Reactive Distillation Reactor Research Articles

Catalytic disproportionation of trimethoxysilane to monosilane: Studies on catalyst, kinetics and reactor modeling

Monosilane is an indispensable special gas used in semiconductor, photovoltaic, LED, TFT, and lithium-ion battery industries. In this work, a chlorine-free route for monosilane by the disproportionation of trimethoxysilane (TMS) was investigated with a novel efficient and stable solid alkaline catalytic system composed of γ-Al2O3 supported K2CO3. TMS conversion of 71.6 % and silane selectivity of 97.6 % were obtained on the 15K2CO3/γ-Al2O3 catalyst with a high WHSV of 8 h−1, which could be operated stably over 300 h. Furthermore, the reaction kinetic model was established based on the E-R mechanism and a catalytic pathway was proposed according to kinetic results and DFT calculation. A novel reactive distillation reactor with cascaded condensers for silane production was simulated by using Aspen Plus. The results showed that the energy consumption of TMS disproportionation is much lower than that in TCS disproportionation.

Effect of Cobalt Doping on the Stability of CaO‐Based Catalysts for Dimethyl Carbonate Synthesis via the Transesterification of Propylene Carbonate with Methanol

AbstractTo improve the stability of the a CaO catalyst with high activity in the synthesis of dimethyl carbonate (DMC) at low‐temperatures via the transesterification of propylene carbonate (PC) with methanol, a series of Co‐doped CaO nanoparticles were synthesized with different cobalt contents via the sol‐gel method, and the catalytic performance of these catalysts increased in the order of 0.7Ca0.3Co<0.8Ca0.2Co<CaO<0.95Ca0.05Co<0.9Ca0.1Co. The characterization results of BET, XRD, FT‐IR, SEM, TEM, CO2‐TPD and XPS indicated that the addition of cobalt to CaO could form a novel layered structure of the Ca3Co4O9 carrier, which favoured the formation of strongly basic sites and then improved the activation of PC and methanol. The catalytic activity of traditional metal oxide catalysts is lower than that of pure CaO; however, the initial activity of the novel layered structure of the 0.9Ca0.1Co catalyst reached 72.9 %, which is obviously higher than that of 65.8 % for CaO. Furthermore, the results of long‐term catalytic evaluation showed that the best 0.9Ca0.1Co catalyst exhibited a stable PC conversion of 95.4 % and DMC yield of 93.1 % at 65 °C even after 168 h in the reactive distillation reactor. The deactivation mechanism showed that the layered structure of Ca3Co4O9 could stabilize CaO and prolong the life of the catalyst.

Simulation and optimization of Camelina oil fatty acids reaction to produce fatty acid methyl esters in a reactive distillation reactor

Reactive distillation (RD) is a chemical unit operation in which chemical reaction and product separation occurs simultaneously in one unit resulted in reduce the number of downstream steps, energy savings, and greenhouse gases. In the current work, process flow sheets for industrial routes for conversion of camelina oil fatty acids to fatty acid methyl esters (biodiesel) in presence of acid catalyst is modelled in Aspen HYSYS for the purpose to scale up the esters production. The effect of the operating and design parameters is optimized in addition to design the production plant. The simulation results showed that optimum ester yield is obtained for linoleic acid and palmatic components using 6:1 alcohol to oil ratio, reaction temperature 60°C and feeding the oil and the alcohol at stage number 3 and 5 respectively.

A catalytic reactive distillation approach to high density polyethylene pyrolysis – Part 2 – Middle olefin production

A catalytic reactive distillation reactor, previously described, was improved to increase the production of middle and heavy hydrocarbons, to be used as feedstock or fuel in the viewpoint of a Circular Economy of plastics. The thermal and catalytic pyrolysis experiments were run using high density polyethylene (HDPE) under several experimental conditions, with a 1 % (w/w) of HZSM-5 for catalytic pyrolysis. Three different temperatures were tested in each case and the influence of the reaction time was evaluated at 500 °C and 430 °C for thermal pyrolysis and catalytic pyrolysis, respectively. Thermal pyrolysis of HDPE produced the higher amount of solid products (80 %wt. or higher) under the form of a waxy cream-colored material (wax) for all the experimental sets. For catalytic pyrolysis, the major product fraction was always liquid. The analysis of the liquid products showed that, for both thermal and catalytic pyrolysis, the products obtained were within the range of C5 to C11, with a higher yield on C8 and C9 in the case of thermal pyrolysis and on C6 and C7 for catalytic pyrolysis. The aim of this study was the development of an integrated reactor/separation system to increase the middle olefin production. It is possible with this reactor design to direct the pyrolysis of HDPE to the production of middle olefins that can be reused in the petrochemistry industry, as chemical feedstock, including in the production of new plastics.

Kinetic Modeling of the Transesterification Reaction of Dimethyl Carbonate and Phenol in the Reactive Distillation Reactor

The kinetic behavior of preparing diphenyl carbonate by the transesterification of dimethyl carbonate with phenol in a reactive distillation reactor has been explored experimentally and theoretically. The transesterification reaction was described to conform a pseudo-second-order kinetics, and a semi-empirical kinetic model has been derived to explain the kinetic behavior. The model parameters were fitted to experimental data by an improved genetic algorithm. The proposed model was determined to be useful in simulating the rate constant and the mole fraction of components, which agreed well with the experimental data for different operating temperatures and catalyst concentrations.

Direct amination of benzene to aniline by reactive distillation method over copper doped hierarchical TS-1 catalyst

We report an effective method for the direct amination of benzene to aniline where aqueous ammonia was employed as aminating agent with hydrogen peroxide as oxidant and copper doped hierarchical TS-1 as catalyst, using a reactive distillation reactor under mild conditions. A desirable aniline yield (12.4%) with excellent selectivity (84.7%) was obtained under optimized conditions. A probable catalytic pathway of benzene ammoxidation to aniline over hierarchical TS-1 or metal doped hierarchical TS-1 was proposed.

A NOVEL CONTINUOUS-FLOW REACTOR USING REACTIVE DISTILLATION FOR BIODIESEL PRODUCTION

The production of biodiesel through batch and existing continuous-flow processes requires the use of a muchhigher excess alcohol, typically 100%, than the stoichiometric molar requirement in order to drive the transesterificationreaction to completion. This excess alcohol must be recovered in a separate process, which involves additional capital andoperating costs. In this study, a novel reactor system using reactive distillation (RD) was developed and investigated forbiodiesel preparation from canola oil and methanol. The goal was to significantly reduce the use of excess methanol whilemaintaining a high methanol:glyceride molar ratio inside the RD reactor by recycling a small amount of methanol within thesystem. Reactant conversion rate and product yield were used as the criteria for the reactor evaluation. The effect of themethanol:glyceride ratio was studied on a laboratory-scale perforated-tray RD reactor system. Product parameters such asmethyl ester content, glycerides, and methanol content were analyzed. Preliminary results showed that the RD reactor witha methanol:glyceride ratio of 4:1 (molar), in which the use of methanol was cut down by 66%, gave a satisfactory biodieselyield and oil conversion rate at a column temperature of 65C. Total reaction time in the pre-reactor and RD column wasabout 3 min, which is 20 to 30 times shorter than in typical batch processes. The productivity of the RD reactor system wasabout 6.6 m3 biodiesel per m3 reactor volume per hour, which is 6 to 10 times higher than that of batch and existingcontinuous-flow processes.

CaO–ZrO2 Solid Solution: A Highly Stable Catalyst for the Synthesis of Dimethyl Carbonate from Propylene Carbonate and Methanol

CaO–ZrO2 prepared by co-precipitation showed to be a well-performed catalyst for the transesterification of propylene carbonate (PC) and methanol. The characterization by X-ray powered diffraction (XRD) and Raman spectroscopy indicated that CaO was doped into the lattice of ZrO2 to form CaO–ZrO2 solid solution. Such a solid solution was a strong solid base, which was proved by CO2 temperature program desorption (CO2-TPD). As a result, the catalyst showed high stability towards the transesterification of propylene carbonate and methanol into dimethyl carbonate with high PC conversion, especially being subjected to the continuous production of dimethyl carbonate at reactive distillation reactor for 250 h without any obvious loss of activity at the PC conversion of 95%.

EXPERIMENTAL OPTIMIZATION OF A CONTINUOUS-FLOW REACTIVE DISTILLATION REACTOR FOR BIODIESEL PRODUCTION

A comprehensive study of biodiesel preparation from canola oil was performed on a continuous-flow reactivedistillation (RD) reactor system. Optimization of six process variables was studied experimentally and analyzed statisticallyon the overall performance of the RD reactor system. These variables include the feed methanol to triglycerides molar ratio,reaction time, reboiler temperature, catalyst concentration, methanol circulation mode, and catalyst formulation. Anexperimental design was used in the experiments, and statistical multiple response regression models were employed forprocess optimization. Under the operating conditions explored, product yields ranged from 41.5% to 94.9%, productivityranged from 16 to 55.8 kmol/m3h (5.6 to 19.5 m3/m3h), and soap formation varied from 4.44 to 29.1 mol/100 mol (0.19 to1.27%wt.). For different optimization criteria, the following optimum variable ranges were found: feed molar ratio from3.65:1 to 4.50:1, reaction time from 3.76 to 5.56 min, reboiler temperature from 100C to 130C, and catalyst concentrationfrom 0.13 to 0.24 mol/mol. Although the process variables individually affected the system performance to a certain extent,the interactive effect of the process variable combinations affected the system efficiency more significantly. When maximized,the product yields and productivity were 98.8% and 55.6 kmol/m3h (18.5 m3/m3h), respectively. However, when soapformation was minimized, the yield and productivity were 72% and 9.3 kmol/m3h (3.1 m3/m3h), respectively. It isrecommended that the optimization of the RD reactor system be based on the maximization of product yield and reactorproductivity.

Fluid dynamics of a novel reactive distillation reactor

For a reactive distillation column with a novel internal which is made of several structured porous passages, the models of pressure drop and liquid holdup are developed. The simulation from the models shows that the internal can make more than 70% gas contact liquid in cross-current instead of counter-current, so that excessive pressure drop is avoided. In addition, below the load point, only superficial liquid velocity and the volume fraction of the internals have evident effects on the liquid holdup; above the load point, both superficial gas and liquid velocities have great effects on the liquid holdup, and so do the parameters of the internal because they can affect gas flow behavior.

Characteristics of the reactive distillation column with a novel internal

A new catalyst loading method, in which catalyst particles are packed in a reactor with a novel internal, has been studied by measuring pressure drop, RTD, liquid holdup and mass transfer. It can be inferred from experimental results that the internal changes the conventional gas and liquid counter-current flow into a new cross-current flow, so the problems of excessive pressure drop and “flooding” are avoided. When pressure drop, liquid holdup, RTD and mass transfer coefficient are similar, the catalyst loading fraction of the new method is much higher than that of conventional methods. Furthermore, the reactive distillation reactor with the novel internal has advantages such as simple structure, low operating cost, and convenience for installation and removal of the catalyst.