Study On The Preparation Technology Of Isobutene, Isopentene And Its Downstream Products

With the continuous development of the ethylene industry, the resource amount of by-product, isobutene and isopentene was increasing rapidly. The isobutene and isopentene was the highly valuable composition of C4 and C5 fraction respectively. The production technology of isobutene and isopentene with high purity was basically similar at present, the hydrogenation, etherification and decomposition technology were used in the two productions. The isobutene with high purity which was used as monomer to product the polymer such as butyl-rubber and polyisobutene, and also could to product the fine chemical productions such as methyl methacrylate, tert-butylamine, p-tert-butylphenol series antionxidant and allylic alcohols, however, the isopentene was profile to fine chemical field, which was used as the intermediate in the production of pesticide and perfume.Besides the optimization of production technology constantly, reducing the production costs and improving the reaction yield, the research works on lifting production quality, the comprehensive utilization on raffinate C4/C5 fraction and development of downstream production were carried out in the production process of isobutene and isopentene to utilize the raw material effectively and adequately, to enhance the comprehensive competence ability of plant. The preparation technology of isobutene, isopentene and its downstream products was studied in the paper, main research contents including:(1) the preparation of isobutene by ether-solution from MTBE, (2) dimerization process of isobutene and its kinetics, (3) hydrogenation catalyst and process of C4-olefins, (4) decomposition catalyst of TAME and decomposition process, (5)isomerization process of 2M1B, (6)hydrogenation process of crude isopentene. The main conclusions were as follows:1. The optimum operation conditions of product isobutene by cracking from MTBE with the SPC-01 catalyst:reaction pressure of 0.4MPa, temperature was ranging from 210～230℃, liquid hourly space velocity was ranging from 0.5～1.0h-1, the single conversion of MTBE was more than 92.2%, the selectivity of isobutene was more than 99.9%.2. The influence of dimerization process of isobutene conditions on the selectivity of DIB was investigated in the high pressure autoclave with catalyst of strong acid cation exchange resin. The conversion of IB was around 60%, the selectivity of DIB was around 80% at the conditions of the reaction temperature was ranging from 75～95℃, the mass fraction of IB in the raw material was ranging from 17%～20%, the mass fraction of TBA was 0.6%, the stirring rate was 750r/min, and the reaction time was 3h.3. The kinetics experiments of IB oligomerization and model analysis showed that the IB oligomerization was irreversible first-order series reaction. According to the experiments results, the rate equation of IB oligomerization was:4. The kinetics experiments of IB oligomerization with the adding of TBA and process analysis showed that the IB oligomerization was in accord with the characteristics of irreversible first-order series reaction. The IB oligomerization mechanism was changed as the adding of TBA, the measured IB oligomerization reaction activation energy was the IB hydration reaction activation energy in fact. According to the experiments results, the rate equation of IB oligomerization was:5. The Ni/Al2O3-SiO2 catalyst has relatively high hydrogenation activity and excellent stability was used very extensively on hydrogenation of C4 fractions. The conversion of C4-olifiens were all close to 98% at the reaction pressure of 2.0MPa when the mass fraction of mono-olefins in C4 fraction was about 20%, the LHSV was 5.5h-1, the inlet temperature was room-temperature, the ratio of H2 to C4 was 219.6. First industrial application of SPC-01 catalyst in the IA plant in SINOPEC Shanghai Petrochemical Company Limited was rewarded by success,3 years operation results showed that:the catalyst has favorable activity and stability on cracking of TAME to product isobutene, both the conversion of TAME and the selectivity of isobutene were more than 99%. The characterization of fresh and used catalyst found that the coking of catalyst, reducing of specific surface area and acid strength was the main reason of the activity decreased, however the catalyst had a certain activity remained.7. Addition of TAA in the isomerization raw material was regarded to decrease the surface acidity of the strongly acidic ion exchange resin catalyst, thus improved its adsorption ability for 2M1B and effectively suppressed the dimerization. Therefore, the yield of objective product was enhanced and the reaction process was apt to stabilization. The process was applied in a 3.5kt/a industrial isobutene plant, the operation results was basically same to the laboratory. The conclusions were as follows:1) The based theory of isomerization reaction was established. For the isomerization of 2M1B, The mass exchange capacity (acid concentration) and the surface-SO3H (acid strength) acidity of the resin were important factors to determine the isomerization reaction. Only by the favorable matching ability between the acid concentration of resin and the TAA concentration in the raw material, the tenability of conversion and selectivity in the isomerization reaction could realize.2) The selectivity of 2M2B at a high conversion level for the isomerization of crude isobutene was significantly increased by the adding of a small amount of tertiary amyl alcohol in the reaction raw material. Compared with the results from the current isobutene units, the average conversion of 2M1B, the selectivity of 2M2B and the mass ratio of 2M2B to 2M1B were increased from 0.5474,0.6864 and 7.32 to 0.72～0.73,0.95 and 12, respectively, while the dimmers content in the products decreased from 4.38%to below 1.0%. Optimized conditions for isobutene isomerization consisted of temperature between 28 and 33℃, and system pressure of 0.5 MPa, crude isobutene mass hourly space velocity of 8.0h-1 with mass fraction of 0.7～0.9% in raw material.3) Industrial application:the average concentrations of 2M1B,2M2B and dimmer consisted of 7.19%,89.41% and 0.62% in the liquid products after the addition of TAA in the 3.5kt/a industrial isobutene plant, while the concentration of dimmer in raw material was 0.23%, the average conversion of 2M1B was 0.6651, the average selectivity of 2M2B was 0.9727, the average mass ratio of 2M2B and 2M1B was 12.45. The addition of TAA increased the activity of catalyst and the selectivity of objective product, the mass ratio of 2M2B and 2M1B was also significantly increased.8. The industrialization of hydrogenation process on crude isopentene achieved success, the concentrations of alkanes in the hydrogenation products remained at more than 99%, the average concentrations of isopentane and n-pentane was 32.53% and 67.11% respectively, which was superior cracking raw material to improve yield of"two-olefins"in cracking plant. The plant operating stationary at present, the results of hydrogenation were basically agreed with the small experiment. Compared with the results from the conventional hydrogenation process with high temperature and high pressure, the hydrogenation process was more inirritative, and the activity and stability of catalyst was comparatively ideal after the using of Ni/Al2O3-SiO2 catalyst.