rhodium catalysts

PabrikPembuatanAsamAsetat berkapasitas 95.000 ton/tahun inidirencanakandidirikan pada tahun 2021 berlokasi di daerah Bontang, Kalimantan Timurdengan luas area10 Ha.Proses pembuatan Asam Asetat ini mengacu pada US Patent No. US 9302974 B1. Teknologi proses ysng diunggulkan dalam rancangan pabrik ini adalah pada tahap karbonilasi metanol dengan penggunaan katalis rhodium. Reaksi berlangsung pada reaktor bubble column, padatemperatur215oC dan tekanan 15 atm. Untuk membangun pabrik ini akan didirikan perusahaan berbentuk perseroan terbatas (PT) yang dipimpin oleh seorang Direktur Utama. Sistemorganisasi Perusahaan adalah“line and staff”dengan total karyawan 147 orang. Pabrik pembuatan Asam Asetat ini layak didirikan karena telah memenuhi persyaratan parameter ekonomi sebagai berikut.
• Total Capital Investment (TCI) = US$16,633,778.7102
• Total Production Cost (TPC) = US$ 7,211,799.9099
• Selling Price (SP) = US$ 1,236,125,810.4
• Annual Cash Flow (ACF) = US$ 922,972,130.6508
• Pay Out time = 2 tahun 1 bulan
• Rate of Return on Investemnt (ROR) = 55,4105 %
• Break Even Point (BEP) = 30,6685  %
• Service life = 11 tahun

Hydrogen is essentially produced by steam reforming (SR) of hydrocarbon fractions (natural gas, naphtha,. . .) on an industrial scale. Replacing fossil fuels by biofuels for H 2 production has attracted much attention with an increased interest for bioethanol steam reforming. Kinetics and mechanisms of hydrocarbon-SR and alcohol-SR present some similarities but also some very important differences due to alcohol reactivity much more complex than that of hydrocarbons. The scope of this report is to compare the two processes in terms of reaction mechanisms. Attention will also be paid to the case of crude bioethanol.

A 3.7% Rh/CeO 2 catalyst was prepared by wet impregnation of a low-surface-area ceria (23 m 2 g −1) with an aqueous solution of rhodium nitrate. This catalyst was reduced in a flow of H 2 at temperatures T R ranging from 200 to 1000 • C. The number of reduced centres of ceria in Rh/CeO 2 catalysts was measured by in situ reoxidation of these centres at T OX by pulses of water according to the following reaction: Reduced centre + H 2 O → Oxidised centre + H 2. The amount of hydrogen, Q H , evolved in the reaction allows us to calculate the number of reduced centres of the support since the noble metal would not be oxidised. Q H remains relatively small for T R not exceeding 500 • C, then increases rapidly to reach a pseudo-plateau at about 850 • C. At 900–1000 • C, the oxide composition would be close to CeO 1.75. Contrasting with the effect of T R , relatively small variations are recorded with T OX for a catalyst reduced at 850 • C: a maximum value of Q H is reached for T OX close to 850 • C, but 74% of this maximum yield in H 2 is already obtained when the reaction with steam is carried out at 100 • C. Oxidation by steam was also carried out on a catalyst prereduced in deuterium. It was shown that the hydrogen formed comes from the decomposition of water (H 2) and not from the storage of deuterium in the support during the reduction stage. In situ characterisation by XRD showed that there is a deep perturbation of the cubic structure at 850 • C, followed by a reduction of CeO 2 into Ce 2 O 3 (hexagonal) at higher temperatures (900–1000 • C). A treatment in water restores the cubic structure of CeO 2. The support having been previously reduced at 900 • C, there is virtually no sintering of the ceria crystallites upon these high-temperature treatments in hydrogen and steam.

The role of the support in steam dealkylation (SDA) is studied on a series of Group VIII metal catalysts supported on alumina, silica, and titania. When possible turnover frequencies are given on the basis of the free metal fraction during the reaction. The values are generally constant with time-on-stream and represent the actual turnover frequency of the catalyst. Metals can be classified into two groups, namely, support-sensitive metals (Pt, Rh, Pd) and support-insensitive metals (Ni, Co, Ru, and to a certain extent Ir). Support sensitivity is related to the oxidizability of the metallic surface. For metals of the first group, the reaction is probably governed by a noncompetitive mechanism in which the metal coverage by the oxygenated species is negligible. Kinetic derivation leads to a rate law where there is at once intervention of the support site concentration and of the specific perimeter of the metal/support interface. One can thus explain the support effect for this metal group and the slight sensitivity to the crystallite size observed in the Rh/AIZ03 series. For metals of the second group, a competitive mechanism probably takes place on the metal. Kinetic derivation leads to a rate law independent of the support site concentration and accounting for the slight negative order with respect to toluene as previously reported. The conspicuous parallelism between the selectivities of the various metals in SDA, in hydrodealkylation, and in hydrogenolysis is also discussed. In addition to the metal, the support and the crystallite size are determining factors of the selectivity to benzene in SDA.