Kinetika reaksi hidrogenasi isoprena dengan katalis Pd dalam reaktor monolith

DARMADI, Dr.Ir. Bardi Murachman, SU.,DEA

2002 | Tesis | S2 Teknik Kimia

Isoprena adalah salah satu senyawa sangat aktif yang terdapat dalam gasoline hasil perengkahan naphtha. Senyawa ini menyebabkan gasoline tidak stabil. Reaksi hidrogenasi isoprena h e cair dengan katalis Pd pada suhu 273 - 288 K dan tekanan atmosferis dalam reaktor monolith menghasilkan metil-butena. Produk ini merupakan bahan baku pembuatan tert-amyl methyl ether (TAME). Tujuan penelitian ini adalah mempelajari pengaruh konsentrasi awal isoprena dan suhu terhadap laju reaksi. Reaksi hidrogenasi dijalankan d a b reaktor monolilh yang mempunyai square channel dengan 400 cell per square inch (cpsi). Monolith mempunyai panjang 10,16 cm, diameter 1,27 cm, dan luas permukaan spesifik 2640 m2/m3. Preparasi dan karakterisasi katalis masing-masing dilakukan dengan metode hpregnasi dan metode BET. Kandungan alumina washcoating adalah 2,97% berat, SBET,MONO 15,24m2/g, jari-jari pori rata-rata 6,969 Angstrom, dan total volum pori 5,311 10-3 ml/g . Impregnasi katalis Pd dilakukan dan diperoleh 1,95% berat. Reaktor dioperasikan secara semibatch terhadap hidrogen, sedangkan fase cair beroperasi secara batch yang disirkulasikan dari tangki penampung. Konsentrasi awal umpan isoprena addah 0,l - 0,3 M. &an fase cair yang disirkulasikan ke reaktor adalah 1,54 ddetik dan gas hidrogen 1,65 ddetik dengan liquid loading 0,l m3/(m2-detik) dan gas hold-up 5 1%. Aliran umpan fase cair disirkulasikan dari tangki penampung ke reaktor melalui spray nozzle dan aliran gas dilewatkan di bawah spray nozzle. Aliran b e cair dan gas adalah cocurrenl downflow. Hasil percobaan menunjukkan bahwa model kinetika dengan gas hidrogen yang terserap terdisosiasi memberikan ralat rerata cukup baik, yaitu 6,524%- 45,139%. Pengaruh suhu terhadap konstanta kecepatan reaksi pada percobaan ini sangat kecil dan pengaruh suhu terhadap konstanta kesehnbangan adsorpsi dapat diabaikan. Nilai k, K4 I(H2, dan I(B pada suhu 273 K dan konsentrasi awal isoprena 0,l M masing-masing adalah 3,648 kmol/(kgkat.dt.), 9,509 m3/kmol, 9,945 m3h01, dan 41,199 m3/km01. Konversi pada kondisi di atas diperoleh 80,1% pada waktu 5 menit.

Pyrolysis gasoline, a byproduct of naphtha cracker, is unstable because of its highly active content such as isoprene. The hydrogenation of isoprene in a monolithic reactor proceeds at 273 - 288 K and atmospheric condition in the presence of Pd catalyst to give methylbutene. It is used as the feedstock for the tert-amyl methyl ether (TAME) process. The objectives of the research are to study the effects of initial concentrations and temperatures on rate reaction. Hydrogenation was conducted in a monolithic reactor that has 400 cellper square inch (cpsi). The monolith had a cylindrical shape with a length of 10.16 cm, a diameter of 1.27 cm, and a spesific surface area of 2640 m2/m3. The preparation and characterization of catalysts were carried out using the dipping and BET methods, respectively. The washcoated alumina had 2.97 wt%, SBETMONO 15.24 m2/g, average pore radius 6.969 Angstrom, and total pore volume 5.311 10-3 ml/g , respectively. The weight of dipped Pd catalyst was 1.95 wt %. The reactor was operated in fed-batch with respect to hydrogep and batch with respect to liquid phase which was circulated fkom the storage vessel. The initial concentrations of isoprene were 0.1 M - 0.3 M. The liquid phase was charged into the storage vessel and with+awn fkom the vessel by a circulating pump and sprayed into the reactor through a nozzle. Hydrogen was introduced and gas and liquid flow in co-current downflow through the reactor. The liquid and hydrogen flows were 1.54 mVs and 1.65 d s , respectively. The liquid loading and gas hold-up were 0.1 rn3/(m2-s) and 51 %, respectively. Some experimental results showed that the fit of the kinetic model for dissociative adsorption of hydrogen was good enough and the deviations between the experimental and the estimated concentrations were 6.524-45.139%. The rate constant coefficient was only slightly dependent on temperature and the ratio of the adsorption constants was negligible dependence on temperature. The values of k, K4 &, and & at 273 K and initial concentration of reactant 0.1 M were 3.648 kmol/(kgkat.s), 9.509 m3/kmol, 9.945 m3/kmol, and 41.1 99 m3/km01, respectively. A conversion was 80.1 % for reaction time 5 minutes.

Kata Kunci : Reaksi Hidrogenasi,Reaktor Monolith