Chemodivergent assembly of ortho-functionalized phenols with tunable selectivity via rhodium(III)-catalyzed and solvent-controlled C-H activation

Ortho-functionalized phenols and their derivatives represent prominent structural motifs and building blocks in medicinal and synthetic chemistry. While numerous synthetic approaches exist, the development of atom-/step-economic and practical methods for the chemodivergent assembly of diverse ortho-functionalized phenols based on fixed catalyst/substrates remains challenging. Here, by selectively controlling the reactivities of different sites in methylenecyclopropane core, Rh(III)-catalyzed redox-neutral and tunable C-H functionalizations of N-phenoxyacetamides are realized, providing access to both ortho-functionalized phenols bearing linear dienyl, cyclopropyl or allyl ether groups, and cyclic 3-ethylidene 2,3-dihydrobenzofuran frameworks under mild cross-coupling conditions. These divergent transformations feature broad substrate compatibility, synthetic applications and excellent site-/regio-/chemoselectivity. Experimental and computational mechanistic studies reveal that distinct catalytic modes involving selective β-C/β-H elimination, π-allylation, inter-/intramolecular nucleophilic substitution cascade and β-H’ elimination processes enabled by different solvent-mediated and coupling partner-controlled reaction conditions are crucial for achieving chemodivergence, among which a structurally distinct Rh(V) species derived from a five-membered rhodacycle is proposed as the corresponding active intermediates.

Counteracting Rapid Catalyst Deactivation by Concomitant Temperature Increase during Catalytic Upgrading of Biomass Pyrolysis Vapors Using Solid Acid Catalysts

The treatment of biomass-derived fast pyrolysis vapors with solid acid catalysts (in particular HZSM-5 zeolite) improves the quality of liquid bio-oils. However, due to the highly reactive nature of the oxygenates, the catalysts deactivate rapidly due to coking. Within this study, the deactivation and product yields using steam-treated phosphorus-modified HZSM-5/γ-Al2O3 and bare γ-Al2O3 was studied with analytical Py-GC. While at a fixed catalyst temperature of 450 °C, a rapid breakthrough of oxygenates was observed with increased biomass feeding, this breakthrough was delayed and slower at higher catalyst temperatures (600 °C). Nevertheless, at all (constant) temperatures, there was a continuous decrease in the yield of oxygen-free hydrocarbons with increased biomass feeding. Raising the reaction temperature during the vapor treatment could successfully compensate for the loss in activity and allowed a more stable production of oxygen-free hydrocarbons. Since more biomass could be fed over the same amount of catalyst while maintaining good deoxygenation performance, this strategy reduces the frequency of regeneration in parallel fixed bed applications and provides a more stable product yield. The approach appears particularly interesting for catalysts that are robust under hydrothermal conditions and warrants further investigations at larger scales for the collection and analysis of liquid bio-oil.

Conversion of Liquefied Hydrocarbon Gases on Commercial Nickel Catalysts

The two-step conversion of industrial liquefied hydrocarbon gases (LHG) on NIAP-07-01 (NKM-1) and NIAP-03-01 catalysts for the production of hydrogen-containing gases was investigated. The experiments were carried out in flow reactors with a fixed catalyst bed at a pressure of 0.1 MPa under the following conditions: temperature 350–450 °C, gas hourly space velocity (GHSV) 1000–3000 h–1, steam-gas ratio 4 : 1–8 : 1 (pre-reforming); and temperature 700 °C, GHSV 2000 h–1, air-gas ratio 1.2 : 1 (steam-air reforming). Under the studied conditions, the concentrations of components of the converted gas correspond to the equilibrium values calculated within the Peng-Robinson model. The conversion of methane homologs in the pre-reforming step was found to be virtually 100 %; therewith, the methane concentration reached 32–54 %, and that of hydrogen, 24–47 %. To prevent the formation of elemental carbon (carbonization), pre-reforming of hydrocarbon gases with a high methane equivalent should be performed at H2O : C > 2. In the two-step reforming, the yield of hydrogen-containing gas reaches 15.6 m3 from 1 m3 of the initial LHG with the hydrogen content 41.81 %, and the total content of CO and H2 exceeds 52 %.

Unsteady-state operation of reactors with fixed catalyst beds

The review is dedicated to the research and development work made in USSR and Russia in the area of catalytic processes with artificially created unsteady-state conditions. The paper discusses the reverse-flow operation of catalytic reactor, forced feed composition cycling and sorption enhancement of catalytic reactions. It is demonstrated that under proper choice of process concept and control strategy these approaches may result in creation of new technologies with improved efficiency, lower capital and operation costs, higher process stability under variation of process conditions and increased target product yield in thermodynamically limited reaction and complex reaction systems.

Kinetic Studies of Hydrodeoxygenation of Ethyl Ester of Decane Acid over a Ni-Cu-Mo/Al2O3 Catalyst

Nickel-based catalysts for hydrodeoxygenation of vegetable oils are an alternative to the systems based on noble metals and sulfide catalysts for hydrotreatment. Modification of the nickel catalysts with molybdenum and copper allows the yield of target products to be increased and the corrosion resistance of the catalytic system to be improved. The studies were aimed at establishing relationships between temperature, contact time and activity of the modified nickel-containing catalyst to hydroxygenation of esters of fatty carboxylic acids, as well as at determining effective kinetic parameters of the reactant consumption. A flow reactor with the fixed catalyst bed was used for experimental studies at РН2 = 0.25 MPa, temperatures 270, 285, 300 and 315 °C, contact time varied from 600 to 1800 s. It was shown that the selectivity to the main reaction products – nonane and decane – did not change upon varying the reaction temperature and contact time. The experimental data were used for determining the effective rate constants and activation energy of the reaction.

Dehydration of Methylbutenes to Isoprene. Part 3: Comparative Mathematical Analysis of Methylbutene Dehydrogenation in Axial and Radial Reactors

A mathematical model of the process of dehydrogenation of methylbutenes to isoprene was used for comparative analysis of energetic efficiency of two versions of modernization: (1) a system of consecutively connected two axial reactors with a fixed catalyst beds, and (2) adiabatic radial reactor with fixed catalyst bed. The purpose was to determine the dependence of yield (Y) and selectivity (S) to the target product on the heat energyQsupplied with vapor. In the two-reactor system, the best parameters (Y= 53.1 % andS= 82.9 %) were achieved atQ= 9.0 MJ/kg and contact time t = 0.8 s. At the same time, in the radial reactor the best performance (Y= 42.0 % andS= 86.1 %) was observed atQ= 7.8 MJ/kg andt= 0.8 s. Hence, the radial reactor consumes less heat energy (by 13.0 %) than the radial reactor for methylbutene dehydrogenation.

Natural Clays of the Kazakhstan Deposits for Catalysts of Cracking

Presented paper is devoted to the construction of cracking catalysts based on H-form zeolite Y, modifying by heteropolyacids of 12 row decationzed forms of natural clays of Tagan and Narynkol deposits. Conditions of acid activation were compared for Tagan clay. Chemical composition of clays before and after activation was detected by optical emission spectral method; phase composition was detected with X-ray<br />diffraction. It has been shown that activities of composite catalysts are related to the concentration and sequence of HPA adding. From the results the conclusion was drawn that amount of adding HPA influenced the activity and thermal stability of catalysts prepared on the base of Tagan and Narynkol clays deposits. The synthesized catalysts were studied in a laboratory microimpulse catalytic set by the model reaction of isopropylbenzene cracking at temperature 350-500 °C. The optimum compositions of zeolite containing contacts served as the base of creation of cracking catalysts for real raw (kerosene-gas-oil fraction) into quartz reactor with a fixed catalyst bed. These prepared catalysts have demonstrated enhanced thermal<br />stability and high activity. Stronger cracking activity of catalysts prepared on the base of Narynkol clay has been shown.

Removal of Cadmium from Water by CNT–PAC Composite: Effect of Functionalization

Cadmium (Cd[Formula: see text]) is one of the toxic heavy metals that is frequently used in many industrial products. The wastewater from these industries and their products contains residual cadmium that are difficult to be removed economically from the effluent. Carbon nanotubes (CNTs) were synthesized in several batches and tested for their removal efficacy with regards to cadmium removal from synthetic wastewater. Fixed catalyst chemical vapor deposition (FCCVD) reactor system was fabricated in the laboratory for the synthesis of CNTs on the powdered activated carbons (PACs). The PACs were impregnated with Fe[Formula: see text] catalysts, and growth parameters such as the reaction time, gas flow rates and reaction temperature were optimized. The sorption capacity of the raw CNT–PAC was not satisfactory until the sorbents were functionalized which eventually led to high adsorption capacities. The surface properties of CNT–PAC were modified by oxidative functionalization using two different methods: sonication with KMnO4 and refluxing with HNO3 at 140[Formula: see text]C. KMnO4-treated CNT–PAC exhibited the highest sorption capacity for cadmium uptake which increased from 4.77[Formula: see text]mg/g (untreated CNT–PAC) to 11.16[Formula: see text]mg/g; resulting in Cd[Formula: see text] removal efficiency from 38.87% to 98.35%.