in the dimethyl ether-to-olefin (DTO) reaction. The propylene/ethylene ratio in the products was significantly increased by phosphate modification. Phosphate-modified MCM-68 showed high resistance to coke formation, indicating that this modification technique is useful to obtain long-lived catalysts in the DTO reaction. Ce-modification of dealuminated MCM-68 enhanced the stability. Successive calcination at 800 °C generated selective and long-lived catalyst for dimethyl ether-to-olefin reaction, resulting in high propylene yield.
Several SAPO-11-Al2O3 supports with different amounts of SAPO-11 were used to prepare a series of CoMo/ SAPO-11-Al2O3 catalysts by the impregnation method with or without addition of citric acid. Hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene, hydrodenitrogenation (HDN) of acridine, and hydrodearomatization (HDA) of o-xylene, 1-methylnaphthalene and phenanthrene were carried out to evaluate the catalytic activity of the catalysts. The catalysts were characterized by BET, XRF, NH3-TPD, XPS and TEM. The acidity of the supports strongly affected the active slabs structure and activity of the catalysts. 20 wt% SAPO-11 added catalyst showed lower HDA, HDS and HDN activities compared to CoMo/Al2O3 catalyst. The length and stacking number of CoMoS active slabs on the former increased because of decreased dispersion of Mo species due to the reduction in number of strong acid sites on the support surface in the presence of SAPO-11. Addition of citric acid during active metal impregnation decreased HDA activity but increased HDS and HDN activities due to improvement of Mo species dispersion, resulting in formation of shorter length and higher stacking of CoMoS active slabs.
Direct synthesis of methane from glycerol has been carried out over silica-modified nickel catalysts in the presence of water without the supply of hydrogen. The catalysts were synthesized by co-loading nickel species with silica on γ-Al2O3 by using a gel containing nickel and silica sources. In the conversion of glycerol over the Ni–SiO2/Al2O3 catalyst, glycerol was firstly decomposed to CO and H2; subsequently, methane was produced through the methanation of CO and CO2 with H2 generated during the reaction. Higher reaction temperatures and pressures resulted in the enhancement of the methane formation. In addition, the yield of methane was increased by increasing the water content in the glycerol aqueous solution. 20 wt%Ni-20 wt%SiO2/Al2O3 gave the maximum space-time yield (STY) of methane of 122 mol kg–1 h–1 with the feed of 50 wt% glycerol aqueous solution at 673 K under the pressure of 0.3 MPa. Co-loading of nickel species with silica on γ-Al2O3 was effective in suppressing the sintering of nickel particles. The coke deposition on the catalyst was significantly suppressed by modifying nickel particles with silica. The amount of deposited coke was decreased by increasing the amount of silica; the amount of coke deposited on Ni-30 wt%SiO2/Al2O3 was one-third of that on conventional Ni/γ-Al2O3.
We herein report the first study into the use of an enzyme mixture of cellulase and β-glucosidase for cellulose hydrolysis, with the overall aim of expressing the effect of β-glucosidase addition using a simple equation. To achieve this goal, different amounts of commercial cellulase and β-glucosidase were added to a cellulose slurry, and hydrolysis experiments were carried out at 40 °C and 50 °C over 0-48 h in a shaker incubator using a 0.1 mol/dm3 sodium acetate solution to maintain a solution pH of 5. The glucose yield got higher for the larger amount of cellulase and larger amount of β-glucosidase. The yield of glucose recovered at 50 °C was lower than that recovered at 40 °C. Finally, an equation to estimate glucose production using such a cellulase and β-glucosidase mixture was then developed for the first time, and this equation correlated well with the experimental data. The obtained equation expressed the hydrolysis using another bottle of cellulase, too.
Lubrication properties of ionic liquids were examined by friction tests between stainless steel disks and stainless steel balls. 1,3-Dimethylimidazolium dimethylphosphate ([C1C1im][dMp]) was a more effective lubricant for suppressing friction than poly-alpha-olefin, a commercially available hydrocarbon-based synthetic lubricant. [C1C1im][dMp] treated with supercritical carbon dioxide showed further suppression of friction in the initial stage of the friction test.