Synthesis of Faujasite and MCM-41 from fly ash and their applications as hydrocracking nickel based catalysts of heavy petroleum distilates

SUTARNO, Promotor Prof.Dr. Hardjono Sastrohamidjojo

2005 | Disertasi | S3 MIPA (Kimia)

Dalam penelitian ini telah dilakukan sintesis faujasit dan MCM-41 dari abu layang dan aplikasinya untuk katalis hidrorengkah fraksi berat minyak bumi. Faujasit disintesis dari abu layang secara hidrotermal dalam larutan alkali melalui beberapa perlakuan untuk memperoleh hasil secara selektif. Perlakuan dilakukan melalui pembibitan dan pemeraman, refluks dengan HCl, peleburan dengan NaOH, serta gabungan refluks dengan HCl dan peleburan dengan NaOH. MCM-41 disintesis dari abu layang secara hidrotermal dalam larutan alkali dengan menggunakan surfaktan sebagai zat pengarah struktur. Surfaktan kemudian dihilangkan dari MCM-41 hasil sintesis dengan kalsinasi. Faujasit dan MCM-41 hasil sintesis dari abu layang selanjutnya digunakan untuk katalis hidrorengkah fraksi berat minyak bumi. Perlakuan pembibitan dan pemeraman dapat digunakan untuk meningkatkan selektivitas faujasit yang diperoleh dan untuk menurunkan kandungan fasa awal seperti kuarsa dan mullit, namun faujasit yang diperoleh masih terkontaminasi dengan zeolit lain. Perlakuan peleburan abu layang dengan NaOH dapat menghasilkan faujasit secara selektif, namun faujasit yang diperoleh masih menunjukkan stabilitas termal yang rendah akibat masih rendahnya rasio mol Si/Al. Penambahan natrium silikat ke dalam larutan prekursor tidak dapat digunakan untuk meningkatkan rasio mol Si/Al faujasit karena mengakibatkan terjadinya transformasi faujasit. Refluks abu layang dengan HCl sebelum peleburan dengan NaOH merupakan perlakuan yang efektif bukan hanya untuk meningkatkan rasio mol Si/Al namun juga untuk menurunkan logam pengotor dalam abu layang. Sintesis faujasit dari abu layang melalui perlakuan gabungan refluks dengan HCl dan peleburan dengan NaOH dapat menghasilkan faujasit secara selektif dengan rasio mol Si/Al yang lebih tinggi dan memiliki stabilitas termal setingkat dengan zeolit NaY perdagangan. Sintesis faujasit dari abu layang melalui perlakuan peleburan dengan NaOH untuk waktu hidrotermal yang lama dapat menyebabkan terjadinya transformasi faujasit menjadi hidroksisodalit. Transformasi faujasit menjadi hidroksisodalit juga dapat terjadi pada penggunaan konsentrasi NaOH yang tinggi dan pada penambahan natrium silikat dalam larutan prekursor. Sintesisi MCM-41 dari abu layang secara hidrotermal dapat dilakukan menggunakan surfaktan tetrametilammonium hidroksida (TMAOH) dan setiltrimetilammonium hidroksida (CTAOH) sebagai zat pengarah struktur. Surfaktan dapat dihilangkan dari MCM-41 hasil sintesis dengan kalsinasi tanpa merusak struktur. Dalam sintesis MCM-41 dari abu layang secara hidrotermal, rasio berat 41 dengan derajat kristalinitas yang lebih tinggi. Dengan pengaturan pH larutan prekursor, MCM-41 masih dapat diperoleh walaupun dalam larutan prekursor terdapat Na dengan konsentrasi yang relatif tinggi. MCM-41 dapat diperoleh dari larutan prekursor dengan rasio mol Si/Al serendah 9,8 walaupun derajat kristalinitasnya relatif rendah. Kenaikan rasio mol Si/Al dan rasio mol surfaktan/Si larutan prekursor meningkatkan derajat kristalinitas MCM-41. Pembuatan katalis dilakukan dengan pengembanan nikel ke dalam faujasit dan MCM-41 hasil sintesis dari abu layang menggunakan metode pertukaran ion. Dengan konsentrasi larutan nikel yang sama, nikel yang teremban dalam faujasit lebih banyak daripada nikel yang teremban dalam MCM-41 namun kerusakan struktur MCM-41 lebih besar daripada faujasit. Untuk hidrorengkah fraksi berat minyak bumi, baik katalis Ni-faujasit maupun katalis Ni-MCM-41 menunjukkan konversi yang tinggi untuk fraksi minyak gas berat. Dalam hidrorengkah fraksi minyak gas berat, aktivitas katalis Ni-MCM-41 lebih ditentukan oleh porositasnya sedangkan aktivitas katalis Ni-faujasit lebih ditentukan oleh jumlah nikel teremban. Katalis Ni-MCM-41 menunjukkan selektivitas yang lebih tinggi dalam menghasilkan bensin dan minyak tanah daripada katalis Ni-faujasit namun masih lebih rendah daripada katalis pembanding Ni-zeolit Y.

The synthesis of faujasite and MCM-41 from fly ash and its application for hydrocracking catalyst of heavy petroleum distillates have been performed. Faujasite was synthesized from fly ash by hydrothermal reaction in alkaline solution via various pretreatments. The pretreatments were designed to obtain selective faujasite and performed via seeding and aging, reflux with HCl, and fusion with NaOH, as well as combination of reflux with HCl and fusion with NaOH. The synthesis of MCM-41 from fly ash was conducted by hydrothermal reaction in alkaline solution and involved the use of surfactant as structure directing agent. The surfactant was removed from as-synthesized MCM-41 by calcination. The application of faujasite and MCM-41 from fly ash was used for hydrocracking catalyst of heavy petroleum distillates Hydrothermal synthesis of faujasite from fly ash via seeding and aging pretreatment can be used not only to increase the selectivity of faujasite obtained but also to decrease the presence of initial phases such as quartz and mullite, however, the faujasite obtained was still contaminated by other zeolite phases. Although hydrothermal synthesis of faujasite via fusion pretreatment of fly ash with NaOH has resulted selective faujasite without any contamination of other phases, however, the faujasite obtained still showed a relatively low thermal stability due to its relatively low Si/Al mol ratio. Because of phase transformation, therefore, the addition of sodium silicate solution into the precursor solution was not recommended to increase the Si/Al mol ratio of faujasite. Reflux pretreatment of fly ash with HCl before fusion with NaOH was an effective method not only to increase the Si/Al mol ratio but also to decrease the metal impurities in the fly ash sample. Due to higher Si/Al mol ratio of the faujasite obtained, the synthesis of faujasite from fly ash via combination of reflux with HCl and fusion with NaOH has resulted selective faujasite with thermal stability as high as commercial zeolite NaY. In the synthesis of faujasite from fly ash via fusion with NaOH for prolong hydrothermal time, the faujasite obtained was transformed into hydroxysodalite. Transformation of faujasite into hydroxysodalite also occurred at higher NaOH concentration in the precursor solution as well as at the addition of sodium silicate solution into the precursor solution. Hydrothermal synthesis of MCM-41 from fly ash has been successfully conducted using tetramethylammonium hydroxide (TMAOH) and cetyltrimethylammonium hydroxide (CTAOH) surfactants as structure directing agent. By calcination, the surfactant was effectively removed from as-synthesized MCM-41 without structural damage. In the hydrothermal synthesis of MCM-41 from fly ash, the lower NaOH/fly ash weight ratio as well as the lower pH resulted the higher order of crystallinity of MCM-41. Although hydrothermal reaction was conducted under the condition of relatively high Na concentration, however, MCM-41 could be formed as far as the reaction was conducted under controlled pH conditions. MCM-41 could be resulted from the precursor solution with Si/Al mol ratio as low as 9.8, however, the order of crystallinity was still relatively low. Increasing both the Si/Al mol ratio and the surfactant/Si mol ratio of precursor solution increased the order of crystallinity of MCM-41. The preparation of nickel containing catalysts by ion exchange method under similar initial concentration of nickel resulted higher amount of nickel loaded on faujasite than those on MCM-41, however, the structural damage of MCM-41 was higher than those of faujasite. In the hydrocracking of heavy petroleum distillates over Ni-faujasite and Ni-MCM-41 catalysts, the conversion of heavy gas oil fraction was the most pronounced. The activity of the Ni-MCM-41 catalysts in the conversion of heavy gas oil was dominated largely by their porosity. In contrast, the activity of Ni-faujasite catalysts was determined mainly by the amount of nickel loaded. The selectivity toward hydrocarbons in the range of gasoline and kerosene obtained over Ni-MCM-41 catalyst was higher compared to those of Ni-faujasite catalyst, however, Ni-zeolite Y reference catalyst still performed the highest selectivity.

Kata Kunci : Sintesis Faujasite dan MCM,41,Abu Layang,Katalis,Hidrorengkah Fraksi Berat Minyak Bumi, fly ash, hydrothermal, faujasite, MCM-41, hydrocracking