Silver Catalyst Process

In early formaldehyde plant, methanol was oxidized over a copper catalyst, but in recent years this has been almost completely replaced with silver. Domestic licensors include Borden Chemical Company and Davy Powergas, Inc. (Imperial Chemical Industries Ltd., process.

The silver catalyzed reactions occur at essentially atmospheric pressure and 600 to 650 C and can be represented by two simultaneous reactions:

CH3OH+1/2 O2 ------> HCHO+H2O (DeltaH = -156 kJ or -37.28 kcal)

CH3OH ------> HCHO+H2 (DeltaH = 85 kJ or 20.31 kcal)

Between 50 and 60% of the formaldehyde is formed by the exothermic reaction and the remainder by endhotermic reaction with the net result of a reaction exoterm. Carbon monoxide and dioxide, methyl formate, and formic acid are by products. In addition, there are also physical losses, liquid-phase reactions, and small quantities of methanol in the product, resulting in an overall plant yield of 86 - 90% (based on methanol).

The reaction occurs at essentially adiabatic conditions with a large temperaturerise at the inlet surface of the catalyst. The predominant temperature control is thermal ballast in the form of exess methanol or steam, both, which is in the feed. if a plant is to produce a product containing 50 to 55% formaldehide and no more than 1.5 % methano, the amount of steam that can be added is limited, and both exess methanol and steam are needed as ballast. Recycled methanol required for a 50 - 55 % product is 0.25 - 0.50 parts per partof fresh methanol.

With increacing energy cost, maximum methanol conversion is desirable, eliminating the need for the energy-intensive distillation for metanol recovery. If a dilute product containing 40 to 44% formaldehide and 1.0 to 1.5% methanol is acceptable, than the ballast steam can be increased to a level where recycled methanol is eliminated with a significant savings in capital cost and energy.


(Kirk and Othmer vol 11, p237 - p238, 1978)

Kegunaan Formaldehide

Formaldehid untuk industri kimia:
a. Resin, formaldehide banyak digunakan untuk menghasilkan resin bersama dengan urea, melamin, dan phenol. Resin-resin ini dipakai dalam pembuatan particleboards, playwood dan furnitur. Juga sebagai bahan baku pelapis permukaan (coating), sebagai bahan pembantu dalam industri textil, kulit, karet, dan semen.

b. Bahan intermediet untuk sintesis senyawa kimia lain, seperti 1,4 butanadiol, trimetilol propan, neopentil glikol, penta erythritol, hexametilen tetramin, NTA (Nitrilo triacetic Acid), EDTA, dan 4,4 diphenylmethane diisocyanate).

c. Pengunaan langsung formaldehide sebagai penghambat korosi, electroplating dan finishing kaca dalam industri logam, bahan pengawet dan desinfektan dalam dunia kedokteran dan kosmetik.


(Ullman's, Vol.A11, 1988)