Batch hydrogenation

Prior to the first hydrogenation batches, the supported ruthenium catalysts were reduced in the autoclave under hydrogen flow at 200°C for 2 hours (10 bar H2, heating/cooling rate 5°C/min). As the catalyst had been reduced, a lactose solution saturated with hydrogen was fed into the reactor rapidly and the hydrogen pressure and reactor temperature were immediately adjusted to the experimental conditions. Simultaneously, the impeller was switched on. This moment was considered as the initial starting point of the experiment. No notable lactose conversion was observed before the impeller was switched on. 

Figure 57.23. The effect of FT level on the BN hydrogenation batch time without...

Catalyst deactivation during consecutive lactose and xylose hydrogenation batches over Mo promoted sponge nickel (Activated Metals) and Ru(5%)/C (Johnson Matthey) catalysts were studied. Deactivation over sponge nickel occurred faster than on Ru/C in both cases. Product selectivities were high (between 97 and 100%) over both catalysts. However, related to the amount of active metal on the catalyst, ruthenium had a substantially higher catalytic activity compared to nickel. 

Figure 1. A. Consecutive xylose hydrogenation batches over 2.5 wt-% sponge nickel and 1.5 wt-% Ru/C catalyst. B. Catalyst deactivation during consecutive lactose hydrogenation batches over 5 wt-% sponge nickel and 2 wt-% Ru/C catalyst.

Figure 2. A. Consecutive xylose hydrogenation batches over sponge nickel catalyst (XA=xylonic acid). B. Influence of lactobionic acid (LBA) on lactose hydrogenation rate.

When the catalyst was recycled for use in the second batch, the deactivation was found to be rather severe. This, however, was expected - mainly due to the very small amount of catalyst applied into the hydrogenation batch. Nevertheless, the results indicated that ultrasound enhanced the reaction rate. The maximal yields were 0.60/0.08 at 220 min, compared with those obtained by conventional hydrogenation technology, 0.42/0.06 at 345 min. It is probable that the yield of OL would eventually revert in the absence of acoustic irradiation, as well. 

The property of f. to be local irritants of eyes and skin is reduced by ethoxylation. Manufacturing from RR is predominantly done via the fatty nitriles, which are made from fatty acids by reaction with ammonia. The nitriles are reduced by - hydrogenation (batch or continuous) into amines. The reaction conditions determine whether primary, secondary or tertiary amines result. Saturated f are formed when nitriles are hydrogenated at 80-140 °C and 1-4 MPa/lO O bar over Ni catalyst. Unsaturated f can be obtained with Raney Co or Cu-chromite as catalyst. Ammonia has to be present to suppress the formation of secondary amines. Saturated and unsaturated secondary amines are gained in yields of more than 90% if ammonia is vented from the reactor, the reaction temperature is 160-210 °C, and pressure is maintained at 5-10 MPa/50-100 bar. Trialkylamines are produced via the imine R-CH=NH and Schiff base R-CH=N-CH3 with Ni catalyst at 230 °C and 0.7 MPa/7 bar hydrogen pressure. Important amine types, which are the base for making dimethyl dialkyl ammonium compounds, are made by the following reaction ... 

The hydrocracking of a heavy oil at 1,080 °C and 1 atm uses a porous catalyst and excess hydrogen. Batch experiments with finely divided catalyst show a half life for the oil of 0.082 sec. Moreover, the oil has a diffusion coefficient of 0.014 cm /sec in the catalyst. Estimate the apparent rate constant in 0.1-cm spherical catalyst pellets. 

The spent hydrogen fluoride layer, which contains water and sodium bifluoride, from this process is treated with sulfur trioxide or 65% oleum, and hydrogen fluoride is distilled for recycle to the next batch (176,177). 

Direct hydrohquefaction of biomass or wastes can be achieved by direct hydrogenation of wood chips on treatment at 10,132 kPa and 340 to 350°C with water and Raney nickel catalyst (45). The wood is completely converted to an oily Hquid, methane, and other hydrocarbon gases. Batch reaction times of 4 hours give oil yields of about 35 wt % of the feed the oil contains about 12 wt % oxygen and has a heating value of about 37.2 MJ /kg (16,000 Btu/lb). Distillation yields a significant fraction that boils in the same range as diesel fuel and is completely miscible with it. 

Reductive amination of cyclohexanone using primary and secondary aHphatic amines provides A/-alkylated cyclohexylamines. Dehydration to imine for the primary amines, to endocycHc enamine for the secondary amines is usually performed in situ prior to hydrogenation in batch processing. Alternatively, reduction of the /V-a1ky1ani1ines may be performed, as for /V,/V-dimethy1 cyclohexyl amine from /V, /V- di m e th y1 a n i1 i n e [121 -69-7] (12,13). One-step routes from phenol and the alkylamine (14) have also been practiced. 

Dicyclohexylarnine may be selectively generated by reductive alkylation of cyclohexylamine by cyclohexanone (15). Stated batch reaction conditions are specifically 0.05—2.0% Pd or Pt catalyst, which is reusable, pressures of 400—700 kPa (55—100 psi), and temperatures of 75—100°C to give complete reduction in 4 h. Continuous vapor-phase amination selective to dicyclohexylarnine is claimed for cyclohexanone (16) or mixed cyclohexanone plus cyclohexanol (17) feeds. Conditions are 5—15 s contact time of <1 1 ammonia ketone, - 3 1 hydrogen ketone at 260°C over nickel on kieselguhr. With mixed feed the preferred conditions over a mixed copper chromite plus nickel catalyst are 18-s contact time at 250 °C with ammonia alkyl = 0.6 1 and hydrogen alkyl = 1 1. 

A mixture of primary and secondary amines is formed when ammonia is not used during the nitrile reduction. It is possible to prepare high purity secondary amines by carrying the reduction out at low pressure and passing hydrogen through the reaction in a batch process (47,48),... 

In the Bnchamp process, nitro compounds are reduced to amines in the presence of iron and an acid. This is the oldest commercial process for preparing amines, but in more recent years it has been largely replaced by catalytic hydrogenation. Nevertheless, the Bnchamp reduction is still used in the dyestuff industry for the production of small volume amines and for the manufacture of iron oxide pigments aniline is produced as a by-product. The Bnchamp reduction is generally mn as a batch process however, it can also be mn as a continuous (48) or semicontinuous process (49). 

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