Distribution Of Major Products Research Articles

Operation warp speed: Harbinger of American industrial innovation policies

Abstract Operation warp speed (OWS) was a crash effort from 2020 to 2021 to undertake the late-stage development, production, and distribution of vaccines for the coronavirus pandemic. The vaccines were developed, approved, and available in a record time of 8 months using an industrial policy approach. Mainstream economists have long opposed industrial policy approaches as market interference, unless they can be justified by clear market failures. The nation has long had industrial economic policies in such areas as defense, health, transport, and agriculture. However, interventionist policies on the non-defense innovation side of the economy after the research stage have generally been avoided. OWS was a departure, an industrial innovation policy. OWS built a new organization with officials from major health science, regulatory, public health, and research agencies as well as the Defense Department. Elements of its program included: supporting a portfolio of different technology platforms, guaranteed contracts that enable production to evolve alongside development, flexible contracting mechanisms that enabled rapid procurement and intervention into supply chains, rapid technology certification that assured the new vaccines of rapid market entry, mapping supply chains and filling gaps to assure rapid production and distribution, and major product distribution. The elements applied in OWS amount to a new tool kit potentially relevant to other areas, and the USA is now pursuing a series of these in other technology fields.

Nickel promoted Si-rich ZSM-5 nanocatalyst remarkably converts LDPE plastic waste to gasoline range hydrocarbons in a dual-bed semi-batch reactor at atmospheric pressure

Catalytic pyrolysis is an environmentally friendly recycling method, which has attracted remarkable attention due to worldwide issues of the production and accumulation of plastic wastes. In this work, the catalytic pyrolysis of Low-density polyethylene (LDPE) was carried out in a dual-bed semi-batch reactor over the Si-rich Ni/ZSM-5 nanocatalyst at atmospheric pressure. The parent nanocatalyst was prepared by hydrothermal technique and modified with nickel promoter (0–25 wt%). The properties of the nanocatalysts were characterized by XRD, FTIR, FE-SEM, EDX, TEM, BET, NH3-TPD, and TG-DTA techniques. The results showed the high crystallinity, spherical particles, and high specific surface area (376 m2g−1). The impact of operational conditions was evaluated to maximize the production of the high value-added compounds. The high percentage of the Ni promoter (25 wt%) led to the highest amount of gasoline range hydrocarbons (61%). The appropriate operational conditions were temperature of 525 °C, catalyst to plastic ratio of 1:20, and 2.5 ml min−1 nitrogen flow rate, resulting in the best product distribution: aromatics (39.4%), olefins (28.3%), and paraffins (15%). The reusability of the nanocatalyst showed high performance and more aromatic production. The characterization results of the used nanocatalyst confirmed the high stability through the pyrolysis reaction and lack of significant structural defect. The developed nanocatalyst represented the high activity through the pyrolysis of the real LDPE plastic waste, including the major product distribution in the gasoline range hydrocarbons.

Light olefin production by catalytic co-cracking of Fischer–Tropsch distillate with methanol and the reaction kinetics investigation

Abstract Catalytic co-cracking of Fischer–Tropsch (FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions: methanol feed only, olefin feed only and co-feed of methanol with olefins or F–T distillate. The results showed that methanol converted to C2–C6 olefins in first-order parallel reaction at low space time, methylation and oligomerization–cracking prevailed for the co-feed of methanol and C2–C5 olefins, while for C6–C8 olefins, monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C3–C5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.

Evaluation of Major Product Distribution Using Experimental‐Theoretical Comparative Studies on Toluene and Ethylbenzene Ethylation over Catalysts Zeolite MCM‐22 and Modified MCM‐22

AbstractThe activity of zeolite MCM‐22 and modified MCM‐22 catalyst were tested in the vapor phase alkylation of toluene and ethylbenzene by ethanol to investigate the influence of thermodynamic parameters, reaction temperature, and the molar ratio of toluene and ethylbenzene to ethanol. The reactions were evaluated with experimental and theoretical approaches. The catalysts were characterized by XRD, FE‐SEM, TGA, N2‐adsorption, and NH3 & Py‐TPD analyses. The superior catalytic performance of modified MCM‐22 was observed in ethylation of ethylbenzene and ethylation of toluene. The catalytic performance indicates that zeolite MCM‐22 retained shape selectivity resulting into para‐selectivity, while modified MCM‐22 possessed more mesopores and increased accessibility to the acid sites thereby increasing conversion of ethylbenzene.

Identification of products formed during the heterogeneous nitration and ozonation of polycyclic aromatic hydrocarbons

Abstract The 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs) are the most abundant of PAHs in air particulate matter (PM). Thus we have investigated heterogeneous oxidation of 3- and 4-ring PAHs in a small-scale flow reactor using quartz filter as a support. Four representative PAHs, anthracene, phenanthrene, pyrene, and fluoranthene, were exposed to either NO2, O3 or NO2+O3 (NO3/N2O5) with a goal to identify and attempt quantification of major product distribution. A combination of gas chromatography with mass spectrometry (GC–MS) with/without derivatization and liquid chromatography with high resolution MS (LC-HRMS) was used for identification. For the first time, a comprehensive characterization of a broad range of products enabled identifying ketone/diketone, aldehyde, hydroxyl, and carboxylic acid PAH derivatives. Exposure to NO3/N2O5 (formed by reacting NO2 with O3, a more powerful reactant than either O3 or NO2) produced additional compounds not observed with either oxidant alone. Multiple isomers of nitrofluoranthene and, for the first time, nitrophenanthrene were identified. In addition hydroxy-nitro-PAH derivatives were observed for the reaction of anthracene with NO3/N2O5. Monitoring of specific common ions such as those of 176 and 205 m/z attributed to carbonyl phenanthrene and deprotonated phenanthrene ions respectively was shown to be a useful tool for identification of multiple pyrene oxidation products.

Gasification of the Coke on Spent-Residue-Pretreating Catalysts with Steam and Steam–O2 Mixtures

Coke deposited on residue-pretreating catalyst gasification with steam and steam–O2 mixtures was investigated at temperatures between 750 and 900 °C under atmospheric pressure. In a steam atmosphere, major product (H2, CO, and CO2) distribution was less affected by the temperature and yielded syngas containing H2 and CO at approximately 56 and 33 vol %, respectively. However, major product distribution depended upon the nature of coke, and when derived from a lower Conradson carbon residue (CCR) feed, a higher hydrogen concentration was obtained in the syngas. In a steam–O2 mixture atmosphere, primary product (H2, CO, and CO2) distribution was significantly influenced by the temperature and O2 concentration. Both the shrinking-core and homogeneous models match the experimental data during coke-on-catalyst (COC) steam gasification, where the apparent activation energy value is about 230 kJ/mol and the apparent reaction order with respect to gasifying agent is varied with the steam partial pressure. The experimental data of COC gasification with steam–O2 represented using the shrinking-core model are better than those using the homogeneous model, and the apparent activation energy is approximately 98 and 90 kJ/mol for the shrinking-core and homogeneous models, respectively.

A Mechanistic Investigation of Acid-Catalyzed Cleavage of Aryl-Ether Linkages: Implications for Lignin Depolymerization in Acidic Environments

Acid catalysis has long been used to depolymerize plant cell wall polysaccharides, and the mechanisms by which acid affects carbohydrates have been extensively studied. Lignin depolymerization, however, is not as well understood, primarily due to the heterogeneity and reactivity of lignin. We present an experimental and theoretical study of acid-catalyzed cleavage of two non-phenolic and two phenolic dimers that exhibit the β-O-4 ether linkage, the most common intermonomer bond in lignin. This work demonstrates that the rate of acid-catalyzed β-O-4 cleavage in dimers exhibiting a phenolic hydroxyl group is 2 orders of magnitude faster than in non-phenolic dimers. The experiments suggest that the major product distribution is similar for all model compounds, but a stable phenyl-dihydrobenzofuran species is observed in the acidolysis of two of the γ-carbinol containing model compounds. The presence of a methoxy substituent, commonly found in native lignin, prevents the formation of this intermediate. Reacti...

Kinetic Model of Fischer–Tropsch Synthesis in a Slurry Reactor on Co–Re/Al2O3 Catalyst

A kinetic model for Fischer–Tropsch synthesis is derived using a Langmuir–Hinshelwood–Hougen–Watson approach. Experiments were conducted over 25% Co/0.48% Re/Al2O3 catalyst in a 1 L slurry reactor over a range of operating conditions (T = 478, 493, 503 K; P = 1.5, 2.5 MPa; H2/CO = 1.4, 2.1; WHSV = 1.0–22.5 NL/(gcat·h)). Rate equations were based on the elementary reactions corresponding to a form of well-known carbide mechanism. The 1-olefin desorption rate constant was assumed to be a function of carbon number due to the effect of weak interaction of the hydrocarbon chain with the catalyst surface. Values of estimated activation energies are in good agreement with those reported previously in the literature. The kinetic model was able to correctly predict all of the major product distribution characteristics, including the increase in chain growth probability and decrease in olefin-to-paraffin ratio with carbon number, as well as formation rates of methane and ethylene.

Experimental and modeling study of the gas-phase oxidation of methyl and ethyl tertiary butyl ethers

The gas-phase oxidation of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) has been experimentally studied using a jet-stirred reactor between 750 and 1150 K (pressure of 10 atm, equivalence ratios from 0.5 to 2 with an important dilution in nitrogen). These experiments have been modeled using a kinetic mechanism automatically generated by EXGAS, the system developed in Nancy. The modeling of the oxidation of several mixtures of these ethers with n-heptane has also been performed in an extended temperature range, between 580 and 1100 K, covering the regions of cool flames and a negative temperature coefficient. The agreement between the computed and the experimental values is mostly good, both for conversions and for the distribution of major products, except for the lowest temperatures, where catalytic effects should be taken into account. The decrease of reactivity due to the addition of MTBE or ETBE to n-heptane at low temperatures is well predicted by the model.

Polymer-dimer distribution in the electrochemical synthesis of polyaniline

The distribution of major products associated with the process of polyaniline (PANI) synthesis is discussed. On the basis of the results obtained in the cyclovoltammetric ( cv) and constant potential ( cp) synthesis the dependence of that distribution upon monomer concentration, switching potential ( E λ ) and potential of synthesis, E synth , are discussed, the corresponding reaction scheme is given and terms for the reaction rates derived. The conditions governing the polymer-dimer distribution are formulated. The origin of the middle peak, appearing during the PANI synthesis, is discussed in the light of the specific experimental conditions, and species corresponding to it are identified. A reaction scheme for the hydrolysis pathway of dimer is confirmed.

ChemInform Abstract: The Rate Constant for the Intramolecular Isomerization of Pentyl Radicals

The thermal decomposition of n-pentane has been investigated in the temperature range 737 to 923 K. Making various assumptions, the detailed distribution of major products (methane, ethane, ethene, propene, and 1-butene) is used to evaluate the rate constant for the unimolecular isomerization CH 3 CH 2 CH 2 CH 2 CH 2 →CH 3 CHCH 2 CH 2 CH 3 which proceeds via a five-membered, cyclic transition state. Two alternative sets of assumptions are used. Common to both of them are assumptions concerning the thermochemistry and rate constants for decomposition of the C 5 H 11 radicals. Method 1 assumes that all secondary C−H bonds are equally reactive towards hydrogen abstraction in which case, in addition to the value of k 10 , the ratio of the rate constants for abstraction from primary and secondary C−H bonds is evaluated. Values about a factor of two higher than published values for similar molecules are obtained. The alternative, method 2, assumes that the ration of abstraction from the 1- and 2- positions of n-pentane is the same as that published for n-butane, in which case, in addition to the value of k 10 , the ration of the rates of abstraction from the 3− and 2− positions of n-pentane is obtained. The value obtained is 0.401 which is to be compared with the statistically expected (and assumed in method 1) 0.5. Detailed discussions of the values of k 10 obtained leads to the conclusion that method 1 leads to the best value log(k 10 /s −1 )=11.96±0.77−(23.4±2.0)/θ where θ=2.303RT in kcal/mol and error limits are two standard deviations. Combination of this value with values recalculated from published lower temperature data gives log(k 10 /s −1 )=11.08−20.04/θ which, it is concluded, is the best value in the range 438 to 923 K

Effect of feedstock variability on catalytic cracking yields

Nine compositionally distinct vacuum gas oil feedstocks have been studied to develop a rational basis for understanding the distribution of major products in fluid catalytic cracking (FCC) reactions. Key hydrocarbon and carbon types have been quantitated from mass spectrometric data. Product yields were determined, under standardized conditions, using an FCC microactivity test (MAT) system. Severity conditions were varied to obtain yield profiles encompassing that MAT conversion where the yield of C 5F + gasoline was at maximum. These optimum yield profiles were correlated with the feedstock properties which characterized and quantitated those precursors capable of producing gasoline molecules. The correlations were tested against two further vacuum gas oils. The conclusions are that realistic comparisons between feeds may be made at conversions where the yield of gasoline is at maximum.

The rate constant for the intramolecular isomerization of pentyl radicals

AbstractThe thermal decomposition of n‐pentane has been investigated in the temperature range 737 to 923 K. Making various assumptions, the detailed distribution of major products (methane, ethane, ethene, propene, and 1‐butene) is used to evaluate the rate constant for the unimolecular isomerization equation image which proceeds via a five‐membered, cyclic transition state. Two alternative sets of assumptions are used. Common to both of them are assumptions concerning the thermochemistry and rate constants for decomposition of the C5H11 radicals. Method 1 assumes that all secondary CH bonds are equally reactive towards hydrogen abstraction in which case, in addition to the value of 𝓀10, the ratio of the rate constants for abstraction from primary and secondary CH bonds is evaluated. Values about a factor of two higher than published values for similar molecules are obtained. The alternative, method 2, assumes that the ratio of abstraction from the 1‐ and 2‐ positions of n−pentane is the same as that published for n−butane, in which case, in addition to the value of 𝓀10, the ratio of the rates of abstraction from the 3‐ and 2‐ positions of n‐pentane is obtained. The value obtained is 0.401 which is to be compared with the statistically expected (and assumed in method 1) 0.5. Detailed discussions of the values of 𝓀10 obtained leads to the conclusion that method 1 leads to the best value where θ = 2.303RT in kcal/mol and error limits are two standard deviations. Combination of this value with values recalculated from published lower temperature data gives which, it is concluded, is the best value in the range 438 to 923 K.