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Steam cracking of naphtha is an important process for the production of olefins. Applying artificial intelligence helps achieve high-frequency real-time optimization strategy and process control. This work employs an artificial neural network (ANN) model with two sub-networks to simulate the naphtha steam cracking process. In the first feedstock composition ANN, the detailed feedstock compositions are determined from the limited naphtha bulk properties. In the second reactor ANN, the cracking product yields are predicted from the feedstock compositions and operating conditions. The combination of these two sub-networks has the ability to accurately and rapidly predict the product yields directly from naphtha bulk properties. Two different feedstock composition ANN strategies are proposed and compared. The results show that with the special design of dividing the output layer into five groups of PIONA, the prediction accuracy of product yields is significantly improved. The mean absolute error of 11 cracking products is 0.53wt% for 472 test sets. The comparison results show that this indirect feedstock composition ANN has lower product prediction errors, not just the reduction of the total error of the feedstock composition. The critical factor is ensuring that PIONA contents are equal to the actual values. The use of an indirect feedstock composition strategy is a means that can effectively improve the prediction accuracy of the whole ANN model.

By introducing low-entanglement UHMWPE, the mechanical properties of polyolefins are improved to varying degrees. For polypropylene, the lack of interaction between UHMWPE and polypropylene results in an unsatisfactory reinforcement effect, and the disentangled state makes it easier for the particles to form defects driven by a chain explosion. In contrast, regarding polyethylene and elastomer containing ethylene segments, low-entanglement UHMWPE plays a better role in reinforcement. A series of measurements including scanning electron microscopy (SEM), rheological measurements, differential scanning calorimetry (DSC), and mechanical measurement were used to investigate the mechanisms for the different enhancement effects. It originates from interdiffusion and entanglement forming of polyethylene segments across the interface, endowing the material with different aggregated and defect structures. For instance, EPDM possesses a higher optimal dosage of UHMWPE particles reflected in good interfacial interdiffusion with UHMWPE particles, leading to significant optimized mechanical performance.

High density polyethylene/n-Hexane system was adopted to investigate the bubbles nucleation and collapse in polymer melt with a visualization apparatus at different temperatures. The results showed that the initial bubble number, initial total bubble volume and the mean bubble diameter all increased with the temperature increasing, and the bubble diameter distribution changed from single peak distribution to bimodal distribution. Moreover, the effect of temperature on the maximum bubble diameter was mainly reflected in the change of the pressure in bubbles due to the change of the volatile content in the polyethylene melt. For bubble collapse, the collapse time became longer but the bubble collapse rate became faster with the temperature increasing, and a fitting model was established in which the collapse coefficient n was used to describe the collapse rate. Through dimension analysis, the correlation between the collapse coefficient n and the melt surface tension σ, zero-shear melt viscosity η0, diffusion coefficient D, maximum bubble diameter dmax, melt density ρ, initial bubble number density Nini were established and the variation of D with temperature could be predicted as an exponential correlation.

In order to reduce the waste heat emission and environmental impact of industrial processes, Organic Rankine Cycle (ORC) is gradually used for energy recovery. ORC is regarded as the most promising measure for converting low-grade heat into electricity, but commercial applications are still limited due to the high investments and poor economic returns. However, the simultaneous optimization of ORC and Heat Integration can improve system economy. This work proposes a techno-economic optimization model involving the area estimate of heat exchanger based on vertical heat transfer for optimization of ORC and Heat Integration. This model determines the selection of working fluids, the optimal operating parameters of ORC including temperatures, pressures, and flowrate of working fluids. Both of the supercritical and subcritical conditions can be considered in this model. To solve this optimization problem, a bi-level optimization approach is developed, where the outer level uses Genetic Algorithm to identify the promising working fluids and optimize the temperatures and pressures of ORC, and the inner level is an NLP model to find the optimal flowrate of ORC and the vertical matches of streams by minimizing total annual cost. The results represent the necessity of simultaneous optimization of Organic Rankine Cycle and Heat Integration.

Molecular reconstruction is an effective tool to predict the detailed composition of complex mixtures under obtainable bulk properties and chemical details. With the introduction of statistical distribution, although the number of variables in the model is reduced, the ranges of statistical distribution parameters have a great influence on the prediction accuracy. A novel parameter estimation method using the analysis of the probability density plot of gamma distribution based on the basic available information is proposed to obtain parameter ranges with wide universality and non-specificity. The obtained ranges are used in a molecular reconstruction model to predict the bulk properties and molecular composition of naphtha. The model assumes molecular composition within each homologous series follows a gamma distribution against carbon number. The results of a naphtha sample show that the calculated bulk properties and molecular composition are in good agreement with the experimental values.

Limited by harsh reaction conditions, the activation and utilization of methane were regarded as holy grail reaction. Co-reaction with methanol, successfully realizing mild conversion below 450 °C, provides practical strategies for methane conversion on metal-loaded ZSM-5 zeolites, especially for highly efficient Zn loaded ones. However, Zn species, regarded as active acid sites on the zeolite, have not been sufficiently studied. In this paper, Zn-loaded ZSM-5 zeolite was prepared, and Zn was modified by capacity, loading strategy, and treating atmosphere. Apparent methane conversion achieves 15.3% for 1.0Zn/Z-H2 (16.8% as calculated net conversion) with a significantly reduced loading of 1.0 wt.% against deactivation, which is among the best within related zeolite materials. Besides, compared to the MTA reaction, the addition of methane promotes the high-valued aromatic production from 49.4% to 54.8%, and inhibits the C10+ production from 7.8% to 3.6%. Notably, Zn2+ is found to be another active site different from the reported ZnOH+. Medium strong acid sites are proved to be beneficial for methane activation. This work provides suggestions for the modification of the Zn active site, in order to prepare highly efficient catalysts for methane activation and BTX production in co-reaction with methanol.

Hydrogen resource can be saved by reuse and purification reuse between refineries. Thus, it’s necessary to optimize the inter-plant hydrogen network in a petrochemical complex. In a petrochemical complex, purifiers are employed to recover hydrogen components from off gas. However, purifier models such as PSA, membrane units have non-linear characteristics. Even if minimizing hydrogen utility, mathematical programming models adopted by most of the researchers belong to the non-convex and non-linear models, not guaranteeing global optimal solution. In this paper, a novel mathematic programming model for the optimization of inter-plant hydrogen network with purification unit is presented. If only the hydrogen utility consumption is minimized, the model is linear, guaranteeing global optimal solution. If the object comes to economic benefits such as pipeline cost, the objective function is nonlinear. The hydrogen utilities in refinery can be reduced by the inter-plant optimization and the number of inter-plant connections can be optimized to minimum. Case study indicates that the model is effective.

There is a growing interest in developing Total Site Heat Integration methods, since Total Site Heat Integration offers an energy-saving opportunity across multiple plants beyond the traditional intra-plant plant integration. Total Site heat integration can be achieved indirectly by non-isothermal utility loop, such as hot water and thermal oil. The parameters of non-isothermal utility loop, interconnectivity patterns directly determine the energy saving and the capital cost. In this work, a transshipment type Total Site heat exchanger network (HEN) model using non-isothermal utility loop is developed. A new representation method of non-isothermal utility loop is proposed based on transshipment type HEN model to avoid non-linear terms. The model is formulated as a MINLP problem with all linear constraints. The operating cost, capital cost of heat exchangers, pumping and piping cost are holistically considered and optimized. The case study demonstrates the effectiveness of the proposed model.

The quantitative structure-property relationship (QSPR) of constrained geometry catalysts (CGCs) has been analyzed by combining density functional theory (DFT) and multivariate linear regression (MLR). QSPR models for determining the reaction energy barriers of ethylene and 1-octene and molecular descriptors were established and validated with a testing set. At the initiation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.90 and 0.82, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.82 and 0.69. Using the generated QSPR models, the electronic effect was proven to be more critical for determining the energy barriers of ethylene and 1-octene insertion processes. At the propagation stage, the quaternary QSPR models for ethylene and 1-octene feature R² values of 0.97 and 0.96, respectively, while the corresponding leave-one-out Q² values for ethylene and 1-octene are determined to be 0.93. Particularly, the impact of the steric effect on the energy barriers of ethylene and 1-octene insertion is more pronounced. Furthermore, the correlation between the corresponding energy barriers and experimental activities with three series of CGCs was discussed, which revealed that theoretical calculations are consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Soluble poly[styrene- co-(acrylic acid)] (PSA) modified by magnesium compounds was used to support TiCl4. For ethylene polymerization, four catalysts were synthesized, namely PSA/TiCl4, PSA/MgCl2/TiCl4, PSA/( n-Bu)MgCl/TiCl4, and PSA/( n-Bu)2Mg/TiCl4. The catalysts were characterized by a set of complementary techniques including X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and element analysis. Synthesis mechanisms of polymer-supported TiCl4 catalysts were proposed according to their chemical environments and physical structures. The binding energy of Ti 2p in PSA/TiCl4 was extremely low as TiCl4 attracted excessive electrons from COOH groups. Furthermore, the chain structure of PSA was destroyed because of intensive reactions taking place in PSA/TiCl4. With addition of ( n-Bu)MgCl or ( n-Bu)2Mg, COOH became COOMg- which then reacted with TiCl4 in synthesis of PSA/( n-Bu)MgCl/TiCl4 and PSA/( n-Bu)2Mg/TiCl4. Although MgCl2 coordinated with COOH first, TiCl4 would substitute MgCl2 to coordinate with COOH in PSA/MgCl2/TiCl4. Due to the different synthesis mechanisms, the four polymer-supported catalysts correspondingly showed various particle morphologies. Furthermore, the polymer-supported catalyst activity was enhanced by magnesium compounds in the following order: MgCl2 > ( n-Bu)MgCl > ( n-Bu)2Mg > no modifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Reactor blends of ultrahigh-molecular-weight polyethylene (UHMWPE) and low-molecular-weight polyethylene (LMWPE) were synthesized by two-step polymerization using a hybrid catalyst. To prepare the hybrid catalyst, styrene acrylic copolymer (PSA) was first coated onto SiO/MgCl-supported TiCl; then, ( n-BuCp)ZrCl was immobilized onto the exterior PSA. UHMWPE was produced in the first polymerization stage with the presence of 1-hexene and modified methylaluminoxane (MMAO), and the LMWPE was prepared with the presence of hydrogen and triethylaluminium in the second polymerization stage. The activity of the hybrid catalyst was considerable (6.5 × 10 g PE (mol Zr) h), and was maintained for longer than 8 h during the two-step polymerization. The barrier property of PSA to the co-catalyst was verified using ethylene polymerization experiments. The appearance of a lag phase in the kinetic curve during the first-stage polymerization implied that the exterior catalyst (( n-BuCp)ZrCl) could be activated prior to the interior catalyst (M-1). Furthermore, the melting temperature, crystallinity, degree of branching, molecular weight and molecular-weight distribution of polyethylene obtained at various polymerization times showed that the M-1 catalyst began to be activated by MMAO after 40 min of the reaction. The activation of M-1 catalyst led to a decrease in the molecular weight of UHMWPE. Finally, the thermal behaviors of polyethylene blends were investigated using differential scanning calorimetry. Copyright © 2011 Society of Chemical Industry A hybrid catalyst was supported on an inorganic/organic support for use in the preparation of polymer blends with ultrahigh-molecular-weight polyethylene in the first reaction stage and low-molecular-weight polyethylene in the second reaction stage. Fragmentation of the styrene acrylic copolymer (PSA) support was studied. [ABSTRACT FROM AUTHOR]

Hybrid titanium catalysts supported on silicapolystyrenecoacrylic acid SiO2PSA coreshell carrier were prepared and studied. The resulting catalysts were characterized by Fourier transform infrared FTIR spectroscopy, laser scattering particle analyzer and scanning electronic microscope SEM. The hybrid catalyst TiCl3MgCl2THFSiO2·TiCl4MgCl2PSA showed coreshell structure and the thickness of the PSA layer in the two different hybrid catalysts was 2.0 μm and 5.0 μm, respectively. The activities of the hybrid catalysts were comparable to the conventional titaniumbased ZieglerNatta catalyst TiCl3MgCl2THFSiO2. The hybrid catalysts showed lower initial polymerization rate and longer polymerization life time compared with TiCl3MgCl2THFSiO2. The activities of the hybrid catalysts were enhanced firstly and then decreased with increasing PH2PC2H4. Higher molecular weight and broader molecular weight distribution MWD of polyethylene produced by the coreshell hybrid catalysts were obtained. Particularly, the hybrid catalyst with a PSA layer of 5.0 μm obtained the longest polymerization life time with the highest activity 2071 kg PE mol−1Ti h−1 and the resulting polyethylene had the broadest MWD polydispersity index 11.5 under our experimental conditions. The morphology of the polyethylene particles produced by the hybrid catalysts was spherical, but with irregular subparticles due to the influence of PSA layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

The coabsorptions of ethylene and iso‐pentane, and ethylene and n‐hexane were measured by the use of a pressure decay method. The solubility data of ethylene‐iso‐pentane and ethylene‐n‐hexane in semicrystalline polyethylene (PE) of crystallinity of 48.6% were obtained at temperatures 70, 80, and 90 °C, and the total pressure 2 MPa, iso‐pentane partial pressure 80–190 KPa, n‐hexane partial pressure 20–90 KPa. The presence of iso‐pentane or n‐hexane in the corresponding ternary system leads to increase the solubility of ethylene, while the solubility of iso‐pentane or n‐hexane remains unchanged with an increase of the ethylene partial pressure, even slightly decreases. Assumed that the presence of iso‐pentane or n‐hexane decreases the crystallinity of the polymer sample, a coabsorption model was built to model the solubility of each gas in the ternary systems. The relative root mean square errors of the coabsorption model for ethylene‐iso‐pentane‐PE system and ethylene‐n‐hexane‐PE system are 5.13% and 4.64%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3654–3662, 2007 [ABSTRACT FROM AUTHOR]

Diffusion coefficients of four organic solvents: dichloromethane, trichloromethane, tetrachloromethane and n-hexane in polyethylene particles at infinite dilution were determined by use of inverse gas chromatography (IGC). The polymer particles were used as supplied by the producer to pack the chromatographic columns. This allowed a direct measurement of the interested properties in a particle with the same morphology obtained at the reactor outlet. The particle morphology was investigated and classical mathematical model for chromatographic process was adopted based upon the analysis of particle microstructure. It was found that the limitation step for mass transfer was in the polymer matrix rather than in macropores, and when interpreted in terms of diffusion coefficients for spherical particles, the measured diffusion coefficients compared favourably with predicted values from literature relationships and free volume theory. [ABSTRACT FROM AUTHOR]

An absorption model of gases in semicrystalline polymer was built that was based on the activity coefficient theory in polymer solution and associated with crystallinity dependent on temperature. The solubility of ethylene, isopentane, and n‐hexane in three types of polyethylene (PE) were obtained by the use of a pressure‐decay method at temperatures of 333–363 K and pressures of up to 2 MPa, 80–300 KPa, and 19–100 KPa, respectively. Experimental data from three gases in each PE sample were used for the single‐parameter fitting, and fitting error was within about 12%. It was found that a single parameter was merely dependent on the properties of PE used. It was shown that, unlike with the Flory–Huggins model and the UNIFAC–M‐H method, correlation between the crystallinity of the semicrystalline polymer and temperature had to be taken into account in order for the solubility data of alkane, olefin, and aromatic hydrocarbons in polyethylene to fit well, especially in the temperature range near the melting point of the polymer. The four free‐energy contributions to the total gas activity were experimentally determined to be about 47%–60% combined, the free‐volume contribution about 12%–25%, and the elastic effect about 22%–35%, but the interactional contribution was zero. The contributions changed with the size of the gas molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1737–1744, 2007 [ABSTRACT FROM AUTHOR]

The conventional methods for recovering effluent gas in polyethylene processes include compression condensing, membrane separation, cryogenic separation systems and pressure swing adsorption. Since the effluent gas content varies with the process, there is no single recovery technic can meet all effluent gas content conditions. Therefore, a systematic strategy is needed to guide the selection of recovery technologies. This article introduces a method to select the best recovery system for certain compositions of effluent gas. After searching the feasible content region for the recovery systems according to the specified concentration of recycle stream and outlet streams, it shows PSA system has the largest feasible region while compression condensation system has the smallest one. In comparison of economic and exergetic performance, the cryogenic separation system shows its outstanding peculiarity to recover the effluent gas. The obtained result is effective in guiding the design of recovery system. [ABSTRACT FROM AUTHOR]

The performance of gas-solid fluidized bed reactors (FBRs) strongly depends on the behavior of gas bubbles. Mechanical agitation is widely used in industrial FBRs to enhance gas-solid mixing; however, its influence on bubble behaviors has been poorly studied, especially in experimental study. Pressure fluctuations in a 300 mm inner diameter plexiglas column fluidized bed of Geldart D particles with an arch agitator were measured under various gas velocities and agitation speeds. The bubble sizes were evaluated by incoherent analysis of pressure fluctuations. The effects of mechanical agitation on axial bubble growth, bubble sizes, regime transition velocity and fines elutriation were comprehensively investigated. Results show that mechanical agitation promotes bubble growth at 1.7 Umf but reduces the bubble sizes with increasing gas velocities. The axial maximum bubble size with increasing gas velocity occurs at 1.2 m/s without agitation and 1.0 m/s with agitation speeds of 14 and 21 rpm. Interestingly, mechanical agitation leads to a small increase in minimum fluidizing velocity and a slight decrease in critical turbulent velocity. Furthermore, the entrainment rate is reduced with mechanical agitation, due to the decreasing bed height and small fines ejection at the bed surface. The arch agitator helps to reduce the channel flow, enhance the gas-solid contact efficiency and improve the fluidization quality. [ABSTRACT FROM AUTHOR]