چكيده به لاتين
Para-xylene (PX) is the raw material to produce Terephthalic acid also important Dimethyl terephthalate mediums which ultimately are utilized to produce Polyester fibers also plastics. Increasing the content of PX in xylene mixture is one the concerns in industry, considering that PX is one of the demanding isomers compared to Meta & Ortho isomers. The other obstacle in PX plants in Iran is related to supplying catalysts from abroad, especially after sanctions in 2011 which purchasing channels are not available anymore for national companies, that’s the root cause which PX catalyst synthesis is playing a great role in Iran. Reactions leading to increase in PX content in xylene mixture are isomerization also disproportionation reactions which should progress in presence of catalytic molecular sieves. Consequently, the other aspect related to increase PX content is about applying modifications on the catalyst. This project includes two phases; First phase is related to catalyst synthesis & the second one relates to the design also installation of experimental setup to conduct cata-tests. One of the outstanding features of this project compared to other relevant studies which are mentioned in the article, is about equipment used in the cata-test experimental setup which has the closest resemblance in the aspect of process also operational condition with industrial plants of PX production in Iran. In many references, not just the cata-test facility is limited to the reactor, but also the operational condition & process is far from current status in industry, consequently generalizing results in articles to industrial plants in experimental or pilot scale is not practical, subsequently no proper results would be gained.
Two phases of this project deployed also modified in parallel. By parallel it’s meant that with respect to late studies on this matter, it was approached to proper selection of the catalyst, synthesis also modification method, condition of synthesis & modification, design & installation of the cata-test setup. In this project 20 samples of catalyst were synthesized/modified, went through characterization tests also experienced cata-test. At first considering the characterization results of synthesized/modified samples were studied, then loaded for cata-test. The ultimate catalyst selection was the sample with most proper characterization test also cata-test results, which had the most PX conversion of 17%, PX conversion in similar studies mentioned in the article is 14%, also the industrial catalyst had conversion of 13% in the setup. Considering characterization also cata-test results, continuously we tried to optimize/improve the condition of catalyst synthesis, design & installation of more equipment on the setup also cata-test. This improvement process was continued till reaching the optimal condition. The selected catalyst sample is being referred as AHFS0.1M-120min in this thesis which was leached with 0.1 Molar AHFS (Ammonium Hexa- FluoroSilicate), with duration of 120 minutes of leaching with the target of dealumination. Optimum cata-test condition was pressure of 8 bar, temperature of 390⁰C, WHSV 4 hr-1, molecular ratio H2/HC=4. The selection process of optimum catalyst also cata-test was based on the results of cata-test & characterization tests (both before & after cata-test) regarding Taguchi method. In order to study the kinetics of the reaction, a set of cata-tests were especially implemented to this matter and operational parameters in the cata-test were set to have a conversion close to zero; through conducting reactions in very high WHSVs, and ultimately a kinetic model is represented in this project.
