Catalysis – Innovative Applications in Petrochemistry and Refining DGMK Conference October 4-6, 2011, Dresden, Germany
DISY: The Direct Synthesis of Hydrogen Peroxide, a Bridge for Innovative Applications R. Buzzoni, C. Perego Eni S.p.A., Research Center for Non-Conventional Energies, Istituto eni Donegani, Novara, Italy
Abstract Hydrogen peroxide is largely recognized as the green oxidant of choice for future sustainable processes. The current industrial production still goes through the old anthraquinone process, a complex, two-step process suffering from a low specific productivity. Following the development of TS-1/H2O2 based selective oxidation processes e.g. propylene epoxidation, cyclohexanone ammoximation and the new benzene direct oxidation to phenol, there has been an incentive for the development of a new technology, simpler and with better economics. DISY process, based on direct synthesis of hydrogen peroxide from hydrogen and oxygen, is highly suitable to the design of integrated selective oxidation processes as well as for production of commercial-grade high concentration aqueous hydrogen peroxide solutions. Catalyst and process development up to pilot scale are described.
Introduction Hydrogen peroxide is largely recognized as the green oxidant of choice for future sustainable processes. The only current commercial method for hydrogen peroxide manufacture is still the anthraquinone process dating back to II World War. This very complex, two-step process suffers from a low specific productivity, so that a remarkably high investment for an industrial plant is required and the economics of the process result in a relatively high production cost. New greener bulk industrial selective oxidation processes using H2O2 and Ti zeolite-like catalyst have been established (e.g. for producing caprolactam, propylene oxide), or are under an advanced development stage (phenol). These processes will require a lot of additional H2O2; in early 2000 decade hydrogen peroxide worldwide demand [1,2] was close to 2•106 metric ton per year (2 MT/y), actually is estimated higher than 3MT/y; in this context we have to remember that about 0,1-0,3 MT/y are needed just for a world scale PO plant.
Therefore, there has been an incentive for the development of a new technology, suitable to large scale production, simpler and with better economics. This goal can be reached in different ways 1. Improvement of the classical process: hydrogen peroxide producers have claimed the ability to build anthraquinone H2O2 plants of up to 0,2 MT/y capacity using a single train of equipments. 2. New production way(s), viz. H2O2 one-pot direct synthesis process from H2 and O2. 3. H2O2 in situ generation from H2 and O2: a field of growing interest, pursued by many groups, in particular for PO and phenol production.
In this frame, the direct reaction of hydrogen and oxygen in a one step process has come out as the most promising approach and the best candidate to an easy, large, on-site, integrated H2O2 production. A direct synthesis technology is forecast to afford lower production cost and especially quite a lower investment.
DGMK-Tagungsbericht 2011-2, ISBN 978-3-941721-17-3 75 Catalysis – Innovative Applications in Petrochemistry and Refining
Although this reaction has been known for some decades, its industrial development is still under active investigation in order to overcome the hurdle of combining meaningful performances with proper process safety. Based on the above premises and looking at the innovative industrial oxidation routes where hydrogen peroxide is used in combination with its proprietary TS-1 catalyst, Polimeri Europa, the petrochemical company of eni, focused on developing the new DISY process (H2O2 production technology through DIrect SYnthesis) [3]. Some of the results of the development up to pilot scale (5 l/h) for the direct synthesis of hydrogen peroxide from hydrogen and oxygen in methanol, carried out in very safe conditions, are reported.
Experimental ¾ Reactor and reaction conditions: a scheme of the pilot equipment is depicted in Fig 1. A continuous slurry-type reactor was used. Gaseous feed was make-up O2, H2, N2 and recycle gas. Liquid feed was solvent + promoters (see below). Liquid effluent was drawn from the reactor through a sintered candle-type filter, de-pressurized and gathered for analysis or further processing. After purging effluent gas was recycled to the reactor by means of a compressor. Typical reaction conditions are reported below: H2 (inlet) < 3.5%v; O2 (inlet) < 12%v; N2 to balance; reaction temperature 40-50°C; reaction pressure 50-100 bar; solvent (feed): CH3OH + water; catalyst Pd-Pt/C; Promoters:H2SO4, HBr.
H2O2 Solution O2
Methanol Solution H2
N2
Fig. 1. Continuous pilot plant (5 l/h) scheme operation with gas recycle
¾ Catalyst: was a bimetallic Pd-Pt co- or sequentially supported on activated carbon powder. Catalyst is finely tuned to obtain a controlled nanometric metal particle size with a uniform distribution on the carbon and a low impurities level.
DGMK-Tagungsbericht 2011-2 76 Catalysis – Innovative Applications in Petrochemistry and Refining
Results and Discussion Using reaction conditions as described, easy to be further scaled-up, a concentration of hydrogen peroxide higher than 7%w and a molar selectivity based on hydrogen higher than 75% were obtained. Higher concentrations could be reached with lowering selectivity (Fig. 2).
1,00
0,90
0,80 Selectivity 2 H 0,70
0,60
0,50 6,0 8,0 10,0 12,0 14,0 H O (% w) 2 2 Fig. 2. Hydrogen selectivity (absolute value) vs. H202 concentration at the exit of reactor
A productivity in the range of 120-200 kg/(m3*h) was attained and a catalyst life of more than 2000 hours was assessed on the pilot scale (Fig. 3).
Pd-Pt catalysts with crystal size lower than 5 nm diameter (Fig. 4, left), were consistently prepared and scaled-up to kg scale. A typical mean diameter of about 2nm was measured by HRTEM (based on at least 150 metal particles measurement). Uniform metal distributions on the activated carbon powder were obtained. Catalysts discharged after > 500-1000 hours t.o.s., showed an increase in the mean particle size of about 3-5x. For a catalyst discharged after 2100h t.o.s. mean metal particle size was 12nm (Fig. 4 right). An important fraction of this increase occurred in the first 100-200 hours (Fig. 5).
The reaction effluent of the direct synthesis approach, i.e. a solution of H2O2 ca. 7% in methanol/water, was proved suitable both to be directly reacted in TS-1 catalyzed selective oxidations, e.g. ammoximation of cyclohexanone and oxidation of propylene [4] and to produce commercial-grade high concentration aqueous hydrogen peroxide solutions by distillation and methanol recycle [5].
DGMK-Tagungsbericht 2011-2 77 Catalysis – Innovative Applications in Petrochemistry and Refining
H2O2 (%) H2 Selectivity
10 0,9
8 0,7
)
y
t
i
w
v
i
%
t ((%w) 6 0,5
c 2
e
l
O
e 2
4 0,3 S
H
2 0,1
600 800 1000 1200 1400 1600 1800 2000 t.o.s. (h) Fig. 3. A typical pilot run: hydrogen peroxide concentration and hydrogen-based selectivity vs. time on stream (t.o.s.). All values, including those measured during change in reaction parameters and plant stop & go procedures, are shown.
50nm 20nm
Fig. 4. HRTEM picture of Pd-Pt catalyst supported on activated carbon. Fresh catalyst (left), after 2100 hours t.o.s. (right).
DGMK-Tagungsbericht 2011-2 78 Catalysis – Innovative Applications in Petrochemistry and Refining
13
11
9
7
5 diameter (nm) diameter
3
1 0 500 1000 1500 2000 time on stream (h)
Fig. 5. Catalyst Active Phase Sintering (by HRTEM) in function of t.o.s. Different catalysts and different test runs are reported.
Conclusions A direct synthesis process for the production of hydrogen peroxide from hydrogen and oxygen (DISY process) was scaled up and tested to pilot scale. Some of the caught key points are the following: a. The gaseous mixtures employed lie well outside the explosion limits. Process safety was witnessed by over 15,000 hours of trouble-free pilot operation. b. Optimization of reaction formula (solvent, promoters) and conditions allowed to achieve low corrosion, long catalyst life and product stability. c. An heterogeneous catalyst, based on palladium and platinum as active components, has been developed on-purpose. d. Both integrated selective oxidation processes as well as production of commercial-grade high-concentration aqueous hydrogen peroxide are easily afforded.
References
[1] Chemical Week, July 2/9, 2003, 44 [2] J.M. Campos-Martin, G. Blanco-Brieva and J.L.G. Fierro, Angew. Chem. Int. Ed. 45, 6962 (2006) [3] G. Paparatto, F. Rivetti, P. Andrigo, G. De Alberti, ENI SpA-Polimeri Europa SpA, EP1160196 (2001). [4] G. Paparatto, R. D’Aloisio, G. De Alberti, P. Furlan, V. Arca, R. Buzzoni, L. Meda, Polimeri Europa SpA, EP 0978316 (1999). [5] G. Paparatto, F. Rivetti, P. Andrigo, G. DeAlberti, U. Romano, ENI SpA - Polimeri Europa SpA, WO0214217 (2001).
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