Performance Study of Zn-Co-Ni/AC Catalyst in Acetylene Acetylation

Zinc acetate (Zn(OAc)2) loaded on activated carbon (AC) is the most commonly used catalyst for the industrial synthesis of vinyl acetate (VAc) using the acetylene method. The aim of this study is to optimize the Zn(OAc)2/AC catalyst by adding co-catalysts to improve its activity and stability. Ternary catalysts were synthesized by adding Co and Ni to the Zn(OAc)2/AC catalyst (Zn-Co-Ni/AC). Due to the strong synergistic effect among promoter Co, Ni, and the active component of Zn(OAc)2, the resulting catalyst is capable to absorb more acetic acid and less acetylene. The stability and activity of Zn-Co-Ni/AC catalyst have been improved through electron transfer to alter the electron cloud density around the Zn element. Under the same reaction conditions, the activity of Zn-Co-Ni/AC catalyst was enhanced by 83% compared to that of Zn(OAc)2/AC, and the activity was still as high as 30.1% after 120 h of testing.

Effects of Oxygenated Acids on Graphene Oxide: The Source of Oxygen-Containing Functional Group

Graphene oxide is an important member of the graphene family which has a wide range of applications. The chemical method, especially the liquid phase method, is one of the most common and important methods for its preparation. However, the complex solution environment not only gives them rich structure, but also brings great challenges for its large-scale industrial synthesis. In order to better realize its industrial application, it is important to understand its structure, such as the source of oxygen-containing functional groups. Here we studied the contribution of four oxygenated acids to oxygen-containing functional groups in Hummers’ method using first principles. We found that the permanganic acid molecules that exist instantaneously due to energy fluctuations can be the source of oxygen-containing functional group. In addition, Stone-Wales defect have a certain effect on the formation of oxygen-containing functional groups, but this effect is not as good as that of solvation effect. This work provides a guide for exploring the source of oxygen-containing functional groups on graphene oxide.

A novel tyrosinase from Armillaria ostoyae with comparable monophenolase and diphenolase activity suffers substrate inhibition

Tyrosinase is a bifunctional enzyme mediating the o-hydroxylation and two-electron oxidation of monophenols to o-quinones. The monophenolase activity of tyrosinase is much desired for the industrial synthesis of catechols. However, the generally low ratio of monophenolase/diphenolase activity of tyrosinase limited its utilization in the industry. In this study, a novel tyrosinase from Armillaria ostoyaestrain C18/9 (AoTyr) was characterized and the results showed that the enzyme has an optimal temperature of 25°C and an optimal pH of 6. The enzyme has comparable monophenolase and diphenolase activities and exhibits substrate inhibition in both of the two activities. In silico analysis and mutagenesis experiments showed that residue 262 and 266 play important roles in modulating the substrate inhibition and enzymatic activities of AoTyr, and the substitution of D262 with asparagine significantly increased the monophenolase/diphenolase catalytic efficiencies (kcat/Km) (1.63 folds) of the enzyme. The results from this study indicated that this novel tyrosinase could be a potential candidate for the industrial biosynthesis of catechols. IMPORTANCE Tyrosinase is able to oxidize various phenolic compounds and its ability to convert monophenols into diphenols has caught great attention in the research field and industrial applications. However, the utilization of tyrosinase for the industrial synthesis of catechols has been limited due to the fact that the monophenolase activity of most of the known tyrosinases is much lower than diphenolase activity. In the present study, a novel tyrosinase with a comparable monophenolase/diphenolase activity ratio was characterized. The enzyme exhibits substrate inhibition in both monophenolase and diphenolase activities. In silico analysis followed by mutagenesis experiments confirmed the important roles of residue 262 and 266 in the substrate inhibition and activities modulation of the enzyme, and the variant D262N showed an enhanced monophenolase/diphenolase catalytic efficiency ratio as compared to the wild type enzyme.

CALCULATION AND DESIGN OF AN INDUSTRIAL REACTOR FOR PYRROLES SYNTHESIS

Industry of pyrroles synthesis on the basis of acetylene, ammonia and amines over polyfunctional catalyst can be organised only when for its recovery the rational industrial technology allowing to synthesize this product in necessary quantity and demanded quality cheap enough from accessible raw materials is developed. Considering the issues related to the development of a new reactor with high productivity and economic efficiency, the processes running in the reactor were studied. Phase characteristics have been investigated in response to changes in acetylene conversion rate due to the height of the catalyst layer. As a result, high productivity of acetylene production with zinc-chromaluminum catalyst at the temperature range of 340-440оС is achieved for 92% when the layer height is 1200 mm from the reactor top point. Based on the mass balance as well as the experimental result, a reactor for the industrial synthesis of pyrroles has been proposed.

Electrocatalytic Fixation of N2 into NO3-: Electron Transfer between Oxygen Vacancies and Loaded Au in Nb2O5-x Nanobelts to Promote Ambient Nitrogen Oxidation

The electrocatalytic nitrogen oxidation reaction (NOR) is a promising alternative to the industrial synthesis of nitrate. However, with the enhancement of the NOR activity by modification methods, the competitive oxygen...

Nanomaterials for Nitrogen Electrochemical Reduction Reactions under Ambient Conditions

As an important chemical product and carbon-free energy carrier, ammonia has a wide range of daily application in several related fields. Although the industrial synthesis method using the Haber-Bosch process...

An Enantioselective Approach to 4-Substituted Proline Scaffolds: Synthesis of (S)-5-(tert-Butoxy carbonyl)-5-azaspiro[2.4]heptane-6-carboxylic Acid

A catalytic and enantioselective preparation of the (S)-4-methyleneproline scaffold is described. The key reaction is a one-pot double allylic alkylation of an imine analogue of glycine in the presence of a chinchonidine-derived catalyst under phase transfer conditions. These 4-methylene substituted proline derivatives are versatile starting materials often used in medicinal chemistry. In particular, we have transformed tert-butyl (S)-4-methyleneprolinate (12) into the N-Boc-protected 5-azaspiro[2.4]heptane-6-carboxylic acid (1), a key element in the industrial synthesis of antiviral ledipasvir.

Features of the internal structure of high-pressure metal-diamond composites

In the present work, composites were obtained by sintering a metal-diamond charge at a pressure of 4 GPa and a temperature of 1300°C. the experiments were carried out on a high-pressure apparatus of the split sphere “bars” type. Synthetic microcrystals of industrial synthesis were used as a diamond. The initial metal component for the experiments was copper and iron. it was shown that when sintering at high pressure, diamond crystals are tightly packed in the composite, while the metal phase completely fills the intergranular space, acting as a matrix. chemical analysis of the metal component of the samples revealed the presence of the following phases: copper-iron alloy, iron oxide and iron carbide. the results obtained indicate that several processes occur simultaneously in the diamond-copper-iron-oxygen system at high pressures and temperatures, which can significantly affect the characteristics of the resulting composite as a whole.

Technology of large volume alcohols, carboxylic acidsand esters

Paper describes industrial synthesis of the most important alcohols (methanol and ethanol), organic acids (acetic and lactic), and fatty acid methyl esters (biodiesel). Also, current industrial solutions and global trends in manufacturing of these chemicals are presented. Moreover, several alternative production technologies of these chemical compounds are discussed, which might successfully replace current commercial methods in the future.