نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
سال پنجم شماره 2 (پیاپی 16، تابستان 1400)

Synthesis gas is a mixture of hydrogen gas and carbon monoxide, which usually contains carbon dioxide as an additive. This gas is the raw material in the production of many basic materials of the petrochemical industry such as methanol. Various raw materials have been used to produce synthetic gas, including natural gas (methane), hydrocarbons, and coal. This gas is also very suitable as an intermediate material for the production of industrial products, and depending on the reaction conditions and catalysts used, different chemicals may be produced in large industrial units. Modeling a synthesis gas production reactor as the heart of an operating unit in the petrochemical industry is of particular importance. Simulation of refinery units is always associated with many problems due to the complexity of the process and the lack of proper kinetics. In recent years, software such as Span Plus has been used to simulate and study refinery processes, which in this regard have to some extent facilitated and achieved the appropriate. In this research, the synthesis gas production unit is simulated with two methods of steam reforming and partial oxidation method using Aspen Plus V8.4 software. By examining parameters such as conversion rate, hydrogen to CO ratio, reactor temperature and pressure during the production process and other variables, the simulation results show that after adjusting the reaction coefficients, parameters such as inlet feed temperature, reactor length and time Residues affect the production of desired products that the use of steam reforming in terms of production of synthetic gas has a higher efficiency than the partial oxidation system.

Research subject: Iran is a country with high potentials for access to renewable energy sources such as solar, hydropower, wind, and biomass. Biodiesel is one of the renewable fuels that has always been proposed as a suitable and stable alternative (non-toxic, safe, and degradable) to fossil fuels.
Research approach: The experiences of different countries in the use of edible sources for biodiesel production shows that the use of edible sources has caused problems such as lack of food resources for human communities, lack of feed for livestock, and upsetting the balance in the food industry, and it can lead to a significant increase in the price of these resources. Therefore, many researchers have proposed the use of non-edible sources to address these problems. So far, very large non-edible sources for biodiesel production have been identified. In this paper, non-edible sources of biodiesel that are produced or have the potential to be produced in Iran are introduced and studied and a potential assessment study is presented for them. Main results In this work, the non-edible sources for biodiesel production are classified into four categories: agricultural waste, waste cooking oils, microalgae, and non-edible seeds. These sources are compared based on various parameters such as oil percentage, oil content per hectare, biodiesel production efficiency, viscosity, saponification number, and cultivation period, which according to the results, non-edible seeds, especially Nowruzak seeds, Castor, and safflower have been identified as the most rational and sustainable sources of biodiesel production in Iran. The present work also deals with the policies and incentives that the responsible institutions can apply for the prosperity of the biodiesel industry.

The rise of bacterial infections has become a serious problem in human societies. As a result, the development of nanocomposite materials based on biocompatible and non-hazardous materials, besides having antimicrobial and biocompatibility or non-cytotoxicity, associated with unique structural properties, possesses a great importance. Research approach: In this study, bacterial cellulose (BC)/polypyrrole (PPy) and zinc nanoparticles (ZnO), which simultaneously have antimicrobial properties and cell proliferation, were introduced as a new generation of nanocomposite scaffolds produced by freeze-drying. To begin with, ZnO with different weight percentages of 1%, 3% and 5% was added to BC and then PPy in the amount of 2 mmol was embedded in the structure by in situ polymerization. FESEM images proved that the nanofibrous and porous structure of BC was also preserved in the presence of PPy and ZnO. However, after adding PPy and ZnO, they formed a dense structure and microstructure of grape clusters. By adding 2 mmol PPy into BC and upon in situ synthesizing, the tensile strength and Young modulus of BC were significantly reduced to 71 MPa and 2.5 GPa, respectively. On the other hand, with the addition of ZnO nanoparticles, the mechanical properties significantly increased (both of Young modulus and tensile strength compared to BC/PPy samples) due to the compaction of the nanocomposite aerogel’s structure and the formation of the interface of ZnO nanoparticles with both polymers of BC and PPy. The observation of the inhibition zone in the culture medium containing two gram-positive and negative bacteria, well proved the antibacterial ability of ternary nanocomposite scaffolds. The results of MT9 related to L929 on aerogels showed that by adding 3% of ZnO nanoparticles, adhesion and cell proliferation increased significantly during different days of 1 day, 5 days and 7 days of culture.

In this study, the occurrence of flooding due to the accumulation of sediment in the downcomer area, which led to an excessive increase in liquid on the upper trays of the distillation column was investigated in a refinery.

Vacuum pressure in the upper area of the column, boiler feed water flow from the inlet to the condenser and the discharge of the net product as three very important and effective operational parameters in controlling the severity of the flooding phenomena and the amount of coking value as an important laboratory parameter to reduce the volume of inlet sediments entering the distillation column. Data and results of changes made on each of these three operational parameters showed their effectiveness in controlling the severity of the flooding phenomena.

In order to control and reduce the problems caused by the simultaneous flooding phenomena around the vacuum pump, the boiler feed water flow of the inlet to the condenser and the flow of the net output product were proportionally increased until the operating conditions of the distillation column are normalized. In this study, how to control the flooding phenomena and reduce the adverse effects due to the accumulation of sediments in the downcomer area of tray No. 22 and above was investigated. To overcome these problems, first the vacuum pump rotation speed was increased from 850 rpm to 1250 rpm and the boiler feed water inlet to the condenser from 1.95 m3/hr to 3.2 m3/hr was increased. On the other hand, in order to prevent contamination of the pure product, the net output product flow rate also increased from 925 kg/hr to 2300 kg/hr. Also, with regular and accurate control of the coking value index as a very important laboratory parameter, the volume of coke sediments in the coal tar feed entering the distillation column was reduced from 37.5% by weight to 18.4% in a 30-day period after centrifugation.

As a low price biomass, rice husk is able to accumulate a large amount of silica in its texture. The process for extracting this silica is greener than the conventional ones. The present research addresses the effects of the different process parameters on amorphous silica extraction from rice husk through a precipitation method.

In the extraction process, first the rice husk was burned in the open air and then turned into white ash in an electric furnace. This ash was converted into sodium silicate solution using NaOH, and finally the silica was precipitated from this solution by sulfuric acid. The effect of solid to solvent ratio, the duration of the alkaline dissolution step as well as the pH and temperature of acid precipitation step have been investigated. Moreover, a special application of the amorphous silica in rubber industry was also investigated.

The results showed that a low solid to solvent ratio at the alkaline dissolution stage as well as an acidic pH along with a high precipitation temperature are required to obtain the highest production efficiency and to obtain high purity amorphous silica. The purity and chemistry of obtained silica were quite similar to commercial sample in the rubber industry; however, the surface area and pore volume of obtained silica was less than the commercial one. It was also found that prolonging the alkali dissolution step slightly increases the production efficiency. The obtained silica exhibited very close performance to the commercial sample, in the rubber-to-fiber adhesion system (RFS). This indicates the high ability of precipitated silica to be replaced by commercial types, which are mainly produced by more cost-effective and less biocompatible processes.

Superplasticizers can be synthesized in different ways. The aim of this study is to present a two-step method for the synthesis of polycarboxylate ether and to investigate the temperature change in synthesis. In the first stage synthesis, the main chain and in the second stage synthesis, the side chains are created.

The synthesis of the primary copolymer was done by mass method and free radical mechanism. FTIR analysis was performed to identify the functional groups formed according to the predictions and to reach the desired copolymer. Then the copolymer viscosity was determined as a parameter determining the progression of the main chain length and in the second step, polycarboxylate ether was synthesized by solution using an optimized AA copolymer. First, FTIR analysis was performed to confirm the structure and HNMR test was performed to confirm the final synthesis. Then, GPC test was performed to determine the characteristics of the synthesized ether polycarboxylate, including the average molecular weight of the polymer and the molecular weight distribution curve, and MW and PDI values ​​were reported. Finally, the slump test was performed to confirm the performance.

With increasing the temperature of copolymer synthesis, the length of the main chain also increases and the intensity of this increase is higher at high temperatures, but on the other hand, temperatures higher than 70 ° C also caused the destruction of the copolymer, which was detectable in the form of viscosity reduction and discoloration of the solution. Therefore, the initial synthesis should be performed at 70 ° C for 8 hours. The synthesis of polycarboxylate ether with equal molar ratios and maintaining the same conditions and only at different temperatures showed that the best synthesis temperature is 70 ° C for 6 hours. By increasing the molecular weight of polycarboxylate ether, by increasing the side chain, a better slump and flow in concrete was created.

Ethylene is a very important material in petrochemical industries, whose chief application is producing polymers such as polyethylene. The steam cracking of ethane or naphtha is commonly used to produce ethylene. A small amount of acetylene is produced in this process. The amount of acetylene in the product stream should not exceed 1 ppm, because it is harmful to polymerization catalysts in downstream units. The acetylene hydrogenation unit is designed for acetylene removal in industrial plants. In this unit, the removal of acetylene up to 1 ppm in the product stream and ethylene’s selectivity are of great importance.

In this paper, the modeling and the dynamic simulation of acetylene hydrogenation reactors of Marun petrochemical complex with considering catalyst deactivation are presented. Then, here investigated is the effect of the operating conditions such as temperature, pressure and flow rate of the reactor feed on the amount of outlet acetylene as well as ethylene’s selectivity.

The simulation results show that in order to compensate for catalyst deactivation, it is necessary to gradually increase the reactor inlet temperature. With a linear increase in the inlet temperature of the reactors from 55 to 90 ˚C in a period of 720 operating days, the amount of outlet acetylene and ethylene’s selectivity are decreased. The reactions of acetylene to ethylene and ethylene to ethane are increased by increasing the inlet temperature of acetylene hydrogenation reactors. By increasing the feed flow rate from 50 to 100 kg/s, the amount of outlet acetylene and ethylene’s selectivity are increased. The residence time is decreased by increasing the feed flow rate and thus the conversion of acetylene to ethylene is decreased (increasing the outlet acetylene in the product). The amount of outlet acetylene and ethylene’s selectivity are decreased by decreasing the inlet pressure from 40 to 33 barg.

Expandable Poly Styrene (EPS) has many applications. This polymer prepared by the radical polymerization. This material has many uses in packaging and insulation industries Some of the properties of this polymer like low mechanical strength caused its applications to be limited. By adding some materials, these properties can be improved. Styrene Butadiene Styrene (SBS) is from the materials that which by adding it to the EPS it can improve its quality.

In this research, EPS having different percentages of SBS (0, 0.01, 0.02, 0.03) in different conversion percentages (0.6, 0.63, 0.66, 0.69) has been prepared. Different tests like Impact Test, Modular Melt Flow test, Vicat Softening Temperature test, Tensile at Break test, K-value test, Rochwell Hardness test and Elongation at Break test are done on the prepared polymer. Laboratory gained data has been simulated by Multi-Layer Perceptron (MLP) method of artificial neural networks (ANN) and the simulated data covers the laboratory data perfectly.

Investigating the tests show that in constant percentages of SBS in EPS with increase in conversion percentage of EPS, the numerical amount of the tests increases except MFI test (low MFI number means better quality). Increase in SBS percentage in the EPS, increases the properties of polymer. In addition, the results of simulation show that the laboratory data covers the the simulated data perfectly. The data obtained from the results of this reasearch can be used for predicting the data for the points which has not been tested. Adding SBS in different weight percentages of poly styrene in different conversion percentages in order to increase the properties of poly styrene has been used for the first time in this research and the laboratory data results in points which has not been tested has been acquired by applications of ANN.